Durability Criteria Research Articles

Application of structural methods to assess the reliability of ship’s mechanical systems

At present, reliability indicators are of great importance at the design stages, during operation and in cases of extending the technical life. This is one of the reasons for choosing the research topic on the application of structural methods for evaluating the reliability of ship mechanical systems. The operational stage of the life cycle of ship’s mechanical systems is considered in the paper. Durability criteria such as service life, operating time, frequency of repairs are chosen as reliability indicators. In turn, work on the repair, maintenance or replacement of ship’s mechanical systems elements is carried out in accordance with the assigned regulations or in the case of an unforeseen failure. The comparison of event models of changes in the operating conditions of ship’s mechanical systems is carried out. To estimate the remaining resource in the form of graphs, events are shown by service life and operating hours, distributed by years. In order to improve the existing methods for assessing reliability, a set of elements of the average values of the residual resource and residual output is considered. The approach proposed by the authors for assessing both element by element and the entire ship mechanical system as a whole allows us to consider the residual resource from the moment of monitoring its technical condition to the transition to the limit state, to plan technical measures and prevent possible malfunctions. Three different time slices models corresponding to planned repairs and maintenance of systems, replacement of system elements and unforeseen accidents are considered in the study. The difference in the amplitudes of the calculated indicators of the ship’s mechanical systems reliability has shown that the closer the options between the maximum and minimum values are to the average, the more accurately the statistical indicators characterize this pattern. However, amplitude deviations can be used to apply fault risk assessment. This line of research seems to be important for ships in the Arctic navigation area, which are characterized by increased requirements for ship survivability.

Mechanical, Microstructural, and Durability Properties of Soil Stabilized with Alkali-Activated Jarofix for Road Applications

In this study, we investigated the feasibility of jarofix [a zinc (Zn) smelter by-product] as a potential geopolymer binder in soil stabilization for road applications. Different combinations of soil–jarofix (SJ) mixtures were prepared using sodium hydroxide (NaOH), sodium silicate (Na2SiO3), and a combination of NaOH + Na2SiO3 as alkali activators. Unconfined compressive strength (UCS) tests were performed to examine the mechanical performance of SJ mixtures, and the effects of the jarofix content, curing conditions, and curing time were investigated. Changes that occurred during the geopolymerization process were further corroborated using field-emission scanning electron microscope (FESEM) images and energy-dispersive X-ray spectroscopy (EDS) analysis. Durability tests were also performed to examine the weathering resistance of selected SJ mixtures against 12 cycles of alternating wetting and drying. Based on the experimental results, the compressive strength of bare soil was increased 8.8 times, from 0.31 to 2.75 MPa, under ambient curing (AC, at 27 ± 2°C) conditions and 6 times, from 1.1 to 6.55 MPa, under dry curing (DC, at 60°C) conditions. This increase in compressive strength was attributed to the formation of sodium alumino-silicate hydrate (N–A–S–H) gel structures during the geopolymerization process, which led to a compact soil matrix, as confirmed by the FESEM images. The specimens cured under DC conditions showed greater strength improvement than those cured under AC conditions owing to the faster rate of the geopolymerization reaction at elevated temperatures. In addition, the Na2SiO3 and NaOH + Na2SiO3 solutions were found to be the most efficient alkali activators for the SJ mixtures cured under AC and DC conditions, respectively. This durability study revealed that the alkali-activated SJ mixtures exhibit a significantly smaller loss in mass than bare soil when exposed to 12 cycles of alternating wetting and drying. Moreover, the specimens cured under DC conditions were found to be more resistant to weathering than those cured under AC conditions. Overall, soil amended with 15% jarofix (through alkali activation) satisfies the minimum strength and durability criteria recommended by Indian standards for its use as a subbase and subgrade material. The current study shows that jarofix has the potential to be used as a geopolymer binder for soil stabilization, which can help the mining sector in minimizing the volume to be stored in tailings storage facilities.

Selection of preload in tapered roller bearingsarrangement according to durability criterion

The main purpose of using tapered roller bearings is to obtain high bearing stiffness. High bearing stiffnessis achieved by using an appropriate mounting clamp in the bearing system. The mounting clamp, or in otherwords, the pre-clamp, is currently selected based on experience. The literature lacks precise indicationsregarding the size of the initial clamp of the bearing arrangement depending on the external load, and it isselected intuitively. The wrong choice of preload can have a disastrous effect on the life of the entire bearingarrangement.This study aims to determine the maximum preload in the tapered roller bearing system, taking into accountits durability and the elasticity of the bearings and the shaft.In this article, different load variants are analysed, considering the effect of preload on the fatigue life of thebearing system, and recommendations are proposed for the acceptable preload value depending on the size ofthe bearings used.

