Crack-Resistant Metals: New Research & Promising Applications

Metals are used in a wide variety of engineering and construction projects – from the pipes that carry water and gas, to reinforcement beams and protective roofs. However, one problem with metal infrastructure is that it can corrode and crack under stress and over time. Researchers at Arizona State University have been experimenting with crack-resistant metal designs that could change the face of infrastructure construction.

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Small-Scale Metal Testing

To better understand how different types of metals interact with outside forces, researchers recently conducted studies at very small nanometer and atomic scales. Materials science and engineering professor Karl Sieradzki is leading the ASU team to find out why the metals we use in construction projects today are still cracking under stress corrosion and what can be done about it.

The studies utilized ultra-high-speed photography and digital image correlation to observe the events that led up to metal fractures and develop ways to prevent them. According to an ASU press release, “They measured cracks moving at speeds of 200 meters per second corresponding to about half of the shear wave sound velocity in the material. This is a remarkable result, Sieradzki said, given that typically only brittle materials such as glass will fracture in this manner and that gold alloys are among the most malleable metals.”

The Study Results

The ASU team published their findings of the study in a Nature Materials article titled, “Potential-Dependent Dynamic Fracture of Nanoporous Gold,” earlier this year. Although the study focused on gold alloys, many of the same principles apply to aluminum alloys, stainless steel, and brass. Ultimately, the engineers reported a better understanding about the behaviors of metals that cause them to break down and fail.

The researchers wrote in their report, “The experiments reveal that at electrochemical potentials typical of porosity formation6 these structures are capable of supporting dislocation-mediated plastic fracture at crack velocities of 200 m s−1. Our results identify the important role of high-speed fracture in stress-corrosion cracking and are directly applicable to the behaviour of monolithic dealloyed materials at present being considered for a variety of applications.”

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Crack-Resistant Materials

Polyethylene pipe has been widely used in the oil and gas industries and by utility companies because of its proven strength and durability. However, some trench-less installation projects have used alternative plastic materials, such as the BorSafe HE3490-LS-H.

Potential Applications

Not only are these types of metals used in our buildings, but also in the framework of airplanes, the transport of fossil fuels, and the infrastructure system of nuclear power stations. Crack-resistant metals are especially important in times that water transport is urgently needed because of an emergency and in oil drilling when older wells have high levels of hydrogen sulphide. Rocky soil and climates with extreme temperatures also requires crack-resistant materials for construction.

It has always been very difficult for engineers to control external stresses and environmental conditions, even when stress-corrosion cracking can be predicted. Perhaps this new research can aid construction professionals in materials selection and placement techniques to make pipes, buildings, and all types of infrastructure more durable than in the past.

Photo credit: Sherrie Thai & Idaho National Laboratory via Flickr

 

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