Contact Pressure Model Research Articles

Enhancing Biosignal Quality in Electrocardiogram Monitoring Garments: Validation of a Simulation-Based Contact Pressure Model

Enhancing Biosignal Quality in Electrocardiogram Monitoring Garments: Validation of a Simulation-Based Contact Pressure Model

A new modelling method of material removal profile for electrorheological polishing with a mini annular integrated electrode

This paper addresses the problem of material removal in electrorheological (ER) polishing with a mini annular integrated electrode both theoretically and experimentally. The model of the material removal profile in ER polishing is proposed based on the evaluation of the amount of material removed from the surface along the direction orthogonal to the tool path. Firstly, the electric field distribution around the tool head is deduced theoretically. On this basis, the contact pressure model in the ER polishing area is established. Considering the feed rate and tool spindle speed of ER polishing, the distribution of the relative sliding velocity in the polishing area is modeled. On the basis above, the innovative approach to calculate the material removal profile is developed for the ER tool polishing along a straight path. The model is validated by a series of designed polishing experiments, which demonstrates that the material removal model established in this paper has high prediction accuracy of material removal profile in ER polishing.

Curvature effect-based modeling and experimentation of the material removal in polishing optical surfaces using a flexible ball-end tool.

Optical surfaces with high quality have been widely applied in high-tech industries for their excellent performances. To precision manufacture those surfaces efficiently and effectively, various machining technologies involved become extremely crucial. As one of the promising ultra-precision machining technologies, inflated or solid elastic tool polishing has attracted more attention for its own superiority. However, there is still lack of understanding on material removal mechanisms especially with the consideration of curvature effect, and it is of great importance to determine the surface quality and form control in ultra-precision polishing process. In this paper, originating from the famous macro-scale Preston equation, the curvature effect-based material removal model in polishing using a flexible ball-end tool has been developed successfully on the basis of two key sub-models, one is the generic model of effective relative velocity and the other refers to the semi-experimental contact pressure model. A series of spot polishing experiments subsequently are conducted on concave surfaces with a curvature radius range from 75 mm to 225 mm. The experimentally measured section profiles of polishing spots do match well with the predicted data, which verifies the effectiveness of the proposed material removal model. On the measured polishing spots, it is also observed that there have two nonuniform material removal phenomena, one is analyzed along the central axis and the other is discussed by two regions symmetrical about the central axis. Compared with the effective relative velocity, it is found that, the contact pressure is more sensitive to curvature effect by investigating the variation of maximum removal depth within a broader curvature radius range from 75 mm to 1000 mm. This study can provide a valuable foundation for polishing optical surfaces with deterministic removal.

The Springer Model for Lifetime Prediction of Wind Turbine Blade Leading Edge Protection Systems: A Review and Sensitivity Study.

The wind energy sector is growing rapidly. Wind turbines are increasing in size, leading to higher tip velocities. The leading edges of the blades interact with rain droplets, causing erosion damage over time. In order to mitigate the erosion, coating materials are required to protect the blades. To predict the fatigue lifetime of coated substrates, the Springer model is often used. The current work summarizes the research performed using this model in the wind energy sector and studies the sensitivity of the model to its input parameters. It is shown that the Springer model highly depends on the Poisson ratio, the strength values of the coating and the empirically fitted constant. The assumptions made in the Springer model are not physically representative, and we reasoned that more modern methods are required to accurately predict coating lifetimes. The proposed framework is split into three parts—(1) a contact pressure model, (2) a coating stress model and (3) a fatigue strength model—which overall is sufficient to capture the underlying physics during rain erosion of wind turbine blades. Possible improvements to each of the individual aspects of the framework are proposed.

Improvement of evaluation of the contact pressure upon the penetration of a reactor lower head during a severe accident: Part 1. Conceptualization considering elastic deformation

When damaged core materials are relocated to the reactor lower head with penetrations during a severe accident, the loss integrity of the reactor pressure vessel caused by ejection of a penetration tube will occur earlier than the global failure of the reactor lower head. The overall aim of this study is to review and improve the previous contact pressure evaluation models. In this part of the study, it was shown that the previous model in the elastic region only considers the deformation of a penetration tube itself by assuming one hollow cylinder with a limited stress-strain condition. Therefore, the new expression of the contact pressure at the interface was derived by stress analysis with assumption of additional concentric outer cylinder for a reactor lower head. The new contact pressure model was validated using finite element analysis.

