A updating method using strain frequency response function with emphasis on local structure

Model updating using correlation analysis of strain frequency response function

A mechanical-magnetic-electro bidirectional coupled dynamic model of a composite cantilever with magnetostrictive shunt damper is established, and the system's transfer functions and a key impedance impact factor are derived. For shunt vibration damping, H2 optimization criterion and the Nelder-Mead search method are used to obtain the optimal parameters of three circuits: resistance shunt (RS), capacitance shunt (CS), and resistance-CS (RCS). Comparisons between the calculated and measured results show that the proposed model can accurately describe the transmissibility vibration frequency responses of the system under RS and CS, and can predict the changing laws of the resonant frequency and the resonant peak with the shunt impedance. It is found that the RCS with negative shunt resistance can provide the peak attenuation rate 90.78%, which is higher than 70.44% of CS and 53.29% of RS, and has wider frequency broadband and faster vibration damping performances than CS and RS.

Dynamic multi-objective optimization problem is one of the most current popular research hotspots and faces great difficulties. In this work, based on the multiple objectives of structural optimization of the management space of forest ecosystems, a dynamic multi-objective optimization model of forest spatial structure is constructed by using the variation of forest growth with time. In order to make the model solve the problem more efficiently, an algorithm which focuses on solving multi-objective optimization problems is applied with a new environment detection mechanism. Compared with two multi-objective optimization algorithms PDMIOA and dDMSMOPSO, four test functions i.e., FDA1, FDA3, dMOP1, and dMOP2, are used. The results show that the proposed algorithm is superior to PDMIOA and dDMSMOPSO in convergence performance, distribution performance, and tracking performance. We have also applied the model to the natural secondary forest stand of the Longhushan Stateowned Forest Farm in South Dongting Lake, and analyzed the model output. The results show that after optimization, the forest structural indicators such as homogeneity index, mixed degree, competition index, health degree, spatial density index and open ratio, are obviously better than those without optimization. In addition, the forest structure is also greatly improved. The proposed dynamic multi-objective optimization model of forest spatial structure can provide both theoretical basis and technical support for intelligent forest management.

Dynamic parametric modeling-based model updating strategy of aeroengine casings

This paper proposes an entity local structure comparison approach based on inexact subgraph matching. The comparison results are used for mislabeling correction in the local structure. The latter represents a set of entity attribute labels which are physically close in a document image. It is modeled by an attributed graph describing the content and presentation features of the labels by the nodes and the geometrical features by the arcs. A local structure graph is matched with a structure model which represents a set of local structure model graphs. The structure model is initially built using a set of well chosen local structures based on a graph clustering algorithm and is then incrementally updated. The subgraph matching adopts a specific cost function that integrates the feature dissimilarities. The matched model graph is used to extract the missed labels, prune the extraneous ones and correct the erroneous label fields in the local structure. The evaluation of the structure comparison approach on 525 local structures extracted from 200 business documents achieves about 90% for recall and 95% for precision. The mislabeling correction rates in these local structures vary between 73% and 100%.

Structural dynamic and stress wave models for the analysis of shotcrete on rock exposed to blasting

Residual stiffness assessment of structurally failed reinforced concrete structure by dynamic testing and finite element model updating

We estimate the costs of financial distress prior to default (predefault costs) separately from the loss incurred at default (the loss given default) using a dynamic tradeoff model of capital structure. We show that predefault costs account for a large fraction of total distress costs, approximately 64.1%. At the same time, they vary across industries ranging from 32.1% to 75%. We demonstrate that the expected predefault costs of financial distress vary significantly across industries with a range between 3.2% and 8.3% and are higher for small firms relative to larger ones. This paper was accepted by Lukas Schmid, finance. Supplemental Material: The data files are available at https://doi.org/10.1287/mnsc.2023.4974 .

