On the Mechanics of Crack Initiation and Propagation in Elasto-Plastic Materials in Impact Fretting Wear

2004 ◽  
Vol 126 (2) ◽  
pp. 395-403 ◽  
Author(s):  
Y. B. Gessesse ◽  
M. H. Attia
Keyword(s):  
Crack Initiation ◽  
Contact Pressure ◽  
Coefficient Of Friction ◽  
Contact Area ◽  
Plastic Material ◽  
Oblique Impact ◽  
Fretting Wear ◽  
Isotropic Hardening ◽  
Friction Forces ◽  
The Coefficient Of Friction

Normal and oblique impact wear processes are characterized by unique features, which include the development of some residual stress components that vanish in unidirectional sliding. Parametric finite element analyses were conducted to estimate the likelihood locations for crack initiation, and the subsequent direction and rate of crack propagation in an elasto-plastic material with bi-linear isotropic hardening properties. The results showed that the increase in contact pressure can cause a significant increase in the size of the plastically deformed crack initiation zone and allows it to reach the surface. Such behavior is not predicted under continuous sliding conditions. The presence of surface friction forces in oblique impact, can also result in the development of a secondary region of high tensile stresses at the contact area. Using the crack tip slip displacement CTSD method, the rate of crack growth was found to be linearly proportional to the crack length, and significantly dependent on the contact pressure and the coefficient of friction at the crack surface. The small effect of the coefficient of friction at the micro-contact area on wear suggests that the effect of shear traction is mainly due to the increase in the depth of the crack nucleation zone. As expected, the increase of the material flow stress with strain-hardening has a wear reducing effect.

Stresses Due to Tangential and Normal Loads on an Elastic Solid With Application to Some Contact Stress Problems

1953 ◽  
Vol 20 (2) ◽  
pp. 157-166
Author(s):  
J. O. Smith ◽  
Chang Keng Liu
Keyword(s):  
Plane Strain ◽  
Coefficient Of Friction ◽  
Contact Area ◽  
Normal Load ◽  
Elastic Solid ◽  
Real Variable ◽  
The Body ◽  
Shearing Stress ◽  
Tangential Load ◽  
The Coefficient Of Friction

Abstract The results of two-dimensional approach using real variable method to Hertz’s problem of contact of elastic bodies are presented. Both normal and tangential loads are assumed to be distributed in Hertzian fashion over the area of contact. The magnitude of the intensity of the tangential load is assumed to be linearly proportional to that of the normal load when sliding motion of the body is impending. The stresses in the elastic body due to the application of these loads on its boundary are presented in closed form for both plane-stress and plane-strain cases. A numerical value of f = 1/3 is assumed for the linear proportionality (coefficient of friction) between the tangential and normal loads in order that the distribution of stresses may be illustrated. The significance of the stress distribution, across the contact area and in the body, is also discussed. It is shown that when the combination of loads considered in the paper are applied at the contact area of bodies in contact the maximum shearing stress may be at the surface instead of beneath the surface. For example, for plane strain, if the coefficient of friction is f = 1/3, the maximum shearing stress is at the surface and is 43 per cent larger than the maximum shearing stress, which would be below the surface, that occurs when the normal force acts alone. The effect of range of normal stress and of shearing stress on the plane of maximum shear and on the plane of maximum octahedral shear on failure by progressive fracture (fatigue) is discussed.

scholarly journals Limiting shape of profile due to dual-mode fretting wear in contact with an elastomer

2015 ◽  
Vol 230 (9) ◽  
pp. 1417-1423 ◽  
Author(s):  
Xinyu Mao ◽  
Wei Liu ◽  
Yuanzhi Ni ◽  
Valentin L Popov
Keyword(s):  
Coefficient Of Friction ◽  
Contact Area ◽  
Constant Coefficient ◽  
Analytic Solutions ◽  
Slip Zone ◽  
Fretting Wear ◽  
Contact Interface ◽  
Dual Mode ◽  
Elastic Bodies ◽  
Initial Forms

We consider fretting wear due to superimposed normal and tangential oscillations of two contacting bodies, one of which is an elastomer with a linear rheology. Similarly to the contact of elastic bodies, at small oscillation amplitudes, the wear occurs only in a circular slip zone at the border of the contact area and the wear profile tends to a limiting form, in which no further wear occurs. It is shown that under assumption of a constant coefficient of friction at the contact interface, the limiting form of the wear profile does depend neither on the particular wear criterion nor on the rheology of the elastomer and can be calculated analytically in a general form. The general calculation procedure and explicit analytic solutions for two initial forms, parabolic and conical, are presented for various combinations of frequencies and phases of normal and tangential oscillations as well as for various linear rheologies of the elastomer.

scholarly journals Fretting wear rate of sulphur deficient MoSx coatings based on dissipated energy

