Computational Finite Element Analysis Research Articles

The impact of geometrical parameters on acoustically driven drug delivery to maxillary sinuses

Acoustically driven nebulized drug delivery (acoustic aerosol delivery) is the most efficient noninvasive technique for drug delivery to maxillary sinuses (MS). This method is based on the oscillation of the air plug inside the ostium to transport drug particles from the nasal cavity (NC) to the MS. The larger the wavelength of the air plug oscillation in the ostium, the greater the penetration of drug particles to the MS. However, using this technique, the maximum drug delivery efficiency achieved to date is 5%, which means 95% of the aerosolized drugs do not enter the MS and are wasted. Since the largest amplitude of the air plug oscillation occurs at its resonance frequency, to achieve an improved MS drug delivery efficiency, it is important to determine the resonance frequency of the nose-sinus combination accurately. This paper aims to investigate the impact of geometrical parameters on the resonance frequency of the nose-sinus model. Both experimental and computational acoustic models, along with the theoretical analysis, were conducted to determine the resonance frequency of an idealized nose-sinus model. The computational modeling was carried out using computational fluid dynamics (CFD) and finite element analysis (FEA), whereas in the analytical solution, the mathematical relationships developed for a conventional Helmholtz resonator were employed. A series of experiments were also conducted to measure the resonance frequency of a realistic NC-MS combination. The results demonstrated a good agreement between the experimental and CFD modeling, while the FEA and theoretical analysis showed a significant deviation from the experimental data. Also, it was shown that the resonance frequency of the idealized nose-sinus model increases by up to twofold with increasing the ostium diameter from 3 to 9mm; however, it has an inverse relationship with the ostium length and sinus volume. It was also reported that the resonance frequency of the nose-sinus model is independent of the NC width and MS shape.

Математическое моделирование конденсации рабочего тела в системе отдачи тепла холодному источнику энергоустановки малой мощности

The purpose of the paper is to offer a method for reducing the temperature and condensation of the working fluid circulating in the power plant due to the fact that the Russian Federation is characterized by uneven provision of electricity and heat (the problem of energy shortage is most acute in the Far East and the Far North regions). The major shortcomings of the current centralized energy supply are great losses during energy delivery and transformation, as well as the possibility of de-energizing a large number of consumers in case of an accident at the сentral power plant. In this regard, the idea of decentralized energy production free from the named shortcomings due to its autonomy and proximity to the places of consumption is becoming increasingly relevant. One of the methods of decentralized generation of heat and electricity is the use of Rankine cycle-based low-capacity power plants with an organic working fluid. Their design includes a boiler heating the working fluid, a turbine driving the electric generator, condenser and a pump. To condense the coolant the organic Rankine cycle must be provided with heat dissipation to the environment. This paper deals with the method of lowering the temperature and condensation of the working fluid circulating in the power plant (by means of a horizontal pipeline plunged to a certain depth in the ground). It is assumed that available temperature potential of the soil provides complete condensation of the working fluid without excessive overcooling. The study of intensity of working fluid cooling and condensation in the pipeline is carried out using a homogeneous and ring flow model. The temperature fields and steam dryness degree are determined by two approaches: in the software package of finite element modeling ANSYS CFX and by the finite difference method (engineering calculation methods). The paper also presents the analysis of the results obtained in the course of solving the problem by means of the finite element analysis and engineering calculation by the finite difference method.

