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An extended Rice model for intergranular fracture

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arXiv

arXiv 2024年

作者： Zhao, Kai Ding, Yu Yu, Haiyang He, Jianying Zhang, Zhiliang School of Mechanical Engineering Jiangnan University Wuxi214122 China Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology Wuxi214122 China Trondheim7491 Norway Division of Applied Mechanics Department of Materials Science and Engineering Uppsala University Uppsala75121 Sweden

The plastic events occurring during the process of intergranular fracture in metals is still not well understood due to the complexity of grain boundary (GB) structures and their interactions with crack-tip dislocation plasticity. By considering the local GB structural transformation after dislocation emission from a GB in the Peierls-type Rice-Beltz model, herein we established a semi-analytical transition-state-theory-based framework to predict the most probable Mode-I stress intensity factor (SIF) for dislocation emission from a cracked GB. Using large-scale molecular dynamics (MD) simulations, we studied the fracture behaviors of bi-crystalline Fe samples with 12 different symmetric tilt GBs inside. The MD results demonstrate that the presence of GB could significantly change the SIF required for the activation of plastic events, confirming the theoretical predictions that attributes this to the energy change caused by the transformation of GB structure. Both the atomistic simulation and the theoretical model consistently indicate that, the critical dynamic SIF (KKIIcc(tt)) at which the dynamic SIF KKIIcc(tt) deviates from the linearity with respect to the strain ΕΕ, increases with the increasing loading rate. However, the classical Rice model underestimates the KKIIcc(tt) due to its failure to consider the effects of localized fields. The present theoretical model provides a mechanism-based framework for the application of grain boundary engineering in the design and fabrication of nano-grained metals. © 2024, CC BY.

关键词： Grain boundaries

Perfect Static Balancing Using Cardan-Gear Spring Mechanisms

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SSRN 2022年

作者： Kuo, Chin-Hsing Wu, Yi-Xin School of Mechanical Materials Mechatronic and Biomedical Engineering Faculty of Engineering and Information Sciences University of Wollongong WollongongNSW2522 Australia Department of Mechanical Engineering National Taiwan University of Science and Technology Taipei106 Taiwan

This paper presents the static balancing designs (i.e., gravity compensation) for a rotating link by using a special straight-line geared mechanism with springs. The design scenario is to attach the rotating link yet to balance onto an inverted Cardan gear mechanism which has linear springs installed for balancing the weight of the links. It is found that the whole mechanism can be perfectly balanced in theory through either one or two linear springs. The significance of the proposed designs is that the derived solutions for perfect balancing are general. That is, 1) all the masses of the mechanism links are taken into account in the design for balancing, 2) the design geometry of the mechanism is described based on real springs (i.e., not zero-free-length springs), 3) the linear springs can be either compression or extension springs, and 4) the installation, preloaded lengths, initial tensions, and stiffness of the springs are considered altogether in the design process. Based on the original mechanism, several design variations are suggested. Applications of the design for balancing two special robotic manipulators are illustrated. As the proposed balancer involves gear contacts, an experimental test about the friction effect on the balancing performance was performed. © 2022, The Authors. All rights reserved.

关键词： Manipulators

Improved Precision and Accuracy of Local mechanical Properties Based on Instrumented Macroindentation Testing

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SSRN 2023年

作者： Troost, Nicolaas Cornelis Hugo Millan-Espitia, Natalia Kalidindi, Surya R. Popovich, Vera A. den Besten, Johannes H. Delft University of Technology Mekelweg 5 Delft2628 CD Netherlands George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology AtlantaGA30332 United States Department of Materials Science and Engineering

