Method for experimental determination of static-dynamic characteristics of concrete
SUBSTANCE: method is realised by fixation of an experimental concrete sample in the form of a prism in clamps of a test bench using an alignment device, providing for central application of stretching load in process of loading, and registration of a force and deformations of the sample in time using a dynamometer and a strain gauge station during loading executed via a lever system in two stages: at the first stage - stepped static loading of the sample to the specified level by means of laying of piece weights onto a load platform, at the second one - instant or stepped dynamic additional loading or unloading by means of short-term variation of the axis diameter in the point of force transfer from the lever to the compensating element, setting, if necessary, the value of movements in the elastic element.
EFFECT: simplified methodology and increased validity and reliability of test results.
5 dwg, 2 ex
The invention relates to the construction, in particular to the determination of the parameters of deformation of concrete under static loading concrete samples to a level not exceeding the ultimate strength of the concrete in compression Rband tensile Rbt, dynamic loading to failure with a constant velocity and dynamic loading unloading.
Design of reinforced concrete structures are based static application of the load and further its impact, while using prism strength of concrete as determined during phase (degrees) loading concrete samples using press . The disadvantage of this method is the relatively low loading rate of concrete prisms, which does not allow to judge about the deformation of the specimen under high-speed loading. Determination of strength of concrete in tension is carried out using a tensile machine, which also allows to obtain the characteristics of the deformation of the sample under high speed loading.
In the calculation of reinforced concrete structures to explosive and impact loading using the values of ultimate strength and ultimate strain of concrete samples defined at the moment of their destruction when dynamic loading is not superior to the similar value found during static tests�Oia.
One of the solutions that allow the testing of concrete to dynamic loading is the pneumodynamic installation for high-speed loading of concrete prisms .
The disadvantage of this solution is the inability to create a certain level of static loading, the previous high-speed loading of the concrete prism.
The closest solution to the claimed invention is a method for experimental determination of the static-dynamic charts of concrete, in which the instantaneous speed or dynamic loading case is falling with decreasing current in the electromagnet load .
The disadvantage of this solution lies in the inconvenience of the necessity of the presence of electromagnetic systems; the inability of the implementation of dynamic load cases on a predetermined displacement; in the impossibility of achieving the deformation of the sample during high-speed unloading to a preselected value different from the value of pogrujeniya; the inability to repeated dynamic loading of the sample in alternation with unloaded; in high error obtained in the experiment data.
The technical result of the invention is to facilitate the testing method, improving the accuracy of the obtained data, empowerment of experimentalgameplay static-dynamic properties of concrete, consisting in the possibility to pre-set displacement in kompensirujushhego element under dynamic loading and unloading.
The technical result is achieved in that in the method of experimental determination of static-dynamic characteristics of concrete, which consists in securing an experienced concrete sample in the form of a prism in the clamps of the test bench using a centering device which provides a Central load application in the process of loading, and registration efforts and deformations of the prism in time by using the dynamometer and tantostanze, according to the invention the loading is performed via a lever system in two stages: first - stage static loading of the specimen to a predetermined level by laying a piece of cargo on the cargo platform, the second is the instantaneous speed or dynamic loading case or unloading by short-term changes in the diameter of the axis at the connection of the lever and the compensating element.
Fig.1A presents a diagram of the device for implementing the proposed method in a tensile test. Fig.1B is a diagram of a device for compression testing. Fig.2A is a diagram of the offset axis in the implementation of dynamic loading in a tensile test. Fig.2B is illustrated a method of IP�of itania sample in case when a pre-set displacement in kompensirujushhego element under dynamic loading. Fig.3 is a diagram of the loads acting on the lever when a tensile test.
Specially designed installation comprises a frame 1, the device for centering and gripping of the specimen 2, the lever 4 to be transmitted to the test specimen 3 is connected through a rack 5 with the frame 1, the compensating element 6 resting on a base frame 1 and connected with the lever 4 through the axis 7, the metal ball 10, the bolt 9, the load platform 8 for the application of the static load, piece goods 11 and nut 12.
