Читать книгу Materials for Biomedical Engineering - Mohamed N. Rahaman - Страница 122

The transition from elastic to plastic deformation is commonly called the yield point. Some stress–strain curves show a well‐recognized bump in this transition region which is taken as the yield point (Figure 4.3a). On the other hand, it is often difficult to locate the yield point in some stress–strain curves because they change gradually in this region (Figure 4.3b). When difficult to locate, the yield point is often taken at what is called an offset strain, equal to 0.2% strain. A straight line is drawn from the strain axis at 0.2%, parallel to the line for elastic deformation, and where this line crosses the stress–strain curve is taken as the yield stress.

Figure 4.3 Schematic diagrams to illustrate two types of plastic deformation and yield behavior of ductile materials.