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Welded assemblies are commonly used in the shipbuilding industry. Because of the combination of stress concentration and cyclic loading, welded joints could be a critical area for fatigue damage. Thus, knowing stress and strain histories at the critical points of the structure is necessary, particularly when a confined plasticity occurs, to determine the fatigue life of welded assemblies. To avoid time-consuming nonlinear finite element analyses (FEA), simplified estimation methods of the elastic-plastic strain/stress can be used. In a previous work, an approach to estimate stress state at critical points was developed and employed in the case of double-notched specimens. The present paper focuses on welded joints in order to validate this strategy with the aim to estimate the fatigue crack initiation life of T-joints. To go further, a parametric approach has been adopted to take into account the local geometries of welded joints and to determine the constraint operator without any FEA. The results predicted by this approach are compared with experimental fatigue results. [ABSTRACT FROM AUTHOR]

Heterogeneous dissipation in steel sheets due to cyclic loading is difficult to measure, especially in the transverse direction because of the high conductivity and low thickness of the sheets. The goal of this article is thus to develop an experimental protocol allowing for the dissipation field determination from infrared thermography. The protocol is based on a specific differential measurement and an asynchronous acquisition. It reduces measurement artefacts due to coating, rigid body motion, convection, and optical deleterious effects. It is eventually applied to different specimens. [ABSTRACT FROM AUTHOR]

The specific behaviour of shape memory alloys (SMA) is due to a martensitic transformation [Shape Memory Materials. Cambridge University press, Cambridge] . This transformation consists mainly in a shear without volume change and is activated either by stress or temperature. The superelastic behaviour and the one-way shape memory effect are both due to the partition between austenite and martensite. The superelastic effect is obtained for fully austenitic SMA: loaded up to 5% strain, a sample recovers its initial shape after unloading with a hysteretic loop. The one-way shape memory effect is obtained when a martensitic SMA, plastically deformed, recovers its initial shape by simple heating. Superelasticity and one-way shape memory effect are useful for several three-dimensional applications. Despite all these phenomena are well known and modelled in 1D, the 3D behaviour, and especially the one-way shape memory effect, remains quite unexplored [Mater. Sci. Res. Int., 1 (1995) 260]. Actually, the development of complex 3D applications requires time-consuming iterations and expensive prototypes. Predictive phenomenological models are consequently crucial objectives for the design and dimensioning of SMA structures. Therefore, a series of 2D proportional and non-proportional, isothermal and non-isothermal tests have been performed. This database will be used to build a phenomenological model within the framework of irreversible processes. [ABSTRACT FROM AUTHOR]

A probabilistic framework developed to model multiaxial high cycle fatigue tests is proposed. Up to now, with a probabilistic point of view (i.e., Weibull law), models account for the stress heterogeneity effect by introducing the concept of effective volume. It is proposed to extend this concept to multiaxial load histories. It consists in introducing a factor representing the distribution of activated slip directions. The non-proportionality effect is taken into account with no additional parameter with respect to traditional (i.e., Weibull) probabilistic approaches. The proposed model is validated on a large experimental data base and compared with other models. [ABSTRACT FROM AUTHOR]

It is proposed to develop and identify a probabilistic two-scale model for HCF that accounts for the failure of samples, but also for the thermal effects during cyclic loadings in a unified framework. The probabilistic model is based on a Poisson point process. Within the weakest link theory, the model corresponds to a Weibull law for the fatigue limits. The thermal effects can be described if one considers the same hypotheses apart from the weakest link assumption. A method of identification is proposed and uses temperature measurements to identify the scatter in anS/ Ncurve. The validation of the model is obtained by predictingS/ Ncurves for different effective volumes of a dual-phase steel. [ABSTRACT FROM AUTHOR]

The present paper deals with self‐heating phenomenon under cyclic loading at high loading frequency 20 kHz and low stress amplitude (i.e., far below the yield stress). The main goal is to propose two different methods to determine the heat source field at the origin of this temperature change. To do that the local expression of the 1D heat diffusion equation and experimental thermal data fields obtained by an infrared camera are used. The proposed methodology is applied to experimental results from tests performed on a ML340 maraging steel. [ABSTRACT FROM AUTHOR]