A compensating element 6 represents a spring or a torque ring, the rigidity of which is determined in advance by calibration.
The axis 7 is a metal rod with different diameter cross sections. At half the length of the rod is threaded for the nut 12.
The diameter of the hole in the lever 4 exceeds the larger diameter section of the axle 7. A larger diameter section of the axle 7 exceeds its smaller diameter section to a maximum amount of movement of the lever 4 along the axis of the compensating element 6 at the time dynamic loading and unloading.
Metal ball 10 and the different diameters of the cross section axis 7 necessary to implement drastic dynamic loading and unloading of the sample 3. Nut 12 �of neobhodimo for to test the axis 7 is not shifted further pre-defined value.
The bolt 9 is required to restrict movement of the metal ball 10 at the moment of fast loading and unloading at offset axis 7, i.e. at the time of decrease or increase of the diameter of the cross section axis 7 under the balloon 10.
The method is as follows.
Loading is carried out via a lever system in two stages. In the first stage, create stress in kompensirujushhego element 6 by means of the stacking unit loads 11 to the load platform 8. When the ball 10 rests on the axle 7 in place of a larger cross-section axis. In the second stage, fix the specimen 3 in the 2 clips, then move the axis 7 so that the ball 10 turned out to be over a smaller cross-section axis, wherein the load acting on the compensating element 6, abruptly jumps to the sample 3 through the lever 4, by dynamic loading of the concrete sample. If the movement of the lever 4 should be set in advance, used the nut 12.
Further displacement of the axis 7 will increase the diameter of the axle under the ball 10 and the removal of the load from the test sample.
In the process of testing a dynamometer to measure the force acting on the prism, and the parameters of deformation of the prism under static loading and dynamic loading case are measured by means of tantostanze with a built-in ten�hosilities, for connecting the load cells without the use of intermediate amplifiers, and having the ability when connected to the computer and use specialized software to record and display the converted signals of multiple input channels depending on time.
In the case of static loading in a tensile test the load acting on the sample, is determined by the formula:
where P is the applied load; K is the force in kompensirujushhego element; l is the length of the lever 4; a, b - distance from the rack 5 to the sample 3 and the elastic element 6, respectively.
In the case of dynamic loading is a sharp redistribution of the load compensating element 6 on the sample 3.
The tensile test samples were subjected to a rectangular shape, length 16 cm, height 4 cm and width 4 cm, made of fine concrete B20 with ratio W/C=0,741, C/N=1:to 3.789.
The distance from the sample to the column 5 a=0.1 m =100 mm from the rack 5 to the axis of the compensating element b=0.1 m =100 mm, the length of the lever 4 l=0.6 m =600 mm. elements of the communication efforts made of PT.3.
1) the Loading platform P=200 H. Napr�CAD on compensating element was K=1000 N, the deformation of the compensating element is equal to 0.2 mm. After fixing the specimen in the clamps of the stand shifted the axis 7. The compensating element is unloaded, K=0 N. Dynamic loading of the sample was N=1000 H, elongation of the sample was 0.2 mm.
2) the Loading platform P=100 H. Load compensating element amounted to K=500 N, the deformation of the compensating element is 0.1 mm. Fix the specimen in the clamps of the stand. Load the platform up to P=200 N. The total deformation of the elastic element was 0.16 mm, the deformation of the sample was 0.06 mm (static loading). Forces in the elastic element is equal to 800 H, the sample was 200 H. Displace the axis 7, reducing its diameter. Efforts in the sample was 1000 H (dynamic loading case), efforts in kompensirujushhego element become equal to 200 H. Deformation in the sample was 0.16 mm. With a sharp displacement of the axis 7 in the direction of increasing the diameter of the section's efforts in the sample amounted to 200 H (unloading), the deformation of the sample was 0.06 mm, while efforts in kompensirujushhego element become equal to 800 H.
