Analysis of Explosively Actuated Valves

1994 ◽  
Vol 116 (3) ◽  
pp. 809-815 ◽  
Author(s):  
B. K. Jones ◽  
A. F. Emery ◽  
M. F. Hardwick ◽  
R. Ng
Keyword(s):  
Finite Element ◽  
Critical Factor ◽  
Disk Model ◽  
Interference Fit ◽  
Elastic Plastic ◽  
Drag Forces ◽  
Plastic Materials ◽  
Elastic Plastic Materials ◽  
Thin Disks ◽  
Plastic Disk

Explosive valves are generally composed of a plunger which is explosively driven along the bore of a cylindrical housing. The plunger is forced to stop at a location designed to alter a particular fluid flow configuration. The stopping point of the plunger is determined by the drag forces between the plunger and the housing and is the critical factor in obtaining the desired flow. One way of calculating these drag forces is to model the valve as a series of thin disks and to assume an elastic interference fit between the disks of the plunger and the disks of the housing. Explosive valves constructed with new materials and new geometries, however, have made it necessary to account for plastic deformations, including strain hardening. This paper introduces an elastic-plastic disk model based on a combination of closed form and finite element results. The behavior of the calculations with elastic-plastic materials is compared to various finite element representations of an explosive valve to verify the disk model and to quantify the effects of plasticity and large deformations. Finally, the elastic-plastic calculations are compared to experimental results obtained from actual valves with various materials and geometries.

On Determining Elastic Modulus from Instrumented Indentation

2013 ◽  
Vol 668 ◽  
pp. 616-620
Author(s):  
Shuai Huang ◽  
Huang Yuan
Keyword(s):  
Finite Element ◽  
Elastic Modulus ◽  
Plastic Material ◽  
Instrumented Indentation ◽  
Computational Simulations ◽  
Elastic Plastic ◽  
Modified Method ◽  
Plastic Materials ◽  
Elastic Plastic Material ◽  
Elastic Plastic Materials

Computational simulations of indentations in elastic-plastic materials showed overestimate in determining elastic modulus using the Oliver & Pharr’s method. Deviations significantly increase with decreasing material hardening. Based on extensive finite element computations the correlation between elastic-plastic material property and indentation has been carried out. A modified method was introduced for estimating elastic modulus from dimensional analysis associated with indentation data. Experimental verifications confirm that the new method produces more accurate prediction of elastic modulus than the Oliver & Pharr’s method.

Solid Formulation, Comparison of Two Formulations, and Concluding Remarks

1989 ◽  
Author(s):  
Shiro Kobayashi ◽  
Soo-Ik Oh ◽  
Taylan Altan
Keyword(s):  
Finite Element ◽  
Field Equation ◽  
Boundary Value Problem ◽  
Metal Forming ◽  
Large Strain ◽  
Boundary Value ◽  
Elastic Plastic ◽  
Plastic Materials ◽  
Elastic Plastic Materials ◽  
Selection Of

In the previous chapters we have discussed only the applications of flow formulation to the analysis of metal-forming processes. Lately, elastic-plastic (solid) formulations have evolved to produce techniques suitable for metal-forming analysis. This evolution is the result of developments achieved in large-strain formulation, beginning from the infinitesimal approach based on the Prandtl–Reuss equation. A question always arises as to the selection of the approach—“flow” approach or “solid” approach. A significant contribution to the solution of this question was made through a project in 1978, coordinated by Kudo, in which an attempt was made to examine the comparative merits of various numerical methods. The results were compiled for upsetting of circular solid cylinders under specific conditions, and revealed the importance of certain parameters used in computation, such as mesh systems and the size of an increment in displacement. This project also showed that the solid formulation needed improvement, particularly in terms of predicting the phenomenon of folding. For elastic-plastic materials, the constitutive equations relate strain–rate to stress–rates, instead of to stresses. Consequently, it is convenient to write the field equation in the boundary-value problem for elastic-plastic materials in terms of the equilibrium of stress rates. In this chapter, the basic equations for the finite-element discretization involved in solid formulations are outlined both for the infinitesimal approach and for large-strain theory. Further, the solutions obtained by the solid formulation are compared with those obtained by the flow formulation for the problems of plate bending and ring compression. A discussion is also given concerning the selection of the approach for the analysis. In conclusion, significant recent developments in the role of the finite-element method in metal-forming technology are summarized. The field equation for the boundary-value problem associated with the deformation of elastic-plastic materials is the equilibrium equation of stress rates. As stated in Chap. 1 (Section 1.3), the internal distribution of stress, in addition to the current states of the body, is supposed to be known, and the boundary conditions are prescribed in terms of velocity and traction-rate.

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