scholarly journals Nonproportional Intentionally Mistuned Turbine Blisk Design with Improved Component Modal Synthesis

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Bin Bai ◽  
Qi Yang ◽  
Guang Wei Zhu ◽  
Qi Liang Wu ◽  
Xin ye Li
Keyword(s):  
Degrees Of Freedom ◽  
Engineering Practice ◽  
Finite Element Models ◽  
High Fidelity ◽  
Vibration Characteristic ◽  
Modal Shape ◽  
Disk Structure ◽  
Modal Synthesis ◽  
Amplitude Fluctuations ◽  
Turbine Blisk

An improved component modal synthesis-based nonproportional mistuning method (ICMS-NPMM) is proposed to investigate mistuned turbine blisks (MTBs) since the high-fidelity finite element models (HFEMs) involve large number of computations, which leads to low calculation efficiency. To reduce degrees of freedom and suppress the flutter of MTB, it is divided into mistuned blade structure and tuned disk structure, and the intentional mistuning is considered. Furthermore, the mistuned parameters, nonproportional mistuning, and complex loads are also considered. Firstly, the basic theory of ICMS-NPMM is investigated; secondly, the model of MTB is established via ICMS-NPMM; finally, the intentionally mistuned design of modal shape amplitudes (MSAs) is investigated via ICMS-NPMM. The results indicate that the calculation efficiency is enhanced via ICMS-NPMM relative to that of via HFEM. In addition, the sensitivity and the flutter are decreased; meanwhile, the amplitude fluctuations of MSAs are distinctly decreased and become comparatively smooth. This investigation provides an important guidance for the vibration characteristic study of complex mechanical structures in engineering practice.

scholarly journals A Finite Element Approach to the Analysis of Rotating Bladed-Disk Assemblies Coupled With Flexible Shaft

1994 ◽  
Author(s):  
Wen Zhang ◽  
Wenliang Wang ◽  
Hao Wang ◽  
Jiong Tang
Keyword(s):  
Finite Element ◽  
Degrees Of Freedom ◽  
Coupled System ◽  
Equation Of Motion ◽  
Coupled Systems ◽  
The Finite Element Method ◽  
Bladed Disk ◽  
Modal Synthesis ◽  
Element Approach ◽  
Final Equation

A method for dynamic analysis of flexible bladed-disk/shaft coupled systems is presented in this paper. Being independant substructures first, the rigid-disk/shaft and each of the bladed-disk assemblies are analyzed separately in a centrifugal force field by means of the finite element method. Then through a modal synthesis approach the equation of motion for the integral system is derived. In the vibration analysis of the rotating bladed-disk substructure, the geometrically nonlinear deformation is taken into account and the rotationally periodic symmetry is utilized to condense the degrees of freedom into one sector. The final equation of motion for the coupled system involves the degrees of freedom of the shaft and those of only one sector of each of the bladed-disks, thereby reducing the computer storage. Some computational and experimental results are given.

A Parallel Solution Strategy for Finite Element Models

1996 ◽  
Author(s):  
Jordan J. Cox ◽  
Jeffrey A. Talbert ◽  
Eric Mulkay
Keyword(s):  
Finite Element ◽  
Degrees Of Freedom ◽  
Element Model ◽  
Decomposition Methods ◽  
Finite Element Models ◽  
Unique Contribution ◽  
Matrix Equations ◽  
Parallel Solution ◽  
The Finite Element Model ◽  
Parallel Fashion

Abstract This paper presents a method for naturally decomposing finite element models into sub-models which can be solved in a parallel fashion. The unique contribution of this paper is that the decomposition strategy comes from the geometric features used to construct the solid model that the finite element model represents. Domain composition and domain decomposition methods are used to insure global compatibility. These techniques reduce the N2 behavior of traditional matrix solving techniques, where N is the number of degrees of freedom in the global set of matrix equations, to a sum of m matrices with n2 behavior, where n represents the number of degrees of freedom in the smaller sub-model matrix equations.

An Integrated Software Tool for High Fidelity Probabilistic Assessments of Metallic Aero-Engine Components

2016 ◽  
Author(s):  
R. Craig McClung ◽  
Paul Wawrzynek ◽  
Yi-Der Lee ◽  
Bruce J. Carter ◽  
Jonathan P. Moody ◽  
...  
Keyword(s):  
Crack Growth ◽  
Degrees Of Freedom ◽  
Software Tool ◽  
High Fidelity ◽  
Fatigue Lifetime ◽  
Turbine Engine ◽  
Engine Components ◽  
Integrated Software ◽  
Combined Work ◽  
Exchange Data

