Physical-mechanical Characteristics Research Articles

The application of freeze-thaw cycle treatment on landfill sludge: Impact on physicochemical properties and physical-mechanical characteristics

The physical-mechanical properties of dewatered sludge are important for the stability of landfills and their resource utilization. In this study, the physical-mechanical properties of sludge were comprehensively investigated by considering its various properties (e.g., particle morphology and size, compression and consolidation characteristics, shear strength, dewatering capacity, and microstructure) under different freeze-thaw cycles. The results indicated that extracellular polymers (EPS) will be destroyed during freeze-thaw cycles, and bound and interstitial water are converted to free water, which also enhances the sludge's dewatering efficiency and strength. Furthermore, multiple freeze-thaw cycles significantly enhanced the consolidation efficiency, leading to a denser sludge cake under pressure. A dense sludge structure enhances particle interlocking, improving internal friction angle and shear strength. The highest treatment efficiency was observed after 1–3 freeze-thaw cycles. Sludge properties tend to be stable when the freeze-thaw cycles are over 6. The research results will provide a reference for sludge dewatering reduction and its resource utilization.

Multi-objective parametric optimization process of hybrid reinforced titanium metal matrix composite through Taguchi-Grey relation analysis (TGRA)

Hybrid titanium metal matrix composites (HTMMCs) are advanced composite materials that can be tailored to a variety of applications. Because of their decreased fuel consumption and cost, they are popular in the transportation industry. Using multi-objective optimization and Taguchi-based Grey relational analysis (TGRA), this study investigates the impact of hybrid reinforced HTMMCs synthesized using powder metallurgy on their physic mechanical properties. The research investigates reinforcements such as B4C, SiC, ZrO2, and MoS2 at various compaction pressures, milling durations, and sintering temperatures. The best powder metallurgy control parameters for HTMMC synthesis, with a milling time of 5 h, a compaction pressure of 40 MPa, a sintering temperature of 1200 °C, and a sintering time of 1 h, and a compaction time of 40 min. According to validation results, HTMMC material with optimized process parameters had experimental densities, porosities, hardness, compressive strength, and wear rates of 4.29 gm/cm3, 0.1178%, 71.53RHN, 2782.36 MPa, and 0.1519 mm3 correspondingly. The material hardness was increased by 1.99% and compressive strength by 2.87%. The use of Taguchi and GRA techniques strongly verified that the impact of milling duration and sintering temperature was the greatest of all five factors. The novel synthesized hybrid reinforcing HTMMCs outperformed pure Ti grade 5 and single and double fortified HTMMCs in terms of physic mechanical characteristics. As a result, the newly developed tetra hybrid reinforced HTMMC material is expected to be used in heavy-duty vehicles, aerospace, automobiles, maritime, and other industries.

Evaluation of the Productivity and Potential Utilization of Artemisia dubia Plant Biomass for Energy Conversion.

Field studies with the large-stemmed plant Artemisia dubia (A. dubia) have been carried out at the Vėžaičiai Branch of LAMMC since 2018. According to three years of experimental results, annual dry matter (DM) yield varied from 7.94 to 10.14 t ha-1. Growing conditions, nitrogen application level, and harvesting time had statistically significant impacts on A. dubia productivity. The most important tasks of this article were to investigate and determine the factors influencing A. dubia plant biomass productivity and the evaluation of technological, power, and environmental parameters of plant biomass utilization for energy conversion and the production of high-quality solid biofuel pellets. For the experiments, six variants of A. dubia samples were used, which were grown in 2021. Plants were cut three times and two fertilization options were used: (1) no fertilization and (2) fertilization with 180 kg ha-1 of nitrogen fertilizer. These harvested plants were chopped, milled, and pressed into pellets. The physical-mechanical characteristics (moisture content, density, and strength) of the A. dubia pellets were investigated. During this study, it was found that the density in the dry mass (DM) of the pellets ranged from 1119.86 to 1192.44 kg m-3. The pellet moisture content ranged from 8.80 to 10.49%. After testing pellet strength, it was found that the pellets which were made from plant biomass PK-1-1 (first harvest without N fertilization) were the most resistant to compression, and they withstood 560.36 N of pressure. The dry fuel lower heating value (LHV) of the pellets was sufficiently high and was very close to that of the pine sawdust pellets; it varied from 17.46 ± 0.25 MJ kg-1 to 18.14 ± 0.28 MJ kg-1. The ash content of the burned pellets ranged from 3.62 ± 0.02% to 6.47 ± 0.09%. Emissions of harmful pollutants-CO2, CO, NOx, and unburnt hydrocarbons (CxHy)-did not exceed the maximum permissible levels. Summarizing the results for the investigated properties of the combustion and emissions of the A. dubia pellets, it can be concluded that this biofuel can be used for the production of pressed biofuel, and it is characterized by sufficiently high quality, efficient combustion, and permissible emissions to the environment.

