Individual Material Properties Research Articles

FIRE SPREAD MECHANISM ON SURFACE OF CONSTRUCTION FIT WITH FAÇADE HEAT INSULATION BASED ON COMBUSTIBLE INSULANT AND FINISHED WITH PLASTER

The article is dedicated to the use of structures of external walls with facade insulation with plaster, which is widespread and popular in our country and abroad, as well as the problems associated with their fire hazard. The work of domestic and foreign researchers dealing with fire safety issues of facade systems has been analyzed. Classification of prefabricated systems of facade insulation is performed depending on the design decision, as well as on the main features in accordance with: the type of applied insulation material; a method of fastening a heat-insulating layer; composition of the base plaster layer; kind of decorative protective layer. The structure of prefabricated systems with complete sets of insulation with prefabrication of light, thick-layer plaster or fine-wares products is represented. The peculiarities of the processes that occur during combustion of the thermal insulation and finishing system of the outer walls of residential buildings are analyzed and revealed. Typical scenarios of fire spreading are presented with a surface of the design of external walls with a facade heat insulation with a fuel heater and a stucco coating. The mechanism of propagation of fire through a window opening by a surface of a facade heat insulation on the basis of foam polystyrene is described. The conclusion is made that the use of structures of exterior walls of residential buildings with facade insulation with combustible insulant and stucco coating significantly increases their level of fire hazard. This danger will depend on both the properties of individual materials (including insulant), as well as on the design features of the entire thermal insulation system and the building as a whole. For plaster systems, the thermal insulation of facades is a major threat to the rapid spread of fires on the floors above and below the building. The most common causes of thermal insulation fires is the transfer of fire from the windows during intense fire inside the rooms.

Characterization of Sodium and Potassium Nitrate Contaminated Polyaniline-Poly (Ethylene Oxide) Composites Synthesized via Facile Solution Casting Technique.

Fabrication of composites by developing simple techniques can be an effective way to modify some properties of individual materials. The present study relates to facile synthesis of sodium nitrate (NaNO3) and potassium nitrate (KNO3) contaminated polyaniline (PANI) and poly (ethylene oxide) (PEO) composites without using any additives, plasticizers, or fibers. The physic-chemical and rheological properties of synthesized composites were analyzed. The composites showed enhancement in both storage and loss modules in comparison with the polymer matrices. The dynamic viscosity of the synthesized materials has inverse relation with that of temperature and shear stress. Rheological analysis reveals a continuous drop off in viscosity by increasing shear stress. The flow behavior was affected little by temperature. However, the overall results showed a shear thinning effect suggesting that polymer composites show non-Newtonian behavior. The addition of NaNO3 and KNO3 had a profound effect on shear viscosity of the materials, although the overall shear thinning behavior prevails. The PANI-PEO composite follows, as the first approximation models, both Bingham and modified Bingham models, while the salt contaminated system follows only the Bingham model. Both show shear stress values. The greater values of storage (G′) and loss (G″) modulus of composites than PANI-PEO blend suggests excellent elasticity, better stiffness, and good mechanical strength of the composites. Furthermore, the composites were more thermally stable than pure polymers.

The Impact of Coordination Environment on the Thermodynamic Stability of Uranium Oxides

Amorphous uranium oxides are known to arise via industrial processes relevant to the nuclear fuel cycle yet evade rigorous structural characterization. A promising approach is to develop statistical relationships between uranium–oxygen coordination environments and thermodynamic stability from which general statements about the likelihood of observing particular U–O arrangements can be made. The number of known crystalline uranium oxides is insufficient to build statistical relationships. We have developed a database of theoretical compounds using genetic algorithms with the density functional theory as a foundation to analyze coordination geometries in the uranium–oxygen phase space. We draw fundamental insights into the nature of uranium–oxygen interactions by correlating total energy with the coordination environment. The most stable configuration of U cations with O anions is in an environment with coordination numbers 5–8 in a cubic configuration. Higher and lower coordination numbers are observed only in metastable phases. General trends are observable in the relationships between the coordination number, density, and uranium fraction in each structure. The new insight into uranium coordination enabled by these analyses is foundational for further studies into the characteristic properties of individual uranium oxide materials and for elucidation of potential oxidation pathways for uranium metal.

