Estimation Of Contact Area Research Articles

Estimation of Tyre Deflection and Contact Area of Tubeless Tyre on Firm Surface for Traction Studies

Estimation of Tyre Deflection and Contact Area of Tubeless Tyre on Firm Surface for Traction Studies

Fundamental study on estimation of tooth contact area based on combined image from temperature monitor images of tooth surface with a high-speed-camera thermography and on meshing vibration for high reduction ratio hypoid gear with a three-tooth pinion

Fundamental study on estimation of tooth contact area based on combined image from temperature monitor images of tooth surface with a high-speed-camera thermography and on meshing vibration for high reduction ratio hypoid gear with a three-tooth pinion

Estimating Facet Joint Apposition with Specimen-Specific Computer Models of Subaxial Cervical Spine Kinematics.

Computational models of experimental data can provide a noninvasive method to estimate spinal facet joint biomechanics. Existing models typically consider each vertebra as one rigid-body and assume uniform facet cartilage thickness. However, facet deflection occurs during motion, and cervical facet cartilage is nonuniform. Multi rigid-body computational models were used to investigate the effect of specimen-specific cartilage profiles on facet contact area estimates. Twelve C6/C7 segments underwent non-destructive intervertebral motions. Kinematics and facet deflections were measured. Three-dimensional models of the vertebra and cartilage thickness estimates were obtained from pre-test CT data. Motion-capture data was applied to two model types (2RB: C6, C7 vertebrae each one rigid body; 3RB: left and right C6 posterior elements, and C7 vertebrae, each one rigid body) and maximum facet mesh penetration was compared. Constant thickness cartilage (CTC) and spatially-varying thickness cartilage (SVTC) profiles were applied to the facet surfaces of the 3RB model. Cartilage apposition area (CAA) was compared. Linear mixed-effects models were used for all quantitative comparisons. The 3RB model significantly reduced penetrating mesh elements by accounting for facet deflections (p=0.001). The CTC profile resulted in incongruent facet articulation, whereas realistic congruence was observed for the SVTC profile. The SVTC profile demonstrated significantly larger CAA than the CTC model (p<0.001).

Vision-Based Tactile Sensor Mechanism for the Estimation of Contact Position and Force Distribution Using Deep Learning.

This work describes the development of a vision-based tactile sensor system that utilizes the image-based information of the tactile sensor in conjunction with input loads at various motions to train the neural network for the estimation of tactile contact position, area, and force distribution. The current study also addresses pragmatic aspects, such as choice of the thickness and materials for the tactile fingertips and surface tendency, etc. The overall vision-based tactile sensor equipment interacts with an actuating motion controller, force gauge, and control PC (personal computer) with a LabVIEW software on it. The image acquisition was carried out using a compact stereo camera setup mounted inside the elastic body to observe and measure the amount of deformation by the motion and input load. The vision-based tactile sensor test bench was employed to collect the output contact position, angle, and force distribution caused by various randomly considered input loads for motion in X, Y, Z directions and rotational motion. The retrieved image information, contact position, area, and force distribution from different input loads with specified 3D position and angle are utilized for deep learning. A convolutional neural network VGG-16 classification modelhas been modified to a regression network model and transfer learning was applied to suit the regression task of estimating contact position and force distribution. Several experiments were carried out using thick and thin sized tactile sensors with various shapes, such as circle, square, hexagon, for better validation of the predicted contact position, contact area, and force distribution.

Modeling of 3D Surface Morphologies for Predicting the Mechanical Contact Behaviors and Associated Electrical Contact Resistance

The accurate estimation of real contact area plays an important role in predicting the mechanical contact situation and associated electrical contact resistance for engineering rough surfaces. In this work, an improved peak identification method is proposed to reconstruct the rough surface morphologies numerically. A universal calculation process of real contact area and load force under the progressive indentation depth for rough surfaces is developed. Furthermore, a three-dimensional finite element model for analyzing the mechanical contact problem is built and the electromechanical coupling simulation results are compared with that obtained by our novel calculation method. The proposed solution is beneficial for accurate calculation of contact area, which is featured by high aspect ratio in the case of micro-contact. The relationship between electrical contact resistance and load force is also captured in the initial contact process.

Finger Pad Topography beyond Fingerprints: Understanding the Heterogeneity Effect of Finger Topography for Human-Machine Interface Modeling.

With the rapid development of haptic devices, there is an increasing demand to understand finger pad topography under different conditions, especially for investigation of the human-machine interface in surface haptic devices. An accurate description of finger pad topography across scales is essential for the study of the interfaces and could be used to predict the real area of contact and friction force, both of which correlate closely with human tactile perception. However, there has been limited work reporting the heterogeneous topography of finger pads across scales. In this work, we propose a detailed heterogeneous finger topography model based on the surface roughness power spectrum. The analysis showed a significant difference between the topography on ridges and valleys of the fingerprint and that the real contact area estimation could be different by a factor of 3. In addition, a spatial-spectral analysis method is developed to effectively compare topography response to different condition changes. This paper provides insights into finger topography for advanced human-machine interaction interfaces.

