Finite Element Simulation Study Research Articles

Simulation of metallic powder bed additive manufacturing processes with the finite element method: A critical review

This article provides a literature review of finite element simulation studies for metallic powder bed additive manufacturing processes. The various approaches in the numerical modeling of the processes and the selection of materials properties are presented in detail. Simulation results are categorized according to three major findings’ groups (i.e. temperature field, residual stresses and melt pool characteristics). Moreover, the means used for the experimental validation of the simulation findings are described. Looking deeper into the studies reviewed, a number of future directions are identified in the context of transforming simulation into a powerful tool for the industrial application of additive manufacturing. Smart modeling approaches should be developed, materials and their properties should be further characterized and standardized, commercial packages specialized in additive manufacturing simulation have to be developed and simulation needs to become part of the modern digital production chains. Finally, the reviewed studies are organized in a table and characterized according to the process and material studied, the modeling methodology and the experimental validation method used in each of them. The key findings of the reviewed studies are also summarized.

A risk-based methodology to assess run-off-road crashes on austrian motorways – The Riskant Project

Run-off-road (ROR) crashes are extremely severe road accidents that often result in serious injuries or fatalities. On Austrian motorways, about 40% of all injury accidents are ROR crashes, which account for more than 60% of the fatalities on the primary road network. This is one of the reasons why the Austrian highway operator (ASFINAG) postulates in its road safety program till 2020 that new safety strategies and new road safety measures have to be developed to prevent vehicles from running off the road and (in a worst case scenario) collide with stationary obstacles on the roadside. RISKANT is a research project funded within the 2011 Call “Transportation Infrastructure Research (VIF)” of the Austrian Research Promotion Agency (FFG) in conjunction with ASFINAG. The main objective of RISKANT was to develop a risk model for crashes with stationary obstacles along the roadside. In order to achieve this goal, a so-called accident prediction model was used to estimate the probabilities of ROR crashes due to the characteristics of the road and the road environment. Furthermore, Finite element simulation studies were conducted to incorporate the severity of injuries due to collisions with different stationary obstacles. Two indices, the Acceleration Severity Index (ASI) and Theoretical Head Impact Velocity (THIV) were used to evaluate the injury risk level for vehicle occupants.

A study on protective performance of bullet-proof helmet under impact loading

A large number of brain injuries and casualties can be caused by the impact of bullets on the bullet-proof helmets, for which the underlying mechanisms are unclear and are likely to be complex. In the current study, an American advanced combat helmet was scanned to obtain 3-dimensional (3D) geometric information, from which a 3D finite element (FE) model of a ballistic helmet was developed. With this model, FE simulation was conducted and the results were compared with and verified by data from a ballistic test and a FE simulation study previously reported. Furthermore, the protective performance of the ballistic helmet was investigated using the FE model. The verification results show that the FE model of this ballistic helmet is effective, and data from the current study should be useful in providing theoretical guidance in the design of ballistic helmets.

Finite Element Simulation and X-Ray Microdiffraction Study of Strain Partitioning in a Layered Nanocomposite

The depth-dependent strain partitioning across the interfaces in the growth direction of the NiAl/Cr(Mo) nanocomposite between the Cr and NiAl lamellae was directly measured experimentally and simulated using a finite element method (FEM). Depth-resolved X-ray microdiffraction demonstrated that in the as-grown state both Cr and NiAl lamellae grow along the 111 direction with the formation of as-grown distinct residual ~0.16% compressive strains for Cr lamellae and ~0.05% tensile strains for NiAl lamellae. Three-dimensional simulations were carried out using an implicit FEM. First simulation was designed to study residual strains in the composite due to cooling resulting in formation of crystals. Strains in the growth direction were computed and compared to those obtained from the microdiffraction experiments. Second simulation was conducted to understand the combined strains resulting from cooling and mechanical indentation of the composite. Numerical results in the growth direction of crystal were compared to experimental results confirming the experimentally observed trends.

Electrical-thermal-structural finite element simulation and experimental study of a plasma ion source for the production of radioactive ion beams.

The production target and the ion source constitute the core of the selective production of exotic species (SPES) facility. In this complex experimental apparatus for the production of radioactive ion beams, a 40 MeV, 200 μA proton beam directly impinges a uranium carbide target, generating approximately 10(13) fissions per second. The transfer line enables the unstable isotopes generated by the (238)U fissions in the target to reach the ion source, where they can be ionized and finally accelerated to the subsequent areas of the facility. In this work, the plasma ion source currently adopted for the SPES facility is analyzed in detail by means of electrical, thermal, and structural numerical models. Next, theoretical results are compared with the electric potential difference, temperature, and displacement measurements. Experimental tests with stable ion beams are also presented and discussed.

