Shock Machine Research Articles

A comprehensive study on the effects of surface post-processing on fatigue performance of additively manufactured AlSi10Mg: An augmented machine learning perspective on experimental observations

In this study, the efficacy of 21 distinct surface post-processing methods on the fatigue behavior of an additively manufactured (AM) material was investigated. Various treatments, encompassing single-step processes like sand blasting (SB), conventional shot peening (CSP), severe shot peening (SSP), gradient severe shot peening (GSSP), ultrasonic shot peening (USP), severe vibratory peening (SVP), ultrasonic nanocrystal surface modification (UNSM), laser shock peening (LSP), laser polishing (LP), tumble finishing (TF), chemical polishing (CP), electro-chemical polishing (ECP), and machining (M), as well as hybrid treatments, were systematically investigated for their impact on the fatigue behavior of hourglass laser powder based fused (LB-PBF) AlSi10Mg specimens. A comprehensive series of experimental tests were carried out, covering surface texture analyses, microstructural characterizations, porosity measurements, hardness, residual stresses (RS), monotonic tensile tests, and rotating bending fatigue tests at four stress levels. Following the experimental investigations, the acquired data were leveraged to develop a machine learning (ML)-based model to correlate the fatigue life with the influencing factors and conduct parametric and sensitivity analyses. The model utilized a deep learning approach to predict the fatigue response of LB-PBF AlSi10Mg, incorporating various artificial neural networks (ANNs) and considering input parameters such as yield strength, ultimate tensile strength, elongation to fracture, porosity, depth of pore closure, surface hardness, depth of hardness variation, surface RS, maximum compressive residual stresses (CRS), depth of the CRS field, top surface grain size, surface layer mean grain size, surface roughness, and stress amplitude. Depending on the life regime, the factors influencing fatigue behavior can vary significantly. In higher stresses, dominated by plastic strains, surface residual stress emerges as the primary factor. Conversely, in lower stresses, dominated by elastic strains, the significance of surface roughness becomes more pronounced, followed by surface residual stress, surface hardness and other factors. These findings underscore the contextual importance of different influencing factors for enhancing fatigue resistance based on varying loading conditions.

DETERMINATION OF ELASTIC CHARACTERISTICS OF BUILDING INDUSTRY VIBRATION SYSTEMS

The design of the difficult dynamic systems is examined with removable descriptions ofresilient elements and analytical dependences are got for realization of multimode resonances and the card ofstability of vibration of shock machines is offered.

Collective motion in hcp-Fe at Earth’s inner core conditions

Earth's inner core is predominantly composed of solid iron (Fe) and displays intriguing properties such as strong shear softening and an ultrahigh Poisson's ratio. Insofar, physical mechanisms to explain these features coherently remain highly debated. Here, we have studied longitudinal and shear wave velocities of hcp-Fe (hexagonal close-packed iron) at relevant pressure-temperature conditions of the inner core using in situ shock experiments and machine learning molecular dynamics (MLMD) simulations. Our results demonstrate that the shear wave velocity of hcp-Fe along the Hugoniot in the premelting condition, defined as T/Tm (Tm: melting temperature of iron) above 0.96, is significantly reduced by ~30%, while Poisson's ratio jumps to approximately 0.44. MLMD simulations at 230 to 330 GPa indicate that collective motion with fast diffusive atomic migration occurs in premelting hcp-Fe primarily along [100] or [010] crystallographic direction, contributing to its elastic softening and enhanced Poisson's ratio. Our study reveals that hcp-Fe atoms can diffusively migrate to neighboring positions, forming open-loop and close-loop clusters in the inner core conditions. Hcp-Fe with collective motion at the inner core conditions is thus not an ideal solid previously believed. The premelting hcp-Fe with collective motion behaves like an extremely soft solid with an ultralow shear modulus and an ultrahigh Poisson's ratio that are consistent with seismic observations of the region. Our findings indicate that premelting hcp-Fe with fast diffusive motion represents the underlying physical mechanism to help explain the unique seismic and geodynamic features of the inner core.