Prediction of tensile behavior of compression therapeutic biomedical materials by mesoscale laid-in loop model

Tubular laid-in weft-knitted compression (LWC) therapeutic materials have been extensively applied in medical clinic treatment and daily healthcare management. Limited studies have explored the mechanical mechanisms through the numerical analytical models for the development and performance prediction of laid-in fabrics. This study developed the three-dimensional (3D) finite element (FE) laid-in loop model to simulate and predict the tensile behaviors of LWC materials based on the determination of geometric models and investigation of yarn mechanical properties. Through the constructed FE mesoscale models with various physical-mechanical characteristics of inlay yarn materials, it was found that the ground yarns and inlay yarns played distinct roles in producing tensile stresses under the course and wale direction of stretching strains. These tensile stresses determined the selection of yarn materials for controlling the tension of laid-in knitted fabrics in end applications. Then, the interfacial pressure dosages exerted by LWC materials were quantitively obtained based on the simulated Young's moduli values and modification of Laplace's Law model. The accuracy and acceptability of proposed mechanical laid-in models (mean error: 10.22 %) and pressure prediction models (mean error: 14.70 %) were validated by the comparative studies. The simulation methods and results created a visual tool for dynamically illustrating the tensile behaviors and predicting pressure performances of the elastic therapeutic materials in functional material design of biomedical compression textiles.

Obtaining and Characterizing New Types of Materials Based on Low-Density Polyethylene and Thermoplastic Starch

Significant interest is devoted to the development of new polymer blends by using concepts of the circular economy. Such materials have predetermined properties, are easy to recycle, ecological, and have a low carbon footprint. This research presents obtaining and characterization of polymer blends based on low-density polyethylene (LDPE) and thermoplastic starch (TPS). In the first stage, TPS was obtained through the gelatinization process, and, in the second stage, mixtures of LDPE and TPS were obtained through a melt mixing process at 150 °C for 7 min. The physical–mechanical characteristics of the samples, like hardness, elongation at break, rebound resilience, and tensile strength, were determined. The sample containing maleic anhydride grafted low-density polyethylene (LDPE-g-MA) as a compatibilizer shows improvements in elongation at break and tensile strength (by 6.59% and 40.47%, respectively) compared to the test sample. The FTIR microscopy maps show that samples containing LDPE-g-MA are more homogeneous. The SEM micrographs indicate that TPS-s is homogeneously dispersed as droplets in the LDPE matrix. From the thermal analysis, it was observed that both the degree of crystallinity and the mass loss at high temperature are influenced by the composition of the samples. The melt flow index has adequate values, indicating good processability of the samples by specific methods (such as extrusion or injection).

Influence of Conditions for Obtaining Polylactide-Based Materials on Their Physical-Mechanical and Rheological Characteristics

Influence of Conditions for Obtaining Polylactide-Based Materials on Their Physical-Mechanical and Rheological Characteristics

METHODS OF INJECTION STRENGTHENING OF FOUNDATIONS IN CONSTRUCTION

The article discusses the problems of strengthening strip foundations of buildings and structures. In accordance with the main reasons for strengthening foundations and artificially improving the construction properties of the soil foundation, the reserves and reserves of the bearing capacity of the soil foundation were assessed by analyzing the results of the technical condition of the building and analyzing its physical condition and mechanical characteristics. The exact dimensions of the foundation structures, their condition and the loads acting on them were determined, and the geological and hydrogeological conditions of the surrounding area were studied. A classification of methods for strengthening foundations and artificially improving the construction properties of the soil foundation is given; it is proven that strengthening methods depend on the design features of the building, types of foundations, operating loads, engineering-geological and hydrogeological conditions. In addition to the need to strengthen, as well as the capabilities and technical equipment of organizations performing this type of work, there are many other methods. Pile reinforcement methods are one of the most effective types of foundations. Research has proven that piles are not used to strengthen foundations, since the resulting dynamic impacts can lead to additional settlement of the building being restored. The study noted the basic requirements for reliable strengthening of the foundation and artificial improvement of the construction properties of the soil foundation, especially when water-saturated salty clay soils are formed at the base of the building.

