Additive manufacturing (AM) can enable complex and novel designs that are otherwise infeasible with traditional metal manufacturing techniques. In low-volume production scenarios, particularly for specialized applications which can benefit from customized designs, traditional metal manufacturing techniques may be limited by costs associated with tooling. The ability to produce novel designs is particularly interesting in heat exchanger (HX) design where performance is often largely based on the achievable geometry. However, consequences of the AM process such as surface roughness, deviation from specified dimensions, and defects such as cracks and voids could also affect HX performance. These effects may vary between identically designed AM parts based on AM machine settings. The goal of this work is to gain a better understanding of the performance variations across several different implementations of the same heat exchanger design. More specifically, the objective of this work is to experimentally compare the thermal and hydraulic performances of a traditionally manufactured, stamped-aluminum aircraft oil cooler and three geometrically equivalent, additively manufactured counterparts. Compared to the traditionally manufactured heat exchanger, the AM HXs exhibited significantly higher air-side pressure loss and higher heat transfer despite having nominally similar geometries. Between AM HXs, there were slight differences in surface roughness characteristics based on optimal profilometry measurements. In addition, the thickness of the air-side fins varied as much as 15 percent between the AM HXs. The net effect, without the contribution of each cause clear, was higher air-side pressure loss and slightly higher heat transfer for the AM HX with thicker fins. This study indicates that functional heat exchangers built using AM vary in performance even when the same digital model is used to print them, and that AM HXs as a group perform considerably differently than their traditional counterparts. Thus, there is a need to account for anticipated surface roughness, geometric deviations, and potential defects when designing HXs. Proper consideration could result in improved thermal performance for future heat exchangers.

This research presents laser ablation characteristics of an aluminum alloy after nanosecond pulsed laser ablation (PLA) with a 1064 nm Nd:YAG laser. White light interferometry and scanning electron microscopy were used to establish relationships between laser ablation characteristics and the number of pulses at different beam energies. Laser ablation features studied in this research are crater profiles, radii and depth, and extent of surface damage. An extensive damaged area around the laser ablation crater was found and is believed to be produced by the laser-induced plasma generated during PLA. Spectroscopic analysis showed that there is a correlation between the plasma formation threshold and the initiation of the plasma-affected area, and laser ablation at different angles of incidence between the beam and the sample showed a correlation between the plasma shape and the shape of the damaged area around the ablation crater. However, the variables influencing the occurrence of the plasma-affected and the extent of plasma-induced damage are not yet fully recognized and understood.

Polycarbonate glass is one of the most widely used materials in the optical industries for making impact resistance lenses. Besides optical applications, polycarbonate glass has found applications in automotive and biomedical industries. The objective of this study is to investigate the effect of tool coating on the reduction of tool wear and cutting forces during micro-milling of polycarbonate glass. Both numerical modeling and experimental investigation have been carried out to investigate the effectiveness of various tool coatings on the carbide tool in minimizing the cutting forces, and hence tool wear. A series of experiments were conducted using CNC micro-milling of polycarbonate glass by varying feed rate, depth of cut, and tool coating. The three types of cutting tools used in this study were uncoated, titanium nitride (TiN) coated, and titanium aluminum nitride (TiAlN) coated tungsten carbide tools. The cutting forces have been recorded using the Kistler force dynamometer and the tool wear were analyzed using scanning electron microscope (SEM). It was found that all tools had reduced instances of failure, chipping, and abrasion at a moderately higher feed rate and depth of cut. Both very low and high feed rate were found to result in comparatively higher tool wear. The cutting forces increased with an increase of depth of cut, except for the TiAlN coated tool in some instances. With the increase of feed rate, the cutting forces gradually increased or stayed relatively constant across all depths of cut. It was found that the TiAlN coated tool reduced the amount of tool wear and cutting force across all feed rates and depths of cut. There is also a critical depth of cut around 0.3–0.5 mm and feed rate around 576–768 mm/min that reduced the amount of tool wear for the micro-milling of polycarbonate glass. Finally, the numerical modeling and simulation results of cutting forces were found to be in good agreement with the experimental cutting forces and the validated FEM models were then used to predict the cutting forces for higher spindle speed.

