SU1758499A1 - Device for investigating micromechanical properties of materials - Google Patents

Abstract

The invention relates to the testing of materials, in particular to the measurement of microhardness, micro-fragility and other methods by pressing or scratching a sample. The purpose of the invention is to improve the accuracy of control and reduce the complexity of measurements. The device contains a block of microdisplacements of the indenter, including piezoceramic nodes with rods, elastic rings with strain gauges and an electronic circuit including a strain gauge, a comparator, a switch, an analog-to-digital converter, a micro-ЗММ, digital-analogue converter, a linearly varying voltage generator and high voltage source. Improving accuracy is achieved by ensuring uniform loading, and reducing labor intensity by automating the measurement process. 2 yl

Description

The invention relates to testing equipment, in particular, to devices for studying the micromechanical properties of materials (microhardness, microbrittleness, etc.) by pressing and scratching.

Widely known are devices for studying the micromechanical properties of materials by the indentation method, in particular, a device comprising a housing on which a sample table is mounted for swinging, and plane-parallel springs on which the indenter is mounted in the form of a rod with a tip at one end and a counterweight at the other. , sensors for measuring the load and depth of the indenter. interacting with the rod, the registration unit in the form of a two-coordinate recorder, a function generator, an adder, and a signal level coordinator.

The disadvantage of this device is that the measurement results in the form of a diaphragm load-depth of introduction require further processing to calculate the desired parameters, which greatly complicates the measurement process, reduces its performance. In addition, the known device allows measurements to be made only by the indentation method and, when studying by the scratching method, there is a need for another device.

The closest in technical essence to the claimed is a device for the study of the microhardness of materials, comprising a housing mounted on

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in mutually perpendicular planes, piezoelectric nodes with rods, a loading device in the form of two elastic rings arranged one above the other and interconnected by a bridge with which the rods of the piezoelectric nodes interact, strain gages mounted on elastic rings and a generator of linearly varying stress, a high voltage source, a strain gauge station and a chart recorder, on which a chart is plotted for indentation depth versus load and sclerometry is normal and the tangential component of the scratch force from the depth of the scratch.

The disadvantage of this device is the low accuracy of measurements, due to the fact that the rate of penetration of the indenter into the sample is not uniform when the indenter is indented or horizontally moved during the scratching process of the sample. Processing of measurement results is also time consuming and laborious.

The aim of the invention is to improve the accuracy and reduce the complexity of the measurements.

The goal is achieved by the fact that a device comprising a case, piezoelectric assemblies with rods fixed to it in mutually perpendicular planes, a loading mechanism made in the form of two elastic rings arranged in one plane, one above the other, and connecting them jumpers designed for interaction with the rods of the piezoelectric assemblies, strain gauges mounted on elastic rings, an indenter, a strain gauge station whose inputs are connected to strain gauges, and a series-connected linear generator According to the invention, a variable voltage and a high voltage source, the outputs of which are connected to piezoelectric nodes, are equipped with a series-connected switch, an analog-to-digital converter and a micro-computer, a comparator whose input is connected to strain gauges and the output is connected to a control input of the switch, and a digital-analog converter, the input of which is connected to the micro-e B V M output unit, and the output to the generator input of a linearly varying voltage.

Fig. 1 shows a block diagram of a device for studying the micromechanical properties of materials; Fig.2 diagram of the loading mechanism.

The device contains a block of microdisplacements 1. including two piezoelectric assemblies 2, 3. loading mechanism in the form of two elastic rings 4.5c with a rigid bridge b, which the piezoelectric assemblies 2, 3 press through their rods 7, 8, strain gauges 9-12 mounted on elastic rings 4. 5, indenter 13, table with test sample 14, tensor metric station 15, compiler 16, whose input is connected to strain gauges 9-12 of microdisplacement unit 1, and output to switch 17, whose input is connected to a strain gauge analog to digital conversion5 ovatel 20, generator linearly varying voltage 21, a high voltage source 22, whose output is connected to the piezoelectric nodes 2, 3. The measurement results are latched output unit

0 23, including the decoder and indicator. The device works as follows.

The memory of the microcomputer 19 introduces the initial data on the depth and speed of implementation

5 of the indenter 13 to sample 14 or the depth of penetration and the rate of horizontal movement of the indenter along the surface of the sample, depending on the method to be tested. Indenter

0 is manually applied to the surface of the sample and turn on the micro-computer 19 on the measurement mode. Having received the signal for work permitting, the microcomputer supplies to the inputs of the digital-analogue converter 20 a series of pulses,

5 which are converted to an analog signal, which is fed to the input of a generator of a linearly varying voltage 21, which in turn controls a source of high voltage 22, the outputs of which are connected to the piezoelectric nodes 2,3.

