The Contact of a Compliant Curved and a Nominally Flat Rough Surfaces

The contact problem of a compliant curved beam loaded by a rigid flat surface is analyzed. This problem is typical of compliant metallic configured seals and electrical connectors. Both the elastic deformation of the curved beam and elastic-plastic deformation of the asperities are considered. A model for calculating the contact parameters like minimum separation, contact length and real area of contact is developed. The effect of the applied load as well as the plasticity index and other geometrical variables on the various contact parameters is investigated. It is shown that, contrary to common intuition, smaller radius of curvature is beneficial for both the sealing and electrical connector applications.     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

Simulated Effects of Measurement Noise on Contact Measurements Between Rough and Smooth Surfaces

To test the accuracy of optically measuring contact, we examined the height distribution histogram of a simulated rough surface contacting a smooth surface. We qualified the technique sensitivity as a function of the inverse signal-to-noise ratio having values ranging from 0 to 0.3. An explanation of how the analysis technique can be applied to Dual Emission Laser-Induced Fluorescence (DELIF) measurements is provided.     

具有啮合齿面接触对的谐波传动有限元模型建立与分析

现有谐波传动有限元分析模型过于简化,与实际情况差别较大,为此,在ANSYS中建立带有整圈轮齿的刚轮和柔轮模型,利用其接触分析要素在啮合齿面间定义面-面接触对,使得各对轮齿在啮合时产生作用力,从而提出了一种与实际较接近的谐波传动有限元模型建模方法;以50机型为例,用该方法得到了负载作用下柔轮的等效应力、变形、各啮合齿面接...     

Theoretical and Experimental Study of a Thermal Contact Conductance Model for Elastic,Elastoplastic and Plastic Deformation of Rough Surfaces

This study developed a thermal contact conductance model that takes into account surface asperities with elastic, elastoplastic and plastic deformation. The surface asperity model considers the continuity and smoothness of variables across different modes of deformation. Experiments were also conducted to measure thermal contact conductance for samples with different surface roughness when the contact pressure was increased or decreased. The trend of the test data supports the theoretical results.     

On Material Removal Regimes for the Shaping of Glass Edges: Force Analysis,Surface Topography and Damage Mechanisms

Glass shaping, which corresponds to the removal of the edges of a specimen, is the last finishing operation in glass manufacturing. This process has several functions on the final shaped glass including removing sharp edges, improving mechanical resistance, decreasing surface damage and giving it an aesthetical aspect. This article addresses the effects of working parameters, including grinding forces and consumed power, on surface edge finishing and damage mechanism induced during glass grinding. Microscopic observations and multi-scale analysis have also been conducted to investigate the surface edge characteristics. Experimental results show three damage regimes. The first (regime I) is a partial ductile regime with cutting action accompanied by chip formation. The second (regime II) is a crushing (or fragmentation) regime. The last (regime III) is also a partial ductile regime but by ploughing action with displaced material. The shaped surface obtained in the regime II has a better roughness than that obtained in regime I and III. However, regimes I and III include streaks and form defects which are not present in regime II. Similar to metallic materials, the evolution of force components show a linear relationship between normal and tangential forces. This implicates a constant average contact pressure and friction coefficient (μ) between the flat grains and the workpiece.     

Discussion of the Paper: Optical In Situ Micro Tribometer for Analysis of Real Contact Area for Contact Mechanics, Adhesion, and Sliding Experiments

The article by Krick et al. [1], describes an optical in situ tribometer that was used to study the contact area of an elastic sphere loaded against a transparent rigid flat under various loading conditions. A few comments relevant to the presented tribometer and study are in place for the benefit of the readers interested in this field of contact mechanics.     

A Novel Method for Quantitative Determination of Ultra-low Wear Rates of Materials, Part II: Effects of Surface Roughness and Roughness Orientation on Wear

A novel method of measurement of the very low wear-rates of materials in the ultra-mild wear regime, which involves the use of implanted gold as a marker, was used to understand the effects of surface roughness and roughness orientation on wear under reciprocating sliding conditions. AISI 1095 steel coupons with various Vickers hardness values and different surface roughness and roughness orientation relative to the sliding direction were tested under the same sliding conditions. It was found that parallel sliding causes more wear compared with transverse sliding for the harder samples (Vickers hardness (VH); 450 HV, 650 HV and 1000 HV). Furthermore, the average friction coefficient of parallel sliding is also higher than that of transverse sliding for these samples. Severe wear takes place when the samples are too soft (250 HV), resulting in the complete loss of implanted gold. Surface topographic images were taken before and after the wear tests. It was found that parallel sliding dramatically increases the surface roughness, while transverse sliding does not increase the surface roughness for harder samples (450 HV, 650 HV and 1000 HV). For the soft sample (250 HV), the surface roughness increases significantly under parallel or transverse sliding.