Strenghth of Materials

Many efforts have been made to understand the effects of hydrogen on steels, resulting in an abundance of theoretical models and papers. However, a fully developed and practically applicable predictive physical model still does not exist industrially for predicting and preventing hydrogen damage. In practice, it is observed that different types of damages to industrial boiler components have been associated with the presence and localization of hydrogen in metals. In this paper, a damaged boiler tube made of grade 20 – St.20 (or 20G, equivalent to AISI 1020) was investigated. The experimental research was conducted in two distinctive phases: failure analysis of the boiler evaporator tube sample and subsequent postmortem analysis of the viable hydrogen embrittlement mechanisms (HE) in St.20 steel. Numerous tested samples were cut out from the boiler tubes of fossil fuel power plant, damaged due to high temperature hydrogen attack (HTHA) during service, as a result of the development of hydrogen-induced corrosion process. Samples were prepared for the chemical composition analysis, tube wall thickness measurement, tensile testing, hardness measurement, impact strength testing (on in-strumented Charpy machine), analysis of the chemical composition of corrosion products – deposit and the microstructural characterization by optical and scanning electron microscopy – SEM/EDX. The HTHA damage mechanism is a primary cause of boiler tube fracture. Based on the multi-scale special model, applied in subsequent postmortem investigations, the results indicate a simultaneous action of the hydrogen-enhanced decohesion (HEDE) and hydrogen-enhanced localized plasticity (HELP) mechanisms of HE, depending on the local concentration of hydrogen in investigated steel. The model is based on the correlation of mechanical properties to the SEM fractography analysis of fracture surfaces.

Resumo: O trabalho consiste na montagem e estudo de deflexão em uma viga de Alumínio 6060 engastada em uma estrutura de aço 1020. Os cálculos são feitos segundo as equações da literatura das disciplinas de Resistencia dos Materiais I e II e a montagem realizada em um laboratório de metal mecânica. O objetivo é calcular qual a deflexão em três diferentes pontos do comprimento da viga com a aplicação de uma carga em sua extremidade livre, comparar as flexas calculadas com as do experimental e consequentemente mostrar onde há a maior deflexão em todo o comprimento da viga. Anteriormente a isto, é feita a verificação de se o material resiste em regime elástico, à carga aplicada. Como a viga suporta a força, os cálculos são realizados e, assim, obtidos os resultados das flexas e ângulos de inclinação da deflexão. Os valores obtidos através da medição, na pratica, da deflexão em cada um dos pontos foram próximos dos calculados, assim comprovando tais resultados. Abstract: This work consist in a building and study of Aluminum's 6060 deflection champed in a 1020 steel structure. The calculations are made under the equations from the literature of the Materials Resistance I and II subjects. The objective is calculate the deflection in three different points of the beam length with a charge application on a free extremity, to compare the calculated arrows with the experimental and consequently show where the larger deflection happens. Previously of it, it has made a verification if the material resists the charge application in the elastic regime. When the beam support the charge, the calculation are made and, as soon, obtain the arrows results and the deflection's inclination angles. The values obtaining by measures, in practice, of the deflection in itch one of the points were close to the calculated, thereby demonstrating these results. Introdução: vigas são estruturas submetidas às cargas perpendiculares ao seu eixo longitudinal, sendo um dos elementos estruturais e mecânicos mais importante e utilizado na engenharia, o que justifica o estudo das cargas e tensões a elas submetidos assim como dos métodos para seu dimensionamento [1]. O problema em questão trata-se de uma viga de alumínio engastada submetida a uma força vertical para cima. O objetivo é o cálculo de deflexão, ou seja, o deslocamento da linha elástica (eixo longitudinal que passa pelo centroide de cada área da secção transversal do elemento) da vida, em regime elástico, em três diferentes pontos com a aplicação de uma carga (P) na extremidade da viga e apresentar onde está ocorrendo a maior deflexão. Isto envolve a determinação do ângulo e da flexa de deflexão, que é verificada com um relógio comparador. Esta carga é transmitida à estrutura por meio de um cabo de aço passado em uma roldana e preso à extremidade da viga, o que faz com que esta sofra um deslocamento para cima em relação ao eixo longitudinal inicial da estrutura. Nestas condições, criam-se Força Cortante interna, V, (ou Força de Cisalhamento, força que se encontra no plano da área e tende a provocar o deslizamento de um segmento do corpo em relação a outro) e Momento Fletor, M, (momento gerado por cargas que tendem a fletir o corpo em torno de um eixo que se encontra no plano da área) na viga [1]. Estas cargas resultantes internas geram, respectivamente, Tensão Cisalhante e Tensão Normal na estrutura. Portanto, para dimensionar qual o valor de flexa (deflexão) é preciso, primeiramente, determinar se o material resiste à carga de 21,75N sem ultrapassar o regime elástico, utilizando conceitos de Resistencia dos Materiais I. Já o método utilizado para o cálculo de deflexão é o Método da Descontinuidade, ou Método de Macaulay.