In case the distribution of mechanical material properties is inhomogeneous, for example in welded joints, an indentation based measure can be adopted to obtain local estimates. However, the property precision and accuracy is often lacking and a next step to reveal the one-to-one relation between instrumented macroindentation and material stress strain curve was set, proposing semi-analytical model improvements and deploying Monte Carlo based numerical model simulations. Utilizing experimental data for DH36 and S355 steel, high-precision Young’s modulus estimates were obtained within 95 [%] reliability of the uniaxial tensile test reference values, with less than a 10 [%] error. For high reliability, the number of indentation tests must be sufficiently large. Contact radius information is at least required to obtain the yield strength and several formulations provide estimates within ∼ 20 [%] error for a large range of material properties. A significantly more accurate value can be obtained if the Young’s modulus is not involved, providing an error within 10 [%]. Introducing a proportional plastic strain offset criterion rather than the well-established constant one to obtain an indentation based yield strength estimate, the strength-to stiffness ratio dependency was eliminated. Accuracy is improved to a ∼ 20 [%] error range with 95 [%] reliability. The accuracy can be even further improved using the material proof strength rather than the yield strength, reducing the 95 [%] reliability error estimate to ∼ 15 [%]. Experimental instrumented macroindentation based yield strength estimates are within 10 [%] error compared to the uniaxial tensile test values. © 2023, The Authors. All rights reserved.

关键词： Yield stress

Multi-layered coatings for improving implant performance of titanium

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Ceramics International 2025年

作者： Safaee, Sirus Abe, Shigeaki Nesabi, Mahdis Moghanian, Amirhossein Asadi, Parviz Yoshida, Kazuhiro Okazaki, Hitomo Harada, Kae Watanabe, Ikuya Murata, Hiroshi Department of Prosthetic Dentistry of Biomedical Sciences Nagasaki University 1-7-1 Sakamoto Nagasaki852-8588 Japan Department of Dental and Biomedical Materials Science of Biomedical Sciences Nagasaki University 1-7-1 Sakamoto Nagasaki852-8588 Japan Department of Materials Engineering Faculty of Engineering Imam Khomeini International University Qazvin34149-16818 Iran Department of Mechanical Engineering Engineering Faculty Gebze Technical University Kocaeli Gebze41400 Turkey

This study assesses the mechanical and biological properties of bioactive glass 58S (BG) coating on titanium (Ti) surfaces. Abraded Ti was alkali-treated for 12 h at 60 °C using 8 mL of 5 M NaOH aqueous solution, followed by coating in BG sol to create a novel hybrid nanostructure layer on the Ti surface. Another experimental group involved abraded Ti substrates blasted with alumina powder, followed by sol-dip coating in BG sol. Characterization, adhesive strength, and cell responsiveness of individual and combined treatments were examined. Alkali-treated BG-coated Ti presented superior performance compared to alumina-blasted BG-coated Ti. Adhesive strength results confirmed that the hybrid alkali-BG treatment enhanced the bond between coating and substrate by creating a nanoporous structure layer on the Ti surface, achieving the highest bond strength values among treatment groups with excellent cell response. Improvements from combined alkali-BG treatment are attributed to the required porosity nanostructure and apatite transformation ability. Thus, alkali-BG hybridization could be a viable surface modification method for implant applications. © 2025 Elsevier Ltd and Techna Group S.r.l.

关键词： Bioactive glass

Wavy Whiskers in Phocid Seals Exhibit High Signal-to-Noise in Sensing Hydrodynamic Flows

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Wavy Whiskers in Phocid Seals Exhibit High Signal-to-Noise i...

IEEE International Conference on Cyborg and Bionic Systems (CBS)

作者： Xingwen Zheng Amar M. Kamat Ming Cao Michael S. Triantafyllou Ajay G. P. Kottapalli Engineering and Technology Institute Groningen Faculty of Science and Engineering University of Groningen Groningen the Netherlands State Key Laboratory of Industrial Control and Technology Zhejiang University Hangzhou China Department of Control Science and Engineering Institute of Cyber-Systems and Control Zhejiang University Hangzhou China MIT Sea Grant College Program Massachusetts Institute of Technology (MIT) 77 Massachusetts Avenue Cambridge MA USA Department of Mechanical Engineering MIT Cambridge MA USA

