Influence Of Friction Conditions Research Articles

Influence of Friction Conditions and Structural Refining on the Tribological Behavior of Titanium

Influence of Friction Conditions and Structural Refining on the Tribological Behavior of Titanium

Pressure-Assisted Lubrication of DC01 Steel Sheets to Reduce Friction in Sheet-Metal-Forming Processes

Friction in sheet-metal-forming processes not only affects the values of the force parameters of the process but also determines the quality of the surface of the drawpieces. This paper presents an approach to reducing the coefficient of friction by directly applying pressurized oil to the contact zone. For this purpose, a special test stand was built to carry out the strip draw test, commonly used to model the phenomenon of friction in the deep-drawing process. This test consisted of pulling a strip between flat countersamples made of 145Cr6 cold-work tool steel covered with an abrasion-resistant Mtec (AlTiN) coating. During the pilot tests, various contact pressures, lubricants with different viscosities, and different lubricant pressures were used. The influence of friction conditions on the surface roughness of the samples and the relationship between the friction conditions and the value of the coefficient of friction were determined. The supply of the lubricant under pressure into the contact zone has a beneficial effect on reducing friction. The coefficient of friction decreases with increasing lubricant pressure for contact pressures of 2–6 MPa. For a contact pressure of 8 MPa, the lubricant pressure is the least favorable for reducing the coefficient of friction. At higher lubricant pressures (12 and 18 bar), the lubrication efficiency depends on the viscosity of the lubricant and decreases with increasing contact pressure.

Experimental and Numerical Study on the Influence of Lubrication Conditions on AA6068 Aluminum Alloy Cold Deformation Behavior

The aim of this manuscript is the experimental and numerical study regarding the influence of friction conditions on plastic deformation behavior by upsetting the A6082 aluminum alloy. The upsetting operation is characteristic of a significant number of metal forming processes: close die forging, open die forging, extrusion, and rolling. The purpose of the experimental tests was to determine: by the ring compression method, the friction coefficient for 3 surface lubrication conditions (dry, mineral oil, graphite in oil) by using the Coulomb friction model; the influence of strains on the friction coefficient; the influence of friction conditions on the formability of the A6082 aluminum alloy upsetted on hammer; study of non-uniformity of strains in upsetting by measuring hardness; change of the tool-sample contact surface and non-uniformity of strains distribution in a material by numerical simulation. Regarding the tribological studies involving numerical simulations on the deformation of metals, they mainly focused on the development of friction models that characterize the friction at the tool-sample interface. The software used for the numerical analysis was Forge@ from Transvalor.

STUDY OF THE EFFECT OF FRICTION ON THE POWER PARAMETERS OF ROLLING WITH ONE DRIVE ROLL

The influence of friction conditions in the deformation cell is studied, taking into account the differences of the distribution of contact stresses on the drive and non-drive rolls, on the normal pressure and rolling force. The research methodology involved the development of a mathematical model of the process and conducting a numerical experiment. The rolling process model is based on the numerical solution of the Karman`s equation using the Coulomb friction law and boundary conditions appropriate of the rolling process with a single drive roll. When conducting a numerical experiment, the coefficient of friction in the deformation cell was changed at four levels in the range from 0.15 to 0.30. The coefficient of friction in the journal bearings non-drive rolls was varied at three levels. From the analysis of the obtained distributions of contact stresses along the length of the deformation cell by the drive and non-drive rolls, it was found that with decreasing the coefficient of friction in the deformation cell, the normal pressure decreases proportionally, as well as the difference between the pressure on the drive and non-drive rolls. The occurrence of longitudinal tensile stresses with a coefficient of friction in the deformation cell of 0.25 and more is noted. The coefficient of friction in the non-drive roller bearings, for the entire range of values taken, does not have a significant effect on the contact stresses, pressure and rolling power. The presence of tensile stresses when rolling with one drive roll leads to a decrease in the average pressure and rolling power within 8-10%. Therefore, rolling with one drive roller can be used to reduce energy costs. In addition, the presence of tensile stresses, at certain values of the coefficient of friction in the deformation cell, accordingly affects the mechanical and technological properties of the rolled products, but this feature of the process requires additional study.