► A kind of Elastic Composite, Reinforced Lightweight Concrete (ECRL.C) with the mentioned specifics is a type of "Resilient Composite Systems (RCS)" in which, contrary to the basic geometrical assumption of the flexure theory in Solid Mechanics, "the strain changes in the beam height during bending" is typically "Nonlinear". (The RCS could be counted as "The Methodically Reinforced Nonlinear Porous Materials", also having the high specific modulus of resilience in flexure.)

♦ Through employing this integrated structure, with significantly high strain capability and modulus of resilience in bending, we can achieve the high bearing capacities in beams with the secure fracture pattern, in less weight.

♦ Due to the system particulars and its behavior in bending, the usual calculation of the necessary equilibrium steel amount to attain the low-steel bending sections with the secure fracture pattern in the beams and its related limitations do not become propounded. Thereby, the strategic deadlock of the high possibility of the brittle fracture pattern in the bending elements made of the usual reinforced lightweight concretes, especially about the low-thickness bending elements as slabs, is unlocked.

♦ This simple, applied technology and the related components and systems can have several applications in the road and building industries. (It can also be used in making the resilient pieces and constructions "with appropriate behavior and high resistance against severe blasts and shocks.)

♦ Regarding the "strategic importance of Lightweight and Integrated Construction in the practical increase of the resistance and safety against earthquake" and considering the appropriate behavior of this "resilient", durable structure against the dynamic loads, shakes, impacts, blasts, and shocks and the possibility of making some lightweight and insulating, non-brittle, reinforced sandwich panels and pieces, this resilient system and its components can especially be useful in the "seismic areas".

♦ This system can also be employed in constructing the vibration and impact absorber bearing pieces & slabs, which can be used in the "Railroad & Subway Structures" too.

