A vibration test system is a device used to simulate and measure the performance and reliability of objects under vibration environments. It simulates vibration conditions in real-world environments to assess the tolerance and performance of products. You can also call them vibration shaker systems or electric shaker systems. You can use the vibration test system to determine if a product can withstand this environment and find early failures, simulate actual use, and assess structural strength.
1) How does the vibration test system work?
For most vibration test machines, the vibration controller works by cutting a magnetic field during excitation. The internal armature of the vibration shaker system moves when applying a voltage current of the appropriate power. In this way, the vibration controller amplifies the driving signal that generates the vibration waveform and transmits it to the shaker to make the shaker vibrate.
The accelerometer of the electric shaker monitors the acceleration signal of the armature and transmits it to the controller for closed-loop control. The cooling system of the shaker controls the heat generated by the magnetic field generated by the internal excitation coil.
In addition, your horizontal slip table will require a hydraulic control mechanism.
2) What testing functionalities can a vibration test system provide?
A vibration test system can provide various testing functionalities, including fixed-frequency vibration testing, random vibration testing, shock vibration testing, and vibration transfer function testing. It can simulate different vibration conditions such as sine waves, random noise, shocks, and seismic waves to evaluate the performance and reliability of products under vibration environments.
Nowadays, people use vibration shaker systems in many industries, such as automotive, aerospace, aviation, communications, electronics, defense, and other industries…
When developing a machine, you will need reliability tests to assess its ability to withstand external or self-generated vibrations during transport and operation without damage, to work as expected, and to last for a given time. As an important part of reliability test equipment, the vibration test system is becoming more and more important with the increasing reliability requirements of products, especially aerospace products.
Here are the advantages of a vibration test system include:
- Providing repeatable and controllable vibration environments to accurately evaluate product performance and reliability.
- Simulating different types of vibration conditions to meet various application requirements.
- Assisting in the discovery and resolution of design flaws and structural weak points.
- Offering comprehensive vibration performance assessment and analysis capabilities to improve product quality and reliability.
- Enhancing product development efficiency and reducing testing and trial cycles.
A vibration test system typically consists of a vibration table, vibration controller, accelerometer sensor, power amplifier, and control software. The vibration table generates the vibration force, the vibration controller adjusts the amplitude and frequency of vibration, the accelerometer sensor measures the vibration levels, the power amplifier provides driving force, and the control software sets and controls the vibration test parameters.
Here are the common structures of a vibration shaker system, you can reference them:
1) Vibration Generator
Here is some information about vibration generators for you.
#1. Introduction of vibrator
The vibration shaker system drive coil current can be generated directly or induced. The drive coil is the main component of the exciter, adding current directly from the amplifier output. The induction type consists of applying an alternating current to a fixed coil to induce a current in the drive coil.
What we can tell you is that the vibrator is simple in structure and does not require a drive coil with a lead connection, but its efficiency is not very high. This structure is used by some UD shakers in the United States. Since the problem of driving the coil leading out the cable is well solved, the direct project of our vibration system is more useful.
Permanent magnet type and excitation type are two different ways of generating a magnetic field in the exciter. Since it is challenging for us to manufacture large magnets, permanent magnetic fields are generated by long-lasting magnets, but such magnets are now only suitable for small shakers. For large shakers, the excitation coil receives direct current to provide you with a stable magnetic field.
#2. Classification of excitation type shaker
Our excitation-type shaker is divided into single excitation and double excitation two types. The magnetic field ring is generated by a set of excitation coils in a single excitation. Although the excitation efficiency of this structure is low, the power consumption is high, and the leakage is serious, to ensure that the magnetic field on the bench is low, you need a demagnetization coil.
The magnetic field on our platform is small because the double excitation is generated by two sets of excitation windings located on either side of the operating magnetic gap. For example, the magnetic fields in your working magnetic gap are superimposed on each other, canceling each other on the table, and because the length of the double excitation magnetic circuit is reduced, the magnetic resistance is reduced, and your excitation efficiency is greatly improved than that of the single excitation.