Investigation on influence of mandrel shape on shear stress in pure shearing test of thin-walled aluminum alloy tubes

A novel testing method of pure shear loading for tubes is proposed in this paper. A special designed tubular sample and two semicircle mandrels are used in this test. The interface between the two half tube on the whole tube zone of the sample is under shearing deformation with relative movement of the two mandrels, and the middle point of the shearing zone is under a pure shearing stress state. The influence of friction condition between the two mandrels caused by the relative movement of the mandrels was analyzed. Three different friction conditions of semi-circle mandrels were used in the simulation and the relation between the loading force and mandrel displacement was obtained. It is shown the friction force has very small influence on the loading force. This shearing test can be used to get the shearing property of tubes, also, it is a testing method of tubes except the axial and circumferential direction.

A study of brake contact pairs under different friction conditions with respect to characteristics of brake pad surfaces

Abstract In the present study, influences of friction conditions on friction and wear behaviors, as well as characteristics of brake pad surfaces were investigated. Low metallic (LM), semi metallic (SM) and non-asbestos organic (NAO) brake pads sliding against an iron disc were tested using a pin-on-disc tribometer. Results show that the friction coefficient and specific wear rate decrease with increasing contact pressure and sliding velocity. For the morphology of brake pad surface, friction layers are large with few cracks on surfaces of SM and LM brake pads. While for NAO brake pad, friction layers have a comparatively slender and irregular shape. From fractal analysis, the fractal dimension of brake pad surface is in the range of 2.38–2.84 for all brake pads.

Simulation Study on the Influence Law of Two-body Wear in Sliding Guide Ways

In view of the typical two-body wear issue in sliding guide ways, this paper established the two-body wear simulation model of the guide ways by the finite element software. Based on the friction and wear mechanism, and the influence of friction conditions on the two-body wear of the guide ways was considered. The wear process of the guide ways was analysed, and the influence of load and sliding speed on the wear of the guide ways was researched. The simulation results showed that large sliding speed with the wear would accelerate and a large load would increase the wear of the guide ways.

Plastic Deformation Components in Mandrel Free Infeed Rotary Swaging of Tubes

Abstract In metal forming processes, the forging load as well as the mechanical and geometrical properties of the final product are affected by the actual material flow. Especially for incremental open die forming processes like rotary swaging, the material flow is very complex. By a profound knowledge about how to control this material flow during the process, the final product properties can be controlled. By using FEM, the material flow during infeed rotary swaging of tubes without mandrel was investigated by the history of the plastic strain components (PEi) in different directions. The influence of the friction coefficient value on the material flow for steel tubes was studied. By the history of plastic strain components tracked during the process, the material flow was analyzed in different radial positions. Based on that, the influence of friction conditions on PEi was discussed during one single stroke. It was found that with an increasing friction coefficient value, the radial plastic strain firstly increased and then decreased, while the axial plastic strain behaved just the other way round. Thus, the material flow is significantly affected by friction conditions. The simulation results were validated by measurements of wall thickness values of physically formed tubes.

Influence of friction condition on failure location of AA5754 aluminium sheet in Nakajima test

Influence of friction condition on failure location of AA5754 aluminium sheet in Nakajima test

Physical modeling of friction conditions on the wall thickness variation during sheet hydroforming

In order to research the influence of friction conditions on the sheet metal deformation behavior under the fluid pressure, the experimental method that can test the relationship between fluid pressure and wall thickness was proposed in this paper. The theoretical model about the quantitative variation relationship between fluid pressure and wall thickness together with the theoretical model about the quantitative variation relationship between friction coefficient and wall thickness, was obtained by theoretical derivation. At the same time, it could be concluded that friction contact region close to the tensile end was easier to satisfy the plastic yield criterion. Therefore, the plastic deformation initially occurred at this area and fracture emerged on account of excessive reduction of the sheet thickness. Simulation analysis with 304 stainless steel was carried out. The result indicated that the capacity of sheet uniform deformation decreased with the increasing of the friction coefficient. When the friction coefficient increased from 0.08 to 0.20, the uniform elongation decreased by 32%. But when other conditions were kept unchanged, the greater the fluid pressure was, the thinner the sheet would be. Experiments indicated that the necking and fracture appeared in the gauge length near the tensile end with different lubricants. And these provided a theoretical basis for the process and device design of sheet metal hydroforming.

