bluuebunny/crossref_metadata_2025 huggingface dataset:
Crashworthiness Performance of Space Frame Aluminum Structure in NCAP’s 35 MPH Full Frontal
Authors: Baccouche Mohamed Ridha , Mahmood Hikmat F. , Shivakumar Arkalgud K. , Jawad Saad A.
Published: December 2021

The quest for lighter crash energy absorbing automotive structures has increased the use, parallel with other materials, of the 5xxx sheet and 6xxx extruded aluminum structures. These aluminum structures, when properly designed and joined, are able to demonstrate a very high crash energy absorbing capability.

This paper summarizes the CAE and development work performed in the design of the front end structure of a four door C-class space frame aluminum vehicle. Component and system CAE modeling of the front end were conducted under NCAP’s 35 mph full frontal impact using rigid body dynamic, nonlinear beam finite element and stability codes. Component loads versus crash distances and system deceleration versus time responses were computed.

A 3D spring mass model was built for the front end structure using the rigid body and finite element code MADYMO. Spring characteristics for each component, derived from test data and component CAE models, were input into the MADYMO model. The deceleration-time response generated by the MADYMO model was used as input for the sled testing. The effects of four parameters were studied and discussed in this paper. These parameters are the steering column angle, IP, Pyro Buckle Pretensioner and airbag vent size. Dummy HIC; chest deceleration; neck shear, tension, compression, flexion and extension; femur load, pelvis acceleration and displacement; retractor load; shoulder belt load; lap belt load and other injury numbers, measured from sled test, are summarized and discussed in this paper.
Crashworthiness of Aluminum Structures
Authors: Warren A. S. , Wheeler M. J.
Published: December 2021

There is a growing recognition by the auto makers of the benefits of aluminum for vehicle structures. While there is now no doubt that the structural demands of vehicles can be met with aluminum, it is less well appreciated that such structures can also be designed to provide a high level of crashworthiness.

This paper summarizes the basic work that has been carried out to demonstrate and quantify the behavior and energy absorption of aluminum vehicle structures under impact collapse conditions. Aluminum, like steel, collapses under high load conditions by folding and the resulting work of deformation absorbs the vehicle’s kinetic energy. It follows that most of the general rules for designing crashworthy structures in steel, in terms of ensuring progressive collapse, avoiding premature bending failures, and transferring load as the collapse event proceeds, apply equally well to aluminum structures. There are, however, differences from steel due to the greater thickness of aluminum material used. This increases resistance to local buckling, and results in larger volumes of the material becoming involved in the energy absorbing collapse events.

There are other material characteristics that have a bearing on developing crashworthy aluminum structures, and the paper covers the more significant material and related design guidelines that should be followed in the development of the main energy absorbing structural members in vehicle structures. Finally, reference is made to results from NHTSA’s NCAP program for appraising the crashworthiness of new vehicles. These have demonstrated in a very practical way the excellent crashworthiness of vehicles with well designed aluminum structures.
A Comparison of Mathematical Neck Models for Rear Impact Occupant Simulation
Authors: Marshall Rob , Altamore Paul , Wu Wei-Pin , Griffioen Jan A.
Published: December 2021

Occupant injury in automobile rear-end collisions is becoming one of the most costly and aggravating traffic safety problems. Designing seat and head restraints to help limit injury associated with rear-end impact can become more efficient by using new mathematical modeling techniques. Using the facet surface modeling technique in MADYMO a model is developed that captures the interaction between occupants and seat/head restraints with a high degree of geometric accuracy while maintaining efficient computer run times. One such model is validated using a prototype seat/head restraint and the TRID (TNO Rear Impact Dummy), both using facet surface techniques. From this model a study is done to compare the results of the TRID model and the results from a Hybrid III model with the results from a Human neck model. This study is performed in several different head restraint positions.
Micromechanics Based Composite Material Model for Impact and Crashworthiness Explicit Finite Element Simulation
Authors: Tabiei Ala
Published: December 2021

A micro-mechanical model is developed for laminated composite materials and implemented in the explicit finite element method. The objective of this study is to get an accurate and simple micro-model, which can be used in the displacement-based explicit finite element packages. The micro-mechanical model implemented in the explicit finite element code can be used for simulating the behavior of composite structures under various loads such as impact and crash. The stress-strain relation for the micro-model is derived for shell element. As a demonstration case of the developed micro-model a finite element model of Graphite/Epoxy tube structure is developed and simulated under axial crash.
An Optimized Methodology for the Creation of Highly Detailed Finite Element Models of Road Vehicles for Use in Crash Simulation
Authors: Monclus-Gonzalez Jesus , Kan Cing-Dao , Bedewi Nabih E.
Published: December 2021

