bluuebunny/crossref_metadata_2025 huggingface dataset:
Freezing of Aqueous Solutions of Glycosylated Bovine Beta-Casein
Authors: Hoke John L. , Georgiadis John G. , Jimenez-Flores Rafael
Published: January 2022

Genetic engineering of milk proteins allows control of their physicochemical properties in foods and dairy products during processing, storage, and consumption. Robust methods for the estimation of the quality and function of the proteins during downstream processing are sought. The focus of this study is a systematic microscopic investigation of the freezing of sub-microliter pendent droplets of buffer solution of glycosylated bovine beta-casein. The freezing and crystallization is observed with a scanning confocal microscope fitted with a stage cooled with vapor boiled off a liquid nitrogen dewar. Four liquid samples (with glycosylated bovine beta-casein concentrations of 35, 125, 500, and 1000 μg/ml) are compared against the control (10 mg/ml of wild type non-glycosylated bovine beta-casein). The freezing of similar size samples consisting of de-ionized water, ice-nucleating mixture (Pseudomonas syringae), and pure buffer solution is also examined for comparison. Higher concentrations of the engineered-beta casein result in increasing antifreeze action, corresponding to depression of the freezing point, and thermal stabilization of the supercooled liquid. This conclusion is supported by a non-parametric statistical analysis based on the Jonckheere test. A freezing point assay can thus be made to assess the quality of glyco-bovine beta-casein.
An Improved Diffusion Model for Radiative Transport in Turbid Media
Authors: Venugopalan V. , You J. S. , Tromberg B. J.
Published: January 2022

The diffusion approximation to the Boltzmann transport equation is commonly used to analyze data obtained from biomedical optical diagnostic techniques. Unfortunately, this approximation has significant limitations which constrains its applicability to highly scattering systems and over length scales much larger than the transport mean free path l*. Using an approach formulated independently by Prahl and Star [11, 13, 14], we present a form of the diffusion approximation which adds a delta function term to both the radiance and phase function expressions. This formulation is presented and solved for steady illumination in infinite media with a collimated source of finite size exhibiting spherical symmetry. The solution is compared to results given by standard diffusion theory and to measurements made in a strongly scattering and strongly absorbing turbid phantom with reduced single scattering albedos a’ of 0.997 and 0.248, respectively. The results show that this approach provides accurate predictions of optical dosimetry in both low and high scattering media and at positions proximal to collimated light sources.
Non-Invasive Evaluation of Biological Materials Using Pulsed Photothermal Tomography
Authors: Milner Thomas E. , Telenkov Sergey A. , Tanenbaum B. Samuel , Nelson J. Stuart , Goodman Dennis M.
Published: January 2022

Progress is reported on the development of pulsed photothermal tomography (PPT) for determination of the initial three-dimensional temperature increase in biological materials immediately following pulsed laser irradiation. PPT uses a fast infrared focal plane array (IR-FPA) to detect temperature rises in a substrate, induced by pulsed radiation. The temperature rise, due to the selective optical absorption of pulsed laser light, creates an increase in infrared emission that is measured by a fast IR-FPA. A tomographic reconstruction algorithm computes the initial space-dependent temperature increase in subsurface chromophores from a time sequence of recorded infrared emission images. We present tomographic reconstructed images of laser heated blood vessels in the in-vivo chick chorioallantoic membrane (CAM) model.
Defining the Quality of Indoor Air Supply Based on Dilution and Ventilation Concepts
Authors: Beyene Asfaw
Published: January 2022

Empty space could be ventilated continuously to keep some level of Indoor Air Quality (IAQ) in order to eliminate or minimize accumulation of pollutants, and to reduce odors in the air channels or in enclosed spaces. With the exception of some applications, such as hospital rooms where air is supplied to create a positive pressure, such an air amount that can be used for empty space ventilation can be taken as the minimum air supply that has to be provided at all times. Any additional air supply to the conditioned space is primarily for respiration purposes. This respiration amount has a minimum based on ;i per person oxygen need, and an additional amount to dilute whatever pollutants are present in the conditioned space, as defined by standards, codes, and regulatory aerosol concentration limits. This paper discusses and defines the minimum air supply, the respiration air need, and the dilution terms. It combines these terms into a basic air supply equation to serve IAQ criteria. The approach can be used as a practical guideline for the designer to calculate the total air supply needs to a conditioned space.
Incorporating Cogeneration Into a Geothermal Power Plant to Enhance Utilization and Profitability
Authors: Kanoğlu Mehmet , Çengel Yunus A.
Published: January 2022

