Contact Area Distribution Research Articles

Ring only repair of bileaflet mitral valve prolapse with mitral regurgitation: Insights from computational modeling

This study evaluates the efficacy of annuloplasty repair as a standalone procedure for treating bileaflet mitral valve prolapse with mitral regurgitation (MR). Various flexible ring bands for MR of different severities were compared to assess their biomechanical impact and treatment outcomes. Computational beating heart models, based on the Living Heart Human Model, were utilized to simulate annuloplasty repairs. Repairs using bands of varying lengths were modeled on moderate and severe MR cases, considering bileaflet mitral valve prolapse. Key parameters, including regurgitant orifice area (ROA), prolapse severity, coaptation length, leaflet position, and deformation, were computed to compare conditions before and after implantation. Annuloplasty repairs effectively reduced the ROA in both moderate and severe MR cases, achieving complete sealing in selective instances. Additionally, annuloplasty repair corrected bileaflet prolapse, with prolapse severity decreasing as the annular size increased. Successful coaptation was indicated by the expansion of each leaflet’s contact area distribution and percentage in contact with the opposing leaflet. The risk of systolic anterior motion, that may obstruct the left ventricular outflow tract, was minimized, as the anterior leaflet was directed towards the posterior position. In conclusion, annuloplasty repair alone can effectively treat MR when an appropriate band length is selected. It facilitates a significant reduction in ROA, correction of bileaflet prolapse, and improvement in leaflet coaptation. These findings have important clinical implications, potentially offering a less complex surgical treatment avenue and reducing complications in the management of MR.

Frictional Contacts Between Rough Grains With Fractal Morphology

AbstractSurface morphology plays a crucial role in friction between two contacting geomaterial surfaces, yet many questions remain unanswered regarding how detailed frictional responses deviate from analytical solutions for smooth surfaces due to the presence of roughness. In this study, we revisit the Cattaneo‐Mindlin problem for contacts between two fractally rough elastic or elasto‐plastic spheres generated based on ultra‐high degree (e.g., up to 2,000) spherical harmonics with the corresponding wavelength less than a thousandth of the mean grain diameter. Transverse contacts are simulated by finite element method, validated by the extended Cattaneo‐Mindlin solution to full slide regime for smooth sphere contacts. Extensive simulations are conducted to study contacts between two rough spheres with various surface geometries, micro friction coefficients, normal contact distances, relative roughness, fractal dimensions, and wavelength ranges. Out results indicate that: (a) the new analytical solution can approximately predict the macro contact response except for extremely high relative roughness and narrow wavelength range; (b) deviations induced by roughness from smooth sphere contacts can be neutralized by plasticity, high normal contact interference, and high micro friction coefficient; and (c) fractal dimension impacts frictional contacts less than relative roughness. The main cause of these phenomena can be credited to the underlying microscale contact information. Contact area and stress distributions and their evolutions provide concrete evidence of these observed behavior. This work provides a pathway for applying computational contact mechanics to many geophysical fields, such as the asperity model in earthquake science and the mechanics of granular materials.

Examining the adaptive elastic anisotropy of granular materials

Changes of granular material anisotropy with stress are a function of numerous microscale attributes, such as contact network, particle size uniformity and shape. Such influences are often represented with fabric variables. Although multiple choices for fabric exist, the question of which variable best explains why and how granular materials adapt to stress is still open. In this study, the effectiveness of different fabric variables in tracking stress-induced anisotropy is compared. The analysis is restricted to a simple, yet fundamental, range of behavioir: elastic deformation. Both particle-scale simulations and continuum analyses are deployed. Analyses based on the discrete-element method (DEM) reveal that, depending on the contact behaviour, anisotropy may emerge even if the topology of the grain contact network is unchanged. The inspection of these results through a continuum-scale hyperelastic constitutive law further reveals that the computed trends cannot be captured without an evolving fabric variable. A comparison between such fabric and multiple microstructural indicators extracted from DEM simulations suggests that elastic stress-induced anisotropy is primarily a manifestation of changes in the anisotropic particle contact area distribution in response to the current magnitude and orientation of force chains. These results not only offer opportunities to enhance current continuum elastic models for granular materials, but can also be used to design testing strategies quantifying changes in fabric anisotropy through multi-scale measurements.

