Finite Element Computer Model Research Articles

Study on Earthquake Failure Mechanism and Failure Mode of Cable-Stayed Pipeline Bridge Considering Fluid–Structure Coupling

To investigate the failure mode of the cable-stayed pipeline bridge under seismic loading, this study focuses on an oil and gas cable-stayed pipeline bridge as the research subject. A full-scale finite element calculation model of the structural system is established using ANSYS Workbench 14.0 software, considering the stress characteristics and structural properties of the oil and gas pipeline. Additionally, a fluid–structure coupling effect finite element model is developed to account for the influence of medium within the pipeline. The analysis includes evaluating deformation, stress, strain, and other responses of the oil and gas pipeline subjected to seismic waves from different directions. The results indicate that the overall damage in the pipeline is consistent with maximum deformation, stress, and strain, concentrated at both the inlet/outlet ends and side spans; however, variations exist in terms of seismic damage depending on wave directionality. Furthermore, by considering interactions between various components within the oil and gas cable-stayed pipeline bridge’s structural system during strong earthquakes, this study analyzes failure mechanisms caused by the support–pipeline interaction as well as excessive displacement-induced failure patterns in bridge towers. Finally, a proposed failure mode for pipe bridge systems resulting from longitudinal slip between supports and pipelines, along with excessive displacement of bridge towers, is presented.

Geometric nonlinear analysis of slender layered non-prismatic beams with interlayer slip

This paper presents a novel model that, for the first time, simultaneously captures the effects of variable cross-section and interlayer slip on the geometrically nonlinear response of slender symmetrically layered beams within the framework of a beam theory. While the central layer has a constant cross-section along its length, the height of the two outer layers can vary arbitrarily. A nonlinear axial strain–displacement relationship captures the influence of moderately large deflections for immovably supported beams. The kinematic hypothesis of the Euler–Bernoulli theory is applied layerwise. The relationship between the interlaminar shear tractions and the interlayer slips is assumed to be linear. The Galerkin method is used to solve the derived initial–boundary value problem. Several application examples demonstrate the influence of the interlayer slip, the variable cross-section, and the geometrically nonlinear formulation of the equations of motion on the static and dynamic response. The results of comparative analyses with a numerically much more computational expensive finite element model discretized by plane stress continuum elements are in excellent agreement with the outcomes of the presented theory.

Biomechanical properties of artificial bones made by Sawbones: A review.

Biomedical engineers and physicists frequently use human or animal bone for orthopaedic biomechanics research because they are excellent approximations of living bone. But, there are drawbacks to biological bone, like degradation over time, ethical concerns, high financial costs, inter-specimen variability, storage requirements, supplier sourcing, transportation rules, etc. Consequently, since the late 1980s, the Sawbones® company has been one of the world's largest suppliers of artificial bones for biomechanical testing that counteract many disadvantages of biological bone. There have been many published reports using these bone analogs for research on joint replacement, bone fracture fixation, spine surgery, etc. But, there exists no prior review paper on these artificial bones that gives a comprehensive and in-depth look at the numerical data of interest to biomedical engineers and physicists. Thus, this paper critically reviews 25 years of English-language studies on the biomechanical properties of these artificial bones that (a) characterized unknown or unreported values, (b) validated them against biological bone, and/or (c) optimized different design parameters. This survey of data, advantages, disadvantages, and knowledge gaps will hopefully be useful to biomedical engineers and physicists in developing mechanical testing protocols and computational finite element models.

