Resonance testing for quality control
Resonance testing is a valuable technique used in various industries to assess the structural integrity and quality of mechanical components or systems by analyzing their natural vibration frequencies and modes. It involves exciting the component with a mechanical or acoustic force or input and then measuring the response of the component to determine its resonance characteristics. Resonance testing describes the analysis of resonances of a sample by characterizing its vibrational signature. In industrial manufacturing, the resonant inspection often as an end-of-line test, allows clear pass-fail decisions, detecting defects for excluding maleficient parts from production lines.
Optical vibraiton sensors like laser Doppler vibrometers provide a non-contact, high precision alternative measurement solution for determining the resonance frequency, resulting in many advantages in the context of acoustic resonance testing.
Polytec Magazine
Effects of mass loading
When to choose a laser Doppler vibrometer for vibration measurement
Measuring acoustic signatures and testing resonances at production level
Measuring the resonance frequency from DC to MHz and GHz
Typical phases and steps in resonance testing
Resonance analysis typically includes the following steps:
- Excitation: A force or input signal is applied to the component under test. This input can be mechanical, such as a shaker or hammer strike, or acoustic, such as a sound wave. The goal is to excite the component at a range of frequencies to identify its natural resonance frequencies.
- Measurement: Sensors are placed at various points on the component to measure its response to the excitation. These sensors record data, such as displacement, velocity, or acceleration, which is crucial for the subsequent analysis.
- Data Analysis: The collected data is then analyzed to identify the resonance frequencies or mode shapes of the component. Resonance frequencies are the frequencies at which the component vibrates most strongly, indicating potential structural weaknesses and defects, providing information about material propoerties and health status.
- Interpretation: Engineers interpret the resonance data to assess the health and quality of the component. Any deviations from expected resonance frequencies or unusual mode shapes can indicate defects, fatigue, or other structural issues that may compromise the component's performance or safety.
Optical, non-contact resonance testing using laser sensors
Resonance analysis seeks to identify the natural frequencies or resonant modes of an object. When an object is subjected to vibrations at or near its natural frequencies, it tends to vibrate with larger amplitudes. This effect allows for detecting structural issues, defects, or weaknesses. By analyzing the frequency response, engineers can gain insights into the structural characteristics of the object being tested, including its stiffness and mechanical properties, damping properties and overall integrity.
Laser Doppler vibration measurement is an advanced optical technology that offers several advantages in the context of resonance testing:
- High precision: Laser-based measurement systems provide extremely accurate and precise data, enabling engineers to detect even subtle changes in an object's vibrational behavior.
- Non-contact: Laser vibrometers do not physically touch the object being tested, minimizing interference and ensuring that measurements do not alter the object's properties. This is crucial when testing delicate and sensitive components or even hot objects where sensors cannot be applied.
Wide frequency range: Laser vibrometers can measure a wide range of frequencies, making them suitable for low-frequency up to high-frequency (GHz) resonance analysis.
Remote sensing: Laser vibrometers can be used to measure vibrations from a distance, allowing engineers to assess components in situ without the need for direct physical access. This is indispensable in danger zones like high voltage or explosive areas.
Rapid data acquisition: Laser vibrometers can capture data quickly with both analog and digital data transfer, thus enabling real-time analysis and immediate feedback during testing.
Optical metrology and laser sensors for resonance measurement
Become an expert: tips, tricks & video tutorials
The IVS-500 Industrial Vibration Sensor from Polytec is a dedicated and flexible measuring device for the vibroacoustic end-of-line test. This exclusive section (login) presents the basics of optical resonance testing using laser vibrometers including a technology benchmark for resonance testing and valuable tips & tricks video tutorials for the use and handling of the IVS-500 Industrial Vibration Sensor - for starters, current users, integrators and testing experts.
Testing resonances of hard disk drives and precision parts
As a case study, hard disk drives – with their ever growing storage densities and shorter access times – require extremely high levels of stability as regards the read/write head’s location and positioning in relation to the disk drive interface. The flying height is a compromise between competing effects. A lower flying height enables better local resolution for read/write operations and thus a higher data density; meanwhile the risk of collisions with the medium grows at the same time. The flying height is just a few nanometers and very much depends on the ambient pressure due to the aerodynamic bearing. The aerodynamic bearing, however, has resonances that depend on the ambient pressure too and that may lead to instabilities.
