Contact Finite Element Method Research Articles

Acoustic and Vibration Response and Fatigue Life Analysis of Thin-Walled Connection Structures under Heat Flow Conditions

Thin-walled connection structures are commonly used in the hot-end components of aerospace vehicles. Large deflection nonlinear responses and fatigue failure occur due to their discontinuous mass distribution and prominent cross-sectional changes under the action of complex thermal, aerodynamic, and noise loads. A thermoacoustic fatigue test was carried out to obtain the acoustic and vibration responses and fatigue life changes of the connection structure under heat flow conditions in engineering applications. The high-temperature acoustic fatigue test system of aviation thin-walled structures was used, taking the high-temperature alloy thin-walled plate-load-bearing frame bolted connection structure as the research object. As a result, the vibration response and fatigue life under different thermoacoustic loads were obtained. The contact finite element method was used to simulate the connection pre-tightening force, and the coupled finite element/boundary element method was used to calculate the acoustic and vibration response of the heat flow conditions. The changing rules of the frequency response peak value at the critical point of the thin-walled connection structure under the effects of different temperature fields, fluid fields, and sound fields were obtained through the processing and analysis of the calculation results. Considering the structural vibration fatigue damage mechanism, this study employed an improved rainflow counting method to compute the rainflow circulation matrix (RFM) and rainflow damage matrix (RFD) of the vibration stress time history at critical points within the structure framework. Said method was combined with Miner’s linear cumulative damage theory to estimate the fatigue life under various thermal-fluid-acoustic coupled loads. A comprehensive analysis validates the accuracy of the established numerical simulation calculation model in identifying critical connection points within structures subjected to pre-tightening forces. This model effectively characterizes thermal, aerodynamic, and acoustic loads on high-temperature alloy thin-walled-load-bearing frame bolted connection structures. It delineates the relationship between vibration response and fatigue life while assessing the impact of three distinct load parameters.

Coarse-grained elastic network modelling: A fast and stable numerical tool to characterize mesenchymal stem cells subjected to AFM nanoindentation measurements

The knowledge of the mechanical properties is the starting point to study the mechanobiology of mesenchymal stem cells and to understand the relationships linking biophysical stimuli to the cellular differentiation process. In experimental biology, Atomic Force Microscopy (AFM) is a common technique for measuring these mechanical properties.In this paper we present an alternative approach for extracting common mechanical parameters, such as the Young's modulus of cell components, starting from AFM nanoindentation measurements conducted on human mesenchymal stem cells. In a virtual environment, a geometrical model of a stem cell was converted in a highly deformable Coarse-Grained Elastic Network Model (CG-ENM) to reproduce the real AFM experiment and retrieve the related force-indentation curve. An ad-hoc optimization algorithm perturbed the local stiffness values of the springs, subdivided in several functional regions, until the computed force-indentation curve replicated the experimental one. After this curve matching, the extraction of global Young's moduli was performed for different stem cell samples. The algorithm was capable to distinguish the material properties of different subcellular components such as the cell cortex and the cytoskeleton. The numerical results predicted with the elastic network model were then compared to those obtained from hertzian contact theory and Finite Element Method (FEM) for the same case studies, showing an optimal agreement and a highly reduced computational cost.The proposed simulation flow seems to be an accurate, fast and stable method for understanding the mechanical behavior of soft biological materials, even for subcellular levels of detail. Moreover, the elastic network modelling allows shortening the computational times to approximately 33% of the time required by a traditional FEM simulation performed using elements with size comparable to that of springs.

An efficient three-dimensional dynamic contact model for cylindrical gear pairs with distributed tooth flank errors

Coupled loaded tooth contact analysis (LTCA) model and lumped-parameters model, an efficient three-dimensional dynamic contact model for cylindrical gear pairs with distributed tooth flank errors is established. The solution scheme of the proposed model is constructed using a combination of the loaded tooth contact algorithm and the Newmark integration method. The dynamic load distributions at different input speeds can be determined, and the dynamic time-dependent mesh stiffness and dynamic composite mesh error are proposed and calculated. The proposed model is validated by comparing the obtained numerical results with the experimental results from the published works, and has much higher efficiency compared with three-dimensional dynamic contact finite element method. The effects of helix angle, mesh damping, distributed tooth flank errors and output torque on the vibration behaviors and dynamic load distributions of cylindrical gear pairs under different working conditions are investigated and discussed. The proposed model can also be used to predict the vibration behaviors and the instantaneous three-dimensional dynamic contact state of cylindrical gear pairs with different distribution forms of tooth flank errors and various tooth surface modifications.

