This paper presents an analytical solution to predict the transient temperature distribution in fillet arc welding, including the effect of the molten metal generated from the electrode. The analytical solution is obtained by solving a transient three-dimensional heat conduction equation with convection boundary conditions on the surfaces of an infinite plate with finite thickness, and mapping an infinite plate on to the fillet weld geometry, including the molten metal with energy equation. The electric arc heat input on the fillet weld and on the infinite plate is assumed to have a travelling bivariate Gaussian distribution. To check the validity of the solution, flux cored arc (FCA) welding experiments were performed under various welding conditions. The actual isotherms of the weldment cross-sections at various distances from the arc start point are compared with those of the simulation result. As the result shows a good accuracy, this analytical solution can be used to predict the transient temperature distribution in the fillet weld of finite thickness under a moving bivariate Gaussian distributed heat source. The simplicity and short calculation time of the analytical solution provides the rationale for using the analytical solution to model the welding control systems or to obtain an optimization tool for welding process parameters.
This paper introduces a new analytical solution to predict the transient temperature distributions in a finite thickness plate during arc welding. This analytical solution is obtained by solving a transient three-dimensional heat conduction equation with convection boundary conditions at the surfaces of the weldment. The heat source due to electric arc is assumed to take a travelling Gaussian distribution. T o prove the validity of the model, a series of G T A bead-on-plate welding were performed on a medium carbon steel under various welding conditions. The isothermal lines of the cross-sectional view at various distancesfrom the arc start were examined and compwed with those predicted by the proposed analytical model. The results show that the finite thickness solution well predicts the transient temperature distribution of the finite thickness or thin plates with satisfactory accuracy. Due to the simplicity of the solution method, the developed analytical model may be implemented to the feedback control of the arc welding process or to the optimization of the process parameters.
The dynamic characteristics of currently used, multi-degrees-of-freedom robots are too complex to analyse and thus it is not possible to design an implementable control algorithm. This paper proposes the guidelines to use in designing an ideal robot whose dynamics are much simpler than those of the conventional robot. It is shown that, even if the proposed design criteria are fulfilled with respect to the wrist only, the dynamic complexity can be drastically removed so that the conventional robot approaches very close to an ideal robot having simple dynamic characteristics. This paper further shows that the ideally designed robot dynamics can be very easily derived from Lagrangian formulation.
SummaryDespite its known effectiveness, a typical vibratory assembly method tends to generate adverse impact forces between mating parts commensurate with the relatively large vibratory motion required for reliably compensating positioning errors of arbitrary magnitude. To this end, this paper presents a neural network-based vibratory assembly method with its emphasis on reducing the mating forces for chamferless prismatic parts. In this method, the interactive force is effectively suppressed by reducing the amplitude of vibratory motion, while the greater part of the relative positioning error is estimated and compensated by a neural network. The estimation performance of the neural network and the overall performance of the assembly method are evaluated experimentally. Experimental results show that the assembly is efficiently accomplished with small reaction forces, and the possible insertion error range is also expanded
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