Application of a combined metal magnetic memory–magnetic Barkhausen noise technique for on-site detection of the stress-free temperature of a continuous welded rail

A change in the actual stress-free temperature of a continuous welded rail (CWR) has a major influence on its strength and stability. Therefore, it is necessary to appropriately select the stress-free temperature in each region when laying CWR. However, due to the difficulty of performing nondestructive testing, the possible application of a combined metal magnetic memory-magnetic Barkhausen noise (MMM-MBN) technique is explored in this paper and its features, such as hardware circuit, control algorithm and control system, are investigated. Also, a stability model and its associated formula for CWR are established. Additionally, formulas for the stress-free temperature of CWR and methods for its on-site detection and implementation are established based on the thermal stress and the temperature of the CWR. A support vector machine algorithm is used to calculate the thermal stress in a CWR, and the value detected using an in-house built measurement system is compared with the theoretically calculated value; a relative error of less than 4.78% is obtained.