bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observation and Prediction of Damage Evolution in Continuous Fiber Titanium Matrix Composites
Authors: Allen David H. , Foulk James W. , Helms Kayleen L. E. 
Published: March 2022

Abstract
Titanium matrix composites (TMC’s) are known to undergo significant environmental degradation at elevated temperatures. As a part of this research effort the TMC SCS-6/Ti-ß21S [0]4 has been fatigue tested at 482°C and 650°C. Additional specimens have been oxidized at 700°C and then fatigued at 482°C to failure. The life limiting physical mechanisms identified from the experiments are material inelasticity, surface embrittlement and subsequent surface cracking, fiber/matrix debonding, fiber-bridging, and eventual fiber failure.
A model incorporating all of these physical phenomena has been developed in an ongoing effort by the authors. This model will be briefly presented herein. The model utilizes the finite element method coupled with models for material inelasticity, surface embrittlement. and crack propagation. Material inelasticity is predicted using Bodner’s unified viscoplastic model. Crack propagation is modeled via the inclusion of cohesive zone elements. Surface embrittlement is accounted for through the degradation of material properties. Both monotonic and fatigue loadings have been modeled at 482°C and 650°C for oxidized and unoxidized specimens. Results indicate that surface crack propagation rates are significantly slower when matrix viscoplasticity is included in the model instead of elasticity. Furthermore, surface cracking in degraded specimens enhances fiber stresses compared to undegraded specimens. This difference apparently causes premature failure of the degraded composite.
Material Modeling for Cross-Ply Ceramic Matrix Laminates With Progressive Damages and Environmental Degradation
Authors: Yen Chian-Fong , Jones Mark L. 
Published: March 2022

Abstract
A physically-based damage model has been developed to predict the nonlinear behavior of cross-ply ceramic matrix laminates due to progressive failures. It has been shown to model the nonlinear stress-strain response of chemical vapor infiltrated (CVI) SiC/SiC composites under tension loading accurately. This model utilizes a consistent set of measurable material parameters as inputs and shows good agreement with measured tensile stress-strain curves for a variety of ply thickness ratios. The material model is also utilized to characterize the environmentally induced property degradation in CMC’s.
Failure Mechanisms in Off-Axis and Angle-Ply Fiber Reinforced Ceramic Composites
Authors: Selvarathinam A. S. , Weitsman Y. J. 
Published: March 2022

Abstract
Continuous fiber reinforced ceramic composites (CFCC) consist of brittle ceramic matrix (ϵum ≈ 0.15%) reinforced by relatively ductile ceramic fibers (ϵuf ≈ 1.1%), with intentionally weak interfaces. This combination of material properties enhances the ductility of the CFCC in the fiber direction.
Evaluation of Stress Redistribution and Notch Sensitivity in Ceramic Matrix Composites (CMCs)
Authors: Roberts Mark C. , Mackin Thomas J. 
Published: March 2022

Abstract
Damage tolerance, which depends upon inelastic mechanisms, is crucial to the general utility of ceramic matrix composites (CMCs). Recent experiments have confirmed several damage mechanisms and revealed that stress redistribution does occur in CMCs. The current composite paradigm relies on fiber coatings to achieve this damage tolerance. More recently, an Al2O3/ Al2O3 CMC was developed which attains damage tolerance through the use of a porous matrix. To evaluate this all-oxide material, tensile experiments were conducted on double edge-notched test specimens. An infrared imaging technique, known as thermoelastic stress analysis, was used to classify the damage mechanism and measure the extent of stress redistribution in double edge-notched specimens. Results indicate that the subject alumina/alumina composite exhibits a measurable degree of ductility by developing shear band damage zones.
Stress Redistribution and Notch Sensitivity in Ceramic Matrix Composites (CMCs)
Authors: Mackin Thomas J. , Roberts Mark C. , Anderson David 
Published: March 2022

