根据英国标准BS7448,制备带预制疲劳裂纹的三点弯曲(three point bent,TPB)标准试样,对X80管线钢焊缝、热影响区和母材进行0℃断裂韧度试验,根据CTOD(crack tip opening displacement)试验结果,结合材料的力学性能、载荷条件,采用英国BS...根据英国标准BS7448,制备带预制疲劳裂纹的三点弯曲(three point bent,TPB)标准试样,对X80管线钢焊缝、热影响区和母材进行0℃断裂韧度试验,根据CTOD(crack tip opening displacement)试验结果,结合材料的力学性能、载荷条件,采用英国BS7910结构完整性评定方法的1A、2A评定曲线,针对焊缝内部的深埋裂纹,对X80钢管道焊缝进行安全评定。通过迭代计算确定含有深埋裂纹X80钢管道焊缝中的容许裂纹尺寸。展开更多
基于BS7910《金属结构缺陷可接受性评定方法指南》标准的高强钢焊接接头CTOD(crack tip opening displacement)值的评定方法可以有效克服各国规范CTOD允许值的差异,但是评定结果的保守度一直被关注.文中通过高强钢E47的CTOD试验测试数据...基于BS7910《金属结构缺陷可接受性评定方法指南》标准的高强钢焊接接头CTOD(crack tip opening displacement)值的评定方法可以有效克服各国规范CTOD允许值的差异,但是评定结果的保守度一直被关注.文中通过高强钢E47的CTOD试验测试数据,以有限元模拟辅助手段通过δ5法模拟得到裂纹尖端的真实应力.基于BS7910中的2A级评定方法,对失效评定曲线评估点的横坐标即载荷比进行修正.结果表明:修正后横坐标值小于1,评估点在失效评定曲线安全范围内,且修正后的评估点位置偏于安全.由临界韧度比确定的CTOD允许值δmin较修正前有明显降低,使基于失效评定曲线求CTOD允许值方法更为精确.展开更多
Industry design standards such as BS 7910 deployed some empirical formulas for the prediction of stress intensity factor(SIF) based on simulation results from traditional finite element method(FEM).However,such FEM si...Industry design standards such as BS 7910 deployed some empirical formulas for the prediction of stress intensity factor(SIF) based on simulation results from traditional finite element method(FEM).However,such FEM simulation occasionally failed to convince people due to the large discrepancies compared with engineering practice.As a consequence,inaccuracy predictions via such formulas in engineering standards inevitably occur,which will compromise the safety of structures.In our previous research work,an abnormal phenomenon of SIF in a cracked T-butt joint accounting for welding effect has been observed.Compared with BS 7910,the calculation results of SIF at the surface points of welded specimens cannot be well predicted,with a large discrepancy appearing.In order to explore such problem with an abnormal increase at the surface points of cracked welded specimens,a numerical investigation in terms of SIF among BS 7910,XFEM,and FEM is performed in this paper.Numerical models on both a simple cracked plate without welding effect and a cracked T-butt joint with welding effect are developed through ABAQUS.Parametric studies in terms of the effects of varied crack depth to thickness ratio(a/T) and the effects of crack depth to crack half-length ratio(a/c) are carried out.Empirical solutions from BS 7910 are used for comparison.It is found that the XFEM can provide predictions of SIF at both the crack deepest point and crack surface point of a simple cracked plate as accurate as FEM.For a T-butt joint with a transverse stiffener,a large discrepancy in terms of the weld magnification factors(Mk) occurs at the crack surface point compared with empirical predictions.An exceptional increase of von Mises stress gradient in regions close to the weld-toe is found through the simulation of FEM,whereas a constant stress gradient is obtained through XFEM.The comparison results indicate an inappropriate prediction of SIF by the utilization of the empirical formulas in BS 7910.A more reasonable prediction of the SIF at the surface point of a crack is obtained by the XFEM.Therefore,further updating of the empirical solutions in BS7910 for SIF accounting for welding effect is recommended.展开更多
文摘根据英国标准BS7448,制备带预制疲劳裂纹的三点弯曲(three point bent,TPB)标准试样,对X80管线钢焊缝、热影响区和母材进行0℃断裂韧度试验,根据CTOD(crack tip opening displacement)试验结果,结合材料的力学性能、载荷条件,采用英国BS7910结构完整性评定方法的1A、2A评定曲线,针对焊缝内部的深埋裂纹,对X80钢管道焊缝进行安全评定。通过迭代计算确定含有深埋裂纹X80钢管道焊缝中的容许裂纹尺寸。
文摘基于BS7910《金属结构缺陷可接受性评定方法指南》标准的高强钢焊接接头CTOD(crack tip opening displacement)值的评定方法可以有效克服各国规范CTOD允许值的差异,但是评定结果的保守度一直被关注.文中通过高强钢E47的CTOD试验测试数据,以有限元模拟辅助手段通过δ5法模拟得到裂纹尖端的真实应力.基于BS7910中的2A级评定方法,对失效评定曲线评估点的横坐标即载荷比进行修正.结果表明:修正后横坐标值小于1,评估点在失效评定曲线安全范围内,且修正后的评估点位置偏于安全.由临界韧度比确定的CTOD允许值δmin较修正前有明显降低,使基于失效评定曲线求CTOD允许值方法更为精确.
文摘Industry design standards such as BS 7910 deployed some empirical formulas for the prediction of stress intensity factor(SIF) based on simulation results from traditional finite element method(FEM).However,such FEM simulation occasionally failed to convince people due to the large discrepancies compared with engineering practice.As a consequence,inaccuracy predictions via such formulas in engineering standards inevitably occur,which will compromise the safety of structures.In our previous research work,an abnormal phenomenon of SIF in a cracked T-butt joint accounting for welding effect has been observed.Compared with BS 7910,the calculation results of SIF at the surface points of welded specimens cannot be well predicted,with a large discrepancy appearing.In order to explore such problem with an abnormal increase at the surface points of cracked welded specimens,a numerical investigation in terms of SIF among BS 7910,XFEM,and FEM is performed in this paper.Numerical models on both a simple cracked plate without welding effect and a cracked T-butt joint with welding effect are developed through ABAQUS.Parametric studies in terms of the effects of varied crack depth to thickness ratio(a/T) and the effects of crack depth to crack half-length ratio(a/c) are carried out.Empirical solutions from BS 7910 are used for comparison.It is found that the XFEM can provide predictions of SIF at both the crack deepest point and crack surface point of a simple cracked plate as accurate as FEM.For a T-butt joint with a transverse stiffener,a large discrepancy in terms of the weld magnification factors(Mk) occurs at the crack surface point compared with empirical predictions.An exceptional increase of von Mises stress gradient in regions close to the weld-toe is found through the simulation of FEM,whereas a constant stress gradient is obtained through XFEM.The comparison results indicate an inappropriate prediction of SIF by the utilization of the empirical formulas in BS 7910.A more reasonable prediction of the SIF at the surface point of a crack is obtained by the XFEM.Therefore,further updating of the empirical solutions in BS7910 for SIF accounting for welding effect is recommended.
