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- 2018
- Phase difference method
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- Plastic optical fiber
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- National Institute of Technology, Warangal
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Sheath-Core Fiber Strain Sensors Driven by In-Situ Crack and Elastic Effects in Graphite Nanoplate Composites
摘要： The flexible and stretchable electronics, e.g., graphite nanoplatelets (GNPs) based nanocomposite devices, have attracted great interest due to their potential application in healthcare, robotics, and mechatronics technology. However, the deficient sensors with manipulation of low sensitivity, sluggish responsivity, sophisticated fabrication process and poor repeatability notoriously limit their industrial applications. To enhance the spontaneous sensitivity, flexibility and wearability in GNPs based strain sensors, in this report, the synergistic crack and elastic effects engineering is employed and in turn significantly enhances the sensitivity with the gauge factor of 20 at the strain of 30% and the stability in our developed sheath-core fiber (SCF) strain sensors. Upon reliable devices integration, it is demonstrated that the developed SCF strain sensor could detect the movement of human joint effectively with generating a resistance change rate ΔR/R0 up to 600%. Furthermore, a controlling devices system based on SCF strain sensor has been manufactured in circuit level to realize the real-time control of a robot hand, such as copying gestures and playing piano.
关键词： Graphite nanoplatelets (GNPs),Robotic mechatronics,Sheath–core structure,Strain sensors,Crack and elastic effects
更新于2025-09-23 15:23:52
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Growth of high quality AlN/sapphire templates with high growth rate using a medium-temperature layer
摘要： In this work, crack-free 3.3-μm-thick AlN ?lms with high crystalline quality and atomic smooth surfaces were achieved on sapphire substrates at a high growth rate of 2.9 μm/h. Double-axis x-ray rocking curves showed a full width at half maximum of 315 and 419 arc sec for (0002) and (101ˉ2) re?ections, respectively, corresponding to a total threading dislocation (TD) density of 9.79 × 10^8 cm^-2. Cracks were suppressed and crystalline quality was improved by introducing a medium-temperature (MT) layer. It was found that the density of both screw- and edge-type TDs could be signi?cantly reduced by introducing the MT-AlN layer under appropriate temperature. The crystalline improvement is attributed to the delayed coalescence of the AlN islands and higher probability for the annihilations of TDs by the MT-AlN layer under appropriate temperature. This method provides a promising way in growing practical thick AlN templates suitable for large-scale industrial production.
关键词： High growth rate,MOCVD,Crack-free,Medium-temperature layer,AlN
更新于2025-09-23 15:22:29
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Elasticity, Hardness, and Fracture Toughness of Sodium Aluminoborosilicate Glasses
摘要： Due to an increasing demand for oxide glasses with a better mechanical performance, there is a need to improve our understanding of the composition-structure-mechanical property relations in these brittle materials. At present, some properties such as Young’s modulus can to a large extent be predicted based on the chemical composition, while others – in particular fracture-related properties – are typically optimized based on a trial-and-error approach. In this work, we study the mechanical properties of a series of twenty glasses in the quartenary Na2O-Al2O3-B2O3-SiO2 system with fixed soda content, thus accessing different structural domains. Ultrasonic echography is used to determine the elastic moduli and Poisson’s ratio, while Vickers indentation is used to determine hardness. Furthermore, the single-edge precracked beam (SEPB) method is used to estimate the fracture toughness (KIc) for some compositions of interest. The compositional evolutions of Vickers hardness and Young’s modulus are in good agreement with those predicted from models based on bond constraint density and strength. Although there is a larger deviation, the overall compositional trend in KIc can also be predicted by a model based on the strength of the bonds assumed to be involved in the fracture process.
