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Finite elements analysis

Fei Hu Du, Ni Yizhou, Ye Wang, Dong Wang, Qi Ge, Shuo Chen, Hui Ying Yang
Designing yolk-shell nanostructures is one of the most effective strategies in addressing large volume expansion problem for high-capacity anode and cathode materials in Li-ion batteries (LIBs). Most previous studies have focused on adopting SiO2 template through HF etching to create the yolk-shell nanostructures. However, HF etching is highly corrosive and may result in a significant reduction of Si content in the composite. Herein, a silkworm cocoon-like silicon-based composite is synthesized through a green approach in which Al2O3 is selected as a sacrificial template...
August 11, 2017: ACS Nano
Libor Necas, Maros Hrubina, Zoltan Cibula, Jiri Behounek, Stanislav Krivanek, Zdenek Horak
The study was aimed at the clinical and biomechanical analyses of the sliding hip screw breakage with the use of finite element method. We have identified two patients with the sliding screw breakage. In the first patient, the biomechanical analysis revealed the reduced stress values σHMH not exceeding the yield limit or strength limit of the implant. The yield limit was exceeded in second one. Clinical and biomechanical analyses have demonstrated that adherence to technical requirements of the appropriate osteosynthesis implementation is the principal condition of timely healing since it prevents the material failure...
August 9, 2017: Computer Methods in Biomechanics and Biomedical Engineering
Rajiv Chopra, Sumbul Shaikh, Yonatan Chatzinoff, Imalka Munaweera, Bingbing Cheng, Seth M Daly, Yin Xi, Chenchen Bing, Dennis Burns, David E Greenberg
Treatment of prosthetic joint infection (PJI) usually requires surgical replacement of the infected joint and weeks of antibiotic therapy, due to the formation of biofilm. We introduce a non-invasive method for thermal destruction of biofilm on metallic implants using high-frequency (>100 kHz) alternating magnetic fields (AMF). In vitro investigations demonstrate a >5-log reduction in bacterial counts after 5 minutes of AMF exposure. Confocal and scanning electron microscopy confirm removal of biofilm matrix components within 1 minute of AMF exposure, and combination studies of antibiotics and AMF demonstrate a 5-log increase in the sensitivity of Pseudomonas aeruginosa to ciprofloxacin...
August 8, 2017: Scientific Reports
M Amparo Callejon, P Del Campo, Javier Reina-Tosina, Laura M Roa
Intrabody Communication (IBC) uses the human body tissues as transmission media for electrical signals to interconnect personal health devices in wireless body area networks. The main goal of this work is to conduct a computational analysis covering some bioelectric issues that still have not been fully explained, such as the modeling of the skin-electrode impedance, the differences associated to the use of constant voltage or current excitation modes, or the influence on attenuation of the subject's anthropometrical and bioelectric properties...
August 2, 2017: IEEE Journal of Biomedical and Health Informatics
Shaozheng Ji, Luca Piazza, Gaolong Cao, Sang Tae Park, Bryan W Reed, Daniel J Masiel, Jonas Weissenrieder
Efforts to understand matter at ever-increasing spatial and temporal resolutions have led to the development of instruments such as the ultrafast transmission electron microscope (UEM) that can capture transient processes with combined nanometer and picosecond resolutions. However, analysis by UEM is often associated with extended acquisition times, mainly due to the limitations of the electron gun. Improvements are hampered by tradeoffs in realizing combinations of the conflicting objectives for source size, emittance, and energy and temporal dispersion...
September 2017: Structural Dynamics (Melville, N.Y.)
Jordan Ramsey, Jerry L Prince, Arnold D Gomez
Noninvasive analysis of motion has important uses as qualitative markers for organ function and to validate biomechanical computer simulations relative to experimental observations. Tagged MRI is considered the gold standard for noninvasive tissue motion estimation in the heart, and this has inspired multiple studies focusing on other organs, including the brain under mild acceleration and the tongue during speech. As with other motion estimation approaches, using tagged MRI to measure 3D motion includes several preprocessing steps that affect the quality and accuracy of estimation...
