bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Lumped-Parameter Method for the Computation of the Temperature of Hot Combustion Gases Flowing Inside Chimneys
Authors: Cortés C. , Campo A. , Correas L. 
Published: March 2022

Abstract
This paper addresses the practical calculation of the thermal performance of industrial chimneys by means of recent results in forced convection heat transfer. The temperature decay of the combustion gases is a result of heat transfer processes involving both internal forced convection and external heat transfer to the surroundings, and the analysis of the problem is scarcely treated in the energy- and environmental-related literature. Thermal design and performance estimations of chimneys are therefore based on engineering rules of thumb dictated by experience.
The aim of this paper is to introduce rigorous heat transfer results into the subject, but from a framework accessible to design engineers. To this end, a 1-D lumped model of this kind of situations is used (Campo and Lacoa, 1994). Although largely simplified, the model provided adequate estimates of the mean bulk temperatures when compared with those computed with a 2-D distributed model (Campo and Lacoa, 1995), thus satisfying the requirements of simplicity and accuracy for the present purpose. The paper describes the design criteria for thermal calculation of industrial chimneys, the application of the 1-D lumped model through the use of standard heat transfer correlations, and several examples. The sequence of calculations is easy to accomplish and it is explained in such a way that it can be directly employed by engineers engaged in thermal design of tall chimneys.
Experimental Investigation of Passive Boiling Enhancement Within the Suction-Line Accumulator During Reverse-Cycle Defrost
Authors: Roberts Terrance M. , Nutter Darin W. 
Published: March 2022

Abstract
The heating seasonal performance factor (HSPF) of an air-source heat pump is degraded by the defrost cycle. Investigations have been performed previously which looked at active enhancement within the suction-line accumulator. This paper presents the results of a similar study with the use of passive enhancement techniques in lieu of active. A layer of small 3.6 or 5.0 mm diameter steel spheres was placed at the base of the accumulator and used to increase the rate of refrigerant boiling during the initial few minutes of the reverse-cycle defrost. Components from a 10.6 kW air-source heat pump were used to perform the experimental study.
The accumulator was equipped with a site glass for visualization purposes. Refrigerant-to-water/glycol heat exchangers replaced the refrigerant-to-air heat exchangers and conditions were set to simulate the pre-melt and melt stages of a defrost cycle. Waterside conditions were maintained for the outdoor coil at 0°C and indoor coil at 21.1 °C dry bulb. Overall performance characteristics of particular interest were refrigerant flow rates, compressor power, refrigerant temperatures and refrigerant pressures. Tests with both the 3.6 mm and 5.0 mm diameter steel spheres enhancement showed increased mass and net energy flow rates to the outdoor coil. Compared to baseline tests, peak mass flow rates were increased by up to 16%.
A Numerical Study of Instantaneous Heat Transfer During Compression and Expansion in Piston-Cylinder Geometry
Authors: Catto A. G. , Prata A. T. 
Published: March 2022

Abstract
A numerical analysis of the flow and heat transfer in gas springs is presented. A gas spring is a volume of gas with constant mass confined by a moving piston inside a valveless cylinder. Repeated compression and expansion of the gas in the cylinder causes it to heat up. Although there is a heat transfer to and from the gas at different times during a cycle, there is a net flow of heat out of the gas which is equal in magnitude and opposite in direction to the net work done per cycle on the gas. The net work is not recoverable and is called the hysteresis loss. Furthermore, during compression and expansion the in-cylinder heat transfer is out of phase with the bulk gas-wall temperature difference and the conventional Newton’s law is not applicable. Instead of being proportional to bulk gas-wall temperature difference the heat transfer should also depend on the time derivative of the bulk gas temperature. An understanding of the in-cylinder heat transfer is essential in modeling compressors, internal combustion engines and other reciprocating machines. Gas springing is a starting point in constructing correlations for heat transfer during compression and expansion, and in the present paper the unsteady compressible axisymmetric flow inside the cylinder was modeled using a moving coordinate system and a finite volume methodology. Results for instantaneous temperature, pressure and heat flux are presented and discussed. The existing phase difference between the heat transfer and the gas-wall temperature difference is explored. Available correlations are compared with the numerical results showing that the time variation of the bulk gas temperature plays an important role in the heat transfer, this effect tend to decrease as both the crank shaft speed and the volume ratio increase.
Rocket Noise Propagation
Authors: McInerny S. A. , Wickiser J. K. , Mellen R. H. 
Published: March 2022

