Steel Stress Measurement Using an Orthogonal LC Resonance Sensor and Chip-Based Frequency and Impedance System

Stress measurement in steel materials is important for structural integrity determination, failure prediction and preventative maintenance. This paper proposed an orthogonal inductor-capacitor (LC) resonance sensor, combined with the miniaturized inductance-to-digital converter (LDC) system, to measure the stress of ferromagnetic materials. The orthogonal LC resonance sensor consisted of a vertical and transverse LC resonance sensor. A carbon steel specimen was loaded and unloaded using a tensile testing machine to test the performance of the proposed sensor and measurement system. Results indicated the vertical LC sensor outperformed the transverse one with minimal hysteresis since the loading direction was parallel with the vertical LC sensor. Both LC resonance sensors exhibited the stress measurement capability at a lift-off of 1.5 mm. The proposed sensor and the measurement system are highly effective for stress measurement in ferromagnetic materials, offering benefits of cost, portability, and miniaturization.