An existing binary geothermal power plant in Nevada with a rated power of 1.2 MW is investigated. The current performance of the plant is assessed, and it is found that the power output of the plant could be increased by about 12% by simply upgrading one of the two turbines of the plant. There also appears to be a great potential for better utilization of this geothermal resource by incorporating cogeneration into the power plant. Using the geothermal brine after being used for power generation to preheat fresh water needs of a nearby plastics plant appears to be feasible and financially attractive. Selling thermal energy of the geothermal brine for preheating water has an annual revenue potential of about $18,000. This is about 5% of the revenue currently generated by the sale of electricity. The payback period for the initial cost of this project is determined to be less than 6 years. The preheating process could be met by only a small fraction of geothermal brine available. The region where the geothermal plant is located is expected to develop by new industrial facilities, and therefore, the potential of selling thermal energy of geothermal brine for preheating water could greatly improve in the future. Utilization of the entire brine available after being used for power generation for preheating water and possibly for space heating has an annual revenue potential of up to $5 million, which corresponds to 10 times increase in the revenue from this geothermal site.
The Maximum Power Cycle: A Model for New Cycles and New Working Fluids
Authors: Ibrahim Osama M. , Arnold Douglas G.
Published: January 2022

The objective of this paper is to extend a previously presented finite-time thermodynamic framework that explains the conceptual differences between power and efficiency optimization and defines the Maximum Power cycle. The shape and the performance of the Maximum-Power cycle are used as criteria to study and evaluate alternative working fluids that can improve the performance of the power cycle for low temperature heat sources, such as solar energy and waste heat. In this study, pure fluids, non-azeotropic and azeotropic mixtures in a single or multi-stage Rankine cycle are considered. The results show that pressure-dependent azeotropic mixtures have the potential to improve the performance of the Rankine cycle. The results also show that the Maximum Power cycle provides a useful tool for studying power cycles and forms the basis for making design improvements.
Thermoeconomic Analysis of Combined Cycle Units With Intercooled Gas Turbine, Derived From Existing Steam Power Plants
Authors: Negri di Montenegro G. , Peretto A. , Mantino E.
Published: January 2022

The paper presents a thermoeconomic analysis of three pressure level reheat combined cycles derived from existing steam power plants. The gas turbine employed is an intercooled gas turbine, proposed and investigated in the Collaborative Advanced Gas Turbine program by the major aero-engine manufacturers and international electric and natural gas industry sponsors.

The steam power plants to repower are conventional steam power plants of three different sizes, 320 MW, 160 MW and 70 MW, easily found in Italy.

Firstly, a thermodynamic analysis is performed for the different repowered plants, also in the presence of supplementary firing at the gas turbine outlet.

Subsequently, the economic analysis of the repowered plants is carried out determining the cost per kWh, the payback period and the internal rate of return. These economic variables, for each combined cycle derived from existing steam power plants, are discussed and compared with those relating to a new combined cycle power plant also equipped with intercooled gas turbine.

Finally, a sensitivity analysis is developed by using a sensitivity parameter. In this way, the influence of some economic parameters on the cost per kWh, pay back and internal rate of return is numerically evaluated.

On the basis of a plausible cost per kW for the intercooled gas turbine, the study reveals that the transformation of old conventional fossil fuel power plants, performed with intercooled gas turbine, supplies a cost per kWh lower than that of a new combined cycle power plant, also equipped with intercooled gas turbine. It occurs for all the repowered plants analyzed with or without supplementary firing.

Comparison of the costs per kWh for the repowered plants, employing either an intercooled gas turbine or a Brayton cycle gas turbine available on the market, indicated that the solution with an intercooled gas turbine may be worthy of consideration only for the combined cycles derived from the smallest size steam power plant. This remains valid also in the hypothesis of decreasing the cost of the intercooled gas turbine.
Some Simple and Economical Ways of Saving Energy in Industrial Facilities
Authors: Çengel Yunus A. , Çerci Yunus , Turner Robert H.
Published: January 2022

About 37% of the energy consumed in the United States is used by industrial facilities, and a considerable fraction of this energy can be saved by practicing simple energy conservation measures. In this paper we give an overview of such conservation measures complete with the analysis, the potential energy and cost savings, the implementation costs, and simple payback periods. The proposed measures are intended as a retrofit for existing facilities, and most of them can be implemented by the maintenance personnel of the facilities. The recommendations are based on our observations and measurements during energy audits of numerous manufacturing facilities in Nevada and California during the last three years. In a recent paper (Cerci et al, 1995) we discussed energy conservation opportunities related to compressors. In this paper we extend the discussions to other areas, and present economically attractive common sense measures such as (1) insulating hot and cold surfaces, (2) adjusting the air-fuel ratio in the furnaces, (3) installing programmable thermostats, (4) installing high efficiency fluorescent lamps, (5) installing occupancy sensors, (6) using reflective film on glazing, (7) improving the power factor, and (8) installing high efficiency motors. These measures are described in sufficient detail, and the energy and cost savings are analyzed and quantified. The typical potential savings from these measures are illustrated with examples taken from real-life applications. Our goal in this paper is not to present something new, but rather, to raise awareness and to show the tremendous energy and cost saving opportunities missed as a result of overlooking some simple and obvious conservation measures.
Thermoeconomic Evaluation of a Gas Turbine Cogeneration System
Authors: Guarinello Flávio , Cerqueira Sérgio A. A. G. , Nebra Silvia A.
Published: January 2022