Electrosynthesis of Unusual Nonfcc Palladium Hydride Nanoparticles.

Intercalation of hydrogen into the palladium atomic layers during the growth of Pd nanoparticles can lead to the synthesis of unique palladium hydride phases. Here, we discover an unusual nonfcc palladium hydride nanoparticle, a structure that is not face-centered cubic (fcc), formed through coreduction of water molecules and Pd ions in solution. Crystal structure determination based on atomic electron tomography points to potential triclinic unit cells, indicating the presence of more than one nonfcc phase, with some of those being a stack of loosened and distorted close-packed layer of atoms. The probability of finding the nonfcc phase in single-crystalline particles varies depending on the number and distribution of contact area with other particles. Roughly half of the isolated and one side-coalesced single-crystal particles exhibit a nonfcc structure, while fcc dominates multiple side-coalesced single crystals as well as polycrystal particles. These observations suggest a coalescence-induced phase transition from a nonfcc to a stable fcc structure, due to the metastable nature of the nonfcc phases. While hydrogen is proven to be a key component for the synthesis of the nonfcc structure, there was limited formation of the unusual phase in a H2 gas bubbling system. Thus, electrochemical pathways can be promising for the in situ creation and study of unique metastable nanomaterials.

Simulation on metal-rubber contact behavior based on a reconstructed 3D topography of rough surfaces

A contact model with refined surface topography is important to the frictional wear study of rubber seal. But the traditional modeling method relies on the measurement of surface characteristics of rubber material, which increases the cost due to high-precision instruments and complex data processing. In the paper, a new modeling method on reconstructing the 3D surface topography is proposed. The coordinate cloud of the surface is generated based on the random distribution of asperity height, which is established according to the initiate parameters of the surface roughness. The metal-rubber assembly model with 3D topography of rough surfaces are built. The simulation on metal-rubber contact behavior is conducted in ANSYS. The result shows a power-exponent relation is between the real contact area and the external pressure, and three contact states of no contact, adhesion and slippage are defined to describe the dynamic distribution of real contact area. The authors proved the reliability of the topography reconstruction method by an indentation experiment on rubber material. The area ratio reflects not only the change rule of contact area under an increasing pressure, but also the difference of contact behavior of the contact pairs under different surface roughness.

Distribution of Shear Stresses and Actual Contact Area along the Length of Interference Joints as a Factor of Their Tightness

Distribution of Shear Stresses and Actual Contact Area along the Length of Interference Joints as a Factor of Their Tightness

Real area of contact and tractions on the patterned surfaces generated by spinodal decomposition and amplified instability

Past decades featured significant advancements in additive and micromanufacturing that facilitated the creation of functional patterned surfaces with impressive spatial resolutions. However, these techniques are expensive and require a considerable amount of time and energy, and hence lack scalability to practical surfaces. Recent techniques employing spinodal decomposition and instabilities amplified via centrifugal acceleration offer viable and cheaper alternatives. The patterns created by those techniques, however, vary randomly in geometry. When interfacing those patterned surfaces with other components and under self-contact scenarios, geometric variations lead to stress concentration and abrupt failure around the contact. In this study, we investigate numerically real contact areas, contact tractions, and stress concentration. We generate patterned surfaces in congruence with actual surfaces created by those techniques. Then, we conduct normal-contact analyses of those surfaces boundary element method (BEM) under nominal mean pressures ranging from 0.001E* to E*, where E* is the contact modulus. We record real contact areas and stress concentration as a function of nominal mean pressures. We compare these values with the analytical solutions from sinusoidally-patterned and randomly rough surfaces. Randomness in pattern geometry is primarily influenced by the processing parameters such as the degree of anisotropy in spinodal decomposition and acceleration in amplified instabilities. To understand the influence of the processing parameters, we perform a parametric study. We find isotropic spinodal decomposition creates patterns that deliver contact area and traction distributions similar to randomly rough surfaces, and lead to high-stress concentrations. Such high-stress concentrations are expected to occur under self-contact loading scenarios, and thus can explain the compromised resilience and strength in recently-proposed spinodal metamaterials. For patterned surfaces created by amplified instabilities, high-stress concentrations are obtained for the surfaces created at high accelerations. At high accelerations, increased elastic instabilities and stochastic growth result in a more skewed and broader distribution in heights. Therefore, high-stress concentrations are inevitable. To account for combined loading scenarios, we conduct additional simulations on the same surface patterns with frictional pre-sliding contacts. We find the frictional tractions play a secondary role in stress concentrations where the primary factor is the processing parameters determining the degree of randomness in pattern geometry.