2001 ◽  
Vol 16 (12) ◽  
pp. 3567-3574 ◽  
Author(s):  
Xiaoling Zhang ◽  
W. Lauwerens ◽  
L. Stals ◽  
Jiawen He ◽  
J-P. Celis
Keyword(s):  
Relative Humidity ◽  
Wear Rate ◽  
Coefficient Of Friction ◽  
Contact Stress ◽  
Ambient Air ◽  
Fretting Wear ◽  
Dissipated Energy ◽  
Wear Volume ◽  
The Coefficient Of Friction ◽  
Crystallographic Orientations

The fretting wear of sulphur-deficient MoSx coatings with different crystallographic orientations has been investigated in ambient air of controlled relative humidity. The coefficient of friction and the wear rate of MoSx coatings sliding against corundum depend not only on fretting parameters like contact stress, fretting frequency, and relative humidity, but also strongly on the crystallographic orientation of the coatings. For randomly oriented MoSx coatings, the coefficient of friction and the wear rate increased significantly with increasing relative humidity. In contrast, basal-oriented MoSx coatings were less sensitive to relative humidity. The coefficient of friction of both types of MoSx coatings decreased on sliding against corundum with increasing contact stress and decreasing fretting frequency. A correlation between dissipated energy and wear volume is proposed. This approach allows detection in a simple way of differences in fretting wear resistance between random- and basal-oriented MoSx coatings tested in ambient air of different relative humidity.

scholarly journals Contact pressure and sliding velocity ranges in sheet metal forming simulations

2021 ◽  
Author(s):  
Joseba Cillaurren ◽  
Lander Galdos ◽  
Mario Sanchez ◽  
Alaitz Zabala ◽  
Eneko Saenz de Argandoña ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Contact Pressure ◽  
Sheet Metal ◽  
Coefficient Of Friction ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Sliding Velocity ◽  
Wide Range ◽  
The Coefficient Of Friction ◽  
Friction Models

In the last few years many efforts have been carried out in order to better understand what the real contact between material and tools is. Based on the better understanding new friction models have been developed which have allowed process designers to improve numerical results in terms of component viability and geometrical accuracy. The new models define the coefficient of friction depending on different process parameters such as the contact pressure, the sliding velocity, the material strain, and the tool temperature. Many examples of the improvements achieved, both at laboratory scale and at industrial scale, can be found in the recent literature. However, in each of the examples found in the literature, different ranges of the variables affecting the coefficient of friction are covered depending on the component analysed and the material used to produce such component. The present work statistically analyses the contact pressure and sliding velocity ranges achieved during numerical simulation (FEM) of sheet metal forming processes. Nineteen different industrial components representing a high variety of shapes have been studied to cover a wide range of casuistic. The contact pressure and sliding velocity corresponding to typical areas of the tooling have been analysed though numerical simulation in each case. This study identifies the ranges of contact-pressure and sliding velocities occurring in sheet metal forming aimed to set the characterization range for future friction studies.

Finite element analysis of fretting wear considering variable coefficient of friction

2018 ◽  
Vol 233 (5) ◽  
pp. 758-768 ◽  
Author(s):  
Ling Li ◽  
Le Kang ◽  
Shiyun Ma ◽  
Zhiqiang Li ◽  
Xiaoguang Ruan ◽  
...  
Keyword(s):  
Finite Element ◽  
Coefficient Of Friction ◽  
Variable Coefficient ◽  
Friction Model ◽  
Slip Condition ◽  
Fretting Wear ◽  
Partial Slip ◽  
Wear Volume ◽  
The Coefficient Of Friction ◽  
Contact Surfaces

Fretting wear is a kind of material damage in contact surfaces caused by microrelative displacement between two bodies. It can change the profile of contact surfaces, resulting in loosening of fasteners or fatigue cracks. Finite element method is an effective method to simulate the evolution of fretting wear process. In most studies of fretting wear, the coefficient of friction was assumed to be constant to simplify model and reduce the difficulty of solving. However, fretting wear test showed that the coefficient of friction was a variable related to the number of fretting cycles. Therefore, this paper introduces the coefficient of friction as a function of the number of fretting cycles in numerical simulation. A wear model considering variable coefficient of friction is established by combining energy consumption model and adaptive grid technique. The nodes of contact surfaces are updated through the UMESHMOTION subroutine. The effects of constant coefficient of friction and variable coefficient of friction on fretting wear are analyzed by comparing the wear amount under different loading conditions. The results show that when compared with coefficient of friction model, fretting wear is obviously affected by variable coefficient of friction and the variable coefficient of friction model has a larger wear volume when the fretting is in partial slip condition and mixed slip condition. In gross slip condition, the difference of wear volume between variable coefficient of friction model and coefficient of friction model decreases with the increase in the displacement amplitudes.