The main purpose of this work is to apply the Thermoeconomics concepts to a projected steam injected gas turbine cogeneration system which aims at providing the thermal and electrical demands of an industrial district, sited in Cabo (Pernambuco-Brazil). The power plant is evaluated on the basis of the First and Second Laws of Thermodynamics. A Thermoeconomic analysis, using the Theory of Exergetic Cost, was performed, in order to determine the production costs of electricity and steam. Two hypothetical operational conditions, as regards to the level of electric power generation, were considered.
Design Improvements to Waste-to-Energy Plants Using Exergetic Analysis as a Project for the Second Course in Thermodynamics
Authors: Wong Kau-Fui Vincent , Witmer M. , Crowder B. , Han S. Y. , Serretti D. P.
Published: January 2022

It has been a concern that mechanical engineering graduates may not have enough exposure to real world engineering situations. A design project was assigned in conjunction with the second thermodynamics course in mechanical engineering to help alleviate this problem. The objective of the design project was to take an existing operating waste-to-energy plant, and modify it so that both its first and second law efficiencies are improved. The project indeed helped the students understand and use the second law effectively. The project exposed the students to real world situations, provided them with a chance to visit plants in operation, and gave them the confidence to apply theories and methods taught in the classroom. Student response was favorable and it gave them another opportunity to work in teams on design, as emphasized by ABET. This paper selects for presentation the analyses of the performance of two waste-to-energy plants.
Two-Shift Operation Economic Benefits for Conventional and Advanced Fossil Fueled Power Plants
Authors: Bianchi M. , Gadda E. , Peretto A.
Published: January 2022

In the context of cycling duty, two main operating schedules are prevalent: load following, in which the unit remains in service but changes load to match the system requirements, and two-shift operation, in which some units are shutdown during the night and the weekend/holiday.

The present paper analyses the economic benefits obtainable from the two-shift operation of fossil fuel power units with respect to load following. In particular, two different types of thermoelectric power units are considered:

• conventional steam power units;

• advanced fossil fuel power units (i.e. gas-steam combined cycle units).

Firstly, a thermodynamic analysis is carried out evaluating the off-design heat rate of the power units during the part load operation.

Subsequently, the economic hourly and annual savings, obtained by shutting down one unit, are performed.

Appreciable benefits are found for a large range of the system load requirements, thus indicating the two-shift operation as a strategy that can be pursued.
Performance of a Residential Sized GAX Absorption Chiller
Authors: Priedeman Douglas K. , Garrabrant Michael A. , Mathias James A. , Stout Roger E. , Christensen Richard N.
Published: January 2022

This research effort involved experimentally testing an advanced-cycle, ammonia-water absorption chiller with a cooling capacity of 17.6 kW (5 refrigeration tons (RT)). The system was a Generator-Absorber Heat Exchange (GAX) cycle and was sized for residential and light commercial use, where very little absorption equipment is currently used. The components of the cycle were assembled with instrumentation, including flow meters, pressure transducers, and thermocouples. The findings of the research were cycle cooling load and Coefficient of Performance (COP), as well as many component heat duties and working fluid state points throughout the cycle. The COP of the chiller at essentially full load was 0.68.

Existing market research shows that significant business opportunities exist for a GAX heat pump or chiller with a cooling COP of 0.70 or greater. The work performed in this study provides a breadboard cycle with performance approaching the target value and identifies improvements that must be made to achieve a packaged unit operating with a cooling COP of 0.70.
Piston Lubrication Model for Reciprocating Compressors
Authors: Prata A. T. , Fernandes J. R. S. , Fagotti F.
Published: January 2022

Piston dynamics plays a fundamental role in two critical processes related to fluid flow in reciprocating compressors. The first is the refrigerant leakage through the radial clearance, which may cause considerable loss in the pumping efficiency of the compressor. The second process is the viscous friction associated with the lubricant film in the radial clearance; certainly a significant factor in the compressor energy consumption. In the present contribution a numerical simulation of the piston movement inside the cylinder of a reciprocating compressor is performed. The compressor considered here is a small hermetic compressor employed in domestic refrigerators. For the problem formulation both the axial and the radial piston motion is considered. In operation, the piston moves up and down along the axis of the cylinder, but the radial oscillatory motion in the cylinder bore, despite being usually small, plays a very important role on the compressor performance and reliability. The compromise between sealing of the gas leakage through the piston-cylinder clearance and the friction losses requires a detailed analysis of the oscillatory motion for a good design. The forces acting on the piston are the hydrodynamic force due to the pressure build up in the oil film (lubrication effects), the force due to the connecting rod, the viscous force associated with the relative motion between the piston and oil, and the force exerted by the gas on the top of the piston. All corresponding moments are also included in the problem formulation of the piston dynamics, in order to determine the piston trajectory, velocity and acceleration at each time step. The hydrodynamic force is obtained from the integration of the pressure distribution on the piston skirt, which, in turn, is determined from a finite volume solution of the time dependent equation that governs the oil flow. A Newton-Raphson procedure was employed in solving the equations of the piston dynamics. The results explored the effects of some design parameters and operating conditions on the stability of the piston, its sealing performance and friction losses. Emphasis was placed on investigating the influence of the pin location, radial clearance and oil viscosity on the piston dynamics. The complexity of the piston movement in reciprocating compressors was demonstrated and the detailed model presented can be employed as an useful tool for engineering design.
A Mathematical Analysis of Accumulator Heat Exchangers to Achieve Liquid Overfeeding Effects in Small Air Conditioning Systems
Authors: Wood Craig W. , Meyer Josua P.
Published: January 2022