An Improved Model for Evaluating the Hydraulic Behaviour of a Single Rock Joint Considering Contact Area Evolution During Shearing

The contact of rock joints during shearing induced by underground excavation significantly impacts the hydro-mechanical behaviour of fractured rock mass, since fluid tends to flow through a rough-walled fracture along connected channels while bypassing the contact areas with tortuosity. However, previous research mostly considered joint roughness or aperture changes based on 2D joint profiles, while the contact and tortuosity using 3D surfaces were often overlooked. This paper considers the evolution of contact area and aperture distribution during shearing. The concept of the critical inclination angle is introduced and correlated with the contact area during shearing based on Grasselli’s criterion. The standard deviation of the mean mechanical aperture is calculated using the modified algorithm. An improved model for estimating the hydraulic aperture with the mechanical aperture is then developed, applying an aperture correction term and a contact correction term. A number of shear-flow tests on artificial joint samples under constant normal loads are conducted. The accuracy and reliability of the proposed model are verified by comparing it against the experimental results and by comparing the prediction performance with other published models. Results show that the proposed model can improve the prediction of the hydraulic aperture and hydraulic conductivity of a single rock joint during shearing.

Development of a scheme for the distribution of contact areas between the plate and offset cylinders

The object of the research is the distribution of contact areas between the plate and offset cylinders. For printing impression in the offset printing process, it is necessary to ensure the transfer of printing ink from the ink unit to the printing plate, from the mold to the rubber-fabric material (deckel) of the offset cylinder and from the deckel to the printed material. At the same time, the quality of the prints is ensured by creating the necessary technological pressure between the plate, offset and printing cylinders, which also contributes to the deformation of the elastic deckel and the transfer of the ink layer in the contact zone. The transfer of illustrative and textual information from the form to the deckel of the offset cylinder occurs due to the actual touch area. Therefore, the study and calculation of the actual contact area is necessary to study the transfer of the paint layer in the contact zones. For this purpose, a review of some studies on contact problems was carried out, their advantages and disadvantages were discussed. Theoretical and experimental relations are given. It has been established that micro protrusions of the surface roughness of the printing plate significantly affect the deformation of the deckel. To study the influence of the surface roughness distribution of the printing plate on the actual deckel contact area in the contact zone, the interaction of micro protrusions of the surface roughness of the printing plate with the deckel surface, leading to additional displacements, was taken into account. A method for calculating the number of roughness protrusions is proposed to further determine the actual deckel contact area and the actual pressure in the contact zone, taking into account the surface roughness of the printing plate. Based on the parameters calculated by the proposed method with known values of the surface roughness of the printing plate in the future it is possible to determine the actual deckel contact area and the actual contact pressure the optimal values of which are necessary to ensure the required ink transfer and print quality during printing. The data obtained also contribute to the determination of the modes of the printing process when printing the entire circulation, which leads to an increase in the circulation stability of printing forms. Increasing the circulation stability of printing plates allows to save the number of consumed printing plates. In the future, according to the results obtained, it is recommended to compile reference data, which are necessary when setting up and operating the printing machine.