From the examples it is seen that through the use of axis with different diameters of the cross sections, the deformation of the specimen during sudden loading of a given size. Achieved technical result: the possibility of multiple dynamic loading of the sample in alternation with the unloading, achieved high �echnosti obtained in the experiment data.
1. The state standard 24452-80 Concretes. Methods for determination of prism strength, modulus of elasticity and Poisson's ratio. - M.: NEIGBD. 1982. - 15 p.
2. Bazhenov. Y. M. Concrete under dynamic loading. - M.: Stroiizdat, 1970. - 272.
3. RF patent №2482480, CL G01N 3/00, 2006.
Method for experimental determination of static-dynamic characteristics of concrete, which consists in securing an experienced concrete sample in the form of a prism in the clamps of the test bench using a centering device which provides a Central load application in the process of loading, and registration efforts and deformations of the prism in time by using the dynamometer and tantostanze, characterized in that the loading is performed via a lever system in 2 stages: first - stage static loading of the specimen to a predetermined level by laying a piece of cargo on the cargo platform, the second is the instantaneous speed or dynamic loading case or unloading by short-term changes in the diameter of the axis at the connection of the lever and a compensating element, specifying, if necessary, the magnitude of the movements in this item.
FIELD: test equipment.
SUBSTANCE: method relates to test methods of porous water-saturated bodies. It provides for production of a series of concrete specimens, saturation of specimens with water, measurement of specimens, determination of their initial volume, their frosting/defrosting to specified temperatures and recording of deformation. In addition, long-term strength limit of each specimen is determined by a non-destructive method under tension conditions. After defrosting, relative residual deformation of specimens is determined and energy dissipated in unit volume of each specimen is determined during its frosting/defrosting. Then, they are loaded under conditions of uniaxial compression to an extreme load meeting short-term strength limit; energy dissipated in unit volume of the specimen is determined during its compression to an extreme load, and as per the obtained results, grade is calculated as per freeze resistance of each specimen. Grade of concrete as to freeze resistance is determined as an arithmetic mean for grades of specimens.
EFFECT: increasing flexibility, reducing labour intensity and enlarging the number of hardware.
SUBSTANCE: previously prepared samples with various quantity of a filler in a highly dispersed condition for a dry construction mix are placed into a hollow part of metal washers, placed on a metal plate, are compacted by any available method under permanent load of up to 5 MPa per 1 cm2 of sample surface for 10-15 seconds, then marks are applied on the surface of each sample in the form of drops of a solution of various concentration, wetting angles of samples are measured θ, a curve of dependence is built cosθ-1=f(1/σl), where σl - surface tension of the liquid, they determine the angle of inclination of this functional dependence a for each sample of different composition, the curve of dependence a is built on quantity of mix components, and by the point of break of the curve of dependence they define the optimal content of a modifier in the tested object.
EFFECT: reduced number of tests and higher accuracy of mixture composition selection.
2 cl, 2 dwg, 1 tbl
FIELD: test equipment.
SUBSTANCE: at the first stage they determine process mode of manufacturing of ceramic items providing for required operability reserve. Using the produced operability reserve and knowing the suggested time, during which ceramic items must preserve strength parameters, they assess the permissible rated speed of produced reserves consumption. At the second stage, modelling conditions of real operation by means of reproduction of accelerated cyclic variations of temperature with simultaneous impact of possible mechanical factors, they determine actual speed of consumption of the same reserves. Received results of rated permissible speed and actual speed produced for imitation of operation conditions are compared, and results are produced, making it possible to judge on ceramic items.
EFFECT: possibility to determine durability of ceramic items with regard to certain conditions of use.
FIELD: measurement equipment.
SUBSTANCE: invention relates to the field of tests of cement plastering compounds for tensile strength under static loading. Substance: the value of the limit tensile strength is defined by testing steel beams with applied plastering compound according to the scheme of the double-point bend with smooth loading by small steps and fixation of the loading step corresponding to the moment of cracking, and the value of the limit tensile strength is calculated using the formula.
