Background

Main desired features of biaxial tests are: uniformity of stresses and strains; high strain levels in gauge areas; reliable constitutive parameters identification. Despite cruciform specimen suitability to modern tensile devices, standard testing techniques are still debated because of difficulties in matching these demands.

Objective

This work aims at providing rational performance objectives and efficient cruciform specimens shapes in view of constitutive characterization.

Methods

Objective performance is evaluated along particular lines lying on principal directions in equibiaxial tensile tests. A rich specimen profile geometry is purposely optimized via finite elements analysis by varying cost function and material compressibility. Experimental tests, monitored via digital image correlation, are carried out for validation.

Results

New shapes are designed and tested in a biaxial tensile apparatus and show to perform better than existing ones. Elastic parameter identification is efficiently performed by only exploiting full field strain measurements along statically significant lines.

Conclusions

Small gauge areas and small fillet radii cruciform specimens approach the ideal deformation behaviour. For the constitutive parameters identification in planar tensile experiments, it suffices to monitor strains along the gauge lines.

中文翻译：

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十字形样品的双轴延伸：将平衡嵌入到设计和本构表征中

背景

双轴试验的主要期望特征是： 应力和应变的均匀性；应变区域的高应变水平；可靠的本构参数识别。尽管十字形样品适用于现代拉伸装置，但由于难以满足这些要求，标准测试技术仍然存在争议。

客观的

这项工作旨在根据本构表征提供合理的性能目标和有效的十字形标本形状。

方法

客观性能是沿着等双轴拉伸试验中主方向上的特定线进行评估的。通过有限元分析，通过改变成本函数和材料压缩率，有目的地优化丰富的样本轮廓几何形状。通过数字图像相关性监测进行实验测试以进行验证。

结果

新形状在双轴拉伸设备中进行了设计和测试，并显示出比现有形状更好的性能。仅通过沿静态显着线利用全场应变测量即可有效地执行弹性参数识别。

结论

小规格面积和小圆角半径的十字形试样接近理想的变形行为。对于平面拉伸实验中的本构参数识别，监测沿标距线的应变就足够了。