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| 1.
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立矢, 宏 ; 江端, 泰之 ; 茶谷, 明義 ; 放生, 明廣
概要:
Kinematic and static characteristics of robotic parallel crank mechanisms have been analyzed and represented in the form of charts which support rational syntheses of the mechanisms as robot and legs. Namely the value of torque of
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motive shafts to hold attitudes of mechanisms and the static compliance of the work points when the mechanisms take arbitrary shapes have been formulated by the total link lengths and by introducing four dimensionless parameters. Characteristic charts of statics have been made by plotting lines of positions of the output point where both of the factors are constant in dimensionless working spaces. Making use of several characteristic charts and simple transformation formulas, the values of the two factors can be analyzed, respectively, when the mechanisms take arbitrary positions and attitudes.
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| 2.
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穴田, 賢二 ; 宮崎, 祐介 ; 西, 貴士 ; 立矢, 宏 ; 放生, 明廣 ; 阪本, 雄一郎
概要:
The purpose of this study is to examine the effect of head rotational motion on brain shear strain. A head physical model constructed from individual medical images of a head was used for the experiments. The model consists of the parts
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reconstructing the skull, falx, cerebrospinal fluid (CSF) and brain, which represents actual human head shape. Rotational impacts were applied around frontal axis of the model under the conditions in the case that maximum angular acceleration and angular velocity were controlled. As the results of experiments, shear strain in brain part correlates strongly with peak change of angular velocity but correlates poorly with maximum angular acceleration which has been often proposed as a head injury criterion. The reason is that brain shear strain is relatively small at the time when angular acceleration reaches the peak value because relative motion of skull and brain occurs due to the structure of the head consisting brain, falx, skull and CSF. Thus, peak change of angular velocity of a head should be included in the injury criterion in the case that rotational motion of a head occurs.
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| 3.
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放生, 明廣 ; 茶谷, 明義 ; 野村, 泰雄
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| 4.
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放生, 明廣 ; 茶谷, 明義 ; 立矢, 宏
概要:
In this paper, Laplace transformed expressions for the torque and the bending moment in a curved beam under impact out-of-plane load were shown. Applying them to a closely coiled helical spring and using the numerical inverse
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transformation with FFT. the torque and the bending moment in the spring were examined for two types of boundary condition ; the first case was that impact force was applied to the end of the spring wire, and the second case was that impact force was applied on the center axis of the spring. As a result, the followings were found. The Torque induced in the spring wire propagates along its axis macroscopically with the velocity of surge wave, although it is preceded by very small one propagating with the velocity of shear wave. And large bending moment comparable with torque occurs near the end of spring just after the impact in the case of center impact, while bending moment can not occur statically.
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| 5.
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新本, 哲平 ; 立矢, 宏 ; 放生, 明廣 ; 茶谷, 明義 ; 湯浅, 紘二
概要:
Blue brittleness is exhibited by some steels after being heated to an elevated temperature. Although at high temperature a given strain is associated with a lower stress level, at the temperature at which blue brittleness is observed
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there is a pronounced work-hardening effect. Furthermore, the temperature at which blue brittleness occurs is a function of the strain rate. Therefore, to improve the accuracy of numerical simulations of hot or warm working which utilizes the thermal softening of steels, a dynamic constitutive equation which can model the blue brittleness phenomenon is needed. In this paper we present such a constitutive equation, which has two parts : one models the ordinary constitutive relation and the other the phenomenon of blue brittleness. Unknown material constants in the equation are determined by a non-linear least-squares method from uniaxial impact and static compressive test results. The equation is then evaluated by comparing it to experiments over a wide temperature range.
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| 6.
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宮崎, 祐介 ; 立矢, 宏 ; 放生, 明廣 ; 阪本, 雄一郎
概要:
A Three dimensional transparent physical model of a human head with real shape was constructed to visualize and measure relative motion between skull and brain in order to clarify the mechanism of acute subdural hematoma. The model consists
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of a transparent skull, brain made of silicone gel, cerebrospinal fluid to reconstruct relative motion between brain and skull, and meninges which constraints the motion. The shape was based on real-shaped three dimensional CAD data constructed from CT/MRI images of a specific individual. The results of experiments in the cases of impactor collision to the occipital skull showed that shape of impact force pulse applied to the head was not affected on peak bridging vein stretch ratios because significant relative motion between skull and brain occurred by existence of cerebro spinal fluid.
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| 7.
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放生, 明廣 ; 茶谷, 明義
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| 8.
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放生, 明廣 ; 立矢, 宏 ; 茶谷, 明義
概要:
An estimation method of the dynamic constitutive equations using the method of least squares is described. In this paper, the unknown parameters in the constitutive equations of which the functional form is known were estimated. The
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estimation is performed by using the method of nonlinear least squares utilizing the Gauss-Newton method because the constitutive equations are nonlinear. Numerical simulation were done such that the unknown parameters in the constitutive equation were estimated from the value of the strain wave in a long bar subjected to longitudinal impact. The stability of the estimation and influence of experimental error on the estimated parameters were examined. As a result, it was concluded that the present method is practically useful.
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| 9.
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茶谷, 明義 ; 放生, 明廣 ; 立矢, 宏 ; 鈴木, 尚志
概要:
The present study deals with impact fatigue of materials subjected to repeated stress due to impact loading. It has been pointed out by investigators that the behaviour of materials under the impact sterss is different from that under the
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static one. In this study, we observed the slip bands of the metal surface of specimen by optical microscope after test for a given repeated impact tension. The stress of specimen was measured by the two point gage method based on the stress wave propagation. As a result, we showed that the number of repetitions to fracture has a close relation with slip bands.
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| 10.
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茶谷, 明義 ; 放生, 明廣
概要:
40番および50番チェーンの一端に約25m/sまでの速度を与えて発生荷重とその伝ぱ状況を示し,チェーンの衝撃塑性引張特性を明らかにした.すなわち,引張速度と発生荷重の関係はチェーンピッチ,1リンクの平均重量,静引張りによる荷重-ひずみ関係か
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ら決定され,塑性波の一次元伝ぱ理論を適用することによって得られる.また短時間の衝撃引張りによるチェーンの不均一残留ひずみ分布も同理論によって説明される.
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