Impact Machine Research Articles

Influence of Particle Size of Explosive on Ignition Mechanism Under Low Velocity Impact

AbstractDrop‐weight impact experiments are performed on different particle size Octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX) granular explosives. The drop‐weight impact machine is equipped with the high‐speed photographic systems for obtaining a mechanical‐chemical image of the impact process. The experimental image shows that the small particles of 700 μm have melted for a long time and over a large area during the loading process. HMX particle size affects the ignition mechanism. For a single particle, the ignition mechanism changes from friction to viscous heating with the decrease of particle size. The ignition mechanism of 6000 μm and 1800 μm HMX particles is friction work. The ignition mechanism of HMX small particles of 700 μm includes friction work and viscous heat under drop weight impact.

A Proposed Estimation of the Expanded Uncertainty of Charpy Impact Testers

Uncertainty estimation is one of the very delicate tasks in the field of measurements. For the purpose of calibration of Charpy impact testing machines, it is necessary to evaluate and identify the expanded uncertainty. Factors affecting the uncertainty estimations are; the uncertainty of reference force and length measuring devices and its long-term instability (drift), machine resolution, rated energy error, indicated energy error, losses due to the drag of the pointer, friction losses in the bearing and air resistance, and other geometric parameters. In this study, the uncertainty estimation of the Charpy impact machines is based on the direct verification used in the BS DIN ISO 148-2 standard.

Methodology for evaluating energy-saving technical solutions of impact machines and equipment

The paper proposes a method of sequential exclusion at the stage of designing feature elements in known and synthesized pneumatic impact mechanisms in order to select preferred constructive solution of machine mechanism for destruction of mountain ranges in preparing the bases for construction of buildings and structures. The method involves a phased analysis of several variants of mechanisms at the same time with exception of the same structural features, elements that have the same effect on the work process and resource mechanisms. Thus, only original compositions remain that characterize distinctive qualities of technical solution of the pneumatic impact mechanism variant corresponding to its intended purpose.

Neutrophils as Main Players of Immune Response Towards Nondegradable Nanoparticles.

Many nano/microparticles (n/µP), to which our body is exposed, have no physiological way of removal. Our immune system sense these “small particulate objects”, and tries to decrease their harmfulness. Since oxidation, phagocytosis and other methods of degradation do not work with small, chemically resistant, and hydrophobic nanoparticles (nP). This applies to soot from air pollution, nano-diamonds from cosmic impact, polishing and related machines, synthetic polymers, and dietary n/µP. Our body tries to separate these from the surrounding tissue using aggregates from neutrophil extracellular traps (NETs). This effectively works in soft tissues where n/µP are entrapped into granuloma-like structures and isolated. The interactions of hydrophobic nanocrystals with circulating or ductal patrolling neutrophils and the consequent formation of occlusive aggregated NETs (aggNETs) are prone to obstruct capillaries, bile ducts in gallbladder and liver, and many more tubular structures. This may cause serious health problems and often fatality. Here we describe how specific size and surface properties of n/µP can activate neutrophils and lead to aggregation-related pathologies. We discuss “natural” sources of n/µP and those tightly connected to unhealthy diets.

Experimental and numerical investigations of the influence of partial replacement of coarse aggregates by plastic waste on the impact load

ABSTRACT The effect of partial replacement of coarse aggregate by plastic waste on the performance of concrete under impact three-point bending loading was investigated experimentally and numerically. Specimens were prepared for 5%, 10% and 20 % replacements by volume of coarse aggregate. For each case, three beams of 100 mm wide, 50 mm deep and 400 mm long were loaded to failure in a drop-weight impact machine by subjecting it to 30 N weight from 400 mm height, while another three beams of the same size were tested under static load. The load-displacement of beams of concrete with plastic waste subjected to static and impact loads were studied. The dynamic beam behaviour was also analysed numerically using the finite-element method (FEM) based LUSAS software. In general, the experimental results reveal that the impact tup, inertial load and bending load increase with the increase in the percentage of coarse aggregate replacement by plastic waste, while the static peak bending load always decreases. The concrete with plastic waste is stronger and more energy-absorbing under impact loading, than under static loading. The predicted load against displacement behaviours of both ordinary concrete and concrete with plastic waste, are well matched with the experimental results.

