Manufacturing Systems Introduction To Manufacturing Systems by Ed Red

What we will cover Process Models - Force - Power - Wear Electronics manufacturing (1/3rd of all manufacturing) Electronics production machines and processes Process Models - Force - Power - Wear - Production rate - Etc. L Do Df p Fundamental metal forming and removal technologies Flexible manufacturing systems

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

Material Behavior in Metal Forming Engineering Stress and Strain (used by engineering designers): Engineering stress se = F/Ao Engineering strain e = (L - Lo)/Lo Hooke's Law (elastic region): se = E e

Material Behavior in Metal Forming Stress - strain diagrams (tensile and compression): Ultimate strength se Plastic region Yield strength Elastic region e 0.2% offset

Material Behavior in Metal Forming Common parameter values: Al Steel E psi 10 x 106 30 x 106 MPa 70 x 103 210 x 103 Yield strength psi 4000 60,000 MPa 28 400 Ultimate strength psi 10,000 90,000 MPa 70 600

Material Behavior in Metal Forming True Stress and Strain (used by manufacturing engineers): True stress s = F/A True strain e = dL/L = ln(L/Lo) s Start of necking Plastic region Elastic region e

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

Material Behavior in Metal Forming Strain hardening - Resistance to increasing strain. Stress-strain can be related in the plastic region by the form s = K en 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.

Material Behavior in Metal Forming Material Strength coeff, K Strain hardening exp, n psi MPa Aluminum 30,000 210 0.18 Steel 125,000 850 0.15

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 in2: Load (lb) 0 4000 5180 6200 6500 6200 4600 Length (in) 5.000 5.009 5.25 5.60 5.88 6.12 6.40 Determine the yield strength Y, modulus of elasticity E, and tensile strength TS. Also determine the strength coefficient K and the hardening exponent n.

Some relations you need to know s = se (1 + e) 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 = Ao Lo

What have you learned?