Abstract
In this paper, we review known characteristics of rocket noise. These include low peak frequencies, a high radiation efficiency and a large angle of peak directivity relative to that of subsonic and supersonic jets. The extended source region and high temperatures in a rocket plume are discussed. Evidence is presented to support the contention that it is Mach wave radiation from the transonic region of the plume that governs the sound power. We summarize properties of noise measured in the far-field during rocket launches. This high intensity noise is rich in shocks and the time domain data are positively skewed. Far-field noise spectra do not decrease with distance as would be expected on the basis of linear absorption theory. We briefly discuss signal processing techniques that have the potential to better distinguish the unique properties of rocket noise and we explore the idea of using non-linear acoustic propagation codes to better understand these properties. We conclude by soliciting input on the best way to proceed in these research efforts.
Acoustic Scattering by Two Submerged Elastic Spherical Shells: Mutual Validation of the Normal Mode Series and B.E.M. Solutions
Authors: Everstine Gordon C. , Gaunaurd Guillermo C. , Huang Hanson 
Published: March 2022

Abstract
We validate, using a coupled finite element/boundary element computer code, a recently-developed series solution for the structural acoustics problem of scattering from two submerged spherical elastic shells. Although the general purpose computational tools for acoustic scattering have never been restricted to single scatterers, the availability of the series solution provides, for the first time, the mutual validation of both exact and numerical approaches for a multiple elastic scatterer problem. The excellent agreement between the two solutions presented thus allows this problem to be added to the short list of existing benchmark structural acoustics problems possessing an analytic solution. For the purposes of this comparison, the direction of incidence is taken as parallel with the axis joining the two shells. The numerical solution uses the NASHUA code, which couples a finite element shell model of the two shells with a boundary element model of the surrounding fluid. The exact (series) solution is found by expanding in terms of classical modal series and uses the addition theorem for the spherical wave functions. The exact solution requires coupling coefficients that are expressed in terms of sums of products of Wigner 3-j symbols (or Clebsch-Gordan coefficients).
Qualification of the Sound Field in a Metadyne Anechoic Chamber
Authors: Duda John , Hastings Mardi C. , Godfrey Richard D. 
Published: March 2022

Abstract
The results of an experimental performance evaluation of a Metadyne chamber in both full anechoic and hemi-anechoic configurations over the frequency range from 60 to 10,000 Hz are presented. The Metadyne anechoic wedge, a fiberglas-filled wedge fully encapsulated in a perforated metal casing, was developed several years ago as an alternative to conventional fiberglas and foam wedges. The results of this evaluation show that the Metadyne chamber meets or exceeds all acoustic performance requirements for proper free field environmental conditions, noise reduction, and inside ambient levels. They also indicate that free field conditions exist much closer than a quarter wavelength from the wedge tips which allows use of nearly all the chamber volume for measurements. This chamber provides an environment for conducting highly accurate sound measurement tests.
Natural Frequencies and Mode Shapes of Composite Plates or Panels With a Central Stiffening Plate Strip
Authors: Yuceoglu U. , Özerciyes V. 
Published: March 2022

