This paper investigates the stress fields for a crack located at the fusion line of a weldment. The strength mis-matching and the size of the HAZ were varied, and the corresponding distribution of the maximum principal stress was examined. The weld metal strength was globally overmatched with respect to the base material, but locally over- and undermatched with respect to the heat affected zone. Three cases of mis-match were compared, and it was found that reducing the strength of the HAZ lowered the maximum principal stresses. 相似文献
This paper presents numerical studies on strength mis-match effects in welded joints. Crack growth in a mis-matched single
edge notched specimen under pure bending, with a crack lying at the center line of the weld metal, is simulated via a two-dimensional
plane strain finite element analysis (FEA). The fracture process is modeled using a cohesive zone model (CZM). The work is
focussed on the effects of yield strength mis-match as well as thickness of the weld metal on fracture resistance and load-deformation
for both under- and overmatched specimens. Weld metal mis-match is achieved by keeping the same weld metal and changing the
strength of the base metal.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
In order to reduce production costs, it is of great interest to use longitudinal seam welds when manufacturing large diameter pipes. The cost reduction can be as high as 30%. However, severe inservice accidents for this type of pipes working in the creep regime have occurred mainly due to mismatch in weldment creep properties.
In many cases, creep tests of cross-weld specimens, taken from the seam weld, are used to predict the behaviour of the seam weld, assuming that the creep behaviour of specimen and weldment is equivalent. Experiences of this procedure indicate that further knowledge is required before translation between specimen and component can be made.
In the present paper, both full scale seam welded pipes and cross-weld specimens are studied with the damage mechanics concept using finite element, FE, technique. The same mechanical model of multiple material zones is used for the two components. Both the influence of differences in creep properties between the weldment constituents and the size effect of the cross-weld specimen, are studied.
It is found that the cross-weld test results can not directly be translated to the full scale component. Factors such as the creep properties and the relative geometry of the weldment constituents and the size of the cross-weld specimen have to be considered when performing creep life assessment. 相似文献
The present work provides mis-match limit loads for welded pipes with constant-depth, circumferential part-through surface cracks in the centre of the weld metal. As limiting cases, circumferential through-wall and fully circumferential cracks are also considered. Based on systematic finite element limit analyses, mis-match limit loads are quantified by the strength mis-match ratio and only one geometry-related slenderness parameter, not requiring additional geometry-related parameters. This implies that mis-match limit loads for surface cracked pipes can be found from those for idealized axi-symmetric problems, which offers significant benefit in assessment of surface cracks in welds of pipes. 相似文献
A new upper bound solution for highly undermatched welded DE(T) specimens is proposed. A distinguished feature of this solution is that it accounts for the thickness of the specimen. Even though this case is more general than plane-strain and plane-stress solutions, the final result is given in terms of ordinary and double integrals. Comparison with a plane strain solution shows that the thickness of the specimen has a great effect of the limit load. 相似文献
In our previous paper, it was found that the mis-match effect in creep on steady-state stresses within the weld metal for a large bore branch junction could be uniquely quantified by the mis-match factor defined as a function of the creep stress exponent and the ratio of creep constants for the base and weld materials. Furthermore ratios of section-averaged (effective and maximum principal) stresses for the mis-matched case to those for the even-matched case were linearly dependent on the mis-match factor. Above results were obtained for a specific branch geometry under single loading. This paper extends our previous analysis to other branch geometries and to combined loading. It is found that above conclusions can be applied to general branch components under combined loading. 相似文献
It has been well known that ductile fracture of steels is accelerated by triaxial stresses. The characteristics of ductile crack initiation in steels are evaluated quantitatively using a two-parameter criterion based on equivalent plastic strain and stress triaxiality.The present study focuses on the effects of geometrical discontinuity, strength mis-match, which can elevate plastic constraint due to heterogeneous plastic straining, and loading rate on the critical condition for ductile fracture initiation using a two-parameter criterion. Fracture initiation testing has been conducted under static and dynamic loading using circumferentially notched round-bar specimens. In order to evaluate the stress/strain state in the specimens, especially under dynamic loading, a thermal elastic-plastic dynamic finite element (FE) analysis considering the temperature rise due to plastic deformation has been carried out.The tensile tests on specimens with an undermatching interlayer showed that the relationship between the critical equivalent plastic strain to initiate ductile fracture and stress triaxiality was equivalent to that obtained on homogeneous specimens under static loading. Moreover, the two-parameter criterion for ductile fracture initiation is shown to be independent of the loading rate. It was demonstrated that the critical global strain to initiate ductile fracture in specimens with strength mis-match under various loading rate can be estimated based on the local criterion, that is two-parameter criterion obtained on homogeneous specimens under static tension, by mean of FE-analysis taken into account accurately both strength mis-match and dynamic loading effects on stress/strain behaviors. 相似文献