A Study of Whole Joint Model Calibration Using Quasi-Static Modal Analysis

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
David A. Najera-Flores ◽  
Robert J. Kuether
Keyword(s):  
Modal Analysis ◽  
Model Calibration ◽  
Computational Cost ◽  
Element Model ◽  
Calibration Method ◽  
Joint Model ◽  
Reduced Order Model ◽  
Order Model ◽  
Reduced Order ◽  
Joint Parameters

Abstract Small length and time scales resulting from high-fidelity frictional contact elements make long duration, low frequency simulations intractable. Alternative reduced order modeling approaches for structural dynamics models have been developed over the last several decades to approximate joint physics based on empirical or mathematical models within a whole joint model representation. The challenge with nonlinear constitutive elements based on empirical models is that the parameters must be calibrated to either experimental or simulation data. This research proposes a model calibration technique that identifies the joint parameters of a four-parameter Iwan element based on the nonlinear natural frequencies and damping ratios computed with quasi-static modal analysis (QSMA). The QSMA algorithm is applied to the full-order finite element model (FEM) to obtain reference data, and a genetic algorithm optimizes the joint parameters within a reduced order model (ROM) by minimizing the difference between the nonlinear modal characteristics for the modes of interest. The calibration method is demonstrated on a C-Beam bolted assembly and the resulting reduced order model is validated by comparing simulations of broadband, forced transient response. The resulting calibrated model captures the nonlinear, multimodal response at a significantly reduced computational cost and can be utilized for producing efficient models that do not have supporting experimental data for calibration.

Intentional Mistuning With Predominant Aerodynamic Effects

2018 ◽  
Author(s):  
Carlos Martel ◽  
José J. Sánchez
Keyword(s):  
Finite Element ◽  
Traveling Waves ◽  
Element Model ◽  
Simple Expression ◽  
Reduced Order Model ◽  
Action Mechanism ◽  
Aerodynamic Forces ◽  
Order Model ◽  
Reduced Order ◽  
Random Mistuning

Intentional mistuning is a well known procedure to decrease the uncontrolled vibration amplification effects of the inherent random mistuning and to reduce the sensitivity to it. The idea is to introduce an intentional mistuning pattern that is small but much larger that the existing random mistuning. The frequency of adjacent blades is moved apart by the intentional mistuning, reducing the effect of the blade-to-blade coupling and thus the effect of the random mistuning. The situation considered in this work is more complicated because the main source for the blade damping is the effect of the aerodynamic forces (as it happens in a blisk for a family of blade dominated modes with very similar frequencies). In this case the damping is clearly defined for the tuned traveling waves but not for each blade. The problem is analyzed using the Asymptotic Mistuning Model methodology. A reduced order model is derived that allows us to understand the action mechanism of the intentional mistuning, and gives a simple expression for the estimation of its beneficial effect. The results from the reduced model are compared with those from a finite element model of a more realistic rotor under different forcing conditions.

Efficient Component-Based Vibration and Power Flow Analysis of a Vehicle Structure

2001 ◽  
Author(s):  
Yung-Chang Tan ◽  
Soo-Yeol Lee ◽  
Matthew P. Castanier ◽  
Christophe Pierre
Keyword(s):  
Power Flow ◽  
Flow Analysis ◽  
Element Model ◽  
Reduced Order Model ◽  
Order Model ◽  
Component Structure ◽  
Modeling And Analysis ◽  
Reduced Order ◽  
Vehicle Structure ◽  
Entire Vehicle

Abstract A case study on the efficient prediction of vibration and power flow in a vehicle structure is presented. The modeling and analysis technique is based on component mode synthesis (CMS). First, the finite element model (FEM) of the entire vehicle structure is partitioned into component models. Then, the Craig-Bampton method is used to assemble a CMS model of the vehicle. The CMS matrices are further reduced by finding characteristic constraint (CC) modes. A relatively small number of CC modes are selected to capture the primary motion of the interface between components, yielding a highly reduced order model of the vehicle vibration in the low- to mid-frequency range. Using this reduced order model (ROM), the power flow and vibration response of the vehicle is analyzed for several design configurations. A design change in one component structure requires a re-analysis of the FEM for that component only, in order to generate a new ROM of the entire vehicle. It is found that this component-based approach allows efficient evaluation of the effectiveness of the vehicle design changes.

Prediction of Geometrically Induced Localization Effects Using a Subset of Nominal System Modes

2019 ◽  
Author(s):  
Thomas Maywald ◽  
Christoph R. Heinrich ◽  
Arnold Kühhorn ◽  
Sven Schrape ◽  
Thomas Backhaus
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Reduced Order Model ◽  
Vibration Measurement ◽  
Mode Shapes ◽  
Compressor Stage ◽  
Order Model ◽  
Reduced Order ◽  
Numerical Predictions

Abstract It is widely known that the vibration characteristics of blade integrated discs can dramatically change in the presence of manufacturing tolerances and wear. In this context, an increasing number of publications discuss the influence of the geometrical variability of blades on phenomena like frequency splitting and mode localization. This contribution is investigating the validity of a stiffness modified reduced order model for predicting the modal parameters of a geometrically mistuned compressor stage. In detail, the natural frequencies and mode shapes, as well as the corresponding mistuning patterns, are experimentally determined for an exemplary rotor. Furthermore, a blue light fringe projector is used to identify the geometrical differences between the actual rotor and the nominal blisk design. With the help of these digitization results, a realistic finite element model of the whole compressor stage is generated. Beyond that, a reduced order model is implemented based on the nominal design intention. Finally, the numerical predictions of the geometrically updated finite element model and the stiffness modified reduced order model are compared to the vibration measurement results. The investigation is completed by pointing out the benefits and limitations of the SNM-approach in the context of geometrically induced mistuning effects.

