不锈钢复合板(16MnR+314L)是由两种金属材料通过压制构成，用超声波测厚仪难以对其厚度进行测量。利用超声波探伤仪对不锈钢复合板进行了测厚试验，发现该复合板基层与复层之间存在超声波反射波，说明在其两种材料之间会存在少量的杂质(如空气，灰尘等杂质 )。利用超声波在不同材料中传播声速不同的原理，通过测试与换算得出复合板厚度测量的修正公式，最终测量出不锈钢复合板的厚度。

This paper mainly studies how to use the ultrasonic flaw detector for the determination of the thickness of composite plate of stainless steel. Composite plate of stainless steel is often used in structures, and the plate is composed of two different materials, so ultrasonic thickness gauge can not measure its thickness. By analysis of manufacturing process of the composite plate, the author found that there might be some small amounts of impurities (such as air, dust and other impurities) in between the interface of the two materials. In order to confirm that, the author carried out the ultrasonic flaw detector test and found that ultrasonic reflected wave exists at between the basis and complex layer of the composite stainless steel plate ( 16MnR+314L ), proving the correctness of the above-mentioned conclusions. Finally the author uses the principle related with the propagation velocity of ultrasonic wave for different materials to draw thickness correction formula in the measurement of composite plate, and makes an ultimate measure of the thickness of stainless steel composite plate.