Mass Savings Research Articles

A comparison of the manufacture and mechanical performance of porous aluminium and aluminium syntactic foams made by vacuum-assisted casting

This paper compares key aspects of the manufacture and mechanical performance of porous Al, made by replication using salt beads, and structurally similar syntactic metal foams, made by replacing the salt with porous, expanded glass particles. Despite significant increases in stiffness, strength and energy absorbed, power law relationships between properties and relative density demonstrate that adding expanded glass particles is a less efficient route to increasing performance than increasing the metal fraction. That said, merit indices do indicate that 20% savings in mass are possible for stiff beams by substituting aluminium with syntactic metal foams. The manufacturing process for syntactic metal foams is shown to be simpler, driven by the lower thermal mass of the expanded glass particles and no requirement to dissolve a space holder from the structure. The balance of good performance and good manufacturability demonstrated herein, coupled with predicted low costs for raw material and manufacturing, highlights the scope for syntactic metal foams containing weak expanded glass particles to be researched and developed more widely.

Nickel percolation and coarsening in sintered Li4Ti5O12 anode composite

AbstractInherently safe all‐solid‐state lithium‐ion battery anodes with high electronic and ionic conductivity are sought to enable next‐generation electric propulsion systems. In novel architectural concepts, multifunctionality of battery materials will provide simultaneous mechanical load bearing and electrochemical energy storage functionality for systems level mass savings. Co‐processing of strain‐free lithium titanate anode and nickel current collector was explored to provide structural integrity and electrical conductivity for a load‐bearing anode with bulk current collection capability. In this study, the effects of processing conditions on densification, electrical conductivity, and microstructural evolution were characterized for Li4Ti5O12‐Ni (LTO‐Ni) composites. Densification of LTO‐Ni was achieved at 900°C and above, and nickel content had minimal effect on final density compared to sintering temperature and time. Electronic conductivity was modeled by percolation theory, exhibiting a large dependence on nickel content and bulk density. Bulk electrical conductivity greater than 1 S/cm was achieved at volume fractions above the percolation threshold. Modeling of microstructural evolution applied Ostwald ripening theories to describe diffusion governing the growth of average nickel particle size and the change in size distributions. Volume fraction effects resulted in larger average Nickel particle sizes and an activation energy of 1.04 eV was measured for nickel particle coarsening.

Impact of High Performance Combustion Chamber Alloys on Fuel Efficiency

<div class="section abstract"><div class="htmlview paragraph">Internal combustion engines have been developed for over one hundred and twenty years and are a very mature technology. Over this time, significant improvements in power density and brake thermal efficiency have been realized from improvements in design, processing and material properties. Huge advances in computer simulation capability over the past thirty years have enabled the former two categories to be explored and exploited very thoroughly, leaving materials specifications as the fundamental key to unlocking further efficiency gains. This paper summarizes the design advantages of a range of alternative materials developed for piston, ring connecting rod and bushing applications. A Ford Ecoboost 2.3l RS engine was selected as a baseline engine and the reciprocating parts were re-designed to take advantage of the improved characteristics of these materials. Reciprocating mass, mechanical efficiency and crevice volume savings have been demonstrated from the re-designed components: piston, pin, ring, connecting rod and bushing. A dynamometer test program was devised to evaluate the net improvements in engine operating efficiency from the modified engine, based on a series of steady-state reference points comparing the baseline OEM and modified engines for future engine testing.</div></div>

Structure Design and Analysis of a Novel Forward-folding Rotor used in a Downwind Horizontal-axis Turbine

To alleviate the stiffness constraints of the conventional blade and thus reduce the rotor mass, a novel forward-folding rotor (Downwind Forward-folding Rotor, DFFR) used in a downwind horizontal-axis turbine is presented. This novel rotor is designed to align the combination of gravitational, centrifugal, and thrust forces along the blade path, resulting in primarily tensile loads instead of cantilever loads on the blades. The DFFR blades fold forward at a power-limited condition, which induces the change of the blade pitch angle and cone angle and thus maintains a constant power output. To quantify the mass savings, a 5-MW DFFR was designed based on the NREL 5-MW reference rotor. According to the results calculated by an improved BEM method, the rotor power and torque of the 5-MW DFFR have a slight increase compared with those of the NREL-5MW reference rotor, while the rotor thrust of the 5-MW DFFR is smaller than that of the NREL-5MW reference rotor. Furthermore, based on the finite element analysis, the blade of the 5-MW DFFR had an 18.9% mass saving and an 8.4% peak stress reduction compared with the blade of the NREL-5MW reference rotor, over a range of operating wind speeds and azimuthal angles.

