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The acoustic black hole (ABH) structure has gradually become a research hotspot in recent years due to its ascendant capacity of vibration attenuation and energy accumulation. To further improve the performance of vibration and noise reduction, the ultra-low frequency broadband gap of a one-dimensional structure embedded ABHs with power-law material properties is investigated in this paper. Based on the Euler-Bernoulli theory, the Transfer Matrix Method (TMM) is used to establish the dynamic model of the dual power-law ABH (DP-ABH) beam. The band structure results obtained by TMM and the finite element method are compared with each other to verify the ultra-low broadband gap of the structure. Comparison with the traditional ABH show that the ultra-low frequency performance of the DP-ABH is due to the enhanced local resonator properties with reduction of dual power-law local stiffness. Parameter analysis served as a guide for optimization is carried out and a method of combining NSGA-II and TMM is applied to optimize the ABH section with full parameters, to consider a trade-off between lower bandgaps and higher stiffness. The investigation shows that the ultra-low broadband gaps of the periodic DP-ABHs structure, which meets adequate stiffness requirements, can be designed by optimized configuration. [ABSTRACT FROM AUTHOR]

• Broadband gap in low frequency is obtained by the novel locally resonant metastructure. • Calculation and verification methods include Gaussian expansion method, finite element method and experiment. • The property of lightweight with resonable stiffness. • Practical engineering applications in vibration attenuation in broad and low frequency. Metastructure has been discovered as a new and effective means of vibration suppression in recent studies. Based on the basic principle of the locally resonant (LR) metastructure, a novel two-dimensional LR metastruture is proposed in this paper. The host plate is punched out several concentric holes and filled with soft materials, with the resonator installed in the center. The band structure of an infinite structure is calculated by using Gaussian expansion method as well as the finite element method. To further evaluate the vibration attenuation performance, the vibration transmission of a finite plate is obtained by both numerical and experimental methods. Formation mechanism of band gaps (BGs) is revealed by analyzing eigenmodes at boundary frequencies. The significance of the novel design is clarified from the mechanism level, about the characteristics of generating broad band gaps in low frequencies. The influence of both geometric parameters and material damping properties on BGs are discussed, including examples of a non-periodic plate and a periodic damped plate. Because of its features and simple design, it can be expected to be widely applied in engineering. [ABSTRACT FROM AUTHOR]

The objective of this investigation is to analyze the influence of trabecular microstructure modeling on the biomechanical distribution of the implant-bone interface. Two three-dimensional finite element mandible models, one with trabecular microstructure (a refined model) and one with macrostructure (a simplified model), were built. The values of equivalent stress at the implant-bone interface in the refined model increased compared with those of the simplified model and strain on the contrary. The distributions of stress and strain were more uniform in the refined model of trabecular microstructure, in which stress and strain were mainly concentrated in trabecular bone. It was concluded that simulation of trabecular bone microstructure had a significant effect on the distribution of stress and strain at the implant-bone interface. These results suggest that trabecular structures could disperse stress and strain and serve as load buffers. [ABSTRACT FROM AUTHOR]

The objective of this investigation is to construct a high quality complete dentate mandible model with detailed biological structures, and assign mandibular bone with inherent orthotropic material characteristics. Three different types of scan data are used to elaborate detailed mandibular structures, including the cortical and cancellous bone, tooth enamel, dentin, periodontal ligament, temporal fossa, TMJ articular disk, temporal cartilage, and condylar cartilage. In addition, an extended orthotropic material assignment methodology based on harmonic fields is used to handle the alveolar ridge region of dentate mandible, to generate compatible orthotropic axes fields. The influence of orthotropic material on the biomechanical behavior of complete dentate mandible is analyzed compared with commonly used isotropic model. The result revealed that the orthotropic model would induce higher stress values and more well-distributed stress pattern than the isotropic model, especially for the cancellous bone. And the orthotropic model would induce lower volumetric strain values than the isotropic model on the cortical bone. It was concluded that elastic orthotropy had a significant effect on the simulated stress value and distribution pattern, as well as the volumetric strain, and demonstrated the mechanical optimality of the mandible. [ABSTRACT FROM AUTHOR]