Expansion Level of Steel Slag Aggregate Effects on Both Material Properties and Asphalt Mixture Performance

The influence of steel slag expansion level on the early stage performance of hot mix asphalt (HMA) is evaluated. Initially, samples of Linz-Donawitz type steel slag with different levels of expansion (6.71%, 3.16%, 1.33%) were submitted to physical, mechanical, and morphological characterization to assess the effects of expansion on individual material properties. Steel slag was then used as aggregate in HMA to verify the effects of its expansion characteristics on the volumetric and mechanical performance of the asphalt mixture. Four different asphalt mixtures were designed based on Marshall mix design, using asphalt cement (pen. grade 50/70), natural aggregate (granite), and steel slag (in three different levels of expansion). The mechanical characteristics of the asphalt mixture were evaluated based on results from Marshall stability, indirect tensile strength, and resilient modulus testing. A modified Pennsylvania testing method (PTM) was also performed on the studied asphalt mixtures to verify the potential of asphalt binder film to minimize the expansive reactions of steel slag. It was observed that the level of steel slag expansion changes some of the material’s individual properties, which can affect the volumetric parameters of the mix design. The use of steel slag as aggregate in HMA also improves the mechanical properties of non-aged asphalt mixtures. Moreover, the expansive characteristics of this material could be minimized when combined with other asphalt mixture components.

Analysis of the Strain Energy Release Rate for a Delamination Crack in a Multilayered Beam with Material Non-Linearity

The strain energy release rate for a delamination crack in a multilayered cantilever beam which exhibits material non-linearity is derived by considering the energy balance. The material non-linearity is described by the Ramberg-Osgood stress-strain relation. A cantilever beam made of adhesively bonded lengthwise vertical layers is studied. Each layer has individual widths and material properties. Besides, the delamination is located arbitrary between layers. The strain energy release rate is derived also by differentiating the complementary strain energy with respect to the crack area for verification. It is shown that the solution derived is useful for parametric investigations of delamination in multilayered beams.

Influence of sine material gradients on delamination in multilayered beams

The present paper deals with delamination fracture analyses of the multilayered functionally graded non-linear elastic Symmetric Split Beam (SSB) configurations. The material is functionally graded in both width and height directions in each layer. It is assumed that the material properties are distributed non-symmetrically with respect to the centroidal axes of the beam cross-section. Sine laws are used to describe the continuous variation of the material properties in the cross-sections of the layers. The delamination fracture is analyzed in terms of the strain energy release rate by considering the balance of the energy. A comparison with the J-integral is performed for verification. The solution derived is used for parametric analyses of the delamination fracture behavior of the multilayered functionally graded SSB in order to evaluate the effects of the sine gradients of the three material properties in the width and height directions of the layers and the location of the crack along the beam width on the strain energy release rate. The solution obtained is valid for two-dimensional functionally graded non-linear elastic SSB configurations which are made of an arbitrary number of lengthwise vertical layers. A delamination crack is located arbitrary between layers. Thus, the two crack arms have different widths. Besides, the layers have individual widths and material properties.

Automatic re-contouring of repair-welded tool moulds

The process of repairing damaged tool moulds is conducted manually in the industry. This results in long process times as well as a high dependence of the repair result on the experience of the worker. After a visual inspection, the detected damages are removed by metal cutting and the missing material is filled by a build-up welding process. Afterwards, the target geometry is restored via machining re-contouring process. Because of the individual tool mould surface and welded seam, each repair case requires an individual machining strategy as well as toolpaths and process control parameters to ensure high surface quality and shape accuracy. This paper introduces an innovative design for re-contouring of repair-welded tool moulds, which takes into consideration the individual mould surface, repair welding and material properties. For that purpose, the actual geometry of the tool mould is measured directly in the CNC machine using an optical profile line sensor. Based on the measurement, the re-contouring process is planned automatically by means of a computer aided manufacturing (CAM) software. A material removal simulation with cutting force prognosis is carried out to adapt the process parameters individually with regard to repair time and surface quality. To set up the force and surface simulation model with high model quality, re-contouring experiments are carried out on welded seams made of 1.2343 (AISI H11) as well as on Toolox 44 and 1.2343 workpieces for comparison.