Abstract
A new generation of relatively ‘ductile’ CMCs is being developed that expands the general utility of structural ceramic composites. These new materials rely on inelastic mechanisms such as interface failure, matrix cracking, fiber failure and fiber pullout to redistribute stress away from locations of stress concentration (Evans et al., 1995). The combined effect of these mechanisms can be summarized in three macroscopic damage classifications (Mackin et al., 1995): Class I damage is the development of a single matrix crack bridged by fibers; Class II damage involves the development of multiple cracks in the matrix; and Class III damage involves the development of a shear damage zone. The operative damage mechanism depends upon the composite constituent properties, while the extent of stress redistribution depends upon the damage mechanism.
In Situ Control of Interface Coatings on Fibers Using CVD
Authors: Jones John G. , Busbee John D. , Jero Paul D. , Kent David J. , Liptak David C. 
Published: March 2022

Abstract
Most ceramic matrix composites (CMC’s) require a fiber interface coating in order to exhibit the desirable properties that make them potentially useful high temperature structural materials.6,9 Although interface coatings are widely recognized as a key to these properties, fiber coating technology has received relatively little attention, hindering successful application of CMC’s. Additionally, in today’s search for new oxidation resistant interfaces, the inability to deposit coatings of controlled chemistry, thickness, and morphology is a significant problem.5
Computational Analysis of Mixed-Mode Delamination Crack Growth in a Woven Laminated Ceramic Matrix Composite
Authors: Krishnappa M. , Newaz G. M. 
Published: March 2022

Abstract
Mixed-mode delamination crack growth characteristics in a SiC/SiC woven laminated ceramic matrix composite is analyzed. Delamination crack growth under mixed mode conditions was investigated using a computational mechanics approach. For the purpose of this study the CMC specimen considered was in 4-point bending. A notch, of 1/3 of the specimen width was considered in the analysis. In this paper only symmetric delamination crack growth were investigated and results presented. Effects of other parameters, such as loading configuration, material properties, crack configuration, and effect of temperature on the energy release rates were also investigated.
Experimental and Numerical Analysis of Ceramics With Microcracking
Authors: Yin Gang , Xu Ling , Jiang Lin 
Published: March 2022

Abstract
The application of ceramic materials in engineering structure has increased significantly for their outstanding hardness and yield stress under compressive loading. However, fracture behavior of ceramic materials is closely related to microcracking. Continuum damage mechanics is considered as a powerful theoretical framework. It is fairly difficult to obtain analytically as well as experimentally evolution equations for ceramic with microcracking. In the present study, an effective computational procedure is employed in a dynamic fracture analysis of ceramic materials with microcracking. The computational analysis is carried out for simulation of fracture experiment using notched specimens. This procedure can be used for better interpretation of experimental data as well as fracture simulations of complex structural models. Additionally, ceramic specimen is applied to the finite element analysis of microcracking near the microcrack-tip in a tensile stress field. The simulations were not only consistent with the experiments, but also revealed a possible damage mechanism which helps to explain the experimental data.
Vibration and Flutter Analysis of Stiffened Composite Plate Considering Thermal Effect
Authors: Lee In , Oh Il-Kwon , Lee Dong-Min 
Published: March 2022

Abstract
Vibration and flutter analyses have been performed for stiffened composite laminated plates considering thermal effect. The FSDT (First order Shear Deformable plate Theory) and Timoshenko beam theory are used for the finite element modeling of a skin panel and stiffeners, respectively. The von Karman nonlinear strain-displacement relation is adopted to consider a large deflection due to the thermal buckling loads and severe aerodynamic loads. The first order piston theory is used for the modeling of aerodynamic loads. The temperature distribution is assumed to be constant over the surface and has a thermal gradient through the thickness of the plate. It is assumed that a degradation of the elastic properties of the constituent materials is a function of the temperature field itself. Guyan reduction method is employed to reduce the problem size and computational time. Newton-Rhapson iteration method is used to obtain the postbuckled deflection. Complex eigenvalue solver with LUM/NTF approximation method is used to obtain vibration and flutter characteristics. The effects of various parameters, such as ply orientation, temperature gradient, material property degradation and the stiffening scheme on flutter characteristics are investigated through some numerical examples. The degradation of material properties affects the aero-thermo-postbuckled deflection, vibration characteristics and flutter boundary. The selection of proper stiffening scheme results in great improvements of flutter characteristics of laminated panels without introducing considerable weight penalty.
Minimum Deflection Design of Piezothermoelastic Laminated Composite Plates
Authors: Tauchert Theodore R. , Adali Sarp , Verijenko Viktor E. , Richter Alexander A. 
Published: March 2022