Comparison between finite element and hybrid finite element results to test data for the vibration of a production car body

The Hybrid Finite Element Analysis (Hybrid FEA) method is based on combining conventional Finite Element Analysis (FEA) with analytical solutions and energy methods for mid-frequency computations. The method is appropriate for computing the vibration of structures which comprises stiff load bearing components and flexible panels attached to them and for considering structure-borne loadings with the excitations applied on the load bearing members. In such situations, the difficulty in using conventional FEA at higher frequencies originates from requiring a very large number of elements in order to capture the flexible wavelength of the panel members which are present in a structure. In this presentation a three-way comparison will be offered for the vibration of a production vehicle body in the frequency range 200 Hz–1000 Hz. Six different excitation locations are utilized (one at a time); for each excitation the mobility of five reference body points on the load bearing members, and the mobility of eight flexible vehicle panels is measured and the measurements are compared with both conventional FEA results and with Hybrid FEA computations. Discussion about the development of the Hybrid FEA model and the correlation of both numerical solutions to the test data will be presented.The Hybrid Finite Element Analysis (Hybrid FEA) method is based on combining conventional Finite Element Analysis (FEA) with analytical solutions and energy methods for mid-frequency computations. The method is appropriate for computing the vibration of structures which comprises stiff load bearing components and flexible panels attached to them and for considering structure-borne loadings with the excitations applied on the load bearing members. In such situations, the difficulty in using conventional FEA at higher frequencies originates from requiring a very large number of elements in order to capture the flexible wavelength of the panel members which are present in a structure. In this presentation a three-way comparison will be offered for the vibration of a production vehicle body in the frequency range 200 Hz–1000 Hz. Six different excitation locations are utilized (one at a time); for each excitation the mobility of five reference body points on the load bearing members, and the mobility of eight ...

Research on Bearing Stress Characteristics of Stacking Robot Base under New Engineering Background

Under the background of the continuous development of new engineering, more and more researches are aiming at new cutting-edge technologies, among which industrial robots have attracted much attention. Based on typical trajectory and a given load condition of the palletizing robot, the dynamics analysis and calculation was accomplished by using the dynamics analysis and calculation module of Adams software under the condition that the palletizing robot was working normally, then obtained the dynamic load variation when rolling bearing was running, furthermore, the contact stress change rule was obtained by using the finite element analysis calculation method, and the rule was regard as the basis of rolling bearing fatigue life analysis and evaluation. Judging from the results of analysis and calculation, the contact stress distribution of rolling bearing under the combined effect of both external load and dynamic load, which was similar to the phenomenon of commonly used rolling bearing stress fatigue destruction, this method can effectively overcome the deficiencies of traditional rolling bearing fatigue life calculation method that only consider static load, and reference for relevant engineering and technical personnel.

Computational analysis of airflow dynamics for predicting collapsible sites in the upper airways: machine learning approach.

Obstructive sleep apnea (OSA) is a common sleep breathing disorder. With the use of computational fluid dynamics (CFD), this study provides a quantitative standard for accurate diagnosis and effective surgery based on the investigation of the relationship between airway geometry and aerodynamic characteristics. Based on computed tomography data from patients having normal geometry, 4 major geometric parameters were selected and a total of 160 idealized cases were modeled and simulated. We created a predictive model using Gaussian process regression (GPR) through a data set obtained through numerical method. The results demonstrated that the mean accuracy of the overall GPR model was ~72% with respect to the CFD results for the realistic upper airway model. A support vector machine model was also used to identify the degree of OSA symptoms in patients as normal-mild and moderate and severe. We achieved an accuracy of 82.5% with the training data set and an accuracy of 80% with the test data set.NEW & NOTEWORTHY There have been many studies on the analysis of obstructive sleep apnea (OSA) through computational fluid dynamics and finite element analysis. However, these methods are not useful for practical medical applications because they have limited information for OSA symptom. This study employs the machine learning algorithm to predict flow characteristics quickly and to determine the symptoms of the patient's OSA. The overall Gaussian process regression model's mean accuracy was ~72%, and the accuracy for the classification of OSA was >80%.

Biomechanical Restoration Potential of Pentagalloyl Glucose after Arterial Extracellular Matrix Degeneration.

