Further investigation on the definition of the representative strain in conical indentation

2006 ◽  
Vol 21 (7) ◽  
pp. 1810-1821 ◽  
Author(s):  
Yanping Cao ◽  
Norbert Huber
Keyword(s):  
Material Properties ◽  
Limited Range ◽  
Representative Strain ◽  
Plastic Materials ◽  
Acta Mater ◽  
Engineering Materials ◽  
Definition Of ◽  
High Level ◽  
Highly Elastic Materials ◽  
Conical Indentation

Further investigation on the definition of the representative strain in conical indentation was performed in this work. In particular, the representative strains proposed in the work of Cao et al. [J. Mater. Res.20, 1194 (2005)] and Ogasawara et al. [J. Mater. Res.20, 2225 (2005)] were discussed in detail. For the method using the energy-based representative strain [Cao et al., J. Mater. Res.20, 1194 (2005)], it is shown that it can be extended to a wider range of material properties (from nearly fully plastic materials to highly elastic materials). For the stress-state-based definition of the representative strain, we found, in contrast with the results reported in the work of Ogasawara et al. [J. Mater. Res.20, 2225 (2005)], that similar to the constant representative strain reported by Dao et al. [Acta Mater.49, 3899 (2001)], it works well only for a limited range of engineering materials. Based on this premise, novel definitions of the representative strain, which can lead to a one-to-one relationship with high level of accuracy between the reduced Young's modulus, the indentation loading curvature, and the representative stress are further presented. Detailed numerical analysis performed on nine kinds of engineering materials verified the effectiveness of the proposed representative strains and corresponding dimensionless functions. Experimental verification using the data for the ultrafine crystalline Ni further showed that the results reported in this paper have the potential to be applied in practice.

Representative Strain of Indentation Analysis

2005 ◽  
Vol 20 (8) ◽  
pp. 2225-2234 ◽  
Author(s):  
Nagahisa Ogasawara ◽  
Norimasa Chiba ◽  
Xi Chen
Keyword(s):  
Mechanical Properties ◽  
Stress State ◽  
Work Hardening ◽  
Biaxial Loading ◽  
Representative Strain ◽  
Indentation Analysis ◽  
Reverse Analysis ◽  
Engineering Materials ◽  
Definition Of ◽  
New Formulation

Indentation analysis based on the concept of representative strain offers an effective way of obtaining mechanical properties, especially work-hardening behavior of metals, from reverse analysis of indentation load–displacement data, and does not require measuring of the projected contact area. The definition of representative strain adopted in previous studies [e.g., Dao et al., Acta Mater.49, 3899 (2001)] has a weak physical basis, and it works only for a limited range in some sense of engineering materials. A new indentation stress-state based formulation of representation is proposed in this study, which is defined as the plastic strain during equi-biaxial loading. Extensive numerical analysis based on the finite element method has shown that with the new formulation of representative strain and representative stress, the critical normalized relationship between load and material parameters is essentially independent of the work-hardening exponent for all engineering materials, and the results also hold for three distinct indenter angles. The new technique is used for four materials with mechanical properties outside the applicable regime of previous studies, and the reverse analysis has validated the present analysis. The new formulation based on indentation stress-state based definition of representative strain has the potential to quickly and effectively measure the mechanical properties of essentially all engineering materials as long as their constitutive behavior can be approximated into a power-law form.

An energy-based method to extract plastic properties of metal materials from conical indentation tests

2005 ◽  
Vol 20 (5) ◽  
pp. 1194-1206 ◽  
Author(s):  
Yan Ping Cao ◽  
Xiu Qing Qian ◽  
Jian Lu ◽  
Zhen Han Yao
Keyword(s):  
Stable Solution ◽  
Strain Hardening Exponent ◽  
Simple Method ◽  
Plastic Properties ◽  
Representative Strain ◽  
Plastic Materials ◽  
Wide Range ◽  
Indentation Tests ◽  
Elastoplastic Materials ◽  
Conical Indentation

