Method to measure stresses in structure without removal of static loads
SUBSTANCE: measurements of surface deformations ε are carried out in controlled points on a structure, which is in stressed-deformed condition. Controlled points are selected so that they are capable of additional loading regardless of the structure. In controlled points they create with the help of the available external force P, additional stresses that match in direction with the measured ones, deformation is stepwise increased by Δε, change of the external force is measured ΔPi. Loading is increased until
EFFECT: simplified process of measurement and no damage to integrity of the investigated structure.
3 cl, 3 dwg
The invention relates to the field of determining and controlling the stress-strain state of the structure (object), under load, and can be used to assess its strength and prediction of bearing capacity. Thus the design needs to be known about the material properties (modulus of elasticity E, the deformation of the limit of proportionality ε0.02and the elasticity ε0.2etc).
The method can be widely applied in monitoring the structural ability of industrial and civil buildings, special buildings (metro, bridges, nuclear plants, etc.).
The known method of non-destructive testing of materials [RF Patent №2146809], consisting in the fact that measure parameters of a magnetic field on the surface of the investigated object: to measure the absolute value of the maximum normal component of the magnetic field and calculate the value of stresses in the structure. Also known method [RF Patent №2146818], consisting in the fact that in the investigated object outraged ultrasonic normal waves take through the object vibrations, measure their parameters by which to judge the magnitude of the stress.
A disadvantage of the above analogs of determining the stresses in design is a significant scatter of experimental�social data the imperfection of methods of recalculation of the velocity of acoustic waves and magnetic parameters in the characteristics of the stress state of structures and, consequently, lower the accuracy and reliability of measurements.
As the prototype accepted method [RF Patent №2302610] closest to the proposed to the technical essence and the achieved effect. The method consists in that on the surface of the structure in the stress-strain state, fix the strain gauges and make measurements of surface deformations that take at the end. Then perform the cutting of the material around the strain gages to a depth corresponding to removal of the stress state of the structure at the points of deformation measurement, and measure the surface deformation of the structure, which one takes the initial. Based on these initial and final deformations determine the surface tension under load.
However, in the prototype there are drawbacks, namely:
- cutting material in the investigated structure around measuring resistance strain gage violates the integrity of the study design. The study of stress-strain state of the structure, as a rule, is carried out in the most loaded areas, it reduces the structural safety during the study;
The technical result of the invention consists in maintaining the integrity of the study design and the simplification of the measurement process.
The essence of the proposed method of measuring stress in a structure without removal of static loads is that in controlled points on the structure in the stress-strain state, make measurements of the surface strain ε. Moreover, the finer points chosen so that they have the possibility of additional loading, regardless of the design. In controlled locations create using a known external force P additional voltage, coincident in direction with the measured, stepwise increase strain Δε, measures the change in the external force ΔPi. The loading increases until such time as
Step additional strain Δε select eno�but small,
the measurement error of
Then stop loading, and deformation and, consequently, stresses in the structure is determined by subtracting from the known values of the deformation for the early known mechanical characteristics of the material of construction of additional measured deformation.
For structures of low-alloy steels it is advisable to use as normalized deviations from Hooke's law the elastic limit, and for structures of high-strength steel, carbon fiber, iron - proof strength, as in this case, it is possible to reduce the accuracy requirements for measuring equipment.
The proposed method of determining the stress-strain state of structures without removal of static loads is illustrated by drawings, where
- figure 1 - chart changes additional external force P in some controlled point loaded structures from additional deformation ε;- figure 2 - diagram of the metal box-shaped superstructure of the bridge and its cross-section;
- figure 3 - example of additional loading in a controlled point.