2) Cooling System
The following is information about our cooling systems for your reference.
#1. Cooling mode of the shaker
Our vibration shakers’ cooling methods include natural cooling, forced air cooling, water cooling, oil cooling, and so on. Natural cooling is only suitable for small shakers with very low power. Due to the complex structure of our newly developed shaker, oil cooling is not common, so the oil-cooled shaker you are still using should pay attention to maintain the quality and quantity of oil.
Forced air cooling is a common cooling method for small and medium-sized shakers, which uses high-pressure fans to continuously pump hot air out of the surface to achieve the purpose of cooling. When you cool in this way, the structure of the drive coil and excitation coil is relatively simple, the equipment is easy to install, the cost is low, and your machinery will not have the common water leakage, water blockage, and other failures of the water cooling table.
However, the high-pressure fan is very noisy when working, and it has a great impact on your operator when you use it. Air-cooled cooling efficiency is relatively low, and not suitable for large shaking table cooling. However, water cooling is a common cooling method for large and medium-sized shaking tables. If you are using a large shaking table, it is recommended that you use water cooling.
#2. Additional information about the cooling system
Usually, the winding of the water-cooled meter is wound with a hollow enameled wire, and the cooling water is cooled directly into the hollow enameled wire, which has high cooling efficiency and little noise. However, the structure of the shaking table is more complex and the water quality of the cooling water is higher, so we commonly use distilled water or deionized water.
In the water cooling table, our investigation learned that there are serious defects in the equipment of several companies in the United States and the United Kingdom. Their drive coil into the structure of the cable and water pipe is unreasonable, and the waterway of the excitation coil is unreasonable, resulting in frequent leakage of this structure. So the water quality requirements are extremely high, and the water should be changed frequently.
Our vibration shaker system adopts the new structure of parallel connection of water circuit, a series connection of circuit, and the threaded connection of water and electricity joints, which solves these problems very well, and it does not require high water quality, low water pressure, and rarely leaks.
3) Power Amplifier
You can understand that the power amplifier is an important part of an electrodynamic shaker system, and its own performance and matching conditions with the shaker are directly related to the performance of your system. The development of power amplifiers has experienced three generations from tube amplifiers to transistor linear amplifiers and then to digital switching amplifiers.
In our new production equipment, we did not use Electronic tube amplifiers, foreign in recent years to develop switching amplifiers, it uses the switching characteristics of transistors, tube consumption is minimal, the efficiency can be as high as 90%, and the efficiency of an ordinary linear amplifier is only about 50%.
It is precise because the switching amplifier itself generates less heat, its cooling is very simple, and you can only use a very small axial flow fan can cool the output power of tens of kVA amplifiers, making the structure of the device simple and reliable. By comparison, we found that the same linear amplifier must be cooled with water and has a complex structure.
#1. Technical specifications of electric shaker
The technical specifications of the electrodynamic shaker are: rated sinusoidal force, random force RMS, operating frequency range, *maximum acceleration, *maximum velocity, *maximum displacement, the effective mass of the moving part, allowable direct loading mass of the working table, allowable bias moment of the working table, stray magnetic field, distortion of the acceleration waveform, uniformity of acceleration of the working table and transverse vibration ratio, etc.
The excitation force of the shaker is the mass of its moving part multiplied by the acceleration that can be achieved at that mass, not just the weight of the test piece. Upon inquiry, we learned that: the rated sinusoidal force is the effective mass of the moving part multiplied by the *maximum acceleration peak value, and the random force effective value is the effective mass of the moving part multiplied by the *maximum acceleration effective value that can be achieved when the shaker is experimented with the power spectral density curve according to the standard (such as ISO5344).
4) Horizontal slip table
Our horizontal slip table is the auxiliary device for the horizontal test of the vibration test system, which is convenient for us to test large samples. There are 4 types of horizontal slip tables, including hydrostatic bearing support type, ball bearing support type, and oil film support type, large sliding table adopts oil film + hydrostatic bearing support mode.