Experimental determination of the impact energy of horse kicks

Kicking is a natural behaviour of horses, but it can become problematic if stall components are hit and do not withstand the impact load. Injuries may occur due to material failure or hoof entrapment. In Germany, while the Animal Protection Law is intended to prevent such incidents, neither the law nor the corresponding interpretation aid indicates how this requirement should be fulfilled. This paper gives an overview of the methods of determining horse kick energy and presents results of own kick energy measurements. The outcome of a re-evaluation of literature data is presented and two attempts to roughly estimate the expected kick load are introduced. The developed measuring device consists of a steel-made framework, mechanical energy sensors, and an impact panel. Its verification was carried out by loading with impacts of defined energy applied by a pendulum impact machine. The measurement of kick energy was taken at a stud farm in the context of heat detection by observing the response of a mare to the presence of a stallion, whereby the kicks of the stallion were measured. With regard to the kick-resistance and entrapment-safety calculation, a representative value of 71 J was calculated and using a safety factor of 1.5 this gives a design value of 106 J. The presented results and the theoretical background of kick energy measurements described should in the future form the basis for the dimensioning of kick-resistant and entrapment-secure stall planks. • Theory background of horse kick energy determination. • Horse kick measurement applying specially designed dynamic energy sensors. • Kick energy determined to 106 J (design value) for stall plank dimensioning. • Result validation performed by application of various estimation approaches. • Kick-resistant and entrapment-safety stall plank dimensioning now possible.

The Use of Viscoelastic Layers in GFRP, a New Vision of Planning Hull

The planning hull, are types of boats very used in our days, and require special maintenance and repair. It is proposed the insertion of a viscoelastic layer inside the laminated panels of the ships built with GFRP, to protect them from the impacts of slamming. Unmodified and modified laminate panels were manufactured to perform result comparisons. With the reproduction of the phenomenon of fatigue in the laboratory, testing them in the impact machine, the use of strain gauges and by characterization with fluorescent penetrating inks to observe the evolution of micro cracks. It is verified that the proposed modification is the future of shipbuilding of this type of vessel.

Justification of pneumatic percussion machine performance in formation of main cracks from holes in natural stone

The study focuses on a percussive machine for directional fracturing of natural stone. The impact machine forces a rock-breaking tool to make a hole and penetrate it. Stone is propped as a result, and a main crack is formed finally along the row of holes. For the gravity-type pneumatic percussion machines, the circuit design is justified, and the numerical analysis of structural constants and performance of the machines is carried out based on the modeled dynamics of basic units. The operating cycle of the machine was evaluated by blow energy, blow frequency and compressed air flow rate. It is found that the operating cycle of the gravity-type pneumatic percussion machine with elastic valve ensures effective consumption of compressed air and high energy of impact. The numerical modeling data are proved by experimental results at the Institute of Mining, SB RAS.

Effect of Impact Load on Concrete Containing Recycled Tire Rubber Aggregate With and Without Fire Exposure

