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Virtual instrumentation system to automatically determine the stress-strain curve of Tensile Test

Abstract:

The objective of this project is to design and development a Virtual Instrumentation System (VIS) applied to automate tensile tests to characterize materials in Electromechanical Engineering Laboratories. The developed system is based on a robust hardware architecture, data acquisition has high levels of accuracy, and the virtual instrument automatically determines the test curve and the test characteristic. The developed system consists of three modules: The Sensor Module, which is composed of the load cell and the strain gauges; the Data Acquisition Module, which is composed of the Compact FieldPoint device and an expansion card for conditioning signals from strain gauges; finally the Software Module which is composed of parameter calculation algorithms and data display algorithms. For the evaluation of the VIS was carried out two experiments: 1) experiment with the initial testing machine, equipped with analog meters and manual processing of the measured data; and 2) experiment with the final testing machine, equipped with the VIS, which automatically acquires and processes the test data. Then the results of experiment 1, experiment 2, and the manufacturer's data were compared. As obtained results: VIS shows a better definition of the stress-strain curve; the maximum error between the values obtained by VIS and the data obtained in the traditional form using manual calculations is equal to 4.6 %; and, the reliability of the tensile test has been improved from 89.5% (without VIS) up to 95% (with VIS).