Finite Element Simulation Study Research Articles

Effect of CuO and SnO2 particle size on hot extrusion deformation of AgCuOSnO2: Finite element simulation and experimental study

Effect of CuO and SnO2 particle size on hot extrusion deformation of AgCuOSnO2: Finite element simulation and experimental study

Finite element simulation study on influence of spacecraft stiffener structure on elastic wave propagation

Aiming at the propagation process of elastic wave in spacecraft stiffener structure. In this paper, the phase and energy changes of elastic waves propagating in the wall structure of stiffeners at different frequencies are analyzed by using finite element method and laser Doppler vibrometer (LDVS). Meanwhile, the relationship between the parameters of stiffeners and the diffusion of acoustic wave energy and the phase change of elastic waves respectively is obtained. The results show that in the range of parameters involved in this paper, the stiffener has a significant effect on elastic waves propagation. When wavelength λ > 10mm, most of the elastic waves are reflected by the stiffener, while when λ < 6mm, elastic waves propagate more easily across the stiffener, and the proportion of those propagated by the stiffener increases. Moreover, the functional expression of the relationship between the height of the stiffener and the frequency of the elastic wave which can easily propagate through the stiffener is obtained.

The Influence of Difference of Top-Coat Composition and Thickness on the Residual Stress of Ebcs Fabricated by APS: A Finite Element Simulation Study

The Influence of Difference of Top-Coat Composition and Thickness on the Residual Stress of Ebcs Fabricated by APS: A Finite Element Simulation Study

Dependancy of Three Phase Induction Motor Derating Aspects on Complex Voltage Unbalance Factor: A Calorimetric and Finite Element Simulation Study

It is well known that three-phase induction motors have to be derated in the presence of supply voltage unbalance (negative sequence) exceeding a stipulated limit of 1% based on several widely used standards. Generally, voltage unbalance limits are decided based on the magnitude of negative sequence voltage unbalance factor which is quantified as the ratio of negative sequence voltage to positive sequence voltage. However, a specified voltage unbalance magnitude can arise as a result of numerous possibilities of the three phase supply voltages. Therefore, it is hypothesised that the current derating curve, which defines a derating factor that is dependent on the magnitude of the voltage unbalance, is not optimal and may not be economical and/or safe for some voltage unbalance conditions. To examine the validity of this hypothesis, modelling and experimental validation need to be carried out considering motor losses and temperature rise which are the main factors that help determine the derating factor of an induction motor. Realising these requirements, the emphasis of this study is to examine the dependency of losses, temperature rise and torque oscillations of a three-phase induction motor on the complex nature of voltage unbalance through calorimetric and finite element simulation-based studies. The outcomes are expected to assist in the development of suitable derating factors.

Studies on the effect of inclination of reinforcement and wave propagation in concrete cores through finite element simulations

A core test is practiced to determine in-situ cube strength, but most codes give different results depending on the factors used. The general problems of core testing are well known. The factors including core diameter, length-to-diameter ratio (L/d), concrete age, aggregate characteristics, the direction of coring, and the moisture condition at the time of testing are known, which affect the relationship between core strength and the corresponding standard cube or cylinder strength. Another potential factor influencing the testing of cores is the presence of reinforcing bars within the core. Only a few researchers have investigated the effects of steel bars on the strength of cores.Along with these existing factors, the inclination of rebar is believed to influence the core strength, but which has not been taken into consideration so far. In this paper, the finite element simulation studies carried out on concrete cores embedded with reinforcing bars at various inclination is described in detail. The wave propagation through the concrete core is studied, and regression analysis is carried out considering the multiple factors.

A Review of Fine Blanking: Influence of Die Design and Process Parameters on Edge Quality

Conventional blanking is the single-stroke shearing of closed contour profiles. However, the blanked pieces have inherent errors like fractured cut surface and blank dishing necessitating further sizing and/or finishing operations. Fine blanking is a more precise version of the blanking operation with lesser errors such that post-forming steps required will be minimal. Thus, it is an ideal candidate for manufacturing precision machine components. This review paper starts with the introduction to the process. Then, studies aimed at the analysis of fine blanking tooling and process parameters and their effect on fine-blanked part characteristics are presented. Inferences from studies on the design of equipment for fine blanking, deformation mechanics involved and the fine blanking performance of different materials are also discussed. The use of finite element simulation studies to understand the process better has also been determined. Various reported strain measurement techniques are then discussed. The recent improvement in techniques like in situ digital image correlation enables accurate experimental measurement of strain in the shear zone which can be used to validate the findings from FE simulations. Fine blanking process modifications that aimed at cost reduction or improvement in product quality are summarized as well.