Using a conductive sphere as a probe to characterize the sensitivity of soft piezoresistive films

AbstractFlexible piezoresistive films, such as, carbon black/polydimethylsiloxane (C‐PDMS) composites, are often used as skin analogs and integrated into complex array sensors for tactile sensing. The uniformity of the sensor characteristics heavily depends on the homogeneity of the composite. Therefore, the ability to locally characterize a film that will be integrated into a complex force sensor could be critical. Here, a method to characterize the local sensitivity of flexible piezoresistive films is presented. Using a conductive sphere, which was chosen over a flat probe to eliminate misalignment issues, the surface of a thin film composite is indented to characterize the change in resistivity in terms of average strain. Experiments were performed with 15 and 18 wt% carbon black C‐PDMS films of varying thickness. The contact radius of the probe with the piezoresistive film was estimated using the Johnson‐Roberts‐Kendall contact theory. Theoretical contact area estimates were found to agree with contact radius measurements carried out using optically transparent PDMS films observed through an optical microscope. Results show that C‐PDMS with 15 wt% carbon black exhibit a higher rate if change of resistivity and gauge factor than films of same thickness with 18 wt% carbon black. On the other hand, thicker films exhibit higher gauge factors for the two tested carbon black contents. Tests carried out at multiple locations yielded consistent sensitivity values, making these types of composites suitable for array type force sensors.

Contact area and thermal conductance estimation based on the actual surface roughness measurement

Thermal contact conductance (TCC) plays a vital role during any thermo-mechanical based analysis of the contacting surfaces. Inherently, it depends upon the actual contact-area at the interfaces, which is quite complex to estimate. This work aims to perform the micro-contact based structural, and thermal analysis of stochastically re-created rough surfaces, while using actual surface profile measurement, and proposes an experimentally validated FEM based approach for real contact area and TCC estimation. Different surface topography parameters estimation methods are compared, and a semi-deterministic based approach is evolved for the construction of surface topographies from actual roughness measurements. The asperities interactions and large deformation effects are incorporated during analysis. Close agreement between numerical and experimental TCC values shows the efficacy of the present approach.

A Study of Contact Interface for an Anti-Rotation Rivet Using Ultrasonic Detection

This work measures the contact area between an anti-rotation rivet and an aluminum plate under different riveting loads based on the regional scanning of ultrasound. The contact image is a novel disclosure for the anti-rotation rivet contact. The 2D maps show an apparent change not only in area sizes but also in contact shapes under various normal forces applied. The 3D contact images also provide useful information to show the intensity of contact. The contact area between the anti-rotation rivet and the aluminum is calculated using an image analysis software package. The range of contact areas varies from 6.3 mm2 to 57.2 mm2, depending on the applied forces and the definition of the contrast ratio. Furthermore, a calibration of data fitting is performed to provide a useful polynomial equation for contact area estimation. In addition, maps of both a reflection coefficient and a pressure contour distribution are presented. The range of peak contact pressure varies from 7.1 MPa to 11.2 MPa.

Conductive contact area estimation for carbon nanotube via interconnects using secondary-electron imaging

A major challenge for carbon nanotube (CNT) to become a viable replacement of copper and tungsten in the next-generation on-chip via interconnects is the high contact resistance between CNT and metal electrodes. A first step in meeting this challenge is an accurate characterization of via contact resistance. In this paper, the scanning electron microscope (SEM) image contrast at low landing energy is employed to estimate the conductive CNT area inside vias. The total conductive CNT area inside each via is deduced using SEM image with 0.1 keV landing energy and a specified threshold brightness, yielding via resistance versus CNT area behavior, which correlates well with electrical nanoprobing measurements of via resistance. Monte Carlo simulation of secondary electron generation lends further support for our analysis and suggests that the residue covering the CNT does not affect the conduction across the contact for residue thickness below 1 nm. This imaging and analysis technique can add much value to CNT via interconnect contact characterization.

Contact simulation of soft micro/nano bioparticles for use in identification of mechanical properties and manipulation based on atomic force microscopy

The aim of this paper is to develop and simulate elastic-perfectly plastic contact theories for proper determination and estimation of contact area in manipulation of micro/nano bioparticles. The n...