Experimental Studies of Deformation and Temperature Processes Mandrelling in the Deform-3D System

2021 ◽  
Vol 1037 ◽  
pp. 357-368
Author(s):  
Mikhail F. Selemenev ◽  
Arkady A. Cherepenko ◽  
Elena A. Zvyagina ◽  
Artem N. Tkachenko ◽  
Elena M. Selemeneva
Keyword(s):  
Heat Transfer ◽  
Coefficient Of Friction ◽  
Experimental Studies ◽  
Contact Stresses ◽  
Temperature Analysis ◽  
Friction Forces ◽  
The Coefficient Of Friction ◽  
Cutting Zone ◽  
Deform 3D

The article discusses the effect of epilamated coatings during mandrelling. The picture of the change in contact stresses in the DEFORM-3D system is presented. It was established that a decrease in the coefficient of friction from 0.9 to 0.6 leads to a decrease in the number of foci and areas of contact stresses, as well as temperature analysis showed that a decrease in the friction forces reduces heat transfer in the cutting zone by about 40 ° C.

Observation of Water Behavior in the Contact Area between Porous Rubber and a Mating Surface during Sliding

2012 ◽  
Vol 40 (3) ◽  
pp. 186-200
Author(s):  
Yusuke Minami ◽  
Tomoaki Iwai ◽  
Yutaka Shoukaku
Keyword(s):  
Water Flow ◽  
Coefficient Of Friction ◽  
Contact Area ◽  
Real Contact Area ◽  
The Real ◽  
Air Bubble ◽  
Real Contact ◽  
Rear Edge ◽  
The Coefficient Of Friction ◽  
Dove Prism

ABSTRACT Porous rubber is often used as the tread rubber of studless tires because of its higher coefficient of friction on icy surfaces, as the real contact area is larger because of its lower elastic modulus. It is said that the real contact area increases owing to the water absorption into the pores. The purpose of this study was to clarify the effect of pores on the surface of porous rubber during sliding under wet conditions. In this experiment, porous rubber was rubbed with a dove prism under wet conditions, so as to measure the coefficient of friction in concurrence with observing the friction surface. The total internal reflection method was adopted to distinguish the real contact area from the wet contact area. The real contact area was observed as a black area in captured image. Particle-tracking velocimetry was also conducted to visualize the water flow in the vicinity of pores during the sliding. The results of this study show that the absorption of water into the pores was not observed. The pore contained an air bubble during the sliding. The water flow detouring around the air bubble in the pore was also observed. In regard to contact, the front edge of the pore was not in contact with the mating dove prism. On the other hand, the rear edge of the pore was clearly seen as a black arc even if the pore left the dove prism. Thus, the rear edge of the pore contacting with the dove prism most likely wipes the water, so that the coefficient of friction of rubber with the pore was higher than that without the pore.

Effects of process variables on fretting fatigue crack initiation in Ti-6A1-4V

2002 ◽  
Vol 37 (6) ◽  
pp. 535-547 ◽  
Author(s):  
S A Namjoshi ◽  
S Mall ◽  
V K Jain ◽  
O Jin
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Coefficient Of Friction ◽  
Fatigue Crack Initiation ◽  
Orientation Angle ◽  
Fretting Fatigue ◽  
Multiaxial Fatigue ◽  
Process Variables ◽  
Critical Plane ◽  
The Coefficient Of Friction

A fretting fatigue crack initiation mechanism (number of cycles, location and orientation angle) using critical plane based parameters has been addressed by several researchers. There are several process variables that can affect these parameters and thereby the prediction of fretting fatigue crack initiation behaviour. Effects of two such parameters, viz. process volume and the coefficient of friction, were investigated in this work. Fretting fatigue experiments with a titanium alloy were conducted with different contact pad geometries. Finite element analysis (FEA) was used to obtain a stress state in specimens for the experimental conditions used during fretting fatigue tests. Analysis was carried out for two values of the coefficient of friction, thereby providing a framework for calculation of several critical plane based multiaxial fatigue parameters for different process volumes. A program was developed to compute these multiaxial fatigue parameters from the FEA data for different values of process variables. It was observed that parameters for cylindrical pad geometries with no singularity-type behaviour were inversely proportional to the size of process volume and directly proportional to the coefficient of friction. There was no change in the predicted orientation of the primary crack for this geometry, due to variations in these process variables. Parameters for flat-pad geometries with behaviour approaching that of a singularity were also inversely proportional to the size of process volume, but the coefficient of friction had a minimal effect on their values. Predicted orientation of the primary crack for these geometries changed slightly when the process volume increased from that of a grain size of the tested material to a larger size, and then did not change with the increase of process volume size. Overall, the effect of these process variables on the critical plane based parameters was similar in all five contact geometries used in this study, when the scatter in fatigue data is kept in mind. Finally, the modified shear stress range parameter satisfactorily predicted the crack initiation location, orientation angle and number of cycles to fretting fatigue crack initiation independent of the contact geometry for a given process volume size and coefficient of friction.

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