1) The document discusses different types of threaded and welded joints. It describes various threaded fasteners like bolts, studs, screws and their characteristics.
2) For threaded joints subjected to eccentric loads, it explains how to calculate the primary and secondary shear forces on each bolt. This involves finding the center of gravity of the bolt system and determining the forces based on the load direction.
3) Sample problems are included to demonstrate how to select the bolt size based on the maximum resultant shear force and required factor of safety. Calculations are shown for eccentrically loaded bolted joints with the load in the plane of bolts.
- The document discusses different types of springs including helical compression springs, helical extension springs, helical torsion springs, and multileaf springs.
- It describes the functions and applications of springs which include absorbing shocks and vibrations, storing energy, and measuring forces.
- Key terms related to helical spring design are defined such as wire diameter, mean coil diameter, spring index, solid length, compressed length, free length, and pitch. Stress and deflection equations for helical spring design are also presented.
1. Shaft couplings are used to connect shafts that are manufactured separately or to introduce flexibility between shafts. The main types are rigid and flexible couplings.
2. Rigid couplings transmit torque without losses but require perfectly aligned shafts. Flexible couplings allow for misalignment. Common rigid couplings are sleeve, clamp, and flange couplings.
3. Flange couplings use separate cast iron flanges keyed to each shaft end and bolted together. The flanges and bolts are designed to transmit the torque between the shafts. Flexible couplings like bush pin couplings introduce mechanical flexibility.
Unit 2 Design Of Shafts Keys and CouplingsMahesh Shinde
Ā
This document provides information about the design of shafts, keys, and couplings. It discusses transmission shafts, stresses induced in shafts, and shaft design based on strength and rigidity. It presents formulas for shaft design using maximum shear stress theory, distortion energy theory, and the ASME code. Several examples are provided to demonstrate how to calculate the diameter of a shaft given the power transmitted, loads on the shaft, material properties, and other parameters using these theories and codes. Assignments involving similar calculations of shaft diameters are presented.
A coupling is a mechanical device that rigidly joins two rotating shafts together. There are three main types of couplings: rigid couplings for perfectly aligned shafts, flexible couplings for shafts with misalignment, and flange couplings which can transmit high torque capacities but do not tolerate misalignment or shocks/vibrations. Design of couplings involves calculating shaft diameters, sleeve/flange dimensions, key dimensions, and bolt diameters based on the transmitted power, material properties, and safety factors. Dimensional relationships and equations are used to check stresses in the various coupling components.
This document discusses different types of screw threads, their purposes, and terminology. It describes threads in terms of pitch, lead, thread form, and various thread standards. It also covers thread representation, types of threaded fasteners like bolts and screws, nuts, and thread gauging. The overall purpose of threads is to hold parts together, adjust parts relative to each other, and transmit power or motion between parts.
This document discusses machine design and the basic procedures and requirements for designing machine elements. It defines machine design as using scientific principles, technical information, and imagination to describe machines that perform functions with maximum economy and efficiency. The basic requirements for machine elements are then listed, including strength, rigidity, wear resistance, manufacturability, safety, and more. The basic procedure for designing machine elements is then outlined in 6 steps: specification of function, determination of forces, selection of material, failure criterion, determination of dimensions, and preparation of working drawings. Materials that could be used like cast iron, plain carbon steel, and alloy steels are then described in more detail.
This document discusses the design of a socket and spigot cotter joint. A cotter joint is used to rigidly connect two coaxial rods subjected to axial tensile or compressive forces. It consists of a tapered wedge-shaped cotter that fits into slots in the spigot and socket. The document outlines various failure modes of the joint and provides examples of sizing a cotter joint to withstand specified loads.
,
diploma mechanical engineering
,
mechanical engineering
,
machine design
,
design of machine elements
,
knuckle joint
,
failures of knuckle joint under different streses
,
fork end
,
single eye end
,
knuckle pin
- The document discusses different types of springs including helical compression springs, helical extension springs, helical torsion springs, and multileaf springs.
- It describes the functions and applications of springs which include absorbing shocks and vibrations, storing energy, and measuring forces.
- Key terms related to helical spring design are defined such as wire diameter, mean coil diameter, spring index, solid length, compressed length, free length, and pitch. Stress and deflection equations for helical spring design are also presented.
1. Shaft couplings are used to connect shafts that are manufactured separately or to introduce flexibility between shafts. The main types are rigid and flexible couplings.
2. Rigid couplings transmit torque without losses but require perfectly aligned shafts. Flexible couplings allow for misalignment. Common rigid couplings are sleeve, clamp, and flange couplings.
3. Flange couplings use separate cast iron flanges keyed to each shaft end and bolted together. The flanges and bolts are designed to transmit the torque between the shafts. Flexible couplings like bush pin couplings introduce mechanical flexibility.
Unit 2 Design Of Shafts Keys and CouplingsMahesh Shinde
Ā
This document provides information about the design of shafts, keys, and couplings. It discusses transmission shafts, stresses induced in shafts, and shaft design based on strength and rigidity. It presents formulas for shaft design using maximum shear stress theory, distortion energy theory, and the ASME code. Several examples are provided to demonstrate how to calculate the diameter of a shaft given the power transmitted, loads on the shaft, material properties, and other parameters using these theories and codes. Assignments involving similar calculations of shaft diameters are presented.
A coupling is a mechanical device that rigidly joins two rotating shafts together. There are three main types of couplings: rigid couplings for perfectly aligned shafts, flexible couplings for shafts with misalignment, and flange couplings which can transmit high torque capacities but do not tolerate misalignment or shocks/vibrations. Design of couplings involves calculating shaft diameters, sleeve/flange dimensions, key dimensions, and bolt diameters based on the transmitted power, material properties, and safety factors. Dimensional relationships and equations are used to check stresses in the various coupling components.
This document discusses different types of screw threads, their purposes, and terminology. It describes threads in terms of pitch, lead, thread form, and various thread standards. It also covers thread representation, types of threaded fasteners like bolts and screws, nuts, and thread gauging. The overall purpose of threads is to hold parts together, adjust parts relative to each other, and transmit power or motion between parts.
This document discusses machine design and the basic procedures and requirements for designing machine elements. It defines machine design as using scientific principles, technical information, and imagination to describe machines that perform functions with maximum economy and efficiency. The basic requirements for machine elements are then listed, including strength, rigidity, wear resistance, manufacturability, safety, and more. The basic procedure for designing machine elements is then outlined in 6 steps: specification of function, determination of forces, selection of material, failure criterion, determination of dimensions, and preparation of working drawings. Materials that could be used like cast iron, plain carbon steel, and alloy steels are then described in more detail.
This document discusses the design of a socket and spigot cotter joint. A cotter joint is used to rigidly connect two coaxial rods subjected to axial tensile or compressive forces. It consists of a tapered wedge-shaped cotter that fits into slots in the spigot and socket. The document outlines various failure modes of the joint and provides examples of sizing a cotter joint to withstand specified loads.
