Tarek Merzouki

Finite Element analysis of a shape memory alloy actuator for a micropump

Abstract This paper deals with a Finite Element (FE) behavior analysis of a shape memory alloy actuator for a micropump. It is composed of two membranes of NiTi shape memory alloy (SMA) in a martensitic state at room temperature. They have an initial flat shape and are bonded together with an intermediate spacer. The thermal loading allows the actuator to move up and down in the membrane normal direction. A detailed analysis of sensibility to material and geometric parameters of the SMA actuator is undertaken by FE method. The actuation capability and reliability are studied in order to lead to optimal parameters set providing a higher stroke (deflection) with a low heating temperature. The shape memory effect exhibited by these membranes is simulated by means of the phenomenological constitutive law based on Chemisky–Duval model [1] , [2] , and implemented in the Abaqus® FE code. The obtained numerical results were detailed proving the ability of the proposed modeling to reproduce the actuator behavior under thermal loading. This analysis showed that it is possible to provide a large stroke for a minimal geometry of the actuator.

Reliability Based Design Optimization of Shape Memory Alloy

“Smart Materials” become more and more used due to their physical properties compared to other materials. Shape memory alloys (SMA) could be classified as one of them. Such material is characterized by the ability to remember its original shape after deformation. SMA provides high structural performance. However, this kind of material increases the cost of structures. Thus, optimization techniques have been applied in order to obtain minimum the volume structure. As SMA requires a global optimization tool, the evolutionary algorithms such as particle swarm optimization (PSO) is well suited. In deterministic optimization, the uncertainties of the system parameters are not taken into consideration. As a result, the optimal design obtained does not ensure the target reliability level. Thus, reliability based design optimization (RBDO) method was applied to provide an enhanced design. However, classical RBDO leads to high computational time. So, the purpose of this paper is to optimize SMA structure taking into consideration uncertainties in the structural dimensions. Therefore, a proposed RBDO methodology based on safety factors derived from Karush Kuhn Tucker (KKT) methodology coupled with PSO is developed. Compared to deterministic optimization, the proposed method guarantees the target reliability level of the structure but requires little extra computational effort.

Uncertainty analysis of an actuator for a shape memory alloy micro-pump with uncertain parameters

Abstract In this paper, we propose a method for taking into account uncertainties of a micro-pump system using Shape Memory Alloy (SMA), based on the perturbation method. The proposed method is used to determine the thermo-mechanical response of a system. Comparisons with the mean value reference solution, illustrate the efficiency of the proposed method. The results are discussed in order to investigate the influence of the most influential parameters of the thermomechanical SMA model. The simulation results are obtained by the proposed method for static analysis with uncertainties.The perturbation method results are compared with the mean value reference solution. The results are discussed in order to investigate the influence of the Youngs modulus E, the two transformations strain magnitude ɛ t r a c T and ɛ t r a c T F A , the martensite start Ms and austenite finish Af temperatures and the stress reorientation Fe on the static response of a micro-pump system.

Cooling of Circuit Boards Using Natural Convection

In this paper, we study the air cooling of circuit boards populated with multiple integrated circuits using natural convection. The simulation and the modeling results of the model are obtained by digital software Comsol Multiphysics. The results then accurately describe the heat transport and temperature changes. From such simulations, it is also possible to derive accurate estimations of the film coefficients. The objective is to determine the evolution of the temperature and the flow of the velocity of the fluid. The results show that the temperature of the ICs (the heat sources) increases considerably under a constant heating load from the components. The temperature increase of the sources varies from 30 K for the lowest IC up to 90 K at the top IC. For the velocity of the fluid, the circuit board contributes a large amount of cooling power on its backside, although the thermal conductivity is quite small.

Modelling of the Swelling of SiC-Based Refractory Lining Used in Waste-to-Energy Plants

This work provides a computational model of the chemo-mechanical behavior of based refractories used in waste to energy plant (WTE) linings. In this application, oxygen gas present in the atmosphere diffuses through the porosity and reacts with the refractory producing silica (SiO2). This new phase clogs gradually the pores and causes swelling of the refractory lining. The proposed thermo-chemo-mechanical model which simulates these phenomena is briefly summarized. The results obtained from the model implemented in a F.E code prove the ability of the model to reproduce qualitatively the swelling of post-mortem bricks taken from WTE linings.Copyright