Increasing bending: A novel straightforward method for testing the mechanical behaviour of coatings and deposited films

This paper presents a new method for carrying out bending tests which we believe to be much simpler and faster than current more conventional methods. We subjected our sample to the whole desired range of curvatures within a single experimental step. The typically blade-shaped sample was gradually pressed against and fixed on a specific template (bending snail), the curvature of which varied continuously along its functional surface. A simple formula was used to determine the strain (directly proportional to the sample thickness in elastic materials) applied to the sample external surface. The method is particularly appropriate for studying coatings as, when calibrated, the device enables fast and easy determination of the critical strain values at which different types of damage appear.Some peculiarities of continuously increasing bending are also discussed, having come to light in the specific context of our multicracking tests of coatings. As an illustration, the method was applied to a multilayered DLC (Diamond-Like Carbon) coating.

► A new straightforward method to perform bending tests. ► The curvature of the jig varies continuously along its functional surface. ► Easy determination of critical values of strain regarding damages. ► Multilayer DLC coating.