scholarly journals Updating Stiffness and Hysteretic Damping Matrices Using Measured Modal Data

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Jiashang Jiang ◽  
Yongxin Yuan
Keyword(s):  
Finite Element ◽  
Direct Method ◽  
Original Model ◽  
Numerical Results ◽  
Material Damping ◽  
Modal Data ◽  
Model Based ◽  
Hysteretic Damping ◽  
Vibration Modal ◽  
Damping Model

A new direct method for the finite element (FE) matrix updating problem in a hysteretic (or material) damping model based on measured incomplete vibration modal data is presented. With this method, the optimally approximated stiffness and hysteretic damping matrices can be easily constructed. The physical connectivity of the original model is preserved and the measured modal data are embedded in the updated model. The numerical results show that the proposed method works well.

scholarly journals Seismic site response of layered saturated sand: comparison of finite element simulations with centrifuge test results

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Sparsha Sinduri Nagula ◽  
Yu-Wei Hwang ◽  
Shideh Dashti ◽  
Jürgen Grabe
Keyword(s):  
Finite Element ◽  
Seismic Response ◽  
Site Response ◽  
Numerical Results ◽  
Centrifuge Test ◽  
Test Results ◽  
Saturated Sand ◽  
Hypoplastic Model ◽  
Model Based ◽  
Seismic Site Response

AbstractA numerical model based on the finite element framework was developed to predict the seismic response of saturated sand under free-field conditions. The finite element framework used a non-linear coupled hypoplastic model based on the u-p formulation to simulate the behaviour of the saturated sand. The u-p coupled constitutive model was implemented as a user-defined routine in commercial ABAQUS explicit 6.14. Results of centrifuge experiments simulating seismic site response of a layered saturated sand system were used to validate the numerical results. The centrifuge test consisted of a three-layered saturated sand system subjected to one-dimensional seismic shaking at the base. The test set-up was equipped with accelerometers, pore pressure transducers, and LVDTs at various levels. Most of the constitutive models used to date for predicting the seismic response of saturated sands have underestimated volumetric strains even after choosing material parameters subjected to rigorous calibration measures. The hypoplastic model with intergranular strains calibrated against monotonic triaxial test results was able to effectively capture the volumetric strains, reasons for which are discussed in this paper. The comparison of the numerical results to centrifuge test data illustrates the capabilities of the developed u-p hypoplastic formulation to perform pore fluid analysis of saturated sand in ABAQUS explicit, which inherently lacks this feature.

A modified damping model of vector form intrinsic finite element method for high-speed spiral bevel gear dynamic characteristics analysis

2021 ◽  
pp. 030932472110188
Author(s):  
Xiangying Hou ◽  
Yuzhe Zhang ◽  
Hong Zhang ◽  
Jian Zhang ◽  
Zhengminqing Li ◽  
...  
Keyword(s):  
Finite Element ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Numerical Solutions ◽  
Bevel Gear ◽  
Spiral Bevel Gear ◽  
Vector Form ◽  
Good Efficiency ◽  
Spiral Bevel ◽  
Damping Model

The vector form intrinsic finite element (VFIFE) method is springing up as a new numerical method in strong non-linear structural analysis for its good convergence, but has been constricted in static or transient analysis. To overwhelm its disadvantages, a new damping model was proposed: the value of damping force is proportional to relative velocity instead of absolute velocity, which could avoid inaccuracy in high-speed dynamic analysis. The accuracy and efficiency of the proposed method proved under low speed; dynamic characteristics and vibration rules have been verified under high speed. Simulation results showed that the modified VFIFE method could obtain numerical solutions with good efficiency and accuracy. Based on this modified method, high-speed vibration rules of spiral bevel gear pair under different loads have been concluded. The proposed method also provides a new way to solve high-speed rotor system dynamic problems.

scholarly journals Correction of Finite Element Models Using Experimental Modal Data.

1991 ◽  
Vol 57 (537) ◽  
pp. 1591-1595 ◽  
Author(s):  
Kukil SOHN ◽  
Masaaki OKUMA ◽  
Akio NAGAMATSU
Keyword(s):  
Finite Element ◽  
Finite Element Models ◽  
Modal Data

Effects of Out-of-Plane Displacements on Load Capacity of Gusset Plates in Buckling Restrained Braced Frames

2018 ◽  
Vol 763 ◽  
pp. 892-899 ◽  
Author(s):  
Saul Y. Vazquez-Colunga ◽  
Chin Long Lee ◽  
Gregory A. MacRae
Keyword(s):  
Finite Element ◽  
Finite Element Methods ◽  
Load Capacity ◽  
Numerical Results ◽  
Numerical Analyses ◽  
Braced Frames ◽  
Gusset Plates ◽  
Out Of Plane ◽  
Buckling Restrained Braced Frames ◽  
Monotonic Load

This study sets out to investigate the effect of out-of-plane (OOP) displacements on the monotonic load capacity of gusset plates (GPs) via numerical analyses using finite element methods. Two models were used: a) models with in-plane (INP) actions only; and b) models with both INP and OOP actions. The numerical results show that the load capacity of GPs is reduced with the presence of OOP displacements. For an OOP drift of 2.5%, the reduced capacity ranges from 95% to 80% with an average of 88% of the load capacity when only INP actions were applied.