PURPOSE: To explore an effective method to construct and validate a finite element model of the unilateral cleft lip and palate (UCLP) craniomaxillary complex with sutures, which could be applied in further three-dimensional finite element analysis (FEA). METHODS: One male patient aged 9 with left complete lip and palate cleft was selected and CT scan was taken at 0.75mm intervals on the skull. The CT data was saved in Dicom format, which was, afterwards, imported into Software Mimics 10.0 to generate a three-dimensional anatomic model. Then Software Geomagic Studio 12.0 was used to match, smoothen and transfer the anatomic model into a CAD model with NURBS patches. Then, 12 circum-maxillary sutures were integrated into the CAD model by Solidworks (2011 version). Finally meshing by E -feature Biomedical Modeler was done and a three --dimensional finite element model with sutures was obtained. A maxillary protraction force (500 g per side, 20°downward and forward from the occlusal plane) was applied. Displacement and stress distribution of some important craniofacial structures were measured and compared with the results of related researches in the literature. RESULTS: A three-dimensional finite element model of UCLP craniomaxillary complex with 12 sutures was established from the CT scan data. This simulation model consisted of 206 753 individual elements with 260 662 nodes, which was a more precise simulation and a better representation of human craniomaxillary complex than the formerly available FEA models. By comparison, this model was proved to be valid. CONCLUSIONS: It is an effective way to establish the three-dimensional finite element model of UCLP cranio-maxillary complex with sutures from CT images with the help of the following softwares: Mimics 10.0, Geomagic Studio 12.0, Solidworks and E-feature Biomedical Modeler. [ABSTRACT FROM AUTHOR]

Abstract: Although it is well known that human bone tissues have obvious orthotropic material properties, most works in the physical modeling field adopted oversimplified isotropic or approximated transversely isotropic elasticity due to the simplicity. This paper presents a convenient methodology based on harmonic fields, to construct volumetric finite element mesh integrated with complete orthotropic material. The basic idea is taking advantage of the fact that the longitudinal axis direction indicated by the shape configuration of most bone tissues is compatible with the trajectory of the maximum material stiffness. First, surface harmonic fields of the longitudinal axis direction for individual bone models were generated, whose scalar distribution pattern tends to conform very well to the object shape. The scalar iso-contours were extracted and sampled adaptively to construct volumetric meshes of high quality. Following, the surface harmonic fields were expanded over the whole volumetric domain to create longitudinal and radial volumetric harmonic fields, from which the gradient vector fields were calculated and employed as the orthotropic principal axes vector fields. Contrastive finite element analyses demonstrated that elastic orthotropy has significant effect on simulating stresses and strains, including the value as well as distribution pattern, which underlines the relevance of our orthotropic modeling scheme. [Copyright &y& Elsevier]

Background: Many clinical observations have shown that immediate loading is indicated when the stabilization of the bone/implant is optimal and when the estimated loads are not excessively high. Nonetheless, more experimental studies are needed to consider the immediate loading protocol as a safe procedure. Mechanical analysis using the finite element (FE) method analysis has been employed by many authors to understand the biomechanical behavior around dental implants. Purpose: This study was to evaluate the effect of the diameter and length on the stress and strain distribution of the crestal bone around implants under immediate loading. Materials and Methods: By an ad hoc automatic mesh generator, high-quality FE models of complete range mandible was constructed from computer tomography, with three Straumann (Straumann Institute, Waldenburg, Switzerland) implants of various sizes embedded in the anterior zone. The implant diameter ranged from 3.3 to 4.8 mm, and length ranged from 6 to 14 mm, resulting in seven designs. The implant–bone interface was simulated by nonlinear frictional contact algorithm. For each design, vertical and oblique loadings of 150 N were applied, respectively, to each implant, and stresses and strains in the surrounding cortical bone were evaluated. Results: The biomechanics analysis provided results that the oblique loading would induce significantly higher interfacial stresses and strains than the vertical loading, while the intergroup stress difference significant levels was evaluated using t-tests method and the level of significance (.05) that was accepted for significance. Under both loadings, the maximal values were recorded in the 3.3 (diameter) × 10 (length) mm implant configuration, whose mean and peak values were both higher than that of others with significant statistical differences. The second maximal one is 4.1 × 6 mm configuration, and the minimal stresses were recorded in 4.8 × 10 mm configuration, whose strains were also near to lowest. Conclusions: Increasing the diameter and length of the implant decreased the stress and strain on the alveolar crest, and the stress and strain values notably increased under buccolingual loading as compared with vertical loading, but diameter had a more significant effect than length to relieve the crestal stress and strain concentration. [ABSTRACT FROM AUTHOR]

