| Linear elastic fracture mechanics is the basic theory for studying the fracture of sharp cracks in elastomers,and it is the basis for evaluating the stress field and fatigue of structures with notches or cracks.Geometric discontinuities are the main parts of stress concentration,which will greatly reduce the fatigue performance of the structure.The stress field analysis of geometric discontinuities,especially the stress field analysis of V-notch,is the key to evaluate the fatigue performance of this kind of structure.Welded structures with V-notch are widely used in aerospace and marine structures,so the simple evaluation formula of stress field of V-notch is studied emphatically.The assessment process of notch stress field is greatly simplified,which lays a foundation for fatigue assessment of welded structures or structures with notches.The main work of this paper is as follows:(1)Based on the notch stress intensity theory,considering the influence of structural geometry and welding geometry on notch stress field,the concept of singular strength factor "as" is introduced,and a simple evaluation formula for evaluating notch stress field distribution of infinite plate with cracks is put forward.By establishing infinite plate models with notches at different opening angles,numerical analysis of notch stress field is carried out,and a simple formula of singular intensity factor "as" is obtained by fitting,which can be used for rapid evaluation of stress field of notch structures.Compared with the traditional notch stress field evaluation formula and numerical results,the simple formula in this paper has higher evaluation accuracy,which can reduce the influence of mesh sensitivity on notch stress field evaluation,and greatly simplifies the notch stress field evaluation process.(2)Based on the evaluation formula of notch stress field with infinite plate width,this paper deduces and verifies the simplified calculation formula of notch stress distribution and N-SIF of V-notch plate with finite plate width.By establishing a series of finite plate width double-sided notch models with different geometric sizes and different opening angles,the stress field formula with double-sided V-shaped notch is simplified and fitted.On this basis,the relationship curves between "as" and geometric parameters and notch opening angle are obtained by using the control variable method,and the unified calculation formula of singular intensity factor "as" is obtained by fitting.By constructing the relationship between singular intensity factor as and N-SIF,the dimensionless N-SIF is further obtained.Comparing the prediction results of simple formula with those of finite element method and traditional formula,the results show that this formula can simply and accurately predict the stress field and N-SIF of the specimen with limited plate width and bilateral notch.(3)On the basis of the evaluation formula of notch stress field with limited plate width,the simple formula of notch stress field is extended to complex inclination angles.By establishing a series of oblique crack notch models with finite plate width under different geometric sizes,opening angles and inclination angles,the stress field of oblique crack notch is simplified and fitted.On this basis,the relationship curves of "as" and dimensionless N-SIF with geometric size,inclination angle and opening angle are obtained by using the control variable method,and the calculation formula of dimensionless N-SIF of oblique crack notch with finite plate width is fitted.Finally,by analyzing the error between the prediction result of simple formula and the finite element result,it is found that the error between the dimensionless N-SIF calculated in this paper and the finite element result is within 10%,and the calculation error of more than 90% results is within 3%.Compared with the traditional N-SIF evaluation formula,the simple formula in this paper has higher accuracy and wider application range of opening angle. |
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