Miniature uncooled and unchopped fiber optic infrared thermometer for application to cutting tool temperature measurement

A new infrared thermometer, sensitive to wavelengths between 3 μm and 3.5 μm, has been developed. It is based on an Indium Arsenide Antimony (InAsSb) photodiode, a transimpedance amplifier, and a sapphire fiber optic cable. The thermometer used an uncooled photodiode sensor and received infrared radiation that did not undergo any form of optical chopping, thereby, minimizing the physical size of the device and affording its attachment to a milling machine tool holder. The thermometer is intended for applications requiring that the electronics are located remotely from high-temperature conditions incurred during machining but also affording the potential for use in other harsh conditions. Other example applications include: processes involving chemical reactions and abrasion or fluids that would otherwise present problems for invasive contact sensors to achieve reliable and accurate measurements. The prototype thermometer was capable of measuring temperatures between 200 °C and 1000 °C with sapphire fiber optic cable coupling to high temperature conditions. Future versions of the device will afford temperature measurements on a milling machine cutting tool and could substitute for the standard method of embedding thermocouple wires into the cutting tool inserts. Similarly, other objects within harsh conditions could be measured using these techniques and accelerate developments of the thermometer to suit particular applications

A multi-layer active elastic metamaterial with tuneable and simultaneously negative mass and stiffness

All conventional acoustic/elastic media are restricted to possess positive constants for their constitutive parameters (density and modulus). Metamaterials provide an approach through which this restriction can be broken. By making these parameters negative and/or tuneable a broader range of properties becomes possible. This paper describes the first experimental implementation of an acoustic/elastic metamaterial in which the material parameters can be both simultaneously negative in a finite frequency band and the magnitude of the parameters independently tuneable on demand. The design is an active metamaterial (meta-mechanical-system) which is realized by directly applying feedback control forces to each layer within the metamaterial. The ability to tune the magnitude of the negative parameters has important implications for the use of a standard design that can be tuned to a particular application, or one which can adapt to a changing performance requirement. The implementation of the design is relatively large scale and low frequency, but the unit-cell length is significantly smaller than the wavelength in the double negative band. Importantly, assuming appropriate control hardware is available, the design can be both reduced in scaled and expanded to greater degrees of freedom. © 2014 IOP Publishing Ltd

A comparative review of thermocouple and infrared radiation temperature measurement methods during the machining of metals

During the machining process, substantial thermal loads are generated due to tribological factors and plastic deformation. The increase in temperature during the cutting process can lead to accelerated tool wear, reducing the tool’s lifespan; the degradation of machining accuracy in the form of dimensional inaccuracies; and thermally induced defects affecting the metallurgical properties of the machined component. These effects can lead to a significant increase in operational costs and waste which deviate from the sustainability goals of Industry 4.0. Temperature is an important machining response; however, it is one of the most difficult factors to monitor, especially in high-speed machining applications such as drilling and milling, because of the high rotational speeds of the cutting tool and the aggressive machining environments. In this article, thermocouple and infrared radiation temperature measurement methods used by researchers to monitor temperature during turning, drilling and milling operations are reviewed. The major merits and limitations of each temperature measurement methodology are discussed and evaluated. Thermocouples offer a relatively inexpensive solution; however, they are prone to calibration drifts and their response times are insufficient to capture rapid temperature changes in high-speed operations. Fibre optic infrared thermometers have very fast response times; however, they can be relatively expensive and require a more robust implementation. It was found that no one temperature measurement methodology is ideal for all machining operations. The most suitable temperature measurement method can be selected by individual researchers based upon their experimental requirements using critical criteria, which include the expected temperature range, the sensor sensitivity to noise, responsiveness and cost

Active elastic metamaterials with applications in vibration and acoustics

Elastic metamaterials provide a new approach to solving existing problems in vibration and acoustics. They have also been associated with novel concepts such as acoustic invisibility and subwavelength imaging. To be applied to many of the proposed applications a metamaterial would need to have the desired mass density and elastic moduli over a prescribed frequency band. Importantly active metamaterials provide a degree of adaptability. This paper will focus on extending a previous theoretical concept to a more realistic experimental design. This will include a consideration of the problems which arise when the theory and simulation are developed into an experimental demonstration, including the role which the control system dynamics play in the achievable performance. The adaptability of the bandwidth in which the properties achieve their desired values will also be investigated

Élimination, par dialyse, des gaz dissous dans un liquide

Les gaz dissous physiquement dans un liquide peuvent être éliminés, comme d'autres solutés, par dialyse à travers une membrane permsélective et contre un milieu dans lequel ils sont solubles. Suivant le principe établi dans cette étude, l'épuration par dialyse, des gaz non métabolisés du plasma sanguin et des tissus, permettera aux plongeurs de revenir plus rapidement à la surface en situation d'urgence, avec un moindre risque de subir la maladie de décompression

Élimination, par dialyse, des gaz dissous dans un liquide

Les gaz dissous physiquement dans un liquide peuvent être éliminés, comme d'autres solutés, par dialyse à travers une membrane permsélective et contre un milieu dans lequel ils sont solubles. Suivant le principe établi dans cette étude, l'épuration par dialyse, des gaz non métabolisés du plasma sanguin et des tissus, permettera aux plongeurs de revenir plus rapidement à la surface en situation d'urgence, avec un moindre risque de subir la maladie de décompression

Performance and stability analysis of active elastic metamaterials with a tunable double negative response

Metamaterials can possess material parameters which do not exist in conventional materials. Consequently metamaterials provide a novel way to control wave propagation within a structure. These characteristics are achieved by designing a material with a particular sub-wavelength structure which leads to negative constitutive parameters in the long wavelength limit. For elastic materials these parameters are the density and modulus. In a previous study, a theoretical design for a novel active elastic metamaterial (AEM) was proposed. In this material control forces are applied to an array of resonant units in order to achieve a simultaneously negative effective density and modulus over a prescribed frequency band. This design potentially overcomes some of the restrictions imposed by previous passive designs. In this paper a new design of AEM is proposed which compensates for actuator dynamics and provides a basis for practical implementation. This design is shown to have a stable response with a tunable double negative frequency band

Active elastic metamaterials with applications in acoustics

International audienceElastic metamaterials provide a new approach to solving existing problems in acoustics. They have also been associated with novel concepts such as acoustic invisibility and subwavelength imaging. To be applied to many of the proposed applications a metamaterial would need to have the desired mass density and elastic moduli over a wide frequency band. To minimise scatter in acoustics applications the impedance of solid elastic metamaterials also need to be matched to the impedance of the surrounding medium. Previous work has looked at the trade-off between achieving the desired mass density and Youngs modulus, combined with an impedance which is matched to the surrounding medium. This paper will focus on extending the bandwidth of the desired properties presented in previous work to an extent where the material could be applied to some of the novel applications. This will include a consideration of the problems which arise when the previously developed theory and simulation is developed into an experimental demonstration. This includes the role which the control system dynamics play on the achievable performance. It will also consider the problems which arise when the previous one-dimensional concept is extended to higher dimensions