An Inverse Approach to the Validation of Pressure Predictions in Rough Elastohydrodynamic Contacts

2001 ◽  
Vol 124 (1) ◽  
pp. 103-108 ◽  
Author(s):  
C. J. Hooke ◽  
K. Y. Li
Keyword(s):  
Residual Stress ◽  
Yield Strength ◽  
Rough Surface ◽  
Experimental Technique ◽  
Von Mises Stress ◽  
Stress Distributions ◽  
Inverse Approach ◽  
Controlled Conditions ◽  
Steel Disc ◽  
Von Mises

A simple experimental technique is developed that allows the pressures and stresses predicted by EHL analyses to be checked. A soft, rough steel disc is run, under controlled conditions, against a harder, smooth counterface. The pressures generated cause the soft disc to plastically deform. Once deformation ceases the residual profile may be measured and used as input to an EHL solver. The calculated pressures are then used to determine the stress distributions as the rough surface passes through the conjunction. After allowing for the build up of residual stress the maximum von Mises’ stress should be equal to the yield strength of the disc. This provides an accurate, quantitative check on the theoretical values.

Elastic-Plastic Contact Analysis of Materials with Gradient Yield Strength

2006 ◽  
Vol 532-533 ◽  
pp. 881-884
Author(s):  
Qin Xie ◽  
Geng Liu ◽  
Tian Xiang Liu ◽  
Jane Q. Wang
Keyword(s):  
Yield Strength ◽  
Yield Criterion ◽  
Contact Model ◽  
Von Mises Stress ◽  
Stress Distributions ◽  
Initial Stiffness ◽  
Programming Technique ◽  
Elastic Plastic ◽  
Von Mises ◽  
Yield Strength Variation

Reported in the paper is an elastic-plastic contact model developed to analyze the contact performance characteristics of materials with gradient yield strength. Plastic yielding and the strain-hardening properties of the materials are taken into account. The finite element method, the initial stiffness method, and a mathematical programming technique are utilized to solve the contact model. The von Mises yield criterion is used to determine the inception of plastic deformation. Results indicate that nitrided material with appropriate gradient of yield strength may greatly alter the distributions of contact stress, contact pressure as compared with untreated material in contact. The effects of different yield strength variation path of material on von Mises stress distributions are numerically investigated and discussed.

scholarly journals Elasto-plastic analysis of the contact region between a rigid ellipsoid and a semi-flat surface

2018 ◽  
Vol 10 (9) ◽  
pp. 168781401879739 ◽  
Author(s):  
Pengyang Li ◽  
Lingxia Zhou ◽  
Fangyuan Cui ◽  
Quandai Wang ◽  
Meiling Guo ◽  
...  
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Plastic Strain ◽  
Contact Pressure ◽  
Contact Region ◽  
Three Dimensional ◽  
Von Mises Stress ◽  
Effective Plastic Strain ◽  
Normal Forces ◽  
Von Mises

When the load acting on a mechanical structure is greater than the yield strength of the material, the contact surface will undergo plastic deformation. Cumulative plastic deformation has an important influence on the lifespan of mechanical parts. This article presents a three-dimensional semi-analytical model based on the conjugate gradient method and fast Fourier transform algorithm, with the aim of studying the characteristic parameters of the contact region between a rigid ellipsoid and elasto-plastic half-space. Moreover, normal forces and tangential traction were considered, as well as the contact pressure resulting from various sliding speeds and friction coefficients. The contact pressure, effective plastic strain, von Mises stress, and residual stress were measured and shown to increase with increasing sliding velocity. Finally, when the friction coefficient, contact pressure, and effective plastic strain are increased, the von Mises stress is also shown to increase, whereas the residual stress decreases.

Investigation on stress distribution and pressure capacity of two-layer split high-pressure die based on finite element analysis

2019 ◽  
Vol 233 (14) ◽  
pp. 5048-5055
Author(s):  
Z Yi ◽  
WZ Fu ◽  
MZ Li
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
High Pressure ◽  
Stress State ◽  
Von Mises Stress ◽  
Stress Distributions ◽  
Element Analysis ◽  
Round Cylinder ◽  
Von Mises ◽  
Supporting Ring

In order to obtain a higher pressure capacity for the high-pressure die with a larger sample cavity, two types of two-layer split dies with a round cylinder and a quadrate cylinder were designed based on the conventional belt-type die. Finite element analysis was performed to investigate the stress distributions and pressure capacities of the high-pressure dies using a derived Mohr–Coulomb criterion and the von Mises criterion for the cylinder and supporting rings, respectively. As predicted by the finite element analysis results, in the two-layer split dies with a round cylinder, the stress state of the cylinder can be only slightly improved; and the von Mises stress of the first layer supporting ring can be hardly decreased. However, in the two-layer split dies with a quadrate cylinder and sample cavity, the stress state of the cylinder can be remarkably improved. Simultaneously, the von Mises stress of the supporting rings, especially for the first-layer supporting ring, can be also effectively decreased. The pressure capacities of the two-layer split dies with a round cylinder and a quadrate cylinder are 16.5% and 63.9% higher with respect to the conventional belt-type die.