An optimization method based on the evolutionary and topology approaches to reduce the mass of composite wind turbine blades

The design of large and lightweight wind turbines is a current challenge in the wind energy industry. In this context, this work aims to present a novel methodology to reduce the mass of composite wind turbine blades by combining evolutionary and topology optimization schemes in a staggered mode. First, the optimal laminate layout in the outer shell skin of the blade is determined by using genetic algorithms and by assuming that the shear webs are fully dense. Considering this optimized shell skin, the material is removed from the shear webs by using topology optimization. In both cases, the blade is assumed to be subjected to an extreme load scenario, with constraints on the tip displacement, the stresses, the natural vibration frequencies, and buckling phenomena. As an extra feature, the methodology integrates the inverse finite element method to recover the aerodynamically efficient shape of the blade when it is working in normal load scenario as well as to increase the tower clearance safety margin under the extreme load scenario. To illustrate the performance of the methodology, the design of a 28.5-m composite blade is presented. Results show mass savings of up to 23% and a significant increase of the tower clearance safety margin. Furthermore, it is observed that after the classical genetic optimization of the shell skin, there is still margin to achieve additional mass savings via topology optimization of the shear webs without compromising the structural response of the blade.

Low cost satellite constellations for nearly continuous global coverage

Satellite services are fundamental to the global economy, and their design reflects a tradeoff between coverage and cost. Here, we report the discovery of two alternative 4-satellite constellations with 24- and 48-hour periods, both of which attain nearly continuous global coverage. The 4-satellite constellations harness energy from nonlinear orbital perturbation forces (e.g., Earth’s geopotential, gravitational effects of the sun and moon, and solar radiation pressure) to reduce their propellant and maintenance costs. Our findings demonstrate that small sacrifices in global coverage at user-specified longitudes allow operationally viable constellations with significantly reduced mass-to-orbit costs and increased design life. The 24-hour period constellation reduces the overall required vehicle mass budget for propellant by approximately 60% compared to a geostationary Earth orbit constellation with similar coverage over typical satellite lifetimes. Mass savings of this magnitude permit the use of less expensive launch vehicles, installation of additional instruments, and substantially improved mission life.

LINEAR FRICTION WELDING – PROCESS DEVELOPMENT AND APPLICATIONS IN AEROSPACE INDUSTRY

Linear Friction Welding (LFW) is a solid-state joining process very well adapted to titanium alloys, producing high integrity joints with fine grain, hot-forged microstructure and narrow heat affected zone. The first industrial application of this process was found in aircraft engines, for the manufacturing of “blisks” (“bladed disks”): linear friction welding the blades onto a disk provides economic savings and reduces the manufacturing time, compared to machining the whole blisk from solid. While the diffusion of LFW process in the blisk manufacturing market is still at the early stages and have promising growth potential, the process is now being developed for aircraft structures such as clips, brackets, hinges, fittings, and larger parts like seat rails, wing ribs, lintels and fuselage frames. The LFW process allows not only to manufacture a given part at a lower cost, it also open new part design possibilities, that were not available with traditional manufacturing processes. The manufacturing process of Ti-6Al-4V structural and engine parts by LFW is explained, highlighting advantages, limitations and part design best practices. Several LFW candidate parts are introduced and evaluated through feasibility, mass savings, post weld operations and overall cost savings.

Measurement and modelling of the elastic defection of novel metal syntactic foam composite sandwich structures in 3-point bending

This paper presents a process for creating syntactic metal foam sandwich structures which, for the first time, manufactures both the syntactic foam core and metal face sheets in a single step. Unlike previous research, the face sheets are made from the same material, are integral with the sandwich structure and are relatively thick compared to the core. Via comparison with experimental measurements in 3-point bending, it is shown that accurate prediction of the elastic deformation of these sandwich structures necessitates FE-based modelling, but that the methodology is simple. A reliance on predictions from established analytical models, which have proven themselves accurate for foam sandwiches with thin face sheets, leads to significant over-estimations of the stiffness. Modelling, based on the FEA approach developed herein, shows that mass savings between 20 and 30% are achievable for these novel structures, produced using simple and low cost casting methods, but are dependent upon the deflection response required.