Distribution patterns of occlusal contact areas on natural posterior teeth – Evaluations of a cross-sectional population-based study with the Greifswald Digital Analyzing System (GEDAS)

AimThe aim of our investigations is to optimize the anatomical basis for the design of a sufficient occlusal relationship, especially in view of the innovative technologies by analyzing the occlusal contact point patterns at cusp structures according to A-, B-, C- localization tooth by tooth on the individual occlusal surfaces in the posterior region in static habitual occlusal position. Materials and methodsIn 3300 subjects of the population-based Study of Health in Pomerania (SHIP 1) the interocclusal registration in habitual intercuspation using silicone registration was used and analyzed by using the special evaluation software Greifswald Digital Analyzing System (GEDAS II).Chi square test was used to investigate whether the distribution of contact areas differed in the group of premolars or molars - each considered separately for maxilla and mandible - on the basis of the probability of error p < 0.05. ResultsIn 709 subjects (446 male with a mean age of 48.9 ± 13.04 years; 283 female with a mean age of 52.4 ± 14.23 years) the antagonistic situation was specifically considered on natural posterior teeth without conservative or restorative-prosthetic interventions, i.e. without caries, fillings, crowns or other restorations. On the basis of these subjects, the silicone registrations were analyzed using GEDAS II. For the first and second upper molars, the ABC contact distribution was the most frequent: 20.4 % for the first and 15.3 % for the second molar. The second most frequent contact area for maxillary molars was area 0. The upper molars had contact areas only at the maxillary palatal cusp (B-/C-contacts). This contact relationship was most frequent in the maxillary premolar (18.1–18.6 %). In mandibular premolars, with the buccal cusps areas A and B were frequently involved (15.4–16.7 %). Mandibular molars showed a frequent contact pattern involving all A-, B-, C- and 0- contact areas (13.3–24.2 %). To capture the possible influence of the antagonistic dentition situation, the antagonistic situation was specifically considered and except for the mandibular premolars (p < 0.05) the contact distribution did not differ for molars and maxillary premolars regarding the dental status of the antagonistic teeth.Natural posterior teeth without occlusal contacts were observed from 20.0 % in the second lower molars to 9.7 % in the first upper molars. ConclusionOur results suggest a clinically relevant due to the fact, that this study is the first population-based epidemiological study to analyze the occlusal contact point patterns at cusp structures according to A-, B-, C- localization tooth by tooth on the individual occlusal surfaces in the posterior region in static habitual occlusal position in order to optimize the anatomical basis for the design of a sufficient occlusal relationship.

Effect of load, ski and snow properties on apparent contact area and pressure distribution in straight gliding

Modeling of ski friction requires an in-depth understanding of the ski-snow contact. For this aim, we implemented the Euler–Bernoulli beam equations for an embedded cross-country skating ski. Apparent contact area and pressure distribution were calculated from the ski’s penetration depth using a hypoplastic force-penetration relation of snow. In a static validation experiment on an elastomer foundation, the difference between measured and calculated pressure of a loaded ski was below 5.1 kPa. For cross-country skis gliding on snow, the apparent contact area increased for increased normal load, softer snow, and decreased ski stiffness and camber. The pressure along the ski showed separated parts. The maximum pressure increased for increased normal load and harder snow. Overall, we observed an apparent contact area between 23.6 and 57.8% and a maximum pressure between 27.4 and 110.7 kPa. Concluding, a model for the ski-snow contact in straight gliding ski was developed. Apparent contact area and pressure distribution was affected by normal load, snow hardness, and ski stiffness and camber. Effects on the pressure should be considered in applications like ski construction, waxing, and modeling friction along the ski.

Experimental Methods for Studying the Contact Mechanics of Joints.

Biomechanics researchers often experimentally measure static or fluctuating dynamic contact forces, areas, and stresses at the interface of natural and artificial joints, including the shoulders, elbows, hips, and knees. This information helps explain joint contact mechanics, as well as mechanisms that may contribute to disease, damage, and degradation. Currently, the most common in vitro experimental technique involves a thin pressure-sensitive film inserted into the joint space; but, the film's finite thickness disturbs the joint's ordinary articulation. Similarly, the most common in vivo experimental technique uses video recording of 3D limb motion combined with dynamic analysis of a 3D link-segment model to calculate joint contact force, but this does not provide joint contact area or stress distribution. Moreover, many researchers may be unaware of older or newer alternative techniques that may be more suitable for their particular research application. Thus, this article surveys over 50 years of English-language scientific literature in order to (a) describe the basic working principles, advantages, and disadvantages of each technique, (b) examine the trends among the studies and methods, and (c) make recommendations for future directions. This article will hopefully inform biomechanics investigators about various in vitro and in vivo experimental methods for studying the contact mechanics of joints.

