Shock Test Machine Research Articles

Dynamic measuring of force-displacement-characteristics of shockmounts

Shockmounts are widely used to isolate sensitive equipment from vibrations and mechanical shock. Despite the highly dynamic nature of shock events, the force-displacement-characteristics of shockmounts which are provided by manufacturers are gained by static measurements. Therefore, this paper presents a dynamic mechanical model of a setup for dynamic measurements of force-displacement-characteristics. The model bases on acceleration measurement of an inert loading mass, which displaces the shockmount, when the arrangement gets excited by means of a shock test machine. The influence of the shockmount’s mass in measuring setup is considered as well as special needs for handling measurements under shear or roll loading. A method for allocating the measured force data on the displacement axis is developed. An equivalent of a hysteresis-loop in a decaying force-displacement-diagram is proposed.Based on exemplary measurements, error calculation and statistical analysis show the qualification of the proposed method for attaining dynamic FDC.

A Study on Shock Test Design Method Using Linear Dynamic Model of Light Weight Vertical Shock Test Machine

Naval surface ships and submarines could be exposed to non-contact underwater explosion(UNDEX) environment. Equipment installed on the ships and submarines could be damaged by shock load generated by UNDEX environment. Therefore, shock survivability of equipment generally evaluated by shock tests. Ground based shock test machine such as Light weight shock test machine(LVSM) is developed to simulate shock load caused by UNDEX environment. In this study, linear dynamic model of LVSM is proposed and evaluated to improve shock test design procedure. Parameters of the model are decided by optimizing time domain response compared to zero payload experiment. Proposed model is verified by comparing simulation results and test results of maximum payload experiment. Finally, shock test design using the model is described for various test equipment weight. Keywords: 수중 폭발, 충격 시험, 충격 시험 장비 Keywords: UNDEX, Shock Test, Shock Test Machine

The measurement of deformation of elastic shapers of various stiffness and assessment of the influence of shaper deformation on the parameters of the shock pulse

In this paper the influence of the deformation of the shapers of various stiffness on the vibration characteristics of the impact is estimated. In particular, the influence of the deformation on the high-frequency vibrations that appears during the operation of the shapers is also estimated. Both analytical and experimental results of measuring of deformation of shapers are presented. The structure of the model of the shock testing machine developed in Peter the Great St. Petersburg Polytechnic University is described in details. An algorithm for the analysis of vibration characteristics obtained during the tests on the model of an impact machine is presented. The results of studies of the characteristics of the materials which the shock pulse shapers are made of are presented. The life of the shapers made of various materials is estimated. Analytic and experimental dependences of the shaper deformation on the lifting height of the shock table are presented. Conclusions about the effect of shaper deformation on impact parameters are drawn.

Method for determining dynamic coefficient of friction of bodies

To study the effect of the material and the roughness of the impact surface, the velocity of impact interaction and the properties of bodies on the value of the dynamic coefficient of friction, a shock testing machine is proposed that provides an impact contact effect on the bodies in a plane located at an angle adjustable from 0 to 45 ° relative to the normal line drawn to the point of impact, in the range of speeds from 12 to 72 m/sec. It is found that at an impact velocity of 25 m/sec with an increase in the angle of inclination of the impact steel plane, the angle of friction and the corresponding dynamic coefficient of friction increase in a linear relationship. The maximum values of angles φ and dynamic coefficients of friction f make: - for steel balls φ = 8.3°, f = 0.146; - for lead balls φ = 11.4°, f = 0.167; - for grains of the wheat φ = 6.8°, f = 0.12. The results obtained indicate that the elastoplastic properties and shape of the bodies do not have any significant effect on the angles of reflection of bodies from the impact plane.

Shock machines for testing Arctic robotics

All industrial products including robots used for various works in arctic zone, can be exposed to various shock loads. In arctic conditions, such loads are: tectonical impacts, impacts from snow mass and other phenomena. To confirm the durability of products exposed to shock loads during exploitation, the impact tests ma products should be preliminary carried out. Such tests are performed in special equipment - shock machines. Shock machines are complex highly automated equipment. The development and production of machines of this type require advanced high technology and serious financial investments. Therefore, a deep understanding of operation principles of shock-testing machines, their design and methods of adjusting is very important. In the current paper the structures and designs of several types of developed shock machines are analyzed in details: single-shock machine, multiple-shock machine, machine with a pneumatic accelerator. Data on the development of a positional multi-motor pneumatic drive by the High School of Automatics and Robotics of Peter the Great St. Petersburg Polytechnic University are presented. The interface of the operation panel of the multiple shock machine is described according to operating modes, recording and processing the results of measuring the parameters of the shock pulse. Directions of research in the field of synthesis of shock machines for testing Arctic robotics are defined.

