Modeling for wave propagation and energy losses in solids with cracks: the MMD-FEM Code

The importance of modeling in NDT is due to the fact that it allows one to interpret experimentally measured indicators and finally retrieve parameters of damage. This concern stimulated us to develop modeling support for nonlinear ultrasound techniques by combining an available finite element software with a realistic crack model based on an original method of memory diagrams (MMD). The method has been recently proposed for automating the account for friction-induced hysteresis in the mechanical response of rough surfaces excited by arbitrarily changing normal and tangential displacements. The resulting load-displacement relationship represents a boundary condition that has to be set at surfaces of inner boundaries appearing in a material with cracks. The boundary condition is then used by the FEM code for calculation of stresses and strains in material’s volume. In practice, the FEM part has been programmed in COMSOL that enables one to implement user-defined boundary conditions calculated in an external MATLAB procedure. The advantage of the MMD-FEM modeling toolbox is in its computational efficiency that results from the multiscale approach in which the influence of microscopic features (roughness) is integrated in the response of a mesoscopic cell (crack segment) that drastically simplifies the account for rough contact geometry. Moreover, the instantaneous friction-induced loss of mechanical energy is also easily calculated that makes it possible to add the heat transport module and to study heat diffusion in materials with cracks excited acoustically. We give some calculation examples and show how the suggested toolbox assists NDT thermography methods. Examples concerning the ultrasound propagation and nonlinear acoustic effects are also considered.

Jaar van publicatie:2018

Toegankelijkheid:Open