РОЗРИВАЛЬНІ ХАРАКТЕРИСТИКИ КОМПЛЕКСНОЇ ПОЛІЕТИЛЕНОВОЇ НИТКИ

Purpose. To investigate the influence of the number of threads resisting to break, the griping length, and the change in the position of the interlacing point when threading with a loop the breaking characteristics of complex polyethylene threads in the form of a loop.Methodology. In the course of the research, experimental research methods were used to determine the breaking characteristics of high molecular weight polyethylene threads on a WDW-5ES tensile machine in accordance with DSTU ISO 2062: 2004, the main provisions of textile materials science and knitting theory, methods of analysis and synthesis of the results obtained. Results. Based on the results of the studies, the influence of different factors on the breaking characteristics of complex multifilament threads was determined, namely: the influence of the number of threads resting on the break, the griping length and the change in the position of the weave point when threading with a loop. In the course of research, the griping length was changed in the range from 25mm to 300mm, and with a stable griping length (100 mm), the location of the thread weave point relative to the lower grip (25mm, 50mm, 75mm) was changed. It has been found that the breaking characteristics of a complex polyethylene yarn are influenced by both the griping length and the location of the weave point in the case of a loop-shaped break. The magnitude of the specific breaking force in the study of loop-shaped rupture is greater than in the study of straight segments of the thread. This is due to parallelization and compaction of the filaments due to the presence of the weave point on the thread that resists tearing. Scientific novelty. Regularities of the effect of griping length, linear density, and location of the point of weave of the complex high molecular threads in relation to the downer and upper grip are established provided that the griping length (100 mm) remains unchanged on the value of breaking load and elongation.Practical significance. Determination of the factors affecting the breaking characteristics of a complex polyethylene yarn will allow in the future, at the stage of designing the structure of knitwear in computer 3D modeling systems, to provide for the magnitude of the breaking force.

COMPREHENSIVE ASSESSMENT OF A NEW FLAX VARIETY "CHANCE" OF THE PSKOV SELECTION ACCORDING TO THE MAIN ECONOMICALLY VALUABLE CHARACTERISTICS

Целью исследований являлась комплексная оценка нового сорта льна-долгунца Шанс по основным хозяйственно ценным признакам и параметрам адаптивности в условиях Северо-Западного региона на основе конкурсного сортоиспытания, проводимого в 2016-2018 годах и производственной проверки в 2019 году. ГТК за период вегетации был равен 1,98 в 2016 г., в 2017 г. – 1,60 и в 2018 г. – 0,95. Как показали расчеты индекса среды, наиболее благоприятные условия для роста и развития льна-долгунца сложились в 2017 г. (Ij = +3,98), и худшие – в 2018 г. (Ij = -3,68). Сорт Шанс раннеспелый (период вегетации 71-85 дней), высокорослый (82-88 см), относительно устойчив к фузариозу (89-94%) и полеганию (4-5 баллов), отличается высоким содержанием волокна в соломе (всего 36,0-36,5%, в том числе длинного 27,3-28,1%). По содержанию всего волокна он превышал стандарт на 2,4% (абс.), а длинного – на 0,8% (абс.) В среднем за годы исследований урожайность льносоломы составила 52,1 ц/га, семян 6,0 ц/га, что незначительно превышало стандарт соответственно на 3,6 и 7,1%. По урожайности всего льноволокна (18,9 ц/га) он достоверно превысил стандарт на 1,9 ц/га при НСР0,95 или на 10,4%. По прочности волокна, которая измеряется по разрывной нагрузке, сорт Шанс в среднем за 2 года имел равный стандарту Восход показатель (10,5 кгс), а по гибкости превосходил последнего на 2,5 мм (50,5 мм). Сорт Шанс в сравнении со стандартом в большей степени адаптирован к условиям внешней среды. Он характеризуется более низкой вариабельностью урожайности волокна по годам исследований (Cv – 4,75%), более высокой стрессоустойчивостью (-5,3) и генетической гибкостью. Сорт Шанс пластичный (bi – 0,91), относится к сортам нейтрального типа, которые слабо отзываются на улучшение условий среды, но более эффективны на более низких агрофонах и в зонах рискованного земледелия, к которым относится и Псковская область. В производственных условиях урожайность льноволокна у нового сорта составила 22,5 ц/га, что на 2,0 ц или 12,1% больше стандарта (НСР0,95 – 0,92 ц/га). В настоящее время сорт находится в государственном сортоиспытании. The purpose of the research was a comprehensive assessment of a new variety of flax «Chance» according to the main economically valuable characteristics and adaptability parameters in the conditions of the North-Western region on the basis of a competitive variety testing conducted in 2016-2018 and a production inspection in 2019. The SCC for the growing season was equal to 1.98 in 2016, 1.60 in 2017 and 0.95 in 2018. As the calculations of the environment index showed, the most favorable conditions for the growth and development of flax were formed in 2017 (Ij = +3.98), and the worst-in 2018 (Ij = -3.68). The «Chance» variety is early-maturing (the growing season is 71-85 days), tall (82-88 cm), relatively resistant to fusarium (89-94%) and lodging (4-5 points), has a high fiber content in straw (only 36.0-36.5%, including 27.3- 28.1% long). In terms of the content of the entire fiber, it exceeded the standard by 2.4% (abs.), and the long fiber -by 0.8% (abs.). On average, over the years of research, the yield of flax straw was 52.1 c/ha, seeds 6.0 c/ha, which slightly exceeded the standard by 3.6 and 7.1%, respectively. In terms of the yield of all flax fiber (18.9 c/ha), it significantly exceeded the standard by 1.9 c/ha at NSR0.95 or by 10.4%. According to the strength of the fiber, which is measured by the breaking load, the «Chance» grade on average for 2 years had an indicator equal to the standard of the Sunrise (10.5 kgf), and in terms of flexibility it exceeded the latter by 2.5 mm (50.5 mm). The «Chance» variety is more adapted to the environmental conditions in comparison with the standard. It is characterized by a lower variability of fiber yield over the years of research (Cv-4.75), higher stress resistance (-5.3) and genetic flexibility. The plastic «Chance» variety (bi – 0.91) belongs to neutral-type varieties that respond poorly to improving environmental conditions, but are more effective at lower agricultural zones and in risky farming zones, which include the Pskov region. Under production conditions, the yield of flax fiber in the new variety was 22.5 c/ha, which is 2.0 c or 12.1% more than the standard (NSR0,95-0.92 c/ha). Currently, the variety is in the state variety testing.

