Abstract
The biaxial tensile testing of cruciform specimens is an effective way to create complex loading, and is a feasible experimental method for studying the subsequent yield behavior. However, relevant knowledge gaps still exist in the geometric design of miniaturized cruciform specimens which are applicable to test machines with maximum load less than 5000 N. The present work outlines the systematic investigations of the optimal design of the miniaturized cruciform specimen of a commercial pure titanium TA2 for biaxial tensile testing. Finite element modeling (FEM) coupled with the orthogonal design is employed to explore the influence of various geometric parameters, i.e., the thickness of the central gauge region, the width, the length, and the number of the slit, and the radius of the inner chamfer, on the stress distribution of the central gauge region. The optimal geometric design of the miniaturized cruciform specimen is successfully obtained, simultaneously considering the stress uniformity in the central gauge region and economic factors. The full-field strain distributions are also determined via the digital image correction (DIC) technique, which confirm the accuracy of the results achieved from FEM. This work provides a complete and reliable procedure for optimizing the geometry of miniaturized cruciform specimens, whose application can be expanded to other metals in the future.
Highlights
Commercial pure titanium, e.g., TA2, has been widely used in medical, aerospace, and automotive fields due to its high specific strength, good biocompatibility, excellent heat resistance, and corrosion resistance [1]
According to prior works of plastic yield behavior of pure titanium plates under different loading paths [2,3], the biaxial tensile testing of cruciform specimens was found to be one of the most realistic techniques to create biaxial stress states that are closer to the actual situation
For the biaxial tensile testing, the basic principle is that the four cross arms of the cruciform specimen are stretched separately and the plastic flow should be restricted in the central region of the specimen
Summary
Commercial pure titanium, e.g., TA2, has been widely used in medical, aerospace, and automotive fields due to its high specific strength, good biocompatibility, excellent heat resistance, and corrosion resistance [1]. Standard shape and dimensions of the cruciform specimen were recommended; this type of cruciform testing specimen has been extensively adopted for measuring stress-strain curves. It is at least worth noting, that the thinning of the central gauge was not proposed in this standard. These studies focus on the optimal design of the cruciform specimen via experimental methods but lack a comprehensive analysis on the effect of specimen geometry. To date, the shape and dimensions of cruciform specimen studied in prior works is designed for testing on a high-power test machine, while the design of miniaturized specimens tested on low-power testing machines (the maximum applied load P ≤ 5000N) remains challenging. An optimal design of the miniaturized specimen that is applicable to the low-power stretching machine is successfully attained
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