​The testing methods of conductivity

The testing methods of conductivity 

According to Boeing’s specification,if making sure that whether  the conductivity of some parts on the plane is changed, we    should check visually at first，observe whether its surface has  

Thermal damage trace,such as the colour has changed ,lacquer   layer ablation and other external characteristic ,so as to make sure the area where conductivity need to be detected。Before  detecting ,we should be prepared:polish the skin needling in    this area and wipe off destroyed loose paint lawyer ,greasy dirt ,and aquaseal,so as to make sure the detecting probe of conductivity meter is touching detected surface well,and make testing  value more accurate 。

1.the equipment and accessories:according to Boeing NDT manual requirements ,the frequency of operating instrument is in     range of KHz,accuracy requirement is ≤0.5%IACS the probe is matched with instrument 。

test specimen:according to Boeing manual and BAC5946         requirements ,the test specimen is needed ,and conductivity   nominal value is 16±3%IACS、29±3%IACS、42±3%IACS respectively 。The range is conductivity range of alloy material on        producing plane in England。

2. Instrument calibration ,when doing calibration ,the instrument and probe as well as test specimen and under test are are in  the same environment temperature level,we use two reference   block (a conductivity nominal value of test specimen is more    than under detect accessories or regional  IACS value )，another  conductivity nominal value of test specimen is lower than       under detect accessories or regional IACS value)。Boeing NDT manual recommends that most of conductivity range of aluminum alloy material is 29≈42%IACS。According to conductivity equipment operating manual then adjust instrument well and calibrate  instrument refer to the NDT standard:choose the frequency which is match with the probe (some instrument is automatically identify probe) if there is no automatic regulating function ,then need a non conductive film which thickness is the same as detected area  surface non conductive lawyer thickness,Boeing specification requires that when calibrating ,the difference between the value of instrument on the test specimen conductivity and the  nominal value of test specimen is lower than 0.5%IACS。

Testing steps

A.Put probe on the surface of no thermal damage area to test a base value。If there are different shapes in detecting area,then we should test relative base value in different shapes。

B.Put the probe on the surface middle position where is thought as thermal damage area to test the conductivity value。        According to NDT manual requirements ,and compare tested    conductivity with relative base value,if more than of equal to 1%IACS,then this place has thermal damage,no matter it is accepted or not。

C.If it is just need to test certain area conductivity value，then  compare Testing value with nominal value given by NDT or BAC standard and conclude the report on whether exceed given range to relative department。

D.4.marking boundary of good area and thermal damage area