Since the measurement process is both non-contact and non-intrusive, in this situation using laser vibrometers is the only way of measuring the response behaviour of the read/write head including its suspension following dynamic excitation. When performing resonance test measurements with single-point and scanning vibrometers, the frequency spectrum of the read/write head’s deflection is measured as a function of the ambient pressure. You can use this to identify critical conditions and then make constructive changes. The goal of the optimization process is to develop read/write units that respond robustly to resonances caused by aerodynamic excitation.
Laser sensors for fast and reliable resonance measurement
Related products
VibroGo
VibroGo® is the truly portable, battery powered digital laser vibrometer for field studies and quick and easy condition monitoring of machines and facilities on the go. It allows the non-contact measurement of vibrational displacement, velocity and acceleration up to 320 kHz and from safe distances up to 30 m. Integrated on-board data recording, live monitoring and quick analysis of measurement data make VibroGo® more autonomous than ever before.
VibroFlex
With the modular laser vibrometer VibroFlex, Polytec introduces the new flexibility in optical vibration measurement with a modular sensor solution up to 24 MHz that adapts to the user’s needs: Add microscope objectives for observing tiny structures or measure noise, vibration, harshness (NVH) on large, complex samples like machinery, motors etc. Discover acoustics and vibration phenomena in research and product development for a faster time-to-market or reliably and cost-efficiently inspect production parts in-line. Also, find out how the new and patented QTec® multi-path interferometry pushes the limits for best SNR.
IVS-500 Industrial Vibration Sensor
The IVS-500 Industrial Vibration Sensor is key to fast and non-contact vibro-acoustic quality inspection, structure-borne noise analysis and reliable pass-fail decisions. Its robust and compact design enables a smooth integration into process control systems for in-line and production testing up to 100 kHz, whenever requiring short cycle times like for end-of-line tests. The sensor is wear-free and avoids expensive servo-mechanisms or noise protection cabins.
PSV QTec Scanning Vibrometer
PSV QTec Scanning Vibrometers take full-field vibration mapping to the next level with unrivalled optical sensitivity! Their innovative, patented QTec® technology uses multi-path interferometry based on infrared (SWIR) laser granting high-fidelity measurements on all surfaces from DC to 25 MHz. PSV QTec significantly reduce testing time - especially on dark, biological, rotating or moving objects, determining operational deflection shapes and Eigenmodes for NVH, acoustics, structural dynamics, ultrasonics, FEM validation and NDT.
MSA-600 Micro System Analyzer
The all-in-one optical measurement solution for static and dynamic 3D characterization of MEMS and microstructures- now for up to 6 GHz! The MSA-600 enhances microsystem development and quality inspections - also allowing testing on wafer-level when integrated into commercially available probe stations.
VibroFlex Range
VibroFlex Range is the outdoor-proof long-range vibration measurement solution designed for remote analysis of vibrating structures, model validation and health monitoring on large and distant structures from more than 300 m. The laser sensor conveniently monitors structural dynamics and stability of buildings, operating machinery and critical production facilities, providing a fast and efficient on-site testing solution.
Further applications
- Amplitude measurement
![Measure vibration amplitudes optically: analyze structure-borne sound for amplitude measurement using laser measurement technology]( "Measure vibration amplitudes optically: analyze structure-borne sound for amplitude measurement using laser measurement technology")
Measure vibration amplitudes optically: analyze structure-borne sound for amplitude measurement using laser measurement technology - Actuators and drives
![Production testing of electric drives using in-line laser vibration measurement]( "Production testing of electric drives using in-line laser vibration measurement")
Production testing of electric drives using in-line laser vibration measurement - White goods
![Production testing on white goods, using laser vibration sensors for automated quality inspection]( "Production testing on white goods, using laser vibration sensors for automated quality inspection")
Production testing on white goods, using laser vibration sensors for automated quality inspection - Injection valves
![Production testing and quality control of fuel injectors with laser vibrometers]( "Production testing and quality control of fuel injectors with laser vibrometers")
Production testing and quality control of fuel injectors with laser vibrometers - Medical devices
![Production testing with industrial laser vibrometers on membranes in medical technology]( "Production testing with industrial laser vibrometers on membranes in medical technology")
Production testing with industrial laser vibrometers on membranes in medical technology - Engine cold test
![Non-contact vibration measurement as end-of-line production testing]( "Non-contact vibration measurement as end-of-line production testing")
Non-contact vibration measurement as end-of-line production testing
