Published on March 6, 2014
Material Selection for Shark Resistant Chainmail Gloves By: Zack Davison Cody Potyczka Juho Vaittinen Joel Lappalainen
Our goal was to create a high quality chainmail glove, specifically geared toward scuba divers. This product is mainly to protect against manageable sharks, which would be up to 6 feet, which one could come into contact with while in the ocean. The goal of the glove is keep appendages from being torn off or removed from the sharpness and abundance of teeth that sharks have in the event of a shark attack. Our target demographic is chosen based on people that are part of dive clubs, since only experienced and serious scuba divers have a real need for a product such as this. This is projected to range between 148,000 to 482,000 divers per year as the average amount of people who become certified each year sits around 500,000. The worldwide population of divers is about 3 to 6 million. The quality is excellent for this product, which only means that the cost will be high, but also worth the money. Throughout the report you’ll find the material that we selected and how we decided to choose it. These gloves can be fitted to the user in a small variety of general sizes. (Courtesy of www.stephenfrinkphoto.com)
Benchmark material We chose 304 stainless steel for our benchmark material because it is most widely used grade of stainless steel on the market. It has excellent corrosion resistance so it can be used in sea water conditions and has excellent forming properties to bend the wire to the desired ring form. 304 stainless steel also has great welding properties to keep the rings together. 304 can be bought for about $1.30 a pound, so it’s fairly cheap considering the quality we want in our product. We decided that corrosion resistance is a priority so it needed to be excellent. 304 stainless has a shear strength of 36.6 ksi which we thought was a little more than we needed so we lowered it to 25 ksi. The wire that we are forming is only 1-‐3mm in diameter, which makes it easy to bend. 304 stainless has a 40% elongation to break so we decided to lower it to 20% because the wire is so thin and we are using a machine to close the rings. 304 stainless has a hardness of 70 Rockwell B scale but we placed our target value a little lower because it was more than we needed. Weldability in 304 is excellent but we don’t need it to be better than “good” so we lowered our target to “good” weldability. Weight for our product was somewhat important of a factor and 304 stainless has a density of 0.289lb/in³ so we only lowered that to 0.250lb/in³. The 304 stainless wire has a yield strength of 31,200 psi which is much more than what we needed so we lowered that to 20,000 psi. Our final factor was cost, which wasn’t that important because our product was meant to be high-‐end shark resistant gloves which are sold to mostly experienced divers because of their reliability to resist shark attacks. The 304 stainless is fairly cheap so we decided to increase the price to $2,500 per ton to put higher quality metals in the mix. The 304 stainless steel wire we chose is used to manufacture a similar glove so it our choice will be fairly close to that or better.
Manufacturing Process Start with coiled wire from supplier. The diameter can range from 1 to 2.3 mm. Place the end of the wire into the former (smooth bar with a hole through it and crank on the end) and wrap tightly around and together until the former is full. The former can range from 2-‐5 mm and dictates the inside diameter of the ring. (Mandrel Courtesy of metalsmithing.wonderhowto.com) The rings are then joined Remove the coiled up wire from the together by way of a “4 in 1” former and cut through all of the coils pattern where 1 ring has 4 so that the rings are all open. attached to it. A ring mesh-‐joining machine squeezes the (Ring mesh joiner Courtesy of Azon.com) desired ring together and welds it at the same time, which is controlled by the operator as well as the pace of the work.
Material Screening Matrix 304 Stainless Characteristic Import Benchmark Target (Property) Rating Corrosion 10 Resistance Shear 9 (1/2 UTS) Formability 7 (Ductility) Abrasion Wear 7 (Rockwell B) Weldability 6 Weight (Density 4 lb/in3) Bending (YS) 3 Cost 2 ($ per ton) Marine Grade Aluminum Value Pure Grade Austenitic Titanium Stainless Steel Matl Ind. Matl Ind. Matl Ind. Value Value Rate Score Rate Score Rate Score Good Excell. Excell. 10 100 Excell. 10 100 Good 7 70 36600 25000 21000 5 45 25000 10 90 37500 10 90 40% 20% 22% 10 70 20% 10 70 55% 10 70 70 Rb 65 Rb 44 Rb 4 28 70 Rb 10 70 95 Rb 10 70 Excellent Good Good 10 60 Fair 6 36 Excell. 10 60 0.289 lb/in3 .250 lb/in3 .096 lb/in3 10 40 .163 lb/in3 10 40 .291 lb/in3 5 20 31200 20000 21000 10 30 50000 10 30 30000 10 30 $1,000 $2,500 $1,500 10 20 25,000 1 2 $2,500 10 20 Overall Score 393 Overall Score 438 Overall Score 430
Specific Material Matrix Grade 1 Grade 2 Grade 3 Grade 4 Characteristic Matl Matl Matl Matl Value Value Value Value (Property) Rate Rate Rate Rate Corrosion Good 2 Good 2 Excellent 4 Good 2 Resistance Shear 17500 1 25000 2 32500 3 40000 4 (1/2 UTS) Formability 25% 4 20% 3 18% 2 15% 1 (Ductility) Abrasion Wear (Rockwell B) 70 1 80 2 90 3 100 4 Weldability Excellent 4 Excellent 4 Good 2 Good 2 Bending (YS) 25000 1 40000 2 55000 3 70000 4 $25 3 $40 1 $30 2 Cost $23 4 ($ per kg) Gr1 17 Overall Score Gr2 18 Gr3 18 Gr4 19
