Developed FEM Model Research Articles

Coupled heat transfer–crystallization analysis in continuous carbon fiber-reinforced thermoplastic composites 3D printing: simulation and experimental validation

AbstractThis study proposes an advanced progressive numerical modeling approach to investigate heat transfer phenomena occurring in the 3D printing of continuous carbon fiber-reinforced co-polyamide (Copa) composites. The material extrusion process is simulated using element activation techniques and active cooling methods, while thermal boundary conditions are updated during the printing process. Differential Scanning Calorimetry (DSC) tests are conducted on composite and neat polymer samples to include the crystallization behavior, where the Hoffman–Lauritzen model is employed for crystallization modeling based on the input data from DSC tests. It is demonstrated that the proposed modeling approach, coupled with the Hoffman–Lauritzen crystallization model, accurately predicts the thermal history of the composite extrudate post-deposition. In the case of a neat polymer, the results of the developed FEM model align well with existing literature. Experimental in-situ temperature measurements utilizing thermal vision agree very well with the predictions of the heat transfer model developed for 3D printing of continuous fiber-reinforced Copa composites, demonstrating the model's capability to predict temperature profiles during printing.

Damage sensitivity studies of composite honeycomb sandwich structures under in-plane compression and 4-point bending: Experiments and numerical simulations

Honeycomb sandwich structures, especially those with carbon-fiber panels and Nomex-honeycomb cores, are widely employed in automobiles and aircraft due to their excellent mechanical properties. Here, in-plane compression and 4-point bending experiments, as well as FEM simulations, are performed for a composite honeycomb sandwich structure with face-core de-bonding defects or impact damage to evaluate the damage sensitivity. It is found that the structure exhibits a higher sensitivity to impact damage than to de-bonding defects. Impact damage caused by an energy of 3 J–5.5 J can alter the failure mode under both in-plane compression and 4-point bending loads, and reduce in-plane compression strength by more than 50 % and 4-point bending strength by 15 %. In comparison, de-bonding defects of the same size can change the failure mode and decrease the strength by only 10 % under in-plane compression. The developed FEM model predicts all failure modes and residual strengths obtained from experiments. The simulation results show that the structural characteristics of producing concaves in the facesheet and core are the dominant contributors to structural failure. Our model, covering all geometric and structural details of the honeycomb core, provides a useful tool for studying the mechanical behaviors of such structures.

FEM investigation of full-scale tests on DSSI, including gravel-rubber mixtures as geotechnical seismic isolation

Soil-rubber mixtures underneath foundations are an eco-sustainable and low-cost Geotechnical Seismic Isolation (GSI) solution. Using rubber grains from end-of-life tyres in the mixtures can provide a modern recycling system that reduces the stockpile of scrap tyres worldwide. In recent years, gravel-rubber mixtures (GRMs) properties have been investigated, finding good behaviour in static and dynamic conditions. Laboratory tests on GRMs advantages as GSI in the form of a layer underlying the foundation of a structure are available in the literature. Nevertheless, only one experimental campaign on a full-scale prototype structure resting on GRMs with 0% and 30% rubber content per weight was performed (SOFIA-SERA Research Programme).This paper presents 3D advanced nonlinear FEM analyses to reproduce and furnish new results about the above-mentioned full-scale test. The calibration of the parameters of the different constitutive models used for modelling the foundation soil and the GRMs was supported by an extensive geotechnical characterization. The developed FEM model was validated by the results from the above-mentioned full-scale test in terms of accelerations and velocities. Then, the dynamic behaviour of the GRMs was studied, also considering the shear strains versus the shear stresses and the horizontal and vertical displacements, quantities not investigated experimentally. Finally, the GRMs static behaviour was also investigated, considering the GRMs axial strains and the GRMs and foundation vertical displacements.The paper highlights the fundamental role of both experimental tests and numerical modelling, as invaluable tools for coupled analyses of the seismic behaviour of soil-structure systems, including innovative materials, such as GRMs, and the main advantages of using GRMs as GSI.

