Materials Science Forum Vols. 575-578

Abstract: The high speed rotating arc welding sensor (RAWS) driven by motor with air axis is widely used in seam tracking system. Using the characters of the RAWS, the purpose of this study based on Genetic Algorithm (GA) is to optimize welding process parameters of the RAWS for obtaining satisfied seam geometry. The output variables are penetration, width and height of the seam geometry. These output variables are determined by input variables, which are the welding current, welding voltage, welding speed, rotating arc radius, rotating arc frequency and rotating arc direction. Experimentations are made according to the optimal welding process parameters, and the result shows that the GA is an effective method to optimize the welding process parameters of the RAWS. The described computational methodology enables obtaining a seam with desired geometry.

Abstract: By using FEA software-ANSYS, distribution of 3D temperature field in laser welding for aluminum alloy with different thickness was simulated. In order to improve solution accuracy and efficiency, the transition mesh was used. In view of the characters of laser welding, a travel heat source combined with Gauss function was designed by analyzing both the temperature relativity of the thermal physical parameters of material latent heat of fusion and the effect of convection radiation and characteristics of different thickness on temperature field. By using high-temperature thermocouple, the temperature field was measured. It is shown that the simulation results are in accordance with the experimental results.

Abstract: The diesel engine in the merchant ship is being operated in severe environment more and more because temperature of exhaust gas of combustion chamber is getting higher and higher with increasing of using the heavy oil of low quality as the oil price is significantly being jumped for recent some years. As a result, the degree of wear and corrosion in between spindle and seat ring of exhaust valve are more particularly serious compared to the other parts of the engine. Thus the repair weld to the spindle and the seat ring is a unique method to prolong the life of the exhaust valve in an economical point of view. In this study, corrosion property of both weld metal and base metal was investigated with some electrochemical methods in natural sea water solution, in case of being welded with some welding methods and welding materials to the exhaust valve specimen as the base metal. In all cases, corrosion resistance of the weld metal was considerably superior to the base metal. In particular the weld metal of A2F(AC Shielded Metal Arc Welding with two pass by foreign electrode) showed a relatively good corrosion resistance compared to the other weld metals Furthermore pitting was somewhat observed at the corroded surface of the base metal while there was no its phenomenon on the surface of the weld metal.

Abstract: In this paper the processes of melting and transfer of an electrode metal to the molten pool, hydrodynamics of molten pool in controlled pulsed arc welding in carbon dioxide have been investigated. The process of pulsed arc welding with systematic short-circuits of the arc gap is realized by adaptive algorithms of pulsed control over main energetic parameters of welding - arc current and voltage, arc heated efficiency, peak short-circuiting current, which provide the dosage of energy for melting and transfer of every drop of an electrode metal, the control over fluidity of the weld pool. Physical and mathematical models describing such processes in CO2, original software have been developed. The results of physical simulation and mathematical modelling permit to determine the influence of energetic parameters of the process on the condition of the “power source – electrode – arc – molten pool” electrodynamic system at each moment of time.

Abstract: A bimetal composite material is a variant of the typical composite that is composed of two materials joined at their interface surface. The advantage of clad material is that the combination of different properties of materials can satisfy both the need of good mechanical properties and the demand of user such as electrical properties simultaneously. This paper is concerned with the hydrostatic extrusion process of copper-clad aluminum rod. The commercially available finite element program ANSYS was used to simulate the process of hydrostatic extrusion for Cu/Al bimetal composite through the equal-strain contour concave dies. The relative slippage between the inner and outer metals under the condition of different friction factors is studied, and the stress-strain distribution in the billet was analyzed. Experiment test was carried out; it was found that the experimental result has good agreement with relative slippage from the finite element analysis.

Abstract: The structures of existing wings had holes for light weight and plates and frames were fixed with rivets or screws, thus, there were difficulties and limits in light weight. Welding process generates distortion and residual stress in the welding due to rapid heating and cooling. Welding distortion and residual in the welded structure result in many troubles such as dimensional inaccuracies in assembling and safety problem during service. The accurate prediction of welding residual stress is thus very important to improve the quality of welding and find the way to reduce itself. In this study, an improvement was made in current joint methods through EB welding and laser welding for light weight of wings and welding strength was measured through strength test. In addition, finite element analysis was performed for welding process so as to induce optimum welding condition.

Abstract: Using two-dimensional Eulerian formulations coupling viscoplastic flow and heat transfer, the behaviors of aluminum alloys and stainless steel during FSW were overviewed. The plastic behaviors of the materials are complicated and the flow stresses are depending on deformation rate, temperature and deformation histories. Constitutive equations considering both strain hardening from accumulation of crystal defects and softening from recovery or recrystallization were used to model the materials. Strain hardening is incorporated with a strength that evolves with deformation rate and temperature along streamlines in the flow field. Strength evolutions have a Voce-like saturation limit because of the severe plastic deformation during FSW process. The model equations for kinematic and temperature were solved using the standard finite element method. The evolution equation for the strength is integrated along streamlines. The strength and temperature distribution vary with process conditions and constitutive equations. Stainless steel and AA6061 have different strengthening mechanisms. Modified constitutive equations were applied to reflect microstructural features of each material.

Abstract: Linear friction welding (LFW) has become a key manufacture and repair technology in the aeronautical engine manufacturing, especially in the blisk manufacturing. The kinematic equation during LFW was built, based on which the friction heat in the whole process was computed. With thermal- mechanical coupling technique, and considering the geometrical non-linearity, the material property non-linearity and the interface frictional non-linearity, a Finite Element Model (FEM) of temperature, stress and deformation fields were constructed. The distribution contour of temperature, plastic flow, stress and strain during LFW were plotted. The simulated temperature and axial shortening results were also validated by experimental data.

Abstract: The distribution and value of welding residual stress for 1Cr18Ni9 stainless steel stud welding joints was systemically simulated by ANSYS FE software. The mathematical estimating models of strength of the welded joints were established. Simulation results showed that the welding residual stress was tensile at the edge of the stud, while it was compressive stress at the position near axis center. The largest tensile stress did not exceed yield limit of material. The residual stress had more influence on the strength of welded joints.

Abstract: Welding heat cycle computer software is developed successfully, bases on experiential and practical mathematic model, uses LabVIEW7.1 to program, it can draw single or multi-process welding heat cycle curve conveniently and quickly. This paper puts emphasize on explaining the realization of multi-process heat cycle curve which is drawn by the same or different mathematic model, and the research of heat cycle curve’ change which is caused by the change of parameters. It introduces the comparison between practical curve which is obtained from experiment and settled curve after this software is embedded in MMS-200 thermo-mechanical simulator. The development of this software has important value on the research of welding process, fills up the blank of domestic thermo-mechanical simulator at the aspect of welding thermo-simulation, consummates the function of thermo-mechanical simulator, and broadens its applying field further.