1,721,903 research outputs found
Finite element simulation of three dimensional superplastic blow forming
No full textSuperplastic blow forming processes are simulated with a finite element method which adopts the convective coordinates system. The code developed is applied to cylindrical cup and the square cup blow forming processes to predict the optimum forming pressure cycle. The numerical result demonstrates the validity and accuracy by comparing with the experimental result and the numerical result by a continuum finite element method The numerical results also provide the pole height, the intermediate and final deformed shapes and the thickness distribution with respect to time
Simulation of superplastic forming diffusion bonding with finite-element analysis using the convective coordinate system
No full textSuperplastic-forming processes are simulated with finite-element analysis in the convective coordinate system. The finite-element code developed is applied to blow-forming processes for demonstration of its validity by predicting the optimum forming pressure cycle. The numerical results provide the pole height and intermediate deformed shapes with variation of the forming time, as well as thickness distribution. The results are compared with those from the experiment and finite-element analysis with a continuum element. The finite-element code is applied to the analysis of a superplastic-forming/diffusion-bonding (SPF/DB) process of four-sheet sandwich parts. The result shows that the deformed shape with the three-dimensional analysis is different from that with the two-dimensional plane strain because of the end effect, and so is the thickness distribution. The analysis enables accurate prediction of thickness distribution, which is necessary for the good design of multi-sheet sandwich parts such as an aircraft part. (C) 1999 Elsevier Science S.A. All rights reserved
Numerical simulation of the superplastic moving die forming process with a modified membrane finite element method
No full textIn superplastic forming, a number of processes have been developed and designed to reduce the thickness deviation that is inevitable in simple female-die forming. Some of the forming processes require tool movements for better thickness distribution than simple female forming. It is-common to use techniques based on male tool movement for relatively deep and complex shapes. The process has to deal with the optimum pressure cycle considering the moving die, the thickness distribution and the final shape. Calculation of the thickness distribution is a key for the optimum process design to produce good quality parts of uniform thickness distribution. In this paper, superplastic forming processes with a moving die are simulated with the finite element method (FEM) with modified membrane elements in the convective coordinate system. The numerical result provides the optimum pressure cycle and intermediate deformed shapes with the variation of the forming time as well as the thickness distribution. The result is compared with that obtained from simple female-die forming to demonstrate that the thickness distribution with a moving die is more uniform than that with a simple female die. The analysis enables accurate prediction of the thickness distribution in blow forming processes with a moving die. (C) 2001 Elsevier Science B.V. All rights reserved
Estimation methods for strain-life fatigue properties from hardness
No full textSeveral methods for estimating fatigue properties from hardness are discussed, along with all existing estimation methods. The (direct) hardness method proposed by Roessle and Fatemi provides excellent estimation results for steels. So-called indirect hardness methods utilizing the ultimate tensile strength predicted from hardness were proposed in this study and successfully applied to estimate fatigue properties for aluminum alloys and titanium alloys. The medians method proposed by Maggiolaro and Castro is found to provide the best estimation results for aluminum alloys. Based on the results obtained, some guidelines are provided for estimating fatigue properties from simple tensile data or hardness. In addition, a new relationship of ultimate tensile strength versus hardness is proposed for titanium alloys. (c) 2005 Elsevier Ltd. All rights reserved
FINDING THE SHORTEST-PATH IN RAILROAD SYSTEMS USING THE SUPER-NETWORK
No full textThe shortest path problem is discussed to develop an automatic control system of the railroad in a factory. The super-network is proposed and an algorithm is given to find the shortest path on the super-network. The super-network is useful to model the railroad system because it can represent important factors in finding paths which cannot be represented by an ordinary network. An example is also given to show how a railroad system can be modelled using a super-network and how the shortest path can be found by the proposed algorithm
Fabrication and characterization of ZnO/Multi wall carbon nanotube(MWNT) nanocomposite for supercapacitors
No full textMolecular dynamics simulation of energetic ion bombardment onto a-Si(3)N(4) surfaces
No full textEnergetic ion (Ar+) bombardment onto a silicon nitride substrate was modeled using molecular dynamics simulation. An empirical potential energy function developed by Vashishta was used to describe the interactions in substrate atoms. An amorphous surface configuration was prepared by simulating the surface evolution due to successive ion impacts and structure relaxation at high temperature. We considered Art ion bombardment on this amorphous surfacer for various incident angles (phi (i) = 0 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees and 85 degrees) and incident energies (E-i = 100 and 200 eV). The reflection characteristics of impact ions can be obtained, in addition the plasma sputtering process can also be investigated with these atomic scale simulations, The sputtering yield had its maximum in the range of incident angle, 60 degrees < phi (i) < 75 degrees, and nonstoichiometric surface atom removal (Si-sput:N-sput = 1:2.5) was observed. (C) 2001 Elsevier Science B.V. All rights reserved.The authors acknowledge the support by the BK 21 project
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