The Single Degree of Freedom Simulation Model of Underwater Explosion Impact

The hulls of naval ships are exposed to forces and moments coming from internal and external sources. Usually, these are interactions that can be described mathematically by harmonic and polyharmonic functions. The shock of UNDEX type (underwater explosion) works completely differently and its time waveform is difficult to describe with mathematical functions as pressure vs. time. The paper presents a simplification of physical and mathematical models of 1-D kickoff pressure whose aim is performance the simulation of the external force of the detonation wave. The proposed models were verified and tuned on naval, sea trials. The main goals of the proposed models are to perform simulation calculations of the detonation pressure for different explosion charge weights from different distances of the UNDEX epicentre for the design process of machine foundation. The effects of pressure are transformed as impulses exposed on shock absorber mounted at light shock machine.

Characterization of underwater shock transient effects on naval E-glass biaxial fiberglass laminates: An experimental and numerical method

Non-contact underwater explosions (UNDEX) can cause extremely large deformations on naval composite structures related to heavily nonlinear phenomena. For this reason, for military purposes, used materials must have excellent shock resistance properties. Historically, the underwater shock transient effects on fiberglass laminates are predicted using quasi-static approaches. In this paper, the composite materials are characterized by experimental modal analysis as well as by a comprehensive series of shock tests, whose results are compared with numerical models. Namely, the MIL S 901 D Medium Weight Shock Machine (MWSM) was used to perform dedicated shock tests, in which composite specimens are supported on a special constraining structure designed to create large deflections and providing reproducible results. A dynamic implicit finite element model has been set, validated by modal analysis at first, and then applied to simulate the MWSM test behavior and to predict the structural response of different E-Glass polyester resin laminates. In the end, the complete comparison of numerical results and experimental data is reviewed to validate the modeling strategies for shock design of navy ships.

Hydropulse small-sized vibrators based on slotted springs

The article presents constructions and descriptions of the principles of operation of single-stage pressure pulse generators which are the main elements of the hydropulse drive used to generate vibrations of actuators in vibrating and vibratory shock machines for various purposes. Namely the pressure pulse generator with a solid body the pressure pulse generator with a floating seat and the pressure pulse generator with valve sealing degrees which were developed on the basis of Vinnytsia National Technical University. In the considered devices have the slotted spring as an elastic element which is executed as a separate detail or as a constructive element of other details which are a part of the device is used. The use of such elastic elements allows to ensure the speed of the devices and accordingly to increase the frequency characteristics of their operating modes. It is established that hydropulse vibrators - hydraulic cylinders based on cut or ring springs have the smallest dimensions with significant vibration force parameters.The text of the article highlights the main conditions for stable operation of these pressure pulse generators indicates and analyzes the mathematical dependences between the operating parameters of devices and the size of their structural elements offers the necessary correlation between structural dimensions of working surfaces of actuators and features of their positional parameters. The offered mathematical dependences can be used both for optimization of work of the designs of devices considered in article and at designing of new generators of pressure pulses with the hydropulse drive of various function. The shortcomings of individual designs of pressure pulse generators which may be related to the ways of sealing the working chambers of devices or options for interaction of structural elements of the device are identified and considered.

MODELING THE PROCESS OF INTERACTION OF THE MAIN ELEMENTS OF THE HAMMER WITH THE MPSSRP MEANS OF THE .NET FRAMEWORK PLATFORM

In this work, a diagram of a shock machine with a variable structure mechanism with a separable slider is shown, the principle of its operation is described. In order to reduce dynamic loads on the track water, it is proposed to interact the carrier with the striker by means of an air cushion. The article considers dependencies that allow to model the process of air flow from the air cushion through gaps between structural elements of the carrier and striker. The influence of the engine power on the maximum speed developed by the striker is revealed.

