Purpose Finite Element Analysis Research Articles

Real-Time Hybrid Simulation Using Nonlinear Autoregressive with Exogenous Input Model through Data-Driven Arbitrary Polynomial Chaos Surrogate

The current practice of real-time hybrid simulation (RTHS) often requires specialized finite element programs for computational modeling of the analytical substructures. Considering the limited nonlinear modeling capacity or the increasing computation cost for complex modeling, surrogate models of the analytical substructure provide novel alternatives for RTHS to avoid finite element analysis with fast computation. This study explores the use of arbitrary polynomial chaos expansion (APC) and nonlinear autoregressive with exogenous input (NARX) model to emulate the dynamic behavior of analytical substructures in RTHS. The NARX model training can be conducted numerically in an off-line mode using existing general purpose finite element analysis software, and its implementation presents minimum computational demands on the RTHS equipment. RTHS of a single-degree-of-freedom structure with a self-centering viscous damper is conducted as proof of concept to experimentally demonstrate the effectiveness and superiority of the proposed APC-NARX-based approach. The APC is further compared with other metamodeling techniques including polynomial chaos expansion (PCE) and Kriging to surrogate NARX model coefficients to account for ground motion uncertainties in RTHS. It is demonstrated that APC-NARX modeling with optimal order enables better accuracy of RTHS results than those of Kriging- and PCE-NARX.

Modified scarf osteotomy for hallux valgus: From a finite element model to clinical results.

Finite element (FE) analysis and clinical follow-up were used to evaluate the efficacy of modified scarf osteotomy for moderate-to-severe hallux valgus (HV). We retrospectively evaluated 42 patients (44 feet) who underwent modified rotational scarf osteotomy for moderate-to-severe HV at our institution between January 2010 and January 2019. Radiological indicators and subjective scores were recorded at different time points. To compare the results and elemental characteristics, a FE model of the metatarsophalangeal (MTP) joint that included anatomically realistic geometrical and structural characteristics was built. The biomechanical features and correction differences in dynamic loads as well as the incidence of troughing were estimated. Both the hallux valgus angle (HVA) and intermetatarsal angle (IMA) showed significant improvement 6weeks postoperatively (p < 0.05); additionally, the HVA increased from 6weeks postoperatively to the last follow-up, while the IMA showed no significant changes (p > 0.05). The subjective scores significantly improved from the preoperative period to the last follow-up. The percentages of troughing and recurrence were remarkably low in our pilot study because of the innate stability of the modified rotated fixation. Our preliminary findings suggest that modified rotational scarf osteotomy offers sufficient stability, correct HV deformity effectively, and good clinical outcomes for moderate to severe HV.

Biomechanical Effects of Different Miniplate Thicknesses and Fixation Methods Applied in BSSO Surgery Under Two Occlusal Conditions

PurposeFinite element analysis (FEA) was used to evaluate the effects of different thicknesses, numbers, and positions of the miniplate applied in bilateral sagittal split osteotomy (BSSO) under two occlusal conditions.MethodsAn FEA model of the mandibles was constructed and combined with different thicknesses (0.6 or 1 mm), number (one or two), positions (upper or lower) of a miniplate and was divided into six models. In addition, external forces were applied to the muscles to simulate the intercuspal position (ICP) and right unilateral molar clench. This study used the reaction force of the temporomandibular joints and the stress of the mandible as observation indexes.ResultsThe results of this study show that, under ICP, the 0.6 mm lower model generated greater TMJ force reaction compared to the 0.6 mm upper model. The same trend was seen in the 1 mm lower model compared to the 1 mm upper model. Regarding the stress of the bone on the screw-implanted sites, under ICP, screw 10 showed greater stress than screw 2, and screw 11 showed greater stress than screw 3. The stress values of the miniplates showed, under ICP, point 1-c was greater than point 3-c, and point 1-b was greater than point 3-b.ConclusionIn the case of BSSO mandibular advancement surgery, implanting the miniplate at the upper position can reduce the force on the TMJ and the stress on the distal segment of the mandible. The miniplate can also resist the tensile stress more effectively. In addition, implanting two miniplates with thinner sizes may be an alternative in clinical practice.

