Increase In Density Of Material Research Articles

Aerodynamic analysis of a windmill water pump using blade element momentum theory

A windmill water pump has been designed based on simulation data using the Blade Element Momentum Theory (BEMT) method. According to the simulation data, a 10-blade configuration with an incidence angle of 7 degrees is predicted to produce an output torque of 40 Nm. To simplify the turbine manufacturing process, a turbine cross-sectional profile with a bent flat plate-based airfoil was selected. The simulation results indicate that providing an incidence angle of 7 degrees compensates for the resulting decrease in aerodynamic performance compared to using a cambered airfoil. Furthermore, a dynamic analysis was conducted to predict the turbine's rotational speed. With a 10-blade configuration and a blade material density of 2900 kg/m³ at a wind speed of 5 m/s, it is predicted to rotate at a steady speed of 167 rpm. When the material density is increased to 3500 kg/m3, the rotor's predicted rotational speed is 160 RPM. While the difference in rotational speed due to the increase in material density is not very significant, the time to reach steady-state conditions varies considerably. Specifically, a turbine with a material density of 2900 kg/m3 requires a settling time of 168 seconds, while a turbine with a density of 3500 kg/m3 requires a settling time of 310 seconds. This notable difference suggests that mass inertia primarily influences the dynamic response of the turbine in achieving a steady rotational speed without significantly affecting the turbine's aerodynamic performance.

Research on Thermal Insulation Performance and Impact on Indoor Air Quality of Cellulose-Based Thermal Insulation Materials.

Worldwide, the need for thermal insulation materials used to increase the energy performance of buildings and ensure indoor thermal comfort is constantly growing. There are several traditional, well-known and frequently used thermal insulation materials on the building materials market, but there is a growing trend towards innovative materials based on agro-industrial waste. This paper analyses the performance of 10 such innovative thermal insulation materials obtained by recycling cellulosic and/or animal waste, using standardised testing methods. More precisely, thermal insulation materials based on the following raw materials were analysed: cellulose acetate, cigarette filter manufacturing waste; cellulose acetate, cigarette filter manufacturing waste and cigarette paper waste; cellulose acetate, waste from cigarette filter manufacturing, waste cigarette paper and waste aluminised paper; cellulose from waste paper (two types made by two independent manufacturers); wood fibres; cellulose from cardboard waste; cellulose from waste cardboard, poor processing, inhomogeneous product; rice husk waste and composite based on sheep wool, recycled PET fibres and cellulosic fibres for the textile industry. The analysis followed the performance in terms of thermal insulating quality, evidenced by the thermal conductivity coefficient (used as a measurable indicator) determined for both dry and conditioned material at 50% RH, in several density variants, simulating the subsidence under its own weight or under various possible stresses arising in use. The results showed in most cases that an increase in material density has beneficial effects by reducing the coefficient of thermal conductivity, but exceptions were also reported. In conjunction with this parameter, the analysis of the 10 types of materials also looked at their moisture sorption/desorption capacity (using as a measurable indicator the amount of water stored by the material), concluding that, although they have a capacity to regulate the humidity of the indoor air, under low RH conditions the water loss is not complete, leaving a residual quantity of material that could favour the development of mould. Therefore, the impact on indoor air quality was also analysed by assessing the risk of mould growth (using as a measurable indicator the class and performance category of the material in terms of nutrient content conducive to the growth of microorganisms) under high humidity conditions but also the resistance to the action of two commonly encountered moulds, Aspergillus niger and Penicillium notatum. The results showed a relative resistance to the action of microbiological factors, indicating however the need for intensified biocidal treatment.

Investigation of performance of hydraulic excavators by co-simulation of multibody dynamics and discrete element method

Modelling of machine-material interaction system is challenging. Many efforts have been made in the past to predict machine-material interactions through analytical and numerical models. However, few studies have focused on the dynamic response of machine to materials in automated machine operations. In this work, the co-simulation of multibody dynamics for excavators and discrete element method for granular materials is employed to evaluate the excavator performance. The results show that the full working cycle of excavators can be well captured by the co-simulation method, and the variations of the hydraulic pressure and flow rate and the power consumption with cylinder positions can be obtained. The results also demonstrate that with the material density increasing, the bucket payload experiences small changes. The complex bucket-particle interactions mainly occur in the process of the digging, loading, and lifting, while the significant hydraulic power consumption and intense particle-to-bucket interactions take place in the digging process. • Excavator performance is evaluated by MBD-DEM co-simulation. • Bucket payload experiences small changes with the increase of material density. • Larger material density results in more hydraulic power consumption. • Bucket-particle interaction forces increase with the material density increasing. • Severe wear on the bucket occurs primarily during the digging process.

