Non-destructive inspection method and apparatus for through holes

Abstract

A non-destructive inspection method and apparatus are provided for inspecting for defects in through-holes. The non-destructive inspection apparatus for through-holes includes: a heated laser 1 that emits periodically heated laser light with sinusoidal intensity variation to a measuring unit 12 directly above the through-hole 11; a laser intensity detection means that detects the intensity of the periodically heated laser light in the measuring unit 12; an infrared sensor 6 that detects the intensity of the sinusoidally varying emitted infrared light from the measuring unit 12; a phase difference detection means that acquires the detection signal from the laser intensity detection means and the detection signal from the infrared sensor 6, and detects the phase difference between the two; and a defect presence determination mechanism that treats the detected phase difference as the value of the thermal time constant (the product of heat capacity and thermal resistance) in the through-hole 11, and determines the presence of a void when a decrease in heat capacity and an increase in temperature are observed, and determines the presence of a crack when an increase in thermal resistance is observed.

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