Finite Element Contact Analysis Research Articles

Identification of contact stiffness of shrink-fit tool-holder joint based on fractal theory

Shrink-fit holders are used widely in high-speed machining because of their high concentric and rigid clamp performance. In this paper, a method to determine the contact stiffness and contact force of shrink-fit tool-holder joint is proposed. The relationship between the contact stiffness and the normal contact load is deduced based on Hertz contact theory and fractal geometry theory. The contact force at the interface is obtained through finite element contact analysis. The identified contact stiffness is incorporated into the finite element model of the tool-holder assembly, which is used to predict the tool point frequency response function of the assembly. The predicted frequency response function agrees with that of the experiment, which verifies the proposed identification method. The effect of radial interference, tool insertion length, and rotational speed on contact behaviors between the shrink-fit tool-holder connection is determined, which is informative for the application and design of the tool-holder assembly.

Interface contact pressure-based virtual gradient material model for the dynamic analysis of the bolted joint in machine tools

Bolted joints have significant influence on the dynamic characteristic of the machine tool assembly. This study proposes a new modeling method using virtual gradient material. On the basis of Hertz contact theory and fractal geometry theory, the relationship between contact stiffness and normal contact load is deduced. The contact pressure distribution at the interface is obtained through finite element contact analysis. An orthogonal material model is introduced to describe the properties of virtual material. The virtual material is divided into several layers, and the elastic modulus and shear modulus in each sub-layer are derived based on Hooke’s Law. Both experimental and theoretical results for a bolted lap structure are obtained. The experimental results are compared with theoretical ones in terms of qualitative comparison of similar mode shapes and quantitative comparison of corresponding natural frequencies. The comparison shows that the theoretical first three-order vibration mode shapes are in good line with the experimental ones. The relative errors of corresponding natural frequencies between the virtual gradient material model and the experiment are less than 9%, which are smaller than those between the traditional virtual uniform material model and the experiment. The proposed virtual gradient material method would be useful to accurately model the bolted joint in CNC machine tools.

An Approach to Calculate Leak Channels and Leak Rates Between Metallic Sealing Surfaces

Surface topography of sealing interface is a key factor affecting sealing performance. In industry, it has always been desirable to optimize the performance of static seals by optimizing the surface topography. The evolution of leak channels and the quantitative effects of surface topography on leak rates are expected to be clarified. This paper proposes a novel approach to calculate leak channels and leak rates between sealing surfaces for specific surface topographies, based on three-dimensional (3D) finite-element contact analysis. First, a macromechanical analysis of the entire sealing structure is conducted to calculate the interfacial pressure. Second, the surface topography data are measured and processed. Third, the interfacial pressure is used as the boundary condition applied on the microscale 3D finite-element contact model, which is built based on the specific surface topography. Fourth, the geometrical models of leak channels are extracted from the finite-element contact model, and the leak rates are calculated using the computational fluid dynamics (CFD) method. The proposed approach was applied to a hollow bolt-sealing structure. Finally, experimental results verified the accuracy and effectiveness of the proposed approach, which can provide valuable information for optimizing surface processing techniques, surface topography, and static seal performance.

Geometry and contact characteristics of torus involute gears

Aimed at overcoming high sensitivity to machining or mounting error of line-contact conjugate surfaces, a novel torus involute gear drive is proposed which can compensate large axial misalignments and possess good meshing characteristics without lead correction. The torus involute gear is essentially a special spur gear with continuous shifting in the second order. Based on the processing principle of the torus involute gears, their mathematical models are established according to the corresponding imaginary rack cutter. In order to provide the approach to choose proper designing parameters, geometry characteristics of the torus involute gear are investigated: condition equations of tooth undercutting for a convex torus involute gear and tooth pointing for a concave torus involute gear are formulated utilizing the developed mathematical models, and the approach to checking tooth flank interference is provided. Contact characteristics of the gear set is studied through tooth contact analysis and finite element analysis. The simulated results produce useful information about tooth contact pattern, stress distribution, and transmission errors of the gear set.

