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Finite element modeling

Grzegorz Psuj
Nowadays, there is a strong demand for inspection systems integrating both high sensitivity under various testing conditions and advanced processing allowing automatic identification of the examined object state and detection of threats. This paper presents the possibility of utilization of a magnetic multi-sensor matrix transducer for characterization of defected areas in steel elements and a deep learning based algorithm for integration of data and final identification of the object state. The transducer allows sensing of a magnetic vector in a single location in different directions...
January 19, 2018: Sensors
Katrina Knight, Pamela Moalli, Steven D Abramowitch
Pelvic organ prolapse meshes are exposed to predominately tensile loading conditions in vivo that can lead to pore collapse by 70-90%, decreasing overall porosity, and providing a plausible mechanism for the contraction/shrinkage of mesh observed following implantation. To prevent pore collapse, we proposed to design synthetic meshes with a macrostructure that results in auxetic behavior, the pores expand laterally, instead of contracting when loaded. Such behavior can be achieved with a range of auxetic structures/geometries...
January 19, 2018: Journal of Biomechanical Engineering
Piotr Prochor, Eugeniusz Sajewicz
Nowadays, numerous internal bone remodelling concepts are under development, in order to estimate long-term functionality of implants by evaluating the intensity of stress-shielding effect. This effect is also analysed for the implants for direct skeletal attachment, considered as a better exoprosthesis fixation method than prosthetic sockets. Most of bone remodelling approaches are based on basic concepts, differing with certain assumptions, which may affect the accuracy of the results. This article compares commonly used internal bone remodelling concepts and evaluates the functionality of the proposed Limb Prosthesis Osseointegrated Fixation System for direct skeletal attachment of limb prosthesis in comparison with two currently available implants: the Intraosseous Transcutaneous Amputation Prosthesis and the Osseointegrated Prostheses for the Rehabilitation of Amputees...
January 1, 2018: Proceedings of the Institution of Mechanical Engineers. Part H, Journal of Engineering in Medicine
Qiang Liu, Jun Zhang, Shu-Chun Sun, Fei Wang
The finite element model is one of the most important methods in study of modern spinal biomechanics, according to the needs to simulate the various states of the spine, calculate the stress force and strain distribution of the different groups in the state, and explore its principle of mechanics, mechanism of injury, and treatment effectiveness. In addition, in the study of the pathological state of the spine, the finite element is mainly used in the understanding the mechanism of lesion location, evaluating the effects of different therapeutic tool, assisting and completing the selection and improvement of therapeutic tool, in order to provide a theoretical basis for the rehabilitation of spinal lesions...
February 25, 2017: Zhongguo Gu Shang, China Journal of Orthopaedics and Traumatology
Xuejiao Liu, Benzhuo Lu
Potassium channels are much more permeable to potassium than sodium ions, although potassium ions are larger and both carry the same positive charge. This puzzle cannot be solved based on the traditional Poisson-Nernst-Planck (PNP) theory of electrodiffusion because the PNP model treats all ions as point charges, does not incorporate ion size information, and therefore cannot discriminate potassium from sodium ions. The PNP model can qualitatively capture some macroscopic properties of certain channel systems such as current-voltage characteristics, conductance rectification, and inverse membrane potential...
December 2017: Physical Review. E
Gerald G Pereira, Bisheng Wu, Shakil Ahmed
We develop a gray-scale lattice Boltzmann (LB) model to study fluid flow combined with heat transfer for flow through porous media where voxels may be partially solid (or void). Heat transfer in rocks may lead to deformation, which in turn can modulate the fluid flow and so has significant contribution to rock permeability. The LB temperature field is compared to a finite difference solution of the continuum partial differential equations for fluid flow in a channel. Excellent quantitative agreement is found for both Poiseuille channel flow and Brinkman flow...
December 2017: Physical Review. E
S S Melnik, O V Usatenko
The main goal of this paper is to develop an estimate for the conditional probability function of random stationary ergodic symbolic sequences with elements belonging to a finite alphabet. We elaborate on a decomposition procedure for the conditional probability function of sequences considered to be high-order Markov chains. We represent the conditional probability function as the sum of multilinear memory function monomials of different orders (from zero up to the chain order). This allows us to introduce a family of Markov chain models and to construct artificial sequences via a method of successive iterations, taking into account at each step increasingly high correlations among random elements...
