Finite Element Modeling Approach Research Articles

Numerical Investigation of Effects of Camlock System on Thermal Conductivity of Structural Insulated Panels

Structural insulated panels (SIPs) are widely used in residential and commercial buildings due to their reliable mechanical and thermal performance. However, using framing members and nails to join SIPs causes thermal bridging across the insulation and thus increases heat losses from the building envelope. Alternatively, SIPs joined with embedded camlock systems can overcome this issue. In this paper, a parametric study of the effects of the camlock system material and SIP geometric design on the thermal performance of SIP walls was investigated using a multi-scale finite element modeling approach. The model considers the structural design details of the camlock system. In addition, the effects of the SIP materials, SIP thickness, and the number of camlock systems per unit area on the through-thickness thermal conductivity of the SIP walls are examined. It was found that the SIP thickness is a dominating factor influencing the thermal performance of the SIP. The through-thickness (overall) thermal conductivity of the SIP wall increases linearly with the increase in the number of camlock systems used per unit area. However, it rises exponentially with the increasing SIP thickness. The reduction in the overall R-value of the SIP caused by the camlock system embedded in the SIP did not exceed 13.8%.

Investigation of Corroded Bond-Slip Effects for Corroded RC Columns

Steel bar corrosion is one of the most common causes of structural performance degradation for reinforced concrete (RC) columns subjected to extreme loads such as earthquakes. Due to the different characteristics of corrosion effects, a comprehensive and efficient finite element (FE) modeling approach is necessary for the performance assessment of corroded RC columns. To this end, this study provides an effective FE modeling approach using a recently developed geometrically nonlinear fiber-based frame element that considers bond-slip, allowing for explicit representation of corrosion-affected bonding. This aspect necessitates the use of an explicit material model for corroded bond-slip and its associated corroded properties. Since the existing models of corroded bonding properties in the literature were developed based on the highly scattered and limited experimental data, this study develops a new probabilistic model for corroded bonding properties based on more experimental data compiled from the literature and quantifies the prevailing uncertainties. To facilitate its use for modeling corroded RC structures, a cyclic corroded bond-slip model in an open-source FE software framework is implemented. In this paper, the FE modeling approach is first used to model two corroded RC columns tested in the literature, with comparison to the conventional modeling approach (i.e., assuming perfect bonding). The influence of corroded bonding on the static and dynamic behaviors of RC columns is further explored deterministically. Furthermore, the impact of uncertainty in corroded bonding properties on the static and dynamic behavior simulations of RC columns is examined. This work is concluded that (1) the FE modeling approach provided for corroded RC columns proves to be effective in capturing corrosion effects; and (2) corroded bonding plays an important role in simulating the behavior of corroded RC columns, and thus cannot be neglected. This is particularly true considering its associated uncertainty and its impact on the performance assessment of RC columns under severe corrosion conditions.

Advancing OHL Rating Calculations: Modeling Mixed-Convective Cooling and Conductor Geometry

The existing standard current-temperature calculations for overhead line (OHL) conductors have been adequate for conventional conductors and their operating temperatures. However, these calculations make assumptions and include simplifications about conductor geometry and aero-thermal-dynamics, introducing an error in the High-Temperature Low-Sag conductors operating temperatures. To quantify the error introduced by the shape of strands, the paper employs a Multi-Physics Finite Element Modeling approach that calculates the conjugate heat transfer for trapezoidal stranded OHL conductors. Furthermore, it proposes corrective equations to improve the accuracy of existing methods. The equations incorporate a new Nusselt number correlation for mixed convection and capture the surface area ignored by current calculations. The outer conductor geometry assumptions and the combined natural and forced convective cooling omission in the IEEE and CIGRE methods introduce an error at low (below 0.12 m/s) cross-flow wind speeds suggesting an underestimation of conductor temperature by up to 4%. In medium wind speeds, typically at 0.5 m/s–0.61 m/s, the standard methods overestimate the conductor temperature limiting its current-carrying capability. A 5% uprating for existing OHLs is potentially feasible, particularly for the trapezoidal stranded conductors, when removing the assumptions made in existing methods.