Figure 1 presents the diagram of loading of the structure material in the stress-strain state of its own weight. Point 1 corresponds to the initial measured amount of deformation εK. With the help of external forces P speed create additional strain on the value of Δε, coinciding in direction with the measured. The measure also the variations of the external power ΔPi. Step ∆ Ε is chosen small. For the case when the normalized deviations from Hooke's law the mechanical characteristics of the material of construction was adopted by the limit of proportionality ε0.02the measurement error of
After reaching the material of construction of the limit of proportionality in point 2, on the next step in the point 3 the value of
Figure 2 shows a drawing of a typical metal box-shaped superstructure 1 of the bridge and its cross-section. Controlled selected point on the bottom surface of the bottom plate at the edge of the side shelf 2. At the initial moment of tensile deformation in the controlled point is equal to the deformation of all points of the bottom plate section 1-1 from its own weight, but the lower surface side shelf 2 can be further stretched regardless of the point of the mid-section.
The method can be implemented, for example, the following device (figure 3). The Jack 3 oil pressure sensor 4 is installed between the flange 2 and beam 5 with hooks 6, geared to the lower surface of the shelf 2, on which is mounted a strain gauge 7. The outputs of both sensors are connected to the inputs of the transmitter 8, the control output of which seediness controlled pump station 9 (the transmitter station 8 and 9 schematically depicted). Under the action of force from the Jack 3 phase 2 shelves between the hooks 6 is bent, and on its lower surface tensile stresses occur, additional to the existing bend all of the superstructure 1 of the bridge.
Take measurements as follows. Pump station 11 by the command transmitter 8 delivers the oil in the Jack 3 to sample all gaps in the structure, which is determined by the change of the readings of the strain gauge 7. Then the pressure in the Jack 3 is increased until, until you reach the first level of strain increment Δε. After that, the evaluator determines the value of the
Conducted by the authors numerical simulation (finite element method) showed that errors due to the biaxial stress state of the shelf 2 described above, when the nature of its additional loading does not exceed 1%.
The positive effect of the application of the proposed method definitions� stress-strain state of structures without removal of static loads is in the measurement process is not violated the integrity of the examined structure in controlled locations. This increases the safety of the measurement process. In comparison with the prototype, the measurement process is simplified, as it does not need to cut the material of construction in controlled locations, but just enough to set the device further loading.
1. Method for determining stresses in structures without removing the static loadings, consisting in the fact that in controlled points on the structure, which is deformed in a state of stress, produce measure the surface strain ε, characterized in that the controlled point is selected so that they have the possibility of additional loading, regardless of the design, in controlled locations create using a known external force P additional voltage, coincident in direction with the measured, stepwise increase strain Δε and measures the change in the external force ΔPias long as the valuedoes not increase more value corresponding to the normalized deviation from Hooke's law the mechanical characteristics of the material of construction, after which the deformation and, consequently, stresses in the structure is determined by subtracting from the known values of pre-strain for the Glo�Noah the mechanical characteristics of the material of construction of additional measured deformation.
2. Method of determining stress-strain state of structures without removing the static loads according to claim 1, characterized in that for the controlled points of the structure of low-alloy steels as normalized deviations from Hooke's law take the limit of proportionality.
3. Method of determining stress-strain state of structures without removing the static loads according to claim 1, characterized in that for the controlled points of the structure of high-strength steel, carbon fiber, iron as normalized deviations from Hooke's law take proof strength.
FIELD: measurement equipment.
SUBSTANCE: invention relates to the field of measurement of voltage of initial shift (plasticity) of liquids in pipelines, for example milk in hoses of milking machines. The offered method of measurement of voltage of shift of milk column consists in that using one pressuriser the water column pressure h1 = 20 - 25 mm is pre-set in a glass vessel connected by piping with a differential water manometer and a capillary, and the capillary piping is locked by a clip, and using the second pressuriser the portion of milk is sucked into the capillary to the column length l0 = by 1 - 2 cm, then the pipeline is locked by a clip, the water column h2 = 25 - 30 mm is established, the clip is unlocked. Meanwhile, using a stop watch the time of shift of milk column t1 under the action of h1 pressure is measured, and then the time of shift of the milk column t2 under the action of the pressure h2 is measured. The voltage of initial shift τ0 is determined by the formula τ0=9.8(D/4l0)(t1 _t2)(t1/h1-t2/h2), where D - diameter of the capillary, mm. The device for measurement of voltage of shift of milk column contains the pressuriser connected with piping with the differential water manometer and glass vessel to which the horizontally located capillary and the second pressuriser is connected, and the piping from the vessel to the capillary and to the second supercharger is designed with a possibility of locking by a clip.