Study on a Nonlinear Dynamic Model and Its Parameters Determination Method for Half-Sine Programmer

A nonlinear dynamic model for describing shock response of half-sine programmer in shock test is constructed, in which many important factors in half-sine programmer such as size, hard nonlinearity, damping and initial impact velocity are considered, based on the damped Duffing equation, and the empirical static stiffness and shock stiffness calculation formulas of cylindrical rubber isolator. The shock pulse of half-sine programmer is measured and calculated by using shock test machine and Runge-Kutta method. Taking the minimum determination coefficient between the calculated and the measured shock pulse as the optimization objective, the parameters in the present model are determined by using quantum genetic algorithm (QGA), and meanwhile the extreme capacity in the present model for describing the dynamic behavior of half-sine programmer under shock excitations can also be verified. Experiments were implemented with drop shock test machine. The experimental results show that the present model is precise and efficient, and the prediction errors of pulse peaks and pulse widths were all below 5%, the waveform fitting errors between the calculated and the measured pulses are all less than 15%. The present results are helpful for designing the half-sine programmer.

Mechanical performance evaluation of sandwich panels exposed to slamming impacts: Comparison between experimental and SPH results

Slamming is a dynamic phenomenon in which a high magnitude pulse peak pressure occurs in a short time duration when the bottom structure of a ship impacted against the sea surface. This phenomenon can cause damage in the structure due to fluid-structure interaction (FSI) thus, plays a vital role in designing and manufacturing of ships for naval applications. In this paper, high performance sandwich structure, having many opportunities and challenges for the marine structural design, were studied experimentally using a high-speed shock test machine to examine the water entry problem. In addition, a velocity control system was used to calibrate and preserve the approximately uniform velocity throughout the slamming impact. Sandwich panels with different thicknesses i.e. 27 mm and 37 mm therefore, having different stiffness’s were exposed under constant impact velocities of 6 and 8 m/s at the deadrise angle 10°. Experimental results were then compared and verified by the numerical investigation based on explicit Smoothed Particle Hydrodynamics (SPH) method. This study focuses on the overall structural response, deformation, and hydrodynamic response of the structure during the dynamic impact designed for naval applications.

The Damping Capacity of Damping Devices during Rotor-over-Stator Rolling

The article presents results of investigating the influence of elastic damping devices that secure the rotor and the stator under high-amplitude oscillations under unfavorable development of an accident, e.g., upon rubbing of the rotor against the stator. Motion equations for the oscillations of the rotor in the clearance between the rotor and the stator and the oscillations of the rotor rubbing against the stator are written at adopted parameters of the stator considering not only the rigidity of the stator but also the energy losses under deformation of the stator components during the oscillations. Sudden unbalance of the rotor is taken as the initial excitation. A case of severe unbalance of the rotor is examined when, under oscillations accompanied by rubbing, the damping devices experience fairly severe strains in different rolling modes. The investigations were conducted using a rotor that had been affected by accidents accompanied by destruction of the bearings under rubbing in the absence of damping devices. A dynamic model of a symmetrical two-bearing rotor is considered. ADP-2400 shock absorbers served as dampers; the dynamic impact properties of the former had been determined using shock-testing machines. A possibility of the development of self-excited oscillations in the form of asynchronous rolling is considered depending on the absorption factor of the elastic damping devices. It is shown that no asynchronous rolling develops at definite absorption factor values. The oscillations of the rotor are restricted to the synchronous rolling at rotor–stator contact interaction forces that do not endanger the integrity of the turbine plant structure. The elastic damping devices with absorption factors above certain values eliminate the possibility of the development of self-excited oscillations in the form of asynchronous rolling and a practically unlimited increase in the rotor–stator interaction forces and, consequently, eliminate the danger of destruction (self-destruction) of the power-generating plant. In a sense, we can speak about the damping capacity of elastic damping devices during the evolution of an accident accompanied by rubbing of the rotor against the stator. The rigid mount of the stator on the foundation in the absence of damping devices increases the risk of the catastrophic development of the emergency considerably reducing the evolution time of the rolling and the possibility of using safety devices. A conceptual scheme that systemizes the general regulations for preventing TP accidents is provided.

