Scratch test equations

The scratch test is a method to determine the adhesion strength of a coated layer. In the scratch test, as schematically shown in Fig. 22.10, an indenter is translated across a coated substrate at a constant velocity under a normal force applied. The stresses are introduced to the interface between coating and substrate and at the critical load, the delamination of the coating occurs. Benjamin and Weaver (1963) performed a simple analysis for the scratch test by using the following equations. 

Swain (1978) analysed in detail the critical load inducing crack formation around a scratch in scratch hardness test, and Veldkamp et ah (1978) determined this critical point from the equation... 

From the equations presented in under Theoretical Backgroimd, it can be derived that materials properties, such as modulus and yield strength, and any modifications that might affect them will influence the scratch behavior of polymers. The unique characteristics of poljnners make research in polymer scratch particularly challenging. First, as mentioned in the previous section, polymers are viscoelastic-viscoplastic in nature. This makes polymer properties very sensitive to test conditions, especially temperature and strain rate (21,34,56,63,64). 

Section 1.4.5 describes the early origins of this test and contains equations that can be used to quantify it more usefully than the early scratch... 

Equation (1.52) can be used to predict the size of debris particles formed in scratch hardness testing. Figure 1.9 contains some typical scratch widths obtained at different loads for three important ceramics. 

---