USING .NET FRAMEWORK COMPONENTS TO ANALYZE THE IMPACT OF AIR CUSHION DURATION ON DYNAMIC PARAMETERS OF SVMSS

In this work, a diagram of a shock machine with a variable structure mechanism with a separable slider is shown, the principle of its operation is described. In order to reduce dynamic loads on the track water, it is proposed to interact the carrier with the striker by means of an air cushion. The article considers dependencies that allow to model the process of air flow from the air cushion through gaps between structural elements of the carrier and striker. Structural parameters determining duration of air cushion action are revealed. Influence of duration of air cushion action on dynamic parameters of impact machine is shown.

OPTICAL SENSOR FOR THE MOVEMENT OF THE LEASH OF THE SHOCK MACHINE AND THE METHOD OF DIGITAL PROCESSING OF ITS SIGNALS

OPTICAL SENSOR FOR THE MOVEMENT OF THE LEASH OF THE SHOCK MACHINE AND THE METHOD OF DIGITAL PROCESSING OF ITS SIGNALS

Means of Air Bleed in the Working Process of a Pneumatic Percussion Mechanism for Construction, Installation and Reconstruction of Structures

The features of synthesized mechanisms with changes in the striker design elements represented as bypass channels made by straight broken lines and curved lines of at least second order of curvature on the side surface along the rod forming part of the stepped striker are considered in the paper. A physical and mathematical description and qualitative assessment of changes in air distribution processes during air bleed between working chambers are presented. Differences in description restrictions for the air bleed process when changing the shape of bypass channels made in the form of channel flats on the rod part of the stepped striker are shown. Differences in bypassing systems imply realization of different processes of force pulse formation in working chambers in pneumatic percussion mechanisms. A list of the constructive solutions’ considered variants directions in pneumatic machines of impact action on the machined medium with any acceptable values of energy parameters in the presence of appropriate equipment for compressed air supply by pressure and productivity is offered. The recommendations on the use of design solutions of the specified channels implementing shock and vibration working processes in the mechanisms of pneumatic shock machines of a particular purpose have been developed.

Shock Signal Trend Term Error Correction Method Based on Discrete Wavelet Transform and Low-Frequency Oscillator Combination

Shock response spectrum (SRS), calculated according to shock loading signal, is the primary metric for assessing the shock resistance ability of shipborne equipment. Nevertheless, the measured shock acceleration signal contains a trend term error that severely distorts the low frequency of the SRS. The accuracy of present correction methods cannot be assured due to a lack of reference. A discrete wavelet transform (DWT) and low-frequency oscillator combination method is proposed for correcting shock signals in this paper. The optimal wavelet parameters can be selected according to a low-frequency spectrum baseline fitted by the measured relative displacement to reject low-frequency trend term errors. Shock machine test results show that the average difference between the low-frequency spectrum baseline and uncorrected SRS is reduced from 89.8% to 3.2%, while the SRS slope rolled off to 5.8 dB/oct after imposing the proposed correction. The corrected SRS can faithfully show the actual shock loading characteristics of shipborne equipment in shock tests.

Designing a shock test system prototype based on a hydroelastic drive

Laboratory shock tests involve the reproduction of simple one-time and repeated pulses of a certain waveform. In practice, such mechanical impacts on an object are implemented at specialized testing equipment ‒ shock systems. A promising direction in the development of shock machines includes the structures that operate on the energy of elastic deformation of the compressed liquid and the shell of the vessel that contains it. Such systems make it possible to improve the versatility, manageability, and accuracy of impact tests. Underlying this study is the use of a hydroelastic drive to design a prototype of the automated electro-hydraulic system for a shock test system. The proposed shock test system prototype makes it possible to expand the functionality of the installations to perform impact tests with a series of pulses, as well as improve manageability and increase the level of automation. The main feature of the proposed structural scheme is that the reconfiguration for a new impact pulse occurs very quickly. Owing to the presence of a driven rotary drum with braking devices, the bench makes it possible to generate a shock pulse repetition frequency of 1‒2 Hz. The constructed mathematical model of the shock machine takes into consideration the inertia of moving masses, the rigidity of the liquid or "one-way" spring of the charging chamber, as well as the influence of dampers on which the test platform rests. The variables in the mathematical model are linked by differential equations describing two periods within a shock system work cycle: charging and pulse generation. The model's practical value is to determine the dynamic characteristics of the test installation, as well as to calculate the required structural and technological parameters. The differential equations describing the movements at the shock machine have been solved in a numerical way. The study results have established the optimal value (in terms of minimizing the overload on an article on the return stroke of the rod) for the damping factor of the braking device, which is 13,000 kg/s. In this setting, the ratio of the amplitude of acceleration on the reverse stroke to the amplitude of effective acceleration during tests is reduced to a minimum of 0.195