The objective of this study was to quantify pentagalloyl glucose (PGG) mediated biomechanical restoration of degenerated extracellular matrix (ECM). Planar biaxial tensile testing was performed for native (N), enzyme-treated (collagenase and elastase) (E), and PGG (P) treated porcine abdominal aorta specimens (n = 6 per group). An Ogden material model was fitted to the stress–strain data and finite element computational analyses of simulated native aorta and aneurysmal abdominal aorta were performed. The maximum tensile stress of the N group was higher than that in both E and P groups for both circumferential (43.78 ± 14.18 kPa vs. 10.03 ± 2.68 kPa vs. 13.85 ± 3.02 kPa; p = 0.0226) and longitudinal directions (33.89 ± 8.98 kPa vs. 9.04 ± 2.68 kPa vs. 14.69 ± 5.88 kPa; p = 0.0441). Tensile moduli in the circumferential direction was found to be in descending order as N > P > E (195.6 ± 58.72 kPa > 81.8 ± 22.76 kPa > 46.51 ± 15.04 kPa; p = 0.0314), whereas no significant differences were found in the longitudinal direction (p = 0.1607). PGG binds to the hydrophobic core of arterial tissues and the crosslinking of ECM fibers is one of the possible explanations for the recovery of biomechanical properties observed in this study. PGG is a beneficial polyphenol that can be potentially translated to clinical practice for preventing rupture of the aneurysmal arterial wall.

Leakage Flux of the Trans-Rotary Magnetic Gear

This paper investigates the leakage flux of the trans-rotary magnetic gear (TROMAG). TROMAG is a magnetic gear that converts a high-force low-speed linear motion to a low-torque high-speed rotation and vice versa. TROMAG is tailored to force-intensive linear motion applications such as backpack energy harvesting and artificial heart in which the gear is positioned close to the human body and/or electronic devices. In such applications, it is critical to ensure the TROMAG’s magnetic field penetrating the surrounding environment (referred to as the leakage flux hereafter) is below the limits permitted by standards. This paper employs 3-D finite-element analysis (FEA) to study spatial distribution and magnitude of the leakage flux. The FEA calculations of magnetic field are verified by experimental measurements. Both radial and quasi-Halbach configurations are investigated, and it is revealed that the quasi-Halbach configuration exhibits less leakage flux. Moreover, it is shown that the use of a thin iron shield surrounding the TROMAG can effectively reduce the leakage down to permissible values.

Application of mesh generation technology in bone mechanics research

High quality mesh is the basis of bone mechanics research and the precondition to ensure the accuracy of FEA (Finite Element Analysis) calculation. In order to obtain high accuracy and low distortion mesh of bone, the CFD (Computational Fluid Dynamics) meshing method is applied in this paper. The main process of bone finite element model construction consists of three parts, including CT (Computed Tomography) imaging, three-dimensional reverse modeling and meshing. By mesh optimization and boundary conditions imposition, the stress distribution of the occipital-atlantoaxial complex model and the relative motion angle between the Occipital Atlas and Atlantoaxial are obtained. According to the rotation angle checks, it is known that all the simulation results are within the range of cadaveric test data. The mesh generation technology provides a good idea and method for the study of bone mechanics.

Rotational stiffness of inter-module connection in mid-rise modular steel buildings

The inter-module connection used for the assembly of prefinished modules is a unique key issue for modular steel buildings (MSBs). Previous types of inter-module connection require additional operation spaces and have conflicts with architecture decoration. To overcome these limitations, this study proposed an innovative rotary inter-module connection applied at the end of modular columns with corner fitting. The working mechanism of the rotary connection was introduced through a bending resistance test. Then, finite element analysis (FEA) and theoretical derivation were conducted to investigate the initial rotational stiffness obtained through the preceding test. In terms of the feature of double beams in MSBs and the results obtained, the influence of the stiffness ratio of double beams on the internal force distribution was investigated via FEA and theoretical calculation. Some recommendations for the design were also presented. Finally, the manner in which stiffness characteristics of the inter-module connection is considered accurately in the structural design was discussed and the conceptual design procedure of the inter-module connection was given accordingly. The results obtained could serve as a reference for the design of mid-rise MSBs.