CONTACT INTERACTION OF SIMILAR SHAPE BODIES AT SMALL DISTURBANCE OF INITIAL GAP DISTRIBUTION

In this work, on the development of previous research, a model of contact interaction of similar shape bodies is built. Contact in the system "punch - stamped material - matrix" is considered. A gap is set between the material to be stamped and the matrix, which varies in circular coordinate. The regularities of the change of contact pressure and contact areas with variation of the law of distribution of the initial gap are determined. The influence of the load level on these parameters is also determined. In particular, the analysis of the influence of the number of waves in the distribution of the initial gap in the circular direction on the nature of the distribution of contact areas and contact pressure. It is established that at low level of loads significant non-uniformity of the contact pressure distribution along the circular coordinate is realized. In the future, with increasing load levels, this unevenness decreases. The distribution of contact pressure tends to the case of contact with nominally coincident surfaces of the matrix and the material to be stamped, i.e. at zero gap. Thus, an analytical-numerical method for studying the contact interaction of closely shaped bodies with low perturbation of the initial gap distribution has been developed. Regularities of influence of constructive and technological parameters on contact interaction of these bodies on an example of elements of stamp equipment are also established. Keywords: contact interaction; stress-strain state; elements of stamps; contact area; contact pressure

(Digital Presentation) Validation of Python-Based Automated Analysis Approach for Processing STEM/EDS Maps of Catalyst Samples in AEMFCs – a Comparative Study

Technological innovations in the field of materials science are often connected to the nanometric scale material evaluation which requires utilizing a combination of advanced characterization techniques. The extensive data acquired from these characterization techniques necessitates meticulous and efficient analysis, which can only be accomplished by automated digital image and data processing techniques. The development of such techniques will aid further advancements in the design of functional materials. In this work, we report a novel automatic analysis approach using data acquired by the Scanning Transmission Electron Microscopy (STEM) and Energy Dispersive Spectroscopy (EDS) to determine the component distribution and microstructure descriptors for an anion exchange membrane fuel cell (AEMFC). The current research aims to validate the automated approach by comparison to a manual image processing method based on ImageJ reported in a previous study [1]. STEM and EDS data for three different Pd/CeOx-based catalyst samples with varying bulk atomic fractions of Ce/Pd were collected and analyzed. The STEM/EDS data was used to investigate how the interfacial contact area and agglomerate size distributions of Pd and Ce can be related to the microstructural-level interactions and processes and potentially affect the electrochemical performance of an anion exchange membrane fuel cell (AEMFC). The comparison highlighted the strengths and limitations of both automated and manual approaches and offered substantial justification to predict how excessive Ce agglomeration can be linked to a reduction in the electrochemical performance of the fuel cell.[1] R. K. Singh et al., “Synthesis of CeOx-Decorated Pd/C Catalysts by Controlled Surface Reactions for Hydrogen Oxidation in Anion Exchange Membrane Fuel Cells,” Adv. Funct. Mater., vol. 30, no. 38, 2020, DOI: 10.1002/adfm.202002087.

Contact analysis and performance evaluation of ring type traveling wave ultrasonic motors based on a surface contact model

A surface contact model of ring type traveling wave ultrasonic motors is proposed in this paper in order to describe the circular three-dimensional contact and friction problem between the stator and rotor accurately. Differing from previous contact models of traveling wave ultrasonic motors, the flexibility of the rotor, which results in the irregular shape of contact area and inhomogeneous distribution of contact pressure along radial direction, is taken into account in the proposed model. The normal contact between the stator and rotor is analyzed with finite element method and the tangential force transmission on the contact surface is investigated with analytical method. The contact pressures and the tangential stresses on the contact surface are obtained. Mechanical performances of the motor are also studied based upon the proposed model. Finally, torque-speed curves of a prototype motor are measured and compared with the calculated results of the proposed model, and good agreements are obtained. In addition, the proposed surface contact model is compared with previous line contact models. It is found that the calculated results of the surface contact model are closer to measured results than those of line contact models. The comparison results verify the accuracy of the proposed surface contact model.

