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The valves of an internal combustion engine play an essential role in the automobiles and their surroundings significantly affect their thermo-mechanical behavior. The work aims to assess numerically the effect of the real thermo-mechanical boundary conditions on the valves by considering the actual complex surrounding. For this purpose, we have subdivided the valve into seven adequate zones. We have evaluated the average values of the transient heat transfer coefficient, the adiabatic wall temperature and the mechanical load at each subdivision are during the opening and the closing periods. A transient Finite Element Model under ANSYS APDL software is developed and simulations are carried out until reaching the steady state. The temperature distribution and the thermal stresses at each valve position is obtained and then analyzed. The main findings show that the stress intensity distribution is developed in the zones labelled stem guide port and seat local of large temperature gradients, which causes high thermal stresses responsible of cracks or thermal fatigue damage. In addition, knowing the temperature map, the thermal gradient and stress under actual conditions will surely help manufacturers to better design exhaust valve, avoid early failure and enhance the durability of valves.

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This paper presents some experimental investigations about the origins of the anisotropic behaviour in cyclic loadings of AA2017 aluminium alloy. In the first step, fatigue damage evolutions were quantified for controlled proportional cyclic loadings in axial and shear directions. In this stage, the aim was to confirm the anisotropic mechanical behaviour, which has recently been revealed. To this end, several models of fatigue damage quantification were used. After a comparative study between the obtained results we confirmed the anisotropic nature of the used material. In the second step, microstructural investigations were performed in order to understand the origins of the anisotropic mechanical behaviour. We used scanning electron microscopy to analyse phases and precipitates in the transversal and the longitudinal sections. It was deduced that the structure and the morphology of these entities are responsible for the anisotropic behaviour of the used aluminium alloy. Moreover, the results obtained using Kikushi diagrams, poles figure and inverse poles figures have also confirmed these conclusions. Indeed, these results have shown great differences in crystallographic texture of the material.

This work investigated the mechanical properties of glass/epoxy laminates reinforced by kaolin powder with graded properties by performing tensile, 3-point bending, impact tests, and compression after impact (CAI) tests. Firstly, we evaluated the effects of mixing parameters on particle dispersion and the effect of kaolin powder rate on the epoxy properties. It was found that the optimal parameters for a good distribution are a temperature of 60°C with 10 min of stirring time and the optimum kaolin powder rate is 5 wt %. Secondly, four graded heterogeneous laminates were elaborated with increased powder rate at each 1, 2, 3, and 4 layers named models 1/1, 2/2, 3/3, and 4/4, respectively. The test results showed that the powder gradient distribution considerably influences the behavior of the composite, with a significant improvement in mechanical properties compared to unreinforced glass/epoxy laminates. The model 1/1 on the top side exhibits the most significant increase in flexural modulus and maximum flexural strength, respectively, compared to the unfilled specimen. The impact tests showed that the powder distribution gradient is essential in absorbing the leading force and energy. The model 1/1 on the top side showed the best impact strength. According to this previous finding, adding ceramic particles in a polymer matrix; with a particular gradient distribution; significantly enhances the composite laminates' properties, especially under bending load. This heterogeneous composite type finds its application in closed structures where the load side is known, such as tanks and aircraft wings, and will allow a considerable weight gain.