Automation studies of thermo-stressed state of the core when exposed to local heat fluxes, heat transfer

Many load-bearing elements of power plants are influenced by local heat flows and convective heat exchangers. Because of this, a deformed thermostress state is formed in the bearing elements in the form of a rod of limited length. Therefore, it is important to develop special computational algorithms and corresponding programs for automated research of rods of limited length. At the same time, the developed system must take into account the physical-mechanical and geometric characteristics of the studied core and the simultaneous presence of local convective heat exchange.This work uses the fundamental laws of energy saving. The developed calculation algorithm is implemented in the form of an IBM PC Python program. The results are presented in tables.

Ecologization of Waste from the Steel Industry in Civil Engineering Works

The massive industrialization of the last century has come with the drawback of creating large waste deposits. Over the past century, steel mills have generated significant quantities of steel slag, deposited in heaps that occupy vast land areas. The desire to recycle steel slag arises from both ecological and economic interests. To achieve this goal in the steel industry, it was necessary to recycle steel slag (waste from the technological process of steel production) by using them as aggregates in civil constructions. In this work, the optimal option will be determined based on the mathematical modelling of the main physical-mechanical characteristics of the asphalt mixtures used in wear layers made with steel slag aggregates in comparison with classic asphalt mixtures.

ASSESSING MECHANICAL PROPERTIES FOR STRUCTURAL UTILIZATION OF GUADUA ANGUSTIFOLIA KUNT

This research focuses on guadua cane, one of the most representative bamboo species in Colombia, Ecuador, and Peru. Its importance lies in the physical-mechanical characteristics of each cluster, which will be presented in the development of this research. The study includes results for different structural solicitations, such as compression, flexural, and tensile strength, characterizing it as a suitable material for use in construction, distinguishing itself from wood due to its rapid growth. This research work outlines the criteria used for the experimental analysis of the material. Laboratory tests are employed to determine the physical-mechanical characteristics of guadua bamboo, including compressive strength, flexural strength, material elasticity modulus, and natural moisture content. The resulting experimental values obtained through laboratory tests will be compared with the permissible values indicated by the Ecuadorian Construction Standard NEC–SE–GUADÚA. If the values are lower than the permissible ones, the permissible value is considered. This process allows the use of these results in the structural design of houses with guadua bamboo.

Effect of Roller Burnishing and Slide Roller Burnishing on Surface Integrity of AISI 316 Steel: Theoretical and Experimental Comparative Analysis

The article presents a new method called slide roller burnishing (SRB) for the cold working of cylindrical surfaces on machine tools implemented with a novel multi-functional device. The machined material is chromium–nickel austenitic stainless steel. The deforming element is a toroidal roller whose axis crosses that of the workpiece. As a result, a relative sliding velocity occurs in the contact zone between the roller and the machined surface. The sliding velocity vector is set using the burnishing device. The theoretical background of SRB is presented. When the two axes are parallel, the well-known roller burnishing (RB) method is implemented. Thus, RB is a special case of SRB. Both processes are realized using the multi-functional burnishing device. The RB process was studied experimentally and optimized according to three criteria, based on the relationship between the surface integrity and operating behavior of the respective component, to achieve three processes: smoothing, hardening, and mixed burnishing. Using the optimal RB parameters obtained, the dependence of the results of SRB on the crossing angle was investigated and optimized. A comparative analysis was performed between the optimized RB and SRB processes (respectively for their three variants: smoothing, hardening, and mixed) based on geometrical and physical–mechanical characteristics of the surface integrity. The main advantage of the SRB is that it provides smaller height roughness parameters (improvement by 42%) and a higher surface microhardness (improvement by 7%) than RB.

