In this paper, a weighted residual method for the elastic-plastic analysis near a crack tip is systematically given by taking the model of power-law hardening under plane strain condition as a sample. The elastic-plas...In this paper, a weighted residual method for the elastic-plastic analysis near a crack tip is systematically given by taking the model of power-law hardening under plane strain condition as a sample. The elastic-plastic solutions of the crack lip field and an approach based on the superposition of the nonlinear finite element method on the complete solution in the whole crack body field, to calculate the plastic stress intensity factors, are also developed. Therefore, a complete analvsis based on the calculation both for the crack tip field and for the whole crack body field is provided.展开更多
The method of complex function and the method of Green's function are used to investigate the problem of SH-wave scattering by radial cracks of any limited length along the radius originating at the boundary of an...The method of complex function and the method of Green's function are used to investigate the problem of SH-wave scattering by radial cracks of any limited length along the radius originating at the boundary of an elliptical hole, and the solution of dynamic stress intensity factor at the crack tip was given. A Green's function was constructed for the problem, which is a basic solution of displacement field for an elastic half space containing a half elliptical gap impacted by anti-plane harmonic linear source force at any point of its horizontal boundary. With division of a crack technique, a series of integral equations can be established on the conditions of continuity and the solution of dynamic stress intensity factor can be obtained. The influence of an elliptical hole on the dynamic stress intensity factor at the crack tip was discussed.展开更多
This work examines the fracture behavior of a functionally graded material （FGM） plate containing parallel surface cracks with alternating lengths subjected to a thermal shock. The thermal stress intensity factors ...This work examines the fracture behavior of a functionally graded material （FGM） plate containing parallel surface cracks with alternating lengths subjected to a thermal shock. The thermal stress intensity factors （TSIFs） at the tips of long and short cracks are calculated using a singular integral equation technique. The critical thermal shock △Tc that causes crack initiation is calculated using a stress intensity factor criterion. Numerical examples of TSIFs and △Tc for an Al2O3/Si3N4 FGM plate are presented to illustrate the effects of thermal property gradation, crack spacing and crack length ratio on the TSIFs and △Tc. It is found that for a given crack length ratio, the TSIFs at the tips of both long and short cracks can be reduced significantly and △Tc can be enhanced by introducing appropriate material gradation. The TSIFs also decrease dramatically with a decrease in crack spacing. The TSIF at the tips of short cracks may be higher than that for the long cracks under certain crack geometry conditions. Hence, the short cracks instead of long cracks may first start to grow under the thermal shock loading.展开更多
Based on the crack tip field expansion of the Reissner plate, a special high order bending crack tip element is developed, and the element stiffness matrix is given in the explicit form, which is especially convenien...Based on the crack tip field expansion of the Reissner plate, a special high order bending crack tip element is developed, and the element stiffness matrix is given in the explicit form, which is especially convenient for engineering analyses. A numerical example is presented and compared with previous results to demonstrate the efficiency and accuracy of the special element.展开更多
The incompatible numerical manifold method （INMM） is based on the finite cover approximation theory, which provides a unified framework for problems dealing with continuum and discontinuities. The incompatible numer...The incompatible numerical manifold method （INMM） is based on the finite cover approximation theory, which provides a unified framework for problems dealing with continuum and discontinuities. The incompatible numerical manifold method employs two cover systems as follows. The mathematical cover system provides the nodes for forming finite covers of the solution domain and the weighted functions, and the physical cover system describes geometry of the domain and the discontinuous surfaces therein. In INMM, the mathematical finite cover approximation theory is used to model cracks that lead to interior discontinuities in the process of displacement. Therefore, the discontinuity is treated mathematically instead of empirically by the existing methods. However, one cover of a node is divided into two irregular sub-covers when the INMM is used to model the discontinuity. As a result, the method sometimes causes numerical errors at the tip of a crack. To improve the precision of the INMM, the analytical solution is used at the tip of a crack, and thus the cover displacement functions are extended with higher precision and computational efficiency. Some numerical examples are given.展开更多
Preventive maintenance is an accepted practice in engineering to keep the structural reliability of ship hulls at the highest possible level.Designers ensure a longer period in between the consecutive maintenance of s...Preventive maintenance is an accepted practice in engineering to keep the structural reliability of ship hulls at the highest possible level.Designers ensure a longer period in between the consecutive maintenance of ship hull parts to optimize expenditure.This is relevant in view of the difficulty in reaching farthest corners in ballast tanks,fuel storage tanks,cofferdams etc.Prior maintenance of the deck and hull parts save a considerable amount of the owner's budget.A portable technology like patching becomes more handy and economic.Performance of both unpatched and patched samples during dynamic loading conditions being examined in the present investigation.The high strength steel panels with a dimension of 70mm×15mm×3mm were edge cracked for lengths of 4mm and 7mm,with width of 1mm for both.The edge cracked high strength steel panels are repaired with composite patches using GFRP(glass fiber reinforced plastic),CFRP(carbon fiber reinforced plastic)and AFRP(aramid fiber reinforced plastic).The patching was done by 3 and 5 layered and impact tested by Charpy impact tester at ranges of high temperatures.The amount of energy absorbed in the impact is converted to dynamic fracture toughness values and compared for evaluating the performance of FRP(fiber reinforced plastics).Finite element analysis was done for evaluating the stress intensity factors at different types of patching and testing conditions.Comparatively the AFRP patched samples showed better dynamic fracture toughness values at different temperatures.展开更多
文摘In this paper, a weighted residual method for the elastic-plastic analysis near a crack tip is systematically given by taking the model of power-law hardening under plane strain condition as a sample. The elastic-plastic solutions of the crack lip field and an approach based on the superposition of the nonlinear finite element method on the complete solution in the whole crack body field, to calculate the plastic stress intensity factors, are also developed. Therefore, a complete analvsis based on the calculation both for the crack tip field and for the whole crack body field is provided.