July 2017: Physical Review. E
Qiang Ma, Zhenqian Chen, Hao Liu
In this paper, to predict the dynamics behaviors of flow and mass transfer with adsorption phenomena in porous media at the representative elementary volume (REV) scale, a multiple-relaxation-time (MRT) lattice Boltzmann (LB) model for the convection-diffusion equation is developed to solve the transfer problem with an unsteady source term in porous media. Utilizing the Chapman-Enskog analysis, the modified MRT-LB model can recover the macroscopic governing equations at the REV scale. The coupled MRT-LB model for momentum and mass transfer is validated by comparing with the finite-difference method and the analytical solution...
July 2017: Physical Review. E
Fanette Chassagne, Jerome Molimard, Reynald Convert, Pascal Giraux, Pierre Badel
OBJECTIVE: To develop a new method for the prediction of interface pressure applied by medical compression bandages. METHODS: A finite element simulation of bandage application was designed, based on patient-specific leg geometries. For personalized interface pressure prediction, a model reduction approach was proposed, which included the parametrization of the leg geometry. Pressure values computed with this reduced model were then confronted to experimental pressure values...
February 2018: IEEE Transactions on Bio-medical Engineering
Marco Marques, Jorge Belinha, Lúcia Maria Js Dinis, Renato Natal Jorge
This work has the objective to compare the mechanical behaviour of a brain impact using an alternative numerical meshless technique. Thus, a discrete geometrical model of a brain was constructed using medical images. This technique allows to achieve a discretization with realistic geometry, allowing to define locally the mechanical properties according to the medical images colour scale. After defining the discrete geometrical model of the brain, the essential and natural boundary conditions were imposed to reproduce a sudden impact force...
January 1, 2018: Proceedings of the Institution of Mechanical Engineers. Part H, Journal of Engineering in Medicine
Claire Acevedo, Meghan Sylvia, Eric Schaible, James L Graham, Kimber L Stanhope, Lionel N Metz, Bernd Gludovatz, Ann V Schwartz, Robert O Ritchie, Tamara N Alliston, Peter J Havel, Aaron J Fields
Adults with type 2 diabetes (T2D) have a higher fracture risk for a given bone quantity, but the mechanisms remain unclear. Using a rat model of polygenic obese T2D, we demonstrate that diabetes significantly reduces whole-bone strength for a given bone mass (micro-CT-derived BMC), and we quantify the roles of T2D-induced deficits in material properties versus bone structure, i.e., geometry and microarchitecture. Lumbar vertebrae and ulnae were harvested from 6-month-old lean Sprague-Dawley rats, obese Sprague-Dawley rats, and diabetic obese UCD-T2DM rats (diabetic for 69 ± 7 days; blood glucose >200 mg/dl)...
January 17, 2018: Journal of Bone and Mineral Research: the Official Journal of the American Society for Bone and Mineral Research
Tao Zhang, Lei Li, Shi-Hong Lu, Hai Gong, Yun-Xin Wu
Asymmetrical shear rolling with velocity asymmetry and geometry asymmetry is beneficial to enlarge deformation and refine grain size at the center of the thick plate compared to conventional symmetrical rolling. Dynamic recrystallization (DRX) plays a vital role in grain refinement during hot deformation. Finite element models (FEM) coupled with microstructure evolution models and cellular automata models (CA) are established to study the microstructure evolution of plate during asymmetrical shear rolling. The results show that a larger DRX fraction and a smaller average grain size can be obtained at the lower layer of the plate...
January 17, 2018: Materials
João Paulo Mendes Tribst, Vinícius Anéas Rodrigues, Alexandre Luiz Souto Borges, Dimas Rennó de Lima, Renato Sussumu Nishioka
PURPOSE: To evaluate the stress and strain generated in a fixed four-element prosthesis under the application of axial and nonaxial loads using a simplified implant-supported fixed prosthesis model. MATERIALS AND METHODS: A 3-dimensional model was constructed containing 3 implants with a conventional anatomical prosthesis (G1). The second model with the same implant system received the simplified prosthesis (G2). A load of 300 N was applied at an axial point and a nonaxial point through finite element analysis software...