A frictional contact finite element for wheel/rail dynamic simulations

The main purpose of this paper is to develop a simple-model moving wheel/rail contact element, so that the sticking, sliding, and separation modes of the wheel/rail contact can be appropriately simulated. In the proposed finite element, the wheel and rail are simulated using the cubic-spline contact element, and a power function normal stiffness and a constant horizontal stiffness are connected to the cubic-spline contact stiffness. The three-dimensional (3D) contact finite element analysis for a realistic wheel and rail was used to accurately model the wheel/rail contact stiffness. The validated examples show that the proposed nonlinear moving wheel element can simulate the complicated sliding, sticking, and separation contact problems with good accuracy. The complicated contact modes, including the multiple contact situation between wheel flange and rail side, can also be simulated accurately. Moreover, the computer memory and CPU time required to achieve this are much less than needed with the 3D finite element contact model.

Verified and validated finite element analyses of humeri

Background: Although ~200,000 emergency room visits per year in the US alone are associated with fractures of the proximal humerus, only limited studies exist on their mechanical response. We hypothesise that for the proximal humeri (a) the mechanical response can be well predicted by using inhomogeneous isotropic material properties, (b) the relation between bone elastic modulus and ash density (E(ρash)) is similar for the humerus and the femur, and may be general for long bones, and (c) it is possible to replicate a proximal humerus fracture in vitro by applying uniaxial compression on humerus׳ head at a prescribed angle. Methods: Four fresh frozen proximal humeri were CT-scanned, instrumented by strain-gauges and loaded at three inclination angles. Thereafter head displacement was applied to obtain a fracture. CT-based high order (p-) finite element (FE) and classical (h-) FE analyses were performed that mimic the experiments and predicted strains were compared to the experimental observations. Results: The E(ρash) relationship appropriate for the femur is equally appropriate for the humeri: predicted strains in the elastic range showed an excellent agreement with experimental observations with a linear regression slope of m=1.09 and a coefficient of regression R2=0.98. p-FE and h-FE results were similar for the linear elastic response. Although fractures of the proximal humeri were realised in the in vitro experiments, the contact FE analyses (FEA) were unsuccessful in representing properly the experimental boundary conditions. Discussion: The three hypotheses were confirmed and the linear elastic response of the proximal humerus, attributed to a stage at which the cortex bone is intact, was well predicted by the FEA. Due to a large post-elastic behaviour following the cortex fracture, a new non-linear constitutive model for proximal humerus needs to be incorporated into the FEA to well represent proximal humerus fractures. Thereafter, more in vitro experiments are to be performed, under boundary conditions that may be well represented by the FEA, to allow a reliable simulation of the fracture process.

歩行サイクルにおける寛骨臼移動術による股関節内接触応力の変化

Due to the inadequate development of acetabulum and consequently the stress concentration in cartilage, acetabular dysplasia not only causes instability of the hip joint, but is also associated with the development of osteoarthritis. Periacetabular osteotomy is a useful treatment for acetabular dysplasia by moving the bone fragment, cut off from the bone around the acetabulum, to improve the actabulum coverage and contact stress distribution of the hip joint. However, there is still no effective and practical analysis technique that can demonstrate the effect of the operation and provide biomechanical data such as stress distribution for treatment. In this study, three dimensional models of pre-and post-operative acetabulum have been constructed, and then computer simulations for gate cycle have been performed to evaluate the biomechanical effect of the periacetabular osteotomy by applying finite element contact analysis.

Wheel-rail Rolling Contact Finite Element Analysis of the Wear State on the Curve of Subway Line

Wheel-rail Rolling Contact Finite Element Analysis of the Wear State on the Curve of Subway Line

Load sharing characteristics of multi-stage planetary gear train using analytical and finite element model

The dynamic load sharing characteristics of a two-stage planetary gear train are analysed using a a lumped-parameter analytical model and b a finite element model. Both models include time-varying mesh stiffness, several manufacturing errors and assembly variations. The varying step Gill numerical integration algorithm is used to solve Model a, where lumped inertias represent gears, nonlinear springs with periodically varying stiffness represent gear meshes, and linear springs represent supports. Model b is developed from a finite element-contact analysis of gear dynamics and solved using dynamic explicit algorithm. Time-varying mesh stiffness excitation, tooth contact and loss are intrinsic to Model b. All errors deemed as approximately equivalent to a comprehensive mesh error are also considered. Float system parameters, assembly variations, and manufacturing errors are identified to quantify their effects on dynamic load sharing factor. Results from the two models are compared qualitatively and quantitatively validating the effectiveness of the both.