The cost and quality of aluminum produced by the reduction process are strongly dependent on heat treated (baked) carbon anodes. A typical aluminum smelter requires more than half a million tons of carbon anodes for producing one million ton of aluminum. The anode baking process is very energy intensive, approximately requires 2GJ of energy per ton of carbon anodes. Moreover, pollutant emissions such as NOx and soot formation are of major concern in the aluminum anode baking furnace. The current study aims at developing an accurate numerical platform for predicting the combustion and emissions characteristics of an anode baking furnace. The Brookes and Moss model, and the extended Zeldovich mechanism are employed to estimate soot and NOx concentration, respectively. Considering a fire group of three burner bridges, one after the other in the fire direction, combustion and emissions features of these three firing sections are interrelated in terms of oxidizer’s concentration and temperature. In the present study, considering this interconnection, the effect of diluted oxygen concentration at elevated oxidizer’s temperature (∼1200°C), which are the key features of the moderate or intense low oxygen dilution (MILD) combustion are analyzed. It is observed that by circulating some of the exhaust gases through the ABF crossovers, oxygen dilution occurs which results in higher fuel efficiency, lower pollutant emissions, and more homogeneous flow and temperature fields.

Hybrid energy harvesting is a concept that can be applied to improve the performance of the conventional standalone energy harvesters. In this study, a hybrid energy harvesting device is presented that harvests energy from solar radiation and mechanical vibration by simultaneously combining the photovoltaic, piezoelectric, electrostatic, and electromagnetic mechanisms. The device consists of a bimorph piezoelectric cantilever beam having Lead Zirconate Titanate crystal layers on top and bottom surfaces of an Aluminum substrate. Two sets of comb electrodes (capacitors) are attached on two sides of the substrate. A permanent magnet is attached at the tip which oscillates within a stationary coil inside a casing. The exterior surface of the casing is covered by organic photovoltaic panel that captures energy from illumination. All the segments are interconnected by an electric circuit to generate combined output when subjected to solar radiation and mechanical vibration. Results for power output are obtained at the first resonance frequency of the beam with a common optimum load resistance. As the power outputs of all the mechanisms are combined, a high power efficiency can be achieved by the proposed hybrid energy harvester.

Solar thermal collectors are efficient components that provide hot water for residential and commercial use. Over the years many techniques and approaches have been proposed in order to improve the efficiency of these systems. One of the improvements suggested has been the use of minichannel tubes as the absorber for a flat plate collector which has been found to be more efficient than a conventional flat plate collector. These collectors have received attention recently with significant research pertaining to enhancing performance. This paper discusses the effect of incorporating a Phase Change Material (PCM) storage system within an aluminum based solar collector. Three different configurations of integrating the PCM next to the aluminum minichannel based absorber plate have been analyzed. The simulations are performed in COMSOL Multiphysics ® and the results analyzed to determine the most efficient configuration.

This work presents an experimental and numerical study of the melting and solidification processes of Solar Salt in a finned square metallic container with a constant heat flux source inside for the latent heat thermal energy storage (LHTES) for medium temperature applications. During the experiments the temperature of the PCM in several locations were recorded and used to validate results of numerical simulations that were conducted deploying the enthalpy method in Ansys FLUENT. Two prototypes of the container were tested, one with fins made of steel and the other with fins and casing made of aluminum, to compare the charging and discharging time in both configurations. The modelling results are in good agreement with experimental data for the charging of aluminum container and slightly higher deviation are found in the other cases. The validated simulation model can be used as a design tool to achieve the optimal geometry of the full scale LHTES for the required charging and discharging periods.

