Blow Energy Research Articles

МЕТОДЫ ОПРЕДЕЛЕНИЯ ОСНОВНЫХ ФАКТОРОВ, ВЛИЯЮЩИХ НА ЭФФЕКТИВНОСТЬ ТЕХНОЛОГИИ ДОБЫЧИ БЛОКОВ КАМНЯ МАШИНАМИ УДАРНОГО ДЕЙСТВИЯ

This paper presents the main factors influencing the efficiency of rock destruction by impact loading along the contour during mining of blocks in strong rocks, such as the magnitude of impact loading (energy of a single impact), geometric parameters of the working tool, parameters of the fracture scheme, etc. Approaches applied by research institutions in mining science have been scrutinized. A methodology of experimental work to determine the main parameters of fracture depending on the force, energy, and design parameters of the tool is developed. The graphs of dependence of specific energy consumption on the height of the craggy layer as well as of dependence of specific energy consumption of destruction on the energy of a single blow A and of specific energy consumption of marble destruction by a chisel on the height of the craggy layer and change of work value A on the depth of wedge penetration h into the rock are presented.

ENERGY PARAMETERS OF ROCK FRACTURE WITH A WEDGE-SHAPED TOOL

This paper reviews energy parameters of rock fractures made using a wedge-shaped tool. The paper provides diagrams of distribution of forces and stresses under the impact of a wedge-shaped tool and stress components from two sources in the form of a wedge, localized in one row. There is a theory of energy intensity of rock fracture and energy of a single blow with a wedge-shaped tool which explains the energy parameters of rock fracture with a wedge-shaped tool. The new machine is based on static-dynamic methods of applying stresses to rock masses, which justifies the development of machines and mechanisms whose operating principle is based on static-dynamic methods of applying loads to rock masses

STRUCTURAL ORGANIZATION OF RAT TISSUES IN EXPERIMENTAL COMBINED TRAUMA OF THE CHEST AND BOTH THIGHS

Background. In cases of severe trauma, fractures of long bones are the most often combined with trauma of the chest, head, and abdomen, as well as development of hemorrhagic shock. Therefore, it is reasonable to study the combined trauma of the chest and lower extremities in details, as well as the post-traumatic multiple organ dysfunction especially in early manifestation stage. Objective. The aim of the study was to identify the features of structural organization of the lungs, heart and liver with underlying combined trauma of the chest and both thighs on the 7th day of the post-traumatic period. Methods. The experimental study involved 22 adult nonlinear white male rats with body mass of 200-210 g, kept on a standard diet at animal facility with food and drinking regimes recommended by the standards for laboratory animals. All animals were divided into 2 groups: the control group (1st, n=10), the experimental group (the 2nd) chest trauma and both thighs trauma, observation for 7 days (n=12). The animals of the experimental group were simulated for right-sided closed pneumothorax with a rib fracture by a trocar under thiopental-sodium anesthesia (40 mg/kg of body weight of the rat, intraperitoneally); it was combined with a fracture of the left and right femurs. Skeletal injury was modeled on each thigh that caused a closed fracture by a single dosed blow with a specially designed device. The blow energy was 0.375 J that corresponds to a severe injury. The associated injury was simulated by successive infliction of both injuries. Results. Examination of the liver of animals on the 7th day of the experiment revealed a rapid growth of lesions in their parenchyma. The central veins were poorly visible and contained single erythrocytes; the vessels of medium caliber of myocardial stroma were dilated and blood-filled, which was manifested by the development of perivascular oedema. In the lungs of experimental animals, a moderate decrease of interstitial tissue oedema of the interalveolar septa was present, while cellular infiltration of mast cells, macrophages and lymphocytes also decreased significantly. Conclusions. Multiple organ injuries, which are characterized by structural changes in the liver, heart and lungs in the combined trauma of the thorax and thighs on the 7th day of experiment were evidenced.

Increase in rock drill penetration depth

The application range of remote drilling machines is described. The common shortage of these machines is the dependence of the blow energy transfer to the bottomhole on the bottomhole depth. Aimed to reduce the influence of this factor, it is proposed to use the mixed-type method of drilling with a downhole rock drill to be placed directly at the bottomhole. The key element of this method is a small-size DTH rock drill. The layout of the rock drill and its prototype testing results are presented.

