Engineering Mechanics

Proceedings Vol. 19 (2013)

ENGINEERING MECHANICS 2013

Copyright © 2013 Institute of Thermomechanics, Academy of Sciences of the Czech Republic, v.v.i., Prague

 

Dobeš M., Vrbka J.
pages 70 - 77, full text

Unfilled polymer materials exhibit a high ductility, which is moreover located in small neck area. Material producers deliver usually the yield strain and break (ultimate) strain values calculated on the basis of material tensile tests for normalized active sample length. Application of so defined material characteristic in the case of Finite Element Method (FEM) analyses of real constructions made of TSCP (typical semi-crystal polymer) led to significantly conservative (smaller) values of limit (ultimate) loads compared with the measured ones. To obtain more precise results the material characteristics used should be in correlation with the size of finite elements. A special experimental method making use of high-speed camera has been developed to determine the strain in defined small area of local strain concentration (neck area) on the specimen during tensile test. The true stress-strain curve till the sample rupture is here calculated and break strain is determined. Application of more realistic (higher) break strain value by the FEM analyses of real TSCP constructions led to the much better agreement between the calculated and measured construction stiffness and limit (ultimate) load.

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