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Tire rubber testing procedure over a wide range of strain rates

Baranowski P., Janiszewski J., Małachowski J.

Journal of Theoretical and Applied Mechanics

2017

Vol. 55 nr 2

727--739

The main aim of the paper is to present the procedure allowing one to determine correct mechanical characteristics of a rubber material compressed within a wide range of strain rates. In order to obtain a satisfactory wide spectrum of material data, a number of tests were conducted both under low and high strain rates with the use of a universal strength machine and split Hopkinson pressure bar set-up equipped with polymethyl methacrylate and 7075- T6 alloy bars. During the investigations, the necessity of performing pre-compression tests and the problem of specimen geometry were pointed out as key methodical requirements to guarantee achieving valid experimental data both from quasi-static and high strain rate tests.

Strain measuring accuracy with splitting-beam laser extensometer technique at split Hopkinson compression bar experiment

Panowicz R., Janiszewski J., Traczyk M.

Bulletin of the Polish Academy of Sciences. Technical Sciences

2017

Vol. 65, nr 2

163--169

An accuracy problem of strain measurement at compression split Hopkinson compression bar experiments with a splitting-beam laser extensometer was considered. The splitting-beam laser extensometer technique was developed by Nie et al. to measure strain of a specimen during its tension under a high strain rate loading condition. This novel concept was an inspiration for the authors to develop own laser extensometer system, which allows for simultaneous and independent measurement of displacement of bar ends between which a compressed material specimen is placed. In order to assess a metrological property of this measuring system, a wide range of high strain rate experiments were performed, including tests with various sample materials (Al 5251, Cu OFE) with different rate of strain, and with the use of two bars material. A high accuracy of the developed laser extensometer was found in measurement of specimen strain, for which uncertainty is not greater than 0.1% and, for a typical specimen dimension, the maximum permissible error is 4.5 μm.