♦ Here, the "Resilient Composite Systems (RCS)" and particularly, the ECRLC as a type of the RCS have been concisely presented. [By the way, an instance of the said new structure and its components and the results of some performed experiments (as bending loading and compressive loading of the slabs made of this structure, similar to ASTM E 72 Standard) have been shown in the related pictures & figures.]
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/ ● Key Words: Strength of materials (solid mechanics), Civil (construction), Materials, Earthquake (resistance and safety), Resilient concrete (flexible concrete, bendable concrete, elastic concrete), Composite concrete, Lightweight concrete, Reinforced concrete, Fibered concrete, Lightweight and integrated construction, Rail (railroad, railway), Subway, Road, Bridge, Resilience, Energy absorption, Fracture pattern, Non-linear, Strain changes, Beam, Ductility, Toughness, Insulating (insulation), Thin, Slab, Roof, Ceiling, Wall (partition), Building, Tower, Plan of mixture, Insulating reinforced lightweight pieces, 3d, Sandwich panel, Dry mix, Plaster, Foam, Expanded polystyrene (EPS), Polypropylene, Pozzolan, Porous matrix (Pored matrix), Mesh (lattice), Cement, RCS, ECRLC
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/ ► Contents:
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* ABSTRACT
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* I. INTRODUCTION
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* II. WHAT ARE THE RESILIENT COMPOSITE SYSTEMS
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- A. General Review
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- B. Components
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. - 1) Mesh or Lattice
. - 2) Fibers or Strands
. - 3) "Matrix" With the Suitable Hollow "Pores (Voids)" and/or "Lightweight Aggregates" in its Context
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- C. More Explanations About the RCS
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- D. Why Are These Systems Called "Composite"?
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- E. The General Structural Particulars and Functional Criteria as the Necessary Specifications of the Compound Materials Generally Called "Resilient Composite Systems"
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. - 1) General Structural Criteria
. - 2) Functional Criteria (Required Specifications)
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* III. "ELASTIC COMPOSITE REINFORCED LIGHTWEIGHT CONCRETE (ECRLC)" AS A TYPE OF THE RESILIENT COMPOSITE SYSTEMS (RCS)
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- An Instance of the Lightweight Concrete That Could be Used in Making the ECRLC
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* IV. REVIEW OF SOME EXPERIMENTS, AND MORE DESCRIPTION ABOUT ECRLC
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* V. SUPPLEMENTARY ELEMENTS
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* VI. APPLICATIONS
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* VII. FINAL REVIEW
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* ACKNOWLEDGEMENTS
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* REFERENCES 
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***
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/ ● General Review:
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• A kind of "Elastic Composite, Reinforced Lightweight Concrete" with the said specifics is a type of the "Resilient Composite Systems (R.C.S.)" in which, contrary to the basic geometrical assumption of flexure theory in the Solid Mechanics, the strain changes in the beam height during bending is typically "Non-linear".
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• Indeed, the RCS, as the Elastic Composite, Reinforced Lightweight Concrete (ECRLC), do not behave as most of the solid materials in bending.
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• In the "Resilient Composite Systems", distributed pores and/or appropriate lightweight aggregates or beads, accompanied by the reticular structure of the strengthened conjoined matrix, bring about the expedient internal shape changes during bending and continuing the elasticity in bending with the said nonlinearly pattern. This means better distribution of the stresses and strains and better utilizing the potential capacities of the employed reinforcements in bending and tension; whereas, in the usual lightweight concretes for instance, distributed hollow pores (such as the gas bulbs in the cellular concretes) or lightweight aggregates (such as Plastic, Rubber or polystyrene beads or any other kind of lightweight aggregates such as Perlite and Vermiculite) decrease the modulus of resilience in bending and could increase "the possibility of beam fracture of brittle and primary compressive type" in bending (compared to the concrete with higher density) according to the case.
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• In this way, by using the mentioned method to make the said particular composite systems, we could considerably increase the modulus of resilience and bearing capacity in bending "together with" significant decrease of the weight and also the possibility of beam fracture of primary compressive type. Through making these particular integrated functioning systems, for the first time, the said (paradoxical) properties have been concomitantly fulfilled in "one functioning unit" altogether.
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• Respect to the special pattern of the strain changes during bending in the particular Resilient Composite System termed ECRLC, this system as an integrated functioning unit with the reticular arrangement and texture has more strain capability (particularly within the elastic limit), energy absorption and load bearing capacities in bending compared to the usual reinforced concrete beams.
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• Thereby, through employing this applied structure, solving some of the main problems in lightweight concretes application, especially the deadlock of brittle and insecure being of fracture pattern in many of the usual reinforced lightweight concrete structures, is provided; reaching to the high bearing capacities in bending elements (even with low dimensions & weights) is to hand, and getting access to a simple and practical opportunity for "qualitative development of possibilities of using lightweight concretes" (especially with oven-dry densities of < 1350-1400kg/m3 and compressive strengths of <14-17mpa, and even with oven-dry densities of < 800kg/m3) is conceivable.
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• Naturally, by more studies in the field, these structures and their applications in various fields could be developed more.
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/ ► FULL TEXT (Open Access):
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- http://arxiv.org/abs/1510.03933 
( https://arxiv.org/ftp/arxiv/papers/1510/1510.03933.pdf ) ;
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. Kamyar Esmaeili: "Elastic Composite Reinforced Lightweight Concrete as a Type of Resilient Composite Systems";
The Internet Journal of Innovative Technology and Creative Engineering (IJITCE); 2012; 2(8): 1-22.
- http://ia800305.us.archive.org/34/items/IJITCE/vol2no801.pdf [Also archived at: http://www.webcitation.org/6B2pFPpBh ] ;
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- https://www.scribd.com/doc/11530978/Elastic-Composite-Reinforced-Lightweight-Concrete-ECRLC-as-a-type-of-Resilient-Composite-Systems-RCS-http-arxiv-org-abs-1510-03933 ; 
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- https://sites.google.com/site/NEWSTRUCTURE1 ;
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- https://sites.google.com/site/newstructure1/publications-page/ELASTIC%20COMPOSITE%2C%20REINFORCED%20LIGHTWEIGHT%20CONCRETE%20AS%20A%20TYPE%20OF%20RESILIENT%20COMPOSITE%20SYSTEMS.pdf ;
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- http://www.pdf-archive.com/2015/09/22/elasticcomposite-reinforcedlightweightconcreteasatypeofrcs/elasticcomposite-reinforcedlightweightconcreteasatypeofrcs.pdf ;
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- The link to the document in PDF format on this site:
file:///C:/Users/pc5/Downloads/ELASTIC_COMPOSITE_REINFORCED_LIGHTWEIGHT.pdf ;
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- ...