A new methodology for the mechanical behavior analysis of polyvinyl chloride and recycled polyethylene terephthalate foams: Finite element model updating using mechanical field measurements

This paper aims to characterize the intrinsic mechanical behavior of an eco-friendly foam core used in sandwich materials dedicated to the maritime sector. A thorough understanding of intrinsic properties is essential for accurate dimensional structure characterization. The model setup is based on the choice of materials that meet the criteria of sustainable development, mechanical performance, and durability to promote ecological practices in the nautical industry. Experimental tests, instrumented by a digital image correlation technique, were carried out on two types of foams: polyvinyl chloride (PVC), which is the reference foam traditionally used in marine applications, and recycled polyethylene terephthalate (rPET), the substitute foam. The sample sizes recommended by compression test standards often lead to complex stress states that do not allow direct determination of the foam's intrinsic mechanical properties. Therefore, a finite element model updating method was required to identify the anisotropic elastic behavior of these two types of foams.

Comparison of Mechanical Properties of Ductile/Brittle Epoxy Resin BFRP-AL Joints under Different Immersion Solutions.

The bonding properties of BFRP composites have been demonstrated in previous studies, satisfying the strength and durability criteria. In this paper, a further in-depth study is carried out to bond Basalt Fibre Reinforced Polymer (BFRP) to Aluminum Alloy 5052 using two bonding agents, Aralite® 2012 and Aralite® 2015, respectively. The salt sprays under 80 °C, 3.5% NaCl environment; 80 °C, 5% NaCl environment; and pure water environment are also considered for comparison. Experimental results show that joints created with Araldite® 2012 adhesives show higher average breaking strength (10.66 MPa at 720 h) and better ductility in a 5% NaCl environment. While the Araldite® 2015 adhesive joint exhibits a combination of tear failure and interface failure, along with thin-layer cohesion failure. In the SEM images of the two adhesive joints' failure, fiber pullout due to tension and damage at the interface between fiber and resin is apparent. To validate the experimental outcomes, water absorption testing, DSC, TGA-DTG, and FTIR experiments were conducted on dog-bone-shaped adhesive specimens to elucidate the results.

Effects of Mixture Proportions and Levels of Vibration on the Physical Characteristics and Durability of Concrete Used in Korean Pavements

This study investigated the effects of mixture proportions and vibration levels on the physical properties, durability and performance of concrete used in Korean pavements. The strength and durability characteristics varied depending on the mixture proportions and level of vibration, and samples with fly ash (i.e., F-CON) did not meet the strength and durability criteria when low levels of vibration were applied. Therefore, intermediate or higher levels of vibration should be applied to satisfy strength and durability criteria. Meanwhile, there was little difference in the performance tests (i.e., skid resistance, surface abrasion, and IRI) of concrete pavements depending on the mixture proportions and vibration levels. However, the sample with an intermediate level of vibration had a relatively higher performance than the other samples.

Durability Criterion for Lubricant Oils Alloyed with Micro/Nanoparticles of Insoluble Friction Modifiers

Durability Criterion for Lubricant Oils Alloyed with Micro/Nanoparticles of Insoluble Friction Modifiers

Development of Vertical Axis Wind Turbine Charger as Alternative Power Source

The study was focused on the development of Vertical Axis Wind Turbine Charger with D.C Air Compressor to address power shortage in the coastal area in the Province of Isabela. This project development research tried to achieve the following objectives; a) Design and Construct Vertical Axis Wind Turbine Charger with D.C Air Compressor; b) Test the functionality of the project by conducting various activities concerning to basic electrical and electronics circuits, blade adjustment and experiments; c) Determine the acceptability of the project in terms of functionality, workability, durability, safety and instructional applicability as evaluated by the respondents; and d) Make an activity manual to supplement the developed project. The five-point’s Likert’s scale was used to determine the descriptive meaning of the indicators of the variables used. Furthermore, the Weighted Average Mean (WAM) was used to interpret the equivalent meaning of the data gathered. The Analysis of Variance (ANOVA) was employed to determine the significant difference between the evaluations of the respondents. The completed project was evaluated by selected twenty (20) technology instructors 25 students, ten (10) Engineers from Isabela State University-Ilagan, Roxas, San Mateo, Cauayan Campus and TESDA Ilagan Evaluation result shows that the project obtained an overall mean of 4.52 which means the Vertical Axis Wind Turbine Charger is “HIGHLY ACCEPTABLE” to the evaluators based on the criteria of functionality, aesthetics, workability, durability, economy, safety and instructional applicability.

