Pomiary odkształceń lokalnych w przestrzeni

W pracy przeanalizowano dokładność optycznych systemów pomiaru deformacji. Opisano sposób kodowania wielu punktów pomiarowych, budowę systemu do analizy odkształceń, a także dynamikę przyrządu i dostępne zakresy pomiarowe. Zbadano wpływ wielkości próbki na dokładność pomiaru. Porównano wyniki z efektem symulacji z wykorzystaniem MES. Wprowadzono pojęcie naprężeń lokalnych. W ostatniej części wskazano ograniczenia metody i sposoby ich usunięcia. We wnioskach pojawiają się potencjalne aplikacje dla systemu pomiarowego.

Optical systems are becoming more and more popular in quality control, even if there are some physical limitations coming form the light nature. New instruments, that are built by people who can accept those boundaries, are very versatile measuring system. In the first section of this paper a concept of local deformation measurements is presented. The name "local deformation" is used to distinguish it from global deformation [8, 10] occurring between two clearly distant points of any specimen characteristic for typical, mechanical extensometer (Fig. 1). The method for quick marking many measuring points [5] on the surface (Fig. 2) as well as construction and advantages of the system making use of the light reflection to analyze deformation are described. There is also given an answer to the question how to characterize the shape change in dynamic systems. The relationship between the recorder optical configuration and available measuring range as well as the influence of specimen dimensions on the instrument accuracy are characterized [1, 9]. Next, the difference between FEM results and those obtained from real measurements is explained [2, 3]. The notion of local strain [4] was introduced (based on the static deformation of specimen for strength test), which means that the deformation signal was completed by the force signal from a universal testing machine. In the last section of this paper there are considered limitations of the measuring system and a possible way of their elimination. To sum up, the direction of future research is given and the field of deformation (or strain) measuring applications [6,7], including those in which 3D distribution of stress or strain will be necessary, is described.