Measurement of heat input in complex wave form welding

Abstract

Heat input is an essential variable in many codes and industry specifications due to the relationship between heat input and the mechanical properties of a weldment. However, the current and voltage values displayed by many welding power sources or traditional hand-held meters often do not reflect the energy input to a weld with pulsing or other modern welding waveforms.Modern welding waveforms are often not symmetric. They operate on inductive loads, contain high frequency harmonics and are not repetitive. Traditional methods of calculating heat input involve the measuring of either average or RMS voltage and average or RMS current. While traditional methods produce relatively consistent results with high energy processes, such as traditional spray arc, the results become less consistent or accurate with short arc and pulse modes due to the continually changing output of the machine.This work identifies modern waveforms and describes the means for accurately measuring the energy input into a weld. This measurement system lays a foundation which code bodies may use to enable a continued correlation between heat input and the mechanical properties of a weldment, and suggests a method that allows previously qualified procedures to use this measurement system.