scholarly journals A Comprehensive CFD Model for Dual-Phase Brass Indirect Extrusion Based on Constitutive Laws: Assessment of Hot-Zone Formation and Failure Prognosis

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1043 ◽  
Author(s):  
George Pashos ◽  
George Pantazopoulos ◽  
Ioannis Contopoulos
Keyword(s):  
Stokes Equations ◽  
Metal Flow ◽  
Computational Cost ◽  
Constitutive Laws ◽  
Reduced Order Model ◽  
Preliminary Evaluation ◽  
Order Model ◽  
Zone Formation ◽  
Reduced Order ◽  
Prediction And Prevention

A numerical method for the precise calculation of temperature, velocity and pressure profiles of the α-β brass indirect hot extrusion process is presented. The method solves the Navier–Stokes equations for non-Newtonian liquids with strain-rate and temperature-dependent viscosity that is formulated using established constitutive laws based on the Zener–Hollomon type equation for plastic flow stress. The method can be implemented with standard computational fluid dynamics (CFD) software, has relatively low computational cost, and avoids the numerical artifacts associated with other methods commonly used for such processes. A response surface technique is also implemented, and it is thus possible to build a reduced order model that approximately maps the process with respect to all combinations of its parameters, including the extrusion speed and brass phase constitution. The reduced order model can be a very useful tool for production, because it instantaneously provides important quantities, such as the average pressure or the temperature of hot-spots that are formed due to the combined effect of die/billet friction and the generation of heat from plastic deformation (adiabatic shear deformation heating). This approach can assist in the preliminary evaluation of the metal flow pattern, and in the prediction and prevention of critical extrusion failures, thus leading to subsequent process and product quality improvements.

A Method for Reducing the Order of Nonlinear Dynamic Systems

1984 ◽  
Vol 51 (2) ◽  
pp. 391-398 ◽  
Author(s):  
S. F. Masri ◽  
R. K. Miller ◽  
H. Sassi ◽  
T. K. Caughey
Keyword(s):  
Dynamic Systems ◽  
Three Dimensional ◽  
Element Model ◽  
Random Excitation ◽  
Reduced Order Model ◽  
Order Model ◽  
Reduced Order ◽  
Dimensional Finite Element ◽  
Restoring Forces ◽  
Three Dimensional Finite Element

An approximate method that uses conventional condensation techniques for linear systems together with the nonparametric identification of the reduced-order model generalized nonlinear restoring forces is presented for reducing the order of discrete multidegree-of-freedom dynamic systems that possess arbitrary nonlinear characteristics. The utility of the proposed method is demonstrated by considering a redundant three-dimensional finite-element model half of whose elements incorporate hysteretic properties. A nonlinear reduced-order model, of one-third the order of the original model, is developed on the basis of wideband stationary random excitation and the validity of the reduced-order model is subsequently demonstrated by its ability to predict with adequate accuracy the transient response of the original nonlinear model under a different nonstationary random excitation.

Computationally Efficient Approaches to Simulate the Dynamics of Microbeams Under Mechanical Shock

2006 ◽  
Author(s):  
Mohammad I. Younis ◽  
Danial Jordy ◽  
James M. Pitarresi
Keyword(s):  
Hybrid Approach ◽  
Computational Cost ◽  
Nonlinear Behavior ◽  
Reduced Order Model ◽  
Beam Model ◽  
Mechanical Shock ◽  
Computationally Efficient ◽  
Order Model ◽  
Reduced Order ◽  
Dynamic Loading Conditions

We present computationally efficient models and approaches and utilize them to investigate the dynamics of microbeams under mechanical shock. We explore using a hybrid approach utilizing a beam model combined with the shock spectrum of a spring-mass-damper model. We conclude that this approach is computationally efficient and yields accurate results in both quasi-static and dynamic loading conditions. We utilize a reduced-order model based on the nonlinear Euler-Bernoulli beam model. We demonstrate that this model is capable of capturing accurately the dynamic behavior of microbeams under shock pulses of various amplitudes (low-g and high-g), in various damping conditions, structural boundaries (clamped-clamped and clamped-free), and can capture both linear and nonlinear behavior. We investigate high-g loading cases. We report significant increase in the computational cost of simulations when using traditional nonlinear finite-element models because of the activation of higher-order modes. We demonstrate that the developed reduced-order model can be very efficient in such cases.

Reduced-Order Modeling of Two-Sided Frictional Interfaces

2007 ◽  
Author(s):  
Jason D. Miller ◽  
D. Dane Quinn
Keyword(s):  
Modal Analysis ◽  
Computational Efficiency ◽  
Order Approximation ◽  
Reduced Order Modeling ◽  
Original Model ◽  
Reduced Order Model ◽  
Order Model ◽  
Reduced Order ◽  
Overall Response

We consider a model describing the behavior of a two-sided interface allowing for both elasticity and microslip of the joint. A reduced-order approximation of this system is developed based on a decomposition of the original model into an elastic chain and a dissipative component equivalent to a series-series Iwan chain. The Iwan chain is then solved using a quasi-static complementarity formulation while the order of the elastic chain is reduced using modal analysis. The computational efficiency of the resulting reduced-order model is significantly increased, while the overall response of the interface to realistic forcing conditions is maintained.

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