Computational and experimental analyses of martensitic transformation propagation in shape memory alloys

This study investigates the creation of heterogeneous martensitic transformation field in shape memory alloy structures with geometrical nonuniformity through experiments and finite element computational analysis. Geometrically graded superelastic NiTi thin plates with series and parallel design configurations with respect to the loading direction have been created. The nonuniform transformation evolutions within these structures are presented by thermal images captured by an infrared camera during tensile experimentation. It is found that the transformation propagation is along the loading direction in a sample with the series design configuration unlike that in a sample with the parallel design configuration. Also, the geometrically graded structures exhibit stress gradient over stress-induced transformation. The transformation propagation and the deformation behaviour of these structures are presented by numerical modelling which is in good agreement with experimental data.

Fluid structure interactions modelling in vented lean deflagrations

The standard 20 ft ISO containers are studied both experimentally and numerically with model obstacles to ascertain the peak overpressures generated in case of an accidental fast deflagrations. Apart from overpressure its often important to know the maximum deflections of the enclosures to examine the structural integrity. The container walls are not rigid; they not only contribute through acoustic response to the pressure waves but also through structural resonance response to the generated overpressures, to capture these effects its necessary to do the Fluid Structure Interaction (FSI) or in simple terms the coupled Computational Fluid Dynamics (CFD) and Finite element analysis (FE) simulations. Alternatively, the structural response can be coupled to CFD simulation in either one-way or two-way interactions to reduce the associated computation efforts. Numerical simulations have been conducted with a pseudo two-way coupled CFD & FSI, to aid our understanding of the combination of various factor contributing for the generation of overpressures using an in-house solver developed based on open source CFD code OpenFOAM named as HyFOAM. The CFD solver solves the compressible Navier-stokes equations along with the spring-mass-damper system's single degree of freedom motion equation for coupled fluid structure interactions. The turbulent flame deflagrations are modelled using the flame area combustion model, the necessary modification are incorporated to governing equations to include the dominant flame instabilities present during the vented deflagration process. For lean hydrogen mixtures the Lewis number effects are important hence suitable modelling improvements are added to the combustion model. The numerical results are validated against the recent experiments conducted at Gexcon, Norway as part of the HySEA project supported by the Fuel Cells and Hydrogen 2 Joint Undertaking (FCHJU) under the Horizon 2020 Framework Programme for Research and Innovation. Numerical predictions of CFD and FSI coupled, are assessed against the experimental results to study the contributing factors affecting the generated overpressure with in the ISO containers in view to overall improve the numerical predictions.

Integrated circuit failure analysis and reliability prediction based on physics of failure

It is difficult to obtain the failure data of actual prototype to support reliability analysis because the development stage has been shortened drastically and the traditional reliability tests are gradually unaffordable under the market pressure. In this paper, a reliability simulation based on physics of failure is proposed to test the reliability of a CPU circuit board, in which the digital model of the circuit board, Computational Fluid Dynamics (CFD) method and Finite Element Analysis (FEA) are used synthetically to perform the analysis. The failure points of the circuit board are analyzed and the failure distribution is obtained by fitting the simulation data, so the life can be predicted by Monte Carlo simulation. Moreover, some improvement measures and suggestions can be supplied based on the failure mechanism of the circuit board to improve its inherent reliability. Comparing with the traditional methods, the method of reliability simulation prediction based on physics of failure has the advantages of fast, accurate, economical, efficient and can identify more detailed failure information.

Biomechanical Analysis of the Forces Exerted during Different Occlusion Conditions following Bilateral Sagittal Split Osteotomy Treatment for Mandibular Deficiency.

