Numerical and Experimental Investigation of an Elliptical Paraboloid Shell Model
For practical engineering purpose, a new flat shell element baptized (ACM_Q4SBE1) is presented in this paper. The formulated element can be used for the analysis of thin shell structures; no matter how the geometrical shape might be. Tests on standard problems have been examined. Since, the analysis of thin shell structures has generally been purely carried out on a theoretical basis; it is of importance to present some experimental results of an elliptical paraboloid under uniformly distributed load pressure. The results obtained from both numerical and experimental work are presented. Index Terms— Elliptical Paraboloid, finite element, flat shell element.
BASIS FOR DERIVATION OF MATRICES FOR THE DIRECT STIFFNESS METHOD
Previous developments in the direct stiffness method are reviewed. The advantages of extending the definitions to make the method a variational approach are cited. The finite element formulation of the method of minimum potential energy is given. Explicit requirements of potential energy displacements are presented, and a criterion insuring monotonic convergence is developed. Illustrative displacements yielding matrices resulting in monotonic convergence are included. Available matrices are reviewed with respect to the extended developments.
Effects of reservoir volume on performance of pulse tube cooler.
A pulse tube cooler has the advantages of long-life and low-vibration over conventional cryocoolers such as G-M and Stirling coolers because of the absence of moving parts at low temperature. On the other hand, the combination of a reservoir and orifice is indispensable to optimize the performance of pulse tube coolers. In order to make the pulse tube cooler compact for practical applications, the volume of reservoir should be minimized. This paper analyzes the effects of the reservoir volume on the thermodynamic performance of various components in a simple orifice and a double-inlet pulse tube cooler by combining a linearized model with a thermodynamic analysis. Expressions of entropy production for those components are presented. The results show that the reservoir volume has a significant influence on the entropy production in the various components when the reservoir to pulse tube volume ratio is smaller than about 5. The ratio is important to determine the minimum reservoir volume for a pulse tube cooler. Optimum settings for a double-inlet pulse tube cooler are also discussed.