Lecture 1 (2).pdf
- 1. Welcome to Metal Forming Course D. Ravi Kumar email: dravi@mech.iitd.ac.in Tel: (2659) 1144 M: 9968475190 Office: II-357 TAs: Archit, Srijan, Vinay and Reeturaj
- 2. Metal Forming – Course Contents Lecture Class Topic 1 Fundamentals of Metal Forming 2 Plastic Deformation of Materials 3 Bulk Forming Processes 4 Sheet Metal Forming Processes 5 Advanced Forming Technology Practical Class Topic 6 Spinning, Nibbling and Vacuum Forming 7 Rolling, Blanking, Deep drawing and Bending 8 Formability Test and Simulation 9 Forging and Extrusion Simulation Practical classes will be held in Sheet Metal Shop (Central Workshop) and DFM Lab (II-429)
- 3. Suggested books for reference 1. Metal Forming Handbook: Schuler (Springer) 2. Manufacturing Processes for Engineering Materials: S. Kalpakjian and R Schmid (Pearson Education) 3. Fundamentals of Modern Manufacturing: M. Groover (Wiley).
- 4. How is a beverage can manufactured?
- 5. Manufacturing of Al sheets
- 6. Manufacturing of beverage cans
- 8. Forming of cast products
- 9. Fundamentals of Metal Forming • A metal forming or a metal working operation is a plastic deformation process in which the volume and mass of metal are conserved and the metal is displaced from one location to another. • The primary objective of a metal forming process is to convert cast products like ingots and billets into useful shapes such as tubes, rods and sheets. • Equally important is the control of mechanical properties by the metal working processes.
- 11. Classification of MF processes Based on applied stress state: • Direct compression - Forging, rolling. Metal flows perpendicular to the direction of major principal stress. • Tension and compression- wire drawing, deep drawing • Pure tension: stretch forming • Bending: Application of bending moments to the sheet • Shearing: Application of high shear forces to cause the rupture of metal in the plane of shear.
- 12. Classification of forming processes • Bulk forming processes Ex: Rolling, Forging, Extrusion, Drawing etc. • Sheet metal forming processes Ex: Deep drawing, Stretching, Bending etc.
- 14. Products of Bulk Forming Processes
- 15. Sheet Forming Processes • Deep Drawing • Stretch forming • Bending • Shearing • Embossing • Coining
- 16. Products of Sheet forming
- 19. Materials for aircrafts Material Airbus A350 Boeing 787 Plastics and Composites Al alloys Ti alloys Steel Others 40% 31% 14% 9% 6% 50% 20% 15% 10% 5%
- 20. Classification of Metal Forming Processes Based on the temperature of working: ➢ Cold working : Below the recrystallization temp (< 0.3 Tm) ➢ Warm Working: 0.3-0.5 Tm ➢ Hot working: above the recrystallization temp (0.5-0.7 Tm)
- 21. Mechanical Working Cold working Hot Working
- 22. Hot working Cold working 1.Temp of working above Trecryst. 2. At high temp, ductility is high, so large strains can be given. Temp of working below Trecryst. At low temp, ductility is low, large strains can not be given. For large dimensional changes, intermediate annealing is necessary.
- 23. Hot working Cold working 3. At high temp, flow stress is low, required forming loads are low. No need for presses with high capacity. 4. Need for high temp facilities increases cost. For reactive metals inert atmosphere is required. Flow stress is high, required forming loads are high. Need for high capacity presses. Need for intermediate annealing facilities for large strains.
- 24. Hot working Cold working 5. Automation is difficult. 6. Surface oxidation problem leads to poor surface finish, wastage of material. Defects like rolled in oxides occur. 7. Poor dimensional accuracy due to large strains and thermal expansion/contractions. 8. Structure and properties are not uniform. Automation is easy. No oxidation problems, good surface finish, less wastage of material. Better dimensional accuracy due to small strains and good control of the process. Better uniformity of properties.
- 25. Metal Forming System • The deformation-processing situation in any metal forming is best viewed as a total system.
- 27. Important considerations 1. Properties of material: Flow stress and its dependence on strain, strain rate and temperature. 2. Deformation zone: Distribution of stress, strain and particle velocities, overall pressure required to perform the operations. Applied forces, metallurgical phenomena such as strain hardening, recrystallisation etc. are important.
- 28. Important considerations 3. Friction and lubrication: Contact between workplace and tools, type of friction, mechanism of lubrication 4. Heat Flow: Heat transfer during deformation. 5. Tool wear and tool life: Friction, lubrication, forces applied, tool material, surface quality of deforming material. 6. Product: Surface finish, dimensional accuracy, properties.
- 29. Analysis of metal forming processes Principal uses of analytical studies of metal forming processes: 1. Determination of the forces required for producing the desired deformation. 2. Selection and design of the equipment/tools for a particular job. 3. Prediction and prevention of defects during forming. 4. Prediction of the limiting deformation at which fracture will occur.
- 31. Effect of temperature on flow stress
- 32. Effect of temperature on flow stress • Above a certain temperature, strain hardening is nullified by softening mechanisms like recovery and recrystallisation that occur simultaneously with deformation (dynamic recrystallization). • Flow stress decreases with temperature and above recrystallisation temperature, flow stress remains almost constant as the deformation proceeds.