Abstract
The converse piezo effect is used to minimize the deflection of a given point for antisymmetrically laminated rectangular plates. The piezoelectric layers are bonded to the top and bottom surfaces of the laminate and are subjected to an electrical field. The deformation generated by the piezo effect counteracts the deflections induced by mechanical and/or thermal loads. Moreover, the ply angles can be used as additional design variables to minimize the deflection. In the numerical examples, the mid-point of the plate is specified as the point deflection of which is to be minimized. It is shown that, depending on the magnitudes of the mechanical and thermal loads, the deflection of this point can be reduced to zero by applying a certain voltage to piezoelectric layers.
On the Response of a Sandwich Panel With a Bilinear Core
Authors: Sikarskie David L. , Mercado Lei L. 
Published: March 2022

Abstract
Sandwich panels can fail in a variety of ways. In the present paper one type of failure is investigated and modeled which has a number of important applications, e.g., marine hulls. Here core yielding is assumed to initiate and grow in the sandwich panel while the face sheets remain bonded, unbuckled and in the elastic range. For elastic face sheets, the core shear stresses can be determined from equilibrium of the face sheets independent of core yield. Core shear strains can then be found from the stress-strain curve and an algorithm is constructed for determining shear deflection. Bending deflection is found from the elastic solution. This approach works well except when the bilinear stress strain behavior approaches the perfectly plastic core. With the aid of a detailed finite element solution it is shown that the classical sandwich theory assumptions begin to break down and that the face sheets now carry an appreciable part of the shear load. This effect is shown in detail for four point beam bending where the classical sandwich solution is 20∼30% below the ABAQUS results and the experimental data. For the bilinear case, not close to perfectly plastic, however, the extension of the classical theory to the core yielding problem provides excellent results.
Variability of Rotor Wake Interactions and Airfoil Unsteady Aerodynamics
Authors: Sanders Albert J. , Fleeter Sanford 
Published: March 2022

Abstract
Multistage interaction effects on rotor blade-to-blade wake variability and the resulting downstream vane row unsteady aerodynamic response are experimentally investigated in a high speed fan stage. Multistaging effects on the rotor wake are quantified by acquiring data over two complete rotor revolutions at each of several IGV clocking positions relative to downstream stationary probes. The resulting downstream vane response data are acquired over a range of steady loading conditions, with both design and off-design operation of the rotor considered. Multistage interactions are shown to significantly affect the rotor wake characteristics and lead to the generation of rogue wakes. The fundamental periodicity of these interactions is one complete rotor revolution due to the unequal number of blades and vanes in the machine. The rotor wake and resultant vane row unsteady aerodynamic response variability are also quantified. Off-design rotor operation results in wakes with the largest variability, on the order of the average velocity deficit. The vane response variability is even more pronounced, being as large as 160% of the maximum average unsteady lift over one blade pass period.
Microphysics of Turbulent Transport Processes at Gas-Liquid Interface
Authors: De Angelis V. , Banerjee S. 
Published: March 2022