Finite-element simulation study of an underwater active electrolocation system based on Cole-Cole model

The underwater active electrolocation method is a promising technology, which can be used to locating and navigation. This method is invented by simulating a kind of weakly electric fish detect target. This kind of fish can generate a low frequency electric field by its electric organ discharges (EOD), and can sense the electric field change in surrounding area by its electroreceptors. This function of weakly electric fish is called active electrolocation system. The weakly electric fish can detect the target in complete darkness by their active electrolocation system. In order to understand the active electrolocation system, it has been researched by biologists for almost 60 years. At recently two decades, the underwater active electrolocation system has been investigated by many engineers. All of these scientists focused on setting up the active electrolocation test platform by experiment or building the active electrolocation system model by theoretical analysis or the finite element emulation method. But the physical mechanism of the active electrolocation system of weakly electric fish still is a contentious issue. In previous experiments, the amplitude information-frequency characteristics (AIFC) for active electrolocation system has been studied, and the detect frequency dead zone (DFDZ) and frequency inflection point (FIP) phenomena of AIFC for active electrolocation system has been found. In this paper, to understand this special phenomenon, a finite element model based on the ideal electromagnetic theory was built to simulate the active electrolocation system. But the DFDZ and FIP phenomena of AIFC for active electolocation system cannot be really simulated by this model. Then, we assumed that DFDZ and FIP phenomena are induced by phenomenon (IP) effect at the boundary between the target and water in the process of detecting target. In order to validate this assumption, the Cole-Cole model was used to fits the IP effect, and a finite element model of coupling the Cole-Cole model and ideal electromagnetic theory was created. Large numbers of simulation calculations based on this new finite element model were carried out. The simulation calculations results of the new finite element model were found to be in line with the experimental results. The simulation calculations calculation results of the new model indicate that: (1) the underwater active electrolocation system can be simulated by the new finite element model of coupling the Cole-Cole model and ideal electromagnetic theory; (2) it is a reasonable fact that the DFDZ and FIP phenomena of AIFC for underwater active electrolocation system can be explained by the IP effect; (3) the frequency inflection point (FIP) is varies with the parameters of the Cole-Cole model, and it is also can be speculated that the parameters of the Cole-Cole model reflect the changing of the DFDZ and FIP phenomenon of AFIC for electrolocation system. In this paper, the IP effect is introduced to the model of underwater active eletrolocation system for the first time. It will be of great benefit to us to understand the physical mechanism for active electrolocation system of weakly electric fish and provided an active electrolocation system finite element model for simulation. And it may be helpful for designing the equipment of active electrolocation system.

Experimental and numerical study of drill string dynamics in gas drilling of horizontal wells

The combination of gas drilling and horizontal well has been considered as an effective technique for the exploitation of low permeability reservoirs to protect reservoir, enlarge drainage area and increase production. Given the currently inadequate understanding about drill string dynamic characteristics in gas drilling of horizontal wells, a theoretical model of drill string dynamics is established in this paper. The nonlinear dynamics equations are derived to study the motion state of drill string. Meanwhile, an experimental apparatus is developed according to similarity principle, and the kinetic characteristic of drill string is investigated based on the simulation experiment. Particular attention is focused on the lateral vibration which results from the impact and frictional interaction with wellbore constraint. The effect of weight on bit and rotary speed on drill string motion pattern is also discussed based on experimental results. Finally, the buckling and contact of drill string are analyzed through finite element simulation study. The results indicates that the contact force between wellbore and drill string is relatively large and helical buckling of drill string can be caused without the lubrication and damping effects of drilling fluid in gas drilling. The work presented in this paper can provide theoretical foundation and technological basis for drill string dynamics analysis and drilling parameter optimization in horizontal wells drilled with gas.

