Material and fatigue life models for thermo‐mechanical loaded components

Abstract

Today, specific material data, mainly from static material tests, are not sufficient to design parts of a product to assess lifetime behaviour, especially when local complex loading occurs like low cycle fatigue (LCF) and thermo mechanical fatigue (TMF). In this work, specimen tests are carried out under LCF and TMF loading with different materials, where mechanical and thermal properties are considered. The investigated materials are an aluminium alloy, cast iron, copper alloy and nickel. The TMF tests are performed by using a TMF test rig, designed by the Chair of Mechanical Engineering (AMB). The results of these tests allow a description of the material behaviour depending on the mechanical and thermal boundary conditions. Commercial Software for Finite Element Analysis (FEA) enables a fit with the test results to calculate stress and strain values for different loading conditions. These results are the input data for the final lifetime calculation. A number of approaches are given to determine the lifetime for the investigated materials. Finally, a special modified energy method -"unified energy approach" -is presented and compared with conventional approaches.Key

Effect of Strain Rate on the Deformation Behaviour of A356-T7 Cast Aluminium Alloys at Elevated Temperatures

“…This problem is further aggravated with hybrid powertrains, as the number of such engine start-stop thermomechanical cycles are considerably increased. Reliable numerical models to predict both the structural deformation and thermomechanical fatigue durability of cylinder heads are essential to shorten the development times and reduce developmental costs with the computer-aided engineering (CAE) approach [6,8]. Thus, to develop a better understanding of the continuum deformation and fatigue behaviour of the alloy, it is essential to investigate the effect of strain rate on the deformation and fatigue behaviour.…”