The Fundamentals of Metalworking (PDF)

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Effect of residual stresses • Residual stresses are only elastic stresses. The maximum value which a residual stress can reach is the yield stress of the material. • Residual stresses can be considered the same as ordinary applied stresses. • Compressive residual stress can effectively subtracts from the applied tensile stresses. • Metals containing residual stresses can be stress relieved by heating to a temperature where the yield strength of the material is the same or lower than the value of the residual stress such that the material can deform and release stress. • However slow cooling is required otherwise residual stress can again develop during cooling. Suranaree University of Technology Tapany Udomphol Jan-Mar 2007
Workability • Workability is concerned with the extent to which a material can be deformed in a specific metal working process without the formation of cracks. • Cracks which occur in metal working processes can be grouped into three broad categories: Dependence of forming limit of mean normal stress σσσσ m. 1. Cracks at a free surface 2. Cracks that develop in a surface where interface friction is high 3. Internal cracks. Examples of cracks in metalworking (a) free surface crack (b) surface crack from heavy die friction in extrusion, (c) centre burst or chevron cracks in a drawn rod. Suranaree University of Technology Tapany Udomphol Jan-Mar 2007
Page 1 and 2: Fundamentals of metalworking Subjec
Page 3 and 4: Classification of metal forming pro
Page 5 and 6: • Tension type processes: the app
Page 7 and 8: Mechanics of metal working • Meta
Page 9 and 10: • However the convention is rever
Page 11 and 12: Yield criteria and stress-strain st
Page 13 and 14: Tresca yield criterion Yielding occ
Page 15 and 16: FEM analysis • Finite element met
Page 17 and 18: Determination of flow curve Stress-
Page 19 and 20: Flow curve • Strain hardening occ
Page 21 and 22: • The products resulting from the
Page 23 and 24: Effects of temperature on metal for
Page 25 and 26: Recrystallisation • Recrystallisa
Page 27 and 28: Effects of grain size and strain on
Page 29 and 30: Effects of strain rate and temperat
Page 31 and 32: Polygonization Recovery • Recover
Page 33 and 34: Static and dynamic changes of struc
Page 35 and 36: Advantages and disadvantages of hot
Page 37 and 38: Advantages and disadvantages of col
Page 39 and 40: Increasing reduction Effects of met
Page 41 and 42: Effect of principal stresses in met
Page 43 and 44: Effects of friction and lubrication
Page 45 and 46: σσσσ σσσσ Example : homogen
Page 47: Effect of residual stresses • Res

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