Analysis of performance characteristics of common universal material testing machine

Along with the progress of the society, the national strength has been enhanced, various new materials have emerged in an endless stream, the performance of the original materials has been further improved, and the use surface has been continuously expanded. Therefore, higher requirements have been put forward for the inspection of materials. As we all know, before the 1980s, the use of material testing machines was limited to a few fields such as metal. Today, the use of material testing machines is no longer limited to metals, but it has been extended to all industries. The material testing machine has been developed from the past manual hydraulic testing machine to the present day. Various control modes coexist, performance characteristics are different, and the era of flowers blooms. In this dazzling test machine, how to choose a test machine that suits your own characteristics is what most users care about. Since most of the current material tests are static performance tests, the following are common to the current market.

A simple comparative analysis of the performance characteristics of the test machine can be made, and a selection principle is proposed for your reference.

I. Types of common universal material testing machines At present, there are two major series of universal material testing machines commonly available on the market, four types:

1. Hydraulic series: manual hydraulic universal material testing machine, electro-hydraulic servo hydraulic universal material testing machine

2, electronic universal series: conventional electronic universal material testing machine, high-performance electronic universal material testing machine.

Their performances vary, their strengths and weaknesses coexist, and each has its own user base.

Second, the performance characteristics

1, hydraulic series

1) Manual hydraulic universal material testing machine Manual hydraulic universal material testing machine mainly uses simple high-pressure oil source as power source, manual adjustment valve as control element, and manual manual loading. Therefore, it belongs to open-loop control system. Due to the limitation of the oil source flow and the structure of the main engine, its cylinder piston stroke is small, and the common one is generally about 300mm, and its test speed is generally small. Affected by the price factor, the load cell generally uses a pressure sensor (a large tonnage basically uses a pressure sensor). Therefore, the accuracy is low, the range is small, the general accuracy is 1 or 2, and the range is generally 4%-100% F.S. Due to the friction of the oil cylinder, the tonnage is generally difficult to achieve very small, the domestic minimum is 5T. However, due to its unique low price and large tonnage characteristics, it is still widely used in the inspection of finished products and single material indicators.

2) Electro-hydraulic servo universal material testing machine It mainly uses precision high-pressure oil source as power source, and uses servo valve or proportional valve as control element for closed-loop automatic control, so the control performance is high, generally can realize load, strain and displacement. Three control modes. Like the manual hydraulic universal material testing machine, his test speed is lower due to the limitation of the oil source flow. Due to the closed loop automatic control, the system stiffness becomes the key to the normal operation of the entire system. As we all know, the stiffness of the liquid is relatively low. In order to reduce the influence of the liquid on the rigidity of the whole machine as much as possible, the stroke of the electro-hydraulic servo testing machine is not large, and it is also affected by the rigidity of the whole machine. The electro-hydraulic servo type testing machine Tonnage is impossible to do very small, basically more than one ton. However, due to its multiple control modes, it is flexible and has high performance.

2, electronic universal series

1) Conventional electronic universal material testing machine Conventional electronic universal mainly uses servo motor as the power source, screw and silk nut as the execution components, realizes the speed control of the moving beam of the testing machine, and its test speed range can be adjusted to CPQ- For example, WD can test speeds of 0.001mm/min-500mm/min, and the speed ratio can reach 500,000 times. The test stroke can be as needed, up to several meters. This is a hydraulic test machine that can‘t be realized anyway. With the development of electronic technology and the improvement of servo motor performance, the motor used in electronic universal has been from the early DC servo motor to the present.

More use of AC servo motor, from the early power components using thyristor for phase shift trigger control to today‘s use of a variety of power modules to achieve pulse width modulation control, electronic versatile performance has a qualitative leap, people‘s minds The high electronic failure rate and poor performance are no longer there. Since the conventional electronic universal speed control, the requirements on the rigidity of the system are not high, which creates favorable conditions for the realization of the small tonnage testing machine. From the current international and domestic situation, the test machines below one ton are basically conventional electronic universal testing machines. It is the most versatile and cost-effective.

2) High-performance electronic universal testing machine High-performance electronic universal testing machine is the same as the conventional electronic universal testing machine. It also uses servo motor as the power source, screw and silk nut as the execution components, and it is combined with the conventional electronic universal testing machine. The difference is that it can be controlled by load or by strain control or displacement control. In addition to the wide speed of the conventional electronic universal, the large stroke characteristics, it also has all the advantages of the electro-hydraulic servo test machine, so it is the best performance universal material testing machine. At present, the leader of this type of testing machine basically uses the EDC 120 series produced by Doli of Germany as the core control component. Of course, this type of testing machine also has its drawbacks. Because of the three control modes of load, strain and displacement, the stability of the whole machine is directly related to the stiffness of the system, and the stiffness of the sample directly affects the stiffness of the system. Therefore, when there are many types of samples to be tested, the change in stiffness of the whole machine will be large, so it is difficult to ensure that all tests can be performed normally. In order to satisfy all the tests, it is necessary to adjust the parameters of the control system (P, I, D parameters) at any time, which is difficult for non-automatic control professionals, so that this can not be fully played. The advantages of a class test machine. The price of this type of testing machine is relatively high.