Background: For the standard ISO 16842 cruciform test specimen, stresses obtained from the gauge area are far below the ultimate tensile strength due to high stress concentrations at the slit ends which lead to premature failure. Objective: To introduce a new cruciform specimen design which has been optimized with respect to the determination of yield surfaces. Methods: The proposed design differs from the ISO standard by an additional thinning of the gauge area and wider slits in the arms to avoid stress singularities. Compared to other cruciform test piece designs found in the literature, the stress distribution is still homogeneous and there is no need to reduce the size of the gauge area, thanks to the specimen’s well-balanced proportions. Results: Biaxial tensile tests have been conducted with aluminium 5754 alloy samples of different thicknesses. For the standard cruciform test piece, the maximum strain achieved at the gauge area is only 25% of the fracture strain. The optimized cruciform test piece can attain about 66% of the fracture strain before breaking. Conclusions: The optimized specimen design enables the measurement of yield surfaces at higher stress levels. In case of other materials such as elastomers, the slit length has be to adjusted accordingly.

中文翻译：

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根据 ISO 16842 使用优化的十字形试样测定屈服面

背景：对于标准 ISO 16842 十字形试样，由于狭缝端的高应力集中导致过早失效，因此从测量区域获得的应力远低于极限抗拉强度。目的：介绍一种新的十字形试样设计，该设计针对屈服面的确定进行了优化。方法：所提议的设计与 ISO 标准的不同之处在于，测量区域额外变薄，臂中的狭缝更宽，以避免应力奇异。与文献中发现的其他十字形试件设计相比，由于试样的比例均衡，应力分布仍然均匀，无需减小测量区域的尺寸。结果：已经对不同厚度的铝 5754 合金样品进行了双轴拉伸试验。对于标准十字形试件，在标距区域获得的最大应变仅为断裂应变的 25%。优化后的十字形试件可达到断裂前断裂应变的66%左右。结论：优化的试样设计能够在更高的应力水平下测量屈服面。如果是其他材料，如弹性体，则必须相应地调整狭缝长度。