Influence of material inhomogeneity and non-linear mechanical behavior of the material on delamination in multilayered beams

The delamination fracture in four-point bending beams made of adhesively bonded lengthwise vertical layers is studied assuming that each layer exhibits smooth material inhomogeneity along the width and length of the layer. The study aims at determining the strain energy release rate with applying the Ramberg-Osgood equation for modeling the non-linear mechanical behavior of the material in each layer. Cosine laws are used to describe the continuous variation of the modulus of elasticity in width and length directions of layers. Beams made of an arbitrary number of vertical layers which have individual widths and material properties are considered. Besides, the delamination crack is located arbitrary between layers, i.e. the two crack arms have different widths. The J-integral is applied for verification of the non-linear solution to the strain energy release rate derived in the present paper. The solution is used to investigate the influence of material inhomogeneity in width and length directions of layers, the crack location along the beam width, the non-linear mechanical behavior of the material and the crack length on the delamination fracture behavior. The approach developed is expected to be useful in structural design of multilayered inhomogeneous beams with considering the delamination fracture behavior.

Non-linear delamination in two-dimensional functionally graded multilayered beam

PurposeA delamination fracture analysis of two-dimensional functionally graded multilayered end-loaded split beam configuration with non-linear mechanical behaviour of material is conducted. The beam is made of an arbitrary number of longitudinal layers. Perfect adhesion between layers is assumed. The material is two-dimensional functionally graded in the cross-section of each layer. Also, each layer has individual thickness and material properties. A delamination crack is located arbitrary along the beam height. The paper aims to discuss these issues.Design/methodology/approachThe delamination fracture behaviour is investigated analytically in terms of the strain energy release rate by analysing the balance of the energy. An additional analysis of the delamination fracture is performed by applying the J-integral approach for verification.FindingsThe solutions derived are used to evaluate the effects of crack location, material gradients and material non-linearity on the delamination fracture behaviour of end-loaded split beam. The effect of material gradient on the distribution of the J-integral value along the crack front is elucidated too.Originality/valueDelamination in the multilayered functionally graded end-loaded split beam exhibiting non-linear mechanical behaviour of the material is analysed assuming that the material property is distributed non-linearly in both thickness and width directions in each layer.

Analysis of cylindrical delamination cracks in multilayered functionally graded non-linear elastic circular shafts under combined loads

This paper is focused on delamination fracture analyses of a multilayered functionally graded circular shaft under two loading combinations (centric tension and torsion, and bending and torsion) assuming non-linear elastic mechanical behavior of the material. The loading combinations under consideration generate mixed-mode II/III delamination crack loading conditions (the centric tension and bending generate mode II crack loading, while the torsion is responsible for mode III crack loading). The shaft is made by concentric longitudinal layers. The number of layers is arbitrary. Besides, each layer has individual thickness and material properties. The material in each layer is functionally graded in radial direction. Hyperbolic laws are used to describe the continuous variation of material properties in radial direction. A cylindrical delamination crack (the crack front is a circle) is located arbitrary between layers. The delamination fracture is studied in terms of the strain energy release rate by analyzing the energy balance. In order to verify the solution obtained, the strain energy release rate is derived also by differentiating the complementary strain energy with respect to the delamination crack area. Parametric investigations of the behavior of the cylindrical delamination crack are carried-out. The present paper is a contribution in the fracture mechanics of multilayered functionally graded non-linear elastic circular shafts under combined loads.

