Seismic Evaluation of Large Server Computer Structure

2009 ◽  
Author(s):  
Budy D. Notohardjono ◽  
Shawn Canfield ◽  
James A. Cooke
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Experimental Testing ◽  
Element Model ◽  
Frame Structure ◽  
Seismic Evaluation ◽  
Modal Data ◽  
Server Systems ◽  
Computer Structure ◽  
Vibration Tests

This paper discusses the analysis and verification of a finite element model which simulates the robustness of a high end computer server structure during a severe seismic event. The server consists of the frame which is the structure that components are installed into, such as processor units, input-output units and power components. The finite element modeling of this server frame is presented here not only to inform on creating an accurate model for simulation purposes, but also to provide guidelines as to the critical factors in setting up a large assembly finite element model (FEM) and to establish the optimum methodology for modeling this complex assembly with the available analysis software tools. For verification, the simulated modal data is compared to both modal data measured from an instrumented impact hammer, and to measured swept sine data. The simulated results compare favorably with the measured data, and it has been determined that location and integrity of the welded connections are critical for an accurate vibration response of the finite element model. The analysis frame model was subjected to loads and environmental conditions similar to those endured under horizontal table vibration tests and seismic events. The results of the experimental testing and simulations were compared and proved to be in a good correlation. Based on this verified finite element model, any additional redesign of the frame structure and its stiffening members can proceed very efficiently. This design study builds toward the objective of constructing a verified model of the server frame and components which will lead to a guideline for implementing stiffener designs on high-end server systems.

Finite Element Analysis of Structural Strength of Concrete Mixing Truck’s Frame

2014 ◽  
Vol 945-949 ◽  
pp. 1143-1149
Author(s):  
Hai Xia Sun ◽  
Hua Kai Wei ◽  
Xiao Fang Zhao ◽  
Jia Rui Qi
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Finite Element Model ◽  
Structural Strength ◽  
Element Model ◽  
Basic Element ◽  
Operating Conditions ◽  
Frame Structure ◽  
Element Analysis ◽  
The Finite Element Model

The finite element model of the concrete mixing truck’s frame is builded by using shell as basic element, and the process of building the finite element model of the balance suspension is introduced in detail. Based on this, frame’s stress on five types of typical operating conditions are calculated by using the finite element analysis software, NASTRAN, and results can show the dangerous position and the maximum stress position on the frame. The analysis result on structural strength can provide the basis for further improving the frame structure.

Verification of Mainframe Computer Structure Finite Element Model Under Vibration and Seismic Tests

2018 ◽  
Author(s):  
Budy Notohardjono ◽  
Shawn Canfield ◽  
Suraush Khambati ◽  
Richard Ecker
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Frame Structure ◽  
Element Analysis ◽  
Physical Test ◽  
Design Cycle ◽  
Nonlinear Contact ◽  
The Finite Element Model ◽  
Sine Sweep

Shorter development design schedules and increasingly dense product designs create difficult challenges in predicting structural performance of a mainframe computer’s structure. To meet certain certification benchmarks such as the Telcordia Technologies Generic Requirements GR-63-CORE seismic zone 4 test profile, a physical test is conducted. This test will occur at an external location at the end of design cycle on a fully functional and loaded mainframe system. The ability to accurately predict the structural performance of a mainframe computer early in the design cycle is critical in shortening its development time. This paper discusses an improved method to verify the finite element analysis results predicting the performance of the mainframe computer’s structure long before the physical test is conducted. Sine sweep and random vibration tests were conducted on the frame structure but due to a limitation of the in-house test capability, only a lightly loaded structure can be tested. Evaluating a structure’s modal stiffness is key to achieving good correlation between a finite element (FE) model and the physical system. This is typically achieved by running an implicit modal analysis in a finite element solver and comparing it to the peak frequencies obtained during physical testing using a sine sweep input. However, a linear, implicit analysis has its limitations. Namely, the inability to assess the internal, nonlinear contact between parts. Thus, a linear implicit analysis may be a good approximation for a single body but not accurate when examining an assembly of bodies where the interaction (nonlinear contact) between the bodies is of significance. In the case of a nonlinear assembly of bodies, one cannot effectively correlate between the test and a linear, implicit finite element model. This paper explores a nonlinear, explicit analysis method of evaluating a structure’s modal stiffness by subjecting the finite element model to a vibration waveform and thereafter post processing its resultant acceleration using Fast Fourier Transformation (FFT) to derive the peak frequencies. This result, which takes into account the nonlinear internal contact between the various parts of the assembly, is in line with the way physical test values are obtained. This is an improved method of verification for comparing sine sweep test data and finite element analysis results. The final verification of the finite element model will be a successful physical seismic test. The tests involve extensive sequential, uniaxial earthquake testing in both raised floor and non-raised floor environments in all three directions. Time domain acceleration at the top of the frame structure will be recorded and compared to the finite element model. Matching the frequency content of these accelerations will be proof of the accuracy of the finite element model. Comparative analysis of the physical test and the modeling results will be used to refine the mainframe’s structural elements for improved dynamic response in the final physical certification test.

scholarly journals Assessment of the dynamic structural behaviour of footbridges based on experimental monitoring and numerical analysis

