Rubber tension testing machine test tracking data analysis
Rubber tension testing machine test tracking data analysis
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Haida Instrument Co., Ltd. specializes in producing various kinds of tensile testing machines, including rubber tensile testing machines specially used by rubber manufacturers. There are two data that need to be tracked during the rubber testing process: tension force value and gauge change amount. Therefore, the rubber tensile tester used to test the tensile properties of rubber must meet the following requirements:
1 , there is a long enough range of movement of the fixture.
Due to the large amount of deformation of the rubber during stretching, especially for latex products, the elongation may be as high as more than 1000 %. Therefore, before the rubber specimen breaks, it must be ensured that the gripper has enough stroke. Standard rubber thickness of the sample (GB 1, 2, 4-type dumbbell specimen thickness is 2.0 ± 0.2mm, thickness 3 type sample was 1.0 ± 0.1mm) from the standard at break is generally less than 1 m; special Thickness specimens, such as those for medical rubber gloves, may have a gauge length of more than 1 meter at break. Therefore, the range of movement between the clamp is generally between 1 meter and 1.5 meters, so that a tensile test may be for a variety of rubber samples.
2 , there is a sufficient accuracy of the tension measurement and recording device.
Rubber stretching does not require much force, and the tension measurement range does not need to be large, but it has certain accuracy requirements, and the general accuracy is 0.01N . In addition, since the tensile properties of the test rubber require several tensile values ​​during the drawing process, and the tensile test is not repeatable, the accurate and timely recording of the tensile force values ​​of each test section plays an important role in the success or failure of the test. A rubber tension tester equipped with a high-accuracy load cell can accurately record real-time tensile values ​​and process them through computer programs to meet the requirements of rubber tensile tests.
The gauge measurement of rubber is an important part of the tensile test and directly affects the accuracy of the test. At present, there are mainly two kinds of gauge measurement methods: manual measurement and automatic measurement.
Manual measurement is to set a ruler and two horizontal gauge bars that can be moved in the vertical direction at the side of the gripper's moving rod. During the tensile test, visually observe the change of the gauge length on the sample and manually control it. Two gauge rods are synchronized with the gauge length on the specimen, and the distance of the gauge rod on the scale is recorded. The error of manual measurement is very large: (1) Visual observation of the specimen gauge distance will cause a certain deviation; (2) The gauge length change of the specimen cannot be accurately tracked by manually moving the gauge rod; (3) The tester moves the gauge length while It is difficult to record the gauge value on one side of the bar, and it is impossible to accurately describe the stress-strain curve after the end of the test.
Automatic measurement of gauge length is more conducive to the detection of rubber tensile properties. Nowadays, many automatic rubber gauge testing machines use a contact sensor to measure the change of gauge length.
There are two main installation positions for the sensor moving device: (1) Mounted on the holder. Sensors that mount the mobile device on the holder have certain limitations on the sample. Because the elastic deformation of rubber is very large, there is a big gap between the moving distance of the gripper and the change value of the gauge length of the specimen, so the gauge sensor installed on the gripper is more suitable for detecting the elastic deformation ( such as metal material ) tensile properties of the sample, but not for detecting the tensile properties of rubber. (2) Installed on the gauge length. A scale and two vertically adjustable rods with small clips can be placed vertically in the gripper moving rod edge. The installation method of this kind of sensor is the same as the above-mentioned principle of manual measurement, except that the scale is changed to a scale and the manual operation is changed to move the gauge rod by the sample. Sensors mounted on the gauge length are suitable for tensile testing of metal or standard-thickness rubber specimens because the force values ​​for stretching these specimens are large, and the force that drives the gauge rod to move is small compared to It will have a certain impact on the sample, but not enough to affect the success or failure of the entire test.
However, there are some special specimens in the tensile test of rubber that can not be measured by a contact sensor for measuring the distance, such as medical rubber gloves. The main component of natural latex rubber gloves, the tension value used during the tensile test is smaller than a general rubber products, while GB7543 - 2006 "single use sterile rubber surgical gloves" test specimen in the tensile properties specified directly The rubber medical gloves are cut directly from the finished product, so the sample thickness is very small, only about 0.2mm , so that the thickness of the latex sample requires only a small force to stretch the sample. . Therefore, the contact gauge measurement method will have a great impact on the tensile test of the specimen. The reasons are as follows: First, the gauge weight of the gauge rod that contacts the specimen will pull the specimen downward and affect the tensile force measurement; Second, the clamping of the gauge rod has a certain influence on the stretching of the clamped part, making it unable to stretch freely.
3. Devices that can accurately describe the stress-strain curve.
There is a close relationship between the tension value and the gauge length in a tensile test specimen. For example, the specimen's constant stress needs to measure the force at which the specimen is stretched to a given elongation, and the constant stress needs to measure the specimen. Stretch the gauge length to a given stress. After the test is completed, the accurate stress-strain curve can reproduce the test process, and clearly reflect the value of each test section, to facilitate the calculation of the test required items.
4 , there is enough precision gauge measurement.
The measurement of the gauge length of the specimen is an important data for calculating the rubber elongation. Therefore, the rubber tensile tester in the rubber tensile test must accurately measure the strain amount of the specimen and record it immediately.
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