Artykuły w czasopismach: „Thermal and optical stress”

1

Shiue, Sham-Tsong, i Wen-Hao Lee. "Thermal stresses in carbon-coated optical fibers at low temperature". Journal of Materials Research 12, nr 9 (wrzesień 1997): 2493–98. http://dx.doi.org/10.1557/jmr.1997.0329.

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The thermal stresses in carbon-coated optical fibers at low temperature have been analyzed. The thermally induced lateral pressure in the glass fiber would produce microbending loss. In order to minimize such a microbending loss, the thickness, Young's modulus, and Poisson's ratio of the carbon coating should be decreased. On the other hand, the maximum thermal stress is the tangential stress in the carbon coating that occurs at the interface of the carbon coating and glass fiber. It was experimentally observed that if the maximum thermal stress is larger than the tensile strength of the carbon coating, the carbon coating will be broken along the axial direction. In order to minimize such a maximum thermal stress, the thickness of the carbon coating should be increased, but Young's modulus, thermal expansion coefficient, and Poisson's ratio of the carbon coating should be decreased. Finally, an optimal selection of the carbon coating for optical fiber is discussed.

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2

HIGUCHI, Masaya, i Koji SHIMIZU. "Evaluation of thermal stress by optical interferometric method". Proceedings of Autumn Conference of Tohoku Branch 2004.40 (2004): 49–50. http://dx.doi.org/10.1299/jsmetohoku.2004.40.49.

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Evans, K. E. "Thermal stress mechanisms in optical storage thin films". Journal of Applied Physics 63, nr 10 (15.05.1988): 4946–50. http://dx.doi.org/10.1063/1.340438.

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Huang, Cai Hua, Xiao Hua Sun, Yi Hua Sun i Jun Zou. "Thermal Effects Caused by Inclusions in Optical Films Irradiated by CW Laser". Advanced Materials Research 634-638 (styczeń 2013): 2609–12. http://dx.doi.org/10.4028/www.scientific.net/amr.634-638.2609.

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A steady thermal conduction model was presented to study the temperature field and thermal stress distribution in film irradiated by continuous wave laser. The thermal effects may arise from either the absorbing inclusions or the intrinsic absorption of film. Based on the plane thermal conduction assumption, the characteristics of damage resulted from local melting or evaporation and thermal stress were discussed. The damage region resulted from local melting or evaporation smaller than that from thermal stress. The circumferential stress σθis the main cause accounting for the stress damage. The normal stress perpendicular to the interface between film and substrate is the direct cause of drum type damage. The characteristics of damage in unsteady thermal conduction caused by pulse laser can be analyzed qualitatively by means of this model.

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5

Hu, Fu Kai, De Jian Zhou i Lei Cheng. "Research and Design of Optical-Fiber-Embedded Structure in Optical Printed Circuit Board under Thermal Shock". Advanced Materials Research 763 (wrzesień 2013): 238–41. http://dx.doi.org/10.4028/www.scientific.net/amr.763.238.

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To improve the serviceability of embedded optical fiber in OPCB, the paper discussed the optical-fiber-embedded structure in OPCB from the aspects of stress. Firstly, discussed optical fiber, groove and whether to use filler and provided six kinds of embedded structures. Then, finite element models were built for thermal simulation and thermal stress in fiber was calculated. Finally, compared different embedded structures from the stress in fiber and gave some suggestion about the design of embedded structure. The study proved that glass fiber is a better selection for OPCB; the stress concentrate easily appears in the edge of glass fiber; using filler can protect uncoated glass fiber, but increase the thermal stress is in coated glass fiber; when embedding uncoated fiber, U-groove is a better choice; when embedding coated fiber, U-groove without filler is the best choice. The results are helpful to the application of glass fiber in OPCB.

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6

Liu, Yueai, B. M. A. Rahman i K. T. V. Grattan. "Thermal-stress-induced birefringence in bow-tie optical fibers". Applied Optics 33, nr 24 (20.08.1994): 5611. http://dx.doi.org/10.1364/ao.33.005611.

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Wong, D. "Thermal stability of intrinsic stress birefringence in optical fibers". Journal of Lightwave Technology 8, nr 11 (1990): 1757–61. http://dx.doi.org/10.1109/50.60576.

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Gao, You Tang, Shuo Liu i Yuan Xu. "Analysis of Thermal Shock and Stress with Infrared Optical Domes". Applied Mechanics and Materials 325-326 (czerwiec 2013): 332–35. http://dx.doi.org/10.4028/www.scientific.net/amm.325-326.332.

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The development of infrared optical materials is always closely related to the research and exploration of material science. The infrared optical domes bears shock and produces stress when the infrared optical domes mounted on the missile moving at a high speed is shocked by high temperature. According to aerodynamics theory and thermo shock theory, the surge current will be transferred to optical parts through holding up layer and warms the surface of optical parts when infrared optical parts are shocked by high temperature. A compress stress is formed on the hot external surface of optical parts forms and a tension stress is formed on the internal surface or optical parts under the circumstance of the edge of optical parts being fixed. The windows of optical parts become curvature radius of lens with the function of pressure difference which can cause aberration change. The brittle fracture of material will be caused if peak stress is beyond the strength which is permitted for infrared materials. Therefore, limits to design of windows thickness is proposed in this paper.

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Lee, Kyoungho, i Joong Seok Lee. "Optimal Design of the Flexure Mount for Optical Mirror Using Topology Optimization Considering Thermal Stress Constraint". Journal of the Korea Institute of Military Science and Technology 25, nr 6 (5.12.2022): 561–71. http://dx.doi.org/10.9766/kimst.2022.25.6.561.

