36 Gear Dynamics Characterization by Using Order-Based Modal Analysis 391 36.4 Test Rig Description The technique has been validated by considering a numerical example. In this paper a dedicated test rig has been used for performing an experimental validation and for evaluating the performances of the order tracking techniques available in commercial software and of the ones implemented in a Matlab environment. The test rig has been built for simulating different working conditions for the gears at a subsystem level without any other influence coming from the interaction with other systems [10]. A very precise and highly instrumented device is needed in order to get reliable results. Only a few precision gear test rig have been used for research so far. Figure 36.1 shows the CAD model of the test rig which has been used in our studies. It is composed by two main parts: the test side, which is dedicated to testing a cylindrical gear pair, and the reaction side, that is needed for retaining a torque preload in the system by means of a second gear pair. Its specification are reported in Table 36.1. The test rig is mounted on a concrete base suspended on air springs which allows to isolate the overall system and separate the two sides for avoiding the propagation of stray vibrations between them. Such vibrations are damped through the concrete. A temperature-controlled pressurized lubrication system feeds oil to the test and the reaction side bearings and gears. High-precision spherical roller bearings are chosen to support test gears and maximize stiffness. Several different gears are used for the test side and they provide a very repeatable meshing excitation due to two main reasons: the gear ratio is equal to 1 and gears are precision ground to ISO 1328 Quality 3 standard. Furthermore, test gears and reaction gears are designed to have different tooth number to be able to distinguish the excitation belonging to each gear pair. Test gears have 57 teeth, while reaction gears have 64. Angular misalignment in an arbitrary plane and parallel misalignment in the transverse plane can be imposed thanks to the bearings: they are mounted in eccentric caps that can be turned to orient the eccentricity at a given angle. Same angles for the two caps on the same shaft result in imposing a parallel misalignment, while opposite angles result in imposing angular misalignment. Fig. 36.1 Test rig three-dimensional representation. 1. Test gears; 2. Reaction gears; 3. Bearings support plates; 4. Flexible couplings; 5. Flywheel; 6. Clutch flange for preload Table 36.1 Test rig specifications Parameter Range Uncertainly Speed 0–4500 rpm (0–75 Hz) Measured Torque 0–500Nm 0.05% Angular misalignments 0–2 mrad 0.1mrad Parallel misalignments 0–0.3 mm 0.020mm
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