,
diploma mechanical engineering
,
mechanical engineering
,
machine design
,
design of machine elements
,
knuckle joint
,
failures of knuckle joint under different streses
,
fork end
,
single eye end
,
knuckle pin
The document discusses various topics related to screwed joints and fastenings including:
1. The advantages and disadvantages of screwed joints.
2. Important terms used in screw threads such as major diameter, pitch, and crest.
3. Different types of screw threads including British Standard, American, and metric threads.
4. Factors to consider when locating screwed joints such as reducing bending stresses.
5. Common types of screw fastenings like through bolts, studs, and set screws.
1. A shaft transmits power and rotational motion and has machine elements like gears and pulleys mounted on it.
2. Press fits, keys, dowel pins, and splines are used to attach machine elements to the shaft.
3. The shaft rotates on rolling contact or bush bearings and uses features like retaining rings to take up axial loads.
4. Couplings are used to transmit power between drive and driven shafts like between a motor and gearbox.
The document discusses stresses in flywheel components and design considerations. It describes:
1. A flywheel consists of a rim to concentrate mass, a hub to attach to a shaft, and arms to support the rim.
2. Stresses induced in the rim include tensile stress from centrifugal force, tensile bending stress from arm restraint, and shrinkage stresses from uneven cooling.
3. The tensile stress in the rim from centrifugal force is calculated similarly to a thin cylinder under pressure. Stresses in the arms include tensile stress from centrifugal force and bending stress from transmitting torque.
A cotter joint connects two coaxial rods subjected to axial forces. It uses a tapered wedge-shaped cotter inserted into slots in the overlapping ends of the rods. The cotter prevents longitudinal movement but allows for disassembly. Cotter joints are commonly used to connect piston rods, pump parts, flywheels, and foundation bolts. The document provides design considerations and equations for sizing the rods, slots, and cotter to withstand various failure modes from the tensile, compressive, and shear stresses based on the applied load and material properties. It also presents three example problems of designing cotter joints for specified loads.
6 shaft shafts subjected to fluctuating loadsDr.R. SELVAM
Ā
Shafts are often subjected to fluctuating loads in practice rather than constant loads. To design shafts like line shafts and counter shafts that experience fluctuating torque and bending moments, combined shock and fatigue factors must be accounted for in calculating the twisting moment and bending moment. These equivalent moments are calculated using combined shock and fatigue factors for bending (Km) and torsion (Kt), with recommended values for Km and Kt provided in a table.
This document discusses helical springs and U-clamps. It defines springs and their main uses which include exerting force, providing flexibility, and storing energy. The most common spring materials are discussed along with the types of springs including helical, flat, and special shaped. Helical springs are further broken down into open coil, closed coil, torsion, and spiral varieties. U-clamps are metal clamps used to mount pipes and are made of stainless steel or mild steel for durability.
1. The document describes a clamp or compression coupling, which uses two halves of a cast iron muff that are bolted together around the abutting ends of two connected shafts. A single key fits in the keyways of both shafts to transmit power.
2. Design considerations for this type of coupling include sizing the clamping bolts to withstand the frictional forces between the muff and shafts, which transmit the torque. The proper bolt root diameter is calculated based on these frictional forces.
3. Tolerances for misalignment are provided by a bushed-pin flexible coupling. It uses rubber or leather bushes around coupling pins to connect two flanged halves with some clearance, absorbing misalignment
The document discusses stress concentration and fatigue failure in machine elements. It defines stress concentration as irregular stress distribution caused by abrupt changes in cross-section shape. Stress concentration factors are introduced to quantify the maximum stress compared to nominal stress. The document also discusses endurance limit and fatigue strength testing methods. Factors that affect fatigue strength like material properties, surface finish, size and temperature are summarized. Methods to evaluate and reduce stress concentration in designs are provided.
Basic types of screw fasteners, Bolts of uniform
strength, I.S.O. Metric screw threads, Bolts under
tension, eccentrically loaded bolted joint in shear,
Eccentric load perpendicular and parallel to axis of
bolt, Eccentric load on circular base, design of Turn
Buckle.
,bearings ,function of bearing ,footstep or pivot bearing ,bush and direct-lined housing ,thrust bearing ,journal bearing ,ball and roller bearings ,types of rolling bearing ,sliding contact bearing ,applications of roller bearings
The document discusses the design of welded joints. It begins by defining a welded joint as a permanent fusion of two parts achieved through heating and optionally applying pressure and a filler material. Welding provides advantages over riveted joints like lighter weight and greater efficiency. Various welding processes are described including gas, electric arc, thermit and forge welding. Common welded joint types like lap, butt, corner and T-joints are also outlined. The document then examines the strength calculations for transverse and parallel fillet welds as well as butt joints. It concludes by discussing stresses in eccentrically loaded and unsymmetrical welded sections.
The document summarizes key concepts about screws, fasteners, and bolted joints from Shigley's Mechanical Engineering Design textbook. It discusses thread standards and definitions, types of bolts and screws, mechanics of power screws, stiffness of bolted joints, preload in bolts, and factors that affect fatigue loading of bolted joints. Examples are provided to illustrate calculation of power screw torque and analysis of bolted joint stiffness.
This document discusses riveted joints, which are used to join metal plates. It describes the different types of rivet heads, riveted joint configurations like lap joints and butt joints, and how rivets are installed through heating and hammering. The document also discusses factors that determine the strength of riveted joints like the tearing resistance of plates, shearing resistance of rivets, and crushing resistance of plates and rivets. It explains how riveted joints can fail through tearing of plates, shearing of rivets, or crushing of plates/rivets. The efficiency of riveted joints is defined as the ratio of the joint's strength to the strength of an unriveted solid
This document discusses different types of machine keys used to connect rotating elements like shafts, gears, and pulleys. It describes saddle keys, sunk keys, taper keys, parallel keys, and feather keys. Design considerations for keys include preventing slippage while transmitting torque. Keys are designed based on withstanding shear and compressive stresses. Sample problems demonstrate how to calculate the required key dimensions given input torque and shaft dimensions. Splines are also discussed as an alternative to keys, with their torque capacity determined by factors like spline area, mean radius, and permissible pressure.
The document discusses different types of springs including their materials, applications, advantages, and designs. It provides details on helical, leaf, volute, beam, and Belleville springs. Formulas are given for calculating stresses in helical compression springs based on wire diameter, spring diameter, shear modulus, and applied force. Key aspects of helical spring design like space requirements, forces, tolerances, and environmental conditions are also outlined.
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Belt is a Flexible Mechanical element that transmit power from one shaft to another
Belt is a Flexible Mechanical element that transmit power from one shaft to another
Gear Train
Ex: Automobile, engines etc.
Chain Drive
Ex : Bi-cycle , Motor cycle etc.
Belt Drive
Ex: Rice mills, sewing machine etc.
