Platform Centered Reduction: a Process Capturing the Essentials for Blade-Damper Coupled Optimization

2020 ◽  
Author(s):  
Chiara Gastaldi ◽  
Muzio M. Gola
Keyword(s):  
Complex Shape ◽  
Contact Forces ◽  
Fe Model ◽  
Euler Beam ◽  
Final Design ◽  
Neck Thickness ◽  
Turbomachinery Blades ◽  
Speed Up ◽  
Clear Identification ◽  
Resultant Forces

Abstract The purpose of this paper is to develop an attractive tool for designers in the initial design phase of the damping of turbomachinery blades through dry friction underplatform dampers. The paper shows how, to this purpose, certain reasonable simplifications are introduced in the procedure and in the model, leaving the customary full high fidelity computations to the final design verification analysis. The key simplifications here considered are: the blade neck is modelled with Euler beam finite elements (FE) to speed up the updating of its dimensions during the optimisation process; the contact forces exerted by the dampers on the blade platform are represented by the resultant forces and moments applied to a reference point on the platform, associated to its displacements and rotations; the airfoil, which, due to its complex shape, is considered fixed during the coupled optimization of the damper, is obtained from a full 3D FE model after a component mode synthesis reduction. It is shown that the process captures the essentials of the nonlinear dynamics of the blade-damper problem without sacrificing in any way the accuracy of the results. This hybrid model is then employed in the process where the domains of optimal matching between the damper and the blade is searched for by exploring the influence of blade neck thickness (flexibility) and damper mass. Such a purposely simplified process allows a clear identification of relationships between relevant blade features and response with a focus on fatigue life.

Platform Centered Reduction: A Process Capturing the Essentials for Blade-Damper Coupled Optimization

2020 ◽  
Author(s):  
Chiara Gastaldi ◽  
Muzio M. Gola
Keyword(s):  
Contact Forces ◽  
Fe Model ◽  
Euler Beam ◽  
Final Design ◽  
Neck Thickness ◽  
Turbomachinery Blades ◽  
Speed Up ◽  
Clear Identification ◽  
Resultant Forces ◽  
Two Sides

Abstract The purpose of this document is to continue along the line of research of the authors in the direction of developing an attractive tool for designers in the initial design phase of the damping of the turbomachinery blades. In particular, in order to guide their initial choice of a dry friction underplatform damper in the most appropriate way. The paper shows how, to this purpose, certain reasonable simplifications are introduced in the procedure and in the model, leaving the customary full high fidelity computations to the final design verification analysis. The key simplifications here considered are: – the blade neck is modelled with Euler beam finite elements so to speed up the updating of its dimensions during the optimisation process; – the contact forces exerted by the dampers on the two sides of the blade platform are represented by the resultant forces and moments applied to a reference point on the platform, associated to its displacements and rotations; – as an improvement to the model proposed in the paper presented at Turbo Expo 2019, the airfoil is now obtained from a full 3D FE model after a component mode synthesis reduction; this choice is justified by the facts that the airfoil is by large the item with most complex shape and that during the coupled optimization of the damper the airfoil is considered to be of fixed shape. It is shown that the process captures the essentials of the nonlinear dynamics of the blade-damper problem without sacrificing in any way the accuracy of the results. This hybrid model is then employed in the process where the domains of optimal matching between the damper and the blade is searched for by exploring the influence of blade neck thickness (flexibility) and damper mass. Such a purposely simplified process allows a clear identification of relationships between relevant blade features and response with a focus on fatigue life. At the same time, it allows an assessment of the interplay between blade parameters and damper parameters in determining the modal features and the damping capabilities. It is shown how different matching solutions may be identified depending on the expected forcing level on the blade.

