ABSTRACT
Of particular interest is the linear portion of the curve. Point A is defined as the proportional limit where the linear relationship between stress and strain stops. Point B is defined as the elastic limit. Beyond this point, the specimen has been plastically deformed (strained) and will not return to its original length when the stress is removed. Point C is defined as the yield point. This is typically characterized by a specified amount of plastic strain, usually 0.2%. While many fasteners are intentionally preloaded beyond the yield point, determination of the stiffness of a fastener is confined to the elastic region. By combining Eqs. (1)-(4) and rearranging terms, an equation defining the deflection can be written:
Further manipulation produces the equation defining the stiffness:
However, the preceding equation is applicable only to parts with a uniform cross section.