Physical analog of shock pulse generator and high-frequency pneumatic hammer

Many special construction operations need pneumatic percussion machines. The feasibility of increasing the penetration rate in driving of rods in soil is assessed via physical modeling. The promising nature of high-frequency pulse load generators in rock fracture at the ensured threshold value of the unit impact energy is justified. The best approach to this effect is the valve-aided air distribution implemented in pneumatic hammers of variable impact capacity. Such air distribution system uses a ring-shaped elastic valve at the compressed air exhaust from the back stroke chamber. The stable operation conditions of the ring-shaped rubber valve are determined within a wide range of impact frequency adjustment. The authors have experimentally determined the elastic valve temperature versus impact frequency, the influence of the angular orientation of the ring-shaped elastic valve cross-section on the air tightness of the back stroke chamber, as well as the values of radial and axial crumpling of the elastic valve with increasing radial gap between the piston and the device housing. The studies into pipe driving by a compound generator composed of two coaxial tandem impact facilities are analyzed. The increased impact on the pipe by the united percussive facilities at the unit blow energy higher than the threshold value ensures higher penetration rate of the pipe owing to the improved bottomhole interaction. Duty harmonization of two percussive facilities by means of frequency synchronization ensures reliable and stable operation of the compound generator. The capabilities of the machine were tested using a prototype model with smooth variation of impact frequency in a vertical channel in soil. The article describes the designs of the pneumatic hammer prototypes with smooth blow frequency variation and with mechanical synchronization of two impact bodies placed in the common housing and having the joint air distribution system.

EXPERIMENTAL VALIDATION OF PARAMETERS OF HEAVY GRAVITY PNEUMATIC HAMMERS FOR CASING PIPE RAMMING IN SOIL

Vertical penetration of steel pipes with a diameter of 530-1420 mm and to 100-150 m long in soil requires high blow energy (10-100 kJ). Design of the percussion machines using the available pneumatic hammers is constrained due to the high flow rate of an energy source required. It is of the current concern to design an air-driven percussive tool capable to ensure high blow energy at low flow rate of compressed air. This study describes the testing data of a breadboard model of a new gravity pneumatic hammer. The operating mode of the model hammer is studied, and the blow energies, blow frequencies and compressed air flow rates are evaluated as functions of air pressure in the main line. The tests proved stability of cycling operation of the model tool at the high blow energy and low flow rate of the energy source at the main line pressure of 0.36-0.77 MPa. Using the dynamic similarity criteria, the standard sizes of heavy pneumatic hammers are developed, their blow energy and air flow rate are determined, and the efficiency is evaluated.

EXPERIENCE OF STEEL PILE DRIVING BY PNEUMATIC HAMMERS IN UNDERGROUND CONSTRUCTION BY THE CUT-AND-COVER METHOD

The timeliness of application of pneumatic hammers in the deep bore tunneling in underground construction is justified. The penetration resistance forces in steel pipe driving in soil are determined. The analysis of long-term operation of adjustable capacity pneumatic hammers shows the conformity of the blow energy and the driven pipe diameter. The relationship between the unit blow energy and the open-ended pipe diameter is proposed. The main pneumatic hammer parameter to govern the machine performance is substantiated. The standard pneumatic hammers of adjustable capacity are characterized. The cases of vertical pipe driving at construction sites in Russia are described. The technological capability of construction of retention wall in soil using rolled steel, namely, I-beams, U-sections, piling bars, etc. is illustrated. The production tooling arrangements to ensure secure mounting of the hammer on the axial element driven in soil are described.

Dynamics of gravity-type pneumatic percussion machine for drain hole drilling

The author presents and justifies a construction diagram of a gravity-type pneumatic percussion machine for drain hole drilling with efficient penetration of casing in soil. The working cycle parameters of the machine, efficient design variables, as well as the blow energy, blow frequency and compressed air flow rate depending on the line pressure are determined by the numerical modeling. The weight, size and dynamics of the gravity-type machine are compared with the known analogous facilities.

Effect of elastic valve characteristics on pneumatic impact ring machine capacity

The paper presents a case-study of the effect exerted by a ring-shaped elastic valve as a promising lock-and-control element of air distribution on the performance of a pneumatic impact ring machine. The design model of the machine is presented. The authors determine the blow energy and frequency of the machine, as well as the compressed air flow rate versus the preload of the valve and the elasticity modulus of the valve material. The recommendations on design of the elastic air distribution elements for pneumatic percussion machines subject to their operational conditions are given.

Modeling operation of sliding valve distribution in hydraulic percussion device with adjustable blow energy

The authors discuss the simulation model of a sliding valve distributor enabling adjustment of capabilities of hydraulic percussion devices. The paper presents the theoretical oscillograms of the valve characteristics and the plots of change in the valve mode versus the valve parameters.

