scholarly journals Динамическая модель упруго-пластического нормального столкновения сферических частиц при нелокальной пластичности

2018 ◽  
Vol 60 (3) ◽  
pp. 560
Author(s):  
Я.А. Ляшенко ◽  
В.Л. Попов
Keyword(s):  
Plastic Deformation ◽  
Spherical Particle ◽  
Half Space ◽  
Initial Velocity ◽  
Experimental Results ◽  
Contact Radius ◽  
Normal Velocity ◽  
Strengthening Effect ◽  
Strength Limit ◽  
Dimensionless Coefficient

AbstractThe problem of normal collision of a spherical particle with a half-space is considered with allowance for nonlocal plastic deformation in the case where the strength limit depends on the contact radius, as well as for the strengthening effect in the deformed material. The dimensionless coefficient of normal velocity restitution has been calculated numerically as a function of the initial velocity of the spherical particle. The obtained data coincide well with experimental results available in the literature.

scholarly journals Динамическая модель упруго-пластического нормального столкновения сферической частицы с полупространством с учетом адгезионного взаимодействия в зоне контакта

2019 ◽  
Vol 61 (2) ◽  
pp. 302
Author(s):  
Я.А. Ляшенко
Keyword(s):  
Experimental Data ◽  
Plastic Deformation ◽  
Energy Dissipation ◽  
Initial Velocity ◽  
Mechanical Energy ◽  
Normal Velocity ◽  
Plastic Deformations ◽  
Homogeneous Particle ◽  
Mechanical Energy Dissipation ◽  
Simulation Results

AbstractThe problem of a collision of a spherical homogeneous particle with a half-space is solved numerically. The coefficient of the normal velocity restitution is calculated as a function of the initial velocity in the presence of the mechanical energy dissipation due to plastic deformations and adhesion interaction between the surfaces of contacting bodies. The strain hardening effect is taken into account using the criterion of nonlocal plasticity introduced before. The study is carried out in dimensionless parameters, which makes it universal. The analytical expression is found for the critical initial velocity above which a plastic deformation starts. The simulation results agree well with the available experimental data.

Analytical Modeling of Residual Stresses in Burnishing

2010 ◽  
Vol 139-141 ◽  
pp. 921-924
Author(s):  
Jing Zhao ◽  
Wei Xia ◽  
Feng Lei Li ◽  
Zhao Yao Zhou ◽  
Zheng Qiang Tang
Keyword(s):  
Plastic Deformation ◽  
Residual Stresses ◽  
Half Space ◽  
Power Law ◽  
Analytical Modeling ◽  
Normal Force ◽  
Experimental Results ◽  
Concentrated Force ◽  
Plastic Properties ◽  
Elastic Plastic

. An analytical model is developed for the prediction of residual stresses in burnishing. The model is simplified as a concentrated force pressing on elastic-plastic half-space using the solution to the Boussinesq-Flament problem. The treated material admits the elastic-plastic properties with hardening using a power law constitutive relation. Trial computation using Johnson-Cook model on AISI 1042 steel is presented and the results are verified with the experimental results given by Bouzid’s previous work. The residual stresses in the feed direction show the same trend with the experimental results while some differences still exist near the surface because of the concentrated normal force assumption and such stresses increase with the increase of burnishing force, decrease with the increase of depth and turn to zero beyond the plastic deformation boundary.

scholarly journals Axial Behaviour of Slender RC Circular Columns Strengthened with Circular CFST Jackets

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Yiyan Lu ◽  
Tao Zhu ◽  
Shan Li ◽  
Weijie Li ◽  
Na Li
Keyword(s):  
Bearing Capacity ◽  
Ductile Failure ◽  
Steel Tube ◽  
Experimental Results ◽  
Strengthening Effect ◽  
Load Bearing Capacity ◽  
Rc Columns ◽  
Load Bearing ◽  
Cfst Columns ◽  
Material Utilization

This paper investigates the axial behavior of slender reinforced concrete (RC) columns strengthened with concrete filled steel tube (CFST) jacketing technique. It is realized by pouring self-compacting concrete (SCC) into the gap between inner original slender RC columns and outer steel tubes. Nine specimens were prepared and tested to failure under axial compression: a control specimen without strengthening and eight specimens with heights ranging between 1240 and 2140 mm strengthened with CFST jacketing. Experimental variables included four different length-to-diameter (L/D) ratios, three different diameter-to-thickness (D/t) ratios, and three different SCC strengths. The experimental results showed that the outer steel tube provided confinement to the SCC and original slender RC columns and thus effectively improved the behavior of slender RC columns. The failure mode of slender RC columns was changed from brittle failure (concrete peel-off) into ductile failure (global bending) after strengthening. And, the load-bearing capacity, material utilization, and ductility of slender RC columns were significantly enhanced. The strengthening effect of CFST jacketing decreased with the increase of L/D ratio and D/t ratio but showed little variation with higher SCC strength. An existing expression of load-bearing capacity for traditional CFST columns was extended to propose a formula for the load-bearing capacity of CFST jacketed columns, and the predictions showed good agreement with the experimental results.

