Prévision de la durée de vie d’une structure précontrainte

Ahdad, F.; Desvignes, M.; Castex, L.; Journet, Bernard; Pons, Gema Valero; Ericsson, Torsten; Ahmad, M.

doi:10.1051/mattech/199583100013

Cited by 1 publication

(2 citation statements)

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“…Besides compressive residual stresses, shot-peening generates an important hardening at the samples surface. As a first approximation, the residual stresses are generated by the fictitious thermal method [9]. It consists in introducing fictitious dilatation coefficients α in a partitioned part, apply a fictive thermal load ΔT which generate residual stresses due to incompatible plastic strains.…”

Section: Simulationmentioning

confidence: 99%

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Analysis of Residual Stress Relaxation Under Mechanical Cyclic Loading of Shot-Peened TRIP780 Steel

2016

Residual Stresses 2016

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Abstract. Shot-peening is a common mechanical surface treatment used in automotive and aeronautical industries to enhance life duration of mechanical parts by introducing compressive residual stresses. TRIP 780 steel fatigue type specimens are shot-peened and loaded under cyclic bending. The martensite phase transformation and the evolution of residual stresses in the different phases are determined by XRD at different numbers of cycles. A FEM model is also proposed to better understand the evolution of residual stresses in the first cycles. IntroductionMost surface treatments aim at enhancing life duration of mechanical parts by introducing compressive residual stresses. Shot-peening (SP) process generates a compressive residual stress by deformation of the surface which is accommodated by elastic residual strains. However, those induced stresses may not be stable during the life of a part submitted to thermal and mechanical fatigue. This study deals with the analysis of mechanical stress relaxation and microstructure evolutions of a TRIP-aided steel, TRIP780 [1, 2], after shot peening and subsequent cyclic mechanical loading. This steel exhibits a multiphase microstructure (ferrite, bainite, and austenite) where each mechanical constituent participates to the global behavior [3,4]. Austenite is a metastable phase which can transform into martensite under a thermomechanical loading.To reach this goal, the mechanisms responsible for relaxation (plasticity, phase transformation) have to be identified. The first part presents the experimental set-up of the performed analysis and the obtained results are presented and discussed. In a second part, a FEM model using a phenomenological approach is presented in order to understand the redistribution of mechanical fields (macroscopic stress and plastic strain) during the first cycles.

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Section: Simulationmentioning

confidence: 99%

“…In the hypothesis of an orthotropic residual stress state, dilatation coefficients are given by the following equation [9]:…”

Section: Simulationmentioning

confidence: 99%