Shock Test Machine Research Articles

MECHANISM ANALYSIS AND SIMULATION FOR A NOVEL ANTI-SHOCK TESTING SYSTEM FOR HEAVY-WEIGHT SHIPBOARD EQUIPMENT

In order to improve the shock resistance of shipboard equipment as well as to increase the testing capability of the shock testing system,a novel high-energy hydraulically-actuated anti-shock testing system is proposed.The key techniques to store and release high energy instantly,and to avoid second impacting during shock tests are related with a novel velocity generator.A nonlinear dynamic model of this system is established, which can produce the required shock pulse in a given time duration.Then a numerical simulation about the system is carried out to evaluate the prospective capability of the shock testing machine under different shock velocity inputs.The simulation results show that the shock testing machine proposed in this paper can produce nearly the same shock acceleration waveform as opecified by the new shock resistance standard BV043/85 and MIL-S-901D.Moreover,this shock testing machine can be adjusted conveniently to test different types of equipment and be extended easily to satisfy more severe shock standard and heavier equipment.

Numerical modeling of dual-pulse shock test machine for simulating underwater explosion shock loads on warship equipments

In order to qualify shock resistance performance of shipboard equipments and simulate real underwater explosion environment, a novel dual-pulse shock test machine is proposed. The new machine will increase testing capability and meet special shock testing requirement. Two key parts of the machine, the velocity generator and the shock pulse regulator, play an important role in producing the positive acceleration pulse and the succeeding negative acceleration pulse, respectively. The generated dual-pulse shock for test articles is in conformity with an anti-shock test specification. Based on the impact theory, a nonlinear dynamic model of the hydraulically-actuated test machine is established with thorough analysis on its mechanism that involves conversion of gas potential energy and dissipation of kinetic energy. Simulation results have demonstrated that the proposed machine is able to produce a double-pulse acceleration shock in the time domain or a desired shock response spectrum in the frequency domain, which sets up a base for the construction of the machine.

The Dynamics of Multiple Pair-Wise Collisions in a Chain for Designing Optimal Shock Amplifiers

The major focus of this work is to examine the dynamics of velocity amplification through pair-wise collisions between multiple masses in a chain, in order to develop useful machines. For instance low-cost machines based on this principle could be used for detailed, very-high acceleration shock-testing of MEMS devices. A theoretical basis for determining the number and mass of intermediate stages in such a velocity amplifier, based on simple rigid body mechanics, is proposed. The influence of mass ratios and the coefficient of restitution on the optimisation of the system is identified and investigated. In particular, two cases are examined: in the first, the velocity of the final mass in the chain (that would have the object under test mounted on it) is maximised by defining the ratio of adjacent masses according to a power law relationship; in the second, the energy transfer efficiency of the system is maximised by choosing the mass ratios such that all masses except the final mass come to rest following impact. Comparisons are drawn between both cases and the results are used in proposing design guidelines for optimal shock amplifiers. It is shown that for most practical systems, a shock amplifier with mass ratios based on a power law relationship is optimal and can easily yield velocity amplifications of a factor 5–8 times. A prototype shock testing machine that was made using above principles is briefly introduced.

The Dynamics of Multiple Pair-Wise Collisions in a Chain for Designing Optimal Shock Amplifiers

The major focus of this work is to examine the dynamics of velocity amplification through pair-wise collisions between multiple masses in a chain, in order to develop useful machines. For instance low-cost machines based on this principle could be used for detailed, very-high acceleration shock-testing of MEMS devices. A theoretical basis for determining the number and mass of intermediate stages in such a velocity amplifier, based on simple rigid body mechanics, is proposed. The influence of mass ratios and the coefficient of restitution on the optimisation of the system is identified and investigated. In particular, two cases are examined: in the first, the velocity of the final mass in the chain (that would have the object under test mounted on it) is maximised by defining the ratio of adjacent masses according to a power law relationship; in the second, the energy transfer efficiency of the system is maximised by choosing the mass ratios such that all masses except the final mass come to rest following impact. Comparisons are drawn between both cases and the results are used in proposing design guidelines for optimal shock amplifiers. It is shown that for most practical systems, a shock amplifier with mass ratios based on a power law relationship is optimal and can easily yield velocity amplifications of a factor 5-8 times. A prototype shock testing machine that was made using above principles is briefly introduced.

