Measurement of contact parameters on under-platform dampers coupled with blade dynamics

Umer, Muhammad; Botto, Daniele

doi:10.1016/j.ijmecsci.2019.06.010

Cited by 24 publications

(8 citation statements)

References 19 publications

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“…The authors [24,25] presented the functionally graded rotating composite Timoshenko beams that were reinforced by carbon nanotubes or graphene platelets for studying their linear and non-linear free vibrations. Umer and Botto [26] studied experimentally the non-linear contact forces effect on the vibration amplitude of a rotating blade. Yang et al [27] investigated the presence of 1 : 2 internal resonance, primary parametric resonance, and 1/2 subharmonic resonance to explore the non-linear vibrations of a carbon fiber-reinforced polymer laminated cylindrical shell.…”

Section: Introductionmentioning

confidence: 99%

Influence of Time Delay on Controlling the Non-Linear Oscillations of a Rotating Blade

Hamed

Kandil

2021

Symmetry

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Time delay is an obstacle in the way of actively controlling non-linear vibrations. In this paper, a rotating blade’s non-linear oscillations are reduced via a time-delayed non-linear saturation controller (NSC). This controller is excited by a positive displacement signal measured from the sensors on the blade, and its output is the suitable control force applied onto the actuators on the blade driving it to the desired minimum vibratory level. Based on the saturation phenomenon, the blade vibrations can be saturated at a specific level while the rest of the energy is transferred to the controller. This can be done by adjusting the controller natural frequency to be one half of the blade natural frequency. The whole behavior is governed by a system of first-order differential equations gained by the method of multiple scales. Different responses are included to show the influences of time delay on the closed-loop control process. Also, a good agreement can be noticed between the analytical curves and the numerically simulated ones.

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Section: Introductionmentioning

confidence: 99%

Influence of Time Delay on Controlling the Non-Linear Oscillations of a Rotating Blade

Hamed

Kandil

2021

Symmetry

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“…Later, the correlated models can be successfully used to develop predictive tools to supplement parametric sensitivity study with sufficient confidence. Several detailed studies focussing on fretting wear and evolution of contact parameters are available in the literature [23][24][25][26][27][28][29][30][31][32][33][34][35].…”

Section: Introductionmentioning

confidence: 99%

A novel test rig to study the effect of fretting wear on the forced response dynamics with a friction contact

2021

Self Cite

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This paper presents a novel test rig to study the effect of fretting wear and of the contact surface evolution on the forced response of systems with dry friction contact. This rig allows simulating contacts similar to the type of contacts present between the shrouds at the blade tip. Several research groups have been studying how fretting wear affects the dynamic response of mechanical systems, developing numerical prediction tools that consider dry friction contact and nonlinearity. The aim of this work is to experimentally study the evolution of contact interfaces and how this evolution affects the system dynamics. Experimental results will aid to validate the numerical predictions. The test rig developed for this activity is made of a cantilever beam fixed at one end and with a friction contact at the free end. The contact couple is made of two replaceable specimens. The contact is loaded via a lifting mechanism through a screw with fine thread. Fretting wear test was performed at a constant frequency and force amplitude, exciting the beam with an electromagnetic shaker. To emphasize the change of the dynamic response, frequency sweeps were performed at various intervals during the wear test. The full range test with ‘changing preload’ due to progressing wear was performed until a full loss of contact. This paper describes the test rig design, intent, set-up, instrumentation, test plan and results. Results include the frequency response curves for unworn contact, wear profiles at multiple intervals and the effect of wear on the frequency response. Though energy dissipation per cycle is quite small, wear leads to material loss at the contact with a sufficiently large number of cumulative cycles and substantially affects the dynamic response. Results collected in this research activity are of particular importance to validate numerical tool that aim to simulate the dynamic behaviour of systems with dry friction contacts that undergo material loss caused by wear.

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“…The term conformity here denotes the existence of well-defined pairs of nodes sharing the same geometric location on the contact plane. This condition allows the application of node-to-node contact elements whose parameters (i.e., the contact stiffnesses and the friction coefficient) can be experimentally identified [21,22]. However, the mentioned approach holds unless the mesh conformity remains preserved despite to the variable, but negligible mesh misalignments caused by vibrations.…”

Section: Introductionmentioning

confidence: 99%

“…Fig 22. Comparison of the FRFs obtained from ROM1 and ROM2 for a preload n 0 = 113 N, for the mode shape M2…”

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confidence: 99%

Self-adaptive macroslip array for friction force prediction in contact interfaces with non-conforming meshes

Battiato

2021

Nonlinear Dyn

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The steady-state nonlinear forced response (NFR) of finite element (FE) models with friction joints is usually computed in the frequency domain through the combination of node-to-node contact elements and the Harmonic Balance Method (HBM). In the current state of the art, rare are the cases where the friction forces are estimated for contact interfaces with non-conforming mesh grids. This need is nowadays taking place due to the improving capability of commercial FE software to manage any kind of boundary condition (i.e., either coupling or contact), without requiring coincident pairs of nodes at the joint interfaces. Such an advantage becomes a drawback when the analysts are requested to investigate the NFR of the assembly by using build-in codes, where the contact forces prediction usually requires node-to-node contact elements whose parameters (i.e., the contact stiffnesses and friction coefficients) can be easily identified by means of experiments. This paper addresses the mentioned limitation, and proposes a novel self-adaptive macroslip array (SAMA) model for the estimation of the nonlinear friction forces on FE contact interfaces with non-conforming meshes. The SAMA model consists on a set of node-to-node contact elements ordered in parallel, whose contact parameters and normal preloads are identified through a step-by-step self-adaptive weighting algorithm that depends on the topology of the meshes in contact. The goodness of the proposed model is assessed on the calculation of the NFR of a bladed disk with shroud contacts, under the hypotheses of cyclic symmetry and HBM. The nonlinear dynamic behavior of the bladed disk is evaluated in two different cases. First, in the case of lack of node-to-node congruence at the contact interface for the structure being in its undeformed configuration, and second, in the case of a relevant static misalignment of the contact interfaces due to the application of large static loads.

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Measurement of contact parameters on under-platform dampers coupled with blade dynamics

Cited by 24 publications

References 19 publications

Influence of Time Delay on Controlling the Non-Linear Oscillations of a Rotating Blade

Influence of Time Delay on Controlling the Non-Linear Oscillations of a Rotating Blade

A novel test rig to study the effect of fretting wear on the forced response dynamics with a friction contact

Self-adaptive macroslip array for friction force prediction in contact interfaces with non-conforming meshes

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