Types Of Finite Element Models Research Articles

Thermomechanical behavior of lattice structures: An analytical, numerical, and experimental study

In this study, thermomechanical behavior of regular porous materials is studied using analytical, numerical, and experimental approaches. Analytical relationships for octahedral lattice structure have been obtained based on Euler-Bernoulli beam theory. Three types of finite element models, two based on beam elements and one based on volumetric elements, are made. Additive manufacturing technique is also used to fabricate lattice structures with different relative densities. The manufactured samples are heated to a certain temperature in a closed chamber, and the displacements are measured and compared to their analytical and numerical counterparts. Based on the results, the analytical, numerical, and experimental results are in excellent agreement with each other. The methodologies introduced in this study would be beneficial for further studies on porous materials and lattice structure with other topologies and higher degrees of freedom.

Cartilage thickness mismatches in patellar osteochondral allograft transplants affect local cartilage stresses.

Osteochondral allograft implantation is a form of cartilage transplant in which a cylindrical graft of cartilage and subchondral bone from a donor is implanted into a patient's prepared articular defect site. No standard exists for matching the cartilage thickness of the donor and recipient. The goal of this study was to use finite element (FE)analysis to identify the effect of cartilage thickness mismatches between donor and recipient cartilage on cartilage stresses in patellar transplants. Two types of FE models were used: patient-specific 3D models and simplified 2D models. 3D models highlighted which geometric features produced high-stress regions in the patellar cartilage and provided ranges for the parameter sweeps that were conducted with 2D models. 2D models revealed that larger thickness mismatches, thicker recipient cartilage, and a donor-to-recipient cartilage thickness ratio (DRCR) < 1 led to higher stresses at the interface between the donor and recipient cartilage. A surface angle between the donor-recipient cartilage interface and cartilage surface normal near the graft boundary increased stresses when DRCR > 1, with the largest increaseobserved for an angle of 15°. A surface angle decreased stresses when DRCR < 1. Clinical Significance: This study highlights a potential mechanism to explain the high rates of failure of patellar OCAs. Additionally, the relationship between geometric features and stresses explored in this study led to a hypothetical scoring system that indicates which transplanted patellar grafts may have a higher risk of failure.

Structural connection with predetermined discrete variable friction forces

This paper presents a simple and practical structural connection able to develop predetermined discrete variable friction forces at target design displacement levels. The innovative connection is termed Modified Friction Device (Modified FD). Modified FDs are used to transfer the seismic induced horizontal forces from the floors to the core wall seismic force-resisting system of a building. The schematics of the physical embodiment of the Modified FD are presented. The components and the assembly of the Modified FD are discussed. The mechanics of the Modified FD are explained. Results from static structural analyses of two types of finite element models of the Modified FD are presented. The first model is developed using solid finite elements and it is used to assess the expected kinematics and the expected force-displacement response of the Modified FD. The second model is developed using a truss finite element and it can be used to efficiently simulate the force-displacement response of the Modified FD in numerical earthquake simulations of structural systems. The force-displacement response of the Modified FD computed using a numerical earthquake simulation of an eighteen-story reinforced concrete core wall building model is presented. The seismic response of the building model with Modified FDs is compared with the seismic response of the building model with monolithic connections and the seismic response of the building model with friction devices with constant friction forces. The results presented in this paper show that it is possible to develop a simple and practical structural connection with predetermined discrete variable force-displacement response to limit the seismic induced horizontal forces transferred between the floors of the flexible gravity load resisting system and the core wall piers in high-performance earthquake resilient buildings.

