Reliably testing fatigue behavior
Reliable material parameters are essential if simulation models are to make safe predictions – especially when durability of the service life is being calculated. Structures in automotive engineering, medicine and energy technology are exposed to load changes of more than ten million cycles over the course of their expected lifetime –due to either high-frequency stress or a long operating time of up to 30 years. This range is referred to as the very high cycle fatigue (VHCF) range and extends far beyond the range of classic S-N curves. Extensive knowledge of the fatigue behaviour of the materials used is thus of vital importance if these high-performance components are to operate reliably in the VHCF range. To be able to go through the high load changes of 1010 in a reasonable time period of less than one month, the samples are offset in resonance vibration at frequencies in the kHz range.
With regard to verifying the simulated sample model, Polytec’s 3D scanning vibrometry provides a direct way of measuring the real fatigue sample’s eigenmodes and eigenfrequencies. Another potential application lies in the field of high-frequency stress and strain analysis, since contact measurement methods such as strain gages are not suitable for this type of endurance stress.
Operational reliability in high-stress train components (wheel rims), wind turbines and ultrasonic scalpels (medical technology).
PSV-3D Scanning Vibrometers measure 3D dynamics in research and product development in a reliable and precise way. The deflection shapes and Eigen modes detected help you with everything from NVH, acoustic and structurally dynamic issues to ultrasonic...
Determining material parameters in a non-destructive way
Material properties are determined with zero contact using laser vibrometers. Conclusions can be drawn as to a material sample’s strength by determining the resonance frequency during broadband excitation. This method is used to ensure quality when manufacturing different building materials, since it is completely non-destructive. Often expensive test objects can be saved, and it can also be easily automated.
Knowledge of the temporal and local changes to the material properties of cement-bonded systems is vitally important for both materials research and for planning and implementing construction projects. The material properties can be described using ultrasound parameters. Cement-bonded building materials have a high ultrasonic wave absorption capacity straight after mixing, as well as a low sound velocity. Depending on how structure development progresses, the sound velocities and signal amplitudes then increase continuously. The surface’s ultrasound-induced deflection is recorded with zero contact using laser vibrometers. Calculating Young’s modulus and Poisson’s ratio – the elastic variables – also allows for a more extensive assessment of the materials inspected.
The flexible vibration-measuring device with an integrated camera and a compact design is ideal for quality assurance and research. Additional microscope lenses expand the range of possible tasks that you can complete to include very small samples.
Visualizing surface waves at a high resolution
When it comes to fiber-reinforced composites, it is extremely important that damage such as delamination or cracks are detected and localized in good time – both in production and during operation. “Lamb waves” – surface waves that propagate on thin plate structures – play a major role in non-destructive materials testing, since they interact with different types of material faults, thereby making them visible. Lamb wave based, materials testing is increasingly gaining in significance – particularly in the maintenance of modern aircraft, where fiber-reinforced composites (CFRP) are increasingly being used.
The non-contact PSV-500-3D Scanning Vibrometers visualize the temporal propagation of Lamb waves with a high spatial resolution. You can record the entire 3D vibration vector for each scan point, so that the typical S and A waves that are primarily described as in-plane and out-of-plane waves are broken up during the analysis. Laser vibrometers are thus indispensable as tools for researching Lamb waves and developing methods that are suitable for industrial purposes.
A practical example:
Polytec Scanning Vibrometers are therefore also suitable for designing component-integrated sensor networks, which are increasingly being used in critical structural elements, including aircraft, so as to continually monitor them during operation (structural health monitoring). In such situations, a multitude of vibration sensors are permanently integrated in a component, and their distribution is optimized so that structural damage on the component is reliably recorded by the sensors.