Computation of Tense-Deformed State of the Die Mold Matrix

A method of computation of the tense-deformed state of the die mold matrix is described in the given article. Using the criterion of the same durability an algorithm of minimization of its weight is built after the structural parameters. The stress-strain state of the matrix was calculated in the AUTODESK INVENTOR . Research and analysis of the stress-strain state of the matrix was carried out and its optimal parameters were determined. As a result, it makes it possible to optimize the structure of the matrix in terms of stiffness and stability and ensure its optimal performance

Towards the design of eco-efficient concrete mixtures: An overview

Sustainability is one of the major issues faced by the concrete industry due to the high CO2 emissions caused by cement production. Although most of the conventional mix-design approaches account for requirements in the fresh and hardened states, along with durability criteria, sustainability is a new key parameter that must be evaluated in concrete production. This paper focuses on disseminating the environmental concerns related to cement, highlighting the importance of using alternative materials as cement partial replacement. Moreover, advanced mix-design techniques must be used to further enhance concrete eco-efficiency; hence, an overview of the different types of particle packing models (PPMs) is presented. Combining PPM with limestone fillers as an alternative ready-to-apply method to produce eco-efficient mixtures is then proposed enabling concrete future competitiveness as a sustainable material. Finally, a brief discussion on the fresh and hardened performance of sustainable concrete along with its global warming impact is conducted.

Effect of Bacillus subtilis bacteria on waste foundry Sand-Containing concrete

The solid waste generated by industrial enterprises is expanding at an alarming and continuous rate. Waste Foundry Sand is one type of industrial solid waste (WFS). Fine aggregates used in concrete, on the other hand, are typically river sand or M−sand, which is limited, and the high cost and mining of river sand contribute to environmental deterioration. As a result, there is a strong need to develop an alternative method of disposing of WFS and to minimize the usage of river sand or M- sand. In this investigation, WFSwas partially substituted with M−sand. The durability and mechanical properties of concrete with M30 mix are estimated experimentally. Additionally, the study's objective was to discover a novel bacteriological technique for improving the concrete's strength by partly substituting waste foundry sand. In order to obtain this effect, bacteria like Bacillus Subtilis are entrenched in ordinary concrete in addition to providing waste foundry sand and cured at 7, 14, and 28 days. The samples are examined for mechanical and durability criteria as sorptivity, water absorption, tensile strength, compressive strength, and flexural strength. Evaluation is also done on the results of curing concrete using waste foundry sand and bacterial solution.

Evaluation of optimal grain hardening modes to increase fatigue resistance of parts made of high-strength steels

Recommendations on the choice of optimal modes of shot blasting hardening of steel 30HGSN2A (30XГCH2A) according to the criterion of cyclic durability are given. On the basis of experimental studies of the influence of technological parameters and properties of the surface layer, a generalized technological parameter was proposed, including the values of the diameter of the shot and its velocity at 98% coverage of the surface of the part with 4-6 times fraction prints.

ИССЛЕДОВАНИЕ СИЛ РЕЗАНИЯ ПРИ ТОЧЕНИИ СМЕННЫМИ МНОГОГРАННЫМИ ПЛАСТИНАМИ

This article discusses the methodology for studying the durability of turning tool plates used in the processing process on CNC equipment. The nature of the change in chip shrinkage depending on the processing period is investigated. It is proposed to take the coefficient of transverse chip shrinkage as a criterion of tool durability. The study draws attention to the relationship between the growth of cutting forces and the destruction of the front surface of the cutter. The measurement results are compared with the theoretical calculation, a conclusion is made about the nature of the influence of the tool use period on the parameters of the cutting process.

Estimation of the stress state of a cylindrical shell by analogy with a beam

The analysis of the stability and strength criterion of reinforced concrete shells during deformation according to the harmonic law under the action of axial compression is carried out. A method for determining the criterion of durability of reinforced concrete according to the momentless theory is presented. Options for estimating the stress-strain state of shells at a constant and variable modulus of elasticity are considered. An analogy is given between the behavior of quantities in the semi-momentless and momentless theories of zero-curvature shells. A method for calculating reinforced concrete structures of coatings under conditions of rheological deformation is presented, reflecting their real work, as well as taking into account the random nature of the values taken in the calculation.

