RU2227282C1 - Sheet material tensile tester - Google Patents

Abstract

FIELD: mechanical engineering; testing facilities. SUBSTANCE: proposed tester contains sample loading mechanism with clamps for sample, thermostating container with cooling liquid, breaking force meter and temperature meter. Thermostating container is made in form of cell of low heat conduction and heat capacity material, and sample clamps are arranged horizontally the same as cell. Sample loading mechanism is made in form of winch. Wire rope of winch is connected to some clamps of sample to provide displacement relative to second clamps through breaking force meter made in form of dynamometer with breaking force recorder. EFFECT: possibility of making thin plastic sheet material tensile tester operating within wide temperature range under all-round cooling conditions. 3 dwg

Description

The invention relates to the field of testing equipment for tensile testing of sheet materials.

Known installations for testing sheet metal tensile [1], in which the test sample is fixed vertically in the clamps of the testing machine, then placed in a thermostatic container - a cryostat and evenly cooled on all sides using a coolant (liquid nitrogen or ethyl alcohol, cooled by ice or solid carbon dioxide), maintained for uniform cooling, then apply a mechanical tensile force, bring the sample to rupture, fixing the temperature uru coolant temperature gauge, and a yield point stress of tensile force to rupture.

Also known is an installation for testing sheet metal tensile materials according to the patent [2], containing a rod with two traverses, two loading mechanisms of the sample with clamps of the sample, with rotation mechanisms, with heaters. The installation also contains brackets with direction indicators and limit switches.

The disadvantages of such plants are their large size and high cost, associated with significant time spent on testing and high consumption of coolants (for the first type of plants), as well as the unacceptability of existing tensile testing machines for testing thin sheet plastic materials (with a sheet thickness of 0.1-0 , 5 mm) due to the large difference in the tensile forces for metals and plastic materials, the latter cannot even withstand the preliminary tension of the sample due to the severity of the bottom their jaws.

A known installation for testing sheet materials in tension [3], used to test thin sheet plastic materials (sheet thickness of at least 1 mm), in the clamps of which a sample is fixed with marks applied to it to measure elongation, is held (conditioned) for at least 16 hours at a temperature of 23 ± 2 ° C and a relative humidity of 50 ± 5%, and then tear at a speed of 100 to 500 mm / min, while measuring the yield strength and tensile strength using a tensile strength meter.

The disadvantages are the impossibility of testing samples thinner than 1 mm and the inability to take temperature curves of fluidity and strength of samples (their cooling is not provided).

The closest of the analogues is the installation for testing sheet materials in tension - “Tiratest 2300” [4], selected as a prototype, which contains a thermostatic tank in the form of a sealed tempering chamber connected to a Dewar vessel with a cooling liquid, such as liquid nitrogen. The sample is placed inside the chamber in an upright position by clamps.

The disadvantages of the prototype are: fixing the sample in an upright position, causing a large volume and tightness of the chamber, a significant consumption of liquid nitrogen, which is most often used as a coolant, a long time for one measurement, the high cost of testing, the impossibility of testing thin samples with a sheet thickness of 0 , 1-0.5 mm.

The objective of the invention is to provide an installation for tensile testing of sheet materials from thin 0.1-0.5 mm thick plastic sheets in a wide temperature range (from room to cryogenic) under conditions of comprehensive cooling.

The technical result that can be obtained using the inventive installation is to reduce the loss of liquid nitrogen and other coolants, reduce the test time of one sample by 10-15 times, increase the efficiency of the tests by increasing the sensitivity of the tests with manual loading of the samples, obtaining the possibility of express -testing samples.

The task is to achieve the specified technical results is solved by the fact that in the installation for testing sheet materials in tension, containing the loading mechanism of the sample with clamps of the sample, a thermostatic tank with coolant, a tensile force gauge and a temperature meter, in contrast to the prototype, thermostatic tank is made in in the form of a cuvette made of a material with low thermal conductivity and low heat capacity, the clamps of the sample are placed horizontally, like the cuvette, and the sample loading mechanism is made in the form of a winch, the cable of which is attached to one of the clamps of the sample, mounted movably, through a tensile strength meter, made in the form of a dynamometer with a clamp of tensile forces.