Non-Newtonian modeling of contact pressure in fused filament fabrication

The nozzle pressure was monitored in a fused filament fabrication process for the printing of high impact polystyrene. The contact pressure, defined as the pressure applied by the newly deposited layer onto the previous layer, is experimentally calculated as the difference between the pressure during printing and open discharge at the same volumetric flow rates. An analytical method for estimating the contact pressure, assuming one-dimensional steady isothermal flow, is derived for the Newtonian, power-law, and Cross model dependence of shear rates. A design of experiments was performed to characterize the contact pressure as a function of the road width, road height, and print speed. Statistical analysis of the results suggests that the contribution of the pressure driven flow is about twice that of the drag flow in determining contact pressure, which together describe about 60% of the variation in the observed contact pressure behavior. Modeling of the elastic and normal stresses at the nozzle orifice explains an additional 30% of the observed behavior, indicating that careful rheological modeling is required to successfully predict contact pressure.

Microscopic contact pressure and material removal modeling in rail grinding using abrasive belt

Recently, the emerging rail grinding method using abrasive belt has been proposed to efficiently achieve the required geometric profile and the surface quality of the railhead. Although the abrasive features indeed have a great influence on this rail grinding process, the surface topography of abrasive belt regarding grits at the microscopic scale is neglected. In this article, a microscopic contact pressure model was developed to reveal the contact behavior of every active grit based on the digital representation of the surface topography of abrasive belt. Then a numerical model of material removal quantity was also established based on the consideration of the characteristics of abrasive grits and their interactions. Finally, the series of finite element simulations and grinding tests were successively implemented. The normal load and the surface topography of abrasive belt significantly affected the microscopic contact behavior of grits, thus confirming the proposed theoretical models of microscopic contact pressure and material removal quantity.

Computational Procedure of Wear Resistance of Gear Transmission Teeth under Skew of the Axes of Conjugated Wheels

This paper considers the wear process of the teeth of straight spur gear transmissions under the conditions of skew of the axes of conjugated wheels. The method for determining the magnitude of wear of tooth profiles, taking the skew angle into account, is based on the dependence of average contact pressure on the skew angle. To determine the contact pressure, the physical and mathematical model of contact interaction of cylindrical elastic bodies is used when they are skewed using the Winkler model of elastic foundation. It is established that the presence of skew angle of teeth of 0.1° increases the wear rate by 3.61 times.

Modeling of interlayer contact and contact pressure during fused filament fabrication

An in-line rheometer and data acquisition system are used to monitor the melt pressure, melt temperature, and environmental temperatures while producing parts via fused filament fabrication (FFF). Melt pressures are observed to increase when printing parts with small layer heights, which is attributed to the confined space created between the nozzle and the previous layer (i.e., an exit pressure). These exit pressures (referred to as contact pressure) and the resulting interlayer contact areas are analyzed for 2863 layers created at 21 different processing conditions. The measured contact pressure was found to directly influence the shape of the layers and the resulting interlayer contact. An intimate contact model based on contact pressure is combined with a wetting model to accurately predict the interlayer contact of FFF parts. This pressure-driven intimate contact model for FFF shows strong agreement with the observed interlayer contact. No theoretical model has previously existed for predicting interlayer contact, so this research provides a critical component for developing a comprehensive part strength model. Both the measurements and proposed model are sufficiently simple and accurate for real-time analysis of FFF quality, so the described in-line sensors provide valuable quality insights and are recommended for future researchers, printer manufacturers, and end-users.

