Santosh Angadi

A Multi-Physics Finite Element Model of an Electrical Connector Considering Rough Surface Contact

Any engineering component possesses roughness on its surface when it is observed microscopically, including electrical connectors. Electrical connectors usually consist of a spring and a pin. In this study, the spring part is in the shape of a compliant curved beam whereas the pin one is of a flat form and these two parts are in contact during operation. This work presents a multi-physics (structural, electrical and thermal) finite element model of the bulk region of an electrical connector. The rough surfaces of the spring and pin parts are considered using a multi-scale sinusoidal rough surface (MSRS) contact model. The resulting coupled multi-physics connector model is used to analyze the performance of the connector while the applied current is incremented from 5 to 20 A. As expected, this produced a proportional rise in voltage drop and temperature across the bulk regions of the connector parts. The coupled multi-physics model together with the MSRS model should provide greater accuracy in the prediction of contact forces, electrical contact resistance (ECR) and thermal contact resistance (TCR). The present work also provides valuable information on stresses and strains distributions, current flow and temperature variations in the bulk regions of the electrical connector.

A Simplified Model of Multiscale Electrical Contact Resistance and Comparison to Existing Closed Form Models

The prediction of the electrical contact resistance due to the contact of rough surfaces is important for electrical connectors, relays, circuit breakers, compliant pins, and many other applications. When modeling the contact between surfaces it is important to consider the multiple scales of roughness that exist. Many recent rough surface contact models exist in the literature, but can be difficult to implement. The current work derives and presents a simplified closed-form multiscale model of electrical contact resistance. The results are then compared to other existing closed form models of rough surface contact. The comparison shows that some existing models are in relatively close agreement with the multiscale model results which adds validity to both.

A Multiphysics Finite Element Model of a 35A Automotive Connector Including Multiscale Rough Surface Contact

Electrical contacts influence the reliability and performance of relays, electrical connectors, high power connectors, and similar systems, and are therefore a key region which needs to be considered. In the current study, a new inclusive multiphysics (involving mechanical, electrical, and thermal fields) finite element model (FEM) of a 35A automotive connector has been developed. The contact resistance is predicted using a multiscale rough surface contact method and is embedded in the multiphysics FEM. The coupled connector model is solved to obtain stresses, displacements, contact pressures, electrical and thermal contact resistances, voltage, current density, and temperature distributions. It appears that the current flows mostly through very small regions that are usually near the contacting surfaces in the connector, thereby suggesting that the available conducting material can be more efficiently used by developing optimized connector designs. Through analytical calculations and experimental measurements of temperature rise (ΔT or change in temperature) for the cable and the connector, it is believed that a large portion of the temperature rise in actual 35A connectors is due to the Joule heating in the supply cables. The model is a powerful tool that can be used for the basic connector characterization, prototype evaluation, and design through various material properties, and surface finishes.

The Effect of Initial Connector Insertions on Electrical Contact Resistance

This work attempts to quantify the effect of repeated initial connector insertions and roughness on electrical contact resistance. Experimental measurements show that the electrical contact resistance increases measurably with repeated insertions. They also show that with repeated insertions the connector spring is plastically deformed, thus causing the force closing the contact across the surfaces to decrease. A multi-scale rough surface contact model was used to estimate the actual electrical contact resistance (ECR) versus applied force curve of the connector. As expected, the multiscale ECR model predicts that the ECR will decrease with applied force. Since the contact force decreases with each insertion of the connector due to plastic deformation, the model will predict that the ECR will also increase with each insertion. When the added resistance from a measurable layer of tin oxide is included, the multiscale ECR model shows fairly good agreement with the experimental measurements.

Reliability and Life Study of Hydraulic Solenoid Valve - Part 1 - A Multi-physics Finite Element Model

A comprehensive multi-physics theoretical model of a solenoid valve used in an automobile transmission is constructed using the finite element method. The multi-physics model includes the coupled effects of electromagnetic, thermodynamics and solid mechanics. The resulting finite element model of the solenoid valve provides useful information on the temperature distribution, mechanical and thermal deformations, and stresses. The model results predict that the solenoid valve is susceptible to a coupled electrical–thermomechanical failure mechanism. The coil can generate heat which can cause compressive stress and high temperatures that in turn could fail the insulation between the coil wires. The model facilitates the characterization of the solenoid valve performance, life and reliability and can be used as a predictive tool in future solenoid design. 2008 Elsevier Ltd. All rights reserved.

A Study of the Average Real Contact Pressure Between Rough Surfaces

It is well known that the friction, wear, fatigue life, and contact resistance (electrical and thermal) are dependent on the contact between the rough profiles of the surfaces. Several different techniques have been used to model this contact (fractal, wavelet, statistical, multiscale, and deterministic methods). Several of these methods have found that the relationship between the real area of contact and load is linear. This suggests that there is a constant contact pressure between two surfaces (the average real contact pressure). Somewhat surprisingly, several works have found that this pressure may be greater than traditional hardness, even when the contact is heavily loaded and the contacts are deforming plastically. This mechanism is often called the asperity persistence. The current work uses a recent multiscale contact model and other theories to explain this mechanism and to help predict the average real contact pressure, especially during heavily loaded contacts.Copyright

Reliability and Life Study of Hydraulic Solenoid Valve - Part 2 - Experimental Study

Article history: Received 3 July 2008 Accepted 2 August 2008 Available online 15 August 2008

Surface Separation and Contact Resistance Considering Elasto-Plastic Multi-Scale Rough Surface Contact

The current work considers the multiscale nature of surface roughness in a new model that predicts the real area of contact and surface separation, all as a function of load. By summing the distance between the two surfaces at all scales, a model of surface separation as a function of dimensionless load is also obtained. The model is also able to make predictions for thermal (and electrical) contact resistance. In striving for a more realistic model, the multi-scale model accounts for the effects of a rough surface geometry ranging from macro down to the nano scale. A previous rough surface contact model was based on stacked elasto-plastic spheres. This work uses stacked 3-D sinusoids to represent the asperities in contact at each scale of the surface. The results are also compared to several other existing rough surface contact models and experimental results.© 2007 ASME