Justification of layout diagrams hydraulic percussion mechanisms by the comparative analysis of dynamic parameters

The simulation models are used to compare achievable dynamic parameters of layout diagrams of hydraulic percussion mechanisms having similar size and weight. The comparison results prove application feasibility of these layouts in engineering hydraulically driven percussion machines. The optimization methods are used to find the optimal values of design variables to meet the criterion of maximal blow energy.

Optimum energy calculation for a drill hammer-blow RH571-4W

Consumption of raw materials has steadily increased. Rich countries explore several raw materials such as phosphate, ore and copper. For this, exploitations must be large, highly mechanized and produce in large quantities to be profitable. Also, the use of drilling means requires good productivity on the one hand and a long service life on the other hand. The satisfaction of these requirements is possible if the drilling method chosen is suitable for the geological and mining conditions as well as the drilling parameters. The choice of the machine therefore has a direct impact on costs and results. The aim of this work is to ensure a proper exploitation with an optimum energy calculation for a drill hammer-blow taking into account their economic or technical conception characteristics. To find out the energy losses of a hammer blow, the Baron and Ghrainer formula which, has been applied, allows us to calculate the drilling speed and to deduce the blow energy. Then, to calculate the energy losses and to extract the optimal values for different parameters, a statistical model of GAUSS-MARKOV theorem has been introduced.

Analysis of a Novel Automatic Control Approach for the Free Forging Hammer

This paper proposes an electro-hydraulic servo control method and realizes the automatic control and remote control of free forging hammers for the first time. A configuration and control strategy for the program-control free forging hammer are constructed. Based on the configuration, a single-acting differential servo cylinder system is proposed to drive the follow-up spool valve and then control the motion state of the hammerhead. Furthermore, a non-contact measurement method is adopted to detect the real-time position of the hammerhead, and the installation position of the measuring sensor is isolated from the hammer body and foundation, thereby reducing the influence of vibration and impact on the accuracy of the feedback signal and ensuring the successive forming process of the forging hammer. In addition, a blow energy model of the forging hammer processing system is established, and a fuzzy-PID control scheme for the forging hammer is then adopted. Based on the control strategy, the striking accuracy of the proposed automatic forging hammer is significantly improved compared with the traditional forging hammer. Finally, the method is applied to an 8 MN forging hammer, and the results show its better processing performance than traditional hammers in terms of all indices.

Analysis the effect of piling activity using diesel hammer on surrounding construction

Construction starts with earth work that takes a long time. To reducing these problems, acceleration is usually done on the site. For example, doing basement excavations at same time with driven piling. Early basement excavation work has the potential to cause the foundation piles that has been driven will be slided. Besides being supported by expansive soil, use of diesel hammer which has large blow energy as driven machine will also affect additional lateral load on the ground which causes pile or wall to slide or roll. In this study, the calculation of additional loads due to piling and soil using Boussinesq and Rankine Theory. The Reese and Matlock Method is used to calculate the lateral deflection of the pile. Pile will experience lateral deflection 30 mm exceeding the permit tolerance of 25 mm. Earth retaining wall with 3,2 m and 6,4 m excavations, the wall does not slide and roll. On the earth retaining wall with 9,6 m excavations, the wall does not slide but it will be rolled. The conclusion of this study is doing excavation when piling work has not been fully completed, it will potentially causing damage to the construction that has been made.

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.

Design of the stamping process of large-sized turbine blades taking into account the technological characteristics of titanium alloys

The concept of designing a multi-stage stamping process on a steam-air hammer is described on the example of the manufacturing cycle of large-sized turbine blades made of VT6 titanium alloy. The features of the process, factors affecting the properties of the final product are revealed. The requirements for the part blank and stamped blanks are determined. The processes of rough forming of the workpiece are modeled and analyzed. The die tooling is designed, the mathematical model of the steam-air anvil block stamping hammer is set up, namely: hammer energy of blow, blow effervescive. The simulation of the stamping process is done. The analysis of factors affecting the accuracy characteristics of finished products and workpieces during hot plastic deformation is carried out in order to create a method for calculating distortion. A strong scatter in the values of the Young's modulus was determined both at room and at elevated temperatures. The physical and mechanical properties of the material are obtained. A preliminary simulation of the distortion process was carried out, according to the results of which the economic effect of reducing allowances for machining of blades was calculated. A technique was developed for constructing titanium alloy recrystallization diagrams, diagrams were constructed for two heat treatment conditions.