Rope Drive
Ex: lift, crane etc
The document discusses gears and their classification. It defines various gear types including spur gears, helical gears, bevel gears, worm gears, and rack gears. It covers gear terminology such as pressure angle and describes how parameters like pressure angle and center distance affect gear performance and interference. Methods to avoid interference include increasing center distance, tooth modification, and changing the number of teeth. Backlash is also defined as the clearance between mating gear teeth.
A bearing is a machine element that supports another moving element, known as a journal, and allows relative motion between their surfaces while carrying loads. There are two main types of bearings: sliding contact bearings and rolling contact bearings. Sliding contact bearings include journal or sleeve bearings, which support radial loads and come in full or partial designs. Rolling contact bearings use balls or rollers between surfaces to reduce friction. Key considerations in bearing design include load capacity, friction, lubrication, and heat dissipation.
Shaft & keys (machine design & industrial drafting )Digvijaysinh Gohil
Ā
This document discusses different types of shafts, keys, and their design considerations. It contains the following key points:
1. Shafts can be classified based on their shape (solid or hollow), application (transmitting, machine, spindle), and construction (rigid or flexible).
2. Keys are used to connect rotating machine elements to shafts and prevent relative motion. Common types include rectangular, square, parallel, gib-head, feather, and woodruff keys.
3. Shaft design considers factors like bending moment, shear stress, and material properties. Hollow shafts have higher strength-to-weight ratio than solid shafts of the same size.
5 shaft shafts subjected to combined twisting moment and bending momentDr.R. SELVAM
Ā
1. The document discusses the design of shafts that are subjected to both twisting moments and bending moments.
2. It describes two theories for analyzing combined stresses: maximum shear stress theory for ductile materials like steel, and maximum normal stress theory for brittle materials like cast iron.
3. It provides an example of determining the diameter of a shaft made of 45 C 8 steel that is subjected to a bending moment of 3000 N-m and torque of 10,000 N-m, with a safety factor of 6.
The document discusses the design of various types of screw fasteners. It describes screw threads as helical grooves cut into cylindrical surfaces. Screw joints are commonly used for assembly and have advantages of being convenient to assemble/disassemble, reliable, and inexpensive due to standardization. The main types of screw fasteners are bolts, screws, studs, tapping screws, and set screws. Stresses in screw joints include tension, torsional shear, shear across threads, crushing stress, and bending stress. Screw joints are also subjected to stresses from initial tightening and external loads. Design considerations are discussed for bolted joints under eccentric loading parallel or perpendicular to the bolt axis.
Threaded fasteners such as bolts and nuts are used to join machine parts. They allow parts to be dismantled without damage. Threaded joints provide clamping force through wedge action of threads. They are reliable, have small dimensions, and can be positioned vertically, horizontally, or inclined. However, they require holes which cause stress concentrations and can loosen under vibration. Bolts have heads and threaded shanks, while nuts have internal threads. Washers distribute load and prevent marring. Bolts are subjected to both tension and shear stresses, and standard nuts have a height of 0.8 times the bolt diameter to prevent shear failure. Eccentric loads on bolts cause additional stresses.
The document discusses various topics related to screwed joints and fastenings including:
1. The advantages and disadvantages of screwed joints.
2. Important terms used in screw threads such as major diameter, pitch, and crest.
3. Different types of screw threads including British Standard, American, and metric threads.
4. Factors to consider when locating screwed joints such as reducing bending stresses.
5. Common types of screw fastenings like through bolts, studs, and set screws.
1. A shaft transmits power and rotational motion and has machine elements like gears and pulleys mounted on it.
2. Press fits, keys, dowel pins, and splines are used to attach machine elements to the shaft.
3. The shaft rotates on rolling contact or bush bearings and uses features like retaining rings to take up axial loads.
4. Couplings are used to transmit power between drive and driven shafts like between a motor and gearbox.
The document discusses stresses in flywheel components and design considerations. It describes:
1. A flywheel consists of a rim to concentrate mass, a hub to attach to a shaft, and arms to support the rim.
2. Stresses induced in the rim include tensile stress from centrifugal force, tensile bending stress from arm restraint, and shrinkage stresses from uneven cooling.
3. The tensile stress in the rim from centrifugal force is calculated similarly to a thin cylinder under pressure. Stresses in the arms include tensile stress from centrifugal force and bending stress from transmitting torque.
A cotter joint connects two coaxial rods subjected to axial forces. It uses a tapered wedge-shaped cotter inserted into slots in the overlapping ends of the rods. The cotter prevents longitudinal movement but allows for disassembly. Cotter joints are commonly used to connect piston rods, pump parts, flywheels, and foundation bolts. The document provides design considerations and equations for sizing the rods, slots, and cotter to withstand various failure modes from the tensile, compressive, and shear stresses based on the applied load and material properties. It also presents three example problems of designing cotter joints for specified loads.
6 shaft shafts subjected to fluctuating loadsDr.R. SELVAM
Ā
Shafts are often subjected to fluctuating loads in practice rather than constant loads. To design shafts like line shafts and counter shafts that experience fluctuating torque and bending moments, combined shock and fatigue factors must be accounted for in calculating the twisting moment and bending moment. These equivalent moments are calculated using combined shock and fatigue factors for bending (Km) and torsion (Kt), with recommended values for Km and Kt provided in a table.
This document discusses helical springs and U-clamps. It defines springs and their main uses which include exerting force, providing flexibility, and storing energy. The most common spring materials are discussed along with the types of springs including helical, flat, and special shaped. Helical springs are further broken down into open coil, closed coil, torsion, and spiral varieties. U-clamps are metal clamps used to mount pipes and are made of stainless steel or mild steel for durability.
1. The document describes a clamp or compression coupling, which uses two halves of a cast iron muff that are bolted together around the abutting ends of two connected shafts. A single key fits in the keyways of both shafts to transmit power.
2. Design considerations for this type of coupling include sizing the clamping bolts to withstand the frictional forces between the muff and shafts, which transmit the torque. The proper bolt root diameter is calculated based on these frictional forces.
3. Tolerances for misalignment are provided by a bushed-pin flexible coupling. It uses rubber or leather bushes around coupling pins to connect two flanged halves with some clearance, absorbing misalignment
The document discusses stress concentration and fatigue failure in machine elements. It defines stress concentration as irregular stress distribution caused by abrupt changes in cross-section shape. Stress concentration factors are introduced to quantify the maximum stress compared to nominal stress. The document also discusses endurance limit and fatigue strength testing methods. Factors that affect fatigue strength like material properties, surface finish, size and temperature are summarized. Methods to evaluate and reduce stress concentration in designs are provided.
Basic types of screw fasteners, Bolts of uniform
strength, I.S.O. Metric screw threads, Bolts under
tension, eccentrically loaded bolted joint in shear,
Eccentric load perpendicular and parallel to axis of
bolt, Eccentric load on circular base, design of Turn
Buckle.
