Maximum Contact Stress Research Articles

Research on bar deflection of low-stress cropping process under bending-shear coupling effect

In view of the influence of shear effect on bar deflection in low-stress cropping, which makes it difficult to control the loading die and seriously affects the surface quality of cropping bar, based on the energy balance theory in this paper, the stiffness equivalent transformation of the bar with annular V-shaped notch and dynamic crack is carried out, and the coupling effect of bending moment and shear force on the bar deflection before and after crack initiation is quantified. Based on it, the deflection characterization formula for the whole cropping process of the bar with different length-diameter (L/2R) ratios is established. The change laws of bar deflection with different L/2R ratios are analyzed by XFEM method. Especially for the bar with L/2R ≤ 2.84, it is pointed out that it is necessary to consider the influence of shear deflection on the basis of bending deflection, and its influence degree decreases with the increase of L/2R. The real-time synchronous dynamic deflection test platform is built on the cropping machine of rotary bending. The research shows that the calculated values obtained by the deflection characterization formula proposed are in good agreement with the corresponding experimental results. The evaluation parameter, maximum contact stress reduction ratio ξ(p-l)/p, is proposed to characterize the degree of surface contact stress reduction under line contact loading relative to point contact loading. It is pointed out that the variation range of ξ(p-l)/p of the bar with different L/2R ratios under the influence of deflection is as high as 49.8%-64.1%. And further application of double bearings outer ring loading is also beneficial to obtain high cropping quality.

A Comprehensive Optimization Model of Tooth Surface Parameters for the Minimization of Contact Stress of Helical Face Gears by Considering the Avoidance of Edge Contact

Optimization with edge contact avoidance and contact stress minimization is essential for gear design. Due to the complex geometry of modified helical face gear drives, it is complicated to find the optimal design parameters with the consideration of issues including loading, assembly errors, and edge contact. As the finite element method is tedious and time-consuming, an optimization model with a simplified algorithm of the loaded tooth contact analysis with errors (ELTCA) for modified helical face gears is presented, and it can programmatically optimize the contact stress with edge contact avoidance. Firstly, a simplified ETCA algorithm is introduced, which reduces the five unknowns in the traditional contact equations to three. Secondly, the LTCA is analytically implemented according to the Hertz theory. Subsequently, an optimization model with the objective function of avoiding edge contact and reducing maximum contact stress is proposed. Furthermore, the proposed model is applied to reveal the effects of design parameters and assembly errors on the optimized contact path and stress. The results show that the optimization model is accurate and efficient; the design parameters and assembly errors have great effects on the meshing of modified helical face gears.

Triaxial Contact Stresses of the Green Bus Tire Including Complex Rubber Materials and Rim

The primary purpose of the research is to explore triaxial contact stresses of the green bus tire including complex rubber materials and rim. An accurate finite element model of the bus tire is constructed using ABAQUS software after verification. The measured and calculated values have good consistency under different tire loads and inflation pressures. The finite element model is applied for quantitative research by changing tire loads, inflation pressures, and rolling conditions. The analysis results show that higher inflation pressure increases vertical contact stress, which requires a reasonable balance between high load and high inflation pressure. When the inflation pressure increases, the position of the maximum longitudinal contact stress shifts forward, and the maximum transverse contact stress shifts inboard in the transverse direction. When the tire load becomes larger at the free rolling condition, the position of the maximum vertical contact stress moves forward, and the position at the full braking condition is more advanced under the same load conditions. Overload not only causes great damage to the tire during the braking condition but also accelerates the appearance of the rutting and shoving of the road.