scholarly journals Effect of Fiber Posts on Stress Distribution of Endodontically Treated Upper Premolars: Finite Element Analysis

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1708 ◽  
Author(s):  
Maciej Zarow ◽  
Mirco Vadini ◽  
Agnieszka Chojnacka-Brozek ◽  
Katarzyna Szczeklik ◽  
Grzegorz Milewski ◽  
...  
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Resin Composite ◽  
Von Mises Stress ◽  
Stress Distributions ◽  
Stress Concentrations ◽  
Element Analysis ◽  
Endodontically Treated Tooth ◽  
Maxillary Premolars ◽  
Von Mises

By means of a finite element method (FEM), the present study evaluated the effect of fiber post (FP) placement on the stress distribution occurring in endodontically treated upper first premolars (UFPs) with mesial–occlusal–distal (MOD) nanohybrid composite restorations under subcritical static load. FEM models were created to simulate four different clinical situations involving endodontically treated UFPs with MOD cavities restored with one of the following: composite resin; composite and one FP in the palatal root; composite and one FP in the buccal root; or composite and two FPs. As control, the model of an intact UFP was included. A simulated load of 150 N was applied. Stress distribution was observed on each model surface, on the mid buccal–palatal plane, and on two horizontal planes (at cervical and root-furcation levels); the maximum Von Mises stress values were calculated. All analyses were replicated three times, using the mechanical parameters from three different nanohybrid resin composite restorative materials. In the presence of FPs, the maximum stress values recorded on dentin (in cervical and root-furcation areas) appeared slightly reduced, compared to the endodontically treated tooth restored with no post; in the same areas, the overall Von Mises maps revealed more favorable stress distributions. FPs in maxillary premolars with MOD cavities can lead to a positive redistribution of potentially dangerous stress concentrations away from the cervical and the root-furcation dentin.

Plasto-Elastohydrodynamic Lubrication in Point Contacts for Surfaces With Three-Dimensional Sinusoidal Waviness and Real Machined Roughness

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Tao He ◽  
Ning Ren ◽  
Dong Zhu ◽  
Jiaxu Wang
Keyword(s):  
Plastic Deformation ◽  
Rough Surface ◽  
Mechanical Design ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Von Mises Stress ◽  
Asperity Contacts ◽  
Lubrication Characteristics ◽  
Von Mises

Efficiency and durability are among the top concerns in mechanical design to minimize environmental impact and conserve natural resources while fulfilling performance requirements. Today mechanical systems are more compact, lightweight, and transmit more power than ever before, which imposes great challenges to designers. Under the circumstances, some simplified analyses may no longer be satisfactory, and in-depth studies on mixed lubrication characteristics, taking into account the effects of 3D surface roughness and possible plastic deformation, are certainly needed. In this paper, the recently developed plasto-elastohydrodynamic lubrication (PEHL) model is employed, and numerous cases with both sinusoidal waviness and real machined roughness are analyzed. It is observed that plastic deformation may occur due to localized high pressure peaks caused by the rough surface asperity contacts, even though the external load is still considerably below the critical load determined at the onset of plastic deformation in the corresponding smooth surface contact. It is also found, based on a series of cases analyzed, that the roughness height, wavelength, material hardening property, and operating conditions may all have significant influences on the PEHL performance, subsurface von Mises stress field, residual stresses, and plastic strains. Generally, the presence of plastic deformation may significantly reduce some of the pressure spikes and peak values of subsurface stresses and make the load support more evenly distributed among all the rough surface asperities in contact.

scholarly journals A Finite Element Study of the Residual Stress and Deformation in Hemispherical Contacts

2005 ◽  
Vol 127 (3) ◽  
pp. 484-493 ◽  
Author(s):  
Robert Jackson ◽  
Itti Chusoipin ◽  
Itzhak Green
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Yield Criterion ◽  
Contact Region ◽  
Element Model ◽  
Von Mises Stress ◽  
Contact Radius ◽  
Perfectly Plastic ◽  
Von Mises

This work presents a finite element model (FEM) of the residual stresses and strains that are formed after an elastoplastic hemispherical contact is unloaded. The material is modeled as elastic perfectly plastic and follows the von Mises yield criterion. The FEM produces contours for the normalized axial and radial displacements as functions of the removed interference depth and location on the surface of the hemisphere. Contour plots of the von Mises stress and other stress components are also presented to show the formation of the residual stress distribution with increasing plastic deformation. This work shows that high residual von Mises stresses appear in the material pileup near the edge of the contact area after complete unloading. Values are defined for the minimum normalized interference, that when removed, results in plastic residual stresses. This work also defines an interference at which the maximum residual stress transitions from a location below the contact region and along the axis of symmetry to one near to the surface at the edge of the contact radius (within the pileup).

