Models of ideal materials have shown that this zone of plasticity is centered at the crack tip. This equation gives the approximate ideal radius of the plastic zone deformation beyond the crack tip, which is useful to many structural scientists because it gives a good estimate of how the material behaves when subjected to stress. In the above equation, the parameters of the stress intensity factor and indicator of material toughness, K C , and the yield stress, σ σ Y , are of importance because they illustrate many things about the material and its properties, as well as about the plastic zone size. For example, if K c is high, then it can be deduced that the material is tough, and if σ σ Y is low, one knows that the material is more ductile. The ratio of these two parameters is important to the radius of the plastic zone. For instance, if σ σ Y is small, then the squared ratio of K C to σ σ Y is large, which results in a larger plastic radius. This implies that the material can plastically deform, and, therefore, is tough. This estimate of the size of the plastic zone beyond the crack tip can then be used to more accurately analyze how a material will behave in the presence of a crack.