This paper explains the improvements introduced in the existing methodology for the development of Finite Element (FE) models of road vehicles for crashworthiness purposes. The improvements were implemented during the creation of a highly detailed FE model of the frontal section of a 1997 Dodge Grand Caravan. Lessons learned during the reverse engineering are presented, with emphasis on the definition of the global and local coordinate systems. Detailed information regarding the time invested in the geometry discretization phase is offered. Also, the main aspects of the modeling phases are summarily explained. The pre-processor used for the development of this model was MSC/PATRAN, while the finite element solver was LS-DYNA. The resulting FE model of the frontal section of the 1997 Dodge Grand Caravan includes 334 parts, 196,447 nodes, 189,785 elements and 3,238 connections. Finally, the benefits of the improved methodology are discussed and several examples of quality achievements are commented.
Prediction of Heat Transfer in Turbulent Decaying Swirling Flow
Authors: Uskaner Yusuf A.
Published: December 2021

This paper presents an aproach for the prediction of heat transfer augmentation in decaying swirling flow in a pipe by making an analogy between the increase in friction factor due to swirl and increase in heat transfer due to swirl. The proposed method can be used to predict heat transfer for decaying swirling flow in smooth and rough pipes which can be applied to different swirl generators based on the known inlet swirl conditions. An experimental study is performed regarding the swirling flow of air in smooth and rough pipes. The experimental study covered only the fluid dynamics of swirling flow. No heat transfer experiments were done. It is determined experimentally that in swirling flows degree of swirl decays continuously along the smooth and rough pipes and the total loss factor is the sum of friction factor for non-swirling flow and the swirl loss factor. Swirl loss factor is found to be a function of the degree of swirl and pipe relative roughness. Using the relations obtained experimentally for the variation of swirl strength and loss factor along the pipe, an equation is proposed to be used for the prediction of heat transfer in turbulent decaying swirling flows.
Improved Correlation for Natural Convection Heat Transfer From Inclined Cylinders Having Different Emissivities
Authors: Stewart Jeffrey C. , Janna William S.
Published: December 2021

The purpose of this study was to develop an improved correlation for natural convection heat transfer from inclined cylinders having different emissivities. The angle of cylinder inclination varied from horizontal to vertical in 15° increments. The heat transfer coefficient was obtained experimentally with the cylinder in a state of constant heat flux. Three surface finishes were used in the experiment, which consisted of polished copper, black paint, and aluminum paint. The heat transfer coefficients in all cases varied from 1.21 to 1.65 BTU/(hr·ft2·R) [6.87 to 9.37 W/(m2·K)]. Rayeigh numbers for all experiments varied from 1.31 × 103 to 2.23 × 103. The heat transfer coefficient decreased for each cylinder with an increasing angle of inclination (from horizontal to vertical). The goal of this study was to produce Nusselt-Rayleigh number correlations for each cylinder, and then ultimately produce a single equation that can be applied for all emissivities. The Rayleigh number included a geometry term to account for the inclination of the cylinder. The form of the equation that best represented the data was a power law equation.
Effect of Transversal Aspect Ratio on Natural Convection Inside Open-Ended Cavities With Uniformly Heated Horizontal Walls
Authors: Manca Oronzio , Morrone Biagio , Nardini Sergio
Published: December 2021

An experimental analysis of effects of transversal aspect ratio on air natural convection between horizontal parallel plates, with the lower plate heated, was carried out by means of visualization of flow and air temperature measurement. The distance between the plates, b, in the experiments was 40.0 mm and the width of the plates, W, was 100, 200 and 460 mm. The corresponding transversal aspect ratios, W/b, were 2.5, 5.0 and 11.5. The main flow pattern resembles a C shape (C-loop) in the longitudinal section. In fact, the flow penetrates inside the cavity close to the leading edge of the lower plate and exits from the upper part, by reversing its motion between the plates. The flow visualization and the temperature time records indicate that the lateral walls have significant impact on the secondary flows. As a matter of fact, when the transversal aspect ratio decreases the temperature fluctuations at any location became more regular. The average temperature values, instead do not present marked dependence on W/b.
Estimating the Maximum Splat Diameter of a Solidifying Droplet
Authors: Hadjiconstantinou Nicolas G.
Published: December 2021

We present a simple analytical model for the estimation of the maximum splat diameter of an impacting droplet on a subcooled target. This work is an extension of the isothermal model of Pasandideh-Fard et al. (1996). The model uses an energy conservation argument, applied between the initial and final drop configurations, to approximately capture the dynamics of spreading. The effects of viscous dissipation, surface tension, and contact angle are taken into account. Tests against limited experimental data at high Reynolds and Weber numbers indicate that an accuracy of the order of 5% is achieved with no adjustable parameters required. Agreement with experimental data in the limit We → ∞ is also very good. We additionally propose a simple model for the estimation of the thickness of the freezing layer developed at the droplet-substrate contact during droplet spreading. This model accounts for the effect of thermal contact resistance and its predictions compare favorably with experimental data.
Drag Reduction on Microscale Concave-Convex Surface
Authors: Hasegawa Masato , Nariai Hideki , Kaneko Kazufumi , Maki Hiroshi , Yabe Akira , Matsumoto Sohei
Published: December 2021

