An Empirical Method for Dynamic Stress Prediction in Turbomachinery

2009 ◽  
Author(s):  
Timothy C. Allison ◽  
J. Jeffrey Moore
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Dynamic Stress ◽  
Axial Compressor ◽  
Element Model ◽  
Identification Problem ◽  
Empirical Method ◽  
Impulse Response Functions ◽  
Data Set ◽  
Filter Noise

The effectiveness of fatigue and life prediction methods depends heavily on accurate knowledge of the static and dynamic stresses acting on a structure. Although stress fields may be calculated from the finite element shape functions if a finite element model is constructed and analyzed, in many cases the cost of constructing and analyzing a finite element model is prohibitive. Modeling errors can severely affect the accuracy of stress simulations. This paper presents an empirical method for predicting a transient dynamic stress response of a structure based on measured load and strain data that can be collected during vibration tests. The method applies the proper orthogonal decomposition to a measured data set to filter noise and reduce the size of the identification problem and then employs a matrix deconvolution technique to decouple and identify the reduced coordinate impulse response functions for the structure. The method is applied to simulation data from an axial compressor blade model and produces accurate stress predictions compared to finite element results.

The Application of AAR Load Spectrums in the Fatige Assessment for G70 Tank Carbody

2013 ◽  
Vol 690-693 ◽  
pp. 1960-1965 ◽  
Author(s):  
Sheng Qu ◽  
Ping Bo Wu ◽  
Zhuan Hua Liu
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Finite Element Model ◽  
Dynamic Stress ◽  
Element Model ◽  
Fatigue Analysis ◽  
Static Method ◽  
Analysis Method ◽  
Major Class ◽  
Calculated Stress

G70 Tank car uesd for transportation on liquidsliquids of gas and bulck goods in form of powder,is one of the major class of Chinese railroad freight cars.And the tank car makes about 18% of the toatal amount of freight cars. In this stduy, the carbdoy finite element model of tank car was constructed,and calculated stress of carbody both empty car and fully loaded car,then get the results of key postsitions. According to the AAR load spectrums on the part of the tank car,translated the results into dynamic stress through the quasi-static method. Calculated the damage of carbody with the fatigue analysis method provied in AAR, compared the fatigue life under various comonent.

scholarly journals Total Knee Replacement: Subject-Specific Modeling, Finite Element Analysis, and Evaluation of Dynamic Activities

2021 ◽  
Vol 9 ◽  
Author(s):  
Iliana Loi ◽  
Dimitar Stanev ◽  
Konstantinos Moustakas
Keyword(s):  
Finite Element ◽  
Total Knee Replacement ◽  
Finite Element Model ◽  
Knee Replacement ◽  
Element Model ◽  
Grand Challenge ◽  
Data Set ◽  
Subject Specific ◽  
Total Knee ◽  
Contact Pressures

This study presents a semi-automatic framework to create subject-specific total knee replacement finite element models, which can be used to analyze locomotion patterns and evaluate knee dynamics. In recent years, much scientific attention was attracted to pre-clinical optimization of customized total knee replacement operations through computational modeling to minimize post-operational adverse effects. However, the time-consuming and laborious process of developing a subject-specific finite element model poses an obstacle to the latter. One of this work's main goals is to automate the finite element model development process, which speeds up the proposed framework and makes it viable for practical applications. This pipeline's reliability was ratified by developing and validating a subject-specific total knee replacement model based on the 6th SimTK Grand Challenge data set. The model was validated by analyzing contact pressures on the tibial insert in relation to the patient's gait and analysis of tibial contact forces, which were found to be in accordance with the ones provided by the Grand Challenge data set. Subsequently, a sensitivity analysis was carried out to assess the influence of modeling choices on tibial insert's contact pressures and determine possible uncertainties on the models produced by the framework. Parameters, such as the position of ligament origin points, ligament stiffness, reference strain, and implant-bone alignment were used for the sensitivity study. Notably, it was found that changes in the alignment of the femoral component in reference to the knee bones significantly affect the load distribution at the tibiofemoral joint, with an increase of 206.48% to be observed at contact pressures during 5° internal rotation. Overall, the models produced by this pipeline can be further used to optimize and personalize surgery by evaluating the best surgical parameters in a simulated manner before the actual surgery.

scholarly journals Identification of crack-like defect and investigation of stress concentration in coated bar

2019 ◽  
pp. 165-174 ◽  
Author(s):  
B V Sobol ◽  
A N Soloviev ◽  
E V Rashidova ◽  
P V Vasiliev
Keyword(s):  
Neural Network ◽  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Learning Technologies ◽  
Internal Crack ◽  
Cauchy Kernel ◽  
Physical Parameters ◽  
Geometrical Parameters ◽  
Data Set

