Main Structural Material Research Articles

Corrodibility and Adherence of Reinforced Concrete Rebars Electroplated with Zinc and Zinc-Nickel Alloys

Reinforced concrete is the main structural material used in the world in the construction of bridges, roads and commercial and residential buildings. One effective method for preventing corrosion of steel reinforcement is the application of galvanic coatings to the reinforcement itself. The present study evaluated the performance of three groups of reinforcing steel bars (black steel, used as a reference and rebars electroplated with Zinc and Zinc-Nickel alloys) to corrosion and adherence to the concrete matrix. For the analysis of corrosion, the specimens were subjected to two different accelerated corrosion tests: salt spray exposure and wet and dry semi-cycles. The corrosion potential was measured for the qualitative monitoring of the corrosion process and the corrosion rate was estimated. In order to evaluate the steel-concrete adherence, the pullout test was used, in accordance with RILEM-CEB-FIP. The results showed that Zinc and Zinc-Nickel coatings increased the durability of the reinforcing bars and the accelerated corrosion test of wetting and drying cycles proved to be more aggressive compared to the salt spray method to evaluate the corrosion process in the reinforced concrete specimens. Additionally, galvanized reinforcement reduced adherence to the concrete matrix.

An experimental investigation on precision machining mechanism of carbon fibre reinforced polymer

With the rapid development of carbon fibre reinforced polymers (CFRPs) as main aerospace structural materials, it is necessary to manufacture CFRP structural components for high dimensional accuracy by means of precision machining. In this paper, orthogonal cutting was used to investigate machining process and surface quality of CFRP materials for precision machining. An intensive discussion was given about fibre orientation and cutting parameter range when machining CFRP for high accuracy application and optimised cutting method, including cutting speed, cutting depth, edge radius, fibre orientation, was obtained to reduce cutting force and surface roughness and get smooth surface topography. The cutting speed over 200 m/min and small cutting depth slightly large than edge radius were advisable, the fibre direction 0~45° and 90° were found suitable for precision machining. This paper provides theoretical and experimental supports for application of precision machining of CFRP materials.

An experimental investigation on precision machining mechanism of carbon fibre reinforced polymer

With the rapid development of carbon fibre reinforced polymers (CFRPs) as main aerospace structural materials, it is necessary to manufacture CFRP structural components for high dimensional accuracy by means of precision machining. In this paper, orthogonal cutting was used to investigate machining process and surface quality of CFRP materials for precision machining. An intensive discussion was given about fibre orientation and cutting parameter range when machining CFRP for high accuracy application and optimised cutting method, including cutting speed, cutting depth, edge radius, fibre orientation, was obtained to reduce cutting force and surface roughness and get smooth surface topography. The cutting speed over 200 m/min and small cutting depth slightly large than edge radius were advisable, the fibre direction 0~45° and 90° were found suitable for precision machining. This paper provides theoretical and experimental supports for application of precision machining of CFRP materials.

Measurements and Model Calculations of Activation Reaction Rate for (n, p) Reaction on 54Fe Isotope

In China Fusion Engineering Testing Reactor research, the neutronics experiment is essential in validating the neutronics codes and tools used in a blanket. Reduction activation ferritic-martensitic steel is the main structural material of the water-cooled ceramic breeder blanket, of which the main composition is Fe. However, the activation reaction of 54 Fe(n, p) 54 Mn will bring the long half-life product of 54 Mn. Therefore, the reaction rate of the reaction channel 54 Fe(n, p) 54 Mn was investigated with accuracy in this paper. In a fusion reactor, neutron is generated not only from deuterium tritium reaction but also from the deuterium deuterium (DD) reaction. The spontaneous neutron source, 3 × 10 8 n/s 252 Cf, was used to simulate DD neutron field. After irradiated for about 5 days, the activated Fe foil was measured by a high-resolution gamma-ray spectrometer with a high-purity germanium detector. The neutron flux was calculated using a Monte Carlo transport code and Fusion Evaluated Neutron Data Library (FENDL) 3.0 Files. The neutron group cross section was processed by NJOY. The relative error between the calculated value and the experimental value is less than 7%. The error of the database EAF2010 is the smallest in this paper. The self-shielding factor has a greater impact on FENDL 3.0 database.