This paper derives a calculation procedure for sizing a heat exchange accumulator according to the required heat transfer. The model determines all the required diameters and pipe lengths according to the inner coil diameter (which is determined by physical pipe dimensions). The model ensures that refrigerant velocity through the accumulator is the same as the refrigerant velocity maintained in the original system.
Performance of a Series Air-to-Air Heat Pump for Continuous and Intermittent Drying
Authors: Fatouh M. , Abou-Ziyan H. Z. , Metwally M. N. , Abdel-Hameed H. M.
Published: January 2022

A series air to air heat pump assisted-dryer has been designed and tested under various operating conditions. Air flow rates of 500 to 1400 m3/hr at supply air temperatures of about 25 to 50 °C are used. This temperature range covers ambient air and warm air heated by either solar collector or waste heat recovery device. R22 is used as the working fluid in the heat pump circuit. The results showed that average refrigerant temperature lift of 33°C and Rankine coefficients of performance (COPR) up to 4.6 are obtained. This (COPR) proved that the heat pump is an efficient device that saves energy and money. Also, exergetic efficiency of the heat pump up to 0.35 and outlet air temperatures of 55°C are achieved. This air temperature level is adequate for drying of many products.

The heat pump assisted-dryer is tested with continuous and intermittent drying techniques. The continuous drying is used to dry onion, carrot, potato and sweet potato in which specific energy consumption lower than the conventional dryers by 18 to 32% are achieved. The intermittent and continuous drying techniques are compared for onion drying. The results showed that the use of intermittent drying saves about 30% of the energy consumed by the continuous drying when the appropriate heating and resting periods are used.
Heat Transfer Enhancement of Direct Contact Melting Process by Vibration
Authors: Oka Mineo
Published: January 2022

Direct contact melting process takes place in many natural and technological processes. One of the important application of this process is thermal storage system. Phase change material (PCM) is stored in a small capsule that is melted by heating peripherally. In this melting process, melting rate is important factor for the efficiency of the system. In this paper, utilization of vibrating motion of heating wall is proposed to enhance the melting rate. Effect of vibrating motion of the heating wall is studied. Non-steady heat transfer phenomena of direct contact melting process is studied theoretically while only steady state is studied in recent analytical researches. In this paper, it is clarified that the vibrating motion of heating wall enhances the heat transfer and melting rate.
Temperature Effect on Power MOSFET Devices
Authors: Lu W. , Chow L. C. , Sundaram K. B.
Published: January 2022

The development of the power MOSFET allows an electronic circuit designer greater flexibility in high power applications. Over the last several years, it has been demonstrated that there are marketable advantages of operating the power MOSFET devices at cryogenic temperature. This paper demonstrates by experiment and theoretical derivation that the on-resistance decreases significantly when the operating temperature decreases. Such a decrease leads to a considerable reduction in heat generation inside the MOSFET device. In other words, it becomes possible to push higher current through the MOSFET device with the same heat generation. It makes higher integration of MOSFET devices possible. This paper shows an experimental measurement of on-resistances at 77 K, 173 K, 243 K and 295 K by applying cryogenic cooling techniques. The results have been confirmed by comparing them with the threshold voltage calculations. Another important advantage of operating MOSFET devices under cryogenic temperature is that the thermal resistance of the device decreases. The thermal conductivity of silicon material increases about nine times when the temperature decreases from 295 K to 77 K (148 W/mK to 1340 W/mK). This will significantly decrease the internal thermal resistance of a MOSFET device. The junction temperature is the parameter under which all the characteristics of MOSFET should be evaluated. When the MOSFET is operating under an extremely high power condition, although there are several effective cooling techniques to maintain the heat sink temperature within a certain range, the junction temperature can be kept at a reasonable temperature only if the internal thermal resistance is small. By knowing the internal thermal resistance, heat generation rate and the sink temperature, the junction temperature can be calculated. This paper proposes a simple method to determine the internal thermal resistance under any power and any operating temperature. The experiment found that at liquid nitrogen temperature (77 K), the internal thermal resistance drops to 1/5 of that at room temperature (295 K). These results indicate that at cryogenic operating temperature, it is possible to obtain high power application while still maintain relatively low temperature at the junction.
A Study of Residual Stress and Property Mismatch on SIF Distributions for Cracks Parallel to and Within Bondlines
Authors: Smith C. W. , Finlayson E. F. , Liu C. T.
Published: January 2022

