强度不均匀焊接接头的应力分布及变形

为解释强度不均匀焊接接头最软区的强度及宽度与其承载能力的关系,用有限元对这类接头的单轴拉伸试样上应力分布及变形进行分析,当外加应力超过最软区的屈服应力时,在最软区及其邻近区域出现三轴应力状态;在有屈服应力差别的区域交界处Mises等效应力发生阶跃变化,其变化幅度与交界面两侧材料的屈服应力差值有关,随外加载荷的增加而增大.最软区Mises等效应力的降低量和与之相邻区域的增加量在试样长度上的积分相等.当Mises等效应力达到接头上最软区的抗拉强度时,在该处发生颈缩;随最软区的宽度减小或屈服应力增加,发生颈缩所需的外加应力增加;当最软区相对厚度小于0.2或相对屈服应力大于0.9时,在最软区已无明显颈缩.

Stress distribution and deformation within strength mismatched welded joints

In order to explain the relation between bearing capacity of mismatched welded joints and the width and strength of the softest zone in them, the stress distribution and deformation in the monoaxial tensile specimen of such joints is analyzed by employing the finite element method.While applied stress is greater than the yield stress of the softest zone, a triaxial stress state occurs in the softest zone and its adjacent zones.At the boundaries of zones with different yield stress,the Mises equivalent stresses change in step manner,the amplitude of this step change depends upon the difference in yield stresses on the both sides of the boundary, and increases with applied stress.Along the longitude of the tensile specimen,the integration of the decrease in Mises equivalent stress in the softest zone is equal to that of the increase in its adjacent zones.As the Mises equivalent stress approaches to the tensile strength of the softest zone,the necking in the softest zone occurs.In the softest zone,the increase in the tensile strength and a decrease in its width will make the applied stress required for necking increase.Apparent necking does not occur in the softest zone providing that its relative width is less than 0.2 or its relative yield stress is greater than 0.9.