An Analytical Model for Dynamic Wear

1989 ◽  
Vol 111 (3) ◽  
pp. 468-474 ◽  
Author(s):  
Ji-Yi Lin ◽  
H. S. Cheng
Keyword(s):  
Steady State ◽  
Stress Field ◽  
Wear Rate ◽  
Frictional Force ◽  
Wear Behavior ◽  
Time Dependent ◽  
Material Strength ◽  
Wear Model ◽  
Asperity Contacts ◽  
Dynamic Wear

A wear model which permits the wear rate to be dependent on time is introduced to study the dynamic wear behavior observed in practice. In this model, it is postulated that the wear rate is proportional to a forcing term, I, which is contributed by the stress field induced by the frictional force at the asperity contacts; and inversely proportional to a wear resisting term, S, which is related to the material antiwear strength near the surface. One of the important characteristics of the dynamic wear model is that both I and S are now time dependent or wear dependent because when wear progresses the material strength at various layers would change and the stress field would also change as a result of the change of surface topography. Using this dynamic wear model, it is shown that the commonly observed running-in, steady-state, or accelerated wear phenomena can be explained.

Experimental Evaluation of a Steady-State Model for the Wear of Particle-Filled Polymer Composite Materials

1997 ◽  
Vol 119 (4) ◽  
pp. 694-699 ◽  
Author(s):  
Sung Won Han ◽  
Thierry A. Blanchet
Keyword(s):  
Steady State ◽  
Composite Materials ◽  
Wear Rate ◽  
Polymer Composite ◽  
Wear Behavior ◽  
Polymer Composite Materials ◽  
Volume Fractions ◽  
Rule Of Mixtures ◽  
Filler Particles ◽  
Inverse Rule

A model for the steady-state wear behavior of polymer composite materials, including the effects of preferential load support by and surface accumulation of wear-resistant filler particles, is further developed. It is shown that the resultant inverse rule-of-mixtures description of steady-state composite wear rate behavior is independent of the assumed form of filler contact pressure, though preferential load support does affect the degree of surface accumulation of filler particles that occurs. The validity of these descriptions of steady-state wear behavior and surface accumulation as functions of bulk filler volume fraction are investigated by experiments with copper particle-filled PTFE composites for bulk filler volume fractions from 0 to 40 percent. The applicability of the description of surface accumulation for this composite system was limited to bulk filler volume fractions less than 20 percent, a hypothesized result of transition in load-sharing between filler and matrix. The inverse rule-of-mixtures description of steady-state wear rate, however, was maintained over the full range of volume fractions investigated.

A nanosized rigid spherical inclusion with interfacial diffusion and sliding

2017 ◽  
Vol 23 (7) ◽  
pp. 1049-1060
Author(s):  
Xu Wang
Keyword(s):  
Steady State ◽  
Stress Field ◽  
Normal Stress ◽  
Spherical Inclusion ◽  
Surface Elasticity ◽  
Relaxation Times ◽  
Imperfect Interface ◽  
Time Dependent ◽  
Interfacial Diffusion ◽  
The Matrix

We examine the time-dependent deformations around a nanosized rigid spherical inclusion in an infinite elastic matrix under uniaxial tension at infinity. The elastic matrix is first endowed with separate Gurtin–Murdoch surface elasticity. Furthermore, interfacial diffusion and sliding both occur on the inclusion–matrix interface. Closed-form expressions of the time-dependent displacements and stresses in the matrix are derived by using Papkovich–Neuber displacement potentials. A concise and elegant expression of the steady-state normal stress on the surface of the inclusion is also obtained. It is seen that the displacements and stresses in the matrix evolve with two relaxation times which are reliant on three size-dependent parameters, one from surface elasticity and the other two from interfacial diffusion and sliding. Numerical results are presented to demonstrate the influence of surface elasticity on the relaxation times and on the stress distribution near the inclusion. It is observed that the surface elasticity can alter the nature of the steady state normal stress on the surface of the inclusion from tension to compression. When the radius of the inclusion is not greater than the ratio of residual surface tension to remote tension, the steady state normal stress on the surface of the inclusion is always compressive. The related problem of a nanosized rigid spherical inclusion with a spring-type imperfect interface is also solved. We find that it is feasible to design a neutral spherical inclusion that does not disturb a prescribed uniform uniaxial stress field or even any uniform stress field outside the inclusion through a judicious choice of the four imperfect interface parameters.

