A holographic measurement of microscopical sliding of electrical contact due to contact spring thermal deformation

Contact spring deflection occurs with environmental temperature change or Joule heating due to current flow, causing a microscopic slide of the contact point and sometimes so-called fretting corrosion. To analyze the microscopic deformation due to thermal stress, a holographic pattern measuring system (HPMS) that combines holography and graphic image processing has been developed for measuring the contact point displacement in a noncontact way. The HPMS was applied to a thermally deformed contact spring, and the distribution was shown automatically as a three-dimensional graphic image. For an electric contact thermally excited by current flow, a quantitative correlation between the slide of the contact point and the thermal deformation of the spring was obtained, and some irregularity in contact voltage was found. From the deformation analysis the relationship between the contact voltage and the deformation of the spring due to current flow was made clear