The role of torsional stress in the development of subchondral insufficiency fracture of the femoral head: A finite element model analysis

BackgroundSubchondral insufficiency fracture of the femoral head generally occurs without evidence of trauma or with a history of minor trauma. Insufficient bone quality is considered one cause; however, the detailed mechanism of fracture development at the subchondral area (SA) is not understood. The aim of this study was to clarify the directions of force that cause subchondral fracture using finite element model analysis. MethodsTwo types of finite element models were generated from the CT data of femurs obtained from three individuals without osteoporosis (normal models) and another three with osteoporosis (osteoporosis models). Three directions of force, including compressive, shearing, and torsional, were applied to the femoral head. The distribution of von Mises stress (Mises stress) was evaluated at the SA, principal compressive trabeculae (PC), and principal tensile trabeculae. ResultsUnder compressive force, the mean Mises stress value was greatest at the PC in both the normal and osteoporosis models. Under shearing force, the mean Mises stress value tended to be greatest at the SA in the normal model and at the PC in the osteoporosis model. Under torsional force, the mean Mises stress value was greatest at the SA in both types of models. ConclusionsThe torsional force showed the greatest Mises stress at the SA in both the normal and osteoporosis models, suggesting the importance of torsion as a possible force responsible for subchondral insufficiency fracture development.

Actual work’s numerical analysis for support joint of vertical cylindrical tank

The article describes the actual work’s numerical analysis for unit joining walls to the bottom of vertical cylindrical tank of 50 thousand m3. Having analyzed the relevant stress-strain state of unit joining walls to the bottom vertical cylindrical tanks for different types of finite element model. Research carried out for the tank with a wall on a rigid base. Features of the unit joining walls to the bottom should include the effect of various loads: static, dynamic, cyclic, corresponding to normal operation. The load on the pressure of the liquid taken appropriate normal operation. Presented and analyzed the main results of numerical studies and get a picture of the stress-strain state of unit joining walls to the bottom vertical cylindrical tank of 50 thousand m3 for different types of finite element model.

Rectangular C-Device with Circular Transitions: Modelling Approaches and Development of an Equivalent Nonlinear Inelastic Spring for Seismic Analysis

Yield devices of “C” shape, known as C-devices, supplement the energy dissipation sources when installed in earthquake resistant structures. However, the explicit modelling of C-devices is time consuming. Accordingly, this paper presents a new reliable methodology to define and calibrate an equivalent uniaxial inelastic spring that effectively reproduces the expected hysteretic response of a C-device. The shape of the C-device under study resembles that of a rectangular portal frame with circular interior corner transitions to avoid stress concentration and to control the extension of the dissipative region. The characterization of the properties of the equivalent spring is supported by both, finite element (FE) analyses of a family of C-devices and by experimental validation. Two types of FE models are used to predict the response of the C-device. A simple FE model idealizes the device as an inelastic frame with pinned supports, whereas the more elaborate model analyses the device as a C-shaped inelastic plate under in-plane actions and explicitly reproduces the boundary conditions of the plate at the device connections. Results indicate that the FE analysis results and those obtained with the equivalent inelastic spring are in a good agreement with experimental tests for monotonic and reversed cyclic loading.

Improved Voigt and Reuss Formulas with the Poisson Effect

The Poisson effect, measured by the Poisson’s ratio, plays an important role in the regulation of the elastic properties of composite materials, but it is not considered in the conventional Voigt (iso-strain) and Reuss (iso-stress) formulas, which explains why the formulas are inaccurate even if the iso-strain or the iso-stress conditions are satisfied. To consider the Poisson effect, we derived a set of new formulas based on the governing equations of elasticity. The obtained formulas show greater mathematical complexity. To further understand how the Poisson effect influences composite elastic properties, two types of finite element models (FEM) were constructed to simulate the situations where the Poisson effect does or does not have an influence. The results show that the conventional Voigt and Reuss formulas are special cases of the newly derived ones. The Poisson effect induces secondary strains and stresses into the phase materials, which demands more strain energy to achieve the same deformation in the primary (loading) direction, and thus increases composite stiffness; the magnitude of the increase is dependent on the contrast of phase properties. The findings may have significant impact on the study of the emerging nanocomposites and functionally graded materials, where the conventional Voigt and Reuss formulas have wide applications.