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An optical mirror assembly is an opto-mechanically coupled system as the optical and mechanical behaviors interact. In the assembly, a flexure mount attached to an optical mirror should be flexible in the radial direction, but rigid for the remaining degrees of freedom for supporting the mirror rigidly and suppressing the wavefront error of the optical mirror. This work presents an optimal design of the flexure mount using topology optimization with thermal stress constraint. By simplifying the optical mirror assembly into finite shell elements, topology optimization model was built for efficient design and good machinability. The stress at the boundary between the optical mirror and the mount together with the first natural frequency were applied as constraints for the optimization problem, while the objective function was set to minimize the strain energy. As a result, we obtained the optimal design of the flexure mount yielding the improved wavefront error, proper rigidity, and machinability.

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Chen, Tei-Chen, Ching-Jiung Chu, Chang-Hsien Ho, Chung-Chen Wu i Cheng-Chung Lee. "Determination of stress-optical and thermal-optical coefficients of Nb2O5 thin film material". Journal of Applied Physics 101, nr 4 (15.02.2007): 043513. http://dx.doi.org/10.1063/1.2435796.

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Blázquez-Castro, Alfonso. "Optical Tweezers: Phototoxicity and Thermal Stress in Cells and Biomolecules". Micromachines 10, nr 8 (31.07.2019): 507. http://dx.doi.org/10.3390/mi10080507.

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For several decades optical tweezers have proven to be an invaluable tool in the study and analysis of myriad biological responses and applications. However, as with every tool, they can have undesirable or damaging effects upon the very sample they are helping to study. In this review the main negative effects of optical tweezers upon biostructures and living systems will be presented. There are three main areas on which the review will focus: linear optical excitation within the tweezers, non-linear photonic effects, and thermal load upon the sampled volume. Additional information is provided on negative mechanical effects of optical traps on biological structures. Strategies to avoid or, at least, minimize these negative effects will be introduced. Finally, all these effects, undesirable for the most, can have positive applications under the right conditions. Some hints in this direction will also be discussed.

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12

Huang, M., i X. Yan. "Thermal-stress effects on the temperature sensitivity of optical waveguides". Journal of the Optical Society of America B 20, nr 6 (1.06.2003): 1326. http://dx.doi.org/10.1364/josab.20.001326.

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Nkansah, M. A., i K. E. Evans. "Modeling delamination due to thermal stress in optical storage media". Journal of Applied Physics 67, nr 7 (kwiecień 1990): 3243–48. http://dx.doi.org/10.1063/1.345356.

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Fu, Libin, Hugh A. McKay i Liang Dong. "Extremely large mode area optical fibers formed by thermal stress". Optics Express 17, nr 14 (29.06.2009): 11782. http://dx.doi.org/10.1364/oe.17.011782.

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Knoll, R. W., i C. H. Henager. "Optical and physical properties of sputtered Si:Al:O:N films". Journal of Materials Research 7, nr 5 (maj 1992): 1247–52. http://dx.doi.org/10.1557/jmr.1992.1247.

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Mechanical and optical properties and structural characteristics are described for Si:N films with Al and O additions (SixAl1−xOyN1−y) deposited by reactive RF diode sputtering on Si and SiO2 substrates. The thermal and intrinsic stress components, elastic stiffness, coefficient of thermal expansion (CTE), and refractive index were measured for films ranging in thickness from ∼2 μm to 50 μm. Some structural and microstructural data were obtained using x-ray diffraction, optical and scanning-electron microscopy, and surface profilometry. Alloying Si:N with Al to form Si:Al:N greatly reduced the compressive intrinsic and total stress found in pure Si:N films on Si. Addition of O to the Si:Al:N moderately increased the intrinsic stress, decreased the elastic stiffness, and produced a smoother, more glassy (amorphous) film.

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Ching-Kong Chao, Shih-Yu Hung i Cheng-Ching Yu. "Thermal stress analysis for rapid thermal processor". IEEE Transactions on Semiconductor Manufacturing 16, nr 2 (maj 2003): 335–41. http://dx.doi.org/10.1109/tsm.2003.811884.

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Liu, Shuaishuai, Bin Yang, Yuan Zhi i Xiaohui Yu. "Thermal-mechanical performance analysis of parabolic trough receivers under various optical errors based on coupled optical-thermal-stress model". Renewable Energy 210 (lipiec 2023): 687–700. http://dx.doi.org/10.1016/j.renene.2023.04.091.

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Ylivaara, Oili M. E., Andreas Langner, Satu Ek, Jari Malm, Jaakko Julin, Mikko Laitinen, Saima Ali i in. "Thermomechanical properties of aluminum oxide thin films made by atomic layer deposition". Journal of Vacuum Science & Technology A 40, nr 6 (grudzień 2022): 062414. http://dx.doi.org/10.1116/6.0002095.

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In microelectromechanical system devices, thin films experience thermal processing at temperatures some cases exceeding the growth or deposition temperature of the film. In the case of the thin film grown by atomic layer deposition (ALD) at relatively low temperatures, post-ALD thermal processing or high device operation temperature might cause performance issues at device level or even device failure. In this work, residual stress and the role of intrinsic stress in ALD Al2O3 films grown from Me3Al and H2O, O3, or O2 (plasma ALD) were studied via post-ALD thermal processing. Thermal expansion coefficient was determined using thermal cycling and the double substrate method. For some samples, post-ALD thermal annealing was done in nitrogen at 300, 450, 700, or 900 °C. Selected samples were also studied for crystallinity, composition, and optical properties. Samples that were thermally annealed at 900 °C had increased residual stress value (1400–1600 MPa) upon formation of denser Al2O3 phase. The thermal expansion coefficient varied somewhat between Al2O3 made using different oxygen precursors. For thermal-Al2O3, intrinsic stress decreased with increasing growth temperature. ALD Al2O3 grown with plasma process had the lowest intrinsic stress. The results show that ALD Al2O3 grown at 200 and 300 °C is suitable for applications, where films are exposed to post-ALD thermal processing even at temperature of 700 °C without a major change in optical properties or residual stress.