The Mechanical Characteristics and Sealing Performance Evaluation of Bolted Pipe Flange Connections With Metallic Flat Gaskets Subjected to Internal Pressure

2016 ◽  
Author(s):  
Koji Kondo ◽  
Koji Sato ◽  
Satomi Takahashi ◽  
Toshiyuki Sawa
Keyword(s):  
Plastic Deformation ◽  
Mechanical Characteristics ◽  
Experimental Results ◽  
Leak Rate ◽  
Effect Of Temperature ◽  
Load Factor ◽  
Stress Distributions ◽  
Bolt Preload ◽  
Sealing Performance ◽  
Higher Temperature

Bolted pipe flange connections with metallic gaskets have been used under higher pressure as well as higher temperature. However, a few researches on the mechanical characteristics in connections with metallic gaskets have been carried out. It is necessary to examine the mechanical characteristics such as the contact gasket stress distributions which govern the sealing performance, the deformation of the metallic gaskets, changes in axial bolt forces and the hub stress under higher pressure and temperature. In the present paper, the objectives are to examine the changes in axial bolt forces, the hub stress and the contact gasket stress distributions and the sealing performance of the pipe flange connections with metallic flat gaskets. Firstly, the mechanical characteristics of the connections under higher pressure are analyzed using FEA. Then, experiments were carried out to measure the load factor, the hub stress and the leak rate (the sealing performance). The relationship between the average contact gasket stress and the leak rate was measured using platen device at room temperature. The FEA results are fairly coincided with the experimental results. It is shown that the leak rate decreases as the contact gasket stress increases and when the plastic deformation of gaskets occurs, the sealing performance increases. The leak rate was measured in the range of 10−4∼10−7 [Pa·m3/s]. It is found that the sealing performance increases as the gasket width increase in the elastic deformation range while it is independent of the gasket width when the plastic deformation occurs. The effect of temperature on the mechanical characteristics of the connection is also examined. The FEA results are in a fairly good agreement with the experimental results. It is found that the sealing performance increases as the temperature increases. In addition, a method how to determine the bolt preload for increasing the sealing performance is proposed.

Research on Cold Orbital Forming of Complex Sheet Metal of Aluminum Alloy

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Xinghui Han ◽  
Qiu Jin ◽  
Lin Hua
Keyword(s):  
Plastic Deformation ◽  
Finite Element ◽  
Aluminum Alloy ◽  
Mobile Phone ◽  
Sheet Metal ◽  
Experimental Results ◽  
Complex Motion ◽  
Flow Lines ◽  
Inner Surface ◽  
Orbital Forming

This study aims at exploring the potentialities of cold orbital forming in forming complex sheet metal. Aiming at a complex mobile phone shell component of aluminum alloy, two technical schemes for cold orbital forming are first presented. Then, the optimized one, i.e., the more complex inner surface of mobile phone shell is arranged to be formed by the rocking punch with a complex motion, is determined by analyzing the nonuniform plastic deformation laws and punch filling behaviors. On the basis of the optimized technical scheme, the blank geometry in cold orbital forming of mobile phone shell is also optimized based on the forming status of the most difficult forming zone. The consistent finite element (FE) simulated and experimental results indicate that under the optimized technical scheme, not only the bosses in the mobile phone shell are fully formed but also the obtained flow lines are reasonable, which proves that the technical scheme presented in this study is feasible and cold orbital forming exhibits huge potentialities in forming complex sheet metal.

Effect of Body Lateral Extension Upon the Elastic Contact

2009 ◽  
Author(s):  
Marilena Glovnea ◽  
Emanuel Diaconescu
Keyword(s):  
Half Space ◽  
Outer Radius ◽  
Force Balance ◽  
Contact Theory ◽  
Contact Radius ◽  
Elastic Contact ◽  
Space Theory ◽  
Lateral Extension ◽  
Load Direction ◽  
Force Balance Equation

Half-space contact theory cannot be applied when either contacting bodies are thin or they possess small transversal dimensions. The former situation is often dealt with, but the latter seems to be neglected. This paper investigates the effect of outer radius of cylindrical bodies upon the contact stress field. The method consists in adding supplementary displacements and stresses to the half-space solution in order to fulfill the boundary conditions and the force balance equation on load direction. It is found that the half-space theory is applicable if transversal radius exceeds contact radius.

