Обґрунтовано критеріальні значення глибини потенційних трішиноподібних дефектів профільних елементів стріли бурто укладника. Ви користана концепція «опірності конструкційного елемента росту тріщини», яка характеризується швидкістю зміни коефіцієнта інтенсивності напружень у вершині тріщини. Враховано результати експериментальних досліджень тріщиностійкості матеріалу в різних се редовищах. Сформульовано інженерні рекомендації щодо прогнозування розвитку тріщиноподібних дефектів Ключові слова: стріла буртоукладника, профільний елемент, тріщиноподібний дефект, опірність росту тріщини Обоснованы критериальные значения глубины потенциальных трещинообразных дефектов профильных элементов стрелы буртоукладчика. Использована концепция «сопротивляемости конструкционного элемента росту трещины», которая характеризуется скоростью изменения коэффициента интенсивности напряжений в вершине трещин. Учтены результаты экспериментальных исследований трещиностойкости материала в различных средах. Сформулированы инженерные рекомендации по прогнозированию развития трещинообразных дефектов Ключевые слова: стрела буртоукладчика, профильный элемент, трещинообразный дефект, сопротивляемость росту трещины
It is shown that with a cyclic loading in the vicinity of the stress concentrator within the static and cyclic plastic zones, a specific volume of material is gradually formedthe fatigue process zone. Its size d * determines the length of non-propagated cracks or safety defects in the material and can be a determining factor in the diagnosis of material damage. For these materials, the size d * does not depend a lot on the type and geometric characteristics of the stress concentrator. It can be determined by laboratory conditions. While detecting the defects which are longer than d * , it is decided to reduce the intervals between inspections of the construction element, repair or replace it. Keywords: fatigue, durability, fatigue process zone, crack initiation and growth, defects of materials OSOBLIWOŚCI TWORZENIA STREFY PROCESU ZMĘCZENIOWEGO W MATERIAŁACH KONSTRUKCYJNYCH Streszczenie Pokazano, że cykliczne obciążenie w pobliżu koncentratora naprężeń w statycznych i cyklicznych strefach plastycznych stopniowo tworzy specyficzną objętość materiału-strefę procesu zmęczeniowego. Jej rozmiar d * określa długość nierosnoncych pęknięć lub innych bezpiecznych defektów i może być czynnikiem decydującym w diagnozie uszkodzeń materiału. Dla badanych materiałów rozmiar d * mało zależy od rodzaju i geometrycznych charakterystyk koncentratora naprężeń. Jego można wyznaczyć w warunkach laboratoryjnych. Po ujawnieniu defektów, dłóższych niż d * , podejmuje się decyzja o skróceniu czasu między przeglądami elementa konstrukcji, jego remoncie lum zamianie. Słowa kluczowe: zmęczenie; trwałość; strefa procesu zmęczeniowego; inicjacja i propagacja pęknięcia; defekty materiałowe
A high resolution sensor of linear displacements has been elaborated for diagnosing the size of the crack tip opening in standard test specimens. Based on the data measured during fatigue crack growth resistance tests of a wheel steel heat treated after various modes, calculations of the strain and energy parameters of local fracture were performed for the corresponding variants of treatment, and fatigue crack growth rate diagrams were constructed using different approaches of fatigue fracture mechanics. It was established that the diagrams obtained using the strain and energy approaches are more sensitive to material microstructure and its mechanical properties than the traditional diagrams obtained using the stress approach. Based on the parameters of the fatigue crack growth resistance estimated using the strain and energy approaches, the effective diagnostics and the best heat treatment mode for the wheel steel was developed. It comprises the stages of isothermal quenching and tempering at a temperature of 500 °С, providing the highest fatigue fracture toughness of the steel.
The purpose of the article. In the process of our empirical research, we had the aim to examine the level of professional reliability of doctors who performed their professional duties during the COVID-19 pandemic in Ukraine. We assumed that the higher the level of professional reliability was, the more effectively doctors will perform their own professional activities in unusual, extreme conditions of their professional activity. The research involved 550 doctors of Rivne Regional Hospital (Rivne, Ukraine). Methods and methodical instrumentation of the research. To solve the problem of our research, a set of methods was used, the choice and combination of which have been determined by the subject, the purpose and the objectives of this research: - theoretical methods – theoretical and methodological analysis of scientific sources and available according to the problem of our research psychological approaches: their systematization, classification, generalization, theoretical modeling to study the phenomenon of professional reliability of doctors who worked in difficult conditions of the COVID-19 pandemic in Ukraine; - empirical methods – the observation, the interview, a questionnaire, testing, the method of expert assessments, which have been used for a deeper, holistic research of the structure of professional reliability of doctors; psychological and pedagogical experiment in the form of the empirical studying of the formation of a structure of professional reliability of doctors. The results of the research. We proved, that for specialists of medical sphere of the activity with a high level of professional reliability there was a main characteristic: the ability to perform professional activities in special and extreme conditions, the formation of professional and moral culture of a doctor, the constant development of components of his/her professional competence, professional readiness and professional reflection, the ability to implement effective psychological and acmeological influences, the development of reflective culture, the formation of a harmonious “self-concept” in professional and managerial activities, the actualization of psychological mechanisms, conditions, factors and determinants of the person’s professional development, etc. In our opinion, the professional reliability of a doctor is characterized by: a high level of stable productivity (or efficiency) of the professional activity; a high level of professional qualification and developed professional competence; optimal intensity of the professional activity; a high level of accuracy and reliability; a high level of organization of the professional activity; low indirectness (depending on purely external factors); creativity; the possibility of developing the subject of the professional activity and ensuring the actual professional growth; focus on achieving positive socially significant goals and results. Conclusions. We proved that bifurcation space of a professionally reliable Doctor includes: the ability to transfer professional experience; a high stable productivity of professional activity; the responsibility for the decisions having been made and their implementation; the ability to achieve own goals in any case; professional knowledge and the experience to be the director of some medical organization; the ability to act in critical situations and situations of cognitive dissonance; the ability to control the flow of doctors’ professional activity; a high level of professional competence; the ability to make and clearly implement their own decisions. If these components of a professionally reliable Doctor are formed at a high level, the Doctor can perform his/her professional activity with a high degree of its productivity, in difficult pandemic conditions, in situations of stress and cognitive dissonance. The latter emphasizes on the difference between the capabilities and the style of internal activity of Doctors who provide their activity in a period of COVID-19 pandemic: the ability to achieve meanings until the moment of meaningful acceptance of surrounding us reality and move on – to expand the meaning of the symbolic space (which is the COVID-19 pandemic) and, according to this, to show the measures of our own meaningful space (human life in a pandemic). Such conditions significantly encourage doctors to improve themselves as real professionals, to update their own professional reliability.
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