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19

Aversano, Lerina, Mario Luca Bernardi i Marta Cimitile. "Water stress classification using Convolutional Deep Neural Networks". JUCS - Journal of Universal Computer Science 28, nr 3 (28.03.2022): 311–28. http://dx.doi.org/10.3897/jucs.80733.

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In agriculture, given the global water scarcity, optimizing the irrigation system have become a key requisite of any semi-automatic irrigation scheduling system. Using efficient assessment methods for crop water stress allows reduced water consumption as well as improved quality and quantity of the production. The adoption of Neural Network can support the automatic in situ continuous monitoring and irrigation through the real-time classification of the plant water stress. This study proposes an end-to-end automatic irrigation system based on the adoption of Deep Neural Networks for the multinomial classification of tomato plants’ water stress based on thermal and optical aerial images. This paper proposes a novel approach that cover three important aspects: (i) joint usage of optical and thermal camera, captured by un-manned aerial vehicles (UAVs); (ii) strategies of image segmentation in both thermal imaging used to obtain images that can remove noise and parts not useful for classifying water stress; (iii) the adoption of deep pre-trained neural ensembles to perform effective classification of field water stress. Firstly, we used a multi-channel approach based on both thermal and optical images gathered by a drone to obtain a more robust and broad image extraction. Moreover, looking at the image processing, a segmentation and background removal step is performed to improve the image quality. Then, the proposed VGG-based architecture is designed as a combination of two different VGG instances (one for each channel). To validate the proposed approach a large real dataset is built. It is com- posed of 6000 images covering all the lifecycle of the tomato crops captured with a drone thermal and optical photocamera. Specifically, our approach, looking mainly at leafs and fruits status and patterns, is designed to be applied after the plants has been transplanted and have reached, at least, early growth stage (covering vegetative, flowering, friut-formation and mature fruiting stages).

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20

Sasaki, Yoshida, Ogawa, Shitaka i McGibboney. "Effect of Residual Stress on Thermal Deformation Behavior". Materials 12, nr 24 (10.12.2019): 4141. http://dx.doi.org/10.3390/ma12244141.

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This paper discusses a non-destructive measurement technique of residual stress through optical visualization. The least amount of deformation possible is applied to steel plates by heating the specimens +10 °C from room temperature for initial calibration, and the thermal expansion behavior is visualized with an electronic speckle pattern interferometer sensitive to two dimensional in-plane displacement. Displacement distribution with the thermal deformation and coefficient of thermal expansion are obtained through interferometric fringe analysis. The results suggest the change in the thermal deformation behavior is affected by the external stress initially applied to the steel specimen. Additionally, dissimilar joints of steel and cemented carbide plates are prepared by butt-brazing. The residual stress is estimated based on the stress dependence of thermal expansion coefficient.

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Liu, Shen, Hang Xiao, Yanping Chen, Peijing Chen, Wenqi Yan, Qiao Lin, Bonan Liu i in. "Nano-Optomechanical Resonators Based on Suspended Graphene for Thermal Stress Sensing". Sensors 22, nr 23 (23.11.2022): 9068. http://dx.doi.org/10.3390/s22239068.

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Nanomechanical resonators made from suspended graphene combine the properties of ultracompactness and ultrahigh detection sensitivity, making them interesting devices for sensing applications. However, nanomechanical systems can be affected by membrane stress. The present work developed an optomechanical resonator for thermal stress sensing. The proposed resonator consists of a section of hollow core fiber (HCF) and a trampoline graphene–Au membrane. An all-optical system that integrated optical excitation and optical detection was applied. Then, the resonance frequency of the resonator was obtained through this all-optical system. In addition, this system and the resonator were used to detect the membrane’s built-in stress, which depended on the ambient temperature, by monitoring the resonance frequency shift. The results verified that the temperature-induced thermal effect had a significant impact on membrane stress. Temperature sensitivities of 2.2646 kHz/°C and 2.3212 kHz/°C were obtained when the temperature rose and fell, respectively. As such, we believe that this device will be beneficial for the quality monitoring of graphene mechanical resonators.

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Shi, Nannan, Yanyu Chen i Zhenbao Li. "Crack Risk Evaluation of Early Age Concrete Based on the Distributed Optical Fiber Temperature Sensing". Advances in Materials Science and Engineering 2016 (2016): 1–13. http://dx.doi.org/10.1155/2016/4082926.

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Cracks often appear in concrete arch dams, due to the thermal stress and low tensile strength of early age concrete. There are three commonly used temperature controlling measures: controlling the casting temperature, burying cooling pipe, and protecting the surface. However, because of the difficulty to obtain accurate temperature and thermal stress field of the concrete, the rationality and economy of these measures are not assessed validly before and after construction. In this paper, a crack risk evaluation system for early age concrete is established, including distributed optical fiber temperature sensing (DTS), prediction of temperature and stress fields, and crack risk evaluation. Based on the DTS temperature data, the back-analysis method is applied to retrieve the thermal parameters of concrete. Then, the temperature and thermal stress of early age concrete are predicted using the reversed thermal parameters, as well as the laboratory test parameters. Finally, under the proposed cracking risk evaluation principle, the cracking risk level of each concrete block is given; the preliminary and later temperature controlling measures were recommended, respectively. The application of the proposed system in Xiluodu super high arch dam shows that this system works effectively for preventing cracks of early age concrete.

