On Environmental Vibration Power Spectra and Accelerated Testing for Medical Devices

1999 ◽  
Author(s):  
Jingshu Wu ◽  
Ruichong Zhang ◽  
Karl K. Stevens
Keyword(s):  
Medical Devices ◽  
Random Vibration ◽  
Power Spectra ◽  
Field Testing ◽  
Accelerated Testing ◽  
Quality Analysis ◽  
Ground Vehicles ◽  
Operational Conditions ◽  
Analysis And Design ◽  
Environmental Vibration

Abstract This paper proposes field-testing-based power spectra of vibration in such environments as helicopters and ground vehicles. The spectra could then be used as important input data to guide accelerated testing, quality analysis and design for medical devices (or products) used in the aforementioned transportation means. Specifically, a broad spectrum of environmental vibration is first measured in a series of field vibration tests at various locations inside the transportation means and at different operational conditions (e.g., take-off, cruise, and landing conditions if medical devices are used in helicopters). Consequently, comprehensive field-testing-based power spectra are constructed, in an attempt to catch the inherent nature of random vibration environment in each and every type of the transportation means, which is not adequately specified in standard codes. As one of the applications of the proposed spectra, accelerated random vibration testing for medical devices used in either helicopters or ground vehicles is proposed, which could be used not only for product field life prediction but also for its consequent reliability analysis and design.

Water quantity and quality assessment on a tertiary treatment wetland in a tropical climate

2014 ◽  
Vol 71 (4) ◽  
pp. 511-517 ◽  
Author(s):  
Guangzhi Sun ◽  
Tanveer Saeed ◽  
Guangxin Zhang ◽  
Nagaratnam Sivakugan
Keyword(s):  
Oxygen Demand ◽  
Field Testing ◽  
Tropical Climate ◽  
Surface Flow ◽  
Quality Analysis ◽  
Treated Wastewater ◽  
Wetland Soil ◽  
Tertiary Treatment ◽  
Wet Season ◽  
Treatment Wetland

This study aimed to assess the quantity and quality of water in a surface flow constructed wetland in Australia's far north Queensland. Owing to tropical climate in the region, the wetland provided dual functions: retention of a treated wastewater for zero discharge during the dry season and tertiary treatment prior to discharge during the wet season. Rainfall data, permeability of wetland soil, evaporation, inflow and outflow were analysed in a water balance analysis; the results showed that based on a 72-year-average rainfall pattern, daily wastewater inflow of 85 m3/d is the maximum this wetland can cope with without breaching its discharge certificate. In water quality analysis, the K-C* model was used to predict changes of biochemical oxygen demand (BOD, suspended solids (SS), total nitrogen (TN), total phosphorus (TP) and faecal coliforms (FC) in the wetland. Model predictions were compared with field sampling results. It was found that the wetland was effective in removing FC (>99.9%), TN (70.7%) and TP (68.2%), for which the predictions by the K-C* model were consistent with field testing results. However, significant disparities between the predictions and testing results were found for BOD and SS. A revised K-C* equation was proposed to account for the internal generation of organics in constructed wetlands with a long retention time.

Modeling of upset sensor operation for autonomous unmanned systems applications

2019 ◽  
Vol 7 (1) ◽  
pp. 19-34 ◽  
Author(s):  
Mofetoluwa Fagbemi ◽  
Mario G. Perhinschi ◽  
Ghassan Al-Sinbol
Keyword(s):  
Flight Control ◽  
Simulation Environment ◽  
Control Laws ◽  
Content Type ◽  
Autonomous Flight ◽  
Operational Conditions ◽  
Analysis And Design ◽  
Sensor Model ◽  
Comprehensive Framework ◽  
Sensor Modeling

Purpose The purpose of this paper is to develop and implement a general sensor model under normal and abnormal operational conditions including nine functional categories (FCs) to provide additional tools for the design, testing and evaluation of unmanned aerial systems within the West Virginia University unmanned air systems (UAS) simulation environment. Design/methodology/approach The characteristics under normal and abnormal operation of various types of sensors typically used for UAS control are classified within nine FCs. A general and comprehensive framework for sensor modeling is defined as a sequential alteration of the exact value of the measurand corresponding to each FC. Simple mathematical and logical algorithms are used in this process. Each FC is characterized by several parameters, which may be maintained constant or may vary during simulation. The user has maximum flexibility in selecting values for the parameters within and outside sensor design ranges. These values can be set to change at pre-defined moments, such that permanent and intermittent scenarios can be simulated. Sensor outputs are integrated with the autonomous flight simulation allowing for evaluation and analysis of control laws. Findings The developed sensor model can provide the desirable levels of realism necessary for assessing UAS behavior and dynamic response under sensor failure conditions, as well as evaluating the performance of autonomous flight control laws. Research limitations/implications Due to its generality and flexibility, the proposed sensor model allows detailed insight into the dynamic implications of sensor functionality on the performance of control algorithms. It may open new directions for investigating the synergistic interactions between sensors and control systems and lead to improvements in both areas. Practical implications The implementation of the proposed sensor model provides a valuable and flexible simulation tool that can support system design for safety purposes. Specifically, it can address directly the analysis and design of fault tolerant flight control laws for autonomous UASs. The proposed model can be easily customized to be used for different complex dynamic systems. Originality/value In this paper, information on sensor functionality is fused and organized to develop a general and comprehensive framework for sensor modeling at normal and abnormal operational conditions. The implementation of the proposed approach enhances significantly the capability of the UAS simulation environment to address important issues related to the design of control laws with high performance and desirable robustness for safety purposes.

