Topic: Auto Tech: High Strength Steel, Hyundai Style

[Sir Osis of Liver]

Out of curiosity, do the Asian companies tend to use more high strength steel in their vehicles than American companies? I'm trying to understand why comparable Asian vehicles always way weigh less than their American counterparts.

I don't think it's a matter of the type of steel used to denote why non-domestic vehicles tend to weigh less - I think it's more a function of domestic brands caring very little about keeping weight down and focusing instead on 'more is better'.

I'm sure there are some examples out there of domestic vehicles weighing less than their non-domestic competitors.

Like for like, the Germans have typically built the heaviest cars. That has been changing lately as they use more exotic materials and focus more on fuel efficiency.

Building a rigid structure traditionally meant adding material, so you ended up with a 560SEL weighing as much as a Fleetwood even though it had a much smaller footprint. The 560 was like a bank vault, the Fleetwood could best be described as "willowy".

Companies have also identified that quieter cars are seen as being more upscale than louder ones when tested with focus groups, so they have been looking closer at sound level and sound quality. Sound deadening is heavy, so the manufacturer has to make a trade off as far as weight vs sound.

[dirtyjeffer]

basically, what Sir 'O said...cars like the Civic (etc) were always relatively light in terms of weight...it was more about the design of the vehicle (light weight can provide a more nimble feel, reduces fuel consumption and keeps the cost down)...sure, it won't have that "thud" that some of the larger cars offer, but buyers of these vehicles value doors that close with a "thud" far less than things like handling, fuel consumption and price...now, if it were a premium car, where price, fuel economy, etc is less important than "substance", quietness, "solid" road feel, the car is designed with those attributes as more important...if a (example) Mercedes 560SEL felt like a Civic, no one would buy it.

[chignectohead]

As a mechanical engineer, I have to agree with Rupert.

This high strength steel is what, maybe 6% STIFFER than regular steel. Sure it has much higher yield strength, so will deflect more under higher load before it permanently bends.

Hence its use in the safety structure. It will absorb more energy than regular steel before the cabin crushes.

But these marketing types go on and on about HSS being responsible for more rigid bodies. Utter rubbish! Good thing they're not responsible for putting a Professional Engineer's stamp on a design. No, they just go on inventing brand new old wives' tales.

More rigid car bodies come from better geometric design of the parts (moment of inertia), more welds holding stampings together, and simply more material.

Viz. The new Sonata 2.0t is the FAT BOY of the midsizers at 3600 lbs, up 150 from the old model. An Altima is under 3200 lbs.

Wish I'd been there to interview this Hyundai joker to see if he really had a clue. I'm betting not. Hyundai has always been a bit economical with the truth: first, inflated power ratings, second, inflated fuel economy claims. Now this BS about HSS.

[EV-Light]

cost savings? they sure do! 

https://www.youtube.com/watch?v=6s0Oq2SPu48
https://www.youtube.com/watch?v=xC3ZeJ0JNXE

the small overlap test has nothing to do with high strength steel or not...it is based on the design of the vehicle...the 2013 Tuscon was designed prior to the small overlap test...the new Sonata performs better because it was designed afterwards.

http://www.sciencedirect.com/science/article/pii/S0734743X12002011

[Sir Osis of Liver]

As a mechanical engineer, I have to agree with Rupert.

This high strength steel is what, maybe 6% STIFFER than regular steel. Sure it has much higher yield strength, so will deflect more under higher load before it permanently bends.

Hence its use in the safety structure. It will absorb more energy than regular steel before the cabin crushes.

But these marketing types go on and on about HSS being responsible for more rigid bodies. Utter rubbish! Good thing they're not responsible for putting a Professional Engineer's stamp on a design. No, they just go on inventing brand new old wives' tales.

More rigid car bodies come from better geometric design of the parts (moment of inertia), more welds holding stampings together, and simply more material.

Viz. The new Sonata 2.0t is the FAT BOY of the midsizers at 3600 lbs, up 150 from the old model. An Altima is under 3200 lbs.

