Service life of a belt chamber-plasticity aspects

Abstract

The life time of the belt compound vessel is solved from the point of view of a fracture mechanics. It is shown that the existence of plastic deformations created in the matrix of the vessel during working state has practically no influence on the behaviour of the dominant crack and that for estimation of the critical state of the vessel the knowledge of the corresponding stress intensity factor is sufficient. The dominant crack grows under small scale yielding conditions until final fracture of the matrix.     

壳体初始形状对球形容器液压胀形结果的影响

借助于数值模拟研究了锥台形壳体液压胀形过程中可能出现的质量问题，以及壳体的初始形状对成形结果的影响，在此基础上提出了锥台形壳体的改进方案，以避免壳体的起皱，并最终获得预期的球形容器或椭球形容器。     

血管位移波的力学模型

本文在临床观察和模型实验的基础上提出了血管位移波的力学模型,并归结出了位移波的控制方程。应用摄动理论和数值方法,求得了位移波的波形和位移波产生的判别准则。从中我们发现,位移波仅和血流的脉动速度及血管壁力学特性有关,而和压力波无直接关系。最后本文还给出了一个适用于临床的位移波发生判别准则,实验发现它和临床观察是相符合的。     

应变式压杆压力传感器在冲击波载荷测试中的应用

在近区爆炸冲击波载荷测量中,压电式压力传感器因上升时间短且强度高的高频压力脉冲作用而可能产生疲劳和过载失效。本文根据应力波在细长圆柱弹性杆中的传播特性,设计了一种应变式压杆压力传感器,当圆柱杆的一端受到压力波作用时,产生的弹性应力波沿杆轴向传播,通过测量杆的轴向应变可计算出杆中传播的应力波,从而得到作用在杆端的压力波。为了检验压杆压力传感器的性能,采用一个厚壁圆柱形爆炸容器,并将传感器安装在容器壁面不同位置上,测量中心装药产生的爆炸冲击波载荷,经反复试验,结果表明这种传感器性能是稳定可靠的。     

NONLINEAR MOTION MECHANICS MODEL OF CURVED BLOOD VESSEL

A geometric model of curved blood vessels is established based on some reason-able hypotheses;the nonlinear motion mechanics model of the curved blood vessel is establishedaccording to basic mechanics laws.This model includes much more physiological factors.It cou-ples the interaction of blood flow with mechanical factors such as the displacement,deformation,strain and stress etc.of the curved blood vessel.It is of great importance for investigating thecirculation rules of the cardiovascular system and the nonlinear pulse wave propagation in curvedblood vessels.     

PRESSURE AND PRESSURE GRADIENT IN AN AXISYMMETRIC RIGID VESSEL WITH STENOSIS

Based on an improvement of the Karman-Pohlhausen's method, using nonlinear polynomial fitting and numerical integral, the axial distributions of pressure and its gradient in an axisymmetric rigid vessel with stenosis were obtained, and the distributions related to Reynolds number and the geometry of stenotic vessel were discussed. It shows that with the increasing of stenotic degree or Reynolds number, the fluctuation of pressure and its gradient in stenotic area is intense rapidly, and negative pressure occurs subsequently in the diverging part of stenotic area. Especially when the axial range of stenosis extends, the flow of blood in the diverging part will be more obviously changed. In higher Reynolds number or heavy stenosis, theoretical calculation is mainly in accordance with nast experiments.     

Investigation of the Stress State of Pressure Vessels of Inhomogeneous Structure Made of Composite Materials

The problem on the stress-strain state of layered cylindrical shells with bottoms of intricate shape under the action of internal pressure is considered. The elastic system examined is formed by spiral-circular winding. Two variants of the shell bottom structure are investigated. In the first variant, one spiral layer is installed, which leads to great variations in the bottom thickness along the meridian. In the second one, the bottoms are formed according to the zone-winding scheme. The stress state of the shell constructions of the classes considered is determined by solving boundary-value problems for systems of ordinary differential equations. The solution results for cylindrical shells with elliptic bottoms for the two types of winding are given. It is shown that the zone winding leads to smaller deflections and stresses than the conventional ways of reinforcing shell bottoms.     

Estimation of Bluish Appearance of Veins in Skin Tissue Using Spectrocolorimetry

The bluish appearance of veins in the skin tissue was experimentally investigated by in vivo and in vitro spectrophotometric measurements. Color of the skin surface including the veins was quantitatively evaluated by employing color perception on the basis of CIEXYZ and CIELAB colorimetric systems. For in vivo measurements, the bluish appearance of veins was successfully estimated using a dominant wavelength, excitation purity, and color difference. Results of in vitro experiments using a simple skin tissue model demonstrated that the degree of bluish appearance depends on the vessel depth, diameter, and the blood content in the surrounding medium.     

Mixing time of a non-Newtonian liquid in an unbaffled agitated vessel with an eccentric propeller

Experimental study of mixing time of non-Newtonian shear-thinning fluids within the transitional regime (3 × 10² < Re < 3 × 10³) of liquid flow is presented. The purpose of this study was to analyze the effect of eccentricity and pumping mode of the impeller as well as of position of the tracer dosage point into the agitated liquid on mixing time. The measurements were conducted in an unbaffled agitated vessel with inner diameter D = 0.7 m equipped with an up-or down-pumping propeller located centrically (e/R = 0) or eccentrically (e/R ≠ 0) in the vessel. Experiments were carried out by means of computer-aided unsteady-state thermal method for three positions of the tracer dosage point. The experimental data show that eccentric position of the propeller in an unbaffled vessel causes a decrease of the mixing time compared to that obtained in a vessel with a centrically located propeller. Mixing time depends also on the pumping mode of the propeller as well as on the position of the tracer dosage point. Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May 2007.     

Distribution of local heat transfer coefficient values in the wall region of an agitated vessel

Experimentally found local heat transfer coefficients are analyzed as a function of the measuring point on the heat transfer surface area of the agitated vessel wall and of the impeller eccentricity. Eccentric Rushton turbine and A 315 impeller are considered. Local heat transfer coefficients were measured by means of the computer-aided electrochemical method. The measurements were performed in an agitated vessel with inner diameter 0.3 m, filled with liquid up to the height equal to the vessel diameter. The experiments were carried out within the turbulent regime of the Newtonian liquid flow in the agitated vessel. The results were compared with the data obtained for the agitated vessel equipped with an eccentrically located axial flow propeller or an HE 3 impeller. Experimental studies show that the distributions of the heat transfer coefficient values depend on the impeller eccentricity, impeller type and the direction of the liquid circulation in the agitated vessel. Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May 2007.