Papers by Keyword: Shock

Abstract: We have studied spallation in single crystal of metals under shock at very high strain rate. Our work has been devoted to understanding, and predicting the dynamic ductile damage processes of nucleation, growth and coalescence of voids in these extreme conditions of impact. Recovered sample only indicates final state of damage. Molecular Dynamics calculations are predicting the phenomenon over time. However we need experimental results to validate and improve simulations and models. X-ray tomography analyses are appropriate to extract pore volume distributions. Our study on ductile materials allowed us to conclude that experimental analyses exhibit two power laws attributed to growth and coalescence regimes. Moreover power law is scale invariance so it is possible to compare experiment (macroscopic) to calculation (microscopic). We show that there are good correlations between experimental and Molecular Dynamics pore volume distribution. Thanks X-ray microtomographies findings we progress in understanding the phenomenon of dynamic damage.

Abstract: In blast field test, strong mechanical shock and vibration affect the output of blast pressure sensors. To avoid this phenomenon, a pressure sensor vibration reduction installation structure was designed for the measurements of ground reflection pressure. The damping material was used in the installation structure. And certain blast field test had been carried out. The data from the field blast test was compared to transducers with vibration reduction and transducers without vibration reduction. The results show that the obvious effect of the vibration reduction can eliminate vibration interference. And it is suitable for the measurements of shock wave over-pressure in blast field test.

Abstract: By destructive car tests are used acceleration sensors for the determination of a time courses of kinematic variables. The main task is to determine the velocity of measured points of selected objects. The fundamental problem in the solution of this problem is the fact that the acceleration sensor simultaneously record two mechanical movements. One of them is the movement of the object as a rigid body and the other is damped vibration of the object itself as a flexible body which is characterized by its dynamic parameters.

Abstract: The important part of the validation and certification of the new product are vibration and shock testing of mechanical, electrical and electronic equipment components that are mounted on rail vehicles. The hydraulic shaker is possible to use as the vibration and shock exciter to simulate the effect of the environment to the specimen. It is necessary to fulfil the prescribe condition of the level of mechanical vibration and the acceleration peak of the shock test signals. The specific hydraulic motor produced by INOVA is designed for the specific vibration test and the aim is to use it also for the shock tests. The control algorithm uses two iteration methods in time and frequency domain and their use depends on test prescription.

Abstract: Solving gear meshing impact force problems by using ADAMS software is studied.A pair of tooth meshing model is established based on UG, modal neutral file is generated by using ANSYS software, calculating gear meshing impact after Importing ADAMS. The relationship between the impact velocity and the impact force by taking reasonable key parameter about penetration depth in ADAMS simulation.A new approach for studying gear meshing impact is proposed here, and the simulation results show that ADAMS software is a very useful tool for solving gear corner contact shock problems outside the normal path of action line.

Abstract: Horizontal shock testing table can be used to evaluate shock resistance ability of warship equipments. Based on this theory, the level of flexible plate oriented shock testing platform is raised. Using the finite element method, the output waveform of the testing platform and the stress distribution of the flexible plate are analyzed in this paper. It can be concluded that flexible plate can be used to store elastic potential energy during the impact and have a certain impact on test waveforms. Theoretical maximum displacement of the platform body is 94mm, the calculated value is 89.5mm, decrease by 4. 8%; theoretical maximum speed of the platform body is 4m/s, the calculated value is 3.93m/s, reducing to1.75%; theoretical, the value of positive wave peak acceleration of platform body is 571m/s², the calculated value is 532 m/s², decrease by 6.8%; theoretical platform body negative wave peak acceleration values is 175m/s², the calculated value of 183 m/s2, an increase of 4.6%. The research shows that flexible plate as a guide device can meet the impact test table for error waveform requirements..

Abstract: The dithered ring laser gyro (DRLG) strapdown inertial navigation system (SINS) is widely used in many applications, including military and commercial systems for the advantages such as high accuracy, wide dynamic range and bandwidth, outstanding scale factor stability over temperature, compactness and lower cost. However, the dither motion introduced to eliminate the lock-in error which is the inherent phenomena in the ring laser gyro also brought the adverse disturbance to the inertial measurement unit (IMU). Meanwhile, the installation environment of the SINS may also bring undesirable vibration and shock. For these reasons, a feasible and reliable suspension system is required to provide decoupling of the translational and rotational vibrations of the inertial sensor assembly (ISA) and attenuating the outside vibration and shock. Based on this, the isotropic design method of suspension system of DRLG strapdown IMU is proposed in this paper. The method consists four principles: 1) the input axes of sensors should be placed symmetrically along the ISA symmetric axes which are also the principle inertial axes; 2) the mass center of ISA is also the center of the geometric structure; 3) the elastic center of the suspension system is overlapped on the mass center by placing mounting isolators in the ISA structure corner in the isotropic manner and 4) the first mode frequency of ISA structure should be twice or more higher than the maxim mechanical dither frequency of DRLG triad. Following these principles, a design practice is implemented. The simulation and the experiment result show that the IMU using isotropic design method is proved to be feasible and reliable even in the extreme temperature ambiance.

Abstract: In the article, the study focus on the computer aid finite element analysis of the rolled-steel pallet. The value of various parameters is determined by the force analysis according to the relevant standard in working condition of shock. Meshing the modal and defining the force and constraint are discussed before the simulation. The calculated value based on Ansys is very similar to the result in the actual situation, which proved that the computer aid analysis can be used in the rolled-steel pallet detection in order to decrease the cost and increase the accuracy.

Abstract: Supersonic swirling separator has been developed for natural gas dehydration in recent years. Compared to Twister-I supersonic swirling separator, Twister-II type overcomes the disadvantage of uncontrolled shock and the steady swirling flow field contributes to high efficiency of gas-liquid separation. The design method is discussed. For the Laval nozzle, the contraction section is designed by double cubic curve method, while the method for expansion section is tapered tube method the same as the divergent tube, throat is smooth circular arc; the length of straight swirling pipe section for separation is 3-8 times of the diameter. The paper simulates the applicability of the supersonic swirling separator by Fluent. Studies have shown that the lower environmental temperature, the lower the outlet temperature, the easier water to cool, and the higher the separation efficiency. If the volume flow rate rises, the inlet velocity and the mass flow rate can be effectively improved. We can control the shock location by adjusting the pressure at the outlet of divergent pipe. The shock appears at the inlet in the working condition designed. When the outlet pressure is lower, the shock occurs in divergent tube; on the opposite, it moves forward. Beyond a certain degree, shock occurs at the Laval nozzle, the device fails to work.

Abstract: The effect of inner nozzle lip thickness on the co-flow jet characteristics has been studied experimentally. Co-flow nozzles with inner nozzle lip thicknesses of 3 mm and 15 mm have been investigated. The thick-lip nozzle promotes mixing better than the thin-lip nozzle, for all the underexpanded operating conditions. The co-flow nozzle with thin-lip is effective in preserving the shock-cells nature, bringing down the longer shock-cell into shorter one and increasing the number of shock-cells compared to that of the co-flow nozzle with thick-lip.