Optimization of high-efficiency tooth surface accuracy of spiral bevel gears considering machine-tool motion errors

With the continuous improvement of the requirements of spiral bevel gear transmission for low noise and high precision, the optimization of high-efficiency tooth surface accuracy considering the motion axis error of machining machine tool has become a key point in the process of designing and manufacturing spiral bevel gear. Based on the theory of the multi-body dynamics system and the principle of gear meshing, a new tooth surface error model of spiral bevel gear considering the error of machine-tool moving axis is proposed and optimized, so as to obtain higher tooth surface accuracy and meshing efficiency. Firstly, according to the motion and machining principle of spiral bevel gear NC grinding machine, the corresponding relationship between the motion error of each axis of the NC gear grinding machine and the variation of cutting parameters of spiral bevel gear is analyzed, and the geometric motion error model of spiral bevel gear grinding machine is given; secondly, the tooth surface equation of the spiral bevel gear considering the machine-tool motion axis error is established; then, in view of Powell's dog leg optimization algorithm, the tooth surface considering the motion axis error of the machine tool is optimized, and the optimal cutting parameters of spiral bevel gear tooth surface machining are obtained. Finally, the simulation results show that the difference between the peak and peak values of transmission error and the maximum contact stress of the tooth surface is reduced by 72.6% and 1.62%, respectively, and the meshing efficiency is improved from 0.9798 to 0.9803 after optimization; by comparing the rolling experiment and simulation results, the maximum error between the quantitative parameters of the two groups of tooth surface contact marks is no more than 9%, which verifies the effectiveness and feasibility of this method, and provides a certain theoretical basis for practical production and processing.

Analysis of Initial Cracking of an Interface between a Bundled Lipped Channel–Concrete Composite Wall and an Infill Wall

The bundled lipped channel–concrete (BLC-C) composite wall structure is a new structure with several advantages such as a high bearing capacity and good seismic performance. However, interface cracks between a BLC-C composite wall and the infill wall (non-structural wall) are a severe problem and need to be urgently resolved. Interface cracks affect not only the esthetics, but also the normal use of a building. The presence of interface cracks changes the perceptions of the owners of a structure, forcing them to question its safety and even take legal action against its developer. Therefore, in this study we aimed to investigate the initial cracking of the interface between a BLC-C composite wall and an infill wall. Unidirectional horizontal loading tests were conducted on two infill wall specimens constrained by BLC-C composite walls on both sides. The finite element analysis software ANSYS was used to simulate the loading process of the tests. The test results were compared to verify the accuracy of the finite element model. A finite element analysis was conducted to determine the effect of the horizontal displacement of the specimens when the interface initially cracked under different parameters such as the widths of the BLC-C composite wall, infill wall, and opening as well as the strength grade of the bricks and maximum normal contact stress. The results showed that a decrease in the width of the BLC-C composite wall or a rise in the width of the infill wall delayed the appearance of interface cracks. A large opening also delayed the occurrence of interface cracks. An enhancement in the strength grade of the bricks led to an earlier appearance of interface cracks. Interface cracks occurred later with an increase in the maximum normal contact stress between the BLC-C composite wall and the infill wall.

Failure analysis of POM ternary nanocomposites for gear applications: Experimental and finite element study

The main purpose of the present study is to assess the failure behavior of polyoxymethylene/carbon black/CaCO3 ternary nanocomposite gears by employing an experimental gear test setup and a gear renewal technique. The failure-related factors including surface temperature, tooth wear, and failure analysis at macro- and micro-scales were studied. The tooth surface temperature was measured continuously based on an online-measuring approach. The tooth wear was calculated using microscopic images and software analysis. The maximum contact stress on meshing teeth surfaces was specified by finite element analysis. According to SEM micrographs, the application of both nanostructures contributed to a more uniform distribution of each nanophase within the POM matrix. The gear test results indicated an enhanced tooth resistance and service life of up to 58% and 125%, respectively, for ternary nanocomposites relative to neat POM gears. The tooth surface temperature was reduced for nanocomposite gears due to the promoted heat transfer and thermal stability. The tooth deformation and cracking were highly suppressed for ternary nanocomposite gears at failure. The evaluation of teeth surface damages at micro-scale revealed the suppression of plastic flow and material adhesion for ternary nanocomposites.

Biomechanical guidance can improve accuracy of reduction for intra-articular tibia plafond fractures and reduce joint contact stress.