Abstract
Gas and moisture transfer at continuous interfaces between turbulent air and water streams are controlled by layers ∼ O(10−2mm) and ∼ O(1mm) thickness, respectively. This suggests that direct numerical and large eddy simulations could be used to clarify microphysical processes controlling scalar transfer rates, since such scales are resolvable with available computational resources. To this end, numerical procedures using a pseudospectral method, together with a projection algorithm, have been developed and applied to coupled gas-liquid flows. The initial studies focused on flows under conditions where interface deformations were small — a situation corresponding to a series of laboratory experiments where detailed measurements of the near-interface turbulence characteristics were made. The simulations agreed very well with measurements. The next step was to calculate gas flow over wavy solid surfaces, where the wavelengths corresponded to those of capillary waves. The simulation maintained spectral accuracy, and agreed with experimental data, which included waves of sufficient steepness that separation occurred behind the crests. Finally, simulations were conducted for conditions under which capillary waves developed at the interface — the physical properties being those of air and water at atmospheric conditions. The program of simulations, supported, where possible, by experiments, clarified that the scalar transfer rates on each side of the interface were correlated with the sweeps on each side, i.e. fourth-quadrant events which bring high speed fluid close to the interface, forming regions of high shear stress and high scalar transfer rates. Furthermore, the simulations, and experiments indicated that the sweep frequency could be expressed in terms of the frictional drag, but not in terms of the total drag, which includes form drag. From this, using surface renewal theory, it was found that simple parametrizations for the scalar transfer rates could be derived in terms of the frictional drag, with no adjustable parameters. It appeared that capillary wave characteristics affect the scalar transfer rates by affecting the frictional drag, i.e. indirectly, by affecting sweep frequencies, and by affecting the Sc numbere dependency in the case the flow shows recirculation. Parameterizations based on these considerations are in excellent, agreement with large-scale laboratory experiments, some of which were done after the parametrizations were proposed.
Entrained Fraction in Inclined Annular Gas/Liquid Flow
Authors: Azzopardi B. J. , Zaidi S. H. , Jepson D. M. 
Published: March 2022

Abstract
Light scattering measurements have been used to determine entrained liquid flow rates in annular gas/liquid flow. Data have been obtained for vertical upflow and horizontal flow as well as for inclined flow at 10° intervals in between, The vertical flow data show trends similar to previous published work. In particular, they suggest that, unlike at higher gas velocities, at lower gas velocities the entrained fraction increases with decreasing gas velocity. The inclined flow data show that this parameter does not react to inclination as rapidly as does the asymmetry in film thickness.
Measurement of Two-Phase Mass Flow Rate and Quality Using Venturi and Void Fraction Meters
Authors: Moura Luiz F. M. , Marvillet Christophe 
Published: March 2022

Abstract
The measurement of the mass flow rate and quality of a two-phase gas-liquid flow is of interest in many fields of engineering such as refrigeration, power cycles, chemical processes, nuclear plants and petroleum production. This paper presents the use of a venturi and a void fraction meter for the measurement of refrigerant R-134a liquid-vapor mass flow rate and quality in vertical pipes.
Measuring a single-phase mass flow is comparatively easy. The medium is a continuum with either a laminar or a turbulent flow. Measurements of the pressure drop produced by a venturi meter allow the instantaneous mass flow rate to be determined unequivocally and with great accuracy. In two-phase flow, the phases occurring in the flow channel are discontinuous. There may be such flow regimes as bubbly, slug, churn, annular and dispersed flows, which are difficult and expensive to identify. Even pressure drop measurements do not allow the mass flow to be derived unequivocally and precisely because there is a strong dependency on the flow regime and the vapor quality (vapor mass fraction). Since these quantities are not known in practical measurements, the measuring errors of such techniques frequently range between 5 and 20%.
Fundamental improvements in the accuracy of measuring two-phase flows can only be attained with the measurement of at least two independent parameters. These are typically a measure of velocity or volumetric flow rate and a measure of the mixture density or void fraction.
Differential pressure instruments, such as orifice, venturi, and nozzle meter, were the earliest and simplest forms of metering devices used in two-phase mass flow rate and quality measurements. The venturi meter induces the lowest pressure loss relative to the other differential pressure instruments.
In this work, the measurement of the pressure drop in a venturi meter is complemented with the measurement of the void fraction by a electrical impedance sensor. Then, the two-phase mass flow rate and quality were determined from a theoretical model. It was found that proposed theoretical model provides a good accuracy for all experimental conditions.
Thermal-Hydrologic-Mechanical Analyses of the In Situ Single Heater Test, Yucca Mountain, Nevada
Authors: Francis Nicholas D. , Sobolik Steven R. , Ballard Sanford 
Published: March 2022

