| Plate components are crucial elements in construction machinery,aviation,automotive,ships,and other fields.They are often subjected to stress concentrations caused by opening holes,resulting in hole-edge cracks,and suffer from manufacturing defects,leading to linear cracks.The further propagation of these cracks can compromise the functionality of components and even lead to sudden failures.Crack propagation directly hinges on the magnitude of the stress intensity factor(SIF)at the crack tip.Currently,research on hole-edge cracks predominantly centers on resolving the SIF of a single regular hole with symmetric cracks in isotropic plates.Studies on linear cracks primarily focus on the interaction between straight linear cracks,while there are limited investigations into the interaction between hole-edge cracks at various positions and the interaction between arbitrarily shaped linear cracks.Additionally,research on hole-edge cracks in anisotropic plate components is still in its early stages.Based on that,this article employs successive conformal mapping to derive the mapping function of a circular hole with asymmetric cracks,and employs numerical methods to obtain the mapping function of an arbitrarily shaped hole.Then,on the basis of improved Muskhelishvili method and the superposition method,the influence of the interaction between multiple arbitrary-located hole-edge cracks in an isotropic plate on the SIF is studied;A SIF calculation method for cracks at the edges of circular,elliptical,and square holes in a three parameter orthotropic plate is proposed by extending the improved Muskhelishvili method;The influence of the interaction between multiple arbitrarily-shaped line cracks on the SIF is studied using the distributed dislocation method;Finally,the research methods of this article combined with the residual strength criterion are used to predict and verify the residual strength of plates with hole edge cracks and linear cracks.The main research work is as follows:(1)The successive conformal mapping method is utilized to analytically derive the mapping function for a circular hole with asymmetric cracks,while numerical methods are employed to establish a universal mapping function applicable to holes of any shape.on account of the challenge posed by the complex forms of irrational integrand functions encountered during the integration process in solving SIF for asymmetric cracks originating from a hole,the Muskhelishvili method,traditionally used for stress analysis in isotropic plates,has been improved.This improvement yields a universal quasi-analytical method for solving hole-edge cracks,termed the Improved Muskhelishvili method.In the analysis of stress under the interaction of linear cracks,these line cracks are treated as equivalent to continuously distributed dislocation arrays.Utilizing the distributed dislocation method in conjunction with the Gaussian Chebyshev numerical technique,the stress field and SIF at the crack tip are analyzed under the interaction of multiple cracks.(2)Through comparison with other methods,it has been confirmed that the improved Muskhelishvili method is universal and has high accuracy in solving the SIF of hole-edged cracks;The method is used to analyze the variation law of the SIF.The results show that as the cracks continue to expand,the influence of the hole on the SIF gradually weakens.The order of the influence from different hole shape on SIF is: circular hole>elliptical hole>square hole.The loading angle doesn’t affect the variation law of SIF,but it would affect its numerical value;Based on the principle of superposition,a calculation method for the multiple interactive hole-edge cracks at arbitrary position is derived,and the interaction law of the multiple hole-edge cracks is analyzed.Results indicate that with increasing orientation angle,the effect of elliptical holes on the SIF of cracks originating from circular holes transitions from amplification to suppression,with a critical orientation angle of43°.Decreasing the aperture of adjacent holes mitigates their influence on the SIF of hole-edge cracks.The interaction effect on the SIF of elliptical hole-edge cracks is smaller than that on circular holes.The prediction results of the residual strength of the plate under the interaction of multiple hole-edge cracks using the ligament yield criterion combined with the improved Muskhelishvili method are in agreement with the experimental results,with a relative error less than 7.5%.The prediction accuracy is significantly better than the net section criterion and the apparent fracture toughness criterion.(3)The improved Muskhelishvili method is extended to the analysis of hole-edge cracks in anisotropic materials.Taking the commonly used three elastic parameter materials of titanium and graphite as examples,the calculation method for solving the SIF of hole-edge cracks is derived.The method is used to analyze the variation law of the SIF for hole-edge cracks.The results show that the variation law of the SIF for the three elastic parameter materials is the same as that for isotropic materials.As the crack continues to propagate,the influence of the hole on SIF gradually weakens;Compared with isotropic plates,the three elastic parameter plates have easier crack propagation at an early stage,while graphite plates have faster crack propagation than titanium plates;The mode I SIF of the cracks emanating from hole in the titanium plate increases with increasing applied load angle,while the Mode II SIF initially increases and then decreases with increasing load angle,reaching a critical angle of 45°.(4)Through comparison with other methods,the distributed dislocation method demonstrates favorable applicability in analyzing the interaction between linear cracks.With the help of the stress field under crack interaction,the influence of parameters such as orientation angle,inclination angle,center distance,and crack length on the SIF is analyzed.The results show that as the orientation angle increases,the interaction between cracks shifts from amplification effect to suppression effect,and the critical orientation angle is related to the crack tip distance;The crack inclination angle,center distance,and crack length do not change the way in which cracks interact with each other,they only decide the level of interaction.A SIF calculation model for arbitrarily shaped linear cracks is devised,extending the distributed dislocation method to address the SIF under the interaction of arbitrary-shaped linear cracks.An analysis is conducted on the influence of orientation and inclination angles of straight cracks on the SIF of curved arbitrary-shaped cracks.Results indicate that the influence of straight cracks on Mode I SIF of arbitrary-shaped cracks remains consistent regardless of crack shape,while the influence from the shape of the curve on the mode II SIF of curved crack modes is more significant.The prediction results of residual strength of plates under the interaction of multiple linear cracks using the combination of ligament yield criterion and distributed dislocation method are in agreement with experimental results,with an error less than 15.5%.The prediction accuracy is significantly better than that of the Faber series method combined with ligament yield criterion. |
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