Viability of joined flight for small unmanned aerial vehicles

ABSTRACTThe range of small, electrically powered UAVs is still limited by the mass specific energy of batteries. This paper investigates the idea that, in cases where multiple aircraft must transit to the same location, savings in mass or an extension of achievable range are possible when they join wingtip-to-wingtip. The viability of joined flight is investigated by quantifying the relative magnitude of savings resulting from increased aerodynamic efficiency and that of penalties due to the increased structural and component weights. Through a parametric analysis the level of savings achievable is found to be greatly dependent on the proportion of the flight spent in a joined configuration and aircraft design parameters such as wing loading, aspect ratio and the added weight of the joining mechanism. A custom, multidisciplinary UAV sizing algorithm is presented and utilised to design several sample aircraft, featuring two different joining mechanism architectures. The results verify the findings of the parametric study and indicate that mass savings are possible only for moderate to low aspect ratios, with semi-permanent magnetic joining mechanism performing better than rigid structural ones, even when the joined fight segment accounts for only 30% of the total airborne time.

Highly Multifunctional Dopamine-Functionalized Reduced Graphene Oxide Supercapacitors

Summary Batteries and supercapacitors that possess the mechanical properties of structural composites are desirable for electric vehicles and aerospace applications, as energy may be stored within structural panels to realize significant mass and volume savings. However, current electrode materials suffer from poor mechanical performance, as described by a low multifunctional efficiency parameter (

Cold Technique in Adult Tonsillectomy Reduces Waste and Cost

To quantify differences in waste and cost of disposable equipment between different tonsillectomy techniques. Prospective study of waste attributable to disposable waste produced by tonsillectomy surgery. Disposable equipment required for tonsillectomy using cold, monopolar electrocautery (ME), and coblation techniques was measured; and differences in mass, volume, and cost of equipment between the 3 techniques were quantified. Cold technique was found to produce the least waste and have the lowest cost attributable to disposable surgical equipment. Projected single-case savings in mass and volume of waste resulting from using cold technique compared to ME were 1.272 kg and 1.013 L, respectively, and 1.043 kg and 1.723 L compared to coblation. Projected single-case savings in cost of disposable equipment for cold technique compared to ME were US$9.35 and US$185.05 compared to coblation. Using cold technique for adult tonsillectomy reduces waste and cost of disposable equipment compared to ME and coblation. Implications for Practice: Surgeons desiring to reduce cost and waste associated with tonsillectomy surgery may consider transitioning to cold technique.

Lightweighting of railway axles for the reduction of unsprung mass and track access charges

The potential for lightweighting of railway axles was investigated to primarily reduce the unsprung mass of rail vehicles. The reduction of unsprung mass equates to an overall lighter train, which will help to reduce track damage, energy consumption and total operating costs. Two approaches were considered for the lightweighting of railway axles, which include a hollow axle design and material substitution using advanced composite materials, to offer a more track-friendly design. The first approach showed that if the outer diameter of a hollow axle is increased by 30% over that of the solid axle diameter, a mass reduction of 56% is achievable for a hollow steel axle design. The second approach explored further mass savings that could be achieved through material substitution of a hollow axle. A systematic approach to material selection for the design requirements and constraints of a railway axle was considered to identify the candidate materials for the application. The optimum material identified was a ‘bismaleimide matrix + carbon fibre composite.’ A hollow axle manufactured from this composite material offered 64% savings in mass when compared to a hollow steel axle, and 84% savings in mass when compared to a solid steel axle. Estimates for the cost savings of lightweighting of an axle were quantified by utilising Network Rail’s variable usage charge calculator, to assess the track access charge savings that can be achieved. For the scenario described in this paper, a potential £5.58 million per year could be saved for an intercity 220/M Voyager train, in terms of variable usage charges, over the entire fleet of 34 trains (four carriages per train) by implementing hollow composite axles. This is an example of a costing approach to support the decision making of lightweighting of rail vehicles.

Benefits and Application Bandwidth of Phenolic Piston Material in Opposed Piston Calipers