Articular fracture malreduction increases posttraumatic osteoarthritis (PTOA) risk by elevating joint contact stress. A new biomechanical guidance system (BGS) that provides intraoperative assessment of articular fracture reduction and joint contact stress based solely on a preoperativecomputed tomography(CT) and intraoperative fluoroscopy may facilitate better fracture reduction. The objective of this proof-of-concept cadaveric study was to test this premise while characterizing BGS performance. Articular tibia plafond fractures were created in fivecadaveric ankles. CT scans were obtained to provide digital models. Indirect reduction was performed in a simulated operating room once with and once without BGS guidance. CTscans after fixation provided models of the reduced ankles for assessing reduction accuracy, joint contact stresses, and BGS accuracy. BGSwas utilized 4.8 ± 1.3 (mean ± SD) times per procedure, increasing operative time by 10 min (39%), and the number of fluoroscopy images by 31 (17%). Errors in BGS reduction assessment compared to CT-derived models were 0.45 ± 0.57 mm in translation and 2.0 ± 2.5°in rotation. For the fourankles that were successfully reduced and fixed, associated absolute errors in computed mean and maximum contact stress were 0.40 ± 0.40and 0.96 ± 1.12 MPa, respectively. BGS reduced mean and maximum contact stress by 1.1 and 2.6 MPa, respectively. BGSthus improved the accuracy of articular fracture reduction and significantly reduced contact stress. Statement of Clinical Significance: Malreduction of articular fractures is known to lead to PTOA. The BGS described in this work has potential to improve quality of articular fracture reduction and clinical outcomes for patients with a tibia plafond fracture.

Computerized design, simulation of meshing and stress analysis of pure rolling internal helical gear drives with combined tooth profiles

The computerized design of non-generated pure rolling internal helical gear drives with combined transverse tooth profiles based on the active design of the meshing line function is presented. The application of different combinations of curves, namely circular arcs and involutes, to form the gear active tooth profiles is discussed. The parametric equations for tooth surfaces and the basic design parameters and equations of geometric sizing are proposed. The meshing performance and mechanical behavior are studied in terms of the contact patterns, maximum contact and bending stresses and peak-to-peak level of loaded transmission errors compared with a design of internal helical gear drive with corrected fillet. The combination of a circular arc and an involute connected at the pitch point to form the active tooth profile for both the pinion and the internal gear shows reduced maximum contact and bending stresses and lower peak-to-peak level of the loaded function of transmission errors. The proposed design of combined tooth profiles will contribute to lower the noise and vibration of the proposed gear drives, increase the endurance and life of the gear drive, and lower the heat generation due to pure rolling conditions of the achieved bearing contact.

Analysis and validation of a 3D finite element model for human forearm fracture.

Most researchers have performed finite element (FE) analysis of the human forearm fracture by exploring the strength and load transmission of the bones. However, few studies concentrated a complete simulation of the whole forearm complex including ligaments. This paper aims to investigate the load transmission through the bones, contact stress at the joints and strain in the ligaments by using an elaborate FE model, further validating the fracture condition for human forearm. The interosseous ligament was separated into three regions based on the distance to the proximal and distal ends. The FE simulation results were slightly more or less than a previous experimental data in the literature, but generally provided a close approximation of the bone and ligament behaviors. Compared with the experiment results under different loading conditions, maximum contact stress at the proximal radio ulnar joint (PRUJ) and distal radio ulnar joint (DRUJ) of the simulations was higher with an average of 13.4%, and peak strain in the interosseous ligament (IOL) was lower with an average of 11.0%. Under 10kg load, the maximum stress in the radius (2.25 MPa) was less than double the value in the ulna (1.43 MPa). Finally, the FE model has been validated with the onset and location of the Colles' fracture in the literature. This study will provide a great benefit in terms of surgical and medical applications related to forearm fracture that require an extensive knowledge of the behavior of the bones and ligaments under various loading conditions.

