Contents
What is vibration failure?
Vibration Fatigue is a specific type of mechanical fatigue that is caused by the vibration of equipment during operation. Like other forms of fatigue, vibrations can initiate a crack which may lead to propogation of the crack and eventual failure of the equipment.
Why vibration test is required?
Shock and vibration testing ensures product performance under extreme conditions. Vibration testing and shock testing are used to simulate in a controlled laboratory environment the extreme conditions that a product may face during use, such as mishandling, dropping, and various modes of shipment.
How do you carry out a vibration test?
The simplest vibration testing procedure, sine vibration testing uses a single sinusoidal tone following simple harmonic motion input to the test specimen. This sinusoidal tone can be swept across the test frequency range, or it can be fixed on a single frequency, depending on the requirement.
How does random vibration testing work?
A random vibration test is one comprised of vibration energy at all frequencies over a specified range. The vibration frequency components that make up the input signal for a random test combine in amplitude and phase to create a time waveform which appears on an oscilloscope as random noise.
What forced vibration?
Musical instruments and other objects are set into vibration at their natural frequency when a person hits, strikes, strums, plucks or somehow disturbs the object. The tendency of one object to force another adjoining or interconnected object into vibrational motion is referred to as a forced vibration.
What can vibration analysis detect?
Frequency domain vibration analysis excels at detecting abnormal vibrating patterns. By studying the frequency spectrum, the periodicity of the collisions can be discovered and thus detect the presence of bearing faults.
What are vibration limits?
The vibration limits according to ISO 10816 (bearing vibrations) and ISO 7919 (shaft vibrations) are as follows: Classification of vibration evaluation zones: Vibration values within this zone are normally considered to be of sufficient severity to cause damage to the machine.
What is 1g in vibration?
Amplitude: The amplitude for a sine vibration test is usually specified as displacement or acceleration. G: One G is equal to the acceleration produced by earth’s gravity and is equal to 386.1 inches/sec^2 or 9.8 m/sec^2.
What should the vibration level be for a vibration test?
MIL-STD-810H (2019) recommends using an m value of 7.5 for random vibration excitations, “but values between 5 and 8 are commonly used.” However, a value can be derived by testing several units with several different vibration levels until failure and then finding the value of m that is most suitable for the data.
Is there a true to life vibration test?
A product is likely to experience a range of vibration environments in its lifetime and, in many cases, a vibration environment will be more complex than a simple sinusoid or Gaussian random waveform. The FDS can be used to incorporate all vibration environments to create a true-to-life test.
How is a PSD used in vibration testing?
The resulting PSD can be used in many stages of vibration testing, from initial product development to re-creating field failures in a lab environment. The quality factor determines the damping value of an oscillation. A higher Q value will result in a lower rate of energy loss and, therefore, a slower end to the oscillation.
How is the FDS of a vibration test calculated?
The FDS is calculated using a time-domain analysis that includes rainflow analysis and cycle counting. Using time domain analysis and defined material property (m), the relative damage can be calculated and an FDS can be created. For test purposes, the FDS can then be converted into a PSD using Henderson-Piersol’s fatigue calculation method.