Papers by Keyword: Distortion

Abstract: Sintering involves several interactions as particles bond and enable microstructure evolution toward a minimized energy condition, resulting in a complex interplay of measurement parameters. Overriding the evolution is energy minimization, and from that perspective some simple relations emerge. The natural progression is determined by energy reduction, measured by surface area, density, and grain boundary area (grain size). Contrary to the usual sintering analysis that starts with atomic level mass transport mechanisms, presented here is an approach that links to global energy reduction during sintering to simple monitors. Initially sintering converts surface area into lower energy grain boundary area. Subsequently grain growth annihilates grain boundary area. Thus, grain boundary area peaks at intermediate sintered densities, while surface area continuously declines. The trajectory follows a straightforward dependence on density as illustrated using data for a wide variety of materials and consolidation conditions.

Abstract: Composite materials have been introduced in the 90’s in the car racing, naval and aeronautic sectors for weight reduction purposes. In the automotive industry, the introduction of composite materials to reduce also the weight of the vehicles leads to additional challenges for Virtual Prototyping on top of difficulties already encountered with metallic structures modeling. The impact of manufacturing on product performance is critical for composites, as the imperfections from the process may greatly affect the statics and crash performance of the final composite component. The paper will describe the state of the art of ESI Composite Solution on global composite manufacturing simulation chain (Forming, Injection, Curing, and Distortion) and how it couples to Structure/Crash through selected industrial examples.

Abstract: Heat treatment is one of the major sources of dimensional inaccuracy in the manufacturing of fine blanked parts. Tools and equipment often need to be iteratively corrected in order to achieve the desired quality. Numerical simulation of the heat treatment process can substantially reduce these efforts. The simulation accuracy on the other hand is strongly dependent on the accurate characterization of the thermo-mechanical boundary conditions as well as material properties. The present contribution aims to propose a novel approach in the calibration of numerical models by using a modified Jominy test as well as heat treatment experiments with parts having residual stresses from a bending process. The results are validated by comparing numerical phase content and hardness values with the corresponding experiments.

Abstract: The concept of multi-point stretch bending of rectangular tube is ​​proposed, and the FEM of rectangular tube with multi-point stretch bending is set up. The phenomenon of section distortion of rectangular tube generated by stretch bending is analyzed. The feasibility of integral die repalced by multi-point die used for stretch bending of rectangular tube is proved by comparing the section distortion value. Numerical simulation of distortion value of rectangular tube with different materials, bending radius and thickness are carried out through mutli-point stretch bending, the results show that the larger the yield strength of rectangular tube is or the larger the bending radius is or the thicker the rectangular tube is, the smaller the distortion value of rectangular tube will be. Then the method of filling pressure is applied to decrease the distortion of rectangular tube, and the results shows that larger the filling pressure is, the smaller the distortion value will be.

Abstract: In order to predict the shape change in hot press forming of a TWB made with HPF1470 boron steel and HSLA340 micro-alloyed steel sheets, a coupled thermo-mechanical-metallurgical finite element model was developed to simulate the process. The simulation consisted of air cooling, forming, die-quenching and, finally, by a treatment designed to relax residual stresses. It is shown in this paper that the experimentally observed distortion in the TWB part was reasonably captured by the simulations.

Abstract: Welding is a reliable and effective metal fabrication process which is widely used in industries. Localized heating during welding, followed by rapid cooling generates residual stress and distortion in the weld and base metal. In the last few decades various research efforts have been directed towards the control of welding process parameters aiming at reducing the residual stress and distortion. In the present paper the distortion in fillet welds and the affect of the distortion control techniques on the welded joint are studied. The welding is done with different process parameetrs and under different surrounding conditions. Due to this the distortion level in the T Joint was measured and observed. The study is necessarily aimed at developing the prediction and controlling techniques for distortion in welded T-joints. Key Words: Distortion, preheating, peening, leg length, Shielded metal arc welding (SMAW), Manual metal-arc welding (MMAW)

Abstract: The ZnO and ZnO: Cu Pellets are fabricated by using the Co-Precipitation technique. The effect of different concentration of doping agent on the optical, structural and surface morphological properties of ZnO Pellets were investigated as a function of Cu concentration from 0 to 30 at % in this paper. The spectrophotometric properties of the pellets were carried out for the absorbance and transmittance. The pellets showed absorbance ranging from 0.1-3.0 in UV-VIS regions. The maximum percentage transmittance is 90% within the same region. As the concentration of dopant increases, the pellets become more brittle and the band gap decreases. The XRD pattern reveals the polycrystalline nature of the powder and it is also found that, the lattice spacing is changed with Cu doping in ZnO. This is purely due to distortion of lattice owing to the strain induced by the Cu doping. SEM studies show that, as concentration of copper increases, the porous morphology is vanished giving more dense structure.

Abstract: In the development of socialist modernization today, the social gap between rich and poor is still very large. Poor university students account for a quite large proportion in university students' whole groups. How to ensure poor university students' rights and interests is very important. From the analysis of poor university students’ all aspects of rights, this paper compared the difference of two countries’ protecting the rights of poor university students by analysis of grey theory and anonymous questionnaire survey. It analyzes the reasons of difference and explores the basic methods of educating poor students, establishing and perfecting contemporary university students' education system, so as to help poor students gain legal safeguard of rights and interests and lay a solid foundation for the construction of a harmonious campus and a harmonious society.

Abstract: Wire + Arc Additively Manufactured components contain significant residual stresses that manifest in distortion. Each layer of an additively manufactured wall was rolled with the aim of reducing the residual stress. Neutron diffraction and contour method measurements show that the residual stresses were reduced particularly at the boundary with the substrate. The process also reduced distortion, and refined the microstructure which may facilitate implementation on aerospace components.

Abstract: The relation between the Electro Motive Force (EMF) and Total Harmonic Distortion (THD) was compared and verified by magnet arrangement. Using Halbach array, thrust was more increase by change of magnet arrangement. Moreover, the variable trend of cogging and THD by magnet ratio and magnet form change was checked.