Based on dimensional analysis and finite element computations, an energy-based representative strain for conical indentation in elastoplastic materials has been proposed to establish an explicitly one-to-one relationship between the representative stress σr, the indentation loading curvature C, and the ratio of reversible work We to total work Wt performed by the indenter, i.e., σr/C = F0(We/Wt), where σr is the flow stress corresponding to the representative strain. The relationship provides a very simple method to evaluate the representative stress σr from the three directly measurable quantities We, Wt, and C. Numerical examples and further theoretical analysis reveal that a unique, stable solution can be obtained from the present method for a wide range of material properties, including both highly plastic materials (e.g., Ni for which E/σy = 1070) and highly elastic materials (e.g., materials for which E/σy = 25 and n = 0.5), using indenters with different tip apex angles. Based on the representative strains and stresses given by two indenters with different tip apex angles, e.g., (σr,80, ϵr,80) and (σr,65, ϵr,65), the plastic properties of materials, i.e., the yield strength σy and strain hardening exponent n can be further determined.

Europe

2020 ◽  
pp. 649-666
Author(s):  
Andrea Renda
Keyword(s):  
Artificial Intelligence ◽  
Digital Technology ◽  
Policy Framework ◽  
Expert Group ◽  
Ethical Guidelines ◽  
Ethical Implications ◽  
Strong Focus ◽  
Ethics Guidelines ◽  
Definition Of ◽  
High Level

This chapter assesses Europe’s efforts in developing a full-fledged strategy on the human and ethical implications of artificial intelligence (AI). The strong focus on ethics in the European Union’s AI strategy should be seen in the context of an overall strategy that aims at protecting citizens and civil society from abuses of digital technology but also as part of a competitiveness-oriented strategy aimed at raising the standards for access to Europe’s wealthy Single Market. In this context, one of the most peculiar steps in the European Union’s strategy was the creation of an independent High-Level Expert Group on AI (AI HLEG), accompanied by the launch of an AI Alliance, which quickly attracted several hundred participants. The AI HLEG, a multistakeholder group including fifty-two experts, was tasked with the definition of Ethics Guidelines as well as with the formulation of “Policy and Investment Recommendations.” With the advice of the AI HLEG, the European Commission put forward ethical guidelines for Trustworthy AI—which are now paving the way for a comprehensive, risk-based policy framework.

scholarly journals Shape Sensing of a Complex Aeronautical Structure with Inverse Finite Element Method

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1388
Author(s):  
Daniele Oboe ◽  
Luca Colombo ◽  
Claudio Sbarufatti ◽  
Marco Giglio
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Boundary Conditions ◽  
Strain Field ◽  
Element Analysis ◽  
Inverse Finite Element Method ◽  
Shape Sensing ◽  
Definition Of ◽  
High Level ◽  
Element Method

The inverse Finite Element Method (iFEM) is receiving more attention for shape sensing due to its independence from the material properties and the external load. However, a proper definition of the model geometry with its boundary conditions is required, together with the acquisition of the structure’s strain field with optimized sensor networks. The iFEM model definition is not trivial in the case of complex structures, in particular, if sensors are not applied on the whole structure allowing just a partial definition of the input strain field. To overcome this issue, this research proposes a simplified iFEM model in which the geometrical complexity is reduced and boundary conditions are tuned with the superimposition of the effects to behave as the real structure. The procedure is assessed for a complex aeronautical structure, where the reference displacement field is first computed in a numerical framework with input strains coming from a direct finite element analysis, confirming the effectiveness of the iFEM based on a simplified geometry. Finally, the model is fed with experimentally acquired strain measurements and the performance of the method is assessed in presence of a high level of uncertainty.

scholarly journals A fatal toxic shock-like syndrome post COVID-19 infection in a child

2021 ◽  
Vol 47 (1) ◽  
Author(s):  
Houda Ajmi ◽  
Wissem Besghaier ◽  
Wafa Kallala ◽  
Abdelhalim Trabelsi ◽  
Saoussan Abroug
Keyword(s):  
Ejection Fraction ◽  
Pediatric Intensive Care ◽  
Fresh Frozen Plasma ◽  
Multiple Organ ◽  
Clinical Feature ◽  
Fresh Frozen ◽  
Life Threatening ◽  
High Doses ◽  
Definition Of ◽  
High Level