The effect of microscale residual stress from thermal cooldown on the nanoindentation properties of fibre-reinforced composites

A two-step finite element framework is presented that examines the effect of microscale thermal residual stress on the nanoindentation properties of fibre-reinforced composites. Firstly, micromechanical modelling is used to determine the residual stress state following thermal cooldown of a carbon-fibre composite material from cure temperature. A three-dimensional finite element nanoindentation model is then used to characterise the effects of residual stress on material properties determined by nanoindentation theory. The results show that the hardness of the matrix pockets decreases following thermal cooldown due to the existence of equibiaxial tensile residual stresses. The hardness property is also found to decrease for the majority of interfacial region stress states, while the microstructural areas where the effects of the residual stress are nullified are determined. The indentation modulus property is relatively insensitive to the microstructural residual stress, and thus is the recommended indentation property to be determined when carrying out a comparative parametric analysis between microstructural regions. The property changes are shown to be insensitive to any errors associated with contact area estimation using the Oliver and Pharr method.

Estimation of real contact area during sliding friction from interface temperature

Frictional heat is one of the most important topics in tribological research. The real contact area of the frictional pair plays a significant role in accurately estimating the interface temperature, which is closely related to the frictional heat. However, conventional methods for measuring the contact area, such as constriction resistance measurements, are not suitable for dynamic frictional motion because of the electrical and thermal interferences at the contact region. In this study, a novel method is presented for estimating the real contact area during sliding friction. First, the average interface temperature was experimentally measured by the dynamic thermocouple method. Then assuming that the total frictional heat power is constant, the measured temperature was used as a constraint to determine the contact area in a finite element model, giving an estimation for the real contact area. The calculation results show that the real contact area increases with increasing normal load as predicted by contact theories, and decreases with increasing sliding speed, which could be attributable to the contact dynamics of asperities at the interface. Additionally, the limits of the proposed method is discussed.

Validation of a method for combining biplanar radiography and magnetic resonance imaging to estimate knee cartilage contact

Combining accurate bone kinematics data from biplane radiography with cartilage models from magnetic resonance imaging, it is possible to estimate tibiofemoral cartilage contact area and centroid location. Proper validation of such estimates, however, has not been performed under loading conditions approximating functional tasks, such as gait, squatting, and stair descent. The goal of this study was to perform an in vitro validation to resolve the accuracy of cartilage contact estimations in comparison to a laser scanning gold standard. Results demonstrated acceptable reliability and accuracy for both contact area and centroid location estimates. Root mean square errors in contact area averaged 8.4% and 4.4% of the medial and lateral compartmental areas, respectively. Modified Sorensen-Dice agreement scores of contact regions averaged 0.81 ± 0.07 for medial and 0.83 ± 0.07 for lateral compartments. These validated methods have applications for in vivo assessment of a variety of patient populations and physical activities, and may lead to greater understanding of the relationships between knee cartilage function, effects of joint injury and treatment, and the development of osteoarthritis.

Fuzzy logic system based prediction effort: A case study on the effects of tire parameters on contact area and contact pressure

Various methodologies of artificial intelligence have been recently used for estimating performance parameters of soil working machines and off-road vehicles. Due to nonlinear and stochastic features of soil–wheel interactions, application of knowledge-based Mamdani max–min fuzzy expert system for estimation of contact area and contact pressure is described in this paper. Fuzzy logic model was constructed by use of the experience of contact area and contact pressure utilizing data obtained from series of experimentations in soil bin facility and a single-wheel tester. Two paramount tire parameters: wheel load and tire inflation pressure are the input variables for our model, each has five membership functions. As a fundamental aspect of the fuzzy logic based prediction systems, a set of fuzzy if-then rules were used in accordance with fuzzy logic principles. 25 linguistic if-then rules were included to develop a complicated highly intelligent predicting model based on Centroid method at defuzzification stage. The model performance was assessed on the basis of several statistical quality criteria. Mean relative error lower than 10%, satisfactory scattering around unity-slope line (T), and high coefficient of determination, R2, were obtained by the fuzzy logic model proposed in this study.

Methods and numerical aspects of nanoscopic contact area estimation in atomistic tribological simulations

We show how data obtained from molecular dynamics (MD) simulations of nanoscale friction should be treated for producing constitutive system parameters with a proper error estimation. A visualisation scheme for discrete atomistic geometries based on the smooth particle method (SPM) was parametrised and validated to yield an accurate and computationally robust estimation of the contact area between two touching nanoscopic asperities. We present some thoughts on the error estimation of the contact forces occurring due to the load and the shearing motion. The variance in the friction force constitutes the main source of error for the fitting of the constitutive system parameters. The dependence of the constitutive system parameters on the number of available data points was also studied. It was shown that an equal spacing (by load) of the data points can result in better values for the system parameters than the convergence trend suggests.