Influence of internal oxidation of the bond-coat on the residual stress around the TGO and failure modes of the APS-TBCs: A finite element simulation study

In this paper, the influence of internal oxidation of the bond-coat on the residual stress around the thermally grown oxide (TGO) and failure modes of the TBCs fabricated by atmospheric plasma spraying (APS) has been studied via finite element modeling. Generally, the internal oxidation will occur when the bond-coat (BC) was fabricated by APS. The produced oxide was distributed irregularly at the inner of the bond-coat, and the distribution patterns like some isolated islands, so it was called “island-like” oxide by us. As the BC layer usually consists Ni, Co, Cr, Al and Y etc., the composition of the “island-like” oxide is very complicated due to the formation Gibbs free energy are different when those metallic elements take reaction with exterior [O]. During the subsequent high temperature service conditions, a continuous thin TGO layer will be formed. In addition, the BC layer will be further endured with inner oxidation due to the [O] diffuse to the interface, the mixture oxide will appear below the TGO layer randomly, which will lead to a complicated stress distribution at the TGO/YSZ interface directly. Moreover, a small amount of Cr2O3 was formed in TGO layer, the distribution of interfacial stress was strongly influenced, resulting in complicated fluctuance of interface and unpredictable failure modes simultaneously. So, to systematically discuss the distribution of residual stress state along YSZ/TGO interface, the influence of the composition of TGO and the location of internal oxides on the distribution of interfacial stress were studied via FEM. The results show that with the increase of the percentage of Cr2O3 (wt.%) in TGO, the maximum tensile stress and compressive stress have changed evidently at the peak of TGO. Besides of considering the percentage of Cr2O3 (wt.%) in TGO, the internal oxides existed below the TGO layer have been taken into account simultaneously.

Understanding the effect of tool geometrical aspects on intensity of mixing and void formation in friction stir process

The reduction of agglomeration of particulate reinforcement in friction stir processing and elimination of joint line remnant in friction stir welding depends on stirring ability of friction stir tool. The magnitude of stirring is indicated by the intensity of material inter-mixing in tool interacted region. Present investigations analyse the influence of geometrical aspects of classical friction stir tool on the intensity of material intermixing, location of high stir regions and void formation during the steady-state phase of friction stir welding. The classical tool was chosen as its geometrical features undergo minimal wear in the harsher processing environment. Investigating material mixing using metallic inserts have their shortcomings due to different flow properties of insert/marker and parent material. Therefore, bi-colour plasticine configuration possessing primary colours was adopted to understand the level of intermixing. The hue attribute of the generated secondary colour was utilised to identify and quantify material mixing. Experimental results revealed that the pin diameter positively influenced mixing and negatively affected void formation. Shoulder size and pin taper angle aided in the closure of void with inferior mixing. The intensity of mixing enhances on selection of tools possessing a shoulder to pin diameter ratio of 2.5. Finite element simulation studies were conducted to understand the reasons for mixing under certain tooling conditions. Since material subjected to stirring is concentrated primarily on a portion of advancing side, components of shear strain, shear strain rates, shear stress and velocity were tracked for this portion of processed material during its interaction with tool pin for one complete rotation.

High Temperature Deformation Behavior and Constitutive Modeling for Flow Behavior of Alloy 718

In the present work, hot deformation behavior of Alloy 718 was investigated over a temperature range of 1223–1373 K and strain rate range of 10−2–10 s−1. The flow curves were corrected for adiabatic temperature rise, particularly at high strain rates. Arrhenius type constitutive equations were derived for Alloy 718 to model the peak flow stress from apparent and physically based approaches. A stress exponent of 5 was obtained from the power-law equation, indicating that the deformation is governed by the dislocation climb mechanism within the aforementioned processing domain. Further, to model the flow behavior, a generalized constitutive equation was derived in which the effect of strain on the flow stress was incorporated. In addition, artificial neural networks (ANN) method was also employed to model the flow behavior. Statistical parameters such as regression coefficient (R) and average absolute relative error (AARE) indicated that the ANN method was more accurate in predicting the flow behavior with R = 0.99 and AARE = 0.79% compared to the apparent-based constitutive equation with R = 0.99 and AARE = 4.5%. Accuracy of the derived constitutive equation as a material model in finite element (FE) simulation studies was also evaluated. Flow curve predictions obtained from the FE simulation were comparable to the experimental results. The microstructure and hardness at different locations in the deformed samples were consistent with the strain distribution map generated by the FE simulation.

