Basic Material Characteristics Research Articles

Characteristics of Phase Change Material for NaCl Solution and Optimization of as a Kind of Coolant in the Storage-Transportation of Frozen Pork

In this study, NaCl solution was investigated the basic characteristics of phase change materials. The volumes of NaCl solution (as coolant) were studied in storage-transportation of frozen pork. The mathematical models were established between the coolant volumes and cargo capacity. A theoretical basis was provided for the srorage-transportation of fresh foods when NaCl solution was the coolant of phase change materials. The volumes of coolant were optimized in the sorage-srorage-transportation of fresh foods. The logistics costs would be reduced because of our results.

DETERMINATION OF YIELD POINT OF STRUCTURAL MATERIALS WITH USING THE METRIC ENTROPY

The yield point is one of the basic characteristics of construction materials, which are used in the design engineering calculations. The methods used to determine the yield point is based on the interpretation of the geometric shape of the curve uniaxial tension. This shape is specific for different construction materials and depends among others to the conditions carrying trials. Specific guidelines for determining the yield point were included in the standards specification. The conventionality of procedure concerns especially materials, which, in their deformation characteristic do not have a distinct top of knee. The authors propose an alternative method based on the use of the concept of the metric entropy by Kolmogorov-Sinai. The metric entropy by Kolmogorov-Sinai is used to study the phenomena about a dynamic character. Therefore, this method requires the recording of more number of measuring points: from a few hundred to a dozen thousand, depending on the type of research of constructional materials. A dynamic character of measurement data results from their scatter, which consists of local, non-linear disturbances occurring during deformation of the material and the noise, associated from the action of acquisition path. The aim of the study is to present a more objective method of determining the yield point structural materials, which do not require the use of conventional procedures. The paper presents the results determining of this constant material on the basis of data records monoaxially stretching of tests for metals used in shipbuilding.

Tutorial on the Fundamental Characteristics and Practical Properties of Nanostructured Thin Film (NSTF) Catalysts

This tutorial reviews the key aspects and literature to date around the nanostructured thin film (NSTF) electrocatalyst technology platform for PEM fuel cells and electrolyzers. The NSTF technology is to date the only practical example of an extended surface area catalyst shown to effectively address several of the performance, cost and durability barriers facing cathode and anode catalysts for fuel cell vehicles. The unique physical characteristics of these ultra-thin, low Pt-loaded electrodes also require alternative solutions for water management and impurity tolerance. We present an overview of the NSTF electrocatalysts’ four primary differentiating features, to show how their material and basic geometric and material characteristics translate to functional performance factors. We conclude by briefly recounting the historical origins of the NSTF material with the recommendation that the field of ordered organic molecular solids represents a large opportunity for developing tailored support materials for heterogeneous catalysis.

Verification of Surface Conductance Model of Textile Materials

Surface conductance is one of the main parameters which describes basic characteristics of specific textile materials. These textile materials are used, for example, in environments with higher requirements on hardware electrostatic protection during their production process. Published measurement standardized methods are followed by modeling methods which do not reach satisfactory results. This paper is therefore focused on the modeling of surface conductance of textile materials. The results show that the structure of textile materials can be seen as serial-parallel connections of resistors. A derivation of this model is described.

Nanostructured Thin Film Electrocatalysts for PEM Fuel Cells - A Tutorial on the Fundamental Characteristics and Practical Properties of NSTF Catalysts

This tutorial reviews the key aspects and literature to date around the nanostructured thin film (NSTF) electrocatalyst technology platform for PEM fuel cells and electrolyzers. The NSTF technology is to date the only practical example of an extended surface area catalyst shown to effectively address several of the performance, cost and durability barriers facing cathode and anode catalysts for fuel cell vehicles. The unique physical characteristics of these ultra-thin, low Pt-loaded electrodes also require alternative solutions for water management and impurity tolerance. We present an overview of the NSTF electrocatalysts' four primary differentiating features, to show how their material and basic geometric and material characteristics translate to functional performance factors. We conclude by briefly recounting the historical origins of the NSTF material with the recommendation that the field of ordered organic molecular solids represents a large opportunity for developing tailored support materials for heterogeneous catalysis.