Purpose: To establish a 3D finite element model of a mandible with dental implants for immediate loading and to analyze stress distribution in bone around implants of different diameters. Materials and Methods: Three mandible models, embedded with thread implants (ITI, Straumann, Switzerland) with diameters of 3.3, 4.1, and 4.8 mm, respectively, were developed using CT scanning and self-developed Universal Surgical Integration System software. The von Mises stress and strain of the implant–bone interface were calculated with the ANSYS software when implants were loaded with 150 N vertical or buccolingual forces. Results: When the implants were loaded with vertical force, the von Mises stress concentrated on the mesial and distal surfaces of cortical bone around the neck of implants, with peak values of 25.0, 17.6 and 11.6 MPa for 3.3, 4.1, and 4.8 mm diameters, respectively, while the maximum strains (5854, 4903, 4344 μℇ) were located on the buccal cancellous bone around the implant bottom and threads of implants. The stress and strain were significantly lower ( p < 0.05) with the increased diameter of implant. When the implants were loaded with buccolingual force, the peak von Mises stress values occurred on the buccal surface of cortical bone around the implant neck, with values of 131.1, 78.7, and 68.1 MPa for 3.3, 4.1, and 4.8 mm diameters, respectively, while the maximum strains occurred on the buccal surface of cancellous bone adjacent to the implant neck, with peak values of 14,218, 12,706, and 11,504 μm, respectively. The stress of the 4.1-mm diameter implants was significantly lower ( p < 0.05) than those of 3.3-mm diameter implants, but not statistically different from that of the 4.8 mm implant. Conclusions: With an increase of implant diameter, stress and strain on the implant–bone interfaces significantly decreased, especially when the diameter increased from 3.3 to 4.1 mm. It appears that dental implants of 10 mm in length for immediate loading should be at least 4.1 mm in diameter, and uniaxial loading to dental implants should be avoided or minimized. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a novel inhomogeneous volumetric mesh deformation approach by gradient field manipulation, and uses it for maxillofacial surgery simulation. The study is inspired by the state-of-the-art surface deformation techniques based on differential representations. Working in the volumetric domain instead of on only the surface can preserve the volumetric details much better, avoid local self-intersections, and achieve better deformation propagation because of the internal mesh connections. By integrating the mesh cell material stiffness parameter into our new discrete volumetric Laplacian operator, it is very convenient to incorporate inhomogeneous materials into the deformation framework. In addition, the system matrix for solving the volumetric harmonic field to handle the local transformation problem is the same used for Poisson reconstruction equation, thus it requires solving essentially only one global linear system. The system is easy to use, and can accept explicit rotational constraints, or only translational constraints to drive the deformation. One typical maxillofacial surgery case was simulated by the new methodology with inhomogeneous material estimated directly from CT data, and compared to the commonly used finite element method (FEM) approach. The results demonstrated that the deformation methodology achieved good accuracy, as well as interactive performance. Therefore, the usage of our volumetric mesh deformation approach is relevant and suitable for daily clinical practice. [Copyright &y& Elsevier]

Abstract: This paper reveals the influence of elastic anisotropy for the peri-implant stress and strain in personalized mandible. First, from CT data, the individual geometry of the complete range of mandible was well reproduced, also the separation between cortical and cancellous bone. Then, by an ad hoc automatic mesh generator integrated with anisotropic material assignment function, high quality anisotropic finite element model of the complete mandible was created, with two standard threaded implants embedded in posterior zone. The values of principal stress and strain in surrounding bone were evaluated under buccolingual oblique loading, and compared to that of the same FE model with equivalent isotropic material. Results of the analyses demonstrated that the percentage increase of stress and strain in anisotropic case reached up to 70%. It is concluded that anisotropy has significant effects on peri-implant stress and strain and careful consideration should be given to its use in biomechanical FE studies. [Copyright &y& Elsevier]

Abstract: This paper presents an ad hoc modular software tool to quasi-automatically generate patient-specific three-dimensional (3D) finite element (FE) model of the human mandible. The main task is taking into account the complex geometry of the individual mandible, as well as the inherent highly anisotropic material law. At first, by computed tomography data (CT), the individual geometry of the complete range of mandible was well reproduced, also the separation between cortical and cancellous bone. Then, taking advantage of the inherent shape nature as ‘curve’ long bone, the algorithm employed a pair of B-spline curves running along the entire upper and lower mandible borders as auxiliary baselines, whose directions are also compatible with that of the trajectory of maximum material stiffness throughout the cortical bone of the mandible. And under the guidance of this pair of auxiliary baselines, a sequence of B-spline surfaces were interpolated adaptively as curve cross-sections to cut the original geometry. Following, based on the produced curve contours and the corresponding curve cross-section surfaces, quite well structured FE volume meshes were constructed, as well as the inherent trajectory vector fields of the anisotropic material (orthotropic for cortical bone and transversely isotropic for cancellous bone). Finally, a sensitivity analysis comprising various 3D FE simulations was carried out to reveal the relevance of elastic anisotropy for the load carrying behavior of the mandible. [Copyright &y& Elsevier]

