Recent Developments in ARCMAC and Related Creep Strain Monitoring Techniques

Abstract

Developments have been made to E.ON’s Auto-Reference Creep Management and Control (ARCMAC) system to measure strain at high temperature using both Digital Image Correlation (DIC) and conventional ARCMAC techniques. These techniques are aimed at measuring creep strain rate in power plant steam pipes and associated weldments operating at high temperatures and pressures for the purposes of estimation of remaining life of such components. The ARCMAC optical strain measurement system is used to measure point to point strain through the capture and analysis of images of a pair of Inconel gauges, with Silicon Nitride spheres, welded to steam pipe and other components. A modified ARCMAC image capture system has been developed using a DSLR camera, with higher resolution offering the potential to capture DIC images suitable for measuring strain accurately. Development of the system to measure strain using both ARCMAC gauges and DIC at high temperature offers the potential to obtain full-field strain measurement across features such as welds, giving a useful improved research tool for creep evaluation. The recently developed DSLR-ARCMAC camera system has been optimised to measure strain using a number of optical strain measurement techniques, including the ARCMAC strain measurement procedure and DIC. These techniques have been used to measure strain during room temperature tensile tests prior to their use at high temperatures. Following these experiments, creep testing of CMV steel specimens is planned paying particular attention to the evaluation of the ARCMAC system at high temperatures.