Determination of the Thickness of a Resistive Material Layer in a Finite Volume Conductor using Focused Impedance Method (FIM) – a simulation study

Focused Impedance Method (FIM) is an innovative and relatively new electrical impedance measurement technique that allows localized measurement of the properties of electrically conducting materials in a volume conductor such as the human body using simple measurement setups. In a previous work, FIM, with dual electrode separation, was used to determine thicknesses of subcutaneous fat layers through experimental study on phantoms and human subjects. The present work, carried out using COMSOL Multiphysics software package, is a finite element simulation study for a similar target object that verifies and extends the results of the previous experimental work. A rectangular box of different heights containing a material of uniform conductivity such as saline together with internally embedded layers of resistive materials of different thicknesses were used for this study. The measured transfer impedance in the FIM method showed marked change with the variation of the thickness of the resistive layer and with electrode separation, showing a point of maximum curvature in the latter. We obtained a calibration curve for the thickness from the electrode separation of this point. This allowed a unique method for the determination of thickness of embedded resistive layers which is more general than what had been done in the previous experimental work. This work will help standardize the application of 4-electrode FIM for determination of the thickness of less-conducting material layer in any finite volume, including determination of fat layer thickness, etc.Bangladesh Journal of Medical Physics Vol.7 No.1 2014 8-23

A low-power, low-cost soil-moisture sensor using dual-probe heat-pulse technique

This paper presents the development and testing of an integrated low-power and low-cost dual-probe heat-pulse (DPHP) soil-moisture sensor in view of the electrical power consumed and affordability in developing countries. A DPHP sensor has two probes: a heater and a temperature sensor probe spaced 3mm apart from the heater probe. Supply voltage of 3.3V is given to the heater-coil having resistance of 33Ω power consumption of 330mW, which is among the lowest in this category of sensors. The heater probe is 40mm long with 2mm diameter and hence is stiff enough to be inserted into the soil. The parametric finite element simulation study was performed to ensure that the maximum temperature rise is between 1°C and 5°C for wet and dry soils, respectively. The discrepancy between the simulation and experiment is less than 3.2%. The sensor was validated with white clay and tested with red soil samples to detect volumetric water-content ranging from 0% to 30%. The sensor element is integrated with low-power electronics for amplifying the output from thermocouple sensor and TelosB mote for wireless communication. A 3.7V lithium ion battery with capacity of 1150mAh is used to power the system. The battery is charged by a 6V and 300mA solar cell array. Readings were taken in 30min intervals. The life-time of DPHP sensor node is around 3.6 days. The sensor, encased in 30mm×20mm×10mm sized box, and integrated with electronics was tested independently in two separate laboratories for validating as well as investigating the dependence of the measurement of soil-moisture on the density of the soil. The difference in the readings while repeating the experiments was found out to be less than 0.01%. Furthermore, the effect of ambient temperature on the measurement of soil-moisture is studied experimentally and computationally.

Estimation of THIV for Car Crash against Attachable Roadside Barriers Made of the High Strength Steel

A finite element simulation study was performed to gain the theoretical head impact velocity about the crash test details. Accuracy of the simulation was verified using qualitative and quantitative comparisons. Based on in-depth examination of crash simulation recordings, energy distributions occurred in the barrier against the car are determined. In this paper, the existing finite element crash analysis of barriers using the LS-DYNA program is further extended to study the dynamic response of the barrier with module structures connected by anchor bolt inserted through concrete bridge decks. The numerical results for various parameters are verified by comparing different models with or without the high strength steel such as HS800.

Residual Stress Analysis of Strongly Textured Materials by Means of the Incremental Hole-Drilling Method – Survey on the Application Limits

AbstractIn sheet metal forming, residual stress distributions are often accompanied by crystallographic texture. Incremental hole-drilling for stress analysis is only reliably applicable for isotropic materials. The objective of this study is to determine the influence of texture on residual stress analysis using conventional evaluation methods and to specify the application limits in case of textured material states. A systematic finite element simulation study for ideal texture orientations is conducted with respect to the strain gage rosette orientation. The results of the numerical investigations show that reliable stress analysis on strongly textured materials is not feasible using the existing evaluation method. The application limits are given for the application of commercially available evaluation software with respect to degree of anisotropy, stress state and strain gage orientation.