Aperiodic Deformation Occurring as a Result of Thermoplastic Instability of Metals

2007 ◽  
Vol 537-538 ◽  
pp. 541-548 ◽  
Author(s):  
Zoltán Pálmai
Keyword(s):  
Plastic Deformation ◽  
Shear Stress ◽  
Shear Strain ◽  
Three Dimensional ◽  
Experimental Results ◽  
Reverse Effect ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Periodic Fluctuation ◽  
Linear Nature

The author developed a three-dimensional model for the description of fast plastic deformation of metals in the case of cutting. Shear strain occurring as a result of shear stress has a reverse effect on stress, while the temperature of the material is increasing. These counteracting effects may lead to thermomechanic instability, which may result in aperiodic chaotic conditions besides periodic fluctuation due to the non-linear nature of the process. Apart from bifurcation and multi-cycle periodic deformation, the model also describes aperiodic chaotic deformation, which is proven by experimental results.

scholarly journals Design and Demonstration of a Flying-Squirrel-Inspired Jumping Robot with Two Modes

2021 ◽  
Vol 11 (8) ◽  
pp. 3362
Author(s):  
Fei Zhao ◽  
Wei Wang ◽  
Justyna Wyrwa ◽  
Jingtao Zhang ◽  
Wenxin Du ◽  
...  
Keyword(s):  
Pitch Angle ◽  
Initial Velocity ◽  
Experimental Results ◽  
Flying Squirrel ◽  
Flexible Wing ◽  
Flying Squirrels ◽  
Jumping Robot

The jumping–gliding robot is a kind of locomotion platform with the capabilities to jump on the ground and glide through the air. The jumping of this robot has to juggle the requirements of initial velocity and posture for entry to gliding and progressing on the ground. Inspired by flying squirrels, we proposed the concept of flexible wing-limb blending platform and designed a robot with two jumping modes. The robot can takeoff with different speeds and stances, and adjust aerial posture using the swing of forelimbs. To the best of our knowledge, this is the first miniature and bio-inspired jumping robot that can autonomically change the speeds and stances when takeoff. Experimental results show that the robot can takeoff at about 3 m/s and pitch angle of 0° in the mode of jumping for gliding and adjust the pitch angle at the top to 0°~10° by actuating the forelimbs swing according to the requirement of gliding. In the mode of jumping for progress, the robot can takeoff at about 2 m/s with a pitch angle of 20° and then intermittently jump with a distance of 0.37 m of once jump and an average progress speed of 0.2 m/s. The robot presented in this paper lays the foundation for the development of flexible wing-limb blending platform, which is capable of jumping and gliding.

A Unified Treatment of Axisymmetric Adhesive Contact on a Power-Law Graded Elastic Half-Space

2013 ◽  
Vol 80 (6) ◽  
Author(s):  
Fan Jin ◽  
Xu Guo ◽  
Wei Zhang
Keyword(s):  
Half Space ◽  
Power Law ◽  
Contact Region ◽  
Adhesive Contact ◽  
Elastic Half Space ◽  
Hertzian Contact ◽  
Contact Radius ◽  
Abel Transformation ◽  
Numerical Solution Methods ◽  
Special Cases

In the present paper, axisymmetric frictionless adhesive contact between a rigid punch and a power-law graded elastic half-space is analytically investigated with use of Betti's reciprocity theorem and the generalized Abel transformation, a set of general closed-form solutions are derived to the Hertzian contact and Johnson–Kendall–Roberts (JKR)-type adhesive contact problems for an arbitrary punch profile within a circular contact region. These solutions provide analytical expressions of the surface stress, deformation fields, and equilibrium relations among the applied load, indentation depth, and contact radius. Based on these results, we then examine the combined effects of material inhomogeneities and punch surface morphologies on the adhesion behaviors of the considered contact system. The analytical results obtained in this paper include the corresponding solutions for homogeneous isotropic materials and the Gibson soil as special cases and, therefore, can also serve as the benchmarks for checking the validity of the numerical solution methods.

The Effect of Flatness of Joint Faces upon the Static Stiffness of Machine Tool Joints

1967 ◽  
Vol 182 (1) ◽  
pp. 463-476 ◽  
Author(s):  
R. H. Thornley ◽  
R. Connolly ◽  
F. Koenigsberger
Keyword(s):  
Plastic Deformation ◽  
Machine Tool ◽  
Empirical Relation ◽  
Experimental Results ◽  
Static Stiffness ◽  
Interface Pressure ◽  
Surface Deflection ◽  
Machining Operations

This paper looks into the types of flatness errors produced in typical machining operations. The effect of these flatness errors on the pressure/deflection curves of the surfaces is reported. An empirical relation, based on the experimental results, between surface deflection and mean interface pressure is suggested. The effect of bonding joints is shown to eliminate plastic deformation of the surfaces and produces a joint having linear characteristics.

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