Friction Fatigue Research Articles

Frictional Fatigue of a Polymer in Friction on Steel

This paper presents friction fatigue and wear-rate curves plotted using experimental data for a steel 45–polymer F4-VM friction unit. We have found low- and high-cycle fatigue regions and high-fatigue-life regions. The parameters which describe and separate these regions turn out to be stable, e.g., irrespective of which wear-rate characteristic is accepted. The paper provides a phenomenological description of wear processes in these typical regions.

Analysis of relationships governing wear-fatigue damage. Report 2

The main results of investigations of direct (effect of the friction and wear processes on the variation of the fatigue resistance characteristics) and reversed (effect of cyclic stresses on intensification of wear) effects are presented. The diagram of limiting states of the force systems characterized by complex-wear-fatigue-damage is analyzed. The problems of calculating the strength and endurance of these systems are discussed. It is shown that, in particular, in contact-mechanical friction (CMF) and friction-mechanical fatigue (FMF) under specific conditions the force systems can operate reliably with a strength margin factor smaller than unity. An equation for calculating the endurance and FMF is derived.

Characteristic features of blanking die wear with consideration for the change in composition, structure and properties of contact surfaces

Blanking dies constitute heavily loaded tribosystems with low-cycle friction fatigue being the primary mechanism of their wear. In this paper the authors consider characteristic features of steels with 12% chromium content which are widely used in the manufacture of blanking dies. It has been found that in the course of die operation certain secondary protective structures are formed on its surface, significantly influencing the wear process. Structural changes in subsurface layers as well as the role of these changes in blanking die friction have been studied. Principles of friction control have been advanced for the tribosystems under analysis.

The limiting state of force systems and processes of damage of them. Report 2. Life and measures of the degree of damage

A composite criterion of a force system reaching the limiting state based on life has been obtained, an equation for calculation of the life of a system under conditions of force, frictional, and thermal actions is proposed, composite indices of forward and reverse effects are found, partial equations of the curves of thermal force and thermal friction fatigue are derived, a concept of the energy measures of damage, partial and also composite, is given, and a composite parameter for analysis of the mechanism of damage is determined. It is shown that the basic solutions satisfactorily agree with the experimental results. The reverse effect, which consists of intensification of the wear processes of both elements of the system even if cyclic stresses are excited in only one of them, is described and analyzed. It is called the scatter effect of multiple microshear.

Statistical model for a deformable solid with a critical volume and some of its applications. Communication 3

It is shown that wear intensity as applied to friction fatigue is governed by relative critical volume with wear. Equations are derived on the basis of energy and fatigue theories using the DBCV model. Similarity criteria are suggested for wear intensity and the life of friction assemblies. Combined indices and damage criteria for friction-mechanical fatigue, and also for the limiting condition of a metal-polymer power system constructed using the DBVC model are presented. Using them it is possible to calculate the reliability of assemblies which operate with repeated alternating loads and simultaneous sliding friction. Equations for calculated and experimental estimation of durability before main fatigue crack formation (life to the first stage of fretting fatigue) are obtained on the basis of a well-known model for fretting wear and the DBCV model. Some ideas for further studies are formulated.

Computation of wear in artificial heart valves.

In order to assist with the prognosis of wear processes in low profile disc heart valves, an approximate haemodynamic theory has been used for the determination of opening and closing dynamics of these valves, together with the most developed theory to date of frictional fatigue. The heart valve element wear was defined by solving the contact problem, which takes account of changes to the contact surface form as a consequence of wear. Calculated values are compared with in vivo wear data for artificial heart valves. The proposed model for estimating wear in artificial heart valves allows an optimization to be made of the wear resistance in available designs and to predict the wear resistance of artificial heart valves at the design stage.

