Material testing machine analysis and selection

Material testing machine analysis and selection-mechanical properties inspection

With the progress of society and the development of science and technology, a variety of new materials are emerging, especially polymer materials have developed rapidly in recent years. As a branch of plastic, various properties have been significantly improved, and in some fields, there has been a trend to replace wood and metal materials. In order to enable the safe and reliable use of plastic materials and their products, it is very necessary to perform performance tests on them, of which mechanical property tests are one of the most important tests.

Characteristics of common universal material testing machines

1. Conventional electronic universal material testing machine is the mainstream product of today's universal material testing machine. It uses a servo motor as a power source, and a screw and a wire nut as actuators to realize the speed control of the moving beam of the testing machine. It is simple to operate and is suitable for testing. The requirements of the staff are not high, and the test stroke can be arbitrarily customized as needed. Although the control method is relatively simple, there is only one control method for speed, but its control accuracy and control range are very wide. Taking Jiangdu Kaiyuan Experimental Machinery Factory as an example, its speed adjustment range can reach 0.001mm / min ～ 1000mm / min, stepless speed regulation, control accuracy can reach 0.5%, and small tonnage models are easy to implement. When the friction coefficient is used, the full load is only 5N. It has great configuration flexibility, and can be equipped with sensors, fixtures, and accessories of different tonnages as needed to achieve multi-purpose, complete the functions of pulling, pressing, bending, shearing, peeling, tearing, friction coefficient, and twisting. Throughout the relevant standards of plastics mechanical properties inspection, the control method requirements of the testing machine are almost all speed control, so no matter from the control mode or speed range, test stroke and tonnage of the testing machine, this type of model is plastic mechanics First choice for performance inspection.

2. The three closed-loop electronic universal material testing machine has the characteristics of wide speed range, large test stroke and flexible configuration of the conventional electronic universal testing machine, and has the advantages of electro-hydraulic servo testing machine force, displacement and deformation control. Therefore, it is a kind of testing machine with better performance, but the stability of the machine is closely related to the rigidity of the host and the rigidity of the sample during the force control and deformation control. Generally, the testing machine for plastics has a small tonnage, so the rigidity of the host is low, and the rigidity of the sample itself is not too large, so this type of testing machine rarely has models below 10KN, while models below 10KN are plastics. most commonly used. As mentioned above, the stability of this type of model is related to the sample. If the sample is single, the test method is relatively simple, and it can also be selected. Otherwise, you need to adjust the control parameters of the test machine at any time (that is, conventional P, I, D Parameter), which is almost unimaginable for non-automatic testers. Therefore, in general, in addition to the specific requirements for the control method, it is not easy to choose to do the test of plastic materials.

3. Simple electrical pulling Since the tensile strength of plastic is a very important index for testing the mechanical properties of plastics, in the past few years, there are not many types of plastics, and the application is not very wide. The mechanical property testing items of plastics are still relatively single The corresponding standards are not perfect. During this period, a structure is very simple, the purpose is very single, and the performance index is very lacking, but the single-purpose tensile test machine with a motor as the power source is very cheap and is widely used. As the name implies, it can only be used for a single tensile test, and the data it can process is very limited, and the control measurement accuracy is relatively low. Although it is still used in some occasions, it has gradually been used because of its single function. Eliminated by the market.

4. The manual hydraulic universal material testing machine is the "ancestor" of the testing machine family. It has a long history, simple to use, low price and large tonnage. As the name implies, manual hydraulic pressure indicates that it is open-loop control, the performance is not good, the operation process is completely dependent on the operator's operation level. In addition, because its mechanical structure and hydraulic loading principle determine its loading speed, the test stroke is small. At present, the smallest model of this type of testing machine is 50KN, so its small load measurement accuracy is very low, and the expansion configuration ability is very poor. Generally, it is only used for structural component tests or simple material performance tests, such as the pull-out of connecting parts , Tensile strength of steel bars, etc.

5. The electro-hydraulic servo universal material testing machine is a kind of testing machine with better performance at present. Because it adopts electro-hydraulic servo control technology, it can realize the closed-loop control of force, displacement and deformation, and has good control performance. Currently in metal and building materials