周期的な凹凸表面上を摺動するゴムの摩擦係数の解析

The friction coefficient between tire tread rubber and road surface is an important property for tire performances and the prediction of the friction coefficient is also important．In this study, the general purpose finite element analysis software “Abaqus” is used to obtain the hysteresis friction behavior between periodic rigid surfaces and rubber models in which hyperelastic and viscoelastic properties are taken into account．A multi-scale analysis is used to calculate the friction coefficients of each scale．The contact load between a road surface and a rubber model is determined by the average contact pressure calculated by a larger scale model analysis．As the model scale is smaller, the deformation of the rubber model and the friction coefficient become larger. The maximum friction coefficient is about 0.8 in λ = 1×10-4 mm scale model.

Local and global tensile deformation behavior of AA7075 sheet material at 673oK and different strain rates

The constitutive behavior of AA7075 aluminum sheet like other metallic sheet materials is highly temperature and strain rate dependent at elevated temperatures. The uniaxial tensile test is commonly employed to characterize the temperature and strain rate dependent deformation behavior. However, the traditional uniaxial tensile testing and data analysis procedure treats the gauge length of sample as a uniformly-deforming (or homogeneous) region. This may not be accurate due to early localized deformation that is initiated in the gauge region at elevated temperatures. Treating the post-necking hardening behavior of uniaxial tensile samples has been an important task to expand the effective range of true stress-true strain curves at elevated temperatures for metal and alloys. To explore this issue, uniaxial tensile tests on AA7075-F sheets (with as-fabricated temper) were conducted at 673o K and four different test speeds. The test procedure also utilized an on-line 2-D digital image correlation (DIC) system method to obtain full-field strain map from the deforming gauge region of the test specimen. Local stress-strain curves at different points along the gauge length were then calculated based on the recorded local in-plane principal stress and strain values from macroscopic force data and current cross-section of the specimen at the chosen points. In this manner, the DIC strain analysis not only enabled the determination of stress-strain response but also the determination of strain rates at specific chosen points along the gauge length. The local stress-strain curves revealed significant deviation at an earlier stage of deformation from the global (or macroscopic) stress-strain response based on the entire gauge region. To estimate the constitutive behavior at different strain rates, a correction method to traditional stress-strain curves was applied to obtain a family of stress-strain curves at different constant strain rates based on the local stress-strain curves. Additionally, the material deformation response in the stress, strain and strain rate space in the 3D Cartesian coordinate system was also constructed for tests conducted at different stretching speeds. Further, a verification test was conducted to see if the above methodology could provide an accurate estimation of local deformation behavior of AA7075 sheet. Furthermore, the above experimental method was also coupled with the Gurson-Tvergarrd-Needleman (GTN) ductile void damage model and incorporated into ABAQUS-Explicit general purpose finite element (FE) analysis code via a VUMAT material subroutine. Good agreement was obtained for both the local and global stress-strain curves between the FE test simulation and experimental stress-strain results. The proposed experimental methodology and the resulting stress-strain-strain rate behavior is believed to be applicable in describing the strain rate-dependent constitutive behavior of AA7075-F sheet metals at 673o K.

Static structural and thermal analysis of disc brake pad model

This paper attempts to present a study of the automotive disk brake’s thermo-mechanical behaviour during the braking period using the Static Structural and Transient Thermal analysis for vehicle disk brake pad system using finite elemental analysis. In this work Thermal and static analysis was performed on solid and ventilated disc for two configurations of pads using ANSYS 15. Two pad Profiles with pure and single slot along with both discs have been studied. The analysis is conducted on the model that lacks thermal properties first. It is predicted for structural performance such as deformation and von-mises stress. After that, with the introduction of heat flux, convection and adiabetic components, thermo-mechanical analysis is performed on the same model. The estimate results of temperature distribution, total deformation and von-mises stress are presented. The software tools CATIA and ANSYS Workbench have been selected for modelling and analysis. CATIA is a widely used 3D modelling technology in the design process. ANSYS is a software package for general purpose finite element analysis (FEA). The outcome of this investigation assists brake engineers in choosing appropriate research to determine the disk brake assembly in structural and contact behaviour.

