A modelling technique for predicting compound impact wear

doi:10.1016/j.wear.2007.01.032

Wear

Volume 262, Issues 11–12, 10 May 2007, Pages 1516-1521

https://doi.org/10.1016/j.wear.2007.01.032 Get rights and content

Abstract

Wear problems are consistently arising as a result of the introduction of new or alternative materials to situations where components are impacting.

Impact wear has generally not been studied as extensively as other wear mechanisms and as a result information on the causes and actual impact wear data is quite scarce. There are also few impact modelling techniques and those that exist have not been extensively applied.

In this work, a new modelling technique for predicting compound impact wear was developed. This was found to give improvements when compared with existing models in terms of both usability and accuracy of results.

Introduction

Impact or percussive wear has been defined as: “the wear of a solid surface that is due to percussion, which is a repetitive exposure to dynamic contact by another body” [1].

Two modes of impact wear are apparent (as shown in Fig. 1). Normal impact wear occurs when the relative approach of the impacting bodies contains no tangential or rotational elements. Where a shear component is added, either when normal impact occurs with a component of sliding or the bodies impact at a tangent, the term compound impact wear is used. Most impact situations actually involve impact with a small amount of sliding. Compound impact wear has been shown to lead to much higher wear rates than normal impact alone [2], [3]. This is thought to be due to enhanced removal of wear debris that occurs with the introduction of a shear component.

There are many industrial situations in which impacting bodies are employed where failures due to wear can be costly and safety, reliability and quality reduced greatly. Excessive wear of impacting poppet valves in automotive engines can lead to loss of cylinder pressure and ultimately engine failure. Failure of tools used for drilling rock and other media raise cost concerns, not only associated with the need for frequent replacement of parts, but also in the down time incurred [4]. Impact wear of printer typefaces will lead to loss of definition and a subsequent reduction in print quality [5]. Unintentional impacts, such as the chattering of tubes carrying, for example, waste from nuclear reactors, can give rise to situations where safety and reliability are of critical concern [6]. Potential impact wear problems are also being found in dental implants and heart valves, where health and well-being are at stake.

Problems due to impact wear are starting to arise more when new or alternative materials are introduced in situations where components are impacting, usually in order to reduce costs or for environmental reasons. An example of this is the increasing use of sintered materials, ceramics and plastics in the production of automotive engines (see for example, [7]). These are being introduced to ease manufacture by increasing machinability or to reduce weight, etc. However, all have raised impact wear issues not previously apparent.

Impact wear generally has not been studied as extensively as other wear mechanisms and information on the causes and actual impact wear data is hard to find. There are also few dedicated impact wear modelling techniques and those that exist have not been extensively applied. In this work, extant impact wear models were assessed. A new improved modelling technique was then developed to predict compound impact wear, which was compared with experimental data to provide validation and with existing models to assess its relative performance.

Section snippets

Extant impact wear models

A compound impact wear modelling approach has been established based on two assumed stages of wear progression [8]. The first is an induction period (see Fig. 2), during which deformation occurs and a wear scar is formed, but there is no measurable material loss. The end of this stage is defined as the zero wear limit. This constitutes the initial point of the measurable wear region. As indicated in Fig. 2, the progression of wear in this region can take on a number of forms. These will depend

Model structure

There is a clear a need for an easy to apply model for predicting compound impact wear that is able to cope with any contact geometry. Such a model will now be outlined. It is simply comprised of two wear models; one for predicting impact wear and one for sliding wear.

A relationship of the same form as that used in erosion studies to model wear mass, W [8] (based on impact energy) (Eq. (4)), is used to model impact wear.

The equation for impact wear is combined with an equation for sliding wear

Conclusions

•
A technique for predicting compound impact wear rates (that involving impact and sliding) has been developed. Although requiring a number of empirical wear factors it is easy to use and can quickly give an idea of a likely wear rate given a contact geometry and a set of operating parameters.
•
The technique has been compared to existing experimental data and predictions using extant wear models. Good correlation exists with the experimental data, except at low numbers of cycles where plastic