Thermomechanical mortar contact problems with hierarchical refined NURBS for adhesion and anisotropic friction

AbstractIn this contribution, we present a novel thermodynamically consistent contact formulation [1]. The thermomechanical framework is written in terms of the first and second law of thermodynamics, providing suitable restrictions on the constitutive law. The contact formulation involves mechanical and thermal contributions across the interface. For the mechanical contribution we apply different contact reactions in normal and tangential direction and decompose the Piola‐traction vector t on the interface. The modeling of contact pressure and adhesion leads to an exponential constitutive model in terms of the normal gap function. Furthermore, the tangential traction is additively decomposed into isotropic and anisotropic parts. For the spatial discretization we employ hierarchical refined NURBS (B‐Splines) and apply a variationally consistent mortar method for the thermomechanical contact interface, see e.g. [2]. In particular, linear Lagrangian shape functions are used for the discrete traction field. The capabilities of this framework are shown within a representative example.

Influencing Mechanism of Rubber Wheel on Contact Pressure and Metal Removal in Corrugated Rail Grinding by Abrasive Belt

Rail grinding has been widely recognized as an essential measure in routine maintenance of railway network in the world. Compared with other technologies, the emerging abrasive belt grinding process for direct rail maintenance rather than limited polishing finish has shown the convincing potential to improve metal removal rate and surface quality. However, the influencing mechanism of the rubber wheel on contact pressure and metal removal for the corrugated rails is yet unknown. This paper develops a contact pressure model to obtain the boundary curve and the stress distribution of the contact zone between the rubber wheel with concave peripheral surface and the rail surface with corrugation. Based on this, the metal removal model is subsequently established through the abrasive processing theory. Finite element (FE) simulations and grinding tests are finally implemented. Results confirm the above-mentioned theoretical models of contact pressure and metal removal and show the significant influences of the rubber wheel's feature on contact pressure and metal removal.

Contact Pressure Algorithm of Multi-Layer Interference Fit Considering Centrifugal Force and Temperature Gradient

In order to optimize the algorithm on contact pressure and interference magnitude of multi-layer interference cylinders, the effects of centrifugal force and temperature gradient on the performance of multi-layer interference cylinders are considered. The mathematical matrix model of contact pressure and interference magnitude of multi-layer interference cylinder is constructed under centrifugal force and temperature gradient. Four kinds of interference cylinder models are established, and the numerical solutions using finite element methods are compared with the analytical solutions. The results show that the contact pressure of each contact surface of multi-layer interference cylinder decreases with speed increase; the slip rate of contact pressure increases with speed increase; the maximum radial displacement of an interference cylinder under centrifugal force occurs at the outermost layer. The contact pressure of a multi-layer interference cylinder decreases linearly with the increase of temperature gradient. The analytical solution is basically consistent with the numerical solution, and the maximum relative error of midpoint is 11.62% and −7.69% under two factors. It means that the algorithm can provide a theoretical guide for the design of a multi-layer interference cylinder considering centrifugal force and temperature gradient.

Tire–rim interface pressure of a commercial vehicle wheel under radial loads: theory and experiment

The simulation of the radial fatigue test of a wheel has been a necessary tool to improve the design of the wheel and calculate its fatigue life. The simulation model, including the strong nonlinearity of the tire structure and material, may produce accurate results, but often leads to a divergence in calculation. Thus, a simplified simulation model in which the complicated tire model is replaced with a tire-wheel contact pressure model is used extensively in the industry. In this paper, a simplified tire–rim interface pressure model of a wheel under a radial load is established, and the pressure of the wheel under different radial loads is tested. The tire–rim contact behavior affected by the radial load is studied and analyzed according to the test result, and the tire–rim interface pressure extracted from the test result is used to evaluate the simplified pressure model and the traditional cosine function model. The results show that the proposed model may provide a more accurate prediction of the wheel radial fatigue life than the traditional cosine function model.

Modeling and experimental identification of contact pressure and friction for the analysis of non-conforming elastic contact

In this paper, we propose an experiment-based method for the modeling and the identification of the contact pressure and friction distribution on the interface of a non-conforming contact. In this method a two-dimensional contact model is established. The distributed contact pressure and friction are approximated by Taylor series and their relationship with the local displacements near the contact interface are modeled by using a half-space based approach. The parameters of the proposed contact model include the contact center, the half length of the interface, and the orders and coefficients of the Taylor series. They are identified by minimizing the residual between the computed displacement field and the measured one through an alternating optimization. The contact pressure and friction are reconstructed by the optimal parameters. A full-field optical method, namely segmentation-aided digital image correlation, is used not only to experimentally measure the local displacements but also to initialize the model parameters. The proposed mechanical modeling requires fewer assumptions compared with the classic models. The parameter identification only uses the local displacements and does not require boundary conditions of the contact members. The results of the simulated and real-world experiments show that the proposed method is able to reliably recover the contact stress and it is robust against the displacement measurement uncertainty.