,bearings ,function of bearing ,footstep or pivot bearing ,bush and direct-lined housing ,thrust bearing ,journal bearing ,ball and roller bearings ,types of rolling bearing ,sliding contact bearing ,applications of roller bearings
The document discusses the design of welded joints. It begins by defining a welded joint as a permanent fusion of two parts achieved through heating and optionally applying pressure and a filler material. Welding provides advantages over riveted joints like lighter weight and greater efficiency. Various welding processes are described including gas, electric arc, thermit and forge welding. Common welded joint types like lap, butt, corner and T-joints are also outlined. The document then examines the strength calculations for transverse and parallel fillet welds as well as butt joints. It concludes by discussing stresses in eccentrically loaded and unsymmetrical welded sections.
The document summarizes key concepts about screws, fasteners, and bolted joints from Shigley's Mechanical Engineering Design textbook. It discusses thread standards and definitions, types of bolts and screws, mechanics of power screws, stiffness of bolted joints, preload in bolts, and factors that affect fatigue loading of bolted joints. Examples are provided to illustrate calculation of power screw torque and analysis of bolted joint stiffness.
This document discusses riveted joints, which are used to join metal plates. It describes the different types of rivet heads, riveted joint configurations like lap joints and butt joints, and how rivets are installed through heating and hammering. The document also discusses factors that determine the strength of riveted joints like the tearing resistance of plates, shearing resistance of rivets, and crushing resistance of plates and rivets. It explains how riveted joints can fail through tearing of plates, shearing of rivets, or crushing of plates/rivets. The efficiency of riveted joints is defined as the ratio of the joint's strength to the strength of an unriveted solid
This document discusses different types of machine keys used to connect rotating elements like shafts, gears, and pulleys. It describes saddle keys, sunk keys, taper keys, parallel keys, and feather keys. Design considerations for keys include preventing slippage while transmitting torque. Keys are designed based on withstanding shear and compressive stresses. Sample problems demonstrate how to calculate the required key dimensions given input torque and shaft dimensions. Splines are also discussed as an alternative to keys, with their torque capacity determined by factors like spline area, mean radius, and permissible pressure.
The document discusses different types of springs including their materials, applications, advantages, and designs. It provides details on helical, leaf, volute, beam, and Belleville springs. Formulas are given for calculating stresses in helical compression springs based on wire diameter, spring diameter, shear modulus, and applied force. Key aspects of helical spring design like space requirements, forces, tolerances, and environmental conditions are also outlined.
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Belt is a Flexible Mechanical element that transmit power from one shaft to another
Belt is a Flexible Mechanical element that transmit power from one shaft to another
Gear Train
Ex: Automobile, engines etc.
Chain Drive
Ex : Bi-cycle , Motor cycle etc.
Belt Drive
Ex: Rice mills, sewing machine etc.
Rope Drive
Ex: lift, crane etc
The document discusses gears and their classification. It defines various gear types including spur gears, helical gears, bevel gears, worm gears, and rack gears. It covers gear terminology such as pressure angle and describes how parameters like pressure angle and center distance affect gear performance and interference. Methods to avoid interference include increasing center distance, tooth modification, and changing the number of teeth. Backlash is also defined as the clearance between mating gear teeth.
A bearing is a machine element that supports another moving element, known as a journal, and allows relative motion between their surfaces while carrying loads. There are two main types of bearings: sliding contact bearings and rolling contact bearings. Sliding contact bearings include journal or sleeve bearings, which support radial loads and come in full or partial designs. Rolling contact bearings use balls or rollers between surfaces to reduce friction. Key considerations in bearing design include load capacity, friction, lubrication, and heat dissipation.
Shaft & keys (machine design & industrial drafting )Digvijaysinh Gohil
Ā
This document discusses different types of shafts, keys, and their design considerations. It contains the following key points:
1. Shafts can be classified based on their shape (solid or hollow), application (transmitting, machine, spindle), and construction (rigid or flexible).
2. Keys are used to connect rotating machine elements to shafts and prevent relative motion. Common types include rectangular, square, parallel, gib-head, feather, and woodruff keys.
3. Shaft design considers factors like bending moment, shear stress, and material properties. Hollow shafts have higher strength-to-weight ratio than solid shafts of the same size.
5 shaft shafts subjected to combined twisting moment and bending momentDr.R. SELVAM
Ā
1. The document discusses the design of shafts that are subjected to both twisting moments and bending moments.
2. It describes two theories for analyzing combined stresses: maximum shear stress theory for ductile materials like steel, and maximum normal stress theory for brittle materials like cast iron.
3. It provides an example of determining the diameter of a shaft made of 45 C 8 steel that is subjected to a bending moment of 3000 N-m and torque of 10,000 N-m, with a safety factor of 6.
The document discusses the design of various types of screw fasteners. It describes screw threads as helical grooves cut into cylindrical surfaces. Screw joints are commonly used for assembly and have advantages of being convenient to assemble/disassemble, reliable, and inexpensive due to standardization. The main types of screw fasteners are bolts, screws, studs, tapping screws, and set screws. Stresses in screw joints include tension, torsional shear, shear across threads, crushing stress, and bending stress. Screw joints are also subjected to stresses from initial tightening and external loads. Design considerations are discussed for bolted joints under eccentric loading parallel or perpendicular to the bolt axis.
Threaded fasteners such as bolts and nuts are used to join machine parts. They allow parts to be dismantled without damage. Threaded joints provide clamping force through wedge action of threads. They are reliable, have small dimensions, and can be positioned vertically, horizontally, or inclined. However, they require holes which cause stress concentrations and can loosen under vibration. Bolts have heads and threaded shanks, while nuts have internal threads. Washers distribute load and prevent marring. Bolts are subjected to both tension and shear stresses, and standard nuts have a height of 0.8 times the bolt diameter to prevent shear failure. Eccentric loads on bolts cause additional stresses.
Design of steel structure as per is 800(2007)ahsanrabbani
Ā
It does not offer resistance against rotation and also termed as a hinged or pinned connections.
It transfers only axial or shear forces and it is not designed for moment
It is generally connected by single bolt/rivet and therefore full rotation is allowed
This document provides an overview of the Mechanical Measurement and Metrology subject for B.Tech Mechanical Engineering students. The objectives are to develop knowledge of measurement basics, methods, and devices. Key topics covered include linear, angular, thread and gear measurement, as well as force, torque, pressure, temperature and strain measurement. Specific techniques discussed include thread measurement methods using wires, gear metrology, and advancements like coordinate measuring machines and machine vision systems. Measurement of screw thread elements like diameter, pitch, and errors are explained in detail.
Threaded fasteners such as bolts and screws join components together through the transformation of rotational motion into linear motion. There are various thread standards that specify attributes like diameter, pitch, class of fit, and thread type. Early threaded fasteners lacked standardization but efforts in the 18th-19th centuries established conventions for sizes. Modern standards include metric and unified external and internal thread systems.
The document discusses different types of fasteners used to join machine parts, including screwed fasteners, riveted joints, and keys. It describes various threaded components like bolts, nuts, and studs. It discusses different thread profiles like metric, square, and ACME threads. It also covers rivet types, dimensions of riveted joints, and types of keys used in pin joints.
