http://phys.org/news/2019-04-mit-nasa-kind-airplane-wing.html

Dansk delvis tilrettet maskinoversættelse:

MIT og NASA ingeniører demonstrerer en ny slags flyvinge

Et team af ingeniører har bygget og testet en radikalt ny slags flyvinge, der er samlet fra hundredvis af små ensartede stykker. Vingen kan ændre form og derved styre flyet og tænkes at ville kunne have betydelig værdi inden for flyproduktion og give stor vedligeholdelseseffektivitet, siger forskerne.

Den nye vingekonstruktion er blevet testet i en NASA-vindtunnel og beskrives i tidsskriftet "Smart Materials and Structures". Blandt forfatterner er forskeringeniør Nicholas Cramer på NASA Ames i Californien; Kenneth Cheung, tidligere hos MIT og nu hos NASA Ames; Benjamin Jenett fra MIT's Center for Bits and Atoms; og otte andre.

I stedet for at kræve adskilte bevægelige overflader, som konventionelle vinger, gør det nye samlingssystem det muligt at deformere hele vingen eller dele af vingen ved at inkorporere en blanding af stive og fleksible komponenter i vingestrukturen. De små underenheder, der er boltet sammen for at danne en åben, letvægt-gitterramme, dækkes derefter med et tyndt lag polymermateriale.

Resultatet er en vinge, der er meget lettere og dermed meget mere energieffektiv end de konventionelle design, der enten er lavet af metal eller af kompositter, siger forskerne. Fordi strukturen, der består af tusindvis af små trekanter af tændstik-lignende stave, hovedsagelig består af tomt rum, udgør det et mekanisk "metamateriale", der kombinerer den strukturelle stivhed som en gummiagtig polymer og den ekstremt lette densitet af en luftholdig airgel .

Jenett forklarer, at hver fase af en flynings start, landing, cruising, manøvrering osv. hver sit eget forskellige sæt optimale vingeparametre, så en konventionel vinge må nødvendigvis være et kompromis, der ikke er optimeret til nogen af disse, og derfor koster dette effektivitet. En vinge, der konstant er deformerbar, vil kunne give en langt bedre tilnærmelse til den optimale konfiguration for hvert trin under flyvningen.

Det vil være muligt at bruge motorer og kabler til at frembringe de kræfter, der kræves for at deformere vingerne, men forskerholdet har designet et system, som automatisk reagerer på ændringer ved de aerodynamiske belastningsbetingelser ved at skifte form – dvs. som en slags selvjusterende, passiv vinge-rekonfigurationsproces.

"Vi kan opnå effektivitet ved at matche formen til belastningerne ved forskellige angrebsvinkler," siger Cramer, der er artiklens hovedforfatter. "Vi kan producere den nøjagtig samme adfærd, som man ville gøre aktivt, men vi får det altså til at blive gjort passivt."

Dette opnås ved omhyggelig udformning af de relative positioner af stiverne med forskellige mængder af fleksibilitet eller stivhed, designet således, at vingen eller dele af den bøjer på bestemte måder som reaktion på bestemte former for belastninger.

Forskergruppen demonstrerede det grundlæggende princip for nogle år siden og producerede i første omgang en 1 meter vinge, som kan sammenlignes med størrelsen af ​​typiske fjernstyrede modelfly. Den nye version, der er cirka 5 meter, kan sammenlignes i en vinge af et en-personers fly og ville være let at fremstille.

Denne version blev dog håndsamlet af et hold af kandidatstuderende. Dens design af ens elementer betyder, at samlingen vil kunne ske ved hjælp af en sværm af små, enkle, autonome robotter. Design og test af robotmonteringssystemet omtales i en anden artikel, siger Jenett.

Man bruger sprøjtestøbning med polyethylenharpiks i en kompleks 3-D-form til at frembringe hver del i en hul kube, der består af stivere i størrelse som tændstikker.

"Nu har vi en fremstillingsmetode," siger han. Den indledende investering i værktøj er gjort og delene er billige," siger han. "Vi har kasser og kasser af dem, og de er ens."

Det resulterende gitter har en vægt på 5,6 kg pr. kubikmeter. Til sammenligning har gummi en vægt på ca. 1.500 kg pr. kubikmeter. "De har samme stivhed, men vores har en densitet, der er omkring en tusindedel," siger Jenett.

Fordi den samlede konfiguration af vingen er opbygget fra små underenheder, er det virkelig ligegyldigt, hvad formen er. "Man vil kunne lave en hvilken som helst geometri, som man måtte ønske sig", siger han. "Den kendsgerning, at de fleste fly er af samme form" – hovedsageligt bestående af et rør med vinger – "er som nævnt ikke den mest effektive form."

Undersøgelser har vist, at en integreret krops- og vingestruktur ville kunne være langt mere effektiv til mange anvendelser, siger han, og med dette nye system ville de let kunne bygges, testes, ændres og testes igen.

"Metoden vil kunne reducere omkostningerne og øge ydeevnen for store, lette og stive strukturer," siger Daniel Campbell, der er forsker hos Aurora Flight Sciences, et Boeing-selskab, der ikke var involveret i denne forskning. "De mest lovende umiddelbare anvendelser ville være i luftskibe og rumbaserede strukturer, f.eks. i antenner."

Den nye vinge blev designet til at være så stor, at den kunne være i NASAs højhastighedstunnel ved Langley Research Center. Vingen fungerede bedre end forventet, siger Jenett.

