Noncentral Force Model for h.c.p. Metals

1973 ◽  
Vol 51 (6) ◽  
pp. 616-623 ◽  
Author(s):  
S. S. Kushwaha
Keyword(s):  
Coulomb Potential ◽  
Short Range ◽  
Closed Shell ◽  
Experimental Results ◽  
Force Model ◽  
Dynamical Matrix ◽  
Screened Coulomb Potential ◽  
Shell Part

The elements of the dynamical matrix are separated into two parts : (i) a short-range closed-shell part and (ii) an ionic part. The effect of the former is calculated using noncentral forces involving central as well as angular forces whereas the latter part is evaluated on the lines of Krebs using a screened Coulomb potential. The calculated phonon frequencies along symmetry directions and θ–T curves for Mg, Be, and Tl have been plotted and compared with the experimental results.

Optimization Design of Drawbead in Drawing Tools of Autobody Cover Panel

2002 ◽  
Vol 124 (2) ◽  
pp. 278-285 ◽  
Author(s):  
Gang Liu ◽  
Zhongqin Lin ◽  
Youxia Bao
Keyword(s):  
Optimization Algorithm ◽  
Optimization Design ◽  
Design Method ◽  
Experimental Results ◽  
Hybrid Optimization ◽  
Force Model ◽  
Hybrid Optimization Algorithm ◽  
Design Plan ◽  
Formed Part ◽  
Restraining Force

In the tooling design of autobody cover panels, design of drawbead will affect the distribution of drawing restraining force along mouth of dies and the relative flowing velocity of the blank, and consequently, will affect the distributions of strain and thickness in a formed part. Therefore, reasonable design of drawbead is the key point of cover panels’ forming quality. An optimization design method of drawbead, using one improved hybrid optimization algorithm combined with FEM software, is proposed in this paper. First, we used this method to design the distribution of drawbead restraining force along the mouth of a die, then the actual type and geometrical parameters of drawbead could be obtained according to an improved drawbead restraining force model and the improved hybrid optimization algorithm. This optimization method of drawbead was used in designing drawing tools of an actual autobody cover panel, and an optimized drawbead design plan has been obtained, by which deformation redundancy was increased from 0% under uniform drawbead control to 10%. Plastic strain of all area of formed part was larger than 2% and the minimum flange width was larger than 10 mm. Therefore, not only better formability and high dent resistance were obtained, but also fine cutting contour line and high assembly quality could be obtained. An actual drawing part has been formed using the optimized drawbead, and the experimental results were compared with the simulating results in order to verify the validity of the optimized design plan. Good agreement of thickness on critical areas between experimental results and simulation results proves that the optimization design method of drawbead could be successfully applied in designing actual tools of autobody cover panels.

PRESSURE-INDUCED STRUCTURAL EFFECTS IN SEMICONDUCTORS

1993 ◽  
Vol 07 (27) ◽  
pp. 4555-4593 ◽  
Author(s):  
J. CRAIN
Keyword(s):  
High Pressure ◽  
Computational Methods ◽  
Short Range ◽  
Short Range Order ◽  
Computational Physics ◽  
Range Order ◽  
Experimental Results ◽  
Structural Effects ◽  
Electronic Effects ◽  
Structural Polymorphism

Recent advances in the understanding of pressure-induced structural and electronic effects in semiconductors have been made possible through developments in both experimental and computational physics. It is shown that the A N B 8−N compounds which include the tetrahedrally coordinated III–V semiconductors exhibit a far richer degree of pressure-induced structural polymorphism than was originally believed. In addition, entirely new factors such as defects, short-range order and irreversibility have been identified as playing potentially important roles in the high pressure behavior of semiconductors. The experimental results are reviewed and discussed in the context of models which are amenable to investigation by modern theoretical and computational methods.

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