Proposed Heat Source Research Articles

A study on an efficient prediction of welding deformation for T-joint laser welding of sandwich panel PART I : Proposal of a heat source model

The use of I-Core sandwich panel has increased in cruise ship deck structure since it can provide similar bending strength with conventional stiffened plate while keeping lighter weight and lower web height. However, due to its thin plate thickness, i.e. about 4~6 mm at most, it is assembled by high power CO2 laser welding to minimize the welding deformation. This research proposes a volumetric heat source model for T-joint of the I-Core sandwich panel and a method to use shell element model for a thermal elasto-plastic analysis to predict welding deformation. This paper, Part I, focuses on the heat source model. A circular cone type heat source model is newly suggested in heat transfer analysis to realize similar melting zone with that observed in experiment. An additional suggestion is made to consider negative defocus, which is commonly applied in T-joint laser welding since it can provide deeper penetration than zero defocus. The proposed heat source is also verified through 3D thermal elasto-plastic analysis to compare welding deformation with experimental results. A parametric study for different welding speeds, defocus values, and welding powers is performed to investigate the effect on the melting zone and welding deformation. In Part II, focuses on the proposed method to employ shell element model to predict welding deformation in thermal elasto-plastic analysis instead of solid element model.

An investigation of workpiece temperature variation in end milling considering flank rubbing effect

Better prediction about the magnitude and distribution of workpiece temperatures has a great significance for improving performance of metal cutting process, especially in the aviation industry. A thermal model is presented to describe the cyclic temperature variation in the workpiece for end milling. Owing to rapid tool wear in the machining of aeronautical components, flank rubbing effect is considered. In the proposed heat source method for milling, both the cutting edge and time history of process are discretized into elements to tackle geometrical and kinematical complexities. Based on this concept, a technique to calculate the workpiece temperature in stable state, which supposes the tool makes reverse movement, is developed. And a practicable solution is provided by constructing a periodic temperature rise function series. This investigation indicates theoretically and experimentally the impact of different machining conditions, flank wear widths and cutter locations on the variation of workpiece temperature. The model results have been compared with the experimental data obtained by machining 300M steel under different flank wear widths and cutting conditions. The comparison indicates a good agreement both in trends and values. With the alternative method, an accurate simulation of workpiece temperature variation can be achieved and computational time of the algorithm is obviously shorter than that of finite element method. This work can be further employed to optimize cutting conditions for controlling the machined surface integrity.

On the Modeling of Laser as a Moving Distributed Volumetric Heat Source for Laser Cutting Simulation

Laser processing of sheet metals (such as cutting or welding) involves heating of the substrate material by laser beam with temperature in the substrate materials reaching the melting temperature. Therefore, such laser processes consist of heating, melting and solidification of the substrate metal. An important topic in laser processing simulation is the modeling of the heat source (distribution of heat input). The interaction of laser beam with a molten metal pool is a complex physical phenomenon that still cannot be modeled rigorously. Laser beam as a heat source causes highly non-linear temperature distribution across the cut or weld and various heat source modeling approaches have been reported in the literature. In general, the distribution of heat input can be classified as superficial and volumetric. In this paper, a moving volumetric heat source model is presented. Using the proposed heat source model, laser cutting process is simulated and residual stresses generated in the cutting region are predicted.

Relationships between a porphyry Cu-Mo deposit, base and precious metal veins and Laramide intrusions, Mineral Park, Arizona

In the Wallapai mining district, porphyry-style copper-molybdenum mineralization occurs within and near Laramide granitoid stocks at the center of an elongate zone of polymetallic quartz veins. The principal mineralized veins form a well-defined paragenetic sequence, with a simplified mineralogy progressing through: (1) anhydrite-molybdenite (AM) veins of quartz + K-feldspar + anhydrite + pyrite + biotite + molybdenite, (2) quartz-molybdenite (QM) veins with quartz + molybdenite + pyrite, (3) anhydrite-chalcopyrite (AC) veins containing quartz + K-feldspar + anhydrite + pyrite + magnetite + chalcopyrite + chlorite + rutile, (4) quartz-pyrite (QP) veins of quartz + sericite + pyrite, and quartz + pyrite + chalcopyrite + epidote + chlorite, and (5) polymetallic quartz (PMQ) veins, with a gangue assemblage of quartz + sericite + calcite + kaolinite(?) + epidote + chlorite, and a variety of base and precious metal minerals.The coexistence of vapor- and liquid-rich fluid inclusions in vein quartz shows that the molybdenite-bearing anhydrite and quartz veins formed at 360 degrees to 410 degrees C from boiling, low-salinity brines. Chalcopyrite deposition in the anhydrite-chalcopyrite veins was at 380 degrees to 420 degrees C from nonboiling brines averaging 20 equiv wt percent NaCl and 25 equiv wt percent KCl. The quartz-pyrite veins formed at 320 degrees to 350 degrees C from brines of 1 to 13 equiv wt percent NaCl. The polymetallic quartz veins formed from dilute brines of 1 to 7 equiv wt percent NaCl. Temperatures in the first stage of mineralization of the polymetallic-quartz veins abruptly increased to 400 degrees to 450 degrees C in and near Mineral Park, but declined outward to less than 300 degrees C on the district periphery. In subsequent stages, fluid temperatures decreased across the district to less than 200 degrees C. Pressures were 250 to 300 bars, probably in a hydrostatic pressure regime, during boiling related to molybdenite mineralization, but they may have increased to about 1,100 bars lithostatic pressure during chalcopyrite deposition in the anhydrite-chalcopyrite veins. A depth during mineralization of 3 to 4 km is suggested.Copper and molybdenum mineralization occurred in a lithocap environment above a progenitor intrusion but was not directly related to the exposed Ithaca Peak stocks. The evolution from hypersaline fluids in the anhydrite-chalcopyrite veins to low-salinity, lower temperature fluids in the quartz-pyrite veins suggests an influx of meteoric water into the waning porphyry-style hydrothermal system. Brines up to 100 degrees C hotter appeared during the formation of the paragenetically later polymetallic quartz veins and constituted a new, and much larger, hydrothermal system. The heat source, presumably an unexposed intrusion, was much larger than the porphyry-style system. The zonation in base metal ratios of polymetallic quartz veins is symmetrical with respect to the proposed heat source.