Det samme system ville kunne bruges til at lave andre strukturer, siger Jenett, herunder vindmøllernes vingelignende blade, hvor man på grund af muligheden for at lave monteringen på stedet ville kunne undgå de praktiske problemer med at skulle transportere de stadig længere vingeblade. Lignende teknologi ville kunne udvikles til at opbygge rumstationer, broer og andre krævende strukturer.

MIT and NASA engineers demonstrate a new kind of airplane wing

1. apr. 2019 – af David L. Chandler, Massachusetts Institute of Technology

A team of engineers has built and tested a radically new kind of airplane wing, assembled from hundreds of tiny identical pieces. The wing can change shape to control the plane's flight, and could provide a significant boost in aircraft production, flight, and maintenance efficiency, the researchers say.

The new approach to wing construction could afford greater flexibility in the design and manufacturing of future aircraft. The new wing design was tested in a NASA wind tunnel and is described today in a paper in the journal Smart Materials and Structures, co-authored by research engineer Nicholas Cramer at NASA Ames in California; MIT alumnus Kenneth Cheung SM '07 Ph.D. '12, now at NASA Ames; Benjamin Jenett, a graduate student in MIT's Center for Bits and Atoms; and eight others.

Instead of requiring separate movable surfaces such as ailerons to control the roll and pitch of the plane, as conventional wings do, the new assembly system makes it possible to deform the whole wing, or parts of it, by incorporating a mix of stiff and flexible components in its structure. The tiny subassemblies, which are bolted together to form an open, lightweight lattice framework, are then covered with a thin layer of similar polymer material as the framework.

The result is a wing that is much lighter, and thus much more energy efficient, than those with conventional designs, whether made from metal or composites, the researchers say. Because the structure, comprising thousands of tiny triangles of matchstick-like struts, is composed mostly of empty space, it forms a mechanical "metamaterial" that combines the structural stiffness of a rubber-like polymer and the extreme lightness and low density of an aerogel.

Jenett explains that for each of the phases of a flight—takeoff and landing, cruising, maneuvering and so on—each has its own, different set of optimal wing parameters, so a conventional wing is necessarily a compromise that is not optimized for any of these, and therefore sacrifices efficiency. A wing that is constantly deformable could provide a much better approximation of the best configuration for each stage.

While it would be possible to include motors and cables to produce the forces needed to deform the wings, the team has taken this a step further and designed a system that automatically responds to changes in its aerodynamic loading conditions by shifting its shape—a sort of self-adjusting, passive wing-reconfiguration process.

"We're able to gain efficiency by matching the shape to the loads at different angles of attack," says Cramer, the paper's lead author. "We're able to produce the exact same behavior you would do actively, but we did it passively."

This is all accomplished by the careful design of the relative positions of struts with different amounts of flexibility or stiffness, designed so that the wing, or sections of it, bend in specific ways in response to particular kinds of stresses.

Cheung and others demonstrated the basic underlying principle a few years ago, producing a wing about a meter long, comparable to the size of typical remote-controlled model aircraft. The new version, about five times as long, is comparable in size to the wing of a real single-seater plane and could be easy to manufacture.

While this version was hand-assembled by a team of graduate students, the repetitive process is designed to be easily accomplished by a swarm of small, simple autonomous assembly robots. The design and testing of the robotic assembly system is the subject of an upcoming paper, Jenett says.

The individual parts for the previous wing were cut using a waterjet system, and it took several minutes to make each part, Jenett says. The new system uses injection molding with polyethylene resin in a complex 3-D mold, and produces each part—essentially a hollow cube made up of matchstick-size struts along each edge—in just 17 seconds, he says, which brings it a long way closer to scalable production levels.

"Now we have a manufacturing method," he says. While there's an upfront investment in tooling, once that's done, "the parts are cheap," he says. "We have boxes and boxes of them, all the same."

The resulting lattice, he says, has a density of 5.6 kilograms per cubic meter. By way of comparison, rubber has a density of about 1,500 kilograms per cubic meter. "They have the same stiffness, but ours has less than roughly one-thousandth of the density," Jenett says.

Because the overall configuration of the wing or other structure is built up from tiny subunits, it really doesn't matter what the shape is. "You can make any geometry you want," he says. "The fact that most aircraft are the same shape"—essentially a tube with wings—"is because of expense. It's not always the most efficient shape." But massive investments in design, tooling, and production processes make it easier to stay with long-established configurations.

Studies have shown that an integrated body and wing structure could be far more efficient for many applications, he says, and with this system those could be easily built, tested, modified, and retested.

"The research shows promise for reducing cost and increasing the performance for large, light weight, stiff structures," says Daniel Campbell, a structures researcher at Aurora Flight Sciences, a Boeing company, who was not involved in this research. "Most promising near-term applications are structural applications for airships and space-based structures, such as antennas."

The new wing was designed to be as large as could be accommodated in NASA's high-speed wind tunnel at Langley Research Center, where it performed even a bit better than predicted, Jenett says.

The same system could be used to make other structures as well, Jenett says, including the wing-like blades of wind turbines, where the ability to do on-site assembly could avoid the problems of transporting ever-longer blades. Similar assemblies are being developed to build space structures, and could eventually be useful for bridges and other high performance structures.

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Explore further'Morphing' wing could enable more efficient plane manufacturing and flight

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Provided by Massachusetts Institute of Technology

This story is republished courtesy of MIT News (web.mit.edu/newsoffice/), a popular site that covers news about MIT research, innovation and teaching.11004 shares

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