Semi-analytical prediction and experimental evaluation of material damping in wood panels

Holzforschung ◽  
2013 ◽  
Vol 67 (3) ◽  
pp. 333-343 ◽  
Author(s):  
Nathalie Labonnote ◽  
Anders Rønnquist ◽  
Kjell Arne Malo
Keyword(s):  
Material Properties ◽  
Strain Energy ◽  
Goodness Of Fit ◽  
Prediction Models ◽  
Mode Shapes ◽  
Analytical Prediction ◽  
Material Damping ◽  
Intrinsic Properties ◽  
Laminated Veneer Lumber ◽  
Loss Factors

Abstract A semi-analytical prediction model of material damping in timber panels has been developed. The approach is derived from the strain energy method and the input is based on loss factors, which are intrinsic properties of the considered materials, together with other material properties and mode shape integrals, whose calculation can easily be implemented in most finite element codes. Experimental damping evaluations of particleboards, oriented strand boards, and structural laminated veneer lumber panels are presented. Fair goodness of fit between the experimental results and the prediction models – relying only on the loss factors and the mode shapes – reveals an efficient approach for the prediction of material damping in timber panels including all boundary conditions.

LOW CYCLE FATIGUE BEHAVIOR AND LIFE PREDICTION OF A CAST COBALT-BASED SUPERALLOY

2012 ◽  
Vol 06 ◽  
pp. 251-256
Author(s):  
HO-YOUNG YANG ◽  
JAE-HOON KIM ◽  
KEUN-BONG YOO
Keyword(s):  
Fatigue Life ◽  
Strain Energy ◽  
Life Prediction ◽  
Prediction Models ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Total Strain ◽  
Cycle Fatigue ◽  
Total Strain Range ◽  
Different Temperatures

Co -base superalloys have been applied in the stationary components of gas turbine owing to their excellent high temperature properties. Low cycle fatigue data on ECY-768 reported in a companion paper were used to evaluate fatigue life prediction models. In this study, low cycle fatigue tests are performed as the variables of total strain range and temperatures. The relations between plastic and total strain energy densities and number of cycles to failure are examined in order to predict the low cycle fatigue life of Cobalt-based super alloy at different temperatures. The fatigue lives is evaluated using predicted by Coffin-Manson method and strain energy methods is compared with the measured fatigue lives at different temperatures. The microstructure observing was performed for how affect able to low-cycle fatigue life by increasing the temperature.

scholarly journals Application of feed forward and recurrent neural networks in simulation of left ventricular mechanics

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yaghoub Dabiri ◽  
Alex Van der Velden ◽  
Kevin L. Sack ◽  
Jenny S. Choy ◽  
Julius M. Guccione ◽  
...  
Keyword(s):  
Real Time ◽  
Material Properties ◽  
In Silico ◽  
Prediction Models ◽  
Heart Function ◽  
Active Material ◽  
Experimental Studies ◽  
Left Ventricular ◽  
Feed Forward ◽  
Ventricular Mechanics

AbstractAn understanding of left ventricle (LV) mechanics is fundamental for designing better preventive, diagnostic, and treatment strategies for improved heart function. Because of the costs of clinical and experimental studies to treat and understand heart function, respectively, in-silico models play an important role. Finite element (FE) models, which have been used to create in-silico LV models for different cardiac health and disease conditions, as well as cardiac device design, are time-consuming and require powerful computational resources, which limits their use when real-time results are needed. As an alternative, we sought to use deep learning (DL) for LV in-silico modeling. We used 80 four-chamber heart FE models for feed forward, as well as recurrent neural network (RNN) with long short-term memory (LSTM) models for LV pressure and volume. We used 120 LV-only FE models for training LV stress predictions. The active material properties of the myocardium and time were features for the LV pressure and volume training, and passive material properties and element centroid coordinates were features of the LV stress prediction models. For six test FE models, the DL error for LV volume was 1.599 ± 1.227 ml, and the error for pressure was 1.257 ± 0.488 mmHg; for 20 LV FE test examples, the mean absolute errors were, respectively, 0.179 ± 0.050 for myofiber, 0.049 ± 0.017 for cross-fiber, and 0.039 ± 0.011 kPa for shear stress. After training, the DL runtime was in the order of seconds whereas equivalent FE runtime was in the order of several hours (pressure and volume) or 20 min (stress). We conclude that using DL, LV in-silico simulations can be provided for applications requiring real-time results.