Fatigue life estimation of aircraft structural component using FE approach and validation through analytical and experimental methods

Aircraft structural design requirements encompass safe-life and damage-tolerant design, analysis, and verification through testing to arrive at the overall service life. The fatigue phenomenon is most critical and local; hence fatigue studies are necessary to conduct first at the coupon level before attempting at the component or full-scale level. The present work demonstrates the development of fatigue life estimation procedures such as high cycle fatigue (HCF) life and fatigue crack growth (FCG) life on specimens as per ASTM standards.The HCF life is predicted for the Aluminum (Al) 2024-T3 ASTM E466 specimen subjected to constant amplitude loading with a stress ratio (R) of 0.1 based on Basquin's method. The computational 2D finite element (FE) model is developed to predict HCF life using a safe-life approach through Nastran Embedded Fatigue (NEF). The effect of fatigue strength modifying factors affecting fatigue life is also explored. Similarly, the FCG life is predicted for the Al 2024-T3 ASTM E647 specimen subjected to constant amplitude loading with a stress ratio of 0.1 using Walker's equation. The computational 3D FE models with a single edge crack in each are developed to predict FCG life using FRANC3D. The FE-based HCF and FCG life prediction procedures demonstrated in this work are verified by comparing FE results with analytical and experimental ones. Therefore, these FE-based methodologies for HCF and FCG life prediction can be adopted at the feature and structural component levels. The developed computational methods reduce the experimental effort, cost, and time involved in the overall fatigue design of the aircraft structures.

SIMPLIFIED MODELING OF V-SHAPED BRIDGE PIERS

DDesigning a steel, V-shaped bridge pillar requires a complex and detailed finite element calculation model. The calculation can be simplified by using a simple one-dimensional beam model, but then the stress concentrations are not determined in detail. The use of a stress concentration factor, SCF, to make this possible. Before using this method, it is first verified whether both models behave correspondingly, by calculating the internal forces certain sections. Five basic load cases are used to perform this verification. Afterwards the stress concentration factors are determined for those same load cases. This method induces inconsistencies, some predictable but others unpredictable. The conclusion can however be that this simplified meth gives unreliable results. Therefore, a second method is used, where the high stresses in the curvatures of the pillar are related to the stresses in a nearby neutral section. Such a neutral section is defined as a section where the stress peaks due to the geometric effects caused by the actual geometry of the nodes of the V-shaped pilar are not present anymore. This method provides better results for the SCF; however, some issues remain, which are discuss in more detail in the paper. Finally, the impact of a varying radius of curvature on the stresses is also studied. Some clear trends are observed in this paper Overall, this paper discusses a possible simplified design method for V-shaped bridge pillars, at the same time listing the relevant design difficulties and possible pitfalls of a too simplified model.

Multi physical comprehensive design of a new type of FeCo based high speed permanent magnet motor

In order to solve the problem that the design of high-speed permanent magnet motor (HSPMM) is constrained by multi-physical fields, this paper starts with the comprehensive study of multi physical fields, introduces the finite element calculation model of rotor strength-rotor dynamics-electromagnetic field-fluid field and temperature field, carries out the comprehensive design of a 100 kW, 18 000 r/min FeCo based HSPMM, and gives the detailed and complete research process of the main parameters of HSPMM under multi-physical field constraints. First, the initial dimensions of the motor are obtained by electromagnetic and mechanical design theory. Secondly, the influence of design parameters on rotor stress is analyzed in detail, including the influence of bearing rigidity, impeller mass, rotor diameter, rotor core length and gyroscopic effect on critical speed. Subsequently, the electromagnetic characteristics of the motor are comprehensively studied, the cooling system is designed in the Flow-Heat coupling calculation model and the temperature field is studied. Finally, the prototype test verifies the correctness and validity of the comprehensive research method of multi physical field.

Low-velocity impact of square conical gradient aluminium foam-filled automobile energy-absorbing boxes

In this paper, the low-velocity impact and lightweight design of the square conical gradient aluminium foam-filled automobile energy-absorbing boxes (EABes) is numerically studied. Firstly, the validity of the finite element calculation model is verified by comparing with the experimental results. Then, the influences of the conical bottom angle, tube-wall thickness, the number, position, height and depth of induction grooves, and the parameters of gradient foam on the energy absorption properties of the EABes under axial low-velocity impact are studied. After that, the mitigation and energy absorption of square conical gradient aluminium foam-filled automobile EAB are optimised. The results indicate that the aluminium tube-wall thickness has no obvious effect on improving the energy absorption properties of the EAB, and other factors have good effects on improving the energy absorption properties of the EAB. Compared with the constant cross-section EAB before optimisation, the peak impact force (F max) of the finally optimised square conical gradient aluminium foam-filled automobile EAB reduces by 22.4%, and the specific energy absorption (SEA) increases by 59.8%. The investigation is helpful for the design of the square conical gradient aluminium foam-filled automobile EAB.