Hierarchical Bimetallic AgPt Nanoferns as High-Performance Catalysts for Selective Acetone Hydrogenation to Isopropanol

A combinative effect of two or more individual material properties, such as lattice parameters and chemical properties, has been well-known to generate novel nanomaterials with special crystal growth behavior and physico-chemical performance. This paper reports unusually high catalytic performance of AgPt nanoferns in the hydrogenation reaction of acetone conversion to isopropanol, which is several orders higher compared to the performance shown by pristine Pt nanocatalysts or other metals and metal–metal oxide hybrid catalyst systems. It has been demonstrated that the combinative effect during the bimetallisation of Ag and Pt produced nanostructures with a highly anisotropic morphology, i.e., hierarchical nanofern structures, which provide high-density active sites on the catalyst surface for an efficient catalytic reaction. The extent of the effect of structural growth on the catalytic performance of hierarchical AgPt nanoferns is discussed.

Parameters influencing the capacitive behavior of carbon composite electrodes: composition, morphology, electrical conductivity, and surface chemistry

The interplay and overlapping of several factors determine the capacitive behavior of carbon composite electrodes for capacitive energy storage application. General guidelines and, hopefully, design principles would be useful for inspiring further development work in this area, beyond a purely empirical approach. The present work attempts to give a contribution in this direction, through a systematic study of the effect of the composition on the behavior of electrodes prepared via a paste-casting method in three composite classes: AC–CNT, AC–RGO, and AC–CNT–RGO. Fundamental properties of individual materials, such as pore structure, specific surface area, and surface chemistry, or of the electrode pastes, such as the electrical conductivity, were characterized by suitable techniques and linked to the observed electrochemical behavior, which was systematically evaluated as a function of the composition. Basic properties, such as conductivity and surface area, have an overwhelming and interlaced influence and should be taken as prerequisites of the pristine materials. Morphology and dimensionality of individual components determine composition thresholds above which the full exploitation or the synergistic enhancement of the properties of individual components may be effectively achieved. Expectedly, since addressing different performance requirements does not necessarily results in a single composite composition, the appropriate content of any constituent should be adjusted based on the target performance demands.

Application of European design principles to cross laminated timber

The design of cross laminated timber (CLT) structures is not included in the current version of European structural timber design standards of EN 1995 (Eurocode 5, EC 5). Due to the increasing importance of CLT, in different applications such as complete wall or floor elements as well as girders, it is one of the main goals of the currently ongoing revision of EC 5 to provide design principles for CLT structures. In the present paper some general aspects, relevant for the implementation of CLT in European standards in order to be consistent with the general philosophy of the Eurocodes are summarized and discussed. The differences between standard test specimens and structural components as well as the uncertainties related to the production procedure of CLT and the non-standardized test procedure are discussed. An investigation of 12 different test series from five different producers clearly indicates a large variation between different production series. Based on the investigation from the test series a reliability analysis is performed. The results indicate that the same partial safety factor as recommended for glued laminated timber (GLT) is appropriate in order to achieve an acceptable reliability. However, the analysis also indicates the potential for a smaller partial safety factor in the future, in case that the production of CLT is standardized and appropriate standardized test methods for the individual material properties exist.

Effect of modifications in mineralized collagen fibril and extra-fibrillar matrix material properties on submicroscale mechanical behavior of cortical bone.

A key length scale of interest in assessing the fracture resistance of bone is the submicroscale which is composed of mineralized collagen fibrils (MCF) and extra-fibrillar matrix (EFM). Although the processes through which the submicroscale constituents of bone contribute to the fracture resistance in bone have been identified, the extent of the modifications in submicroscale mechanical response due to the changes in individual properties of MCFs and EFM has not been determined. As a result, this study aims to quantify the influence of individual MCF and EFM material property modifications on the mechanical behavior (elastic modulus, ultimate strength, and resistance to failure) of bone at the submicroscale using a novel finite element modeling approach that incorporate 3D networks of MCFs with three different orientations as well as explicit representation of EFM. The models were evaluated under tensile loading in transverse (representing MCF separation) and longitudinal (representing MCF rupture) directions. The results showed that the apparent elastic modulus at the submicroscale under both loading directions for all orientations was only affected by the change in the elastic modulus of MCFs. MCF separation and rupture strengths were mainly dependent on the ultimate strength of EFM and MCFs, respectively, with minimal influence of other material properties. The extent of damage during MCF separation increased with increasing ultimate strength of EFM and decreased with increasing fracture energy of EFM with minimal contribution from elastic modulus of MCFs. For MCF rupture, there was an almost one-to-one linear relationship between the percent change in fracture energy of MCFs and the percent change in the apparent submicroscale fracture energy. The ultimate strength and elastic modulus of MCFs had moderate to limited influence on the MCF rupture fracture energy. The results of this study quantified the extent of changes that may be seen in the energy dissipation processes during MCF rupture and separation relative to the changes in the individual constituents of the tissue. This new knowledge significantly contributes to improving the understanding of how the material property alterations at the submicroscale that can occur due to diseases, age-related changes, and treatments affect the fracture processes at larger length scales.

