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Riveting know-how allows light-weight magnesium fasteners for gasoline effectivity

PNNL’s new Rotating Hammer Riveting know-how allows light-weight magnesium rivets for use with out preheating the rivets. The method can also be quicker than typical riveting. Credit score: Andrea Starr | Pacific Northwest Nationwide Laboratory

If Rosie the Riveter had entry to a brand new riveting know-how, the character of WWII fame may have labored quicker and made lighter merchandise. Right now, a newly patented riveting method developed by Pacific Northwest Nationwide Laboratory (PNNL) makes light-weight magnesium simpler to type and reduces the time wanted to affix every rivet.

Magnesium is likely one of the lightest metals—making it ideally suited for higher gasoline financial system in automobiles. However it trails behind aluminum and metal in industrial use as a result of it is typically brittle and troublesome to form into structural components. The brand new friction-based riveting know-how, known as Rotating Hammer Riveting (RHR), avoids the necessity to pre-heat the metallic to type the rivet and improves the fastening joint. It additionally works on aluminum rivets, that are utilized in airplane building. The processing methodology can also be considerably quicker, which may save money and time in airplane and car building.

Making an previous course of new

Riveting is likely one of the oldest identified strategies for becoming a member of completely different supplies. The traditional Egyptians used wood rivets to affix metallic handles to clay jars. Riveting then handed down via ages and throughout civilizations and could be seen in Roman buildings, Viking ships, Medieval armor, and different historic objects.

With the appearance of latest supplies within the nineteenth and twentieth centuries, metal riveting turned ubiquitous throughout a large array of structural purposes starting from buildings to bridges and battleships to airplanes. However the riveting course of remained nearly unchanged. Take a cylindrical piece of metallic with a mushroom formed cap on one finish, slip the shank or stem via holes within the two supplies you wish to be a part of, then beat on one finish of the shank with a hammer to type a second head that clinches the 2 supplies collectively.

Attempt to try this with a magnesium rivet and it could in all probability shatter. Whereas a magnesium alloy has excessive energy for its mild weight, magnesium tends to be brittle at room temperature. So sometimes, magnesium alloy rivets are heated to get them comfortable sufficient to hammer and bend with out breaking.

Heating every rivet is sluggish and costly, so magnesium rivets are not often used though they’re 30% lighter than the aluminum rivets which are used to affix magnesium sheet metallic.

Hammering a brand new sort of riveting know-how

The RHR know-how, developed by PNNL, doesn’t require pre-heating the magnesium rivets. The method, described within the Journal of Magnesium and Alloys, makes use of magnesium rivets with out pre-heating. And it does so 4 to 12 instances quicker, whereas additionally eliminating the time it takes to pre-heat rivets in typical impression riveting and delivering added advantages of enhanced energy and corrosion prevention properties.

RHR is an offshoot of friction stir welding. The method makes use of a small rotating device, known as a hammer. The rotational power generates warmth by way of friction and deformation, which softens the magnesium sufficient to type the rivet head whereas additionally mixing the underside of the rivet’s head to metallurgically bond with the underlying metallic sheet. This merging of metals varieties a steady bond that wards off corrosion.

“It took many makes an attempt to seek out the best steadiness between the rotational pace of the hammer and the pace at which we plunged it into the rivet,” stated lead researcher Tianhao Wang. “However we finally discovered a candy spot within the processing vary the place the rivet head didn’t adhere to the device, nor crack through the RHR course of.”

The newly patented course of deforms the metallic such that its crystalline construction is altered. Utilizing high-powered microscopes, researchers have been in a position to see how the grains have been refined and reoriented to make the magnesium extra formable and stronger.

Riveting options for plane manufacturing

Corresponding creator Scott Whalen notes that RHR works on aluminum rivets as properly, like these utilized in plane. With lots of of 1000’s of rivets on each industrial airplane—largely constituted of aluminum alloy 2024—Whalen says the method may cut back prices and enhance effectivity on the manufacturing line.

Rivets made from aluminum alloy 2024 are too robust to rivet if saved at room temperature. So, they should be annealed, or softened, after which saved in a freezer to maintain them comfortable earlier than riveting.

“As soon as on the manufacturing line, these “ice field rivets” should be utilized in lower than 15–half-hour, in any other case they turn into too laborious to rivet,” stated Whalen. “Nevertheless, RHR can rivet aluminum 2024 rivets after they’re within the totally hardened state, so chilly storage will not be wanted. This implies rivets would now not have to be saved in a freezer, riveting will not be time delicate, and unused rivets now not have to be re-heat handled and re-placed into chilly storage.”

Sooner friction-based riveting know-how

RHR processing of aluminum is extraordinarily quick. Typical riveting takes between 1–3 seconds per rivet, whereas RHR requires simply 0.25 seconds. That point financial savings may translate into 40 hours saved per 100,000 rivets. “That may imply one full week much less spent riveting on only a fraction of 1 industrial airliner if RHR have been adopted,” stated Whalen.

RHR is only one of a collection of disruptive manufacturing applied sciences to course of metallic alloys and composites being developed by PNNL. These Strong Section Processing strategies contain deforming supplies with out melting to warmth, combine, fabricate, and be a part of metals and different supplies. The ensuing supplies have extraordinary properties in comparison with these produced by typical manufacturing strategies.


System bonds metallic and plastic inside seconds


Extra data:
Tianhao Wang et al, Friction-based riveting method for AZ31 magnesium alloy, Journal of Magnesium and Alloys (2021). DOI: 10.1016/j.jma.2021.06.004

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Pacific Northwest Nationwide Laboratory


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