Abstract
The problem of the free flextural vibrations of a rectangular, orthotropic composite plate or panel system composed of an orthotropic base plate and a dissimilar central stiffening plate strip joined by a thin adhesive layer, is studied. In the formulation, both plates are assumed to be dissimilar orthotropic plates in the manner of the Mindlin Plate Theory. The composite plate or panel system has two opposite edges as simply supported while the other two opposite edges can have arbitrary support conditions. First, classical “Levy Type Solutions” are used for the displacements angle of rotations and the stress resultants. Then, the resulting governing equations of the problem are integrated by a “Modified Version of the Transfer Matrix Method”. The mode shapes and corresponding natural frequencies of the composite plate system are studied for “hard” and “soft” adhesives. It was shown that the normal mode shapes and natural frequencies are very much influenced by the adhesive layer material constants. Also, some parametric studies are presented.
Low Velocity Impact Response and Nondestructive Evaluation of Sandwich Composite Structures
Authors: Vaidya Uday K. , Palazatto Anthony N. , Gummadi L. N. B. 
Published: March 2022

Abstract
Composite sandwich constructions offer light weight and high bending stiffness advantages for aerospace and automotive applications among other structures. The use of a hollow truss core or z-fiber pin core is a new concept in sandwich composites, where the core is hollow and accessible, thereby providing space advantages for fuel cells and/or electronic assemblies besides from possessing high shear and axial stiffness. The z-fiber pins are oriented at predetermined geometry’s and penetrate into the laminated facesheets making-up the sandwich composite. In the reference (Palazatto et. al, 1997), the low velocity response of hollow truss core composites with z-fiber pins oriented at 10 degree and 20 degree angles with respect to the facesheets were investigated by us. The current paper presents the post-impact microstructure, ultrasonic and vibration based nondestructive evaluation (NDE) studies and compression-after-impact response accompanied by acoustic emission (AE) testing of these composites.
Low-Velocity Impact Response and Evaluation of Delamination Damage in CFRP Laminates
Authors: Hosur Mahesh. V. , Murthy C. R. L. , Ramamurthy T. S. 
Published: March 2022

Abstract
In the current study, extensive experimental investigations were carried out on quasi-isotropic Carbon Fiber Reinforced Plastic (CFRP) composite laminates simulating low-velocity impact. Laminates made of three different layups were subjected to impact in the range of 3–30 Joules and their transient response were measured in the form of displacement, energy, velocity and load as functions of time. From these parameters estimates were made of the energy required to initiate damage, onset of delamination and consequent generation of multiple delaminations and their growth. Further, the laminates were tested using ultrasonic NDE technique to quantitatively determine both projected as well as layerwise delamination. From the results obtained, for the range of impact energies tested, threshold energy value for different layups was found to vary from 1.655 to 2.132 Joules/mm. Further, BVID (energy level at which damage is barely visible at the point of impact) was found to be 2.5 Joules/mm. Qualitative indications of damage were observed from load-time plots by sudden drops in load. Ultrasonic evaluation further confirmed these indications. Accurate measure of delamination distribution was obtained by processing the raw scan data using image processing technique. Based on the quantitative data obtained an empirical relation between impact energy and delamination was established.
Finite Element Modeling and Photoelastic Analysis of an Integral Armor Under Flexural Loading
Authors: Mahfuz H. , Lokesh B. R. , Das P. S. , Vaidya U. , Jeelani S. 
Published: March 2022

Abstract
A combined Finite Element Analysis (FEA) and photoelastic study is performed on a hybrid composite, integral armor, to investigate its response under flexural loading condition at room temperature. The layered solid brick element, developed on the basis of constant transverse strain distribution through the thickness, has been used to model the complete integral armor. The transverse normal and shear strain distribution through the thickness becomes significant and severe in failure mechanisms, therefore multiple elements are used in the thickness direction to take care of nonlinearity by piecewise representation. Large deformation has been considered in the finite element analysis to account for the non-linearity encountered during the actual test. Photoelastic analysis is conducted on the integral armor to determine the stress-strain distribution through the thickness. A reflection polariscope is used to observe the fringe pattern developed under flexural loading in the photoelastic coating applied on the test specimen surface. Data generated using photoelastic analysis are presented to corroborate the finite element analysis findings, and a comparison in respect of strain behavior is presented. Reasonable correlation between the finite element modeling and photoelastic analysis results has been established.
Combining Adaptive-Passive and Fully Active Noise Control in Ducts
Authors: Kostek Theodore M. 
Published: March 2022