The document discusses the design of machine elements. It covers factors governing design, general design procedures, stresses in bolts, nuts and keys, and design of cylinder cover bolts. Key points covered include:
1) The factors governing machine element design include strength, cost, reliability, shape, size, friction, corrosion and more.
2) General design procedures include identifying needs, analyzing forces, selecting materials, determining sizes, and producing detailed drawings.
3) Stresses in bolted connections from initial tightening, external loads, and combined loads are analyzed. Formulas to calculate bolt sizes based on allowable stresses are presented.
4) The design of cylinder cover bolts involves calculating the pitch
Unit 4 Design of Power Screw and Screw JackMahesh Shinde
Ā
The document discusses power screws, including their terminology, types of threads, torque analysis, and efficiency. It defines key terms like nominal diameter, pitch, lead, and lead angle. It describes common types of threads like square, ACME, and buttress threads. It discusses torque required to raise and lower loads, including expressions for self-locking and overhauling screws. The document also covers screw efficiency and collar friction torque, providing expressions to calculate overall efficiency. An example calculation is given to find maximum load lifted, efficiency, and overall efficiency of a screw jack.
This document discusses mechanical fasteners. It defines fasteners as mechanical elements that hold two or more machine or structural parts together. Fasteners are classified as detachable or non-detachable. Threaded and non-threaded fasteners are types of detachable fasteners. Common threaded fasteners include bolts, screws, and nuts. The document provides details on threaded fastener terminology, types of threads, thread manufacturing, and considerations for selecting an appropriate fastener.
This document describes different types of cotter and knuckle joints used to connect rods transmitting axial motion. Cotter joints use a wedge-shaped cotter to rigidly connect two rods without rotation. Sleeve and cotter joints use an enlarged sleeve over rod ends. Socket and spigot cotter joints have slots wider than the cotter to pull rods tightly together. Gib and cotter joints add a gib to prevent strap spreading. Knuckle joints connect misaligned rods allowing small angular motion. Applications include steam engines, pumps, valves and elevators. The document also provides design considerations and failure modes for socket and spigot cotter joints.
The document discusses the design of power screws. Power screws convert rotary motion into linear motion and are used in applications like lathes, screw jacks, presses, and vices. There are several types of thread profiles used in power screws including square, acme, trapezoidal, and buttress threads. Square threads provide maximum efficiency but are weaker. Acme threads are stronger and allow for split nuts. The document provides formulas to calculate the torque required to raise or lower a load using a power screw based on factors like thread angle, friction angle, and load weight. It also discusses design considerations for parts of a screw jack like the screw, nut, nut collar, screw head, and handle.
The document provides an overview of plates and screws used in orthopedic surgery. It discusses the different parts and types of screws, including cortical screws, cancellous screws, and locking screws. It also describes the mechanical functions of plates, including neutralization plates, compression plates, and buttress plates. The document outlines the features and uses of various plate systems, such as the dynamic compression plate (DCP), limited contact-DCP (LC-DCP), reconstruction plates, and one-third tubular plates. It also introduces locking compression plates (LCP), which provide angular stability through the locking head of the screw instead of friction between the plate and bone.
The document discusses different types of threaded fasteners including bolts, studs, screws, and set screws. It defines threaded fastener terminology such as external and internal threads, major and minor diameters, pitch, and thread forms. It also provides steps for drawing representations of various threaded fasteners and holes.
The document discusses different aspects of screw thread metrology. It describes the key elements of a screw thread such as major diameter, minor diameter, pitch diameter, pitch, lead, crest, root, depth of thread, flank, and angle of thread. It then discusses different forms of screw threads including British Standard Whitworth, British Association, American National Standard, Unified Standard, square, Acme, knuckle, and buttress threads. The final sections cover various methods for measuring elements of a screw thread such as major diameter, minor diameter, pitch diameter, pitch, and thread angle using instruments like micrometers, thread micrometers, pitch measuring machines, and tool makers microscopes.
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Unit 5 Design of Threaded and Welded Joints
1. Unit 5
Threaded & Welded Joint
Prepared By
Prof. M.C. Shinde [9970160753]
Mech. Engg. Dept., JSCOE, Hadapsar
2. SPPU Syllabus Content: (10 hrs)
Threaded Joint: Basic types of screw fasteners, Bolts of
uniform strength, I.S.O. Metric screw threads, Bolts under
tension, eccentrically loaded bolted joint in shear, Eccentric
load perpendicular and parallel to axis of bolt, Eccentric load
on circular base, design of Turn Buckle.
Welded Joint : Welding symbols, Stresses in butt and fillet
welds, Strength of butt, parallel and transverse fillet welds,
Axially loaded unsymmetrical welded joints, Eccentric load in
plane of welds, Welded joints subjected to bending and
torsional moments
3. Part A
Threaded Joint: Basic types of screw fasteners, Bolts of
uniform strength, I.S.O. Metric screw threads, Bolts under
tension, eccentrically loaded bolted joint in shear,
Eccentric load perpendicular and parallel to axis of bolt,
Eccentric load on circular base, design of Turn Buckle.
5. Need to Use Threaded Joints
.
ā¢To connect the components together which should be
readily disassembled. E.g. Screwed fasteners
ā¢To transmit a power or energy e.g. power screws
ā¢For obtaining accurate movements in measuring
instruments.
6. Advantages of Threaded Joints
.
ā¢They are convenient to assemble and disassemble.
ā¢The assembly and disassembly require only spanners
and do not require any special tooling's;
ā¢Threaded joints are relatively cheap;
ā¢They give high clamping force;
ā¢They are highly reliable.
Note:- Tooling is the process of acquiring the manufacturing
components and machines needed for production
7. Disadvantages of Threaded Joints
.
ā¢The component becomes weak because of the holes;
ā¢There is a possibility of loosening of joint due to
excusive vibrations;
ā¢There is stress concentration in threaded portion,
which may be vulnerable under fatigue load.
8. I.S.O. Metric Screw Thread
.
ā¢fig. shows profile of an ISO metric screw threads which
are commonly used in India.
ā¢It is not easy to get mathematical relation between
d,p,dc ,hence it is necessary to refer the standard tables
to find the dimensions of screw threads.
9. Type of I.S.O. Metric Screw Thread
.
ā¢Coarse threads
ā¢Fine threads
10. Coarse Thread
.
ā¢For given nominal diameter, pitch and hence lead angle
are larger compare to fine threads
Advantages
ā¢They are stronger and hence less possibility of thread
crushing and shearing.
ā¢Due to large lead angle threads offer less resistance to
unscrewing.
11. Designation of ISO Metric
Coarse Thread
.
ā¢It is designated by
letter M followed by
nominal diameter. E.g.
M30
12. Fine Thread
.
ā¢For given nominal diameter, pitch and hence lead angle
are smaller compare to coarse threads
Advantages
ā¢Fine adjustments is possible with fine threads.
ā¢Though, fine threads are weaker its screw body is
stronger.
ā¢Fine threads offer greater resistance to unscrewing.