Influence of the Fastening Modeling on the Vehicle-Track Interaction at Singular Rail Surface Defects

2014 ◽  
Vol 9 (3) ◽  
Author(s):  
Xin Zhao ◽  
Zili Li ◽  
Rolf Dollevoet
Keyword(s):  
Kinetic Energy ◽  
High Frequency ◽  
Surface Defects ◽  
Dynamic Contact ◽  
Rolling Speed ◽  
Contact Forces ◽  
The Other ◽  
Practical Significance ◽  
Fe Model ◽  
Wide Spread

With up to 12 spring-damper groups distributed in the actual area of a rail pad, different fastening models are developed in this paper to include the nonuniform pressure distribution within a fastening system and model the constraints at the rail bottom more realistically for the purpose of high frequency dynamics between vehicle and track. Applied to a 3D transient FE model of the vehicle-track interaction, influence of the fastening modeling on the high frequency dynamic contact forces at singular rail surface defects (SRSDs) is examined. Two defect models, one is relatively large and the other is small, are employed. Such a work is of practical significance because squats, as a kind of SRSD, have become a wide spread problem. Results show that the fastening modeling plays an important role in the high frequency dynamic contact forces at SRSDs. Supports in the middle of the rail bottom, modeled as spring-damper groups located under rail web, are found to be most important. The less the rail bottom is constrained or supported, the more isolated the sleepers and substructure are from the wheel-rail interaction, and the more kinetic energy is kept in the rail after impact at a SRSD. Rolling speed is also varied to take into account its influence. Finally, based on the results of this work, influence of the service states of the fastening system on growth of relatively small SRSDs is discussed.

Simplified Forced Response HCF Assessment of Turbomachinery Blades

2009 ◽  
Author(s):  
Hans Ma˚rtensson ◽  
Johan Forsman ◽  
Martin Eriksson
Keyword(s):  
High Speed ◽  
Damping Ratio ◽  
Tangential Force ◽  
Forced Response ◽  
Fe Model ◽  
Compressor Blades ◽  
Design Data ◽  
Modal Force ◽  
Turbomachinery Blades ◽  
Compressor Performance

A method is proposed for HCF-analysis that is suitable for use in early design stages of turbomachinery blades. Quantitative measures of the risk for later encountering HCF life limiting vibrations are the goal for the development. The novelty of the system is the unique and rational way all design data are processed resulting in a mode risk priority listing. The method makes extensive use of FE calculated modal analyses and simple assumptions on the modal force and damping. The modal force is taken proportional to the tangential force on the blade over the operating range. This choice is made because the tangential force is known early on from the compressor performance map, and gives a reasonable scaling with the operating point. Crossings occurring at low speed get a lower force than at high speed. The system damping used is a constant critical damping ratio. Using a modal force and damping along with the FE model forced response amplitude can be directly computed at resonance crossings inside operating envelope. The modal force calculated this way can be compared to the force amplitude needed to reach the fatigue limit in a Haigh diagram. Using the Haigh diagram this way allows modes with localized high stresses, so-called hot spots, to be highlighted. Taking the ratio of the forces gives a ranking value that can be used to compare risk. Details of the technique along with example applications to compressor blades are presented in the paper. It is found that many mode crossings can be excluded as low risk this way and that a rational way of prioritizing is achieved.

Motorcycle Tire Modeling

2015 ◽  
Author(s):  
Federico Ballo ◽  
Massimiliano Gobbi ◽  
Giampiero Mastinu ◽  
Giorgio Previati ◽  
Roberto Zerboni
Keyword(s):  
Analytical Model ◽  
Lightweight Design ◽  
Experimental Tests ◽  
Contact Forces ◽  
Fe Model ◽  
Actual Distribution ◽  
Axial Forces ◽  
Wide Range ◽  
Tire Modeling ◽  
Explicit Formulae

The knowledge of the actual distribution of the contact forces transmitted by the tire to the rim is of crucial importance for the lightweight design of motorcycles wheels. In this paper, an analytical model of a motorcycle tire is developed and explicit formulae giving the distribution of the static radial and axial forces acting between the tyre and the rim for a given vertical load have been derived. The analytical model has been validated by means of a FE model of the tire and wheel and on the basis of indoor experimental tests. The proposed analytical model is able to predict the radial static deflection of both a front and a rear tire for a racing motorbike with very good accuracy over a wide range of inflating pressures and vertical loads. The force distributions are in very good agreement with the results of the FE model.

