著者

藤川 正毅 山辺 純一郎 小石 正隆

出版者

一般社団法人 日本機械学会

雑誌

計算力学講演会講演論文集

巻号頁・発行日

vol.2017, 2017

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Industrial rubber, commonly used in the fabrication of tires and engine mounts, exhibits nonlinear viscoelastic behavior. In the design of these rubber products, it is important to capture the stress–strain responses under arbitrary loading conditions. However, the stress–strain responses exhibit complicated behavior, which depends on strain rate, strain history, strain amplitude, etc. The main purpose of this study is to develop a new constitutive model that captures the nonlinear viscoelastic stress–strain response of carbon-black-filled styrene-butadiene rubber vulcanizates (SBR-CB). In the assumed micro-mechanical network structure, we decomposed the isochoric free energy into the elastic equilibrium and the viscoelastic overstress response. Based on the results of our performance evaluation of various hyperplastic material models, we used an eight-chain model for the equilibrium network. For the nonlinear viscoelastic network, we used the micro-sphere model. The micro-stress/strain equation was assumed to be in simple phenomenological form, as reported by Miehe. For the revolution equation of the micro-inelastic strain, the Rendek and Lion model was employed. In addition, to reproduce the stress-strain relationship under from infinitesimal to 50% strain amplitude, the relaxation time depending on the strain amplitude of the free dangling chains was proposed as a new metric. The proposed model was able to practically and precisely reproduce the dynamic responses of SBR-CB25 under a wide range of applied strains and strain rates, was thermodynamically consistent for arbitrary deformation, could be implemented in commercial FEM software (Abaqus), and reproduced the stress-strain relationship under various experimental loading conditions.

著者

松岡 三郎 松永 久生 山辺 純一郎 濱田 繁 飯島 高志

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00264-17-00264, 2017 (Released:2017-10-25)

参考文献数

29

被引用文献数

19

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Considering in design by analysis, four types of tests, slow-strain-rate tensile (SSRT), fatigue life, fatigue crack-growth (FCG), and elasto-plastic fracture toughness (JIC) tests, were conducted with low-alloy steels, JIS-SCM435 and JIS-SNCM439, in 115 MPa hydrogen gas and air at room temperature (RT). In addition to above tests at RT, the SSRT tests were also conducted in 115 MPa hydrogen gas and air at 120 oC and in 106 MPa hydrogen gas and 0.1 MPa nitrogen gas at -45 oC. The low-alloy steels used in this study had tensile strengths (σB) ranging from 824 to 1201 MPa with fine and coarse tempered-martensitic microstructures. In the SSRT and fatigue life tests, the tensile strength and fatigue limit were not degraded in hydrogen gas. The FCG tests revealed that the FCG rate (da/dN) was accelerated in hydrogen gas; however, there existed an upper bound of the FCG acceleration, showing the FCG rate in hydrogen gas was about 30 times larger than that in air, when σB was lower than 900 MPa. The JIC tests demonstrated that the fracture toughness (KIC) in air was 207 MPa·m1/2 at σB = 900 MPa, whereas the hydrogen-induced crack-growth threshold (KI,H) was 57 MPa·m1/2 at σB = 900 MPa. Based on these results, we proposed advanced guidelines on the use and design for SCM435 and SNCM439 on design by analysis in 115 MPa hydrogen gas, which enable to design the storage cylinders used in 70 MPa hydrogen station with lower cost without compromising safety.