Contact Properties and Wear Behaviour of Nickel Based Superalloy René 80

Lavella, Mario

doi:10.3390/met6070159

Cited by 30 publications

(19 citation statements)

References 14 publications

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“…Contact parameters (i.e. contact stiffnesses and friction coefficient) are needed as input by the code [41,42]; -presence of the analytical Jacobian computation in the iterative solver to ensure efficiency [20,22,44]; -presence of the in-house Jacobian Alert Algorithm 2 to ensure an accurate solution obtained in a timely manner [22].…”

Section: Numerical Calculation Proceduresmentioning

confidence: 99%

“…-Testing. The strip damper is very flexible: the test rigs found in literature for the determination of contact parameters [12,24,42] apply contact pressure on one of the contacting bodies by means of a set of wires and pulleys connected to dead weights. The strip damper cannot be loaded by wires due to its high flexibility.…”

Section: The Need For a Direct Experimental Investigationmentioning

confidence: 99%

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Modeling and Testing Friction Flexible Dampers: Challenges and Peculiarities

2018

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This paper deals with the dynamic of blades with strip dampers. The purpose is 1) to present the results of the dynamic numerical calculation, 2) to demonstrate the need for the experimental data on the blade-strip contact to be used as input to the calculation, 3) to propose a new test rig design to obtain them and 4) to test the key components of the new test rig. The forced responses of two blades coupled by a strip damper are calculated at different excitation and centrifugal force values. The dependence of the numerical results on the contact parameter values is confirmed in this significant reference case. The design of a new test rig is then proposed: both the blade frequency response function and the contact hysteresis cycles at the blade-strip contact are measured. It is shown how contact parameters can then be derived from experimental data. The main novelty of the test rig here proposed is the strip loading system, which simulates the uniform pressure distribution provided by the centrifugal force in real operating conditions. This loading system is non-contact and uses compressed air. Classical loading systems which see dead weights directly connected to the strip are assessed and their expected inadequacy is confirmed. The compressed air system is tested by measuring the pressure produced between strip and blades: pressure is uniform across the contact patch, constant in time and its mean value corresponds to realistic pressure values actually experienced by strip dampers during service.

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Section: Numerical Calculation Proceduresmentioning

confidence: 99%

Section: The Need For a Direct Experimental Investigationmentioning

confidence: 99%

Modeling and Testing Friction Flexible Dampers: Challenges and Peculiarities

2018

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“…The contact parameters (contact stiffness values and friction coefficient) have to be given as input to the code [38,40,41]; • presence of the analytical Jacobian computation in the iterative solver to ensure efficiency [28,30,31]; • presence of the Jacobian Alert Algorithm to ensure an accurate solution obtained in a timely manner [32].…”

Section: Numerical Calculationmentioning

confidence: 99%

Forced Response Prediction of Turbine Blades with Flexible Dampers: The Impact of Engineering Modelling Choices

2017

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This paper focuses on flexible friction dampers (or "strips") mounted on the underside of adjacent turbine blade platforms for sealing and damping purposes. A key parameter to ensure a robust and trustworthy design is the correct prediction of the maximum frequency shift induced by the strip damper coupling adjacent blades. While this topic has been extensively addressed on rigid friction dampers, both experimentally and numerically, no such investigation is available as far as flexible dampers are concerned. This paper builds on the authors' prior experience with rigid dampers to investigate the peculiarities and challenges of a robust dynamic model of blade-strips systems. The starting point is a numerical tool implementing state-of-the-art techniques for the efficient solution of the nonlinear equations, e.g., multi-harmonic balance method with coupled static solution and state-of-the-art contact elements. The full step-by-step modelling process is here retraced and upgraded to take into account the damper flexibility: for each step, key modelling choices (e.g., mesh size, master nodes selection, contact parameters) which may affect the predicted response are addressed. The outcome is a series of guidelines which will help the designer assign numerical predictions the proper level of trust and outline a much-needed experimental campaign.

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“…Some focus on single flat-on-flat contacts under constant normal loads and high temperatures (Lavella et al, 2011;Botto et al, 2012;Lavella, 2016), and are therefore not useful in this specific case. On the other hand, the Damper Test Rig (Gola and Liu, 2014) aims at estimating contact parameters of UPDs (cylinder-on-flat interfaces as well) under more realistic working conditions in terms of variable normal load and complex interface kinematics.…”

Section: Determination Of Contact Parametersmentioning

confidence: 99%

On the choice of contact parameters for the forced response calculation of a bladed disk with underplatform dampers

Gastaldi

Grossi

Berruti

2017

J. Glob. Power Propuls. Soc.

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Underplatform dampers (UPDs) are still in use to reduce the vibration amplitude of turbine blades and to shift the position of resonant frequencies. The dynamics of blades with UPDs is nonlinear and the analysis is challenging from both the experimental and the numerical point of view. A key point in obtaining a predictive numerical tool is the choice of the correct contact parameters (contact stiffness and friction coefficient) that are required as input to the contact model. The paper presents different approaches to choose these parameters: the contact stiffness in normal and tangential direction are both calculated and measured. The calculation is based on the analytical models in literature, the measurements are carried out on a dedicated test rig. The friction coefficient is also measured. Test results of the forced response of the same bladed disk with UPDs are available for each blade, they come from an experimental campaign under controlled excitation and centrifugal force. The forced response of the bladed disk is not used as a mean to tune the contact parameters, but rather as a validation tool: the effect of the different choices of contact parameters in the code is highlighted by the comparison of the calculated and experimental forced response of the bladed disk.

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Contact Properties and Wear Behaviour of Nickel Based Superalloy René 80

Cited by 30 publications

References 14 publications

Modeling and Testing Friction Flexible Dampers: Challenges and Peculiarities

Modeling and Testing Friction Flexible Dampers: Challenges and Peculiarities

Forced Response Prediction of Turbine Blades with Flexible Dampers: The Impact of Engineering Modelling Choices

On the choice of contact parameters for the forced response calculation of a bladed disk with underplatform dampers

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