Detection of stiffener disbonding in a stiffened aluminium panel using nonlinear Lamb wave

The present research focuses on detection and quantification of disbond present beneath the stiffener in a stiffened aluminium panel, using a Lamb wave based nonlinear technique. For this purpose, both experimental and finite element simulation studies are carried out. The contact nonlinearity at the disbond leads to the generation of higher harmonics in the Lamb wave response. This phenomenon is observed in both the experimental and the simulation studies. A Spectral Damage Index (SDI) defined by the authors is extracted from these higher harmonics. This SDI has a decreasing trend with the increase in the size of the breathing damage. The plots of the SDI against the disbond width observed in the cases of experimental and simulation studies are in the close agreement. Thus, the higher harmonics observed in the Lamb wave response and the SDI obtained from these higher harmonics together found to be effective in detection and quantification of the disbond in the stiffened aluminium panel.

Finite Element Simulation and Experimental Study on Internal Fracture of Railway Sleeper Screw during Cross Wedge Rolling Process

The internal defects in cross wedge rolling process are a big issue restricting the widely use of the technology in industry. Although internal failures in cross wedge rolling have been investigated by several authors, the internal defect generation and effective parameters are still not completely clear. In this study, the internal fracture of 1045 steel railway sleeper crew during cross wedge rolling were investigated numerically by using Johnson-Cook fracture model. Based on analyzing the relationship between stress and strain in the deformed area, the mechanisms of internal fracture of sleeper screw during cross wedge rolling process was explained and made clear. The simulation results are in reasonable agreement with experimental results conducted at the same conditions.

An Evaluation of Primer Preseating in Small Caliber Cartridge Production

This work presents the findings of a study to quantify the relative effectiveness of the primer preseating operation in small caliber cartridge production. In theory, primer preseating would enable cartridge stamping tools to achieve deeper stamping penetration depths and subsequently, greater primer retention forces. This is because, with preseating incorporated in the existing small caliber cartridge production process, a cartridge stamping tool would be fully dedicated to performing the case stamping operation (rather than the simultaneous primer seating and case stamping operations it currently performs). The findings presented in this work include measured percentages of total stamping tool force dedicated to primer seating, stamping tool penetration depths with and without primer preseating and primer retention forces with and without primer preseating. These findings and their underlying principles were produced through a static force equilibrium analysis and finite element modeling and simulation studies.

Investigation of a Bulge Test at High Temperatures and High Strain Rates Using a Finite-Element Simulation Study

In recent years, hot stamping of sheet metal parts has emerged to satisfy the contrary demands of the automotive industry for components with increased strength at reduced weight. To analyse the material behaviour during these processes, a hot gas bulge test at high temperatures and high strain rates is promising, since the bulge test at room temperature has already proven itself as a useful test for the material characterization of sheet metals up to high strains. Therefore, a hot gas bulge test at elevated temperatures and high strain rates is being developed at the Institute of Metal Forming (IBF) in cooperation with the Institute for Fluid Power Drives and Controls (IFAS) at the RWTH Aachen. To verify if the concepts of the membrane theory, which are used for the evaluation of bulge tests at room temperature, are adaptable to such a hot gas bulge test, a simulation study using finite element calculations was conducted. The purpose of this simulation study is is to estimate the errors which occur if the equivalent stress at the bulge pole is calculated by using the membrane theory. In addition to this study several approaches were examined to obtain the sheet thickness at the bulge pole by measuring the bulge height. The study showed that a hot gas bulge test can be described very well by the membrane theory if the sheet thickness, the curvature at the bulge pole and the pressure inside the bulge are exactly known. However, substantial errors can occur if the sheet thickness at the bulge pole is determined by measuring the height of the bulge pole.

Experimental and Finite Element Simulation Study of Thermal Relaxation of Residual Stresses in Laser Shock Peened IN718 SPF Superalloy

An integrated experimental and modeling/simulation approach was developed to investigate and secure a quantified knowledge of the impact of high temperature exposures on the stability of residual stresses in a laser shock peened (LSP) high temperature aero-engine alloy, IN718 SPF (super-plastically formed). Single dimple LSP and overlap LSP treatments were carried out utilizing a Nd:Glass laser (λ = 1.052 μm), and subsequent heat treatments on the LSP-treated coupons were conducted at different temperatures between 550 and 700 °C. A 3-D nonlinear finite element (FE) computational model and the rate-dependent Johnson-Cook material model were calibrated using the experimental results of residual stress from the single dimple LSP and thermal relaxation treatments, and were further extended to the overlap LSP treatment case. Both experimental and FE simulations show that: a) a high level of compressive residual stress (~700 MPa at surface) and residual stress depth (~0.4–0.6 mm) were achieved following LSP, and b) the overlap LSP treatment gave higher residual stress and greater depth. The magnitudes of the initial residual stress (and plastic strain), heating temperature and exposure time were identified as the key parameters controlling the thermal relaxation behavior. The stress relaxation mainly occurs initially before 20 min exposure and the extent of relaxation increases with an increase in temperature and a higher magnitude of the initial as-peened residual stress. In addition, in regions deeper than ~300 μm or after initial thermal exposure where the residual stress was lower than ~300 MPa, stress relaxation was found to be negligible. Kinetic analysis of the experimental thermal relaxation data based on Zener-Wert-Avrami model gave an activation enthalpy of 2.87 to 3.77 eV, which is near that reported in the literatures for volume and/or substitutional solute diffusion in Nickel. These results suggest that thermal relaxation of the LSP-induced residual stress occurs by a creep-like mechanism involving recovery, rearrangement and annihilation of dislocations by climb.