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Miller, W., C. W. Smith, P. Dooling, A. N. Burgess i K. E. Evans. "Tailored thermal expansivity in particulate composites for thermal stress management". physica status solidi (b) 245, nr 3 (marzec 2008): 552–56. http://dx.doi.org/10.1002/pssb.200777710.

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OZAKI, Tsuyoshi, i Shigenori Kabashima. "256 Thermal stress analysis of OSR (Optical Solar Reflector) in satellite structures". Proceedings of the 1992 Annual Meeting of JSME/MMD 2001 (2001): 227–28. http://dx.doi.org/10.1299/jsmezairiki.2001.0_227.

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Yan, Dan, Wei Lu, Lili Qiu, Zihui Meng i Yu Qiao. "Thermal and stress tension dual-responsive photonic crystal nanocomposite hydrogels". RSC Advances 9, nr 37 (2019): 21202–5. http://dx.doi.org/10.1039/c9ra02768h.

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Hirokawa, Yoshihiro, Haruki Nishi, Minoru Yamada, Shinsaku Zama i Ken Hatayama. "Fracture Probability Analysis of Crack Occurrence on a Floating Roof due to Thermal Stress". Advanced Materials Research 622-623 (grudzień 2012): 1539–44. http://dx.doi.org/10.4028/www.scientific.net/amr.622-623.1539.

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Several cracks were found on some actual floating roofs of a crude oil tank in the oil refinery located in southern Japan. We assumed that one of reasons would be due to thermal stress caused by temperature changes during the day. In order to consider whether the thermal stress could the cause damages on the floating roof, strain and temperature were measured on the actual floating roof by using optical fiber gauges. Furthermore, fracture possibility due to thermal stress was calculated to discuss whether thermal stress could cause fracture or not. As a result, the probability showed that thermal stresswasnot enough to cause fracture. Anotherexternal factor such as Typhoon could be related.

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Tzeng, P. Y., C. H. Liu, W. K. Li i C. Y. Soong. "Theoretical Analysis of Cylindrical Microparticle Photophoresis in a Perpendicular Optical Field with Thermal Stress Slip Model". Journal of Mechanics 28, nr 1 (marzec 2012): 113–21. http://dx.doi.org/10.1017/jmech.2012.12.

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ABSTRACTThe present study is concerned with a theoretical analysis of the photophoresis of a microsized long cylinder in a perpendicular optical field. Different from previous studies of photophoresis, thermal stress slip usually neglected is taken into account in the analysis. The gaseous fluid relative to the microparticle in photophoretic motion falls into slip-flow regime. Asymmetric distribution of the absorbed heat energy within the particle becomes the driving force for photophoretic motion of the cylinder-shaped particle. By evaluating heat source function distributions at various conditions, the study focuses on the effects of particle size and optical properties on the energy distribution and the resultant influences on the photophoresis. The photophoretic mobility is developed by the slip flow model with consideration of thermal stress slip. The results reveal that the photophoretic mobility decreases with the increase of particle thermal conductivity (k*) and increases with Knudsen number (Kn). The thermal stress slip effect on photophoretic velocity is more noticeable at high Kn, but disappears at the continuum limit. A long cylinder-shaped particle has higher photophoretic velocity than a spherical particle at low k*, while the situation reverses at high k*. With thermal stress slip considered, the critical condition for crossing of the photophoretic velocity curves of cylindrical and spherical particles is mildly influenced by Kn.

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Hirokawa, Yoshihiro, Haruki Nishi, Minoru Yamada, Shinsaku Zama i Ken Hatayama. "Study on Damage of a Floating Roof-Type Oil Storage Tank due to Thermal Stress". Applied Mechanics and Materials 232 (listopad 2012): 803–7. http://dx.doi.org/10.4028/www.scientific.net/amm.232.803.

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Several cracks were found on some actual floating roofs of a crude oil tank in the oil refinery located in southern Japan. We assumed that one of reasons would be due to thermal stress caused by temperature changes during the day. In order to consider whether the thermal stress could the cause damages on the floating roof, strain and temperature were measured on the actual floating roof by using optical fiber gauges. Furthermore, thermal stress analysis was carried out as effective analysis.

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Benino, Yasuhiko, Takumi Fujiwara i Takayuki Komatsu. "Development of New Crystallized Glasses with Nanocrystals and Nonlinear Optical Properties". Advanced Materials Research 11-12 (luty 2006): 189–92. http://dx.doi.org/10.4028/www.scientific.net/amr.11-12.189.

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New crystallized glasses with nonlinear optical properties are developed by various thermal processes for glassy materials which involve the precisely controlled heat-treatment and the novel crystallization patterning using laser spot heating technique. The nonlinear optical functions and their applications are discussed based on the morphologies of the precipitated crystalline phases. The enhancement of the nonlinear optical properties can be expected by introduction of internal stress during the thermal process.

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Guo, Y., i S. Liu. "Development in Optical Methods for Reliability Analysis in Electronic Packaging Applications". Journal of Electronic Packaging 120, nr 2 (1.06.1998): 186–93. http://dx.doi.org/10.1115/1.2792619.

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The mechanical analysis of electronic packaging has significant impact on the system reliability of an electronic device, and, therefore, is critical in packaging design and manufacturing. The main concerns of the mechanical analysis are the thermal strain/stress, interfacial failures, and the fatigue life of components and interconnections. As electronic technology advances, electronic packages are becoming smaller and smaller. Strain/stress concentrations are frequently localized in very tiny zones with high magnitudes. Determinations of thermal strain/stress and predictions of failure and reliability become more and more difficult. Recently, advanced optical techniques have been developed for electronic packaging analysis and have accomplished many tasks that could not be accomplished by conventional experimental methods. Optical techniques have been used for experimental stress/strain analysis, on-line inspections, simulation validations, and hybrid methods in many packaging areas. In this paper, recent developments in optical techniques are discussed. Several techniques are demonstrated by applications that are directly related to new electronic product development. The examples show the results and impact of using these optical techniques in the electronics industry to assist in product designs, qualifications, reliability improvements, and cycle time reductions.