Research and simulation of the influence of three-axial compaction on powder metallurgic product properties

The warm powder compaction process is simulated by the finite element analysis software, MSC/MARC. The thermal mechanically coupled analysis method is applied on the basis of the updated Lagrangian Method, to simulate the warm powder compaction process. The warm powder compaction process is simulated, and the influence of friction condition and pressing styles are researched on the density of powder green and the mechanics behavior at certain temperature. The results indicate that for cylindrical compacts, with the improvement of the friction condition, the uniformity of distribution of green relative density is largely improved, the pressing force and stress decrease, and the nonconforming pressing processes influence the distribution of green density to some degree. The status of stress distribution of the process that punches firstly press and die finally press is different from the other three processes, and presents the figure of ‘flume’.

Modeling Texture Evolution During Friction Stir Welding of Stainless Steel With Comparison to Experiments

Texture evolution during friction stir welding of stainless steel was investigated using a polycrystal plasticity model together with a three-dimensional, thermomechanically coupled, finite element formulation. The influence of frictional conditions with the tool pin and shoulder on the flow in the through-thickness direction was examined in terms of their impact on the evolving crystallographic texture. Trends in regard to the strengthening and weakening of the texture are discussed in relation to the relative magnitudes of the deformation rate and spin. Finally, the computed textures are compared to electron backscatter diffraction measurements and are discussed with respect to distributions along orientational fibers and the dominant texture components along the fibers.

Model-based analysis of the “Cold Start Squeal” phenomenon of clutches

This article describes a strategy developed to explain and solve the phenomenon of a squealing noise of the clutch system of a new powertrain. To support the hardware-based problem solution proces at GM Powertrain Europe, a MBS-model of the troublesome region was developed by the chair of machine elements of Kaiserslautern Technical University. A sensitivity study of the influences of friction conditions, manufacturing tolerances and of the bearing pretension enabled the explanation the squeal noise creation in good agreement with experimental observations.

직사각형 용기의 후방 충격압출 성형에 대한 마찰의 민감도 해석

In this paper, the influence of frictional conditions on the backward impact extrusion of aluminum battery casing with large aspect ratio has been investigated. In the simulation, MSC.Superforge, a package based on the finite volume method, is used for the extrusion analysis. The formability and earing problem during the production have been evaluated by studying the sensitivity to frictional effects. During the sensitivity analysis, the friction factor was varied from 0.02 to 0.24. As the friction factor is increased, the forming height of the narrow edge is decreased, and the forming height of the wide edge is increased. When the friction factor becomes 0.2, the earing problem does not occur The experimental results show a good agreement with analytical results.

Influence of friction on the material flow during precision forging of helical gears

At the Institute of Metal forming and Metal forming machine tools (IFUM), University of Hannover, helical gearwheels are produced from cylindrical billets using single state precision forging processes. For a process integrated heat treatment, the workpiece materials need to be carburized already before the forming operation. Thus, in contrast to conventional manufacture, an inhomogeneous case depth distribution is obtained resulting from the material flow during forming. A numerical process simulation with the finite element method (FEM) enables to predict this distribution along the shape of the teeth. The performed experimental and numerical investigations illustrate the influence of friction conditions on the material flow and thus its influence on the case depth distribution.

Influence of friction conditions on tribochemical stability of lithium lubricants

Influence of friction conditions on tribochemical stability of lithium lubricants

Influence of friction conditions on the lattice constant of the ?-phase during the wear of austenitic manganese cast iron

1. Heat treatment influences the crystal lattice and the saturation of the solid solution of the γ-phase of austenitic manganese cast iron. 2. Regardless of the friction and wear conditions (friction without lubrication or with lubrication containing abrasive) the lattice constant of the heat treated cast iron decreases with increasing pressure and the lattice constant changes in the same way. 3. The more saturated the solid solution before the wear resistance tests, the greater the change in the lattice constant.