Development and Experimental Research on the Electromagnetic Induction Lithium Coolant Transfer Pump of a High-Power Space-Based NPP High-Temperature Cooling System

In the project of a modular submegawatt space-based thermionic NPP for the interorbital tug Gerkules, niobium alloy is used as the main structural material and isotopically pure lithium-7 is used as a coolant. To transfer lithium coolant, a series of electromagnetic induction pumps (EMP) have been designed, manufactured, and tested. The main requirement for EMPs is to ensure lithium transfer at high operating temperatures up to 900°C. This required high-temperature structural, magnetic, conductive, and electrical insulating materials. The design and technological features of the developed EMP are given. The tests were carried out in a pressure chamber as part of the lithium-niobium circuit simulating the NPP cooling system unit. The dependences of the EMP head-flow characteristics on the current strength and frequency, the temperature of transferred lithium, and other parameters are presented. The scatter of the same EMPs does not exceed 6%.

Cradle-to-gate life cycle assessment of energy and carbon of a residential building in Sri Lanka

The growing concerns over the environment have led to increasing demand for environmentally-friendly buildings. So far, only a few studies on environmental impacts of buildings have been conducted in the context of Sri Lanka. Reliable data sources that match the specific conditions of the country are limited. Using the life cycle assessment (LCA) methodology, this paper presents a cradle-to-gate energy and carbon emission study of a multi-storey residential building in a Sri Lankan university. The total embodied energy and carbon of the building are 3.84 GJm-2 and 229.34 kgCO2m-2, respectively, which are comparable with results of similar studies found in literature. Reinforced concrete, the main structural material, contributed to 61 % of total embodied energy and 71 % of total embodied carbon of the building. Despite the relatively low material quantity used, aluminium, ceramic tiles and paint shared 18.67 % of total embodied energy. In order to achieve low-energy and low-carbon buildings in Sri Lanka, several strategies were identified; suitable construction practices and building designs to reduce quantities of mass materials, use of alternative materials with low energy and carbon intensities, material recycling and reuse, use of clean and renewable energy for production processes and popularising the concept of eco-labels for building materials. The reduction of embodied energy and carbon is expected to lighten the environmental footprint of buildings.

Instability of MX and M23C6 type precipitates in F82H steels under 2.8 MeV Fe2+ irradiation at 673 K

The purpose of this study is to investigate the response of the precipitates against irradiation in F82H steels which are considered as main candidate structure material for the fusion DEMO reactor blanket. M23C6-type precipitates contained F82H-IEA steel, and MX- and M23C6-type precipitates contained F82H-BA12 steel were selected as experimental specimens. Iron irradiation at 673 K using ion accelerator was performed on both steels up to 50 dpa. After irradiation, the instability behavior of precipitates was characterized using transmission electron microscopy. It is found that in F82H-IEA specimens, the number density of radiation defects at 20 dpa was 3.26 × 1021 m−3, and the amorphization of M23C6 was undetected up to 50 dpa. Although Ostwald ripening occurred in M23C6 precipitates, the average size of M23C6 mildly decreased with irradiation dose within this study. For F82H-BA12 specimens, the shrinkage rate of MX- and M23C6-type precipitates was estimated respectively as 0.06 and 0.03 nm/dpa. Hence, the MX and M23C6-type precipitates in F82H steel exhibit an excellent irradiation resistance under the present irradiation condition. Moreover, the behaviors like amorphization and weakening in contrast were not observed in M23C6 precipitates in both specimens, which is different from electron irradiation, presumably due to the factors such as different damage rate.

Estimation of Factors of Aggressive Influence and Corrosion Wear of Underground Structures

There is an intensive construction of sewage collectors in the cities. The main structural material used in the construction of collector tunnels is reinforced concrete. Services engaged in the operation of sewage systems, increasingly began to face the destruction of concrete of non-pressure sewer collectors as a result of gas corrosion. Concrete corrosion takes place only in non-pressure manifolds, in the protruding part of the water pipeline or tunnel. The maximum intensity of corrosion is observed in the area, adjacent to the axis of the arch. Сorrosion damage can occur intensively on the walls and in the zone of variable water level. The article analyzes the causes leading to corrosion of reinforced concrete in tunnels.

Audible Sound-Based Intelligent Evaluation for Aluminum Alloy in Robotic Pulsed GTAW: Mechanism, Feature Selection, and Defect Detection

Aluminum alloy is the main structure material in aerospace industry. Online defect detection for aluminum alloy in pulsed gas tungsten arc welding (GTAW) is still challenging, especially for increasing application of robotics. This paper presents an intelligent methodology for real-time evaluation of weld penetration defects based on arc audible sound sensing for aluminum alloy in robotic-pulsed GTAW. The generation mechanism of arc sound was investigated using correlation analysis, high-speed camera observing and frequency spectrum analysis before denoising of arc sound. Two feature selection approaches based on Fisher distance and principal component analysis (PCA) were developed to select the frequency components related to seam defects, and then, their performance were qualitatively and quantitatively analyzed. Finally, a new classification model integrating support vector machine with grid search optimization and cross-validation (SVM-GSCV) was established to identify underpenetration, normal penetration, and burning through. The proposed methodologies were verified to be effective with high accuracy and robustness. This paper can provide some guidance for condition monitoring of additive manufacturing (AM) or process industry.