Impact Mitigation for Buried Structures: Demolition of the New Haven Veterans Memorial Coliseum

2007 ◽  
Author(s):  
Pawel Woelke ◽  
Margaret Tang ◽  
Scott McClennan ◽  
Najib Abboud ◽  
Darren Tennant ◽  
...  
Keyword(s):  
Impact Loading ◽  
Field Testing ◽  
Hazard Evaluation ◽  
New Haven ◽  
Buried Structures ◽  
Analysis And Design ◽  
Numerical Investigations ◽  
Impact Mitigation ◽  
Underground Utilities

We present an overview of the analysis and design of mitigation schemes for buried structures subjected to impact loading, with a focus on the hazard evaluation to underground utilities from the demolition by implosion of the Veterans Memorial Coliseum in New Haven, CT, due to implosion. We discuss analytical and numerical investigations validated by field testing conducted prior to the implosion and leading to the design of the mitigation schemes aimed at protecting the utilities buried under the roadway. The mitigation schemes were successful during the January 2007 implosion of the Veterans Memorial Coliseum.

Shaker Simulation of Random Vibration with a High Kurtosis Value

1997 ◽  
Vol 40 (3) ◽  
pp. 33-43
Author(s):  
A. Steinwolf
Keyword(s):  
Random Vibration ◽  
Fourier Expansion ◽  
Experimental Tests ◽  
Ground Vehicles ◽  
Test Technique ◽  
Power Spectral ◽  
Kurtosis Parameter ◽  
Harmonic Components ◽  
Gaussian Simulation ◽  
Phase Angles

This paper presents a vibration test technique for extending the tails of amplitude probability distribution beyond the Gaussian values as is characteristic for vibration of ground vehicles on a rough road or terrain. The method proposed uses the commonly accepted approach of applying pseudorandom excitation in the form of a Fourier expansion. The procedure described in this paper can be implemented by updating currently available digital vibration controllers. The solution for amplitude domain fitting is based on an analytical expression derived for the kurtosis parameter of the polyharmonic process in terms of amplitudes and phase angles for any number of harmonic components. The results of theoretical analysis are embodied in software subjected to verification in computer and experimental tests. Even with additional kurtosis control, the closeness of the generated and desired spectra is the same as for the Gaussian simulation of power spectral density. Hence, this new technique for amplitude domain matching is not accompanied by the deterioration of ordinary test capabilities in the frequency domain.

scholarly journals Identification of Pedestrian Bridge Dynamic Response trough Field Measurements and Numerical Modelling: Case Studies

2014 ◽  
Vol 44 (2) ◽  
pp. 3-24
Author(s):  
George D. Manolis ◽  
Asimina Athanatopoulou-Kyriakou ◽  
Kosmas D. Dragos ◽  
Argyris Arabatzis ◽  
Alexandros Lavdas ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Numerical Models ◽  
Field Measurements ◽  
Response Spectra ◽  
Structural Data ◽  
Field Testing ◽  
Mode Shapes ◽  
Operational Conditions ◽  
Pedestrian Bridges ◽  
Identification Software

Abstract In this work, we develop a technique for performing system identification in typical pedestrian bridges, using routine equipment at a minimal configuration, and for cases where actual structural data are either sparse or absent. To this end, two pedestrian bridges were examined, modelled and finally instrumented so as to record their dynamic response under operational conditions. More specifically, the bridges were numerically modelled using the finite element method (FEM) according to what was deduced to be their current operating status, while rational assumptions were made with respect to uncertain structural properties. Next, results from field testing using a portable accelerometer unit were processed to produce response spectra that were used as input to a structural identification software program, which in turn yielded the excited natural frequencies and mode shapes of the bridges. The low level of discrepancy is given between analytical and experimental results, the latter are used for a final calibration of the numerical models.

