The Experts below are selected from a list of 162 Experts worldwide ranked by ideXlab platform

Mauri´cio J. Monteiro - One of the best experts on this subject based on the ideXlab platform.

  • Arc Stability Indexes Evaluation on Underwater Wet Welding
    29th International Conference on Ocean Offshore and Arctic Engineering: Volume 6, 2010
    Co-Authors: Ezequiel Caires Pereira Pessoa, Alexandre Queiroz Bracarense, Leandro F. Ribeiro, Weslley C. Dias, Luciano G. D. Andrade, Stephen Liu, Valter Rocha Dos Santos, Mauri´cio J. Monteiro
    Abstract:

    Underwater wet welding (UWW) with shielded metal arc welding (SMAW) is employed basically in repairs of offshore structures, including platforms, ships and others. The main problems of this type of welds are related, of course, with water presence in the electric arc that causes higher cooling rates, Oxygen and Hydrogen availability in the arc atmosphere and arc instability. Many of research and test welding programs in laboratory are undertaken in shallow water performed by automatic devices using hyperbaric chambers to simulate depths. Also, welding arc signals are acquired using data acquisition systems and the arc stability is estimated through indexes calculated from values acquired and analyzed. It is very well known the reduced stability of the wet welding process at shallow depths — less than approximately five meters. So this effect would be considerable significant since it can be used to make correlations between the arc stability indexes and the welds quality results. The main objective of this work was to evaluate the efficiency of the most used arc stability indexes reported in the literature in detect the arc instability effect of shallow water wet welding. Bead-on-plate welds had been made using a gravity feeding system device inside a hyperbaric chamber, applying Straight Polarity (DCEN) in ASTM A36 steel plates, using the same weld parameters in two different depths, 0.5 and 20.0 meters. Rutile, basic and oxidizing commercial electrodes types prepared for UWW with 3.25mm rod diameter were used. Visual analysis, bead morphology and arc stability were the criteria used to evaluate the weld quality. The voltage and current arc signals were acquired at 10 KHz rate. The arc stability indexes measured were average voltage and current and its standard deviation, S (Imax/Imin) parameter, voltage and current square mean, arc “re-ignition” voltage and current, metal transfer time and its deviation, metal transfer frequency and its deviation, short circuit time and its deviation and the voltage versus current graph area. The results shown that none of the stability indexes tested has been shown to indicate, alone, a good relationship to the surface appearance obtained for the three electrodes studied. The rutile type electrode was the only one that clearly produced better weld appearance at 20 meters than in shallow water depth. The rutile and oxidizing electrodes showed better surface appearance with the increased number of short circuits. For the rutile electrode, the globular transfer mode with high voltage were directly related with poor weld bead surface appearance.Copyright © 2010 by ASME

Dominiek Reynaerts - One of the best experts on this subject based on the ideXlab platform.

  • Study of alternating current flow in micro-EDM through real-time pulse counting
    Journal of Materials Processing Technology, 2016
    Co-Authors: Jun Wang, Fei Yang, Jun Qian, Dominiek Reynaerts
    Abstract:

    Abstract Following the general guidance on the influence of the machining Polarity in micro-EDM, usually a Straight Polarity is applied (with the tool electrode being connected to the negative pole of the generator output), since the bombarding of the “light” electrons on the workpiece is assumed to be the primary material removal mechanism. Therefore, a flipping of the Polarity in the micro-EDM machining process shall result in a high volumetric relative wear, which has been experimentally verified. The initial objective of this research is to reduce the tool wear by inserting a diode in the discharge circuit to block the reverse current flow. However, in the experiments an even higher volumetric relative wear has been observed with the inclusion of a diode. To investigate in depth the influence of the alternating current flow on the tool-material interaction, a pulse counting method based on the detection of the current peak has been proposed to count the number of effective pulses. This counting of the effective sparks enables the subsequent analysis of the mean material removal per discharge and tool wear per discharge. The analysis of the measurements obtained in both sparking cases, with a diode and without a diode, indicates that the reverse current is contributing positively to the material removal on the workpiece and the volumetric relative wear. Therefore, it is not economically proper to block the reverse the current flow in micro-EDM milling. At lower open voltage, the simple empirical linear model without reverse current flow can still serve as a reference for the in-situ tool wear prediction and the subsequent tool wear compensation. However, a correction to the model has to be made at a setting of higher open voltage.

Ezequiel Caires Pereira Pessoa - One of the best experts on this subject based on the ideXlab platform.

  • Arc Stability Indexes Evaluation on Underwater Wet Welding
    29th International Conference on Ocean Offshore and Arctic Engineering: Volume 6, 2010
    Co-Authors: Ezequiel Caires Pereira Pessoa, Alexandre Queiroz Bracarense, Leandro F. Ribeiro, Weslley C. Dias, Luciano G. D. Andrade, Stephen Liu, Valter Rocha Dos Santos, Mauri´cio J. Monteiro
    Abstract:

    Underwater wet welding (UWW) with shielded metal arc welding (SMAW) is employed basically in repairs of offshore structures, including platforms, ships and others. The main problems of this type of welds are related, of course, with water presence in the electric arc that causes higher cooling rates, Oxygen and Hydrogen availability in the arc atmosphere and arc instability. Many of research and test welding programs in laboratory are undertaken in shallow water performed by automatic devices using hyperbaric chambers to simulate depths. Also, welding arc signals are acquired using data acquisition systems and the arc stability is estimated through indexes calculated from values acquired and analyzed. It is very well known the reduced stability of the wet welding process at shallow depths — less than approximately five meters. So this effect would be considerable significant since it can be used to make correlations between the arc stability indexes and the welds quality results. The main objective of this work was to evaluate the efficiency of the most used arc stability indexes reported in the literature in detect the arc instability effect of shallow water wet welding. Bead-on-plate welds had been made using a gravity feeding system device inside a hyperbaric chamber, applying Straight Polarity (DCEN) in ASTM A36 steel plates, using the same weld parameters in two different depths, 0.5 and 20.0 meters. Rutile, basic and oxidizing commercial electrodes types prepared for UWW with 3.25mm rod diameter were used. Visual analysis, bead morphology and arc stability were the criteria used to evaluate the weld quality. The voltage and current arc signals were acquired at 10 KHz rate. The arc stability indexes measured were average voltage and current and its standard deviation, S (Imax/Imin) parameter, voltage and current square mean, arc “re-ignition” voltage and current, metal transfer time and its deviation, metal transfer frequency and its deviation, short circuit time and its deviation and the voltage versus current graph area. The results shown that none of the stability indexes tested has been shown to indicate, alone, a good relationship to the surface appearance obtained for the three electrodes studied. The rutile type electrode was the only one that clearly produced better weld appearance at 20 meters than in shallow water depth. The rutile and oxidizing electrodes showed better surface appearance with the increased number of short circuits. For the rutile electrode, the globular transfer mode with high voltage were directly related with poor weld bead surface appearance.Copyright © 2010 by ASME

Jun Wang - One of the best experts on this subject based on the ideXlab platform.

  • Study of alternating current flow in micro-EDM through real-time pulse counting
    Journal of Materials Processing Technology, 2016
    Co-Authors: Jun Wang, Fei Yang, Jun Qian, Dominiek Reynaerts
    Abstract:

    Abstract Following the general guidance on the influence of the machining Polarity in micro-EDM, usually a Straight Polarity is applied (with the tool electrode being connected to the negative pole of the generator output), since the bombarding of the “light” electrons on the workpiece is assumed to be the primary material removal mechanism. Therefore, a flipping of the Polarity in the micro-EDM machining process shall result in a high volumetric relative wear, which has been experimentally verified. The initial objective of this research is to reduce the tool wear by inserting a diode in the discharge circuit to block the reverse current flow. However, in the experiments an even higher volumetric relative wear has been observed with the inclusion of a diode. To investigate in depth the influence of the alternating current flow on the tool-material interaction, a pulse counting method based on the detection of the current peak has been proposed to count the number of effective pulses. This counting of the effective sparks enables the subsequent analysis of the mean material removal per discharge and tool wear per discharge. The analysis of the measurements obtained in both sparking cases, with a diode and without a diode, indicates that the reverse current is contributing positively to the material removal on the workpiece and the volumetric relative wear. Therefore, it is not economically proper to block the reverse the current flow in micro-EDM milling. At lower open voltage, the simple empirical linear model without reverse current flow can still serve as a reference for the in-situ tool wear prediction and the subsequent tool wear compensation. However, a correction to the model has to be made at a setting of higher open voltage.

Valter Rocha Dos Santos - One of the best experts on this subject based on the ideXlab platform.

  • Arc Stability Indexes Evaluation on Underwater Wet Welding
    29th International Conference on Ocean Offshore and Arctic Engineering: Volume 6, 2010
    Co-Authors: Ezequiel Caires Pereira Pessoa, Alexandre Queiroz Bracarense, Leandro F. Ribeiro, Weslley C. Dias, Luciano G. D. Andrade, Stephen Liu, Valter Rocha Dos Santos, Mauri´cio J. Monteiro
    Abstract:

    Underwater wet welding (UWW) with shielded metal arc welding (SMAW) is employed basically in repairs of offshore structures, including platforms, ships and others. The main problems of this type of welds are related, of course, with water presence in the electric arc that causes higher cooling rates, Oxygen and Hydrogen availability in the arc atmosphere and arc instability. Many of research and test welding programs in laboratory are undertaken in shallow water performed by automatic devices using hyperbaric chambers to simulate depths. Also, welding arc signals are acquired using data acquisition systems and the arc stability is estimated through indexes calculated from values acquired and analyzed. It is very well known the reduced stability of the wet welding process at shallow depths — less than approximately five meters. So this effect would be considerable significant since it can be used to make correlations between the arc stability indexes and the welds quality results. The main objective of this work was to evaluate the efficiency of the most used arc stability indexes reported in the literature in detect the arc instability effect of shallow water wet welding. Bead-on-plate welds had been made using a gravity feeding system device inside a hyperbaric chamber, applying Straight Polarity (DCEN) in ASTM A36 steel plates, using the same weld parameters in two different depths, 0.5 and 20.0 meters. Rutile, basic and oxidizing commercial electrodes types prepared for UWW with 3.25mm rod diameter were used. Visual analysis, bead morphology and arc stability were the criteria used to evaluate the weld quality. The voltage and current arc signals were acquired at 10 KHz rate. The arc stability indexes measured were average voltage and current and its standard deviation, S (Imax/Imin) parameter, voltage and current square mean, arc “re-ignition” voltage and current, metal transfer time and its deviation, metal transfer frequency and its deviation, short circuit time and its deviation and the voltage versus current graph area. The results shown that none of the stability indexes tested has been shown to indicate, alone, a good relationship to the surface appearance obtained for the three electrodes studied. The rutile type electrode was the only one that clearly produced better weld appearance at 20 meters than in shallow water depth. The rutile and oxidizing electrodes showed better surface appearance with the increased number of short circuits. For the rutile electrode, the globular transfer mode with high voltage were directly related with poor weld bead surface appearance.Copyright © 2010 by ASME