Simulation of the Time-Dependent Wear and Surface Accumulation Behavior of Particle-Filled Polymer Composites

1998 ◽  
Vol 120 (2) ◽  
pp. 152-158 ◽  
Author(s):  
Thierry A. Blanchet ◽  
Sung Won Han
Keyword(s):  
Wear Rate ◽  
Polymer Composites ◽  
Volume Fraction ◽  
Wear Behavior ◽  
Flow Simulation ◽  
Time Dependent ◽  
Wear Volume ◽  
Filled Polymer ◽  
The Matrix ◽  
Nonsteady State

A simulation has been developed to model the transient wear of particle-filled polymer composites as a function of sliding distance. All inputs are parameters of physical significance, including filler bulk volume fraction, specific wear rate (relative to that of the matrix), and contact pressure. Run-in wear behavior is simulated by consideration of the accumulation of wear-resistant filler particles and the formation of a volume fraction profile near the composite sliding surface, facilitated by matrix cold flow. Simulation outputs include time-dependent volume fraction profile, and composite wear rate and wear volume. The simulation may be used for evaluation of candidate materials for applications in which nonsteady-state run-in wear effects are important, as well as a guide for the engineering of composite surfaces with graded volume fraction profiles that may provide resistance to initial transient wear contributions.

Prediction of Steady State Adhesive Wear in Spur Gears Using the EHL Load Sharing Concept

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
S. Akbarzadeh ◽  
M. M. Khonsari
Keyword(s):  
Steady State ◽  
Wear Rate ◽  
Thermal Effects ◽  
Sliding Wear ◽  
Adhesive Wear ◽  
Load Sharing ◽  
Spur Gears ◽  
Wear Model ◽  
Wear Calculation ◽  
Simulation Results

The concept of load sharing between asperities and fluid film is applied in conjunction with lubricated sliding wear formulation proposed by Wu and Cheng (1991, “A Sliding Wear Model for Partial-EHL Contacts,” ASME J. Tribol., 113, pp. 134–141; 1993, “Sliding Wear Calculation in Spur Gears,” ASME J. Tribol., 115, pp. 493–500) to predict the steady state adhesive wear in gears. Thermal effects are included using a simplified thermoelastohydrodynamic analysis. The prediction of the model is verified by comparing simulation results with published experimental data pertinent to steady state wear rate. The main advantages of this method are the accuracy and the remarkable computational efficiency. The results of parametric simulation study are presented to investigate the effect of speed and surface roughness on a portion of load carried by asperities and wear rate.

Effect of High Temperature on Wear Behavior of Stir Cast Aluminium/Boron Carbide Composites

2020 ◽  
Vol 22 (4) ◽  
pp. 1031-1046
Author(s):  
X. Canute ◽  
M. C. Majumder
Keyword(s):  
High Temperature ◽  
Wear Rate ◽  
Boron Carbide ◽  
Wear Behavior ◽  
Base Alloy ◽  
Weight Fraction ◽  
Sliding Velocity ◽  
Wear Properties ◽  
High Temperature Wear ◽  
The Matrix

AbstractThe need for development of high temperature wear resistant composite materials with superior mechanical properties and tribological properties is increasing significantly. The high temperature wear properties of aluminium boron carbide composites was evaluated in this investigation. The effect of load, sliding velocity, temperature and reinforcement percentage on wear rate was determined by the pin heating method using pin heating arrangement. The size and structure of base alloy particles change considerably with an increase of boron carbide particles. The wettability and interface bonding between the matrix and reinforcement enhanced by the addition of potassium flurotitanate. ANOVA technique was used to study the effect of input parameters on wear rate. The investigation reveals that the load had higher significance than sliding velocity, temperature and weight fraction. The pin surface was studied with a high-resolution scanning electron microscope. Regression analysis revealed an extensive association between control parameters and response. The developed composites can be used in the production of automobile parts requiring high wear, frictional and thermal resistance.

scholarly journals Ground- and excited-state characteristics in photovoltaic polymer N2200

RSC Advances ◽  
2021 ◽  
Author(s):  
Guanzhao Wen ◽  
Xianshao Zou ◽  
Rong Hu ◽  
Jun Peng ◽  
Zhifeng Chen ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Excited State ◽  
Steady State ◽  
Excited States ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Time Dependent ◽  
Functional Theory ◽  
Time Resolved ◽  
Dependent Density

Ground- and excited-states properties of N2200 have been studied by steady-state and time-resolved spectroscopies as well as time-dependent density functional theory calculations.

scholarly journals Experimental Wear Behavior Analysis of Coated Spindle Hook Teeth under Real Harvesting Work Conditions

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2487
Author(s):  
Yanqing Gu ◽  
Hongwen Zhang ◽  
Xiuqing Fu ◽  
Lei Wang ◽  
Zhenyu Shen ◽  
...  
Keyword(s):  
Wear Rate ◽  
Wear Behavior ◽  
Field Work ◽  
Work Conditions ◽  
Tooth Surface ◽  
Wear Area ◽  
Cutting Surface ◽  
Spatial Distribution Characteristics ◽  
Process Failure ◽  
Major Chemical