Experimental work on the drag reduction phenomena on the highly water-repellent wall has been done. Fabricated surface, which has concave-convex structure of micrometer scale, was implemented as the tested plate in cone-plate viscometer. The surfaces exhibited the increase of the frictional torque with the projection height of 5 μm. The case of 1.15μm did not show the increase of flow resistance while the result of case of 1.4μm depended on Reynolds number. Another set of the ultra small-scale concave-convex surface was made on 4 inches silicon wafer by lithography and RIE (Reactive Ion Etching), with hydrophobic coating. The surface with high contact angle of 150 degrees for water droplet of 1.4mm diameter showed the drag reduction by maximally 9 percent at Reynolds number around 6.5 × 104. The hydrophobic surface exhibited the decrease in friction coefficient by 6 percent even when it was smooth. PTFE membrane filters have also been tested since the filters can trap gas or bubble on surface, considering that the existence of gas layer at solid liquid interlace is necessary for slip at the boundary to be occurred. The filters showed reduction in friction coefficient, maximally about 6 percent. The rate of the reduction slightly changes related to the size of pores in the filters.
Thermal Conductivity of Nano-Porous Bismuth Thin Films for Thermoelectric Applications
Authors: Song David W. , Shen Wei-Ning , Zeng Taofang , Liu Weili , Chen Gang , Dunn Bruce , Moore Caroline D. , Goorsky Mark S. , Radetic Tamara , Gronsky Ronald
Published: December 2021

Good thermoelectric materials require a small thermal conductivity while maintaining a high electrical conductivity and Seebeck coefficient. Nano-porous systems provide one possible route of increasing the thermoelectric figure-of-merit by disturbing phonon transport more than electron transport. In this work, the temperature dependent thermal conductivity of nano-porous bismuth thin films was measured. Thin Bi films of various porosity and thickness were deposited by metal-organic deposition onto Si substrates. The thermal conductivity of Bi films was measured using a differential 3-ω method, in which the temperature rise across a Bi film was experimentally measured and used to calculate its thermal conductivity. Experimental results show an order-of-magnitude reduction in the porous Bi thin film thermal conductivity due to nano-pores compared to non-porous films. The drastic reduction in thermal conductivity cannot be explained by available models on the thermal conductivity of porous media.
Two-Phase Transport in Proton Exchange Membrane Fuel Cells
Authors: Wang C. Y. , Wang Z. H. , Pan Y.
Published: December 2021

Proton exchange membrane (PEM) fuel cells have emerged, in the last decade, as a viable technology for power generation and energy conversion. Fuel cell (FC) engines for vehicular applications possess many attributes such as high fuel efficiency, low emission, quiet and low temperature operation, and modularity. An important phenomenon limiting fuel cell performance is the two-phase flow and transport of fuel and oxidant from flow channels to reaction sites. In this paper a mathematical model is presented to study the two-phase flow dynamics, multi-component transport and electrochemical kinetics in the air cathode, the most important component of the hydrogen PEM fuel cell. A major feature of the present model is that it unifies single- and two-phase analyses for low and high current densities, respectively, and it is capable of predicting the threshold current density corresponding to the onset of liquid water formation in the air cathode. A numerical study based on the finite volume method is then undertaken to calculate the detailed distributions of local current density, oxygen concentration, water vapor concentration and liquid water saturation as well as their effects on the cell polarization curve. The simulated polarization curve and predicted threshold current density corresponding to the onset of liquid water formation for a single-channel, 5cm2 fuel cell compare favorably with experimental results. Quantitative comparisons with experiments presently being conducted at our laboratory will be reported in a forthcoming paper.
Models for Annular Film Condensation in Vertical Tubes With Vapour Downflow: A Critical Review
Authors: Briggs Adrian
Published: December 2021

Various approaches to the problem of modelling annular film condensation in a vertical tube with downflow are analysed. Laminar and turbulent film models are discussed and applied to intube condensation. The results are compared to several empirical and semi-empirical models for intube condensation.
Heat and Mass Transfer in Granular Potash Fertilizer With a Surface Dissolution Reaction
Authors: Peng Shi-Wen , Besant Robert W. , Strathdee Graeme
Published: December 2021

Potash is a widely used granular fertilizer and when exposed to high humidities it readily adsorbs water forming a liquid electrolyte solution on each particle. Heat and mass transfer due to air flow through granular potash beds is studied experimentally and numerically. A one dimensional experimental set-up is used to measure the temperature and air humidity response and mass gain of a potash bed subject to a step change in air flow. A porous media mathematical model is developed to predict the transient temperature and moisture content distributions. The transport processes are modelled as non-equilibrium heat and mass transfer between the porous solid and air flow gaseous phases. The state of the surface electrolyte solution is modelled by the thermodynamics of electrolyte solutions. Experimental and numerical results shows that when there is a strong surface heat source due to phase change, especially near the entrance region, non-equilibrium internal moisture and heat transfer processes exist. The temperature difference between potash granules and the air flowing through the potash bed is significant.
Heat Transfer Characteristics in Convective Melting of a Solid Particle in a Fluid
Authors: Hao Y. L. , Tao Y.-X.
Published: December 2021