As a result of the need to extend the storage life of rocket motors, new emphasis has been placed upon the effect of cracks developed during storage and transport on the integrity of motor performance. In addressing this need, the authors have developed a three specimen test procedure for evaluating the stress intensity factor (SIF) distribution for cracks through the thickness of rubberlike materials near to and within simulated bond lines between the motor grain and its liner. A refined frozen stress method is employed for making measurements, and preliminary studies have shown that, for cracks in the bond line under both Mode I and Mixed Mode loads, the stress intensity factors are elevated primarily due to bond line residual stresses and may not be affected by modulus mismatch.
Damage Characteristics Near Crack Tip for a Particulate Composite
Authors: Liu C. T. , Ho H.
Published: January 2022

Nondestructive acoustic imaging experiments and three dimensional finite element analyses were performed to study the crack-damage interaction phenomenon of a particle reinforced polymeric composite. Effects of damage size and degree of damage on the mode I stress intensity factor and the local stress fields near the crack tip were evaluated and the damage and crack growth behavior were discussed.
Buckling Characteristics of Regular and Irregular Asymmetric Laminated Composites
Authors: Vinogradov Aleksandra M.
Published: January 2022

The paper examines the effects of composite material properties on the nonlinear buckling response of irregular asymmetric composite structures through the analysis of asymmetric laminated beam-columns composed of an arbitrary number of different material layers. The nonlinear buckling behavior of the structures subjected to combined compression and bending is examined as a function of the number, orientation and stacking sequence of the layers that make up the laminate. The analysis demonstrates that, typically, buckling of asymmetric composites is initiated immediately at the load application, however, under certain conditions, the structures exhibit bifurcation. In such cases, the critical load can be optimized through tailoring the material properties of the laminates.
Study of Effectiveness of Countermine Boots
Authors: Kwon Young W. , Muschek Richard C.
Published: January 2022

The goal of this study was to conduct a qualitative analysis to determine the effectiveness of countermine boots. This was done by determining their ability to dissipate a blast force equivalent to a typical anti-personnel landmine. This was followed by a parametric study that which involved altering the component materials in an effort to determine if the effectiveness of the boots varied as the materials changed. A finite element analysis was conducted to evaluate the effectiveness of the countermine boot based upon accepted tolerance levels of the lower extremity of the body. The materials and their dimensions were modified in the finite element model to determine how these modifications would impact the boots’ effectiveness.
Fatigue Analysis of 5-1/2 F.H. Threaded Connection
Authors: Hommel Mark
Published: January 2022

This paper examines the fatigue behavior of the 5-1/2 F.H. threaded connection. The finite element method was used to calculate the static and bending stresses in the pin and box for the purpose of estimating fatigue life of the connection. These stresses were compared with the material properties of the steel and a fatigue life was thereby predicted for a given dogleg.

The Gerber criterion was selected as the theoretical basis for combining mean and fluctuating stresses. Mean stress was linearized from the static case associated with the preload from make-up torque. Alternating stress was obtained from applying a bending moment associated with a prescribed dogleg. The last engaged thread in the pin, closest to the shoulder, and the last engaged thread in the box, farthest from the shoulder, were seen to be the sites of maximum stress. The pin stresses govern fatigue life because mean stress is higher than for the box.

In a parallel effort, a roll test was set up to examine fatigue life experimentally. A BHA was made up and installed horizontally in the roll machine. The deflection at the threaded connection was measured, and the assembly was rotated at a measured speed until the pin part of the threaded connection failed.

Next, the finite element results were compared with roll test data and good agreement was obtained. The data was then extrapolated to generate a graph showing expected life as a function of dogleg severity for the 5-1/2 F.H. connection. Finally, the maximum dogleg for which the connection has a 10 million cycle life was predicted.
Application of Topology and Finite Element Shape Optimizations in the Design of a Pusher for a Crimp Machine
Authors: Krishna Murali M. R.
Published: January 2022

Topology and shape optimization techniques have been applied in combination to design a pusher for a crimp machine. Preliminary topology optimization directed us to do sizing optimization. Topology optimization was again applied to a plate version of the pusher to find out the best form of cut out to reduce its weight further. Shape optimization was then used to find the optimum size of this cut out. The results were verified with solid finite element analysis. In conclusion, both weight and stresses have been brought down drastically. Thus the concept of using both topology and shape optimization has been proved to work successfully with pusher design.
Radiated Noise From a Clamped Circular Plate-Shaft System
Authors: Park Chan Il , Grosh Karl
Published: January 2022