Changes in hip joint contact stress during a gait cycle based on the individualized modeling method of “gait-musculoskeletal system-finite element”

ObjectiveTo construct a comprehensive simulation method of “gait-musculoskeletal system (MS)-finite element (FE)” for analysis of hip joint dynamics characteristics and the changes in the contact stress in the hip throughout a gait cycle.MethodsTwo healthy volunteers (male and female) were recruited. The 3D gait trajectories during normal walking and the CT images including the hip and femur of the volunteers were obtained. CT imaging data in the DICOM format were extracted for subjected 3D hip joint reconstruction. The reconstructed 3D model files were used to realize the subject-specific registration of the pelvis and thigh segment of general musculoskeletal model. The captured marker trajectory data were used to drive subject-specific musculoskeletal model to complete inverse dynamic analysis. Results of inverse dynamic analysis were exported and applied as boundary and load settings of the hip joint finite element in ABAQUS. Finally, the finite element analysis (FEA) was performed to analyze contact stress of hip joint during a gait cycle of left foot.ResultsIn the inverse dynamic analysis, the dynamic changes of the main hip-femoral muscle force with respect to each phase of a single gait cycle were plotted. The hip joint reaction force reached a maximum value of 2.9%BW (body weight) and appeared at the end of the terminal stance phase. Twin peaks appeared at the initial contact phase and the end of the terminal stance phase, respectively. FEA showed the temporal changes in contact stress in the acetabulum. In the visual stress cloud chart, the acetabular contact stress was mainly distributed in the dome of the acetabulum and in the anterolateral area at the top of the femoral head during a single gait cycle. The acetabular contact area was between 293.8 and 998.4 mm2, and the maximum contact area appear at the mid-stance phase or the loading response phase of gait. The maximum contact stress of the acetabulum reached 6.91 MPa for the model 1 and 6.92 MPa for the model 2 at the terminal stance phase.ConclusionsThe “Gait-MS-FE” technology is integrated to construct a comprehensive simulation framework. Based on human gait trajectories and their CT images, individualized simulation modeling can be achieved. Subject-specific gait in combination with an inverse dynamic analysis of the MS provides pre-processing parameters for FE simulation for more accurate biomechanical analysis of hip joint.Graphical abstract

Finite Element Analysis of Contact Stress Distribution on Insert Conformity Design of Total Knee Arthroplasty

The tibial insert conformity is one of the essential parameters concerned with the contact stress distribution of biomechanics characteristics in total knee arthroplasty (TKA). This study aimed to evaluate the effect of tibial insert conformity design on contact stress distribution using Finite Element (FE) analysis. The three-dimensional (3D) FE model of the posterior stabilized type of TKA was analyzed according to the standard knee implant loading. The 3k factorial experimental design was performed for the response surface of different insert curvatures consisting of the curve, partial flat, and flat insert conformity in sagittal and coronal planes. According to the result, the coronal and sagittal plane conformity displayed the effect of the change on the contact stress, including the contact area for the flexion angle of the knee joint. The maximum contact stress increased while the contact area value decreased during the flexion angle of the knee joints raised. The changing insert conformity value in the sagittal plane displayed higher sensitivity to contact stress than the changing conformity in the coronal plane. The relationship between the contact stress and tibial insert conformity under knee flexion angle indicates highly regression suitable for the prediction. In addition, the FE simulation result was then verified by compared to mechanical testing using the Fujifilm technique. The result of FE analysis exhibited similar to that of the mechanical test. The study indicated that the different geometric designs of the insert conformity played a crucial role that influenced and relationship to the contact stress of TKA

Effect of structural parameters on the setting performance of plug slips during hydraulic fracturing

Slip is one of the most critical components for the frac plug, which would lodge into the casing and lock the frac plug in place during the setting and anchoring process. However, fracture failure of slip significantly affects the hydraulic fracturing effects and has attracted tremendous attention. In this paper, a three-dimensional contact model is applied to explore the setting process of slip. The effects of key structural parameters such as apex angle, inclination angle, and wedge angle on the contact characteristics of slip are systematically investigated. Numerical results indicate that the maximum contact stress appears at the contact area between slip tooth and the casing's inner wall. Besides, the maximum contact stress generally increases with the increase of apex angle and inclination angle, while decrease linearly with the rise in the wedge angle. Experimental results show that the slip teeth get blunt and appear severe plastic deformation, which arises from stress concentration. Comparison of biting area indicates that the experimental results are about 21.3% larger, which still have a reasonable agreement with the numerical results. These obtained results can guide the parametric selection of plug slip and other similar components.