For tensile tests, a sample of sheet plastic material (thickness 0.1-0.5 mm) is fixed horizontally in the grips of the installation, not horizontally, after which it is cooled uniformly from all sides using coolant poured into an open horizontal cuvette inside which before that, the sample is placed, kept for 2-3 minutes for uniform cooling, then a tearing force is applied manually, fixing the temperature of the coolant, the moment of the yield point and the tensile strength.

The essence of the proposed solutions are illustrated in figures 1 and 2, which show:

figure 1 is a side view of the installation;

figure 2 is a top view of the installation;

figure 3 is a view along aa.

The drawings show a thermostatic tank in the form of a cuvette 1 with a coolant, a temperature meter 2 immersed in a coolant, a cover 3, a rupture force meter in the form of a dynamometer 4 connected by a cable 5 to the sample loading mechanism in the form of a winch 6. The cuvette 1 is rigidly attached to the base (table) 7. In the lid 3 can be installed glass 8 with the risks applied to it. The dynamometer 4 is equipped with a movable arrow 9 breaking force in the form of a slider 10. The dynamometer is hooked to the eye 11 of the carriage 12, which is rigidly mounted one of the clamps 13 of the sample, moved by the carriage 12, the clamps 14 of the sample are fixed and can be rigidly mounted relative to the base 7. Sample 15 is immersed in coolant.

The test is as follows.

The thermostatic tank, made in the form of a cuvette 1, made of a material with low thermal conductivity and low heat capacity, is filled after the sample 15 is fixed in a horizontal position with clamps 13, 14 with cooling liquid, the temperature of which is measured by thermometer 2. It has been experimentally determined that for testing samples with cryogenic the temperature of the cuvette should be made of a material with a low heat capacity of 0.1-0.12 cal / g · K and a low thermal conductivity in the range of 0.0-0.03 cal / (cm · s · K) to reduce evaporation will cool A because evaporation of the coolant will interfere with the observation of the sample; low thermophysical parameters will allow to save coolant, reduce the influence of the working surface of the table on the test mode. If the coolant evaporates vigorously, such as, for example, liquid nitrogen, then the cuvette is closed by a cover 3. To measure the tensile forces, a spring dynamometer 4 is used, connected by a cable 5 to the winch 6, which is manually rotated. Glass 16 may be provided in the lid with risks applied to it to monitor the behavior of the sample during the yield point. The whole device is rigidly attached to the desktop 8. For accurate fixation of the force when the specimen breaks, a slider 10 is used, which is moved by the arrow of the dynamometer, which, due to its horizontal position, does not slide and remains in place after the specimen breaks and the arrow returns to the zero position. The level of coolant 4 slightly (by 5-10 mm) exceeds the level of the location of the sample. Load with tensile force by rotation of the winch; under the influence of the tension of the cable 5 through the dynamometer, hooked to the eye 11 on the carriage 12, providing movement of the clamps 13 of the sample, the force is transmitted to the sample 15 and it is stretched. The arrow 9 of the dynamometer 6 moves, fixing the magnitude of the force when the yield strength and tensile strength are reached and acting on the slider 10, which at the moment of breaking remains at the mark corresponding to the breaking strength of the sample 15 and is recorded visually or using a recording device, while arrow 9 returns to zero.

Using the inventive installation will reduce the test time of one sample by 10-15 times, increase the efficiency of the tests by increasing the sensitivity of the tests with manual loading of the samples, and get the opportunity to conduct express tests of the samples.

Sources of information

1. GOST 11150-84. Metals Tensile test methods at low temperatures.

2. RU 2089873 C1, G 01 N 3/08, 09/10/1997.

3. GOST 11262-80. Plastics. Tensile test method.

4. Device for testing the strength of Tiratest 2300. “Thuringer Industrialverk", Rauenstein, GDR, 1989 - prototype.

Claims (1)

An installation for testing sheet materials in tension, comprising a mechanism for loading the sample with clamps of the sample, a thermostatic container with coolant, a tensile strength meter and a temperature meter, characterized in that the thermostatic container is made in the form of a cuvette made of a material with low thermal conductivity and low heat capacity, sample clamps placed horizontally, like a cuvette, and the sample loading mechanism is made in the form of a winch, the cable of which is attached to one of the sample clamps to ensure their transfer escheniya respect to the second clamp via the gap meter efforts made as a dynamometer with a clamp gap effort.

Images