Isotropic Damage Analysis of Thermoelastic Problems using BIE

This work presents a quadratic boundary integral equation formulation for isotropic damage analysis of components subjected to mechanical, thermal and centrifugal loads. To evaluate domain-related integrals due to the damage effects, the radial integration method (RIM) based on the use of the approximating the normalized displacements in the domain integrals by a series of prescribed radial basis functions (RBF) is adopted. The density of micro-defects is assumed to be small in the material. The scalar damage parameter expressed in an exponential evolution equation is utilized. Numerical examples including a rectangular plate, thick-walled cylinder and rotating disk problems under the thermal loads are given.

Finite Element Analysis of Influence of Non-homogenous Temperature Field on Designed Lifetime of Spatial Structural Elements under Creep Conditions

The techniques of modeling of continual fracture process for spatial bodies under long-term static force loading condition in non-homogenous temperature field are presented. The scalar damage parameter is used to describe the material continual fracture process. A stress-strain problem solution made with semianalytic finite element method (SFEM). Results of lifetime determination of responsible parts are presented.

Damage Mechanics and Critical Plane Approach to Multiaxial Fatigue

The mechanical behaviour of structural components subjected to multiaxial fatigue loading is very important in modern design. Several approaches have been introduced in recent decades to analyse this problem. The so-called critical plane approach, based on the stresses acting on the plane where the crack nucleation is expected to occur, is widely used. This criterion can give us a fatigue damage measurement, which can be used to evaluate fatigue life. On the other hand, fatigue life under general multiaxial stress histories can also be assessed by applying the damage accumulation method. In such a method, a scalar damage parameter is quantified through the damage increments which develop during the fatigue process up to the critical damage value corresponding to the final failure of the structures. The damage increment approach to fatigue has recently been discussed and connected to the classical crack propagation approach. In the present paper, the interpretation of the critical plane approach based on the continuum damage mechanics concepts is examined. In particular, the physical meaning of the critical plane approach is shown, that is, such an approach can be interpreted as a damage method which takes into account the scalar damage parameter evaluated along preferential directions. Finally, the fatigue behaviour of a metallic material under multiaxial cyclic load histories is analysed through the two above approaches.