Analysis of Modal Parameters of Adhesively Bonded Double-Strap Joints by the Modal Strain Energy Method

1993 ◽  
Author(s):  
Mohan D. Rao ◽  
Krishna M. Gorrepati
Keyword(s):  
Strain Energy ◽  
Natural Frequencies ◽  
Structural Parameters ◽  
Flexural Vibration ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Adhesively Bonded ◽  
Modal Strain Energy ◽  
Joint System ◽  
Damping Material

Abstract This paper presents the analysis of modal parameters (natural frequencies, damping ratios and mode shapes) of a simply supported beam with adhesively bonded double-strap joint by the finite-element based Modal Strain Energy (MSE) method using ANSYS 4.4A software. The results obtained by the MSE method are compared with closed form analytical solutions previously obtained by the first author for flexural vibration of the same system. Good agreement has been obtained between the two methods for both the natural frequencies and system loss factors. The effects of structural parameters and material properties of the adhesive on the modal properties of the joint system are also studied which are useful in the design of the joint system for passive vibration and noise control. In order to evaluate the MSE and analytical results, some experiments were conducted using aluminum double-strap joint with 3M ISD112 damping material. The experimental results agreed well with both analytical and MSE results indicating the validity of both analytical and MSE methods. Finally, a comparative study has been conducted using various commercially available damping materials to evaluate their relative merits for use in the design of these joints.

scholarly journals Looseness localization for bolted joints using Bayesian operational modal analysis and modal strain energy

2018 ◽  
Vol 10 (11) ◽  
pp. 168781401880869 ◽  
Author(s):  
Yu-Jia Hu ◽  
Wei-Gong Guo ◽  
Cheng Jiang ◽  
Yun-Lai Zhou ◽  
Weidong Zhu
Keyword(s):  
Modal Analysis ◽  
Strain Energy ◽  
Damage Index ◽  
Operational Modal Analysis ◽  
Modal Identification ◽  
Bolted Joints ◽  
Mode Shapes ◽  
Bolted Connections ◽  
Modal Strain Energy ◽  
Beam Structures

Bayesian operational modal analysis and modal strain energy are employed for determining the damage and looseness of bolted joints in beam structures under ambient excitation. With this ambient modal identification technique, mode shapes of a damaged beam structure with loosened bolted connections are obtained based on Bayesian theory. Then, the corresponding modal strain energy can be calculated based on the mode shapes. The modal strain energy of the structure with loosened bolted connections is compared with the theoretical one without bolted joints to define a damage index. This approach uses vibration-based nondestructive testing of locations and looseness of bolted joints in beam structures with different boundary conditions by first obtaining modal parameters from ambient vibration data. The damage index is then used to identify locations and looseness of bolted joints in beam structures with single or multiple bolted joints. Furthermore, the comparison between damage indexes due to different looseness levels of bolted connections demonstrates a qualitatively proportional relationship.

scholarly journals The Effect of Inner Reinforcing Cores on Natural Frequencies of the Lathe Tool Body

2013 ◽  
Vol 21 (Special-Issue) ◽  
pp. 186-192 ◽  
Author(s):  
Ladislav Rolník ◽  
Milan Naď
Keyword(s):  
Material Properties ◽  
Machine Tools ◽  
Structural Modification ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Geometrical Parameters ◽  
Structural Modifications ◽  
Modal Properties ◽  
Machine Productivity ◽  
Lathe Tool

Abstract The contribution is mainly focused on research and development of structural modification of machine tools, lathes in particular. The main aim of the modification is to change the modal properties (mode shapes, natural frequencies) of the lathe tool. The main objective of the contribution will be to formulate, mathematical analyse and evaluate the proposed methods and procedures for structural modifications of the tool, represented by beam body. A modification of modal properties by insertion of beam cores into beam body is studied in this paper. In this paper, the effect of material properties and geometrical parameters of reinforcing cores on natural frequencies of beam body is presented. The implementation will bring benefit on machine productivity, decreasing the machine tool wear and in many cases it will lead to better conditions in the cutting process.

scholarly journals The role of triiodothyronine (T3) and T3/free thyroxine (fT4) on glucose metabolism during pregnancy: the Ma’anshan Birth Cohort Study

2021 ◽  
Author(s):  
Beibei Zhu ◽  
Yan Han ◽  
Fen Deng ◽  
Kun Huang ◽  
Shuangqin Yan ◽  
...  
Keyword(s):  
Cohort Study ◽  
Glucose Metabolism ◽  
Birth Cohort ◽  
Goodness Of Fit ◽  
Prediction Models ◽  
First Trimester ◽  
Repeated Measurements ◽  
Free Thyroxine ◽  
Birth Cohort Study ◽  
Goodness Of Fit Test

