Influence of Machining on the Surface Integrity and Fatigue Strength of 34CrNiMo6 Steel

Ataollah Javidi

Research output: ThesisDoctoral Thesis

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Abstract

The specification and manufacture of unimpaired or enhanced surfaces require an understanding of the interrelationship among metallurgy, machinabitity and mechanical testing. To satisfy this requirement, an encompassing discipline known as surface integrity was introduced and it has gained worldwide acceptance. Surface integrity technology describes and controls the many possible alterations produced in a surface layer during manufacture, including their effects on material properties and the performance of the surface in service. Surface integrity is achieved by the selection and control of manufacturing processes, estimating their effects on the significant engineering properties of work materials, such as fatigue performance. The calculation of the fatigue strength for the development of structural components has become more important in recent years. In order to save time and cost, it is attempted to limit the experimental strength testing and to calculate the fatigue strength from material data. The fatigue strength of smooth, polished material specimens can be estimated or obtained from the corresponding fatigue charts with high accuracy. However, the results of fatigue strength determinations on material specimens cannot be directly applied to real components. This is because there are various parameters such as surface topography, residual stresses, hardness, microstructure, etc. that have a large impact on fatigue strength of structural components. The effect of these parameters on the fatigue strength of components is complex and causes difficulty in its evaluation with respect to the fatigue strength of material specimens. The fatigue strength of a metal is generally defined in terms of the endurance limit and the effects of surface integrity are considered by correcting the endurance limit using the appropriate factors. The traditional correction factors provide a simple and useful means to estimate the fatigue strength related to the surface alternation they are, however, generally restricted to surface roughness analysis.Within this work, two new factors, namely, surface fatigue factor and residual stress factor were proposed to evaluate the fatigue strength of different surface conditions. The surface fatigue factor characterizes the surface topography and the residual stress factor takes into account the multiaxiality nature of residual stresses. Both factors are presented by empirical models.
Translated title of the contributionEinfluss des Drehprozesses auf die Randschicht und Schwingfestigkeit von 34CrNiMo6.
Original languageEnglish
QualificationDr.mont.
Supervisors/Advisors
  • Eichlseder, Wilfried, Assessor A (internal)
  • Clemens, Helmut, Assessor B (internal)
Publication statusPublished - 2008

Bibliographical note

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Keywords

  • Surface Integrity Surface Topography Residual Stresses Fatigue Strength

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