Free Vibrational Behavior of Bi-Directional Functionally Graded Composite Panel with and Without Porosities Using 3D Finite Element Approximations

The frequency characteristics of bi-directional functionally graded(FG)rectangular panels with and without porosities are examinedin this workusing 3D finite element approximations.Theproperties ofgraded panel consist metal and ceramic materialvaried smoothly inbi-direction. The material properties of this highly heterogeneous material are obtained using the Voigt material model and Power-law. The present model is developed using a customized computer code anddiscretized using three-dimensional solid 20-noded quadrilateral elements. The mesh refinement isconductedto presentthe convergence test.The validation test is presented by showing comparison ofthe obtained findingswith the results reportedin thepreviousliterature. At a later stage, comprehensive parametric research is presentedthrough numerical illustrations which reveal that the geometrical and material parameters of bi-directional functionally graded panel affect its frequency characteristics,significantly. Finally, the developed 3D FEM model to predict the free vibrational characteristicsof multidirectional FG rectangular plateswith and without porosities will be the reference for the continuation of research in this area.

Analysis of thermal stresses synergy in surface layer of carburised creep-resistant casts during rapid cooling processes

ABSTRACT During the carburising processes, treated elements are transported on a specially designed technological equipment of the furnaces. This equipment works in particularly hard conditions. This is because in each work cycle, apart from the load carried by the charge, it is subjected to harmful effect of many other factors such as the highly carburising technical atmosphere of the furnace and high and rapidly changing temperature. These factors influence fatigue changes in the equipment’s parts, the observable effect of which may be cracks on the surface, propagating deeper into the material in subsequent cycles. A pivotal factor influencing the kinetics of fatigue processes in the carburising furnaces equipment are thermal stresses appearing in each operating cycle, with each temperature change. The thermal stresses in this equipment are caused by the temperature gradient across the section of the heated or cooled element and different thermal expansion of the structural components of the carburised alloy. In the paper, on the developed FEM model of the subsurface layer of a carburised rib of a pallet for transporting the charge in the furnace, analyses of stress distributions during rapid cooling were carried out. These analyses were performed with taking into account the separate impact of the above-mentioned sources of thermal stresses and their simultaneous action. In the analyses which consider the influence of the temperature gradient, the main load factor was the temperature distribution determined on the basis of the heat flow analyses carried out for the analysed section of pallets rib. The conducted analyses made it possible to assess the impact of local stresses caused by different thermal expansion of structural components of the carburised alloy on the change in the distribution of global stresses caused by the temperature gradient formed during rapid cooling. Based on the obtained results, it was assessed how the increased concentration of carbide precipitates, characteristic for the grain boundary of the carburised alloy, favours the formation of cracks observed in real castings, and whether the analysed stress sources have a significant impact on the kinetics of fatigue processes.

Numerical investigation of the performance of geocell-reinforced granular base in inverted pavement systems using nonlinear finite element modeling

The quality of granular base materials plays a key role in the enhanced performance of inverted pavement systems (IPSs). Typically, premium-quality materials are required for the construction of IPS structures. This study investigates the feasibility of geocell reinforcement of lower quality materials to be used as an alternative when premium base materials are not available. To this end, 16 different pavement structures were studied using nonlinear finite element (NL-FEM) models in ABAQUS. The results are validated using those of a full-scale field project, which confirms the reliability of the developed FEM model. It was concluded that geocell reinforcement of granular base layer can increase the fatigue and rutting performances. In all the cases, lower quality aggregates with reinforcement exhibited better performance than the non-reinforced base materials with premium aggregate quality. The findings confirm that in the absence of premium-quality aggregates, good-performing inverted pavement structures can still be achieved.