An experimental investigation is conducted to study the heat transfer characteristics in convective melting of a solid particle in a flowing fluid. An ice sphere is used to represent the solid particle. This experiment serves as a basis for further improvement of numerical modeling on the convective melting of a single particle or a packed bed. The process of convective melting of an ice sphere in a horizontal, flowing water is visualized by using a digital video camera under controlled flow rate and supply water temperature. From the digital video images the shape changes of the ice sphere are measured, and the melting rate and heat transfer rate between fluid and particle is determined. A shape factor that indicates shape variation of particle in the melting process is defined. An empirical correlation that can be used to calculate the liquid-solid heat transfer coefficient in convective melting of a solid particle in a flowing fluid was obtained.
Three-Dimensional Numerical Simulation of Convective Melting of Solid Particles in a Fluid
Authors: Hao Y. L. , Tao Y.-X.
Published: December 2021

A physical model of two-phase flow and heat-mass transfer with the phase changes based on the theory of interacting continua is proposed. All terms in the conservation equations are analyzed and the constitutive equations are presented. A closed set of governing equations describing the convective melting of solid particles in a fluid is obtained. The numerical method is developed for the solution of velocity, temperature, and volume fraction of solid phase for the three-dimensional melting in a rectangular cross-section channel. Preliminary calculation, including gravity effects, shows that the result is reasonable. This study provides a basis for the theoretical and experimental investigation of convective melting of solid particles in a fluid.
Effective Thermal Conductivity of the Mushy Region During Solidification of Aqueous Solutions of Ammonium Chloride
Authors: Bianchi Marcus V. A. , Viskanta Raymond
Published: December 2021

A theoretical and experimental study of the diffusion-controlled solidification process of an aqueous solution of ammonium chloride has been performed to obtain fundamental understanding relevant to metal casting, solidification of alloys, and freezing of biological materials. The effective thermal conductivity of the solidifying system is calculated using different models and the model predictions are compared. The model is validated by comparing the predictions with experimental data. It was found that, for the conditions considered in the present study, the parallel model, which is a simple average of the thermal conductivities of the two phases, leads to acceptable results. The reasons for this are related to the size of the mushy region and the morphology of the crystals during the solidification process.
Solidification Processing of Functionally Graded Materials by Sedimentation
Authors: Gao J. W. , White S. J. , Wang C. Y.
Published: December 2021

A combined experimental and numerical investigation of the solidification process during gravity casting of functionally graded materials (FGMs) is conducted. Focus is placed on the interplay between the freezing front propagation and particle sedimentation. Experiments were performed in a rectangular ingot using pure substances as the matrix and glass beads as the particle phase. The time evolutions of local particle volume fractions were measured by bifurcated fiber optical probes working in the reflection mode. The effects of various processing parameters were explored. It is found that there exists a particle-free zone in the top portion of the solidified ingot, followed by a graded particle distribution region towards the bottom. Higher superheat results in slower solidification and hence a thicker particle-free zone and a higher particle concentration near the bottom. The higher initial particle volume fraction leads to a thinner particle-free region. Lower cooling temperatures suppress particle settling. A one-dimensional solidification model was also developed, and the model equations were solved numerically using a fixed-grid, finite-volume method. The model was then validated against the experimental results, and the validated computer code was used as a tool for efficient computational prototyping of an Al/SiC FGM.
Study on Subcooled-Forced Flow Boiling Heat Transfer and Critical Heat Flux of Solid-Water Two-Phase Mixture
Authors: Koizumi Yasuo , Ohtake Hiroyasu , Mochizuki Manabu
Published: December 2021

The effect of solid particle introduction on subcooled-forced flow boiling heat transfer and a critical heat flux was examined experimentally. In the experiment, glass beads of 0.6 mm diameter were mixed in subcooled water. Experiments were conducted in a range of the subcooling of 40 K, a velocity of 0.17–6.7 m/s, a volumetric particle ratio of 0–17%. When particles were introduced, the growth of a superheated liquid layer near a heat trasnsfer surface seemed to be suppressed and the onset of nucleate boiling was delayed. The particles promoted the condensation of bubbles on the heat transfer surface, which shifted the initiation of a net vapor generation to a high heat flux region. Boiling heat trasnfer was augmented by the particle introduction. The suppression of the growth of the superheated liquid layer and the promotion of bubble condensation and dissipation by the particles seemed to contribute that heat transfer augmentation. The wall superheat at the critical heat flux was elevated by the particle introduction and the critical heat flux itself was also enhanced. However, the degree of the critical heat flux improvement was not drastic.
Dynamics of Intermittent Sprays
Authors: Jawad Badih A.
Published: December 2021

