Impact Piston Research Articles

Experimental study on impact coupling characteristics of high-pressure accumulator for unconstant-pressurized chamber rock drills

In order to improve the efficiency of unconstant-pressurized chamber rock drills in large-hole and hard-rock conditions, the coupling characteristics of high-pressure accumulator and the impact system were analyzed. The multi-parameter mechanism experiment was designed. Piston displacement, oil return flow, main input-oil, and internal chamber pressure were obtained. Combining the structural characteristics and working principles of rock drills, the experiment-based accumulator volume calculation methods was proposed. According to the phase plane analysis of the accumulator diaphragm and the time series analysis of impact performance parameters, which indicate that the high-pressure accumulator and impact system have typical non-contact nonlinear structures. The dynamic performances also present complex nonlinear characteristics. With the increase of gas pre-charge pressure, the bifurcation points were developed from period-one motions to period-two motions, the coupling degree of flow coupling between the accumulator and the impact piston was gradually enhanced, and the impact performance was gradually improved. With the formation of the period-one motions and the increase of bifurcation strength, the diaphragm became more susceptible to fatigue damage. The optimum choice of high-pressure accumulator gas pre-charge pressure is 80–90 bar, which provides a reference for the application and parameter setting of high-pressure accumulators in unconstant-pressurized chamber rock drills.

Developing an Ovine Model of Impact Traumatic Brain Injury

<div>Traumatic brain injury is a leading cause of global death and disability. Clinically relevant large animal models are a vital tool for understanding the biomechanics of injury, providing validation data for computation models, and advancing clinical translation of laboratory findings. It is well-established that large angular accelerations of the head can cause TBI, but the effect of head impact on the extent and severity of brain pathology remains unclear. Clinically, most TBIs occur with direct head impact, as opposed to inertial injuries where the head is accelerated without direct impact. There are currently no active large animal models of impact TBI. Sheep may provide a valuable model for studying TBI biomechanics, with relatively large brains that are similar in structure to that of humans. The aim of this project is to develop an ovine model of impact TBI to study the relationships between impact mechanics and brain pathology. An elastic energy impact injury device has been developed to apply scalable head impacts to rapidly rotate the head without causing hard tissue damage. A motion constraint device has been developed to limit the head motion to a single plane of rotation. The apparatus has been tested using deceased animals to assess the controllability of impact velocities, the repeatability of head kinematics, and the dynamic response of the head to impact. Impact velocities are effectively controlled by modulating the elastic energy stored in the impact piston. The resulting head kinematics are somewhat variable, and are influenced by impact location, time-dependent postmortem tissue changes, and specimen head and neck physiology. Model development will continue, and in vivo testing will be conducted to assess the brain pathology following impacts of varying severity.</div>

Research on correction method of inertia factor of starting section of gap flow opening in hydraulic rock drill

ABSTRACT Large pulsation and impact occur during the working process of hydraulic rock drill, which has a negative influence on the system. Aiming at this phenomenon, the related characteristics of hydraulic fluid inertia are studied in this paper. The dynamic model of impact and reversing mechanism of rock drill is established. Through the parameter analysis of the model, the concepts of hard parameter quantity and soft parameter quantity are proposed. The influence coefficient C of the initial section of crevice flow including the influence of fluid inertia is deduced, and the comprehensive factors such as hydraulic oil velocity, unstable flow and friction resistance are analyzed, The value of soft parameter quantity ζ is (ξ+1) ~ (ξ+ 1.5)。The pressure test of the working chamber is designed and 7 groups of data are obtained. Through data analysis, the influence of C on the simulation results is obtained, which has a great influence on the reversing valve. The deviation of simulation data of left and right valve chamber pressure is increased from ± 8% to ± 3%. It has a certain impact on the impact piston. The deviation of simulation data increases from ± 5% to ± 3%, and has little impact on the accumulator. The deviation of simulation data increases from ± 4% to ± 3%.