Over one billion tires are disposed into the environment each year and this has become a major environmental issue in the globe. Recycling of these waste tire rubbers in concrete has gained attention from researchers all around the world. In this study, the impact resistance of rubberized concrete exposed to fire is investigated experimentally in the laboratory. For that purpose, sixty specimens were made with five different mixes replacing their sand content partially with different percentages of tire rubber by weight ratios of 0% control, 6%, 12%, 18% and 24%. The water/cement ratio was kept constant at 0.393 in all the mixes. In each mix, fifteen concrete specimens with the size of (150 x 150 x 73) mm were prepared to expose to fire. Every three specimens were gradually exposed to fire for four various durations of (0, 15, 30, and 45) minutes. Each specimen was then tested in a drop-weight impact machine by dropping 2240-gr and 4500-gr hammers from heights of 280 mm and 450 mm. The average impact energy of three identical specimens required for the occurrence of the final fracture was calculated. The investigational results are compared with results of control samples. It is found that the impact energy considerably increased with an increase of the rubber replacement. It is, also, noted that any increase in the burning period of specimens results in a reduction of the impact energy and more early crushing of the rubberized concrete.

Influence of Preload Type on the Low Velocity Impact Response of Glass Fiber Reinforced Thermoplastic Composites

Abstract This paper reports the low velocity impact behavior of preloaded E-glass/polypropylene sandwich composite plates. In particular, the effects of the type of preload and pre-strain amount on the impact behavior of composite plates are reported. Low velocity impact tests of specimens subjected to biaxial tension, compression and tension-compression (shear) were carried out using a drop-weight impact machine under a hemispherical impactor. Deformations ranging from 250 to 500 microstrains were imposed by a special fixture fabricated for this purpose. Single impact loadings were applied to the composite sandwich structures at different impact energies which were varied from rebounding case (10 J) to the perforation case (40 J). Impact results were explained in terms of typical contact force – deformation (F-D) curves and energy – time diagrams. The maximum contact force, deformation and absorbed energy of the specimens were compared to investigate the influence of pre-strain amount. In addition to the single impact tests, repeated impact behavior of composite sandwich structures subjected to different preload types were obtained with the same impact energy levels. The experimental results showed that the maximum contact force and maximum absorbed energy were considerably different in these situations. However, the repetition number of the specimens at the higher impact energies subjected to shear preloads was largely unaffected.

Effect of particle size of rice husk ash on aluminium/graphene composites

Aluminium/graphene (Al/G) composite has gained wider engineering applications because of its unique properties such as lightweight, excellent corrosion resistant, improved strength and enhanced thermal conductivity. However, difficulty in dispersing graphene in molten aluminium remains one of the major optimization challenges. This study developed, by stir casting technique, composites of aluminium alloy from recycled aluminium can, 0.4 wt. % graphene (G) and 1.6 wt.% rice husk ash (RHA) with particle sizes of 150, 300 and 600 μm. The tensile, hardness, impact and fatigue properties were analyzed using Instron Extensometer, Vickers hardness tester, Charpy Impact machine and rotating fatigue machine respectively. Furthermore, the cast samples were characterized using scanning electron microscope (SEM) and X-ray diffractometer (XRD). The morphology of the microstructure of all composites showed the retention and uniform distribution of G and RHA particles in the Al matrix devoid of presence of harmful aluminium carbide with improved mechanical properties. The study established a new approach of dispersing graphene in molten aluminium through a stir cast method with 150 μm particle size of RHA given the best mechanical and morphological properties.

Energy accumulation in mechanical resonance and its use in drive systems of impact machines

An innovative method utilizing the phenomenon of mechanical resonance in machine drive systems of impact machines has been described. Energy accumulated in mechanical resonance is typically multiple times larger than the continuously supplied excitation energy. The amount of accumulated energy depends on the amplitude of vibration, mass and stiffness of system and present energy dissipation mechanisms. This form of energy can be extracted periodically each time after the amplitude of vibration reaches its maximum value. This effect could be implemented in drive systems of periodically operating machines, such as punching machines and presses. Significant reduction of energy demand in machines that use mechanical resonance in comparison with conventional machines was confirmed by means of simulations and experiments. Accumulation of the energy at mechanical resonance and its sequential extraction were presented together with a new prototype resonance punching press.