Calibration of a Finite Element Forward Model in Eddy Current Inspection

We report on the use of a novel constrained optimisation algorithm for calibrating the finite element model in an eddy current inspection application. An accurate finite element forward model is often important in such eddy current applications for training neural networks or as part of an iterative solver. However, the subject of calibration of the model has not received much attention in the literature to date. We consider a multi-frequency, eddy current depth profiling application, which is important for non-destructive testing in the nuclear industry. In the optimisation algorithm, we use a Levenberg-Marquardt algorithm and a bisection search to ensure constraints are satisfied, coupled with a truncated Gradient and Hessian method. We calibrate two types of finite element models, one using a filament representation for the coils and the other using a full 3D approach. The results show the feasibility of using the constrained non-linear optimisation algorithm for tuning the finite element model parameters. The mean signal-noise ratio after tuning on a truncated spectrum was 29.47 dB for the 3D model and 28.96 dB for the filament; in contrast the mean SNR using the measured coil parameters was 1.48 dB and 4.98 dB for the two uncalibrated models, respectively. The results show that a filament model is competitive with a 3D model of the coils (within the nuclear graphite application); therefore, a computationally faster filament model can be used with minimal effect on accuracy.

Investigations of the failure behaviors of open-cell copper foam based on in-situ X-ray tomography compression experiments and image reconstructed finite element modeling

Multifunctional open-cell copper foams are widely used in different industrial sections and are featured by their topological microstructures, thus generating robust mechanicalproperties, sound absorption, andthermalconductivity. In this paper, making use of 3D imaging techniques based on micro-CT X-Ray tomography, in situ compression experiments are performed for exploring the deformation features and internal local failure behaviors of open-cell copper foams. During the in-situ compression process, geometrical topological features of deformed samples at different strain levels were reconstructed based on 3D X-ray computed tomography images, and four types of geometrical components were identified in the open-cell copper foam samples, namely strut, node, closed-cell and groove, respectively. Afterwards, several types of finite element models are constructed, finite element analysis is performed and compared with experiments for understanding the deformation process for porous copper samples. In order to improve the mesh quality of finite element models reconstructed from X-Ray tomography images, the mesh was generated through surface fitting technique. Then, the generated mesh was imported into finite element analysis software ABAQUS/Explicit for numerical simulation, simulation results suggest that large amounts of plastic strain localization and structure collapses are formed during the compression process, and such plastic strain localization features are closely related to the initial spatial orientation of struts.

On flexural properties of additive manufactured composites: Experimental, and numerical study

Components prepared by additive technologies are increasingly utilized because of shape freedom and new possibilities of fibre reinforcing. Therefore, it is important to investigate the mechanical properties and possibilities of numerical simulations of theirs. This study is focused on the experimental and numerical examination of the flexural properties of FDM long carbon fibre reinforced composites with polymeric matrix of Onyx by 3-point bending test. Two fibre volumetric contents and two reinforced layer distributions were investigated. The experiments served also as case studies for the verification of numerical models. Four types of finite element models were proposed and examined. Analytical and RVE homogenisation methods were utilized. Except the flexural properties obtained, the results suggested that the reinforced layer distribution is crucial over the fibre content. Both homogenisation methods showed comparable longitudinal material constants but very dissimilar shear and transversal constants. Nonetheless, the results suggested that the influence of transversal constants can be negligible under certain stress states. Layered shell element model and solid element model reinforced by trusses showed excellent accuracy with respect to the experiments. Optical microscopy confirmed the correct distribution of the reinforced fibres and revealed the real structure of the printed composites.

In-situ synchrotron X-ray tomography investigation of the imperfect smooth-shell cylinder structure