EFFECT: group of inventions is aimed at decrease of labour costs and improvement of accuracy of determination of voltage of initial shift of controlled liquid.
2 cl, 1 dwg
FIELD: rescue equipment.
SUBSTANCE: invention relates to reducers of breathing apparatus. The reducer has a housing and three chamber made in it separated by the walls: high-pressure chamber (HPC) and the reduced pressure chamber (RPC), separated by the first wall, the control chamber (CC) separated with the second wall from the RPC; the seat with a hole in the first wall; the partition with a movable plunger and a valve located in the RPC, separating the CC to piston and annular cavities; first channel connecting the RPC with piston cavity of the CC; the second channel connecting the annular cavity of the CC with the environment, the third channel with a throttle, which connects the RPC with the annular cavity of the CC, a check valve connected to the second channel. The method of regulating the gas flow in the reducer comprises supplying gas to the HPC, displacement of the plunger with the valve and forming a gap between the seat and the valve; entering the gas flow from the HPC and the RPC, accordingly, to the gas consumer; entering the gas flow from the RPC to the CC through the first channel; moving the partition with the plunger and the valve under the action of the gas pressure difference on them, changing the gap between the seat and the sealing element of the valve; flowing of gas from the HPC through the third channel with a throttle in the annular cavity of the CC, moving the partition with the plunger and the valve, and changing the gap between the valve and the seat, regulation of supply and pressure of the gas entering the RPC and the consumer.
EFFECT: providing regulation of a gas flow in the reducer with the given value of the reduced pressure of gas at small amplitude of the pressure oscillations.
8 cl, 3 dwg
SUBSTANCE: invention relates to the field of horticulture, namely to control means to assess the physical and mechanical properties of berries. The device consists of a portable housing with control buttons located in it, alphanumeric LCD display, force measuring sensor connected to the electrical measuring device provided with a peak detector and compensator of packaging, as well as a grip for berries mechanically connected to the force measuring sensor through the rod force distributor and made in the form of a hinged fixed and spring-loaded movable gripping cup-shaped jaws, and a control device of gripping berries fixed to the housing, and kinematically connected to the shank of the movable gripping cup-shaped jaw for providing opening and closing the gripping jaws. In addition, the device comprises a movable spring-loaded pressure rod arranged so that its pressure surface is located between the gripping cup-shaped jaws and in its motion without berries there is no mechanical contact with the elements of gripping berries, and in the presence of fruit between the gripping jaws, it presses it with its pressure surface to its the inner surface of the gripping jaws, a mechanical actuator of the pressure rod mounted on the portable housing, and the device of determining the coefficient of relative strength of berries.
EFFECT: device provides improved performance in carrying out control operations by combining the operations.
3 cl, 4 dwg
FIELD: machine building.
SUBSTANCE: in the formula
EFFECT: reduced labour inputs in the determination of pressure of safety valve opening start without the valves' demounting from a pipeline by means of measuring the forces required to open the valves at two different pressures in their inner cavity and by the following calculation of pressure of safety valve opening start.
FIELD: machine building.
SUBSTANCE: invention relates to flow regulators, particularly, to flow regulators with bowl-shape seat. Regulator consists of valve body to define fluid flow and valve seat, drive case engaged with valve body, control member arranged in drive case and adapted to displacement relative to valve body and valve seat for regulation of fluid flow at displacement between open position and closed position whereat said control member engages with valve seat, and spring articulated with control member to displace the latter to open position. Said control member has the surface directed to valve seat and furnished with recess. Recess can be reamed, or concave, or conical or have any other suitable surface.
EFFECT: higher reliability, perfected adjustment.