Effects of ply orientation and material on the ballistic impact behavior of multilayer plain-weave aramid fabric targets

Abstract Virtual testing of fabric armor provides an efficient and inexpensive means of systematically studying the influence of various architectural and material parameters on the ballistic impact behavior of woven fabrics, before actual laboratory prototypes are woven and destructively tested. In this finite element study, the combined effects of individual ply orientations and material properties on the impact performance of multi-layered, non-stitched woven aramid fabrics are studied using 2- and 4- sided clamping configurations. Individual ply orientations of 0°, ±15°, ±30°, and ±45° are considered along with three levels of inter-yarn friction coefficient. Functionally graded fabric targets are also considered wherein the yarn stiffness progressively increases or decreases through the target thickness while keeping the yarn strain energy density constant and with all other material and architectural parameters unchanged for consistency. For each target configuration, one non-penetrating and one penetrating impact velocity is chosen. The impact performance is evaluated by the time taken to arrest the projectile and the backface deformation for the non-penetrating impacts, and by the residual velocity for the penetrating impact tests. All deterministic impact simulations are performed using LS-DYNA. 2-sided clamped targets and lower inter-yarn frictional levels generally resulted in better impact performance. The functionally graded targets generally showed either similar or inferior impact performance than the baseline fabric target configurations for the non-penetrating shots. Some performance improvements were observed for the penetrating shots when the yarn stiffness was progressively decreased through the layers in a direction away from the strike face, with additional performance enhancements achieved by simultaneously reducing the inter-yarn friction.

Analytical Study of Delamination in Multilayered Two-Dimensional Functionally Graded Non-Linear Elastic Beams

AbstractThe present paper is focused on the delamination fracture in a multilayered two-dimensional functionally graded beam configuration which exhibits non-linear behavior of the material. The beam is loaded by two longitudinal forces applied at the beam free ends. The beam contains a delamination crack which is located symmetrically with respect to the beam mid-span. The delamination is studied analytically in terms of the strain energy release rate. TheJ-integral approach is applied for verification of the analysis of the strain energy release rate. The solution derived is valid for a beam made of an arbitrary number of layers. It is assumed that each layer has individual thickness and material properties. Also, the material is two-dimensional functionally graded in the cross-section of each layer. The solution obtained can be applied for a delamination crack located arbitrary along the height of the beam cross-section. It is shown that the solution is very convenient for investigating the influences of material gradients and crack location on the delamination fracture behavior. The results obtained can be used for optimization of multilayered two-dimensional functionally graded structural members and components with respect to their delamination fracture performance.

Various Robots Made from Piezoelectric Materials and Electroactive Polymers: A Review

Over the last two decades, smart materials have drawn significant attention and growing interest in a broad range of engineering applications because of their unique engineering features. In this article, robotic applications using a class of smart materials that have the ability to actuate when subjected to external stimuli, such as magnetic or electric fields, temperature and voltage are comprehensively reviewed. Smart materials used for robotic applications include electro-rheological fluids, magnetorheological fluids, shape memory alloys, and piezoelectric transducers. This article describes the attributes and inherent properties of individual smart materials that make them suitable for actuating robotic applications and discusses their associated technical limitations, in order to address the design challenges. In addition, many types of robots proposed to date, such as flexible robot arm, and biomimetic and soft robots are introduced in terms of their dynamic modeling, design, controlling, and practical applications. This article provides an updated review of recent smart material research for robotic applications, with over a hundred state-of-the-art references categorized into various types of smart materials.

