Durability and Microstructural Behavior of Nano Silica-Marble Dust Concrete

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Deposition Tantalum Nitride on LDX 2101 Duplex Stainless Steel by Reactive Sputtering in Biomedical Applications

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DNN and XGBoost for modelling of strength of porous concrete with recycled aggregates

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Evaluation Of Stress-Strain State Of Vehicles’ Metal Structures Elements

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Determination of conditions for loss of bearing capacity of underground ammonia pipelines based on the monitoring data and flexible search algorithms

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Construction of conical axoids on the basis of congruent spherical ellipses

Purpose: To carry out the transition from a cylindrical gear in which the centroids are congruent ellipses with centres of rotation in the foci, to a bevel gear on the basic of congruent spherical ellipses. Design/methodology/approach: Congruent ellipses with centres of rotation in the foci serve as centroids for the design of cylindrical gears with non-circular wheels. The article analytically shows that the analogues of ellipses on the plane - congruent spherical ellipses are the basis for the construction of the axoids of the corresponding bevel gears. An analogue of the centre-to-centre distance for ellipses in the plane is the angle between the axes of rotation of conical axoids. Findings: Based on the equality of the arcs of ellipses, the dependence of the angle of rotation of one axoid on the angle of rotation of another is found. Graphs of this dependence for separate cases are given. It is shown under what conditions the axes of axoids intersect at right angle. The parametric equations of spherical ellipses and corresponding axoids are given. They were used to construct spherical ellipses and corresponding conical axoids for different cases. For gears with right angle between the axes, separate positions of the axoids with different angles of their rotation around their axes are constructed. Practical implications: Spherical ellipses are directing curves for the construction of the corresponding conical axoids. Originality/value: The paper shows that congruent spherical ellipses act as centroids for the design of axoids of bevel gears. They roll one by one without sliding, rotating around axes that intersect in the centre of the sphere. To design such gears, it is important to know the interdependence between the geometric parameters, especially for common gears with a right angle between the axes.

Sustainable deployment of crushed concrete aggregates strengthened with cement and sand

Purpose: Paper assessed the feasibility of crushed concrete aggregates (CCA), a subsidiary of construction and demolition (C&D) waste, blended with cement and sand to form a composite for civil engineering field applications. Design/methodology/approach: The compaction and strength characteristics of CCA were observed by conducting Proctor compaction and California Bearing Ratio (CBR) tests. Different proportions of CCA, sand and cement were used. Moreover, the effect of curing period (0, 4, 7, 14 and 28 days) was also studied. In addition, regression analyses were performed to develop empirical expressions to predict the compaction and strength characteristics of the CCA composite. Findings: Increasing the CCA content up to 50% increases the maximum dry unit weight (MDUW) and decreases the optimum moisture content (OMC). However, on further increasing its content the MDUW decreases and OMC increases. Percent increase in the CBR value can go up to 412% if the CCA content is increased up to 50%. However, the percent reduction in CBR of about 20% can take place if 100% CCA content is used. Moreover, multiple regression shows that the experimental results are in good agreement with the predicted values. Research limitations/implications: The results obtained are purely dependent on the type of material. However, they are in favour of the used material as a probable option for road sub-base layer, and also for reducing burden on available natural resources. Therefore, it is recommended to conduct some initial tests to confirm the feasibility of the material. Practical implications: The proposed study will guide the design Engineers to choose CCA as one of the potential materials for road construction. Originality/value: It was observed that there is a need to maximize the utilization of C&D waste without making any compromise with its mechanical properties. So keeping that in view, the present study was conducted.

Modern heat-resistant 11%Cr martensitic steel for power industry

Purpose: The purpose of the investigations was to characterise and describe the modern creep-resistant Thor 115 steel for supercritical power units. Design/methodology/approach: The investigations were performed based on the knowledge and experience of the author, the preliminary results of his own research and the available literature on the subject-matter of the considerations presented in the paper. Findings: Modern steel Thor 115 was subjected to overall analysis in terms of its use as a potential heat-resistant structural material for power plant components. Based on the preliminary results of own research and the available literature data, it has been shown that the analysed steel may be a structural material of full value if the assumed creep resistance in the service temperature range of 600-650ºC is confirmed. Research limitations/implications: The comprehensive analysis of degradation of microstructure of the steel after ageing (and/or creep) requires TEM examinations. Finding the correlation between the creep and ageing conditions and changes in the microstructure of the steel. Practical implications: The investigations carried out as part of the paper and the considerations on the subject-matter of the analysed steel may be the basis for the development of a database of material characteristics for steels, alloys and welded joints. Originality/value: The analysis of chemical composition, heat treatment and mechanical properties and the investigations of microstructure of Thor 115 steel are presented.

Estimation of strength properties of functionally graded structures with elliptical stress concentrators

Purpose: The purpose of this paper is to elaborate new calculation schemes for evaluating the strength parameters of railway rolling stock parts with non-local properties of surface layers in the presence of elliptical stress concentrators. Design/methodology/approach: Using the proposed approaches of developed mathematical modelling and open software for calculating FEniCS, it were established the most dangerous angles of stress concentrator orientation and the required thickness of the hardened zones of parts, which ensures their minimum softening during operation. Findings: It is shown that for an elliptical stress concentrator with any orientation angle, there is a certain key size of surface hardening thickness, the exceeding the value of which does not have influence on the operational strength of the parts, but rise the price of technological operations. Research limitations/implications: In this paper proposes a method for computation the impact of the orientation of the surface elliptical stress concentrators on the contact strength of parts under conditions of dominate friction power loads. Practical implications: The obtained results were used to set the modes of plasma hardening, which increase the contact strength of railway parts with elliptical stress concentrators. Originality/value: Using the approaches of contact mechanics, mathematical and computer modelling, methods of controlling the contact strength of the parts with the surface elliptical stress concentrators were proposed for the first time.

Investigation of flowability of the green sand mould by remote control of portable flowability sensor

Purpose: The useful data and information during the sand compaction process steps should be collected. Direct measurement methods of the sand mould properties during the actual moulding process are not adopted yet. Design/methodology/approach: In this work, a remote control system [1] have been integrated into a new flowability sensor [2]. Findings: To overcome the complexity of the tools and equipment that existed in laboratory, and in foundry. Research limitations/implications: In order to investigate, and control behavior of the moulding process of bentonite-bonded green sand process, the sensors have been equipped with the Bluetooth technology for a wireless transmission of the measured data to computers. Originality/value: This technique contributes to improve of the compaction process based on the non-destructive tests, enhances prediction of the optimum parameter conditions, and reduced the energy, and the compaction time consumed for the green sand moulding process.