EVALUATION OF STRESS IN STEEL STRUCTURES USING ELECTROMAGNETIC METHODS BASED ON UTILIZATION OF MICROSTRIP ANTENNA SENSOR AND MONITORING OF AC MAGNETIZATION PROCESS

In this paper the results of utilization of  electromagnetic methods operating in low and high frequency range for evaluation of stress state  and plastic deformation in steel elements are presented. In low frequency range Barkhausen noise and magnetic hysteresis loop method for evaluation of stress level and growth of plastic deformation changes were utilized.  The methods allow to monitor parameters related to magnetization process under AC filed. Additionally in this paper the possibility of utilization of high frequency method for estimation of deformation extent (i.e. elongation) caused by stress will be presented. In this experiment the frequency response (the reflection coefficient S₁₁) is measured. The strong relation of antennas resonant frequency to patch dimensions is utilized in order to obtain information about deformation of the sample.