Finite element simulation and experimental investigation of residual stresses in ultrasonic assisted turning

The residual stresses in the machined workpiece are of great importance due to their influence on the workpiece fatigue life, as well as its dimensional and geometric accuracy. The metal cutting process has always been accompanied by heat generation and severe plastic deformation. This thermo mechanical loading along with the resulted metallurgical changes are the main sources of residual stresses generation at the surface of machined workpiece. The Ultrasonic Assisted Turning (UAT) reduces the temperature in the cutting region and reduces the average machining forces due to the discontinuous contact of the tool and the workpiece. Reducing the intensity of thermo mechanical loading in the UAT process will affect the residual stresses caused by machining. In this paper, the results of thermo mechanical finite element simulation and experimental studies of residual stresses during UAT of AISI 4140 has been studied. The results of this simulation make it possible to determine the effect of vibration and machining parameters (cutting speed and feed rate) on the magnitude and type of surface residual stresses in the workpiece machined by UAT. Finally, the simulation results are compared with experimental measurements of residual stresses using X-ray diffraction technique. Based on the obtained results, the hoop component of the residual stresses in case of UAT became more compressive averagely by about 73.34% compared to the traditional turning; for instance at constant feed of 0.11 mm/rev and cutting speed of 0.261 m/s, for three different vibration amplitudes of 4, 8 and 12 µm, the machining induced residual stresses became more compressive respectively by 53.34%, 73.00% and 100%.

Normal stress effect on plastic yielding of notched metallic glass: a finite element simulation study

The pressure or normal stress effect on the plastic yielding of metallic glasses (MGs) is still poorly understood due to their complex nature of deformation process. A knowledge on the internal stress distribution and evolution around the plastic shearing plane holds the key for understanding the above issue. In this study, we studied the plastic deformation process of a notched bulk metallic glass by finite element simulation using the von-Mises yielding criterion and Mohr-Coulomb yield criterion, respectively. The internal shear stress distribution and evolution on the notched shear plane was analyzed, and the yielding strength is extracted by averaging the shear stress on the shear plane. It was found that the plastic flow of MGs is greatly influenced by the pressure/normal stress effect as captured by Mohr-Coulomb yielding criterion, and the strength extracted with the criterion agrees well with that obtained from experiments. The effect of pressure/normal stress on the plastic flow of MGs are also discussed from the mechanistic viewpoint. Our results may help for understanding the underlying origin for the pressure/normal stress effect on the plastic flow of MGs.

Finite element analysis and simulation study on micromachining of hybrid composite stacks using Micro Ultrasonic Machining process

Hybrid composites stacks are multi-material laminates which find extensive applications in industries such as aerospace, automobile, and electronics and so on. Most hybrid composites consist of multiple layers of fiber composites and metal sheets stacked together. These composite stacks have excellent physical and mechanical properties including high strength, high hardness, high stiffness, excellent fatigue resistance and low thermal expansion. Micromachining of these materials require particular attention as conventional methods such as micro-drilling is extremely challenging considering the non-homogeneous structure and anisotropic nature of the material layers. Micro Ultrasonic Machining (μUSM) is a manufacturing process capable of machining such difficult-to-machine materials with ultraprecision. Experimental study showed that μUSM process could successfully machine hybrid composite stacks at micron scale with a relatively good surface finish. This research uses finite element simulation technique to investigate the material removal during the μUSM process for micromachining hybrid composite stacks. The effects of critical process parameters including the amplitude of vibration, feed rate and tool material on the cavity depth, cutting force and equivalent stress distribution are studied. The outcome of this research can be utilized to further our understanding of performing precision machining of hybrid composite stacks for use in several critical engineering applications.