It is considered that droplet size distribution changes with time and space, since diesel fuel sprays are found to be transient and intermittent due to variations in ambient pressures. Therefore the obscuration signal (extinction of light due to particle field) obtained from a particle sizer for a single injection of fuel over the whole region of spray is necessary to determine the spray characteristics. Previous studies dealing with sprays have observed fuel droplets by use of the sedimentation tower method or liquid immersion sampling technique. However, in these technique droplets are usually sampled after spray formation is complete. The completion time of spray formation appears to vary with ambient conditions, thus making spray measurements under transient conditions during injection difficult. It is the objective of this paper to shine some light on the dynamics of spray motion, leading to a better understanding of the droplet size distributions.
Three-Dimensional Numerical Modeling of Stoker-Fired Power Boilers
Authors: Dudek Scott A. , Wessel Richard A. , Strempek Joseph R.
Published: December 2021

A numerical model has been developed to simulate the various interacting physical processes that occur within any stoker-fired power boiler burning wood, refuse-derived fuel (RDF), coal, or other biomass fuel and operating at steady state. The processes modeled are three-dimensional turbulent gas flow, particle motion (including dispersion and re-entrainment), heterogeneous and homogeneous chemical reactions, and heat transfer. The purpose of this paper is to provide a detailed description of the model and to present an example of its use.

The model can be used as a cost-effective tool to assist in the design of original and retrofit power boiler equipment and in the diagnosis and resolution of boiler operating problems. The effects of modifying operational parameters or the physical arrangement of equipment can be quickly evaluated. Simulations can be used to optimize overfire air distribution and arrangement to produce a more uniform gas flow distribution within the furnace, resulting in more complete combustion and less particulate carryover.

As an example of the model’s capability, simulations were produced for a stoker-fired power boiler using wood, bark-pile reclaim, and waste-treatment sludge for fuel. The results show that changes in the air distribution and in the arrangement of operational overfire air ports can produce a significant reduction in carbon monoxide, unburned carbon loss, and particulate carryover, without increasing furnace exit gas temperature. Field modifications as a result of the modeling study have improved boiler operation and eliminated tube failures caused by flyash erosion.
Numerical Modeling of Combustion and Heat Transfer in a Laboratory Scale Glass Melting Furnace
Authors: Jorgensen K. L. , Ramadhyani S. , Viskanta R.
Published: December 2021

A fully three-dimensional model and computer code has been developed for predicting and analyzing combustion and heat transfer in the combustion space of glass melting furnaces. It is capable of predicting steady state temperature, velocity, and species concentration distributions throughout the combustion chamber and spatially resolving the heat transfer to the surrounding walls and the glass/batch surface. Model predictions are obtained from the solution of coupled conservation equations employing a control volume formulation. The discrete ordinates method along with the weighted-sum-of-gray gases model is used to determine radiative heat transfer to the surfaces enclosing the combustion space and within the flow field. Turbulence is modeled using a high Reynolds number k-ε model. A fast-kinetics, single-step combustion model using an assumed shape clipped Gaussian probability density function is used to determine gas species concentrations. The model predications are compared to test data from a laboratory scale glass furnace simulator at the Institute of Gas Technology. Comparisons of predicted quantities are made for wall temperatures, glass surface heat flux, and exit gas stream temperature. Wall and roof temperatures were predicted on average to within 7 percent and global heat fluxes were with in 10 percent of measured levels. Examples of predicted temperature, velocity, and species concentration are presented.
Radiation Heat Transport in Porous Media
Authors: Travkin V. S. , Catton I.
Published: December 2021

At present most work treats radiative transport in heterogeneous media as if it were a homogeneous medium, then relies on different methods to simulate the medium heterogeneity or uses similar governing equations with assigned distributions for coefficients. This approach is widely used although almost never found in other fields of heat and mass transport. The lack of generality in present theoretical treatments of radiative transport in heterogeneous media is addressed by rigorous development of a set of governing equations. The new rigorous equations for radiation transport in heterogeneous media are presented for the first time. As part of the development of the new set of equations for electromagnetic and spectral intensity fields, the diffusion approximation is explored.
Particle Transport via Three-Dimensional Chaotic Advection to Produce Electrically Conducting Plastics With Powder Additives
Authors: Danescu R. I. , Zumbrunnen D. A.
Published: December 2021

Extended micron-scale structures were produced in thermoplastic melts from initially large clusters of conducting carbon black particles transported by three-dimensional chaotic mixing. The structures formed networks that were captured by solidification and rendered the composite materials electrically conducting. A systematic study was carried out to assess the influence of key parameters and relate the electrical properties to the microstructures. Micrographs showed complex structures exhibiting patterns characteristic of chaos. Electrical measurements indicated that conductivity was achieved at carbon black concentrations significantly lower than achievable by common mixing methods, and lower than reported recently for two-dimensional chaotic mixing.
Photon Counting Temperature Measurements During Pulsed Laser Heating of Al2O3-TiC Ceramics
Authors: Harms Todd M. , Xu Xianfan
Published: December 2021

This work investigates photon-counting measurements during pulsed laser heating of an Al2O3-TiC substrate. The excitation source is a Nd:YAG laser operating at a fundamental wavelength of 1064 nm. The laser fluence is varied in the range from 0.272 J/cm2 to 0.839 J/cm2. The emission spectra, captured by single photon counting, are related to temperature by Planck’s distribution. The suitability of this method is discussed.

