International audienceThe energy release rate of a small crack in an infinite hyperelastic medium, and subjected to large strain multiaxial loading conditions, is derived by considering the balance of configurational stresses acting on two planes: one cutting the center of the crack face, and the other at an infinite distance in front of the crack tip. The analysis establishes that the energy release rate of a small crack is always proportional to the size of the crack, irrespective of the loading conditions and the crack orientation. The balance of configurational stresses is illustrated for several benchmark cases including simple extension, pure shear and equibiaxial extension, and for perpendicular and inclined cracks

A new appendix is introduced in the RSE-M code, devoted to in-service operation on PWRs, dealing with the assessment of a defect in the Reactor Pressure Vessel. This new appendix reflects the current French practice and introduces a second criterion to consider the Warm Pre-Stress (WPS) effect. This appendix is applicable to under clad defects and defects partially in the cladding, and covers nominal, incidental and accidental conditions. The main criterion is the classical comparison between the stress intensity factor (amplified to account for the plasticity of the cladding) and the material toughness (taking into account the irradiation induced ageing). For incidental and accidental situations, if the conventional criterion is not verified, an alternative criterion is proposed to take into account the WPS effect. The criterion corresponds to the ACE criterion developed by AREVA, CEA and EDF taking into account the effective material toughness depending on the loading history. The present paper presents this new RSE-M appendix and provides some basic elements of justification and validation on the ACE criterion.

The Eshelby stress tensor is known to be an appropriate Continuum Mechanics quantity to capture singularities. Nevertheless, even if its use in the calculation of configurational forces is well-established, its peculiar properties were investigated only recently. Here, some new properties of this tensor are studied. In this way, it is assumed that the evolution of microscopic defects in the material can be predicted at the macroscopic scale by examining the components of the Eshelby stress tensor. More precisely, considering that defects can be modeled by material surfaces oriented in all possible directions and assuming that they are able to evolve in every possible directions, it is shown that the maximum amount of energy which can be released by defects evolution is partially contained in the tensor. In the special case of hyperelasticity, the corresponding optimization problem is established and solved for both isotropic and anisotropic materials.