Giovanni is an Application and R&D Mechanical Engineer at Simulia, having joined Safe Technology in 2012. Did some research on fretting and multi-axial fatigue at the University of Brasilia where he started his PhD, which was paused after moving to United Kingdom. Received his masters from the University of Sao Paulo on dynamics and finite element method and his Bachelor's degree in Mechanical Engineering from the University of Uberlandia. Previously worked for MAHLE, General Motors and ESSS. At Simulia, he is responsible for the research and development of General Fatigue Methods. Has been involved with Random Vibration Fatigue, Theory of Critical Distances, Infinite Life Methods, the Prismatic Hull, Multiaxial Rainfllow Counting, Thermo-Mechanical Fatigue, Fatigue of Welds and Nitinol Alloys.
AbstractThe DTMF damage Parameter described in the paper is the generalization of the creep fatigue parameter (DCF) proposed by Riedel, which quantifies the amount of damage produced by a non-isothermal loading cycle. The entire design methodology is outlined in the text, starting with the calibration of Chaboche's viscoplastic model and then the determination of the thermomechanical fatigue (TMF) parameters. Chaboche is generally a good choice for its ability to describe well both kinematic and isotropic hardening behaviors, also enabling stress relaxation and strain rate dependency to be considered. The DTMF method is based on the fracture mechanics concept of cyclic crack tip opening displacement (CTOD) where the effective stress range takes the crack closure effect into account. This method is typically used to describe the thermomechanical low cycle fatigue behavior of cast irons, cast steels, stainless steels, Inconel, HiSiMo and nickel-based alloys. These materials are used in components that need to withstand high temperatures (higher than half of the melting point) in service as exhaust manifolds, cylinder heads, valves, turbochargers and disk brakes. Three failure mechanisms are detailed here: oxidation, creep and fatigue. Oxidation is a complex phenomenon that may occur when the material is hot under tensile in-phase loading or hot under compressive out-of-phase loading. Creep is a time and temperature dependent diffusion process which is incorporated into the DTMF parameter as a multiplicative factor. In this context fatigue life is defined as the number of cycles to propagate an existent microcrack up to an arbitrary size that is defined on a case-by-case basis.
|Thursday 30th November
S11-1 Non-linear behavior and cumulative damage
110 - An overview of the mechanism-based thermo-mechanical fatigue method (DTMF) and its application in the design of automotive components