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Introduction Tres utilisee en pratique courante dans l’enseignement de l’anatomie pathologique, la metaphore designe le savoir par une connaissance de l’apprenant (mot, objet ou idee) liee au savoir par une analogie. On utilise un connu de l’apprenant (connaissance) pour presenter un tout (savoir) de maniere coherente (faire comprendre) sans que l’apprenant novice accede aux attributs du tout (savoir) de maniere profonde. La metaphore cherche a expliciter le lien qui existe entre connaissance generale et connaissance particuliere. Objectif Evaluer l’utilite des metaphores dans l’apprentissage de l’anatomie pathologique. Methodes Nous avons elabore un petit aide-memoire comportant un recueil des differentes metaphores couramment utilisees en anatomie pathologique qui facilitent l’ancrage des connaissances aussi bien des externes en medecine que des residents en anatomie pathologique. Nous avons mene une enquete de satisfaction de ce manuel aupres des etudiants de 3e annee de medecine et des residents en anatomie pathologique. Notre etude s’etait basee sur un questionnaire ecrit. Resultats L’analyse de la perception du manuel des metaphores a revele que les etudiants DCEM1 ainsi que les residents etaient globalement satisfaits et appreciaient les illustrations qui y figurent. Selon les residents en anatomie pathologique, il s’agit d’un outil d’apprentissage concis, precis et ludique permettant l’ancrage des connaissances. Conclusion La metaphore est un instrument cognitif fondamental. Dans l’apprentissage de l’anatomie pathologique, une des competences a developper serait de rendre l’etudiant attentif aux traces d’images conceptuelles dans les recits : « imaginaires qui facilitent ou empechent les communications, les relations, les cooperations et induisent la meconnaissance, l’impense des fixations et qui peuvent tout autant favoriser des constructions creatrices que conduire a des phenomenes destructeurs ».

Studies of connectors for electric and electronic automotive systems have been and still are being pursued. The electrical connector reliability mainly depends on the connector insertion force. This force is related to the contact force which is imposed by the connector design. A nonintrusive technique for contact force determination by deflection measurement of the contact spring during insertion phase using a laser device has been developed. The following insertion parameters during the insertion stroke can be measured: contact deflection which yields the contact force, insertion force, and contact resistance. Regarding the results for real connectors, an experimental sample of a connector based on a cylindrical pin crossed with a cylindrical spring is proposed in this paper. With this simple setup, an mathematical model was developed and permits analysis of the influence of each parameter (width, spring radius, etc). Based on analysis of the influence of the spring width and of the gap, this study offers the possibility of optimizing the design of such connectors for use in the automotive industry.

Automotive connector ageing has been studied in the literature, but none of these studies is completely satisfactory for finding the relation between the insertion force, the contact surface, and the spring deflection and wear after several insertion phases. The main objective of this work is to find and establish a correlation between insertion parameters and wear behaviour using numerical and experimental approaches. This study is concerned with automotive connectors made of copper with a tin coating of thickness 2 μm. The evolution of the insertion force, spring deflection, and contact surface versus the insertion—extraction operation number will provide information about the connector wear behaviour. Using a microbalance, the mass of the sample was determined before and after the experimental insertion test, to quantify the mass loss and the wear evolution. In addition, the wear shape was analysed. The connector includes four spring lamellae on each side and the pin has a flat shape. Owing to the friction effect and after several insertion—extraction tests, eight tracks are visible. Using a scanning profilometer, the length, the depth, and the width of the track can be measured. At the same time, a numerical analysis using the finite element code Ansys is used with an elastoplastic behaviour law to find the fatigue law, to measure the contact surface, and to predict the wearing surface for the materials employed, which can support a long connector use period. The selected assumptions introduced in the numerical modelling lead to a good correlation with the experimental results.