Pulse exposure, the number of pulses that a given surface location receives, is found to be a vitally important parameter. Numerical simulations of transient heat conduction support the results of high pulse exposure measurements. Low pulse exposure experiments exhibit higher temperatures due to chemical reactions at the surface and grain boundary effects.
3-D Sintering of Two-Component Metal Powders With Stationary and Moving Laser Beams
Authors: Zhang Yuwen , Faghri A. , Buckley C. W. , Bergman T. L.
Published: December 2021

Melting and resolidification of a mixture of two metal powders with significantly different melting points under irradiation of a stationary or a moving Gaussian laser beam were investigated numerically and experimentally. The liquid motion driven by capillary and gravity forces as well as the shrinkage of the powder bed caused by the overall density change were taken into account in the physical model. The liquid flow was formulated by using Darcy’s law, and the energy equation was given using a temperature transforming model. Predictions were compared with experimental results obtained with nickel braze and AISI 1018 steel powder. The effects of laser properties and the scanning velocity on the laser sintering process were also investigated. An empirical correlation that can be used to predict the of cross sectional area of the heat affected zone is proposed.
Transport Processes for a Row of Confined Jets Impinging on a Moving Surface
Authors: Dinu Constantin A. , Beasley Donald E.
Published: December 2021

The common architecture of the fluid delivery devices employed in the horizontal processing of printed wiring boards, makes use of high velocity jets directed normally or at some angle towards the board which moves above rollers. Usually, a single slot jet or a linear arrays of jets are employed in order to increase the transport properties of the flow in the vicinity of the printed wiring board. In the present study, a geometry resembling a fluid delivery device used in printed wiring board manufacturing was investigated both experimentally and numerically. The printed wiring board is represented by an endless belt, which is transported horizontally by a system of rollers. The working fluid is delivered by an array of 13 square jets with a hydraulic diameter of 5.02 mm and a separation distance between jets of 4 hydraulic diameters. Two confinement plates located on each side of the jet array are used to confine the flow region and adjust the flow resistance at the two openings — between the rollers and the confinement plates — symmetrically located with respect to the centerline of the row of jets. The experimental setup and the numerical model both allowed the investigation of the effect of complex confinement (due to the board, confinement plates and rollers) and of the moving boundaries (impingement surface and rollers) on the characteristics of impinging flow. The flow field and the heat transfer characteristics were investigated for the jet Reynolds number ranging from 500 to 2000, non-dimensional impingement surface velocity ranging from 0 to 1 and non-dimensional impingement distance of 3 and 5. The CFD simulations were performed using the commercial CFD code PHOENICS. Flow visualization and particle image velocimetry were employed in order to experimentally investigate the flow field and validate the CFD simulations. The predicted results compare well with the observed jet behavior. A detailed description of the flow physics is presented. The numerical simulations show that for the same mass flow rate, the row of jets has a higher transport effectiveness when compared to a slot jet.
Thermal Conductivity Measurement of CVD Diamond Films Using a Modified Thermal Comparator Method
Authors: Cheruparambil Kumar R. , Farouk Bakhtier , Yehoda Joseph E. , Macken Nelson A.
Published: December 2021

Results from an experimental study on the rapid measurement of thermal conductivity of chemical-vapor-deposited (CVD) diamond films are presented. The classical thermal comparator method has been used successfully for the measurement of thermal conductivity of bulk materials having high values of thermal resistance. Using samples of known thermal conductivity, a calibration curve is prepared. With this calibration curve, the comparator can be used to determine thermal conductivity of unknown samples. We have significantly modified and extended this technique for the measurement of materials with very low thermal resistance, i.e., CVD films with high thermal conductivity. In addition to the heated probe, the modified comparator employs a thermo-electric cooling element to increase conductive heat transfer through the film. The thermal conductivity measurements are sensitive to many other factors such as the thermal contact resistances, anisotropic material properties, surrounding air currents and temperature, and ambient humidity. A comprehensive numerical model was also developed to simulate the heat transfer process for the modified comparator. The simulations were used to develop a ‘numerical’ calibration curve that agreed well with the calibration curve obtained from our measurements. The modified method has been found to successfully measure the thermal conductivity of CVD diamond films.
Velocity Statistics of Plane Self-Preserving Buoyant Turbulent Adiabatic Wall Plumes
Authors: Sangras R. , Dai Z. , Faeth G. M.
Published: December 2021