13. Designation of ISO
Metric Fine Thread
.
It is designated by letter
M followed by nominal
diameter and pitch, two
being separated by sign
x. E.g. M30x3
14. Basic types of screw fasteners
.
1) Through bolt
2) Tap bolt
3) Studs
4) Cap screws
5) Set screws
15. Through Bolt
.
ā¢It is cylindrical bar with a head at
one end the threads at other end.
ā¢It is passed through drilled holes in
the parts to be fastened together
and nut is screwed tightened on
the threaded end.
ā¢Nut and bolt heads are hexagonal.
16. Tap Bolt
.
ā¢It is the bolt which passes through a
hole in one part and screwed into a
tapped hole in the second part which
acts as nut thus holding parts together.
ā¢ It does not need nut.
ā¢It is used when arrangement does not
provide any space to accommodate the
nut.
ā¢ Frequent insertion or removal of tap
bolt is likely to damage threads
17. Studs
.
ā¢It is a cylindrical bar threaded at both
ends.
ā¢One end is screwed into tapped hole of
parts to be fastened while nut is
screwed into other end .
ā¢Stud always remains in position when
two parts are disconnected
ā¢Studs are mainly used for connecting
covers like cylinder head of engine.
18. Cap screws
.
ā¢Cap screws are very similar to tap bolts,
but smaller in size as compared to tap
bolts.
ā¢ In addition variety of shapes of heads
are available for cap screws.
19. Set screws
.
ā¢Set screws are very similar to cap screws but
are threaded practically throughout length
and are still smaller in size. Theses are used to
prevent the relative motion between two
parts.
ā¢They are used instead of key in light power
transmission
20. Materials used for screwed fasteners
.
ā¢Materials used for lightly loaded nuts, bolts and studs
are medium carbon steels like: 35C8,40C8,45C8
ā¢Materials used for highly loaded high strength nuts,
bolts and studs are high carbon steels(60C4) and alloy
steels(40Ni4,35Mn6Mo4)
ā¢Materials used for corrosion resistance fasteners are
chromium alloy steels like: 40Cr4Mo2,
40Ni6Cr4Mo2,31Ni100Cr3Mo6
21. Bolts of uniform strength
.
ā¢If a bolt is subjected to shock or impact loading as in
case of connecting rod bolts or fasteners of power
hammers, it should be designed to absorb impact
energy
22. Drawback of ordinary bolt:
.
ā¢In ordinary bolts ,cross-sectional area is minimum in
threaded portion. Hence, stress in threaded portion of
the bolt will be higher than that in shank or body.
ā¢Impact energy absorbed at any point in a body is
directly proportional to square of stress at that point.
ā¢Therefore large portion of impact energy will be
absorbed in the threaded portion and relatively small
portion of energy is absorbed by a shank.
ā¢This uneven distribution of impact energy may lead to
fracture of bolt in threaded portion.
23. Methods of achieving bolts of uniform strength
.
ā¢Reduction of shank diameter
ā¢Drilling axial hole
24. Reduction of shank diameter
.
ā¢If shank diameter is reduced to core diameter as shown
in fig. stress become same throughout length of bolt.
ā¢Hence impact energy is distributed uniformly
throughout the bolt length.
ā¢The bolt in this way becomes stronger and lighter.
ā¢This type of bolt is known as bolt of uniform strength.
25. Drilling axial hole
.
ā¢In this method an axial hole is drilled through the head
down to the threaded portion such that cross sectional
area of threaded portion.
ā¢For bolts of uniform strength
26. Stresses in screw fastener body
.
1) Direct tensile stress
2) Direct shear stress
3) Maximum shear stress
30. Eccentrically loaded bolted joints
.
1) Eccentric load in plane of bolts
2) Eccentric load perpendicular to axes of bolts
3) Eccentric load parallel to axes of bolts
32. Eccentric load in plane of bolts
.
Effect of load W at a distance e from the centre of gravity of the bolt system is
equal to;
1) Direct parallel force (W): the direct parallel force W through CG of bolt system
results in primary shear force on each bolt.
2) Turning Moment(W.e): the turning moment W.e about C.G. of bolt system
results in secondary shear force on each bolt.
34. Step1: Find the C.G. of bolt system
.
ā¢Let A1,A2,A3,A4ā¦ā¦ā¦ cross sectional areas of the
bolts,mm2
ā¢x1,x2,x3,x4ā¦ā¦ā¦distances of bolt centres from Y-axis,
mm
ā¢y1, y2,y3,y4ā¦ā¦ā¦distances of bolt centres from X-axis,
mm
35. Step1: Find the C.G. of bolt system
.
ā¢Distance of C.G. of bolt system from Y-axis is,
36. Step1: Find the C.G. of bolt system
.
ā¢Distance of C.G. of bolt system from X-axis is,
37. Step2: Find the primary shear force on each bolt(Fp)
.
ā¢The direct parallel force W through C.G. of the bolt
system results in primary shear force Fp on each bolt
and is given by
Fp1=Fp2=Fp3=Fp4=Fp=W/n
Where
n=number of bolts
Fp1,Fp2,Fp3,Fp4 =primary shear forces on bolts,N
38. Step3: Find the secondary shear force on each bolt(Fs)
.
ā¢The twisting moment W.e about C.G. of the bolt system
results in secondary shear forces which are not same
on all the bolts.
ā¢secondary shear force on any bolt is proportional to its
distance from C.G.
Let, Fs1,Fs2,Fs3,Fs4 =secondary shear forces on bolts, N
l1,l2,l3,l4=distances of the bolt centres from C.G.
39. Step3: Find the secondary shear force on each bolt(Fs)
.
ā¢w= secondary shear force on bolt per unit distance
,N/mm
Therefore , Fs1=w*l1, Fs2=w*l2
Fs3=w*l3, Fs4=w*l4
ā¢Taking moment about the C.G.
W*e= Fs1*l1+ Fs2*l2+ Fs3*l3+Fs4*l4
41. Step3: Find the secondary shear force on each bolt(Fs)
By putting w in Fs=w.l equations the secondary shear force on
each bolt(Fs) is given by
Note :-the direction of secondary shear force on any bolt is perpendicular to
the line joining the bolt centre and the C.G. of the bolt system
42. Step4: Find the resultant shear force on most heavily
loaded bolt(FR)
Note :-the direction of secondary shear force on any bolt is perpendicular to
the line joining the bolt centre and the C.G. of the bolt system
43. Step5: Find the bolt Size
Where,
FR=Resultant shear force
Ac=Cross-sectional area of bolt
45. Ex.5.1 a steel plate subjected to a force of 8kN is fixed to a channel by
means of three identical bolts as shown in fig. the bolts are made of
45C8 (Syt=380N/mm2). If the required factor of safety is 2.5 determine
size of the bolts.
52. Ex.5.2 a steel plate subjected to a force of 3kN is fixed to a vertical
channel by means of four identical bolts as shown in fig. the bolts are
made of plain carbon steel 45C8 (Syt=380N/mm2). If the required factor
of safety is 2. determine diameter of the bolts.