Lattice materials at micro scale with extraordinary stiffness and strength have demonstrated promising industrial application potentials in aerospace, transport, automotive, biomedical and other sections. However, the complex fabrication process at micro scale will inevitably induce stochastic geometric defects within as-fabricated lattice materials, thus quantitatively evaluation of the mechanical integrity of 3D-printed micro lattice structures becomes a critical important issue. In this paper, mechanical behavior of the micro Schwarz Primitive triply periodic minimal surfaces (P-TPMS) cylinder shell structures fabricated with projection micro-stereolithography (PμSL) 3D printing technique were investigated. Meanwhile, synchrotron X-Ray micro-tomography (SR-μCT) 3D imaging and interrupted in-situ compression experiment were employed for quantifying the effect of defects on the compression mechanical performances. It is found that the thickness along vertical direction was larger than along horizontal direction. Afterwards, three different types of finite element models were developed for understanding the effects of fabrication defects on the mechanical behavior characteristic. Simulation results demonstrated that the statistical model was more accurate and efficient when compared with the ideal model and real geometry reconstructed model. Finally, parametric study was also presented to gain insight into the role of thickness imperfections on the mechanical performance of the shell.

Biomechanical evaluation of different hallux valgus treatment with plate fixations using single first metatarsal bone model and musculoskeletal lower extremity model

A numerical approach is one of feasible ways to discover the biomechanics of hallux valgus deformity with various osteotomy and fixation strategies. In the present study, two types of finite element models for analyzing the biomechanical performances of hallux valgus treatment with plate fixations were developed including the single first metatarsal bone model and the musculoskeletal lower extremity model. There are four types of plate fixations that were used to correct the deformity of hallux valgus. The strengths and limitations of both the single first metatarsal bone model and the musculoskeletal lower extremity model were evaluated and discussed. The results revealed that the single metatarsal bone models can be used to quickly predict the biomechanical performances of different hallux valgus treatments. Additionally, the musculoskeletal lower extremity models can be used to predict the biomechanical performances of different hallux valgus treatments under a physiological loading. The plate fixations with the insertion of all locking screws revealed better osteotomy fixation stability and lower risk of the implant failure compared to the other fixations. Additionally, the plate fixations with the insertion of six bone screws had lower risk of the metatarsal bone failure compared to the plate fixations with the insertion of four bone screws. The six holes plate with the insertion of six locking screws was the best treatment among the four treatment strategies. The numerical models and simulation techniques developed in the present study can provide useful information for understanding the biomechanics of hallux valgus treatments.

Collapse analysis of a wind turbine tower with initial-imperfection subjected to near-field ground motions

As a slender thin-walled structure, wind turbines may be susceptible to pulse-type near-field seismic records. In order to study the effects of near-field records on the imperfection sensitivity and collapse modes of a 1.5 MW land-based wind turbine, two types of finite element model (FEM) are established and investigated through ABAQUS, i.e. FEM with and without initial welding imperfection. The horizontal displacement, horizontal acceleration, shear force and bending moment are investigated and compared. Finally, the incremental dynamic analysis is carried out to study the imperfection sensitivity and collapse analysis of this tower. The results show that the seismic response of this wind turbine subjected to pulse-type near-field seismic records are all significant larger than those under the excitation without velocity pulses. The presence of imperfections increases the variability of the seismic response of this wind turbine, and different defect amplitudes will affect the location of the plastic hinge on the tower. The plastic hinge is easy to occur at approximately 1/2–3/4 height of the tower under the strong pulse-type near-field earthquake excitation. The welding imperfection can significantly reduce the intensity of ground motion required for the nonlinear response of the wind turbine tower, especially for that under pulse-type near-field seismic excitation.

Vibration-Based Damage Detection of a Steel-Concrete Composite Slab Using Non-Model-Based and Model-Based Methods

This paper presents vibration-based damage detection (VBDD) for testing a steel-concrete composite bridge deck in a laboratory using both model-based and non-model-based methods. Damage that appears on a composite bridge deck may occur either in the service condition or in the loading condition. To verify the efficiency of the dynamic test methods for assessing different damage scenarios, two defect cases were designed in the service condition by removing the connection bolts along half of a steel girder and replacing the boundary conditions, while three damage cases were introduced in the loading condition by increasing the applied load. A static test and a multiple reference impact test (MRIT) were conducted in each case to obtain the corresponding deflection and modal data. For the non-model-based method, modal flexibility and modal flexibility displacement (MFD) were used to detect the location and extent of the damage. The test results showed that the appearance and location of the damage in defect cases and loading conditions can be successfully identified by the MFD values. A finite element (FE) model was rationally selected to represent the dynamic characteristics of the physical model, while four highly sensitive physical parameters were rationally selected using sensitivity analysis. The model updating technique was used to assess the condition of the whole deck in the service condition, including the boundary conditions, connectors, and slab. Using damage functions, Strand7 software was used to conduct FE analysis coupled with the MATLAB application programming interface to update multiple physical parameters. Of the three different FE models used to simulate the behavior of the composite slab, the calculated MFD of the shell-solid FE model was almost identical to the test results, indicating that the performance of the tested composite structure could be accurately predicted by this type of FE model.