关键词： Vickers hardness,fracture toughness,glass properties,Elastic moduli,crack path
更新于2025-09-23 15:22:29
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Experimental study and prediction on impact scratching of single abrasive for K9 glass
摘要： The orthogonal test L16 (43) was designed, and the impact scratching experiment for K9 glass was carried out by using Vickers diamond indenter on the DMG ULTRASONIC 70-5 linear. The three-dimensional morphology of the surface for glass was observed by scanning electron microscope (SEM), which was compared with that in the quasi static state. The strain rate of the grinding process was obtained by choosing the contact zone length as the impact contact length, which was the evaluation Index of impact. The relationships between strain rate and the depth of radial crack, strain rate and the depth of transverse crack, strain rate and normal scratching force were first analysed. The results showed that the depth of radial of crack, the depth of transversal crack and the normal scratching force decreased with the increase of strain rate. The two-layer BP neural network was established, which took the strain rate as input variables. The depth of radial crack, the depth of transversal crack and normal scratching force were predicted and the errors were within 10%, which indicated that the prediction results of BP neural network were reliable.
关键词： impact scratching,depth of crack,strain rate,BP neural network,K9 glass
更新于2025-09-23 15:22:29
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Three-Dimensional Scanning Hall Probe Microscopy for Final Stage of Crack Growth of Chromium Molybdenum Steel SCM440
摘要： Crack propagation around the stress concentration area causes fatigue failure. Non-destructive method is necessary for monitoring structure fatigue before destruction. We focused on a magnetic non-destructive evaluation method for crack growth. In order to understand the relation between crack propagation and changes in magnetic flux density, we observed the position of the positive and negative magnetic flux density distributions around the crack of tool steel (SCM440) plate using a scanning Hall probe microscope (SHPM). We found that the vertical component of the three-dimensional magnetic flux density moved as the crack growth. Furthermore, the magnetic component which is parallel to the tensile stress appeared just before destruction of the specimen.
关键词： Crack propagation,Scanning Hall probe microscope,Magnetic flux density
更新于2025-09-23 15:22:29
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[IEEE 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Shanghai (2018.8.8-2018.8.11)] 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - High Power Module Package Mounting and Temperature Cycling Reliability Study by Simulation
摘要： This paper studies the reliability of high power module package in torque mounting assembly process and temperature cycling reliability by simulation. The power module package, which with initial warpage, will be mounted on an outer heat sink with torque first and follow by in temperature cycling test. A complicated 3D non-linear finite element model was developed to simulate these two processes together. The package warpage and die stress/strain are discussed and analyzed to evaluate the die crack risk in customer’s application. A warpage simulation was run firstly to get the package’s initial status before torque mounting. Secondly the package with initial warpage is mounted on an outer heatsink with two screws at package two edges. Small pre-tightening torque and big final tightening torque are applied on two screws step by step. Finally, the temperature cycling loading is applied on the package together with loading. Silicon die stress/strain are studied to evaluate the die crack risk in customer’s application. The actual measured warpage data at room temperature is correlated with the simulation results. Finally, the models with different package warpages and different final-tightening torques at screws were investigated to increase the reliability performance of this power module package.
关键词： Torque Mount,die crack,TMCL,Power Module
更新于2025-09-23 15:22:29
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Sol-Gel Preparation of Thick TiO<sub>2</sub> Films for Structural Coloration
摘要： We studied sol-gel processing of thick and crack-free TiO2 films to synthesize structural color materials. The viscosity of the alkoxide-based precursor sols was stabilized by the addition of acetyl acetone, which improved control of the spin coating thickness. We used a TiO2/SiO2/TiO2 triple-layer structure and second-order reflection conditions to produce structural coloration. This design yielded a sharp spectral peak and bright coloration; however, a TiO2 layer with a thickness greater than 200 nm was required, which is much thicker than that required for the first-order of reflection. Crack formation in the thick films was suppressed by the addition of ethyl cellulose to the precursor sols. As a consequence, color-tuned TiO2/SiO2/TiO2 films were successfully prepared and exhibited various bright colors in the visible light wavelength range, including two primary colors of light, namely blue and green. Green coloration from flake-shaped particles was also demonstrated.