Wish I'd been there to interview this Hyundai joker to see if he really had a clue. I'm betting not. Hyundai has always been a bit economical with the truth: first, inflated power ratings, second, inflated fuel economy claims. Now this BS about HSS.

Strength:
A measure of the maximum load that can be placed on a material before it permanently deforms or breaks. Engineers often use this as yield stress, σy, as a measure of a material's strength.

Stiffness:
A measure of the amount of deflection that a load causes in a material. Engineers use a value called Young's modulus, E, for stiffness.

You seem to be confusing the two. And being stronger while being stiffer, will definitely allow you to design a rigid chassis with less weight.

http://www.thefabricator.com/article/metalsmaterials/introduction-to-advanced-high-strength-steels---part-i

Here is today’s other baffling science story: In its quest to save weight, Volkswagen is ripping aluminum out of plans and bills-of–material, to replace it – with steel. Not good old steel. They replace it with much better new steel. According to Reuters, “Volkswagen AG is using new high-strength steel to make cars lighter and comply with strict emissions rules, confounding forecasts that aluminum would be the metal of choice for reducing weight.”

High tensile steel is up to six times stronger than conventional steel, and helped Volkswagen reduce the new Golf’s weight by about 100 kg, while also saving money. “Aluminum is about a third of the weight of conventional steel but costs three times as much,” says Reuters

http://www.thetruthaboutcars.com/2013/01/volkswagen-replaces-aluminum-with-steel-to-save-weight-and-money/

Of course you're the same engineer that told us this doozy:

Good thing you're not a structural engineer! High strength steel is NO stiffer than regular steel - sorry to diappoint both you and the marketing departments of the car companies. Steel is steel, and its characteristic Young's modulus doesn't change, so stiffness doesn't either. It will bend more before it fails, and thus absorb more impact energy - that's why you find it in the crash structure.

[Rupert]

   Don't confuse strength with rigidity. OK in my opinion, reduced weight stronger steel is good for parts where rigidity has no bearing on the matter. Crash protection beams in doors and other parts perhaps and... maybe wings and door skins themselves. I suspect that the latter has been the case for many years. I seem to remember text from years ago on the subject of thinner and stronger skin steel being used and panels do seem to be thinner than I remember as a younger man. Don't read localised dent resistance into that aspect...a shopping cart can give you a significant bill.  Bear in mind that 'non encounter' yield strength is nowhere near approached in working parts of 'any material' in cars. When a significant encounter occurs you want yield to happen up to a point. I suspect the determination of that point is an engineers nightmare...at least computers help now.
   I suppose that if Young's Modulus varies significantly for steel compositions then these thoughts are wrong on the subject. Also there must be other aspects, on this subject, that are apparent to the current designers and engineers in the industry...not known to the layman.
   Interesting to read about aluminium being dropped by one company. 1/3 the weight but if you need more of it...
   

[dirtyjeffer]

cost savings? they sure do! 

https://www.youtube.com/watch?v=6s0Oq2SPu48
https://www.youtube.com/watch?v=xC3ZeJ0JNXE

the small overlap test has nothing to do with high strength steel or not...it is based on the design of the vehicle...the 2013 Tuscon was designed prior to the small overlap test...the new Sonata performs better because it was designed afterwards.

http://www.sciencedirect.com/science/article/pii/S0734743X12002011

i'm not sure what your point is here.

the reason cars are safer today has more to do with how they are designed than whether or not they are made of lots of HSS...now, if you do both, then yes, of course...but at the same time, a well designed vehicle will be safer in a crash than a poor designed vehicle, even if it is made with HSS.

[Rupert]

I think the discussion here was about body torsional stiffness and the structural members producing it versus higher strength steel. Torsional stiffness being a desirable feature for road holding and general driveability.

[dirtyjeffer]

I think the discussion here was about body torsional stiffness and the structural members producing it versus higher strength steel. Torsional stiffness being a desirable feature for road holding and general driveability.

i agree, which is why i don't understand why he keeps rambling on about crash tests.