A digital torsimeter for torsion testing of materials and shear elasto-plastic parameters evaluation

ABSTRACT In this work, the project, the main components and the results obtained with the prototype of a digital torsiometer that was built to measure the variation of the torsion angle in mechanical tests of materials are shown. A magnetic encoder model AS5048A was used in this device. This encoder has 14 bits of resolution and an Arduino Mega 2560 microcontroller board was used for data processing. In addition to the low cost of electronic and mechanical components, another advantage of the measurement system developed is the large amount of free applications available for processing and acquiring data with the microcontroller board used. Tests were carried out to verify the accuracy in the angular variation readings and torsion tests with aluminum tubular specimens (AA6351T6 alloy) to evaluate the performance of the measurement system in monotonic tests. The Ramberg-Osgood relationship was used to describe the behavior of the material and the shear stresses were evaluated using nonlinear relationships proposed by different authors. The results obtained indicate that the digital torsiometer presented satisfactory results for obtaining the torsion angle and the main advantages of this device include the measurement of the non-contact torsion angle, linearity, good accuracy over the entire measurement range, unlimited measurement range, reduced size and low cost for confection.

摘要 本研究介绍了为测量材料力学试验中扭转角变化而研制的数字扭转计原型的项目概况、核心组成与实测结果。该装置搭载型号为AS5048A的磁编码器，其分辨率达14位；数据处理模块采用Arduino Mega 2560微控制器开发板。本研发的测量系统除电子与机械元件成本低廉外，另一优势在于其所适配的微控制器开发板可依托大量免费应用程序完成数据采集与处理。为验证角位移读数的准确性，研究团队采用AA6351T6合金铝管试样开展扭转试验，以此评估该测量系统在单调加载试验中的性能表现。研究采用拉姆贝里-奥斯古德（Ramberg-Osgood）本构关系描述材料力学行为，并借助不同学者提出的非线性关系式计算剪切应力。实测结果表明，该数字扭转计在扭转角获取方面表现优异；该装置的核心优势包括非接触式扭转角测量、良好线性度、全测量量程内的高精度、无量程限制、体积小巧以及制造成本低廉。