Methods of measuring residual stresses in components

Residual stresses occur in many manufactured structures and components. Large number of investigations have been carried out to study this phenomenon and its effect on the mechanical characteristics of these components. Over the years, different methods have been developed to measure residual stress for different types of components in order to obtain reliable assessment. The various specific methods have evolved over several decades and their practical applications have greatly benefited from the development of complementary technologies, notably in material cutting, full-field deformation measurement techniques, numerical methods and computing power. These complementary technologies have stimulated advances not only in measurement accuracy and reliability, but also in range of application; much greater detail in residual stresses measurement is now available. This paper aims to classify the different residual stresses measurement methods and to provide an overview of some of the recent advances in this area to help researchers on selecting their techniques among destructive, semi destructive and non destructive techniques depends on their application and the availabilities of those techniques. For each method scope, physical limitation, advantages and disadvantages are summarized. In the end this paper indicates some promising directions for future developments

Logisticko-marketingove principy rizeni obchodnich cinnosti firmy

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Examination of Age-related Core Stability and Dynamic Balance in Hockey Players

The purpose of the study was to assess core stability and to determine age-related diff erences in the unilaterality of limb movements in hockey players. The sample included 152 hockey players aged 12 to 35 years. Every player performed the upper quarter and the lower quarter Y-balance tests. Performances of players showed high degree of individuality, which was expressed as the composite score. The diff erence greater than 4 cm in movements performed by a left or right limb indicates imbalance and higher risk of injury. Of 152 players, 27 and 26 players showed a diff erence higher than 4 cm for the lower quarter and the upper quarter, respectively. Of all age categories, 61% of senior players showed muscle imbalance. This may have been caused by factors present at school age because 52% of U13 players showed imbalance. We conducted statistical analysis to determine diff erences for each of the directions in relation to limb length. The cross-sectional data have shown non signifi cant diff erences between age categories studied. For the development of ice hockey players, it is important to eliminate movement imbalance. The results have shown that the category at risk includes the U13 players, who may suff er from movement imbalance in the senior category