QRS Morphology-Based EDR Signal—Factors Determining its Properties

Respiration-induced signals contain a clinically significant information. It could be obtained utilizing both direct and indirect methods. ECG-Derived Respiration (EDR) method is the latter one. However, in this case, two approaches could be distinguished. First one is based on determining changes in the morphology of QRS complexes while the second one is based on the Respiratory Sinus Arrhythmia (RSA) mechanism. The former approach is discussed in the paper. The basic properties of QRS morphology-based EDR signal were evaluated by means of simulations performed using a developed FEM model and appropriate experiments. In effect, basing on changes of the leads’ voltages induced by a heart translation or rotation, or by both mechanisms undergoing simultaneously, the sensitivity-like surfaces and the synthetic EDR signals were obtained. A very good agreement of the experimental and simulation results was achieved. The QRS morphology-based signal’s properties strongly depend on geometrical relation of the used lead to dominating direction of the heart translation, its rotation, and on personal relation between these two mechanisms. The conclusions presented should be taken into account especially when developing or using QRS morphology-based approach in respiratory monitoring systems.

Development of a volumetric compression restrainer for structures subjected to vibration

In the last 2 decades, application of viscous dampers as restrainer device (lock-up) in buildings and bridges to diminish harmful effect of vibrations. However, leakage issue in the viscous luck-up devices requires regular expensive maintenance procedure to prevent device performance failure and many researchers are encouraged to find an alternative system with low maintenance cost. Therefore, in this study the Volumetric Compression Restrainer (VCR) device has been developed as a new effective restrainer system using hyper-elastic rubber material. The VCR device is consisted of multi hyperelastic rubber tubes which positioned within steel cylinder with core and applicable in the structures as vibration resistance system. To develop VCR device, the primary design details are derived and the behavior of proposed VCR subjected to various dynamic load conditions has been assessed through the finite element simulation. In order to define the hyper-elastic characteristics of the rubber material for finite element modeling, the hyperelastic rubber material with 3 different hardness properties have been tested experimentally. Then in the next step, the rubber test data were used to develop the analytical model for the VCR device. So, the performance of the VCR device was determined by applying cyclic load to the developed FEM model. Afterwards, multiple prototypes of VCR devices have been manufactured with four different rubber hardness properties and two different configurations and a series of experimental tests have been conducted to validate the device performance.Then, a three-story concrete frame equipped with supplementary VCR device subjected to seismic loads is considered and the performance of VCR and its efficiency to diminish vibration effect are evaluated. Besides, the hybrid population-based algorithm (PSOGSA) is implemented to optimize design of structure equipped with VCR device under applied earthquake excitation. The results revealed that by implementing VCR device as supplementary restrainer system in the frame structure, lateral displacement is reduced in range of 31.5–61.2% compared to the bare structures which is proving the efficiency of developed VCR device to protect the structures against severer dynamic loads.

Experimental Verification of Contact Acoustic Nonlinearity at Rough Contact Interfaces.

When a longitudinal wave passes through a contact interface, second harmonic components are generated due to contact acoustic nonlinearity (CAN). The magnitude of the generated second harmonic is related to the contact state of the interface, of which a model has been developed using linear and nonlinear interfacial stiffness. However, this model has not been sufficiently verified experimentally for the case where the interface has a rough surface. The present study verifies this model through experiments using rough interfaces. To do this, four sets of specimens with different interface roughness values (Ra = 0.179 to 4.524 μm) were tested; one set consists of two Al6061-T6 blocks facing each other. The second harmonic component of the transmitted signal was analyzed while pressing on both sides of the specimen set to change the contact state of the interface. The experimental results showed good agreement with the theoretical prediction on the rough interface. The magnitude of the second harmonic was maximized at a specific contact pressure. As the roughness of the contact surface increased, the second harmonic was maximized at a higher contact pressure. The location of this maximal point was consistent between experiments and theory. In this study, an FEM simulation was conducted in parallel and showed good agreement with the theoretical results. Thus, the developed FEM model allows parametric studies on various states of contact interfaces.