Finite Element Contact Analysis and Life Analysis of Gears in the Double-Sided Grinding Machine

The contact fatigue life of gears has direct influences on the working life of the double-sided grinding machine, in the actual using process, the contact fatigue life of gears cannot meet the requirements of working because of many factors. This paper uses the finite element software ANSYS, establishs the two-dimensional model of gears, and analyzes and calculates it, the research shows that: life expectancy of gears is 2.13 years, so gears should have carburizing or carbonitriding heat treatment to fit process requirements, gears can live up to 5.82 years, it can fit the technological requirements of gear life of 5 years. It is some practical value for increasing the working life of the double-sided grinding machine and improving the stability and accuracy of the whole machine.

Expedited patient-specific assessment of contact stress exposure in the ankle joint following definitive articular fracture reduction

Acute injury severity, altered joint kinematics, and joint incongruity are three important mechanical factors linked to post-traumatic osteoarthritis (PTOA). Finite element analysis (FEA) was previously used to assess the influence of increased contact stress due to joint incongruity on PTOA development. While promising agreement with PTOA development was seen, the inherent complexities of contact FEA limited the numbers of subjects that could be analyzed. Discrete element analysis (DEA) is a simplified methodology for contact stress computation, which idealizes contact surfaces as a bed of independent linear springs. In this study, DEA was explored as an expedited alternative to FEA contact stress exposure computation. DEA was compared to FEA using results from a previously completed validation study of two cadaveric human ankles, as well as a previous study of post-operative contact stress exposure in 11 patients with tibial plafond fracture. DEA-computed maximum contact stresses were within 19% of those experimentally measured, with 90% of the contact area having computed contact stress values within 1MPa of those measured. In the 11 fractured ankles, maximum contact stress and contact area differences between DEA and FEA were 0.85±0.64MPa and 22.5±11.5mm2. As a predictive measure for PTOA development, both DEA and FEA had 100% concordance with presence of OA (KL grade≥2) and >95% concordance with KL grade at 2 years. These results support DEA as a reasonable alternative to FEA for computing contact stress exposures following surgical reduction of a tibial plafond fracture.

Atomistic and Finite Element Contact Analysis of an Asperity and a Rigid Flat

The elastic-plastic finite element and atomistic models for the frictionless contact of a deformable sphere pressed by a rigid flat is presented. The evolution of the elastic-plastic contact with increasing interference is analyzed using two different analysis tools. The simulation results show that deformation mechanisms revealed in the two different analysis tools are quite different from each other. The physical phenomena “jump-to-contact” and “force drops during dislocation emission” are observed in our atomistic simulations which can not be seen in the continuum analysis.

Analysis of Leakage in Bolted-Flanged Joints Using Contact Finite Element Analysis

The evolution of leakage is studied using detailed contact finite element analysis. The distribution of stress at the gasket is analyzed using a contact condition based on slide-line elements using ABAQUS, a commercial finite element code. Slide-line elements also take into account pressure penetration as contact that is lost between flange and gasket. Results are presented for a particular flange, a raised face flange sealed by a mild steel gasket. A comparison of the results from the gasket contact analysis and the contact conditions specified by the ASME Boiler and Pressure Vessel Code, Sections VIII, Division 1 shows that the conditions specified in the ASME Code predict leakage relatively accurately.

Dynamic Characteristics Study of Geared Rotor System Using Contact Finite Element Analysis Method

Considering each component's elasticity of geared rotor system,a method to simulate the continuous engagement of gear pairs is proposed based on the contact finite analysis. The model is built by solid finite element to analyze structural vibration characteristics. By using the contact finite analysis method to simulate the engagement,the actual excitation like time-varying mesh stiffness,meshing contact can be included in the model,then more comprehensive,accurate response characteristics can be obtained. Solid finite model of a spur geared rotor system is built to simulate the dynamic engagement of gear pairs based on the contact finite element analysis method; the time-domain response of kinetic parameters such as contact force is achieved by resolving the equation of motion. The deviation of center distance,dynamic transmission error and the contact force is used to study the lateral vibration,torsional vibration,the engagement characteristic and coupling relationships of these. The results show that the elasticity of each component especially the rotors have great affection on the dynamic behavior of the system through increasing the nonlinear vibration characteristics such as bilateral impact and disengage of the gear pair.

