Evaluation of impact dynamics of viscoplastic materials with laser displacement sensor

David Ip; Jimin He; Bernd Wendlandt

doi:10.1117/12.269785

20 March 1997 Evaluation of impact dynamics of viscoplastic materials with laser displacement sensor

David Ip, Jimin He, Bernd Wendlandt

Proceedings Volume 2921, International Conference on Experimental Mechanics: Advances and Applications; (1997) https://doi.org/10.1117/12.269785
Event: International Conference on Experimental Mechanics: Advances and Applications, 1996, Singapore, Singapore

Abstract

The dynamic behavior of viscoplastic materials, which are often highly nonlinear in nature, have been extensively investigated during the past thirty years by means of experimental studies. This is perhaps the most reliable means of materials characterization due to the lack of universal theories which are able to describe the materials behavior with a comparable degree of accuracy. Under high strain rates of deformation, e.g . during an impact phenomenon, viscoplastic materials may suffer significant irreversible strains, which are generally much larger than elastic strains. Data of the time history of acceleration are usually obtained from impact tests on samples with uniform dimensions. Stress- strain curves can thus be constructed using double- integrations of the acceleration data to obtain strain values, (epsilon) . However, the accuracy of the stress-strain values often becomes questionable for short-duration tests, e.g. impact tests, since the strain data are obtained indirectly. In this study, strain measurements of some agricultural materials, including apple tissues, as well as cellulosic packaging materials, are obtained using a high-resolution laser displacement sensor with a maximum working range of about 2 cm. The sensor is incorporated to a destructive sample tester, which is found to be very effective in terms of accuracy in direct measurements of the time history of strain, particularly during the initial loading cycle of 1.5 to 2.0 milliseconds (ms) out of a duration of impact of about 4.0 ms, on thin cylindrical fruit samples and square corrugated fiberboard samples with 2 different flute sizes, thus allowing accurate estimation of strain rates, (epsilon) , which are one of the paramount parameters in nonlinear materials characterization.

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David Ip, Jimin He, and Bernd Wendlandt "Evaluation of impact dynamics of viscoplastic materials with laser displacement sensor", Proc. SPIE 2921, International Conference on Experimental Mechanics: Advances and Applications, (20 March 1997); https://doi.org/10.1117/12.269785

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KEYWORDS

Sensors

Signal processing

Data acquisition

Gas lasers

Laser applications

Material characterization

Packaging

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