Basics of Structural Fatigue

Smith, K. N.; Topper, T. H.

doi:10.4271/700555

Cited by 19 publications

(27 citation statements)

References 3 publications

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“…(ii) Adhesion by which we shall generally mean tangential surface forces (resisting tangential movement) arising from a variety of sources, when the two surfaces are at a certain proximity of each other. Thus, not only metallic adhesion (asperity junction shear strength) is considered, but any other, short or long range forces, such as van der Waals, can lie at source of ''adhesion'' [24,25], (iii) Deformation will refer to elasto-plastic, hysteresis losses, of rate-independent nature [10,26] in the bulk materials as a consequence of geometrical deformation of asperities (also called internal friction). In this formulation, only tangential deformation is considered, which, owing to adhesion, may persist long after the bases of the asperity have passed one another (cf.…”

Section: Basic Ingredients Of the Modelmentioning

confidence: 99%

A Novel Generic Model at Asperity Level for Dry Friction Force Dynamics

2004

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This paper presents a theoretical model for (dry, low-velocity, wear-less) friction force dynamics based on asperity interaction considerations subject to the phenomenological mechanisms of creep/relaxation, adhesion and (elasto-plastic) deformation in their most generalized forms. The model simulates the interaction of a large population of idealised, randomly distributed asperities with arbitrarily chosen geometrical and elastic properties. Creep and adhesion are simulated by an expedient local coefficient of friction that increases with time of contact, while deformation effects are accounted for by rate-independent hysteresis losses occurring in the bulk of the material of an asperity that is breaking loose. An energy method is adopted to calculate the instantaneous, local friction force leading to better insight into the problem as well as higher numerical efficiency. The results obtained by this model show both qualitative and quantitative agreement with the known types and facets of friction force dynamic behaviour; in particular, pre-sliding quasi time-independent frictional hysteresis in the displacement, velocity weakening, slider ''lift-up'' effect and frictional lag, in addition to the influence of the various process parameters, all in a single formulation, such as no extant friction model could show before. Moreover, the model is still open for and capable of further refinement and elaboration so as to incorporate local inertia and viscous effects and thus to be extended to include velocity strengthening and lubricated rough contacts.

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Section: Basic Ingredients Of the Modelmentioning

confidence: 99%

A Novel Generic Model at Asperity Level for Dry Friction Force Dynamics

2004

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“…The used critical plane approaches proposed by tensile crack model and shear crack model describe the failure mechanisms because of axial strain and of shear strain [26,27]. The implementation was made relatively easy because of simple formulations and simultaneously the effects of material hardening, residual stress and notch effect is respected.…”

Section: Discussionmentioning

confidence: 99%

“…According to this, two damage mechanic models were used in this study considering different types of micro crack growth. First, for tensile-mode crack initiation, the Smith-Watso-Topper model was used [26]:…”

Section: Fatigue Assessment By Critical Plane Approachesmentioning

confidence: 99%

Numerical fatigue life analysis of a high frequency mechanical impact treated industrial component based on damage mechanics models

Schubnell

Farajian

Däuwel

et al. 2018

Materialwissenschaft Werkst

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After post weld treatment with high frequency mechanical impact (HFMI) treatment of welds, a significant increase of fatigue life (up to a factor of 10) can be achieved. During the last years numerous experimental tests of welded joints with simple geometry under constant amplitude loading have been performed to quantify the positive effect of high frequency mechanical impact treatment. Due to the lack of methods for the prediction of the high frequency mechanical impact benefits, a widespread use of this process is not the case yet. Furthermore, it is still not clear if the results of these fatigue tests can be transferred to complex geometries and complex loading conditions such as in industrial applications. Therefore, an approach to assess the fatigue life of complex welded structures under variable amplitude loading was developed. For this purpose, high frequency mechanical impact treatment and fatigue load of simple welded specimen made of S690QL steel were simulated with finite element analysis (FEA) firstly. Then, the needed damage parameters for the fatigue life correlation were evaluated from the finite element postprocessing. The calculated life time to crack initiation was in good agreement with the experimental fatigue test results. In the next step, this procedure was implemented on a welded arm of an evacuator of type EW180B of the company Volvo Construction Equipment made of S700MC. The variable amplitude load measured under real service condition was transferred to single constant amplitude load cycles using a rainflow-counting algorithm. By simulation and damage mechanics evaluation of each load cycle the total damage sum could be calculated and compared with the experimental results from Volvo Construction Equipment.Keywords: Fatigue / welding / residual stresses / high frequency mechanical impact (HFMI) / finite element analysis (FEA) Nach einer Schweißnahtnachbehandlung mittels Hochfrequenzhämmern (engl. high frequency mechanical impact treatment (HFMI)) kann eine signifikante Lebensdauerverlängerung des Bauteils (bis zu einem 10-fachen) festgestellt werden. Während der letzten Jahre wurde dieser positive Effekt vielfach experimentell mit einfachen Proben-

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“…In fact, models sharing similar ideas have been proposed since the 1920s [33], and gradually formed corresponding modeling systems [34][35][36][37][38][39][40][41][42][43][44][45][46]. Typical achievements including the well-known Smith, Watson and Topper (SWT) model proposed in 1970 [37], which first considered the influence of the average stress. Another model is one concerning the hysteretic plastic work, which was proposed by Santner and Fine [38]; in this model, a relationship between the hysteretic plastic work and the fatigue life had been built up in a form similar to the Coffin-Manson law.…”

Section: Model and Analysismentioning

confidence: 99%

“…However, except for those advantages, the earlier hysteresis energy models also have certain shortcomings. For example, arguments still exist about the method of energy calculation, mainly concentrating on the disposal of the elastic region [37,43,46]; the difficulties of hysteresis energy calculation also hindered the application of the models. Consequently, in the HCF and common LCF regimes, since the criteria of stress and strain amplitude are also an issue, the energybased models have not been generally accepted.…”

Section: Model and Analysismentioning

confidence: 99%