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Wang, C., Y. Z. Wang, X. T. Jiang, Y. F. Song, F. Zhang, J. Liu i H. Zhang. "Thermal stress-induced all-optical modulation in MXene-coated polarization maintaining fiber". Laser Physics Letters 16, nr 6 (16.05.2019): 065107. http://dx.doi.org/10.1088/1612-202x/ab1017.

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Wang, Kai, i Robert R. Reeber. "Thermal Residual Stress Modeling in AlN and GaN Multi Layer Samples". MRS Internet Journal of Nitride Semiconductor Research 4, S1 (1999): 209–14. http://dx.doi.org/10.1557/s1092578300002477.

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Thermal residual stresses can detrimentally affect the electronic and optical properties of epitaxial films thereby shortening device lifetime. Based on our earlier work on thermal expansion of nitrides, we provide a finite element modeling analysis of the residual stress distribution of multilayered GaN and AlN on 6H-SiC. The effects of thickness and growth temperatures are considered in the analysis.

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Zhao, Zhan Feng, i Juan Ye. "Design Key Points for High Power LED Encapsulation". Advanced Materials Research 651 (styczeń 2013): 706–9. http://dx.doi.org/10.4028/www.scientific.net/amr.651.706.

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LED performance was significantly improved because of the improvement of encapsulation design and materials properties. The design key points were reviewed in point view of optical, electrical, thermal, and reliability consideration. It was concluded that the packaging design should be simultaneously implemented with the chip design, integrally considering the optics, electrics, thermal, and reliability together. The interfacial thermal resistance and stress from packaging also play critical roles for the optical efficiency and reliability of packaged LED device.

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Venerus, David C., David Nieto Simavilla i Jay D. Schieber. "THERMAL TRANSPORT IN CROSS-LINKED ELASTOMERS SUBJECTED TO ELONGATIONAL DEFORMATIONS". Rubber Chemistry and Technology 92, nr 4 (1.10.2019): 639–52. http://dx.doi.org/10.5254/rct.19.80382.

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ABSTRACT Investigations on thermal transport in cross-linked elastomers subjected to elongational deformations are reviewed and discussed. The focus is on experimental research, in which the deformation-induced anisotropy of the thermal conductivity tensor in several common elastomeric materials is measured using novel optical techniques developed in our laboratory. These sensitive and noninvasive techniques allow for the reliable measurement of thermal conductivity (diffusivity) tensor components on samples in a deformed state. When combined with measurements of the stress in deformed samples, we are able to examine the validity of the stress–thermal rule, which predicts a linear relationship between the thermal conductivity and stress tensor in deformed polymeric materials. These results are used to shed light on possible underlying mechanisms for anisotropic thermal transport in elastomers. We also present results from a novel experimental technique that show evidence of a deformation dependence of the heat capacity, which implies that, in addition to the usual entropic contribution, there is an energetic contribution to the stress in deformed elastomers.

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Huang, Shengzhou, Chengwei Jiang, Zhaowei Tian, Fanglin Xie, Bowen Ren, Yuanzhuo Tang, Jinjin Huang i Qingzhen Gao. "Mechanism Study of Ultrasonic Vibration-Assisted Microgroove Forming of Precise Hot-Pressed Optical Glass". Micromachines 14, nr 7 (24.06.2023): 1299. http://dx.doi.org/10.3390/mi14071299.

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Microgroove structures with helical pitches in a wavelength level are increasingly required in optical areas. However, conventional manufacturing techniques generate relatively high stresses during pressing, resulting in poor precision when forming microgrooves. This paper reports on the mechanism of the ultrasonic vibration-assisted microgroove forming of precise hot-pressed optical glass. A finite element (FE) thermocompression model of the viscoelastic material was developed and the entire forming process was numerically simulated using coupled thermal-structural analysis. The analysis of several process parameters was carried out using orthogonal experiments, from which the optimum combination of parameters was selected. The glass thermoforming process is also assisted by ultrasonic vibration. The thermal and mechanical effects of vibration improved material flow and optimized forming results. The average maximum stress in the glass during the forming process was only 3.04 × 10−3 Mpa, while the maximum stress in the hot-pressing stage without ultrasound was 1.648 Mpa. The stress results showed that the material-forming stress is significantly reduced.

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Huang, Cai Hua, Xiao Hua Sun, Yi Hua Sun i Jun Zou. "Thermal Effects Induced by Absorbing Inclusions in Laser Optical Films". Advanced Materials Research 602-604 (grudzień 2012): 1427–30. http://dx.doi.org/10.4028/www.scientific.net/amr.602-604.1427.

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The thermal transportation caused by absorbing inclusions in optical films under the radiation of laser pulse is unsteady heat conduction. The temperature distribution in films is ununiform and time-dependent. Considering the small size of inclusions, the absorbing inclusions were treaded as dot-heat sources. Based on this assumption, the unsteady heat conduction model was brought out and the temperature distribution in films was figured out and discussed, the mechanism that the catastrophic damage may avoid with micro-damage or micro-deformation in films through the release of stress concentration is presented. By comparing the thermal effects caused respectively by single inclusion and assembling ones, the effect of inclusion size on thermal damage in films was discussed.

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Chen, Guoxin, Xingyu Lu, Jin Yan, Hongwei Liu i Baoguang Sang. "High-Temperature Deformation Behavior of M50 Steel". Metals 12, nr 4 (23.03.2022): 541. http://dx.doi.org/10.3390/met12040541.