Measurements of the velocity properties of plane buoyant turbulent adiabatic wall plumes (adiabatic wall plumes) are described, emphasizing conditions far from the source where self-preserving behavior is approximated. The experiments involved helium/air mixtures rising along a smooth, plane and vertical wall. Mean and fluctuating streamwise and cross stream velocities were measured using laser velocimetry. Self-preserving behavior was observed 92–156 source widths from the source, yielding smaller normalized plume widths and larger near-wall mean velocities than observations within the flow development region nearer to the source. Unlike earlier observations of concentration fluctuation intensities, which are unusually large due to effects of streamwise buoyant instabilities, velocity fluctuation intensities were comparable to values observed in nonbuoyant turbulent wall jets. The entrainment properties of the present flows approximated self-preserving behavior in spite of continued development of the wall boundary layer. Measurements of temporal power spectra and temporal and spatial integral scales of velocity fluctuations are also reported.
Higher-Order Discretization Method for Computations of Separated Flows
Authors: Song B. , Amano R. S.
Published: December 2021

This paper presents a new higher-order bounded scheme, WACEB, for approximating the convective fluxes in the transport equations. The weighted-average formulation is used for interpolating the variables at cell faces and the weighted-average coefficient is determined from normalized variable formulation and total variation diminishing (TVD) constrains to ensure the boundedness of solution. The new scheme is tested by solving three problems: 1) a pure convection of a box-shaped step profile in an oblique velocity field; 2) a sudden expansion of an oblique velocity field in a cavity, and; 3) a laminar flow over a fence. The results obtained by the present WACEB were compared with the UPWIND and the QUICK schemes and showed that this scheme has at least the second-order accuracy while ensuring boundedness of solutions. Moreover, it was demonstrated that this scheme produces results that better agree with the experimental data in comparison with other schemes.
Investigative Active Learning and the Teaching of Heat Transfer
Authors: Anderson Edward E.
Published: December 2021

The benefits and advantages of investigative active learning are well documented throughout cognition and educational psychology research literature. But, these techniques are not extensively used in higher education and particularly engineering education. In this paper, a model is presented for applying computer based instruction (CBI) techniques to investigative active learning as practiced in a typical undergraduate heat transfer course. This model is demonstrated with the heat transfer through a composite structural wall problem. An investigative approach is used to coach students as they learn the general solution process. Several different active learning techniques are then applied as a student progresses through each step of the general solution process. These techniques are applicable to any heat transfer problem and when properly implemented, they should improve the learning of the general solution process. The demonstration example is best experienced with a computer. Individuals wishing to explore this model may do so at http://129.118.17.180/mvweb.
Response of Loop Heat Pipes to Transient Heat Loads
Authors: Long J. B. , Ochterbeck J. M.
Published: December 2021

Loop heat pipes currently are being used in the thermal control systems for satellites. To expand possible loop heat pipe applications, information regarding response to transient heat inputs is required. In this investigation, two loop heat pipes with dual compensation chambers were subjected to heat inputs of varying magnitude, frequency, and waveform (square and sinusoidal). The performance of each loop heat pipe under these conditions was evaluated in different gravitational orientations. The upper and lower limits of heat transport also were assessed. A principle finding was that cyclic heat loads tended to aid startup of the loop heat pipes at the low power inputs.
Overview of U.S. Process Safety Regulations and ANSI/ISA S84.01 for an Integrated Risk Program
Authors: Doerr William W. , Bhimavarapu Kumar
Published: December 2021

In response to major chemical and nuclear accidents that have occurred during the past two decades, the U.S. government has promulgated two regulations aimed at protecting workers, the community, and the environment from accidental releases of hazardous chemicals. These regulations are the US Occupational Safety & Health Administration’s [OSHA] Process Safety Management [PSM] Standard and the US Environmental Protection Agency’s [EPA] Risk Management Program [RMP]. The applicability for each regulation is discussed with a review of what is affected, who is responsible, when is compliance required, and how is compliance manifested. In addition, the recent ANSI/ISA S84.01 standard for the process industries introduces additional or new responsibilities that are not featured explicitly in either the OSHA or EPA regulations. The pooling of the requirements from these US regulations and voluntary ANSI/ISA standard establishes the requirements for an integrated risk program [IRP]. The objective of an integrated risk program is compliance, reduction in resource requirements, and improvement of productivity at a plant. The general requirements for an IRP are summarized showing the area of regulatory overlap.
A New Interlock System: Movable Interlocked Barrier Guards With Motorized Openers for Testing
Authors: Barnett Ralph L. , Liber Theodore
Published: December 2021

