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Frank E Pfefferkorn - One of the best experts on this subject based on the ideXlab platform.

  • calibration of dynamic tool workpiece Interface Temperature measurement during friction stir welding
    Measurement, 2016
    Co-Authors: Joshua Schmale, Axel Fehrenbacher, Amber Shrivastava, Frank E Pfefferkorn
    Abstract:

    Abstract The objective of this work is to accurately measure the transient Temperatures at the tool–workpiece Interface during friction stir welding (FSW) using thermocouples that are embedded in the tool. Temperature sensors embedded in the friction stir (FS) tool provide a non-consumable localized Temperature measurement capability that is crucial for process research, development, and control. A modification of the ASTM E-1461 standard for measuring thermal diffusivity with pulses of heat flux is proposed for calibrating the transient response of Temperature sensors located near the surface of the FS tool. These tests enable the calculation of each sensor’s time constant, which are used in one-dimensional analytical models of the dynamic response to calculate the true Interface Temperature. Time constants between 21 and 43 ms are measured for 0.25-mm-diameter, sheathed thermocouples located at the FS tool surface.

  • physics based interpretation of tool workpiece Interface Temperature signals for detection of defect formation during friction stir welding
    Manufacturing letters, 2015
    Co-Authors: Amber Shrivastava, Michael R Zinn, Clemens Dingler, Frank E Pfefferkorn
    Abstract:

    Abstract The objective of the work is the reduction and eventual avoidance of post welding inspections that are currently needed to ensure defect-free welds. An analytical thermal model of the FSW process along with an analytical disturbance model is developed. This disturbance model relates defect formation to variations in the measured Temperature and is based on experimental process identification. A dynamic disturbance observer computes an estimate of the disturbance signal, which is further processed in order to provide information about the presence of defects along the weld. Experiments for one kind of disturbance verify that the observer shows good tracking behavior.

  • physics based interpretation of tool workpiece Interface Temperature signals for detection of defect formation during friction stir welding
    Manufacturing letters, 2015
    Co-Authors: Amber Shrivastava, Michael R Zinn, Clemens Dingler, Frank E Pfefferkorn
    Abstract:

    Abstract The objective of the work is the reduction and eventual avoidance of post welding inspections that are currently needed to ensure defect-free welds. An analytical thermal model of the FSW process along with an analytical disturbance model is developed. This disturbance model relates defect formation to variations in the measured Temperature and is based on experimental process identification. A dynamic disturbance observer computes an estimate of the disturbance signal, which is further processed in order to provide information about the presence of defects along the weld. Experiments for one kind of disturbance verify that the observer shows good tracking behavior.

  • measurement of tool workpiece Interface Temperature distribution in friction stir welding
    Journal of Manufacturing Science and Engineering-transactions of The Asme, 2014
    Co-Authors: Axel Fehrenbacher, Michael R Zinn, Joshua Schmale, Frank E Pfefferkorn
    Abstract:

    The objective of this work is to develop an improved Temperature measurement system for friction stir welding (FSW). FSW is a solid-state joining process enabling welds with excellent metallurgical and mechanical properties, as well as significant energy consumption and cost savings compared to traditional fusion welding processes. The measurement of Temperatures during FSW is needed for process monitoring, heat transfer model verification and process control, but current methods have limitations due to their restricted spatial and temporal resolution. Previous work showed that Temperatures at the tool shoulder-workpiece Interface can be measured and utilized for closed-loop control of Temperature. Adding an additional thermocouple at the tool pin-workpiece Interface and performing a calibration of the measurement to gain better insight into the Temperature distribution in the weld zone improved the method. Both thermocouples were placed in through holes right at the Interface of tool so that the sheaths are in direct contact with the workpiece material. This measurement strategy reveals dynamic Temperature variations at the shoulder and the pin within a single rotation of the tool in real-time. It was found that the highest Temperatures are at the shoulder Interface between the advancing side and the trailing edge of the tool, closer to the advancing side. The Temperature distribution was mostly affected by travel speed and the Temperature difference within one tool rotation was found to be between 10 °C and 50 °C, depending on the process parameters. The dynamic Temperature measurements obtained with the current system are of unmatched resolution, fast, and reliable and are likely to be of interest for both fundamental studies and process control of FSW.

  • effects of tool workpiece Interface Temperature on weld quality and quality improvements through Temperature control in friction stir welding
    The International Journal of Advanced Manufacturing Technology, 2014
    Co-Authors: Axel Fehrenbacher, Neil A Duffie, N J Ferrier, Frank E Pfefferkorn, Michael R Zinn
    Abstract:

    A real-time wireless Temperature measurement system has been developed and successfully implemented for closed-loop control of tool shoulder–workpiece Interface Temperature. The system employs two thermocouples in through holes and measures the shoulder and pin Interface Temperatures with an angular resolution as small as 10°. Both Temperatures correlate with weld quality (mechanical testing and weld cross sections), e.g., all welds in 4.76-mm-thick 6061-T6 with an average shoulder Interface Temperature below 520 °C and an average pin Interface Temperature below 460 °C fail in the weld zone instead of the heat-affected zone, have unacceptable tensile strengths and in some cases voids. Similarly, welds with shoulder Temperatures above the solidus Temperature result in a degradation of the weld quality. It was found that a shoulder Interface Temperature of 533 °C results in the highest weld quality; hence, this Temperature should be used as the setpoint Temperature in the control system with a constant travel speed of 400 mm/min. The Temperature measurement strategy was shown to be able to indicate welds with insufficient shoulder–workpiece contact, thus potentially identifying and preventing welds with detrimental weld quality due to lack of penetration. It was shown that backing plates of different thermal diffusivity change the heat flow out of the weld zone, hence weld Temperature, and caused a measurable impact on the weld strength. By changing other process parameters, e.g., through a Temperature control system, weld quality can be maintained in the presence of such changing thermal boundary conditions.

Guoan Luo - One of the best experts on this subject based on the ideXlab platform.

Michael R Zinn - One of the best experts on this subject based on the ideXlab platform.

  • physics based interpretation of tool workpiece Interface Temperature signals for detection of defect formation during friction stir welding
    Manufacturing letters, 2015
    Co-Authors: Amber Shrivastava, Michael R Zinn, Clemens Dingler, Frank E Pfefferkorn
    Abstract:

    Abstract The objective of the work is the reduction and eventual avoidance of post welding inspections that are currently needed to ensure defect-free welds. An analytical thermal model of the FSW process along with an analytical disturbance model is developed. This disturbance model relates defect formation to variations in the measured Temperature and is based on experimental process identification. A dynamic disturbance observer computes an estimate of the disturbance signal, which is further processed in order to provide information about the presence of defects along the weld. Experiments for one kind of disturbance verify that the observer shows good tracking behavior.

  • physics based interpretation of tool workpiece Interface Temperature signals for detection of defect formation during friction stir welding
    Manufacturing letters, 2015
    Co-Authors: Amber Shrivastava, Michael R Zinn, Clemens Dingler, Frank E Pfefferkorn
    Abstract:

    Abstract The objective of the work is the reduction and eventual avoidance of post welding inspections that are currently needed to ensure defect-free welds. An analytical thermal model of the FSW process along with an analytical disturbance model is developed. This disturbance model relates defect formation to variations in the measured Temperature and is based on experimental process identification. A dynamic disturbance observer computes an estimate of the disturbance signal, which is further processed in order to provide information about the presence of defects along the weld. Experiments for one kind of disturbance verify that the observer shows good tracking behavior.

  • measurement of tool workpiece Interface Temperature distribution in friction stir welding
    Journal of Manufacturing Science and Engineering-transactions of The Asme, 2014
    Co-Authors: Axel Fehrenbacher, Michael R Zinn, Joshua Schmale, Frank E Pfefferkorn
    Abstract:

    The objective of this work is to develop an improved Temperature measurement system for friction stir welding (FSW). FSW is a solid-state joining process enabling welds with excellent metallurgical and mechanical properties, as well as significant energy consumption and cost savings compared to traditional fusion welding processes. The measurement of Temperatures during FSW is needed for process monitoring, heat transfer model verification and process control, but current methods have limitations due to their restricted spatial and temporal resolution. Previous work showed that Temperatures at the tool shoulder-workpiece Interface can be measured and utilized for closed-loop control of Temperature. Adding an additional thermocouple at the tool pin-workpiece Interface and performing a calibration of the measurement to gain better insight into the Temperature distribution in the weld zone improved the method. Both thermocouples were placed in through holes right at the Interface of tool so that the sheaths are in direct contact with the workpiece material. This measurement strategy reveals dynamic Temperature variations at the shoulder and the pin within a single rotation of the tool in real-time. It was found that the highest Temperatures are at the shoulder Interface between the advancing side and the trailing edge of the tool, closer to the advancing side. The Temperature distribution was mostly affected by travel speed and the Temperature difference within one tool rotation was found to be between 10 °C and 50 °C, depending on the process parameters. The dynamic Temperature measurements obtained with the current system are of unmatched resolution, fast, and reliable and are likely to be of interest for both fundamental studies and process control of FSW.

  • effects of tool workpiece Interface Temperature on weld quality and quality improvements through Temperature control in friction stir welding
    The International Journal of Advanced Manufacturing Technology, 2014
    Co-Authors: Axel Fehrenbacher, Neil A Duffie, N J Ferrier, Frank E Pfefferkorn, Michael R Zinn
    Abstract:

    A real-time wireless Temperature measurement system has been developed and successfully implemented for closed-loop control of tool shoulder–workpiece Interface Temperature. The system employs two thermocouples in through holes and measures the shoulder and pin Interface Temperatures with an angular resolution as small as 10°. Both Temperatures correlate with weld quality (mechanical testing and weld cross sections), e.g., all welds in 4.76-mm-thick 6061-T6 with an average shoulder Interface Temperature below 520 °C and an average pin Interface Temperature below 460 °C fail in the weld zone instead of the heat-affected zone, have unacceptable tensile strengths and in some cases voids. Similarly, welds with shoulder Temperatures above the solidus Temperature result in a degradation of the weld quality. It was found that a shoulder Interface Temperature of 533 °C results in the highest weld quality; hence, this Temperature should be used as the setpoint Temperature in the control system with a constant travel speed of 400 mm/min. The Temperature measurement strategy was shown to be able to indicate welds with insufficient shoulder–workpiece contact, thus potentially identifying and preventing welds with detrimental weld quality due to lack of penetration. It was shown that backing plates of different thermal diffusivity change the heat flow out of the weld zone, hence weld Temperature, and caused a measurable impact on the weld strength. By changing other process parameters, e.g., through a Temperature control system, weld quality can be maintained in the presence of such changing thermal boundary conditions.

  • combined Temperature and force control for robotic friction stir welding
    Journal of Manufacturing Science and Engineering-transactions of The Asme, 2013
    Co-Authors: Axel Fehrenbacher, Neil A Duffie, N J Ferrier, Frank E Pfefferkorn, Christopher B Smith, Michael R Zinn
    Abstract:

    The objective of this research is to develop a closed-loop control system for robotic friction stir welding (FSW) that simultaneously controls force and Temperature in order to maintain weld quality under various process disturbances. FSW is a solid-state joining process enabling welds with excellent metallurgical and mechanical properties, as well as significant energy consumption and cost savings compared to traditional fusion welding processes.During FSW, several process parameter and condition variations (thermal constraints, material properties, geometry, etc.) are present. The FSW process can be sensitive to these variations, which are commonly present in a production environment; hence, there is a significant need to control the process to assure high weld quality. Reliable FSW for a wide range of applications will require closed-loop control of certain process parameters.A linear multi-input-multi-output process model has been developed that captures the dynamic relations between two process inputs (commanded spindle speed and commanded vertical tool position) and two process outputs (Interface Temperature and axial force).A closed-loop controller was implemented that combines Temperature and force control on an industrial robotic FSW system. The performance of the combined control system was demonstrated with successful command tracking and disturbance rejection. Within a certain range, desired axial forces and Interface Temperatures are achieved by automatically adjusting the spindle speed and the vertical tool position at the same time. The axial force and Interface Temperature is maintained during both thermal and geometric disturbances and thus weld quality can be maintained for a variety of conditions in which each control strategy applied independently could fail.Copyright © 2013 by ASME

Amber Shrivastava - One of the best experts on this subject based on the ideXlab platform.

  • calibration of dynamic tool workpiece Interface Temperature measurement during friction stir welding
    Measurement, 2016
    Co-Authors: Joshua Schmale, Axel Fehrenbacher, Amber Shrivastava, Frank E Pfefferkorn
    Abstract:

    Abstract The objective of this work is to accurately measure the transient Temperatures at the tool–workpiece Interface during friction stir welding (FSW) using thermocouples that are embedded in the tool. Temperature sensors embedded in the friction stir (FS) tool provide a non-consumable localized Temperature measurement capability that is crucial for process research, development, and control. A modification of the ASTM E-1461 standard for measuring thermal diffusivity with pulses of heat flux is proposed for calibrating the transient response of Temperature sensors located near the surface of the FS tool. These tests enable the calculation of each sensor’s time constant, which are used in one-dimensional analytical models of the dynamic response to calculate the true Interface Temperature. Time constants between 21 and 43 ms are measured for 0.25-mm-diameter, sheathed thermocouples located at the FS tool surface.

  • physics based interpretation of tool workpiece Interface Temperature signals for detection of defect formation during friction stir welding
    Manufacturing letters, 2015
    Co-Authors: Amber Shrivastava, Michael R Zinn, Clemens Dingler, Frank E Pfefferkorn
    Abstract:

    Abstract The objective of the work is the reduction and eventual avoidance of post welding inspections that are currently needed to ensure defect-free welds. An analytical thermal model of the FSW process along with an analytical disturbance model is developed. This disturbance model relates defect formation to variations in the measured Temperature and is based on experimental process identification. A dynamic disturbance observer computes an estimate of the disturbance signal, which is further processed in order to provide information about the presence of defects along the weld. Experiments for one kind of disturbance verify that the observer shows good tracking behavior.

  • physics based interpretation of tool workpiece Interface Temperature signals for detection of defect formation during friction stir welding
    Manufacturing letters, 2015
    Co-Authors: Amber Shrivastava, Michael R Zinn, Clemens Dingler, Frank E Pfefferkorn
    Abstract:

    Abstract The objective of the work is the reduction and eventual avoidance of post welding inspections that are currently needed to ensure defect-free welds. An analytical thermal model of the FSW process along with an analytical disturbance model is developed. This disturbance model relates defect formation to variations in the measured Temperature and is based on experimental process identification. A dynamic disturbance observer computes an estimate of the disturbance signal, which is further processed in order to provide information about the presence of defects along the weld. Experiments for one kind of disturbance verify that the observer shows good tracking behavior.

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