Investigation on the parameter determination and implementation of a dual-pulse shock test machine using a MR damper

The characteristics of a dual-pulse shock caused by an UNDEX (underwater explosion) are described through many standards. Shock signals required to evaluate the survivability of equipment by a shock test machine are also described. To generate various types of shock signals described in the standard, Shock test machines (STMs) require adjustment to various levels of shock occurring in surface ships and submarines. Therefore, the characteristics of each component of a STM should be changeable to generate various shock signals. This paper describes the concept of a STM that can generate various types of dual-pulse shocks. Moreover, this paper suggests an analytic method to determine the characteristics of each component of a STM to generate the required shock signal for various specimens. A method for adjusting the shock signals using a magnetorheological damper is specifically suggested. The results of dynamic analysis using the characteristic values of each component determined by this method shows that the required shock signal can be generated by this concept of the shock test machine.

충격시험장치 고속유압 속도발생기 해석 및 설계

기계 및 전자 장비들은 다양한 분야에 여러 형태로 사용되고 있어 충격과 같은 외부 환경에 노출되어 있다. 장비들의 내충격 특성을 평가하기 위해 충격시험장치가 사용되고 있으며, 과도한 응력의 발생에 의한 영구 변형이나 파손, 높은 가속도에 의한 장비 내부 부품의 파손 및 기능정지 등에 대한 평가가 이루어 진다. 이러한 충격시험장치에 있어서 물체를 고속으로 움직이게 하여 물체간의 충격을 유발할 수 있는 속도발생기가 필요하다. 본 연구에서는 유공압을 이용하여 물체를 고속으로 움직일 수 있게 하는 속도발생기를 개념적으로 설계하고, AMESim 을 이용한 해석모델을 통하여 발생 속도를 예측하였다. 해석 결과는 축소 제작된 속도발생기의 시험 결과와 비교하여 검증하였으며, 해석 결과를 이용하여 목표 속도에 적합한 속도발생기를 설계하였다.

A novel heavy-weight shock test machine for simulating underwater explosive shock environment: Mathematical modeling and mechanism analysis

A novel heavy-duty shock test machine is developed to satisfy the newly-built shock resistance standard and simulate accurately the actual underwater explosive environments with increased testing capability. The mathematical model for the shock test machine is created to predict its dynamic performance and analyze its mechanism. Then numerical simulation is carried out to evaluate the prospective capability of the shock test machine under different shock velocity inputs. The double protection system incorporating the stroke limit of the accumulator piston and the unloading circuit can effectively prevent the secondary collision in the testing process. The simulation results have demonstrated that the shock test machine proposed in this paper can produce nearly the same shock acceleration waveform as the new shock resistance standard BV043/85 and MIL-S-901D. Moreover, this shock test machine can be regulated conveniently to adjust to a different type of equipment and be extended easily to suit more severe shock environments and heavier equipment. The proposed system configuration and associated mathematical model provide theoretical basis and useful design techniques for practical applications.

Optimization of Pendulum for a High-Impact Shock Testing Machine with Medium Weight

Collision impulse to pendulum shaft is tend to be generated when hammer impacting the anvil. In order to eliminate the collision impulse and find a preferential size of the pendulum, based on the rigid body dynamical model, the conditions of the coincidence of the center of strike and the center of percussion are established; calculation formula of the distance between the axis of the pendulum shaft and the center of percussion is derived. By selecting certain geometric parameters of the pendulum as design variables and transferring the multi-objective nonlinear optimal design problem into single objective problem, a mathematical model of the optimal design of the pendulum is established. Matlab optimization toolbox is utilized to calculate the model, and a reasonable result is obtained. The work of this paper has considerable significance in the far field of engineering design.

Optimal Design of Pendulum in High Impact Shock Testing Machine for Middleweight

Impact test of shipboard systems must be taken before navy ships take service. Only in this way can we ensure the safety and reliability of them. In middle-weight high impact testing machine which is one of main devices to test medium weight equipments, pendulum is the most important as well as the most perishable part of this machine. Good quality of pendulum should be ensured. Energy demands, reliability, service life and deformation of the pendulum must be taken into account when design pendulum of this tester part. An optimization methods to design pendulum is presented in this paper. By means of optimization of the position of mass centre, percussion centre and impact point, the reliability and service life of pendulum can be improved.

High-Speed Image Measurement Technology and its Application under Toner Drop Impact Test

A transport package cushioning property evaluation test system is established to achieve the goal of high-precision, real-time, non-contact, and full-field measurement. It consists of a shock testing machine, a shock measuring instrument and a high-speed image acquisition and processing system. High-speed imaging measurement techniques and digital image processing method are used to make a comprehensive assessment on the cushioning properties of air-cushion package. In this paper, the developed system was used to measure the drop shock responses of the toner and air cushion deformation under drop impact test.

