The torsional waveguide viscosity probe: Design and anomalous behavior

This paper is concerned with the design of viscosity sensors based on a torsional waveguide. The advantages of using guided wave attenuation instead of speed for viscosity estimation are established. The effects of probe material, dimensions and operating frequency on viscosity measurement are discussed in the context of a requirement to match the measured attenuation to the range of viscosity values that are required to be measured, given the constraints on measurability imposed by the overall signal and noise conditions. A prototype probe is shown to work well with Newtonian liquids but to appreciably underestimate the viscosities of polymeric oils; these anomalies are explained quantitatively on the basis of a model of intramolecular relaxation. The probe was unsuccessful when applied to slurries, and a basic explanation is given

The torsional waveguide viscosity probe: design and anomalous behavior

This paper is concerned with the design of viscosity sensors based on a torsional waveguide. The advantages of using guided wave attenuation instead of speed for viscosity estimation are established. The effects of probe material, dimensions and operating frequency on viscosity measurement are discussed in the context of a requirement to match the measured attenuation to the range of viscosity values that are required to be measured, given the constraints on measurability imposed by the overall signal and noise conditions. A prototype probe is shown to work well with Newtonian liquids but to appreciably underestimate the viscosities of polymeric oils; these anomalies are explained quantitatively on the basis of a model of intramolecular relaxation. The probe was unsuccessful when applied to slurries, and a basic explanation is given

Rate of shear of an ultrasonic oscillating rod viscosity probe

Ultrasonic oscillating rod probes have recently been used by researchers to measure viscosity and/or density in fluids. However, in order to use such probes to characterise the rheological properties of fluids, it is necessary to define the shear rate produced by the probe. This paper proposes an analytical solution to estimate the shear rate of ultrasonic oscillating rod viscosity probes and a method to measure their maximum operational shear rate. A relationship is developed which relates the torsional surface velocity of an oscillating cylindrical rigid body to the rate of shear in its vicinity. The surface displacement and torsional surface velocity of a torsional probe of length 1000 mm and diameter 1 mm were measured over the frequency range from 525 to 700 kHz using a laser interferometer and the maximum shear rate estimated. The reported work provides the basis for characterising shear rate for such probes, enabling their application for rheological investigations

An integrated measurement method for complex micro-scale geometries

Micro-scale geometries are becoming commonplace in many high-precision manufacturing applications. Micro-drilling processes, for example, are being employed for producing holes in demanding applications involving fluid transfer, atomisers and micro-mechanics. This paper explores the measurement and characterisation of a high aspect-ratio micro-hole (nominal diameter approximately 1000 pm, aspect-ratio 1:10), produced using abrasive waterjet in Ti6AI4V. X-ray computed tomography, contact micro-coordinate metrology and focus-variation microscopy are used for measuring the hole surfaces, and dedicated computational geometry algorithms are applied to obtain critical hole dimensions, such as radius as a function of depth. The comparison of the measurement and characterisation results obtained by means of the different solutions explored hints at new approaches for multisensor data fusion that can help reduce bias in the measurement of high aspect-ratio micro-scale features

Para-cardiac Inflammatory Mass Compressing the Heart: A possible association with COVID-19

Infection with the SARS-CoV-2 virus causes coronavirus disease 2019 (COVID-19). COVID-19 usually affects the lungs but may also involve other organs such as the heart. We report a case of a para-cardiac mass in a previously healthy 45-year-old man who developed persistent dyspnea following SARS-CoV-2 infection. The patient underwent cardiac surgery since the mass was attached to the pericardium and was causing constrictive pericarditis. The pathology report indicated an inflammatory pattern for the mass. Based on our knowledge there has been no previous report of developing a para-cardiac inflammatory mass after SARS-CoV-2 infection. In conclusion, we would like to increase awareness regarding the possibility of developing a para-cardiac inflammatory mass following COVID-19. Keywords: SARS-CoV-2; Pericarditis; Constrictive pericarditis; COVID-19; Cardiac tumor; Mediastinal tumor

Closed Loop Force Control of In-Situ Machining Robots using Audible Sound Features

Detecting, measuring and controlling the forces between cutting tools and machined components is essential in circumstances where direct position control (e.g. depth of cut, feed speed, etc.) is inaccurate and/or impossible. This paper explores the use of airborne sound signals that result from the machining process to control the cutting force in closed loop for generating accurate machined features when performing in-situ robotic repair of complex installations. The sound signals during indentation at various cutting forces are analysed and used to calibrate a remotely mounted microphone sensor and signal processing control system. The power spectral density of the audible sound is used to estimate tool cutting force and the sound intensity used in turn to estimate the resulting process energy. The described controller uses intensity of sound to mitigate the e_ects of resonance with workpiece natural frequencies while controlling the spindle velocity of the tool based on the dominant audible frequency. The performance of the controller is validated using a representative test rig and demonstrated using a robotic arm to machine thin Ni-Cr-Co alloy cantilever beams with a miniature air-driven grinding tool. Results from the test rig show that such a sound-based control approach can achieve consistent cutting forces with an accuracy of 0.08 N. The robot arm is shown to be capable of grinding features of consistent depth (to within 0.05 mm) on beams with surface defects of unde_ned shape using only the sound of the process for closed loop force control

Teleoperated, In Situ Repair of an Aeroengine: Overcoming the Internet Latency Hurdle

There is a substantial financial incentive for in situ repair of industrial assets. However, the need for highly trained mechanics to travel to the location of a repair often results in inconveniently long downtimes. The emergence of robots capable of replicating human interventions on industrial equipment can be coupled with remote-control strategies to reduce the response time from several days to a few hours

Quantum fluctuations can promote or inhibit glass formation

The very nature of glass is somewhat mysterious: while relaxation times in glasses are of sufficient magnitude that large-scale motion on the atomic level is essentially as slow as it is in the crystalline state, the structure of glass appears barely different than that of the liquid that produced it. Quantum mechanical systems ranging from electron liquids to superfluid helium appear to form glasses, but as yet no unifying framework exists connecting classical and quantum regimes of vitrification. Here we develop new insights from theory and simulation into the quantum glass transition that surprisingly reveal distinct regions where quantum fluctuations can either promote or inhibit glass formation.Comment: Accepted for publication in Nature Physics. 22 pages, 3 figures, 1 Tabl

Design and Implementation of an Electronic Front-End Based on Square Wave Excitation for Ultrasonic Torsional Guided Wave Viscosity Sensor

The market for process instruments generally requires low cost devices that are robust, small in size, portable, and usable in-plant. Ultrasonic torsional guided wave sensors have received much attention by researchers for measurement of viscosity and/or density of fluids in recent years. The supporting electronic systems for these sensors providing many different settings of sine-wave signals are bulky and expensive. In contrast, a system based on bursts of square waves instead of sine waves would have a considerable advantage in that respect and could be built using simple integrated circuits at a cost that is orders of magnitude lower than for a windowed sine wave device. This paper explores the possibility of using square wave bursts as the driving signal source for the ultrasonic torsional guided wave viscosity sensor. A simple design of a compact and fully automatic analogue square wave front-end for the sensor is also proposed. The successful operation of the system is demonstrated by using the sensor for measuring the viscosity in a representative fluid. This work provides the basis for design and manufacture of low cost compact standalone ultrasonic guided wave sensors and enlightens the possibility of using coded excitation techniques utilising square wave sequences in such applications