ВЛИЯНИЕ ОБРАБАТЫВАЕМОЙ СРЕДЫ НА ЭФФЕКТИВНОСТЬ ПЕРЕДАЧИ ЭНЕРГИИ УДАРНОГО ИМПУЛЬСА ПРИ ВОЛНОВОМ ДЕФОРМАЦИОННОМ УПРОЧНЕНИИ

The investigations carried out are dedicated to the analysis of the material impact of the loading environment upon the effectiveness of a shock pulse at wave deformation strengthening. To carry out investigations in the specialized program there is developed a finite-element model of an impact system consisting of a head and a waveguide pressed statically to the environment of loading. The impact system effectiveness was estimated on the ratio of shock pulse energy imparted to a deformation source taking into account the material of the loading environment to the energy of a head blow to a waveguide. It is defined that the most significant impact upon a share of transient energy of the shock pulse is rendered by the head parameters the change of which in the range considered allows increasing the effectiveness of the impact system by 15.6 times. The next important factor affecting considerably the effectiveness of shock pulse energy transfer is a ratio of the lengths of a head and a waveguide the change of which in the value range investigated allows increasing a share of energy transferred by 2.8 times. The least impact upon the effectiveness of impact energy transfer in the center of deformation with the impact system is performed by the material of loading environment – 1…3% for the rational values of the parameter ratios of the impact system elements (n more than 80%). At the forced choice of less efficient impact systems (L1/d1=1 ; L1/L2=1…10; n less than 62%) the impact of the material of loading environment may make 6…10%.

Prospects for percussion sawing machines in production of high-strength dimension stone

One of the most labor-intensive operations in production of dimension stone is separation of a stone monolith from rock mass, cutting of the monolith into blocks and sawing of the blocks into slabs. This article reviews in brief the methods of cutting and sawing of high-strength rocks. The new method of percussion sawing is described. Based on the method, the structural layouts of machines for cutting and sawing of stone blocks are proposed. The percussi on sawing method is efficient in brittle hard and super-hard rocks such as granite and sometimes marble, with Protodyakonov-scale hardness from 6 to 20. The method provides high quality finishing of surfaces at average productivity and low cost of sawing. The authors describe various structural layouts and operation modes for different percussion sawing machines suitable for operation in stone quarries, stone working plants and workshops. The basic elements of percussion sawing machines are frame, percussion assembly, tooth saw, vertical and horizontal feed drives, and the cut blowing or washing facilities. The article describes the machine capacity calculation procedure confirmed by the experimental research data. The major machine parameters to affect its capacity are: blow energy of the percussion assembly, number of percussion assemblies, saw area at the contact with stone, seesaw velocity, and ultimate compression strength of stone. A new estimated figure is put forward as specific blow energy per kerf bottom surface. The change in the capacity of a quarry percussion sawing machine as a function of time of one saw pass is determined. The obtained relation is compared with performance of other two types of sawing machines.The comparative analysis of mechanical methods of hard rock sawing is performed. The efficiency of the proposed method for percussion sawing of hard and super hard rocks is proved.

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.

A simulation study on the closed-loop control of screw press forgings using the impact energy as control input

Screw presses are energy-restricted forming machines that use rotational energy stored in a flywheel for forming, which is converted into a linear movement by a threaded screw. Screw presses are widely used for forging steel, aluminum and brass. In a direct-driven electrical screw press, a reversible electric motor is mounted directly on the screw and on the press frame above the flywheel. With directly driven screw presses, the blow energy can be exactly dosed from one blow to the next. However, so far no prior work is known which uses the blow energy as a control input in a targeted manner to influence the properties of the forging. The purpose of the present work is to lay the foundations for property control through blow energy dosing during forging on screw presses. Process control becomes increasingly interesting due to ever increasing customer demands and needs for resource-efficient production. A major challenge is the variation of process parameters, e.g. temperature variations in the furnace, during transport or due to inherent uncertainty in the heat transfer to the dies and the environment. If the process conditions are changing the deviations from the planned process trajectory may lead to an insufficient die filling or undesired final properties. Forged parts require high precision considering the part geometry and material properties. During forming two mechanisms in terms of forming temperature take place: heat conduction due to contact with tools and heat dissipation due to plastic deformation. The heat transfer acts as disturbance, the impact energy can be used as control input. In this work, investigations into process control by impact energy dosing are put forward using FE (finite element) simulations.