high strength steel and stiffness? 1

[ACtrafficengr]

I hope you good folks won't mind educating this civil guy. My day job is usually spent keeping your products from crashing into things or each other, so I haven't been keeping up with materials.

In a recent car review (

http://www.vtec.net/news/news-item?news_item_id=606321)

they say that a manufacturer is using high-strength steel to increase the structural stiffness of a new model without increasing weight. My recollection is E changes little from alloy to alloy. Has there been a breakthrough in this department, or are do the new steels allow more shape manipulation to increase stiffness that way?

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[GregLocock]

No, E hasn't changed by more than 1%.

"The unit-body construction features extensive use of strategically strengthened areas with expanded use of high strength steel to provide high levels of rigidity."

Can be read at least two ways. One way makes sense in engineering terms but is rather confusing grammatically.


Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[CoryPad]

High-strength steels usually allow LESS shape manipulation due to their reduced formability.

As you stated, stiffness is a function of elastic modulus and geometry. Geometry varies by product form (hydroformed tubular frame vs. spot welded channel + hat) but not by material.

In general, high strength steels are used in strength-limited applications like impact beams or B pillar reinforcements or side sill panels. On the other hand, stiffness-limited applications like truck longitudinal rails use the cheapest hot rolled steel possible because their is no benefit to increasing the strength from cold rolling or alloy additions, etc.

Regards,

Cory

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