著者

木村 成竹 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 A編 (ISSN:03875008)

巻号頁・発行日

vol.73, no.734, pp.1105-1110, 2007-10-25 (Released:2011-03-02)

参考文献数

6

被引用文献数

4 4

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A spring washer is widely used as a method for preventing loosening. However, experimental results presented by Sakai and Yamamoto et al., show that the performance of a spring washer as a loosening prevention mechanism is at best equal to that of a washer-less joint, if not worse. In this paper we analyzed loosening under shear loading and as a result were able to explain the mechanism that accelerates loosening in the framework of the three-dimensional finite element method (FEM). A spring washer causes non-uniformity of contact pressure at the washer interfaces, because of its asymmetric shape. When a bolted joint with a spring washer is subjected to shear loading, sticking area on the contact surfaces of the spring washer is limited to two corner points before the bearing surface undergoes gross slip. One of these points is on the upper surface of the spring washer and the other is on the lower surface. In this situation the nut rotation around these sticking points results in drastic loosening. We also conducted comparative simulation with Sakai's experimental results. Compared with experimental results, the bolted joint with the spring washer is easy to loosen according to the simulation results. It is believed that the difference comes from the spring washer's edge cutting into the contact surface of the nut, something not included in this simulation.

著者

木村 成竹 泉 聡志 酒井 信介

出版者

一般社団法人日本機械学会

雑誌

日本機械学會論文集. A編 (ISSN:03875008)

巻号頁・発行日

vol.73, no.734, pp.1105-1110, 2007-10-25

被引用文献数

1 4

---

A spring washer is widely used as a method for preventing loosening. However, experimental results presented by Sakai and Yamamoto et al., show that the performance of a spring washer as a loosening prevention mechanism is at best equal to that of a washer-less joint, if not worse. In this paper we analyzed loosening under shear loading and as a result were able to explain the mechanism that accelerates loosening in the framework of the three-dimensional finite element method (FEM). A spring washer causes non-uniformity of contact pressure at the washer interfaces, because of its asymmetric shape. When a bolted joint with a spring washer is subjected to shear loading, sticking area on the contact surfaces of the spring washer is limited to two corner points before the bearing surface undergoes gross slip. One of these points is on the upper surface of the spring washer and the other is on the lower surface. In this situation the nut rotation around these sticking points results in drastic loosening. We also conducted comparative simulation with Sakai's experimental results. Compared with experimental results, the bolted joint with the spring washer is easy to loosen according to the simulation results. It is believed that the difference comes from the spring washer's edge cutting into the contact surface of the nut, something not included in this simulation.

著者

岡島 智史 泉 聡志 酒井 信介

出版者

公益社団法人 日本材料学会

雑誌

材料 (ISSN:05145163)

巻号頁・発行日

vol.57, no.4, pp.401-407, 2008 (Released:2008-04-18)

参考文献数

6

被引用文献数

1 1

---

Because of the lessening number of maintenance experts, a method to rationalize pipe inspection interval is desired. For this purpose, the evaluation method for the pipe integrity in the form of failure probability has been developed based on the Bayesian inference method in the previous paper. In this paper, the previous method is called the linear-Bayes method. The linear-Bayes method assumes wall thinning due to Flow Accelerated Corrosion (FAC) as the principal damage mechanism, and it can define the safety margin of a pipe's residual life depending on the number of inspections. However, the linear-Bayes method ignores the corrosion rate fluctuation against time, which may be caused by the change of environment such as water chemistry and flow velocity. Therefore, the linear-Bayes method may underestimate the failure probability of the pipe segments if the online monitoring of the environments is not used. In this paper, the linear-Bayes method is extended for the wall-thinning model with the corrosion rate fluctuation. The extension is carried out through following two approaches : correction-term and error-term approaches. In this paper, the formulation and the procedure for each approach are shown at first. And then, the accuracy and the merit of the extended method are examined through the evaluation using the artificial and the actual inspection records. Through the examination, it is confirmed that the extended method makes the evaluation of the pipe integrity available in view of safety margin for the corrosion rate fluctuation, keeping the merits of the linear-Bayes method.

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

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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.

著者

岡島 智史 岩崎 篤 泉 聡志 酒井 信介

出版者

一般社団法人 日本高圧力技術協会

雑誌

圧力技術 (ISSN:03870154)

巻号頁・発行日

vol.43, no.6, pp.335-340, 2005 (Released:2005-12-26)

参考文献数

6

---

The verification test of machine diagnosis techniques was carried out by Japan Power Engineering and inspection Corporation, and a system called as the RET (Residual Life Evaluation of Thermal Power Plants) system was developed as the result of this activity. The RET system can evaluate the primary damage of equipments in boiler or turbine using several residual life evaluation methods. The RET system provides valuable function for the residual life evaluation. However, this system is not necessarily utilized widely. In this study, online version of the RET system is developed for the purpose of populization of the RET system. The online RET system can evaluate the primary damage of the equipments in boiler or turbine without any extra application, and is easy to reflect new information.

著者

戒田 拓洋 最上 雄一 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A編 (ISSN:18848338)

巻号頁・発行日

vol.77, no.777, pp.731-735, 2011 (Released:2011-05-25)

参考文献数

5

---

In order to rationalize the safety margin of pressurized components subject to local metal loss, we applied a probabilistic reliability method. The modeling of the local metal loss is based on API 579-1/ASME FFS-1 and we investigated the safety margin for the pressure equipment subjected to local metal loss utilizing the actual corrosion rate data. Probabilities of failure of both shallow metal loss and deep metal loss were calculated. These results showed the relation between time until next inspection and probability of failure was cleared. We also analyzed the sensitivity of an assessment curve based on the reliability index for local metal loss. The reliability-based assessment curve was available regardless of COV of the shape of metal loss.

著者

泉 聡志 横山 喬 寺岡 卓也 岩崎 篤 酒井 信介 斎藤 金次郎 名川 政人 野田 秀樹

出版者

一般社団法人日本機械学会

雑誌

日本機械学會論文集. A編 (ISSN:03875008)

巻号頁・発行日

vol.71, no.703, pp.380-386, 2005-03-25

被引用文献数

8 16

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We have developed a new nut named 'super slit nut (SSN)', which realizes anti-loosening performance without complicated tightening procedures. In this study, tightening behavior and loosening behavior caused by shear load are analyzed by mean of three-dimensional finite element method. It is found that SSN has a prevailing torque of 15 to 19Nm, which closely agrees with experimental data. The load distribution of thread depends on the rotation angle of nut. At the angle of 24.6 degree, the distribution of 1st pitch turns to be 10% larger than that of conventional nut, reflecting the decrease in the thread at slit region. It is also found that the anti-loosening performance cas be realized by the thread contact force at the slit region. Since its contact force does not depend on the tightening force, the effect of anti-loosening performance drastically increases as the tightening force is decreased. Shear fracture would initiate not at slit region but at the bottom of 1st thread, whose stress is about 10% larger, as compared with conventional nut. Moreover, by mean of tensile and fatigue experiments, it is concluded that SSN involves sufficient strength in practical use.