Gate Damages Induced in SiC Power MOSFETs During Heavy-Ion Irradiation—Part I

Experimental characterization of the damage induced to SiC power MOSFETs by heavy-ion irradiation is presented as a premise to a finite element simulation study aimed at gaining an insight into the physics of damage formation. Thanks to the new experimental setup, which is capable of accurately measuring the time evolution of the gate and drain leakage currents during irradiation, we herein demonstrate that the gate of a SiC power MOSFET is damaged by heavy-ion irradiation at biasing drain voltages lower than 100 V, which is less than 10% of the nominal blocking voltage of the tested devices. The evolution of the gate and drain leakage currents during irradiation is explained considering that localized resistive paths due to damage sites are formed across the gate oxide. The results presented herein indicate the strong sensitivity of SiC power MOSFETs to gate rupture even if the main concern in the literature addressed so far is the rupture of the drain structure due to single-event burnout.

Gate Damages Induced in SiC Power MOSFETs During Heavy-Ion Irradiation—Part II

This article presents the results of a 2-D finite element simulation study of the gate damages induced by heavy-ion irradiation in SiC power metal–oxide–semiconductor field-effect transistors (MOSFETs). The time evolution of the electric field in the gate oxide is studied. Two effects are investigated: the first is associated with the charge deposition in the SiC portion of the MOSFET, with the time evolution studied using the 2-D finite element simulator; the second one results from holes generated during the ion transit, trapped in the gate oxide after the fast electrons have been quickly swept away by the electric field. Two different techniques have been combined for estimating the hole concentration in the gate oxide: the well-known recombination rate was modified to consider the trapped charge yield, as was recently done to better interpret single event gate rupture (SEGR) failure of silicon power MOSFETs. Under ion irradiation test conditions at which the gate damage experimentally starts to be observed, we demonstrate that, because of the ion impact, regardless of the ion linear energy transfer (LET), the peak value of the electric field in the gate oxide becomes practically equal to the oxide breakdown field (~12–15 MV/cm). Moreover, we show that simulations can be used to predict the test conditions at which gate damage starts to appear as a function of LET and the range of heavy ions used in the irradiation experiments.

Finite element simulation and experiment study of residual stress distribution of CVD Nb-C/SiC composites

Residual stresses induced in the cooling process of deposited Nb connection layer on C/SiC composite have significant impact on their mechanical properties. This work aims to characterize the residual stresses and investigate the change rule of the residual stress by the x-ray scattering technique and finite element method (FEM). Nb connection layer was deposited on C/SiC composites by chemical vapor deposition method (CVD). The result shows that temperature of CVD Nb-C/SiC composites is linear over time, the temperature gradient between connection layer and matrix is almost zero. During cooling process, interface residual stress is mainly caused by the large difference of thermal expansion coefficient of both materials. Due to the size effect of the geometrical model, the interface stress gradient is small along the radial direction but large along the axial direction. C/SiC substrate is subjected to compressive stress while Nb layer bears tensile stress. Along the ring direction, equivalent stress from C/SiC substrate to Nb layer presents linearly downward trend. The calculated value is nearly the same with the XRD testing result on the side of Nb layer, which further confirms the correctness of the finite element model.

Finite element analysis and simulation study of CFRP/Ti stacks using ultrasonic additive manufacturing

The hybrid laminar composite stack of carbon fiber reinforced polymer (CFRP) and titanium (Ti) are widely used in several critical engineering applications, including aerospace and automobile sectors. The joining of CFRP and Ti through conventional methods has several limitations such as weight additional, material damage, and lower fatigue life. Ultrasonic additive manufacturing (UAM) is a solid-state manufacturing process capable of joining layers of dissimilar materials. Experimental studies have successfully demonstrated the welding of CFRP and Ti through UAM process. However, there is a lack of understanding of the exact bonding process and influence of process parameter on weld quality during UAM. The present study investigates the bonding process and the effects of critical parameters in the UAM process of CFRP and Ti layers using finite element analysis and simulation technique. The simulation study reveals that the CFRP/titanium stacks encounter interfacial cyclic shear stresses and shear strains. The study found that the vibrational amplitude and surface roughness of the substrates play a critical role in achieving a proper weld. The simulation results are validated using experimentation. The finding of this study can help advance the commercialization of UAM process for welding dissimilar materials and composites.

