Achintha, Mithila

He, Binyan

Reed, Philippa

You, Chao

Southampton (e-Prints Soton)

Important notes:  Do NOT write outside the grey boxes. Any text or images outside the boxes will be deleted.  Do NOT alter the structure of this form. Simply enter your information into the boxes. The form will be automatically processed – if you alter its structure your submission will not be processed correctly.  Do not include keywords – you can add them when you submit the abstract online.   Title: Numerical modelling of the effects of shot peening on crack shape evolution under low-cycle fatigue  Authors & affiliations: Chao You1, Mithila Achintha1, Binyan He1, Philippa Reed1 1Engineering Materials, Engineering and the Environment, University of Southampton, Highfield, Southampton SO17 1BJ, UK  Abstract:  (Your abstract must use Normal style and must fit in this box.  Your abstract should be no longer than 300 words. The box will ‘expand’ over 2 pages as you add text/diagrams into it.) Preparation of Your Abstract 1. The title should be as brief as possible but long enough to indicate clearly the nature of the study. Capitalise the first letter of the first word ONLY (place names excluded). No full stop at the end. 2. Abstracts should state briefly and clearly the purpose, methods, results and conclusions of the work. Introduction: Clearly state the purpose of the abstract Methods: Describe your selection of observations or experimental subjects clearly Results: Present your results in a logical sequence in text, tables and illustrations Discussion: Emphasize new and important aspects of the study and conclusions that are drawn from them Shot peening is an important fatigue amelioration strategy. The current paper presents a finite element (FE) analysis of the effects of shot peening on crack aspect ratio (a/c) evolution in the early stages of crack growth in a low pressure (LP) steam turbine material, FV448. The fatigue behaviour of this material has been experimentally evaluated using a U-notched specimen (representing the fir tree root geometry of the turbine blade) under 3-point bend tests. Two different shot peening intensities were considered in this study: an industrially applied shot peening process and a less intense shot peening process. The un-peened (polished) condition was also considered as a baseline comparison.  FE models have been developed, incorporating both compressive residual stress and strain hardening effects caused by shot peening. Static cracks with varying surface lengths (2c) and depths (a) were also introduced into the model. The J-integral and stress intensity factors of these cracks were then calculated at both the surface point and the deepest point along the crack front for the shot-peened and un-peened conditions. The obtained results were used to explain and predict the experimental observation that crack aspect ratio evolution in the early stages of crack growth in un-peened and shot-peened conditions is quite different: shallower a/c values are typically observed in the shot-peened condition. The relative contributions of compressive residual stresses and strain hardening to this effect were concluded by separately assessing their effects on crack growth. In addition, incorporation of the effects of the aspect ratio evolution into fatigue life assessment methods has been adopted in order to improve the current overly-conservative fatigue life predictions of shot-peened components.   

Numerical modelling of the effects of shot peening on crack shape evolution under low-cycle fatigue

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