Research on Fixture's Effect on Properties of Single-Shear Bolt Jointed Composite Laminates Structure

The testing on the bearing strength of single-shear bolt jointed composite laminates structure is done.And the effect of the fixture on the testing results is analyzed. Then a macro-micro multi-scale analytical model combined with the improved"Generalized Method of Cells( GMC) "is developed,which is used to predict the macro bearing strength and to characterize the micro constitute material failure of the bolt jointed composite laminates structure. Both the contact conditions at the bolt/hole boundary and the contact conditions at the specimen/fixture boundary,progressive damage,and the material properties degradation are all taken account into the analytical model. Thus,the numerical simulation results agree well with the experimental results.Finally,the effect of the fixture on the testing results is characterized. The results show that the incomplete contaction between the fixture and the specimen or the lack of the lateral constraint on the specimen will affect the limited bearing strength and the offset bearing strength of the bolt jointed composite laminates structure. In addition,the lower support rigid of the fixture will affect the rigid of the bolt jointed composite laminates structure.

RELIABILITY OF TEST LANDS TARGETING IN BED-OF-NAILS STYLE TEST FIXTURE

A systematic, accurate and robust evaluating method for fine pitch printed circuit board （PCB） positioning assessment in testing fixture is developed. Targeting reliability of bed-of-nails tester is successfully evaluated by the 2D pattern transform. Probe offset vector with its Weibull and Gaussian distribution estimates are obtained for further investigation about the causes of misalignment on the basis of a batch tests for same kind of PCBs.

A thru-reflect-line calibration for measuring the characteristics of high power LDMOS transistors

The impedance and output power measurements of LDMOS transistors are always a problem due to their low impedance and lead widths.An improved thru-reflect-line(TRL) calibration algorithm for measuring the characteristics of L-band high power LDMOS transistors is presented.According to the TRL algorithm,the individual two-port S parameters of each fixture half can be obtained.By de-embedding these S parameters of the test fixture,an accurate calibration can be made.The improved TRL calibration algorithm is successfully utilized to measure the characteristics of an L-band LDMOS transistor with a 90 mm gate width.The impedance of the transistor is obtained,and output power at 1 dB compression point can reach as much as 109.4 W at 1.2 GHz, achieving 1.2 W/mm power density.From the results,it is seen that the presented TRL calibration algorithm works well.