Numerical study of cold-formed steel channel sections under combined web crippling and bending action

Cold-formed steel sections used in floor systems are vulnerable to web crippling, and with increasing span lengths, they are likely to fail under combined web crippling and bending action. A numerical study was therefore undertaken to investigate the combined web crippling-bending interaction behaviour of unlipped channel sections used as bearers in floor systems with fastened supports. Web crippling finite element models developed and validated by the authors in a recent study were extended to investigate the behaviour of unlipped channels under combined action of web crippling and bending while new finite element models were developed for bending and validated using available experimental results. All three types of finite element models were used in a detailed parametric study to obtain the capacities of 12 unlipped channel sections made of G250 and G450 steels under pure and combined web crippling and bending actions. Comparison of the combined web crippling and bending capacities obtained from finite element analyses with the interaction equations in three cold-formed steel design standards, AISI S100, AS/NZS 4600 and Eurocode 3 Part 1.3, showed that the current design equations are accurate for 50 mm bearing length. However, they can also be used to predict the combined web crippling-bending capacities conservatively for bearing lengths of 100 and 150 mm. A new design equation with a suitable capacity reduction factor was then proposed to improve the accuracy of predicting the mid-span load capacity of channel sections subject to combined web crippling and bending actions. • Investigated the behaviour of unlipped channels with fastened supports under pure and combined web crippling and bending. • Developed and validated finite element models for web crippling and bending actions. • Recommended ABAQUS quasi-static analysis based on explicit conditions instead of general static method. • Current web crippling and bending interaction equations were shown to be conservative. • Proposed new equations to predict the mid-span load capacity under combined web crippling and bending action.

The use of extruded finite-element models as a novel alternative to tomography-based models: a case study using early mammal jaws

Finite-element (FE) analysis has been used in palaeobiology to assess the mechanical performance of the jaw. It uses two types of models: tomography-based three-dimensional (3D) models (very accurate, not always accessible) and two-dimensional (2D) models (quick and easy to build, good for broad-scale studies, cannot obtain absolute stress and strain values). Here, we introduce extruded FE models, which provide fairly accurate mechanical performance results, while remaining low-cost, quick and easy to build. These are simplified 3D models built from lateral outlines of a relatively flat jaw and extruded to its average width. There are two types: extruded (flat mediolaterally) and enhanced extruded (accounts for width differences in the ascending ramus). Here, we compare mechanical performance values resulting from four types of FE models (i.e. tomography-based 3D, extruded, enhanced extruded and 2D) in Morganucodon and Kuehneotherium. In terms of absolute values, both types of extruded model perform well in comparison to the tomography-based 3D models, but enhanced extruded models perform better. In terms of overall patterns, all models produce similar results. Extruded FE models constitute a viable alternative to the use of tomography-based 3D models, particularly in relatively flat bones.

Dynamic Collapse Mechanism of Global Hull Girder of Container Ships Subjected to Hogging Moment

The purpose of the present study is to investigate dynamic ultimate strength of global hull girder of container ships using large-scale nonlinear finite element analysis (FEA). A series of time domain nonlinear finite element (FE)-simulation is carried out using large-scale FE models of a 8000 twenty-foot equivalent unit (TEU) container ship where a hogging moment is applied to the midship section. Five types of finite element models (three full models, a half hold model, a one transverse model) are used. These models adopt elastoplastic material model, which includes strain rate effect. The hogging moment, which is modeled by sinusoidal impulse, is applied to these models, and collapse mechanism as well as dynamic hull girder ultimate strength is investigated by varying the load time duration. Moreover, effects of load time duration, mass inertia, strain rate, and analysis models are investigated in detail. It is found from the present study that ultimate strength as well as collapse mode is significantly dependent on load time duration of hogging moment.