Mechanical, fracture-mechanical, hydric, thermal, and durability properties of lime–metakaolin plasters for renovation of historical buildings

An extensive set of parameters of several lime–metakaolin plasters, including basic material characteristics, mechanical and fracture-mechanical properties, durability characteristics, hydric parameters and thermal properties, is presented. In a comparison with the reference lime plaster without any additives, the experimental results show three- to five-fold increase in strength, about 25% decrease of water vapor diffusion coefficient, 20% decrease of water absorption coefficient and a very high increase of freeze/thaw resistance. Using the lime of very high purity in lime–metakaolin plasters (98.0% of CaO+MgO) is found preferable to lower-purity limes; the main differences are observed in the freeze/thaw resistance, mechanical and fracture-mechanical parameters. A comparison with two commercial renovation plasters shows that the only notable advantage of the best commercial plaster studied over the best lime–metakaolin plaster is in its lower moisture diffusivity but it can be matched relatively easily by using hydrophobization admixtures. Therefore, it can be concluded that the lime–metakaolin plasters can find a wider application range in the renovation of historical buildings in the future and may at least partially replace the current renovation plasters as a cheaper and equally effective solution.

A Review of Some Biomechanical Principles That Govern the Response Characteristics of Anatomic Materials.

Biomedical/biomechanical engineers testifying on behalf of their clients are often asked to render expert opinions about whether or not certain anatomical tissues/organs will fail when exposed to various types of biomechanical loading. Questions arise as to whether or not the loading poses a risk factor for potential failure of the material so-exposed; and whether or not the loading on the respective tissues/organs is excessive, unsafe, and/or otherwise trending toward the ultimate wear out of the material, with significant pathological consequences. In order to express their opinions to a reasonable degree of scientific certainty, these expert witnesses must have a working knowledge of certain, very basic biomechanical response characteristics of biological materials. Toward that end, formulated in this paper is a paradigm for the evaluation of expert testimony. The model is based on five fundamental principles that govern such material responses, along with specific implications that can be deduced from them. These implications derive from a consideration of three attributes of living (mainly soft) biological tissues, that are conspicuously absent in all other materials subjected to the same or similar types of loading. The three attributes are: viscoelastic material properties, the ability of these organs/tissues to adapt, and their capacity to heal.

Properties of lime composites containing a new type of pozzolana for the improvement of strength and durability

The basic material characteristics, mechanical and fracture-mechanical properties, durability characteristics, hydric parameters, and thermal properties of several lime–pozzolana composites with different dosage of the burnt Czech clay shale are investigated. Within the studied range of the pozzolana:lime (P:L) ratio of 0.2:2.3–1.7:0.8, the mix with P:L=0.9:1.6 is found to be the most effective solution. Its compressive strength, bending strength, effective fracture toughness, fracture toughness, and fracture energy are up to ten times higher, as compared with the reference lime composite without pozzolana addition, the water transport parameters are several times lower, the water vapor transport parameters are only about two times higher, the freeze/thaw resistance is significantly better, and the thermal properties are comparable. In a comparison with the reference lime–metakaolin composite, the corresponding material with burnt Czech clay shale is found to achieve similar mechanical and fracture-mechanical properties, its freeze/thaw resistance is somewhat worse, the water absorption coefficient is slightly lower, the water vapor diffusion coefficient is slightly higher, and the thermal properties are comparable. Therefore, the new lime–pozzolana composites have a good potential to be used as surface layers of building structures instead of lime composites without any addition, as an alternative solution to lime–metakaolin composites.