Structure and properties of the contact wire obtained by ECAP with forming

This paper presents the results of the development of a promising method for manufacturing contact wires for high-speed railways. The developed method is based on the principles of severe plastic deformation and the combination of metal-forming processes. The solution obtained is a combination of equal-channel angular pressing with the forming of a shaped contact wire with a cross-sectional area of 120 mm2 in one tooling. A feature of the work is that with the help of a comprehensive study by the methods of finite element computer modeling and a physical experiment, not only the stress-strain state of the deformation zone was investigated but also an analysis was made of the effect of deformation heating, which plays an important role when working with dispersion-hardened alloys, such as Cu-0.65Cr. It was established that the temperature in the equal-channel angular pressing zone reached 490℃ to 505℃, and during shaping, it rose to 510℃ to 530℃. In the course of a physical experiment, a laboratory sample of a contact wire with a tensile strength of 410 ± 8 MPa and an electrical conductivity of 35 ± 2% IACS was obtained. Post-deformation aging led to an increase in tensile strength up to 540 ± 20 MPa and restoration of electrical conductivity up to 76 ± 2% IACS. Due to the formation of a stripe structure of a grain-subgrain type with recrystallized grains along the boundaries, the plasticity of the contact wire sample reached 20%.

Dynamic Effect of Fluid–Structure Interaction and Modal Analysis of Crude–Pipeline Interaction System Considering the Fluctuating Pressure of Medium

This work explored the fluid–structure interaction (FSI) effect of crude oil and pipeline and the vibration characteristics of the pipe–crude oil structural system. A finite element computational analysis theory and corresponding simulation method were proposed for crude oil pipelines considering the FSI effect. Meanwhile, the spring model of the FSI interface between crude oil and pipeline was proposed. The experimental simulation and neural network were adopted to obtain the flow-excited pulsation pressure (FEPP), and the kinetic equations of the pipe–crude oil FSI were analyzed. The finite element computation (FEC) model for pipe–crude oil bi-directional FSI dynamics was established, which was composed of five support span lengths and four pipe liquid levels and can provide five different crude oil fluid velocities. One hundred orthogonal simulation test conditions were designed. In addition, the displacement response and acceleration response under FSI of the pipe wall were calculated, and the first six orders of inherent frequencies and main vibration patterns of the FEC model were analyzed. The results revealed that the dynamic effect of FSI between the crude oil transport medium and pipeline was complex and was influenced by the length of the pipeline crossing section, medium flow velocity, difference of liquid surface height, and displacement response. The acceleration response possessed prominent vibration decay characteristics, and the response peak in the same condition was about 8.2 times larger than that of the steady-flow state response. Therefore, the effect changed the inherent frequency and vibration pattern of the pipeline, to which the engineering design should pay sufficient attention.

Mathematical model of knee joint degenerative dystrophic changes formation in its flexion contracture at late stages of rheumatoid arthritis