Abstract
Presented in this paper is a hybrid noise control scheme for one dimensional acoustic systems. By-combining fully active noise control with adaptive-passive elements to form a hybrid system, the control effort required for a given reduction in sound pressure level is reduced. The adaptive-passive element is a tunable Helmholtz resonator. While previous work has focused on tuning Helmholtz resonators subjected to pure tone disturbances, this work contains an algorithm which tunes the resonator in the presence of unmeasurable broadband disturbances. Because the disturbance is assumed unmeasureable, the active noise control scheme developed is a fixed filter feedback design (as opposed to adpative feedforward) and uses the dynamics of the acoustic system to achieve performance. Experimental verification is included.
A Formulation of Unequal Impedance Boundary Conditions in Boundary Element Acoustics
Authors: Vlahopoulos Nickolas , Raveendra S. T. 
Published: March 2022

Abstract
The boundary element method (BEM) has been utilized extensively in numerical simulations of engineering acoustics problems. The indirect boundary element formulation (IBEM) allows the simulatneous modeling of the acoustic spaces on both sides of a thin vibrating structure. In order to exploit the full potential of the IBEF a new formulation was developed in this work, allowing the application of separate impedance boundary conditions on each side of the vibrating structure. This situation is often encountered in practical applications (engine enclosures, computer boxes, car bodies, etc.), where noise isolation material is applied on only one side of a vibrating structure.
Overview of Applications for High-Frequency Automotive Noise Prediction Using Statistical Energy Analysis
Authors: Kaminsky Cliff , Bremner Paul , Cimerman Benjamin 
Published: March 2022

Abstract
For all transportation equipment, there is a strong emphasis on reducing weight and cost while improving comfort. Unfortunately, reduced weight is often synonymous with increased sound pressure level (SPL), which is not acceptable from the viewpoint of security and comfort.
In this paper we discuss the application of Statistical Energy Analysis (SEA) to the prediction of noise in vehicles such as passenger cars. After a brief theoretical review of the method, we present simple guidelines for the SEA modeling of automobiles. These guidelines are the result of practical experience in the field, also described here, since SEA is already used at many industrial sites. Finally, we discuss promising new directions in automobile SEA modeling.
An Entropy-Based Index Evaluation Scheme for Multiple Sensor Fusion in Classification Process
Authors: Chen Yubao , Orady Elsayed 
Published: March 2022

Abstract
Sensor fusion aims to identify useful information to facilitate decision-making using data from multiple sensors. Signals from each sensor are usually processed, through feature extraction, into different indices by which knowledge can be better represented. However, cautions should be placed in decision-making when multiple indices are used, since each index may carry different information or different aspects of the knowledge for the process/system umber study. To this end, a practical scheme for index evaluation based on entropy and information gain is presented. This procedure is useful when index ranking is needed in designing a classifier for a complex system or process. Both regional entropy and class entropy are introduced based a set of training data. Application of this scheme is illustrated by using a data set for a tapping process.
A Thermomechanical Model of Machine Tool Spindles for Use in the Design of Reconfigurable Angular Contact Spindle Bearing Load Control Systems
Authors: Gibson Alex O. , Stein Jeffrey L. , Tu Jay F. 
Published: March 2022