关键词： TiO2,structural color,crack formation,flake-like powders,sol-gel method
更新于2025-09-23 15:22:29
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Rapid and non-invasive surface crack detection for pressed-panel products based on online image processing
摘要： Crack detection during the manufacturing process of pressed-panel products is an important aspect of quality management. Traditional approaches for crack detection of those products are subjective and expensive because they are usually performed by experienced human inspectors. Therefore, the development and implementation of an automated and accurate inspection system is required for the manufacturing process. In this article, a crack detection technique based on image processing is proposed that utilizes the images of panel products captured by a regular camera system. First, the binary panel object image is extracted from various backgrounds after considering the color factor. Edge lines are then generated from a binary image using a percolation process. Finally, crack detection and localization is performed with a unique edge-line evaluation. In order to demonstrate the capability of the proposed technique, lab-scale experiments were carried out with a thin aluminum plate. In addition, a test was performed with the panel images acquired at an actual press line. Experimental results show that the proposed technique could effectively detect panel cracks at an improved rate and speed. The experimental results also demonstrate that the proposed technique could be an extension of structural health monitoring frameworks into a new manufacturing application.
关键词： crack detection,image processing,signal processing,percolation,Non-contact sensing
更新于2025-09-23 15:22:29
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Atomic picture of crack propagation in Li <sub/>2</sub> Oa??2SiO <sub/>2</sub> glassa??ceramics revealed by molecular dynamics simulations
摘要： Fundamental understanding of the interaction between glass and ceramic phases with a running crack and the mechanisms by which propagation is hindered or altered as compared to the precursor parent glasses remains elusive for the lithium disilicate glass-ceramics. We herein conduct extensive molecular dynamics simulations to reveal some atomic details that are otherwise extremely challenging to be probed by experiments. The results show that the crack propagation pathway in glass-ceramics is dramatically different as compared to the precursor parent glass. In glassy sample, clean crack branching seems to be triggered by multiple cavitation events ahead of crack tip. In glass-ceramic samples, however, branching is characterized by microcracks at multiple glass-nanocrystal interface sites, clean nanocrystal cleavage along certain crystalline plane, and even secondary cracks due to the percolation of multiple microcracks. Additionally, the nanocrystal distribution, total volume fraction, and aspect ratio also have pronounced effects on the propagation of a primary crack and can lead to very diverse crack patterns.
关键词： lithium disilicate glass-ceramics,crack branching,microcracks,crack propagation
更新于2025-09-23 15:21:01
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Influence of laser weld shape on mechanical and fatigue behaviour of single lap laser welded joints
摘要： Traditional manufacturing processes, like arc welding and resistance spot welding, are still the main welding processes to join structural components used across the on/o?-road vehicle industry. Due to the abundance of data, experiences and insights over the decades of usage, lot of fatigue design data has been generated for different joint geometries produced using these methods. The laser welding process has excellent capabilities to join thin sheet metal structures with minimum heat input resulting into lower deformation and improved productivity that offers significant benefit as compared to the arc and resistance welding processes. However, due to the agility of designing joint configurations and limited availability of understanding regarding the fatigue behaviour of laser welded joints, the need arises for the fatigue design data. Most of the research presents the use of straight linear shape laser welds and limited knowledge exist regarding the influence of shape of laser welds on mechanical and fatigue performance of the laser welded joints. The laser welded joints produce small notch like radius at the root of laser weld which could act as a stress raiser causing early crack initiation. For this work, C-shape laser weld has been selected as the geometric shape in comparison to the straight linear shape of laser weld produced on a series of single lap joints. Detailed fatigue experimental investigation has been carried out for linear and C-shape laser welded joints tested in 3 different orientations with respect to the applied cyclic load and several different R-ratio’s and the results are compared. The metallurgical studies have been carried out to understand the failure mode and micro-hardness variations across the weld and heat affected zone. Further, the residual stress profiles have been compared for the C-shape laser weld with the linear welds using detailed X - Ray Diffraction based residual stress measurement.
关键词： Laser Weld,Ultra-high strength steel,C Shape,Crack propagation,High strength low alloy steel,Crack initiation
更新于2025-09-23 15:21:01