Fatigue failure in random vibration and accelerated testing

2011 ◽  
Vol 18 (8) ◽  
pp. 1199-1206 ◽  
Author(s):  
Ashwini Pothula ◽  
Abhijit Gupta ◽  
Guru R Kathawate
Keyword(s):  
Fatigue Failure ◽  
Random Vibration ◽  
Accelerated Testing

A Practical Response Spectrum Method in Considering the Input Angle of Seismic Excitation

2013 ◽  
Vol 438-439 ◽  
pp. 1506-1509
Author(s):  
Shi Mei Liu ◽  
Ling Tao Xia
Keyword(s):  
Random Vibration ◽  
Response Spectrum ◽  
Power Spectra ◽  
Structural Response ◽  
Seismic Excitation ◽  
Response Spectrum Method ◽  
Displacement Response ◽  
Spectrum Method

To the asymmetric-plan structures, the torsion model is obvious, and the influence of input angle of excitation on structural response is sensitive, so a practical response spectrum method for analyzing the behaviors of this kind of structure is studied. Based on the achievements about the multi-components accelerations power spectra matrix, a rational formula, considering the input angle of excitation, is deduced by using stationary random vibration principle. A practical formula is proposed by introducing displacement response spectrum as equally as to considering the non-stationarity of excitation.

Matrix Analysis and Design Based on Algorithm of Paper Analysis

2014 ◽  
Vol 945-949 ◽  
pp. 2443-2446
Author(s):  
Cai Li Fang ◽  
Ying Du
Keyword(s):  
Teaching Methods ◽  
Paper Analysis ◽  
Matrix Analysis ◽  
Quality Analysis ◽  
Test Paper ◽  
Analysis And Design ◽  
Quality Of Teaching ◽  
Reform Teaching ◽  
The Matrix

Paper analysis is the main content of the educational measurement. Through the statistical analysis of the paper for scientific and objective. It can optimize teaching contents and reform teaching methods and grasp the teaching focus. The analysis also can provide the most direct help to improve the quality of teaching, so it achieves more focused, more fair, impartial assessment test on the knowledge grasping situation. Based on the paper analysis, it put forward the matrix which is used in the algorithm of test paper quality analysis, then the contents from the database will be analysed and the accessing speed is fast and strong pertinence.

BIFURCATION ANALYSIS IN FLEXIBLE ROTOR SUPPORTED BY ACTIVE MAGNETIC BEARING

2001 ◽  
Vol 11 (08) ◽  
pp. 2163-2178 ◽  
Author(s):  
MING-JYI JANG ◽  
CHA'O-KUANG CHEN
Keyword(s):  
Dynamic Behavior ◽  
Bifurcation Analysis ◽  
Coupling Effect ◽  
Power Spectra ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Flexible Rotor ◽  
Factors Affecting ◽  
Operational Conditions ◽  
Amb System

In this paper, bifurcation analysis of the dynamic response of active magnetic bearing (AMB) with flexible rotor is presented, which includes the coupling effect between X-Y directions caused by rotational motion. The AMB systems include many nonlinear factors, such as mass imbalance, mass ratio with disk and journal, material property of shaft, and magnetic forces, etc., and its dynamic behavior are inherently nonlinear. Bifurcation diagrams of shaft journal's center, trajectories, power spectra, and Poincaré maps are used to analyze the dynamic behavior of the AMB system under different operational conditions. The key factors affecting the dynamic characteristics of the AMB system are identified. It will be beneficial to the design of AMB system.

Distortion Energy Based Design of Structures Under Random Excitations

1997 ◽  
Author(s):  
Mu-Tsang Chen
Keyword(s):  
Finite Element ◽  
Stress Responses ◽  
Random Vibration ◽  
Safety Margin ◽  
Von Mises Stress ◽  
Design Strength ◽  
Analysis And Design ◽  
Distortion Energy ◽  
Von Mises ◽  
Energy Based Design

Abstract Random vibration analysis (RVA) of structural systems is a rapidly growing branch of engineering mechanics. The theory of random vibration is central to the analysis and design of structures in a variety of engineering fields. In recent years, RVA in conjunction with finite element methods has been available in several commercial computer-aided-engineering software, such as ANSYS, NASTRAN, etc. The finite element-based RVA is being widely adopted for computing stochastic responses, such as displacements, stresses and strains in terms of statistical quantities, i.e., root-mean-square responses. However, these statistical responses from RVA are limited to Cartesian responses which depend on the coordinate system of use. In structural design, a failure criterion using distortion energy known as the von Mises theory is more appropriate and of interest in this paper. The statistics of von Mises stress can not be obtained in terms of the statistics of Cartesian stresses. Simulation-based von Mises stress responses corresponding to a covariance matrix of Cartesian stresses are used to perform scatter and failure analyses. Based on a sufficient number of stress samples, a probability distribution of von Mises stress response may be obtained. Given a specified design criterion, statistical moments of safety margin as well as a safety index can be computed. In addition, a required design strength corresponding to a desired probability of failure can be provided in this study.

Sign in / Sign up

Export Citation Format

Share Document