RU2279658C1 - Device for tensile and compression tests - Google Patents

Abstract

FIELD: testing engineering.

SUBSTANCE: device comprises testing setup (20) with movable traverse and mechanism for its moving made of a pair of screw gearings and clamps for locking specimen (11). The device additionally has programmable loading (strain) unit (15) that sends the signal corresponding to the load defined by operator to comparator (16) connected to the closed circuit of automatic control. The circuit comprises controller (17) of the velocity of movable traverse, controlled electric drive (18) with motor (19), testing setup (20) with specimen (11), dynamometer (12), meter of displacement of traverse (13), and unit (14) for determining rigidity of the device-specimen system. The inputs of unit (14) are connected with the dynamometer (12) and meter of displacement of traverse (13). The outputs of unit (14) are connected with the velocity controller (17).

EFFECT: enhanced precision.

1 cl, 2 dwg

Description

The invention relates to testing equipment, namely to machines for testing samples in tension and compression.

Known test machines that provide a constant rate of increase in load (voltage) in the samples (see Golubkov BC, Pirogov K.M., Smushkovich B.L. Testing machines in textile materials science. "Legprombytizdat." M, 1988, p.205, p. 8-9). The disadvantages of these machines are the limited maximum load and the inability to register the falling sections of the tensile diagram, due to the presence of inertial masses in the loading system.

Closest to the technical nature of the claimed machine is the explosive machine IR 5143-200 selected as a prototype, containing a test rig (power frame) with a movable traverse and a mechanism for its movement, made in the form of a pair of helical gears, an adjustable electric drive with an electric motor, a speed controller, force meter with a force sensor, displacement meter of a movable beam with a displacement (deformation) sensor. The IR 5143-200 machine also allows testing samples for compression and bending.

The speed controller provides a given traverse speed (see. Discontinuous machines ИР 5143-200-10 and ИР 5143-200-11. Prospect of OJSC "Tochpribor", Ivanovo, 2001. Brown ED, Gorbunov VN, Smushkovich BL Methods and equipment for predicting the friction-wear characteristics of friction units of heavy engineering products // Heavy Engineering (Journal), 2001, No. 4, p. 18).

A disadvantage of the known machine is the impossibility of automatically maintaining a given rate of increase in load (stress), which is necessary, for example, to ensure accuracy in determining the yield strength (see GOST 1497-84. Metals. Tensile test methods). The objective of the invention is to increase the accuracy and reproducibility of test results by automatically maintaining a given rate of increase in load (voltage) or, in general, programming a load (deformation).

This goal is achieved by the fact that the machine for testing samples in tension and compression, containing a test setup (power frame) with a movable traverse and a mechanism for moving it, made in the form of a pair of screw gears, an adjustable electric drive with an electric motor, a speed controller, a force meter with a force sensor , a moving crosshead displacement meter (sample deformation) with a displacement (deformation) sensor, is additionally equipped with a load (deformation) programming unit, the signal from which is applied by force to a comparison unit arranged in a closed loop automatic control. The closed loop also includes a movable crosshead speed regulator, an adjustable electric drive with an engine, a test setup with a sample, a force meter, a movable crosshead displacement meter (sample deformation) and a stiffness unit for the machine-sample system. The loop of the automatic control loop is closed by negative force feedback so that the specified law of the load (deformation) is maintained with the necessary accuracy by changing the engine speed within a certain section of the sample deformation diagram.

In addition, the use of a machine-specimen stiffness determination unit in a machine, the inputs of which are connected to a force meter and a traverse displacement meter, and the outputs to a speed regulator, will improve the speed of the control system.

Comparative analysis with the prototype shows that the inventive machine is characterized in that it is additionally equipped with a load (deformation) programming unit, the signal from which is supplied by force to a comparison unit located in a closed loop of automatic regulation, which also includes a moving beam speed controller, adjustable electric drive with an engine, a test setup with a sample, a force meter, a meter for moving the movable beam (deformation of the sample) and a unit for determining the weight of the machine-specimen system, and circuit closure is carried out by negative force feedback so that the specified law of the load (deformation) is maintained with the necessary accuracy by changing the engine speed within a certain section of the sample deformation diagram. In addition, the inputs of the stiffness determination unit of the machine-specimen system are connected to a force meter and a meter for moving the movable crosshead, and the outputs to a speed controller.

Figure 1 shows a diagram of a test installation, and figure 2 is a block diagram of a machine.

The test setup (Fig. 1) consists of a base 1, an upper fixed crosshead 2 and a movable crosshead 3, guides (columns) 4 and spindles 5. A force sensor 6 is installed on the base, and a fixed clamp 7 is connected to it. Movable clamp 8 is connected with traverse 3.

The test sample 11 is fixed in the grips. A displacement sensor 10 is installed on one of the synchronously rotating spindles. If it is required to measure the deformation of the sample, a deformation sensor (strain gauge) 9 is installed on it.

The power frame of the installation, containing elements whose rigidity affects the overall rigidity of the machine, is shown by a dotted line.

The force sensor can also be installed on traverses 2 and 3. In addition, a compression and bending test is possible, then the grippers 8 and 9 are replaced with support plates or special supports (not shown in the drawing), and the movement of the traverse 3 is directed in the opposite direction to Vo .