Most current tools and methodologies to predict the life and reliability of fracture critical gas turbine engine components rely on stress intensity factor solutions that assume highly idealized component and crack geometries, and this can lead to highly conservative results in some cases. This paper describes a new integrated methodology to perform these assessments that combines one software tool for creating high fidelity crack growth simulations (FRANC3D) with another software tool for performing probabilistic fatigue crack growth life assessments of turbine engine components (DARWIN). DARWIN employs finite element models of component stresses, while FRANC3D performs automatic adaptive re-meshing of these models to simulate crack growth. Modifications have been performed to both codes to allow them to share and exchange data and to enhance their shared computational capabilities. Most notably, a new methodology was developed to predict the shape evolution and the fatigue lifetime for cracks that are geometrically complex and not easily parameterized by a small number of degrees of freedom. This paper describes the integrated software system and the typical combined work flow, and it shows the results from a number of analyses that demonstrate the significant features of the system.

scholarly journals On Hurty/Craig-Bampton Substructuring With Interface Reduction on Contacting Surfaces

2017 ◽  
Author(s):  
Robert J. Kuether ◽  
Peter B. Coffin ◽  
Adam R. Brink
Keyword(s):  
Degrees Of Freedom ◽  
Local Level ◽  
Cost Savings ◽  
Synthesis Methods ◽  
Finite Element Models ◽  
Interface Reduction ◽  
Restoring Forces ◽  
Fixed Interface ◽  
The Cost ◽  
Dynamics Models

Structural dynamics models with localized nonlinearities can be reduced using Hurty/Craig-Bampton component mode synthesis methods. The interior degrees-of-freedom of the linear subcomponents are reduced with a set of dynamic fixed-interface modes while the static constraint modes preserve the physical coordinates at which the nonlinear restoring forces are applied. For finite element models with a highly refined mesh at the boundary, a secondary modal analysis can be performed to reduce the interface down to a truncated set of local-level characteristic constraint modes. In this research, the cost savings and accuracy of the interface reduction technique are evaluated on a simple example problem involving two elastic blocks coming into contact.

Jumping behaviour for a wheeled quadruped robot: simulation and experiments

2013 ◽  
Vol 01 (01) ◽  
pp. 41-60 ◽  
Author(s):  
Adam Harmat ◽  
Michael Trentini ◽  
Inna Sharf
Keyword(s):  
Genetic Algorithm ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Parameter Tuning ◽  
Quadruped Robot ◽  
Knee Joints ◽  
High Fidelity ◽  
Quadratic Response Surface ◽  
Quadratic Response ◽  
Hybrid Locomotion

In this paper, we describe a new jumping behaviour developed for the quadruped robot, PAW (Platform for Ambulating Wheels). The robot has very few degrees of freedom and no knee joints. It employs springy legs and wheels at the distal ends of the legs to achieve various modes of legged, wheeled, and hybrid locomotion, such as high-speed breaking, bounding, and presently jumping. The jumping maneuver developed in this manuscript is designed specifically to take advantage of the wheels on the robot and compliance in its legs and it involves the following principal stages: acceleration to jumping speed, body positioning via front hip thrusting, rear leg compression and thrusting, and flight. A high-fidelity MSC.ADAMS/Simulink co-simulation was developed and used to test and optimize the jumping process. Because of the strong coupling between the parameters defining the jump maneuver, manual parameter tuning is difficult and thus a genetic algorithm is employed for the optimization process. The data generated by the genetic algorithm is further used for the fitting of a quadratic response surface, which allows identifying those parameters that contribute most to a successful jump. Finally, the jumping maneuver is implemented on the physical PAW to demonstrate its feasibility on a hybrid quadruped, and to provide insights into the robot response during this highly dynamic maneuver.

The Gap Nonlinear Characteristics of Gear Transmission System under External Excitation

2012 ◽  
Vol 215-216 ◽  
pp. 1067-1070
Author(s):  
Kang Huang ◽  
Jue Li ◽  
Xin Jin ◽  
Qi Chen
Keyword(s):  
Dynamic Characteristics ◽  
Nonlinear Dynamic ◽  
Degrees Of Freedom ◽  
Transmission System ◽  
Gear Transmission ◽  
Engineering Practice ◽  
Nonlinear Dynamic Model ◽  
Gear Transmission System ◽  
Nonlinear Dynamic Characteristics ◽  
Domain Of Parameters

For the study of nonlinear dynamic characteristics of a pair of gears in an external torque under gear meshing error excitation, we will establish two degrees of freedom nonlinear torsional vibration model. The use of Matlab / Simulink for numerical simulation solves the nonlinear dynamic model of the gear gap. Study the dynamic characteristics of the system in a certain domain of parameters on external incentive conditions, as well as external motivation of gear transmission system dynamic characteristics influence. The results have important practical value for future engineering practice on gear transmission system's dynamic design, and have important theoretical significance for complex gear transmission system dynamics study.