Time-varying stiffness model of spur gear considering the effect of surface morphology characteristics

The nonuniform cantilever beam and Hertzian contact model have been widely used to derive the mesh stiffness of spur gear assuming that the contact surface is absolutely frictionless. However, studies have confirmed that machined surfaces are rough in microscale and can be simulated by the Weierstrass–Mandelbort function. In order to get a reasonable and precise mesh stiffness model, the M-B contact model and finite element method are combined to express the local contact stiffness Kh. Through the simulation and comparison, the analytical finite element method is proved to be consistent with the traditional models and introduces the roughness parameters of machined tooth surface into the meshing process. Furthermore, the results also show that it is advantageous to improve the total mesh stiffness by increasing the fractal dimension D and input torque T as well as decreasing the roughness parameter G. In this paper, a relationship is built between the total mesh stiffness of gear sets with tooth surface characters and input torque, which can be a guidance in the design of the tooth surface parameters and the choice of the processing method in the future.

Finite Element Analysis of the Stress of Premium Connection Loaded by Combined Loads

Considering the helix angle and using the elasto-plastic contact finite element method, a 2-D and 3-D finite element models are established by the finite element analysis software ANSYS. The stress distribution of special thread tubing joints under different combined loads are analyzed and compared. The analysis results shows that the effect of different composite loads on the joint strength and sealing performance of oil casing joint are different. Under different internal pressure of combined load, the joint strength of oil casing joint has little influence, but with the increase of pipe pressure, the leakage resistance of tubing joint is enhanced. Under combined load, with the increase of axial tension, the stress of oil pipe joint which is generated in the initial meshing position and near the end of the thread is much higher than that of middle thread and large axial tension easily lead to thread failure phenomenon. Besides, it is important to compare the calculated stress contour curve with 2D and 3D finite element models which are the reason why comparative analysis is used.

Finite Design for Critical Stresses of Compressed Biomaterials under Transportation

This paper focuses on the evaluation of critical stresses of biomaterials of spherical shape under radial and axial compression employing Hertz contact theory and finite element method. The mechanical properties of UTC tomatoes were determined with a compression test rig for radial and axial compression contacts with metal plate. The maximum contact pressure Pmax was evaluated as 0.063MPa while the maximum shear stress was 0.022MPa. The finite element analysis gave the von mises stresses for axial and radial contacts as 0.001699MPa and 0.012271MPa. The design yield stress was predicted for UTC tomatoes and specified as 0.0012MPa for UTC containers design for transportation. The results of this study will therefore be relevant in the design of transportation for fruits of spherical shape.

Parametric modeling and contact analysis of helical gears with modifications

An approach for a mathematical model and contact analysis of helical gears including tip relief, root relief, end relief and longitudinal crowning modification was developed. First, tooth profile equations of non-modified involutes, tip reliefs, root reliefs and fillets were derived after applying gear principles and coordinate transformation to transverse cross section profiles of a rack cutter. Then the intersecting lines between different profiles were solved through by Gauss-Newton numerical method. Parametric modeling program of modified helical gears was obtained to automatically generate exact gear surfaces of tip reliefs, root reliefs, end reliefs and longitudinal crowning modifications via Matlab code. Subsequently, an example of helical gear pair in practical engineering was presented, and the solid model and finite element model with modification were established. Finally, the dynamic contact characteristic of helical gear pair was calculated by three-dimensional dynamic contact finite element method. It is expected that the proposed approach can be applied in analyzing the effect of modification on radiation noise prediction of gear system in further study.

An innovative contact partition model for wheel/rail normal contact

Wheel/rail contact modelling is essential in railway vehicle dynamic simulation, wheel/rail wear and fatigue. For this purpose, the tiny contact area at wheel/rail interface needs to be carefully investigated. In this paper a Partition Model (P_M) method is proposed to solve the wheel/rail normal contact problem. In the model, the contact region is divided into zones according to different curvature radii of wheel/rail profiles, and each zone is modified by the principle (the normal gaps of contact patch boundaries being equal to each other). For the sake of accuracy, both the iterative algorithms of wheel/rail normal force and elastic compression are also introduced in this model. Three typical test cases are designed to verify the feasibility and accuracy of the proposed method, and the results are compared to those provided by Kalker׳s CONTACT program and Finite Element (FE) method. The results show that the P_M method is fast and accurate for calculating normal contact problems in non-Hertzian cases. The good agreement with CONTACT and finite element method indicates that the capability of P_M method in railway vehicle simulation, wheel/rail wear and fatigue.

