CBE30361 Midterm: Materials exam 2 review
22 Apr 2016
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Smaller grain sizes -> more barriers to slip. Impurity atoms distort the lattice, creating lattice strain. This strain can act as barriers to motion. Precipitates cause difficulty to shear: the idea is that the precipitates have a larger repulsion to shear stress than the parent material, so these increase the overall strength. Dislocations entangle w/ one another and average dislocation distance decreases. This increases tensile strength and yield strength, but causes ductility to decrease. Different influence on the mechanisms (only 2 affected) Causes malleable metals to become much more brittle. Temperature effect -- ductile-to-brittle temperature- why it is important. The fatigue limit is the stress amplitude that, once applied, causes fatigue. This varies with the number of cycles, and usually plateaus at a certain number of cycles. No fatigue if s (stress amplitude) < fatigue limit. Stress at which fracture occurs after a certain number of cycles fatigue strength fatigue life.
