Computational Parametric Studies Research Articles

An origami-inspired energy absorber

The design of effective and compact energy absorption systems is key to the survivability and durability of many man-made structures and machines. To this end, this work presents the design, assessment, and implementation of a novel origami-inspired energy absorber that is based on the Kresling origami pattern. The absorber consists of a Kresling origami column positioned between the loading point and an energy dissipation module. By exploiting its unique inherent translation-to-rotation coupling feature, the primary function of the Kresling column is to transmit uniaxial incident loads (shock or impact) into localized rotational energy that can then be dissipated in a viscous fluid chamber. The proposed system has several unique advantages over traditional designs including the ability to (i) dissipate energy associated with both torsional and uniaxial loads, (ii) control the rotational velocity profile to maximize energy dissipation, and (iii) customize the restoring-force behavior of the Kresling column to different applications. Furthermore, the proposed design is more compact since it can realize the same stroke distance of the traditional translational design while being considerably shorter. Through extensive computational modeling, parametric studies, and experimental testing, it is demonstrated that the proposed design can be optimized to absorb all the imparted energy; and out of the absorbed energy, around 40% can be dissipated in the viscous fluid, while the rest is either dissipated by the viscoelasticity of the origami column or stored in it as potential energy.

An axial mode magnetoelectric antenna: Radiation predictions via multiphysics modeling with experimental validations

This study investigates an axial extension mode magnetoelectric antenna designed for near-field communication in dielectric cluttered environments. The antenna configuration consists of two magnetostrictive Metglas-polymer composites bonded on opposite sides of a PZT-5A actuator, creating a dumbbell configuration. Operating at its 88 kHz mechanical resonance, the antenna emits electromagnetic radiation in the near field by applying an AC voltage to the piezoelectric material, generating an acoustic wave that propagates through the volume and induces oscillating magnetizations. The design uses a system of uncoupled models: an electrostatic finite element model to predict strain that feeds into a Landau–Lifshitz–Gilbert micromagnetic model to predict magnetic moment changes and, subsequently, a dipole model to forecast near-field radiation characteristics. Measurements were conducted on the antenna’s impedance, quality factor, mechanical resonance, transmitted magnetic signal strength, and radiation patterns, with variations in the bias magnetic field, frequency, and applied voltage. The results exhibit a strong correlation with model predictions, and the radiated signal strengths compare favorably with those of state-of-the-art pacemaker communication devices. Computational parametric studies using Galfenol and Terfenol-D suggest the potential for up to a three order of magnitude reduction in the antenna's volume, which is critical for implanted medical devices.

Stochastic Levenberg–Marquardt Neural Network Implementation for Analyzing the Convective Heat Transfer in a Wavy Fin

The present research examines the steady, one-dimensional thermal distribution and heat transfer of a wavy fin. This heat transfer analysis considers convective effects as well as temperature-dependent thermal conductivity. Furthermore, a novel implementation of a neural network with backpropagated Levenberg–Marquardt algorithm (NN-BLMA)-based machine learning intelligent strategies is provided to interpret the heat transfer analysis of a convective wavy fin. The non-linear ordinary differential equation (ODE) of the study problem is converted into its non-dimensional form using the similarity transformation technique. The dimensionless equation obtained is then numerically explored via the Runge–Kutta–Fehlberg scheme. A data set for varying the pertinent parameters is generated, and an artificial neural network model is designed to estimate the heat transfer behavior of the wavy fin. The effectiveness of the proposed NN-BLMA is subsequently endorsed by analyses using a regression model, mean square error, and histograms. The findings of comprehensive computational parametric studies illustrate that the presented technique, NN-BLMA is an effective convergent stochastic numerical solver employed for the heat transfer model of the convective wavy fin. The wavy fin’s temperature dispersion optimizes as the thermal conductivity parameter rises. Heat transfer rate is higher in wavy fin compared to rectangular fin.

Effects of randomly distributed defects on Mode-I interlaminar fracture of composite materials

Effects of defects on the mode-I interlaminar fracture behavior of composite materials are studied using computational fracture mechanics. Cohesive-zone Finite Element (FE) models of both the Interlaminar Tension (ILT) and Double Cantilever Beam (DCB) test configurations are simulated where randomly distributed defects are explicitly modeled on a critical fracture plane. The effective interlaminar tensile strength and the effective mode-I fracture energy are derived by matching the simulation results with appropriate homogenized models that do not consider the defects explicitly. The results from the computational parametric studies show that both the effective ILT strength and the effective mode-I fracture energy are quite sensitive to defects, scaling linearly with the defect area fraction on the critical fracture plane. The effects of defect size on the mode-I fracture behavior are also studied. It is shown that, for a fixed area fraction of the defects, the ILT strength is not sensitive to the defect size. On the other hand, the mode-I fracture propagation behavior is sensitive to the defect size especially when the defect size is greater than the fracture process-zone size of the delamination crack.