2020 ◽  
Vol 13 (3) ◽  
pp. 563-577
Author(s):  
G. L. DEBONA ◽  
J. G. S. da SILVA
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Rio De Janeiro ◽  
Research Work ◽  
Experimental Tests ◽  
Element Model ◽  
Modal Testing ◽  
Structural Behaviour ◽  
Human Comfort ◽  
Vibration Tests

Abstract This research work aims to investigate the dynamic structural behaviour and assess the human comfort of footbridges, when subjected to pedestrian walking, based on experimental tests and tuning of finite element model. Therefore, the investigated structure is associated to a real pedestrian footbridge, spanning 24.4m, located at the campus of the State University of Rio de Janeiro (UERJ), Rio de Janeiro, Brazil. Initially, an experimental modal testing was conducted using two data acquisition strategies. After that the experimental forced vibration tests were performed on the footbridge, considering the pedestrians walking with different step frequencies. In sequence of the study, a finite element model was developed based on the ANSYS computational program. The experimental footbridge tests were used for the calibration of results on the numerical model. Finally, a human comfort assessment was performed, based on the comparisons between the results (peak accelerations), of the dynamic experimental monitoring and the recommendations provided by design guides SÉTRA, HIVOSS and AISC.

Damage Assessment in Structures Using Incomplete Modal Data and Artificial Neural Network

2015 ◽  
Vol 15 (06) ◽  
pp. 1450087 ◽  
Author(s):  
Seyed Sina Kourehli
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Finite Element ◽  
Finite Element Model ◽  
Structural Damage ◽  
Element Model ◽  
Mass System ◽  
Modal Data ◽  
Artificial Neural ◽  
Propagation Network

This paper presents a novel approach for structural damage detection and estimation using incomplete noisy modal data and artificial neural network (ANN). A feed-forward back propagation network is proposed for estimating the structural damage location and severity. Incomplete modal data is used in the dynamic analysis of damaged structures by the condensed finite element model and as input parameters to the neural network for damage identification. In all cases, the first two natural modes were used for the training process. The present method is applied to three examples consisting of a simply supported beam, three-story plane frame, and spring-mass system. Also, the effect of the discrepancy in mass and stiffness between the finite element model and the actual tested dynamic system has been investigated. The results demonstrated the accuracy and efficiency of the proposed method using incomplete modal data, which may be noisy or noise-free.

Identification of Free-Free Modes From Constrained Vibration Data for Flexible Multibody Models

1999 ◽  
Author(s):  
Tong Y. Yi ◽  
Parviz E. Nikravesh
Keyword(s):  
Finite Element ◽  
Boundary Conditions ◽  
Finite Element Model ◽  
Degrees Of Freedom ◽  
Multibody System ◽  
Element Model ◽  
Flexible Body ◽  
Fe Model ◽  
Modal Data ◽  
Vibration Data

Abstract This paper presents a method for identifying the free-free modes of a structure by utilizing the vibration data of the same structure with boundary conditions. In modal formulations for flexible body dynamics, modal data are primary known quantities that are obtained either experimentally or analytically. The vibration measurements may be obtained for a flexible body that is constrained differently than its boundary conditions in a multibody system. For a flexible body model in a multibody system, depending upon the formulation used, we may need a set of free-free modal data or a set of constrained modal data. If a finite element model of the flexible body is available, its vibration data can be obtained analytically under any desired boundary conditions. However, if a finite element model is not available, the vibration data may be determined experimentally. Since experimentally measured vibration data are obtained for a flexible body supported by some form of boundary conditions, we may need to determine its free-free vibration data. The aim of this study is to extract, based on experimentally obtained vibration data, the necessary free-free frequencies and the associated modes for flexible bodies to be used in multibody formulations. The available vibration data may be obtained for a structure supported either by springs or by fixed boundary conditions. Furthermore, the available modes may be either a complete set; i.e., as many modes as the number of degrees of freedom of the associated FE model is available, or it can be an incomplete set.

Evaluation and Validation of a Multiphysics Finite Element Model for a Piezoelectric Energy Harvester

2021 ◽  
Author(s):  
Andrew Melro ◽  
Kefu Liu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Finite Element Model ◽  
Energy Harvester ◽  
Proof Mass ◽  
Experimental Testing ◽  
Element Model ◽  
Load Resistance ◽  
Piezoelectric Energy ◽  
The Finite Element Model

This paper explores the applicability of using the multiphysics finite element method to model a piezoelectric energy harvester. The piezoelectric energy harvester under consideration consists of a stainless-steel cantilever beam attached by a piezoelectric ceramic patch. Two configurations are considered: one without a proof mass and one with a proof mass. Comsol Multiphysics software is used to simultaneously model three physics: the solid mechanics, the electrostatics, and the electrical circuit physics. Several key relationships are investigated to predict the behaviours of the piezoelectric energy harvester. The effects of the electrical load resistance and a proof mass on the performance of a piezoelectric energy harvester are evaluated. Experimental testing is conducted to validate the results found by the finite element model. Overall, the results from the finite element model closely match those from the experimental testing. It is found that increasing the load resistance of the piezoelectric energy harvester causes an increase in voltage across the load resistor, and matching the impedance yields the maximum power output. Increasing the proof mass reduces the fundamental frequency that results in an increase of the displacement transmissibility and the impedance matched resistance. The study shows that the multiphysics finite element method is effective to model piezoelectric energy harvesters.

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