The main purpose of Structural Tests is to get breakage which present a physical engineering meaning: a breakage, in most cases, can be found useful if it occurs inside the specimen, as far as possible from the constraints and the loading systems.
In addition, though optional, we consider it very important to make an accurate stress analysis during the testing, as it serves to confirm the correct application of constraints and loads, allows in-depth analysis of local phenomena which are otherwise difficult to detect by other means. Further, it can be a valuable support to the project, with continuous feedback between design and testing.
We perform Structural Tests of various type:
mono-axial for simple components and specimens
multi-axial for complete structures and complex components
A fundamental requirement of a fatigue test is to obtain useful results in the construction of the Wöhler diagram. The latter is necessary to determine the resistance of any component subject to repeated load cycles. In order to obtain meaningful data, the component should be subject to stresses (loads and/or deformations) higher than the operating maximum; moreover, the stresses must be much higher when the number of tests one would perform is lower.
Given the need to obtain reliable results, we pay special attention to the study and realization of:
specimen constraint systems, which are responsible of locking it to the ground. We adopt isostatic schemes as much as possible, possibly floating
connections among external load-generation systems and specimen, which allow for the gradual introduction of the loads, without concentrations of unwanted efforts
Moreover, in multi-axial tests, systems are especially critical in which some applied load is predominant. To avoid the phenomenon of mutual influence (cross-talk) between the loads, it is vital that the loads are applied in a very accurate way, perfectly balancing all forces.
Below, we show some examples of tests we have designed and performed in full compliance with the a.m. general principles:
Test of Main Rotor of Helicopter (6 independent axes)
These tests allow to obtain the certification necessary to let the helicopter flight.
Floating test, wherein the movements are obtained with perfectly balanced pivoting servo actuators. The video shows how the specimen is deformed without constraints. In fact, while subject to loads of several tons in the horizontal direction, it is possible to move it by hand without exerting significant loads. To contemporarily achieve compactness, accuracy and speed, we use various type of our servo actuators, both Integrated, and Pivoting.
Very significant is the symmetric bilateral rupture obtained at the end of the test (watch the video), because it is indicative of the presence of correct constraints to the ground and precision and symmetry in the application of the loads.
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Test of Tail Rotor of Helicopter (4 independent axes)
These tests allow to obtain the certification necessary to let the helicopter flight.
In this floating test the stresses acting on the tail rotor during the flight are reproduced on the ground. To combine compactness, accuracy and speed we use various type of our servo actuators, both Integrated, and Pivoting. The verification of the resistance to fatigue without breakage even after millions of cycles, as calculated in the design phase, is fundamental.
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Dynamic Test of Motorcycle Forks (mono-axial at high speed)
Execution of dynamic tests to evaluate the mechanical behaviour of shock absorbers, outputting a load-deformation diagram at various speeds.
The accuracy of the motion at controlled speed is especially significant. It is obtained with our multi-valve servo-actuators, which allow to reproduce perfect sinusoidal movements.
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Triaxial Dynamic Test of Motorcycle Forks (3 independent axes)
Execution of high-speed dynamic tests on motorcycle forks.
To combine compactness, accuracy and speed, we adopt different types of our servo actuators: Hydrostatic, Integrated and Multivalve.
Our constraints and isostatic loading systems allow to achieve a nearly null cross talk. This allows you to setup much different tests with the same Bench, by combining axial loads in function of the Customer's specific requirements. In the video various test configurations are shown, in each of which loads are set with totally independent amplitudes, waveforms, phases, and frequencies.
In this video, it can be noted that the number of constraint degrees corresponds to the number of degrees of freedom.
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Testing Railroad Tracks (mono-axial)
Mono-axial fatigue test of railroad tracks junctions. In particular, repetitive vertical stresses due to the passage of trains are here simulated and the tracks resistance is evaluated.
The test reports are then used to program the frequency of maintenance to be carried on railway lines, in order to avoid interruption of the line during normal operation and the reduction of operating costs.