Background. Rheumatoid arthritis (RA) is an immunomodulatory, chronic inflammatory disease accompanied by the proliferation and articular cartilage destruction that cause disability. Biomechanical factors in RA can play an important role in the onset and progress of the joint degenerative processes, secondary to the inflammation process. The biomechanical factors in RA can play an essential role in the start and progress of the degenerative processes within the joint that are secondary to the inflammatory process. Materials and methods. A solid simulation 3D-model of the knee joint was created that contained both tibia and fibula, the femur bone, femoral condyle cartilage and tibial plateau cartilage, menisci. It was done for further analytical calculations and finite element modeling calculations. Analytical calculations are based on the data of previous studies of quantitative evaluation of the knee joint contracture (compliance of contracture to the external corrective action) and on calculations data of the joint forces that manifest in ambulation of the patient with RA. Results. The created simulation computer 3D-model of a knee joint with its flexion contracture at late stages of RA shows that the forced passive flexion in the knee joint to 6°, the load on the condyles of the tibial plateau increased by 12.8 %, and as a result of forced passive flexion in the knee joint to 3°, the load on the condyles of the tibial plateau increased by 95.2 %, which is critical and may cause degradation of the bone tissue in the contact area. Conclusions. Increase of load on the lateral areas of the tibial plateau and, correspondingly, the tensions on the contact areas of the femur bone condyles with the tibial plateau, may contribute to the progress of the clinical picture of RA with the increase of arthrofibrosis and osteoarthritis events, particularly in the lateral areas of the knee joint.

Study on Temperature Field Distribution Law and Mechanical Properties of Hydraulic Tunnel-Surrounding Rock under the Action of Large Temperature Differences

This study aims to explore the temperature field and mechanical characteristics of hydraulic tunnels during operation in an area with large temperature differences throughout a year. By relying on the measured displacement field change results of a water transmission tunnel in Xinjiang, a finite element calculation model applicable to the hydraulic tunnel-surrounding rock under the action of large temperature differences was established. Then, the FEM model was used to analyze the temperature field distribution and stress field variation of hydraulic tunnel-surrounding rock under the effect of large temperature differences. The results showed that, under the action of large temperature differences, the displacement of the cave top was the largest, followed by the cave bottom, and finally the cave waist. The obtained displacement field data using the calculation model in this study were basically consistent with the on-site measured data, and the displacement field change law was the same, indicating that the established finite element calculation model is reliable. When the ambient temperature was below zero, the freezing front gradually expanded to the depth of the surrounding rock along the tunnel radial direction, while the frozen rock at the intersection of the lining and the surrounding rock melted first when the ambient temperature was above zero. The stress in various parts of the surrounding rock of the hydraulic tunnel increased continuously. To be specific, the growth rate of the tensile stress at the cave bottom, the tensile stress at the cave top, and the compressive stress at the cave waist of the tunnel reached 0.052 MPa/year, 0.053 MPa/year, and 0.096 MPa/year, respectively, in the first year, but the increasing rate subsequently tended to slow down continuously. Therefore, in actual projects, attention should be focused on the effect of large temperature differences on the stress growth of tunnel-surrounding rocks at an early stage, especially the growth of compressive stress at the cave waist. Notably, there are a large number of symmetrical and asymmetric phenomena related to engineering in this study.

Influence of Heterogeneous Foundation on the Safety of Inverted Cone Bottom Oil Storage Tanks under Earthquakes

In order to study the mechanical properties of inverted cone bottom oil storage tanks under earthquakes when the foundation is uneven, finite element modeling calculation for a 20,000 m3 storage tank is carried out based on ANSYS Workbench. Wind load, hydraulic pressure load, and seismic load are all equalized as distributed loads with varying spatial positions. Considering various combinations of different heterogeneous foundations and seismic loads, and by adjusting the preset foundation bed coefficient, the final foundation bed coefficient and the maximum foundation settlement value when the equivalent stress of the tank floor reaches yield strength under different conditions are calculated. The results show that under the condition of heterogeneous foundation stiffness considering seismic action, when the coefficient of local foundation bed is higher than that of natural silty clay, the requirement for safe use of the inverted cone bottom storage tank can be met. Among the seven simulated heterogeneous foundation forms, the form with high foundation stiffness on the windward side has a great influence on the safety of storage tanks.