Finite Element Model Tuning Using Analytical Sensitivity Values

This paper presents an efficient approach for tuning finite element models to match the measured ground vibration test and proof test data. Frequencies, mode shapes, total weight, location of the center of gravity, and static deformation computed from the finite element model are matched to the measured data. The model tuning procedure used in this work is based on solving an optimization problem in which the errors for the considered metrics, between the finite element prediction and the measured data, are minimized. Analytical sensitivity values of performance indices are computed using the NASTRAN-generated sensitivity values together with the in-house computer programs, which allow for faster computational time and the use of gradient-based optimizers. The method is applied to the Aerostructures Test Wing 4 model. The study shows that the military standard and the NASA standard for comparing analytical and experimental modal data are all satisfied. The final finite element model correlates well with the test data. The flutter speed decreases by 8.91% after model tuning compared with the original Aerostructures Test Wing 4 design.

A finite element analysis of load distribution during donning and orthostatic posture in the ITOP hybrid subischial socket.

Pressure and shear stresses applied to the stump of a transfemoral amputee wearing a newly designed prosthetic socket have been analyzed by a finite element modeling approach. The new socket was developed by the Istituto Tecnico Ortopedico Preneste, and it was named the "hybrid subischial socket." This work aimed at understanding the loads' distribution on the stump surface in 2 operative conditions: at the end of the wearing phase and during the orthostatic posture. The model of the stump was composed of 4 different materials: the femoral bone, the muscle tissue, the fat, and the skin layers. Except for the bone (rigid), the biological tissues were modeled as Neo-Hookean, and their mechanical properties were taken from the literature. The socket was composed of a containment frame, made of carbon fiber composite material, a shell made of flexible silicone, and a liner made of hyperelastic silicone. The results of our simulation show that the main support areas are located in a proper position, in agreement with the ideal principles of this prosthetic design, and the maximum pressures are well below the pain threshold reported in the literature for the same contact areas. We can conclude that although the upper rim of the socket is well below the ischiatic area, the new socket design allows for a safe and comfortable support of the body weight. This is in agreement with the evidence of a good functionality and acceptance of this prosthetics gathered in the many real applications.

Standard versus natural fire resistance for partially restrained composite floor beams: 2-Analysis

A thermo-structural reduced-order finite element modeling approach is used to evaluate the results of two fire tests (presented in Part 1 of this study) on identically designed, highly composite floor beam specimens with SFRM protection, shear tab connections at each end, a lightweight concrete slab on a corrugated metal deck, and partial restraint of both axial thermal expansion and connection rotation. Model validation is performed for both an ASTM E119 standard fire and a parametric natural fire, with a constant load applied to the specimens via four-point bending to a maximum service condition. Predictions of temperature increase in the protected steel beam and the composite slab show good agreement with experimental measurements by implementing a series of weighted averaging strategies on thermal FE results for 2D cross-sections at the thick and thin portions of the composite slab. Predictions of temperature-induced deflections, which used the results of thermal FE analysis as input, also show good agreement with experimental results when little-to-no rotational stiffness is applied to the connections. The numerical models are then re-analyzed at a reduced loading level (representing a middling service condition) and with varying rotational stiffness in the shear tab connections. The results of parametric analysis are used to draw correlations between standard fire resistance and natural fire robustness as a function of applied loading and temperature increase in the steel beam. Simplified modeling strategies and recommendations for performance-based structural-fire design are discussed, and opportunities for future research are highlighted.

Application of finite element model of middle ear in the study of the middle ear biomechanics in normal and diseased states