60. Ex.5.3 a bracket made of steel subjected to a force of 8kN is fixed to a
vertical channel by means of four identical bolts as shown in fig. the
bolts are made of plain carbon steel 45C8 (Syt=254N/mm2). If the
required factor of safety is 2. determine diameter of the bolts.
68. Ex.5.4 a bracket is bolted to a column by 6 bolts of equal size as shown
in fig. it carries a load of 50kN at the distance of 150mm from the
centre of column. If the maximum stress in the bolt is to be limited to
150N/mm2. determine diameter of the bolts.
77. Eccentric load perpendicular to axis of bolts
.
Effect of load W at a distance e from the centre of gravity of the bolt system is
equal to;
1) Force in a plane between wall & bracket: force W between the wall & bracket
results in the direct shear force on each bolt.
2) Turning Moment(W.e): the turning moment W.e tends to cause tilting of
bracket about an edge O-O. this results in tensile force on each bolt.
78. Procedure for design of bolted joints with load
perpendicular to axes of Bolts
.
82. Step3: Find the tensile stress in most heavily loaded bolt
.
ā¢w= tensile force on bolt per unit distance ,N/mm
Therefore , Ft1=w*l1, Ft2=w*l2
Ft3=w*l3, Ft4=w*l4
ā¢Taking moment about the C.G.
W*e= Ft1*l1+ Ft2*l2+ Ft3*l3+Ft4*l4
83. Step3: Find the tensile stress in most heavily loaded bolt
.
84. Step3: Find the tensile stress in most heavily loaded bolt
By putting w in Ft=w.l equations the tensile force on each bolt(Ft)
is given by
85. Step3: Find the tensile stress in most heavily loaded bolt
Note :-in this case most heavily loaded bolts are upper bolts 2 & 3
86. Step4: Find the maximum shear stress in most heavily
loaded bolt
87. Step5: Find the bolt Size
By knowing value of permissible shear stress for bolt material the
size of bolt can be determined by using equation
88. Ex.5.5 fig. shows a pulley bracket supported to vertical wall by 4 bolts
,two each at locations A & B. the pull W on each side of the wire rope
over the pulley is 22kN. determine the size of the coarse threaded
metric bolts using allowable shear stress of 30MPa for bolt material.
Bolts may be selected from following table.
93. Step4: Find the maximum shear stress in most heavily
loaded bolt
94. Step5: Find the bolt Size
M30 bolt with a stress area of 561 mm2 is selected
95. Ex.5.6 a bracket shown in fig. is fixed to the support by means of 3 bolts.
The dimensions given in figures are in mm. the bolts are maded of plain
carbon steel 45C8 (Syt=380N/mm2) and factor of safety is 2.5 .specify
the size of bolts.
103. Ex.5.7 a steel bracket is fixed to vertical support by 3 bolts of size M20,
two at the top and one at the bottom, as shown in fig. if The permissible
tensile stress for the bolt is 60N/mm2. determine the maximum load
that can be supported by bracket at 350mm from the vertical support.
110. Eccentric load parallel to axis of bolts
.
Effect of load W is equal to;
1) Parallel force through CG of bolt system(W): Parallel force through CG of bolt
system result in primary tensile force on each bolt.
2) Turning Moment(W.e): the turning moment W.e tends to cause tilting of
bracket about an edge O-O. this results in secondary tensile force on each
bolt.
114. Step2: Find the secondary tensile forces in most heavily
loaded bolt
.
ā¢w= tensile force on bolt per unit distance ,N/mm
Therefore , Ft1=Ft4=w*l1, Ft3=Ft2=w*l2,
ā¢Taking moment about the C.G.
W*e= Ft1*l1+ Ft2*l2+ Ft3*l3+Ft4*l4
116. Step2: Find the secondary tensile forces in most heavily
loaded bolt
By putting w in Ft=w.l equations the tensile force on each bolt(Ft)
is given by
117. Step3: Find the resultant tensile force in most heavily
loaded bolt
119. Ex.5.8 a cast iron bracket fixed to the steel structure, as shown in fig.
supports a load W of 25kN. There are two bolts each at A & B. if
permissible tensile stress for bolts is 50N/mm2,determine the size of the
bolts.
126. Eccentric load on circular base
.
In some applications, the base of a bracket is made circular as in case of
a flanged of a heavy machine tool or a pillar crane.
127. Eccentric load on circular base
.
Let,
R=outside radius of the flange, mm
r=radius of the bolt pitch circle, mm
l1,l2,l3,l4=distances of bolt centres from the tilting edge, mm
W=load per unit distance from tilting edge, N/mm
ā¢ l1=R-r cosĘ
ā¢ l2=R+r sinĘ
ā¢ l3=R+r cosĘ
ā¢ l4=R-r sinĘ
128. Ex.5.9 the bracket is bolted to the support and subjected to the load of
20kN as shown in fig. the bolts are made of 45C8(Syt=360N/m2). If the
required safety of margin is 1.8. find the size of bolts.
138. Turn Buckle
A turnbuckle, stretching screw or bottle screw is a device for adjusting the tension
or length of ropes, cables, tie rods, and other tensioning systems.
A turnbuckle or coupler is mechanical joint used for connecting two members
which are subjected to tensile loading and which require slight adjustment of
length or tension under loaded condition.
139. Components of Turn Buckle
i. Threaded tie rod with right hand thread
ii. Threaded tie rod with left hand thread
iii. coupler
140. Threaded tie rod
ā¢ Two threaded rods are used.
ā¢ One of the tie rods has right hand threads
ā¢ Other has left hand threads.
141. Coupler
ā¢ It connects two tie rods.
ā¢ It is of hexagonal or
rectangular cross
section in the centre in
order to facilitate the
turning with help of
spanner and round at
both ends.
ā¢ Sometimes it is also
known as tommy bar
142. Materials for Turn Buckle
Normally tie rods are made of steel, while coupler is made of steel or
cast iron
Applications for Turn Buckle
Tie rod of wall crane, tension members of bridges, steel structures
,electric poles
144. Design of Turn Buckle
ā¢ Diameter of tie rod(d)
ā¢ Stresses in tie rod
ā¢ Length of coupler nut(Ln)
ā¢ Outside diameter of coupler nut(D)
ā¢ Outside diameter of coupler(D2)
ā¢ Length of coupler between nuts(L)
147. Torsional Shear Stresses in tie rod
ā¢ dm=pitch diameter of tie rod
ā¢ l=lead
ā¢ Ī¼1=virtual coefficient of friction= (Ī¼/ cos Ī²)
ā¢ Š¤1=virtual friction angle=tan-1 Ī¼1
ā¢ Ī²=Semi thread angle=30 for ISO Metric Screw Threads
ā¢ Ī»=lead angle=tan-1[ Ī»/ Ļ.dm]
153. Ex.5.10 the pull in tie rod of an iron truss is 50kN. If the permissible
stresses are 75MPa in tension,45MPa in shear and 90MPa in crushing,
design a suitable adjustable steel screwed joint.