19 cl, 4 dwg
SUBSTANCE: reference sample comprises a metal base with a central zone of reference complex stressed condition through the base thickness. At the edges of the base at one or different sides there is one or several zones of pad welds from another metal, coefficient of linear expansion and yield point of which is lower than the coefficient of linear expansion and yield point of the base metal. The base is first exposed to high-temperature tempering, afterwards control marks or a grid of measurement bases are applied onto surfaces of the central zone of the base at two sides, for two test measurements after high-temperature tempering of the base before applying pad welds and in the end of thermal treatment of the base already with pad welds. The form of the base, locations of pad welds and the mode of thermal treatment are defined in advance as a result of computer simulation modelling by the method of finite elements with account of grades of the base metal and pad welds metals and the required reference complex stressed condition of the central zone of the base through its thickness.
EFFECT: increased validity of results of measurements of mechanical stresses in cross sections of various thick-walled metal structures.
2 cl, 5 dwg
SUBSTANCE: method of determining tangential stress in steel pipelines involves making a sample in form of a hollow cylinder from the same material as the structure; step by step loading of the sample; measuring coercitive force indicators at each loading step, with a defined orientation of magnetic flux generated in the coersimeter relative the sample; obtaining a relationship between the coercitive force indicators and values of stress in the sample; measuring the coercitive force indicators of the metal of the structure; determining stress values using the obtained relationship; tangential stress in the sample is generated by applying torque to the sample; the coercitive force is measured along the axis of the sample or the pipeline twice, while directing magnetic flux in opposite directions. The coercitive force indicator used when determining tangential stress is the magnitude of the difference between measured values of the coercitive force.
EFFECT: high accuracy of determining tangential stress in surface steel pipelines.
1 dwg, 1 tbl, 1 ex
FIELD: measurement equipment.
SUBSTANCE: method for determining residual hardening stresses involves hardening of samples and determination of residual hardening stresses; at that, a pack is formed of plates of similar size, which are numbered and marked in advance; then, the above pack is subject to hardening; after that, plate bending deformations are measured in two planes, as per which residual hardening stresses are calculated.
EFFECT: improving accuracy of determination of residual hardening stresses.
FIELD: measurement technology.
SUBSTANCE: invention relates to determination of the stress-strain state of metal structures of high-risk facilities in the oil, gas and chemical industry, transportation systems and oil and gas processing using brittle strain-sensitive coatings, which enables to obtain a clear picture of the highest stress concentration and obtain data for evaluating strength of potentially hazardous structures. The brittle coating for deformation and stress analysis is made from a mixture containing water and sugar, with the following ratio of components, wt %: water 65-75, sugar 25-35.
EFFECT: reduced harmful effect on the environment.
SUBSTANCE: invention relates to machine building. Load limiter comprises force transducer and electronic device to generate warning signal of interlocking the load lifting mechanism actuator in machine reloading. Force transducer converts the force acting threat into pressure and, further, into electric signal and comprises base and loose piston separated by layer of elastomer. Transducer is composed of, particularly, false cradle of automatic hydro lifter or is adapted for fitting under traveler winch drum support body and may be shaped to a ring or parallelepiped with holes for attached at the machine. Said transducer can incorporate several pressure transducers to define mean load and load application point with generation of data or control signals. Clearance between sidewall of loose piston and base inner sidewall is selected to prevent extrusion of elastomer while its length is selected to protect against lateral loads. Electronic device is built around microcontroller and incorporates output device and wire or wireless interface.
EFFECT: impact and vibration resistance, expanded applications, higher safety.
8 cl, 1 dwg
FIELD: measurement equipment.
SUBSTANCE: invention relates to measurement equipment and may be used to measure deformations under conditions of homogeneous deformation fields in process of strength testing. Substance: the gage comprises a carrier 1 from thin metal foil. In the carrier 1 by means of rectangular holes 2 there are two thin threads 3 and a site 4 between them. A thin separating dielectric film 5 is deposited onto the carrier 1, which follows the shape of the carrier 1. Strain-sensing elements 6, 7 from samarium monosulphide are deposited on the dielectric film 5 and are connected into a Wheatstone bridge, as well as metal contact sites 8, which are inlet and outlet contacts of the gage. In the carrier 1 there might be two additional through slots arranged, each starting from the middle of the appropriate extreme rectangular hole 2 and is perpendicular to it, creating sites, where metal contact sites are arranged.