Effect of Texture on Total Energy Consumption of High Frequency Hydraulic Impact Piston Pair

Limited by the influence of the traditional clearance seal structure on the leakage and friction loss of piston pair, the energy utilization ratio of the hydraulic impactor is difficult to improve effectively. To solve this problem, a novel micro-texture clearance seal structure of impact piston cylinder was proposed, and an integrated energy consumption evaluation index considering leakage and friction loss of impact piston pair was proposed. Based on the average Reynolds equation, a comprehensive energy consumption analysis model for a textured high-frequency hydraulic impact piston pair was established, and the influence of piston texture parameters on the comprehensive energy consumption under rated working conditions was studied. The results show that the cylindrical texture clearance seal structure provided an effective way to improve the energy utilization ratio of hydraulic impactor, with energy consumption 13~15% less than the traditional structure. Variation of area rates textured made the amplitude value of integrated energy consumption of the piston pair decrease by 4~15%, and the optimum area rate was 0.2~0.4. Depth ratio of texture could also reduce the integrated energy consumption of the piston pair, but the reduction range was small.

Analysis of lubrication and sealing performance on textured piston pair with multi-factor coupling

PurposeThis paper aims to study the lubrication and sealing performance on the textured piston pair under the cross action of the shape and structure parameters. This paper further carries out the optimization design of low energy consumption hydraulic impact piston pair.Design/methodology/approachBased on the characteristics of the ring gap seal piston pair, the flow field analysis model of the whole film gap is established for its periodic treatment. The friction power loss of the piston pair is defined as the evaluation index of the lubrication performance and the leakage power loss as the evaluation index of the sealing performance. The orthogonal test design and CFD software were used to analyze the lubrication and sealing performance of the textured piston pair.FindingsThe cross action of shape and structure factors has a great influence of the lubrication and sealing performance on the textured piston pair. Clearance and shape parameters have great influence on it, while seal length and depth diameter ratio have little influence. The sealing performance of conical textured piston pair is good, while the lubrication performance of square textured piston pair is good. The primary and secondary order of influence of shape and structure on energy consumption on piston pair is B (seal clearance) > C (texture shape) > D (area ratio) > A (seal length) > E (depth diameter ratio).Originality/valueBreaking the defect of local optimization design on traditional piston pair structure, then find the matching relationship of structural parameters on textured piston pair. Further improve the lubrication and sealing performance of the piston pair, and provide reference for the global optimization design of the low energy consumption hydraulic impact piston pair.

Research on the Matching of Impact Performance and Collision Coefficient of Hydraulic Rock Drill

The stress wave produced by the piston impact, on the drill rod, is an important factor affecting impact performance. It is particularly important to control the stress waveform generated by the piston impact on the drill rod to meet the requirements of efficiency and component durability of some impact mechanical systems. Based on wave theory, the impact stress wave model of rock drilling is established, a dimensionless collision coefficient γ is put forward, and the matching relationship between different collision coefficients γ and stress waveforms is analysed. The length of the impact piston under the same material condition determines the change rule of the waveform. The stress waveform experimental verification is thus designed. The pressure chamber curves of different pistons in the rock drill were tested, the collision velocity of the piston was obtained, and the impact energy and impact power were calculated. The relationship between the impact performance and the collision coefficient γ is analysed. When γ is in the range of 9–11, the impact piston’s design of a high‐power rock drill can be satisfied. When γ is in the range of 3∼5, it is mainly designed for low‐power rock drills.

A Large-Flowrate On–Off Valve with Hollow Structure for High-Frequency Hydraulic Vibration and Impact System