FLEXURAL BEHAVIOR OF HYBRID FRP-CONCRETE BRIDGE DECKS

The main aim of this study is to investigate the behaviour of hybrid FRP-concrete decks. The hybrid FRP-concrete bridge systems consisting of different FRP cell units available on the market such as trapezoidal, triangular, honeycomb, rectangular with alternating diagonal, half-depth trapezoidal, hexagonal and arch cell units were computationally compared and examined using the finite element (FE) analysis to decide the most appropriate FRP composite deck for bridge systems. Design criteria such as the deflections were considered in selecting the most effective unit system. Different FRP bridge deck panels were analysed under static loading representing the standard European truck wheel. The finite element analysis of bridge deck systems was performed using a general purpose finite element analysis package ABAQUS, and the behaviour of these systems was then be compared in terms of stiffness and strength criteria.The results showed that Delta, Super and ASSET hybrid decks are stiffer than other deck systems. The results from FEA approach also indicated that the layer of concrete on the top surface of bridge deck reduces the vertical displacement of FRP bridge systems approximately 60%.

Analysis of 3D linear elastic masonry-like structures through the API of a finite element software

A new numerical procedure is presented to perform the analysis of three-dimensional linear elastic no-tension structures exploiting the application programming interface of a general purpose finite element analysis software. Masonry is replaced by an equivalent orthotropic material with spatially varying elastic properties and negligible stiffness in the case of cracking strain. A non-incremental algorithm is implemented to define the distribution of the equivalent material, minimizing the strain energy so as to achieve a compression-only state of stress for any given compatible load. Applications are shown for masonry-like solids of general shape visualizing load paths in walls subject to dead loads and out-of-plane live loads, circular domes under self-weight and a groin vault acted upon by both vertical and horizontal seismic loading.

Two-Dimensional Model Analysis for Extended Finite Element Method(XFEM) Verification of General Purpose Finite Element Analysis Program

범용유한요소프로그램인 Abaqus의 확장유한요소법(XFEM)의 사용성 검증을 위하여 2차원 모델에 적용하여 수치해석을 수행하였다. 기존의 연구에 많이 사용되었던 응집요소(cohesive element) 모델은 균열 경로를 예측하고 요소를 삽입하여야 하는 단점 때문에 실제 균열을 모사하는데 한계가 있다. 이러한 이유로 응력의 방향성 및 특이성을 바탕으로 균열의 경로를 예측하는 확장유한요소법(XFEM)이 균열 해석에 있어서 더 발전된 방법으로 이용되어 왔다. 이번 연구에서는 균열의 경로 가 자명한 2차원 모델에 사용하여 응집요소해석과 XFEM에 응집요소의 물성을 적용한 해석을 비교하고 XFEM 적용의 타 당성을 확인하였다. 수치해석으로 균열 발생 직전의 응력분포 및 응력 특이성을 확인하고 실제 균열 발생경로와의 비교를 한다. 본 연구를 바탕으로 몇 가지의 한계를 극복하면 실제 복잡한 모델의 실제 균열진전해석을 수행하여 균열을 모사할 수 있을 것으로 기대된다.