EFFECT: simplified technology for testing, exclusion of the necessity to apply strain metering facilities, higher accuracy of detection of limit tensile strength and completion of tests on plaster layers with specifically small thickness from several mm to 2-3 cm.
1 tbl, 1 dwg
SUBSTANCE: method involves measurement of hardening concrete temperature at given time moments and calculation of concrete strength over three days for hardening in standard conditions by the formula:
EFFECT: reduced labour consumption of monitoring.
1 tbl, 2 dwg
SUBSTANCE: apparatus has at least two sealed chambers with a U-shaped pipe filled with water for releasing excess pressure in the chamber, inlet and outlet gas-distributing manifolds, filters for cleaning the gas-air medium collected from the chambers and the inside of each chamber is fitted with a ventilator and a bath with a saturated salt solution for creating and maintaining given relative air humidity inside the chamber, connected to the sealed chambers through the inlet gas-distributing manifold and, installed on pipes, electromagnetic valves, a carbon dioxide gas source, an automatic gas analyser with a gas flow activator, a gas distribution switch for alternately collecting samples from the chambers and transferring the samples to the gas analyser through the gas flow activator; the gas analyser is also connected to a computer for automatic monitoring of gas concentration in the sealed chambers and feeding gas into the chambers through the electromagnetic valves.
EFFECT: high information value and faster determination.
SUBSTANCE: previously they make at least two samples with different water-cement ratios, thermal cycling and cyclic compression of the sample with the least water-cement ratio are alternated until proportion is disturbed between relative residual deformation and number of cycles, the ratio is calculated between relative reduction of threshold load and relative residual deformation, the concrete grade of frost resistance is determined, as well as relative residual deformation εm, corresponding to reduction of the strength limit specified by the standard for the frost resistance grade of the investigated concrete, they alternate thermal cycling and cyclic compression of other samples with higher water-cement ratios until residual deformation is achieved εm, the number of cycles required for this purpose is accepted as the grade of concrete frost resistance with higher water-cement ratio, using the produced results, they calculate parameters of the function that approximates experimental results.
EFFECT: expanded arsenal of technical facilities for detection of concrete frost resistance dependence on water-cement ratio.
SUBSTANCE: in the method including drying of a sample to permanent mass, hydraulic insulation of its side surfaces and water saturation, nonwetting of the upper end surface of the sample is provided, and a light-reflecting water impermeable coating is applied on it, and continuous even water saturation is carried out via the bottom end surface of the sample, at the same time the sample is installed onto fixed supports inside a reservoir for water saturation, the reservoir is filled with water, and even contact is provided between the lower end surface of the sample with water during the entire cycle of measurements, then with the help of laser radiation a series of holographic interferograms is registered on a non-wetted surface of the sample in process of water saturation, at the same time position, speed and acceleration of moisture movement front are determined by comparison of changes in the field of movements of the registered surface, produced according to interferograms, with the rated field of movements of a geometrically similar sample.
EFFECT: improved information value and reliability of detection.
2 cl, 1 dwg
SUBSTANCE: method is realised by fixation of an experimental concrete sample in the form of a prism between bearing plates of a test bench using a centring device, providing for central application of a compressing load in process of loading, and registration of a force and deformation of a prism in time using a dynamometer and a strain station with loading, realised through a lever system in two stages: at the first stage - stepped static loading of a sample to the required level in different shares of the crack formation load by means of laying of unit weights onto a loading platform, at the second stage - instantaneous or stepped dynamic additional loading with a weight dropping during reduction of current force in an electromagnet, the axis of the centre of gravity of which matches with the axis of the loading platform.
EFFECT: increased reliability of tests.