Elastic Analysis of Journal Bearings

Volume 1 ◽  
2004 ◽  
Author(s):  
M. M. Villar ◽  
M. M. Pe´rez
Keyword(s):  
Stress Distribution ◽  
General Purpose ◽  
Von Mises Stress ◽  
Elastic Analysis ◽  
Stress Distributions ◽  
Finite Element Program ◽  
Relative Significance ◽  
Element Program ◽  
Von Mises ◽  
Hoop Stresses

In this paper a numerical model is used to investigate the effect of the elasticity of the bearing in the pressure distribution in the lubricant and the stress distribution in the bearing. The lubricant film, as well as a bearing, including the lining and the backing of the insert, and the housing, are modeled using the general-purpose ANSYS®5.7 commercial Finite Element program. Results have been obtained for the pressure, radial displacement, hoop and von Mises stress distributions at the surface of the bearing, as well as for the shear stress distribution at the interface between the lining and the backing. A number of conclusions have been drawn regarding the relative significance of the steep pressure gradient at the end of the lubricated region on the hoop stresses that cause localized bending distortions at the surface of the lining. These localized bending distortions, in turn, are likely to cause fatigue failure of the lining.

Numerical Simulation of Thermal/Mechanical Coupling in Laser Transmission Microjoining of PET and Titanium

2010 ◽  
Vol 160-162 ◽  
pp. 1118-1125 ◽  
Author(s):  
Zhen Kai Xu ◽  
Hui Xia Liu ◽  
Pin Li ◽  
Xin Hua Song ◽  
Kai Wang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Residual Stress ◽  
Laser Beam ◽  
Dissimilar Materials ◽  
Good Combination ◽  
Von Mises Stress ◽  
Mechanical Coupling ◽  
Element Technique ◽  
Von Mises ◽  
Traveling Speed

Laser transmission microjoining of two dissimilar materials has become a very significant technique. In this research, a numerical method is developed using finite element technique to determine the condition of joining two dissimilar materials namely Polyethylene terepthalate (PET) and titanium. First the model is used to optimize the laser parameters like laser traveling speed and power to obtain good bonding. A good combination is achieved at the power of 8W and laser traveling speed at 150mm/min.After the verifications, the profile of residual stress of the laser microjoint has been calculated using the developed model. The residual is low near the centerline along the traveling laser beam, and a higher values is away from the centerline at the x-direction shown by the contours on the PET surface. Higher residual von Mises stress near the centerline along the traveling laser beam and the stresses reduce as the distance away from the centerline.

Numerical Study on Elastic-Plastic Stress Field Near the Cooling Holes of Nickel-Based Single Crystal Air-Cooled Blades

2006 ◽  
Vol 324-325 ◽  
pp. 563-566 ◽  
Author(s):  
Qing Min Yu ◽  
Zhu Feng Yue ◽  
Yong Shou Liu
Keyword(s):  
Shear Stress ◽  
Stress Field ◽  
Numerical Study ◽  
Von Mises Stress ◽  
Shear Stresses ◽  
Slip Systems ◽  
Stress Distributions ◽  
Elastic Plastic ◽  
Von Mises ◽  
Plastic Stress

In this paper, a plate containing a central hole was used to simulate gas turbine blade with cooling hole. Numerical calculations based on crystal plasticity theory have been performed to study the elastic-plastic stress field near the hole under tension. Two crystallographic orientations [001] and [111] were considered. The distributions of resolved shear stresses and strains of the octahedral slip systems {110}<112> were calculated. The results show that the crystallographic orientation has remarkable influence on both von Mises stress and resolved shear stress distributions. The resolved shear stress distributions around the hole are different between the two orientations, which lead to the different activated slip systems. So the deformed shape of the hole in [001] orientation differs from that in [111] orientation.

Falling Simulation of Free-Standing Museum Cultural Relics Supported by Soft Pad

2014 ◽  
Vol 670-671 ◽  
pp. 715-719
Author(s):  
Qian Zhou
Keyword(s):  
Material Properties ◽  
Element Model ◽  
Von Mises Stress ◽  
Stress Distributions ◽  
Acceleration Response ◽  
Response Curves ◽  
Free Standing ◽  
Cultural Relic ◽  
Von Mises ◽  
Cultural Relics

Free-standing museum cultural relics are easy to fall off exhibition booth and get damaged under earthquakes. To find an effective method to mitigate damage of cultural relics due to fall off, influences of soft pad under relic was studied by ANSYS/LS-DYNA program. A bronze relic supported by a soft pad was selected for analysis. Based on material properties of both the relic and the pad, finite element model of the relic was built. By simulation, Von mises stress distributions, acceleration response curves as well as kinetic energy curves of the relic were obtained; effects of the soft pad to mitigate damage of the relic were discussed. Results show that collision between the falling museum cultural relic and ground can be mitigated by soft pad due to its buffer as well as energy absorption effects. It is suggested to use soft pad under relic to provide protection. Besides, by ANSYS/LS-DYNA program, falling off process of free-standing museum cultural relics can be effectively simulated.

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