Influence of the shaper parameters on the characteristics of acceleration pulses reproduced by mechatronic shock machines

In this paper the influence of the shaper parameters on the characteristics of acceleration pulses (peak value and duration) reproduced on mechatronic shock machines is analyzed. A comparison of the acceleration pulses obtained experimentally and by computational methods is presented. Recommendations for clarifying the requirements for methodological calculations of pulse parameters are given. The dependence of the elastic force of the shock pulse shaper on its deformation is presented. The influence of this characteristic on the peak value and duration of the acceleration pulse is estimated. The influence of the height of the shaper on the parameters of the acceleration pulses is analyzed. The concept of a device that allows you to automatically change the height of the shaper to obtain a wider range of acceleration pulses is presented. The interaction of the shock table with the shaper by means of computer modeling is modelled. Conclusions about the dependences of the duration and peak value of the acceleration pulses on the parameters of the shaper (stiffness and height) are drawn. Recommendations for selecting the parameters of the shaper to obtain acceleration pulses with the desired parameters are given.

New solutions to the problems of stripping of ore bodies using inclined workings driven downward in conditions of increased water cut

The authors of this paper describe the face transport system that ensures the stripping of ore bodies using the underground development method with inclined narrow workings driven downward, including in conditions of increased water cut. The face transport system will allow the preparation of a new 500-thousand-ton mine with minimum general construction and mining construction works as well. The article contains an engineering study of the transition of the road heading to blastless continuous-flow methods of rock development using hydraulic impulse or mechanical shock machines, which are under development. For deep and ultra-deep developments starting from 250-300 m and deeper, a new technical solution is given for the construction of a downhole mine airlift with the lowest capital and operating costs and sufficiently high reliability and productivity. New technical solutions will ensure the radical transition of the technological concept of mining production from the drilling-and-blasting cyclic to blastless continuous-flow one.

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.

Investigation of Shock Signals from SAE J577 Mechanical Shock Machine

In this study, acceleration signals measured from the SAE J577 mechanical shock machine are investigated in detail. The aim of this investigation is to derive representative standard acceleration signals to be used as acceleration loads for finite element fatigue analysis of Automotive Lighting parts. These signals can also be used as load inputs for vibration shakers which have the capability of driving time domain signals. First of all, acceleration signals have been measured from the free machine table and by the help of the signal analysis software, automatic averaging operation has been performed from the long train of shock signals to have a single average acceleration shock signal. Furthermore; because the machine is force controlled, it is understood that the total weight and the overall dimensions of the device under test (DUT) and the fixture have significant effect on the severity of the test. Thus, measurements are repeated from the different sized fixtures and the results are compared in order to understand the effects of the fixture size and the weight on test severity.

Method for Reproducing Shock Acceleration in Mechanical Testing

Several issues concerning shock accelerations production by pneumatic shock machines are considered in the paper. A new method of the required half-sine pulses amplitude ensuring is proposed and theoretically justified. The method is based on the dependence of a shock machine rising height on speed and duration of compressed air supply to pneumatic cylinders that ensure rising and dropping of a test object. A design of the SMU300 pneumatic shock machine used to conduct the method experimental research is considered here. Experimental data have confirmed the effectiveness of the method. An algorithm for setting the design and technological parameters of a shock machine ensuring the required test parameters is proposed.

