What is the importance of strength to weight ratio in material selection for design quality?

New alloy claimed to have higher strength-to-weight ratio than any other metal

Strength to weight ratio might be completely unimportant or irrelevant in material selection, or it might be the most important aspect of a quality industrial design. It depends entirely on the product’s intended use or application.

If you are, for example, selecting material that will be static and load bearing, such as a structural foundation, strength is incredibly important, but weight matters very little as long as the substrate can handle the weight without significant compression. Steel, stone, concrete might be good choices. They may have a terrible strength to weight ratio, but it d…

An international team of researchers has developed a new metal alloy that has a higher strength-to-weight ratio than any other known metal material on the planet.

The team, from North Carolina State University in the US and Qatar University, combined lithium, magnesium, titanium, aluminium and scandium to make a nanocrystalline alloy that has low density, but extremely high strength. 

The strength-to-weight ratio — also known as specific strength — relates to how long a piece of the material can be to suspend its own weight when held up vertically and supported only at the top. Strong but light, high specific strength metals such as titanium, aluminium, and magnesium are often used in aerospace design, where any increase in weight is a major concern. «The density is comparable to aluminum, but it is stronger than titanium alloys,” lead researcher and materials science and engineering professor at North Carolina State University, Carl Koch, said in a press release

«It has a combination of high strength and low density that is, as far as we can tell, unmatched by any other metallic material. The strength-to-weight ratio is comparable to some ceramics, but we think it’s tougher — less brittle — than ceramics,» says Koch

The new material is also a high-entropy alloy — a recently-developed class of material that includes equal amounts of five or more types of metals. There has been significant interest in high-entropy alloys of late, and according to a review of them earlier this year in the journal Materials Research Letters, their unique set of properties mean they can be used as «hydrogen storage materials, radiation resistant materials, diffusion barriers for electronics, precision resistors, electromagnetic shielding materials, soft magnetic materials, thermoelectric materials, and anti-bacterial materials”, to name just a few.

The main challenge in getting this new alloy to the market is the fact that it’s made of 20 percent scandium, which is an extremely expensive material. «We still have a lot of research to do to fully characterise this material and explore the best processing methods for it,» Koch said. «One thing we’ll be looking at is whether scandium can be replaced or eliminated from the alloy.»

The results have been published in the current editon of Materials Research Letters.

Sources: North Carolina State University, Materials Research Letters

When it comes to metal that’s being used in the automotive or aerospace industries, the higher its strength-to-weight ratio, the better. With that in mind, researchers from North Carolina State University and Qatar University have developed a new alloy that reportedly has a low density similar to that of aluminum, but that’s stronger than titanium.

The material is a type of high-entropy alloy, meaning that it’s made up of at least five metals in more or less equal amounts. In this case, those metals are lithium, magnesium, titanium, aluminum and scandium.

«It has a combination of high strength and low density that is, as far as we can tell, unmatched by any other metallic material,» said NCSU’s Dr. Carl Koch, senior author of a paper on the research. «The strength-to-weight ratio is comparable to some ceramics, but we think it’s tougher – less brittle – than ceramics.»

He additionally informed us that while carbon fiber very likely has a higher strength-to-weight ratio than the alloy, it also wouldn’t be as tough – in other words, the alloy would be more likely to bend under an amount of stress that would cause the carbon to fracture.

More work still has to be done in the testing of the alloy, along with establishing a practical production method. Koch and his colleagues are also looking into replacing or eliminating the scandium that makes up 20 percent of the material, as it’s very expensive.

The research paper was published this week in the journal Materials Research Letters.

Source: North Carolina State University

Firstly, weight isn’t a material property — the weight of a steel girder is very different to the weight of a steel pin — so let’s replace that with density.

Now we have a question we can answer using a material property map:

Image source.

Look at the three dashed lines on the right of the figure. The one marked [math]dfrac{sigma_f}{rho}=C[/math] is the one you’re interested in — a line parallel to that guide line links all materials with the same ratio of strength to density.

You asked about the material with the highest weight (density) to strength ratio). This is actually the least useful engineering material, and found by t…

Rafia, it is a fairly literal meaning. All materials have a known strength for a given cross sectional area and all materials have a density. The ratio of the two is the strength to weight ratio.

This ratio is used universally but often subconsciously. This is because a lot of the time the decision on which material to choose is clear.

Here is an example, a rocket has to be as light as possible to increase its payload and minimize the amount of fuel required to launch. So it is made out of lighter alloys if the loading permits. A rocket made purely of steel would not take off. Aircraft have s…

The stuff with the really high strength-to-weight (carbon fiber reinforced polymer, kevlar, and other exotic polymers) is too expensive for most general construction applications, though you see it in some special purpose conditions (ballistic-resistant doors, for instance) .

Titanium has begun making an appearance, particularly in exterior cladding — a number of Frank Gehry icons use titanium skin panels. Stainless steel is used similarly, and has a similar strength to weight.

After that, you’re into aluminum alloys (curtain wall extrusions and exterior cladding) or high-strength structural …

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14.1 Introduction

The high strength-to-weight ratio of magnesium (Mg) alloys has attracted increasing interest in almost all areas where weight reduction is critical, because replacement of heavy metals, such as steels and even titanium and aluminum, with lighter Mg alloys can significantly reduce the weight.

However, wider application of Mg alloys has been limited due to the poor wear and corrosion resistance (An et al., 2007; Song {amp}amp; Atrens, 2007; Song, Atrens, {amp}amp; Dargusch, 1998), particularly for outdoor applications, where exposure to a harsh environment is unavoidable.

In addition, in recent years magnesium and its alloys have attracted attention for biomedical applications, because they are biocompatible and have mechanical properties close to those of human bones.

The implants made of Mg alloys have potential to function as osteoconductive and biodegradable substitutes in load-bearing applications in the field of hard-tissue engineering. However, the effects of corrosion and degradation in the physiological environment of the human body have prevented their actual applications to date.

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