The possible effect of high magnetic fields on the aqueous corrosion behaviour of Eurofer

In defining the corrosion control requirements for DEMO, the impact of the mixed Eurofer-97/AISI 316 steel system and plant specific effects should be considered throughout, in particular, the effect of the intense magnetic fields present. A substantial amount of data related to corrosion resistance of structural materials is available for industrial applications in fission, but applies to different materials and neutronic conditions. Experimental work is being carried out under the DEMO Breeding Blanket Project of the EUROfusion programme, which will further develop the understanding of irradiation effects. However, there is very limited information regarding magnetic field-assisted corrosion under conditions relevant for the fusion environment readily available in the literature. This work reviews current knowledge and progress in establishing the possible influence of the intense magnetic field on corrosion behaviour of the main structural material, Eurofer-97, in the breeding blanket. To support the relevance of this problem statement, preliminary corrosion experimental results of Eurofer-97 coupons, obtained by using a simple apparatus that allows exposure to a magnetic field intensity of 0.88 T and temperatures up to 80 °C in water at atmospheric pressure, are presented as an initial qualitative investigation of possible magnetic field related effects.

The Construction History and Assessment of Two Heritage Industrial Buildings in Wrocław

Industrial buildings from the beginning of the 20th century can still be found in Polish cities. Some of them have already been listed as heritage objects. Those structures where new technical solutions and materials were used, for example concrete, are especially interesting. Some of those objects are currently under a process of restoration with the aim to reconstruct and adapt them for completely new and different utility functions but without losing their important heritage value. In this paper, elements of the assessment procedure of the technical state regarding a historical survey, material examination and structural analysis, are presented on the example of two selected industrial buildings in which reinforced concrete was used as the main structural material. The main aim of the performed diagnostic procedure was verification of the load-bearing capacity of structures of the examined buildings. The calculation made confirmed that in case of not damaged concrete elements they have enough capacity to carry on newly designed loads. That confirmed that old concrete structures, especially in industrial buildings, sometimes have capacity reserves. On the other hand it allows to perform the design of less invasive renovation works or strengthening solutions with the aim to respect their industrial heritage value.

Paper domes and shelters

This part of the dissertation is dedicated to the practical approach to cardboard as a building material through prototyping. Taking a practical approach here means conducting research by design and prototyping architectural structures in which paper and its derivatives are used as the main structural material. The theoretical research and knowledge presented in the previous chapters of the dissertation will be now used as input. The research by design and the realised prototypes will guide us to the solution that answers the question to what extent cardboard can be used as a suitable building material for emergency architecture. The research and development of cardboard architecture used as input for this dissertation were derived from research previously conducted at TU Delft’s Faculty of Architecture. The Cardboard in Architecture research group, which was set up in the department of Building Technology in 2003 and ceased to exist in 2008 due to the great fire that destroyed the building of TU Delft’s Faculty of Architecture (13 May 2008), made a great contribution to this research. The fundamental and technical research was included in the previous chapters. The designs and development of products in the form of prototypes of cardboard structures are presented in this chapter.