Heating performance of a novel externally-heated geothermal bridge de-icing system: field tests and numerical simulations

An external geothermal bridge de-icing system deploys hydronic loops covered in insulation and attached to bridge decks to heat the bridge using geothermal energy. Several studies were performed on the laboratory system under controlled temperatures and showed promising results for field deployment. However, no field tests or investigations of its heating performance were conducted during snow events. In this study, the external geothermal bridge de-icing system was deployed on a mock-up bridge deck in the field and tested during several winter events, providing an opportunity to conduct non-heating, heating, and de-icing tests. A 3-dimensional multi-physics finite element model of the heated deck was developed in COMSOL and fully calibrated with the field tests in transient analyses. The simulated temperatures were verified with the measured thermocouple readings at the inlet and outlet of the bridge loops and different bridge deck depths. Based on the calibrated FEM model, a record snowfall event in the Spring of 2015 was simulated using the equivalent snow-melting heat flux loss on the deck surface. The heated bridge deck maintained a minimum temperature of 0.3 °C (32.6 °F) during the snow event with a supplied inlet temperature of 43.3 °C (110 °F), and the equivalent heat flux loss on the deck surface was around 220 W/m2. The developed FEM model provided satisfactory simulations of bridge heating in winter events. The external geothermal bridge de-icing system maintained a snow-free deck during the record snow event and is ready for implementation.

Numerical and experimental analysis of a flame-retardant polymer material after extrusion through the printing nozzle of fused filament fabrication system

Research focuses on developing a novel flame-retardant filament utilizing acrylonitrile–butadiene–styrene (ABS) and ammonium polyphosphate (APP) by the numerical approach using finite element analysis (FEM)-based software, COMSOL Multiphysics to overcome nozzle clogging and establish optimal three-dimensional (3D)-printing parameters. The developed FEM model enabled the numerical testing of differently shaped nozzles and proven the benefit of using a low-convergence angle (60°) nozzle because of the greater magnitude of pressure drop at nozzle tip compared with that of a high-convergence angle (120°) nozzle, a slightly better temperature distribution at the nozzle region, and smoother flow of the melted filament. Experimental tests results demonstrated the feasibility of using fused filament fabrication 3D printing to apply on ABS composite directly, and the printed samples retain their properties. An improvement in the burning test showed a V 0 rating, thermal stability 13% at 800 °C, and the heat release rate of ∼390 W/g compared with neat ABS (∼501 W/g).

FEM analysis of the elastic behavior of composites and nanocomposites with arbitrarily oriented reinforcements

This work is aimed at studying the effect of different morphological features on the stiffness of discontinuous fiber reinforced composites and nanocomposites by means of FEM analysis. The morphological features include not only volume fraction and aspect ratio of reinforcement, but also its orientation. The FEM approach, based on continuum mechanics, required the definition of a proper representative volume element, in which reinforcement is randomly dispersed in the simulation domain. The developed model has been used in order to calculate the stiffness matrix of unidirectional discontinuous glass fiber reinforced composite (DGFRC) as well as carbon nanotubes reinforced nanocomposites (CNTRNC). Comparison with closed form analytical models showed that the Halpin-Tsai (HT) model is able to predict the evolution of the elastic constants over a wide range of volume fractions and aspect ratio. The Tandon-Weng (TW) model, in contrast, shows a poor agreement with the simulation results.On the other hand, the developed FEM model also allowed accounting for reinforcement orientation. The calculated elastic properties are in excellent good agreement with the corresponding values calculated according to the classical lamination theory, indicating the accuracy of the developed FEM model for estimation of stiffness of composites and nanocomposites, also accounting for reinforcement orientation.