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The hot deformation characteristics of M50 steel in the temperature range of 900–1150 °C and strain-rate range of 0.01–10 s−1 was investigated in this study using a Gleeble-3800 thermal simulation testing machine. The true stress–strain curves showed that the deformation resistance increased with decreasing deformation temperature, and increasing strain rate before the peak stress was reached. After the peak stress, dynamic reversion occurred, and consequently, the deformation stress decreased. The softening phenomenon was more obvious when the strain rate was low. The calculated values of the thermal deformation-activation energy Q and stress index n were 233,684.2 J/mol and 5.025568, respectively. On this basis, the Arrhenius-type constitutive equation was established, and in addition, a polynomial fit based on strain was performed to obtain the 9th-order strain-compensated constitutive equation with high fitting accuracy. By processing the flow stress curves, the processing maps of M50 steel were constructed, and the optimal processing range was predicted to be in the range of 1070–1150 °C and 0.01–1 s−1. The recrystallization behavior of M50 steel was also studied by constructing a dynamic recrystallization kinetic model and combining optical microscope (OM) and electron backscatter diffraction (EBSD) observation. The results show that with the increase of deformation temperature, the degree of recrystallization transformation increased accordingly, and the original grains were gradually replaced by recrystallized grains. Besides, in the optimal process zone for thermal processing, the recrystallized grains grew with decreasing strain rate and increasing temperature.

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van den Bogert, W. F., D. J. Belton, M. J. Molter, D. S. Soane i R. W. Biernath. "Thermal stress in semiconductor encapsulating materials". IEEE Transactions on Components, Hybrids, and Manufacturing Technology 11, nr 3 (wrzesień 1988): 245–52. http://dx.doi.org/10.1109/33.16648.

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Van Den Bogert, W., D. Belton, M. Molter, D. Soane i R. Biernath. "Thermal Stress in Semiconductor Encapsulating Materials". IEEE Transactions on Components, Hybrids, and Manufacturing Technology 11, nr 3 (wrzesień 1988): 245–52. http://dx.doi.org/10.1109/tchmt.1988.1134918.

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Stack, J. G., i M. S. Acarlar. "Heat Transfer and Thermal Stress Analysis of an Optoelectronic Package". Journal of Electronic Packaging 113, nr 3 (1.09.1991): 258–62. http://dx.doi.org/10.1115/1.2905404.

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The reliability and life of an Optical Data Link transmitter are inversely related to the temperature of the LED. It is therefore critical to have efficient packaging from the point of view of thermal management. For the ODL® 200H devices, it is also necessary to ensure that all package seals remain hermetic throughout the stringent military temperature range requirements of −65 to +150°C. For these devices, finite element analysis was used to study both the thermal paths due to LED power dissipation and the thermally induced stresses in the hermetic joints due to ambient temperature changes

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Kim, Jong Sun, Kyung Hwan Yoon i Julia A. Kornfield. "Measurement of Stress-Optical Coefficients of COC’s with Different Composition". Key Engineering Materials 326-328 (grudzień 2006): 183–86. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.183.

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Rheo-optical and mechanical properties of Cyclic Olefin Copolymers(COC’s) with different composition have been investigated across the glass transition temperature. Accurate measurement of stress or strain-optical coefficients and elastic modulus data across the glass transition are essential for predicting optical anisotropy in many optical products like pickup lenses and waveguides in LCD backlight unit since the material of these products have both flow and thermal history from the melt to glass. To obtain stress-optic behavior in the wide frequency region including rubbery, glassy and glass transition regime, extensional bar-type device was used. A shear-sandwich tool was used in the melt region. Master curves for modulus, stress-optical and strain-optical coefficients have been obtained in wide frequency region. The stress-optical coefficients of COC’s with mol fraction of norbornene, 60 ~ 70%, showed almost constant between -8 and -9 Br at glassy region and between +920 and +1,160 Br in the melt region. Even though the glass transition temperature showed the difference of 35, the stress-optical coefficients of COC’s with different composition showed almost same extreme values

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Jassim, Abdulsattar M. "Thermal performance of Parabolic Trough Solar Collector". Al-Salam Journal for Engineering and Technology 3, nr 1 (31.12.2023): 128–40. http://dx.doi.org/10.55145/ajest.2024.03.01.011.

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The research progress of numerical simulation of parabolic trough solar collector was introduced. Especially the numerical simulation studies of the internal flow field in the collector tube and the external flow field of the concentrator were reviewed. In the study of the internal flow field in the collector tube, the type of heat transfer fluids and the characteristics of optical concentration have a significant effect on the heat collection performance and thermal stress distribution, especially in the water/steam medium heat collection loop. The unique gas-liquid two phase flow superposition of the non-uniform heat flux distribution outside the tube may lead to serious thermal stress bending deformation of the collector tube. In the study of the external flow field of the concentrator, due to the high actual wind speed and the low structural strength of the ultra-thin lens, the concentrator is subjected to wind load deformation, resulting in the loss of optical efficiency, and even leading to the failure of the parabolic trough collector structure, which directly affects the normal operation of the whole collector field.

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Sokalski, Peter, Zherui Han, Gabriella Coloyan Fleming, Brandon Smith, Sean E. Sullivan, Rui Huang, Xiulin Ruan i Li Shi. "Effects of hot phonons and thermal stress in micro-Raman spectra of molybdenum disulfide". Applied Physics Letters 121, nr 18 (31.10.2022): 182202. http://dx.doi.org/10.1063/5.0122945.