Finite element simulation and experimental investigation of tool temperature during ultrasonically assisted turning of aerospace aluminum using multicoated carbide inserts

This paper summarizes the results of thermal finite element simulation and experimental studies of tool temperature in ultrasonic-assisted turning (UAT) of aerospace aluminum using multicoated carbide inserts. At first, mathematical models were developed in order to study the effects of tool coating, rake angle, cutting speed, and feed rate on the friction coefficient. Then with respect to the kinematics of the process, the cutting velocity model would be presented. This velocity model is used in combination with the mathematical model to define the friction coefficient during UAT. The mentioned frictional model is used to write a user subroutine to incorporate the effect of friction coefficient as a function of cutting parameters in the finite element program Abaqus. The results of this simulation make it possible to determine cutting temperature patterns accurately. It is also used to study the effect of cutting parameters (cutting speed, feed rate, rake angle, and vibration amplitude) on UAT. Finally, the simulation results are compared with experimental measurements of cutting temperatures from ultrasonic-assisted turning tests. The results show that ultrasonic-assisted turning is able to lower the maximum cutting temperature in cutting tool, about 29 %, in low feed rates (≈0.14 mm/rev), with a vibration amplitude of ≈10 μm and work velocity of ≈0.5 m/s.

Non-linear Correlation Between Uniaxial Tensile Properties and Shear-Edge Hole Expansion Ratio

Stretch flanging of steel sheets is an important formability issue for automobile industry. Finite element simulation study confirms that the edge of the hole deforms in a uniaxial tensile manner during the hole expansion process. To understand the effect of various tensile properties on hole expansion ratio, current experimental data and collected data from published work have been used. Yield stress, ultimate tensile stress, coefficient of normal anisotropy, total elongation, and post uniform elongation are closely related to hole expansion ratio. A non-linear relationship between hole expansion ratio and tensile properties (ultimate tensile stress, coefficient of normal anisotropy, and total elongation) is developed in the present investigation.

A Finite Element Simulation Study on Effects of Variation in Machining and Geometrical Parameters in Turning

In this work, the influence of variation in machining parameters cutting speed, feed rate and depth of cut and geometrical parameters cutting insert shape (included angle), relief angle and nose radius is studied using DEFORM-3D, a finite element simulation software. The cutting tool inserts of various geometries are evaluated to study its performance for varying conditions considering contact temperature and mean stress. Effect of individual parameter is analyzed by varying its value by three different level values, while the other parameter values are set at the optimum condition, likewise for all input parameters. From the results obtained, it is observed that the performances of cutting inserts are good at the optimum level of parametric values than at the other level values.

Precision stress localization during mechanical harvesting of vertically oriented semiconductor micro- and nanostructure arrays

A facile protocol of channeling the applied force onto the roots of 1-dimensional (1-d) semiconductor arrays during their mechanical transfer from their mother substrate is presented. This is achieved by fully encasing them in thermally processable matrices with high moduli and impact strength. This approach significantly differs from other complimentary methods as it ensures that the shearing force applied during their transfer is precisely localized at their roots rather than along their full length. The structures remain heterogeneously embedded in the matrix upon transfer, with retention of their pitch, lengths, and integrity. The process is solventless, recycles polystyrene, is rugged, and can potentially be used to transfer a variety of 1-D structures with disregard of their aspect ratio, pitch, and dimensions. We show that millions of micropillars over a large area can be harvested with little sophistication using a hotplate as the only required equipment practically as well as using finite element simulation studies. The protocol is henceforth ripe for high throughput manufacturing.