Cruciform flat specimen is mostly used to investigate experimentally the in-plane biaxial mechanical behavior of sheet metals. In this study, a modified cruciform specimen design is proposed and validated against the performance of current standard design. The existing standard cruciform specimen prepared through laser cutting for sheet metal can accurately provide biaxial stress–strain curve through biaxial tensile test by ensuring superior homogeneous stress and strain field in gauge section. However, preparation of such specimen using laser cut is cumbersome, expensive and prone to errors. The current standard cruciform specimen design features slotted arm of fixed length and width with specific gauge. Few other designs also feature reduced gauge section to localize failure. Both need high precision of laser cutting and machining to prepare specimens which can achieve biaxial stress–strain curve for more than 4% equivalent plastic strain level. The proposed specimen design features running slits in all four arms of specimen with uniform gauge section machined using electrical discharge machining (EDM) owing to higher accuracy and minimum heat-affected zone (HAZ). This technique also avoids machining effects with an understanding that proposed specimen design is to determine the yield behavior of material only. Also, specimen fabricated from as received sheets and without any thickness reduction in gauge area allows the user to keep full thickness in biaxial condition. The modified design qualifies the commonly accepted performance criteria for cruciform specimen, i.e., stress and strain distribution in the gauge section is found to be homogeneous and the biaxial stress–strain curve can be generated until 4% of equivalent plastic strain. The proposed specimen design is evaluated experimentally by conducting biaxial test at various stress ratios, and it is compared with alike experiments using standard specimen design. One automotive grade material, interstitial-Free high-strength (IFHS) steel sheet of thickness 0.70 mm is tested in this study to validate the specimen design.

十字形扁平试样主要用于实验研究钣金的面内双轴力学行为。在这项研究中，提出了一种改进的十字形试样设计，并针对当前标准设计的性能进行了验证。现有的通过钣金激光切割制备的标准十字形试样可以通过确保规范截面中的卓越均匀应力和应变场，通过双轴拉伸试验准确地提供双轴应力-应变曲线。然而，使用激光切割制备这种样品麻烦，昂贵并且容易出错。当前的标准十字形样本设计具有固定长度和宽度并带有特定规格的开槽臂。很少有其他设计具有减少标距部分来定位故障的功能。两者都需要高精度的激光切割和机加工来制备能够达到双轴应力-应变曲线且等效塑性应变水平超过4％的标本。所提出的样品设计特点是，由于具有更高的精度和最小的热影响区（HAZ），因此采用电火花加工（EDM）加工了具有均匀规格截面的样品的所有四个臂中的运行缝隙。这项技术还避免了机加工效果，前提是建议的样本设计仅确定材料的屈服行为。而且，由原样制成的样品制成，并且在厚度方向上没有任何厚度减小，使用户可以在双轴状态下保持整个厚度。修改后的设计符合十字形试样的公认性能标准，即 发现应变仪部分的应力和应变分布是均匀的，并且可以生成双轴应力-应变曲线，直到等效塑性应变的4％。通过在各种应力​​比下进行双轴试验对建议的试样设计进行实验评估，并将其与使用标准试样设计的类似实验进行比较。本研究中测试了一种汽车级材料，厚度为0.70 mm的无间隙高强度（IFHS）钢板，以验证样本设计。