Physicochemical fracture mechanics of bodies with cracks: achievements and prospects

Modern concepts for the assessment of strength and local fracture of structural metals and alloys that are under the simultaneous action of corrosive media and sustained static or cyclic loads are presented. Model schemes and methodology of investigations of a localized interaction of corrosive media with deformed metals near crack-like defects are proposed. Criteria and approaches to the determination of basic crack resistance characteristics of materials with regard to the stress-strain state of a material and physicochemical processes that occur during its interaction with a corrosive medium at its tip are formulated.

Laser Bead-on-Plate Welding and Overlap Seams for Increasing the Strength and Rigidity of High Strength Steel

Nowadays, high requirements are being placed on producing lighter automobiles with a higher strength. To achieve graded strength properties and to improve the rigidity of high strength thin steel sheets, the side effects of laser joining processes can be used. Local physical and geometrical effects which have previously only been observed as side effects can be purposefully used to increase the rigidity and strength of sheet metal structures. By using a focused laser beam with a diameter of several tenths of a millimetre, bead-on-plate and overlap welding seams have been produced. The energy needed to produce this kind of welding seam can be limited to a small area of the workpiece. In comparison to other procedures, the basic material characteristics are retained after welding, the main reason for this being localized heat input. The continual development of laser beam sources to provide higher output powers has extended their spectrum of use in the field of joining technologies. One aim of the research is to produce local physical and geometrical effects with two different laser systems, on the one hand, with an Nd:YAG laser with a maximum output power of 4 kW, and on the other hand with a Yb:YAG laser with an maximum output power of 3 kW. Bead-on-plate and overlap welding seams were produced to demonstrate that rigidity and strength can be increased in metal sheets. The investigations were carried out on two high strength steels H340LA with two different zinc coatings (D and ZE) and TRIP700. The sheets were tested using tensile tests, 3-point bending tests and fatigue strength tests. During the tests, metallographic analyses were carried out. Seven different specimens were investigated, one without bead-on-plate welding seams, and six with different welding geometries, expect the material H340LAZE which was investigated with three various welding geometries. To analyse the complex stress status, investigations of the residual stress and the fracture were done. Calculations of the seam volume were done to be able to calculate the tensile strength for linear bead-on-plate welding seams and the maximum force for bending overlap welding seams. The tensile and bending tests showed that higher forces were needed before failure occurred, e.g. bending the specimens. Furthermore, the investigations showed that the strength of the specimens with welding seams increased, in comparison to the specimens without welding seams. Another result of the experiments is that there is a dependency between the fatigue strength and the position of the seam relative to the direction of the testing force.

Theoretical foundations of the grinding of heterogeneous materials

It is shown that a reduction in the energy consumption during the grinding of heterogeneous materials, including polymers, could be achieved by organizing the mechanochemical process of avalanche-like fracturing in such materials. An original classical Hamiltonian formalism based the approach to the description of crack propagation dynamics in homogeneous and heterogeneous solids is developed. The complete analytical dependences of the maximal (ultimate) velocity of supercritical crack propagation in homogeneous materials and the values of crack acceleration (retardation) in different components of stressed heterogeneous materials on the basic mechanical characteristics of such materials are obtained. The conditions of crack propagation, arrest, and multiplication in heterogeneous materials with different scales of heterogeneity are analyzed.

Effects of RC beams reinforcement using near surface mounted reinforced FRP composites

This paper analyzes application of modern reinforcement methods for reinforced concrete (RC) beams using fiber-reinforced polymer (FRP) materials. Basic characteristics of FRP materials and the method of mounting the FRP bars within concrete, that is, near the surface of the beams (NSM method) are presented. The properties of this method and its advantages in comparison to externally bonded reinforcement laminate method (EBR) have been analyzed. The results of measured deflections and width of the cracks of the beams reinforced by FRP bars, depending on the load are presented and discussed, in comparison to the results obtained from the non-reinforced beams. The experimental research was published at the Faculty of Civil Engineering and Architecture of Nis in 2009.

