Nowadays, more and more plastics processing enterprises are buying the so-called universal testing machine "universal" testing machine, using it to carry out tensile, bending, compression and shear tests to evaluate the performance of materials, application development research and quality control. Developed electronics have improved the performance of these devices, making them easier to operate and lower prices.
The universal testing machine stretches, bends, compresses or draws the plastic material spline through the adjustment of different speed levels, which is the most common equipment in the plastic mixing laboratory. During the preparation of the compound, the test material can be used to determine whether the material is suitable for certain specific processing applications or end applications. It can also be used for product quality control to ensure consistency between batches of product quality.
The testing machine includes one or more vertical bearing columns, a fixed horizontal base is installed on the column, and a movable horizontal cross head (cross beam) is also on the top. In the current universal testing machine, there is usually a ball screw on the column to fix the movable cross head. The size of the universal testing machine is characterized by the maximum load level of the frame and the dynamometer that measures the load / tension. The dynamometer is attached to a movable crosshead driven by an electric motor or hydraulic device. A series of dynamometers with clamps measure the force, and the results can be displayed on a digital display or a PC. Many universal testing machines have interchangeable dynamometers, so they can be matched to the different materials tested. The static test is carried out using a standard electronic universal testing machine, usually with a loading speed range of 0.001 to 20 in./min (1 in. = 2.54 cm). Dynamic tests or cycle tests such as crack growth and fatigue tests are usually carried out using a hydraulic servo system universal testing machine, which takes a long time and has a low load. At present, the most common items tested with a universal testing machine are tensile strength and tensile modulus, bending strength and modulus. When performing tensile tests in accordance with ASTM D 638 and ISO 527, clamps are clamped at both ends of the spline, one is stationary, the other is fixed on the crosshead, moves away from the fixed clamp, and the spline is pulled until the spline appears Break, the crosshead will stop automatically when broken. During the bending test (ASTM D790, D6272 and ISO178), the spline is placed on the two supports of the fixed machine of the testing machine. In this test, the crosshead moved in the opposite direction of the tensile test, pushing the spline toward an unsupported center instead of pulling it until the spline was bent or even broken. Because most thermoplastic materials will not break in this test, it is impossible to calculate the bending strength at break. Therefore, the standard test method requires calculation of the bending stress at 5% strain. The capacity of the commonly used electronic universal testing machine is 100 ~ 135000 lb. The larger the size, the higher the cost. In general, the vertical equipment is smaller and easier to operate, and can also rely on the gravity of the sample itself to make difficult samples such as films as easy to handle as heavier injection molded parts. The single-column universal testing machine has a lower force range and a lower price, and the structural capacity is generally 1000 lb. The structure capacity of the portal type universal testing machine can reach 1000 ~ 135000 lb. The dynamometer is also based on a certain maximum force value applicable to the structure and sample of the universal testing machine. For example, a 100 lb dynamometer installed in a 1000 lb mold frame can provide a 100 lb test load. The capacity of the dynamometer should not exceed the predicted fracture load of the sample, otherwise it will affect the accuracy of the test results.
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