Implementation of laboratory works on the modern laboratory equipment

The Department “Mechanization of Construction” of Moscow State University of Civil Engineering continues to work in the implementation of the concept of development of educational disciplines in terms of the widespread use of computers and software in the educational process. This paper determines the main characteristics of two types of impact machines: electric hammers with vacuum magnetic angle valve and impact wrenches using NATIONAL INSTRUMENTS equipment and, in particular, the NATIONAL INSTRUMENTS ELVIS workstation.

Machine Learning and Computational Mathematics

Neural network-based machine learning is capable of approximating functions in very high dimension with unprecedented efficiency and accuracy. This has opened up many exciting new possibilities, not just in traditional areas of artificial intelligence, but also in scientific computing and computational science. At the same time, machine learning has also acquired the reputation of being a set of "black box" type of tricks, without fundamental principles. This has been a real obstacle for making further progress in machine learning. In this article, we try to address the following two very important questions: (1) How machine learning has already impacted and will further impact computational mathematics, scientific computing and computational science? (2) How computational mathematics, particularly numerical analysis, {can} impact machine learning? We describe some of the most important progress that has been made on these issues. Our hope is to put things into a perspective that will help to integrate machine learning with computational mathematics.

Structural Aspects of Zones of Plastic Strain. Part II. Effect of Mass Transfer

The structure of steel 09G2S is studied after high tempering in different zones of plastic strain (ZPS) after testing for impact bending and dynamic crack resistance, i.e., in the starting zone, in the core, and in the region of the force impact of the hammer of the impact machine. The proportions, the sizes, and the elemental compositions of carbide particles in the matrix metal, in the zones closest to the place of the impact, and in the regions of mass transfer are determined. The features of the structure in the starting region of the ZPS and in the region of the force impact of the hammer are determined after additional annealing at 600°C for 1 h.

Development and characterization of structural adhesives for aerospace industry with alumina nanoparticles under shear and thermo-mechanical impact loads

The present work aims to improve the mechanical properties of Epocast 50-A1/946 epoxy via incorporation of alumina nanoparticles using an ultrasonic agitation method. The optimum weight percentage of alumina nanoparticles was determined based on the improvement in the shear and impact properties of the nanocomposites at room temperature and 50 ℃. Accordingly, neat epoxy panels and nanocomposite panels with 0.5, 1.0, 1.5, and 2.0 wt% alumina nanoparticles were fabricated. The shear and thermo-mechanical impact properties of the panels were measured using an instrumented drop-weight impact machine and an Iosipescu shear test fixture, respectively, according to ASTMs D5379 and D7136. The maximum improvement in shear strength and modulus was 10.9% and 8.1%, respectively, for the nanocomposites containing 1.0 and 1.5 wt% alumina nanoparticles. The predicted shear moduli of the nanocomposites agreed well with the measured values with a maximum error of 6.52%. The optimal performance of impact properties was achieved by incorporating 1.0 wt% of alumina nanoparticles. Namely, the maximum impact-bending stiffness, contact force, and absorbed energy were increased by 12.9%, 13.0%, and 23.4%, respectively. The test temperature of 50 ℃ was found to have a negative effect on the impact-bending stiffness and the maximum contact force. On the other hand, the absorbed energy was increased up to 12.1%.

Effects of High Strain Rate and Self-heating on Plastic Deformation of Metal Materials Under Fast Compression Loading