Analysis of the cold recycling asphalt pavements method from Romania

The present paper presents a documentation on the realization of the dosages from recycled mixtures, highlighting the change in the test methods regarding the composition and the determination of the physical-mechanical characteristics according to the latest technical regulations. Practically, the structure of the new norm for cold recycled road materials aligns with the new European requirements in accordance with the provisions that the mixtures must meet, but still the problem remains on how to prepare the samples in the laboratory and determine the value of the stiffness modulus of the considered mixture, value which practically in the norm is considered based on good practice. Determining the real value of the stiffness modulus is a decisive factor in the dimensioning of the road structure reinforcement because it can considerably influence the thickness of the layers that make up the resistance structure. Therefore, the paper presents a study on the new methods of making samples in the laboratory and values of the stiffness modulus taken into account when dimensioning the reinforcement of road structures according to the composition of the considered materials.

Структура и свойства покрытий SiO2 – Cr2O3, полученных методом импульсного магнетронного распыления на керамической основе ZrO2

The technology for SiO2 – Cr2O3 coatings on a ceramic Y-TZP (ZrO2 stabilized by Y2O3) zirconia base has been proposed. The coating was produced in three stages: 1) formation of SiO2 adhesion layer by application of 5-amino-propyltriethoxysilane alcohol solution to the ceramic base surface followed by heat treatment at 450 ± 5 °C for 30 min. The next step was application of Cr at purity of 99.9 % by pulse magnetron sputtering; 3) diffusion oxidation of Cr, applied on the ceramic base, to Cr2O3 in the muffle furnace at 450 ± 5 °C for 30 min. Dependence of physical-mechanical characteristics of coating depending on preparatory and finishing operations (abrasive blasting, polishing) has been investigated. Samples with submicron coating with thickness of 150 ± 20 nm, having nanostructured lamellar structure, possessing open porosity value of 1.3 %, microhardness 2000 HV, roughness Ra 0.32 – 0.63, friction coefficient 0.175 and increased by 184 % wear resistance to abrasion loadings in comparison with pure zirconia ceramics were obtained.

Analysis of the choice of the method for the elaboration of dosages for an asphalt mixture

The purpose of this paper is to perform an analysis regarding the choice of a method for designing a dosage of an asphalt mixture. There have been concerns in the field of asphalt mix dosing since 1920 when Field and Hubbard introduced the impact compaction with the Proctor hammer for laboratory testing. Later, Marshall introduced the method that bears his name and which remained the most used method for determining the asphalt mixture dosages in Romania. Since it was found that the density of the samples obtained in the laboratory did not correspond to the density of the cores extracted from the compacted asphalt layers, the gyratory compaction was introduced, which is now frequently applied in the USA and other European countries. The study presented in this paper deals with the problem of establishing the mixture of aggregates, filler and binder in terms of the volumetric method (Superpave) and Marshall method, presenting both theoretically and experimentally the dosage study of an asphalt mixture type BA16 (asphalt concrete with maximum grain size of 16 mm) but also the physical-mechanical characteristics obtained following the application of the two methods for determining the dosage for the studied BA 16 type asphalt mixture.

Old Sulfidic Ore Tailing Dump: Ground Features, Mineralogy, Biodiversity—A Case Study from Sibay, Russia

The Urals (Russia) are among the largest mining areas in the world, with millions of tons of mine waste deposited. An old sulfidic tailing dump formed over decades of mining activities at the Sibay ore-processing plant is a typical cause of acid mine drainage (AMD) formation, posing a threat to ecosystems of neighboring environments. In this study, the formation of oxidized surface soil layers in four zones of the Sibay tailing dump was revealed, and their chemical–mineralogical and physical–mechanical characteristics were analyzed. According to the results of the metabarcoding of hypervariable regions of the 16S rRNA genes, oxidation in soil layers was associated with the activity of sulfur- and iron-oxidizing acidophiles represented by a few genera: Ferroacidibacillus, Sulfoacidibacillus, Sulfobacillus, and Ferroplasma. The structure of the microbial communities in soil layers differed depending on the zone and depth of sampling. In the samples characterized by the weak oxidation of sulfide minerals, microbial communities were dominated by bacteria of the genus Pseudomonas. The data obtained in this research are of importance to predict the oxidation/leaching processes in mine wastes and their negative environmental impacts in the mining region, as well as to develop technologies for processing these raw materials.