Conclusions

This study has demonstrated how paper and its derivatives can be used as a building material and main structural material in design and architecture. The usage of paper in architecture is limited by many factors, including its vulnerability to moisture, humidity and water, creep and the limited variety of products created by the paper industry. However, paper and paper products can be successfully used in several types of architecture and design. The advantages of using paper in architecture are its low price, the fact that it is mass-produced, its ease of recycling and the mechanical properties of the material. The paper industry’s current focus seems to be on packaging materials and new functionalities of paper and cellulose-based materials. Paper will never replace traditional building materials, but it can fulfil a niche demand created by certain designers and architects. It can be used for products such as interior and industrial design, including everyday objects, partition wall systems, furniture, exhibition pavilions, stage sets, venues for temporary events such as trade fairs or major sporting events, medium-lifespan housing (with a lifespan of up to twenty years) for the private and public sectors, public buildings emergency shelters. This Chapter 8 presents the conclusions of this thesis. First, the research questions and sub-questions are discussed. The research questions are answered in the relevant chapters of the thesis. Chapter 2 presents the some fundamental research on paper, including its history, production, mechanical properties and products produced by the paper industry. Chapters 3 and 4 present the scope of paper usage in design and architecture. Chapter 3 presents the types of paper designs in architecture, while Chapter 4 outlines developments in paper architecture on the basis of sixteen realised structures. The buildings are described in detail, with a particular focus on structural engineering and the paper products used in the various projects. Chapters 3, 4, 5 and 6 follow a research-by-design approach which includes engineering and prototyping. These chapters present prototypes of paper furniture, pavilions, domes and shelters, made of paper products such as corrugated cardboard, honeycomb panels, paper tubes and U- and L-shaped cardboard profiles. The prototypes in question were built by the author of this thesis and his students and partners. They demonstrate different approaches to the potential use of paper in architecture. Chapter 7 presents the project of the Transportable Emergency Cardboard House. TECH is the final project encompassing the author’s fundamental, material and design research and previous prototypes. There are three generations of TECH, each of which is subsequently improved with regard to its design, structural system and method of impregnation. Chapter 1 outlined two primary research questions, as well as seven secondary research questions. The answers to these questions can be found in the present chapter.

EFFECT OF EXTRUSION ON MICROSTRUCTURE OF AZ31 TYPE MAGNESIUM

The use of magnesium as structural engineering material has been becoming more widespread. It promises an important future as a main structural material especially in fields such as aviation and automotive because of its higher mechanical properties and lower weight. In this study, the microstructure of extruded AZ31 type material was investigated. The change of grain size was examined by using optical microscope and SEM microscope and EDX data mapping were obtained. The change in the microstructure was investigated. It was observed that grain size was reduced after extrusion and the alloy elements’ distribution was homogeneous.

Nano-Hydroxyapatite Stimulation of Gene Expression Requires Fgf Receptor, Phosphate Transporter, and Erk1/2 Signaling.

Hydroxyapatite (HAp) is critical to health both as the main structural material of the skeleton and storage material of calcium and phosphate. Nanosized HAp (nHAp) is naturally produced by mineralizing cells during bone formation and remodeling and is the main constituent of the skeleton. As such, HAp is currently being investigated as a therapeutic biomaterial for orthopedic and dental purposes. Recent studies have suggested that extracellular nHAp can influence osteoblast lineage commitment and cell function through changes in gene expression; however, the mechanisms remain to be elucidated. Here, the cellular and molecular mechanism by which rod-shaped nHAp (10 × 100 nm) stimulates gene expression in preosteoblast bone marrow stromal cells was investigated. Electron microscopy detected a rapid and stable interaction of nHAp with the cell membrane, which correlated with a strong stimulation of the Erk1/2 signaling pathway. Results also identified the requirement of the Fgf receptor signaling and phosphate-transporters for nHAp regulated gene expression whereas a calcium-sensing receptor inhibitor had no effect. Collectively, the study uncovers novel signaling pathways and cellular events specifically stimulated by and required for the cellular response to free extracellular HAp. The results provide insight into the osteoblastic response to HAp relevant to functional mineralization and pathological calcification and could be used in the development of biomaterials for orthopedic purposes.

Long-term creep strength and fracture of Gr.91 steel welds

Mod.9Cr–1Mo steel (ASME Gr.91 steel) is widely used as a main structural material for boiler components in ultra-supercritical (USC) thermal power plants at about 600 °C. Decrease of the creep strength of welded joints due to Type-IV failure is a critical issue, however creep rupture data longer than 10,000 h are scarcely obtained. The present paper conducted long-term creep tests of welded joints from 30,000 to about 70,000 h at 600 and 650 °C. For the specimens fractured after about 35,000 h at 600 and 650 °C, creep damage was mainly observed in the fine-grained heat-affected zone (HAZ) (Type-IV), however damage was also observed in the weld metal. The welded joints crept at 600 °C and 50 MPa for about 50,000 and 70,000 h fractured in the weld metal. It was found that the hardness of 9Cr weld metal decreased after about 30,000 h creep at 600 °C due to the recovery of microstructures. Therefore it is considered to be necessary to monitor creep damage not only in the HAZ but also in the weld metal.