Study of the sealing performance of tubing adapters in gas-tight deep-sea water sampler

ABSTRACT Tubing adapter is a key connection device in Gas-Tight Deep-Sea Water Sampler (GTWS). The sealing performance of the tubing adapter directly affects the GTWS's overall gas tightness. Tubing adapters with good sealing performance can ensure the transmission of seawater samples without gas leakage and can be repeatedly used. However, the sealing performance of tubing adapters made of different materials was not studied sufficiently. With the research discussed in this paper, the materials match schemes of the tubing adapters were proposed. With non-linear finite element contact analysis and sea trials in the South China Sea, it is expected that the recommended materials match schemes not only meet the requirements of tubing adapters’ sealing performance but also provide the feasible options for the following research on tubing adapters in GTWS.

Gear Meshing Noise of the Closed Gearbox

The dynamic excitation and the noise of meshing gears were analyzed quantitatively using the three-dimensional finite element contact analysis and the boundary element method. The distribution and variation roles of the gear mesh noise were obtained. The simulation result was verified by sound power measurement. The main excitation was determined additionally. It provides the theory basis for the control of the gearbox noise.

Stress Analysis of Interference Fit in Wheelset

The locomotive wheelset running with a high-speed, the wheels and axles of wheelset usually assembled by interference fit, the radial contact stress produced by interference cause the friction on the contact area, the axial force and torque of the wheelset transmitted by the friction. The value of prestress produced by the magnitude of interference change small in each load case, and it plays the main role in total stress of wheelset. So it’s very important that choosing a appropriate interference for the wheelset assembly base on the results solved by the finite element contact analysis.

Computerized Simulation of the Double Circular Arc Spiral Bevel Gear Meshing

The authors propose approaches for computerized simulation of meshing of DCAPSBG (double circular-arc profile spiral bevel gear). Algorithms for TCA (Tooth Contact Analysis) computer programs were proposed. This paper presented the key contents and method of TCA computer programming. TCA is an effective tool for meshing analysis of the DCAPSBG, and it is the basis of load tooth contact analysis and finite element analysis. The proposed approach is based on the tooth profile characteristic of the DCAPSBG and developed by Visual Basic and MATLAB mixed programming method. In addition, this paper made TCA analysis and contact area check experiment on gear meshing, and the program had been verified by real examples. This provided an effective approach for the design of DCAPSBG.

Lifting Platform Hinge Shaft Contact Finite Element Analysis

The lifting platform connecting hinge shaft finite element analysis by ANSYS software, and the fork arm is connected to the hinge bearing contact surface using spring element, the spring element contact stress situation to determine the hinge bearing and internal and external fork arm, solves the contact with the fork arm of the hinge shaft stress relationship problems, finite element analysis. The model is more accurate. The analysis of ideas can be widely applied to the similar finite element contact analysis.

Load distribution analysis of clearance-fit spline joints using finite elements

Splines are widely used in mechanical drive systems to transfer rotary motion from an input to an output. Despite their wide application in rotating machinery, very little is known about their contact behavior and load distribution characteristics. In this study, a combined finite element and surface integral contact analysis model is employed in order to investigate load distribution along the spline interfaces. Three loading cases are considered: (i) purely torsional loading representing power transfer through two concentric shafts, (ii) combined torsional and radial loading representing a spur gear–shaft interface, and (iii) combined torsional, radial, and moment loading representing a helical gear–shaft interface. The effect of spline misalignment is investigated along with intentional lead crowning of the contacting surfaces. In addition to spur spline teeth, helical spline teeth are investigated. Influence of intentional mismatch of splines through a slight helix angle applied to the external spline is also investigated within a range of torque transmitted. Finally, the effects of manufacturing tooth indexing error on spline load distributions are quantified using the proposed model.