Ultrasonic fatigue testing machine is a new generation of devices designed to perform VHCF tests in a very short time. The lifetime approach in fatigue design based on S_N curves establish an infinite life when the cyclic stress applied is below than the endurance limit. Results in this field revealed fatigue failures beyond 10e7 cycles, indicating that there´s no endurance fatigue limit, however obtaining this data with servo-hydraulic testing machine can be very time-consuming and expensive.
Ultrasonic fatigue testing is one of a few methods which allow investigating fatigue properties in the ultra-high cycle region. The method is based on exposing the specimen to longitudinal vibrations on its resonance frequency close to 20 kHz. With use of this method, it is possible to significantly decrease the time required for the test, when compared to conventional testing devices usually working at frequencies under 200 Hz. Ultrasonic fatigue testing is a kind of accelerated resonance type fatigue test method, which can significantly reduce the test time and is the only available solution for aero-engine blade ultra-long life fatigue test.
Ultrasonic fatigue testing machine is used to carry out the fatigue characteristics, fatigue life, prefabricated crack and crack extension test of metal and alloy materials and their components under tensile, compression, or tensile-compression alternating load at room temperature.
Ultrasonic fatigue test is an accelerated resonance fatigue test method, which establishes a mechanical resonance wave on the loaded sample. Based on the principle of piezoelectric stretching and using high-energy ultrasonic resonance technology, its testing frequency (20kHz) far exceeds the frequency of conventional fatigue testing. The fatigue degree and data near the threshold can be obtained within the actual test time. Due to the high frequency, the fatigue limit of various industrial materials with high repetition cycles can be quickly detected.
Ultrasonic fatigue testing machine is based on the principle of ultrasonic resonance, which generates high-frequency vibration load on the sample to complete the (ultra) high cycle fatigue performance test of the material. Meet the requirements of modern mechanical equipment for ultra-long life and ultra-high reliability of parts.
Our company developed the third generation of multi-functional ultrasonic fatigue tester with a wide range of working frequency, output amplitude, high control accuracy, can carry out a variety of metal materials and composite materials of variable stress ratio axial symmetric tensile compression, irregular stress ratio three-point bending, vibration bending and other forms of loading ultrasonic fatigue test. Simultaneously, to provide axial tension, three-point bending, vibration bending, and different types of specimens of the additional optimization design software.
Advantages of ultrasonic fatigue testing
- Random variable amplitude loading, including low-level loading, can be made closer to the engineering reality.
- Fatigue damage caused by minor defects can be reproduced simply by using a computer to set and control the test.
- Since the test is conducted in a resonant state, high stresses can be generated, and the 1000 MPa class’s steel tests can be performed.
- The test equipment requires low output power (tens to hundreds of watts), saving a lot of energy and test money.
- At the end of the specimen during resonance, the stress level is shallow, simplifying specimen clamping, requiring only one end to be clamped, which is advantageous for brittle materials.
- Rapid evaluation of metallic materials’ fatigue life with a repetition frequency of 20 kHz reduces the test time hundreds or thousands of times.
Mainly used in aerospace, high-speed rail cars and power stations and other fields, to carry out alloy steel, aluminum alloy and titanium alloy and other metal materials, as well as carbon fiber composite materials (ultra) high cycle fatigue performance test. Compared with the conventional fatigue test method, the test time can be shortened by more than 90%, and the test cost can be greatly saved.
The control system is the main software part of the ultrasonic fatigue test system, including four parts: high-precision electromechanical coupling excitation control, fatigue test process monitoring, sample aided design, test remote monitoring and so on. The system has the function of intermittent loading, and can set the continuous and intermittent loading test and intermittent time according to the program; Intermittent loading shall have the function of preventing damage to the sample caused by excessive starting power; The loading can be controlled, and the user can input the load according to the test scheme; The working frequency range can be set. When it exceeds the range, the equipment stops working and a prompt message is displayed on the interface; It has the function of specimen aided design, which is used to assist the user to design the specimen according to the test purpose and material parameters before the test; The software can display the working frequency and nominal displacement data of the ultrasonic generator, and realize the variable load output function of ultrasonic vibration.