Aim: The aim of this study was to create a three-dimensional model of the middle ear by finite element (FE) analysis, using measurements performed on human and cadaveric high-resolution computed tomography (HRCT) temporal bone, and to study the biomechanics in diseased conditions. Materials and Methods: This observational, cross-sectional study was conducted in Acharya Vinoba Bhave Rural Hospital, Sawangi, Meghe, Maharashtra, in the Department of Otorhinolaryngology. The first step of FE modeling approach comprised computer-aided geometric model incorporating the static dimensions from human and cadaveric temporal bones and dynamic dimensions from prepublished data. HRCT Scans of both sets of temporal bones were performed with 0.5 mm cuts, and measurements of the ossicles, middle ear, and tympanic membrane were taken. The cadaveric temporal bones were drilled, the ossicles dissected out and measured using HRCT as well as vernier calipers. This was followed by construction of the working FE model and application of this FE model for studying middle ear biomechanics in normal and diseased states. Results: The mean measurements of ossicles were calculated, and the movement of tympanic membrane was maximum at the site of umbo and stapes footplate, whereas minimum movement was within the ossicles. Larger peak-to-peak displacement was seen at 1000 Hz to 3000 Hz frequency. Our results suggest that FE model can prove beneficial in the study of middle ear biomechanics. Conclusion: The changes in the tympanic membrane movement in diseased state have been compared to normal ear and can be applied to reconstructed ears. FE analysis can be used to study the effect of material properties of various graft materials used in tympanomastoidectomy.

FEM Analysis of Steel Eccentric Braces for Seismic Retrofitting

The paper discusses issues about the finite element modelling of steel eccentric braces with vertical shear links used as hysteretic dampers to improve the seismic performance of existing reinforced concrete (RC) buildings. To this end, eccentric bracing systems have been designed for seismic upgrading of a case-study existing RC school building in Italy. Multiple finite element modelling approaches are described, using both frame and shell finite elements, various steel stress strain relationships, as well as including both geometrical imperfections and residual stresses. Numerical models were built using two commercial structural analysis programs, SAP2000 and Ansys, and one open-source software, Code_Aster. The numerical study allowed to (i) quantify values of the plastic overstrength factor of the considered shear links; (ii) evaluate the overall system stability and general inelastic response; (iii) compare various modelling approaches.

Finite element analysis to predict the cyclic performance of GFRP-RC exterior joints with diagonal bars

This paper presents a finite element modeling (FEM) approach to predict the cyclic response of glass fiber-reinforced polymer (GFRP) reinforced concrete (RC) exterior beam-column joints with different joint details. Four GFRP-RC exterior beam-column joints detailed with U or L-shaped anchorages at the end of the longitudinal bars of the beam, horizontal stirrups and additional diagonal bars (Z or U-shaped) at the joint region were modeled and analyzed under reversed cyclic loading. The FEM cyclic behavior in terms of load-drift ratio, cracking patterns, joint shear stress and strain evolutions were compared with the experimental behaviors. The FEM predicted load-drift ratio response, cracking patterns and dissipated energy showed good correlations with the experimental results. A parametric study was conducted to evaluate the influence of compressive strength of concrete, column axial load ratio and size of the additional diagonal bar on the performance of the GFRP-RC joints. It was found that an increase in the column axial load significantly degraded the performance in terms of strength, maximum joint shear stress and ductility of the GFRP-RC joints. Also, GFRP-RC joints with additional U-bars were able to resist higher joint shear stress and drift ratio than GFRP-RC joints with additional Z-bars, respectively.

Planar multibody dynamics of floating Y-method installation system and the lowering of subsea equipment based on finite element modeling

The subsea equipment installation is a complex operation that demands a precise and reliable approach to avoid the accidental losses of lives and equipment damage. The multibody installation system is overwhelmed with the dynamic behavior and responses of the system, which signifies the importance of analysis of the Multibody Dynamic System (MBDS). The modeling of MBDS is challenging and complicated due to the interconnectivity and nonlinearity assigned to them. In this paper, the planar dynamics of a floating multibody system are attained by employing two tugboats and a payload with a contextual offshore installation scenario to be applied in a water depth of over 1500 m. The lifting operation is nine degrees of freedom (9-DOF) multibody model done with the help of two strands and three bodies having 3-DOF each. The coupled equations of motion are established by deploying the Velocity Transformation Technique. The hydrodynamic and two-strand forces are simplified as linear, while the hydrostatic and mooring forces are treated as nonlinear external loads. The numerical solution to the equations for the MBDS is obtained from the Runge Kutta Method of Fourth-Order. Furthermore, the Finite Element Modeling approach discusses the installation operation using Y-method. The results of the proposed numerical model are validated by comparing it with the numerical simulation from OrcaFlex, and the results from both models are found to be in good agreement. The findings of this study will help improve the safe and stable installation of deep-water multibody structures.