Partial replacement of copper slag with treated crumb rubber aggregates in alkali-activated slag mortar

Copper slag (CS) is an industrial waste, which is generally disposed of in landfills, posing threats to the environment. Alternatively, it can be used as natural aggregate replacement in concrete/mortar, however, it results in a significant increase in material density, production and handling cost. The use of crumb rubber in combination with CS can overcome these problems, but there was no prior study on effect of such combination on the properties of alkali activated mortars (AAMs). The primary aim of this study is to address the problem stated above by replacing CS with 5, 10, 15% (by volume) crumb rubber in alkali-activated slag mortars. Furthermore, the effect of pre-treatment of crumb rubber aggregates with sodium hydroxide (NaOH) solution for 1 h and 24 h on workability, compressive strength, flexural strength, water absorption, thermal conductivity, and microstructural properties of mortar mixes was investigated. Based on the test results, the use of crumb rubber resulted in inferior workability and mechanical strength, but better thermal insulating capability as compared to the control mix. Alkali treatment promoted the rubber-binder bond and effectively enhanced the strength of mixes, especially at an early-age (up to 59%), however, alkali treatment for 24 h drastically reduced the workability of fresh mix. Thus, it is recommended to use 10% crumb rubber pre-soaked in NaOH solution for 1 h to achieve acceptable performance. Finally, the economic and ecological analysis results revealed that the produced mortar is beneficial to the environment.

Elastic–plastic-damage model of nano-indentation of the ion-irradiated 6061 aluminium alloy

The paper presents experimental and numerical characterization of damage evolution for ion-irradiated materials subjected to plastic deformation during nano-indentation. Ion irradiation technique belongs to the methods where creation of radiation-induced defects is controlled with a high accuracy (including both, concentration and depth distribution control), and allows to obtain materials having a wide range of damage level, usually expressed in terms of displacements per atom (dpa) scale. Ion affected layers are usually thin, typically less than 1 micrometer thick. Such a low thickness requires to use nano-indentation technique to measure the mechanical properties of the irradiated layers. The He or Ar ion penetration depth reaches approximately 150 nm, which is sufficient to perform several loading-partial-unloading cycles at increasing forces. Damage evolution is reflected by the force-displacement diagram, that is backed by the stress–strain relation including damage. In this work the following approach is applied: dpa is obtained from physics (irradiation mechanisms), afterwards, the radiation-induced damage is defined in the framework of continuum damage mechanics to solve the problem of further evolution of damage fields under mechanical loads. The nature of radiation-induced damage is close to porosity because of formation of clusters of vacancies. The new mathematical relation between radiation damage (dpa) and porosity parameter is proposed. Deformation process experienced by the ion irradiated materials during the nano-indentation test is then numerically simulated by using extended Gurson–Tvergaard–Needleman (GTN) model, that accounts for the damage effects. The corresponding numerical results are validated by means of the experimental measurements. It turns out, that the GTN model quite successfully reflects closure of voids, and increase of material density during the nano-indentation.

Investigation of Mechanical and Tribological Properties of Al6061–TiB2 Metal Matrix Composites

Aluminum alloys are commonly used in transportation, manufacturing, and related production fields for commercial applications because they possess high stiffness, strength-to-weight ratio, design flexibility, corrosion, and crack resistance. For this study, an attempt has been made to fabricate and improve the mechanical and sliding wear behavior of in situ–produced aluminum metal matrix composites (MMCs) with the titanium diboride (TiB2) particulate reinforcements by varying weight percentage from zero to six. The addition of TiB2 ceramic particle reinforcements to Al6061 matrix leads to an increase in material density and also results in a significant increase in modulus of the composite and specific strength as they have hardness of 86 HRA and high elastic modulus of 560 GPa. The Brinell hardness values of the composites along with the ultimate tensile strength (UTS) values were witnessed to increase with higher content of ceramic TiB2 because of uniform particle distribution and smaller size of filler at the lower elongation percentage. The microscopic investigations indicated that the change in hardness and UTS with increase in grain boundaries was due to fine interfacial bonding and coarse grain structure. Superior performance in properties was found at 6 wt. % of TiB2. The sliding wear tests were carried out at fixed velocity and at different loads. The wear test results of composites with TiB2 filler showed higher wear resistance because of effective load transfers at matrix ceramic particle interface.

