Rosenda Valdés Arencibia

Incerteza na medição dos parâmetros geométricos do cordão de solda

Palavras-Chave: Soldagem, geometria do cordao de solda, incerteza de medicao, planeza, perpendicularidade. Abstract: This work presents a methodology to estimate the uncertainty associated to the measurement of the weld bead geometric parameters in order to address the requirements of NBR ISO/IEC 17025 Standard. The specimen geometric quality was additionally evaluated through the measurement of flatness and perpendicularity deviations. The following steps were proposed and executed: identification of weld bead geometric parameters; identification and study of the variables that affect measurement of the identified parameters; adoption of a mathematical model to estimate the uncertainty for each parameter; planning and execution of the experiments for data obtaining; uncertainty determination, analysis and discussion of the results. It was concluded that the most important variables influencing the final uncertainty were the uncertainty associated to the measuring system calibration and the perpendicularity deviation. The analysis warned about the permissible values of perpendicularity deviations of specimens used during the measurements.

Incerteza na medição da largura de cordões de solda

This paper addresses the estimation of the uncertainty associated to welding bead width measurement according to the ISO GUM recommendations. The applied methodology consisted of the following steps: identification and study of the variables that affect measurement of the bead width with a caliper; adoption of a mathematical model that relates the input and output variables of the evaluated system; planning and execution of experiments to gather data; estimation of measurement uncertainty and, finally, analysis and discussion of results. By the end of this work it was possible to conclude that the variability associated to the readings was the source of the largest contribution for the final uncertainty, and that the expanded uncertainty has reached the value ± 1,03 mm to 95,45 % of coverage.

Comparison of thermal efficiency between A-TIG and conventional TIG welding

Abstract The A-TIG process (TIG welding with active flux) consists in depositing a thin layer of flux on the workpiece surface just before welding. The layer deposition can be done by brushing or spraying over the surface, and welding is performed after it dries out. It is found that with this process it is possible to increase productivity (travel speed) up to three times higher compared to the conventional TIG process. However, the physical phenomena associated with this practical gain of productivity still remains under discussion. Thus, the aim of this paper is to analyse the thermal efficiency and heat input in the welding process with the A-TIG compared with conventional TIG process using a liquid nitrogen calorimeter as a contribution to better understanding the physical associated phenomena. From the presented results, it is observed that the effects of A-TIG welding on the weld bead geometry are in agreement with previous work. In addition, it is possible to conclude that the thermal efficiency of the A-TIG welding is lower than the efficiency in conventional TIG welding. Thus, it is possible to conclude that the arc constriction is more important than the reduction of thermal efficiency.

Comparação da eficiência térmica entre soldagem A-TIG e TIG convencional

The A-TIG process (TIG welding with active flux) consists in depositing a thin layer of flux on the workpiece surface just before the welding. The layer deposition can be done by brushing or spraying over the surface, and welding is performed after it dries out. It is found that with this process it is possible to increase productivity (travel speed) up to three times higher compared to the conventional TIG process. However, the physical phenomena associated with this practical gain of productivity still remains under discussion. Thus, the aim of this paper is to analyze the thermal efficiency and heat input in the welding process with the A-TIG compared with conventional TIG process by using liquid-nitrogen calorimeter, as a contribution to better understanding the physical associated phenomena. From the presented results, it is observed that the effects of A-TIG welding on the weld bead geometry are in agreement with previous work. In addition, it is possible to conclude that the thermal efficiency of the A-TIG welding is lower than the efficiency in conventional TIG welding. Thus, it is possible to conclude that the arc constriction is more important than the reduction of thermal efficiency.

Measurement uncertainty of mass in the determination of the consumption parameters of hardfacing electrodes

This work presents the evaluation of the uncertainty of the measurements to determine the consumption parameters of hardfacing electrode, emphasizing the mass measurement. The experimentation was carried out obtaining deposits at three levels of current (120 A, 145 A y 160 A) and measuring the time spent in welding, the length of the welds the test plate and electrode mass (initial and final). Based on these results, the consumption parameters were also determined. The uncertainty related to the measurements the mass of the samples, the mass consumption of the electrode, the deposited mass and consumption parameters was determined. The results showed that the deposition efficiency increase as a function of the current, turning the best result (74.12 %) at 120 A. The expanded measurement uncertainty associated to consumption parameters changed between 1.47% and 2.41% for the deposition efficiency, 0.4 g/min and 0.6 g/min for the consumption rate vary of 0.6 g/min to 0.7 g/min for the deposition rate.