Gluteal activation during squatting reduces acetabular contact pressure in persons with femoroacetabular impingement syndrome: A patient-specific finite element analysis

BackgroundFemoroacetabular impingement syndrome is a motion-related clinical disorder resulting from abnormal hip joint morphology. Mechanical impingement, in which the aspherical femoral head (cam morphology) abuts with the acetabular rim, is created with simultaneous hip flexion, internal rotation, and adduction. Impaired function of the gluteal muscles may be contributory to femoroacetabular impingement syndrome progression. The purpose of this study was to assess the influence of gluteal muscle recruitment on acetabular contact pressure during squatting in persons with cam femoroacetabular impingement syndrome. MethodsEight individuals (4 males, 4 females) with a diagnosis of cam femoroacetabular impingement syndrome underwent CT imaging of the pelvis and proximal femora, and a biomechanical assessment of squatting (kinematics, kinetics, and electromyography). Two maximal depth bodyweight squat conditions were evaluated: 1) non-cued squatting; and 2) cued gluteal activation squatting. Utilizing subject-specific electromyography-driven hip and finite element modeling approaches, hip muscle activation, kinematics, bone-on-bone contact forces, and peak acetabular contact pressure were compared between squat conditions. FindingsModest increases in gluteus maximus (7% MVIC, P < 0.0001) and medius (6% MVIC, P = 0.009) activation were able to reduce hip internal rotation on average 5° (P = 0.024), and in doing so reduced acetabular contact pressure by 32% (P = 0.023). Reductions in acetabular contact pressure occurred despite no change in hip abduction and increased bone-on-bone contact forces occurring in the cued gluteal activation condition. InterpretationOur findings highlight the importance of gluteal activation in minimizing mechanical impingement and provide a foundation for interventions aimed at preventing the development and progression of femoroacetabular impingement syndrome.

Temperature-Dependent modelling of tension, in-Plane shear, and bending behaviour in non-isothermal thermo-Stamping process simulation of unidirectional UHMWPE fibre reinforced thermoplastic TPU composites

This study proposes a macroscopic finite element modelling and simulation approach considering the temperature dependency of both in-plane membrane and out-of-plane bending behaviours. This approach enables the investigation of the effect of the deformation mechanisms on the quality of the formed thermoplastic composite parts during the thermo-forming process. The temperature-dependent constitutive model of the in-plane tensional behaviour is considered linear, whereas the in-plane shear stiffness is modelled based on the nonlinear hypoelastic constitutive equation. The out-of-plane bending behaviour is considered by decoupling the membrane and bending method. A numerical simulation strategy is developed by implementing the ABAQUS software via a VUMAT subroutine. Moreover, a modified method is introduced for the qualitative and quantitative assessment of the wrinkling intensity generated in the forming process. The validated strategy is used to investigate the influences of the various temperature conditions of the forming process and the underlying mechanisms to optimise the thermo-stamping process.

A micromechanical based finite element model approach to accurately predict the effective thermal properties of micro-aerated chocolate

Micro-aeration is a method to modify the sensorial attributes of chocolate but also affects the material properties of chocolate, which in turn, determine its material response during manufacturing and oral processes. This study aims to define the effect of micro-aeration on the thermal properties of chocolate by considering the changes of chocolate microstructure due to micro-aeration. Micro-aeration was found to alter the chocolate microstructure creating a layer of a third phase at the porous interfaces, which is argued to consist of cocoa butter of higher melting properties. A multiscale Finite Element Model is developed, which was confirmed by macroscale heat transfer measurements, to parametrically simulate the structural changes of micro-porous chocolates at the microscale level and estimate their effective properties, such as thermal conductivity and specific heat capacity. The developed multiscale computational model simulates the porous chocolate as a two-phase (chocolate- pores) or three-phase material (chocolate-cocoa butter layer- pores). The investigation identified a new, complex transient thermal mechanism that controls the behaviour of micro-aerated chocolate during melting and solidification. The results showed a maximum 13% reduction of keff and 15% increase of Cpeff with 15% micro-aeration resulting to a slower transient heat transfer through the micro-aerated chocolate. The reason is that the micro-aerated chocolate can store a larger amount of thermal energy than its solid counterpart. This effect slows down the transient heat transfer rate in the chocolate and modifies melting/solidification rate and impacts sensorial attributes during oral processing and cooling during manufacturing.