This paper presents an enhanced version and the validation of a recently proposed methodology for earthquake-induced damage detection and localization in masonry towers by using long-term vibration monitoring data. The proposed enhanced method is based on continuous operational modal analysis through stochastic subspace identification, dynamic multiple linear regressive analysis to remove the effects of changing environmental conditions and finite element (FE) model updating. Any anomalous frequency deviation from normal conditions resulting from an earthquake triggers the damage localization process. This task is performed by solving an inverse FE model calibration problem, where equivalent elastic properties of macrostructural elements are identified by minimizing an objective function considering experimentally identified and numerically predicted damage-induced decays in natural frequencies and changes in eigenvector components. To minimize the computational effort of this calibration procedure, a quadratic surrogate model is constructed using a tuned numerical FE model of the structure. The methodology is validated through application to the “Sciri Tower”, an historic civic masonry tower located in Perugia, Italy, that has been continuously monitored by the authors for more than 1 year. The validation is carried out by using simulated damage scenarios and a set of real far-field earthquake data and is based on a FE model of the tower including surrounding buildings, calibrated on the basis of the measured data from ambient vibration tests. The results demonstrate that the proposed procedure is capable of correctly detecting and localizing earthquake-induced damages.

A dynamic phase-field fracture finite element model is applied to discretized high-resolution three-dimensional computed tomography images of human trabecular bone to analyse rapid bone fracture. The model is contrasted to quasi-static experimental results and a quasi-static phase-field finite element model. The experiment revealed complex stepwise crack evolution with multiple crack fronts, and crack arrests, as the global tensile displacement load was incrementally increased. The quasi-static phase-field fracture model captures the fractures in the experiment reasonably well, and the dynamic model converges towards the quasi-static model when mechanically loaded at low rates. At higher load rates, i.e., at larger impulses, inertia effects significantly contribute to an increased initial global stiffness, higher peak forces and a larger number of cracks spread over a larger volume. Since the fracture process clearly is different at large impulses compared to small impulses, it is concluded that dynamic fracture models are necessary when simulating rapid bone fracture.

This paper describes an aero-structural modeling method for the Transonic Truss-Braced Wing (TTBW) aircraft using VSPAERO. A vortex-lattice model of the TTBW aircraft is developed, and a transonic and viscous flow correction method is implemented in the VSPAERO models to account for transonic and viscous flow effects. A correction method for the wing-strut interference aerodynamics is developed and applied to the VSPAERO solver. Also, a structural dynamic finite-element model of the TTBW aircraft is developed. This finite-element model includes the geometric nonlinear effect due to the tension in the struts which cause a deflection dependent nonlinear stiffness. The VSPAERO models are coupled to the finite-element model to provide a rapid capability for aero-structural modeling and flutter analysis. A flight-optimized jig twist model is being developed and will be applied for the purpose of generating a full flight dynamic model of the TTBW aircraft.

Optimal CD4 Count for Initiating HIV Treatment

A DNS study of extreme and leading points in lean hydrogen-air turbulent flames - part II: Local velocity field and flame topology

Particle Swarm Optimization with Sequential Niche Technique for Dynamic Finite Element Model Updating

ABSTRACTA new type of large semi-rigid solar array structure with a new structural concept of rigid-flexible combination has developed for space application. Due to the good features of large scale and lightweight, such structure can well satisfy to the large power requirements of spacecraft and thus has drawn increasing attention recently. However, its structural weakness of inherently flexibility makes low frequency vibrations happen much easier. It is highly required to obtain an accurate dynamic model for predicting the dynamic characteristics of this kind of semi-rigid space structure. Because this structure is composed of different components that have quite different stiffness properties respectively, it is very difficult to build up an accurate dynamic model of this complex structure. In this paper, a novel analytical dynamic model is developed for solving this problem. To validate the correctness of the proposed model, experiment studies are conducted. By comparing the simulation results with experimental results, it can be concluded that this dynamic modeling method presented in the paper is credible. The present study is significant for the structural construction and application of this special structure.