Investigation of the stress-strain state of foundation structures in determining the vertical stiffness of piles using different software systems

The results of numerical modeling of the interaction between a multi-storey building on a pile foundation and the soil base in the "Lira-SAPR" software are presented. A comparison of the stress-strain state of foundation structures was performed using different methods for determining vertical stiffness (Rz) in single-node FE 57 (this element is designed to model the behavior of a pile together with the surrounding soil, similar to FE 56, and can implement the interaction with the "SOIL" system). Piles were modeled by a chain of single-node FE 57 connected by vertical bars.
 In the first variant, the calculation of the building was performed in the "Lira-SAPR" software. To determine the vertical stiffness in FE 57, a soil model with physical-mechanical characteristics was created, and layering was defined according to the engineering-geological cross-section in the "SOIL" system. The calculation of vertical stiffness took into account mutual influence and the model of the conditional foundation.
 In the second variant, the determination of vertical stiffness (Rz) in FE 57 was carried out using the "Plaxis 3D" software. The overall model of above-ground structures, foundations, and all necessary loads were created in the "Lira-SAPR" software. Subsequently, an export to "Plaxis 3D" was performed, where the soil was previously modeled as a three-dimensional soil mass (with characteristics and strengths of layers similar to those created in the "SOIL" system) using the "Hardening soil" behavior model. After the import into "Plaxis 3D," the analysis of the "Soil-Foundation-Structure" system was conducted, and the obtained values of vertical stiffness (Rz) in FE 57 were exported back to "Lira-SAPR". After the export of "refined" values of vertical stiffness to "Lira-SAPR", a general static analysis and comparison of the stress-strain state of foundation structures with the first calculation variant was performed.
 It was established that the vertical stiffness in FE 57 in the first variant is higher than in the second, accordingly, the total displacements for the first variant are smaller. The importance of using the connection between "Lira-SAPR" and "Plaxis 3D" or other specialized geotechnical software complexes was demonstrated to obtain more accurate results of the interaction of the "Soil-Foundation-Structure" system due to the possibility of using nonlinear soil models to better describe the behavior of the foundation.

STUDY OF NON-FUEL APPLICATION OF BROWN COAL DERIVATIVES FOR BITUME MODIFICATION

The article shows research into the non-fuel use of brown coal derivatives for the modification of bitumen. The work used petroleum road grade bitumen BND 60/90 with a flash point in an open crucible of 260 °C, a softening temperature (using the ring and ball method) of 48 °C, resin after lignite thermal destruction and rubber waste. and powder. Based on the fact that the most relevant technologies for the non-fuel use of brown coal concern areas aimed at obtaining wax, humane preparations, adsorbents, obtaining valuable derivatives in the form of resins, GR, etc., an assessment was made of the non-fuel use of brown coal derivatives for modification bitumen. Analysis of the experimental results showed that the studied quality indicators of the composition samples, which include waste rubber powder, have an increased complex of both thermophysical and physical-mechanical characteristics. This is obviously due to the fact that, as a result of thermal destruction of rubber powder, the swelling process occurs faster compared to crumb rubber with a size of 2.5–4.5 mm. However, the process of destruction and dispersion in both cases does not occur completely, of course, and the volume of edematous rubber particles contains resins and polyaromatic components that affect the value of both thermophysical and physical-mechanical characteristics. Thus, it has been established that the optimal composition for creating effective polymer-modified bitumens with an increased complex of thermo-physical and physical-mechanical characteristics is 40 % by weight of rubber powder and 5 % by weight. brown coal resins after thermal destruction. It is shown that the results of laboratory studies have proven the prospects of using brown coal tar after thermal destruction for the modification of road bitumen. Summarizing research into the direction of non-fuel use of brown coal derivatives in the form of liquid products – tar resins of brown coal after thermal destruction for the modification of bitumen materials, it should be noted that the results obtained are moderate in comparison with existing directions for the production of polymer-modified bitumens. Modification of bitumen with primary and secondary polymers makes it possible to significantly improve their adhesion and performance characteristics compared to brown coal resins after thermal destruction. The use of brown coal resins after thermal destruction is much less effective in improving the elasticity, heat resistance and reducing the fragility of bitumen compositions compared to the use of thermoplastic and thermoelastomer modifiers in the production of polymer-modified bitumens.