Nowadays, many surface sensing mechanisms exist, not all of them can be applied in water-based environment. Most of surface sensing techniques were developed in air-based environment. In order to obtain a potential cell-based biosensor, the sensing method needs to be reliable and repeatable in liquid environment. Therefore, we adapt existing air-based surface acoustic sensor and promote the technology into water-based applications. The goal of this study is to apply surface acoustic waves (SAW) for water-based environment sensing. We will use shear horizontal wave (SH wave) as surface sensing mechanism. SH wave is a type of surface acoustic waves (SAW) which can be used for weight/mass sensing in the air environment. Interdigitated transducers (IDTs) induce the deformation of an ST-cut quartz crystal substrate in AC source and generate waves. With a thin layer of polymer like Parylene and polyimide, the SH wave will be confined between the interface of substrate and polymer layer without suffering the energy loss due to the liquid damping from above. The fundamental frequency of the SAW device is defined by the spacing between the electrodes of IDT. The frequency of interests for this research is below 100 MHz in water-based environment. Due to the stable frequency characteristics of ST-cut quartz in room temperature, this SAW device can be a good candidate for field applications. From an early IDTs design, investigation in material and IDTs configuration is necessary to improve signal quality in order to qualify for liquid phase cell-based bio-sensing applications. A simplified 3D unit cell FEM model is created to study the thickness effects of wave-guide and electrodes. Boundary conditions and assumptions are discussed in the modeling. The simulated eigenfrequency of SH mode is close to the theoretical fundamental frequency of the 64μm wavelength IDTs. The mass damping effects from gold electrodes is more significant than aluminum electrodes.

In this study, the thermal characteristics of a high-temperature latent heat thermal energy storage system assisted by highly conductive nanoparticles and finned heat pipes are investigated numerically. A transient two-dimensional model is developed using the commercial CFD package of ANSYS-FLUENT18.2 to analyze the thermal performance of the storage unit during the charging process. Copper oxide (CuO) and aluminum oxide (Al 2 O 3 ) are the nanoparticles introduced to enhance the thermal conductivity of the phase change material (PCM) which is potassium nitrate (KNO 3 ) with melting temperature of 335°C. The effects of different types and volume fractions of nanoparticles, as well as the quantities of embedded heat pipes have been studied. The results revealed that increasing the volume fraction of nanoparticles leads to the increase of the melting rate and input heat flux of the system. It was also found that the dispersion of aluminum oxide in the PCM provides a faster charging process in comparison to the case with copper oxide nanoparticles. In addition, the results showed that the quantity of heat pipes has a significant impact on the thermal performance of the storage unit.

Monolithic plate-type fuel is a fuel form that is being developed for the conversion of high performance research and test reactors to low-enrichment uranium fuels. These fuel-plates are comprised of a high density, low enrichment, U-Mo alloy based fuel foil encapsulated in an aluminum cladding. To benchmark this new design, number of plates has been irradiated with satisfactory performance. As a part of continuing evaluation efforts, a set of plates covering range of operational parameters is scheduled to be tested during MP-1 irradiation experiments. It is necessary to evaluate the thermo-mechanical performance of plates during irradiation. For this, selected plates with distinct operational histories; covering low power, high power and high fission density were simulated. Fully coupled three-dimensional models of plates with a capability to evolve mechanical and thermal properties of constituent materials with irradiation time and burn-up were developed. The models input used projected parameters, including plate geometry, irradiation history and coolant conditions as input. The model output included temperature, displacement and stresses in the fuel, cladding and diffusion barrier. The fuel behavioral model considered inelastic behavior including volumetric swelling due to solid and gaseous products, irradiation induced creep, thermal expansion, conductivity degradation and plasticity. A visco-plastic behavioral model was used for the cladding that included thermal creep, irradiation hardening, growth due to fast neutrons and Mises plasticity. The plates were then simulated by using projected irradiation parameters. The resulting temperature, displacement and stress-strains were comparatively evaluated on the selected paths. The results were then compared with those of plates from previous RERTR experiments.

