The torsion number of drawn fine high carbon steel wires was measured through torsion testing. The angles between the scratches on the tested wire surface and its longitudinal axis were measured. The shear strain calculated from torsion number γ t , shear strain at fractured point γ f , and plastic shear strain γ pc were evaluated. The following results were obtained. First, the shear strain distribution homogenized; further, torsion number per unit length N , γ t , and γ pc increased when decreasing the difference between γ f and γ pc where γ pc subtracted from γ f (=Δ γ fpc ) > 0. Second, the external factors caused non-uniform shear strain distribution and reduction from the potential maximum shear strain, even for the wire that was hardly affected by the internal factors. The difference of shear strain non-uniformity caused a variation in reduction from the potential maximum shear strain. The internal factors included non-uniform microstructure and existence of inclusions and voids. The external factors were caused by the testing machine and setting of the sample. The potential maximum shear strain was obtained when the effects of internal and external factors were inhibited. Finally, two evaluation methods of the potential maximum shear strain were suggested. One method identifies a sample with a small Δ γ fpc , and a large γ pc where Δ γ fpc > 0. This sample can be regarded as having the closest strain to the potential maximum shear strain. The other method determines γ pc when Δ γ fpc is closest to 0. This value can be interpreted as plastic strain of the potential maximum shear strain.

中文翻译：

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在扭转试验中评估细金属线的潜在最大剪切应变的方法

通过扭转试验测量拉制细高碳钢丝的扭转数。测量被测导线表面上的划痕与其纵轴之间的角度。对由扭转数γ t 计算的剪切应变、断裂点处的剪切应变γ f 和塑性剪切应变γ pc 进行了评估。获得了以下结果。首先，剪切应变分布均匀化；进一步地，当γ f 与γ pc 之间的差值减小时，单位长度的扭数N 、γ t 和γ pc 增加，其中γ pc 从γ f 中减去（=Δ γ fpc ）> 0。其次，外部因素导致非均匀的剪切应变分布和潜在最大剪切应变的减少，即使对于几乎不受内部因素影响的线材也是如此。剪切应变非均匀性的差异导致潜在最大剪切应变的减少量发生变化。内部因素包括不均匀的微观结构和夹杂物和空隙的存在。外部因素是由试验机和样品的设置引起的。在抑制内外因素的影响时，获得了潜在的最大剪应变。最后，提出了两种潜在最大剪应变的评价方法。一种方法识别具有小Δ γ fpc 和大γ pc 的样品，其中Δ γ fpc > 0。可以认为该样品具有与潜在最大剪切应变最接近的应变。当 Δ γ fpc 最接近 0 时，另一种方法确定 γ pc。该值可以解释为潜在最大剪切应变的塑性应变。