Analysis of methods for calculating the stability of cellular structures

Introduction. Cellular structures are widely used in world practice to solve various problems. By means of such structures mooring and barrier constructions, and also the cofferdams are erected which allow to drain territory below a water level for the subsequent construction of the main structures on dry land. In domestic practice, these structures are often made of sheet piling profiles with high moment of inertia and moment of resistance as a part of anchored or interanchored thin walls. This design solution requires heavy-duty sheet piling sections and heavy anchoring devices at considerable water depths, which increases the steel intensity of the structure. For temporary structures the material and labor-intensive nature of the structure is undesirable. The honeycomb construction consists of flat sheet piles with cavities filled with soil.
 
 Materials and methods. Various stability tests of the cellular structure variant have been carried out in accordance with the current regulatory documents; recommendations for the design of these structures by the European company ArcelorMittal, which has extensive experience in designing realized projects of structures using this technical solution, have also been used. The stability indicator results are compared with the results of finite-element model calculations performed in the MIDAS FEA NX calculation complex.
 
 Results. Based on the calculation of a three-dimensional model of a cellular structure, a comparison was made with analytical methods for calculating stability. The analytical calculation of stability according to the deep shear scheme in accordance with current regulations has both a close convergence of the stability coefficient and a potential buckling surface in comparison with the FEM problem in a three-dimensional formulation.
 
 Conclusions. The main limiting factor in calculations of stability of cellular structures is the stability coefficient according to the scheme of deep shear.

Non-invasive analysis of macro-crack on the characteristics of ultrasonic guided wave

The effects of macro-crack in plates on the characteristic of ultrasonic guided wave were studied. Using the Finite Element Model and numerical calculation method, the finite element mesh models of various macro-crack in aluminum plate were established. The single S0 or A0 mode Lamb wave was excited in plate by the wave structure loading method. The propagation time and amplitude of wave packet in the received signal were analyzed to study the phenomenon of mode transformation and the relationship between macro-crack size and signal amplitude. The simulation results show that there is mode conversion when the single mode Lamb wave interacts with an asymmetric macro-crack, and no mode conversion with a symmetric macro-crack. The energy of reflected wave increases with the increase of the depth and width of macro-crack, and the energy of transmitted wave decreases correspondingly. The size and inclined angle of macro-crack can be quantitatively estimated by the fitting function from the energies of reflected and transmitted waves. The variation of crack depth, width and angle is approximately linear with the amplitudes of reflected and transmitted wave packets. A fitting function is constructed by using the amplitude ratio of reflected wave packet or transmitted wave packet to total wave packet, which can be used to estimate the macro-crack depth, width and angle. This conclusion is helpful to the detection of macro-crack in the actual production and service of plate structures.

Application of Bayesian Update Method in the Construction Control of Continuous Rigid Frame Bridge Girders with High Piers and Large Spans

In the construction process of large-scale bridges, there are uncertainties and time-varying factors in the environment and construction loads. It is difficult to make accurate estimates of the theoretical calculation models of construction control in advance. In view of this situation, Bayesian dynamic updating method is introduced to re-estimate the predicted results of the theoretical model. When applying this method, first, the finite element calculation model is determined based on the response surface method, and its calculation results are used as prior information. Then, combined with the actual detection data during the construction process, the Bayesian update formula is derived based on the conjugate prior distribution to correct the theoretical prediction results of bridge construction monitoring. Finally, the actual stress detection data of the control section of high-pier and large-span continuous rigid frame bridges during the construction process illustrate the application process of Bayesian updating in improving the theoretical prediction model. Results indicate that the internal force of the bridge control section obtained by re-evaluating by Bayesian theory not only incorporates the priori information models but also actual monitors sample information during the construction process. The predicted results reflect the true deformation and stress state of the bridge during the bridge construction process and improve the precision of construction monitoring.

