著者

波田野 明日可 住吉谷 淳 鈴木 一真 牛流 章弘 加納 明 加藤 光章 廣畑 賢治 泉 聡志

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.84, no.863, pp.18-00015, 2018 (Released:2018-07-25)

参考文献数

16

---

Transluminal attenuation gradient (TAG) is expected as a noninvasive assessment of the functional significance of a stenosis, and has reported relatively high diagnostic performance. TAG measures the gradient of intraluminal radiological attenuation from the ostium at the first pass of the injected contrast agent; therefore, replacement of fluid by jet flow from a stenosis with gradually increasing contrast agent concentration should be investigated. We performed a phantom experiment and ALE fluid-structure interaction finite element simulation on pulsatile flow through a bifurcated flexible tube system with a stenosis. Experiment and simulation showed good agreement with temporal change of flow rate, pressure, and radius under 1 Hz square pulsatile flow. We varied Young modulus and rate of stenosis with 1 Hz sinusoidal input. Young modulus had little effect on the distribution of total flow, but a changed flow rate waveform and faster maximal velocity in the stenosis was observed with a smaller Young modulus. Then we simulated convection of particle tracers generated at the inlet, imitating a gradual increase in contrast agent with 80% and 95% stenosis. With 80% stenosis, axially symmetric flow resulted in reproductive tracer distributions; however, with 95% stenosis, the direction of jet flow from the stenosis and of subsequent helical flow varied every beat, suggesting this variation might lower sensitivity of TAG.

著者

蓮沼 将太 波田野 明日可 泉 聡志 酒井 信介

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.846, pp.16-00264-16-00264, 2017 (Released:2017-02-25)

参考文献数

14

被引用文献数

1

---

In this study, the effect of machined surface layer on residual stress relaxation was investigated. In previous study, low cycle fatigue strength was affected by residual stress. However, residual stress relaxation was complex because local plastic strain occurred by stress near yield stress. Also, machined surface layer affect the yield stress. Therefore, machined surface layer was modeled using the crystal plasticity model, i.e. plasticity model based on crystallographic deformation mechanics. To describe the microstructure of plastic deformation layer, initial dislocation density and back stress near surface were changed. To describe the microstructure of fine grained layer, grain size near surface was changed. Residual stress relaxation was simulated by crystal plasticity finite element method. Three types of machined surface layers were modeled. Two kind of strain amplitude condition was simulated. In simulation results, local plastic strain was occurred under global elastic condition. Residual stress after cyclic load was different from machined surface conditions under low strain loading. Residual stress was largely relaxed in all cases under high strain loading. Comparing fatigue life of experimental results, simulation results were thought to be valid. Therefore, residual stress relaxation is able to be predicted using this model. Hardening in plastic deformation layer prevents yield by tensile load. However, plastic strain was occurred in plastic deformation under compression load. On the other hand, fine grain layer prevent yield by not only tensile but also compression.