Research Of Debonding Flaws Of Multi-layered Interface Bonding Structure Based On The Ultrasonic Testing

Adhesive structure was used in various fields widely due to its many advantages,the bonding structure around the train windows are connected by polyurethane binder,its rim has glass-polyurethane-glass-polyurethane-aluminum structure.Bonding defects were divided into two major categories according to mechanism including produce defect and service defect.The interface debonding defect is the major hidden dangers in operation of the vehicle.Ultrasonic wave impedance,velocity,attenuation and scattering of ultrasonic testing can provide abundant information,considering the particularity of adhesive structure and ultrasonic wave properties are very sensitive,strong penetrating power,high sensitivity and good directivity on the interface bonding,it is the most suitable method for detecting the interface debonding defects.Experiment used the ultrasonic flaw detector,pulse echo method,and oil as a coupling agent.First,summarized ultrasonic testing parameters set rules with not installed windows as exploration object,the results showed that the detection sound velocity general set for the maximum sound velocity of main material;observation scope with characteristics of echo centered advisable can be calculated;gain with a characteristic echo crest reached 80%of the screen was optimum;train window bonding structure detection probe apply to 2.5 P 10.And then,under the condition of reasonable parameters,five kinds of adhesive state of installed windows namely the five-layer structure of were detected,the results showed that 48 mm and 52 mm position has obvious bulge of wave crest when bonding well,96 mm position has obvious crest after increased the gain;when first-interface debond,there was a large number of crest with 8 mm interval and high peak value;there was less crest with 8 mm interval and low peak when second-interface debond;48 mm and 52 mm position has obvious wave crest and the echo peak of 48 mm position reached 80%of the screen when third-interface debond;when fourth-interface debond,48 mm and 52 mm position has obvious wave crest,crest in 96 mm position beyond recognition after increase the gain wave.Experiment used the second-interface echo as a "benchmark",the half-value method and equivalent method were used to analysis on the defect area,the results showed that the half-value method defect appeared high efficiency but low accuracy when defect area is greater than the probe size;equivalent method of first-interface and second-interface was quantitative when defect area less than probe,but poor accurate for third-interface;neither method can quantitative analysis fourth-interface debonding defect.Finally,proposed ultrasonic testing equipment improvement project aimed at adhesive structure.It included functional design,parameter design,main body structure,safety and environmental protection,reliable and durable,appearance design,cost,maintenance and repair.Proposed A type ultrasonic equipment improvement project,including hardware system and software system;and put forward potential problems of equipmen.