During their operating life, electromechanical relays (EMRs) are subjected to external mechanical vibrations that can induce undesirable vibratory responses in the movable part of the relay and thus produce an unwanted temporary break in electric connections. This paper presents a simplified multiphysics model dedicated to the prediction of the maximum vibration levels that these relays can undergo before a loss of contact occurs. Our methodology considers the magnetic aspects as well as the mechanical aspects. The dynamic behaviour of the movable part is modelled as a cantilever beam subjected at its extremity to an elastic force. The dynamic parameters were updated from the identification of the first natural modes of the movable part of the relay. The magnetic force acting on the movable part was computed using a one-dimensional approach with an equivalent magnetic circuit and was corroborated thanks to experimental measurements and two-dimensional Finite Element simulations. The interaction between the electromagnetic and mechanical phenomena was taken into account using a parameterization coupled approach. Our methodology has been applied to the study of the PED PXC-1203 relay. The numerical predictions were validated using experimental data measured in the frequency range [2][3][4][5][6][7][8]. A parametric analysis of our model was performed and shows the influence of some factors, like the air gap and the rated voltage, that affect the performance of the relay under external mechanical vibrations.

This paper is concerned with the numerical simulation of mechanical structures subjected to pyroshocks. In practice, the methodology is applied on the pyroshock test facility, which is used by Thales to qualify the electronic equipment intended to be embarked onboard of spatial vehicles. This test facility involves one plate or two plates linked by screw bolts. The tested device is mounted on one side while the explosive charge is applied on the other side. The main issue of this work is to be able to tune, by simulation, the parameters of the facility (number of plates, material of plate, number of bolts, amount of explosive, etc.) so as to get the required level of solicitation during the test. The paper begins by an introduction presenting the state of the art in terms of pyroshock modeling, followed by a description of the shock response spectrum (SRS) commonly used to represent the test specifications of an embarked equipment. It turns out that there is a lack of computational techniques able to predict the dynamic behavior of complex structures subjected to high frequency shock waves such as explosive loads. Three sections are then devoted to the simulation of the pyrotechnic test, which involves on one hand a model of the structure and on the other hand an appropriate representation of the impulsive load. The finite element method (FEM) is used to model the dynamic behavior of the structure. The FEM models of several instances of the facility have been updated and validated up to 1000Hz by comparison with the results of experimental modal analyses. For the excitation source, we have considered an approach by equivalent mechanical shock (EMS), which consists in replacing the actual excitation by a localized force applied on the FEM model at the center of the explosive device. The main originality of the approach is to identify the amplitude and duration of the EMS by minimizing the gap between the experimental and numerical results in terms of the SRS related to several points of the facility. The identification has been performed on a simple plate structure for different amounts of explosive. The methodology is then validated in three ways. Firstly, it is shown that there is a good agreement between experimental and numerical SRS for all the points considered to identify the EMS. Secondly, it appears that the energy injected by the EMS is well correlated with the amount of explosive. Lastly, the EMS identified on one structure for a given amount of explosive leads to coherent responses when applied on other structures. A parametric study is finally performed, which shows the influence of the thickness of the plate, the material properties, the localization of the EMS, and the addition of a local mass. The different obtained results show that our pyroshock model allows to efficiently estimate the acceleration levels undergone by the electronic equipment during a pyroshock and, in this way, to predict some eventual electrical failures, such as the chatter of electromagnetic relays.

During space flights, pyrotechnic devices are widely used to separate structural subsystems, to unfold solar panels or to activate propellant valves. The firing of these pyrotechnic devices generates severe shock waves (so-called pyroshocks) with high intensity and wide frequency range, which can damage the surrounding electronic equipment. Common observed damages more especially concern relay chatter and transfer, as well as failure of magnetic components. There is a lack of failure criteria for electronic equipment as well as computational techniques able to predict the dynamic behaviour of complex structures subjected to high frequency shock waves. The pyrotechnic shock behaviour is checked experimentally: test specifications imposed through embarked electronic devices are generally defined as a maximum limit imposed to the Shock Response Spectrum (SRS). This paper describes a methodology to check the electrical and mechanical behaviours of some electromagnetic relays submitted to severe mechanical shocks. Experimental results obtained when checking the perturbations induced by shocks on the electrical behaviour of some relays, such as the latching GP250 relay are also presented. Microswitches levels have been correlated with the magnitude and shape of different Shock Response Spectra. This paper presents also a simplified model of electromagnetic relays allowing to predict the electrical dysfunctions such as the micro-openings. The model has been updated using experimental frequency and modal analysis.

An approach is proposed to identify the modal properties of a subsystem made up of an arbitrary chosen inner module of embedded space equipment. An experimental modal analysis was carried out along the equipment transverse direction with references taken onto its outer housing. In parallel, a numerical model using the finite element (FE) method was developed to correlate with the measured results. A static Guyan reduction has led to a set of master degrees of freedom in which the experimental mode shapes were expanded. An updating technique consisting in minimizing the dynamic residual induced by the FE model and the measurements has been investigated. A last verification has consisted in solving the numeric model composed of the new mass and stiffness matrices obtained by means of a minimization of the error in the constitutive equation method.