Abstract
Thermally induced bearing loads have long been recognized as a key factor impacting the reliability and performance of machine tool spindle systems. This is particularly true for reconfigurable machine tool spindles which may experience a wide range of external loads, processes and spindle speeds. Recent research on a roller bearing spindle has shown that it may be possible to control these loads by controlling the temperature distribution within the spindle housing. As this research focused on thermally induced loads in roller bearings, the bearing load model used was largely limited to a radial heat transfer/thermal expansion model. The purpose of this paper is to present a first step model for developing a methodology for designing bearing load monitoring and control systems for reconfigurable angular contact bearing spindles. The proposed model focuses on the thermally and mechanically induced spindle bearing loads in a back to back angular contact bearing pair that are due to radial and axial thermal expansion as well as the centrifugal forces and moments of the bearing balls. Simulation results demonstrate that the proposed model is capable of predicting the interactions between bearing loads and spindle deflections that are likely to be important in the design of future reconfigurable machine tool spindle bearing load monitoring and control systems.
Integrated Digitizing, Path Planning, and Five-Axis Machining for the Refurbishment of Compressor and Turbine Blades
Authors: Fleisig Robert V. , Spence Allan D. 
Published: March 2022

Abstract
The compressor and turbine blades used in jet aircraft engines wear down due to tip rubbing against the outer shroud. To restore the original shape, these blades must be either replaced, or, more economically, refurbished. Refurbishment of blades is accomplished by applying a weld bead to the tip, followed by removal of excess material. This paper describes an overview of an integrated system for accomplishing the material removal step. The separate tasks of digitizing the blade to obtain original shape information, automatically calculating the tool paths, and machining the blades, are combined into a turnkey system implemented using a five-axis machine tool and attached personal computer. Experimental results demonstrate the capability of the system for sample blade shapes.
PC Based Open Architecture Machine Tool Control
Authors: Bailey T. E. , Renton D. D. A. , Elbestawl M. A. 
Published: March 2022

Abstract
This paper describes the design and implementation of a PC based Open Architecture machine tool controller. The PC based OAC is based on a distributed, peer to peer functional model of the entire machine controller system. Machine motion and I/O functionality is provided by a machine server module. The machine server is designed to provide a uniform interface, and layer of abstraction, for user applications to all machine services. A PC based motion and I/O solution was designed to provide an open, standard interface to the machine. The overall cost / performance ratio of the PC based OAC makes it an attractive alternative to conventional machine tool control technologies. Intelligent process monitoring and control strategies are implemented with the OAC on a 3-axis machining centre. Power, force, and vibration monitoring and control applications are discussed in this paper.
Active Structural Control of Vertical Turning Lathe Vibrations
Authors: Miesner John E. , Ghanadan Reza , O’Regan Stephen D. 
Published: March 2022

Abstract
An active control system has been developed to suppress tool vibration on a Vertical Turning Lathe (VTL). This system reduced surface roughness by two-thirds and raised by 23% the metal removal rate achievable before the onset of chatter. The system mechanical and sensor portions are contained completely within the VTL ram envelope. The electronic components are in a separate enclosure which also provides a simple user interface. Accelerometers embedded in the VTL ram sense the ram motion in two directions. Signal conditioning and integration electronics pass the ram velocity to the digital controller which computes the forces needed to reduce the tool tip motion error. Control signals are input to highly-efficient switched-capacitor amplifiers which drive high-force electrostrictive actuators to deliver the required forces in two directions. The controller also executes the system identification programs and tracks the ram length to compensate for resonance changes.
Prediction of Shear Angle in Oblique Cutting With Maximum Shear Stress and Minimum Energy Principles
Authors: Shamoto Eiji , Altintas Yusuf 
Published: March 2022

Abstract
A new shear angle prediction law is proposed for oblique cutting operations. Assuming a thin shear zone model, the oblique cutting mechanics are described by the five angles which show the directions of shear, resultant cutting force and chip flow. Five expressions required to solve the unknown angles are derived from the kinematics of oblique cutting and the physical law of deformation, i.e. either Maximum Shear Stress or Minimum Energy Principle. Unlike the previous solutions which require intuitive or empirical assumptions, the proposed methods use only the tool geometry and the material properties, i.e. shear yield stress and average chip-rake face friction coefficient. The predicted angles and forces agree well with the empirical and experimental results reported in the literature. Furthermore, the proposed models are experimentally verified in predicting forces for practical oblique helical end milling operations.