Papers by Keyword: Local Heating

Abstract: Abstract. Tubes with non-uniform thickness are needed to even out wall thickness in draw bending and provide higher stiffness in specific directions in some applications. Tailored local heating of the tubes in tube sinking operations should reduce the local flow stresses and facilitate differential deformation along the circumference of tubes to form tubes with uneven wall thicknesses. Local heating of tubes prior to entry into the die in tube sinking is implemented in this research to form tubes with higher thickness in desired directions. Initial experiments are conducted using plasma heating by tungsten inert gas (TIG) welding equipment on EN AW 6060 AlMgSi0.5 aluminum tubes. The process window is described by varying the process temperature (weld current between 50 A and 80 A) while altering the degree of deformation, the tube diameter, and tube thickness. Tubes with no defects were formed at 50 A. Increasing the weld current led to a higher wall thickness (up to 25% thickness increase), however, high weld currents also favored the formation of surface defects, wrinkle formation, or burn-through holes depending on the process setup. The process window was larger for tubes with higher wall thickness.

Abstract: Considerable thermal stresses arising in thin-walled metallic materials and structures loaded with tensile stresses can lead either to their complete destruction or to the appearance of discontinuity zones in them.

Abstract: Numerical research of heat and mass transfer processes at dispersed condensed substance ignition by metallic particle heated to high temperatures was developed. It was established the influence of “hot” particle parameters on the main integrated characteristic of process – ignition delay time.

Abstract: The terminal part of the e₊ track (the positron blob) is formed during ionization slowing down and subsequent ion-electron recombinations produced by a positron. It releases up to 1 keV of energy, which is converted into heat within few picoseconds. If a bulk temperature of a medium is below, but close enough to its melting point, some region of a substance may melt, yielding a peculiar temperature dependence of the lifetime (LT) spectra. We have estimated properties of the molten region with a help of macroscopic heat con- duction equation and suggested a model describing temperature dependence of the ortho- positronium lifetime in frozen methanol, ethanol, butanol and water close to their melting points.

Abstract: In order to solve the problem of crack appeared in Francis turbine runner, the welding residual stress of Francis turbine runner is regulated and controlled by means of numerical simulation from the view of subsection welding, local heating and local peening. The results show that the length of welding section of blade outlet and the welding direction in the subsection welding process influence the residual stress of the turbine blade. For the local heating technology, the decreasing effect on residual stress increases with the increase of heating time, heating temperature and heating area. The welding residual stress of dangerous region decreases and then increases with the increase of heating distance. Moreover, the peening effect is very clear when the temperature of material in the peening region reaches its own plastic temperature.

Abstract: The purpose of this study is to identify the principal factors controlling the formability of TMCP steel for curved hull plate. In order to do it, the initial residual stress in TMCP steel was evaluated using flatness measured in the flat bar cut by flame and analytical approach. Changes of the curved profiles in conventional steel and EH 36 TMCP steel of 50mm thick during cold bending and local heating were investigated using 3 dimensional measuring instruments. It was found that the formability in TMCP steel was mainly determined by the excessive distortion by the relaxation of residual stress during cold bending.

Abstract: The focus of this study was on discussing the novel reflow method ISHR (Induction spontaneous heat reflow) used for high-density area array packaging and assembly. Multi-layer under bump metallization (UBM) and Sn3.5Ag lead-free solder ball were laid in the high frequency electromagnetic field. Because of the induction heating, solder balls melted and spread onto the UBM to form solder bumps. The solder bumps could be formed within 2 seconds through this method; meanwhile, the infrared temperature measurement results showed that the rosin substrate temperature was lower. The shear test indicated that the solder bumps made by ISHR can satisfy the mechanical requirement. Finally, the feasibility experiment was performed to demonstrate the application feasibility of this ISHR technology. Through all these experiments, conclusion can be made that the ISHR as a novel reflow method can be applied in microelectronics packaging.