Transverse impact characteristics of a rubber pipe expansion joint

The transverse impact characteristics of a rubber pipe expansion joint are studied. A pair of joints assembled end to end with an inserted middle mass is tested on a drop shock testing machine. Based on the test results, an equivalent fixed-fixed beam model with polynomial stiffness and damping is applied to predict the transverse impact response and identify the nonlinear impact parameters. The least square residual between the computed and test results is defined to drive the identification optimization. The response surface methodology in combination with the generalized reduced gradient method is used to search the best matching coefficients. Final results show that the equivalent bending stiffness of the tested rubber expansion joint gradually decreases with the transverse deformation and is greatly influenced by its internal working pressure.

Mechanism and Dynamic Behavior of a Novel Hydraulic Force Pulse Generator

Based on the concept of hydraulic damper energy dissipation, a passive Hydraulic Force Pulse Generator (HFPG) is presented. The design comprises a conical poppet valve inside a cylindrical hole without any seat. By virtue of aperture and orifice throttling, HFPG dissipates the kinetic energy of a rapidly moving object and cushions it to a halt to produce desired acceleration pulse. Prompt and easy adjustment can be achieved to the damping force by changing the size of the orifice set on cylinder. A mathematical model of the cushion process is developed by way of analyzing the internal fluid dynamic phenomenon of HFPG. And numerical simulation results of the model has exhibited the following features of HFPG: high-efficiency of energy dissipation; easy-regulation of acceleration waveform and being suitable in conditions with large momentum change, especially to be used as the negative pulse generator of dual-wave shock testing machines which can simulate the shock environment of underwater explosion.

Power Flow Method for Determination of Product Shock Fragility

One of necessary prerequisites to design cushioned package is the determination of product shock fragility, which is so far obtained by means of destructive method on shock testing machines. This paper presents a non-destructive method--power flow method to predict the product fragility. The transport package system was first divided into two subsystems to simplify analysis. The energy of critical component of the product was then calculated by applying a power flow equilibrium equation. And finally, the parameters of the transport package system, such as the input power, the internal loss factor and the coupling loss factor, were discussed.

Advances in Shock Testing Facilities for Naval Shipboard Equipments

The capability to withstand non-contact underwater explosions (UNDEX) is an important aspect to be emphasized in the design of modern warships, and shock testing is one of the efficient methods to qualify the ability. A brief history on the research of shock testing of naval shipboard equipment as well as major means in evaluating anti-shock performance of warship equipment is introduced first in this paper. Three prevailing shock test methods: UNDEX testing, virtual shock trial and land-based test with shock test machines are presented with the focus on the advances in shock test machines in US and Europe. Comparison of current shock testing facilities is also given. Moreover, some new concepts of shock test machines are reviewed as well, and three major directions of the development of shock test machines are concluded. The first trend is that shock testing machines are required to generate positive and negative shock pulse to simulate real UNDEX environment made up of shock wave followed by bubble pulse and structural whipping. The second is that shock test machines can test heavy equipments, and the last is that shock pulses can be controlled and customized conveniently.

Shock wave characteristics of a hydraulic damper for shock test machine

A hydraulic damper is developed to generate the shock wave in this paper. The working principle of the damper is explained and the corresponding mathematical model is established. The shock wave characteristics under different shock velocities are obtained by using the numerical computation and experiment. The results show that the shock wave characteristics directly relate to the sectional area of the exhausted passages. The computational results agree well with the experimental data, which means that the proposed mathematical model can be used for the engineering design.

Fracture and strain rate behavior of airplane fuselage materials under blast loading

The dynamic behavior of three commonly used airplane fuselage materials is investigated, namely of Al2024-T3, Glare-3 and CFRP. Dynamic tensile tests using a servo-hydraulic and a light weight shock testing machine (LSM) have been performed. The results showed no strain rate effect on Al2024-T3 and an increase in the failure strain and failure strength of Glare-3, but no stiffening. The LSM results on CFRP were inconclusive. Two types of fracture tests were carried out to determine the dynamic crack propagation behavior of these materials, using prestressed plates and pressurized barrels, both with the help of explosives. The prestressed plates proved to be not suitable, whereas the barrel tests were quite reliable, allowing to measure the crack speeds. The tougher, more ductile materials, Al2024-T3 and Glare-3, showed lower crack speeds than CFRP, which failed in a brittle manner.