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首页> 外文期刊>Welding International >A study of fatigue resistance in joints welded in steel and light alloy according to deformation energy at the weld toes and roots
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A study of fatigue resistance in joints welded in steel and light alloy according to deformation energy at the weld toes and roots

机译：根据焊趾和根部的变形能研究钢和轻合金焊接接头的抗疲劳性

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摘要

The criteria based on factors of tension intensification encompass the ladder effect, directly associated with the gradients of tension present in the most critical zones of the joints. These zones are, as is known, positioned at the weld toes and roots, which the criteria models as V-shaped notches worst case and with a variable opening angle. The dimension of these factors and the ladder effect change according to the geometry of the beads, in accordance with the classic treatment of Williams, which gives a variation of the degree of singularity decreasing from 0.5 to 0 passing through a crack to a V-shaped notch with an opening tending to 180 deg. The statistical analysis of approximately 700 experimental data of fatigue resistance in seams welded in steel and in aluminium alloy has demonstrated that, independent of the material, seams characterised by failure at the toe with an angle of opening of 135 deg (to be considered a typical value) demonstrate an exponent for the reduction of fatigue resistance through the ladder effect of 0.33, whereas the seams with failure at the root the exponent has a value close to 0.5. The use of a 0.25 exponent, as suggested by the 10011 regulation and by Eurocodice, appears not to be cautious. A new band of dispersion has been presented for the cruciform welded joints with carrier weld and with fatigue failure along the roots of the welding, which correlates the total life of the seams to factors of mode I intensification. The data gathered for the seams with failure at the root have been further elaborated according to the variation of the deformation energy mediate in a very precise structural volume, in order to make possible a comparison with numerous other data relative to the fatigue resistance of the joints in question with failure at the weld toe. A single band has been proposed, valid for joints in construction steel with carrier and non carrier welds with failures located both at the weld toe and the weld root. The width of the joints varied from between 3 and 100 mm. The band gives an average value of triangle open W equivalent to 0.105 Nmm/mm~3 at 2 million cycles. At a high number of cycles, joints welded at a reduced width (3 mm) and welds in stainless steel AISI 304L have highlighted average values of deformation energy at failure analogous to the average values expected for the band. Instead, with a reduction in the number of cycles, their resistance appears inferior. In relation to the joints welded in light alloy, the dimensions of the structural volume were inferior to that of the construction steels welded, with a critical radius of 0.12 mm as compared to 0.28 mm in the steels. On the basis of the two different volumes in play, the values of the average energy coincided with the 2 million cycles for the steel joints and for those in light alloy. As we have specified, a direct comparison in terms of N-SIF is not possible in the case of welds with a different opening angle. The criteria based on the average local energy overcomes the problem and allows a standard criteria. In the case of welding in superimposition in light alloy characterised by failure at the root in the presence of distribution of tension with mode II predominant over mode I, the fatigue resistance data in terms of triangle open W were wholly compatible with that of the joints with a seam angle of 135 degrees, interested by the distribution of tension of only mode I and failures along the weld toes.
机译：基于张力增强因素的标准包括阶梯效应，该阶梯效应与关节最关键区域中存在的张力梯度直接相关。众所周知，这些区域位于焊趾和焊根处，这些标准将其建模为最坏情况下的V形缺口并具有可变的张角。根据威廉姆斯的经典处理方法，这些因子的尺寸和阶梯效应根据微珠的几何形状而变化，这使得奇异度的变化从0.5降低到0，并通过裂纹变为V形槽口的开口趋于180度。对钢和铝合金焊接接缝中约700项疲劳强度实验数据的统计分析表明，与材料无关，以趾尖破裂角度为135度（通常被认为是典型的）为特征的接缝值）可以通过0.33的阶梯效应来降低疲劳强度的指数，而在根部失效的接缝处的指数接近0.5。根据10011法规和Eurocodice的建议，使用0.25指数似乎并不谨慎。对于带有载体焊缝的十字形焊接接头，沿着焊缝根部出现疲劳破坏，提出了一种新的分散带，这将接缝的总寿命与I型强化因素联系起来。根据在非常精确的结构空间中传递的变形能的变化，进一步阐述了从根部破裂的接缝处收集的数据，以便可以与许多其他有关接头抗疲劳性的数据进行比较有问题的是在焊趾处出现故障。已经提出了一个单一的带，适用于在带有钢包和非钢包焊缝的建筑钢中的接头，并且在焊趾和焊根处均出现故障。接头的宽度在3至100毫米之间。该带给出了200万次循环时的三角形开放W的平均值，等于0.105 Nmm / mm〜3。在高数量的循环中，以减小的宽度（3 mm）进行焊接的接头和采用AISI 304L不锈钢制成的焊缝突出显示了失效时变形能的平均值，类似于该带的预期平均值。相反，随着循环次数的减少，它们的电阻变差。对于用轻合金焊接的接头，结构体积的尺寸小于焊接的建筑钢的尺寸，其临界半径为0.12 mm，而钢的临界半径为0.28 mm。根据两个不同的体积，钢接头和轻合金接头的平均能量值与200万次循环一致。如我们所指定的，在具有不同张角的焊接情况下，无法直接根据N-SIF进行比较。基于平均局部能量的标准克服了这个问题，并允许使用标准标准。在轻合金中叠加焊接的情况下，特征在于根部存在破坏，并且存在模式II优于模式I的张力分布，关于三角形开口W的疲劳强度数据与具有焊缝角为135度，仅对模式I的张力分布和沿焊趾的破坏感兴趣。

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