ISBN: (数字)9798350388039

ISBN: (纸本)9798350388046

Phocid seals can detect fish from distances up to 180 meters solely using undulating whiskers. The unique undulating surfaces of these whiskers have been found to minimize vortex-induced vibrations (VIVs). In our previous work, we measured the ratios of undulation wavelength (λ) to mean diameter $\left(D_{m}\right),\left(\lambda / D_{m}\right)$ in both harbor and grey seals, yielding values of approximately 4.36 and 4.63, respectively. In this study, we delve into the significance of the $\lambda / D_{m}$ ratio to the vibration responses of seal whiskers in a fluid flow. We conducted comprehensive fluid-structure interaction studies using COMSOL Multiphysics®, wherein we studied vibration responses of harbor and grey seal whisker structures with diverse $\lambda / D_{m}$ values in the oncoming flow. Our results indicate that seal whiskers exhibited a trough in their VIV responses and a peak in wake-induced vibration (WIV) responses at $\lambda / D_{m}$ values around 4 to 5. Our findings could imply that the evolutionary optimization of the $\lambda / D_{m}$ value enables seal whiskers with resistance to VIV and sensitivity to WIV.

关键词： Vibrations Sensitivity Surface waves Biological system modeling Wavelength measurement Seals Fish Robot sensing systems Sensor systems Sensors

Analysis of Flow Field and Pneumatic Noise of The Flow around Series Cylinder

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arXiv

arXiv 2023年

作者： Wu, Yongxi Ji, Guangnian Zhang, Peizhi School of Mechanics and Engineering Science Shanghai University Shanghai200072 China Department of Mechanical Materials and Manufacturing Engineering The University of Nottingham Ningbo China Ningbo315100 China Xingjian College Tsinghua University Beijing100084 China

Noise generation attributed to the flow around a cylinder and its control is of paramount importance in a multitude of engineering applications. In this study, we employ computational fluid dynamics (CFD) coupled with acoustic analogy, complemented by an analysis grounded in vortex dynamics theory, to explore the potential of wavy cylinder shapes in improving aerodynamic performance and mitigating aerodynamic noise. The series cylinder simplified from the aircraft landing gear and elliptical cylinder noise suppression mechanism is *** research outcomes clearly indicate that elliptical ylinder designs have a notable impact on aerodynamic performance and noise reduction. Specifically, these designs effectively lower the average drag coefficient and efficiently suppress lift coefficient fluctuations, resulting in an overall reduction in noise production by the elliptical cylinder. To delve into the underlying mechanisms of noise suppression, our study meticulously examines the process of vorticity generation around the elliptical cylinder's surface. This examination yields profound improvements in the distribution of vorticity on the cylinder's surface, along with a remarkable weakening of the boundary vorticity flux and boundary enstrophy flux distribution. These changes result in a notable reduction in vorticity generation near the elliptical cylinder *** alterations directly lead to a substantial contraction in the distribution of vortex structures in the wake of the elliptical cylinder, especially affecting large-scale vortex *** a result,The elliptical cylinder noise suppression mechanism we propose can effectively reduce aerodynamic noise. © 2023, CC0.

关键词： Cylinders (shapes)

Superelastic Ferroelectric Micropillar with Large Hysteresis and Surper-Durability

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SSRN 2023年

作者： Li, Yingwei Chu, Kangjie Wang, Xiaomei Wu, Zhijun Peng, Qi Li, Jiangyu Chen, Long-Qing Ren, Fuzeng Sun, Qingping School of Civil Engineering Wuhan University Hubei Wuhan430072 China Department of Materials Science and Engineering Southern University of Science and Technology Guangdong Shenzhen518055 China Guangdong Provincial Key Laboratory of Functional Oxide Materials and Devices Southern University of Science and Technology Guangdong Shenzhen518055 China Nanchang Innovation Institute Peking University Jiangxi Nanchang330000 China Department of Mechanical and Aerospace Engineering The Hong Kong University of Science and Technology Clear Water Bay Hong Kong China Department of Materials Science and Engineering The Pennsylvania State University University ParkPA16802 United States

