利用激光-电磁超声检测钛钢复合板脱粘

Debonding Detection of Titanium Clad Steel Plate Using Laser-electromagnetic Ultrasound

结合面质量直接影响钛钢复合板的整体强度。为有效评估粘接性能,提出了脱粘缺陷的激光-电磁超声非接触式检测方案。基于激光超声激励原理,纵波声场指向性以及电磁超声接收理论,搭建了钛钢复合板脱粘缺陷检测系统。在基材侧或复材侧,使用长度10mm、宽度0.2mm的脉冲激光线状光斑辐照于材料表面激励超声波,利用中心频率1MHz的电磁超声纵波换能器在异侧对心处接收信号。探讨了主声束和换能器相对脱粘缺陷移动过程中信号幅值的变化规律,根据试验数据可知,随着换能器被缺陷遮挡长度的增加,信号幅值逐渐降低。当主声束和换能器被遮挡一半时,信号幅值降为粘接良好状态下的0.5倍。因此,可依据信号幅值的变化特征来判定脱粘缺陷,同时也说明了激光-电磁超声技术适用于钛钢复合板结合面的非接触式检测。

Titanium clad steel plate has been widely used because of the excellent corrosion resistance of Ti and the low cost of constituent material,but the quality of the bonding surface directly affects its overall strength.Therefore,an effective nondestructive testing method is needed to detect the debonding.The use of non-contact ultrasonic techniques can have distinct advantages over conventional contact methods,allowing more rapid and practical scanning without suffering from variations introduced by an acoustic couplant.In this paper,a laser-electromagnetic ultrasonic detection method for debonding defects is proposed to evaluate the bonding performance.A linear light spot with a length of 10mm and a width of 0.2mm irradiates the material to produce spattering material.Longitudinal waves are generated in a sample by means of the splash recoil,and they are obscured by debonding defects.Thus,the amplitude of the signal received by the electromagnetic ultrasonic transducer(EMAT)with center frequency of 1MHz at the opposite side is attenuated,and the amplitude decreases with the increase of occlusion length.Especially,when the amplitude attenuation is half of the reference value,the defect boundary is on the line between the spot center and the transducer center.According to the change law of signal amplitude,the defect boundaries and its area can be determined.Theoretical analysis and debonding measurement experiments show that the non-contact laser electromagnetic ultrasonic method can be used as an effective detection technology for debonding defects of titanium clad steel plate.