In this paper, a model problem for helical gear system dynamics is studied. The model problem consists of a shaft coupled to a plate through a bearing stiffness. Gear forces are modeled as a longitudinal excitation of the shaft which in turn drives the gear housing through the bearing. In this study, the shaft is modeled as a rod, while the bearing is modeled as a spring only supporting longitudinal forces. The gear housing is modeled as a clamped circular plate. Transfer functions from the shaft to the circular plate are analytically derived, using a spectral method along with four pole parameters. Finally, radiated noise is computed, using the acoustic relations due to plate surface vibration.
Yield Function for Porous Metals With High Pressure Gas Pores
Authors: Ahmed Shatil S. , Alam M. K. , Gunasekera J.
Published: January 2022

To reduce weight while maintaining high specific strength, Structural Porous Metals (SPM) are being developed. These materials are alloys containing an inert gas at very high pressures in distributed pores. The pores of gas are incorporated into the SPM during processing. Since the pores are closed at high pressures, the material can be processed by standard methods such as rolling or forging without collapsing the gas pores. This paper deals with the determination of the yield stress of these structural porous metals. The yield function is calculated by calculating the energy needed to deform the material to the yield point. In the case of SPM, the yield function must include the work needed to deform the gas pores as the material yields. The energy of deformation for the gas in the pores is evaluated according to the ideal gas law. The result of the analysis is then compared with classic yield functions for monolithic alloys.
The Effect of Annealing, Overheating, and a Sintered Porous Coating Thermal Treatments on the Fatigue Properties of Ti-6.0wt.%Al-4.0wt.%V ELI Alloy Plate Specimens
Authors: Fragomeni James M.
Published: January 2022

The primary objective of this investigation was to determine the effect on the mechanical and fatigue properties induced by sintering powder on Ti-6wt.%Al-4wt.%V ELI (Extra Low Interstitial) alloy substrates as compared to annealing, and overheating thermal treatments. Fatigue tests were conducted using a variable speed plate fatigue machine on various specimens in the different thermally-treated conditions so that a comparison study of the fatigue characteristics could be performed. The heat treatments, which included as-annealed, as-overheated, and sintered porous-coated, were performed on the plate fatigue specimens prior to testing in the variable speed fatigue plate machine. A comparison study of the fatigue results/properties of the samples subjected to the three thermal treatments revealed that the annealed specimens exhibited superior fatigue resistance as compared to the as-overheated and porous-coated samples. However, a substantial decrease in the fatigue resistance of the porous coated sintered to the as-overheated thermal treatment was not evidenced. It was determined that the decrease in the fatigue resistance of the as-overheated, as compared to the annealed heat treatment, was a result of an increase in the macroscopic grain size. Furthermore, for the porous-coated specimens, it was determined that the presence of stress concentrations at the surface irregularities of the sintered bond sites resulted in the decrease fatigue resistance. It was found, from optical metallography on the sintered porous-coated samples, that microscopic fatigue cracks originated at the necked regions of both the particle-substrate interface and the particle-particle interface. From these findings it was determined that the fatigue cracks at the particle-substrate interface contributed to the ultimate fatigue failure of the sintered porous-coated plate fatigue specimens.
Design of Experiments Procedure to Optimize Feedrate in Wire Electrical Discharge Machining
Authors: Billatos Samir B. , Ricci Gregory M.
Published: January 2022

Wire Electro-Discharge Machining (WEDM) is a material removal process that incorporates heat generation through electrical energy and mechanical movement to produce finished designs in electrically conductive workpieces. The WEDM workcenter used in this research is a JAPAX 4G. The unit uses nozzles to guide the wire and apply the dielectric fluid to the workpiece. The wire is the conductive electrode and the dielectric fluid produces a localized ionized field between the workpiece and the wire. The dielectric fluid also, clears the debris and cools the wire. The most common problem in WEDM is the optimization of cycle times. The amount of time needed to produce a finished part determines the profitability of the workcenter. Industry is continually searching for procedures to decrease cycle times and increase profit. This research uses a design of experiments (DOE) method to optimize the WEDM process.

The key parameters of the WEDM process are modified during the DOE trials. The results are applied to produce an optimal machining condition. The three conditions: Manufacturers Settings, E-Chip Settings, and Optimized Settings are used to produce the rough-cut of three identical designs. The rough-cut is the first pass to produce a finished workpiece. It is during this pass that material removal rate and the risk of wire rupture are the greatest. The overall cycle time is mainly impacted by the time required to perform the rough-cut. The three designs produced are examined for surface finish. The key parameter settings that are used during the rough-cut must not produce a surface finish that requires the addition of cutting passes to produce the final design. Also, the risk of wire rupture during the rough-cut must be acceptable. If wire rupture were to occur during the rough-cut then all benefits of increased speed are lost.
Potential of Porous Microcellular Polymers in Biomaterials Research
Authors: Kumar Vipin
Published: January 2022