When testing an indentation method, the voltage is applied to the piezoelectric unit 2, it is extended and through

5, the rod 7 presses against the jumper b, the indenter 13 is thus moved downwards. In places where the strain gauges 9 are applied, the inner fibers of the ring 4 are stretched and the outer fibers are compressed. The deformation of the fibers leads to a change in the resistance of the strain gauges 9 assembled in a bridge circuit. On the bridge diagonal, an imbalance voltage appears, which is amplified by the strain gauge 15 and fed to the switch 17. At the moment of contact

5, the indenter 13 of the surface of the sample 14 begins to deform the fibers at the glueing points of the strain gauges 10, the voltage unbalance of the bridge circuit of the strain gauges 10 is transmitted to the switch 17. The output of the comparator 16 is connected to the resolution input

the passage of signals from the switch 17. Thus, the switch 17 begins to pass signals only at the moment when the indenter touches the sample. The signals are then converted by the analog-to-digital converter 18 to digital form, fed to the inputs of the microcomputer 19, and recorded in its memory. The microcomputer 19 monitors the vertical movement signal of the indenter 13, arriving when the bridge is unbalanced, assembled on strain gauges 9, and corrects using feedback — a digital-to-analog converter 20, a linear voltage generator 21, a high voltage source 22, a piezoelectric node 2 load on rod 7. Thus, the rate at which the indenter 13 is inserted into sample 14 is kept constant. When the predetermined penetration depth of the indenter 13 into the sample 14 of the microcomputer 19 is removed, the load is removed and after the indenter returns to its initial position, it performs calculations according to the program and the result goes to the output device 23.

When testing a sample by scratching a microcomputer 19 through a digital-to-analog converter 20, a generator of linearly varying voltage 21, a high voltage source 22 supplies voltage to the piezoelectric node 2, the indenter 13 is inserted into sample 14 to a predetermined depth, The computer 19 sends a voltage supply command to the piezoelectric unit 3, it lengthens and presses the rigid bridge 6 through the rod 8, the indenter 13 begins to move in the horizontal direction. The horizontal movement signal of the indenter 13 (scratch length) is taken from the diagonal of the bridge circuit assembled on the strain gauges 11, amplified in the strain gauge 15 and transmitted through the switch 17 to the analog-digital converter 18, then to the inputs of the micro-computer 19. From the diagonal bridge circuit collected on strain gauges 12, a signal is received that is the tangential component of the corpane force, this signal is also transmitted to the inputs of the microcomputer 19. The digital signals are recorded in the memory cell of the micro-ЗВМ 19, and the signal is horizontal Nogo movement of the indenter 13 is monitored, and in accordance with its voltage variation is corrected by the piezoelectric unit 3, i.e. The load on the rod 8 is maintained so that the speed of the horizontal movement of the indenter 13 along the surface of the sample 14 is uniform.

When the maximum voltage on the piezoelectric node 3 of the micro-computer is reached, it turns off and, when this voltage is zero, turns off the voltage applied to the piezoelectric node 2. After the indenter 13 returns to its original position, the micro-computer performs calculations according to the program and displays the result on block 23. The device 10 allows you to automatically control the amount of microhardness, microbrittleness and other micromechanical properties of the sample directly during the process of inserting the indenter into the sample when tested and indentation or in the process of horizontal movement of the indenter along the surface of the sample when tested by scratching.

The positive effect of the proposed

Compared to the known prototype, the device consists in increasing the measurement accuracy by automatically fixing the beginning of the measurement and uniformly introducing it into the sample or by uniformly horizontal movement of the indentor along the sample surface, as well as reducing the labor intensity of the measurements by eliminating the manual processing of the results.

Claims (1)

0 claims A device for examining the micromechanical properties of materials, comprising a housing fixed thereon in mutually perpendicular planes 5 piezoelectric nodes with rods, a loading mechanism, made in the form of two elastic rings located in one plane, one above the other, and a jumper connecting them, designed to 0 interaction with the rods of the piezoelectric assemblies, strain gauges mounted on elastic rings, an indenter, a strain gauge, whose inputs are connected to strain gauges, and serially connected 5 a linearly varying voltage generator and a high voltage source, the outputs of which are connected to piezoelectric nodes, characterized in that, in order to increase the control accuracy 0 and reducing the complexity of the measurements, it is equipped with a switch connected in series, an analog-digital converter and a microcomputer, a comparator whose input is connected to strain gauges. 5 and the output is from the control input of the switch, and a digital-to-analog converter, the input of which is connected to the output unit of the microcomputer, and the output to the input of the generator of a linearly varying voltage. 15 L IB /9 23 P & 1 3 P