Tribo Test

Comparison of two test methods for evaluation of forming tool materials, Tribotest, v 14, n 3, July 2008, p 147-58

M. Hanson

Anders Gåård

S. Hogmark

Pavel Krakhmalev

Jens Bergström

Tribotest

两种成形工具材料评价试验方法的比较，Tribotest，第14卷，第3期，2008年7月，第147-158页

两种成形工具材料评价测试方法的比较，Tribotest，第14卷，第3期，2008年7月，第147-158页

Abstract A comparative study of the microtribological properties of native oxide on Si (100), Si (100) coated with octadecyltrichlorosilane (OTS) and perfluorode‐cyltrichlorosilane (FDTS) self‐assembling monolayers (SAMs) is presented. The frictional properties between these samples and a bare silicon sphere were examined using a microtribometer. Microfriction was investigated as a function of the normal load and relative humidity. Also, the microfriction of OTS‐ and FDTS‐coated surfaces was studied as a function of sliding time and normal load to examine the lifetime of these monolayers. Confirming the results of earlier studies, in the microtribological regime OTS and FDTS significantly reduce the friction force in comparison to the bare, native oxide covered (hydrophilic) silicon surface. The friction vs. normal load curve of oxide‐covered surfaces as well as the SAMs can be described by contact mechanics. Lifetime measurements of the SAMs, examined as a function of the normal load and relative humidity, indicate that the OTS monolayers wear quickly in both dry and moist environments, while the lifetime of FDTS monolayers appears to increase in moist environments. Copyright © 2006 John Wiley &amp; Sons, Ltd.

W. Hild

S.I.‐U. Ahmed

G. Hungenbach

M. Scherge

J.A. Schaefer

Load dependence and lifetime studies of self‐assembled monolayers

自组装单层膜的负载依赖性与寿命研究

两种成形工具材料评价试验方法的比较，摩擦学试验，第14卷，第3期，2008年7月，第147-158页

Abstract Iron‐based hardfacing alloys are widely used to protect machinery equipment. A strong correlation is given between microstructure and chemical composition of welding deposit with the resulting wear behaviour. Concerning precipitation of metallurgical hard phases and synthetic added hard particles, the bonding strength of the hard phases in the metallic matrix seems to play a dominating role to obtain high wear resistance. The main objective of this study was to evaluate the wear behaviour for pure abrasion, combined impact/abrasion and high impact wear, respectively, for four different Fe‐based hardfacing alloys. Tests were performed with a standard ASTM G65 dry‐sand/rubber‐wheel tester. An impeller–tumbler apparatus enabled investigation of impact abrasion wear tests. Additional wear tests with high impact loading were performed on a drop hammer apparatus. Fracture surface analysis was carried out after drop hammer testing and results were correlated with microstructure and interfacial bonding behaviour of precipitations in metallic matrix. Copyright © 2008 John Wiley &amp; Sons, Ltd.

E. Badisch

M. Kirchgaßner

R. Polak

F. Franek

The comparison of wear properties of different Fe‐based hardfacing alloys in four kinds of testing methods

不同Fe基堆焊合金在四种测试方法中耐磨性能的比较

Abstract In the course of a K plus research project which focused on the internal thread moulding process, a test methodology for evaluating the efficiency of forming oils was developed. The various tests should provide tribological characteristic values, such as coefficient of friction, with respect to the real production environment. To guarantee the transferability of results, the complex of loads acting on the components in the model tests must correspond to the real forming process. Especially parameters such as contact pressure, relative speed in the forming zone and the increase of surface of the workpiece during the forming process must be considered in tribological testing. The tribological data provided information to select components of thread moulding oils and to optimise the formulation. Best practice moulding oils must satisfy different demands in respect of physical, physical–chemical, chemical and additional properties. In addition to the cooling function and the reduction of friction, there is also a significant influence on the quality of the workpiece and the moulding process itself. Copyright © 2008 John Wiley &amp; Sons, Ltd.

