ENGR 0022 Study Guide - Midterm Guide: Rubber Band, Silicon Carbide, Stress (Mechanics)
Document Summary
The burger"s (slip) vector of a screw dislocation is perpendicular to the dislocation line. Increasing the dislocation density decreases ductility of metals and alloys. The yield strength of metals is defined using 1% permanent strain. Thermoplastics deform permanently by breaking of the carbon to carbon bonds in the polymer chains and chain sliding. The failure strength of ceramics in compression is usually much lower than the failure strength in tension. Dislocation density is defined as the number of dislocations per unit volume. The strength of pure metals is well below their ideal strength due to the presence of flaws that create stress concentrations. The unit of slip of an edge dislocation occurs in a direction parallel to the dislocation line. The ideal strength of pure elements is approximately 1% of their young"s modulus. Yield strength is the stress beyond which a material becomes plastic. Yield properties and ductility are measured with standard tensile tests continued to failure.