Comparative hydration studies of microfine SCM to achieve sustainable and durable concrete

Its become imperative to make durable concrete as a means for achieving sustainability and greener concrete by using SCMs. Though use of normal SCMs brings lot of advantages but at the same time comes with many disadvantages like slow gain of strength, shrinkage cracks, pumping issues etc. At the same time, modern day concrete requires to fulfil stringent durability criteria’s along with basic need of early strength gain. Literature survey reveals that lot many comparative studies had been done between microfine SCMs like Alccofine (MFS) & Microsilica on fresh and hardened properties of concrete but not much work was reported on comparative hydration studies. This fact led to conduct a detailed comparative evaluation study on mortar and neat cementitious cubes by taking Alccofine and Microsilica replacements. This study covered material evaluation along with study on chemically bound water by TG-DSC method, free hydrated CaO [Ca(OH)2] determination by Glycol extraction method, mineralogy and rate of Hydration of Cements, determination of degree of hydration based on changes in C3S + C2S peak area, morphology and microstructure of hydrated cement pastes by SEM. The study concludes that Alccofine 10% gives higher strength, shows lower chemically bound water compared to OPC, C-S-H formed (Tobermorite) was comparatively higher when compared with other hydrated cement, observed decrease in the area of the C3S + C2S, SEM indicated more compact and condensed crystals in Alccofine samples.

A Study on Durability Parameters of Ferrocement

Ferrocement is formed of a thin layer of cement mortar that has been strengthened with multiple layers of wire mesh with a diameter of between 0.5 mm to 1 mm. To evaluate the durability criteria for the specimen, a series of cubes and cylinders were cast in this experiment using a mortar mix at a ratio of 1:3 and a water-cement ratio of 0.40 was selected. In this study, the ability of the ferrocement to endure water penetration, sorptivity, and resistance to sulphates were examined. The curing period was chosen to be 28, 56, and 90 days, respectively, in order to track changes in the outcome and investigate the effects of the various curing times on the ferrocement. In order to measure the rate of water absorption by capillarity rise, Sorptivity test was conducted in accordance with ASTM C1585-04. The average absorption rate at day 9 was found to be 84.87 x 10-7 mm/s1/2, 93.78 x10-7mm/s1/2, and 96.34x10-7 mm/s1/2 for 28, 56, and 90 days of curing respectively. The Sulphate attack test was conducted as per ASTM C 1012-2010. The mass loss was observed to be 0.28%, 0.32%, and 0.33% of the original mass, while the strength loss was 6.96%, 6.44%, and 6.33% for the curing periods of 28, 56, and 90 days respectively. According to DIN-1048, part 5, Water permeability test was conducted. Water was pressured with 500 KPa on the specimen to determine its water penetration. The average water penetration of the specimen was found to be 22.33 mm, 18.67 mm, and 14.33 mm for the corresponding curing periods of 28, 56, and 90 days. The results were within the range twaswere specified in the respective code, and they were judged acceptable in terms of the ferrocement's durability guidelines.

POWDER-ACTIVATED CONCRETE WITH A GRANULAR SUR-FACE TEXTURE

In recent years, self-compacting concrete mixtures have been widely used. Such mixtures are characterized by high workability without the use of vibration exposure. The application of innovative technologies allows manufactoring of various materials and products for architectural and construction purposes with improved decorative properties. The paper provides the results of a study on the selection of compositions for decorative-finishing powder-activated concrete with a granular surface texture according to rheological properties, strength and frost resistance had been adopted.
 The following components were adopted for the research. Egyptian white cement was used as a binder, microquartz as a microfiller, screenings of crushing granite and cooper slag of 0–0.63 mm fraction was used as a finely dispersed component, granite cuts 0.63–5.0 mm and cooper slag of 0.63–2.5 mm fraction as an aggregate sand. A new generation superplasticizer of domestic and foreign productionplasticized the mixtures. Structural and rheotechnological parameters of powder-activated concretes were calculated.
 From the obtained values of the conditional rheological criteria of powder-activated concretes, it follows that all of them are much greater than unity and characterize a significant excess of the volumes of rheological matrices over the volumes of fine-grained, coarse-grained components that fit into them with large separation of particles and grains.
 Strength as a complex mechanical characteristic, including a combination of strength, reliability and durability criteria, is the most important quality parameter of the concrete structure as an active and the most massive building material for structural purposes. A significant number of facilities made of concrete and reinforced concrete are being built in the southern and northern regions, characterized by extreme climatic conditions. Buildings and structures are exposed to cyclic loadings of various types and climatic influences, characterized by cyclic manifestations of negative and alternating temperatures. The research revealed high indicators of strength and frost resistance of decorative powder-activated concretes with a granular surface texture.