A computational analysis of methanol autoignition enhancement by dimethyl ether addition in a counterflow mixing layer

To provide fundamental insights into the ignition enhancement of methanol (MeOH) by the addition of the more reactive dimethyl ether (DME), computational parametric studies were conducted in a one-dimensional counterflow fuel versus air mixing layer configuration with the incorporation of detailed chemistry and transport. Various computational analysis tools based on the computational singular perturbation (CSP) framework were employed for detailed identifications of complex chemical pathways. CSP tools were also used to develop a 43-species skeletal mechanism for efficient computation of ignition of methanol-DME blends at engine conditions. The overarching practical question was the extent to which the addition of DME improves the ignitability of the methanol. As a baseline analysis, the results of a uniform temperature condition at 850 K showed that the low temperature chemistry associated with the DME fuel was highly effective in promoting autoignition. The increase in the oxidizer side temperature was found to diminish the ignition enhancement by DME blending, as the overall reactivity increases and the dominant chemical pathways become shifted towards the high temperature reactions. Finally, the strain rate effect on the ignition delay time was found to be significant for the pure methanol case, and then the effect diminishes as the amount of DME addition increases. This behavior was explained by examining the spatial locations of the ignition kernels and the Damköhler number history for different strain rate conditions.

Calculated Estimates for the Thermal State and the Precession Amplitude of the Rotor in the Turbocharger Radial Bearing

A modern turbocharger rotor operates under conditions of high speeds and temperatures. Usually the rotor is based on multilayer plain bearings. The thermal state of each bearing has a great importance. The rotor vibration amplitude determines its performance. Choosing bearings clearances, which provide a stable movement of the rotor, is a very urgent task. The article presents the method of the flexible asymmetric rotor dynamics calculating and the results of the radial plain bearing computational parametric studies. The plan of the experiment based on the orthogonal central composite plan was drawn up. The regression equations for the function of the rotor amplitude and bearing temperature were obtained. The clearances (external and internal), rotor speed, pressure and lubricant temperature were used as variable parameters. The calculation results were compared with experimental results. As a result of the research, the recommendations on the choice of the bearing clearances and their ratio were presented.

Computational simulations and parametric studies for directed self-assembly process development and solution of the inverse directed self-assembly problem

Approaches to the computational simulation of directed self-assembly (DSA) of block copolymers based on Monte-Carlo methods and self-consistent field theory are presented and reviewed, with an emphasis on computational models of DSA processes usable for fabrication of integrated circuits (ICs). Applications of such models are illustrated by presenting the results of simulations used in the development of DSA fabrication processes. The inverse DSA problem, or DSA proximity correction (DSA PC) problem, is formulated, and the methods for its computational solution are presented. The application of one of these methods is illustrated by demonstrating co-optimization of optical proximity correction (OPC) and DSA PC for IC vias fabricated using a graphoepitaxy DSA process.

Evaluation of hazard range for the natural gas jet released from a high-pressure pipeline: A computational parametric study

In the present study, the hazard range of the natural gas (NG) jet released from a high-pressure pipeline was investigated. A one-dimensional integral model was combined with a release model to calculate the length and width (i.e., size), and the shape of NG jet release. The physical parameters affecting the jet release of NG were categorized into three types: source release, environmental and time parameters. The effects of each type of parameters on the gas jet release rate, size and shape were evaluated systematically. The results show that all of these parameters have important influence on the hazard range of NG jet release. The source release parameters, including the pipeline length, the operation pressure of the pipeline, the release hole diameter and the pipe diameter, dominate the gas release rate through a hole and therefore the length and width of gas jet release. The gas jet release rate and size are found to be highly correlative with these parameters in terms of power curve regression analysis. The environmental parameters including the atmospheric stability, the ambient wind speed and the source height, have no influence on the gas jet release rate but have influence on the hazard range of gas jet by the turbulent mixing and dilution of NG with air. The time parameters including the concentration averaged time and the valve closing time which are related to the unsteady state jet release of NG, also show the influence on the hazard range of gas jet release. The results show that the decreasing valve closing time and increasing gas concentration averaged time are in favor of reducing the length and width of gas jet release. In addition, these computational parametric studies indicate that the parameters of source release and time have no significant influence on the shape of gas jet release (i.e., jet length/width ratio, LWR) which can maintain the values between 7 and 8. However, the environmental parameters have influence on the shape of gas jet release. These comprehensive investigations provide useful database of evaluating the hazard range for NG jet released from a hole on a high-pressure pipeline and also provide the foundation of decision-making for further fire and/or explosion evaluation and people evacuation.