Many different materials, both polymers and metals, are used in various applications inside the human body, such as pacemakers, hip joints, heart valves, tooth implants, lenses, drainage shunts, etc. Although the materials undergo extensive evaluation for ‘biocompatibility’, the definition for which continues to evolve, the body seldom welcomes the foreign matter. It has been found that regardless of the type of man-made material, the body builds a wall around it, and encapsulates it with a fibrous material. Thus, the material is basically rejected by the live cells. This phenomenon is responsible for a variety of complications including infections that are sometimes fatal, and prevents or prolongs proper healing.
Dielectric Characteristics of a Relaxor 0.9PMN-0.1PT Synthesized With Hot and Cold Pressing
Authors: Tang F. , Chinkhota M. , Brown W. D. , Wang J. T. , Lian K.
Published: January 2022

Two different processing methods were employed, hot pressing and cold pressing for fabricating Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) ceramic bulk samples, which could be used in the applications of electromechanical actuators in smart material system and structures. The dielectric constant, dielectric loss of these samples versus frequency and temperature were measured and analyzed.
Modeling Nonlinearities in Piezoceramics Associated With Polarization Switchings
Authors: Fotinich Yevgeniy , Carman Gregory P.
Published: January 2022

Piezoelectric materials exhibit nonlinear behavior when subjected to large electric fields. This strong nonlinear material behavior is induced by polarization switching (i.e., change of the polarization direction). In this paper, a nonlinear finite element code for a coupled electro-mechanical problem is presented to model polarization switchings. An isoparametric plane strain four-node element with nodal displacements and voltage as degrees of freedom is used to approximate the geometry. The element incorporates two types of polarization switching: 90° and 180°, where electric flux is used as a switching criterion. Three cases are studied in this paper: a partially electroded specimen simulating 180° polarization switching, a fully electroded specimen simulating 90° switching and a plate containing a void. The analytical results are compared with experimental data obtained from a Moiré interferometer. Comparison between experimental data and theoretical results indicates reasonable agreement between the two suggesting that the correct physics is incorporated in the analytical model.
Development of a Low Frequency High Stroke Proof Mass Actuator With Composite Members
Authors: Dunn Barry , Paine Jeff
Published: January 2022

A design study and hardware evaluation was performed on the use of piezoelectric transducers in an innovative flexure mechanism based actuator to provide control forces for low frequency applications. The specific design concept involves the use of a hybrid composite/solid-state flexure mechanism to create a proof mass actuator (PMA). The new actuator merges the benefits of solid-state piezoelectric actuator technology with low stiffness, composite material, fatigue resistant kinematic elements and low friction sapphire bearings. The novel use of low stiffness composite materials was used to provide greater stroke levels than a pre-existing flexure-based solid-state actuator design giving larger output forces in a similarly sized package. The flexible curved composite components allow a lower natural frequency and therefore higher output forces at lower frequencies. The use of synthetic bearings for the composite arm provides an effective reduction in the resonant frequency of the device. This is due to the change in the composite arm’s boundary conditions from a quasi fixed-fixed to a pinned-pinned condition. The use of different mechanism geometries showed that the construction of the composite arm allows the response of the PMA to be tailored for different operational ranges. The new technology discussed herein is a step ahead of current actuation systems because it combines the attributes discussed above into a mechanism that yields reliable, simple to implement actuation.
Analysis and Control of Mesoscale Actuator Systems
Authors: Kiely Edward , Washington Gregory , Song Jun-Kyung
Published: January 2022

A great deal of literature exists on the modeling and control of piezoelectric materials used as microscale actuators. These actuators take advantage of the converse piezoelectric effect to produce deflections on the order of tens of several microns. Typical applications include active noise control, active vibration control, platform actuation, and many others. Recently the design of mesoscale actuators (deflections from 1 mm – 15 mm) has been a topic of study for many researchers. This study deals with the design and control of a mesoscale actuator comprised of stacked piezoelectric Rainbow wafers. The advantages of using piezoelectric materials for actuation include low power usage, fast response times, accurate displacement, and low cost. However, these advantages do not come without a tradeoff. The effects of hysteresis and creep, while apparent in traditional microscale piezoelectric actuators, are magnified with the increased deflection of these new actuators. Because of this fact, control of the actuator – plant system becomes more difficult. In addition, the uniform manufacture of uniformly spherical Rainbows is difficult, introducing the problem of inconsistent behavior among individual Rainbows. Although numerous, these problems can be overcome by employing various dynamic control techniques. The work in this study presents and experimentally verifies a model of a Rainbow actuator based on shell theory. The system is then controlled using both classical and intelligent control techniques. In addition hardware and circuitry issues are explored.
The Effect of Model Uncertainty on Magnetorheological Fluid Damper Based Systems Under Feedback Linearization Control
Authors: Marathe Sameer S. , Wang K. W. , Gandhi Farhan
Published: January 2022