DIGITAL GOODS AND DIGITAL COMMODITIES

Topicality. The digitalization process of all spheres of the economic life of society is gaining a greater scope. The concept of the commodity as the main category of commodity production was also affected by digitalization: some old products gained a digital form, but new products appeared as well that did not exist at all before the start of the digitalization process. Therefore, the study of these new phenomena becomes especially relevant.Aim and tasks. To substantiate the definition of digital commodities from the perspective of the economic science methodology. Develop a classification of digital commodities based on their durability.Materials and Methods. The paper offers a conceptual view of the digital commodities, studying their essence and features from the fundamental economic science perspective. The paper uses scientific developments of classical and marginalist economic theory of such concepts as “commodities” and “goods”.Research results. The paper proposes to separate information, information good, digital good, and digital commodity concepts. Information is something that can be encoded in the form of a bitstring. Information good is useful information, information that has a use-value and a form that allows this information to be consumed. A digital good is an information good that exists in the form of a bitstring. A digital commodity is a digital good that has a price. The paper considers the characteristics of digital goods, whether they have the same properties public goods have and can be treated as such as researchers argued it. Digital goods can be treated as public goods only if all the copies of digital goods are treated as the same digital good, which is incorrect. The paper elaborates on durability criteria for classifying digital commodities as the ability to preserve an exchange-value.Conclusion. The paper defines information, information goods, digital goods and digital commodities. Arguments are offered that digital goods are not public goods. The differences between digital goods and digital commodities are determined, and the classification of digital commodities according to the durability criterion is proposed.

Laboratory and Field Evaluation of Stabilized Fly Ash as an Alternative Material for Sustainable Pavements

Thermal power plants in India produce a large quantity of fly ash, which is harmful to the environment. Underutilization of fly ash and the scarcity of natural minerals have created the need for an unusual construction strategy to prevent huge waste dumps on valuable land and to preserve fast-depleting resources. A study was conducted to determine the efficacy of lime-stabilized fly ash blended with quarry fines as flexible pavement subbase materials. The laboratory investigations were conducted to determine compaction characteristics, unconfined compressive strength, California bearing ratio (CBR), and durability to obtain the optimal quarry fines, fly ash, and lime (QFL) mix. The durability of QFL mixes was studied using 12 wetting–drying cycles. Using the strength and durability criteria specified by the Indian Road Congress, the optimum mix proportion of 40Q:60F+3L was determined. Pavement analyses were performed using the IITPAVE program. The QFL mix was observed to be superior to conventional granular subbase (GSB) layer material in terms of service life and cost-effectiveness. A field investigation was carried out on trial test sections constructed using the optimum QFL mix and GSB in the subbase layer of pavement. Field dry density and dynamic cone penetrometer (DCP) tests were performed on the compacted subgrade and subbase layers to assess the desired quality assurance in the construction of test sections. The early structural performance assessment of pavement sections using a falling weight deflectometer (FWD) test indicated that QFL could effectively replace conventional GSB.

Study of the effect of cement kiln dust on the mechanical, thermal and durability properties of compressed earth blocks

• Adding CKD to CEB manufactured from local resources improves mechanical, thermal, and durability properties. • Using CKD in building materials assists the reducing the negative impact of this industrial by-product. • The compressive and Flexural strength of CEB increases with increasing CKD content. • The thermal conductivity of CEB slightly varies with the addition of CKD content. • The criteria of durability are respected by the results found in the test of capillary absorption and abrasion resistance. This paper investigates the feasibility of using an industrial by-product from cement manufacturing known as cement kiln dust (CKD) to improve mechanical, thermal and durability properties of compressed earth blocks (CEB). The CEB are made from local clay types partially replaced by CKD at contents of 5 %, 10 %, 15 %, 20 %, and 25 % by mass, and compacted using a hydraulic press. Tests were performed on the blocks to define their properties. The study findings outline an improvement in the mechanical properties and the durability of the CEB without compromising the thermal properties. The compressive strength of the CEB with 25 % CKD at 60 days was about three times higher than those without CKD. With 0 % and 5 % CKD, the best values for thermal conductivity were recorded, i.e. 0.89 W/m K and 0.90 W/m K respectively. The durability criteria of the CEB were respected, with an abrasion resistance characterized by the maximum abrasion coefficient reached with 25 % CKD, which equals about 28.5 cm 2 /g, and a capillary absorption of 0.06 g/cm 2 min 1/2 for the same percentage, thus meeting the recommendations of the French standard NF P13-901.