The slip table supported by the static pressure bearing can work between extremely low frequency and extremely high frequency of your machinery, with small acceleration waveform distortion, high anti-inclination moment and anti-torque moment, and small lateral vibration.
However, for you, this slip table is very expensive and expensive. When your working machine is in the medium frequency to high frequency, you can use ball-bearing slip tables, at low-frequency operation, the acceleration waveform should produce bearing noise. Our oil film slip table has a simple structure, low cost, a good waveform in the low-frequency domain, and easy to achieve large travel.
However, it has low resistance to overturning and torsional moments, and the transverse vibration is large. Due to the difference in manufacturing costs, we recommend the right horizontal slide table according to your test, which can meet all your test conditions. At the same time, we can customize the size of the test table according to your needs.
The function of the fixture is to firmly fix the sample on the vibration table, and transfer the vibration energy from the exciter to the sample, and its quality is directly related to the quality of our test. In general, in the context of a meeting sample installation, we will make the fixture should be as light, strong, and resonant as possible. The materials of the fixture are mostly magnesium and aluminum because these two metals are lighter than steel, the damping characteristics are better than steel, and the processing cost is low.
Usually, we machined our small fixtures from a single material, while manufacturing larger fixtures by using welding and casting methods. Our design should first define the test conditions, such as the energy levels and tolerances of sine and random vibration, the frequency range of sine scanning, the power spectral density curve of random vibration, the installation conditions, the allowable acceleration unevenness, lateral vibration, etc. Then calculate the resonance frequency and quality of the fixture to meet the test and your requirements.
For small specimens, you should not allow the resonance frequency of the fixture to be less than 1000Hz, and should simultaneously reach 3 to 4 times the low frequency of the specimen *.
After you finished the fixture processing, our staff should carry out the necessary inspection, and the important and commonly used fixture, such as the adapter plate, telescopic table, etc., should carry out the performance test to ensure the correctness of our test and the safety of your use.
6) Vibration Test System with Agree chamber
Our comprehensive environmental test has 3 comprehensive test chambers and 4 comprehensive test chambers. Comprehensive tests include temperature, humidity, and vibration tests.
For the three combined tests, the shaker is generally large to assemble as many specimens as possible. The sealing and insulation of the joint between the shaker and the chamber are also important. As you know, silicone rubber is a common sealing material. We are developing four integrated experimental systems. The four integrations refer to integrated environmental tests of temperature, humidity, vacuum, and vibration.
Mechanical shakers, electro-hydraulic shakers, and electrodynamic shakers are the three types of vibration shaker systems used for vibration testing. You can distinguish between one-way (single degree of freedom) and multi-way (multi-degree of freedom) shaker systems based on the direction of excitation of the shaker or the trajectory of the table.
Depending on the function of the shaker, you can distinguish between a single sinusoidal vibration tester and a shaker system that can perform shock tests and other mixed-mode vibration tests. In this short article, we describe the structure, function, and cost of various shakers, mainly electric shakers, and their current development status for your reference.
1) Mechanical Shakers
Usually, two types of mechanical shakers are cam type and unbalanced weight block type. The vibration shaker table is excited by an unbalanced weight block using the centrifugal force produced when it rotates, and the excitation force is proportional to the square of the imbalance torque and rotating speed. Our mechanical shaker can produce sinusoidal vibration, simple structure, and cheap price, but can only operate between 5Hz and 100Hz, the maximum displacement is 4.0mmp-p, and the acceleration is about 10g; If you go beyond this range, your vibration shaker cannot produce random vibrations.
The eccentricity of the cam and the length of the crankshaft arm determine the distance of the moving part of the cam shaker, and the exciting force varies with the mass of the moving part. When the exciting force is large and the acceleration waveform is distorted, our mechanical shaker can help you achieve large displacement in the low-frequency domain.
2) Hydraulic Vibration test system
Usually, you can use a hydraulic shaker to generate exciting force, the frequency range is generally 1-200Hz, the maximum displacement is generally 100-200mm, and the maximum acceleration is generally up to 10g. It has the ability of a horizontal slip table to produce horizontal vibration.