A Theory of Substructure Modal Synthesis

1982 ◽  
Vol 49 (4) ◽  
pp. 903-909 ◽  
Author(s):  
K. Kubomura
Keyword(s):  
Degrees Of Freedom ◽  
Order Approximation ◽  
Second Order ◽  
Natural Mode ◽  
Frequency Range ◽  
Hybrid Mode ◽  
Second Order Approximation ◽  
First Order ◽  
Modal Synthesis ◽  
Modal Coordinates

A theory is presented for representing the displacements of a substructure finite-element mathematical model with a reduced number of degrees of freedom. A first or second-order approximation is used for the substructure’s modal coordinates associated with significantly larger or smaller eigenvalues than the system eigenvalues of excitation. The derived representations of the substructure displacements are capable of employing any type of substructure natural mode; free-free, cantilever or hybrid mode, and of retaining the dynamic behavior of any frequency range. It is shown that the present representations compute the system eigenvalues of interest with satisfactory accuracy, and it appears that the second-order approximation methods compute the system eigenvalues with greater accuracy than the first-order methods.

scholarly journals Vibrations Analysis of the Fruit-Pedicel System of Coffea arabica var. Castillo Using Time–Frequency and Wavelets Techniques

2021 ◽  
Vol 11 (19) ◽  
pp. 9346
Author(s):  
Carlos I. Cardona ◽  
Hector A. Tinoco ◽  
Luis Perdomo-Hurtado ◽  
Juliana López-Guzmán ◽  
Daniel A. Pereira
Keyword(s):  
Coffea Arabica ◽  
Degrees Of Freedom ◽  
Color Space ◽  
Mechanical Impedance ◽  
Coffee Production ◽  
Modal Shape ◽  
Promising Alternative ◽  
Time Frequency ◽  
Test Study ◽  
Three Degrees Of Freedom

Colombian coffee production is well-known, and selective manual harvesting plays a vital task in guaranteeing high ripe coffee fruit rates in this process, leading to its known worldwide aroma and flavor. To maintain this quality approach, selective harvesting methods based on mechanical vibrations are a promising alternative for developing technologies that could accomplish the challenging Colombian coffee production context. In this study, a vibrations analysis in coffee fruits at three ripening stages was carried out to evaluate the dynamic behavior at two frequency windows: 10 to 100 Hz and 100 to 1000 Hz. Two groups of fruits previously classified in the CIELab color space were chosen for the vibration test study samples. Time and frequency signals were characterized via FFT (fast Fourier transform), and bump wavelets were determined to obtain the frequency–time magnitude scalograms. The measurements were obtained in three degrees of freedom over the fruits: one for measuring the input force (computed in voltage way) and the other two measured by the velocity. The results revealed frequency ranges with specific resonant peaks between 24 and 45 Hz, and close to 700 Hz, where the ripe fruits presented higher magnitudes in the calculated parameters. FFT of the velocity and scaled mechanical impedance were used to estimate these frequency ranges. This work is an important step to identify a “vibrational fingerprint” of each Coffea arabica var. Castillo fruit-ripening stage. However, we consider that more experiments should be performed to reconstruct the modal shape in each resonance. In future studies, fatigue analysis could show which are the most effective frequency ranges to detach the ripe fruits from the perspective of a real selective coffee-harvesting scenario.

scholarly journals How to compute invariant manifolds and their reduced dynamics in high-dimensional finite element models

2021 ◽  
Author(s):  
Shobhit Jain ◽  
George Haller
Keyword(s):  
Finite Element ◽  
Degrees Of Freedom ◽  
Invariant Manifolds ◽  
Mechanical Systems ◽  
Forced Response ◽  
High Dimensional ◽  
Nonlinear Phenomena ◽  
Finite Element Models ◽  
Engineering Structures ◽  
Backbone Curves

AbstractInvariant manifolds are important constructs for the quantitative and qualitative understanding of nonlinear phenomena in dynamical systems. In nonlinear damped mechanical systems, for instance, spectral submanifolds have emerged as useful tools for the computation of forced response curves, backbone curves, detached resonance curves (isolas) via exact reduced-order models. For conservative nonlinear mechanical systems, Lyapunov subcenter manifolds and their reduced dynamics provide a way to identify nonlinear amplitude–frequency relationships in the form of conservative backbone curves. Despite these powerful predictions offered by invariant manifolds, their use has largely been limited to low-dimensional academic examples. This is because several challenges render their computation unfeasible for realistic engineering structures described by finite element models. In this work, we address these computational challenges and develop methods for computing invariant manifolds and their reduced dynamics in very high-dimensional nonlinear systems arising from spatial discretization of the governing partial differential equations. We illustrate our computational algorithms on finite element models of mechanical structures that range from a simple beam containing tens of degrees of freedom to an aircraft wing containing more than a hundred–thousand degrees of freedom.

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