A unique system is introduced for monitoring the viability of conventional position switch interlocks on movable barrier guards. At closely spaced intervals a test device motor causes the guard to open slightly to check if the interlock will change state in an attempt to interrupt control power to the protected machine. The machine will not in fact shut down during the testing phase because the interlock system will be isolated from the machine operating motor contactors during the test duration. Testing of a guard is annunciated just before and during the automatic testing phase. Any failures of an interlock or its testing system will also be annunciated until their causes are corrected. When a latching system is used in conjunction with the guard, a faulty interlock will cause the guard to be locked closed until it is convenient to effect a repair. Production is not interrupted because the interlock remains bypassed during this period. If an interlock is temporarily circumvented or if the interlock guard is sabotaged, the test device motor will not cause a change in state of the interlock during the test phase; again, system malfunction will be annunciated and/or the guard will remain latched and/or the machine will be shut down.

The proposed process provides the following advantages:

• A quantum leap in system reliability and safety is obtained using even the most ordinary “limit switch” type interlocks.

• The tamper-resistance of all known interlocks will be greatly enhanced; all popular forms of temporary interlock circumvention are eliminated.

• Long term sabotage which involves simultaneous guard removal and interlock bypassing is addressed for the first time; to defeat the proposed process involves the most outrageous restructuring of the control system.

• The system will safely endure adhesive environments that may cause interlock activators to stick in their “fail to danger” states.

• The monitored machine is almost never shut down nor production interrupted during or after the testing phase even if mischief is uncovered.

• The testing of large numbers of interlocks will not expose the machines’ electric power motors to the frequent restart demand associated with some conventional manual testing procedures.

• Without compromising safety, maintenance of even multiple interlock failures may be deferred until their repair is convenient.

• The assurance of working interlocks may enable OSHA to expand applications where maintenance is performed under “control stop” as opposed to the more elaborate “lock out.”

• The design of the new test and monitoring system may be executed and implemented using straightforward hardware and software that are firmly entrenched technology.
The Float Scaffold
Authors: Poczynok Peter J. , Barnett Ralph L.
Published: December 2021

Unstable work platforms compromise the ability of workers to adjust their bodies to quickly react against the forces generated at their tool/workpiece interfaces. This paper focuses on the flexibility of work platforms with emphasis on the classical float scaffold used by iron workers. The ability to prestress the float gives rise to superior stiffness characteristics.
Influence of the Dynamic Wetting Angle on the Motion of the Triple Line
Authors: Woehl Pierre , Bourgin Patrick
Published: December 2021

The problem of a liquid sheet issuing from an ejector and being coated on a moving solid substrate is considered in taking into account the dynamic behavior of the ambient air. In a previous model, we investigated the possible influence of slight pressure fluctuations in the air on the displacements of the triple line. We propose here to incorporate into our model a non-linear dependence of the dynamic contact angle upon the triple line velocity, in order to be more consistent with the experimental observations reported in the literature.

The main result is that the motion of the triple line induced by pressure oscillations in the air is very sensitive to the dependence of the dynamic wetting angle on its velocity. The respective roles of the liquide wetting properties and of the process conditions are pointed out.
Two Dimensional Transient Thermal Stress Analysis of Adhesive Butt Joints
Authors: Nakano Yuichi , Kondo Hiroki
Published: December 2021

Transient thermal stress distribution in an adhesive butt joint is dealt with in this study. It is assumed that both the upper and lower end surfaces of the joint are subjected to different temperatures at a certain instant in time and the side surfaces of the joint are kept at a constant temperature. In the analysis, two adherends and an adhesive layer are replaced with finite strips and unsteady, two-dimensional temperature distribution in the joint is obtained theoretically. Then, the transient thermal stress distribution in the joint is analyzed using a two-dimensional theory of elasticity. The effects of the adherend to adhesive ratios of the Young’s moduli and thermal expansion coefficients on the transient thermal stress distribution are clarified using numerical calculations.
Elasto-Plastic Analysis of Bolted Joint During Tightening Process
Authors: Fukuoka Toshimichi , Takaki Tomohiro
Published: December 2021

A bolted joint is subjected to high stress concentration at the thread root because of its complicated geometry involved. Plastic regions are produced around the bottom of thread root, even under relatively low bolt axial force. It is predicted that the plastic deformation thus produced might affect such important mechanical behaviors of bolted joint as load distributions along threads, the relationships between bolt axial force and angle of nut rotation, etc. In many practical applications, bolts are tightened with considerably high clamping force, especially when tightening critical structures. Thus, it is considered that numerical studies taking the effects of plastic deformation into account are extremely important. However, many previous studies have only dealt with a bolted joint under pure tension. When tightening bolted joints with torque control shear stresses are generated in addition to the tensile stress due to bolt clamping force. In this study, mechanical behaviors of bolted joint during tightening with torque control are analyzed by FEM as an elasto-plastic contact problem, where three-dimensional analysis is conducted employing two dimensional model with each node having three degrees of freedom.