Objectives: Compared with other thyroid markers, fewer studies explored the associations between triiodothyronine (T3) and T3/free thyroxine (fT4) and glucose abnormality during pregnancy. Thus, we aimed to: (1) examine the associations of T3 and T3/fT4 with glucose metabolism indicators; and (2) evaluate, in the first trimester, the performance of the two markers as predictors of gestational diabetes mellitus (GDM) risk. Methods: Longitudinal data from 2723 individuals, consisting of three repeated measurements of T3 and fT4, from the Man’anshan birth cohort study (MABC), China, were analyzed using a time-specific generalized estimating equation (GEE). The receiver operating characteristic curve (ROC) - area under the curve (AUC) and Hosmer-Lemeshow goodness of fit test were used to assess the discrimination and calibration of prediction models. Results: T3 and T3/fT4 presented stable associations with the level of fasting glucose, glucose at 1h/2h across pregnancy. T3 and T3/fT4 in both the first and second trimesters were positively associated with the risk of GDM, with the larger magnitude of association observed in the second trimester (Odds ratio (OR) = 2.50, 95%CI = 1.95, 3.21 for T3; OR = 1.09, 95%CI = 1.07, 1.12 for T3/fT4). T3 ((AUC) = 0.726, 95%CI = 0.698, 0.754) and T3/fT4 (AUC = 0.724, 95%CI = 0.696, 0.753) in the first trimester could improve the performance of the predicting model; however, the overall performance is not good. Conclusion: Significant and stable associations of T3, T3/fT4 and glucose metabolism indicators were documented. Both T3 and T3/fT4 improve the performance of the GDM predictive model.

Blade Damage Forecast Research Based on Support Vector Machine

2012 ◽  
Vol 588-589 ◽  
pp. 278-282
Author(s):  
Zhi Wei Ma ◽  
Yu Xiu Xu ◽  
Shi Rong Xing
Keyword(s):  
Support Vector Machine ◽  
Strain Energy ◽  
Energy Change ◽  
Mode Shapes ◽  
Support Vector ◽  
Change Rate ◽  
Wind Turbine System ◽  
Mass Eccentricity ◽  
Damage States ◽  
Research Show

By doing modal analysis of the whole wind turbine system, we can get the first twenty orders natural frequencies and corresponding mode shapes, By analyzing the dynamic characteristics of the blade, the weakness points of blade were fund. Under rotor rotating excitation in the normal state, mass eccentricity states and stiffness damage states of blade, the strain energy change rates (SECR) of nacelle are obtained. While based on the SECR of nacelle, the methods of strain energy change rate and support vector machine are introduced to indentify locate the mass eccentricity and stiffness damages of blade. The research show that mass eccentricity and stiffness damages at different location and in different degree can be efficiency identified and forecasted by means of support vector machine classification method.

On Free Vibrations at Temperature-Dependent Material Properties and Transient Temperature Fields

1972 ◽  
Vol 39 (3) ◽  
pp. 723-726 ◽  
Author(s):  
U. Olsson
Keyword(s):  
Temperature Dependence ◽  
Analytical Solutions ◽  
Material Properties ◽  
Free Vibrations ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Material Damping ◽  
Temperature Dependent ◽  
Temperature Variations ◽  
Damping Parameter

The influence of the temperature-dependence of the material properties on the free vibrations of transiently heated structures is investigated. Analytical solutions are given for linear, exponential, and harmonic temperature variations when the material damping parameter, Poisson’s ratio, and Young’s modulus depend on the temperature.

Maximizing the Fundamental Natural Frequency of Triangular Composite Plates

1996 ◽  
Vol 118 (2) ◽  
pp. 141-146 ◽  
Author(s):  
S. Abrate
Keyword(s):  
Natural Frequency ◽  
Material Properties ◽  
Composite Structures ◽  
Natural Frequencies ◽  
Ritz Method ◽  
Laminated Composite ◽  
Composite Plates ◽  
Mode Shapes ◽  
Fundamental Natural Frequency ◽  
Wide Range

While many advances were made in the analysis of composite structures, it is generally recognized that the design of composite structures must be studied further in order to take full advantage of the mechanical properties of these materials. This study is concerned with maximizing the fundamental natural frequency of triangular, symmetrically laminated composite plates. The natural frequencies and mode shapes of composite plates of general triangular planform are determined using the Rayleigh-Ritz method. The plate constitutive equations are written in terms of stiffness invariants and nondimensional lamination parameters. Point supports are introduced in the formulation using the method of Lagrange multipliers. This formulation allows studying the free vibration of a wide range of triangular composite plates with any support condition along the edges and point supports. The boundary conditions are enforced at a number of points along the boundary. The effects of geometry, material properties and lamination on the natural frequencies of the plate are investigated. With this stiffness invariant formulation, the effects of lamination are described by a finite number of parameters regardless of the number of plies in the laminate. We then determine the lay-up that will maximize the fundamental natural frequency of the plate. It is shown that the optimum design is relatively insensitive to the material properties for the commonly used material systems. Results are presented for several cases.

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