On the other side, you can use a random vibration when your work instrument is equipped with a vibration controller. However, it is noisy and very expensive for you to buy and operate. At present, it is widely used in vehicle vibration tests, earthquake simulation vibration tests of construction projects, water conservancy projects, and so on.
3) Electrodynamic Vibration Shaker
The most popular used vibrating test equipment is an electrodynamic vibration shaker. It has a wide dynamic range, making the operation of your automatic or manual control simple. Besides, the shaker also has a good accelerated waveform, making it suitable for creating random waves. It has a frequency range from 0 to 2 KHZ for large shakers and 0 to 10 KHZ for tiny shakers.
According to the principle of electromagnetic induction, we know that the construction of an electric shaker system is such that when the energized conductor is placed in an always present magnetic field, it will be subjected to force and vibrate when you let alternating current pass through it.
When the desired vibration signal is generated by the signal generator or vibration controller, it is amplified by the power amplifier and passed into the drive coil, and the vibration exciter will produce the desired vibration waveform. The drive coil of the exciter is formally in a high magnetic induction gap.
Vibration test systems are widely used in aerospace, automotive engineering, electronic devices, mechanical engineering, civil engineering, and seismic engineering, among other fields. They are used to evaluate the durability, reliability, and performance of products, and to discover design flaws, failure modes, and structural weak points. Here are the details:
1） Vibration Tested Products
You can use vibration tests of your products to determine limits and tolerances. Every product is vulnerable to vibration loads and potential breakage or failure. That includes tiny objects like microprocessors and circuit boards right up to giant structures like bridges and skyscrapers.
Vibration testing lets designers, engineers, and manufacturers know what pressure limits your product can withstand. A product that passes vibration testing meets safety and regulatory standards, as well as ISO requirements. Part of the due diligence for vibration testing determines fatigue testing, failure limitation, and structural integrity screening.
We understand that in many industries, you typically use vibration testing as part of your quality control procedures. It makes good business sense to find out how much vibration your product can withstand before launching. Known limitations allow end users to safely use your products and put them into trouble-free service. Anti-vibration testing prevents your products from being recalled, supports warranty conditions, and provides superior product purchase value.
2) Industries Using Vibration Testing
- Aerospace manufacturers ensure highly sensitive components can withstand enormous takeoff forces as well as extreme space conditions.
- Automotive manufacturers minimize flaws in ride and handling by vibration testing many parts before installation on the production line.
- Aviation manufacturers avoid parts and system failures like wing movements and engine pressures by vibration testing.
- Consumer goods manufacturers involve vibration testing to ensure products withstand everyday rigors in household use.
- You can use vibration testing in defense departments to ensure weapons and equipment are safe for use.
- Electronic manufacturers test complex parts for potential breaking by running prototypes through vibration testing.
- Marine manufacturers reduce driveline wear and hull fatigue by having vibration testing done in controlled facilities.
- Medical equipment manufacturers prevent failure in life-saving hospital equipment by having parts vibration tested.
- Oil and gas manufacturers rely on vibration testing to prevent production problems in a highly volatile industry.
- Power generation stations also use vibration testing to make sure high-voltage equipment operates safely and dependably.
Our understanding of your needs is essential to selecting the proper vibration shaker system. Shaker type, size, and exciter power level are dependent on test requirements. If you’re unfamiliar with your test options, you may want to consult our engineer for guidance. Seek advice early in the selection process as other factors may influence the recommendation. These include:
1) Determining Shaker Sizing
Your correct choice of shaker requires the application of Newton’s second law of motion:
- Force = Mass x Acceleration (F=MA)
Our vibration systems have output force ratings defined in terms of:
- Sine force: kg. f (kN) peak
- Random force: kg. g (kN) rms
- Shock force: kg. f (kN) peak
Applying Newton’s Law In Shaker Selection
If you want to understand the suitability of a particular test system. You can assess it based on the following aspects:
F=Moving MASS x G x 1.30= Desired Force Shaker System
- Maximum Displacement
- Maximum Velocity
- Maximum test frequency
2) Specimen Specifics
You will need the following test article data along with your test specification:
- Specimen Description
- Specimen Test Mass
- Specimen Dimensions
- Specimen Center of Gravity (CG)
- Specimen Mounting Considerations
3) Fixture Specifics
Test fixtures affect quality and resonance, which you must carefully consider. And you should pay attention to the following issues when choosing the shaker system:
- Do your fixtures exist or will they require design and fabrication?
