The inspection of a gear's pitch deviation is one of the most important tests on gears. The specifications of gears are usually assessed using gear measuring instruments or coordinate measuring machines. The National Metrology Institute of Japan and the Physikalisch-Technische Bundesanstalt proposed the closure technique for measuring gear pitch deviation, which can eliminate the systematic errors in pitch measurement, and can also be used for calibrating pitch standards. The reference to a closure technique—a kind of multi-step method for measuring pitch deviation—is introduced, of which the measurement process is relatively simple, and systematic errors can also be eliminated. Two gears’ pitch deviations were measured by adopting the closure technique and multi-step method, respectively. The result shows that the multi-step method can also be used for highly accurate measurements of pitch deviation.
In order to study the critical ricochet velocity and critical penetration velocity of tungsten alloy rod obliquely penetrating a finite-thickness metal plate, experiment and numerical calculation of tungsten alloy rod impacting on homogeneous armor steel plate with a thickness of 30mm at an angle of 60° were carried out. Compared the experimental and numerical results with the results using models, it is found that, the results of the ricochet models proposed by Tate, Rosenberg and Steven B for semi-infinite thick plate are quite different from those of experiment and numerical calculation, so they can not be applied to the ricochet situation of finite-thickness plate. The critical penetration velocity model proposed by De Marre and Zhao are in good agreement with the numerical and experimental results, which can predict critical penetration velocity of tungsten alloy rod obliquely penetrating a finite-thickness metal plate with large impact angle. The penetration depth of the projectile under the critical ricochet velocity is about 1/3 of the thickness of the target plate, and the angle between the ejection trajectory of the fragments produced by projectile and target plate and projectile penetration trajectory is exactly 90° in the first penetration stage.
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