A slow strain rate tensile (SSRT) test was used to investigate the effect of laser shock peening (LSP) on stress corrosion cracking (SCC) behavior of the 304 austenitic stainless steels (ASSs) in acid chloride solution. Mechanical properties and fracture morphology evolutions of the 304 ASSs were studied as a function of the pulse energies through slow speed tensile tester and scanning electron microscopy (SEM). The results showed that the percentage elongation after fracture increased significantly as the pulse energy rose. Fractographic examination revealed that all the samples appeared a tendency to SCC in the given conditions, but specimens treated by LSP had better resistance to stress corrosion.
The basic principles for stabilized gyrocompass initial alignment are analyzed in platform inertial navigation system (PINS), then similar principles and initial alignment algorithms suitable for programming are proposed for strapdown inertial navigation system (SINS). The scheme of SINS gyrocompass initial alignment can be divided into four steps, including leveling alignment with header uncertainty, coarse header alignment, leveling realignment and gyrocompass alignment for header. By simplifying SINS nonlinear error model under header uncertainty, the formula of coarse header alignment is deduced. On the assumption of navigation computer having large memory and powerful computing ability, and basing on the ‘multiformity’ of SINS mathematical platform and the ability to attitude reverse control, a specific progress for SINS rapid gyrocompass alignment is introduced and designed in detail. Finally, some tests prove that the proposed alignment algorithm in this paper is effective.
As aviation technology continues to evolve, the function and safety of a large maneuvering have been required highly. As a large maneuvering system is becoming more and more complex , the trajectory design and simulation of a large maneuvering have become an important mean to ensure the mobile flight safety and design. The main focus of this research is to analyze the accuracy of the strapdown navigation algorithm and its impact in large motorized sport state by the large maneuvering trajectory design and its inertial system simulation. The authors build the model of the maneuvering trajectory by the Matlab program which is based on the design principle of the maneuvering flight path. Then, by using some coordinate system and the classical strapdown algorithm, specially attitude updating algorithm, the location update algorithm and the velocity update algorithm, the designed maneuvering trajectory model has been simulated and the simulation results are analyzed.
The magnetic flux leakage (MFL) testing, as a modern nondestructive testing technology, requires fast and accurate signal progressing methods. A practical signal progressing method for MFL testing was presented, especially for tank floor MFL testing. According to the FFT result of the original signal, a difference amplifier and a low-pass filter were designed in the hardware signal progressing. In the digital signal progressing, a numerical differential progress and an IIR band-pass filter were adopted. Experimental results show that the presented method could effectively eliminate noise. Defect depth measuring results show that, for the 8 mm thickness specimen, the maximum absolute error of depth is 0.23 mm, which means 2.8 % of the 8 mm thickness.
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