Failure analysis of a half-shaft of a formula SAE racing car

2016-07-05_16h47_58An article in progress in « Case Studies in Engineering Failure Analysis », Volume 7 (october 2016).

The formula SAE is a competition among students worldwide, where they are challenged to design, build and test a small formula-type racing car, following rules and specifications defined by the Society of Automotive Engineers (SAE). In the present analysis, a premature failure of a half-shaft of the transmission system of a racing car occurred after circa 100 km of use. The results show that the alloy steel bar used for the half-shaft did not follow specifications, with a consequent lower strength and resulting in a material with insufficient loading capacity and fatigue resistance. As a consequence, the fracture process was a confluence of torsional fatigue crack propagation and overload ductile fracture through the spline section of the half-shaft.

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Failure of Metals I – Brittle and Ductile Fracture

mixteA ne pas manquer de lire sur, trois publications intégrales et récentes sur « La ruptures des métaux » rédigées par André Pineau, A.A. Benzerga et Thomas Pardoen.

La première concerne la rupture ductile et fragile. Il s’agit d’une vue d’ensemble des phénomènes de ruptures sous chargement monotone dans un contexte d’approche globale.

« This is the first of three overviews on failure of metalsHere, brittle and ductile failure under monotonic loadings are addressed  within the context of the local approach to fracture.In this approach, focus is on linking microstructure, physical mechanisms and overall fracture properties….. »

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A detailed review and Prediction of Ductile Fracture

A publication in « IJRAME« , april 2014.

Earlier researchers were studied the failure analysis through various Failure Mode and Effective Analysis (FMEA) technique and tried to predict the fracture before failure occurs. This work attempts to predict the ductile fracture criterion for the sheet metal to avoid the failure by means of considering various controllable and uncontrollable parameters. With the Design of Experiments and the Artificial Neural Network techniques a ductile fracture initiation criteria modeled and the model will be validated through Finite element simulation for the verification of the quality. If comparison results are within the limit condition, the model can be utilized for the prediction of ductile fracture before it happens in the real application.

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Analysis of notch effect in the apparent fracture toughness and fracture micromechanisms

This paper, reported by, presents an analysis of the notch effect on two ferritic-pearlitic steels operating within their corresponding lower shelf, and develops an experimental programme, composed of 28 CT characterisation specimens and 72 CT validation specimens, together with finite elements analysis with the aim of validating the apparent fracture toughness predictions provided by the Theory of Critical Distances. The results have shown how this theory provides reasonable predictions of the apparent fracture toughness of the material .

The research is completed with the analysis of the evolution of fracture micromechanisms when the notch radius increases, revealing a direct relation between this evolution and the apparent fracture toughness observations.