The bilateral sagittal split osteotomy (BSSO) technique is commonly used to correct mandibular deficiency. If the patient is exposed to excessive external forces after the procedure, occlusal changes or nonunion may occur. However, previous studies only focused on single external forces on the mandible and did not conduct relevant research on the forces exerted by different occlusion conditions. The main purpose of this study was to use finite element analysis methods to determine the biomechanics of four common occlusion conditions after BSSO surgical treatment. This study constructed a finite element analysis computer model of a miniplate implanted in the lower jaw. The structure of the model consisted of the mandible, miniplate, and screws. In addition, external forces were applied to the superficial masseter, deep masseter, medial pterygoid, anterior temporalis, middle temporalis, and posterior temporalis muscles to simulate the incisal clench, intercuspal position (ICP), right unilateral molar clench (RMOL), and right group function occlusion conditions. Subsequently, this study observed the effects of these conditions on the miniplate, screws, and mandible, including the von Mises stress values. The results showed that all of the different occlusion conditions that this study evaluated placed high stress on the miniplate. In the ICP and RMOL occlusion conditions, the overall mandibular structure experienced very high stress. The screw on the proximal segment near the bone gap experienced high stress, as did the screw on the buccal side. According to the present analysis, although the data were not directly obtained from clinical practice, the finite element analysis could evaluate the trend of results under different external forces. The result of this study recommended that patients without intermaxillary fixation avoid the ICP and RMOL occlusion conditions. It can be used as a pilot study in the future for providing clinicians more information on the biomechanics of implantation.

Improved Fuzzy-Based Taguchi Method for Multi-Objective Optimization of Direct-Drive Permanent Magnet Synchronous Motors

The original fuzzy-based Taguchi method is restricted with the number of objective functions. Aiming to solve this problem, this paper describes an improved fuzzy-based Taguchi method (IFBTM) coupled with finite-element analysis (FEA) for the multi-objective optimization of direct-drive permanent magnet synchronous motors (DDPMSMs). To reduce the number of dimensions in the fuzzy rule base, the IFBTM uses a factor stratification method to establish multilayer fuzzy rule base. The fuzzy inference system with multilayer fuzzy rule base is introduced to translate the multiple optimization objectives to a single objective. After optimal selection analysis, the best combination of motor structure factors is obtained with small FEA computation. Finally, the performances of DDPMSM are analyzed and compared with those of IFBTM. The results certify the superiority and validity of IFBTM.

Numerical and experimental investigation on limit load of elbow with local thinning area

In this paper, the previous research on the limit load of the pipe is summarized, and the methodology on the limit load of the pipe, including theoretical calculation, finite element analysis (FEA), and experimental validation. Besides, to present the factors of limit load, case studies are showed herein. Currently, several 90° elbows with straight pipe with local defect as the research object. According to the Elastic-plasticity theory, pipes with the same boundary conditions under various defect positions, sizes, were calculated and analyzed by means of finite element (FE) simulation to obtain the limit load to compare the results from FEA and theoretical calculations. Furthermore, a series of complete hydrostatic pressure blasting test and pre-experimental test plans were proposed. The agreement is achieved between test and FEA. The results can point out the direction of research on the limit load carrying capacity of pipes, find the main factors affecting the carrying capacity of pipes, and provide scientific guidance for the safe operation of pipes.

Biomechanical analysis of the computer-assisted internal fixation of a femoral neck fracture

The number and spatial configuration of the screws will affect the stability and prognosis of the fractures. In our study, we assessed the biomechanical effects of the double-head cannulated compression screw (DhCCS) and ordinary cannulated compression screw (OCCS) for the treatment of femoral neck fractures by using computer finite element analysis. The original digital imaging and communications in medicine (DICOM)data of a proximal femur were imported into Materialise's interactive medical image control system (MIMICS)software for modeling. Both DhCCS and OCCS 3D-models were obtained by using the 3D scan technique. Using the fracture model and internal fixation assembly model with an inverted triangle, two horizontal and vertical distribution were established in UG software. Next, the displacement and stress distribution were calculated in ANSYS software. The displacement value of the femoral head in the DhCCS group was smaller than that in the OCCS group, and the displacement value in the two horizontal groups was smaller than that in the vertical group. The stress distribution in the DhCCS group was concentrated on the screw rod at the fracture block and thread end, while only at the fracture block in the OCCS group. The stress in the horizontal group was more dispersed on the screws than that in the vertical group. DhCCS has reliable stability for the fixation of femoral neck fractures and applied in the clinical work and 2 horizontal fixation can be used when two screws are selected.