Modeling ablation of laminated composites: A novel manual mesh moving finite element analysis procedure with ABAQUS

The recent improvements of the commercial, general purpose Finite Element Analysis (FEA) software have allowed them to be used for modeling ablation problems. ABAQUS for example, provides a user-subroutine UMESHMOTION along with the Arbitrary Lagrangian-Eulerian (ALE) adaptive remesh algorithm that enable the users to couple the heat transfer with the progressive surface recession (i.e., ablation). However, such a numerical capability is limited to model ablation problems when the ablation front (i.e., receding surface) is confined within a single material domain (e.g., homogenous material). For ablation problems when the ablation front proceeds from one material domain to another (e.g., laminated composite materials that consist of multiple laminate layers with different material orientations), such a numerical capability is insufficient, since the mesh is not allowed to flow from one material domain to another when the UMESHMOTION subroutine is used. In this paper, a novel computational procedure that sequentially performs the general heat transfer analysis and the general static analysis in ABAQUS, is proposed enabling the capability of ABAQUS for modeling ablation of laminated composites. The proposed procedure is verified by comparing the predictions of temperature and ablation histories of a two-dimensional isotropic panel (i.e., with single material domain) with those obtained using the traditional UMESHMOTION+ALE method. In addition, a case study of applying the proposed procedure to predict the thermal and ablation response of a laminated carbon fiber reinforced epoxy matrix (CFRP) composite panel subjected to a high-intensity and short-duration radiative heat flux is demonstrated.

Nonlinear buckling analysis of 2-D cold-formed steel simple cross-aisle storage rack frames

Industrial storage racks are among the most important structures made from cold-formed steel sections. They are widely used due to the increasing need for rational space utilization in warehouses, and other facilities used to store goods. Pallet rack is a material handling, storage aid system designed to store materials on pallets. Although there are many varieties of pallet racking, all types allow for the storage of palletized materials in horizontal rows with multiple levels. Rack systems are widely used in warehouses where they are loaded with valuable goods. The cold-formed steel columns usually have open cross-sections and are thin walled, making them vulnerable to torsional-flexural buckling and local buckling. The loss of goods may be greater than the total cost of the rack on which the goods are stored, which can indirectly affect the owner. Therefore, understanding the stability of rack structures is very important. This paper deals with numerical linear and nonlinear buckling analysis of 2-D cold-formed steel simple cross-aisle storage rack frames. The main focus of the study is to ascertain the stability of 2-D frames of a pallet racking system. With this objective, a pallet racking system with cold-formed steel sections is simulated by three-dimensional models using shell elements in ABAQUS, a general purpose finite element analysis software. Linear and nonlinear buckling analyses are carried out on these frames. Results are obtained from finite element analysis of frames with 12 types of column sections. Spacer bars and channel stiffeners are used to improve the torsional strength of original open cross sections. Results show that spacer bars and channel stiffeners are very effective in enhancing the strength of cold-formed steel pallet rack structures.

Numerical and experimental investigation of central cavity formation in aluminum during forward extrusion process

In the presented paper central cavity formation during the forward extrusion of commercially pure aluminum was investigated. For this purpose finite element analysis was utilized for simulation of this defect. The experimental tests were carried out on commercially pure aluminum. A good agreement between finite element simulations and experimental tests verified the adaptability of finite element simulations with the real process conditions. Taguchi method was performed for classifying the simulations regarding to consider synergistic parameters. The parameters include reduction of area, friction coefficient and die angle. Critical thickness, the representative waste material, was presented as a new criterion for optimizing the parametric study. By utilizing the Analyze Taguchi design, critical thickness was optimized and the effect of each parameter was recognized for different levels. In addition, the best levels with the minimum waste material were gained in which friction coefficient, die angle and reduction of area were 0.2, 5° and 20%, respectively. Also the amount of waste material was forecasted by just about 2% errors without FEA by Taguchi method.

