PSI - Issue 81

Oleksiy Petrenko et al. / Procedia Structural Integrity 81 (2026) 292–296

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and Bano (2017); Gong et al. (2019); Landis et al. (2002); Gomon et al (2023)). Polymeric and composite materials seek to displace wood from various areas of application. However, due to a complex of physical-mechanical characteristics, resistance to atmospheric (Fojtik (2019); Sinha et al. (2012)) and aggressive production environments (Wang et al. (2025); Roshchuk et al. (2024); Huang et al. (2006); Thygesen et al. (2010)), technical-economic indicators, reproducibility, and low environmental impact, wood remains the primary material in certain structures and manufacturing processes (Zhao et al. (2020); Hua et al. (2025); Andor and Bellovics (2020)). An example of such an application of wood is a technological pallet to produce concrete pavement elements -paving stones. The technological pallet made of wood is used in the production of concrete products – decorative paving elements and small architectural forms. It is used as interchangeable equipment for vibratory presses when forming concrete products from heavy concrete mixtures using the quick demolding method, as well as for the transportation and curing of formed products for cement hardening and concrete strength gain, and for delivering finished products to their packaging location. Under conditions of vibration, mechanical loads, temperature fluctuations, and relative humidity, as well as when the wood comes into contact with the aggressive alkaline environment of the concrete mixture, the warranty period of operation is 1 year. The actual period ranges from 3 to 5 years. During this period, the technological pallet undergoes physical wear, its physical-mechanical characteristics decrease and cease to meet regulatory values, which also reduces the quality of the concrete products manufactured using technological pallets. To prevent defects in concrete products, worn technological pallets should be discarded in a timely manner. Therefore, establishing criteria and developing a methodology for determining the operational suitability of the technological pallet is an important practical task. One of these criteria is the hardness of the wood (Doyle and Walker (2007); Kosmach and Kadyck (2014); Nowak et al. (2015); Sydor et al. (2020). In previous works, we established that the hardness of the wood can serve as one of the criteria for the operational suitability of the technological pallet and justified the use of the Pevzof method for determining hardness. A relevant task remains - to establish the dependence of technological pallets wood hardness on the duration of its operation under conditions of static-dynamic mechanical loads with variable humidity and aggressive environment. 2. Methods of experimental research The technological pallet is a construction assembled from wooden components, reinforced in the transverse direction with cold formed steel C-profiles and in the longitudinal direction with threaded steel tie rods. It is made in the form of a solid shield measuring from 900x1000mm to 1100x1400mm (Fig.1) from a solid board (beam) with a thickness of 45 to 55 mm. The initial moisture content of the wood is from 8 to 14%. Manufacturing concrete products by vibration pressing occurs on the pallet and involves placing the concrete mix into a metal matrix and forming the products by pressing with punches while simultaneously vibrating. For the setting of cement and gaining strength of the concrete, it is sent with newly formed products to a strength gaining chamber for one day. The technological pallet is classified as a board made of solid wood (DSTU EN 335-2:2010). The use class is 3 for solid wood products (DSTU EN 335-1:2010). Thus, the product is protected from weather conditions, however, often the moisture content in the wood of the pallet exceeds 20%. Under such operating conditions, the wood is subject to the influence of biological agents: wood-staining and decay fungi. The risk of beetle infestation may be insignificant according to the specifics of the operating regime of the product. To reduce the risk of biological damage and to decrease the water absorption, the wood of the technological pallet is surface treated with mineral oil or its emulsion before first use. Under the action of primarily mechanical, as well as temperature, moisture, and to a lesser extent biological factors, the wood of the pallet loses its initial physical and mechanical characteristics, it wears out and becomes unsuitable for further use. There is destruction of the wooden surface of the pallet, deviation of the surface from the plane – delamination of the surface, drying of individual beams. In our previous studies, it has been established that the hardness of wood is one of the most significant factors influencing the service life of the production pallet. A visual inspection of newly manufactured pallets of nominal size 1400x1100mm and actual size 1440x1110mm examined the predominant tangential or radial orientation of the working surface of the plank. To determine the daily and annual operating regime of the pallet, documentary analysis and time measurements were conducted, establishing that a number of unfavorable factors affect the technological pallet. The hardness of the wood of the technological pallet at different stages of operation was determined by the non-destructive Pevzof method based on the area of the imprint from the fall of a ball with a diameter of 25 mm from a height of 0.5 m (DSTU EN 335-1:2010; ISO 13061-11:2017; ISO 13061-12:2017), substantiated in our research: the hardness of the wood of the technological pallet at different stages of operation: newly produced untreated protective action, treated protective weapons after three operations, Nomenclature Н wood hardness; t service life of the technological pallet