Остання редакція: 2025-10-20
Тези доповіді
A significant number of studies in the field of materials science has led to the development and investigation of properties of new materials. However, the implementation of these materials is often hindered by the resource intensity of the composition, the energy consumption or labor intensity of the proposed technology, and the poor operational performance of the finished products. Considering the clear research gap in the field of technical and economic justification for the feasibility of using new polymer composite materials, which is underscored by the absence of such justification in a large number of defended dissertations on materials science, there is a need to develop a methodology for conducting such an analysis. This is essential to move new materials from the laboratory to the sphere of practical application.
The total manufacturing () cost of a composite product (UAH/unit) is the sum of the material cost () and the processing cost () (1).
(1)
he cost of materials (for the case of composites based on liquid resins) (2) includes the cost of matrix material (), the cost of hardener material (), the cost of filler material (), the cost of reinforcement material (), and the cost of the mold (), minus the cost of waste material () (in the case of disposal costs, these expenses must be added).
(2)
The processing technology may involve the influence of stationary (thermal, electrical, force, etc.) or variable (magnetic-pulse, ultraviolet, etc.) physical fields on the product, as well as mechanical processing by cutting, pressure, and so on, across a total of n operations, with corresponding costs (, (), () (3).
(3)
After substituting (2) and (3) into (1), we will obtain expression (4).
(4)
The cost of materials can be estimated as:
(5)
where – is the mass of the i-th material (matrix, hardener, filler, reinforcement, waste), in kg;
– is the price of the i-th material, in UAH/kg.
In the case of using composites where the mass fractions of each component , their price, and their density are given, the cost of the composition can be calculated using the following expression:
(6)
The cost of processing for the j-th operation is generally the sum of the worker's labor cost , the cost of electricity , equipment depreciation , and operational expenses (technical maintenance and repair of equipment, tools, fittings, consumables, etc.). Other workshop expenses must also be added here (for the upkeep and maintenance of production areas, occupational safety, etc.).
(7)
(8)
(9)
(10)
where – рower consumed for mechanical processing, kW;
– main processing time, min;
– number of products processed simultaneously, pcs;
– equipment efficiency factor;
– price of electricity, UAH/(kW·h);
– average monthly salary of the respective worker, UAH;
– amount of a worker's paid leave, UAH;
– worker's annual working time fund, h/year;
– calculated time (includes operational time and preparatory-final time for equipment setup), min;
= 22 % – unified social contribution for private entrepreneurs;
– cost of equipment (including tools and fittings), UAH;
– equipment useful life, years (e.g., for metal-cutting machines, it is usually taken as 6…10 years);
– equipment's annual working time fund, h/year.
Operational and other workshop expenses (depending on the level of thriftiness and production organization) are approximately 75...150 % (at enterprises with a less advanced production process, this percentage may be higher) of the worker's labor cost, [1-4]. Considering this, expression (7) for calculating the processing cost at the j-th operation is presented in a form convenient for practical use:
(11)
Using the presented methodology, the cost of bushings for stern tube bearings of ships with the following parameters was calculated: d = 100 mm, D = 132 mm,
l = 270 mm. The materials used were: caprolon PA-6MG, filled with graphite [5] (M1); caprolon PA-6MDM, filled with graphite and molybdenum disulfide [6] (M2); and epoxy composite EKM-3 [7] (M3).
For materials M1 and M2, the processing was assumed to be only mechanical, in a single operation (j = 1) on a lathe, comprising two setups. This included facing the end, external turning of diameter D, drilling, reaming, and boring of hole d, cutting the part from the rod, and facing the opposite end. For material M3, the process involved mold fabrication, polymer composite production according to the technology in [7], and mechanical processing on a lathe. The cutting modes for all materials were considered identical. To compare the practical value of the analyzed materials, we used the results from studies [5-7] on their wear intensity when paired with steel shafts. We also calculated the number of repairs requiring bushing replacement over the total service life of the ships (25 years). The results of these calculations are summarized in Table 1.
Table 1 – Main characteristics of model stern tube bearing bushings made from the analyzed materials
The data in Table 1 indicate that using material M3 for manufacturing the bushings will lead to the highest number of repairs and, consequently, due to the longest downtime and repair costs, the highest specific costs per tonne of cargo transported by the vessel. This will ultimately reduce the profits from operating a vessel equipped with these bushings. Bushings made from material M3 will also cause the greatest friction losses in the stern tube bearing, thereby increasing fuel costs and further raising transportation expenses.
The manufacturing labor intensity of bushings from material M3 is almost 6 times greater than that of bushings from materials M1 and M2, while the manufacturing duration is more than 60 times longer. The manufacturing cost of a bushing from material M1 is = 1573 UAH, from material M2 is = 1877 UAH, and from material M3 is = 1829 UAH. The results obtained make the choice of material for stern tube bearing bushings more well-substantiated and convincingly argue in favor of using materials M1 or M2.
Thus, the presented calculation methodology for determining the main costs that form the prime cost of such products makes it possible to perform practical calculations and simplifies decision-making when selecting composite materials.
References
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2. Rudenko P.O. Design of technological processes in mechanical engineering / P.O. Rudenko. Kyiv: Vyshcha Shkola, 1993. 414.
3. Hryhurko I.O., Brendulya M.F., Dotsenko S.M. Mechanical engineering technology (Diploma design) / I.O. Hryhurko, M.F. Brendulya, S.M. Dotsenko. Lviv: Novyi Svit – 2000, 2020. 744.
4. Sydorenko V.N., Shykhalev V.A., Portniazhkina O.M. Economic efficiency of surfacing mechanization // In: Production of Large Machines. Edited by A.I. Volkonsky, S.E. Poliakov (Works of NIITIAZhMASh Uralmashzavod). Iss. 20, 1971. 124 – 138.
5. Buzkov V.A. Improving the service properties materials for the development of ship stern tube devices and sea protection: dis. ... Dr. Sci. (Eng.): 05.02.01 – Materials Science / V.A. Buzkov; Odesa State Maritime University. Odesa, 1998. 448.
6. Storozhev V.P. Causes and regularities gradual failures of main tribotechnical objects a ship's power system and increasing their service life: dis. ... Dr. Sci. (Eng.): 05.02.02 – Machine Science / V.P. Storozhev; Odesa State Maritime University. Odesa, 2002. 381.
7. Brailo M.V. Development epoxy composites with complex of dispersed and polyamide fillers for parts of friction: dis. ... Cand. Sci. (Eng.): 05.02.01 – Materials Science / M.V. Brailo; Kherson State Maritime Academy. Kherson, 2015. 227.