Monitoring weld parameters and data representing weld resistance curve

摘要

Melting in a resistance spot weld is detected by monitoring the weld resistance R and the electrical power P supplied to the weld. The change in the resistance R is calculated and is divided by the electrical power to obtain a time varying function R/P which represents the inverse specific heat of the weld. The max. value of R/P representing the inverse specific heat for the weld at low temp. is searched for together with a value of R/P subsequent to its maximum to determine when R/P reaches an empirically determined fraction of the max value which occurs upon an increase of specific heat accompanying the start of melting.