Development of a standard materials library for mechanistic-empirical fatigue and stiffness evaluation

Abstract Wood has various mechanical properties, so stiffness evaluation is critical for quality management. Using conventional strain gauges constantly is high cost, also challenging to measure precious wood materials due to the use of strong adhesive. This study demonstrates the correlation between light scattering changes inside the wood cell walls and tensile strain. A multifiber-based visible-near-infrared (Vis–NIR) spatially resolved spectroscopy (SRS) system was designed to rapidly and conventiently acquire such light scattering changes. For the preliminary experiment, samples with different thicknesses were measured to evaluate the influence of thickness. The differences in Vis–NIR SRS spectral data diminish with an increase in sample thickness, which suggests that the SRS method can successfully measure the whole strain (i.e., surface and inside) of wood samples. Then, for the primary experiment, 18 wood samples with the same thickness (2 mm) were tested to construct a strain calibration model. The prediction accuracy was characterized by a determination coefficient (R2) of 0.86 with a root mean squared error (RMSE) of 297.89 με for five-fold cross-validation; for test validation, The prediction accuracy was characterized by an R2 of 0.82 and an RMSE of 345.44 με.

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A New Efficient Stiffness Evaluation Method to Improve Accuracy of Hexapods

Volume 5A: 42nd Mechanisms and Robotics Conference ◽

10.1115/detc2018-85986 ◽

2018 ◽

Author(s):

Vinayak J. Kalas ◽

Alain Vissière ◽

Thierry Roux ◽

Olivier Company ◽

Sébastien Krut ◽

...

Keyword(s):

Evaluation Method ◽

Positioning System ◽

Positioning Error ◽

Stiffness Parameter ◽

Positioning Accuracy ◽

Stiffness Evaluation ◽

Improve Accuracy ◽

Identification Technique ◽

Six Degree Of Freedom ◽

Structural Compliance

Structural compliance of hexapods limits their positioning accuracy. Taking a step towards solving this problem, this paper proposes a new efficient method to evaluate the stiffness of hexapods in order to predict and correct their positioning error due to compliance. The proposed method can be used to predict the six degree of freedom deflection of the platform under load. This method uses a simple lumped stiffness parameter model whose parameters can be estimated using the identification technique presented in this paper. An experimental study with micrometer level measurements performed on a hexapod based micro-positioning system is used to assess the efficiency of the presented method.

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Reduced Order Models for Nonlinear Dynamic Analysis With Application to a Fan Blade

Volume 7B: Structures and Dynamics ◽

10.1115/gt2019-90813 ◽

2019 ◽

Author(s):

Mikel Balmaseda ◽

G. Jacquet-Richardet ◽

A. Placzek ◽

D.-M. Tran

Keyword(s):

Normal Modes ◽

Nonlinear Dynamic Analysis ◽

Evaluation Procedure ◽

Reduced Order Models ◽

Reduced Basis ◽

Reduced Order ◽

Stiffness Evaluation ◽

Fan Blade ◽

Proper Orthogonal ◽

Good Agreement

Abstract In the present work reduced order models (ROM) that are independent from the full order finite element models (FOM) considering geometrical non linearities are developed and applied to the dynamic study of a fan. The structure is considered to present nonlinear vibrations around the pre-stressed equilibrium induced by rotation enhancing the classical linearised approach. The reduced nonlinear forces are represented by a polynomial expansion obtained by the Stiffness Evaluation Procedure (STEP) and then corrected by means of a Proper Orthogonal Decomposition (POD) that filters the full order nonlinear forces (StepC ROM). The Linear Normal Modes (LNM) and Craig-Bampton (C-B) type reduced basis are considered here. The latter are parametrised with respect to the rotating velocity. The periodic solutions obtained with the StepC ROM are in good agreement with the solutions of the FOM and are more accurate than the linearised ROM solutions and the STEP ROM. The proposed StepC ROM provides the best compromise between accuracy and time consumption of the ROM.

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Abstract P269: Cardio-Ankle Vascular Index and the Risk of Cardiovascular Outcomes and All-cause Mortality: A Systematic Review

Circulation ◽

10.1161/circ.137.suppl_1.p269 ◽

2018 ◽

Vol 137 (suppl_1) ◽

Author(s):

Kunihiro Matsushita ◽

Ning Ding ◽

Esther Kim

Keyword(s):

Systematic Review ◽

Arterial Stiffness ◽

Cohort Studies ◽

Statistical Significance ◽

Risk Of Bias ◽

Cvd Risk ◽

Cross Sectional ◽

Stiffness Evaluation ◽

All Cause Mortality ◽

Cross Sectional Studies

Introduction: Arterial stiffness is widely used as an index of arteriosclerosis and is associated with cardiovascular disease (CVD). Recently, cardio-ankle vascular index (CAVI) was developed as a measurement of arterial stiffness that is independent of blood pressure at the time of arterial stiffness evaluation. The associations of CAVI with CVD events and all-cause mortality have not been extensively assessed. We therefore systematically reviewed the studies reporting CAVI and relevant outcomes. Methods: We searched for both prospective and cross-sectional studies using MEDLINE, Embase, and Cochrane from inception to April 11, 2017. Two independent reviewers screened the retrieved papers, extracted relevant data and assessed the risk of bias. Any discrepancy was solved by discussion or a third reviewer. Heterogeneity among studies was assessed using the I 2 statistic. We pooled the results of studies that were sufficiently homogeneous. Results: Among 1,519 records, we identified 9 cohort studies (n=5,292) and 17 cross-sectional eligible studies (n=7,309). All 9 cohort studies reported the outcome of composited CVD (498 cases), but the categorization/modeling of CAVI was not consistent across those studies. The pooled hazard ratio (HR) of CVD for the highest vs. lowest CAVI category in 3 studies was borderline significant (pooled HR=1.34 [0.95, 1.87], p=0.092) (I 2 = 25.2%, p=0.263). For 3 studies examining the continuous association between CAVI and CVD, 1standard deviation (SD) increment of CAVI was significantly associated with CVD risk (pooled HR=1.22 [1.03, 1.45], p=0.023) (I 2 = 27.1%, p=0.253). Only 3 cohort studies investigated CAVI and all-cause mortality, and none of them reported a significant association. All 17 cross-sectional studies reported higher CAVI values in patients with CVD compared to those without CVD, with statistical significance in most studies. Conclusions: CAVI was generally higher in patients with CVD compared to their counterparts. In terms of the prospective prognostic value of CAVI, we found a limited number of studies, but they indicated a modest association between CAVI and CVD risk. Our systematic review highlighted the need for large prospective studies to assess the usefulness of CAVI as a predictor of CVD and mortality.

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