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Microthermomechanical infrared sensors

Steffanson M., Rangelow I. W.

Opto-Electronics Review

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2014

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Vol. 22, No. 1

1-15

EN

We present a state-of-the-art overview of microthermomechanical infrared sensor technology. The working principle of this sensor is based on a bi-material actuated micromechanical deflection, generated by an induced temperature rise due to incident infrared radiation absorption. In order to generate a thermal image the thermomechanical deflections of the freestanding microstructures are read by either capacitive, piezoresistive or optical means. Research and development activities in this field began in the early 1990s. The development of this technology within the last 20 years has resulted in innovations such as uncooled multiband infrared detection, high-speed infrared sensing and uncooled THz imaging. This paper outlines representative milestones of this technology and analyses important results of notable groups. Significant activities on capacitive and optical readout techniques of thermomechanical infrared arrays are presented. Furthermore the advantages of microthermomechanical infrared sensors over current well-established uncooled infrared technologies are summarized. In conclusion the latest developments of this technology offer a highly potential solution for a variety of important energy-saving, safety and security applications.

2

Development and Assessment of Polymeric Laminate blended composites Reinforced with Bi-Woven Aramidic Fiber

Amarababu B., Rangadu V. P.

International Letters of Chemistry, Physics and Astronomy

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2014

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Vol. 19, iss. 1

99--110

EN

In the present paper evaluates laminated aramidic bi-woven fibers reinforced in polyester-vinylester blended composites. The Duo polymers, polyester-vinylester were blended using in situ polymerization technique. Four planar layers were made simultaneously and keeping one over another and each layer make sure to be weighed off 15% were maintained in all layers with different orientations. Pre-assumed Layer-1(50/50) 50 %, 0º; Layer-2(35/35/30) 35 % 0º, 35 % +45º, 30 %,0; Layer-3 (25/50/25) 25 % 0º, 50% +45º, 25-45º; Layer-4 (25/25/25/25) (2 5% 0º, 25 % +45º, 25 % -45º, 25 % 90º). Tthe composite was prepared with the help of hand layup technique. Test ready specimens were the help of shearing machine in accordance with ASTM. It was observed that, polyester and vinylester had good miscibility makes combined solid material. Flexural strength, tensile strength was improved up to 3ed layer, decreases after, whereas flexural modulus and tensile modulus were linearly increased up to 4th layer. Thermal stability and glass transition temperature were also found satisfactory for all the laminated layers. Chemical resistance was good for the entire chemical except toluene.

3

Current developments on the coupled thermomechanical computational modeling of metal casting processes

Agelet de Saracibar C., Chiumenti M., Cervera M.

Computer Methods in Materials Science

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2006

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Vol. 6, No. 1

15-25

EN

In this paper, current developments on the coupled thermomechanical computational simulation of metal casting processes are presented A thermodynamically consistent constitutive material model is derived from a thermoviscoplastic free energy function. A continuous transition between the initial fluid-like and the final solid-like is modeled by considering a J2 thermoviscoplastic model. Thus, an thermoelastoviscoplastic model, suitable for the solid-like phase, degenerates into a pure thermoviscous model, suitable for the liquid-like phase, according to the evolution of the solid fraction function. A thermomechanical contact model, taking into account the insulated effects of the air-gap due to thermal shrinkage of the part during solidification and cooling, is introduced. A fractional step method, arising from an operator split of the governing differential equations, is considered to solve the coupled problem using a staggered scheme. Within a finite element setting, using low-order interpolation elements, a multiscale stabilization technique is introduced as a convenient framework to overcome the Babuska-Brezzi condition and avoid volumetric locking and pressure instabilities arising in incompressible or quasi-incompressible problems. Computational simulation of industrial castings show the good performance of the model.

PL

W artykule opisano stan badań nad cieplno-mechanicznym modelem procesów odlewania metali. Termodynamicznie spójny konstytutywny model materiału został opracowany w oparciu o funkcję termo-lepkoplastycznej energii swobodnej. Ciągłe przejście od cieczy do ciała stałego modelowano za pomocą termo-lepkoplastycznego modelu typu J2. W konsekwencji, stosownie do zmian ułamka objętości fazy stałej termo-sprężysto-lepkoplastyczny model, opracowany dla ciał w stanie stałym, jest przekształcany w termo-lepkoplastyczny model odpowiedni dla cieczy. Do programu wprowadzono termo-lepkoplastyczny model styku, uwzględniający izolacyjny wpływ szczeliny powietrza powstającej w wyniku skurczu objętościowego krzepnącego metalu. W rozwiązaniu sprzężonego problemu zastosowano metodę kroków cząstkowych, wynikającą z operatorowego rozdziału różniczkowego równania cząstkowego. W rozwiązaniu metodą elementów skończonych zastosowano wieloskalową metodę stabilizacji w elementach niskiego rzędu. Jest to efektywna metoda pozwalająca ominąć kryterium Babuski-Brezzi'ego i uniknąć lokingu objętościowego i niestabilności ciśnienia powstających w quasi-nieściśliwych problemach. Symulacje przemysłowych procesów odlewania wykazały dobrą dokładność opracowanego modelu.

4

Thermomechanical investigations of martensitic and reverse transformations in TiNi shape memory alloy

Pieczyska E. A., Gadaj S. P., Nowacki W. K., Tobushi H.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2004

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Vol. 52, nr 3

165-171

EN

Shape memory alloys are characterised by interesting properties, i.e. shape memory effect and pseudoelasticity, which enable their increasing application. Thermomechanical aspects of martensitic and reverse transformations in TiNi shape memory alloy subjected to tension tests were investigated. The stress-strain characteristics obtained during the tests were completed by the temperature characteristics. The temperature changes were calculated on the basis of thermograms determined by an infrared camera. Taking advantages from the infrared technique, the temperature distributions on the specimen's surface were found. Heterogeneous temperature distributions, related to the nucleation and development of the new martensite phase, were registered and analysed. A significant temperature increase, up to 30 K, was registered during the martensitic transformation. The similar effects of the heterogeneous temperature distribution were observed during unloading, while the reverse transformation, martensite into austenite took place, accompanied by significant temperature decrease.