Enchasing the mechanical properties of heavy pseudo-alloys of tungsten by high-voltage electric pulse impact

The article presents a study of the effect of the high-voltage electric pulse modes of impact under pressure on the structural and mechanical properties of compacts of heavy tungsten alloy VNZh 7-3. Identified an increase in density of material, in microhardness and tensile strength with voltage increase in high-voltage discharge. The optimum exposure mode determinate, which provides the highest level of strength and ductility of the sintered material.

Ocean processes underlying surface clustering

AbstractAgeostrophic ocean processes such as frontogenesis, submesoscale mixed‐layer instabilities, shelf break fronts, and topographic interactions on the continental shelf produce surface‐divergent flows that affect buoyant material over time. This study examines the ocean processes leading to clustering, i.e., the increase of material density over time, on the ocean surface. The time series of divergence along a material trajectory, the Lagrangian divergence (LD), is the flow property driving clustering. To understand the impacts of various ocean processes on LD, numerical ocean model simulations at different resolutions are analyzed. Although the relevant processes differ, patterns in clustering evolution from the deep ocean and the continental shelf bear similarities. Smaller‐scale ocean features are associated with stronger surface divergence, and the surface material clustering is initially dominated by these features. Over time, the effect of these small‐scale features becomes bounded, as material traverses small‐scale regions of both positive and negative divergence. Lower‐frequency flow phenomena, however, continue the clustering. As a result, clustering evolves from initial small‐scale to larger‐scale patterns.

Bandgap Engineering and Optical Constants of YxAl1-xN Alloys

We study wurtzite YxAl1-xN (0≤x ≤0.22) films with (0001) orientation deposited by magnetron sputtering epitaxy on Si(100) substrates and we determine the alloys band gap energies and optical constants. Room temperature spectroscopic ellipsometry (SE) is employed in the energy range from 1 to 6.3 eV, and data modeling based on the standard dielectric function model is used. As a result of the SE data analysis the YxAl1-xN refractive index and extinction coefficient are determined. The band gap of YxAl1-xN is found to decrease linearly from 6.2 eV (x = 0) down to 4.5 eV (x = 0.22). We further observe an increase of the refractive index with increasing Y content; from 1.93 to 2.20 (at 2 eV) for x = 0 and 0.22, respectively, reflecting the increase in material density.

Vacancy Generation in Si During Solid–Liquid Transition Observed by Positron Annihilation Spectroscopy

The Doppler broadening of annihilation radiation (DBAR) measurements were performed on Czochralski and floating-zone-grown Si crystals near the melting point using a positron microbeam. Below 1380 °C, the DBAR spectra showed essentially no change. In a very narrow temperature range near the melting point, the peak intensities of the DBAR spectra (S parameter) decreased by approximately 1% suggesting an increase in material density. Upon further heating, the S parameter markedly increased until melting. This indicates the formation of thermal vacancies. Compared with theoretical calculation, both monovacancies and divacancies are considered to be formed.

Experimental and theoretical investigation of stress corrosion crack (SCC) growth of polyethylene pipes

Degradation of polymers is usually manifested in a reduction of molecular weight, increase of crystallinity in semicrystalline polymers, increase of material density, a subtle increase in yield strength, and a dramatic reduction in toughness. Stress corrosion cracking (SCC) results from strongly coupled thermo-mechano-chemical processes, and is sensitive to material composition and morphology. The individual crack propagation stage is critical in determining the lifetime of pipe. Based on author's previous works, crack layer (CL) theory model is adopted in this study to describe the individual stress corrosion (SC) crack propagation kinetics and the time interval from crack initiation to instability and break through. The effect of localized chemical degradation at the crack tip on SC crack growth kinetics is addressed. Typical SC crack growth is presented and discussed as a step-wise manner based on the proposed model. In addition, scanning electron microscopy (SEM) observation and Fourier transform Infrared spectroscopy (FTIR) analysis of failed samples obtained by accelerated SCC tests are applied to validate the proposed model. SEM is useful to identify the change of fracture mechanisms from chemically driven crack to mechanically driven crack by the formation of visible striations. FTIR analysis enables tracking of the accumulation of chemical degradation by detecting the amount of carbonyls on the crack surface. Carbonyl index is defined to compare the amount of chemical degradation quantitatively. The purpose of this paper is to continue to develop the technical theory and understanding behind SCC phenomena to facilitate all polymer pipe industries and in particular the polyethylene pipe industry to design better resins and piping systems.