Influence of Methodological Variables on Fracture Strength Tests Results of Premolars with Different Number of Residual Walls. A Systematic Review with Meta-Analysis

The aim of the current meta-analysis was to assess the impact of methodological variables in performing fracture strength tests of upper premolars. Medline (Pubmed), Embase and Google Scholar were screened for studies performing ex vivo fracture strength tests of intact upper premolars or premolars with 0, 1 or 2 walls lost. The outcome variable for each study was the maximum breaking load expressed in Newton (kg × m/s2). Methodological variables (i.e., simulation of the periodontal ligament, load inclination, tip position, tip diameter and thermocycling) were registered to perform subgroup analyses and meta-regression. Overall, 25 studies and 78 study groups were included in the meta-analysis. Intact premolars (17 study groups) were not significantly influenced by any of the methodological variables considered. Subgroup analysis for load inclination (30°/45° vs. 90°/150°) was significant for premolars with 0 (10 study groups), 1 (6 study groups) and 2 (45 study groups) walls lost; thermocycling was significant for premolars with 1 and 2 walls lost. A strong methodological heterogeneity across studies evaluating the fracture strength of upper premolars was highlighted, especially when 0, 1 or 2 walls were lost. Further studies are needed to standardize the methodology used in order to allow for across-studies comparisons.

Western Sudan Arabi camel hides attributes and leather quality characteristics

This study was aimed to evaluate camel hide attributes and leather quality characteristics of Western Sudan Arabi camel. Thirty pieces of fresh camel hides from three subtypes of Western Sudan Arabi camel ecotype (10 pieces from each of Kababish, Meidob, and Hawawir subtypes) were collected, cured, and tanned. Physical and chemical quality parameters were assessed. The data were analyzed using the Complete Randomized Block design. The results revealed that Significant differences (P≤0.05) were detected among Western Sudan Arabi camel subtypes fresh hides thickness and weight. Kababish hide thickness and weight were recorded the highest value of 0.155±0.4 cm and 11.7±1.3 Kg respectively in comparison to Meidob (0.145±0.3 cm and 8.6±1.2 Kg) and Hawawir (0.143±0.4 cm and 7.7±2.2 Kg). Kababish hides thickness value was above the minimum Sudanese standard threshold specification for cattle leather quality. While Meidob and Hawawir hide thickness values were blew the minimum Sudanese standard threshold specification for cattle leather quality. Physical quality parameters; elongation, tensile strength, resistance to grain cracking, breaking load, and tear strength; were in the Sudanese standard threshold specification for cattle leather physical quality of 100%, 200 Kg/cm2, 7N/cm, 8 N/cm, and 100 Kg/cm2respectively. Whilst flexibility parameter was below the Sudanese standard threshold specification for cattle leather quality. Chemical quality parameters were in the Sudanese standards threshold specification for cattle leather chemical quality of 18%, 4.5%, 2.5%, and 11% for moisture, Ash, chrome oxide, and fat contents respectively.

