GENERAL ACOUSTICS AND VIBRATION MEASUREMENTS
Measurement of forces
Because of and accelerations on chassis components. In most cases, different chassis variants are measured and compared. In addition, the sound pressure in the interior is also measured and evaluated. Evaluations: Spectra, transfer functions, order analysis, frequency distribution, frequency-time representation and time courses.
Comparison of vehicles to vibration test. 'Brake' (test drive)
Inertance and sensitivity measurements
on complete vehicles. Depending on the frequency range to be stimulated, different types of hammer are used (1.2 kg with rubber attachment up to approx. 150 Hz - modal hammer approx. 250 g to approx. 4 kHz - medium electromagnetic hammer up to approx. 6 kHz - small electromagnetic hammer up to approx. 10 kHz ).
Transmission path analysis
from axis coupling points to comfort points. Stimulation by means of a shaker or an impact hammer.
on various components (e.g. generator connection, headrest attachment, etc.)
Measurement of muzzle sound and sound pressure
in the interior during operation (troubleshooting in certain speed ranges).
Driving comfort measurements
Here, route-related standardized evaluations are carried out.
Road profile measurements
By scanning the road surface (in the respective lane) and recording the body movement, the actual road profiles are calculated and evaluated in accordance with DIN. For this purpose, the driving speed is also recorded and evaluated.
Time - frequency evaluations of individual events
All sporadically occurring events can be evaluated here. e.g .: frequency / time display of a sound pressure signal at the driver's ear when crossing a single obstacle.
For information see fig.
Modal analysis on various objects e.g. body shells, trimmed body structures, chassis parts, engine parts, machine parts, steel structures, etc.
Experimental modal analysis is used to determine the structural dynamic properties of an object. The measured transfer functions (FRFs) are used to determine the modal data (natural frequencies with the associated modal damping and the natural mode shapes). These modal data contribute in downstream or accompanying developments to derive measures, e.g. for simulation model validation or for structural modifications.
For this purpose, a force is applied to the structure under test at one point, e.g. by means of an impulse hammer or uncorrelated excitation with several electrodynamic shakers. At further points, the response signal is measured (e.g. as acceleration with suitable accelerometers or as velocity with a laser vibrometer) and the transfer function is calculated.
By determining the transfer functions at a large number of points on the structure (a reasonable spatial resolution or point pitch depends on the frequency range of the excitation), the modes of vibration can be determined. This information can be used to describe the vibration behavior of the measured structure.
At ID Lindner, multi-channel measurement technology coupled with many years of experience and expertise are available for efficient execution of your measurement tasks.
The following are some examples of our activities.
experimental modal analysis of complete wheel
Modal analysis on a complete wheel (rim and tyre) suspended freely in space. The excitation is done with a modal hammer, the measuring points (here about 280) are distributed evenly over the tyre and rim. The response signals (accelerations) are recorded three-dimensionally with a multi-channel measuring system and eigenfrequencies and eigenmodes are determined with suitable software.
approximate free-free mounting of the complete wheel for measurement by means of expander:
OPERATING VIBRATION ANALYZES
are used to determine the operating vibration mode of components, whereby the type of excitation is essential. The behaviour under operating load can be measured. With the signal spectrum, it is possible to determine the structural response at the measuring points in relation to frequency and thus the vibration modes can also be displayed in animated form.
On various objects, e.g. complete vehicles, chassis parts, engine parts, machine parts, etc. with operational stimulation (test drive, machine in production) and with synthetic stimulation (time and frequency animation).
3D GEOMETRY DATA ACQUISITION
Laser scanning for computer-aided manufacturing measurement. With a portable measuring arm system with 7 axes, points can be measured tactile and contactless and recorded and exported in a suitable software application. The objects to be measured range from small components to complete vehicles. Used in many industries: alignment and precision equipment, inspection (proof of the dimensional accuracy of parts), reverse engineering (CAD drawings from real objects) etc.
over different speeds or speeds, over the engine speed, over the wheel speed, over the vehicle speed, over the machine speed Order analysis of an acceleration signal:
The speed detection for order analysis is done either by tapping existing speed sensors or by attaching separate, mostly optical sensors.
DMS APPLICATION TO DIFFERENT MEASURING OBJECTS WITH CALIBRATION
Strain gauges (DMS) are used to determine strains and stresses in the material, which allow conclusions to be drawn about the stress on the component.
We carry out professional strain gauge applications. Thanks to the many years of experience of our employees, we guarantee the highest quality of the measuring points.
Our range of services includes bonding and interconnection as quarter, half or full bridges for torsion, bending, tensile and compressive force measurements for many materials as well as other individual services such as provision and procurement of measuring equipment.
WEIGHT ANALYSIS AND VEHICLE DISASSEMBLY
In every phase of a product development process, it is necessary to intensively include competitor benchmarks. Through consistent benchmarking of costs and characteristics of all manufacturers, derived target costs are validated, cost reduction measures are developed and technical solutions are optimised. A helpful tool for competitive analysis is the detailed disassembly of competitor vehicles, in which vehicles are analysed "down to the last screw". The vehicle disassembly allows a detailed insight into the technical concept of competitors.
E.g. excerpt from an engine dismantling with information on weight and material, as part of a benchmark investigation
MEASUREMENTS OF ALL KINDS, STATIONARY AND MOBILE
e.g .: clearance measurement on various axle components In this case, the travel of the wheel was measured triaxially with respect to the body. In addition, various positions of the chassis in relation to the body were recorded. By adjusting the extreme positions determined in this way in the driving test, the actual problem could be localized and eliminated.
PROBLEM ANALYSIS AND SUGGESTED SOLUTIONS
e.g .: whistling of an intercom in a light armored vehicle.
In the case at hand, there was feedback, which led to very loud whistling. After it was not possible to use an amplifier with feedback suppression, the transmission path was analyzed and attenuated. As a second measure, the critical frequency range at the microphone input was attenuated. A sufficient improvement could be achieved through these measures, which can be implemented very cost-effectively in series.
e.g .: periodicity in the end product of a textile machine
After detailed investigations it was shown that the problem with a resonance of a mech. Component had to do. In order to avoid this problem, the connection was stiffened accordingly. As can be seen from the diagrams below, the measures largely dampened critical resonances or pushed them out of the relevant frequency range. Ultimately, the minimal variant (pink) turned out to be sufficient.
Factory calibration of vibration sensors by comparison with a reference sensor according to DIN ISO 16063-21. Static and dynamic vibration sensors can be checked in a frequency range from 5 to 5 kHz.
With the calibration system, transducers of the type DMS, ICP and charge transducers as well as signal conditioners, charge amplifiers and calibrators can be checked. The calibration of the calibration device is carried out regularly by a DKD-certified laboratory.
SOUND TRANSMISSION (ACOUSTIC LIGHTNESS)
The sound transmission inside the vehicle is measured at the front and rear seat positions at different positions on the vehicle by means of a loudspeaker with an almost spherical sound distribution. The sound source is designed in such a way that the subjective volume is perceived as the same over the entire frequency range. This makes it possible to compare different vehicle types and conditions.
With a portable measuring arm system with 7 axes, points can be measured tactile and contactless and recorded and exported in a suitable software application. The objects to be measured range from small components to complete vehicles. Used in many industries: alignment and precision equipment, inspection (proof of the dimensional accuracy of parts), reverse engineering (CAD drawings from real objects) etc.
Laser scanning or tactile measurement can provide continuous on-site inspection at any stage of a product's lifecycle to predict and prevent defects, and achieve significant cost, scrap and time savings.