English

This paper reports on the application of a special purpose finite element analysis tool that combines augmented finite element methodologies (AFEM) and cohesive zone model (CZM) methods to simulate initiation and propagation of both cohesive and adhesive cracks. The constitutive behaviour of an aluminium/silicon carbide metal matrix composite was predicted and compared with experimental data as an example of a material system controlled by cohesive cracks. The simulation allowed to determine the strain level, at which particle fracture was initiated and illustrates how the overall material response is dominated by particle fracture beyond that strain level. The effects of silica filler particles on the lifetime of polyurethane matrix aircraft coating systems were investigated in a second example in which adhesive cracks at the filler/matrix interface are a dominant failure mechanism. The influence of particle volume fraction and particle/matrix interface adhesion strength on coating lifetime predictions were investigated and the results show that low filler particle volume fraction and high interface adhesion strength improve coating durability. In general, the paper demonstrates the potential of combined AFEM and CZM micromechanical damage simulation to gain improved understanding of damage mechanisms in heterogeneous materials and to support analysis and design of advanced material systems. Key words: Augmented finite element method, phantom node method, cohesive zone modelling, metal matrix composite, aircraft coatings.

A methodology to consider local material properties in structural optimization

We propose a finite element methodology to consider local material properties for large cast iron components in shape optimization. We found that considering local strength instead of uniform strength within shape optimization brings to different results in terms of safety-cost balance for the same component. It is well known that local mechanical properties of large cast iron components are defined by their microstructure and defects, which locally affect the strength of the components. Considering or not local mechanical properties can dramatically change a component reliability evaluation during its design. Since a typical industrial aim for shape optimization is trying to get the optimal solution in terms of component quality and cost, considering local material properties is even more important than in traditional design process where no optimization techniques are used. We compute solidification process parameters via finite element solidification analysis, and then we exploit experimental correlation between these parameters and ultimate tensile strength to evaluate the local reliability of the finished component under its static loading conditions. We believe that this methodology represents an opportunity to better design casting components when mechanical properties are deeply affected by their production process as described in the provided examples. In these examples, we wanted to minimize casting cost constrained by a target reliability and we get component cost reduction by considering local material properties. Future research will address the problem of using dedicated casting simulation software instead of general purpose finite element analysis software to compute solidification analysis and then introducing fatigue analysis and correlation between fatigue material properties and casting process output variables.

Strength Analysis of Mark III Cargo Containment System using Anisotropic Failure Criteria

Membrane type Mark III cargo containment system (CCS) is considered in this study to investigate its strength capability under applied loads due to liquefied natural gas (LNG) cargo. A rectangular plated structure supported by inner hull structure is exemplified from Mark III CCS according to classification society's guidance and it is assumed as multi-layered structure by stacking plywood, triplex, reinforced polyurethane (PU) foam and series of mastic upon inner hull structure. Commercially available general purpose finite element analysis package is used to have reliable FE models of Mark III CCS plate. The FE models and anisotropic failure criteria such as maximum stress, Hoffman, Hill, Tsai-Wu and Hashin taking into account the direction dependent material properties of Mark III CCS plate components and their material properties considering a wide variation of temperature due to the nature of LNG together form the strength analysis procedure of Mark III CCS plate. Strength capability of Mark III CCS plate is understood by its initial failure and post-initial failure states. Results are represented in terms of failure loads and locations when initial failure and post-initial failures are occurred respectively. From the results the basic design information of Mark III CCS plate is given.

Design optimization of spot welded structures to attain maximum strength

This study presents design optimization of spot welded structures to attain maximum strength by using the Nelder-Mead (Simplex) method. It is the main idea of the algorithm that the simulation run is executed several times to satisfy predefined convergence criteria and every run uses the starting points of the previous configurations. The material and size of the sheet plates are the pre-assigned parameters which do not change in the optimization cycle. Locations of the spot welds, on the other hand, are chosen to be design variables. In order to calculate the objective function, which is the maximum equivalent stress, ANSYS, general purpose finite element analysis software, is used. To obtain global optimum locations of spot welds a methodology is proposed by modifying the Nelder-Mead (Simplex) method. The procedure is applied to a number of representative problems to demonstrate the validity and effectiveness of the proposed method. It is shown that it is possible to obtain the global optimum values without stacking local minimum ones by using proposed methodology.