Abstract Background Children affected by Coronavirus disease 2019 (COVID-19) showed various manifestations. Some of them were severe cases presenting with multi-system inflammatory syndrome (MIS-C) causing multiple organ dysfunction. Case presentation We report the case of a 12-year-old girl with recent COVID-19 infection who presented with persistent fever, abdominal pain and other symptoms that meet the definition of MIS-C. She had lymphopenia and a high level of inflammatory markers. She was admitted to pediatric intensive care unit since she rapidly developed refractory catecholamine-resistant shock with multiple organ failure. Echocardiography showed a small pericardial effusion with a normal ejection fraction (Ejection Fraction = 60%) and no valvular or coronary lesions. The child showed no signs of improvement even after receiving intravenous immunoglobulin, fresh frozen plasma, high doses of Vasopressors and corticosteroid. His outcome was fatal. Conclusion Pediatric patients affected by the new COVID-19 related syndrome may show severe life-threatening conditions similar to Kawasaki disease shock syndrome. Hypotension in these patients results from heart failure and the decreased cardiac output. We report a new severe clinical feature of SARS-CoV-2 infection in children in whom hypotension was the result of refractory vasoplegia.

Finite Thickness Influence on Spherical and Conical Indentation on Viscoelastic Thin Polymer Film

2005 ◽  
Vol 127 (1) ◽  
pp. 33-37 ◽  
Author(s):  
V. Gonda ◽  
J. den Toonder ◽  
J. Beijer ◽  
G. Q. Zhang ◽  
L. J. Ernst
Keyword(s):  
Polymer Film ◽  
Material Properties ◽  
Finite Thickness ◽  
Thin Polymer Film ◽  
Spherical Indentation ◽  
Infinite Plane ◽  
Precise Knowledge ◽  
Thin Polymer ◽  
Measurement Results ◽  
Conical Indentation

The thermo-mechanical integration of polymer films requires a precise knowledge of material properties. Nanoindentation is a widely used testing method for the determination of material properties of thin films such as Young’s modulus and the hardness. An important assumption in the analysis of the indentation is that the indented medium is a semi-infinite plane or half space, i.e., it has an “infinite thickness.” In nanoindentation the analyzed material is often a thin film that is deposited on a substrate. If the modulus ratio is small, (soft film on hard substrate) and the penetration depth is small too, then the Hertzian assumption does not hold. We investigate this situation with spherical and conical indentation. Measurement results are shown using spherical indentation on a visco-elastic thin polymer film and a full visco-elastic characterization is presented.

The Impact of the Privacy Rule on Cancer Research: Variations in Attitudes and Application of Regulatory Standards

2009 ◽  
Vol 27 (24) ◽  
pp. 4014-4020 ◽  
Author(s):  
Elizabeth Goss ◽  
Michael P. Link ◽  
Suanna S. Bruinooge ◽  
Theodore S. Lawrence ◽  
Joel E. Tepper ◽  
...  
Keyword(s):  
Cancer Research ◽  
Future Research ◽  
Research Committee ◽  
Data Repositories ◽  
Privacy Rule ◽  
Regulatory Standards ◽  
American Society ◽  
Definition Of ◽  
High Level ◽  
The Impact

Purpose The American Society of Clinical Oncology (ASCO) Cancer Research Committee designed a qualitative research project to assess the attitudes of cancer researchers and compliance officials regarding compliance with the US Privacy Rule and to identify potential strategies for eliminating perceived or real barriers to achieving compliance. Methods A team of three interviewers asked 27 individuals (13 investigators and 14 compliance officials) from 13 institutions to describe the anticipated approach of their institutions to Privacy Rule compliance in three hypothetical research studies. Results The interviews revealed that although researchers and compliance officials share the view that patients' cancer diagnoses should enjoy a high level of privacy protection, there are significant tensions between the two groups related to the proper standards for compliance necessary to protect patients. The disagreements are seen most clearly with regard to the appropriate definition of a “future research use” of protected health information in biospecimen and data repositories and the standards for a waiver of authorization for disclosure and use of such data. Conclusion ASCO believes that disagreements related to compliance and the resulting delays in certain projects and abandonment of others might be eased by additional institutional training programs and consultation on Privacy Rule issues during study design. ASCO also proposes the development of best practices documents to guide 1) creation of data repositories, 2) disclosure and use of data from such repositories, and 3) the design of survivorship and genetics studies.