Computational study of impact wear: Fatigue approach

Impact wear results from the surface failure of engineering components that undergo repetitive contact motion. It reduces their service life. This study investigated the impact wear of alloy steel using computational techniques combined with empirical data. The ultimate objective was to develop an approach requiring low–moderate effort for industrial application using limited resources to predict the average impact wear rate of AISI 4140 alloy steel (one of the most commonly used materials). The wear mechanisms were investigated by scanning electron microscopy (SEM). Indirect monitoring was used to examine the wear stage transition cycle, e.g., from mild to severe wear. The empirical results showed that the transition cycle depended on the impact force. Fatigue was identified as the key damage mechanism, with cracks and lamellar wear appearing under severe deterioration. The average wear rate from the initial impact cycle to the wear stage transition cycle increased as the impact force increased. A simplified computational 2D finite element model assuming a smooth frictionless surface was used to investigate the contact condition. The contact behavior including the stress–strain distribution that developed during first contact was investigated using finite element analysis. A combined empirical and computational approach to predicting average wear rate was developed based on stress distribution data from the FE model and fatigue properties. The prediction results were then validated by comparison with the empirical data. These showed good agreement. The stress amplitude derived from an equivalent high-stress region was also introduced. The predicted curve of average wear rate versus stress amplitude of an equivalent high-stress region improved the design of the component.

Effect of pulmonary regurgitation on cardiac functions based on a human bi-ventricle model

Background and objective: Assessing the severity of pulmonary regurgitation (PR) and identifying optimal clinically relevant indicators for its treatment is crucial, yet standards for quantifying PR remain unclear in clinical practice. Computational modelling of the heart is in the process of providing valuable insights and information for cardiovascular physiology research. However, the advancements of finite element computational models have not been widely applied to simulate cardiac outputs in patients with PR. Furthermore, a computational model that incorporates both the left ventricle (LV) and right ventricle (RV) can be valuable in assessing the relationship between left and right ventricular morphometry and septal motion in PR patients. To enhance our understanding of the effect of PR on cardiac functions and mechanical behaviour, we developed a human bi-ventricle model to simulate five cases with varying degrees of PR severity. Methods: This bi-ventricle model was built using a patient-specific geometry and a widely used myofibre architecture. The myocardial material properties were described by a hyperelastic passive constitutive law and a modified time-varying elastance active tension model. To simulate realistic cardiac functions and the dysfunction of the pulmonary valve in PR disease cases, open-loop lumped parameter models representing systemic and pulmonary circulatory systems were designed. Results: In the baseline case, pressures in the aorta and main pulmonary artery and ejection fractions of both the LV and RV were within normal physiological ranges reported in the literature. The end-diastolic volume (EDV) of the RV under varying degrees of PR was comparable to the reported cardiac magnetic resonance imaging data. Moreover, RV dilation and interventricular septum motion from the baseline to the PR cases were clearly observed through the long-axis and short-axis views of the bi-ventricle geometry. The RV EDV in the severe PR case increased by 50.3% compared to the baseline case, while the LV EDV decreased by 18.1%. The motion of the interventricular septum was consistent with the literature. Furthermore, ejection fractions of both the LV and RV decreased as PR became severe, with LV ejection fraction decreasing from 60.5% at baseline to 56.3% in the severe case and RV ejection fraction decreasing from 51.8% to 46.8%. Additionally, the average myofibre stress of the RV wall at end-diastole significantly increased due to PR, from 2.7±12.1 kPa at baseline to 10.9±26.5 kPa in the severe case. The average myofibre stress of the LV wall at end-diastole increased from 3.7±18.1 kPa to 4.3±20.3 kPa. Conclusions: This study established a foundation for the computational modelling of PR. The simulated results showed that severe PR leads to reduced cardiac outputs in both the LV and RV, clearly observable septum motion, and a significant increase in the average myofibre stress in the RV wall. These findings demonstrate the potential of the model for further exploration of PR.

