1 introduction to dme

8/3/2019 1 Introduction to DME

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Books:

1. Shigleys Mechanical Engineering Design (In SI Units) (TMH)

2. Machine Design An Integrated Approach Robert L. Norton(Pearson Education)

3. Design of Machine Elements M. F. Spotts (Pearson Education)

4. Design of Machine Elements V B Bhandari (TMH)

5. A Textbook of Machine Design Khurmi & Gupta (S. Chand)

6. Machine Design DataBook K. Lingaiah (TMH)

7. Machine Drawing N D Bhatt (Charotar Publication)

Design of Machine Elements + Machine Design Practice


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http://en.wikipedia.org/wiki/File:4StrokeEngine_Ortho_3D_Small.gif


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INTRODUCTIONCreation of new and better machines/machine elements andimproving the existing one. (Practice + Experience)

Efficient Economical Overall cost of production & operation

Knowledge:Mathematics, Engg. Mechanics, Mechanics of Solids, Theory of Machines,Workshop Processes, Engg. Drawing. (AutoCAD, SolidWorks, UG, ProE,ANSYS, NASTRAN, ABAQUS, LS-DYNA, CFD related softwares), CAD,CAM, CAE, Metrology etc.

Classification:1. Adaptive Design2. Development design3. New Design


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General Considerations:1. Load type

2. Stresses developed3. Motion of parts4. Material Selection5. Parts size6. Convenient & economical features7. Use of standard parts8. Safety features9. Workshop facility10.No. of machines to be manufactured

11.Cost of production12.Plant facility for assembling13.Marketability14.Remanufacturing/resource recovery


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Design Tools & Resources:1. Conventional Drawing (Orthographic projections, Isometric

views etc.)2. Computational Tools (CAD, CAE)3. Acquiring Technical Information (Library, Government

sources, Professional societies, Commercial vendors,Internet)

Standards & Codes: AGMA, ASTM, ASME, BSI, BIS, IBR,AWS etc.

Economics

Dimensions & Tolerances: Limits, Fits, Tolerances,Allowances, Clearances etc.


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General Procedure:

1. Recognition of need2. Synthesis (Mechanism)3. Force Analysis4. Material selection5. Design of elements6. Modification7. Detailed drawing8. Production


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Engineering Materials & Properties

Mechanical Properties (Metals):1. Strength

2. Stiffness3. Elasticity4. Plasticity5. Ductility6. Brittleness7. Malleability8. Toughness9. Machinability10.Resilience11.Creep12.Fatigue

13.Hardness

Materials

Manufacturing Processes
http://upload.wikimedia.org/wikipedia/commons/9/90/Rivet01.jpg


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RIVETED JOINTS

Classification of joints:1. Permanent cannot be disassembled without destroying

the connecting parts. Examples: soldered, brazed, weldedand riveted joints.

2. Temporary disassembled without destroying the

connecting components. Examples: keys, cotters, pins,flange couplings etc.

Riveted Joints:

Structural works, ship building,bridges, tanks, boiler shells etc.
http://upload.wikimedia.org/wikipedia/commons/3/32/M3_tank_riveting_LOC_fsa_8e10699.jpghttp://upload.wikimedia.org/wikipedia/commons/d/da/Rivets_on_General_Hertzog_Bridge.jpghttp://upload.wikimedia.org/wikipedia/commons/9/90/Rivet01.jpg


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Methods of Riveting:1. Cold riveting structural joints (upto 12 mm)2. Hot riveting making leak proof joints. (large dia) eg. boiler

Materials: Tough and DuctileSteel (Low Carbon), brass, aluminium, copper etc.When strength and fluid tight joint is the main

consideration

STEEL.Manufactured according to standards:1. IS: 1148-1982 (Reaffirmed 1992) specification for hot

rolled rivet bars (upto 40 mm Dia) for structural purposes.2. IS: 1148-1982 (Reaffirmed 1992) specification for high

tensile steel rivet bars for structural purposes.3. IS: 2100-1970 IS: 1148-1982 (Reaffirmed 1992)

specification for steel rivets and stay bars for boilers.

Manufacture: Cold heading or by hot forging.


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Types of Rivet Heads:IS: 2155 1982 (Reaffirmed 1996), general purpose, Dia < 12 mm.

Snap heads structural work & machine riveting. Counter sunk heads ship

building since flush surface necessary. Conical head

hand hammering. Panheads max strength, but these are difficult to shape


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Types of Riveted Joints:1. Lap joint2. Butt joint


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Caulking and Fullering:


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Failures of a Riveted Joint:

1. Tearing of the Plate at an edge:

m = 1.5 d

2. Tearing of the Plate across a row of rivets:


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3. Shearing of the rivets


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4. Crushing of the plate or rivets:


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Strength of the Riveted Joint:

Efficiency of a Riveted Joint:


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Lozenge Joint (Structural Use):- Roof, bridge work, girders etc.


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1. Diameter of rivet hole: Unwins empirical relation

2. Number of rivets:


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3. From the number of rivets, the number of rows and the number of rivets ineach row is decided.

4. Thickness of butt strap:

5. Efficiency of the joint:


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6. Pitch of the rivets = 3 d + 5

7. Marginal Pitch (m) = 1.5 d

8. Distance between the rows of rivets = 2.5 d to 3 d


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Eccentrically Loaded Riveted Joint:


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Assumption:1. Secondary shear load is proportional to the radial

distance of the rivet under consideration from thec.g. of the rivet system.

2. Direction of the secondary shear load isperpendicular to the line joining the center of the

rivet to the c.g. of the rivet system.


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Design of Boiler:


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Design of Boiler:Longitudinal joint - Butt jointCircumferential joint Lap joint with one ring overlapping the other alternately is

used.

I.B.R. Indian Boiler Regulations

1 introduction to dme

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