166. Problems for Practice
a bracket shown in fig. is fixed to steel column by using 4 bolts of size M14. A load
of W acts on the bracket at a distance of 400mm from the face of the column. The
permissible tensile stress for the bolt and bracket material is 84N/mm2. if the b/t
ratio for the cross-section of the arm of the bracket is 45,determine;
i)The maximum load that can be supported by bracket
ii) Cross section of the arm of bracket
167. Part B
Welded Joint : Welding symbols, Stresses in butt and fillet
welds, Strength of butt, parallel and transverse fillet welds,
Axially loaded unsymmetrical welded joints, Eccentric load in
plane of welds, Welded joints subjected to bending and
torsional moments
168. Advantages of Welded Joints over riveted or threaded
joints
.
ā¢ fluid tight
ā¢ give light weight construction.
ā¢ Economical
ā¢ Can be produced at much faster rate and with automation.
ā¢ The complicated components easily welded.
ā¢ Do not weakens the parts to be connected.
169. Disadvantages of Welded Joints
.
ā¢ Welded components are much poor in vibration.
ā¢ Welding cannot be used to join dissimilar materials.
ā¢ Quality and strength of welded joint depend upon the skill of
operator.
ā¢ For different materials, different welding processes ad hence
different machines are required.
170. Types of Welded Joints
.
1. Butt weld
2. Fillet or lap weld
3. Other types of weld
172. Butt Weld
.
ā¢ Butt weld is obtained by placing the plates to be joined side
by side with their edges nearly touching each other.
ā¢ Small gap is maintained between the edges.
173. Types of Butt Weld
.
1. Square butt weld
2. Single V butt weld
3. Single U butt weld
4. Double V butt weld
5. Double U butt weld
174. Square Butt Weld
.
ā¢ If thickness of the plates is less than 5mm,edges of the plates
do not required bevelling, and hence joint used is known as
square butt weld.
175. Single V-butt or single U-butt Weld
.
ā¢ If thickness of the plates is between 5mm and 12.5mm,edges
of the plates bevelled to V or U groove, and accordingly
single V-butt or single U-butt weld may be used.
176. Double V-butt or double U-butt Weld
.
ā¢If thickness of the plates is between more than 12.5mm,it is
necessary to bevel and weld plates from both sides. In such
cases double V-butt or double U-butt weld may be used.
178. Fillet or Lap Weld
.
ā¢ It is obtained by overlapping two plates and then welding
edges of plates.
179. Types of Fillet or Lap Weld
.
1. Parallel fillet weld
2. Transverse fillet weld
180. Parallel fillet Weld
.
ā¢ If the load axis is parallel to the axis of the fillet ,it is known
as parallel fillet weld.
181. Transverse fillet Weld
.
ā¢ If the load axis is perpendicular to the axis of the fillet ,it is
known as transverse fillet weld.
ā¢ It can be single or double transverse fillet weld.
185. Tensile stress in single V- Butt Welds
ā¢ = average tensile stress in the weld, N/mm2
ā¢P=tensile force on the weld ,N
ā¢h=weld throat thickness of butt weld or plate thickness, mm
ā¢l=length of weld, mm
186. Tensile stress in double V- Butt Welds
ā¢ = average tensile stress in the weld, N/mm2
ā¢P=tensile force on the weld ,N
ā¢h1=throat thickness at the top, mm
ā¢h2=throat thickness at the bottom, mm
187. Shear stress in single butt weld
ā¢ = average shear stress in the weld, N/mm2
ā¢Ps=shear force on the weld ,N
ā¢l=length of the weld, mm
ā¢h=throat thickness or plate thickness, mm
189. ā¢ Weld size or leg size(h): the length of each equal sides of isosceles
triangle is known as weld size or leg size h.
ā¢ Weld throat thickness(t): the perpendicular distance of hypotenuse
from intersection of legs is known as weld throat thickness t.
ā¢ Cross sectional area of weld is minimum at the throat which is located
at 45 to the leg.
190. Shear stress in fillet weld
ā¢ = average shear stress in the weld, N/mm2
ā¢ P=tensile or shear force on the weld ,N
ā¢ l=length of the fillet weld, mm
ā¢ t=weld throat thickness, mm
ā¢ h=weld size or leg size of fillet weld, mm
198. Welded joints with In-plane eccentric loads
.
1) Parallel force (P): Parallel force through CG of bolt system result in
primary shear stress.
2) Twisting Moment(T): the twisting moment about the CG of weld
results in secondary shear stress.
199. Step 1 find polar Moment of Inertia of Weld Group
.
200. Step 1 find polar Moment of Inertia of Weld Group
.
Weld figure Moment of Inertia about XX [Ixx]
201. Step 1 find polar Moment of Inertia of Weld Group
.
Weld figure Moment of Inertia about XX [Ixx]
202. Step 1 find polar Moment of Inertia of Weld Group
203. Step 2 find direct(Primary) Shear stress
ā¢ P=eccentric force on the weld ,N
ā¢ A=throat area of all weld, mm2
=A1+A2+A3=l1*t+l2*t+l3*t=(2*l1+l2)*t
ā¢ t=throat thickness of fillet weld, mm
217. Ex.5.12 fig. shows a rectangular steel plate welded as a cantilever to a
vertical column and supports a single concentrated load of 60kN.
Determine the weld size, if shear stress in the same is not to exceed
140MPa.
227. Ex.5.13 A bracket is welded to the column and carries an eccentric load
P as shown in fig. the size of weld is 12mm. If the maximum shear stress
in the weld is 80MPa,determine the load P.
237. Ex. fig. shows a welded joint subjected to an eccentric load of 20kN. The
welding is only on one side. If the permissible shear stress for the weld
material is 80MPa,determine the weld size.
240. Welded joints subjected to bending moment
.
1) Parallel force (P): Parallel force through the plane of the welds
result in direct shear stress or primary shear stress.
2) Bending Moment(M): the bending moment causes the moment
induced shear stress or secondary shear stress.
241. Step 1 find Moment of Inertia of Weld Group about
horizontal axis through C.G.(Ixx):
.
242. Step 2: find the direct (primary) shear stress
.
243. Step 3: find moment induced (secondary) shear stress:
.
246. Ex.5.14 a solid rectangular bar of cross-section 100mm*150mm is
welded to a support by means of fillet weld as shown in fig. it is
subjected to a load of 25kN at a distance of 500mm from the plane of
weld. If the permissible shear stress for the weld is 85 N/mm2.
determine the weld size and throat thickness.
253. Ex.5.15 a bracket is welded to the vertical plate by two fillet welds, as
shown in fig. determine the weld size, if permissible shear stress is
limited to 70MPa.
261. Ex. 5.16 A circular bar of 50mm diameter is welded to a steel plate by
an annular fillet weld and is subjected to a twisting moment of 2kN-m.
if the allowable shear stress in the weld material is 85MPa, determine
the size of the weld.