In high-frequency hydraulic vibration and impact systems, the high-speed reciprocating motion of the impact piston, as controlled by the main valve, transfers energy to the target. Therefore, the main valve must have a fast response speed and strong flow capacity. A novel two-stage large-flowrate on–off valve is developed in this study. The first stage is a small-flowrate servo valve, and the second stage is a large-flowrate hydraulic control valve with a hollow spool. The hollow structure not only reduces the quality of the spool and improves the valve dynamic characteristics but also improves the flow capacity and reduces the pressure drop at the valve port. A structural strength simulation is performed, and the deformation and stress of the spool are calculated. Then, the internal flow channel is extracted and the pressure drop characteristics of valve are obtained by simulation. To obtain the dynamic characteristics of the valve, the control equations of the valve are established, and the simulation model is built in Simcenter Amesim software. Then, the structural parameters of the valve body are optimized in this model. Finally, a prototype is developed for hydraulic vibration and impact systems. The experimental results show that the prototype works well, the opening time of the second-stage valve is within 6 ms, and the port pressure drop at a flow rate of 1000 L/min is only 30% of the conventional opening and closing valve of the same diameter.

Effect of fish scale texture on friction performance for reciprocating pair with high velocity

PurposeThis paper aims to study the frictional performance of reciprocating pair with high velocity by using hydrodynamic lubrication principle and fish scale textured piston model.Design/methodology/approachBased on the idea of function characteristic approximation and coordinate change, a mathematical representation model of imitating fish scale texture pit section is established. According to the principle of dynamic pressure lubrication of the textured fluid, a three-dimensional numerical model of flow field for fish scale texture is established without considering cavitation. Numerical analysis of the model carp scale texture unit by orthogonal experimental design and FLUENT software is carried out.FindingsEffects of fish scale pit texture on friction properties for a reciprocating pair piston surface with high velocity (impact piston) are acquired. Effects of texture characterization parameters and flow rate on the surface friction performance for impact piston are found. Effects of different characteristic parameters combination of imitating fish scale texture on friction performance for impact piston surface are obtained.Originality/valueThe model is an effective tool to study the friction and wear of reciprocating pair with high velocity. The effects of fish scale textured piston pair supply a theory lead to design the reciprocating pair with better friction performance.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-09-2019-0398

Ignition thresholds of aluminized HMX-based polymer-bonded explosives

The ignition of aluminized HMX-based polymer-bonded explosives (PBXs) under shock loading is studied via mesoscale simulations. The conditions analyzed concern loading pulses of 20 nanoseconds to 0.8 microseconds in duration and impact piston velocities on the order of 400-1000 m/s or loading stresses on the order of 3-14 GPa. The sets of samples studied have stochastically similar microstructures consisting of a bimodal distribution of HMX grains, an Estane binder, and aluminum particles 50-100 µm in diameter. The computational model accounts for constituent elasto-viscoplasticity, viscoelasticity, bulk compressibility, fracture, interfacial debonding, internal contact, bulk and frictional heating, and heat conduction. The analysis focuses on the development of hotspots under different material settings and loading conditions. In particular, the ignition thresholds in the forms of the James relation and the Walker-Wasley relation and the corresponding ignition probability are calculated and expressed as functions of the aluminum volume fraction for the PBXs analyzed. It is found that the addition of aluminum raises the ignition thresholds, causing the materials to be less sensitive. Dissipation and heating mechanism changes responsible for this trend are delineated.

Research on Pneumatic Hammer Used in the Experiment of Forging Process Course

In order to provide simple and practical experimental equipment for the experiment of forging technology course, based on the impact cylinder, the pneumatic hammer used in experiment of forging process course was developed. According to upsetting deformation energy of the lead specimen and the biggest impact energy of impact cylinder, inner diameter and piston stroke of cylinder were chosen. According to the working principle of impact cylinder, the control circuit of the impact cylinder was designed, the electrical components and control components were selected and used, the support bracket of impact cylinder and the anvil block were designed and manufactured. When air pressure is 0.7 MPa, the switch is pressed, after delay the hammer head moves downward at a high speed. The pneumatic hammer has simple structure, small footprint, low noise and vibration. Its impact energy can meet the need of upsetting deformation of lead specimen with a diameter of 20mm at room temperature.