Research on Material Properties of Engineering Materials with Construct Disaster Preparedness of the Four-Dimensional Space in Hilly Cities’ Communities

2014 ◽  
Vol 978 ◽  
pp. 23-26
Author(s):  
Si Ru Qian
Keyword(s):  
Wenchuan Earthquake ◽  
Urban Area ◽  
Material Properties ◽  
Disaster Preparedness ◽  
Dimensional Space ◽  
Materials Research ◽  
5.12 Wenchuan Earthquake ◽  
Engineering Materials ◽  
The University ◽  
Geographical Feature

We take “5.12 Wenchuan earthquake” influence and one of the university in Mianyang urban area as the typical examples of the disaster preparedness community. We discuss how to plan the multiply disaster preparedness which in accordance to the geographical feature of hilly cities through the material properties of engineering materials research and study of the four-dimensional space disaster preparedness model.

FEMLIB: An Object-Oriented Framework for Optimization and Simulation

1995 ◽  
Author(s):  
Michael M. Tiller ◽  
Jonathan A. Dantzig
Keyword(s):  
Material Properties ◽  
Object Oriented ◽  
The Finite Element Method ◽  
Simulation And Optimization ◽  
Gradient Based ◽  
Level Problem ◽  
Simulation Results ◽  
Optimization And Simulation ◽  
High Level ◽  
Simulation Parameters

Abstract In this paper we discuss the design of an object-oriented framework for simulation and optimization. Although oriented around high-level problem solving, the framework defines several classes of problems and includes concrete implementations of common algorithms for solving these problems. Simulations are run by combining these algorithms, as needed, for a particular problem. Included in this framework is the capability to compute the sensitivity of simulation results to the different simulation parameters (e.g. material properties, boundary conditions, etc). This sensitivity information is valuable in performing optimization because it allows the use of gradient-based optimization algorithms. Also included in the system are many useful abstractions and implementations related to the finite element method.

Digital Technology: the Answer to the Art Historical Conundrum of A ccessibility?

2018 ◽  
Author(s):  
Abigail Berry
Keyword(s):  
Digital Technology ◽  
Art History ◽  
18Th Century ◽  
Modern Technology ◽  
Travel Costs ◽  
Special Collections ◽  
The People ◽  
Accessibility Problem ◽  
Definition Of ◽  
High Level

The famous anthropologist Pierre Bourdieu argued that there is an “unnatural idea of inborn culture, of a gift of culture, bestowed on certain people by Nature.” [1] Bourdieu is arguing that people, who have not been born into a higher class, or who cannot receive a high level of education, are unable to appreciate and understand art. The study of art history is expensive, and often involves extremely high travel costs, thus making it inaccessible to anybody who does not enjoy the means to pursue it. How can we address this accessibility problem in the study of art history? Is there any way to bring art to the people who do not possess “inborn culture?” Bourdieu wrote his book on art and class in 1984, at a time when the computer, and its democratizing potential, was a new and little -understood invention. My research proposes that modern technology provides an answer to this problem, which has plagued the discipline of art history. This presentation will examine three research projects that I’ve been working on at Queen’s. Each project uses digital technologies to improve the general public’s knowledge and access to art. The projects are all different: the first focuses on creating a digital model of 18th - century Canterbury Cathedral based on a book from W.D. Jordan Rare Books and Special Collections, the second project works on understanding Herstmonceux Castle and medieval England through technology, and the third involves image processing for art historical investigations. Despite their differences, each project makes art accessible to people who do not possess Bourdieu’s definition of “inborn culture.”        

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