Performance of UHPC bridge piers subjected to heavy vehicle collisions and probability analysis of damage level

Heavy vehicle collisions have been reported as one of the major causes of normal concrete (NC) bridge pier failure due to its low crashworthiness. Ultra-high performance concrete (UHPC), which has been demonstrated as a promising engineering material to resist high strain rate loadings, is deemed as an alternative material to improve the collision performance of bridge piers that would be impacted by heavy vehicles. In this study, the performance of the UHPC pier subjected to heavy vehicle collisions is investigated by using the finite element (FE) modelling approach. Firstly, the damage and energy absorption characteristics of NC and UHPC piers are comparatively studied. The results show that the NC pier is dominated by plastic failure, whereas the UHPC pier essentially presents brittle damage. The kinetic energy of the vehicle is mainly dissipated by the steel reinforcement for UHPC piers whereas by the concrete for NC piers. Then, a comprehensive parametric analysis, with respect to the vehicle weight and velocity, pier diameter, and longitudinal and transverse reinforcement ratios, is performed to investigate the impact performance of UHPC piers. An analysis of the Pearson correlation coefficient for the involved parameters shows that the vehicle weight and velocity are key influential parameters to the peak impact force. Finally, to facilitate the evaluation of the bridge column subjected to heavy vehicle collisions, three regression surrogate models, SVR (support vector regression), kriging, and RBF (radial basis function), are established to predict the equivalent static force (ESF) of the peak impact force on UHPC piers with promising accuracy. Among the presented five damage levels, the probabilities of slight and moderate damages are remarkably larger when UHPC piers are impacted by heavy vehicles. This study can provide guidance for the revision of AASHTO and future engineering practices with considering UHPC piers subjected to heavy vehicle collisions.

Simplified seismic response model for a bulk solid- silo-embedded foundation/soil system

A new analytical procedure encompassing a finite element model approach to perform seismic analysis of a bulk solid-silo-embedded foundation/soil system, as presented here, not only allows for more efficiency in terms of practical design but also successfully accounts for a more thorough evaluation of the behavioral aspects of system. A parametric study was performed on both slender and squat silos with embedded foundations for four different soil types. The research presented here confirms both the efficiency and realiabilty of this new analystical procedure in determining the seismic behavior of silos with embedded foundations.

Aspects of simulating stable low-cycle fatigue crack growth in the main parts of aircraft gas turbine engines

The article presents theoretical basis for the industry-based approach for finite element modeling of stable crack growth in the main parts of an aviation gas turbine engine. An axial compressor disc is used as an example. Parameters of typical FE-models applied are provided. In addition, some effective practices of FE-modeling representing the novelty of this work are described: crack evolution increment under-relaxation and automation of the process of constructing a new crack front. Some simulation results are presented demonstrating implementation of the approach steps and benefits gained from the application of the listed features. Under-relaxation ensures maintaining the stability of a numerical solution for a significantly larger crack increment size. This leads to essential effort decrease as a result of reducing the total number of simulation cycles required. Automatic construction of a new crack front allows significant improvement in crack representation accuracy during the simulation process due to the greater number of points for which crack front evolution is determined.

An inclusive numerical framework to assess the role of feedstock features on the quality of cold spray deposits

Cold spray technology provides unique capabilities for coating, repair, and additive manufacturing. However experimental trial and error to optimize deposit quality indexes, that rely on powder characteristics, can be costly and tedious. In this research, multiple finite element modelling approaches were compared regarding their capability and shortcomings to analyze the role of major powder features on deposit properties. Lagrangian and CEL methods were selected as the most robust approaches for analyzing the single/multi-particle impact condition, respectively. An intricate algorithm was introduced to accurately evaluate the effect of parameters including particle size, shape, oxidation extent, and impact angle on the deposition indicators such as critical velocity, particle flattening, and deposit porosity. The results exhibited a good agreement with the reported experimental data, confirming the capacity of the proposed numerical framework to tune the deposit properties as a function of a wide range of feedstock characteristics. It was concluded that for successful deposition, the effect of various powder properties and their respective effect and contribution towards plastic deformation should be taken into account. The results indicated that for a given particle velocity, smaller particle, more irregular morphology, thicker oxide layer, and smaller impact angle will result in limited particle deformation and a lower possibility of successful adhesion.