Communication—Multi-Physics battery Safety Simulations across Length Scales

The impact events of a pouch cell have been simulated using three types of finite element models. It is shown that all these models can capture the essential features of a cell under impact and give similar results in the evolution of loading force, voltage and temperature. Their computational times, on the other hand, differ by orders of magnitude due to different levels of details contained in the models. It demonstrates that with appropriate strategies, multi-physics battery safety simulations can be extended from cell to module/pack with reasonable accuracy using manageable computational resources.

Numerical comparative study of five currently used implants for high tibial osteotomy: realistic loading including muscle forces versus simplified experimental loading

BackgroundMany different fixation devices are used to maintain the correction angle after medial open wedge high tibial osteotomy (MOWHTO). Each device must provide at least sufficient mechanical stability to avoid loss of correction and unwanted fracture of the contralateral cortex until the bone heals. In the present study, the mechanical stability of following different implants was compared: the TomoFix small stature (sm), the TomoFix standard (std), the Contour Lock, the iBalance and the second generation PEEKPower. Simplified loading, usually consisting of a vertical load applied to the tibia plateau, is used for experimental testing of fixation devices and also in numerical studies. Therefore, this study additionally compared this simplified experimental loading with a more realistic loading that includes the muscle forces.MethodTwo types of finite element models, according to the considered loading, were created. The first type numerically simulated the static tests of MOWHTO implants performed in a previous experimental biomechanical study, by applying a vertical compressive load perpendicularly to the plateau of the osteotomized tibia. The second type included muscle forces in finite element models of the lower limb with osteotomized tibiae and simulated the stance phase of normal gait. Section forces in the models were determined and compared. Stresses in the implants and contralateral cortex, and micromovements of the osteotomy wedge, were calculated.ResultsFor both loading types, the stresses in the implants were lower than the threshold values defined by the material strength. The stresses in the lateral cortex were smaller than the ultimate tensile strength of the cortical bone. The implants iBalance and Contour Lock allowed the smallest micromovements of the wedge, while the PEEKPower allowed the highest. There was a correlation between the micromovements of the wedge, obtained for the simplified loading of the tibia, and the more realistic loading of the lower limb at 15% of the gait cycle (Pearson’s value r = 0.982).ConclusionsAn axial compressive load applied perpendicularly to the tibia plateau, with a magnitude equal to the first peak value of the knee joint contact forces, corresponds quite well to a realistic loading of the tibia during the stance phase of normal gait (at 15% of the gait cycle and a knee flexion of about 22 degrees). However, this magnitude of the knee joint contact forces overloads the tibia compared to more realistic calculations, where the muscle forces are considered. The iBalance and Contour Lock implants provide higher rigidity to the bone-implant constructs compared to the TomoFix and the PEEKPower plates.

Development of spiral auxetic structures

An auxetic tow or fiber bundle that will expand in diameter when extended axially would be very useful. It could be woven into a shape-changing cloth, perhaps used for ballistic protection, or as an easily cleaned filter. To explore this concept, spiral fiber bundle structures under tension were explored. Theory describing the geometry of spiral structures was developed. Several types of finite element models for these spiral structures using laminated plate elements, beam elements and solid elements with contact were then developed and compared at a range of angles. The beam and solid element models provide the best approximation and indicate that a 30°/45° fiber structure is a good angle combination to not only provide significant radial expansion but also show a relatively low stress. Several polymeric specimens were 3D-printed and tested under tension. Testing confirmed that the spiral fiber systems exhibited auxetic behavior. The polymeric specimens exhibited more radial expansion than the finite element predictions. Thus, spiral fiber bundles show promise and will be explored further.