peacefuljeffrey 0 #1 July 23, 2004 Titanium was harder than stainless steel would have been?! ------------------------------------------------------------------------ All I've ever heard about titanium knives is that they are not as hard as stainless steel, for the most part. Now there is a current article (online and in the papers) that says the Concorde crash occurred because the tire was punctured by a piece of debris from a DC-10 that was soooo hard, essentially because it was titanium! Here's a linked article: Runway debris linked to Concorde crash I want to know what knife-people and metallurgists make out of these claims, which seem to come from the "experts" hired by people suing over the crash. Are they employing mysticism and myth about titanium in order to make illegitimate claims? Would a piece of stainless steel have been incapable of doing what titanium did? Here's a quote from an article I have clipped from the local paper: " 'The strip that should have been in stainless steel turned out to be made of titanium, a stronger alloy that made the plane's tire burst and set off a chain reaction that led to the Concorde crash,' said Jerome Boursican, a lawyer for a pilots' union that is a civil party to the legal case over the crash." Seems to me like it's typical B.S. from a hearse-chasing lawyer who is expecting everyone else to be too dumb to know that stainless steel is harder, in general, than titanium. He seems to have seized on the talk of titanium being stronger "ounce-for-ounce" than steel and turned titanium into some sort of super-metal. What do you all think? Blue skies, -Jeffrey-Jeffrey "With tha thoughts of a militant mind... Hard line, hard line after hard line!" Quote Share this post Link to post Share on other sites
sundevil777 102 #2 July 23, 2004 aviationnow.com (Av week & space tech) is the best place I know to get good info on this kind of stuff. I did a search and there was no info on the wear strip material being alum, SS, or titanium.People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am Quote Share this post Link to post Share on other sites
quade 4 #3 July 23, 2004 Quote Structural titanium alloys are coming in for increased use because they are light, ductile and have good fatigue and corrosion-resistance properties As a result, more manufacturing engineers are learning that machining these alloys can be a tricky job due to their unique physical and chemical properties. The problems that arise in drilling, turning, and grinding of titanium can be better understood if we look at these properties. They hold the key to successful machining operations. The specific weight of titanium is about two thirds that of steel and about 60 percent higher than that of aluminum. In tensile and sheet stiffness, titanium falls between steel and aluminum. But titanium's strength (80,000 PSI for pure titanium and 150,000 PSI and above for its alloys) is far greater than that of many alloy steels, giving it the highest strength-to-weight ratio of any of today's structural metals. http://www.titanium.com/titanium/tech_manual/tech2.cfmquade - The World's Most Boring Skydiver Quote Share this post Link to post Share on other sites
jimbarry 0 #4 July 23, 2004 Chemically, titanium is an element, but mills alloy them with other metals for manufacturers. Some softer, some harder, etc. I used to work for a metals distributor. We'd sell bar, tube, and sheet to machine shops and manufacturers like Pratt&Whitney, Otis elevator. In doing so, often these customers would need us to cut large diameter bar into disks. Run of the mill carbon steel and softer stainless would cut fairly easily, but tougher aircraft alloys of steel, and especially the vanadium and chromium alloys of titanium were muthas to cut, needed special band blades, and wore them down quickly. If we had a titanium job running, it would tie up a couple of machines all night long, and cut so damn slow. I don't know what kind of titanium alloys they use in knives, but it's probably the one they mix with aluminum. True, most sports people know that common titanium alloys (like tubing for bike frames, etc.) are about half the weight and almost twice the strength of steel (roughly), but titanium bar and strip certified for aircraft use have a hardness much greater than steel. That said, I'll bet both aircraft alloy stainless AND titanium are harder and stronger than rubber. But that's just my guess... Bottom line, hearse chasing lawyers? Maybe, but since both sides are probably going to have metallurgist experts testify, the end-result could end up being close to correct. Quote Share this post Link to post Share on other sites
peacefuljeffrey 0 #5 July 23, 2004 QuoteTrue, most sports people know that common titanium alloys (like tubing for bike frames, etc.) are about half the weight and almost twice the strength of steel (roughly), but titanium bar and strip certified for aircraft use have a hardness much greater than steel. I have never heard of any titanium alloy that had a hardness greater that that of stainless steel (of which I know there are many types). Not to say that I know they are not, just that I would have expected that high-end titanium knives, which typically cost $100-$400, still are not generally regarded as able to hold an edge (hardness is the factor here) as a high-end stainless steel. I thought that the strength to weight ratio issue still meant that if two pieces of metal -- one titanium, one steel -- are of the same size/volume/shape, that steel would still be stronger because there would still be much more mass (weight) there. EQUAL WEIGHTS of each metal would be a different story, as I understood it. Maybe I'm wrong, but I sure don't think so. QuoteThat said, I'll bet both aircraft alloy stainless AND titanium are harder and stronger than rubber. But that's just my guess... My point exactly. Who's going to say that the airlines are somehow more culpable for the destruction and deaths just because this part was titanium and not steel? What else would be the point of raising the issue? QuoteBottom line, hearse chasing lawyers? Maybe, but since both sides are probably going to have metallurgist experts testify, the end-result could end up being close to correct. I certainly am hoping that if, as I suspect, they are making an issue of this titanium part when there is nothing to it, that experts on the other side set the record straight regarding the relative strength of steel and titanium. --Jeffrey "With tha thoughts of a militant mind... Hard line, hard line after hard line!" Quote Share this post Link to post Share on other sites