Dynamic behavior and retrofitting of RC frame building under vehicular bomb explosion

Although the terrorist explosion attacks on critical buildings caused by the Vehicle-Borne Improvised Explosive Device (VBIED) are low-probability events, the blast-induced progressive collapse of buildings generally lead to the catastrophic consequences of the events. Through the high-fidelity hybrid finite element (FE) model and numerical simulations, this work aims to get a deep insight into the progressive collapse behavior of high-rise reinforced concrete (RC) frame buildings under blast loadings induced by VBIED, as well as the feasibility of two blast-resistant external retrofitting measures, i.e., fiber reinforced polymer (FRP) and steel plate (SP). Firstly, the applicability of the hybrid FE modelling approach, element types and size, material models and parameters, as well as numerical algorithms, i.e., multi-material Arbitrary Lagrangian-Eulerian (MM-ALE) and Fluid-Structure Interaction (FSI), are fully validated by comparing with the explosion tests on 1/4-scale bare and prototype FRP/SP-retrofitted RC frame structures, respectively. Then, a twelve-story RC frame building is designed following the Chinese regulations, and the corresponding hybrid FE model is established. The failure modes and progressive collapse process of building under the explosions of cargo vans bomb (equivalent TNT of 1814 kg) specified by Federal Emergency Management Agency are numerically examined. Furthermore, the effectiveness of FRP/SP-retrofitted frame columns is assessed quantitatively. It derives that, the SP-retrofitted building is not collapsed for both the scaled distance of 1.0 and 0.55 m/kg1/3; by retrofitting FRP warps, the collapse of entire buildings can be prevented with the scaled distance of 1.0 m/kg1/3, while the progressive collapse of the retrofitted building occurs with a scaled distance of 0.55 m/kg1/3. The present work could provide helpful references for the blast-resistant evaluation, design and retrofitting of the as- and newly-built RC building structures.

Evaluation of Train Running Safety on Railway Cable-Stayed Bridge During Seismic Excitation

This research aims to evaluate the dynamic interaction between a cable-stayed bridge (CSB) and operating trains during earthquakes. A three-dimensional finite element modeling approach has been used to analyze the H-shaped pylon CSB along with soil–pile interaction. The train model has been developed using a dynamic system having 10 degrees of freedom. The contact forces between the wheels and the track illustrate the dynamic interaction between the bridge and the train. A Matlab program has been built to receive train–bridge interaction responses. The nonlinear dynamic analysis was performed on CSB using the Bhuj earthquake time history. The structure’s response can then be used to assess the safety of running trains during seismic activity. The dynamic response of the train–bridge interaction system, including the derailment and offloading variables related to the train’s running safety, is evaluated using varied spectral acceleration scaling. The results demonstrate that the acceleration response of the train during seismic events is substantially higher than when there are no earthquake inputs. The operating train’s safety is influenced by both the intensity of the earthquake and the train’s running speed. The operating safety of a moving train during a seismic event is guaranteed by the threshold curve. The proposed bridge modeling technique and simulated results prove that the proposed formulation can accurately envisage dynamic train responses with acceptable computational errors.

Experimental and Crystal Plasticity Finite Element Study of the Deformation Behavior of High‐Mn Steel Micropillars

Experimental and crystal plasticity finite element modeling approaches are used to predict the deformation behavior of micropillar in the 16Mn steel. The intrinsic (crystallographic orientation) and extrinsic (friction coefficient on the micropillar) factors are considered for both experiment and modeling on the deformation behavior of micropillars. When the friction coefficient is low, buckling is occurred by slipping on the top surface of the micropillar, while barreling is accommodated in the high friction coefficient condition. In the multiple slip system, the influence of the friction coefficient is negligible on the deformation behavior of the micropillar because slip initiation can occur at multiple points.