Towards enhanced nanoindentation by image recognition

The Oliver–Pharr method is maybe the most established method to determine a material’s Young’s modulus and hardness. However, this method has a number of requirements that render it more challenging for hard and stiff materials. Contact area and frame stiffness have to be calibrated for every tip, and the surface contact has to be accurately identified. The frame stiffness calibration is particularly prone to inaccuracies since it is easily affected, e.g., by sample mounting. In this study, we introduce a method to identify Young’s modulus and hardness from nanoindentation without separate area function and frame stiffness calibrations and without surface contact identification. To this end, we employ automatic image recognition to determine the contact area that might be less than a square micrometer. We introduce the method and compare the results to those of the Oliver–Pharr method. Our approach will be demonstrated and evaluated for nanoindentation of Si, a hard and stiff material, which is challenging for the proposed method. Graphic Abstract

Contribution to the analysis of the frame stiffness of the cranes with loading-unloading trolley

The paper analyzes the dependence of the stiffness of the support frames of the cranes with loading-unloading trolley on the change of geometrical parameters of the frames. The calculation model of the frames with transverse stiffness was formed because it additionally stiffens the supporting surface of the frames for connection with the axial-radial bearing. The relations of characteristic geometrical sizes of longitudinal and transverse elements were established, at which the necessary stiffness of the frames of loading-unloading trolley was achieved. Also, the variables and constants of geometric size were introduced, as well as the constant values of appropriate coefficients, the variation of which provides the possibility to form the optimal structure of the frames of loading-unloading trolley.

An experimental study on the effect of frame-to-wall connection type on the seismic behavior of steel frames infilled with autoclave-cured aerated concrete blocks

In this article, in order to find some reliable connection types for avoiding the infill failure, an experimental study is conducted on six half-scale single-story single-bay specimens, including one bare frame and five steel frames with autoclave-cured aerated concrete walls, each having different frame-to-wall connection types. Polyurethane adhesive was used in bed joints of the autoclave-cured aerated concrete walls as a mortar. The specimens were tested under displacement-controlled loading to examine their effect on the in-plane behavior of steel frames. The results suggested that V- and T-shaped connectors can be used as prequalified connectors between the wall and the frame. In specimens with these connectors, the interaction between infill and frame was ignorable and the infill remained intact up to life safety performance level (2.5% drift ratio). Furthermore, the application of these connectors resulted in a two-level performance of the infill whereby the frame stiffness degradation and strength deterioration after the drift ratio of 2.5% was compensated.

The effect of the bogie frame stiffness on running properties of rail vehicles

Najważniejszym układem w pojeździe szynowym decydującym o jego komforcie i bezpieczeństwie jazdy jest układ biegowy. Wózek jako integralny element odgrywa podstawową rolę w bezpiecznym i stabilnym poruszaniu się pojazdu po infrastrukturze szynowej. Dopasowana konstrukcja ramy wózka do warunków eksploatacyjnych pojazdu, może w znacznym stopniu poprawić jego własności biegowe. W artykule zostanie dokonana analiza wybranych konstrukcji ram wózków oraz przedstawione zostaną różnice strukturalne.

Seismic Performance and Evaluation of Controlled Spine Frames Applied in High-rise Buildings

A controlled spine frame system consists of moment frames and spine frames with concentrated energy-dissipating members. This system guarantees the continuous usability of buildings against Japanese Level-2 earthquake events (similar to DBE events in California), and the authors have confirmed its excellent performance in preventing damage concentration in low-rise buildings. This study further investigates the effect of diverse structural properties on the seismic performance of controlled spine frames applied in high-rise buildings. The effect of building height, yield drift of dampers, spine-to-moment frame stiffness ratio, and damper-to-moment frame stiffness ratio are illustrated in detail, and optimal values are discussed. Also, a segmented spine frame system is proposed for high-rise buildings. The simple evaluation procedure proposed by the authors for low-rise buildings, based on equivalent linearization techniques and response spectrum analyses, was modified to include higher-mode effects for high-rise buildings based on modal analysis. The modified evaluation method was verified by modal pushover and time-history analyses.