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What is the history of fatigue testing machine?

Author: Weisi instrument time: September 23, 2020 source: unknown
Abstract: the earliest static testing machine is mechanical. For example, in England, the lever weight type material testing machine was produced as early as 1880, and the universal testing machine (the prototype of electronic universal testing machine) loaded with nuts and screws was produced in 1908. These testing machines can be used for material stretching and

The earliest static testing machines were mechanical ones. For example, in England, the lever weight type material testing machine was produced as early as 1880, and the universal testing machine (the prototype of electronic universal testing machine) loaded with nuts and screws was produced in 1908. These testing machines can carry out the tensile, compression, bending and torsion tests of materials. About 90 years ago, Amsler company of Switzerland developed the hydraulic universal testing machine Compared with the mechanical type, this kind of testing machine has the advantages of simple operation, large output force, simple structure and compact volume.

It is not enough to understand the static mechanical properties of materials. In real life, most of the damage is due to fatigue failure. According to foreign statistics, 50% - 90% of the failure parts are fatigue failure. Therefore, many developed countries attach great importance to the study of fatigue strength.

Fatigue problem can be traced back to the early 19th century. After the industrial revolution, with the development of steam locomotives and motor vehicles and the wide application of mechanical equipment, the damage of moving parts often occurs. The failure often occurs at the sudden change of the section of the parts. The nominal stress at the failure site is not high, which is lower than the strength limit of the material and sometimes lower than the yield limit.

The experimenter who first studied the fatigue phenomenon systematically is German A. Wheeler. He has been the director of locomotive and rolling stock plant and machinery plant since 1847, and has carried out in-depth and systematic research on metal fatigue. In 1850, German A. Wheeler designed the first fatigue testing machine for Locomotive Axles (also known as a. Wheeler fatigue testing machine), which was used to carry out the fatigue test of full-scale locomotive axles. After that, he developed various types of fatigue testing machines and carried out fatigue tests with metal samples for the first time. He established the fatigue life and fatigue life of a system based on the concept of fatigue stress and fatigue life. Therefore, it is generally acknowledged that A. Wheeler is the founder of fatigue, known as "the father of fatigue test".

From 1870's to 90's, Gerber W. (Gerber) studied the influence of average stress on fatigue strength, and put forward Gerber parabola equation. British Goodman J. (Goodman) put forward the famous simplified straight line Goodman diagram. In 1884, Bauschinger J. (Bauschinger) discovered the phenomenon of "cyclic softening" in which the elastic limit decreased under cyclic loading, and introduced the concept of stress-strain hysteresis loop. But his work was not paid attention to at that time. It was not until 1952 when keuyon did the copper bar experiment that he proposed it again and named it "Bauschinger effect".

In the early 20th century, metallographic microscope was used to study the fatigue mechanism. In 1903, Ewing J.A. (Ewing) and Humphrey j.c.w. (Humphrey) found slip marks caused by cyclic stress on single lattice aluminum and multi lattice iron, and pointed out that the fatigue deformation was caused by slip similar to monotonic deformation. In 1910, Bairstow studied the change of stress-strain curve under cyclic loading, measured the hysteresis loop, established the concept of cyclic hardening and cyclic softening, and carried out program fatigue test. During this period, Gough H.J. (Goyle), an Englishman, made great contributions to the study of fatigue mechanism; he also carried out bending torsion composite fatigue test, and studied the fatigue strength under bending torsion combined stress; and published a great book metal fatigue in London.

In 1929, Peterson R.E. (Peterson), an American, carried out a series of tests on the size effect and proposed the theoretical value of the stress concentration factor. From 1929 to 1930, Haigh B.P. (haif), an Englishman, reasonably explained the different notch effects of high strength steel and mild steel.

In 1945, American miner M.A. (meiner) formulated the linear cumulative damage theory proposed by palmgren J.V. (palmgren) in 1924 on the basis of a large number of experimental studies on fatigue damage accumulation, forming the famous palmgren Miner linear cumulative damage rule (hereinafter referred to as miner rule). In 1940s, cepehceh C.A. (Xie Lianxian) of the former Soviet Union also put forward the design and calculation formula of conventional fatigue, which laid the foundation for conventional fatigue design.

In 1952, Manson S.S. (Manson) and coffin L.f. (coffin) of Lewis Institute of National Aeronautical administration of the United States put forward Manson coffin equation to express the relationship between plastic strain and fatigue life, which laid the foundation for low cycle fatigue. In the 1950s, the use of electron microscopy opened up a new era for the study of fatigue mechanism.

It is from 1940s that the fatigue test data are processed by probability and statistics method. In 1949, Weibull W. (Weibull) published a famous method for statistical treatment of fatigue test data. In 1959, Pope J.A. (Popper) pointed out that the fatigue life obeys the lognormal distribution. Since the 1960s, statistics has been applied to fatigue test and fatigue design. In 1963, the E9 Committee of American Society for testing and materials (ASTM) summarized the research results in this field, and published the guide to statistical analysis of fatigue test and fatigue data (ASTM stp91a).

In the early 1950s, permanent magnet torque motor with high speed response appeared. In the late 1950s, the electro-hydraulic servo valve with nozzle flapper valve as pilot stage appeared, which made the electro-hydraulic servo system the fastest response and the highest control accuracy at that time. In 1958, Blake boon and others published their research work in MIT, which laid the foundation for the theory and practice of modern electro-hydraulic servo system. In the 1960s, the electro-hydraulic servo valves with various structures came out one after another, especially the emergence of the electro-hydraulic servo valve with dry torque motor as the representative and the application of various kinds of electric feedback technology, which further improved the performance of the electro-hydraulic servo valve. The electro-hydraulic servo technology is becoming more and more mature, and the electro-hydraulic servo system has become a part of the automatic control of weapons, aviation and aerospace It is an important part of automatic control of civil technical equipment.

Under this background, the electro-hydraulic servo dynamic fatigue testing machine is developed with the development of electro-hydraulic servo technology. Because it can not only carry out dynamic high and low cycle fatigue test, program controlled fatigue test, but also carry out static constant rate, constant strain, constant stress control test and all kinds of conventional mechanical property test. It can also carry out fracture mechanics test, part of vibration and impact test according to need, and can also test the fatigue life and crack of materials or components in a broad range It has many advantages over any other testing machine, such as crack propagation, fracture toughness performance test, safety evaluation of actual specimen, working condition simulation, etc.

In the 1960s, with the emergence of large-scale integrated circuits, a random fatigue testing machine which can simulate the service load of components was developed. In the 1970s, the electro-hydraulic servo fatigue test device controlled by computer has been widely used in foreign countries to carry out random fatigue test. In the 1990s, a full digital servo controller with upper and lower computer structure has appeared. The closed-loop control calculation rate has reached 6KHz. 100MB Ethernet card is used for data transmission, which can complete the smooth and undisturbed switching of control mode, multi-channel coordinated loading and laboratory reproduction of various working conditions spectrum.

The appearance of low cycle fatigue Manson coffin equation, electron microscope and electro-hydraulic servo dynamic fatigue testing machine are considered as the three major contributions of fatigue research in the international fatigue research field. The electro-hydraulic servo dynamic fatigue testing machine adopts closed-loop control technology, which can simulate the actual working conditions in the test, and greatly promotes the development of fatigue test.

This paper is written by Fatigue testing machine Weisi, all rights reserved from the original manufacturer!

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