Metal foams enhance heat transfer rates by providing significant increase in wetted surface area and by thermal dispersion caused by flow mixing induced by the tortuous flow paths. Further, jet impingement is also an effective method of enhancing local convective heat transfer rates. In the present study, we have carried out an experimental investigation to study the combined effect of the two thermal performance-enhancement mechanisms. To this end, we conducted a set of experiments to determine convective heat transfer rates by impinging an array of jets onto thin metal foams attached on a uniformly heated smooth aluminum plate simulating a high heat-dissipating chip. The metal foams used were high porosity aluminum foams (ε∼0.94–0.96) with pore densities of 5 ppi, 10 ppi and 20 ppi (ppi: pores per inch) with thicknesses of 19 mm, 12.7 mm and 6.35 mm, respectively. With the jet-to-foam distance ( z/d ) set to zero, we conducted experiments with values of jet-to-jet spacing ( x/d = y/d ) of 2, 3 and 5. The jet plate featured an array of 5 × 5 cylindrical jet-issuing nozzles. The normalized jet-to-jet distance was varied by changing the jet diameter and keeping the jet center-to-center distance constant. Steady state heat transfer and pressure drop experiments were carried out for Reynolds number (based on jet diameter) ranging from 2500 to 10000. We have found that array impingement on thin foams leads to a significant enhancement in heat transfer compared to normal impingement over smooth surfaces. The gain in heat transfer was greatest for the 20 ppi foam (∼2.3 to 2.8 times that for the plain surface smooth target). However, this enhancement came at a significant increase of about 2.85 times in the plenum static pressure. With the pressure drop penalty taken into consideration, the x/d = 3 jet plate for the 20 ppi foam and x/d = 2 jet plate for the 10 ppi foam were found to be the most efficient cooling designs amongst the 18 cooling designs investigated in the present study.

Aluminium based metal matrix composites with nano particle reinforcement are currently finding wide spread applications in automobile, aerospace and space structures because of their high strength, fatigue life, excellent wear resistance, low thermal coefficient value. However, in order to use these materials for critical automotive applications, extensive study in terms of manufacturing feasibility of the composites have to be carried out. Based on the objectives, the present investigation focuses on the development of Aluminium-SiC nano composite for structural applications. The aim of this research work is to arrive at an optimum weight faction of nano particle which gives the highest properties of the nano composite. The composites were produced by stir casting route. The base alloy and the composites were extruded and subsequently subjected to age hardening treatment. Microstructural evaluation, hardness studies were carried out on both the base alloy and the composites in the as-cast and extruded conditions. The effect of extrusion on the microstructure and properties of the AA2014-0.8 wt.%SiC composites have been discussed in detail.

Aluminium based metal matrix composites (MMCs) have received considerable attention in the last decade for its potential industrial applications. One of the challenges encountered using Aluminium based MMCs is understanding the influence of the reinforcement particles on the corrosion resistance and mechanical properties. In this study the corrosion behaviour and mechanical properties of Al6063 reinforced with egg shell ash and rice husk ash were investigated. Waste Egg Shell Ash (ESA) and Rice Husk Ash (RHA) 212 μm in size were used to produce the composites with 10 wt% of reinforcements via stir casting technique. The RHA and ESA were added in the ratios of 10:0, 7.5:2.5, 5:5, 2.5:7.5, 0:10. Unreinforced Al6063 was used as baseline material. Immersion tests, potentiodynamic polarization techniques, tensile tests, optical microscopy (OM) and scanning electron microscopy (SEM) were used to characterize the composites. The results showed that reinforcing with 7.5 wt% RHA + 2.5 wt% ESA provided the highest resistance to corrosion. Generally, a reduction in the corrosion rates were observed for the reinforced composites as the wt% of RHA increased. Porosity levels of the composites reduced with an increase in the percentage of ESA in the matrix. Microstructural characterization using SEM and OM revealed a distribution of pits on the composite surfaces which was more severe with increasing RHA percentage. The UTS (ultimate tensile stress) results revealed that the composite containing 10 wt% RHA had the maximum value of 161 MPa. The results demonstrate that rice husk ash and eggshell ash can be useful in producing low cost Aluminium composites with improved corrosion resistance and tensile properties.

Despite the many advances made in material science, stainless steel and aluminum remain the structural materials best-suited for the naval fleet. While these metallic materials offer many benefits, such as high strength and good toughness, their persistent exposure to the maritime environment inevitably leads to issues with corrosion. Among the various manifestations of corrosion, pitting corrosion is of particular concern because the transition of corrosion pits to stress-corrosion cracks can lead to catastrophic failures. Traditional pitting corrosion analyses treat the pit shape as a semi-circle or ellipse and typically assume a growth pattern that maintains the original geometrical shape. However, when the underlying microstructure is incorporated into the model, pit growth is related to the grains surrounding the pit perimeter and the growth rate is proportional to crystallographic orientation. Since each grain has a potentially different orientation, pit growth happens at non-uniform rates leading to irregular geometries, i.e., non-circular and non-elliptical. These irregular pit geometries can further lead to higher stresses. This work presents a detailed look at corrosion pit growth coupled with mechanical load through a numerical model of a two-dimensional stable corrosion pit. Real microstructural information from a sample of 316 stainless steel is incorporated into the model to analyze microstructural effects on pit growth. Through this work, stress distributions and stress concentration factors are examined for a variety of pit geometries, including comparisons of their range of values to a typical, semi-circular pit. The consequences of these stress distributions and concentration factors are discussed.