Abstract Extraction columns are one of the important liquid–liquid mass transfer equipment with wide applications in industries like petrochemical, chemical, food, pharmaceutical and so on. Therefore, reliability evaluation and failure analysis plays an important role in safe and normal operation of them. In this study, root causes analysis of localized abnormal wear on the inner wall of one extraction column for manufacturing methyl methacrylate (MMA) was addressed. Based on field investigation, wear surfaces analysis, scales inspection, precision testing and finite element analysis, the results showed that out-of-roundness of the sieve plates and deflection of the main shaft were the root causes. The detailed mechanisms were then discussed, and the pertinent countermeasures were proposed to prevent the recurrence of similar cases. Highlights • A localized abnormal wear failure case of MAA extraction column inner wall was investigated. • The wear traces were discovered in different heights and directions, eliminating the possibility of incline of the column. • Pertinent countermeasures were proposed to prevent the recurrence of similar incidents, and were proved effective on site. [ABSTRACT FROM AUTHOR]

Double-pipe heat exchangers are widely used in the high-pressure and high-temperature applications for their simple and tight tube-in-tube configuration, but therefore normal and stable operation of such pressure-bearing equipment turns to be of greater significance because potential safety risks and economic losses will be aroused if failures occur on them. To deal with this issue, abundant researches have been conducted so far, however most of them focused on the flow and fluid characteristics by numerical simulation and experimental verification, while little attention was paid to the actual cases from the engineering practice. In this paper, such an actual failure case study concerning leakage on the jacket pipe of one double-pipe heat exchanger in a high-pressure polyethylene facility is addressed. In order to find out the causes of this failure, investigation including materials inspection, chemical phase analysis, microscopic morphologies observation, micro-area chemical compositions detection and finite element analysis etc. was carried out. The results indicated that the leakage was firstly induced by the uniform corrosion and the under-deposit corrosion successively, and then stimulated by the effect of erosion from the complicated fluid characteristics around the tee structure. Finally, the related mechanisms of this synergistic effect between corrosion and erosion were discussed, and the pertinent countermeasures from both design and maintenance point of view were proposed, including descaling of the fouled inner pipe, improvement of the circulation cooling water quality, and upgrading of the pipe materials etc. Achievement of this paper will supplement the failure cases database of double-pipe heat exchangers, based on which design optimization and failure prevention will be possible. Double-pipe heat exchangers are widely used in the high-pressure and high-temperature applications for their simple and tight tube-in-tube configuration, but therefore normal and stable operation of such pressure-bearing equipment turns to be of greater significance because potential safety risks and economic losses will be aroused if failures occur on them. To deal with this issue, abundant researches have been conducted so far, however most of them focused on the flow and fluid characteristics by numerical simulation and experimental verification, while little attention was paid to the actual cases from the engineering practice. In this paper, such an actual failure case study concerning leakage on the jacket pipe of one double-pipe heat exchanger in a high-pressure polyethylene facility is addressed, seen in Fig.1. In order to find out the causes of this failure, investigation including materials inspection, chemical phase analysis, microscopic morphologies observation, micro-area chemical compositions detection and finite element analysis etc. was carried out. The results indicated that the leakage was firstly induced by the uniform corrosion and the under-deposit corrosion successively, and then stimulated by the effect of erosion from the complicated fluid characteristics around the tee structure, seen in Fig.2 and 3. Finally, the related mechanisms of this synergistic effect between corrosion and erosion were discussed and illustrated in Fig.4, and the pertinent countermeasures from both design and maintenance point of view were proposed, including descaling of the fouled inner pipe, improvement of the circulation cooling water quality, and upgrading of the pipe materials etc. Achievement of this paper will supplement the failure cases database of double-pipe heat exchangers, based on which design optimization and failure prevention will be possible. Image 1 • Present a premature failure case of leaked jacket pipe on double-pipe heat exchanger. • This heat exchanger is used in a high-pressure polyethylene facility in China. • Countermeasures were proposed from both design and maintenance point of view. • The synergism from both corrosion and erosion was addressed in detail in this paper. • Failure analysis case database of double-pipe heat exchangers will be enriched. [ABSTRACT FROM AUTHOR]

In order to solve strip edge drop and crown problem for accurate “dead flat” transverse thickness profile of electrical steel sheet in 4-high tandem cold rolling mills,the 3D finite element model of roll stacks and strip deformation was built in cold rolling process. Through a comparative analysis, the uneven deformation of rolls flattening and the deflection of work rolls caused by the pressure in undesired overhung contact areas between rolls are the main contributions to strip edge drop and crown ratio and make different contributions that can provide a new basis for evaluating different solutions to strip edge drop and crown control in 4-high and 6-high mills. The integrated design of roll contours for EDW (Edge Drop Control Work Rolls) and matched VCR(Varying Contact Backup Rolls) were developed to decrease the uneven deformation of roll flattening and eliminate undesired overhung contact areas for different strip widths, which provides a novel approach for high-quality control of strip edge drop and crown in 4-high tandem cold rolling mills with high-precision quality of strip edge drop and crown controllability. The industrial application gives remarkable results that the rate of transverse thickness profile deviation less than 10 μm is 97.25% in 1700 mm 4-high tandem cold rolling mills. [ABSTRACT FROM AUTHOR]