Double Pulse Low-Frequency Modulation for High-Power Double-Wire Pulsed GMAW

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Kaiyuan Wu ◽  
Zhuoyong Liang ◽  
Tong Yin ◽  
Zuwei He ◽  
Min Zeng
Keyword(s):  
High Power ◽  
Frequency Modulation ◽  
Heat Input ◽  
Energy Input ◽  
Modulation Frequency ◽  
Low Frequency ◽  
Double Pulse ◽  
Weld Quality ◽  
Weld Width ◽  
Input Control

A double pulse low-frequency modulation method was proposed to improve heat input control and enhance weld quality during high-power double-wire pulsed gas metal arc welding (GMAW). By constructing a mathematical model, relationships between parameters of double pulse low-frequency modulation and energy input were analyzed. A correction coefficient was added to overcome physical characteristics of charging and discharging in a welding circuit. Thus, qualitative relationships between parameters of double pulse low-frequency modulation and energy input were described more accurately. Bead-on-plate welding experiments were conducted in a synchronous phase mode. A stable welding process was achieved and perfect weld bead shapes were acquired. Modulation frequency imposed a significant effect on both weld width and penetration, while modulation duty cycle had a significant effect on penetration and little effect on weld width. Modulation frequency significantly influenced refinement of grain size. Weak and strong pulses of low-frequency modulation improved heat input control, strengthened stirring action of double pulse on weld pool, and enhanced fluidity of molten metals, thereby contributing to optimization of weld quality.

scholarly journals Influence of Duty Ratio and Current Mode on Robot 316L Stainless Steel Arc Additive Manufacturing

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 508
Author(s):  
Ping Yao ◽  
Hongyan Lin ◽  
Wei Wu ◽  
Heqing Tang
Keyword(s):  
Stainless Steel ◽  
Additive Manufacturing ◽  
Heat Input ◽  
Low Frequency ◽  
Single Pulse ◽  
Pulse Mode ◽  
Double Pulse ◽  
Duty Ratio ◽  
Utilization Rate ◽  
Specimen Height

Wire and arc additive manufacturing (WAAM) is usually for fabricating components due to its low equipment cost, high material utilization rate and cladding efficiency. However, its applications are limited by the large heat input decided by process parameters. Here, four 50-layer stainless steel parts with double-pulse and single-pulse metal inert gas (MIG) welding modes were deposited, and the effect of different duty ratios and current modes on morphology, microstructure, and performance was analyzed. The results demonstrate that the low frequency of the double-pulse had the effect of stirring the molten pool; therefore, the double-pulse mode parts presented a bigger width and smaller height, finer microstructure and better properties than the single-pulse mode. Furthermore, increasing the duty ratio from 35% to 65% enlarged the heat input, which then decreased the specimen height, increased the width, and decreased the hardness and the tensile strength.

Vocal Tremor Analysis With the Vocal Demodulator

1992 ◽  
Vol 35 (3) ◽  
pp. 562-573 ◽  
Author(s):  
William S. Winholtz ◽  
Lorraine Olson Ramig
Keyword(s):  
Amplitude Modulation ◽  
Frequency Modulation ◽  
Acoustic Analysis ◽  
Modulation Frequency ◽  
Low Frequency ◽  
New Device ◽  
Voice Signal ◽  
Vocal Tremor ◽  
Frequency Demodulation ◽  
Modulation Level

Acoustic analysis of vocal tremor has the potential to make significant quantitative and diagnostic contributions to the study of vocal disorders. This paper presents a new device for analysis of vocal tremor. The Vocal Demodulator produces amplitude- and frequency-demodulated outputs and measures the frequency and level (percent) of low-frequency tremor components in sustained phonation. A standard microphone is used to transduce the voice signal for input to the demodulator. The input fundamental frequency (F o ) range is 70–1200 Hz, and frequency response of the amplitude and frequency demodulation is 2.5–25 Hz. Five parameters are displayed in real time: F o , amplitude-modulation frequency, amplitude-modulation level, frequency-modulation frequency, and frequency-modulation level. Validation, calibration, and reliability data from synthesized test signals with modulation, as well as phonation from subjects with vocal tremor, subjects producing vibrato, and subjects with normal voice are presented. Research and clinical applications of this device are suggested.

scholarly journals Stability and Heat Input Controllability of Two Different Modulations for Double-Pulse MIG Welding