A Numerical Contact Model Based on Real Surface Topography

A numerical finite element contact model is developed to make use of the high precision surface topography data obtained at the nanoscale by atomic force microscopy or other imaging techniques while minimizing computational complexity. The model uses degrees of freedom that are normal to the surface, and uses the Boussinesq solution to relate the normal load to the long-range surface displacement response. The model for contact between two rough surfaces is developed in a step-by-step manner, taking into account the far-field effects of the loads developed at asperities that have come to contact in previous steps. Method accuracy is verified by comparison to simple test cases with well-defined analytical solutions. Agreement was found to be within 1 % for a wide range of practical loads for the high precision models. Applicability of extrapolation from lower precision models is presented. The real contact area estimates for micrometer-size tribology test machine surfaces are calculated and convergence behavior with mesh refinement is investigated.

Modeling pharmaceutical compacts tensile strength based on viscoelastic properties

Abstract Although several researchers acknowledge the effects of viscoelasticity in pharmaceutical powder compaction, no models have been reported that relate compact mechanical properties to the powder viscoelastic properties. The tensile strength of a compact is largely influenced by contact area between deforming particles which depends on the viscoelastic properties and compaction variables. The objective of this research was to develop semi-mechanistic models based on viscoelastic contact area estimates, to predict tensile strength of Microcrystalline Cellulose (MCC) and Acetaminophen (APAP) compacts. Formulations with varying amounts of MCC, APAP and moisture contents corresponding to 50 and 70% RH were prepared. The powders were compressed in a Uniaxial testing machine (Instron) at a punch velocity of 2 mm/min to final pressures in the range of 12.5 to 44 MPa. The diametral tensile strength, compaction and viscoelastic properties were determined. The deformation contact area was estimated using equation by Lum and Duncan-Hewitt [22] based on the median particle size of MCC, compaction and viscoelastic properties as determined from the Maxwell model. It was found that the estimated contact area depended on the APAP composition, moisture content and on compaction pressure. The viscoelastic contact area, density and final compact tensile strength were found to increase with increasing compaction pressure, moisture content and MCC. A unified model that expresses the compact tensile strength as a function of viscoelastic contact area was successfully developed.

Comparison of MRI-Based Estimates of Articular Cartilage Contact Area in the Tibiofemoral Joint

Knee osteoarthritis (OA) detrimentally impacts the lives of millions of older Americans through pain and decreased functional ability. Unfortunately, the pathomechanics and associated deviations from joint homeostasis that OA patients experience are not well understood. Alterations in mechanical stress in the knee joint may play an essential role in OA; however, existing literature in this area is limited. The purpose of this study was to evaluate the ability of an existing magnetic resonance imaging (MRI)-based modeling method to estimate articular cartilage contact area in vivo. Imaging data of both knees were collected on a single subject with no history of knee pathology at three knee flexion angles. Intra-observer reliability and sensitivity studies were also performed to determine the role of operator-influenced elements of the data processing on the results. The method's articular cartilage contact area estimates were compared with existing contact area estimates in the literature. The method demonstrated an intra-observer reliability of 0.95 when assessed using Pearson's correlation coefficient and was found to be most sensitive to changes in the cartilage tracings on the peripheries of the compartment. The articular cartilage contact area estimates at full extension were similar to those reported in the literature. The relationships between tibiofemoral articular cartilage contact area and knee flexion were also qualitatively and quantitatively similar to those previously reported. The MRI-based knee modeling method was found to have high intra-observer reliability, sensitivity to peripheral articular cartilage tracings, and agreeability with previous investigations when using data from a single healthy adult. Future studies will implement this modeling method to investigate the role that mechanical stress may play in progression of knee OA through estimation of articular cartilage contact area.

Effects of diamond size of CMP conditioner on wafer removal rates and defects for solid (non-porous) CMP pad with micro-holes

Wafer removal rates and defects were investigated for 200 mm tetraethyl orthosilicate (TEOS) oxide chemical mechanical planarization (CMP) processes using two types of CMP pads: a porous pad and a solid pad with micro-holes. An initial CMP test conducted with fumed silica based-slurry and a conditioner with 180 μm diamond revealed that the wafer removal rates by the solid pad with micro-holes were approximately 10% lower than those by the porous pad, but scratch type defects were reduced. In order to increase the removal rate of a solid pad with micro-holes to the comparable level of a regular porous pad without changing process parameters, it was decided to modify conditioner design by using different diamond size from 70 to 130 μm. It was found that wafer removal rates increased from 2973 to 2587 Å/min and defect counts reduced from 5.3 to 1.7 by decreasing the diamond size from 180 to 70 μm in the case of the solid pad with micro-holes. Various pad surface analysis results, including contact area estimation and microscopic observations, also revealed that a smaller diamond conditioner generated the pad texture with finer and more regular pad asperities.