Analysis and Design for Inelastic Behavior

Abstract

Increased understanding of the behavior of materials and structural and machine components has led to a change in design emphasis from stress levels to load capacity. In Chapter 10 computed stresses associated with service or working loads were compared to allowable stresses. These allowable stresses were determined by applying a factor of safety to some “ failure ” stress. Traditional designs of the past as well as much current engineering practice has made use of these concepts. However, recent trends have refocused the attention of design engineers on the load-carrying capacity of components and overall structures. Service or working loads are multiplied by load factors greater than unity, and materials and sizes of components are selected to “ fail ” under the action of these factored loads. The term failure is defined in this chapter to mean that the component after being subjected to a maximum load continues to deflect under practically constant load. This concept restricts the discussion to ductile metals under static loading at ordinary temperatures. Once the calculations are completed, the component should safely withstand the service or working loads, which are much smaller than the ultimate or factored loads.