<div class="section abstract"><div class="htmlview paragraph">The use of reinforced phenolic composite material in application to hydraulic pistons for brake calipers has been well established in the industry - for sliding calipers (and certain fixed calipers with high piston length to diameter ratios). For decades, customers have enjoyed lower brake fluid temperatures, mass savings, improved corrosion resistance, and smoother brake operation (less judder). However, some persistent concerns remain about the use of phenolic materials for opposed piston calipers. The present work explores two key questions about phenolic piston application in opposed piston calipers. Firstly, do opposed piston calipers see similar benefits? Do high performance aluminum bodied calipers, where the piston may no longer be a dominant heat flow path into the fluid (due to a large amount of conduction and cooling enabled by the housing), still enjoy fluid temperature reductions? Are there still benefits for judder with the much shorter length to diameter ratio the pistons have in these applications? Secondly - it is clear that the much shorter length to diameter ratio of the piston in opposed piston calipers will result in significant increases in contact stress on the piston material at its contact points to the bore, when it is pressurized against pads with significant taper wear - will the phenolic material have adequate durability to withstand this? Can a simple “application guideline” for phenolic pistons be defined, potentially based on piston diameter (governing peak clamp load) and length to diameter ratio (which determines the correlation between clamp load and contact stress in the piston material at the bore contact points)? To address the first question, a battery of comparative tests was run on a high performance 6 piston aluminum-bodied brake calipers with high performance low-metallic brake pads and a large 18” wheel envelope two piece, cast iron plate and aluminum hub rotor. Fluid consumption, drag, brake torque variation, and fluid temperatures were measured through tests designed to exercise these behaviors, with both the production aluminum pistons and prototype phenolic piston calipers. The second question was explored through lab-based durability testing, abusive inertia dyno testing, and analysis of parts failed during testing. Pistons of the same phenolic material (Durez 29504B) were prototyped in opposed-piston caliper configurations in two sizes (51mm and 34mm) and tested to failure. The analysis of the data changed the authors’ initial thinking substantially about the failure mechanics of the piston in severe use, but still resulted in a simple, free body diagram based application guideline and a clear path for future work.</div></div>

Model of a structural battery and its potential for system level mass savings

Structural batteries are materials that can carry mechanical load while storing electrical energy. This is achieved by combining the properties of carbon fiber composites and lithium ion batteries. There are many design parameters for a structural battery and in order to understand their impact and importance, this paper presents a model for multifunctional performance. The mechanical behavior and electrical energy storage of the structural battery are matched to the mechanical behavior of a conventional carbon fiber composite, and the electrical energy storage of a standard lithium ion battery. The latter are both monofunctional and have known performance and mass. In order to calculate the benefit of using structural batteries, the mass of the structural battery is compared to that of the two monofunctional systems. There is often an inverse relationship between the mechanical and electrochemical properties of multifunctional materials, in order to understand these relationships a sensitivity analysis is performed on variables for the structural battery. This gives new insight into the complex multifunctional design of structural batteries. The results show that it is possible to save mass compared to monofunctional systems but that it depends strongly on the structure it is compared with. With improvements to the design of the structural battery it would be possible to achieve mass saving compared to state-of-the-art composite laminates and lithium ion batteries.

Simulating Heat Transfer During Transient Dropwise Condensation on a Low-Thermal-Conductivity Substrate.

The instantaneous heat-transfer performance of a surface is dictated by the number and sizes of drops on the surface. While performance averaged over longer times is of interest from a technology standpoint, accurate simulation of the transient state is important in condenser design because the maximum heat rejection of the surface occurs in this range. Steady-state dropwise condensation can be thought of as a collection of transient dropwise condensation cycles occurring in parallel. Traditional simulation of dropwise condensation has focused on making comparisons with experimental drop-size distributions at later times, after the process has reached a statistical stationary phase where the heat transfer is lower. Understanding how to model and simulate transient dropwise condensation where a maximum in heat transfer occurs will help us design higher heat-rejecting surfaces. Additionally, a constant temperature difference between the steam and the surface below the drop is assumed. While often valid, there are some cases where this is not valid, and measuring the drop growth rate is required. We report a way to simulate transient dropwise condensation using a measured population averaged drop growth rate. The simulation reasonably predicts the time evolution of the number density of drops, fractional coverage, normalized condensate volume, and median drop radius for pendant mode dropwise condensation experiments on a cooled, horizontal, dodecyltrichlorosilane-coated glass surface. It was also found that assuming a constant temperature difference grossly underpredicts the heat transfer. Modification of the single-drop heat-transfer model to include substrate conduction and a thermal boundary layer shows that in the limit of low thermal conductivity the drop growth rate is constant for large drops. Additionally, a comparison between experiments and simulation shows that condensation might be initialized by nucleation onto fixed sites and then transitions to random nucleation as more sites become activated and more favorable. Understanding how a substrate's thermal properties affect the progression of dropwise condensation is important in determining the removal performance of the surface. With the commercialization of 3D printing, it is possible to fabricate low-cost, lightweight, plastic substrates with physical texturing for condensation applications where mass and cost savings are critical.