The first part of this work is devoted to the location of defects in a coated bar and the identification of their geometrical parameters. Using the methods of finite element modeling, ultrasonic non-destructive testing and machine learning technologies (artificial neural networks), the inverse problem of mechanics has been solved. A finite element model of ultrasonic wave propagation in a bar with a coating and an internal defect is constructed. Compared with previous works, the model used PML (Perfectly Matched Layer) structures, which suppress multiple reflections of the probe ultrasound pulse inside the bar and prevent signal noise. Based on the conducted numerical calculations of the finite element model, a data set was constructed. It contains the geometrical parameters of the defect and the corresponding amplitude-time characteristic of the ultrasonic signal. The architecture of a direct propagation neural network has been developed. The neural network was trained on the basis of previously processed data. As a result, on the basis of ultrasound data obtained from the outer surface of the bar, it is possible to restore the values of such defect parameters as depth, length and thickness. At the second stage, analytical-numerical technology for studying the stress intensity factor (SIF) at the crack tip is described using the example of the problem of a longitudinal internal crack of finite length located in an elastic strip reinforced with a thin flexible coating. The solution to this problem is based on the method of integral transformations, which made it possible to reduce it to a singular integral equation of the first kind with a Cauchy kernel, which is solved by the collocation method in the form of expansion in Chebyshev polynomials with a factor that explicitly takes into account a feature in the vicinity of the crack vertices. The latter allows you to directly find the SIF and evaluate the effect on it of various combinations of geometric and physical parameters of the problem.

A Frequency-Domain Screening Methodology for Flow-Induced Vibration in Piping

2021 ◽  
Author(s):  
Juan P. Pontaza
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Frequency Domain ◽  
Fatigue Damage ◽  
Dynamic Stress ◽  
Element Model ◽  
Tier 2 ◽  
Flow Induced Vibration ◽  
Tier 1 ◽  
Tier 3

Abstract A three-tiered approach is advocated to assess the level of flow-induced vibration (FIV) threat to process piping due to internal flow. The first-tier assessment is a high-level design check on the possibility of FIV. The tier-1 screening does not provide a framework for the direct estimation of vibration levels, stress, or fatigue damage. The third-tier assessment is termed a comprehensive screening and relies on computational fluid dynamics (CFD) to predict the flow-induced forcing, coupled to a structural finite element model to obtain the response of the piping (vibration levels and stresses), from which an estimate of fatigue damage at critical locations is computed. The tier-3 screening may be computationally intense (e.g., for multiphase flow) and is generally not fast to perform. This paper presents a second-tier assessment (intermediate between the tier-1 and tier-3 screenings), where the flow-induced loading is represented by power spectral density (PSD) curves, which are inputs to a structural finite element model of the piping. The structural finite element analysis (FEA) is performed in the frequency domain, implying fast turnaround time requiring short computing time. The FEA yields a prediction of vibration levels and dynamic stress, from which the sought-after estimates of fatigue damage are computed. The outcome of a tier-2 screening for vibrating piping in a metering skid is presented and the predictions compared against field measurements using accelerometer data (vibration levels) and strain gauge data (dynamic stress). A tier-2 screening is performed for a subsea water injection jumper and the results compared against those of a tier-3 screening.

Finite Element Simulation of Tire-Rim Interface

1989 ◽  
Vol 17 (4) ◽  
pp. 305-325 ◽  
Author(s):  
N. T. Tseng ◽  
R. G. Pelle ◽  
J. P. Chang
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Finite Element Simulation ◽  
Contact Pressure ◽  
Element Model ◽  
Experimental Measurements ◽  
Inflation Pressure ◽  
Interference Fit ◽  
Element Simulation ◽  
Rubber Composite

Abstract A finite element model was developed to simulate the tire-rim interface. Elastomers were modeled by nonlinear incompressible elements, whereas plies were simulated by cord-rubber composite elements. Gap elements were used to simulate the opening between tire and rim at zero inflation pressure. This opening closed when the inflation pressure was increased gradually. The predicted distribution of contact pressure at the tire-rim interface agreed very well with the available experimental measurements. Several variations of the tire-rim interference fit were analyzed.

Torsional Analysis of a Steel Cord-Rubber Tire Belt Structure

1996 ◽  
Vol 24 (4) ◽  
pp. 339-348 ◽  
Author(s):  
R. M. V. Pidaparti
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Composite Structures ◽  
Three Dimensional ◽  
Element Model ◽  
Torsional Stiffness ◽  
Element Analysis ◽  
Rubber Belt ◽  
Steel Cord ◽  
Torsional Analysis

Abstract A three-dimensional (3D) beam finite element model was developed to investigate the torsional stiffness of a twisted steel-reinforced cord-rubber belt structure. The present 3D beam element takes into account the coupled extension, bending, and twisting deformations characteristic of the complex behavior of cord-rubber composite structures. The extension-twisting coupling due to the twisted nature of the cords was also considered in the finite element model. The results of torsional stiffness obtained from the finite element analysis for twisted cords and the two-ply steel cord-rubber belt structure are compared to the experimental data and other alternate solutions available in the literature. The effects of cord orientation, anisotropy, and rubber core surrounding the twisted cords on the torsional stiffness properties are presented and discussed.

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