Strength Analysis for the Plate System of the Mark ⅢCargo Containment

Abstract Mark Ⅲ CCS plate is considered in this paper to perform its strength assessment. Mark Ⅲ CCS plate is designed and constructed by stacking various non-metallic engineering materials such as plywood, triplex and reinforced PU foam that are supported by series of mastic upon inner steel hull structure. From the viewpoint of structural analysis, this plated structure is treated as a laminated anisotropic structure. Commercially available general purpose finite element analysis programs such as MSC PATRAN and MARC are used to develop the finite element (FE) model of the Mark Ⅲ CCS plate. Because of the characteristics of LNG cargo that the Mark Ⅲ CCS plate deals with, it is subjected to a wide range of temperature variations, i.e. about -163℃ to 20℃. Different material properties of the Mark Ⅲ CCS plate at these temperature levels are considered in the FE model. Using the developed FE model, strength assessment procedure is developed incorporating various anisotropic failure criteria such as Hashin, Hill, Hoffman, Maximum stress and Tsai-Wu. The strength assessment is performed within the initial failure state of the Mark Ⅲ CCS plate and, as a result, failure details such as failure locations and loads are identified.

Nonlinear finite element analysis of masonry wall strengthened with CFRP strips

In many experimental studies, it has been proved that unreinforced masonry (URM) brick walls have high strength against lateral forces acting in plane. However, out-of-plane strength of URM brick walls against lateral forces has found to be quite low. According to the experiences that were obtained from the major earthquakes, the low out-of-plane performance of URM brick walls resulted in excessive loss of human lives during an earthquake, hence the strengthening of URM brick walls with CFRP strips has been appeared to be a very important subject. However, very limited literature has been found. Especially, the data obtained from experimental studies must be increased for the true understanding of the behavior of strengthened brick walls under out-of-plane lateral forces. However, in most cases, this procedure required large number of expensive experiments. At this stage, numerical analysis can be an appropriate choice, thus in this paper a finite element model is presented for modeling URM brick walls that are strengthened with CFRP strips. The numerical results are compared with the experimental ones and consistent results are obtained from the finite element model. General purpose finite element analysis software ANSYS is used throughout this study. Contact elements are used along the masonry wall–CFRP strip interfaces for the investigation of the stress distribution and load – strain behavior.

Natural vibration analysis of vertical rectangular plates and stiffened panels in contact with fluid on one side

This article presents a simple and efficient procedure for the natural vibration analysis of rectangular plates and stiffened panels in contact with fluid on one side. The assumed mode method is applied, where the natural frequencies and mode shapes are obtained by solving an eigenvalue problem of a multi-degree-of-freedom system matrix equation derived by using Lagrange’s equation of motion. The Mindlin thick plate theory is applied for a plate, and in the case of stiffened panels, the effect of framing is taken into account by adding its strain and kinetic energies to the corresponding plate energies. Potential flow theory assumptions are adopted for the fluid, and free surface waves are ignored. The fluid velocity potential is derived from the boundary conditions for the fluid and structure and is utilized for the calculation of added mass using the assumed modes. The applicability and accuracy of the developed procedure are illustrated with several numerical examples using a developed in-house code. A comparison of the results with those obtained by general purpose finite element analysis software is provided, where very good agreement is achieved.

Computational Methods for Inclined Cracks in Orthotropic Functionally Graded Materials Under Thermal Stresses

This article sets forth two different computational methods developed to evaluate fracture parameters for inclined cracks lying in orthotropic functionally graded materials, that are under the effect of thermal stresses. The first method is based on the J k -integral, whereas the second entails the use of the J 1-integral and the asymptotic displacement fields. The procedures introduced are implemented by means of the finite element method and integrated into a general purpose finite element analysis software. Numerical results are generated for an inclined edge crack in an orthotropic functionally graded layer subjected to steady-state thermal stresses. Comparisons of the mixed-mode stress intensity factors computed by the use of the proposed methods to those calculated by the displacement correlation technique point out that both approaches lead to numerical results of high accuracy. Further results are provided in order to illustrate the influences of inclination angle, material property gradation, and crack length upon the thermal fracture parameters.