Metals are key materials for modern manufacturing and infrastructures as well as transpot and energy solutions owing to their strength and formability. These properties can severely deteriorate when they contain hydrogen, leading to unpredictable failure, an effect called hydrogen embrittlement. Here we report that hydrogen in an equiatomic CoCrFeMnNi high-entropy alloy (HEA) leads not to catastrophic weakening, but instead increases both, its strength and ductility. While HEAs originally aimed at entropy-driven phase stabilization, hydrogen blending acts opposite as it reduces phase stability. This effect, quantified by the alloy's stacking fault energy, enables nanotwinning which increases the material's work-hardening. These results turn a bane into a boon: hydrogen does not generally act as a harmful impurity, but can be utilized for tuning beneficial hardening mechanisms. This opens new pathways for the design of strong, ductile, and hydrogen tolerant materials. Metallic materials are the manufacturing backbone of our industrialized civilization owing to their excellent load bearing capacity, ductility and damage tolerance. They occupy key roles in providing sustainable engineering and manufacturing solutions to such diverse fields as energy supply, transportation, health, infrastructure and safety. This excellent mechanical behavior can drastically deteriorate when metals are exposed to certain elements. Since 1874 it is understood that the lightest of them all, hydrogen, can be dangerous as it causes catastrophic and unpredictable failure, a phenomenon referred to as hydrogen embrittlement. All metallic alloys can suffer from it, be it in engineering parts used in vehicles, planes or power plants or in the context of future fusion and hydrogen fuel and energy storage driven industries. Although these threats and opportunities have motivated nearly one and a half centuries of intense research, hydrogen remains not only a ubiquitous but also a threatening element in engineering metallic alloys. Once hydrogen has entered into metals it accumulates in voids and gets trapped at vacancies, dislocations and internal interfaces, i.e. at lattice defects which determine the physical, chemical and mechanical properties of metals. Once occupying these sites, hydrogen damages the material through enhanced localized plasticity , decohesion , vacancy stabilization  , hydride formation or void coalescence. Although practically all metals suffer from such phenomena, the high-entropy alloy (HEA) investigated here seems to be not only less prone to hydrogen embrittlement but it even profits from its presence. HEAs are a new class of materials originally defined as solid metallic solutions composed of five or more principal elements in equimolar or near-equimolar ratios for yielding high configurational entropy. This concept introduces a new path for developing advanced materials with some unique mechanical properties. The five-component equi-atomic CoCrFeMnNi alloy, also referred to as Cantor's alloy, is one of the most appealing HEAs due to the high thermodynamic stability of its single face-centred cubic (f.c.c.) structure and the excellent mechanical properties under various temperatures. Owing to these features we picked this equiatomic CoCrFeMnNi model HEA for studying its changing mechanical tensile behaviour when exposed to hydrogen. We show that this material is not only resistant to hydrogen embrittlement but we even observe its beneficial role as alloying element as it improves rather than deteriorates both, the material's strength and ductility. The key idea behind this turnaround lies in decreasing the stability of the f.c.c. lattice structure of the matrix via hydrogen alloying to trigger more intense nanotwinning upon loading, thereby improving strain-hardening of the alloy.

Forty years after inaugurating their now eminently successful architectural practice, John and Patricia Patkau are “beginning again.” So they happily declare in their new book Material Operations. This unique survey features eleven experimental works, from their 2010-11 Skating Shelters for Winnipeg’s frozen Red River, to the nearly complete Temple of Light overlooking BC’s Kootenay Bay. Each work is presented more as...