A simple method for measuring J-R resistance curve of PVC plastic based on multi-sample method
The difficulty of obtaining J-R resistance curve and fracture toughness JIC of PVC materials lies in the measurement of crack growth amount Δa.Traditional dyeing treatment and 3D measurement methods make the testing process complicated and expensive.Due to the easy cutting of plastics,the measurement process of Δa can be simplified.Based on the multi-sample method,a 2D measurement method was proposed to measure Δa.The method is to cut the loaded specimen into several pieces longitudinally along the crack according to the requirement of the standard measurement point,and then measure the crack length on each cut piece through the industrial electron microscope to obtain Δa.Using this method,relatively consistent J-R resistance curves and JIC values can be obtained through both GB 21143-2014 and ASTM D6068-10 standards,and the test results are valid and accurate.According to GB 21143-2014,the obtained JIC value of PVC is 8.03 kJ/m2,the coefficient of J-R resistance curve fitting equation is 9.93,and the index is 0.15.According to ASTM D6068-10,the obtained JIC value of PVC is 8.31 kJ/m2,the coefficient of J-R resistance curve fitting equation is 12.7,and the index is 0.3.The results show that the fracture toughness JIC value and the coefficient,exponent of the fitting equation obtained by ASTM D6068-10 are all higher than that obtained by GB 21143-2014.Due to the difference in performance between PVC and metal materials,ASTM D6068-10 standard is more suitable for testing the J-R resistance curve and JIC value of PVC materials.The method simplifies the complex operations such as traditional crack dyeing treatment and 3D measurement to cutting slices and 2D measurement,simplifies the measurement process,reduces the measurement cost,and can be widely applied in the measurement of fracture toughness of plastic materials.
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