In recent years, conventional materials are rapidly replaced by advanced aluminium composites due to its lighter in weight and high-performance characteristics. These materials find vast applications in automotive components because of its excellent combination of properties such as high specific strength, high specific stiffness, better dimensional stability and enhanced wear characteristics. The present work is focused on hybrid composites manufactured by stir casting route where the A356 alloy is the matrix and SiC + Moringa Oleifera Ash (MOA) particles as reinforcements. The influence of Moringa Oleifera Ash (MOA) particles (self-lubricant) on the wear behaviour of the composites is studied. Fabricated composites are tested on a pin-on-disc test rig at dry sliding wear conditions to study the influencing input parameters such as load, sliding distance and composites. A356 Aluminium alloy is reinforced with 5% SiC as primary reinforcement, varying MOA particles with 1% and 3% as secondary reinforcement. The design of experiments (DOE) approach using Taguchi method was adopted to perform the experiments according to L9 orthogonal array and analyse the results. From Taguchi analysis, combination of best suited values is identified and reported. Inquest of influential wear test parameters and its effect on wear and friction is determined using the signal-to-noise ratio and analysis of variance (ANOVA).

In manufacturing processes, the cost of tooling contributes to a significant portion of operating costs. Several papers have been dedicated to various improvements on tool life, including monitoring the effect of temperature conditions and flood cooling. Flood cooling is not economical, so research has also been done to investigate minimum quantity lubrication and the effects of different additives, such as nanofluids. Another additive, ionic liquids, have become popular in tribological studies because they have unique properties that allow them to form ordered molecular structures, which is ideal in lubrication. Research has proven ionic liquids to be effective in reducing wear and friction coefficients. Currently, utilizing ionic liquids specifically to reduce tool wear has been almost exclusively limited to titanium and steel applications. The goal of this study is to improve tribological performance of the subtractive manufacturing process using ionic liquid add-ins to widely available machine shop coolants and oils. A series of reciprocating ball-on-flat experiments will be conducted using a 1.5mm diameter 250 Chrome Steel G25 ball and 6061-T6 aluminum disk to simulate cutting conditions often seen in manufacturing processes. 6061 Aluminum is an alloy commonly seen in machine shops and large-scale manufacturing scenarios because of its versatile material properties and wide availability. The tests were run at constant sliding distance, velocity and load. The lubricating mixtures were prepared by adding 5 wt % of a phosphonium based ionic liquid, Trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide ([THTDP][NTf2]), to the base fluids Trim Sol™ emulsion fluid and Mobilmet™ 766 high performance neat cutting oil. The addition of the ionic liquid to both base lubricants (oil and coolant) increased the friction coefficient (18.60% and 4.89%, respectively) while the wear volume was reduced (28.75% and 7.84%, respectively). The results for the oil provided evidence that the ionic liquid did have an effect to reduce wear, however, the same conclusion could not be drawn for the coolant.