There are no fundamental differences in the operation of the compression or bending test machine.

The block diagram of the machine (figure 2) includes the following elements:

- A force meter (IC) 12, which as a transducer contains a force sensor DC, directly sensing the force in the sample 11.

- Displacement meter (IP) 13, which as a transducer contains a displacement sensor DP moving yoke.

- The unit for determining the stiffness s _{with the} system "machine-sample" (BOZ _s ) 14, performing the function of differentiation (p):

where P is the load

L - movement

- The load programming unit (LOU) 15, which, depending on the operator’s load measurement law, gives out at each moment of time a signal corresponding to a given load value P _ass .

- Comparison unit (BS) 16, which determines the difference between a given and measured value of the load and supplies the value of the speed controller to the input:

- Speed controller (PC) 17, which gives the corresponding signal V _back to the machine drive 18. The transfer function of the controller in the simplest case:

where T _m is the time constant of the electric drive. If a constant rate of increase in load V _p is required, then the speed

- Electric drive (EP) 18 with an electric motor (M) 19, which fulfills a given speed V _ass and drives the movable beam of the machine.

- Test facility UI (power circuit) 20. Contains a base, guides (columns), spindles (transfer function 1 / p) and two cross-arms - fixed and movable.

- Sample 10 - the test sample to be installed in the grips of the machine.

These blocks form a closed loop control, the input of which receives a signal from the BPN. This contour in FIG. 2 is shown in solid lines.

Dotted lines indicate the second circuit, which includes the following elements.

- The strain gauge (ID) 21, which as a transducer contains a strain gauge T mounted on the basis of the sample 11. The actual value of the strain of the sample L _{o is} received at its input.

- A block for determining stiffness c _о sample (BOZ _о ) 22, performing differentiation functions:

where L _o - deformation of the sample.

The corresponding signal is fed to the input of the BPN block.

Structurally, blocks 14, 15, 16, 17 and 22 can be made in the form of a hardware-software device, implemented, for example, using a computer.

The machine operates as follows. The test sample 11 is installed in the grips 7 and 8 of the test setup (Fig. 1). When the screws 4 are rotated (from the electric motor through the gearboxes, not shown in the drawing), the crosshead 3 with the movable gripper 8 moves, deforming the sample 11.

The sensor 6 of the force meter perceives the load acting on the sample, the sensor 10 of the displacement meter - the movement of the traverse (capture), and the strain gauge 9 - directly deformation of the sample.

On the block programming the load 15 (figure 2) set the necessary program for changing the load. For example, if a constant rate of increase in load is required, then it is necessary to set a linear law of increase in load. At the outlet unit 15 at each moment provides a corresponding amount of force F _backside, which is the comparison unit 16 compares the signal from the measuring force F _MOD. The difference of the signals ΔP is fed to the input of the speed controller 17.

The signals from the force meter 12 (P _ISM ) and the traverse meter 13 (L _ISM ) are fed to the input of block 14, which calculates the stiffness c _from the machine-sample system and supplies the corresponding signal to the input of the speed controller.

The speed controller 17 controls the speed of the electric drive so that the motor 19 deforms the sample 11 installed on the test setup 20 with a speed V _o providing the rate of change of load V _p in accordance with the regulation law established on block 15. The required rate of change of speed:

where ΔT is the increment of time;

ΔР - load increment.

In this case, a minimum value of ΔР, tending to 0, should be ensured.

The outline shown in FIG. 2 by a dotted line works as follows. The input detection unit 22, the stiffness of the sample signal from the strain gauge 21 corresponding to the deformation of the sample 11. The signal corresponding to the calculated value of the hardness _of sample is input to the programming unit load 15, where the operation is carried out:

where V _d is the strain rate of the sample.

Thus, block 15 can, in the presence of a second circuit or with c _о = const, act as a programmer for the deformation rate of a sample.

Two private modes that allow the proposed machine to be implemented are important:

1. The force P = const, then V _p = 0. Corresponds to the creep mode.

2. The deformation of the sample L _o = const, then V _d = 0. Corresponds to the mode of relaxation of the load (voltage).

Claims (2)

1. Machine for testing samples in tension and compression, comprising a test setup with a movable traverse and a mechanism for its movement, made in the form of a pair of helical gears, an adjustable electric drive with an electric motor, a speed controller, a force meter with a force sensor, a meter for moving the traverse (deformation of the sample ) with a displacement (deformation) sensor, characterized in that it is additionally equipped with a load (deformation) programming unit, the signal from which is transmitted by force to the comparison unit, located married in a closed loop of automatic control, which also includes a movable traverse speed regulator, an adjustable electric drive with an engine, a test setup with a sample and a force meter, and the circuit is closed by negative force feedback so that the specified law of load (deformation) changes It was maintained with the necessary accuracy by changing the engine speed within a certain section of the sample deformation diagram. 2. The machine according to claim 1, characterized in that the meter of movement of the movable beam and the unit for determining the stiffness of the machine-sample system, the inputs of which are connected to the force meter and meter of movement of the movable beam, and the outputs to the controller, are also included in the automatic control loop speed.

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