文摘The method of complex function and the method of Green's function are used to investigate the problem of SH-wave scattering by radial cracks of any limited length along the radius originating at the boundary of an elliptical hole, and the solution of dynamic stress intensity factor at the crack tip was given. A Green's function was constructed for the problem, which is a basic solution of displacement field for an elastic half space containing a half elliptical gap impacted by anti-plane harmonic linear source force at any point of its horizontal boundary. With division of a crack technique, a series of integral equations can be established on the conditions of continuity and the solution of dynamic stress intensity factor can be obtained. The influence of an elliptical hole on the dynamic stress intensity factor at the crack tip was discussed.
文摘This work examines the fracture behavior of a functionally graded material （FGM） plate containing parallel surface cracks with alternating lengths subjected to a thermal shock. The thermal stress intensity factors （TSIFs） at the tips of long and short cracks are calculated using a singular integral equation technique. The critical thermal shock △Tc that causes crack initiation is calculated using a stress intensity factor criterion. Numerical examples of TSIFs and △Tc for an Al2O3/Si3N4 FGM plate are presented to illustrate the effects of thermal property gradation, crack spacing and crack length ratio on the TSIFs and △Tc. It is found that for a given crack length ratio, the TSIFs at the tips of both long and short cracks can be reduced significantly and △Tc can be enhanced by introducing appropriate material gradation. The TSIFs also decrease dramatically with a decrease in crack spacing. The TSIF at the tips of short cracks may be higher than that for the long cracks under certain crack geometry conditions. Hence, the short cracks instead of long cracks may first start to grow under the thermal shock loading.
文摘Based on the crack tip field expansion of the Reissner plate, a special high order bending crack tip element is developed, and the element stiffness matrix is given in the explicit form, which is especially convenient for engineering analyses. A numerical example is presented and compared with previous results to demonstrate the efficiency and accuracy of the special element.
基金supported by the Natural Science Foundation of Shandong Province for Excellent Young and Middle-aged Scientist (2007BS04045 and 2008BS04009)the Natural Science Foundation of Shandong Province(Y2006B24 and Y2008A 11)
文摘The incompatible numerical manifold method （INMM） is based on the finite cover approximation theory, which provides a unified framework for problems dealing with continuum and discontinuities. The incompatible numerical manifold method employs two cover systems as follows. The mathematical cover system provides the nodes for forming finite covers of the solution domain and the weighted functions, and the physical cover system describes geometry of the domain and the discontinuous surfaces therein. In INMM, the mathematical finite cover approximation theory is used to model cracks that lead to interior discontinuities in the process of displacement. Therefore, the discontinuity is treated mathematically instead of empirically by the existing methods. However, one cover of a node is divided into two irregular sub-covers when the INMM is used to model the discontinuity. As a result, the method sometimes causes numerical errors at the tip of a crack. To improve the precision of the INMM, the analytical solution is used at the tip of a crack, and thus the cover displacement functions are extended with higher precision and computational efficiency. Some numerical examples are given.
文摘Preventive maintenance is an accepted practice in engineering to keep the structural reliability of ship hulls at the highest possible level.Designers ensure a longer period in between the consecutive maintenance of ship hull parts to optimize expenditure.This is relevant in view of the difficulty in reaching farthest corners in ballast tanks,fuel storage tanks,cofferdams etc.Prior maintenance of the deck and hull parts save a considerable amount of the owner's budget.A portable technology like patching becomes more handy and economic.Performance of both unpatched and patched samples during dynamic loading conditions being examined in the present investigation.The high strength steel panels with a dimension of 70mm×15mm×3mm were edge cracked for lengths of 4mm and 7mm,with width of 1mm for both.The edge cracked high strength steel panels are repaired with composite patches using GFRP(glass fiber reinforced plastic),CFRP(carbon fiber reinforced plastic)and AFRP(aramid fiber reinforced plastic).The patching was done by 3 and 5 layered and impact tested by Charpy impact tester at ranges of high temperatures.The amount of energy absorbed in the impact is converted to dynamic fracture toughness values and compared for evaluating the performance of FRP(fiber reinforced plastics).Finite element analysis was done for evaluating the stress intensity factors at different types of patching and testing conditions.Comparatively the AFRP patched samples showed better dynamic fracture toughness values at different temperatures.
