Lack-of-fit Tests to Indicate Material Model Improvement or Experimental Data Noise Reduction

Destruction of bodies is accompanied by formation of both large and microscopic fragments. Numerous experiments on the rupture of different samples show that those fragments carry a positive electric charge. his phenomenon is of interest from the viewpoint of its potential application to contactless diagnostics of the early stage of destruction of the elements in various technical devices. However, the lack of understanding the nature of this phenomenon restricts the possibility of its practical applications. Experimental studies were carried out using an apparatus that allowed direct measurements of the total charge of the microparticles formed upon sample rupture and determination of their size and quantity. The results of rupture tests of duralumin and electrical steel showed that the size of microparticles is several tens of microns, the particle charge per particle is on the order of 10–14 C, and their amount can be estimated as the ratio of the cross-sectional area of the sample at the point of discontinuity to the square of the microparticle size. A model of charge formation on the microparticles is developed proceeding from the experimental data and current concept of the electron gas in metals. The model makes it possible to determine the charge of the microparticle using data on the particle size and mechanical and electrical properties of the material. Model estimates of the total charge of particles show order-of-magnitude agreement with the experimental data.

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Exhaust Noise Reduction by Application of Expanded Collecting System in Pneumatic Tools and Machines

Energies ◽

10.3390/en14061592 ◽

2021 ◽

Vol 14 (6) ◽

pp. 1592

Author(s):

Dominik Gryboś ◽

Jacek S. Leszczyński ◽

Dorota Czopek ◽

Jerzy Wiciak

Keyword(s):

Experimental Data ◽

Mathematical Model ◽

Noise Reduction ◽

Sound Pressure ◽

Acoustic Pressure ◽

Pressure Level ◽

Computational Results ◽

Noise Measurements ◽

Exhaust Noise ◽

Collecting System

In this paper, we demonstrate how to reduce the noise level of expanded air from pneumatic tools. Instead of a muffler, we propose the expanded collecting system, where the air expands through the pneumatic tube and expansion collector. We have elaborated a mathematical model which illustrates the dynamics of the air flow, as well as the acoustic pressure at the end of the tube. The computational results were compared with experimental data to check the air dynamics and sound pressure. Moreover, the study presents the methodology of noise measurement generated in a pneumatic screwdriver in a quiet back room and on a window-fitting stand in a production hall. In addition, we have performed noise measurements for the pneumatic screwdriver and the pneumatic screwdriver on an industrial scale. These measurements prove the noise reduction of the pneumatic tools when the expanded collecting system is used. When the expanded collecting system was applied to the screwdriver, the measured Sound Pressure Level (SPL) decreased from 87 to 80 dB(A).

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Empirical L2-distance lack-of-fit tests for Tobit regression models

Journal of Multivariate Analysis ◽

10.1016/j.jmva.2012.04.015 ◽

2012 ◽

Vol 111 ◽

pp. 380-396 ◽

Cited By ~ 2

Author(s):

Weixing Song ◽

Yi Zhang

Keyword(s):

Regression Models ◽

Tobit Regression ◽

Lack Of Fit ◽

Lack Of Fit Tests

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Role of smooth muscle activation in the static and dynamic mechanical characterization of human aortas

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2117232119 ◽

2022 ◽

Vol 119 (3) ◽

pp. e2117232119

Author(s):

Giulio Franchini ◽

Ivan D. Breslavsky ◽

Francesco Giovanniello ◽

Ali Kassab ◽

Gerhard A. Holzapfel ◽

...

Keyword(s):

Experimental Data ◽

Smooth Muscle ◽

Muscle Activation ◽

Mechanical Response ◽

Mechanical Characterization ◽

Viscoelastic Behavior ◽

Material Model ◽

Suitable Material ◽

Dynamic Mechanical

Experimental data and a suitable material model for human aortas with smooth muscle activation are not available in the literature despite the need for developing advanced grafts; the present study closes this gap. Mechanical characterization of human descending thoracic aortas was performed with and without vascular smooth muscle (VSM) activation. Specimens were taken from 13 heart-beating donors. The aortic segments were cooled in Belzer UW solution during transport and tested within a few hours after explantation. VSM activation was achieved through the use of potassium depolarization and noradrenaline as vasoactive agents. In addition to isometric activation experiments, the quasistatic passive and active stress–strain curves were obtained for circumferential and longitudinal strips of the aortic material. This characterization made it possible to create an original mechanical model of the active aortic material that accurately fits the experimental data. The dynamic mechanical characterization was executed using cyclic strain at different frequencies of physiological interest. An initial prestretch, which corresponded to the physiological conditions, was applied before cyclic loading. Dynamic tests made it possible to identify the differences in the viscoelastic behavior of the passive and active tissue. This work illustrates the importance of VSM activation for the static and dynamic mechanical response of human aortas. Most importantly, this study provides material data and a material model for the development of a future generation of active aortic grafts that mimic natural behavior and help regulate blood pressure.