Particle Size Distribution of Food Boluses and Validation of Simulation During Artificial Indenter Crushing

Abstract To study the effects of indenter surface shapes on the crushing of foods, a double-tooth indenter (DTI), a single-tooth indenter (STI), a cylinder-type indenter (CTI) and a wave-type indenter (WTI) were developed by simulating the crown of human molar. Crushing experiments and analysis of finite element simulation were done. Crushing effect was determined by the wet sieving and weighing method; numerial simulations were performed for the crush process using the non-linear contact finite element method. The results showed that the DTI yielded the smallest median size among the four indenters, and the granulometric characteristics of food bolus are similar to human boluses, have higher von Mises stress value than others, higher crush efficiency, bigger crush stress, more stress concentration area than others. The crushing efficiencies of STI and CTI are very close. This study can improve the indenter parameters of texture analyzers and optimize the design process of a food chewing robot.

Analysis and Optimization of Elastic Expansion Sleeve Based on the Finite Element

The contact finite element method is proposed to analyze the stress and deformation distribution of elastic expansion sleeve in the paper. The maximum stress position of each component under the most dangerous working condition is obtained. The effect of structure dimension on stress and deformation of elastic expansion sleeve is found out. The structure dimension meeting the practical requirements is gotten. The analysis results provide the reliable theory basis for the design. The optimization for the structure and processing technology of elastic expansion sleeve is realized, based on simulating the design structure.

Simulation studies on drilling mud pump plunger seal failure under ultrahigh pressure and ultradeep conditions

Plunger seals are key components in drilling mud pumps. Under ultradeep and ultrahigh pressure conditions, plunger seals often fail and their service life decreases. This leads to lower drilling mud pump efficiency. In this paper, the simulation study is carried out with the contact finite element method, using the stress–strain curves of rubber material tests, Mooney-Rivlin constitutive model material parameters are determined through data fitting. Analyzing the seal mathematical model, building the finite element model, using penalty function algorithm based on the contact surface, applying loads and boundary conditions to simulate the assembly and the actual working conditions of the seal and analyzing the distribution law of the stress, strain and contact pressure of plunger seal, the easily failure places are found, the root causes of failure are analyzed, and the fundamental ways of preventing seal failure are proposed to provide a theoretical basis for the structurally optimized design of the new drilling mud pump plunger seals. The results show that: failure of the rear of the sealing ring, the root of V-type surface between the sealing ring and mantle ring, the sealing surface lips between the seal ring and the plunger, and the sealing surface lips between the seal ring and the cylinder is extensive. The first sealing ring is most damaged. The internal causes of the sealing ring’s failure are the uneven distribution, high stress and stress concentration of stress and contact pressure. However, the root reason for failure is the inadequate sealing ring structure design. Structural improvements should be considered to reduce stress and strain and provide a more even stress distribution. If peak contact pressures reach the outer sealing ring and prevent abrasives from entering the sealing surface, the chance of failure is reduced.

Finite Element Analysis of Gear’s Stress Analysis Based on Accurate Model

The paper established the accurately 3D-modeling of the gear by I-DEAS, and had correlative theoretic analysis and finite element computing technology study on its dynamics meshing structure strength with the contact finite element method. Then, accomplish model studied gear-stress in the process of Gear Drive. The conclusion is used to design an upgrade similar straight gear.

Numerical simulation of gear surface hardening using the finite element method

This paper was devoted to presenting a systematic approach based on finite element method to numerical analysis of gear surface hardening with the consideration of the contact problem. After the contact finite element method theory of gear and rack was introduced, the numerical analysis of gear surface hardening was discussed in detail. The element selection of gear–rack hardening layer based on finite element method was proposed, the algorithm characteristics of gear–rack elastic–plastic contact problems were also put forward, and the material properties and constitutive relations of gear–rack hardening layer were then discussed in detail. The gear–rack elastic–plastic contact analysis results were discussed, and the experimental results with the laser treatment were analyzed with the microstructure changes of the laser hardening layer to measure the performance of the hardening layer. The wear simulating test of gear results in improving the wear resistance greatly, and this surface hardening treatment has been officially put into engineering application.

