1. ME 582 - Manufacturing Systems Introduction To Manufacturing Systems by Ed Red Introduction To Manufacturing Systems by Ed Red

2. ME 582 - Manufacturing Systems Fundamentals of Metal Forming Metal forming is plastic deformation of metals into desired shapes Metal forming is plastic deformation of metals into desired shapes Deformation stresses may be tensile or compressive (usually compressive) Deformation stresses may be tensile or compressive (usually compressive) Metals must exhibit certain properties to be formed efficiently Metals must exhibit certain properties to be formed efficiently Friction is an important factor in metal forming Friction is an important factor in metal forming Strain rate and temperature are important factors in metal forming Strain rate and temperature are important factors in metal forming

3. ME 582 - Manufacturing Systems Material Behavior in Metal Forming Engineering Stress and Strain (used by engineering designers): Engineering stress  e = F/A o Engineering straine = (L - L o )/L o Hooke's Law (elastic region):  e = E e

4. ME 582 - Manufacturing Systems Material Behavior in Metal Forming Stress - strain diagrams (tensile and compression): ee e Elastic region Plastic region 0.2% offset Ultimate strength Yield strength

5. ME 582 - Manufacturing Systems Material Behavior in Metal Forming Common parameter values: AlSteel E psi 10 x 10 6 30 x 10 6 MPa 70 x 10 3 210 x 10 3 Yield strength psi 4000 60,000 MPa 28 400 Ultimate strength psi 10,000 90,000 MPa 70 600

6. ME 582 - Manufacturing Systems  Elastic region Plastic region Material Behavior in Metal Forming True Stress and Strain (used by manufacturing engineers): True stress  = F/A True strain  = dL/L = ln(L/L o )  Start of necking

7. ME 582 - Manufacturing Systems Material Behavior in Metal Forming Why do engineering designers base their design on engineering stress/strain, but manufacturing engineers use true stress-strain?

8. ME 582 - Manufacturing Systems Material Behavior in Metal Forming Strain hardening - Resistance to increasing strain. Stress-strain can be related in the plastic region by the form  = K  n where K is the strength coefficient and n is the hardening exponent. A log-log diagram will show the linear behavior expected for a curve of this form. Note: The greater the n, the greater the strain hardening effect. Necking for many ductile materials begins approximately when the true strain reaches a value equal to n.

9. ME 582 - Manufacturing Systems Material Behavior in Metal Forming Material Strength coeff, K Strain hardening exp, n psi MPa Aluminum30,000 2100.18 Steel125,000 8500.15

10. ME 582 - Manufacturing Systems Material Behavior Example The following data are collected during a tensile test in which the initial gage length is 5 in. and the cross-sectional area is 0.1 in 2 : Load (lb)0400051806200650062004600 Length (in)5.0005.0095.255.605.886.126.40 Determine the yield strength Y, modulus of elasticity E, and tensile strength TS. Also determine the strength coefficient K and the hardening exponent n.

11. ME 582 - Manufacturing Systems Some relations you need to know  =  e (1 + e)  = ln (1 + e) Also note that it is often necessary to use a constant volume relationship for modeling process phenomena. In the case of a tensile test, the appropriate equation would be AL = A o L o

12. ME 582 - Manufacturing Systems What have you learned?