In conventional shock tubes with a diaphragm, many effects related to the burst of the diaphragm can influence shock formation, thus preventing an ideal pressure step change, as predicted by the shock tube measurement model being generated. This paper presents a newly developed diaphragmless shock tube with a quick-acting pneumatic valve, which demonstrates several advantages over conventional shock tubes with a diaphragm. The tests of the developed diaphragmless shock tube were performed using nitrogen at the atmospheric initial driven pressure, and at initial driver gauge pressures from 1 MPa to 7 MPa. The results show that the construction of the developed shock tube effectively reduces the generation of secondary shock waves and mechanical vibrations, which are often generated during the operation of shock tubes, thereby increasing the uncertainty of the shock tube calibration method. The uncertainty analysis shows that the developed diphragmless shock tube can act as a primary time-varying pressure calibration standard, generating pressure steps with a magnitude calculable from its measurement model to characterize the dynamic performance of pressure transducers with a relative expanded uncertainty of less than 0.025.

Technological progress demands accurate measurements of rapidly changing pressures. This, in turn, requires the use of dynamically calibrated pressure meters. The shock tube enables the dynamic characterization by applying an almost ideal pressure step change to the pressure sensor under calibration. This paper evaluates the effect of the dynamic response of a side-wall pressure measurement system on the detection of shock wave passage times over the side-wall pressure sensors installed along the shock tube. Furthermore, it evaluates this effect on the reference pressure step signal determined at the end-wall of the driven section using a time-of-flight method. To determine the errors in the detection of the shock front passage times over the centers of the side-wall sensors, a physical model for simulating the dynamic response of the complete measurement chain to the passage of the shock wave was developed. Due to the fact that the use of the physical model requires information about the effective diameter of the pressure sensor, special attention was paid to determining the effective diameter of the side-wall pressure sensors installed along the shock tube. The results show that the relative systematic errors in the pressure step amplitude at the end-wall of the shock tube due to the errors in the detection of the shock front passage times over the side-wall pressure sensors are less than 0.0003%. On the other hand, the systematic errors in the phase lag of the end-wall pressure signal in the calibration frequency range appropriate for high-frequency dynamic pressure applications are up to a few tens of degrees. Since the target phase measurement uncertainty of the pressure sensors used in high-frequency dynamic pressure applications is only a few degrees, the corrections for the systematic errors in the detection of the shock front passage times over the side-wall pressure sensors with the use of the developed physical dynamic model are, therefore, necessary when performing dynamic calibrations of pressure sensors with a shock tube.

Heat, generated during the drilling of a dental implant site preparation, leads to a temperature rise and consequently to a thermal injury of the bone tissue surrounding the implant site, which can cause the subsequent implant failure. In this article, we present new findings related to the temperature rise during implant site drilling under real conditions on a bovine rib bone specimen. The experiments were designed with the help of a full-factorial design in randomized complete blocks, where the main effects of the drill diameter in combination with the drilling force and the drilling speed, and their interactions, on the temperature rise were determined. The temperature rise in the bone under real conditions was measured as the implant site was being prepared by a dentist using intermittent, graduated drilling and external irrigation. Results show that the drill diameter has statistically significant effect, independent of the drilling procedure used. Among the examined drilling parameters, the drill diameter has the greatest effect, where an increase in the drill diameter first causes a decrease in the temperature rise and further increase in the drill diameter causes its increase. During the continuous and one-step drilling, the temperatures of the bones were up to 40.5 °C and during the drilling under actual conditions up to 30.11 °C.