Parameters Affecting Energy Absorption in Metal Foams

Recent research findings on the mechanical behavior of metal foams are summarized in this work. Thanks to their properties in compressive tests, a wide range of foamed materials has been considered for energy-absorption applications such as Al, Fe, Ti, Ni and its alloys. The main parameters affecting energy absorption are focused and presented: cell size, relative density, strain rate, hybrid foam (Al-Cu, Al-Ni), base metal, and composites structures (Al-foam filled tube and sandwich). Metal foam response, impact resistance and failure are discussed in many configurations and test conditions. The results of finite elements modelling and its validation by means of mechanical tests are discussed too.

Analysis of some key aspects of soil/foundation interaction-Finite elements modelling

This paper is aimed to contribute to the analysis of three important aspects of soil-foundation interaction, which are not clearly investigated, by means of a detailed parametric study based on a finite elements modelling. The first aspect focuses on the effect of the bedrock proximity on the load-settlement behaviour of a continuous or circular shallow foundation. It was found there exists a threshold distance between the foundation base and the top of the bedrock layer beyond which the foundation behaves as in an infinitely deep medium. The second one deals with the behaviour of shallow foundation on a bi-layered soil where the effect of the underlying layer on the bearing capacity as well as on the settlements depends on the distance between the foundation base and the top of the underlying layer, and beyond a threshold value this effect vanishes. The third aspect studied was the interference between two strip footings installed on saturated clay. It was shown within a threshold distance between these foundations, an important modification of the foundation behaviour may occur. Finally, the numerical results were fitted and interpreted which allowed suggesting simple practical formulae for shallow foundations design.

Modelling of fine soils railway embankments behaviour under real cyclic loads

Before the development of regulations, standards and guides for infrastructure building, embankments were generally constructed, by reusing and compacting the excavation materials. Therefore, a large part of existing railway embankments, over the world, is composed of fine compacted soils such as clay or marl. However, the current international trend of the railway undertakings and transport contractors is within the intensification of traffic, and the increase of train’s load and speed. Therefore, infrastructure managers are always called upon to evaluate the bearing capacity of existing infrastructures and define the necessary reinforcement solutions. In this perspective, a better awareness and knowledge of the behaviour of fine soils railway embankments is required to define optimal and efficient reinforcement solutions. In that matter, the article will feature the results of finite elements modelling of instrumented railway embankments that were constructed in Morocco in 1920, with marl compacted soil. The model is based on real applied loads and hydraulic conditions monitored for the last three years, which allow to simulate the hydro-mechanical behaviour of the embankment for this period. The article will be also comparing real monitored deformations recorded by the inclinometers equipping the embankments, with the output of the model using different models and adjustments.

Mesoscale FEM model for the analysis of composite delamination

The article discusses the problem of delamination of layered composite samples according to the mode I (tensile opening mode). It includes the experimental part, which sets the averaged characteristics of delamination of the samples in the relation tensile opening–tensile force as well as the description of mesoscale FEM model of composite, which takes into account its internal structure. The model was used in the simulation of delamination, while the development of the fracture took place in consequence of modifications of finite elements modelling the matrix. The results of the delamination simulation with the use of the developed FEM model were consistent with the results of the experiment.

Comparison of Several Behaviour Laws Intended to Produce a Realistic Ti6Al4V Chip by Finite Elements Modelling

The final aim of finite elements modelling is to help in the choice of the cutting parameters and in the comprehension of the involved phenomena. Representing correctly the behaviour of the machined material is hard due to the extreme conditions encountered, although this is a key parameter to develop a realistic model. Four laws are used in this paper to represent the Ti6Al4V. They are all based on the Johnson-Cook law. This study shows that the influence of the behaviour law is high on the chip morphology and on the forces and that the strain softening phenomenon should be taken into account. For the cutting conditions adopted, it is however necessary to add damage properties in the chip to obtain a morphology and a cutting force evolution close to the experimental reference.