Sealing Contact Transient Thermal-Structural Coupling Analysis of the Subsea Connector

Taking the subsea collect connector as an example, the sealing characteristics of the sealing structure of the subsea connector under transient thermal–structural coupling were studied. Based on Airy’s thermal stress function, the mathematical model was established, the complex stress function was used to solve the problem, and a three-dimensional transient thermal stress model of the core sealing parts was obtained. The transient thermal–structural coupling stress model of the core seal was obtained by linear superposition principle. The transient temperature field of the subsea collet connector under different working conditions was analyzed. It was found that the larger the temperature difference between the components was, the greater the difference of expansion rate was, and the greater the impact on the sealing performance of LSG was in the process of temperature variation from transient to steady distribution. Numerical simulations of various working conditions under the transient temperature field were carried out. The results showed that sudden change of the temperature and oil–gas pressure will bring about large fluctuations of the maximum contact stress and equivalent stress of the seal, which was easy to fatigue wear, and thus affect the reliability of the sealing performance. Finally, the experiment proves that the sealing ring can maintain sealing performance under the conditions of temperature-cyclic loading. The coupled mathematical model proposed in this paper could be used for the transient thermal–structural coupling theoretical analysis of similar subsea equipment.

Analysis of Stresses and Strains in Stainless Steel 316 L Tubes Subjected to Die Expansion

Abstract SS316 L finned tubes are becoming very popular in high-pressure heat exchangers and particularly in CO2 cooler applications. Due to the high pressures present during operation, these tubes require an accurate residual stress evaluation generated by the die expansion process. Die expansion of air cooler fin tubes creates not only high stresses that can surpass the ultimate tensile strength when combined with operation stresses but microcracks during expansion when the process is not well controlled. This research work aims to study the elastic-plastic behavior and estimate the residual stress state of fin tubes subjected to the die expansion process. The stresses and deformations of the expanded SS316 L tube are analyzed numerically using the finite element method. The expansion and contraction process are modeled considering the elastic–plastic material behavior for different die sizes. The maximum longitudinal, tangential, and contact stresses are evaluated to verify the critical stress state of the joint during the expansion process. The importance of the material behavior in evaluating the residual stresses using kinematic and isotropic hardening is addressed. Finally, an experiment was conducted to assess the tangential and longitudinal strains of a 3/8 in. stainless steel tube subjected to expansion with an oval-shaped die.

Hydrogen-accelerated white etching area formation in bearings under rolling contact fatigue

The presence of hydrogen can dramatically facilitate microstructural alterations in components subjected to rolling contact fatigue (RCF) potentially leading to premature failure. A dislocation-assisted carbon migration model is developed to describe the formation of hydrogen-influenced microstructural alterations such as white etching areas; the model incorporates rolling parameters such as maximum contact stress, number of cycles, rotational speed, and temperature. Kinetic Monte Carlo is adopted to describe hydrogen-dislocation interactions which alters dislocation mobility, accelerating white etching area formation whilst reducing fatigue life. The results are experimentally validated by microstructural characterisation and RCF testing.

Research on Prediction Models for the Compression-Resilience Performance of Corrugated Metal Gaskets With Residual Stress

Abstract The manufacturing process is an important factor related to the compression-resilience performance of corrugated metal gaskets, especially stainless steel gaskets. A finite element method was employed to research the mechanical properties of corrugated metal gasket based on the stamping and spring back process analysis. On this basis, the influence of structural parameters of corrugated metal gasket related to the mechanical properties was analyzed. Prediction models of mechanical properties were proposed and validated in this paper. The result shows that the maximum contact stress and resilience rate in the finite element model are in accordance with the experimental results with the relative error of 1.21% and 8.76%, respectively. Critical structural parameters affecting the properties of the corrugated metal gasket are pitch (P), lip height (H), and material thickness (T). The compression and resilience curves obtained from the prediction models are consistent with the finite element method (FEM) simulation. The models can accurately reflect the compression-resilience performance of corrugated metal gaskets with different structural parameters.