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Micro-Raman spectroscopy has become an important tool in probing thermophysical properties in functional materials. Localized heating by the focused Raman excitation laser beam can produce both stress and local nonequilibrium phonons in the material. Here, we investigate the effects of hot optical phonons in the Raman spectra of molybdenum disulfide and distinguish them from those caused by thermally induced compressive stress, which causes a Raman frequency blue shift. We use a thermomechanical analysis to correct for this stress effect in the equivalent lattice temperature extracted from the measured Raman peak shift. When the heating Gaussian laser beam is reduced to 0.71 μm, the corrected peak shift temperature rise is 17% and 8%, respectively, higher than those determined from the measured peak shift and linewidth without the stress correction, and 32% smaller than the optical phonon temperature rise obtained from the anti-Stokes to Stokes intensity ratio. This nonequilibrium between the hot optical phonons and the lattice vanishes as the beam width increases to 1.53 μm. Much less pronounced than those reported in prior micro-Raman measurements of suspended graphene, this observed hot phonon behavior agrees with a first-principles based multitemperature model of overpopulated zone-center optical phonons compared to other optical phonons in the Brillouin zone and acoustic phonons of this prototypical transition metal dichalcogenide. The findings provide detailed insight into the energy relaxation processes in this emerging electronic and optoelectronic material and clarify an important question in micro-Raman measurements of thermal transport in this and other two-dimensional materials.

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Beeri, Ofer, Rom Tarshish, Ran Pelta i Tal Shilo. "Utilizing Optical Satellite Imagery to Monitor Temporal and Spatial Changes of Crop Water Stress: A Case Study in Alfalfa". Water 14, nr 11 (24.05.2022): 1676. http://dx.doi.org/10.3390/w14111676.

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Since the 1980s, thermal imagery has been used to assess crop water stress. The increase in the temporal resolution of optical satellite sensors (in the range of 400–2500 nm) and the better spatial resolution compared to the thermal imagery call for the definition of a new way for crop water stress monitoring. Hence, we are suggesting a new method utilizing spectral indices from three subsequent images to address this challenge. This method predicts the current water stress with the two past images and compares it to the current stress: if the existing conditions are better than the predicted stress, the crop is not under stress and has sufficient water for development. To evaluate the suggested method, we downloaded Sentinel-2 images and compared the stress found with that method to the leaf area index, leaf water potential, and yield from seven alfalfa growth cycles. The results outline the ability of the new optical stress index to depict spatial and temporal changes in the alfalfa water stress and especially illustrated the changes in the crop water stress over the growth cycle and after each irrigation. This new method needs to be validated with different crops and satellite sensors to verify its success.

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Fredi, Giulia, Matteo Favaro, Damiano Da Ros, Alessandro Pegoretti i Andrea Dorigato. "Thermotropic Optical Response of Silicone–Paraffin Flexible Blends". Polymers 14, nr 23 (24.11.2022): 5117. http://dx.doi.org/10.3390/polym14235117.

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Organic phase change materials, e.g., paraffins, are attracting increasing attention in thermal energy storage (TES) and thermal management applications. However, they also manifest interesting optical properties such as thermotropism, as they can switch from optically opaque to transparent reversibly and promptly at the melting temperature. This work aims at exploiting this feature to produce flexible silicone-based blends with thermotropic properties for applications in glazed windows or thermal sensors. Blends are produced by adding paraffin (Tm = 44 °C, up to 10 phr) to a silicone bicomponent mixture, and, for the first time, cetyltrimethylammonium bromide (CTAB) is also added to promote paraffin dispersion and avoid its exudation. CTAB is proven effective in preventing paraffin exudation both in the solid and in the liquid state when added in a fraction above 3 phr with respect to paraffin. Rheological results show that paraffin decreases the complex viscosity, but neither paraffin nor CTAB modifies the curing behavior of silicone, which indicates uniform processability across the investigated compositions. On the other hand, paraffin causes a decrease in the stress and strain at break at 60 °C, and this effect is amplified by CTAB, which acts as a defect and stress concentrator. Conversely, at room temperature, solid paraffin only slightly impairs the mechanical properties, while CTAB increases both the elastic modulus and tensile strength, as also highlighted with ANOVA. Finally, optical transmittance results suggest that the maximum transmittance difference below and above the melting temperature (65–70 percentage points) is reached for paraffin amounts of 3 to 5 phr and a CTAB amount of max. 0.15 phr.

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Gerhards, Max, Martin Schlerf, Uwe Rascher, Thomas Udelhoven, Radoslaw Juszczak, Giorgio Alberti, Franco Miglietta i Yoshio Inoue. "Analysis of Airborne Optical and Thermal Imagery for Detection of Water Stress Symptoms". Remote Sensing 10, nr 7 (19.07.2018): 1139. http://dx.doi.org/10.3390/rs10071139.

