Development of a New Pure Bending Tester for Small-Scale Specimens

Background

The characterization of the moment–curvature relationship for thin components within the elastic–plastic regime yields crucial insights not readily ascertainable through conventional tensile testing. However, most conventional bending testers only measure the force–displacement data of specimens without providing the bending moment and curvature information directly.

Objective

We aim to develop a pure-bending tester based on the cochleoid theory that can directly measure the bending moment–curvature response of thin components.

Methods

The bending moment is determined by employing a flexural pivot with a known spring constant paired with dual laser displacement sensors. By approximating the cochleoid as an eccentric arc trajectory, we move and rotate one end of the specimen to increase the curvature gradually. Finally, the moment–curvature relationship of the specimens can be obtained.

Results

The practical capability of the bending tester is demonstrated by measuring moment–curvature data from various specimens, including PET sheets, aluminum sheets, and Nylon 6 monofilaments. Cyclic bending and relaxation tests are performed on these typical specimens. The measurement results agree well with the theoretical predictions.

Conclusions

The instrument serves as a valuable tool for characterizing the bending properties of diverse small-scale components. Its versatility facilitates comprehensive assessments of the bending behavior of various materials and structures.