Lightweight, electrical insulating, and high thermally conductive all-polymer composites with reinforced interfaces

High thermally conductive materials with good electrical insulating and mechanical properties are indispensable for electronics. Aiming for all-polymer composites with light weight, electrical insulation and high thermal conductivity (TC), ultrahigh molecular weight polyethylene (UHMWPE) fibers/epoxy composites with two kinds of fiber orientation structures (0°/90°, ±45°) were fabricated by hot-pressing. It is found that the in-plane TC of ±45° composite is approximately 1.3–1.4 times that of 0/90° one, and the corresponding mechanism is verified by finite element simulation and model calculation. Thermally conductive pathways formed by UHMWPE fibers endow 0/90° and ±45° composites with the in-plane TC of 9.94 and 13.61 Wm−1K−1, respectively. Through depositing polydopamine (PDA) and grafting polyether amine (PEA) onto the surface of fibers, the poor fiber/epoxy interface was improved, resulting in 40.7% and 52.3% improvement in interlaminar shear strength (ILSS) and shear modulus, respectively. Simultaneously, a higher in-plane TC as high as 15.76 Wm−1K−1 is achieved. The heat dissipation evaluation indicates that the composite can reduce the temperature of the resistance wire by 14 °C. This work reveals the great potential of UHMWPE fibers in heat dissipation and provides a strong candidate for electrical insulating support materials with high TC for heat management of electronics.

Influence of Fatigue Damage on Criticality Cell Ultimate Load Capacity of Steel–Concrete Composite Section

In order to investigate the impact of fatigue damage on the ultimate load capacity of criticality cells in steel–concrete composite segments and to address the complex design challenges associated with bridge steel–concrete composite segments in practical engineering, this study designs two scaled criticality cell specimens with a scale ratio of 1:2 and performs ultimate load capacity tests after fatigue cyclic loading. By analyzing the stress distribution of each component and the force transmission ratio and combining the results from finite element model calculations, this study introduces the degree of structural fatigue damage and proposes a predictive model for the ultimate load capacity of steel–concrete composite segment criticality cells that is easy to apply. This model is compared with the finite element calculation results and experimental values, and the results are found to be in good agreement. Additionally, the number of shear connection members in the model is optimized based on the calculation results. The research findings indicate that the main failure mode of criticality cells is inclined compression failure. The strength of each part decreases in the following order: steel–concrete composite segment, steel structure segment, and concrete segment. Furthermore, fatigue damage has a significant impact on criticality cells. The optimized model exhibits similar stress performance and force transmission ratio to the original model and provides a reference for the design of practical engineering.

Temporally continuous thermofluidic–thermomechanical modeling framework for metal additive manufacturing

Additive manufacturing (AM) is known to generate large magnitudes of residual stresses (RS) within builds due to steep and localized thermal gradients. In the current state of commercial AM technology, manufacturers generally perform heat treatments in effort to reduce the generated RS and its detrimental effects on part distortion and in-service failure. Computational models that effectively simulate the deposition process can provide valuable insights to improve RS distributions. Accordingly, it is common to employ Computational fluid dynamics (CFD) models or finite element (FE) models. While CFD can predict geometric and thermal-fluid behavior, it cannot predict the structural response (e.g., stress–strain) behavior. On the other hand, an FE model can predict mechanical behavior, but it lacks the ability to predict geometric and fluid behavior. Thus, an effectively integrated thermofluidic–thermomechanical modeling framework that exploits the benefits of both techniques while avoiding their respective limitations can offer valuable predictive capability for AM processes. In contrast to previously published efforts, the work herein describes a one-way coupled CFD-FEA framework that abandons major simplifying assumptions, such as geometric steady-state conditions, the absence of material plasticity, and the lack of detailed RS evolution/accumulation during deposition, as well as insufficient validation of results. The presented framework is demonstrated for a directed energy deposition (DED) process, and experiments are performed to validate the predicted geometry and RS profile. Both single- and double-layer stainless steel 316L builds are considered. Geometric data is acquired via 3D optical surface scans and X-ray micro-computed tomography, and residual stress is measured using neutron diffraction (ND). Comparisons between the simulations and measurements reveal that the described CFD-FEA framework is effective in capturing the coupled thermomechanical and thermofluidic behaviors of the DED process. The methodology presented is extensible to other metal AM processes, including power bed fusion and wire-feed-based AM.