A New Numerical Model of Contact Pressure in Vane Seals

The sealing contact pressure is critical in determining the film thickness of elastohydrodynamic lubrication, the friction force on the seal, and the sealing reliability of vane seals, so it is one of the most important parameters in evaluating the sealing performance of vane seals. A numerical model of contact pressure for vane seal is built based on elastic mechanic method, which is used to solve these problems of contact stress, strain and displacement on sealing surface. The interaction between adjacent units during deforming is fully considered for this model, which results in that this model is closer to the actual situation.

Analytical contact pressure model for predicting roughness of ball burnished surfaces

Within this work, an analytical model to predict the roughness after a ball burnishing process for thermally coated surfaces is developed. For this purpose, first a model is derived which determines the contact pressure between rolling ball and workpiece. By extending a previously developed model and by using the calculated contact pressure the prediction of the roughness after a rolling process of total areas without conducting experimental preliminary tests becomes possible. The model and the assumptions are verified in experimental studies for various rolling parameters and materials. The agreement between the calculated values and the experiments is suitable. Furthermore, a discussion of the influence of the individual parameters is carried out based on the developed model.

Investigation of contact pressure and influence function model for soft wheel polishing.

The tool influence function (TIF) is critical for calculating the dwell-time map to improve form accuracy. We present the TIF for the process of computer-controlled polishing with a soft polishing wheel. In this paper, the static TIF was developed based on the Preston equation. The pressure distribution was verified by the real removal spot section profiles. According to the experiment measurements, the pressure distribution simulated by Hertz contact theory was much larger than the real contact pressure. The simulated pressure distribution, which was modeled by the Winkler elastic foundation for a soft polishing wheel, matched the real contact pressure. A series of experiments was conducted to obtain the removal spot statistical properties for validating the relationship between material removal and processing time and contact pressure and relative velocity, along with calculating the fitted parameters to establish the TIF. The developed TIF predicted the removal character for the studied soft wheel polishing.

Transient dynamics of an excavator tyre rolling over speed bump

Analysis of tyre transient dynamics is an important aspect in the study of vehicle ride comfort and handling performance. A three-dimensional finite element excavator tyre model considering intricate tread patterns and reinforced inner layers was developed in this paper. For the validation of the finite element tyre model, simulation and experimental results of tyre stiffness and contact pressure on the tyre–road interaction interface were studied and compared. The validated tyre model was further applied to simulate the tyre–speed bump impact, and transient dynamic responses of the excavator tyre such as tyre acceleration were analysed in the time and frequency domain. The influences of the inflation pressure, the translational velocity and the axle load on the tyre transient dynamics were studied and analysed based on the simulation results.

Contact Pressure Model of Fastener Interface with Stress Singularities

Contact Pressure Model of Fastener Interface with Stress Singularities

Evolution in Surfaces: Interaction of Topography with Contact Pressure During Wear of Composites Including Dinosaur Dentition

A two-parameter elastic foundation model is used to predict the coupled evolution of contact pressure and wear of multicomponent composite surfaces. The iterative model predicts the evolution of surface shape for an initially flat multicomponent surface under uniform applied pressure; where the components of the composite surface are different materials of different wear rates. The model is applied to elucidate the chewing surface morphology of the dentition in a hadrosaurid dinosaur using wear rates measured from fossilized dental tissues. Additionally, to further illustrate the predictive capabilities of the coupled contact pressure and wear model, a two-component polymer sample was fabricated and experimentally evaluated through laboratory wear experiments. Data obtained from the abrasive wear testing of a laboratory multicomponent polymer sample was compared to model predictions using measured system and material parameters. Differences between the measured and predicted surface profiles were on the same order as the sample’s surface roughness (Ra ~3 µm).