February 11, 2017: Proceedings of SPIE
Nobuhiro Kaku, Tomonori Tabata, Hiroaki Tagomori, Tetsutaro Abe, Hiroshi Tsumura
BACKGROUND: Regarding the cup setting in total hip arthroplasty, range of motion and prevention of dislocation are important. From past reports, the wear of the bearing surface may affect long-term results. This study evaluated the stress applied to the bearing surface by the combined use of the three-dimensional rigid spring model and the finite-element analysis. METHODS: For contact pressure distribution of the bearing surface, interference analysis was performed using a three-dimensional rigid body spring model...
August 5, 2017: European Journal of Orthopaedic Surgery & Traumatology: Orthopédie Traumatologie
Paula Pb Silva, Fatemeh Ghazanfari Amlashi, Elaine W Yu, Karen J Pulaski-Liebert, Anu Gerweck, Pouneh Fazeli, Elizabeth A Lawson, Lisa B Nachtigall, Beverly M K Biller, Karen K Miller, Anne Klibanski, M Bouxsein, Nicholas A Tritos
CONTEXT: Both acromegaly and adult growth hormone deficiency (GHD) are associated with increased fracture risk. Sufficient data are lacking regarding cortical bone microarchitecture and bone strength, as assessed by micro-finite element analysis (µFEA). OBJECTIVE: To elucidate both cortical and trabecular bone microarchitecture and estimated bone strength in men with active acromegaly or GHD compared to healthy controls. DESIGN AND SUBJECTS: Cross-sectional study at a clinical research center, including 48 men (16 with acromegaly, 16 with GHD and 16 healthy controls)...
August 5, 2017: European Journal of Endocrinology
Kang Guan, Jianqing Wu, Laifei Cheng
The evolution of the thermal conductivities of the unidirectional, 2D woven and 3D braided composites during the CVI (chemical vapor infiltration) process have been numerically studied by the finite element method. The results show that the dual-scale pores play an important role in the thermal conduction of the CVI-densified composites. According to our results, two thermal conductivity models applicable for CVI process have been developed. The sensitivity analysis demonstrates the parameter with the most influence on the CVI-densified composites' thermal conductivity is matrix cracking's density, followed by volume fraction of the bundle and thermal conductance of the matrix cracks, finally by micro-porosity inside the bundles and macro-porosity between the bundles...
December 13, 2016: Materials
Ning Zhu, Dennj De Meo, Erkan Oterkus
An ordinary state-based peridynamic formulation is developed to analyse cubic polycrystalline materials for the first time in the literature. This new approach has the advantage that no constraint condition is imposed on material constants as opposed to bond-based peridynamic theory. The formulation is validated by first considering static analyses and comparing the displacement fields obtained from the finite element method and ordinary state-based peridynamics. Then, dynamic analysis is performed to investigate the effect of grain boundary strength, crystal size, and discretization size on fracture behaviour and fracture morphology...
December 2, 2016: Materials
Xiangwen Zhang, Deqing Yang
A preliminary study of the mechanical properties of auxetic cellular material consisting of re-entrant hexagonal honeycombs is presented. For different scales of the honeycombs, the finite element method (FEM) and experimental models are used to perform a parametric analysis on the effects of the Poisson's ratio (cell angle) and the relative density (cell thickness) of honeycombs on bearing capacity and dynamic performance of the auxetic material. The analysis demonstrates that the ultimate bearing capacity of the presented auxetic cellular material is scale-independent when the Poisson's ratio and the relative density are kept constant...
November 7, 2016: Materials
Chang-Chun Lee, Pei-Chen Huang, Ko-Shun Wang
The suitability of stacked thin films for next-generation display technology was analyzed based on their properties and geometrical designs to evaluate the mechanical reliability of transparent conducting thin films utilized in flexural displays. In general, the high bending stress induced by various operation conditions is a major concern regarding the mechanical reliability of indium-tin-oxide (ITO) films deposited on polyethylene terephthalate (PET) substrates; mechanical reliability is commonly used to estimate the flexibility of displays...
October 19, 2016: Materials
Paulina Pianko-Oprych, Tomasz Zinko, Zdzisław Jaworski
A typical operating temperature of a solid oxide fuel cell (SOFC) is quite high above 750 °C and affects the thermomechanical behavior of the cell. Thermal stresses may cause microstructural instability and sub-critical cracking. Therefore, a joint analysis by the computational fluid dynamics (CFD) and computational structural mechanics based on the finite element method (FEM) was carried out to analyze thermal stresses in a planar SOFC and to predict potential failure locations in the cell. A full numerical model was based on the coupling of thermo-fluid model with the thermo-mechanical model...
