有限変形下における加硫NBRの力学的性質に関する研究 (レオロジー(特集))

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For the purpose of investigating the mechanical properties of vulcanized rubbers under finite deformation, three kinds of NBR (Butadien-Acrylonitrile copolymer) vulcanizates of different degree of crosslinking were prepared, and their stress relaxation behavior under orthogonal biaxial deformation was observed. The results were compared with those of NR (Natural rubbuer). The results are as follows. (1) It has been ascertained that engineering stress f1 and f2 under single step biaxial deformation (λ1, λ2) at t=0 can be expressed in such a simple form as, and consequently It has been found that the above relations are not valid in strict sense and that fi should be written as and that φi depends on λi more than λj(i, j=1, 2., i≠j). (2) The contour maps of ∂W(I1, I2, t=1.0min.)/∂Ii have been drawn by the method mentioned previously1). The nature of the slope of the surfaces are similar to those of NR at relatively small deformation region in (I1, I2) plane. But, with increase of I1+I2, the contour lines of ∂W/∂I1 and ∂W/∂I2 are respectively oriented in the directions of I1 axis and I2 axis more sharply than those of NR. On the other hand, the dependency of ∂W/∂Ii surfaces on the degree of crosslinking has a typical property in that the surfaces come down with vertical shifting by decrease in the degree of crosslinking. This dependency is different from that of NR as mentioned previously. (3) A postulation for W[W=w(λ1)+w(λ2)+w(λ3)] proposed by Valanis and Landel2) are found to be satisfactory in predicting the true stress σ11-σ23 and σ22-σ33 by using ∂W/∂λ which can be determined by strip-biaxial data with the use of the above postulation. However the values of ∂W/∂Ii have not been predicted with reasonable accuracy from the ∂W/∂λ. This results are discussed in detail in this paper.
公益社団法人日本材料学会の論文

有限変形下における加硫NBRの力学的性質に関する研究 (レオロジー(特集))

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