Validity of the reduced modulus concept to describe indentation loading response for elastoplastic materials with sharp indenters

Recent computational parametric studies have developed reverse algorithms to extract material properties of elastoplastic materials using experimental sharp nanoindentation. These methods used reduced modulus in their parameters to include the effect of indenter compliance. To investigate the validity of using reduced modulus, we conducted experimental indentation of a couple of representative cases for elastoplastic metals with a diamond and a sapphire Berkovich tip. Then, we performed a finite element study for sharp indentation of the same material systems. Both computational and experimental results indicate that the use of reduced modulus is invalid to describe indentation loading response for elastoplastic materials in a certain material regime. Our results show that indenter compliance is overestimated by the previous predictions using reduced modulus. This overestimation leads to underestimation of indenter curvature and causes error in extracting material properties by reverse algorithms.

Interfacial nematodynamics of heterogeneous curved isotropic-nematic moving fronts

The early stages of liquid crystal phase ordering upon thermal quenches of isotropic phases into unstable and metastable temperature ranges is studied using two-dimensional (2D) computational solutions of the governing Landau-de Gennes (L-dG) equations for low molar mass nematic liquid crystals and analysis based on the corresponding interfacial nematodynamic model. The early phase ordering stage, for both unstable and metastable quenches of the isotropic phase, is shown to lead to highly textured nematic spherulites through a mechanism of interfacial defect nucleation. The underlying mechanisms of interface-driven texturing are elucidated using complementary 2D computational parametric studies of the bulk L-dG equation and analysis of the IN model. It is shown that for highly curved nanodomains and realistic elastic anisotropy, sharp interfacial transitions between uniaxial and biaxial states arise and are resolved by interfacial defect nucleation, which upon subsequent migration into the spherulite's interior leads to strong texturing. This paper shows that texture formation in the early stages of phase ordering is interface driven, and due to low interface tension, elastic anisotropy, and large curvature. Interfacial defect shedding in highly curved, low tension, anisotropic interfaces is a significant defect nucleation mechanism that needs to be taken into account when considering texturing processes.

Application of digital image processing for implementation of complex realistic particle shapes/morphologies in computer simulated heterogeneous microstructures

A new methodology is presented for computer simulations of microstructures that incorporates realistic complex particle morphologies/shapes and a specified realistic two-point correlation function. The technique also enables simulations of sufficiently large microstructural windows that include short-range (on the order of particle size) as well as long-range (few hundred times the particle size) microstructural heterogeneities and spatial patterns. Incorporation of such simulated microstructural windows in the finite element-based computations leads to local stresses and strains that have distributions statistically similar to those resulting from the corresponding real microstructure. Therefore, these microstructure simulations provide realistic representative volume elements for computational parametric studies.

Design-of-experiment methods for computational parametric studies in electronic packaging

Design-of-experiment methods are utilized to improve the tractability of numerically intensive design problems in reliable electronic packaging. Fractional factorial parametric studies, commonly used by experimentalists to economize on resources, are shown to provide similar benefits in design simulations also. Response surface analysis is used to develop pseudo-closed-form models from the computational parametric studies. An example is provided to illustrate the use of these concepts and tools in electronic packaging design.

Experimental study on confined two-phase jets

The basic mixing phenomena in confined, coaxial, particle-laden turbulent flows are studied within the scope of ram combustor research activities. Cold-flow experiments in a relatively simple configuration of confined, coaxial two-phase jets provided both qualitative and quantitative insight on the multiphase mixing process. Pressure, tracer gas concentration, and two-phase velocity measurements revealed that unacceptably long ram combustors are needed for complete confined jet mixing. Comparison of the experimental results with a previous numerical simulation displayed a very good agreement, indicating the potential of the experimental facility for validation of computational parametric studies.