Fatigue limit of materials and parts five commonly used fatigue test methods for metallic materials

Date：2022-07-29 14:37:47Views：918

Material fatigue test technology refers to the technology that characterizes the degradation of mechanical properties of materials under alternating load, which is widely used in the study of fatigue resistance of materials and components such as metals, rubber, composites and so on. Fatigue test can predict the fatigue strength of materials or components under alternating load. Generally, this kind of test cycle is long and the required equipment is complex. However, because general mechanical tests such as static tension, hardness and impact tests can not provide the performance of materials under repeated alternating load, it is necessary to carry out fatigue test for important components. This article has collected and sorted out some materials, which are expected to be of great reference value to readers.

Some common test methods of fatigue test of metal materials usually include single point fatigue test method, lifting method, high frequency vibration test method, ultrasonic fatigue test method, infrared thermal imaging technology fatigue test method, etc.

Single point fatigue test method

It is applicable to the service of metal components under rotating bending load at room temperature, high temperature or corrosive air. This method can approximate the fatigue curve and roughly estimate the fatigue limit when the number of samples is limited. The fatigue testing machine required for the test is generally bending fatigue testing machine and tension compression testing machine.

Lifting fatigue test

The lifting method fatigue test is a commonly used and accurate method to obtain the fatigue limit of metal materials or structures. On the basis of the conventional fatigue test method to determine the fatigue strength, or when the fatigue strength of materials or structures with a specified life cannot be directly determined by the test, the lifting method fatigue test is generally used to indirectly determine the fatigue strength.

It is mainly used to determine the random characteristics of fatigue strength of materials or structures in medium and long-life areas. The required testing machine is generally tension compression fatigue testing machine.

High frequency vibration fatigue test method

The frequency of alternating load in conventional fatigue test is generally lower than 200Hz, so it is impossible to accurately measure the fatigue damage of some parts in high-frequency environment. The high-frequency vibration test uses the test equipment to generate an alternating inertia force with the characteristics of cyclic load frequency of about 1000Hz, which acts on the fatigue specimen, which can meet the fatigue performance research of metal materials in service under high-frequency, low amplitude and high cycle environmental conditions.

High frequency vibration test is mainly used for military and civil mechanical engineering. The test device usually includes: controller, charge adapter, power amplifier, accelerometer, shaking table, etc.

Ultrasonic fatigue test

Ultrasonic fatigue test is an accelerated resonance fatigue test method, and its test frequency (20kHz) is far higher than the conventional fatigue test frequency (less than 200Hz). Ultrasonic fatigue test can be carried out under different load characteristics, different environments and temperatures, which provides a good means for fatigue research. Jiayu detection network reminds that ultrasonic fatigue test is generally used for ultra-high cycle fatigue test, mainly for fatigue tests of more than 10^9 cycles. In high cycle fatigue, the material is mainly elastic macroscopically, so the elastic relationship of parameters such as stress and strain is used in the damage constitutive relationship, rather than micro plasticity.

Fatigue test method of infrared thermography

In order to shorten the test time and reduce the test cost, energy method has become one of the important methods of fatigue test research. Fatigue of metal materials is a process of energy dissipation, and temperature change is a very important parameter to study energy dissipation in fatigue process.

Infrared thermal imaging technology is a wavelength conversion technology, that is, the technology of converting the thermal radiation of the target into visible light. It uses the difference of the thermal radiation of each part of the target to obtain a two-dimensional visual image, and uses computer image processing technology and infrared temperature measurement calibration technology to realize the display, analysis and accurate measurement of the temperature field distribution on the surface of the object. The material used in the test is usually the metal material with galvanized surface and normalized treatment. In order to increase the specific emissivity of the metal surface, a thin layer of infrared transmission coating is usually coated on the surface of the sample during the test.

The above is related to the fatigue test of metal materials compiled by the core detection team. I hope it will be helpful to you. Shenzhen Chuangxin Online Testing Technology Co., Ltd. is a well-known professional testing institution for electronic components in China, with 3 standardized laboratories covering an area of more than 1000 square meters. The scope of testing services covers: electronic component testing and verification, IC authenticity identification, product design and material selection, failure analysis, function testing, factory incoming material inspection, component X-ray testing, taping and other test items.