Some problems of hydrogen in reactor structural materials: A review

The review concerns some problems of hydrogen in the main reactor structural materials used in the core of nuclear reactors. Zirconium alloys, steels, and vanadium alloys, as well as the hydrogen and helium synergetic effect exerted on the radiation resistance, are considered. The main sources resulting in the accumulation of hydrogen isotopes in reactor materials are discussed. The causes and consequences of hydride embrittlement of zirconium alloys at relatively low temperatures are analyzed. It is shown that hydrogen can induce the embrittlement of vessel steels through the weakening interatomic bond forces and a stabilization of radiation-induced defects. It is demonstrated that hydrogen in the presence of helium behaves like a gas that enhances the irradiation effect on the microstructure and properties of materials in many cases. The irradiation with simultaneous introduction of hydrogen and helium causes, in particular, a catastrophic swelling of chromium steels and vanadium alloys, whereas in the case of austenitic steel the effect is less pronounced.

Adsorption of volatile polonium species on metals in various gas atmospheres: Part III – Adsorption of volatile polonium on stainless steel 316L

Abstract This article summarizes the results obtained studying the interaction between polonium and stainless steel 316L in different atmospheres by the thermochromatography method. This issue is particularly important in terms of licensing of the MYRRHA prototype ADS reactor, where highly radiotoxic α-emitting polonium isotopes are produced in lead-bismuth eutectic used as both spallation target material and coolant, while stainless steel 316L is going to be the main structural material. The polonium adsorption enthalpy on stainless steel 316L in inert atmosphere was measured as −147±6 kJ mol−1. The findings obtained using reducing atmospheres show that the affinity of polonium for stainless steel 316L increases with the metallic character of the stainless steel surface. The presence of moisture in inert and reducing atmosphere does not significantly influence the polonium adsorption. Oxidizing atmospheres induce the formation of polonium dioxide which has a stronger interaction with the stainless steel 316L, with an adsorption enthalpy of −225±6 kJ mol−1. A prolonged exposure of the stainless steel to strong oxidants, such as pure oxygen, reduces the metallic character of the stainless steel surface and, consequently, its affinity to the polonium oxide. Furthermore, it was found that in all experiments at least 5 ppm of the total polonium present in the starting material were not retained on the stainless steel 316L surface at all.

Impact of pretreatment conditions on defect formation during the fabrication of Al-based corrosion barriers by ECX process

Different breeding blanket designs for DEMO consider Eurofer steel as a main structural material. Nevertheless, RAFM steels suffer from severe corrosion attack if exposed to flowing Pb-15.7Li at high temperatures, as it is considered in the blanket designs HCLL, WCLL and DCLL. Two electroplating processes, i.e. ECA and ECX, were developed in the past to produce protective Al-based coatings on RAFM steels which proved already corrosion protection behavior in flowing Pb-15.7Li under fusion relevant conditions.Both electrochemical processes need reliable pretreatment processes of the RAFM substrates prior to the Al-deposition, to prevent coating defects such as insufficient covering and weak adhesion. These coating failures increase the risk of defects in the corrosion barriers after the heat treatment and therefore may promote early coating breakdowns in flowing Pb-15.7Li. This study examined some influences on defect formation by electrochemical measurements and SEM/BSE examinations. Besides storage time between mechanical preparation of the samples and electrodeposition, the impact of an anodic pretreatment of Eurofer samples prior to the Al-plating by ECX process was investigated. It is shown that the covering of Eurofer samples by aluminum depend on both parameters and optimized pretreatment parameters could be derived from these findings to increase the reliability of the whole barrier fabrication process.

Adhesive joints with improved mechanical properties for aerospace applications

Adhesion is attracting increasing interest in the aerospace field since composite materials have become, together with aluminium alloys, the main structural materials for aircraft primary structures. Nano-graphite was demonstrated to improve the mechanical performance of several polymers used as composite matrices. In this work Single Lap Joints (SLJs) of unidirectional composite laminates were manufactured, tested and simulated: two families of specimens were investigated and compared, one joined using conventional epoxy resin, the other joined with an adhesive obtained mixing the same epoxy resin with nano-graphite particles. The dispersion of expanded and sonicated graphene stacks (EGS, 3% wt) in the epoxy matrix was obtained by the swelling method, dispersing first the filler in acetone and then mixing it with the epoxy oligomers. Finally the solvent was evaporated and the filler-epoxy mixture was degassed under vacuum before adding an amine curing agent in a stoichiometric quantity. The research demonstrates the superior mechanical properties of the adhesive with the addition of nano-graphite through experimental characterization of its behaviour in terms of strength and energy absorption. Finite element numerical simulations have been carried out using the Cohesive Zone Model (CZM) element, obtaining as parameters the maximum shear stress and the critical fracture energy for the two adhesives. A good correlation between numerical and experimental results has been achieved and the criteria for developing reliable and accurate non-linear models of the adhesive failure have been established.