Material Characterization of the Historical Unreinforced Masonry Akaretler Row Houses in Istanbul

The determination of built-in material properties is a difficult step during the structural assessment of historical structures. Large variations of material characteristics and the difficulty of obtaining an adequate number and type of material samples are among the major problems. In this study, the material characterization of the approximately 135 years old historical Akaretler Row Houses was carried out. Since several structural walls of the row house complex were to be removed according to the restoration design, a large number of different types of specimens could be collected for laboratory tests and a considerable amount of in situ destructive and nondestructive tests was carried out. The laboratory tests included mechanical, physical, and chemical tests on original materials such as bricks, mortar, brick prisms, cores consisting of two layers of bricks and one layer of mortar between bricks, and wallets. The in situ tests included destructive shear tests and nondestructive rebound hammer tests. At the end of the extensive experimental study, the basic material characteristics of the late period Ottoman construction system were obtained. In addition relations between various mechanical characteristics of the construction materials, as well as the relations between the results of the laboratory and in situ tests, and destructive and nondestructive tests are presented.

POFA 콘크리트의 재료특성 및 부식 저항성 평가로의 적용

In this study, corrosion resistance of palm oil fuel ash (POFA) concrete as a blended concrete is evaluated by using electrochemical technique. The POFA is an industrial byproduct obtained from fuel ash after extracting palm oil from palm-tree. In order to obtain basic material characteristics of the POFA concrete, tests on compressive strength, slump, weight loss, bleeding and expansion ratio were carried out the early-aged POFA concrete. On the other hand, durability characteristics, both chloride penetration and carbonation depth test, were also conducted. Finally, corrosion resistance were evaluated by applying electro-chemical artificial crack healing technique, and the tests on the impressed voltage characteristic, galvanic current and linear polarization resistance. From the experimental results, it was found that long-term strength, bleeding, lower slump ratio, expansion ratio, chloride penetration, carbonation and corrosion resistance were improved by using the POFA due to activated pozzolanic reaction. It can be also mentioned that POFA concrete has a potential to be used as a cementitious binder for green-recycling resources.

Active Biological Materials

Cells make use of dynamic internal structures to control shape and create movement. By consuming energy to assemble into highly organized systems of interacting parts, these structures can generate force and resist compression, as well as adaptively change in response to their environment. Recent progress in reconstituting cytoskeletal structures in vitro has provided an opportunity to characterize the mechanics and dynamics of filament networks formed from purified proteins. Results indicate that a complex interplay between length scales and timescales underlies the mechanical responses of these systems and that energy consumption, as manifested in molecular motor activity and cytoskeletal filament growth, can drive transitions between distinct material states. This review discusses the basic characteristics of these active biological materials that set them apart from conventional materials and that create a rich array of unique behaviors.

Reduction Kinetics of Iron Ore Materials by Gases

The proposed balance logic-statistical model of the blast furnace process is based on the use of material and thermal balances along with calculations of heat- and mass exchange taking into account the non-uniformity of gas and burden distribution on the radius of the furnace and influence of the basic metallurgical characteristics of iron ore raw materials and coke on the indices of blast furnace operation. As a check of the applicability of the model, calculations on the most critical parameters of the blast furnace process – the smelting of ferromanganese and iron nickel with a graphical representation of heat- and mass exchange processes, dynamics of oxides reduction on the height and radius of the blast furnace have been carried out.

High performance concrete containing lower slag amount: A complex view of mechanical and durability properties

A wide set of parameters of concrete containing 10% of ground granulated blast furnace slag as Portland cement replacement involving basic material characteristics, mechanical and fracture-mechanical properties, durability characteristics, hydric and thermal properties and chloride binding characteristics is determined and compared with the parameters of reference Portland cement concrete with otherwise the same composition. The experimental results show that the replacement of Portland cement by even such a low amount of ground granulated blast furnace slag as environmental more friendly and still valuable alternative binder either affects positively or at least does not worsen in a significant way the substantial properties of hardened concrete mix. The mechanical and fracture-mechanical properties are found to be very similar as compared to the reference mix, the liquid water transport parameters of the mix containing slag are significantly better, the basic durability characteristics such as the frost resistance and corrosion resistance similar and very good, the resistance against de-icing salts slightly worse. These findings may be significant for the future use of slag in the countries where its available amount is decreasing and its more efficient use as a binder than it was common to date can appear necessary.