The results of dynamic tests for compression of four metals after annealing (aluminum alloy, copper, brass, stainless steel) in the range of strain rates 100–10,000 s–1 are presented. To obtain dynamic true stress-true plastic strain curves a specific dynamic upsetting computation method was used starting from time variation of force pulse. The high-speed loading of specimens with a height to diameter ratio equal to 1.5 was carried out using three experimental devices: a drop-hammer with a free-falling mass, a ram impact machine with rubber accelerators and an impact machine with powder acceleration. A technique for direct measuring the specimen temperature during plastic deformation using an “artificial specimen” thermocouple (specimen-thermocouple) was proposed, in which the deformable metal itself is the “hot” junction, while the “cold” junction is connected to the measuring instrument. A thermoelectrode made of an alloy of noble metals tungsten and rhenium with a diameter of 0.1 mm was welded to the specimen by radiation from a pulsed YAG:Nd3+ laser. As a result of the tests, true dynamic stress–strain diagrams and flow stress versus strain rate were obtained. Experimental estimation concerning self-heating temperature variation corresponding to high-speed plastic deformation at room temperature is also developed. Experiments for determining the temperature effect of plastic deformation of the samples after annealing during cold settling showed that at the high speed of ~ 50 m s−1 and high strain-rates of ~ 10,000 s−1 the increase in temperature of the specimens compressed to a degree of deformation of 0.6 reached 55 °C for an aluminum alloy, 60 °C for copper, 80 °C for brass and 140 °C for stainless steel.

Analytical Study of Reinforced Concrete Beams Tested under Quasi-Static and Impact Loadings

During dynamic events (such as impact forces), structures fail to absorb the incoming energy and catastrophic collapse may occur. Impact and quasi-static tests were carried out on reinforced concrete beams with and without externally bounded sprayed and fabric glass fiber-reinforced polymers. For impact loading, a fully instrumented drop-weight impact machine with a capacity of 14.5 kJ was used. The drop height and loading rate were varied. The load-carrying capacity of reinforced concrete beams under impact loading was obtained using instrumented anvil supports (by summing the support reactions). In quasi-static loading conditions, the beams were tested in three-point loading using a Baldwin Universal Testing Machine. ABAQUS FEA software was used to model some of the tested reinforced concrete beams. It was shown that the stiffness of reinforced concrete beams decreases with increasing drop height. It was also shown that applying sprayed glass fiber-reinforced polymers (with and without mechanical stiffeners) and fabric glass fiber-reinforced polymers on the surface of reinforced concrete beams increased the stiffness. Results obtained from the software analyses were in good agreement with the laboratory test results.

Damage investigation and assessment due to low-velocity impact on flax/glass hybrid composite plates

There is limited information available in the body of knowledge regarding to the low velocity impact damage characteristics of sustainable bio-based such as flax fibre reinforced composites. This paper presents the results of full investigation of impact damage mechanisms on flax/vinyl ester laminated composite and flax-glass/vinyl ester hybrid composite laminates caused by low-velocity impact using a drop weight impact machine. The specimens were subjected to incident energy levels of 25 J and 50 J, in order to achieve a damage up to perforation and complete penetration. A 3D Finite Element Analysis (FEA) model was also developed using Hashin failure criteria. The damage and the predicted delaminations were compared using a high-resolution micro-Computed Tomography (μ-CT) technique. The results of the numerical analysis correlated well with the experiments and the imaging, which provided a full verification of the exact position of delaminations due to impact within the composite laminates.

Interfacial bond characteristics of steel fibers embedded in cementitious composites at high rates

In this study, the source of the rate-sensitive steel fiber pullout response in cement-based matrices was investigated at pullout rates of 0.0167–500 mm/s. A new pullout impact machine utilizing elastic strain energy to generate high-rate pullout loads was used in high-rate fiber pullout tests. In ultra-high-performance concrete (UHPC), smooth (S) steel fibers generated a higher peak bond strength dynamic increase factor (DIF, 1.9) than hooked steel fibers (DIF, 1.25), whereas S fibers in high-strength mortar (96 MPa) did not exhibit noticeable rate sensitivity. Furthermore, the addition of a shrinkage-reducing agent to UHPC clearly decreased the rate sensitivity of S fibers owing to the reduced matrix shrinkage: the peak bond strength DIF decreased from 1.9 to 1.77. The theoretical analysis revealed that the fiber pullout rate sensitivity was correlated with the interfacial crack path in a manner that depended on the fiber geometry as well as the matrix composition.