SUBSTANCE: method involves dipping and holding samples of the test materials at room temperature into a weakly aggressive medium - mixture of organic acids: 0.9-1.1% acetic acid, 0.9-1.1% citric acid, 0.09-0.12% oxalic acid, said acids being in ratio of 1.8:2.7:0.8-2.1:3.1:1.2. After exposure, the samples are removed and dried to constant weight and their strength characteristics are then determined.
EFFECT: high efficiency and reliability of tests.
FIELD: test equipment.
SUBSTANCE: invention relates to test equipment, namely to engineering surveys, and can be used to determine a strain-and-stress state of rocks, and namely to determine a stage of development of deformation processes in mass of material (in rock mass, soils under an engineering facility, etc.). Essence of the invention: specimens of material with a brittle skeletal frame are taken. Loading of specimens is performed and physical and mechanical characteristics of material are recorded, and a stress-deformation curve is built up, as per which parameters characterising a precursor of material destruction are determined. At compression of specimens, coefficients
EFFECT: possibility of characterising a stage of material state prior to destruction, which is a precursor of material destruction, by reducing the time of measurement due to reduction of the number of test specimens.
3 cl, 3 dwg
FIELD: testing technology.
SUBSTANCE: determining the current service life of the pipelines, cutting samples for carrying out cyclic tests, fatigue tests of the samples, measurement of hardness of metal surface is carried out. The samples for testing are cut from the material not previously used, similar to the material of the pipeline under study. The measurement of hardness is carried out at least 100 times on each sample. The dispersion of hardness readings is calculated and the remaining operating life of the metal of pipeline is determined from the ratio.
EFFECT: increased reliability and simplification of the method implementation.
SUBSTANCE: method to detect resource of pipeline or vessel metal includes definition of the following: geometric and mechanical parameters of walls (energy of intercrystallite bonds between metal particles in a wall; energy of stress in the wall from action of difference between pressures of fluid and external media; consumption of energy of intercrystallite bonds between metal particles - natural ageing); main parameters of fluid medium (consumption of energy of the flow acting at wall metal; contamination of the flow with particles of abrasive material); resource of metal according to calculation formula that connects these parameters. A feature of the method is taking into account additionally defined value of metal corrosion speed and value of consumption of energy of intercrystallite bonds between metal particles from action of corrosion in calculation of metal resource.
EFFECT: increased accuracy of metal resource detection.
FIELD: machine building.
SUBSTANCE: proposed method consists in definition of maximum gradient of the Earth magnetic field on the valve body surface. Body of all-welded ball valve (full-scale specimen) valve body blank are destructed after reduction without bore for neck, selected from one lot of manufactured articles. Ultimate strength of valve body and valve body blank after reduction without bore for neck is defined to reveal a correlation relationship. Thereafter expected specified life is set proceeding from introduced relationship.
EFFECT: higher accuracy of forecast.
1 dwg, 1 tbl
FIELD: test equipment.
SUBSTANCE: device is intended for high-temperature test of metals and alloys in vacuum or in gas medium. The device includes a detachable pressure-tight chamber consisting of top and bottom parts attached to each other through a flange connection, a melting pot with a metal or alloy test specimen arranged in it, pipelines for pumping the air out of the chamber and supply of gas to it, a temperature metre and an induction heater. In the top part of the detachable pressure-tight chamber an arrangement is made for a cooled box-like element with a detachable cooled plate fixed on it, calibrated as to weight and made from alloyed heat-resistant steel. The melting pot is located inside the detachable pressure-tight chamber. The cooled box-like element is connected via pipelines to a cooling substance supply and circulation unit in the above element.
EFFECT: use of the invention ensures determination of the quantity and chemical composition of solid-phase sublimate formed at melting of metal alloys and performance of metallurgical processes in furnaces.
1 dwg, 1 tbl
FIELD: measurement equipment.