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Data-Driven Lack-of-Fit Tests for General Parametric Models

Springer Series in Statistics - Nonparametric Smoothing and Lack-of-Fit Tests ◽

10.1007/978-1-4757-2722-7_8 ◽

1997 ◽

pp. 208-225

Author(s):

Jeffrey D. Hart

Keyword(s):

Parametric Models ◽

Data Driven ◽

Lack Of Fit ◽

Lack Of Fit Tests

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PROGRESSIVE DAMAGE FAILURE ANALYSIS OF POST-BUCKLED COMPOSITE SINGLE-STRINGER PANEL WITH TEFLON INSERTS

10.12783/asc36/35773 ◽

2021 ◽

Author(s):

VIJAY K. GOYAL ◽

AUSTIN PENNINGTON ◽

JASON ACTION

Keyword(s):

Experimental Data ◽

Composite Structures ◽

Laminated Composites ◽

Compressive Loading ◽

Weight Ratio ◽

High Strength ◽

Material Model ◽

Stiffened Panels ◽

Damage Initiation ◽

Critical Aspects

The high strength-to-weight and stiffness-to-weight ratio materials, such as laminated composites, are advantageous for modern aircraft. Laminated composites with initial flaws are susceptible to delamination under buckling loads. PDA tools help enhance the industry’s understanding of the mechanisms for damage initiation and growth in composite structures while assisting in the design, analysis, and sustainment methods of these composite structures. The global-local modeling approach for the single-stringer post-buckled panel was evaluated through this effort, using Teflon inserts to simulate the defect of damage during manufacturing. This understanding is essential for designing the post-buckled structure, reducing weight while predicting damage initiation location, and addressing a potential design review for future aircraft repairs. In this work, the initial damage was captured with Teflon inserts as the starting configuration; and any reference to the damage initiation refers to any damage beyond the “initial unbonded region.” The effort aims to develop, evaluate, and enhance methods to predict damage initiation and progression and the failure of post-buckled hat-stiffened panels using multiple Abaqus FEA Virtual Crack Closure Technique (VCCT) definitions. Validation of the PDA using the VCCT material model was performed on a large single-stringer panel subjected to compressive loading. The compressive loading of the panel caused the skin to buckle before any damage began to occur locally. In addition, comparisons are made for critical aspects of the damage morphology, such as a growth pattern that included delamination from the skin-stiffener interface to the skin and ply interfaces. When compared against the experimental data produced through the NASA Advanced Composites Project (ACP), the present model captured damage migration from one surface to another, and model validations were ~5% of the experimental data.

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Method and Verification for Material Calibration of the Chaboche Plasticity Model for Multiple Material Directions

10.1115/gt2021-04132 ◽

2021 ◽

Author(s):

Charles R. Krouse ◽

Grant O. Musgrove ◽

Taewoan Kim ◽

Seungmin Lee ◽

Muhyoung Lee ◽

...

Keyword(s):

Experimental Data ◽

Kinematic Hardening ◽

Material Model ◽

Brute Force ◽

Hardening Material ◽

Material Constants ◽

Automated Method ◽

Chaboche Model ◽

Multiple Material ◽

Brute Force Approach

Abstract The Chaboche model is a well-validated non-linear kinematic hardening material model. This material model, like many models, depends on a set of material constants that must be calibrated for it to match the experimental data. Due to the challenge of calibrating these constants, the Chaboche model is often disregarded. The challenge with calibrating the Chaboche constants is that the most reliable method for doing the calibration is a brute force approach, which tests thousands of combinations of constants. Different sampling techniques and optimization schemes can be used to select different combinations of these constants, but ultimately, they all rely on iteratively selecting values and running simulations for each selected set. In the experience of the authors, such brute force methods require roughly 2,500 combinations to be evaluated in order to have confidence that a reasonable solution is found. This process is not efficient. It is time-intensive and labor-intensive. It requires long simulation times, and it requires significant effort to develop the accompanying scripts and algorithms that are used to iterate through combinations of constants and to calculate agreement. A better, more automated method exists for calibrating the Chaboche material constants. In this paper, the authors describe a more efficient, automated method for calibrating Chaboche constants. The method is validated by using it to calibrate Chaboche constants for an IN792 single-crystal material and a CM247 directionally-solidified material. The calibration results using the automated approach were compared to calibration results obtained using a brute force approach. It was determined that the automated method achieves agreeable results that are equivalent to, or supersede, results obtained using the conventional brute force method. After validating the method for cases that only consider a single material orientation, the automated method was extended to multiple off-axis calibrations. The Chaboche model that is available in commercial software, such as ANSYS, will only accept a single set of Chaboche constants for a given temperature. There is no published method for calibrating Chaboche constants that considers multiple material orientations. Therefore, the approach outlined in this paper was extended to include multiple material orientations in a single calibration scheme. The authors concluded that the automated approach can be used to successfully, accurately, and efficiently calibrate multiple material directions. The approach is especially well-suited when off-axis calibration must be considered concomitantly with longitudinal calibration. Overall, the automated Chaboche calibration method yielded results that agreed well with experimental data. Thus, the method can be used with confidence to efficiently and accurately calibrate the Chaboche non-linear kinematic hardening material model.

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Examination of the Convolution Method for Numerical Smoothing and Differentiation of Spectroscopic Data in Theory and in Practice

Applied Spectroscopy ◽

10.1366/0003702834634712 ◽

1983 ◽

Vol 37 (6) ◽

pp. 515-520 ◽

Cited By ~ 36

Author(s):

Peter Gans ◽

J. Bernard Gill

Keyword(s):

Experimental Data ◽

Noise Reduction ◽

Spectroscopic Data ◽

Resolution Enhancement ◽

Signal Distortion ◽

New Criterion ◽

Number Of Passes ◽

New Criteria ◽

Convolution Method ◽

Convolution Function

General expressions have been derived for the effects of convolution on a set of experimental data, from which the noise reduction may be predicted quantitatively. From these, a new criterion is proposed for the choice of convolution function in terms of the degree, number of convolution points, and number of passes of the convolution function through the data. This criterion gives maximal noise reduction with minimal signal distortion, and is particularly applicable in resolution enhancement applications. The new criteria have been tested with experimental data.

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