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1. The importance of rubber tensile testing machine gauge length measurement
The length measurement of Gum is an important link directly affecting the accuracy of the test. For example, in a tensile specimen, there is a close relationship between the value of the tensile force and the gauge length: the constant elongation stress of the specimen must measure the force value of the specimen stretched to a given elongation, while the constant stress requires the measurement of the specimen's gauge length, which is stretched 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, which is convenient for calculating the items required for the test.
Sample gauge length measurement is to calculate rubber elongation Therefore, in the elastic test, the elastic testing machine must accurately measure the elongation of the sample and record it in real time.
Second, the gage length measurement of the elastic testing machine in two ways
At this stage, the main measurement methods of the measurement length are two types: manual measurement and automatic measurement
Manual measurement consists of using a ruler and two set up vertically horizontal measuring rods that can move vertically During the tensile test, visually observe the change in the gauge length on the specimen and control the beiden measuring sticks manually to bring them into line with the sample. Synchronize the measuring length on the scale and at the same time note the distance of movement of the measuring rod on the scale.
The error of manual measurement is very large: First, the visual observation of the measurement length of the sample to a certain deviation; second, it is still impossible to accurately track the change in gauge length of the sample by manually moving the gauge rod; third, it is difficult for the test personnel to record the gauge length value while moving the gauge rod, and it is impossible to accurately describe the stress-strain curve after the test.
Compared to the automatic measurement of gauge length, it is for the Rubber detection of tensile properties more conducive. JNow many automatic gauge length measuring devices of rubber tensile testing machines use contact sensors to measure the change of gauge length in real time. There are two main installation positions of the sensor moving device: ① installed in the gripper; a.
Mounting the mobile device on the gripper The sensor has certain Restrictions. Due to the large elastic deformation of rubber, there is a large gap between the moving distance of the gripper and the change value of the gauge length of the sample, so the gauge length sensor installed on the gripper is more suitable for detecting elasticity. The tensile properties of specimens with very little deformation (such as metal materials) cannot be used to test the tensile properties of rubber.
Using the contact gauge length measureThe reasons for the impact are as follows: first, the dipstick's own weight in contact with the sample The sample is pulled down, which affects the tensile force measurement, and second, the dipstick's clamping has a certain impact on the Stretching of the clamped part, preventing it from stretching freely.Third, the properties of the rubber tensile testing machine
Because of inspectionThe measurement of the tensile properties of rubber requires multiple tensile values during the stretching process, and the tensile test is not repeatable, so instantaneously and accurately recording the tensile value of each test section plays a very important role in the success of the test.
