The first step in selecting a vibration test bench is to gain a deep understanding of the core parameters specified by the test standard. These parameters directly determine the technical specifications that the test bench must meet. Different standard systems, such as the International Electrotechnical Commission (IEC), the International Organization for Standardization (ISO), and national standards, have similar frameworks, but there may be differences in specific parameter requirements. Engineers need to carefully study the standard text, focusing on the following key indicators.
Selection parameters
The selection of vibration test bench should be based on the standard requirements, and the following core performance parameters should be matched and evaluated.
Frequency range
The frequency range refers to the range of effective vibration frequencies that the test bench can generate and control, usually measured in hertz (Hz). The standard specifies the frequency range required for the test, for example, from 5 Hz to 2000 Hz. The frequency range of the selected test bench must fully cover the standard requirements with appropriate margins. The lower limit is determined by the mechanical structure of the table, and the upper limit is closely related to the dynamic coil and power amplifier performance of the shaker. Formula fmax = 1/(2π√(m/k)) It can briefly describe the resonant frequency of the system and the quality of the moving partsmand suspension rigiditykThis affects the upper limit of the available frequency.
Thrust and load
Thrust is a quantitative measure of the driving force of a shaker in Newtons (N) or kilonewtons (kN). It must overcome the inertial forces generated by the moving part (moving coil, fixture) and the total mass of the test piece under target acceleration. The required thrust can be estimated by Newton's second law:F = m × a, among them m is the total motion mass (including specimens, fixtures, moving coils),a is the peak acceleration. The acceleration value of acceleration spectral density (ASD) or sinusoidal vibration specified in the standard is the direct basis for calculating thrust. At the same time, it must be ensured that the nominal maximum load capacity of the test bench is greater than the total weight of the specimen and fixture.
Displacement and acceleration
Displacement (in millimeters, peak-to-peak) and acceleration (in g or m/s²) are direct expressions of the magnitude of vibration. In the low frequency band (usually below 50-100 Hz), the displacement amplitude is often the limiting factor; In the high frequency band, acceleration capability becomes the key. The vibration profile in the standard clearly specifies the magnitude required for each frequency band. When choosing, it is necessary to check whether the envelope of displacement, velocity, and acceleration of the test bench can meet the requirements at the same time in the entire frequency range required by the standard, that is, verify whether its "maximum thrust-frequency-displacement" curve covers the test conditions.
Vibration type and control method
The test standard specifies the type of vibration: sinusoidal vibration, random vibration, or mixed mode. sinusoidal vibration is used to find resonance points and perform fixed-frequency endurance tests; Random vibrations simulate the real environment and are defined by acceleration spectral density (ASD). This directly determines the type of vibration control system required. A complete random vibration control system needs to include digital controllers, sensors, and analysis software to enable precise closed-loop control of power spectral density (PSD).
The selection process that matches the requirements of the standard
Based on the above parameter analysis, the following systematic process can be followed for selection.
Step 1: Clarify the standards and test conditions
Detail the standard code (e.g. IEC 60068-2-64), test type (sine/random), frequency range, vibration magnitude (displacement, acceleration, ASD), test axial and duration.
Step 2: Calculate the critical load parameters
Estimate or weigh the test product quality, design and estimate the fixture quality. The required peak thrust is calculated based on the maximum acceleration or ASD spectrum specified in the standard.
Step 3: Primary selection of platform and amplifier specifications
According to the thrust, frequency range and displacement requirements, select the vibrating table with the appropriate thrust specification and the matching power amplifier. Ensure that its performance curve covers the test conditions.
Step 4: Determine the control system configuration
Depending on the type of vibration (sine, random, shock), select a digital controller with the corresponding control module. Verify that the number of control channels, analysis bandwidth, and dynamic range meet standard accuracy requirements.
Step 5: Consider Assistive Systems and Compatibility
Evaluate the requirements for horizontal slides (for lateral testing), cooling systems (air- or water-cooled), installation foundations, and laboratory power supplies. Ensure that the entire system is compatible with the existing laboratory environment.
Other important considerations
In addition to the technical parameters that directly correspond to the standard, the following factors also have a significant impact on the long-term suitability and test effectiveness of the equipment.
Scalability and versatility
Consider new testing standards that may be introduced in the future. Selecting equipment with a certain degree of redundancy in thrust, frequency range, and control functions can adapt to a wider range of test needs and avoid equipment limitations due to standard upgrades in the short term.
Installation and environmental requirements
Shaking tables, especially high-thrust models, have strict requirements for the installation foundation, and the vibration isolation and load-bearing of the foundation need to be considered. At the same time, the power consumption of the power amplifier, the noise generated by the cooling method (water or air cooling) and the heat dissipation must be properly addressed during the laboratory planning stage.
Calibration and compliance
The chosen vibration test system should be easily connected to a standard accelerometer for calibration, ensuring that its output meets national or international metrology standards. The calibration report and traceability chain provided by the device manufacturer are an important basis for demonstrating the validity of the test data.
Summary
Selecting a vibration test bench according to the test criteria is a systematic matching process. The core is to analyze the parameters such as frequency, thrust, displacement, acceleration and vibration type in the standard item by item, and translate them into specific technical requirements for the vibrating table, power amplifier and control system. Rigorous calculations and comparisons, combined with scalability, installation conditions and compliance, can be selected for vibration testing equipment that can accurately and reliably implement established standards and take into account certain future adaptability. A clear selection process helps you make the right technical decisions within your budget.
References
1. International Electrotechnical Commission. Environmental Testing Part 2-64: Test Methods Fh: Vibration, Broadband Random, and Guidelines. IEC 60068-2-64.
2. International Organization for Standardization. Mechanical vibration and shock Vibration testing machine auxiliary bench characteristics description. ISO 5344.
3. American Society for Testing and Materials. Standard Guidelines for Vibration Test Laboratory Practices. ASTM D3580.