In this study, the tribological behavior of the Trihexyl tetradecylphosphonium-bis(2,4,4-trimethylpentyl)phosphinate [THTDP][Phos] ionic liquid with and without single-wall carbon nanotubes (SWCNT) dispersion as a thin boundary layer was intended for investigation. However, the surface heat treatment process was not sufficient to form a thin film on the sample surfaces. Thus, in each test condition, the lubricating agents were used as external (liquid) lubricants. Specifically, [THTDP][Phos] and ([THTDP][Phos]+0.1 wt.% SWCNT) boundary film layers were applied on 6061-T6 aluminum alloy disk samples and tested under sliding contact with 1.5 mm diameter 420C stainless steel balls using a ball-on-flat linearly reciprocating tribometer. A commercially available Mobil Super 10W-40 engine oil (MS10W40) was also tested and used as this investigation’s datum. The tribological behavior of [THTDP][Phos] and ([THTDP][Phos]+SWCNT) boundary film layers was analyzed via wear volume calculations from optical microscopy measurements, as well as by observation of the transient coefficient of friction (COF) obtained through strain gauge measurements made directly from the reciprocating member of the tribometer. Results indicate the potential for reduction of wear volume and coefficient of friction in the IL lubricated steel-on-aluminum sliding contact through (SWCNT) dispersion in the ionic liquid. Wear results are based on measurements obtained using optical microscopy (OM). Results discussed display improved tribological performance for both [THTDP][Phos] and ([THTDP][Phos]+SWCNT) over baseline MS10W40 oil lubricant for both roughness values tested for the steel-on-aluminum contact. No measurable improvements were observed between [THTDP][Phos] and ([THTDP][Phos]+SWCNT) tests.

In this paper, a crushable absorber system is designed to analyze the dynamic behavior and performance of a helicopter seat. The mechanism of the absorption system makes use of the crash energy to plastically deform the aluminum material of the seat legs. Seat structure is composed of a bucket, two legs and two sliding parts on each leg. Seat legs are made of aluminum and and the sliding parts of the seat are steel. During the impact event, the heavier sliding parts move down and crash the aluminum material for the purpose of deforming the aluminum material under the sliding parts and reduce the crash energy. The designed helicopter seat is analyzed using the explicit finite element method to evaluate how the seat energy absorbing mechanism works. Dynamic simulations are performed in ABAQUS by crashing the seat to a fixed rigid wall. To simulate the plastic deformation, true stress-strain curve of the aluminum material of the seat leg has been used. Time response results are filtered to calculate the meaningful g loads which incur damage to the occupants. Analyses are performed with and without the energy absorption mechanism in order to see the effectiveness of the energy absorption mechanism on the human survivability by comparing the g loads on the seat bucket with the acceptable loads specified by EASA. This study is a preliminary study intended to check the effectiveness of the damping mechanism based on the plastic deformation of the aluminum legs of the seat in the event of a crash.

A comparative experimental analysis of three common hemming processes used in the automotive industry is presented. These processes are die hemming, table hemming, and roll hemming. We aim to determine which one of the three processes provides the better quality hemming. The die hemming and table hemming used in this study were performed with custom made tooling and a 35 tonne hydraulic press. Similarly, roll hemming was performed using a custom made workbench with a three-degree of freedom system of rolls. The material used for testing was aluminum sheet (6011); three rolling directions were taken in account: 0°, 45°, and 90° for the manufacture of the samples. Hemming quality was determined from the geometric variables such as: lip high, pre-hemming angle, tool position, roll radius (roll hemming only). As a result, the comparison of roll in/out and wrinkle defects are reported and compared.

Cutting pressure models have long been utilized for calculating machining force components both tangential and normal. This work lists literature-reported closed form analytical models for torque and thrust of material cutting pressures. Typically, these models are equations formulated in terms of process parameters including mainly cutting speed (V, m/min), feed (f, mm/rev), and tool rake angle (α, degrees). This work aims to benefit from the variation in rake angle and cutting speeds encountered along the lip cutting edge of a standards twist drill to generate normal and tangential cutting pressure empirical models for aluminum 6061-T6 material based on a limited number of drilling feed rate and spindle speed combinations. To isolate the 10mm twist drill bit cutting edge forces, drilling experiments were conducted utilizing 2.5mm pre-cored workpieces. Cutting lip edge toque and thrust data were collected from conducted series of drilling experiments with total number of 10 varying combinations of feed rate and spindle speeds. Values of cutting pressure in terms of feed, speed, and rake angle parameters were identified using a custom-developed MATLAB ® code. Minimized is the difference between the cutting pressure-based closed form torque and thrust models versus the experimentally collected cutting lip torque and thrust measurements. Based on this MATLAB ® code, cutting feed, speed and rake angle parameters found around −0.2, −0.1 and 1.5 respectively based on a convergence criteria of 10 −10 and maximum iteration number of 1000. These optimized cutting pressure parameters were found to predict well the collected experimental forces and were found to be in line with parameter values as reported in the literature.