摘要 :
This is the Final Engineering Report on Phase 2.2 work on the ultrasonic subsystem for the trend inspection station for printed circuit board solder joints. The report discusses activities during this contract period in six major ...
展开
This is the Final Engineering Report on Phase 2.2 work on the ultrasonic subsystem for the trend inspection station for printed circuit board solder joints. The report discusses activities during this contract period in six major areas. Probe assemblies have been refined by redesigning both receiver and transmitter to permit closer spacing of these probes for inspection of small joints. In addition, transmitter design has resulted in a new style probe. Based in part on the characteristics of ultrasonic spectra of the solder joint types of interest, and in part on the mental processes used in visual evaluation of joint spectra to make a judgment on joint quality, several algorithms have been investigated for computerizing the decision making process. A simple but effective algorithm has been devised for use with the latest probe set in inspecting good lap solder joints and those with heel cracks. A probe manipulator for the pilot model of the ultrasonic subsystem was designed and constructed during this contract period. It was used in some of the later experimentation in this period directed to defining performance capability.
收起
摘要 :
The results of the tests performed in air using the S-135 material indicate that lambda is approximately .98 - .89. This value differs somewhat from that obtained on similar strength steels reported by other investigators, wherein...
展开
The results of the tests performed in air using the S-135 material indicate that lambda is approximately .98 - .89. This value differs somewhat from that obtained on similar strength steels reported by other investigators, wherein values of the order of .65 - .75 are usually shown. It may be that this difference is the result of directional properties of the pipe caused by the method of manufacture. The directional working of the material would result in a favorable grain flow for bending and axial fatigue, and a less favorable grain flow for torsional fatigue. Unfortunately, the size of the pipe from which the specimens were obtained, would make it difficult to obtain specimens of different orientation to verify this hypothesis. The data obtained from the tests in air also indicate that the value of lambda may be only slightly affected by the number of cycles of the test. Other investigators have reported similar results. It would appear that the value of lambda decreases slightly with increasing number of cycles. The tests show that the value of lambda decreases markedly when corrosive conditions are encountered, and also show that the value of lambda decreases slightly with increasing number of cucles. Gough and McAdams attribute the lowering of fatigue strength by corrosion to the pitting and notching effect of corrosion, and the results reported in Reference 1 show that notched tests have lower value of lambda than smooth tests, hence these results are substantially in agreement with previous data. (Author)
收起