jimbarry 0 #6 July 23, 2004 QuoteI have never heard of any titanium alloy that had a hardness greater that that of stainless steel There might be titanium alloys softer than steel, but I'm not familiar with those. All I know is that the toughest band saw blades we had would take the most time on the titanium bar we'd cut. That's a rough comparison of hardness to steel. But then as you said, hardness is different than strength/weight. The certs we'd have to ship with metals which would eventually go into aircraft would list the exact proportions of alloy metals in the product (a "heat" number, each mill batch would be slightly different, but all would have to fall in acceptable ranges, or the customer would reject it), along with other properties, like the rockwell score (hardness). That rockwell value on the cert would be a lot higher (like almost twice as high maybe, it was a while ago) than the 300 and 400 series stainless that would go out. One thing I also remember is the fabricator guys in the plant would say that the titanium sheet we had would bend a lot easier than stainless. Diff alloy maybe. Very unscientific I know, but let's say that's true, and the titanium that damaged that tire was thin (< 1/4") strip. The fact that it was titanium might actually be better than if it had been carbon or stainless steel. If the lawyer's going after the scare factor of the word "titanium", who knows, could backfire. When laborers who earn a living working with their hands tell me something's easy or something's difficult, I tend to believe them. Quote Share this post Link to post Share on other sites
MC208B 0 #7 July 23, 2004 Does anyone really give a shit?!? Quote Share this post Link to post Share on other sites
nacmacfeegle 0 #8 July 23, 2004 "I thought that the strength to weight ratio issue still meant that if two pieces of metal -- one titanium, one steel -- are of the same size/volume/shape, that steel would still be stronger because there would still be much more mass (weight) there." A bit of a misconception there. Density of metal has nothing to do with material strength. consider lead and say tungsten, lead is soft, but heavy, tungsten is relatively light but very hard. Or another example, I could make 2 knife blades from the same piece of steel, one would be left in a nutiral state, and the other heat treated to provide good blade properties, essentially the same mass density of metal, but different properties post heat treatment. As has been said, St/St comes in a huge variety of flavours, some of the tougher ones are called Super Duplex (aka Zeron, SMo, 6mo, etc), not the same stuff that the far east make cheap cutlery out of. Strength is a also a bit of a vague term, sometimes you need materials that are hard, eg knife blades, some times you need materials that are more ductile (bendy) eg staples. Its a horses for courses kind of thing.-------------------- He who receives an idea from me, receives instruction himself without lessening mine; as he who lights his taper at mine, receives light without darkening me. Thomas Jefferson Quote Share this post Link to post Share on other sites
kallend 2,150 #9 July 23, 2004 In a former life I was a metallurgist (prof. of materials engineering). Stainless steel has so many grades it's impossible to make a generalization over properties. 18/8 austenitic is fairly soft and is used for making sinks and pans because it is ductile and can be readily drawn into complex shapes. Martensitic grades (less nickel) can be heat treated like carbon steel to be very hard indeed. Ditto for titanium. It has a hexagonal crystal structure which makes it less ductile than the cubic metals like iron (steel), but even so, pure Ti is not especially hard and strong. When alloyed with things like aluminum and vanadium, it can be extremely strong (especially on a strength/weigh ratio basis). Even so, its strength depends on how it has bee processed, just like steel. So the answer is, it all depends on the grade, and how it has been processed.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
billvon 3,120 #10 July 23, 2004 Too little information. It's quite possible that a titanium component would be harder than its stainless-steel counterpart; it all depends on the alloy and the treatment. But that's beside the point. I think the larger issue is that it's unreasonable to expect that all the components of an aircraft be acceptably weak so they do not cause damage to tires when left on the runway. Sort of like a canopy-collision survivor suing the other jumper because he was using 550 microline instead of dacron on his canopy; dacron wouldn't have sliced him up as badly. Quote Share this post Link to post Share on other sites
peacefuljeffrey 0 #11 July 23, 2004 Quote... dacron wouldn't have sliced him up as badly. ICK! I never used to think much about it, but several posts including this one have made me realize what I had never considered: that having another person under canopy slide by you can leave you cut real nasty by his lines! Gross! Are we talkin' like inches deep or anything? --Jeffrey "With tha thoughts of a militant mind... Hard line, hard line after hard line!" Quote Share this post Link to post Share on other sites
sundevil777 102 #12 July 24, 2004 QuoteAre we talkin' like inches deep or anything? All the way to the bone.People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am Quote Share this post Link to post Share on other sites
sundevil777 102 #13 July 24, 2004 The concorde had chunks of tire rip into and through the wing before. I remember there being 5 times from other articles I read at the time. Landing/takeof speeds are much higher than other jets, and the Concorde doesn't have flaps or slats, it just relies on a large angle of attack to get extra lift for takeoff, and so with so much extra drag, requires a lot of power. http://aviationnow.com/avnow/search/autosuggest.jsp?docid=2012&url=http%3A%2F%2Fwww.aviationnow.com%2Favnow%2Fnews%2Fchannel_comm.jsp%3Fview%3Dstory%26id%3D%2Fnews%2Fconc000817.xml http://aviationnow.com/avnow/search/autosuggest.jsp?docid=4712&url=http%3A%2F%2Fwww.aviationnow.com%2Favnow%2Fnews%2Fchannel_maint.jsp%3Fview%3Dstory%26id%3Dnews%2Frconc0110.xml%3EPeople are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am Quote Share this post Link to post Share on other sites
peacefuljeffrey 0 #14 July 24, 2004 QuoteQuoteAre we talkin' like inches deep or anything? All the way to the bone. OUHGH that's fuckin' awful to think of!! --Jeffrey "With tha thoughts of a militant mind... Hard line, hard line after hard line!" Quote Share this post Link to post Share on other sites
