RU2381503C1 - Instrument for strength testing of construction materials - Google Patents

Abstract

FIELD: testing equipment.

SUBSTANCE: invention is related to testing equipment, namely to instruments for strength testing of construction materials. Instrument for strength testing of construction materials comprises unit for installation of sample, loading device with drive and device for measurement of load, which are installed in power frame. Two elastic elements of various pliancy are installed serially with sample, besides one of them, for instance in the form of spring, is installed between sample and drive that deforms it with a certain rate, and the other detector of load measurement, with lower pliancy, is installed between sample and base of power frame.

EFFECT: increased accuracy and reproducibility of test results, improved efficiency of instrument and expansion of its application field.

3 dwg

Description

The invention relates to test equipment, namely, devices for testing building materials for strength.

Strength testing of many building materials (cement, concrete, etc.) according to the standards should be carried out under soft loading, when the rate of increase in load (stress) is normalized, and not the rate of deformation.

Known instruments for testing building materials for strength, operating in the soft loading mode, where the required rate of increase in load on the sample is achieved by uniformly adding time to the mass of the cargo, for example, bulk (see Materials and products for road construction. Handbook. Edited by Professor N .V. Gorelysheva. M.: Transport, 1986, pp. 108-109, Fig. 4.13).

The disadvantages of such devices are the inability to implement large loads, the need to use a mass-metering device, low productivity and accuracy.

The closest in technical essence to the claimed invention is adopted as a prototype device for testing samples of cement 2170P-6, containing the installation site of the samples, a loading device with a drive and a device for measuring the load mounted on the power frame, and the load on the sample according to the double-support scheme a bend is created by a load that, with the help of an electric drive, moves along the loading lever with a constant speed, and this load is determined by the position of the load on the lever (see. The device for testing aztsov of 2170P-6 cement. JSC "Tochpribor" Prospect, Ivanovo).

In this device, the disadvantages noted above are partially eliminated, but the presence of a moving load causes inertial effects that distort the measurement results, and, in addition, the determination of the load acting on the sample by the position of the load on the lever also reduces the measurement accuracy.

The purpose of the invention is to increase the accuracy and reproducibility of test results, increase productivity and expand the scope of the device.

This goal is achieved by the fact that in the device for testing building materials for strength, comprising a sample installation unit, a loading device with a drive and a load measuring device mounted on a power frame, in the loading device, an elastic element, for example, a spring, is applied in series with the sample on the sample and the load measurement sensor.

Comparative analysis with the prototype shows that the inventive device is characterized in that an elastic element is installed in series with the sample in the loading device, for example, a spring acting on the sample and the load measurement sensor.

Figure 1 shows a diagram of the device for the case of direct loading, figure 2 - its replacement power circuit, figure 3 presents a diagram of the installation of an elastic element when loading through a lever.

The test sample 1 (Fig. 1) according to the double-support bending scheme is mounted on supports 2 placed on a plate 3, which is mounted on a load measuring sensor 4. The sensor is mounted on a base 5, which, together with the spindle screws 6, guide columns 7 and the upper fixed crosshead 8 form the power frame of the device. The movable crosshead 9 is moved along the columns 7 using spindles 6, the drive of which is carried out from the electric motor 10 and gearboxes 11. A cup 12 is fixed to the crosshead 9, an elastic element 13 is installed in it (for example, a spring, a bracket), which abuts against the bottom glass, and the other into the piston 14, connected with the tip (roller) 15, directly acting on the sample 1. Connected via spindles with a traverse drive with elements 12, 13, 14 and 15 mounted on it forms a loading device. Measurement of deformation (deflection) δ of the sample is carried out using a displacement sensor (indicator) 16. Secondary measuring equipment is not shown in the drawing.

If it is necessary to realize large loads, the piston 14 (Fig. 3) can be connected to the tip 15 through a transmission mechanism, for example, a lever 17 mounted on a movable crosshead 9.

The principle of operation of the device is based on the following.

This device corresponds to a replacement power circuit (figure 2), on which each element (node) of the device corresponds to its own elastic link with compliance K _j . Since all these links are connected in series, the overall system compliance

where K _y - the compliance of the elastic element 13

To _about - the compliance of sample 1.

The sum of the compliance of the power frame of the device K _cf and the load measurement sensor K _d can be considered as the compliance of the device itself

K _p = K _cp + K _d

If necessary, you can also take into account the compliance and other attached elements. Compliance (or its inverse value - rigidity) of all elements can be determined by calculation (for example, at the design stage) or experimentally known methods.

With a constant value of the drive speed V _o and linear links, the loading speed of the sample is constant and equal to

Из приведенных формул видно, что если в составе прибора имеется специальный деформируемый упругий элемент, установленный последовательно с образцом, то соответствующим выбором величины его податливости К_у можно обеспечить необходимую скорость V_p возрастания нагрузки на образец, т.е. осуществить режим заданного или мягкого нагружения.

It can be seen from the above formulas that if the device has a special deformable elastic element installed in series with the sample, then by appropriate selection of its compliance value K _у , the necessary rate V _{p of} increasing the load on the sample can be provided, i.e. to carry out the mode of a given or soft loading.

From the relations

find tip speed 15

those. the speed of the tip 15 with respect to the speed of the drive (in this case, the yoke 9) decreases i times, where

This allows shockless testing of samples with a small amount of deformation, including from brittle materials such as glass, ceramics, and others. To increase i, it is necessary that К _у > (К _о + К _п ) and, accordingly, always К _у > К _д .

For the device according to the scheme of figure 3

- передаточное число рычага 17.Where

- gear ratio of the lever 17.

The device operates as follows.

A sample 1 is mounted on the supports 2 (Fig. 1). When the electric motor 10 is turned on, the crosshead 9 moves and, resting against the tip 15 against the sample 1, deforms the elastic element 13, creating a load P transmitted therethrough through the tip 15 to the sample 1.

The load P is measured using a load measurement sensor 4, and the deformation of the sample δ by a displacement sensor 16.

The operation of the device according to the scheme of figure 3 is similar, only the load on the sample 1 from the elastic element 13 is transmitted through the lever 17 and the tip 15.

The efficiency of the device is determined by the presence in the design of two elastic elements of different stiffness (K _y > K _d ) installed in series with the sample, one of which (elastic element 13) is deformed using a drive, thereby creating a load P on sample 1, and the other (load measurement sensor 4) senses and measures this load.

This separation of functions allows, within the operating range of the load measuring sensor 4, to make the elastic element 13 replaceable and not to impose strict requirements on its metrological parameters, while ensuring the necessary measurement accuracy due to the appropriate choice of load measuring sensor parameters.

The design of the proposed device does not contain inertial gravitational masses, which eliminates the occurrence of dynamic effects that distort the test results.

It is possible to test various materials on the device, including brittle ones, under various loading schemes, such as bending, compression, shear, tension, and others. In this case, only the installation and fixing pattern of the sample changes, for example, between two plates during compression (not shown in the drawings).

An important advantage of the invention is the possibility of its application using existing laboratory equipment, in particular explosive machines and presses, including hydraulic, with their own drives and measurement systems. In this case, the power frame of the device may also have a different configuration, for example, [-shaped.

Claims (1)

A device for testing building materials for strength, comprising a sample installation unit, a loading device with a drive and a load measuring device mounted on a power frame, characterized in that two elastic elements with different flexibility are installed in series with the sample, moreover, one of them, for example, a spring is installed between the sample and the drive deforming it with a certain speed, and another, a load measuring sensor, is installed with less flexibility between the sample and the base of the power frame .

Images