Material Chosen We chose Pure Titanium Grade 4 as our winning candidate and the decision was very close between the four different grades. Titanium may have been expensive, but since it wasn’t a cost issue but a performance battle with strength and corrosion resistance, which for this product, titanium is excellent. The manufacturing process was our biggest dilemma in choosing our material because titanium is so strong and hard to form and weld, but pure grade titanium is much easier to work with and has perfectly adequate qualities. Prototype Testing Shark gloves are not intended to protect the user from getting their hand bit off in the rare case of a fully-‐grown great white attack. The gloves are designed to protect only against smaller sharks, and the gloves would mainly protect the fingers. The shark makes it’s damage with biting in two ways; first there's the actual impact and pressure of teeth cutting to the object of biting, and then there's the back and forth-‐type of movement by its' jaws it generates to cut through the flesh. Product testing There's basically only one main purpose for this glove to fill its' required function, the testing of this glove would test just that ability – ability to resist a shark's bite. The ultimate simulation of shark's jaws, the shark-‐bite-‐machine would do the final testing. The glove would be put onto artificial hand, and the hand would be put into the machine. The machine bites the jaws together and moves its' jaws back and forth to simulate a real shark bite. The idea is to resist the penetration from the teeth. (Picture from: http://loadoutroom.com/wp-‐content/uploads/2012/05/NTI-‐LOADOUTROOM-‐dot-‐com-‐e1335930849516-‐ 764x1024.jpg )
Manufacturing Testing Although the method of manufacturing will have a reasonable tolerance for the rings, there's still a chance that the rings could come out different sizes in the manufacturing process. Before going to the Ring Mesh Joining machine, the metal rings would be tested for their size every so often to make sure they are similar sizes, which determines how close the rings stay together. The closer they are together the more protection from teeth they will give. The test would include measuring the inner and outer diameter. There would be a pin that acts as a go-‐gage that all the rings would be put through to ensure the right diametrical size. After coming from the Ring Mesh Joining machine and before going to the final product test, there will be a stretching test to make sure the welds are holding up. This method would include pulling a single ring in separate directions until destruction. This is a good way to see how well the Ring Mesh Joining machine is operating with its welds. Executive Summary Our findings have shown that the best material for shark resistant chainmail gloves is Pure Titanium Grade 4. Although Marine Grade Aluminum and Austenitic Stainless Steel are also both great choices, which is shown in our matrices, but they didn’t quite have the qualities that we were looking for. 304 Stainless Steel was our benchmark material as this is the ideal metal for this material based on cost and our desired properties. We wanted a higher quality material so we cut cost out of the equation and came up with titanium. It’s lighter and stronger and has great corrosion resistance. Our manufacturing process includes buying wire by the coil at the desired diameter and creating the links by hand with a simple mandrel machine, which will save money. A Ring Mesh Joining machine is how we will accomplish “sewing” all of the rings together to form the glove. Our projections for the target demographic of experienced divers is somewhere in between 148,000 and 482,000 and we believe this process will suffice for the amount of gloves we will sell. Lastly, we will be testing the product during the manufacturing process and after the product is finished. The manufacturing testing will involve testing the individual rings for weld strength and rigidity. The product testing will involve using a “shark bite” machine, which will simulate a shark latching it’s jaws on to the user’s hand and seeing how the overall glove stands up to puncture into an artificial hand.
References "All About Stainless Steel." Berkley Point. N.p., Web. 3 Dec. 2013. <http://www.berkeleypoint.com/learning/stainless.html>. "Charleston Aluminum Marine Products." . Charleston Aluminum, LLC, 2013. Web. 20 Nov 2013. <http://www.charlestonaluminum.com/marine_products.php>. "Ring Mesh Joining Machine." www.azon.com. Azon Corporation, n.d. Web. 3 Dec 2013. "Titanium Grade 1." . ASM Aerospace Specification Metals Inc., n.d. Web. 19 Nov 2013. <http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=MTU010>. "Titanium Grade Overview." . Titanium Specialists, 2013. Web. 20 Nov 2013. <http://www.supraalloys.com/titanium-‐grades.php>. "Titanium and Titanium Base Alloys." . Dynamic Metals International LLC, 2005. Web. 20 Nov 2013. <http://www.dynamicmetals.net/titanium.html>. Alibaba.com, 2013. Web. 3 Dec 2013. <http://www.alibaba.com/showroom/grade-‐1-‐ titanium-‐sheet.html>. Australian Stainless Steel Development Association (ASSDA). ASSDA, Oct. 1996. Web. 10 Nov. 2013. <http://www.assda.asn.au/index.php?option=com_content&task=view&id=170 &Itemid=152>. Blackwell, Paul, and Trevor Barker. Butted Mail: A Mailmaker's Guide 4th Edition. Ed. Robert F. John. N.p., 2 Apr. 2001. Web. 10 Nov. 2013. Nelson, Bryan. "Which Shark Species Has the Strongest Bite?." www.discovery.com. Discovery Communications, LLC, 21 Oct 2012. Web. 3 Dec 2013. Webb, Brandon. RDT&E Look: The Neptunic Combat Multi-‐Purpose Glove. N.p., 2 May 2012. Web. 3 Dec. 2013. <http://loadoutroom.com/1979/rdte-‐look-‐the-‐neptunic-‐ combat-‐multi-‐purpose-‐glove/>.
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