Hysteresis and durability are generally on the opposite sides of a trade-off for superelastic materials. We herein break this trade-off and report that BaTiO3 (BT) micropillars present size-dependent superelasticity and possess simultaneous large hysteresis and super-durability, sustaining up to 108 cycles without functional degradation and structural failure. The super-durability was attributed to the small stress to drive ferroelastic switching and the moderate mismatch stress between different ferroelectric variants, that are much smaller than the dislocation nucleation activation stress and the compression strength of BT pillars. These discoveries enable ferroelectric micropillars many promising applications such as microdampers, and also provide significant insight into developing superelastic materials with enhanced durability. © 2023, The Authors. All rights reserved.

关键词： Hysteresis

Effect of Seed Priming by Static Magnetic Fields (Smf) and Pulsed Electromagnetic Fields (Pemf) on Seed Germination and Salinity Stress Resistance in Rice Seeds (Oryza Sativa)

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SSRN 2023年

作者： Kunpratum, Narisa Thoradit, Thawatchai Kamoltheptawin, Khwanchai Thongyoo, Kanjana Yodjun, Sawanya Unjunngern, Arada Fuman, Saowanee Tunprasert, Lalin Pooam, Marootpong Department of Biology Faculty of Science Naresuan University Phitsanulok65000 Thailand State Key Laboratory for Mechanical Behavior of Materials School of Material Science and Engineering Xi’an Jiaotong University Xi’an710049 China

The study investigated the effect of magnetic-priming on rice seed germination and seedling growth under saline conditions. Seeds of rice Oryza sativa L. were exposed to either static magnetic field (SMF) or pulsed electromagnetic field (PEMF) using various exposure timings. After exposure, seeds were placed in saline solutions of 0, 75, 125, and 150 mM NaCl, and germination rates were recorded three times/day for five days. Seedling growth and vigor were evaluated under saline conditions. Additionally, hydrogen peroxide (H2O2) levels were determined in both the SMF/PEMF and control groups of rice seeds. Results indicated that SMF/PEMF exposure significantly increased rice seed germination rate and seedling growth and vigor under saline conditions. Furthermore, H2O2 levels were significantly higher in the SMF/PEMF-exposed seeds than in the control seeds, suggesting that magnetic-priming increased H2O2 production, which may have contributed to the observed beneficial effects on rice seed germination and growth under saline conditions. © 2023, The Authors. All rights reserved.

关键词： Seed

Characterization and Modelling of Carbon Black Nanocomposite Strain Sensor on Pneumatic Driven Flexible Catheter for Pulmonary Surgery Robots

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SSRN 2024年

作者： Jia, Yanhong Wu, Yanzhen Chen, Yao Hua, Tingyu Le, Huirong The Future Laboratory Tsinghua University Beijing100084 China Department of Mechanical Engineering Tsinghua University Beijing100084 China Academy of Arts & Design Tsinghua University Tsinghua University Beijing100084 China School of Materials Science and Engineering Tsinghua University Beijing100084 China

The pulmonary surgery robot is equipped with a flexible catheter designed to navigate narrow bronchi and perform precise surgical operations on lesions, offering benefits such as minimal invasiveness and high flexibility. This study focuses on the shape control and strain sensing of the catheter's tip. A gas-driven control platform was developed for a three-channel catheter, incorporating miniaturized precision valves to enhance the accuracy of pneumatic pressure control. Concurrently, ultra-thin flexible strain sensors were fabricated using PDMS and carbon black to detect bending strain, and their sensing performance was assessed to identify optimal fabrication parameters. Finally, the control platform and strain sensors were integrated to validate the system's capability to manage the catheter's bending shape while simultaneously sensing its deformation. This integration provides a theoretical foundation for enhancing the precision and safety of catheters in practical applications of surgical robots. © 2024, The Authors. All rights reserved.

关键词： Catheter tip sensors