Increasing Rigidity and Strength using Local Effects of Bead‐on‐Plate Laser Welding Seams

In order to achieve graded strength properties and to improve the rigidity of metallic materials, side effects of the laser joining process are used. Local physical and geometrical effects which have only been observed as side effects are to be used purposefully. The investigations take place in context of the SFB 675 “high‐strength metallic structures and joints by setting up scaled local material properties”. The energy needed to produce bead‐on‐plate welding seams can be limited to a small area of the workpiece by using a focused laser beam with a diameter of tenths of a millimetre. The heat affected zone of a laser beam is very small. In comparison to other welding procedures, lower heat input is the main reason that basic material characteristics remain unaffected after welding. The progressive development of laser beam sources to higher available laser output power has extended their spectrum of use in the field of joining technologies [1, 2].It should be pointed out that local physical and geometrical effects can be used to achieve specific material characteristics. Bead‐on‐plate laser welding seams were produced to demonstrate that strength and rigidity can be increased in metal sheets. First investigations are carried out on the micro‐alloyed high‐strength steel H340LAD. The sheets were tested using tensile tests and also with 3‐point and 4‐point bending tests. Six different specimens were investigated, one without welding seams and five with different laser based welding seam types. The tensile and bending tests showed that higher forces were needed to rupture or to bend the laser welded specimens. Furthermore, the investigations showed that the strength of the specimens was increased in comparison to the specimens without welding seam.

Modeling the Heat, Air, and Moisture Response of Building Envelopes: What Material Properties are Needed, How Trustful Are the Predictions?

Abstract The physical models which form the basis for the different software tools used to predict heat, air, and moisture response of building envelopes seem quite diverse. For example, various “potentials” are used, and each individual potential demands apparently different properties. Anyhow, when digging into the physics and confronting the theory with what is measurable, then an array of eight basic material characteristics appear, all backed by an experimental rationale. Adapting that array to the potentials in use is not a question of creating new properties but of implementing the basic ones into potential-adapted expressions. A different problem, however, is that these basic properties are macroscopic in nature, i.e., represent the complexity of a material at the micro-scale by one single “average” number. That introduces restrictions as to the use of the property values measured experimentally. Hence, those restrictions are typically mixed up with the inability of the actual software packages to represent reality in full detail. Too many times, assumed incorrectness of the property values are blamed for causing the differences found between the predicted and real heat, air, moisture response of envelope parts. That inability, instead, should convince researchers and building engineers that the way to gain a well balanced understanding of the heat, air, and moisture response of envelopes is not by modeling only but by combining modeling with testing and field experience.

Plastic Ankle Foot Orthosis for Hemiplegics and Structural Analysis

AFO is a device, which is usually recommended for hemiplegics to help their pathologic gait. To date, no good engineering guidance is available. We analyze mechanical characteristics of AFO and evaluate structural stability effect of thickness of ankle foot orthosis (AFO). The study is to provide a guidance to make a functional AFO. Basic material characteristics such as Young’s modulus and Possion’s ratio were measured through material tests. Finite element models were made and analyzed based on various shapes and gait analysis. Young’s modulus of polypropylene is 1.15 GPa and Possion’s ratio is 0.35. Rigidity of AFO is more affected by the ankle width than the thickness of ankle area. The strain calculated by finite element analysis (FEA) in the neck area is twice as much as experimental results but the both of their trend show similar pattern. AFO was studied through its structural and functional analysis. Experimental structural analysis and FEA were made and compared.