This study aimed to investigate the wear failure changes of spindle hook teeth and the reasons for such failure during field work. Spindle samples were obtained from a fixed position of the spindle bar under different field picking area conditions and combined with the spatial distribution characteristics of cotton bolls in Xinjiang. After cutting a spindle sample, a scanning electron microscope and an energy spectrum analyzer were used to characterize the micromorphology and element composition of the hook tooth surface and cross section under different working area conditions. The wear parameters of the hook teeth were then extracted. The results showed that the thickness of the coating on the surface of the hook tooth used in this study was between 66.1 µm and 74.4 µm. The major chemical element was chromium, with a small amount of nickel. During the field picking process, failure of the coating on the surface of the hook teeth initially appeared on the tooth tip and tooth edge, and then spread to the entire hook tooth surface. The wear failure of the hook teeth resulted from abrasive wear, oxidative wear, and fatigue peeling. As the picking area increased, the wear area of the hook teeth increased exponentially, while the wear width increased linearly. When the field picking area reached 533.33 ha, the maximum change rate of the wear area was 2.33 × 103 µm2/ha, and the wear width was 1.84 µm/ha. During field work, the thickness of the coating decreased from the cutting surface to the tooth edge, and the wear rate gradually increased. The wear rate at Position 1 was the slowest, at 0.01 µm/ha, and the wear rate at Position 5 was the fastest, at 0.25 µm/ha.

Long-term performance of prestressed concrete continuous box girders in the natural environment

2020 ◽  
Vol 47 (7) ◽  
pp. 856-864
Author(s):  
Guohui Cao ◽  
Wang Zhang ◽  
Jiaxing Hu ◽  
Xirong Peng
Keyword(s):  
Prestressed Concrete ◽  
Load Test ◽  
Time Dependent ◽  
Material Strength ◽  
Practical Calculation ◽  
Box Girders ◽  
Load Types ◽  
In The Beginning ◽  
Support Reactions

A long-term load test performed for 470 days on two two-span prestressed concrete (PC) continuous box girders is reported in this paper. Load types were selected as the test variates, and structural responses such as support reactions, deflections, and concrete strains were monitored. Simultaneously, affiliated experiments such as material strength, creep, and shrinkage tests were conducted to investigate the time-dependent performances of the materials. Data obtained from these tests showed that deflections, strains, and support reactions develop rapidly in the beginning and stabilize afterward; the reactions of mid- and end-supports decline and rise over time, respectively. Time-dependent patterns of deflections and support reactions were analyzed on the basis of an effective modulus method, and a practical calculation method for long-term deflections considering reaction redistributions was proposed. The effects of the service environment on the performance of PC girders were evaluated through an incremental analysis method.

scholarly journals Determinants of mRNA stability in Dictyostelium discoideum amoebae: differences in poly(A) tail length, ribosome loading, and mRNA size cannot account for the heterogeneity of mRNA decay rates.

1988 ◽  
Vol 8 (5) ◽  
pp. 1957-1969 ◽  
Author(s):  
R A Shapiro ◽  
D Herrick ◽  
R E Manrow ◽  
D Blinder ◽  
A Jacobson
Keyword(s):  
Steady State ◽  
Dictyostelium Discoideum ◽  
Mrna Decay ◽  
Decay Rates ◽  
Time Dependent ◽  
Translational Efficiency ◽  
Cdna Clones ◽  
Dependent Manner ◽  
Significant Difference ◽  
Kinetics Of

As an approach to understanding the structures and mechanisms which determine mRNA decay rates, we have cloned and begun to characterize cDNAs which encode mRNAs representative of the stability extremes in the poly(A)+ RNA population of Dictyostelium discoideum amoebae. The cDNA clones were identified in a screening procedure which was based on the occurrence of poly(A) shortening during mRNA aging. mRNA half-lives were determined by hybridization of poly(A)+ RNA, isolated from cells labeled in a 32PO4 pulse-chase, to dots of excess cloned DNA. Individual mRNAs decayed with unique first-order decay rates ranging from 0.9 to 9.6 h, indicating that the complex decay kinetics of total poly(A)+ RNA in D. discoideum amoebae reflect the sum of the decay rates of individual mRNAs. Using specific probes derived from these cDNA clones, we have compared the sizes, extents of ribosome loading, and poly(A) tail lengths of stable, moderately stable, and unstable mRNAs. We found (i) no correlation between mRNA size and decay rate; (ii) no significant difference in the number of ribosomes per unit length of stable versus unstable mRNAs, and (iii) a general inverse relationship between mRNA decay rates and poly(A) tail lengths. Collectively, these observations indicate that mRNA decay in D. discoideum amoebae cannot be explained in terms of random nucleolytic events. The possibility that specific 3'-structural determinants can confer mRNA instability is suggested by a comparison of the labeling and turnover kinetics of different actin mRNAs. A correlation was observed between the steady-state percentage of a given mRNA found in polysomes and its degree of instability; i.e., unstable mRNAs were more efficiently recruited into polysomes than stable mRNAs. Since stable mRNAs are, on average, "older" than unstable mRNAs, this correlation may reflect a translational role for mRNA modifications that change in a time-dependent manner. Our previous studies have demonstrated both a time-dependent shortening and a possible translational role for the 3' poly(A) tracts of mRNA. We suggest, therefore, that the observed differences in the translational efficiency of stable and unstable mRNAs may, in part, be attributable to differences in steady-state poly(A) tail lengths.

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