Fracture initiation associated with chemical degradation: observation and modeling

The fracture initiation in engineering thermoplastics resulting from chemical degradation is usually observed in the form of a microcrack network within a surface layer of degraded polymer exposed to a combined action of mechanical stresses and chemically aggressive environment. Degradation of polymers is usually manifested in a reduction of molecular weight, increase of crystallinity in semi crystalline polymers, increase of material density, a subtle increase in yield strength, and a dramatic reduction in toughness. An increase in material density, i.e., shrinkage of the degraded layer is constrained by adjacent unchanged material results in a buildup of tensile stress within the degraded layer and compressive stress in the adjacent unchanged material due to increasing incompatibility between the two. These stresses are an addition to preexisting manufacturing and service stresses. At a certain level of degradation, a combination of toughness reduction and increase of tensile stress result in fracture initiation. A quantitative model of the described above processes is presented in these work. For specificity, the internally pressurized plastic pipes that transport a fluid containing a chemically aggressive (oxidizing) agent is used as the model of fracture initiation. Experimental observations of material density and toughness dependence on degradation reported elsewhere are employed in the model. An equation for determination of a critical level of degradation corresponding to the offset of fracture is constructed. The critical level of degradation for fracture initiation depends on the rates of toughness deterioration and build-up of the degradation related stresses as well as on the manufacturing and service stresses. A method for evaluation of the time interval prior to fracture initiation is also formulated.

Ion-beam-induced reconstruction of amorphous GaN

Wurtzite GaN can be rendered amorphous by high-dose heavy-ion bombardment. We show here that relatively low-dose reirradiation of such amorphous GaN (a-GaN) with MeV light ions can significantly change some of the physical properties of a-GaN. In particular, light-ion reirradiation of a-GaN results in (i) an increase in material density, (ii) the suppression of complete decomposition during postimplantation annealing, (iii) a significant increase in the values of hardness and Young's modulus, and (iv) an apparent decrease in the absorption of visible light. Transmission electronmicroscopy shows that a-GaN remains completely amorphous after light-ion reirradiation. Therefore, we attribute the above effects of light-ion reirradiation to an ion-beam-induced atomic-level reconstruction of the amorphous phase. Results indicate that electronic energy loss of light ions is responsible for the changes in the mechanical properties and for the suppression of thermally induced decomposition of a-GaN. However, the changes in the density of a-GaN appear to be controlled by the nuclear energy loss of light ions.

Silicon network relaxation in amorphous hydrogenated silicon

We have investigated nanovoid-free, low-defect-density, amorphous hydrogenated silicon, $a$-Si:H, with variable hydrogen content. We have observed reconstruction of all silicon-silicon bonds at temperatures as low as 430 \ifmmode^\circ\else\textdegree\fi{}C, well below the crystallization temperature. This bond reconstruction leads to a decrease in thin-film thickness and an increase in material density, about 3% for the material with 9 at. % of hydrogen, during slow hydrogen outdiffusion. These results suggest that a long-range structural rearrangement of the silicon network can occur simultaneously with hydrogen motion and this has important consequences for all metastability models in amorphous hydrogenated silicon.

Analysis of Mechanical Properties of Fabrics of Different Raw Material

The study analyzes dependence of mechanical properties (breaking force, elongation at break, static friction force and static friction coefficient) on integrated fabric structure factor j and raw material density r, among the fabrics of different raw material (cotton, wool, polypropylene, polyester and polyacrylnitrile) and woven in different conditions. The received results demonstrate that sometimes strong dependences exist (wool, polypropylene and polyacrylnitrile), whereas in some cases (cotton and polyester) there is no correlation. It was also discovered that the breaking force and elongation at break in the direction of weft increase, when fabric structure becomes more rigid. In the meantime variations of the curves in the direction of warp are insignificant. Regarding static friction force and static friction coefficient (found in two cases, when fabrics were rubbing against leather and materials), it was discovered that consistency of the curves is irregular, i. e. they either increase or decrease, when integrated fabric structure factor j growth. It was also identified that some dependences are not strong and relationship between explored and analyzed factors does not exist. Variation of all these mechanical properties with respect to material density r enables to conclude that increase of material density r results in poor dependences or they are whatsoever non-existent.http://dx.doi.org/10.5755/j01.ms.17.2.487