In a previous work we observe that the vibration of contact interfaces is the main cause of contact voltage fluctuations due to the so called fretting corrosion phenomenon. In fact the process of generated particles by mechanical wear produce the increase of contact voltage frequently assimilated as high contact resistance. The main objective of this work is to examine conjointly contact voltage and the occurrence of arcs during the well-known three successive fretting phases. The arc voltage is measured during fretting with set oscilloscopes which plot the arc voltage histograms in real time. So, a histogram is built and arc duration is determined and the position on the track of fretting. We applied a voltage of 16V and a current of 3A. Samples extracted from commercial contact are used and fixed on vibration system (frequency 20Hz and relative displacement of 0.8 mm). The main results show that the arcs are observed during the first and final phase of fretting. We assume that after the initiation period of fretting, the wear is increased and induce the increase of the contact voltage and it reaches few hundred millivolts (melting and fritting voltage) and induce micro-arcs. In the second phase, it seems that number of arcs decreases. Finally in ultimate stage of degradation, intermittent arcing voltage is detected close 12V due to bounce on degraded surface filed wear debris.

For automotive applications, the stability of the supplied electric power depends of the change of electrical resistance. For the case of automotive connectors, an electrical current goes through the connector wire and can be perturbed by the mechanical behaviour of the connector contact area under vibrations and temperature. Such vibrations on the bulk contact device are typically in the range of 10 Hz–2000 Hz and result in displacements of only a few microns at the contact interface. In the present study, a bench test has been developed to control motions down to 1μm. The objective is to determine the minimum amplitude for fretting-corrosion degradation based on the evolution of contact resistance and to study the effects of the temperature. It was found that the fretting degradation depends on vibration displacements, used materials, loading and applied temperature.

Comfort, safety, communication, control with assistance (antilock brake system, seat heating, multimedia, etc.), and safeguarding the environment are many factors that are included in the new generation of vehicles. The increase in the number of electronic and electric systems leads to a high level of vehicle control. To answer this high electric power demand, it will be necessary to triple the voltage of the batteries (from 14 to 42 V). The objective of this work is to study the arc phenomenon that can occur in an accidental way during the use of a high electric power and particularly during the extraction phase of the male part from the female part of the automotive connector. It was observed that this can be characterized by both its energy and its temperature. The amplification of the contact current from 14 to 42 V d.c. considerably increases arc damage.

This case-control study found an association between Seasonal Affective Disorder (SAD) and a single nucleotide polymorphism (intronic rs2072621) of the gene encoding GPR50 (an orphan member of the G protein-coupled melatonin receptor subfamily) in females. This may represent a gender-specific risk factor and a molecular link between melatonin and SAD.

Fretting corrosion phenomenon is known as the main cause of contact resistance increasing in signal contact. But for power connectors this undesirable phenomenon in embedded systems is more complex because high current induces high voltages and subsequent Joule overheating can be expected during vibration. Our study deals with contact similar power connectors, ones submitted to vibration amplitudes up to 25 micrometres at frequencies of a few 10Hz under a current ramp from 0.1 to 40A under 14VDC. The main measured parameters are the contact voltage during vibration up to a hundred thousand cycles. The average voltage by micro-voltmeter and its fluctuations during one cycle are acquired permanently by oscilloscope. Thermal aspects are also investigated by the use of miniature thermocouples placed as close as possible to the contact zone. It was found that a limiting voltage is reached, similar to the fritting voltage in a tarnished metal film reported by Holm. So contact resistances and the power brought by Joule effect are reduced and the temperature rise is limited. The main factors which playing a role are current, contact materials and its susceptibility to wear and debris oxidation at the interface. This behaviour is confirmed by the SEM-EDX analysis of fretting zone at different steps of fretting.

Contact resistance is usually determined by the ratio of the voltage to the current and the increase of this value means that the contact interface is degraded. However for high currents, this ratio is not constant so Ohm's law does not apply. In this paper, we study the electrical behaviour through degraded surface materials (Ag and Ag with various metal oxides) aged by break arcing up to 90A at 42V DC with a contact force of 14N. In order to make a current voltage characteristic, the samples are tested with increasing current (I) from 50mA to 75A and then decreasing from 75A to 50mA. The main result is that the proportionality between the current and the voltage is ensured up to 70mV. Beyond this value this proportionality is lost and voltage break down takes place at different level of fritting voltage. However this phenomenon is frequently observed during the first applied current ramp (increasing), and disappears at the decreasing current ramp and during further tests. Discussions here are given concerning the constant fritting voltage over a wide current range being related to the breakdown of thin oxide films on the degraded surface and/or the creation of additional contact spots.

