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The significance of micro-destructive testing, which can estimate the durability of reinforced concrete structures with minimal damage and high accuracy, in the investigation and diagnosis of reinforced concrete structures has been increasing. This study aims to evaluate the quality of the surface layer of concrete structures via a small-diameter drilling test, which is one of the micro-destructive tests developed to estimate the strength of concrete. Hence, it would be possible to evaluate the quality and strength of concrete simultaneously, which is very important. In this study, the influence of the bleeding amount which affects the surface quality of concrete on the drilling speed, was experimentally studied, considering the water-cement ratio and unit water content as experimental factors. The influence of bleeding on the drilling speed of the specimen surface was also investigated through measurements at the top and bottom surfaces. The following points were clarified from the experimental results and their analysis. (1) The drilling speed changes depending on the water-cement ratio and the unit water content. (2) The amount of bleeding affects the drilling speed; however the drilling speed is affected by the volume of the fine aggregate in the specimen. Therefore, (3) there is a possibility that it can be used for surface quality evaluation of concrete by examining in detail the method for calculating and correcting the drilling speed. [ABSTRACT FROM AUTHOR]

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Highlights • A novel bone drilling system was designed to achieve high-energy ultrasonically assisted bone drilling. • The drilling temperature was compared with conventional bone drilling. • High-energy ultrasonically assisted bone drilling had slightly higher drilling temperature than conventional bone drilling. • The thermal effect of ultrasonic vibration was a main reason for this phenomenon. Abstract Ultrasonically assisted drilling as a new type of bone drilling technology has received increasing attention. However, the vibration energy of existing studies was limited. In this study, a robot-based ultrasonically assisted bone drilling experimental setup was designed, and high-energy ultrasonically assisted bone drilling (vibration frequency=24.1–41 kHz, and vibration amplitude=150–160 µm) was applied to bovine cortical bone to investigate the drilling temperature compared with conventional drilling. The effect of drilling speed on drilling temperature was also studied. The experiment results showed that, compared with the conventional bone drilling, high-energy ultrasonically assisted bone drilling had slightly higher drilling temperature (0.36–0.86°C), which is in direct contrast to previous reports. We hypothesized that this finding was due to the thermal effect of ultrasonic vibration, which the present study confirmed. Moreover, the drilling temperature increased with higher drilling speed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Residual stress measurements on Titanium grade 5 specimen were carried out. [•] The effects of the choice of a proper analysis area are shown. [•] Effects of using different drilling speeds were examined too. [•] Higher scattering of the data was found for lower speeds. [•] Scattering at low speed was connected with the low quality of the drilled hole. [ABSTRACT FROM AUTHOR]

Taking roof shallow strata as the research object, the field test research on the drilling feedback signal of variable thrust level in drilling construction process and the characteristics of drill deep-drill speed, the results showed that in drilling area drilling speed and thrust level are approximate linear positive correlation. As lithology different its drill speed growth rate is different. In blocking of the mudstone layer the drill speed is negative growth. Under 2.5-3.5 kN thrust level, the drilling speed in the coal seams, mudstone layer and sandstone layer decreases in turn. The coal seam roof of test coal mine is in the drilling area. The average drilling speed is 41. 8-43. 2 mm/s, fluctuation is -4.07% -3.01% ; The average drilling speed in sandstone is 8. 4-9. 8 mm/s, fluctuation is -16.3% -19. 0% ; The average drilling speed in mudstone is 22.4-23.5 mm/s, fluctuation is -28.1%-24.3% ;The integrity of roof mudstone is poor, there is a fissure channel in each range of 1. 1-1.3, 2.7-2.8 and 4. 1-4. 4 m, the fluctuation of drilling speed in channel is up to 122.3%; the characteristic curve of drilling depth-drilling speed can clearly characterize the location of fissure channel. [ABSTRACT FROM AUTHOR]