2019 ◽  
Vol 9 (1) ◽  
pp. 127 ◽  
Author(s):  
Jiaxiang Xue ◽  
Min Xu ◽  
Wenjin Huang ◽  
Zhanhui Zhang ◽  
Wei Wu ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Heat Input ◽  
Double Pulse ◽  
Fish Scale ◽  
Input Energy ◽  
Mig Welding ◽  
Pulse Modulation ◽  
Welding Arc ◽  
Input Control ◽  
Welding Processes

Aluminum alloy welding frequently experiences difficulties such as heat input control, poor weld formation, and susceptibility to pore generation. We compared the use of two different modulations for double-pulse metal inert gas (MIG) welding to reduce the heat input required to generate oscillations in the weld pool. The stabilities of rectangular wave-modulated and trapezoidal wave-modulated double-pulse MIG welding (DP-MIG and TP-MIG) were analyzed by examining their welding processes and weld profiles. We found that the transitional pulse in TP-MIG welding results in smoother current transitions, softer welding arc sounds, and a highly uniform fish-scale pattern. Therefore, TP-MIG welding is more stable than DP-MIG welding. The effects of these double-pulse modulation schemes on welding input energy are presented. We propose methods for reducing welding input energy by varying the number of pulses or the pulse base time of low-energy pulse train while keeping the welding current and welding arc stable and unchanged. Compared to DP-MIG welding, TP-MIG welding reduces the input energy by 12% and produces finer grain sizes, which increases weld hardness. Therefore, TP-MIG welding offers a new approach for heat input control in DP-MIG welding of aluminum alloys. The results of this work are significant for aluminum alloy welding.

scholarly journals A Systematic Study on the Harmonic Overlap Effects for DC/AC Converters under Low Switching Frequency Modulation

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2811
Author(s):  
Ze Wang ◽  
Zhen He ◽  
Chao Gao
Keyword(s):  
High Power ◽  
Frequency Modulation ◽  
Heat Dissipation ◽  
Pulse Width Modulation ◽  
Low Frequency ◽  
Industrial Applications ◽  
Voltage Source ◽  
Switching Frequency ◽  
Ac Converters ◽  
Power Capability

In most high power industrial applications, the low switching frequency modulations (LSFM) are usually implemented to reduce power loss and heat dissipation pressure. However, there are some unexpected influences caused by the low order harmonic sinusoidal pulse width modulation (SPWM), such as the imbalanced submodule power in cascaded half-bridge inverter (CHB) and limited output power capability in H-bridge neutral-point-clamped (HNPC) converter. This paper starts by generalizing the basic characteristic of two-level SPWM, then deeply investigates the influences of low-frequency modulation on the operation of the circuits. They are classified into three mechanisms and generally named as harmonic overlap effect (HOE). The corresponding solutions to copy with the mechanisms are proposed and verified in some topologies through high-power simulations in simulations. In addition, a comprehensive summary of the influences and solutions of these effects on typical high power converters is drawn. The design rules of the modulation schemes for multilevel voltage source converters (VSCs) at low switching frequency are also proposed.

Quantitative FM Spectroscopy at High Temperatures: The Detection of 1CH2 behind Shock Waves

2000 ◽  
Vol 214 (12) ◽  
Author(s):  
G. Friedrichs ◽  
H.Gg. Wagner
Keyword(s):  
High Temperature ◽  
Shock Waves ◽  
High Temperatures ◽  
Frequency Modulation ◽  
Modulation Frequency ◽  
Optical Power ◽  
Time Resolved ◽  
Signal Conversion ◽  
High Modulation ◽  
Singlet Methylene

The technique of time resolved frequency modulation (FM) spectroscopy has been shown to provide a very sensitive means to detect small radicals behind shock waves. Features of high temperature FM spectroscopy behind shock waves will be discussed and a general signal conversion procedure to carry out quantitative concentration measurements will be presented.Using a high modulation frequency, a high modulation index and high total optical power, singlet methylene radicals (α

Heating and low-frequency modulation of electrons observed during electron beam operations on TSS 1

1997 ◽  
Vol 102 (A8) ◽  
pp. 17335-17357 ◽  
Author(s):  
M. P. Gough ◽  
D. A. Hardy ◽  
W. J. Burke ◽  
M. R. Oberhardt ◽  
L. C. Gentile ◽  
...  
Keyword(s):  
Electron Beam ◽  
Frequency Modulation ◽  
Low Frequency
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