Thermal processing and thermal analysis of AlSi12–SiC hybrid composites sintered

Metal powders are used in industry for a diversity of products and applications. Metal matrix composites are materials developed through advanced methods with increased characteristics that surpass those of conventional materials. In recent years, the aluminum alloy matrix composites (AlSiX/graphite, AlSiMg/SiC, Al/SiC) are considered better substitute materials for steel components because of their higher strength-to-mass ratio which results in significant mass savings, these materials being successfully used in the construction of automotive components such as brakes and clutches. The paper presents a study concerning the specificities of the sintering technology using solar energy of an AlSi12–SiC hybrid composite, made by powder metallurgy performed at PROMES-CNRS at Font-Romeu-Odeillo-France (MSSFs facility furnaces). Based on the collected data, conclusions could be drawn on the heating mode and the effect of the concentrated power of the parabola on the sintering curves recorded by thermal analysis. The qualification of the sintered samples is performed by structural, DIL and DSC analyses.

Preparation of PAN-based carbon fiber/Co3O4 composite and potential application in structural lithium-ion battery anodes

Lightweight polyacrylonitrile (PAN)-based carbon fiber can give volume and mass savings, which has been considered as a promising anode material for structural lithium-ion batteries (SLIBs). However, the current issue is the limitation of low capacity. To improve the situation, a novel PAN-based carbon fiber/Co3O4 composite (CF/Co3O4) has been developed through a chemical deposition method. Since combining advantage of high theoretical specific capacity of Co3O4 and great electroconductivity as well as strong mechanical of carbon fiber, the prepared CF/Co3O4 shows excellent performances as an anode material for SLIBs. It presents a coulombic efficiency of over 99% and stable cyclic ability. Even if the number of cycles reaches to 150, a steady discharge reversible capacity up to 625 mAh g−1 can be retained, approximately 2.7 times as much as pure CF (~ 230 mAh g−1). The improved cycling stability of CF/Co3O4 can be owed to the interactions between CF and Co3O4 anchored on the CF. Furthermore, a solid polymer electrolyte was also prepared with the flexibility, which shows a steady discharge reversible capacity of 500 mAh g−1 at 100 mA g−1. The paper provides an affordable method to solve the problem of the limitation of capacity in current SLIBs when using commercial carbon fibers as anode materials.

BISALLOY STRUCTURAL 100 STEEL

Abstract Bisalloy is a series of high-strength, quenched and tempered steels with mass savings of up to 30% over conventional steels. The number in the name indicates the minimum yield strength in ksi. This datasheet provides information on composition, physical properties, hardness, and shear strength. It also includes information on forming and machining. Filing Code: SA-846. Producer or source: Bisalloy Steels Group Limited.

A Cylindrical Linear Permanent Magnet Vernier Hybrid Machine for Wave Energy

In some wave energy converters, there is a need for linear electrical machines where all the active parts are mounted on the stator. For this reason the linear Vernier hybrid machine has been investigated. In other research, it is analyzed in 2D and assumed to have a flat cross section. In this paper a cylindrical version of the Vernier hybrid machine is presented and analyzed. A geometrical model is used to investigate potential mass savings of the cylindrical version, and a finite element analysis design study is used to demonstrate a potential improvement in performance. A proof of concept laboratory scale model has been built and tested to validate the predictions.

Bioinspired Electrodes for Structural Supercapacitors

The demand for efficient energy storage devices has increased tremendously as hybrid vehicles, portable, and even wearable electronics have become a significant and inseparable part of our everyday lives. With respect to the increasing demands for energy storage, new battery and supercapacitor technologies have emerged. However, their high weight and size remain a drag on the development of next-generation electronics. Structural energy storage devices constitute a firm solution since they can potentially address both energy storage and structural functionalities in a single unit leading to mass and volume savings. Here, we utilize the ‘brick and mortar’ structure of nacre to fabricate mechanically strong supercapacitor electrodes. We report on electrodes consisting of branched aramid nanofibers (BANFs) and reduced dopamine functionalized graphene oxide (rGO-DOPA). Branched aramid nanofibers, nanoscale Kevlar® fibers, are promising due to their superior mechanical properties, such as stiffness and tensile strength. Furthermore, rGO is an ideal material for supercapacitor electrodes due to its high surface area and electrical conductivity. Graphene oxide was functionalized with dopamine - a molecule mimicking the highly adhesive mussel proteins - to improve interfacial interactions. The electrodes were fabricated using vacuum filtration, where BANFs interact with GO-DOPA through extensive hydrogen bonding and π-π stacking interactions. Coordination bonding was also achieved by the addition of calcium ions that cause chelation. The electrodes were characterized using scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). We studied the effect of dopamine functionalization, calcium ion addition and BANF composition on the mechanical and electrochemical performance. Tensile testing, cyclic voltammetry, and galvanostatic charge-discharge were used to evaluate the properties.