Abstract
The single heater test (SHT) is up to an eighteen-month-long heating and cooling experiment begun in August, 1996, located underground within the unsaturated zone near the potential geologic repository at Yucca Mountain, Nevada. Experimental measurements at the test site include temperature measurements made at various radial locations and along the length of the heater, moisture concentration measurements around the heater zone, and rock displacement measurements resulting from the development of thermal stresses.
Three-dimensional thermal-hydrologic calculations were performed with an integrated finite difference code. This computer code determines the simultaneous transport of heat and mass in response to a thermal perturbation resulting from an emplaced heat source. The working range in rock permeability (5.1 millidarcy to 5.3 darcy) results in predicted temperature differences of approximately 10°C or less. The high permeability simulations resulted in lower predicted temperatures around the heater along with the formation of an asymmetrical dry-out zone resulting from the development of buoyant gas-phase convection cells. The low bulk permeability simulations resulted in higher predicted temperatures and a symmetrical dry-out zone.
Three-dimensional, elastic thermal-mechanical calculations were performed with a finite element nonlinear structural mechanics computer code. The temperature predictions from the thermal-hydrologic calculations were used as the input temperatures for the thermal-mechanical calculations. Total displacements along the multi-point borehole extensometers (MPBX’s) are predicted to be no more than ∼3 mm for the conditions and properties used.
Improving the Snap-Off Process in Solder Paste Stencil Printing via the Enhancement of Wall Slip
Authors: Mimura Toshinori , Liu Sheng , Asada Haruhiko 
Published: March 2022

Abstract
To successfully print solder paste onto circuit boards using stencils, a properly controlled fill-in process must be followed by an efficient snap-off. Due to the non-Newtonian nature of solder paste, its flow behavior during a snap-off is highly complex and difficult to analyze. In this paper, solder paste is modeled as a dense suspension that flows with a slip at the wall boundary. Based on a visualization technique, the wall slip behavior is studied and its influence on the snap-off process is discussed. In particular, it is found that at higher temperatures, wall slip can be enhanced and the snap-off success rate can be improved. Based on the study of wall slip, practical methods for improving snap-off are proposed.
Numerical Studies on the Transportation of Water Mist for Fire Suppression Applications
Authors: Hung L. S. , Yao S. C. 
Published: March 2022

Abstract
Some phenomena of spray dynamics of water mist for fire suppression are studied numerically. The transport of fine mist sprays is very different than that of the typical large water sprinkler drops because water mist may have a better ability to follow the air streams and to penetrate into hidden locations behind obstructions or through opening slots where fire occurs. First, the free falling of fine droplet in stagnant air is examined to reveal the time delays and change of volumetric number density of the spectrum of droplets. Then, the 2-D numerical simulations of a two-phase gas droplet flow based on Navier-Stokes equations are performed to study the motion of droplets around a rectangular strip obstruction. The deposition of the droplets on the strip and the flow around the strip are investigated. The collection efficiency on the strip is computed numerically as a function of the inertial impaction parameter. In addition, flow over a single strip in a domain with various widths is also examined to reveal the characteristics of the flow over an array of repeated strips. No major variation on the collection efficiency with respect to the single strip is observed if the blockage fraction (B), which is the fraction of the size of strip to the total width of the flow domain, is less than about 0.33. The penetration efficiency of the mist droplets through an array of slots can be evaluated based on the collection efficiency and the geometric fraction of the strip to the flow domain configuration.