A parametric investigation on the fretting fatigue behaviour of heat treated Al 6061-T6 under rotating bending phenomena

ABSTRACT This research investigated the effect of variable fretting parameters on bending fatigue behaviour of heat-treated Al-Mg-Si alloy (Al 6061-T6). Bulk stress, contact pressure, pad geometry, and locations were chosen as variable parameters to measure its consequence on fatigue life. A developed FEM model justified the experimental observation. It observed that, within the lower bulk stress range, fretting action decreases the fatigue life of Aluminium alloy significantly than the plain one. However, this difference almost vanishes at higher-order loading as well as stress in comparison to plain fatigue. Contact pressure and stress distribution along the contact path and non-filleted-edge suggest about the importance of safety design over the fretting zones. The flat on cylinder contacts was found as detrimental at higher-order contact pressure while cylinder on cylinder one reduces notably at low contact pressure. Fuzzy logic, a soft computing technique was implemented to predict the fretting fatigue as well as the effect of pad location from surface graphs. Nevertheless, catastrophic rupture followed the aspect of fretting loading parameter that showed fretting not only affects in quantity but also the quality of the fatigue behaviour of Al 6061-T6.

Finite Element Modelling of Cutting Forces in Face Milling of Duplex Stainless Steel 2205

Duplex Stainless Steels are one of the newest pioneers in the world of super alloys. They exhibit a unique combination of high strength and corrosion resistance and hence are currently giving a strong competition to other nickel based alloys and titanium alloys. Due to the excessive alloying of DSSs, they have a very poor machinability, as result of which the cutting forces associated with machining is very high. In this work, a 3D Finite Element Modelling of cutting forces in milling of DSS 2205 has been developed using FEM software package ABAQUS Oblique cutting has been used so that inaccuracies due to the assumptions in orthogonal machining are avoided. The developed FEM model has been validated experimentally by conduction a series of milling tests. The model results showed close agreement with the experimental results and the forces values were found to be affected most by feed rate. As feed rate per tooth increases, the forces components were also found to be increasing both for experimental and model values.

BEHAVIOUR'S ANALYSIS OF LOAD-CARRYING MEMBERS FOR TIMBER FRAMEWORK BUILDING

The problem of limited raw material and energy resources can be solved by the replacement of non-renewable structural materials by renewable ones. Using of timber structures enables to decrease impact on the planet. It will also help to reverse some of the effects of industrialization. Structural members from solid and glued laminated timber, cross-laminated timber and other timber-based materials are widely used for one-storey and multi-storey buildings. Three-storey timber framework building was considered as an object of investigations. The considered three-storey building has length and width equal to 28 and 13 m, correspondingly. The using of software Autodesk Robot Structural developed FEM model of three-storey platfom framed framework building. Load-carrying structures of considered framework building consist from the load-carrying walls, floors and roofs structures, which develop horizontal and vertical diaphragms providing strength and rigidity of the framework. The rational bay of the light framework structures changes within the limits from 300 to 600 mm. The rational span of beams and purlins does not exceed 4 m. Solid timber with the strength class C24 was assumed as a structural material for timber frameworks members. The OSB sheets were considered as a material of the cladding for external structures. Behaviour of the load-carrying shear walls were analysed by the using of FEM models developed by the software Autodesk Robot Structural and ANSYS 15 so as methods explained in EN 1995-1-1. The software ANSYS 15 was used for the development of separate model of load-carrying shear walls. Initial unit of shear wall – a panel with the dimensions 1.2X2.7 m was considered for the purpose. The bar sub-members of the panel were modelled by the BEAM 188 finite element type. The SHELL 181 and COMBIN 14 finite element types modelled the cladding sub-members and mechanical fasteners. The dependence between the horizontal displacements of the load-carrying wall, intensity of the applied load, area of the openings so as thickness of the wall was obtained as a second power polynomial equation. It was stated, that the obtained FEM models enables to describe the behaviours of the load-carrying shear walls with enough precision.