Subject-Specific Finite Element Models of the Tibia With Realistic Boundary Conditions Predict Bending Deformations Consistent With In Vivo Measurement

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Ifaz T. Haider ◽  
Michael Baggaley ◽  
W. Brent Edwards
Keyword(s):  
Finite Element ◽  
Boundary Conditions ◽  
Internal Rotation ◽  
Stress Fracture ◽  
Contact Forces ◽  
Female Participant ◽  
Fe Model ◽  
In Vivo Measurements ◽  
Subject Specific

Abstract Understanding the structural response of bone during locomotion may help understand the etiology of stress fracture. This can be done in a subject-specific manner using finite element (FE) modeling, but care is needed to ensure that modeling assumptions reflect the in vivo environment. Here, we explored the influence of loading and boundary conditions (BC), and compared predictions to previous in vivo measurements. Data were collected from a female participant who walked/ran on an instrumented treadmill while motion data were captured. Inverse dynamics of the leg (foot, shank, and thigh segments) was combined with a musculoskeletal (MSK) model to estimate muscle and joint contact forces. These forces were applied to an FE model of the tibia, generated from computed tomography (CT). Eight conditions varying loading/BCs were investigated. We found that modeling the fibula was necessary to predict realistic tibia bending. Applying joint moments from the MSK model to the FE model was also needed to predict torsional deformation. During walking, the most complex model predicted deformation of 0.5 deg posterior, 0.8 deg medial, and 1.4 deg internal rotation, comparable to in vivo measurements of 0.5–1 deg, 0.15–0.7 deg, and 0.75–2.2 deg, respectively. During running, predicted deformations of 0.3 deg posterior, 0.3 deg medial, and 0.5 deg internal rotation somewhat underestimated in vivo measures of 0.85–1.9 deg, 0.3–0.9 deg, 0.65–1.72 deg, respectively. Overall, these models may be sufficiently realistic to be used in future investigations of tibial stress fracture.

Experimental and Numerical Coupling Proof of Conical Frictional Joints

2007 ◽  
Vol 347 ◽  
pp. 557-562 ◽  
Author(s):  
Dariusz Szwedowicz ◽  
Jorge Bedolla
Keyword(s):  
Analytical Solution ◽  
Design Process ◽  
Coupling Strength ◽  
Coordinate Measuring Machine ◽  
Contact Forces ◽  
Fe Model ◽  
Fe Method ◽  
Fine Mesh ◽  
Operation Conditions ◽  
Measuring Machine

Conical rings are used to joint a shaft with other mechanical parts through frictional forces induced by clamping of the inner ring into the outer one. In design, their coupling strength and the allowable torque are determined with the well known analytical formulas. However, the assumption of rigid and smooth contacts considered in the analytical solution generates technical uncertainties for reliability of conical joints especially for their small dimensions. The coupling strength of the conical rings is investigated at a set-up and by using Finite Element (FE) Method. A FE model of the analytically analysed conical joint is created with friction contact conditions on all interfaces of the joint. For a very fine mesh with the smooth interfaces, the FE contact forces differ remarkably from the analytical solution. This confirms that the elasticity of parts has to be taken into account in the design process. To assess an influence of real contact profiles on the coupling performance, contours of contact surfaces are measured at a Mitutoyo coordinate measuring machine. Based on the measured height variation in the normal to the contact plane, the surface profiles are extrapolated by approximation functions. Then, the FE mesh is modified locally on the contact with respect to the extrapolated profile functions and coupling strength of the conical joint is computed with friction sliding. According to the obtained results, the implementation of the real profile of the contact is needed in the design process to avoid failures under real operation conditions of conical joints. According to the obtained FE static results, the contour irregularities induces local separations in the contact, which can be monitored by measuring electrical resistance between the outer and inner conical rings.

scholarly journals A New Switch and Crossing Design: Introducing the Back to Back Bistable Switch

