Performance analysis & testing: What distinguishes engineers from technicians is largely the ability to formulate and carry out the detailed calculations of forces and deflections, concentrations and flows, voltages andcurrents, that are required to test a proposed design on paper with regard to failure criteria. The ability to compute is the capability to predict the performance of the design before it is built and tested. By understanding how and why a proposed design can failure, and by being capable to compute the quantities required to assess whether failureconditions prevail, the engineer is capable to test the design on drawing board or on computer screen before any steel is erected, any of the valve is opened, or any switch is thrown.