一种超细晶粒钢焊接宽板抗断裂性能的数值评估

800 MPa超细晶粒钢具有优良的综合力学性能,但焊接热作用可能导致焊接热影响区的晶粒长大及局部软化。通过数值分析方法,以800 MPa超细晶粒钢母材性能为参照,对其实际焊接接头的抗断裂性能进行了评估。采用MARC商用软件,对不同中心贯穿裂纹尺寸的母材及其实际焊接接头拉伸板模型进行了三维有限元计算和拉伸过程模拟。焊接方法为脉冲熔化极混合气体保护焊,焊接板的中心裂纹处于焊缝与热影响区之间的熔合区。用作对比的母材板的裂纹尺寸和位置、网格划分、边界条件等与焊接板完全相同。根据计算结果,分析了焊接接头力学不均匀性对应力应变场的影响,并依据全面屈服理论对裂纹张开位移(CTOD)值进行了分析。结果表明,焊接接头的CTOD值均低于同裂纹尺寸的全母材。因此,该拉伸板的抗断裂性能应优于全母材,焊接接头的局部软化并未对结构承载造成不利影响。

Numerical evaluation of anti-fracture performance for welded wide plate of ultrafine grain steel

800 MPa ultrafine grain steel is a new generation steel with excellent mechanical properties.But thermal effect of welding may lead to grain growth and local softening in heat-affected zone.Evaluation of anti-fracture performance for welded plate was carried out using numerical analysis approach.Using MARC commercial software,tensile plate models of both all base steel and welded joint with various center through crack sizes were computed by three-dimensional finite element method,and the tensile process was simulated at the same time.The welding method used was a PC-GMAW process with mixture gases shielding. Central crack for the welded plate was located in the fusion zone between welding seam and heat-affected zone.The base steel plate for making comparison was the same crack size,crack location,finite element meshes and boundary condition as the welded plate.The effect of weld mechanical heterogeneity on the stress-strain fields of the welded plate was analyzed.On the basis of the full yield criterion,CTOD value of welded joints was compared.The results indicate that the CTOD values of welded joint are lower than those of all base plate of identical crack length.Thus,the welded plate exhibits priority of anti-fracture performance over all base plate.The local softening in the welded joint does not cause unfavorable influence on structural-load-carrying capacity.