ANALYSIS AND SIMULATION ON THE MECHANISM OF A NOVEL DUAL-WAVE SHOCK TEST MACHINE

For qualifying the anti-shock performance of shipboard equipments and simulating actual underwater explosion environments,a novel dual-wave shock test machine is proposed to increase testing capability of shock test machines as well as to meet certain shock testing specification. The machine can generate a double-pulse acceleration shock for test articles according to specification defined in BV043/85. On the basis of the impact theory,a nonlinear dynamic model of the hydraulically-actuated test machine is established with thorough analysis on its mechanism which involves conversion of gas potential energy and dissipation of kinetic energy. Simulation results have demonstrated that the machine can produce a double-pulse acceleration shock in the time domain or a desired shock response spectrum in the frequency domain,which sets a theoretical base for the construction of the proposed machine.

Numerical modeling of multicylinder electro-hydraulic system and controller design for shock test machine

高保真度为重重量设备的一台高精力的激活 hydraulically 的吃惊测试机器的动态模型被介绍满足新建的吃惊抵抗标准并且模仿实际在水下在象增加一样的实验室的爆炸环境吃惊的严峻的能力测试机器。为了生产要求的否定吃惊，在给定的时间持续时间搏动，四个水力的致动器被利用。模型然后被用来提出一个先进前馈控制控制器让系统生产要求的否定波形并且探讨四柱体的运动同步。模型提供一只保险箱和执行的容易可控制的方法一“在在标本上并且到开始潜在地破坏的测试前的虚拟测试”预言系统的性能。模拟结果表明了控制器的有效性。

Effects of the Structure of NiP/Al Substrate on Shock Resistance

The effects of the structure of a conventional NiP/Al substrate on shock resistance were investigated. In this study, a 2.5-inch-type hard disk drive with a thin-film 70%-micro-slider head was used. The tested shock was supplied by a pendulum shock-testing machine with a half-sine shock pulse and a duration of l.0 ms. We defined the shock resistance as the maximum acceleration in a shock for which head slap was not formed. The results showed that the shock resistance increased with increasing hardness of the Al alloy and thickness of the NiP underlayer.

Feature article: Realization of Shock Response Spectra On a Mechanical Shock Test Machine

Some kinds of shock response spectra specified in environmental test standards can be realized on a simple mechanical shock test machine. In this paper, the relationship between an acceleration waveform and a shock response spectrum is analyzed, and the effect on the response spectrum of adjusting the stiffness of the test machine cushions Is studied. A series of shock environmental tests with a given response spectrum was carried out successfully on the shock test machine.

Augment railgun and sequential discharge

The electromagnetic acceleration system for a future tactical gun system and a shock testing machine has been studied since 1988. The main themes of the study are improvement in projectile velocity and sequential discharge. For improvement in projectile velocity, an augmented railgun has been developed. Compared with a two-rail railgun, the projectile velocity improved by 27% and the energy efficiency improved by 66% using this augmented railgun. In the sequential discharge, there was a strong interaction between capacitor bank submodules. Thus, it is dangerous to design a capacitor discharge system in the way of adding each submodule current wave form. If a wrong circuit constant is used, there is the possibility of a reverse current in a capacitor submodule.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Comparison of Shock Test Methods of MIL-S-901 Derived from Tests on a Circuit Breaker &amp; Switchboard

For shipboard equipment to qualify as shock-hardened, it must pass a shock test in accordance with the U.S. military shock test specification, MIL-S-901 [1]. The test methods prescribed by MIL-S-901 have gone essentially unchanged since 1963. All equipment is divided into three test categories, depending on weight, and a different shock test machine is specified for each weight category. The heavy weight category is further subdivided depending on the method of mounting within the ship, namely deck mounted or hull mounted. The authors have observed cases when equipment passing MIL-S-901 shock qualification testing using one method (e.g., the medium weight) failed when tested on another method (e.g., the floating shock platform). Concern about this difference in shock phenomena between the approved equipment performance stimulated the authors to perform the testing and analysis presented in this paper. The thirty year old test methods which have contributed significantly to shock survivability may not always simulate adequately the actual shipboard installation during shock qualification testing, thus leading to a false confidence level that all qualified equipment will perform well in combat. To explore the possible variations in shock phenomena from the different methods, an extensive testing program was conducted whereby a 100 ampere circuit breaker was subjected to shock testing under the four methods outlined in MIL-S-901 D, namely, lightweight, medium weight, heavy weight deck, and heavy weight hull. The data gathered during the testing, and the performance of the equipment under test, were both evaluated and analysed to observe differences in shock phenomena from each of the four different test methods. The shock testing methods, the equipment which was subjected to test, the test procedures, and the results of the investigation are described in this paper. The recommendations suggest improvements to the U.S. Navy shock testing methods and procedures.