FEM simulation of space instruments subjected to shock tests by mechanical impact

Space instruments must be structurally verified to confirm their capability to withstand the severe vibrations and shock environments during the launch phase. The shock loads are caused by the pyrotechnic devices employed for the separation between the launcher stages and for the release of the fairing and the spacecraft. The most recommended verification method for shocks is by testing, which can be performed by different test methods such as electrodynamic shakers, mechanical impact shock machines or pyrotechnic devices. Recently, numerical shock simulations have been incorporated as a part of the structural verification of the space instruments with the aim of providing additional information that cannot be easily obtained from test data. One of most determining aspects to simulate the same environment measured during a shock test by mechanical impact is the definition of the input acceleration, which may be non-uniform and with non-negligible cross levels. The objective of this paper is to propose new techniques that define with precision the input acceleration field measured in the shock test considering the mentioned aspects for the shock simulations by the finite element method. The analyses are performed with the finite element (FE) model of the space instrument STEP of the Solar Orbiter mission and the results are compared with the shock test data to evaluate the improvement of the accuracy achieved from the shock simulations with the different proposed methods.

Evaluation of possibility of using self-ventilation to cool forced electromagnetic shock engines

The use of shock machines with linear electromagnetic engines, for example, for immersing metal rod elements in the ground, seems quite effective due to the relatively low power consumption, the direct conversion of electrical energy into mechanical work and comparatively high specific indicators. At the same time, increased values of the impact power of machines with linear electromagnetic engines are provided under the condition of forced consumption of energy from accumulators or capacitive storage devices. Because of the relatively low voltage, these sources give significant currents (120 … 200 A) to the winding of linear electromagnetic engines during the operating cycle. In this case, the value of the ratio between losses and useful energy of the machine is significant, which limits the possibilities of creating frequency-impact machines with a long operating regime on the basis of pulsed linear electromagnetic engines with natural cooling. Thus, the intensification of the cooling process of linear electromagnetic engines of shock machines is important. In this paper, we estimate the possibility of using self-ventilation for cooling the forced linear electromagnetic engines of shock machines; the dependence of the taken-away power of losses of linear electromagnetic engines on geometrical characteristics of axial ventilating channels is defined.

Operating Member of Shock Machines Based on the Non-axial Slider-crank Mechanism with a Disjointed Slider

To perform various technological operations to process and destruct materials, power pulses of high amplitude and very short duration are necessary. Special devices, which can be hydraulic, pneumatic, electromagnetic or mechanical pulse generators, generate such shock pulses. Mechanical generators of power pulses can be based on the various mechanisms, many of which are among the mechanisms of a variable structure.The Machinery Researching Institute of National Academy of Sciences of Kyrgyz Republic has offered to use the crank-slider mechanism of a variable structure with a disjointed slider in the shock machines. The operation aspect of this mechanism is that at the beginning of the working course a lead (drive dog) and a hammer block, which form the slider, make a joint movement, are separated when the lead movement slows down, and then upon the shock of the hammer block to the tool and the mechanism being under idle operation these two parts again make a joint movement.The shortcoming of this mechanism is that its coefficient of the changing average speed of the slider is equal to unit. But as to the shock machine, it is desirable for this coefficient to be higher than one. In this case the average speed of the slider at the working course will be higher than when idling, and the hammer block can have the higher speed. Also it should be noted that when idling there are more favorable conditions to fix the hammer block, which has made a rebound after the shock to the tool, with a lead at great values of the coefficient of the changing average speed of the slider.The coefficient of the changing average speed of the slider can be increased through the crank support shift in direction, perpendicular to the trajectories of the slider movement, by converting an axial mechanism into the non-axial one. Based on the specified values of frequency and energy of blow and also conditions for ensuring the working capacity and compactness of the shock machine, the paper makes synthesis of key parameters of the operating member of the non-axial slider-crank mechanism with the disjointed slider.