Delamination Analysis of a Multilayered Two-Dimensional Functionally Graded Cantilever Beam

Delamination fracture behaviour of a multilayered two-dimensional functionally graded cantilever beam is analyzed in terms of the strain energy release rate. The beam is made of an arbitrary number of layers. Perfect adhesion is assumed between layers. Each layer has individual thickness and material properties. Besides, the material is two-dimensional functionally graded in the cross-section of each layer. There is a delamination crack located arbitrary between layers. The beam is loaded by a bending moment applied at the free end of the lower crack arm. The upper crack arm is free of stresses. The solution to strain energy release rate derived is applied to investigate the influence of the crack location and the material gradient on the delamination fracture. The results obtained can be used to optimize the multilayered two-dimensional functionally graded beam structure with respect to the delamination fracture behaviour.

Chemical and phase transitions in oxidized manganese ore in the presence of carbon

In the present work, thermodynamic modeling of the chemical and phase transitions in a system consisting of oxidized manganese ore and reducing agent (carbon) is based on Astra 4 software developed at Bauman Moscow State Technical University. The phase composition and equilibrium characteristics are calculated by means of a database regarding the properties of individual materials. The database in Astra 4 software consists of thermodynamic, thermophysical, and thermochemical properties of materials. It includes data systematized at the Institute of High Temperatures, Academy of Sciences of the USSR and at the United States National Standards Bureau; data published in journals, monographs, and handbooks; and also data analyzed and calculated at Bauman Moscow State Technical University. The chemical and phase transformations in the system are simulated in the range 1573–2573 K, with 5, 10, and 15% C in the system, at a pressure of 0.1 MPa. Modeling shows that the maximum conversion of manganese to Mn3Si3 (in the condensed state) is 95.3 at T = 1873 K, with 30% carbon in the system. With further increase in temperature, the manganese begins to enter the gas phase. In comparison with manganese, silicon is less easily reduced and, with increase in the temperature, it begins to enter the gas phase. The best temperature range for the reduction of silicon is 1773–1873 K, with 15–30% C in the system. Calculation of the iron transfer αFe (%) as a function of the temperature and the carbon content indicates that the temperature range 1773–1873 K is optimal, with 15% C. On the basis of thermodynamic modeling of the phase transitions in a system consisting of oxidized manganese ore and reducing agent, it is possible to assess the possibility of producing ferrosilicomanganese by the electrosmelting of Western Kamys ore, which is hard to enrich.

A new approach for determining resilient moduli of marginal pavement base materials using the staged repeated load CBR test method

The selection of marginal materials to construct workable and durable pavement base materials requires an understanding of their resilient moduli properties. Empirical formulations have been developed previously based on quality quarried material with known performance-based behaviour. However, in recent years, there has been an increasing demand to use locally available marginal materials, which do not necessarily meet road authority specification requirements; hence it is imperative to evaluate the performance of these non-standard materials. In this study, the geotechnical properties of two marginal materials, namely limestone (Ls) and sandstone (Ss), were evaluated and compared with a high-quality rhyolite (Rh) crushed rock. In order to improve the performance of the marginal materials, each of Ls and Ss was blended with 20% Rh and 50% Rh. The geotechnical properties of individual and blended materials which were investigated included: particle size distribution, particle density, Atterberg limits, Los Angeles value, modified compaction test, California bearing ratio (CBR) and repeated load triaxial test. A novel test method termed repeated load CBR (RL-CBR) was used to investigate the performance properties of the individual materials and blends. The RL-CBR test was further developed to study the stress-dependent behaviour of the materials, termed as staged RL-CBR test. An in-depth analysis of the staged RL-CBR test confirmed the capability of this test method to determine the resilient modulus of marginal pavement base materials.