Tool profile modification of hypoid gear machined by the duplex helical method

To avoid edge contact and stress concentration on the tooth surface of hypoid gear pairs machined by the duplex helical method for the drive axle of heavy-duty vehicles, a four-segment tool profile was designed for the simultaneous modification of the concave and convex surfaces of the pinion. First, a geometric model of the four-segment tool profile was established. Second, a mathematical model of the duplex helical method based on the four-segment tool profile was established, and a method for solving the tooth surface generated by the connecting points of the four-segment tool profile was presented. Finally, loaded tooth contact analysis based on finite element method was used to analyse the meshing performance of the gear pair obtained by the four-segment tool profile modification. The results of the original and modified gear pairs were compared. The tooth surface modification inhibited edge contact, improved the stress distribution, and decreased the maximum contact stress of the tooth surfaces, thereby improving the fatigue and wear life of the gear pair.

Dynamic Simulation and Analysis of Engagement Process for Logarithmic Spiral Bevel Gear Based on Accurate 3D Model

Based on the accurate 3D model of logarithmic spiral bevel gear, the operation of spiral cone gear engagement is analyzed and simulated by ANSYS. Through the nonlinear static contact analysis of different positions, the stress change rule and the maximum contact stress is obtained. Compared with the theoretical contact stress strength rule, this paper also analyzes the dynamic operation situation of the gear pairs, obtains the dynamic contact situation rule at different engagement times and different rotating speeds, the influence of the rotating speed on the gear contact characteristics is compared too. The static, dynamic performance and change rules of the gear engagement is obtained, which lay a solid foundation for the further research, design and manufacture of spiral bevel gears.

Stress analysis of a gear using photoelastic method and Finite element method: Review

Every day in our life, we use the gear, and it has become an integral and most used component. Gears have been in use for more than 100 years with different shapes and sizes in all the domains. For many decades gear has been the most researched component, and still, much research is going on. Pitting and surface hardness is understood by studying root stress and contact stress. The experimental (Photoelasticity), analytical, and Finite element method research helps develop new gear. Toothed gears transfer both motion and power during transmission. Power initiated at the first gear will have significant power loss when it reaches the final gear. When it comes to the assembled gear's performance and durability, we need to check on fatigue and reliability. The critical parameter for designing the gear is the contact stress created between the mating gear. In a comparison study for maximum contact stress, the load applied is around 300 N, and stress developed by the experimental method is 1775.1 N/mm2, and using the FEM is 1781.1 N/mm2, with a 1% error. Asymmetric gears are the replacement for conventional involute gears, they also provide the required strength, and also, there is a reduction in the weight of the gear. Materials like Metal, Epoxy resin, Polymer, Etc are used to manufacture gear. Composite gears can transmit power up to 175 KW.

A new incremental calculated approach to predict maximum contact stress of compressed packer in large deformation

Compressed packer rubber is large deformation material, which endures biaxial contact friction between oil-pipe and casing-pipe in sitting and sealing process. Large-deformation theory analysis of rubber brings huge difficulties to solve, this is due to the material, geometry and contact non-linearity should be considered. In this article, the deformation of compressed packer rubber tube (CPRT) is divided into free deformation, unidirectional and bidirectional constrained deformations. Based on the theory of thick-wall-cylinder and the linear constitutive of rubber material segment, the CPRT mathematical model in different deformation processes is established and the influences of axial load, axial height of CPRT and contact friction coefficient of casing inner wall etc are considered. Based on incremental calculated approach, the mathematical model is solved. By comparing the results of the theoretical model with the results of finite element method and experimental results, it is found that the theoretical maximum contact stress is more conservative than the FEM and experimental solutions, so the sealing reliability of packer effectively predicted under the premise of allowable contact stress and the theoretical results can provide a lower limit reference value for the contact stress of the packer in the actual seal process. Meanwhile, the deviation of contact stress in FEM and theoretical value at z150 height of CPRT is among 1.13%∼4.90%, which can predict the contact stress in the compressed area near the stress concentration upper end-face of CPRT under the low friction factor, the results provide a reference for the compressed packer design.