September 30, 2016: Materials
Ana María Camacho, Mariano Veganzones, Juan Claver, Francisco Martín, Lorenzo Sevilla, Miguel Ángel Sebastián
Tribological conditions can change drastically during heavy loaded regimes as experienced in metal forming; this is especially critical when lubrication can only be applied at the early stage of the process because the homogeneous lubricant layer can break along the die-workpiece interface. In these cases, adopting a constant friction factor for the lubricant-surface pair may not be a valid assumption. This paper presents a procedure based on the use of dual friction factor maps to determine friction factors employed in heavy loaded regimes...
September 1, 2016: Materials
Jiong-Shiun Hsu, Chang-Chun Lee, Bor-Jiunn Wen, Pei-Chen Huang, Chi-Kai Xie
Stress-induced failure is a critical concern that influences the mechanical reliability of an indium tin oxide (ITO) film deposited on a transparently flexible polyethylene terephthalate (PET) substrate. In this study, a cycling bending mechanism was proposed and used to experimentally investigate the influences of compressive and tensile stresses on the mechanical stability of an ITO film deposited on PET substrates. The sheet resistance of the ITO film, optical transmittance of the ITO-coated PET substrates, and failure scheme within the ITO film were measured to evaluate the mechanical stability of the concerned thin films...
August 24, 2016: Materials
Annamaria Pau, Dimitra V Achillopoulou
This paper investigates the interaction of different shear- and Rayleigh-Lamb-guided waves in plates with a discontinuity such as a notch or an internal void. The problem was solved numerically using a finite element model and by exploiting an analytical solution obtainable for the double sharp changes of the cross-section that served as a reference. We aimed to elucidate the relation between the size and shape of the discontinuity and the reflection and transmission coefficients of the scattered field. Different sizes and profiles of the discontinuity were considered, with the shapes ranging from step changes of the height to ellipses, both symmetric and nonsymmetric...
July 21, 2017: Materials
Dong Hyun Moon, Jeong Yeol Park, Myung Hyun Kim
The constraint effect is the key issue in structural integrity assessments based on two parameter fracture mechanics (TPFM) to make a precise prediction of the load-bearing capacity of cracked structural components. In this study, a constraint-based failure assessment diagram (FAD) was used to assess the fracture behavior of an Al 5083-O weldment with various flaws at cryogenic temperature. The results were compared with those of BS 7910 Option 1 FAD, in terms of the maximum allowable stress. A series of fracture toughness tests were conducted with compact tension (CT) specimens at room and cryogenic temperatures...
July 18, 2017: Materials
Francesco Tornabene, Nicholas Fantuzzi, Michele Bacciocchi
A mathematical scheme is proposed here to model a damaged mechanical configuration for laminated and sandwich structures. In particular, two kinds of functions defined in the reference domain of plates and shells are introduced to weaken their mechanical properties in terms of engineering constants: a two-dimensional Gaussian function and an ellipse shaped function. By varying the geometric parameters of these distributions, several damaged configurations are analyzed and investigated through a set of parametric studies...
July 17, 2017: Materials
Claudio Sbarufatti, Alessio Beligni, Andrea Gilioli, Maddalena Ferrario, Marco Mattarei, Mario Martinelli, Marco Giglio
A novel fiber optic sensing technology for high frequency dynamics detection is proposed in this paper, specifically tailored for structural health monitoring applications based on strain wave analysis, for both passive impact identification and active Lamb wave monitoring. The sensing solution relies on a fiber optic-based interferometric architecture associated to an innovative coherent detection scheme, which retrieves in a completely passive way the high-frequency phase information of the received optical signal...
July 13, 2017: Materials
Yijian Zhan, Günther Meschke
The effective analysis of the nonlinear behavior of cement-based engineering structures not only demands physically-reliable models, but also computationally-efficient algorithms. Based on a continuum interface element formulation that is suitable to capture complex cracking phenomena in concrete materials and structures, an adaptive mesh processing technique is proposed for computational simulations of plain and fiber-reinforced concrete structures to progressively disintegrate the initial finite element mesh and to add degenerated solid elements into the interfacial gaps...
July 8, 2017: Materials
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