Induction Preheating for the Submerged Arc Welded Steel Tube Production

Tenaris is a leading supplier of tubes and related services for the world’s energy industry that manufactures a complete range of seamless and welded steel tubular products. The welding facilities are located in North and South America, and perform three types of welding processes, namely Electric Resistance Welding (ERW), Spiral Submerged Arc Welding, and Longitudinal Submerged Arc Welding (LSAW). Regarding the ERW process, in recent years we studied both the welding using Comsol [1,2], and the ulterior seam heat treatment using an in-house developed FEM model [3,4]. During the LSAW process, after the plate is conformed through the UOE forming process, the butt joint of the pipe is welded in three phases, first of which aims at presenting the edges and joining them but without filling in the bevels, the second one is to fill in the seam region at the inside of the pipe and the third one to do this operation on the outside. The welds are made by melting with an electric arc the bare metal electrodes. Pressure is not applied on the pipe during welding. Depending on the final product properties sought, a preheating near the edges with a relatively narrow temperature range is required for these three welding stages. In this article we focus on the inductive preheating for the tack welding stage of a continuous production line; it involves an open tubular geometry whose edges are facing and separated approximately 10 mm. There is no need to reheat the full tube, but only a region of ±75 mm from the edges approximately. Given the geometry and the required localized preheating, usual solution would be bar type inductors as those used typically for seam annealing. Alternatively, cylindrical coils can be used instead of inductive bars. 2D and 3D numerical models of different inductor bars and cylindrical coils are used in order to assess both kinds of preheaters and to understand the advantages and disadvantages of each one.

Numerical Modelling of Cylindrical Specimen under Mixed-Mode Loading Conditions

Mixed mode loaded fatigue specimens are not used very frequently. The main reason is that there are still very few qualitative results, which would help with better understanding of how the mode II and mode III are affecting the overall crack propagation. On the other hand, there is considerable number of parts loaded in mixed mode. Studying fatigue failure of roller bearing elements made of polymer material was a motivation to design a new experimental specimen for study of fatigue behaviour of the material loaded in mixed mode. The contribution presents developed FEM model of such specimen with focus on determination of fracture mechanics parameters of propagating cracks.

Reverse engineering based integrity assessment of a total hip prosthesis

The structural strength of a total hip prosthesis was investigated based on a 3D scanning procedure of a hip prosthesis and Finite Element Analysis. 3D scanning was performed by the ATOS 3D scanner, and the CAD model was built using Geomagic Design X software. The obtained CAD model was imported to Finite Element simulation software Abaqus to generate a FEM model. By using the developed FEM model stress and strain distribution in the femoral component were calculated for a typical human walking load case. The analysis was performed for a newly implanted prosthesis and for a case with loosened femoral component of the same hip prosthesis. The analysis results show that in case of loosened femoral component stress concentrations occur at locations where fatigue problems in real cases were observed.

Mezoskalowy model MES do analizy delaminacji kompozytu

The article discusses the problem of delamination of layered composite samples according to the mode I (tensile opening mode). It includes the experimental part, which sets the averaged characteristics of delamination of the samples in the relation tensile opening–tensile force as well as the description of mesoscale FEM model of composite, which takes into account its internal structure. The model was used in the simulation of delamination, while the development of the fracture took place in consequence of modifications of finite elements modelling the matrix. The results of the delamination simulation with the use of the developed FEM model were consistent with the results of the experiment.

Analysis of Wheel-Rail Contact under partial slip and low speed conditions

The paper analyzes applicability of rolling contact simulation in low speed and adhesion conditions. Additionally, transition zone of the coefficient of friction is implemented. Efffects of the friction coefficient are examined to the forces which are normal and tangential components. Various comparative studies are also computed and differences between numerical results with results of the comparative studies are observed for validation. The results show that outputs of developed FEM model are compatible with comparative studies. Transition zone of the coefficient of friction directly affects the traction force at low speed conditions.DOI: http://dx.doi.org/10.5755/j01.mech.23.1.13779