Design and Control of a High Velocity, High Force Hydraulic Shock Test Machine

This paper discusses the design and control of a large hydraulic shock testing device. The system is capable of peak velocities up to 10.2 m/s (400 in/sec) and peak forces up to 801 kN (180,000 lbs). The major challenges discussed are: 1) the concept design, 2) the specification and procurement of two very large (2500 gpm) electro-hydraulic servovalves and 3) the failsafe control of the servovalves and system response. The system performance is briefly discussed.

The dynamic mechanical response of fiber-reinforced beams to large transverse loads

The paper describes the results of experiments on fiber-reinforced metal beams which have been subjected to dynamic transverse loading. The beams were fabricated by embedding sets of parallel steel wires in a matrix of lead-tin alloy, and were clamped at one end. The transverse dynamic loading was applied to the tip of the beam so that the problem was one of the transverse deformation of a composite cantilever. Two separate techniques were employed to load the specimens, one being to hit the end with a fast moving hammer in a “Hyge” Shock Testing Machine; the other was to detonate an explosive charge in contact with a small projectile close to the tip. The deformations were monitored by a number of different experimental techniques and the final plastic transverse deflection of the tip as well as the final position of the plastic wave front were compared with the theoretical predictions of Spencer, Jones and their co-workers. The agreement was found to be very satisfactory. In making these comparisons strain rate effects in the lead-tin matrix metal had to be allowed for and this was done with the help of a separate set of tests.

Structural response to low‐frequency acoustic excitation

Many noise sources at Army installations are of a low‐frequency (25 to 125 Hz) impulsive nature (e.g., artillery and explosives training, or helicopters). Mitigation of the impacts due to these sources, both on‐ and off‐post, require an understanding of the response of a structure to low‐frequency excitation. Little information is available in the literature for response below about 63 Hz. In order to study the response below this band, a structure of typical residential construction has been erected inside the CERL Bi‐Axial Shock Test Machine (BSTM) building, and extensively instrumented for vibrational and acoustic response. The BSTM has been utilized to produce impulsive acoustic excitation (114 to 130 dB, 25‐ to 40‐ms duration) of the structure. A set of specially designed speakers has been utilized to produce nearly pure tone excitation (90–100 dB, 20 to 125 Hz). Production of the excitation signals and preliminary structural response results are presented.

The History and Development of the High-Impact Shock-Testing Machine for Lightweight Equipment

The History and Development of the High-Impact Shock-Testing Machine for Lightweight Equipment

VESPA: a servohydraulic shock testing machine

Equipment installed in Swiss civil defense shelters and military fortifications is systematically shocktested. A set of three so-called shock parameters (test table acceleration, velocity and displacement) is defined as test criteria that are simulated on shock testing machines. Some years ago the NC Laboratory Spiez made operational a new vertical shock testing machine, called VESPA. This fully hydraulically driven machine allows to simulate in both directions (,,up and ,,down) a wide range of acceleration-time-histories with test objects weighing up to ten tons. In the tests the motion of the shock table and, if needed, the response of the test object are measured by piezoelectric acceleration transducers. The displacement-time-history of the test table is measured by a special device developed by the NC Laboratory Spiez.

Criteria of failure for a cantilever subjected to repeated shock loading

The results of a theoretical and experimental invetigation to determine the fatigue life of a cantilever (with tip mass) subjected to repeated shock loading of the half-sine-wave form are presented. From a simple law of fatigue-crack propagation cumulative damage criteria for predicting fatigue life under variable-amplitude loading are developed. The unknown constants in these criteria are determined from conventional constant-amplitude fatigue tests on a repeated-bending testing machine. From the response of the shock-excited structure determined from linear single-degree-of-freedom theory and the cumulative damage criteria developed, relations for predicting fatigue life under repeated shock loading are developed. The theoretical predictions are then compared with the experimental dau obtained by actually conducting the repeated shock test on a specially designed shock testing machine. The agreement between theory and experiment is fairly good for steel, the material for which the test results are reported.

Shock test machine for missile components

Shock test machine for missile components