Study on the Contact Stress Distribution Model of Asphalt Mixture Particles

The distribution of contact stress of particles in asphalt mixture could be used to reflect the relationship between the macroscopic mechanical properties and the mesostructure of the material. However, there is no mature method to obtain the internal stress characteristics of asphalt mixture. In this study, the accurate stress distribution and stress transfer state information of particles in asphalt mixture were obtained by using pressure film technology, which provided a good theoretical basis for material gradation design. The pressure film was sandwiched between two Marshall specimens, and the compression part will appear red. After digital processing by software, the total contact area and stress distribution of the two specimens can be obtained. Three kinds of asphalt, three kinds of asphalt pavement gradation, and five kinds of asphalt aggregate ratio were selected to prepare asphalt mixture specimens. The effects of different asphalt, skeleton structure, and asphalt film thickness on the contact characteristics of aggregates were studied. The test results showed that, when the pressure between the two specimens is 0.23 MPa, the contact area of the particles reaches the maximum. The relationship between the contact point distribution probability and the pressure was fitted into a nonlinear curve. The gradation of the mixture, the type of asphalt and the thickness of the asphalt film were used as parameters A, B, and C. The prediction model had a good correlation with the test results. The prediction model proposed in this study could be used to improve the experimental efficiency, save test material and financial resources, as well as get complete contact stress information of the internal particle interface of asphalt mixture.

P4. Independent expansion of the anterior and posterior height of a lateral expandable cage can improve the contact area and load distribution at the cage-endplate interface

<h3>BACKGROUND CONTEXT</h3> Compared to their traditional static counterparts, expandable cages offer clinical advantages by allowing for the use of smaller surgical access corridors to achieve similar lordosis correction without endplate damage from large impaction forces. However, as with static cages, the risk of implant subsidence due to stresses on the vertebral endplate remains an area of concern. Although early clinical outcomes have been reported for individual expandable cage designs, how the endplate contact area and load distribution are affected by specific cage expansion trajectories remains unclear. <h3>PURPOSE</h3> To assess and quantify differences in contact area and load distribution from different lateral expandable interbody cage designs. <h3>STUDY DESIGN/SETTING</h3> Comparative biomechanics analysis using established synthetic spine units. <h3>OUTCOME MEASURES</h3> Cage-endplate contact area, anterior-posterior load distribution, segmental lordosis angle. <h3>METHODS</h3> Discectomies and cage placement were performed on synthetic functional lumbar spine units (n = 3). Three different expandable cage designs were evaluated, each with their own unique expansion trajectory: cranio-caudal, arc-based, and independent anterior and posterior height expansion. For the third cage, a differential expander was used to increase the two heights, anterior and posterior, according to the path of least resistance. A Tekscan calibrated pressure mapping sensor was placed between the cage and the synthetic endplate. The functional spine units were mounted on a servo-hydraulic testing frame and a constant 250N compressive axial preload was applied with unconstrained rotations and translations. The cages were then fully expanded and segmental lordosis angle along with pressure measurements were collected. To allow for a consistent comparison among cages, the surface contact area was normalized by the footprint of each respective cage. To determine the uniformity in the contact load profile, the local load distribution was demarcated in half along the anterior-posterior (A-P) aspect of the cage. The symmetry of the loading profile was characterized by dividing the cumulative anterior force magnitude by the overall force (50% indicates perfectly balanced A-P loading) quantified using the pressure mapping sensor. Friedman's test was performed (α = 0.05) to compare the effect of expansion trajectory on the outcome measures (values reported as median [range]). <h3>RESULTS</h3> Expansion trajectory had a significant effect on cage-endplate contact area and the resultant A-P loading distribution (p = 0.050), but not segmental lordosis angle (p = 0.097). Independent expansion resulted in the highest cage-endplate contact area (93% [92 to 98%]) compared to cranio-caudal (84% [81 to 90%]) and arc-based (62% [56 to 63%]) expansion. Furthermore, independent expansion resulted in a near-even A-P loading distribution (48% [42 to 51%]), compared to cranio-caudal (34% [22 to 36%]), and arc-based (97% [94 to 99%]) expansion. <h3>CONCLUSIONS</h3> Of the cage designs evaluated, the expandable cage with independent anterior and posterior height expansion resulted in the highest cage-endplate contact area and most uniform load distribution, both important considerations fundamental for a successful fusion procedure and the mitigation of implant subsidence risk. With a larger sample size, our continuing studies will investigate the interaction of various cage placement options and expansion mechanisms. <h3>FDA DEVICE/DRUG STATUS</h3> MOD-EX XLIF Interbody System (Approved for this indication), RISE-L Spacer (Approved for this indication)