C. Monetti

B. Buchner

G. Hering

Test methodology for the formulation and selection of components of thread moulding oils

线材成型油组分配方及选择测试方法

Abstract Coefficients of friction and wear rates for polyacetal and polytetrafluoroethylene are measured on small‐scale cylinder‐on‐plate tests and large‐scale flat‐on‐flat tests. Three models for extrapolation between small‐ and large‐scale test results, which are based on experimental parameters, are presented: (i) one single mechanical parameter (normal load), (ii) the contact‐pressure–sliding‐velocity model (temperature limit), and (iii) a macroscopic geometry model. The last model is most extensively evaluated and considers thermal effects, sample geometry and contact conditions. After correction for the thermal sliding regime and viscoelastic deformation, the coefficients of friction can be extrapolated while the wear rates are more sensitive to the contact situation. High‐temperature tests on small scale are not representative for high‐load tests on large scale. Besides mechanical effects such as stress concentrations and debris mobility, variations in polymer structure under sliding (formation of rigid amorphous phase) and chemical interactions (wear debris polymerisation) also change with testing scale. The latter effects are explicitly illustrated from spectroscopic measurements on the worn surfaces. Copyright © 2008 John Wiley &amp; Sons, Ltd.

P. Samyn

G. Schoukens

Tribophyiscal scaling effects in friction and wear of polymers on small‐ and large‐scale tests

聚合物摩擦与磨损在小尺度和大尺度测试中的摩擦物理尺度效应

Abstract Utilisation of hydrogen is expected to be one of the solutions against the problems of exhaustion of fossil fuels and reduction of carbon dioxide emissions. Evaluation of the materials for hydrogen utilisation machines is required. The objectives of this study are the characterisation of fretting fatigue strength of low‐alloy steel SCM435H and heat‐resistant steel SUH660, and the validation of effectiveness of nitriding in hydrogen gas environment. Fretting fatigue tests were conducted up to 3 × 10 7 cycles. The decrease of fretting fatigue strength in hydrogen gas environment was found at the long‐life region exceeding 10 7 cycles. The amount of the decrease of the fretting fatigue limit at 3 × 10 7 cycles was 11% for SCM435H and 15% for SUH660. However, at the stress level above the fretting fatigue limit in air, the finite life in hydrogen gas increased more than that in air. The cause of extension of fatigue life was the delay of start of stable crack propagation. Fretting fatigue crack, which was smaller than 200 µm in length, consumed approximately 60% of the fatigue life in hydrogen gas environment. Fretting fatigue crack was steadily propagated after the test was started in air. Observations of the fretted surface showed that the fretting wear process in hydrogen gas environment was dominated by adhesion. Tangential force coefficient was higher in hydrogen gas environment than that in air. It is considered that the adhesion has a close relation to crack initiation in hydrogen gas environment, and as a result, the failure of specimen occurred at a lower stress level comparing the fretting fatigue limit in air. Copyright © 2008 John Wiley &amp; Sons, Ltd.

M. Kubota

Y. Tanaka

Y. Kondo

Fretting fatigue strength of SCM435H steel and SUH660 heat‐resistant steel in hydrogen gas environment

SCM435H钢和SUH660耐热钢在氢气环境中的微动疲劳强度

Abstract In this study, we present the development of model scale tribological test methods using the model ring‐on‐disc. The methods enable the demonstration of processes that occur in sliding materials during operation and subsequent breakdown. Currently, existing test methods are not able to visualise these complex processes to the same extent. We designed adapted test programmes for the visualisation of different material properties. This paper discusses the suitability and the significance of these test programmes. We benchmarked the test methods on selected metal‐based and plastic tribomaterials (CuPb22Sn2 and Polytetraflaoroethylene (PTFE) and bronze (Bz)) under lubricated and non‐lubricated conditions. We conducted an extensive damage analysis of the surfaces and surface layers. Furthermore, the classification of the damage patterns and the tribometric results are the basis for the development of models that are capable of representing the most important states during operation. The models are of sufficient quality to assist in the further optimisation of the materials. Copyright © 2008 John Wiley &amp; Sons, Ltd.

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Tribo Test

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Comparison of two test methods for evaluation of forming tool materials, Tribotest, v 14, n 3, July 2008, p 147-58

Comparison of two test methods for evaluation of forming tool materials, Tribotest, v 14, n 3, July 2008, p 147-58

Comparison of two test methods for evaluation of forming tool materials, Tribotest, v 14, n 3, July 2008, p 147-58

Load dependence and lifetime studies of self‐assembled monolayers

Comparison of two test methods for evaluation of forming tool materials, Tribotest, v 14, n 3, July 2008, p 147-58

The comparison of wear properties of different Fe‐based hardfacing alloys in four kinds of testing methods

Test methodology for the formulation and selection of components of thread moulding oils

Tribophyiscal scaling effects in friction and wear of polymers on small‐ and large‐scale tests

Fretting fatigue strength of SCM435H steel and SUH660 heat‐resistant steel in hydrogen gas environment

Test methods to characterise differently designed tribomaterials