This paper is concerned with the effects of magnetorheological (MR) fluid damper model uncertainties on system stability, when local feedback linearization schemes are utilized. The objectives of the research are to characterize such effects, and develop a robust control law for given uncertainty bounds. First, deterministic functions are used to represent the possible deviations between the actual MR damper force and the force predicted by the model. Limit cycle behavior is predicted using the Describing Function Method and parameters influencing the limit cycle characteristics are identified. An effort is then made to derive the worst-case model deviation, given the bounds on the possible model uncertainties. Based on such results and the limit cycle analysis, a robust feedback linearization controller is synthesized to eliminate the limit cycle instability.
A Bi-Axial Active Boring Tool for Chatter Mitigation
Authors: Redmond James M. , Barney Patrick S.
Published: January 2022

This paper summarizes results of metal cutting tests using an actively damped boring bar to suppress regenerative chatter. PZT stack actuators were integrated into a commercially available two-inch diameter boring bar to suppress bending vibrations. Since the modified tool requires no specialized mounting hardware, it can be readily mounted on a variety of machines. A cutting test using the prototype bar to remove metal from a hardened steel workpiece verifies that the actively damped tool yields significant vibration reduction and improved surface finish as compared to the open-loop case. In addition, the overall performance of the prototype bar is compared to that of an unmodified bar of pristine geometry, revealing that a significant enlargement of the stable machining envelope is obtained through application of feedback control.
Analysis of Active Doubly Curved Antenna Structures
Authors: Yoon Hwan-Sik , Washington Gregory
Published: January 2022

Recently, aperture antennas that have the ability to change their reflector shape through the usage of piezoelectric actuators have been studied. The results show that those antennas can exhibit beam steering and beam shaping in the far-field. However, the previous studies have been confined to cylindrical shape antennas. This study examines the use of “doubly curved” antenna structures to achieve better performance in controlling an antenna’s coverage area. The spherical antenna is modeled as a shallow spherical shell with a small hole at the apex for mounting. Following Reissener’s approach, a stress function is introduced and two governing equations are derived in terms of the stress function and the axial deflection. Next, the amount of deflections are evaluated from the calculated stress function and the axial deflection. As actuators, four PZT strip actuators are attached along the meridians separated by 90 degrees respectively. The force developed by the actuators are expanded in Fourier series and fed into the governing equations as boundary conditions at the outer edge. Finally, the Deflection vs. Applied Voltage is calculated analytically and its effect on the far-field radiation is given.
An Investigation of Delaminated Smart Composite Plates for Damage Detection
Authors: Chattopadhyay Aditi , Dragomir-Daescu Dan , Nam Chang-ho
Published: January 2022

A refined modeling technique is developed to analyze the effect of delamination on a composite plate with piezoelectric actuators. The analysis uses a refined displacement field, which carefully accounts for both the presence of delamination and distributed actuators. The effect of delamination is investigated under both static and dynamic conditions. The analysis is implemented using the finite element method. Numerical results presented indicate the significant changes in mechanical parameters due to a small delamination. These results can be useful for on line damage detection.
3D Computational and Experimental Fluid Dynamics Analysis for the Automotive Catalytic Converter
Authors: Fu Xiaodong , Lambert David W. , McLaren George S. , Treacy David R. , Then Paul M.
Published: January 2022

Numerical and experimental fluid dynamics analysis has been performed for the automotive catalytic converter under isothermal condition focusing on two primary problems of catalytic converters: (1) the low conversion efficiency; (2) high pressure drop. The K-ε turbulent model based on the eddy viscosity model combined with the fluid flow model in porous media was used as the physical governing equations. The numerical results agreed with the experimental data obtained by LDV and hot wire anemometer. Some insights and optimization design concepts obtained in the present work provide valuable information to the converter designer.
Experimental Determination of the Viscous and Inertial Coefficients in Highly Porous Metal/Ceramic Foams
Authors: Jones Stanley T. , Sommer Martin , Rios-Forscht Alexander , Catton Ivan
Published: January 2022

An experimental program has been conducted to characterize the behavior of a series of highly porous, reticulated metal/ceramic foams composed of silicon carbide. Using information from the manufacturer, an expression was developed by which the volumetric porosity was determined. The range of porosities investigated was 0.72 to 0.90 for most materials investigated.

Flow experiments were conducted to determine the pressure loss as a function of the pore Reynolds number. By implementing a form of the Kozeny-Carman equation for viscous pressure loss, the specific surface area was determined from low flow rate measurements. Air was blown through a 2” diameter circular cylinder of porous media of varying lengths. The mass flow rate and pressure difference were measured under steady flow conditions. Based upon a Reynolds-Forchheimer representation of the pressure loss, these measurements allowed for determination of the viscous and inertial pressure loss coefficients. Based upon these results, a series of expressions for the Fanning friction factor as a function of pore Reynolds number are proposed for this class of porous media.