Fractal Contact Mechanics Model for the Rough Surface of a Beveloid Gear with Elliptical Asperities

Understanding the contact mechanics of rough tooth surfaces is critical in order to understand phenomena such as tooth surface flash temperature, tooth surface wear, and gear vibration. In this paper, the contact behavior between the meshing tooth surfaces of beveloid gear pairs with elliptical asperities is the focus. The contact area distribution function of the elliptical asperity was proposed for the point contact of curved surfaces by transforming the elastic contact problem between gear meshing surfaces into the contact between elastic curved surfaces with an arbitrary radius of curvature. In addition, a fractal contact mechanics model for the rough surface of a beveloid gear with elliptical asperities was established. The influence of tooth surface topography on the contact load and contact stiffness under different fractal parameters was investigated, and the results demonstrated that the real contact load and the contact stiffness of curved surfaces increase with the increase in the fractal dimension D and the contact coefficient λ. Conversely, the real contact load and normal contact stiffness decrease with the increase in the fractal roughness G and eccentricity e.

Reliability of OHM 3000 Plantar Pressure System for Measurement of Plantar Pressures in Healthy Indian Population

Purpose: The aim of this study is to determine intra and inter-session repeatability and reliability of OHM 3000 for reporting static and dynamic pressures in healthy Indian population. Methods: Using OHM 3000, twenty-eight healthy adults who did not present any gait abnormalities or musculoskeletal conditions were assessed one week apart for static and dynamic pressure. Bipedal stance test was used for assessing static variables- maximum pressure, average pressure, contact area, and weight distribution; whereas dynamic test was used for assessing dynamic variables- maximum pressure, average pressure, and contact area. Each participant performed three trials under supervision of each investigator. Results: Reliability was devised using ICC values and coefficient of variance for static and dynamic variables. ICC values for static and dynamic variables were reported to range between 0.88 to 0.94 and 0.61 to 0.98 respectively. Covariance values were reported to be lower than 13% in static and dynamic pressures recorded by both investigators. Conclusion: The study reports that OHM 3000 is a reliable device for assessing static and dynamic pressure in healthy adults demonstrating moderate to good reliability. KEYWORDS: Gait, Foot, Plantar Pressure.

Analysis of Tire‐Pavement Contact Morphology Characteristics during the Virtual Track Train Maneuvering

The tire‐pavement contact morphology during the virtual track train maneuvering has an essential function in assessing vehicle performance and pavement damage. The longitudinal tread tire and viscoelastic asphalt pavement were developed based on the finite element method. Then, the tire‐pavement contact model was developed according to the Euler–Lagrange algorithm and validated. Contact area and stress distribution under uniform, braking, and cornering conditions are explored with the dynamic tire force of the virtual track train as the external load. Also, the effect factors were analyzed. The results indicate that vertical stress distribution is symmetrical along the length and width directions, and contact area is rectangular under uniform condition. Vertical and longitudinal stresses have similar distributions under braking condition, with a wide front and a narrow back along the length direction. Under cornering condition, the closer to the inside of the cornering, the larger the contact area. Vertical stress is similar to the lateral stress distribution, and the larger stress value is concentrated on the inner side of each tread. Load, tire pressure, slip rate, and slip angle have significant effects on contact morphology, while velocity has little effect. Contact area increases with the increase of load and slip rate and decreases with the increase of tire pressure and slip angle. Vertical stress increases gradually with the increase of load. Higher tire pressure makes stress distribution more concentrated. The increase in slip rate increases vertical and longitudinal stresses and gradually moves in the running direction. Vertical and lateral stresses increase with the slip angle and are mainly distributed on the inside of the turn. This research can be used to evaluate and analyze the response and damage of the virtual track train to asphalt pavement under uniform, braking, and cornering conditions. It can be used as a reference for the design and paving of asphalt pavement.