About the effect of plastic dissipation in heat at the crack tip on the stress intensity factor under cyclic loading

Abstract

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. AbstractBecause of the reverse cyclic plastic zone at the crack tip, there is plastic dissipation in heat at the crack tip under cyclic loading. That creates a heterogeneous temperature field around the crack tip. A thermo-mechanical model is proposed in this paper for evaluating the consequence of this temperature field on the Mode I stress intensity factor. Two cases are studied: (i) the theoretical problem of an infinite plate with a semi-infinite through crack under Mode I cyclic loading, and (ii) a finite specimen with a central through crack. In the first case, the main hypothesis and results are presented from the literature but no heat loss is taken into account. In second case, heat loss by convection is taken into account with a finite element analysis, while an analytical solution exists in the literature for the first case. In both cases, it is assumed that the heat source is located in the reverse cyclic plastic zone. The heat source within the reverse cyclic plastic zone is quantified by experiments on a mild steel under R=0.1. It is shown that the crack tip is under compression due to thermal stresses coming from the heterogeneous temperature field around the crack tip. The effect of this stress field on the stress intensity factor (its maximum, minimum and its range) is calculated. This paper shows that experiments have to be carried out to determine the heat source within the reverse cyclic plastic zone. This is the key parameter to quantify the effect of dissipation at the crack tip on the stress intensity factor.

Analysis of the plastic zone of a circle crack under very high cycle fatigue

“…Internal friction produced within a material during cyclic loading results in the generation of several energy forms including elastic strain energy, plastic strain energy, and inelasticity and heat generation and dissipation [2][3][4]. Ultrasonic experiments have demonstrated that energy generation and dissipation in the VHCF regime results in an increase of temperature of the test specimen.…”

Determination of dissipated energy fields from temperature mappings on a rubber-like structural sample: Experiments and comparison to numerical simulations

“…and Louche, 2000). A second way is to use the full temperature field to evaluate the heterogeneous mechanical field, under the hypothesis of thermo-elasticity (Bodelot et al, 2009), adiabaticity (Kapoor and Nemat-Nasser, 1998) or by a comparison to finite element computation (Ranc et al, 2014).…”

“…The second main approach used to evaluate the heat sources is to perform an ''inverse'' analysis where the distribution of the heat sources is assumed and the magnitude is adjusted from the comparison between experimental and computed thermal fields on the basis of an analytical or a finite elements simulation (Ranc et al, 2014;Le Saux et al, 2013). This second option remains difficult for numerous reasons: the thermomechanical problem is usually ill posed and can lead to several solutions, the thermal exchange conditions are difficult to evaluate, especially when large displacements occur and the conversion of mechanical energy into dissipated energy is often complex with numerous parameters.…”

Effect of crack closure on non-linear crack tip parameters

“…This K pc was proposed as a new mechanical driving force parameter for predicting FCG rate, able to explain important phenomena associated with the plastic zone around a fatigue crack tip, such as the effects of load ratio R, single overload and the FCG behavior under cyclic compression. Ranc et al [20] quantified the effect of heterogeneous temperature on stress intensity factor. The energy dissipated in the cyclic plastic zone ahead of crack tip produces thermal expansion of the material which affects the stress field.…”