Research on Impact Performance of Hydraulic Rock Drill with Floating Characteristics of Double Damping System

As a technological innovation of high‐power hydraulic rock drill, double damping system has a very important effect on impact performance. The double damping system is a floating mechanism. The characteristics of the floating mechanism have an important influence on the impact energy, frequency, and power of the hydraulic rock drill. Based on orifice throttling theory, the static equilibrium position of a damping piston was calculated, and the characteristic parameters of the double damping system were summarized as damping flow (Qd) and feed force (Fd). According to the characterization parameters of the double damping system, an experimental scheme of the floating characteristics of the double damping system was designed, and the combined experimental data of Qd and Fd were obtained. The 40 groups of experimental data were extracted, and the relationship between the combination (Qd, Fd) and impact energy and frequency and power were analyzed. The combination (Qd, Fd) with maximum and minimum power was selected to analyze the motion law of an impact piston. The maximum drilling power was obtained at the combination (Qd = 8 L·min−1, Fd = 16.25 kN). The influence factors of the double damping system on impact performance were summarized, and the characteristics of the double damping system under optimal impact performance were obtained.

Fault Diagnosis Research on Impact System of Hydraulic Rock Drill Based on Internal Mechanism Testing Method

In the production and manufacturing process of hydraulic rock drill, there are small impact energy and low impact frequency, and a fault diagnosis method based on the internal mechanism testing and testing of the hydraulic rock drill is proposed. This method is used to test the change law of hydraulic oil in the rock drill, by retaining the test holes on the cylinder body and other important components of the hydraulic rock drill. At the same time, the mathematical method is used to deal with the test curve, and the influence of pressure pulsation characteristics of the front and rear chambers of the impact piston and the left and right valve chambers of the reversing valve on the impact performance of the rock drill is analyzed. Based on Newton’s law, the model of the impact piston and reversing valve is established. According to the velocity and other parameters of the impact piston, the size of the impact piston switch point is calculated. The coupling between the movement of the impact piston and the movement of the reversing valve is analyzed according to the model established. Comparing the results of the experimental data, the correctness of the fault diagnosis analysis method and model is verified. The effect of the fault rock drill and the improved model is compared, and the theoretical basis is provided for the fault diagnosis of the rock drill and the design of a new type of rock drill.

Impact System Dynamic Characteristics of Hydraulic Rock Drill Based on an Overlapped Reversing Valve

For the phenomenon of a hydraulic rock drill based on an underlapped reversing valve, the mechanical structure of the overlapped reversing form was proposed, which affected the pressure pulsation of the impact system, and motion of the impact piston was analyzed. The model of a hydraulic rock drill was built based on Newton’s laws. The initial lead size of the reversing point was calculated by the equilibrium position of the damping piston and final velocity of the impact piston. The size of the overlapped reversing valve was designed and the best impact interval was calculated, according to pressure characteristic curves in the piston of the front‐rear chamber and in the reversing valve of the left‐right chamber, and the damping piston floating feature had an impact on initial lead size of the reversing point. The advantages of the overlapped reversing valve were analyzed, by contrasting the pressure pulsation of the impact system and motion of the impact piston with the underlapped reversing valve. The inner mechanism experiment of the hydraulic rock drill was designed to test the pressure characteristic curves in the piston of the front‐rear chamber and in the reversing valve of the left‐right chamber. The model of the overlapped reversing valve was verified by the experiment.

Design and Research of Deep-Sea Hydrothermal Sampler with Multi-Cavity

In this paper, on the basis of the existing hydrothermal sampling equipment has devised a new hydrothermal sampler. Using Ansys Workbench software to analyze the valve core and valve seat sealing, the valve core half cone Angle is obtained on the influence law of sealing performance. Cavity of hot fluid into the sampling moment of impact piston is analyzed, the analysis shows that the strength of the piston to meet requirements and the impact piston vibration does not affect the o-rings seal performance.

