The Effects of Boundary Conditions, Measurement Techniques, and Excitation Type on Measurements of the Properties of Mechanical Joints

Smith, Scott A.; Bilbao-Ludena, Juan C.; Catalfamo, S.; Brake, Matthew Robert; Reuß, Pascal; Schwingshackl, Christoph W.

doi:10.1007/978-3-319-15221-9_36

Cited by 25 publications

(21 citation statements)

References 5 publications

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“…3a. When evaluating the nonlinear dynamic response caused by friction damping, it is very important that the underlying dynamic system without a damper is linear, and the nonlinearities introduced by possible external sources are minimal [39][40][41]. For this reason the fir-tree attachment that would connect the real blade to the disk was removed here to minimise the number of friction joints, and the blades were clamped tightly to a two ton inertia block via a hydraulic vice capable of 200 kN clamping force.…”

Section: Design Features and Set-upmentioning

confidence: 99%

Modelling the nonlinear behaviour of an underplatform damper test rig for turbine applications

Pesaresi

Salles

Jones

et al. 2017

Mechanical Systems and Signal Processing

145

108

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Underplatform dampers (UPD) are commonly used in aircraft engines to mitigate the risk of high-cycle fatigue failure of turbine blades. The energy dissipated at the friction contact interface of the damper reduces the vibration amplitude significantly, and the couplings of the blades can also lead to significant shifts of the resonance frequencies of the bladed disk. The highly nonlinear behaviour of bladed disks constrained by UPDs requires an advanced modelling approach to ensure that the correct damper geometry is selected during the design of the turbine, and that no unexpected resonance frequencies and amplitudes will occur in operation. Approaches based on an explicit model of the damper in combination with multi-harmonic balance solvers have emerged as a promising way to predict the nonlinear behaviour of UPDs correctly, however rigorous experimental validations are required before approaches of this type can be used with confidence.In this study, a nonlinear analysis based on an updated explicit damper model having different levels of detail is performed, and the results are evaluated against a newly-developed UPD test rig. Detailed linear finite element models are used as input for the nonlinear analysis, allowing the inclusion of damper flexibility and inertia effects. The nonlinear friction interface between the blades and the damper is described with a dense grid of 3D friction contact elements which allow accurate capturing of the underlying nonlinear mechanism that drives the global nonlinear behaviour. The introduced explicit damper model showed a great dependence on the correct contact pressure distribution. The use of an accurate, measurement based, distribution, better matched the nonlinear dynamic behaviour of the test rig. Good agreement with the measured frequency response data could only be reached when the zero harmonic term (constant term) was included in the multi-harmonic expansion of the nonlinear problem, highlighting its importance when the contact interface experiences large normal load variation. The resulting numerical damper kinematics with strong translational and rotational motion, and the global blades frequency response were fully validated experimentally, showing the accuracy of the suggested high detailed explicit UPD modelling approach.

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Section: Design Features and Set-upmentioning

confidence: 99%

Modelling the nonlinear behaviour of an underplatform damper test rig for turbine applications

Pesaresi

Salles

Jones

et al. 2017

Mechanical Systems and Signal Processing

145

108

View full text Add to dashboard Cite

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“…The nominal system has a flat interface, as shown in Figure 2(a). This system, however, has exhibited high variability and low repeatability [11][12][13], and it is hypothesized that this is due to the non-uniform contact pressure across the interface. The four perturbations of this design address two different notions from recent research.…”

Section: Interface Designmentioning

confidence: 99%

Experimental Assessment of the Influence of Interface Geometries on Structural Dynamic Response

Dossogne

Jerome

Lancereau

et al. 2017

Conference Proceedings of the Society for Experimental Mechanics Series

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Jointed interfaces are sources of the greatest amount of uncertainty in the dynamics of a structural assembly. In practice, jointed connections introduce nonlinearity into a system, which is often manifested as a softening response in frequency response, exhibiting amplitude dependent damping and stiffness. Additionally, standard joints are highly susceptible to unrepeatability and variability that make meaningful prediction of the performance of a system prohibitively difficult. This high degree of uncertainty in joint structure predictions is partly due to the physical design of the interface. This paper experimentally assesses the influence of the interface geometry on both the nonlinear and uncertain aspects of jointed connections. The considered structure is the Brake-Reuß beam, which possesses a lap joint with three bolted connections, and can exhibit several different interface configurations. Five configurations with different contact areas are tested, identified, and compared, namely joints with complete contact in the interface, contact only under the pressure cones, contact under an area twice that of the pressure cones, contact only away from the pressure cones and Hertzian contact. The contact only under the pressure cone and Hertzian contact are found to behave linearly in the range of excitation used in this work. The contact area twice that of the pressure cone behaves between the complete contact and contact only under the pressure cone cases.

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“…The same Brake-Reuß beam tested in [47,48] was used to collect forced-response data for this work. Before testing, each bolt was tightened first to 14 N m using a torque wrench, with the center bolt tightened first before the outer two bolts, and then all again tightened to 20 N m in the same order.…”

Section: Methodsmentioning

confidence: 99%

“…The Brake-Reuß beam [47,48] was chosen as the benchmark structure to help facilitate the comparison between the two modeling approaches. The structure consists of two identical, prismatic beams that possess half-height extensions near their ends.…”

Section: The Brake-reuß Beammentioning

confidence: 99%

“…The two approaches are then used independently to create two models of the lap-joint benchmark structure, the Brake-Reuß beam [47,48], and allow, for the first time, a detailed evaluation of their capabilities and restrictions in capturing the dynamic behavior of a bolted lap joint. A linear finite element model of the Brake-Reuß beam was created initially (Section 2), and its linear modes were analyzed to gain insight into the shapes and natural frequencies of its first three bending modes.…”

Section: Introductionmentioning

confidence: 99%

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Nonlinear modeling of structures with bolted joints: A comparison of two approaches based on a time-domain and frequency-domain solver

Lacayo

Pesaresi

Groß

et al. 2019

Mechanical Systems and Signal Processing

129

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Motivated by the current demands in high-performance structural analysis, and by a need to better model systems with localized nonlinearities, analysts have developed a number of different approaches for modeling and simulating the dynamics of a bolted-joint structure. However, it is still unclear which approach might be most effective for a given system or set of conditions. To better grasp their similarities and differences, this paper presents a numerical benchmark that assesses how well two diametrically differing joint modeling approaches -a time-domain wholejoint approach and a frequency-domain node-to-node approach -predict and simulate a mechanical joint. These approaches were applied to model the Brake-Reuß beam, a prismatic structure comprised of two beams with a bolted joint interface. The two approaches were validated first by updating the models to reproduce the nonlinear response for the first bending mode of an experimental Brake-Reuß beam. Afterwards, the tuned models were evaluated on their ability to predict the nonlinearity in the dynamic response for the second and third bending modes. The results show that the two joint modeling approaches perform about equally as well in simulating the Brake-Reuß beam. In addition, the exposition highlights improvements that were made in each method during the course of this work and reveal further challenges in advancing the state-of-the-art.

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The Effects of Boundary Conditions, Measurement Techniques, and Excitation Type on Measurements of the Properties of Mechanical Joints

Cited by 25 publications

References 5 publications

Modelling the nonlinear behaviour of an underplatform damper test rig for turbine applications

Modelling the nonlinear behaviour of an underplatform damper test rig for turbine applications

Experimental Assessment of the Influence of Interface Geometries on Structural Dynamic Response

Nonlinear modeling of structures with bolted joints: A comparison of two approaches based on a time-domain and frequency-domain solver

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