Strength Design on Permanent Magnet Rotor in High Speed Motor Using Finite Element Method

The permanent magnets can be damaged for the tremendous centrifugal stress when the permanent magnet rotor rotates in high-speed. In this paper, the mechanical strength of high-speed permanent magnet rotor was researched. Stability operation mechanical conditions of the surface-mounted permanent magnet rotor were analyzed. The mathematical model between the shrink range of bandage and the maximum operating speed were concluded. The strengths of two kinds of surface-mounted permanent magnet rotors were calculated and compared using contact finite element method. For buried type permanent magnet rotor, the equivalent ring method was put forward to calculate its stress limit. The mathematical relationships between the maximum velocity and iron bridge thickness has been deduced. Using finite element method, the stress distributions was analyzed. The research results have shown that the high speed permanent magnet rotors designed according to the method proposed here had the adequate mechanical strength. DOI : http://dx.doi.org/10.11591/telkomnika.v12i3.4675

Stress Analysis of Asymmetric Spur Face-Gear Pair Based on Finite Element Method

According to the theory of gear geometry, the equations of teeth surface of double pressure angles asymmetric face-gear were conducted. Discrete points were generated in MATLAB according to the surface equations, and then the author established contact finite element models of single-tooth pair in ANSYS. The calculated value of contact pressure of the single tooth contact finite element model and the calculated value of contact pressure which given by the point-contact Hertz theory were compared to verify the effectiveness of the contact finite element method. Several groups of parameters were calculated and the results showed that the use of reasonable asymmetric design can effectively reduce the max surface contact pressure and the max tooth root bending stress.

Crowned Profile Design of Roller Bearings Used in Rolling Mill Based on Three Dimension FEA

Aiming at the characteristic of bearings supported in rolling mill and combining contact mechanics and finite element method, the edge effects of the cylindrical roller bearings used in the rolling mill are analyzed based on FEA for the Roller system of Rolling Mill and FEA of the bearing whole. According to the results of three dimensions FEA on the edge effects, different modification curves are taken to design crowned profiles of the cylindrical roller bearings. And comparison between the effects of the different modification curves is done through the simulation of 3D FEA, so the guides are offered to optimize the cylindrical roller bearings used in the rolling mill.

Conical Surface Sealing Performance of Pipe Connection Fits

The conical surface sealing performance of a pipe connection fit (PCF) has been studied by means of an equivalent mechanical model and the contact finite element analysis (FEA). By building an equivalent mechanical model, we studied the basic mechanical relations between the jointing parts, proposed a sealing mechanism, and identified a basic pretension-relaxation-leakage mode occurring in the sealing process of a conical surface PCF. Then we simulated the contact states of the PCF sealing surface using a multi-body elastic contact finite element method (FEM). In addition, the characteristics of the pretension-relaxation-leakage mode were further discussed in terms of the contact forces as well as the contact areas on the sealing surface. These results revealed some fundamental characteristics inherent in the sealing process of conical surface of PCFs, and demonstrated the potentials of the contact FEA in studying PCF sealing performance.

Contact forces between viscoelastic ellipsoidal particles

The normal (NFD) and tangential contact forces (TFD) between viscoelastic ellipsoidal particles are studied based on the contact mechanics and finite element method. It is found that the NFD and TFD force models previously formulated for spheres are valid for ellipsoidal particles and non-spherical particles of smooth surface, provided that some variables in the models are properly considered. The applicability of the NFD and TFD models are demonstrated in the collisions of two viscoelastic ellipsoids and shown to agree well with the results calculated by means of the finite element method. As part of the study, the applicability of the Linear-Spring-Dashpot (LSD) model which is widely used in the discrete modeling is also examined, and its limitation is identified.

Contact Finite Element Analysis of Spindle-Toolholder Joint

A performance evaluation model for spindle-toolholder joint system is built by applying the contact finite element method (FEM). Contact detection is implemented at the Gaussian integration points of the contact elements. Contact state is determined by calculating normal distance and normal contact force between every two points on the contact surface. Friction state is determined by calculating tangential contact force. The determinations are introduced into the variable principle of nonlinear FEM based on pure penalty method. The updated FE equations are solved using the full Newton-Raphson method. Deformation and contact stress distribution are studied. The stiffness distribution is derived by calculating the displacement increments under the different forces, based on the stiffness definition. The proposed model can well illustrate and evaluate the joint performance.

Research on Three-Dimensional Structure Optimization for Fir-Tree Root and Rim of Turbine Blade with Complex Damping Structure

The research on structure optimization for the fir-tree root and rim of a steam turbine blade with complex damping structure was conducted by three-dimensional contact finite element method and mathematical optimization algorithm. A multi-variable parametric model of three turbine blades and rims with fir-tree root and rim was established. Twelve critical geometrical variables of the root-rim were optimized to minimize the maximum equivalent stress of the root-rim. The optimal structure of the fir-tree root-rim was finally obtained through the optimization process and the equivalent stress of the root and rim both had evident reductions, Compared with the initial structure, the maximum equivalent stress of the root and rim reduced by 13.47% and 12.26%, respectively. Relevant work is expected to support the design of turbine blade root-rim in theory and improve the operation reliability of turbo-machinery to some extent.