SUBSTANCE: method to determine specific adhesion of soils consists in the fact that 6 drops of wetting liquid with available values of surface tension are applied onto a soil sample. Then the shape of the drop on the material surface is used to determine the angle of surface wetting, and using the functional dependence of cosθ-1=f(1/σ), they determine tangent of inclination angle a. Then, using the previously built calibrating dependence, they find the specific soil adhesion.
EFFECT: higher speed of determination, possibility to do tests both with preselected samples and directly at a facility, simplified equipment, possibility to perform analysis on any soils, higher accuracy of determination due to exclusion of impact of soil resistance to impression at side walls of a probe at the result.
1 dwg, 4 tbl
FIELD: measurement equipment.
SUBSTANCE: if the target part of damage detection returned from the plastic condition into the elastic condition, provided that the stress of part return into elastic condition is (x, y)=(σ2, σ1) (maximum main stress: σ1, minimum main stress: σ2) in the coordinate plane (x, y), completion of damage detection for the target part of damage detection with usage of the voltage R of the new start of fluidity determined by the crossing between the straight line that meets the ratio y=(σ1/σ2)x, and the fluidity curve produced on the basis of the plastic condition of the target part of damage detection.
EFFECT: possibility to detect damage with high accuracy, even if a metal structure returned from plastic condition into elastic one.
6 cl, 15 dwg
FIELD: process engineering.
SUBSTANCE: peaks of tolerable load at welded part under appropriate destruction from load destruction, moment destruction and internal destruction of welded point core are defined from at least one sheet thickness t, tensile strength TS, elongation E1 and chemical composition of said core at every point-welded steel sheet, core diameter d efficient thickness B of welded part defined via distance between adjacent welded parts, ribs or crest lines and cross-section height H. Then, in compliance with said destruction modes, tolerable load at every moment after reaching of the peak of tolerable load and defined is shift or time whereat tolerable load is zero, that is, time whereat complete destruction occurs.
EFFECT: possibility to define tolerable load before complete destruction.
8 cl, 10 dwg
FIELD: testing equipment.
SUBSTANCE: with the help of an air fuel mixture under pressure they generate fine-dispersed aerosol areas in several coaxially arranged soft stable shells in the form of a cylinder. To generate an air impact wave the detonation is initiated by means of serial burst of a charge of a TNT primer under statically stable soft shells. The device that realises the method comprises a tight chamber with liquid fuel and a powder charge, channels of fuel supply, an additional chamber, sprayers with jets and possibility of their regulation with a sharpened screw arranged inside the sprayer, a charge of a TNT primer, statically stable soft shells for creation of fine-dispersed aerosols in them.
EFFECT: provision of possibility of structure testing in impact pipes at action of an air impact wave of high duration with increased efficiency of formation of a fine-dispersed aerosol area.
4 cl, 6 dwg
FIELD: process engineering.
SUBSTANCE: invention relates to hot deep drawing and can be used for setting of metal sheets deformation parameters. Several cycles of tests for maximum drawing under isothermal conditions are performed to plot the graph "maximum drawing-test temperature" and to define the parameters of technological process or fitness of tested sheet specimen. Proposed device comprises chamber to house heaters, top thermal rod fitted on axle whereto rigidly secured is die case to receive tested specimen and thermal insert, male die with spherical surface is arranged at bottom thermal rod to be displaced axially by the drive.
EFFECT: higher precision, lower labor input is quality control.
2 cl, 2 dwg
FIELD: building, particularly to perform nondestructive testing of structure concrete strength.
SUBSTANCE: method involves drilling bore-hole in concrete body; cutting annular groove in concrete body coaxial to bore-hole; arranging metal cylindrical ferrule in annular groove, wherein cylindrical ferrule has dimension comparable with that of sample; securing anchoring head in bore-hole and pressing anchoring head into concrete body up to sample destruction. Concrete strength is determined from the following formula: R = (N·10-6)/2πdh, where R is concrete strength, MPa, N - destructive force, H, h is sample height, m.
EFFECT: possibility to determine physical and mechanical concrete characteristics directly in structure body.