International audience; A connector provides a separable interface between two subsystems of an electronic system. The main function of the connector is to transmit a signal or distribute power. For power connectors, heating can lead to an increase in contact resistance and sometimes even to contact surface melting and thus to connector damage. In this study, the mechanical behaviour and heat evolution of a commercial power connector used in the automotive industry was undertaken. Using an experimental set-up, the mechanical insertion force, the temperature and the resistance evolution were measured. To quantify these parameters at the contact zone, two numerical modellings, using the finite element software Ansys, were employed to give the change of the insertion force during several insertion-extraction cycles and to solve the differential equations for heat transfer in a transitory mode. Adapted values of thermal and electrical contact conductances introduced into the numerical modelling, resulted in good values for both contact resistance and contact temperature, which were verified by experiments.

International audience; High copper alloys were required by the industry to improve mechanical and electrical contact resistance for connecting device. This work addresses the electrical contact resistance law versus force in the range (1-100 N) for sphere/plan shapes. The designed samples are submitted to indentation (static contact) and insertion (sliding contact). Experimental power law of contact resistance versus forces was obtained where the law parameters are well related to electrical resistivity, Young modulus, yield stress... Previous analytical relationship R(c) = f(F(c)) in the literature and finite element simulation code are used to discuss the origin and the validity of such practical power law. Nevertheless the analytic expression are found unsatisfactory, the numerical model gives some agreement with this previous experimental law. However better convergence between numerical and experimental data was obtained in indentation when the surface topography is considered. The obtained results are a useful tool to evolve compromise between the electrical and mechanical aspects for a high loading contact. The main statement is that numerical model including the real topography and roughness is robust so it can be used in different contact shape and complex design for contact resistance evaluation. Finally, depending on the hardness and the resistivity, these uncoated materials were found to act on fretting apparitions and its level.

Semi-permanent electrical contacts are found throughout the whole range of instrumentation and control product, connecting devices. The reliability of this kind of connector - designed for long lifetime service is highly dependant on mechanical and corrosion degradations. In this domain, corrosion is avoided by using a thick gold layer while the major cause of connector ageing remains the contact spring degradation (relaxation, loss of force…) leading subsequently to a change of contact resistance. In this paper, a non intrusive (laser) technique is used to view and measure both the deflection and its associated force. These techniques and tools are applied both to new springs and to degraded springs. In the absence of an analytical model due to the complex geometry of the spring, a numerical finite element model has been developed to compute the deflection versus force. Linear deflections are observed for various stiffnesses for different springs located in the same connector. The main explanation for this change is the variation of the embedding length of the spring inside the connector. In addition the stiffness dependence due to ageing by thermal cycling is discussed.

Studies of connectors for electric and electronic automotive systems have been and still are being pursued. The main criterion for the electrical contact reliability is to minimize the connector insertion force, which mainly depends on the contact force determined by the mechanical design. A non-intrusive technique for contact force determination by deflection measurement of the contact spring during insertion and extraction phase using a laser device has been developed. We have access to the following insertion parameters during the insertion stroke: contact deflection /spl delta/ which yields the contact force F/sub c/, insertion force F/sub i/ and contact resistance R/sub c/. Regarding the results for real connectors, an experimental model of a connector based on a cylindrical pin crossed with a cylindrical spring, is proposed in This work. With this simple setup, we have made an analytical model, which permits analysis of the influence of each parameter (width, spring radius etc). Based on analysis of the influence of the spring width and of the gap, this study offers the possibility of optimizing the design of such connectors for use in the automotive industry.

Pulse plated nickel coatings on copper and copper alloys were investigated in view of their use as underlayer in Au/Ni/Cu or as external protective coatings. Deposition parameters were varied in order to determine their influence on the microstructure and consequently on the electrical contact properties of the electrodeposited Ni films. Roughness and hardness measurements as well as SEM studies were performed on these samples. Smooth and dense coatings were obtained for high pause-to-pulse ratio, 25-75 Hz pulse-plating frequencies and low current density. The contact resistances R/sub c/ of the as-deposited samples in approach and insert mode were measured versus load F/sub c/ in the range 0.1-10 N. It was found that initial contact resistance follows the power law R/sub c/=KF/sub c//sup -n/ where n is hardness and coating topography dependent. Moreover, aging samples in daily cyclic atmosphere shows an increase in contact resistance during the test, but ohmic behaviour prevails as verified by the current-voltage characteristics. Finally, the mechanical behaviour investigated by a fretting study shows that the pulse reverse condition improves contact resistance stability.