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High-resolution airborne thermal infrared (TIR) together with sun-induced fluorescence (SIF) and hyperspectral optical images (visible, near- and shortwave infrared; VNIR/SWIR) were jointly acquired over an experimental site. The objective of this study was to evaluate the potential of these state-of-the-art remote sensing techniques for detecting symptoms similar to those occurring during water stress (hereinafter referred to as ‘water stress symptoms’) at airborne level. Flights with two camera systems (Telops Hyper-Cam LW, Specim HyPlant) took place during 11th and 12th June 2014 in Latisana, Italy over a commercial grass (Festuca arundinacea and Poa pratense) farm with plots that were treated with an anti-transpirant agent (Vapor Gard®; VG) and a highly reflective powder (kaolin; KA). Both agents affect energy balance of the vegetation by reducing transpiration and thus reducing latent heat dissipation (VG) and by increasing albedo, i.e., decreasing energy absorption (KA). Concurrent in situ meteorological data from an on-site weather station, surface temperature and chamber flux measurements were obtained. Image data were processed to orthorectified maps of TIR indices (surface temperature (Ts), Crop Water Stress Index (CWSI)), SIF indices (F687, F780) and VNIR/SWIR indices (photochemical reflectance index (PRI), normalised difference vegetation index (NDVI), moisture stress index (MSI), etc.). A linear mixed effects model that respects the nested structure of the experimental setup was employed to analyse treatment effects on the remote sensing parameters. Airborne Ts were in good agreement (∆T < 0.35 K) compared to in situ Ts measurements. Maps and boxplots of TIR-based indices show diurnal changes: Ts was lowest in the early morning, increased by 6 K up to late morning as a consequence of increasing net radiation and air temperature (Tair) and remained stable towards noon due to the compensatory cooling effect of increased plant transpiration; this was also confirmed by the chamber measurements. In the early morning, VG treated plots revealed significantly higher Ts compared to control (CR) plots (p = 0.01), while SIF indices showed no significant difference (p = 1.00) at any of the overpasses. A comparative assessment of the spectral domains regarding their capabilities for water stress detection was limited due to: (i) synchronously overpasses of the two airborne sensors were not feasible, and (ii) instead of a real water stress occurrence only water stress symptoms were simulated by the chemical agents. Nevertheless, the results of the study show that the polymer di-1-p-menthene had an anti-transpiring effect on the plant while photosynthetic efficiency of light reactions remained unaffected. VNIR/SWIR indices as well as SIF indices were highly sensitive to KA, because of an overall increase in spectral reflectance and thus a reduced absorbed energy. On the contrary, the TIR domain was highly sensitive to subtle changes in the temperature regime as induced by VG and KA, whereas VNIR/SWIR and SIF domain were less affected by VG treatment. The benefit of a multi-sensor approach is not only to provide useful information about actual plant status but also on the causes of biophysical, physiological and photochemical changes.

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Hanabusa, Takao, Kazuya Kusaka i Osami Sakata. "Residual stress and thermal stress observation in thin copper films". Thin Solid Films 459, nr 1-2 (lipiec 2004): 245–48. http://dx.doi.org/10.1016/j.tsf.2003.12.102.

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Wang, Feng Hui, Yong Zhang i Hong Wang. "Residual Stress and Damage Evolution in TBCs by Optical Method". Key Engineering Materials 324-325 (listopad 2006): 1047–50. http://dx.doi.org/10.4028/www.scientific.net/kem.324-325.1047.

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In recently years, ruby fluorescence spectroscopy has been demonstrated as a powerful technique for monitoring residual stress evolution in the thermally grown oxide scale in thermal barrier coatings(TBC) systems. The measured residual stresses, in turn can be used to monitor evolution of damage in the coatings. Effective use of this technology for real time damage monitoring require the identification of strength in measured stresses that can be used as indicators of damage evolution.the present work focuses on studying the evolution of residual stresses in TBC systems during oxidation. The coating are atmospheric plasma sprayed (APS), the residual stress were measured at different oxidation time and to identify critical features so as to be used as indicators of failure in TBCs.

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Li, Dongxu, Peng Jiang, Renheng Gao, Fan Sun, Xiaochao Jin i Xueling Fan. "Experimental and numerical investigation on the thermal and mechanical behaviours of thermal barrier coatings exposed to CMAS corrosion". Journal of Advanced Ceramics 10, nr 3 (10.03.2021): 551–64. http://dx.doi.org/10.1007/s40145-021-0457-2.

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AbstractCalcium-magnesium-alumino-silicate (CMAS) corrosion is a critical factor which causes the failure of thermal barrier coating (TBC). CMAS attack significantly alters the temperature and stress fields in TBC, resulting in their delamination or spallation. In this work, the evolution process of TBC prepared by suspension plasma spraying (SPS) under CMAS attack is investigated. The CMAS corrosion leads to the formation of the reaction layer and subsequent bending of TBC. Based on the observations, a corrosion model is proposed to describe the generation and evolution of the reaction layer and bending of TBC. Then, numerical simulations are performed to investigate the corrosion process of free-standing TBC and the complete TBC system under CMAS attack. The corrosion model constructs a bridge for connecting two numerical models. The results show that the CMAS corrosion has a significant influence on the stress field, such as the peak stress, whereas it has little influence on the steady-state temperature field. The peak of stress increases with holding time, which increases the risk of the rupture of TBC. The Mises stress increases nonlinearly along the thick direction of the reaction layer. Furthermore, in the traditional failure zone, such as the interface of the top coat and bond coat, the stress obviously changes during CMAS corrosion.

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Scott, G. C., i G. Astfalk. "Modeling Thermal Stress Behavior in Microelectronic Components". Journal of Electronic Packaging 112, nr 1 (1.03.1990): 35–40. http://dx.doi.org/10.1115/1.2904338.

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Thermal stress cracking is a significant mechanical failure mode in microelectronic components. This failure results from elevated stresses in components exposed to elevated temperatures due to the mismatch of thermal and mechanical properties of the constituent materials. The underlying mechanism responsible for these elevated stresses is not well understood. Therefore, we developed general mathematical and computational techniques for modeling the evolution of these stresses. As a test vehicle, we applied these techniques to thermal stress evolution in multilayer ceramic capacitors (MLCC). Thermal stress cracking has been implicated in significant, industry-wide problems associated with the cracking of these components. The model is used to solve for the transient development of thermal and mechanical gradients across the two spatial dimensions of the MLCC mid-plane. Material types with different thermal and mechanical properties and the interfaces between the material types are specifically included in the model. The stress field solutions are used to indicate when and where mechanical failure is expected to occur. The solutions of the model equations have been obtained using special partial differential equation solvers implemented on a CONVEX C120/220 supercomputer. The model is used to investigate the effects of MLCC termination geometry and material properties on the evolution of thermal stresses.

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