EFFECT: increased output signal, temperature independence.
2 cl, 4 dwg
SUBSTANCE: in an output diagonal of a bridge circuit they install a heat-dependent process resistor Rαt, the par value of which is more than possible values of a compensation heat-dependent resistor Rα. In parallel to the resistor Rαt they install a link. Output resistance of the bridge circuit is measured Rout. The sensor is connected to a low-resistance load Rl=2·Rout. Initial unbalance is measured, as well as the output signal of the sensor at normal temperature t0, and also temperature t+, corresponding to the upper limit of working range of temperatures, and t-, corresponding to the lower limit of working range of temperatures. Measurements are repeated after connection of the sensor to the low-resistance load
EFFECT: increased accuracy of compensation.
FIELD: measurement equipment.
SUBSTANCE: heat-dependent technological resistor Rαt is installed into a diagonal of bridge circuit power supply, the rating of which is higher than possible values of a compensating heat-dependent resistor Rα. In parallel to the resistor Rαt they install a link. They measure initial unbalance and output signal of the sensor under normal temperature t0, and also temperature t+, corresponding to upper limit of working range of temperatures, and t-, corresponding to lower limit of the working range of temperatures. On the basis of performed measurements they calculate temperature coefficient of frequency (TCF) of strain gauges of a bridge circuit
EFFECT: increased accuracy of compensation of multiplicative temperature characteristic of an output signal of a sensor.
FIELD: measurement equipment.
SUBSTANCE: invention relates to measurement equipment. Essence of the invention is as follows: temperature-dependent technological resistor Rαm, the nominal value of which is higher than possible values of compensation temperature-dependent resistor Rα, is installed into an output diagonal of the bridge circuit. A bridge is installed parallel to resistor Rαm. Output resistance of bridge circuit Rout is measured. The sensor is connected to low-resistance load Rl=2·Rout. Initial imbalance and an output signal of the sensor is measured at normal temperature t0, as well as at temperature t+ corresponding to an upper limit of the working temperature range, and t- corresponding to a lower limit of the working temperature range. Measurements are repeated after the sensor is connected to low-resistance load
EFFECT: higher compensation accuracy.
FIELD: measurement equipment.
SUBSTANCE: heat-dependent technological resistor Rαm is installed into a diagonal of bridge circuit power supply, the rating of which is higher than possible values of a compensating heat-dependent resistor Rα. In parallel to the resistor Rαm they install a link. They measure initial unbalance and output signal of the sensor under normal temperature t0, and also temperature t+, corresponding to upper limit of working range of temperatures, and t-, corresponding to lower limit of the working range of temperatures. On the basis of performed measurements they calculate temperature coefficient of frequency (TCF) of strain gauges of a bridge circuit
EFFECT: increased accuracy of compensation of multiplicative temperature error with account of negative non-linearity of temperature characteristic of an output signal of a sensor with usage of widely distributed measurement equipment.
FIELD: measuring instrumentation.
SUBSTANCE: device for dynamic deformation measurement includes resistance strain gauges, reference resistors, amplifier, electronic computer with software, DC voltage source, standard resistor, switch, control unit, analogue programmed multifunctional board with software, connected to PC. Programmed board can be connected to PC via USB interface or by installation into PCI or PCIExpress expansion slot, and the device can include adaptor; connection of power source to the first analogue input of the board, second output of the amplifier to analogue output of the board, control unit input to digital output of the board, amplifier output to analogue input of the board is implemented via respective inputs and outputs of the adaptor connected by interface to compatible socket of the board.
EFFECT: extended range of measured values and linearity of output parameter, improved reliability of device operation.
3 cl, 2 dwg
FIELD: measurement equipment.