An Analysis of Conventional and Self-Aligned four Terminal Resistor Structures for The Determination of The Contact Resistivity from End Resistance Measurements

1986 ◽  
Vol 71 ◽  
Author(s):  
I. Suni ◽  
M. Finetti ◽  
K. Grahn
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Computer Model ◽  
Contact Resistivity ◽  
Experimental Results ◽  
The Finite Element Method ◽  
Model Based ◽  
A Value ◽  
And Diffusion

AbstractA computer model based on the finite element method has been applied to evaluate the effect of the parasitic area between contact and diffusion edges on end resistance measurements in four terminal Kelvin resistor structures. The model is then applied to Al/Ti/n+ Si contacts and a value of contact resistivity of Qc = 1.8×10−7.Ωcm2 is derived. For comparison, the use of a self-aligned structure to avoid parasitic effects is presented and the first experimental results obtained on Al/Ti/n+Si and Al/CoSi2/n+Si contacts are shown and discussed.

Study and Prediction of Bone Strength of Osteoporosis Model Based on Synchrotron Radiation

2021 ◽  
Author(s):  
Wanyu Li ◽  
Jun Xu ◽  
Shunan Zhang ◽  
Han Guo ◽  
Jianqi Sun ◽  
...  
Keyword(s):  
Finite Element ◽  
Synchrotron Radiation ◽  
Bone Strength ◽  
Lumbar Vertebrae ◽  
Bone Microstructure ◽  
Ovariectomized Rats ◽  
Osteoporotic Bone ◽  
Mineral Density ◽  
Model Based ◽  
Osteoporosis Diagnosis

Abstract Background: As the gold standard for clinical osteoporosis diagnosis, bone mineral density has significant limitations in bone strength assessment and fracture risk prediction. The purpose of this study is to explore a new osteoporotic bone quality evaluation criteria from both diagnosis site selection and bone strength prediction. Methods: Ovariectomized rats with different intensity swimming therapy were investigated in this study. The lumbar vertebrae and femurs of all the rats were scanned by synchrotron radiation computed tomography. Bone microstructure analysis and finite element analysis were combined to obtain bone microstructure parameters and estimated bone strength. And the sensitivity of different skeletal sites to therapy was explored. An elastic network regression model was established to predict bone strength by integrating additional bone microstructure characteristics besides bone mass.Results: Histomorphometry analysis showed that swimming therapy could reduce the risk of osteoporosis of lumbar vertebrae and femur and suggested that the femur might be a more suitable site for osteoporosis diagnosis and efficacy evaluation than the lumbar vertebrae. The average coefficient of determination and average root mean squared error of our predictive model were 0.774 and 0.110. Bland-Altman analysis showed that our model could be a good alternative to the finite element method. Conclusions: The present study developed a machine learning model for prediction of bone strength of osteoporosis model based on synchrotron x-ray imaging and demonstrated that different skeletal sites had different sensitivity to therapy, which is of great significance for the early diagnosis of osteoporosis, the prevention of fractures and the monitoring of therapy.

Effective Shear Area in One Dimensional Ship Hull Finite Element Models to Predict Natural Frequencies of Vibration

2013 ◽  
Author(s):  
Osvaldo Pinheiro de Souza e Silva ◽  
Severino Fonseca da Silva Neto ◽  
Ilson Paranhos Pasqualino ◽  
Antonio Carlos Ramos Troyman
Keyword(s):  
Finite Element ◽  
Natural Frequencies ◽  
Three Dimensional ◽  
Experimental Tests ◽  
Numerical Results ◽  
Computational Method ◽  
Scale Model ◽  
Dimensional Model ◽  
One Dimensional ◽  
Shear Area

This work discusses procedures used to determine effective shear area of ship sections. Five types of ships have been studied. Initially, the vertical natural frequencies of an acrylic scale model 3m in length in a laboratory at university are obtained from experimental tests and from a three dimensional numerical model, and are compared to those calculated from a one dimensional model which the effective shear area was calculated by a practical computational method based on thin-walled section Shear Flow Theory. The second studied ship was a ship employed in midshipmen training. Two models were made to complement some studies and vibration measurements made for those ships in the end of 1980 decade when some vibration problems in them were solved as a result of that effort. Comparisons were made between natural frequencies obtained experimentally, numerically from a three dimensional finite element model and from a one dimensional model in which effective shear area is considered. The third and fourth were, respectively, a tanker ship and an AHTS (Anchor Handling Tug Supply) boat, both with comparison between three and one dimensional models results out of water. Experimental tests had been performed in these two ships and their results were used in other comparison made after the inclusion of another important effect that acts simultaneously: the added mass. Finally, natural frequencies experimental and numerical results of a barge are presented. The natural frequencies numerical results of vertical hull vibration obtained from these approximations of effective shear areas for the five ships are finally discussed.

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