2020 ◽  
Vol 9 (4) ◽  
pp. 175-186
Author(s):  
J. -Y. Shih ◽  
R. Ambur ◽  
H. C. Boghani ◽  
R. Dixon ◽  
E. Stewart
Keyword(s):  
Dynamic Modelling ◽  
Design Guidelines ◽  
Contact Forces ◽  
Maintenance Cost ◽  
Fe Model ◽  
Bistable Switch ◽  
Performance Improvements ◽  
Track Stiffness ◽  
Multi Body ◽  
A Current

A new track swtich and crossing (S&C), the back to back bistable (B2B) switch, is proposed that has shown potential to significantly reduce the wheel/rail contact forces through the switch due to its more continuous wheel/rail contact interface and more uniform track stiffness arising from the elimination of the crossing nose. This offers a major reduction on maintenance cost of future S&Cs. The paper explains the concept and identifies the design guidelines for a current layout and uses vehicle/turnout dynamic modelling to predict wheel rail forces through a switch to identify performance improvements relative to a conventional S&C. Both multi-body simulation (MBS) and Finite Element (FE) model have been developed to account for dynamic and thermal analysis. The new design has shown improvements in lateral and vertical wheel-rail contact forces and less relative rail displacements due to thermal effect compared to the conventional S&C.

scholarly journals Design and Development of a Small-Scale Mechanical Energy Conversion Device

2020 ◽  
Author(s):  
Man Djun Lee ◽  
Pui San Lee
Keyword(s):  
Energy Conversion ◽  
Environmental Sustainability ◽  
Material Selection ◽  
Mechanical Energy ◽  
Electrical Power ◽  
Small Scale ◽  
Final Design ◽  
Speed Up ◽  
Rotor Core ◽  
Series Of Experiments

Abstract This study aims to design and construct a small-scale mechanical energy conversion device. It is designed to produce electrical power by harnessing the available mechanical energy from renewable resources. This study started off with literature review for the predominant principles and laws on how the machine shall be fabricated in order to function. The process is followed by the material selection and analysis before proceeding to the final design and construction. The constructed machine is then being tested through series of experiments. It was found that the small scale device was able to produce 6V of maximum voltage with rotor rotation speed up to 3000 RPM. The outcome from the experimentation shows that the small scale device is useful for power generation from renewable sources, such as stream energy with a micro hydro turbine. For future study, the machine shall consider a few improvements, such as rebuilding it using laminated iron as rotor core and increase the number of poles to enhance the performance of the machine in term of energy conversion and extraction. The design and built of this machine would definitely contribute to the environmental sustainability and development of rural area.

Modelling the Effect of Track Stiffness Variation on Wheel Rail Interaction Using Finite Element Method

2021 ◽  
Author(s):  
Lovejoy Mutswatiwa ◽  
Celestin Nkundineza ◽  
Mehmet A. Güler
Keyword(s):  
Prediction Models ◽  
Research Work ◽  
Contact Forces ◽  
Physical Parameters ◽  
Fe Model ◽  
Railroad Track ◽  
Track Stiffness ◽  
Stiffness Variation ◽  
The Cross ◽  
Track Modulus

Abstract For predictive maintenance purpose, wheel and rail wear evolution models have been developed based on wheel rail contact force calculations. These models are known to assume the wheel rotating on a rigid rail. However recent developments have shown that the flexibility of the track plays an important role in wear evolution. On the other hand, vertical track stiffness variation along the track is known to exist and to affect the track flexibility. The present research work investigates the influence of non-uniform track modulus on the wheel rail contact forces using elasto-plastic explicit dynamic Finite Elements (FE). The FE model is composed of a quarter car model running on a rail supported by three cross-ties. The modulus of elasticity of the cross-ties is calibrated to produce the total track modulus of the railroad track infrastructure. Non-uniformity of the track is modeled by assigning distinct elasticity moduli to the cross-ties. The instantaneous contact physical parameters are extracted from FE models repetitively for various cross-tie modulus ratios. The results show that increase in cross-tie modulus variation results in increased fluctuation amplitudes of wheel-rail contact parameters such as force, stress and contact area. This effect leads to changes of the rate of material removal on the wheels and rails. This research work intends to incorporate the spatial variation of the railroad track stiffness into rail vehicle wheel and track wear prediction models.

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