Dimensional Effect of Abrasion Head on Wear Resistance of Spun Yarns

The abrasion resistance of spun yarns has been evaluated by the modified criterion which takes into account the geometrical relationship between the frictional pin and the yarn. When the yarn is in contact for the length H with the frictional pin of diameter D and the pin is reciprocating with a stroke S, the yarn is abraded most severely at the central portion S* =|S-H| of the contact area. Therefore, it is reasonable to suppose that the yarn breakage depends on the wear of the portion S*. The frictional energy dissipated within the region S* is given by Eb* =Eb·|S-H|/S, where Eb is the frictional energy dissipated by the whole yarn up its breakage.The dependence of Eb* on D (0.6mm-10mm) and S (7mm-40mm) has been investigated experimentally for the spun yarn of 63tex made of polyester staples of 51 mm length and 2 denier. When S is smaller than 12mm, the yarn breakage is dominated by the fiber cutting and Eb* increases extraordinary provided that D is larger than 2.5mm. It is considered because the pin of large diameter is not effective to cut the fiber.It has also been found that Eb* does not substantially depend on S under the condition of 15.5mm ≤S≤ 40mm and D=2.5mm-5.0mm, where the yarn breakage is dominated by the fiber pull out. The mechanism of the frictional fatigue behavior of spun yarns and its dependence on D and S can be more clearly understood by the use of the modified criterion Eb*.

On the Experimental Condition of a Wear Resistance Test for Spun Yarns

Effects of the geometrical configuration and dimension of an abrasion tester on the frictional fatigue behavior of spun yarns were investigated experimentally. Spun yarns of 63 tex were made of polyester staples of 51 mm length and 2 denier, and were examined by the abrasion tester which was developed by the authors. The wear and breakage of yarns result from the cutting and /or pull out of fibers. (1) In the region where the diameter D of the frictional pin is smaller than 2.5 mm, the yarn breakage depends on the fiber cutting. With the increase of D the frictional energy Eb consumed up to the yarn breakage increases, because it becomes harder for the pin to cut the fiber. (2) In the region of D≥2.5 mm, the yarn breakage is dominated by the pull out of fibers. The wear and tear of yarns is partially suppressed by the transmission of twist from the thicker part to the abraded thinner part. Therefore, the large tention W applied to the yarn results in a large abrasion resistance Eb. (3) When the stroke S of the frictional pin is too small (S = 12 mm), the yarn breakage depends on the fiber cutting. which brings about remarkably large Eb for the pin with D = 2.5 mm.

Trenie Iznos : A. P. Ramzaev, on the relation of friction fatigue factor and hardness of solids, 5 (2) (1984) 355

Trenie Iznos : A. P. Ramzaev, on the relation of friction fatigue factor and hardness of solids, 5 (2) (1984) 355

Predicting pile driveability: Heather as an illustration of the “friction fatigue” theory : Ground Engng, V13, N3, April 1980, P15–20 Heerema E.P.

Predicting pile driveability: Heather as an illustration of the “friction fatigue” theory : Ground Engng, V13, N3, April 1980, P15–20 Heerema E.P.

Testing of Tire Treadwear under Laboratory and under Service Conditions

Abstract Four different laboratory machines for the evaluation of tire treadwear have been described which used concrete, steel, and tungsten carbide abrasion surfaces at variable speed and slip, but none has satisfactorily replaced highway testing. Predominant sources of wear on passenger tires appear to be cutting and frictional fatigue, the rates of which are influenced differently by temperature and load. Thus, seasonal or climatic, topographical, and geographical effects are evidenced. Treadwear cannot be expressed solely as a property of the tire since it is the resultant of the interaction of the tire with multivariate environmental conditions.

Effect of phase transformations in the surface layer on the resistance of ShKh15 steel to friction fatigue

1. If a thin surface layer of ShKh15 steel undergoes secondary quenching as the result of polishing (a deeper layer becoming tempered) and is removed during the finishing operation, then the tempered layer with a troostite structure (the depth being about 220 μ and the hardness 550 kg/mm2) becomes the surface layer, and as the result the friction fatigue during rolling friction decreases sharply. 2. Residual tensile stresses occurring in the surface layer during polishing are an important factor in the decrease of longevity. The decreased hardness of the surface layer has much less effect. 3. For samples with a surface layer in which the structure is changed as the result of polishing, the variation of longevity at p0=106–290 kg/mm2 is represented by a curve with a minimum at p0=255 kg/mm2. This phenomenon is due to a sharp decrease of residual tensile stresses occurring in the case where the specific pressure during rolling exceeds the yield strength of the surface layer.