The evaluation of the relation between dynamic hip screw positions and its failure in unstable femur fractures

ABSTRACT In this study, effects of the Dynamic Hip Screw (DHS) positions on its failure are investigated in unstable femur fracture using Finite Element Analysis (FEA). The failures of DHS were emphasised in the latest several case studies. In order to create 3D computerised models, the unstable femur fractures were generated in the trochanteric region of the femur obtained from Computerised Tomography Images. The DHS model in 3D CAD form was placed in nine different positions into the fractured femur. Two different Tip-Apex distances (TAD) (20 and 25 mm) were used for each DHS positions. In the FEA, muscles and body forces were applied to the femur according to the maximum value based on regular walking. The best position and TAD value were determined according to the von Mises stresses calculated on the DHS. The FEA calculation showed that the minimum stress value was obtained on the DHS placed in the middle and superior regions of femur head. Higher TAD value (25 mm) were decrease the von Mises stresses of the DHS. In conclusion, the calculated results suggest that the best DHS position is in the spherical centre of the femur head considering the failures of both femur and DHS together.

Guest Editorial: Special Issue on Computational Intelligence in Data-Driven Optimization

The papers in this special section focus on the use of computational intelligence in data driven optimization applications. Most evolutionary algorithms and other meta-heuristic search methods typically assume that there are explicit objective functions available for fitness evaluations. In the real world, such explicit objective functions may not exist in many cases. Instead, computationally very intensive numerical simulations, such as computational fluid dynamic simulations or finite element analysis, must be conducted. In many process industry optimization problems, no analytical mathematical models exist for describing the functional relationship between the final quality of the product and the decision variables, such as temperature and humidity. Thus, only historical experimental data can be used for optimization. There are also cases where only factual data can be collected. The articles in this section aim present the most recent advances in the use of computational intelligence, in particular methodologies integrating evolutionary algorithms and other metaheuristic search methods with machine learning and neural networks, for on-line or off-line data-driven real-world optimization problems.

Reliability Evaluation of SiC Power Module With Sintered Ag Die Attach and Stress-Relaxation Structure

Silicon carbide (SiC) power modules with Ag sinter-bonding die attach were designed on the basis of thermal stress analysis for reliable high-temperature operations. Both the finite-element analysis (FEA) simulations and preliminary experiments confirmed that inserting the direct-bonded-copper (DBC) substrates can effectively reduce the maximum thermal stress in the module. A prototype SiC power module using sintered Ag die attach with a DBC substrate was designed and fabricated. The modules exhibited excellent durability in power cycling between 65 °C and 250 °C up to 20 000 cycles. FEA calculations of cumulative thermal strain and stress distributions adequately predicted the initial cracking position in the specimens after prolonged power cycles, observed by scanning electron microscopy.

A universal elastic-plastic model correlating load-displacement relation and constitutive parameters for typical testing components

Abstract A universal elastic-plastic model (UEM) to describe the nonlinear relation among energy, load, displacement and Hollomon constitutive parameters is proposed for various structural components (SCs) by equivalent energy principle (EEP). The model contains only four parameters related to the effective volume of deformed region and the equivalent strain at energy center. A simple approach to determine these parameters is introduced by five times FEA (finite element analysis) calculations. Then, a systematical verification is conducted with both FEA and some experiments. For pure torsion SC, three bending SCs, two indentation SCs, ring compression SC, compact tension SC and small punch test SC, the universal model predicted elastic-plastic load-displacement curves are excellently consistent with the FEA results. Reversely, it can be applied in predicting the Hollomon parameters of materials when the load-displacement curves are known from FEA or experiments.