January 16, 2018: Implant Dentistry
Oguz Ozan, Sevcan Kurtulmus-Yilmaz
PURPOSE: The aim of this study was to evaluate the effect of implant inclination and cantilever length on the stress distribution in mandibular cortical bone, implant, abutment, prosthetic framework, and prosthetic screw via three-dimensional (3D) finite element analysis (FEA). MATERIALS AND METHODS: Four different finite element models (0-0, 17-17, 30-30, 45-30) were designed according to the tilting angle (0, 17, 30, and 45 degrees) of the posterior implant and angle of multiunit abutments (0, 17, and 30 degrees)...
January 2018: International Journal of Oral & Maxillofacial Implants
Canay Yılmaz Asan, Nükhet Kütük, Gökmen Kurt, Alper Alkan
PURPOSE: Class 3 malocclusions with maxillary deficiency, which are treated surgically and/or ordonotically, are common among adult patients. The aim of this study was to develop a three-directional bone-borne distractor that would allow the transverse expansion and sagittal advancement of the maxilla simultaneously. MATERIALS AND METHODS: Computed tomography images of a patient with maxillary deficiency were transmitted to a software program, and a distractor was designed with different sizes (D1, D2, D3) and manufactured from titanium alloy...
December 18, 2017: Journal of Cranio-maxillo-facial Surgery
Fancheng Chen, Xiaowei Huang, Yingsun Ya, Fenfen Ma, Zhi Qian, Jifei Shi, Shuolei Guo, Baoqing Yu
BACKGROUND: Proximal tibia fractures are one of the most familiar fractures. Surgical approaches are usually needed for anatomical reduction. However, no single treatment method has been widely established as the standard care. Our present study aims to compare the stress and stability of intramedullary nails (IMN) fixation and double locking plate (DLP) fixation in the treatment of extra-articular proximal tibial fractures. METHODS: A three-dimensional (3D) finite element model of the extra-articular proximal tibial fracture, whose 2-cm bone gap began 7 cm from the tibial plateau articular surface, was created fixed by different fixation implants...
January 16, 2018: Journal of Orthopaedic Surgery and Research
Kun Zhang, Wenhui Tang, Kunkun Fu
Carbon fiber-reinforced polymer (CFRP) composites have been increasingly used in spacecraft applications. Spacecraft may encounter highenergy-density X-ray radiation in outer space that can cause severe damage. To protect spacecraft from such unexpected damage, it is essential to predict the dynamic behavior of CFRP composites under X-ray radiation. In this study, we developed an in-house three-dimensional explicit finite element (FEM) code to investigate the dynamic responses of CFRP composite under X-ray radiation for the first time, by incorporating a modified PUFF equation-of-state...
January 16, 2018: Materials
Dimitri Kokkinis, Florian Bouville, André R Studart
Mechanical gradients are useful to reduce strain mismatches in heterogeneous materials and thus prevent premature failure of devices in a wide range of applications. While complex graded designs are a hallmark of biological materials, gradients in manmade materials are often limited to 1D profiles due to the lack of adequate fabrication tools. Here, a multimaterial 3D-printing platform is developed to fabricate elastomer gradients spanning three orders of magnitude in elastic modulus and used to investigate the role of various bioinspired gradient designs on the local and global mechanical behavior of synthetic materials...
January 16, 2018: Advanced Materials
Jianxin Sun, L Moore, Wei Xue, James Kim, Maciej Zborowski, Jeffrey J Chalmers
Magnetic separation of cells has been, and continues to be, widely used in a variety of applications, ranging from healthcare diagnostics to detection of food contamination. Typical, these technologies require cells labeled with antibody magnetic particle conjugate and a high magnetic energy gradient created in the flow containing the labeled cells (i.e. a column packed with magnetically inducible material), or dense packing of magnetic particles next to the flow cell. Such designs while creating high magnetic energy gradients, are not amenable to easy, highly detailed, mathematic characterization...
January 16, 2018: Biotechnology and Bioengineering
Y Chevalier, M Matsuura, S Krüger, C Fleege, M Rickert, M Rauschmann, C Schilling
Anchorage of pedicle screw instrumentation in the elderly spine with poor bone quality remains challenging. In this study, micro finite element (µFE) models were used to assess the specific influence of screw design and the relative contribution of local bone density to fixation mechanics. These were created from micro computer tomography (µCT) scans of vertebras implanted with two types of pedicle screws, including a full region-or-interest of 10 mm radius around each screw, as well as submodels for the pedicle and inner trabecular bone of the vertebral body...
December 26, 2017: Journal of Biomechanics
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