MODERNIZATION OF MOVEABLE CONNECTIONS OF THE SECTION OF THE SOWING COMPLEX

The efficiency of planting seeds and, therefore, the yield of agricultural crops depend significantly on the characteristics of the mechanisms of copying sowing sections. These mechanisms can be conditionally divided into two categories: radial and parallelogram. Radial mechanisms with leashes are used in traditional technologies and require high-quality preliminary processing, and radial mechanisms with pressure rods are suitable for any agrophones The durability of the movable joints of the parallelogram copying mechanism of the sowing complex depends on their resistance to wear. This stability is determined by the mode of operation, chemical composition and structure of the surface layer of parts, as well as physical-mechanical and tribotechnical characteristics. With an average seasonal task for Agro-Soyuz Turbosem II 19-60 sowing complexes within 3–4 thousand hectares, the total service life of experimental parts is at least 4 years, which is at least four times more than in the case of serial parts. The positive effect of the absence (or the presence within the measurement error) of wear of steel parts of movable joints that work in connection with polymer composite material (PCM) was revealed. The average resource of experimental parts in the hinges of the parallelogram copying mechanism for Agro-Soyuz Turbosem II 19-60 seeding complexes is 20589 ha. The average value of the wear of the experimental parts was determined to be 1.78 mm, and the intensity of their wear was 1.02×10-4 mm/ha. It was established that the wear of UPA-6-30 PCM parts in the moving joints of the copying mechanism occurs according to the normal distribution law ( = 0.108), which allows very accurate prediction of their resource. The consistency of the experimental distribution with the theoretical distribution was checked using the Kolmogorov criterion. It is confirmed that the distribution takes place according to the normal law. An analysis of reliability indicators during shortened tests was also carried out and the probability of failure-free operation of experimental parts made of polymer-composite material was determined. According to the results of field tests of the elements of the movable joints of the mechanism of copying the sowing complex, it was established that the resource value of 20,558 hectares exceeds the indicators of serial parts by 4 times.

Environment’s effect on wood characteristics of white jabon grown in West Java and Banten area, Indonesia

This study analyzed the diversity of physical properties and mechanical properties of white jabon (Neolamarckia cadamba (Roxb.) Bosser) from various locations and ecological conditions in West Java and Banten Indonesia. White jabon wood samples were taken from 8 locations in West Java and the Banten region. Tree ages ranged from 5 to 6 years. This wood was then tested to compare physical characteristics (density or specific gravity) and mechanical characteristics (modulus of rupture (MOR) and modulus of elasticity (MOE)). The results showed that wood density ranged from 0.29 to 0.43 g.cm-3, MOR ranged from 361 to 641 kg.cm-2, and MOE ranged from 31,117 to 58,910 kg.cm-2. The highest density average (0.43 ± 0.004 g.cm-3) was produced from Cianjur, and the lowest density average (0.29 ± 0.010 g.cm-3) was from Tanjungsari Sumedang. Environmental factors (precipitation and altitude) affect the density of wood. Separately, rainfall has a low effect and a negative relationship to jabon wood density, while altitude has a high influence and a negative relationship to jabon wood density. Andosol soil types tend to produce low density wood.

Research of a New Chemically Resistant Repair Mortar Modified with Secondary Raw Materials

This paper deals with the research of a new chemically resistant cement repair mortar modified with selected secondary raw materials. The aim of this work is to study the influence of particle distribution of fly ash on selected characteristics of the developed remediation material. This new mortar will be suitable for use in the extremely aggressive environment of sewers. The monitored parameters include key physical-mechanical characteristics and resistance to the attack of aggressive biogenic sulfuric acid. The chemical resistance was tested by simulating the exposure environment in laboratory conditions, according to the methodology of DIN 19573. The obtained results show that by optimizing the particle distribution of fly ash it is possible to maintain the values of physical-mechanical characteristics and improve the chemical resistance of test specimens of new repair mortar.