Experimental Study on Energy Dissipation Performance and Failure Mode of Web-Connected Replaceable Energy Dissipation Link

In the current design method of the eccentrically braced frame structure, the energy dissipation link and the frame beam are both designed as a whole. It is difficult to accurately assess the degree of damage through this method, and it is also hard to repair or replace the energy dissipation link after strong seismic events. Meanwhile, the overall design approach will increase the project’s overall cost. In order to solve the above mentioned shortcomings, the energy dissipation link is designed as an independent component, which is separated from the frame beam. In this paper, the energy dissipation link is bolted to the web of the frame beam. Both finite element simulation and test study of eight groups of energy dissipation links have been completed to study their mechanical behaviors, and the energy dissipation links have been studied in the aspects of length, cross section, and stiffener spacing. The mechanical behaviors include the energy dissipation behavior, bearing capacity, stiffness, and plastic rotation angle. The results indicate clearly that the hysteretic loop of links in the test and finite element analysis is relatively full. By comparing the experimental and finite element simulation data, it can be found that the general shape and trend of hysteretic loop, skeleton curve, and stiffness degradation curve are basically the same. The experiment data explicitly shows that the energy dissipation link of web-connected displays good ductility and stable energy dissipation ability. In addition, the replaceable links possess good rotational capacity when the minimum rotation angle of each specimen in the test is 0.16 rad. The results of the experiment show that the energy dissipation capacity of the link is mainly related to the section size and the stiffening rib spacing of the link. The energy dissipation ability and deformation ability of the link is poorer as the section size becomes larger; meanwhile, these abilities are reduced with the decrease of the stiffening spacing. The experiment result shows that the damage and excessive inelastic deformations are concentrated in the link to avoid any issues for the rest of the surrounding elements, and the links can be easily and inexpensively replaced after strong seismic events. The results are thought provoking, as they provide a theoretical basis for the further study of the eccentrically braced frame structure with replaceable links of web-connected. In future work, the author aims to carry out his studies through optimized design methodology based on the yielding criterion.

Finite element simulation study on pre-stress multi-step cutting of Ti-6Al-4V titanium alloy

The residual stress on the machined surface has a significant impact on the service life and fatigue strength of machined parts. In the former studies, it has been confirmed that both pre-stress cutting process and multi-step cutting process can significantly affect the residual stress distribution of the finishing machined surface, which gives expression to the increasing trend of compressive residual stress. In this paper, a finite element software Abaqus was used to establish a two-dimensional finite element simulation model for titanium alloy cutting. The finite element model was validated by the chip shape characteristics and cutting forces obtained by orthogonal cutting experiments. Based on the validated model, the simulations of single-step cutting, multi-step cutting, pre-stress single-step cutting, and pre-stress multi-step cutting processes were conducted. The chip shape characteristics, cutting forces, and residual stress distribution of the machined surface under four machining processing conditions were comparably investigated. The influence mechanism and coupling effect of multi-step machining and pre-stress machining on residual stress distribution on machined surface was explained. Investigation results indicate that both multi-step cutting and pre-stress cutting processes can increase the compressive residual stress, while multi-step cutting will change the position of minimum residual stress along the depth direction and increase the chip segmentation degree. Among the four cutting processing conditions, the pre-stress multi-step cutting will effectively increase compressive residual stress value to the utmost extent, which should be attributed to the coupled effect of pre-stress cutting and multi-step cutting processes.

Design method for an acoustic cloak in flows by topology optimization

In this paper, a design method for an acoustic cloak in the presence of background mean flows is proposed by using topology optimization, which enables the associated fabrication of the cloaking design. The density-based topology optimization method is used to allocate the designated materials, thus providing the structure of the cloak. The optimization problem is efficiently solved with the gradient-based globally convergent method of moving asymptotes, which utilizes the derivative information from the finite element simulation studies of the linearized acoustic potential equation. This paper introduces the whole design method first then numerically demonstrates the corresponding performance, which shall constitute the main contribution of the present work.

Numerical Validation of Drilling of Al6061-T6 with Experimental Data

Abstract Drilling is a cutting process that uses a drill bit to cut a circular profile in workpiece. Forces acting on the drill bit reduce its life expectance. Analysis of forces acting on the drill bit during drilling prevents the tool from failing prematurely because of wear and excess feed rate. Excess feed rate can induce excessive internal stress on both the tool and workpiece. This paper aims to study the effects of reaction force acting on a drill bit during drilling of Al6061-T6. A numerical finite element simulation study is performed with commercially available software called Abaqus. Simulation results depend on the right choice of material property such as Johnson–Cook material property and Johnson–Cook damage property. Validation of material property is achieved by comparison of experimental results with simulative results. Reaction force acting against the drill bit during drilling is compared.