- What are or will be the approximate dimensions (estimate if necessary) of the fixturing?
- What is or will be the approximate mass (estimate if necessary) of the fixturing?
- Are there any mounting issues (bolt pattern, size)?
- Are you need a head expander?
4) Test Specifications (F=ma)
The maximum Acceleration for the F = MA estimate is derived from the test specification:
- for Sine vibration (G-peak)
- for Random vibration (G-RMS)
- for Classical Shock pulses (G-peak)
Our operators need to be aware of the system’s maximum displacement and velocity.
5) Evaluating the Test Specifications
- Classical Shock
- SRS Shock
- Mixed Mode (Sine on Random and Random on Random)
6) Understanding Random Vibration
We determine our random vibration rating by the guidance of ISO 5344. A flat spectrum with a 3-4 times load on the armature mass is specified in ISO 5344. It can achieve continuity of ratings between different manufacturers.
You can use a non-resonant armature for three to four times the mass load. However, this reduces the resonant frequency of the vibrator armature under test to typically less than 2000hz. This allows our vibration test system to obtain free energy at higher frequencies.
7) Effects of Resonance
You know that every mechanical structure has a resonant frequency, which can lead to significant power absorption at certain frequencies. We must take this phenomenon into account in the estimation process. The force rating defined by our shaker manufacturer is the force rating at the armature surface.
Test systems with associated fixtures, head expanders, slip tables, etc., as force absorbers may overdrive the shaker. In a professional sense, you can install a monitoring accelerometer on the armature surface to determine the “true force” achieved.
Here is a list of common vibration test standards on the market that we have compiled for you:
- AC 156 Seismic: Seismic testing provides validation that vibration shaker systems used in earthquake-prone regions can withstand seismic energy.
- ASTM Standards: Various vibration levels standards published by the American Society for Testing and Materials (ASTM) International apply to various goods, from biomedical equipment and military equipment to aircraft landing gear and automotive parts.
- ISTA Methods: To ensure the safety of equipment used in the industry, the International Safe Transit Association publishes several testing methods.
- ISO Directives: International Organization for Standardization has issued several directives, including directive 10816 for vibration testing, and directive 18436-2 for vibration conditions monitoring certification.
- MIL-STD-202: MIL-STD-202 is a Department of Defense standard that establishes the quality of electronics and electrical components available to the military.
- MIL-STD-810: Under this military standard, people use rigorous testing methods – including vibration testing – to simulate harsh field environmental conditions.
Here are some tips for operating a vibration test system
- Test dynamics: a good understanding of the item under test, fixtures, and shaker armature is important.
- Test frequencies: Please note, you can only run the shaker within both its maximum and minimum frequencies.
- Accelerometers: You should mount all accelerometers and will not fall off during the test.
- Cross-axial motion: You should careful monitoring of the cross-axial motion, it can avoid exceeding the shaker’s overturning moment capability.
- Equipment manual: Users should familiarize themselves with the equipment manuals including any special addenda.
- Before test checks: To ensure that the shaker and other equipment are working correctly before starting tests.
- Test failure: You should record any failure, and efforts made to analyze the cause before repeating the test. Doing so will avoid repeated failures caused by the same problem.
- Shaker specification: You should only run the vibration test system and other related equipment within the vibration shaker specification.
- Test masses: Before starting the vibration test, you should know the exact mass of the payload and fixture. This will avoid overdriving at the shaker.