SUBSTANCE: on surfaces of upper and lower beam flanges at a point of maximum deflection Δ0 there bonded are strain gauges with similar characteristics directly onto the prepared surface of the upper and lower beam flanges. Operating and compensating strain gauges are bonded in the number of 3 to 5 pieces in each flange in a section 15 to 25 cm long with maximum deflection Δ0. The operating strain gauges are fixed along primary stresses σ along the beam, and compensating strain gauges are fixed between the operating strain gauges across the beam, protected against different actions with epoxy resin; bridge circuits are mounted for each pair of strain gauges (operating and compensating) and their wires are connected to a strain station; initial resistance R0 of the operating strain gauges is measured; with that, beam deflection Δ(t) at any point of time t is determined by the following formula: Δ(t)=Δ0+r·(|ΔR1(t)|+|ΔR2(t)|), where Δ0 - initial maximum beam deflection at point of time t=0, which is measured by means of a high-precision station rod and a level unit before bonding of the strain gauges; r - constant coefficient depending on design circuits and dimensions of the beam.
EFFECT: higher measurement accuracy.
4 dwg, 1 tbl
FIELD: measurement equipment.
SUBSTANCE: invention relates to measurement equipment and may be used to tune resistance strain gauge sensors with a bridge measurement circuit according to multiplicative temperature error. Substance: at load resistance Rl≥500 kOhm they determine temperature sensitivity coefficient (TSC) of the bridge circuit
EFFECT: increased accuracy of tuning with positive non-linearity of bridge circuit TSC.
1 tbl, 2 dwg
SUBSTANCE: invention refers to instrumentation and can be used to measure deformations of nonmagnetic materials. Deformation measurement method for nonmagnetic items implies that on the surface of an item or inside it permanent dipole sources of magnetic field based on, for example, magnets from the alloy neodymium-iron-boron, are installed, at least two magnets not located in the same point are used to determine the parameters of linear (along the straight line) deformation, at least three magnets not located along the same straight line are required to determine the parameters of plane deformation, at least four magnets not located in the same plane are used to determine the parameters of volume deformation. At the surface of the examined item opposite each source a system of sensors is installed, the sensors allow for the measurement of 1, 2, 3 components of vector of magnetic field induction in several points concentrated in relatively small region of space if compared to the distance to the field sources, or one-, two- or three axial sensor with 3D-positioning system is used as the system of sensors, the signals from the sensors are amplified and converted into digital ones, numeric measurement data: coordinates of measurement points and values of components of magnetic field induction vectors in them in a laboratory coordinate system are processed by a computer programme, basing on the obtained data an inverse problem is solved for the system of weakly interacting magnets and their position in the laboratory coordinate system is determined as well as the vectors of magnetic moments in the laboratory coordinate system before and after the item deformation and by comparing the said solutions the deformation parameters are calculated. A plant for implementing the said method is also described.
EFFECT: possibility to measure linear (along the straight line), plane (in a plane) and volume (in space) deformation of items made from nonmagnetic materials.
5 cl, 1 dwg, 3 tbl
FIELD: measurement equipment.
SUBSTANCE: sticky foil from plastic metal is used, for instance, aluminium scotch tape. Foil is cut into fragments, stretched within the limits of elastic deformations, and in this condition, using a sticky foil layer, it is applied onto controlled surfaces of parts. Tail sections of fragments are rigidly fixed on the surface of the part with a mechanical or another available method. Afterwards in the transverse plane in the middle of the foil fragment length they make through slots and holes.
EFFECT: expanded arsenal of technical facilities to monitor cyclic deformations of machine parts that arise in process of their operation, higher efficiency of control due to increased sensitivity of sensors to low values of cyclic deformations.
FIELD: electric engineering.
SUBSTANCE: device has three identical distance sensors, connected to appropriate measuring converters and information processing block. Two distance sensors are mounted relatively to controlled object differentially, and third one is rigidly fixed at constant and known distance from controlled object surface. Information processing block has adder block, two subtracting blocks, three multiplication blocks, two division blocks and memory block. As information value, characterizing object movement, displacement of point is taken, which is placed on one of object sides. Value of deformation is determined on basis of integral deformation of object between its extreme points.
EFFECT: higher precision, broader functional capabilities.