Investigation of the deformation and strength characteristics of the thread connection in the manufacture of products from fur waste

By the method of mathematical planning of the experiment, regression equations were obtained for the breaking load and the breaking relative elongation of the thread connection of a special furrier’s seam in the manufacture of products from fur waste. As input factors were taken: the number of stitches in 1 cm., Thread thickness, needle diameter. The features of the behavior of the strength model of this thread connection are revealed.

Recycled Aggregates from Construction and Demolition Waste in the Manufacture of Urban Pavements

Construction and Demolition Waste (CDW) is among the largest waste streams in the world. Therefore, within the Circular Economy concept, there is a growing interest in its reuse. The purpose of this work was to study the use of recycled aggregates (RAs) obtained by a specific separation method from CDW, replacing natural aggregates (NAs) in the manufacture of precast concrete elements, such as kerbstones and paver blocks. The physical and technological properties of precast products formulated with RAs were analysed in accordance with current regulations, comparing them with those of commercial products manufactured with NAs. The results indicated that partial or total substitution of NAs by RAs increased the water absorption and apparent porosity values of the precast elements while reducing the bulk density and compressive strength. However, all units manufactured with RAs showed breaking load values higher than the minimum required by EN 1338 and, in some cases, slightly higher average tensile strength values than the reference material. In addition, some of the compositions including RAs gave rise to pieces that, according to their flexural strength, were classified as class 1 and marked S in accordance with EN 1340. According to abrasion resistance, in most cases, the precast elements are classified as Class 4 and I (≤20 mm). Finally, precast concrete produced from RAs satisfies the tolerance requirements for classification as class 3 (≤1.5 kg m−2). Therefore, it could be suitable for use in high pedestrian or traffic areas.

Analysis of the effect of ionizing radiation on the properties of bulk nonwoven material

At the moment, there is a wide range of bulky nonwovens for various purposes on the market. One of the important areas of using such materials is healthcare. In particular, bulky nonwoven materials are intended for the manufacture of wound dressings, evacuation kits for newborns. Disposable medical devices of this kind are usually subjected to radiation sterilization. As is known from earlier studies, radiation sterilization significantly affects the performance of nonwovens. In this regard, for nonwoven materials for medical use, an important characteristic is the stability of indicators after exposure to radiation sterilization. As a result of the study of bulk nonwovens Holofiber ® after radiation radiation in the dose range from 20-60 kGy, there were no significant changes in operational performance. The stiffness increased by an average of 3-10%. The stiffness indicators after ionizing radiation according to GOST 24684 also meet the requirements. The value of electrification increased due to an increase in the static field under the action of ionizing radiation. It is worth noting that the values of electrification are within the norm established by GOST 32995. The breaking load varies from 1-5%. Thus, non-woven materials Holofiber ® PROFI, article P 35191, Holofiber ® SOFT, article P 5197, Holofiber ® SOFT, article P 5200 are recommended for the production of medical devices.

Influence of electron radiation on the physical and mechanical properties of a nonwoven fabric made using Spunlace technology

The effect of electron radiation on the physical and mechanical properties of Sontara nonwoven fabric produced using spunlace technology has been studied. The initial raw material for the manufacture of materials using this technology, as a rule, are viscose, polyester, polypropylene and cellulose fibers. Such nonwovens are highly breathable and are therefore used in disposable surgical gowns and suits. Since radiation can be used to sterilize disposable surgical gowns, it is important to assess the resistance to ionizing radiation. It was found that the Sontara brand material is resistant to the effects of ionizing radiation - the physical and mechanical characteristics of the material (breaking load and relative elongation) in the longitudinal and transverse directions of the web do not significantly change when irradiated with absorbed doses up to 60 kGy. It should also be noted that a cloth with a basis weight of 68 g/m2 has a significant smell of strength after radiation sterilization.

EXPERIMENTAL STUDY OF PLATES FOR PUNCHING UNDER DYNAMIC LOADING

the issues of strength and deformability of reinforced concrete floors during punching remain insufficiently studied at present, despite the available publications in the technical literature. This article presents the results of experimental studies on punching of fragments of conjugation of flat reinforced concrete monolithic slabs with a column under dynamic loading. The purpose of these studies was to obtain experimental data on the stress-strain state of a fragment of a monolithic floor during dynamic punching with varying thickness and class of concrete, to reveal the failure patterns of experimental samples, and to obtain new experimental data. A setup for dynamic testing is described. Comparison of breaking load for specimens tested under dynamic loading with breaking load for specimens tested for static load is presented. The angles of inclination of the punching shear pyramid under static and dynamic loading are indicated.