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Impact wear results from the surface failure of engineering components that undergo repetitive contact motion. It reduces their service life. This study investigated the impact wear of alloy steel using computational techniques combined with empirical data. The ultimate objective was to develop an approach requiring low–moderate effort for industrial application using limited resources to predict the average impact wear rate of AISI 4140 alloy steel (one of the most commonly used materials). The wear mechanisms were investigated by scanning electron microscopy (SEM). Indirect monitoring was used to examine the wear stage transition cycle, e.g., from mild to severe wear. The empirical results showed that the transition cycle depended on the impact force. Fatigue was identified as the key damage mechanism, with cracks and lamellar wear appearing under severe deterioration. The average wear rate from the initial impact cycle to the wear stage transition cycle increased as the impact force increased. A simplified computational 2D finite element model assuming a smooth frictionless surface was used to investigate the contact condition. The contact behavior including the stress–strain distribution that developed during first contact was investigated using finite element analysis. A combined empirical and computational approach to predicting average wear rate was developed based on stress distribution data from the FE model and fatigue properties. The prediction results were then validated by comparison with the empirical data. These showed good agreement. The stress amplitude derived from an equivalent high-stress region was also introduced. The predicted curve of average wear rate versus stress amplitude of an equivalent high-stress region improved the design of the component.
From atomic attrition to mild wear at multi-asperity interfaces: The wear of hard Si<inf>3</inf>N<inf>4</inf> repeatedly contacted against soft Si
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Wear causes surfaces to be irreversibly damaged, thereby incurring significant economic cost, for instance in the semiconductor industry. Much progress has been made in describing wear at single asperity interfaces between silicon based materials (Si, SiO_x, Si₃N₄), translating the fundamental understanding of wear into wear predictions and control over wear. Yet, predicting and controlling wear at industrially relevant multi-asperity interfaces remains a challenge, especially when considering the wear of the harder material subjected to repeated, nanometric scale displacement. We studied pre-sliding Si₃N₄-on-Si wear using the atomic force microscopy topography difference method and showed that the harder Si₃N₄ wears through either atomic attrition or ductile removal enhanced by subsurface damage, depending on the magnitude of the local Si₃N₄-on-Si contact pressure. Our methods and results bridge fundamental insight into wear based on nanoscale studies to industrial applications.
Analysis of reciprocating hammer type impact wear apparatus
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Repetitive impact wear of metals is caused by primary wear mechanisms removing material from the surfaces and is responsible either solely, or in part, for the failure of engineering components (e.g. automotive valvetrains, wheel-rail contacts, mining equipment). Fundamental work exists, but overwhelmingly considers the impact wear of a particular material or surface treatment.
The mechanisms involved are variously oxidative, adhesion, abrasion, surface fatigue and plastic deformation. The dominance is controlled by stress, sliding conditions, impact energy, and the difference in material properties, particularly those of plastic deformation, between the two surfaces. There is a paucity of published work that solely investigates and characterises the fundamentals of impact wear.
Impact wear test apparatus falls into two groups; projectiles propelled into a stationary target/specimen, or a target/specimen being repeatedly struck by a hammer. The former type is similar to that commonly used for erosive wear, so the reciprocating hammer/striker type design, was chosen for analysis here.
Analysis was performed on specimens with impact wear scars that feature both material displacement and material loss, enabling comparison between different measurement techniques to be made. This provides a protocol for easier comparison of data, promoting improved models, and furthers the understanding of the apparatus’ performance.
A bidirectional wear model based on Inverse Gaussian (IG) process for PEEK against AISI630 stainless steel in seawater hydraulic components
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With the increasing integration of seawater hydraulic components, much attention has been paid to the tribological characteristics of PEEK bidirectional sliding against AISI630 tribopair. In the study, a bidirectional wear model based on Inverse Gaussian (IG) process is proposed based on bidirectional wear experiment. Impact wear occurs when the tribopair changes the motion direction. Through analysing the wear process and worn surface morphology of PEEK against AISI630 tribopairs, it is found that the impact wear would accelerate the formation and uniform distribution of PEEK transfer film, and the increase of reversal frequency can improve the tribological characteristics of the bidirectional tribopairs. The IG model considering the reversal impact can accurately illustrate the performance degradation path of actual impact wear.
A new predictive model for normal and compound impact wear
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Citation Excerpt :
It is important to note that material hardness has not been directly and explicitly considered as a parameter controlling the wear loss of materials under repetitive normal impact. It is often indirectly included, as part of experimentally derived coefficients and constants, from line fitting [20] or in the case of Rabinowicz [17] discounted because in that experimental work stainless steel experienced more wear than the aluminium alloys tested, despite stainless steel having higher hardness than aluminium. Similar results were obtained by Fricke [19], who found that in a high carbon martensitic stainless steel (AISI 440C) with hardness of 710Hv there was more mass loss than in both austenitic stainless steel (AISI 304) (242Hv) and a high chromium martensitic stainless steel (AISI 431) (465Hv), leading to the same conclusion that hardness is not a primary parameter controlling the results of repetitive normal impact.
This work presents a new model that predicts the wear that results from impacts occurring between two solid bodies under both normal and compound impact, a capability lacking from existing approaches. This frequently occurs in many engineering and industrial situations and depending on the relative sizes of the bodies, bulk material properties, and the number and frequency of impacts, damage can result. Although this eventually causes severe wear problems that limit service life, it is one of the least investigated types of primary wear mechanism. Due to this, robust data, and validated models derived from that data, are rare.
The new model considers the contact with respect to shear force. It can predict wear volume loss and be used to improve understanding of the role of different impact angles during impact, and thus inform the design of machines, however it is currently valid for ductile materials only since hardness is a parameter. Empirical inputs to the model were developed using data produced specifically for this work. Predictions made by the model were then validated, with good correlation, for three common metal alloys by means of comparison with experimental data available in the literature.
Investigation on the impact wear behavior of 2.25Cr–1Mo steel at elevated temperature
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The impact wear test of 2.25Cr–1Mo steel against Gr5C12 alloy was performed at a controlled kinetic energy impact wear rig. The effect of temperatures (from 25 °C to 450 °C) on the impact wear damage mechanism was investigated. The contact force, energy absorption, and interface deformation during the impact process were recorded and analyzed in real time. Wear volume, morphology, and elemental distribution of the wear scars were used to characterize wear and tribo-chemistry behavior. Results demonstrate that at varied temperatures, the interface behavior of 2.25Cr–1Mo steel is different. With the rise in temperature, both the contact force, absorption energy, and wear volume first increase and then decrease. The explanation is that higher temperatures can modify the material's surface properties. Delamination, plastic deformation, and oxidative wear are the major mechanisms of impact wear, but the proportions of the three wear mechanisms differ at varied temperature.

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Short communicationA modelling technique for predicting compound impact wear

Abstract

Introduction

Section snippets

Extant impact wear models

Model structure

Conclusions

Wear

Tribol. Int.

Wear

Tribol. Int.

Wear

Wear

Impact wear

Short communication
A modelling technique for predicting compound impact wear