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Operational Stability
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Measuring Mechanical Stress with Strain Gauges

Measure mechanical stresses and forces in assemblies quickly and reliably: Strain and compression measurements with strain gauges provide precise results on the forces acting on assemblies for structural tests, fatigue strength measurements and product and material testing.

In order to design components optimally, precise knowledge of the type, direction and magnitude of the forces acting on them is essential. In order to determine these, strain gauges are applied to the test specimen. CSM supports all common bridge types (quarter, half and full bridges) with its measurement modules.

Transducers

Components must frequently be examined for acting forces and mechanical loads - in road tests or on the test bench. The geometry of the object to be examined or the general space available does not always allow the installation of additional sensors for force or torsion measurement. In such cases, the object itself becomes the sensor: The strain gauges are attached directly to the component, calibrated and then the component is reinstalled into the system. This is done, for example, with a tie rod on which tensile and compression forces are measured.

Measurements in driving operation, on the test site and also on the test bench can thus be easily implemented. The CSM STGMM measurement modules for measurements with strain gauges allow a high resolution at e.g. 5 volt sensor excitation and a small measurement range.

In road tests the ECAT STGMM strain gauge measurement modules are exposed to extreme conditions and precisely record the stresses occurring on the test object. Even strong vibrations do not impair the reliability of the measuring modules. According to the road to rig method, the measured values can then be easily transferred to a fatigue test rig. The same ECAT STGMM measurement modules are used on the test bench as previously in the road test, allowing easy comparison of the measured data. Using the configuration software CSMconfig, the configuration settings from the road test are transferred to the measuring modules on the test bench in the form of .dBc or .a2l files. This speeds up the test considerably by shortening the test cycles.

With the HV STG4, strain gauge measurements can be easily implemented in high-voltage environments.

Truck wheels on uneven road
Mechanical loads have an effect on all components. For a suitable design, forces must be measured during development - preferably under realistic conditions in road tests.

Experimental Stress Analysis

Experimental stress analysis with strain gauge rosette
A strain gauge rosette can be used to analyze stress curves for an unknown principal stress direction.

With strain gauges, calculated mechanical stresses in assemblies can be validated quickly and reliably. Quarter bridges are often used for this purpose (Wheatstone bridge circuit with one active strain gage and three resistors), as these can be implemented quickly and cost-effectively.

If the main direction of the principal stress is known, a quarter bridge is sufficient.

If the direction of the principal stress are unknown before the measurement, two to three quarter bridges are attached to the test specimen as a rosette. The three individual strain gauges of the rosette can each be complemented to a half-bridge with the CSM quarter bridge completion cable K356 and thus easily be integrated into the STGMM measurement module. Thanks to the high measurement range of the STGMM, very small as well as very large strains can be measured. In the evaluation, the previously unknown principal stresses can be determined in magnitude and direction.

Especially on large objects, such as construction machinery, the required measurement points are often far apart. Using the ECAT STGMM this is no problem: The measurement points can be up to 100 meters apart.

Measurement of Mechanical Loads with Sensors

If conditions permit, mechanical loads can also be measured with sensors. Most of the available sensors emit the signal directly, i.e. without amplification or modification by integrated electronics. The very small signal emitted by the sensor places special demands on the measurement technology used. The STGMM meets these requirements by precisely detecting even small signal voltages and offering the needed sensor excitation.

Heavy duty truck
If there is sufficient space, sensors can also determine the mechanical loads. In this way, vehicles are optimally designed for demanding usage.

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