Research on Hydraulic Control System of Jumbolter Based on Intelligent Mix Optimization Algorithm

This paper found the deficiency of classical Z-N method in optimization of PID parameters, proposed the intelligent optimization algorithm of PID parameters .The stimulation and experiment showed that the PID parameters getting from this algorithm are efficient, accurate and speedy. This paper used algorithm for hydraulic control system of jumbolter. The stimulation and experiment showed that when peak oil pressure of relief chamber is changed, optimum algorithm will find suitable and based on MAX power requirement to change displacement of relief surface, which lead to changing displacement of impact piston, at the same time, it will change the impact power and frequency of impactor, and realize impactor auto change working parameters based on the different situation under suitable parameters and MAX power working condition. The experiments show that it has a certain reference value for other control objects and control process.

How Trends in Lubrication Development Impact Sliding Bearings and Piston Rings

How Trends in Lubrication Development Impact Sliding Bearings and Piston Rings

Rational Designing Two-Stage Anvil Block of Impact Mechanisms

In the article the solution of the problem of heightening of efficiency of impact systems for the score of selection of rational shapes anvil blocks is reduced. Shape execution of anvil block in the form of two steps is offered - impact and cylindrical piston, which length steal up by "golden section" rule. Results of a finding of shapes of the impact impulses generated at direct blow on rods two-stage anvil blocks are reduced and analyzed.

Experimental Results for an Acoustic Driver for MTF

General Fusion is planning to form an FRC or spheromak of 1017 cm−3, 100 eV, 40 cm diameter by merging two spheromaks with reverse or co-helicity. This target will be further compressed in a 3 m diameter tank filled with liquid PbLi with the plasma in the center. The tank is surrounded with pneumatically powered impact pistons that will send a convergent shock wave in the liquid to compress the plasma to 1020 cm−3, 10 keV, 4 cm diameter for 7 μs. General Fusion has built a 500 kJ, 80 μs, 6 GW pneumatic impact piston capable of developing 2 GPa (300 kpsi). In this paper we will present the performances achieved to date.

Norepinephrine and traumatic brain injury: a possible role in post-traumatic edema

Unilateral cerebral contusion is associated with an early (30 min) increase in norepinephrine (NE) turnover followed by a later (6–24 h) depression of turnover which is bilateral and widespread throughout the brain. Blockade of NE function during the first few hours after traumatic brain injury (TBI) impedes subsequent recovery of function without enlarging the size of the lesion. The current studies were carried out to characterize further the timing of the switch from increased to decreased NE turnover and to investigate the pathogenesis of the delayed recovery of function associated with blocking NE function. Adult male rats had unilateral somatosensory cortex contusions made with a 5 mm diameter impact piston. They were killed after 2 h and their brains analyzed for NE turnover by HPLC with electrochemical detection. In general, NE turnover (the ratio of 3-methoxy-4-hyroxyphenylglycol to NE levels) had returned to sham-lesion control levels in most brain regions by 2 h after either left or right sided contusions. The only exceptions were a persistent 87% increase at the lesion site after right-sided contusions and 22% and 32% increases in the contralateral cerebellum after right- and left-sided contusions, respectively. Blockade of α 1-adrenoceptors by treatment with prazosin (3 mg/ kg, i.p.) 30 min prior to TBI produced edema in the striatum and hippocampus at 24 h which was not seen saline-treated rats nor in rats where NE reuptake was blocked with desmethylimipramine (DMI; 10 mg/kg, i.p.). DMI increased edema at the lesion site at 24 h, however. These data suggest that the early increase in NE release following unilateral cerebral contusion is protective and that this may act to stabilize the blood–brain barrier in areas adjacent to the injury site. Drugs that interfere with this enhanced noradrenergic function might enhance the damage caused by TBI.

Closed air system seismic wave generator

Apparatus for generating seismic waves including an upstanding hollow cylindrical housing within which an impact piston latched in a cocked position is adapted to be propelled downwardly by high pressure expanding gas in the confined chamber above it within the housing so as to strike a target plate resting on the ground adjacent the lower end of the housing. After each blow against the target, the piston is retracted upwardly by means of hydraulic cylinders which recompress the gas in the chamber to its original pressure. Since there is no need for recharging the pressure chamber after each shot, economical rapid cycle operation is facilitated.