METHOD FOR INSPECTING INNER SURFACE OF TUBULAR BODY

PROBLEM TO BE SOLVED: To provide a method capable of detecting fine unevenness on an inner surface of a tubular body made of stainless steel.SOLUTION: The method includes: a first step of arranging an ultrasonic probe 1 opposite to an outer surface of a tubular body P made of stainless steel; a second step of relatively moving the ultrasonic probe 1 along a circumferential direction of the tubular body P, transmitting an ultrasonic wave from the ultrasonic probe 1 almost perpendicularly to an inner surface of the tubular body P, and obtaining intensity distribution of a bottom surface echo signal in the circumferential direction of the tubular body P; a third step of performing differential processing on the intensity distribution of the bottom surface echo signal in the circumferential direction of the tubular body P so as to obtain differential intensity distribution of the bottom surface echo signal; a fourth step of repeatedly performing the second and third steps while relatively moving the ultrasonic probe 1 along an axial direction of the tubular body P so as to obtain differential intensity distribution of a plurality of bottom surface echo signals along the axial direction of the tubular body P; and a fifth step of detecting unevenness on the inner surface of the tubular body P on the basis of a statistical value obtained by performing statistical processing on the differential intensity distribution of the plurality of bottom surface echo signals.SELECTED DRAWING: Figure 1 【課題】ステンレス鋼製の管状体の内面の微小な凹凸を検出可能な方法を提供する。【解決手段】本発明は、ステンレス鋼製の管状体Ｐの外面に対向して超音波探触子１を配置する第１ステップ、超音波探触子を管状体の周方向に沿って相対的に移動させると共に、超音波探触子から管状体の内面に対して略垂直に超音波を送信し、管状体の周方向についての底面エコー信号の強度分布を取得する第２ステップ、底面エコー信号の強度分布に管状体の周方向の微分処理を施して、底面エコー信号の微分強度分布を取得する第３ステップ、超音波探触子を管状体の軸方向に沿って相対的に移動させて第２ステップ及び第３ステップを繰り返し実行することで、管状体の軸方向に沿って複数の底面エコー信号の微分強度分布を取得する第４ステップ、複数の底面エコー信号の微分強度分布に統計処理を施して得られた統計値の大小に基づき管状体の内面の凹凸を検出する第５ステップ、を含む。【選択図】 図１