Analytic weld pool model calibrated by measurements-part 2: Verification and robustness

More experiments were conducted using different currents to verify the method proposed and estimate the weld depth in stationary gas tungsten arc welding. The excellent accuracy demonstrated for welds produced in different currents proved the effectiveness of the analytic model, calibration-based method. To further ensure the calibration accuracy, the prior diameter and volume accuracies were introduced, and the calibration accuracy was modeled as a function of these prior accuracies. Since prior accuracies can be computed during welding from the measurements of the pool diameter and elevation volume, the final accuracy achieved by the proposed method was estimated, providing a degree of confidence. To predict and maximize the calibration accuracy, the calibration was also modeled as a function of the heat source parameters such that the heat source parameters to be used were optimized offline for the case being studied. To test its applicability under changing conditions, the heat source parameters optimized for the 60-A current case were applied to the cases using 65-and 70-A current. The achieved excellent accuracies proved the robustness of a proposed method that uses the analytic model to calculate the temperature distribution from the predetermined heat source parameters and then calibrates the temperature distribution based on the online measurements of the weld pool diameter and elevation volume. A systematic method was thus established to support the proposed calibration method including selection/optimization of heat source parameters for maximized calibration accuracy and estimation of the resultant accuracy.