Discover Top Posts Tagged with #plastic deformation

Machine learning to predict and optimise the deformation of materials

Researchers at Tampere University of Technology and Aalto University taught machine learning algorithms to predict how materials stretch. This new application of machine learning opens new opportunities in physics and possible applications can be found in the design of new optimal materials. The study has been published in the prestigious journal Nature Communications.

Most regular objects tend to stretch 'evenly', that it: scientists can predict how much force is required to make a material stretch by a certain distance. Recent experiments have shown that these predictions don't hold up at the micrometre scale. The stretching of microscopic crystals happens in discrete bursts with a very wide size distribution. Since the bursts occur sporadically, seemingly identical micro-scale samples can stretch in very different ways. This variability of the strength characteristics of the samples poses a challenge for the development of novel materials with desired properties. In their article "Machine learning plastic deformation of crystals" published in Nature Communications, the researchers use machine learning to predict the characteristics of individual samples.

"The machine learning algorithms succeeded in measuring how predictable the stretch process of small crystalline samples is. This would have been practically impossible with traditional means, but machine learning enables the discovery of new and interesting results," explains Associate Professor Lasse Laursonfrom the Laboratory of Physics at Tampere University of Technology.

Team uses severe deformation method on bulk magnetic alloys for high performance

In a collaborative study involving Equal Channel Angular Extrusion (ECAE), a unique severe plastic deformation (SPD) process, researchers Dr. Ibrahim Karaman from Texas A&M University and Drs. Don Susan and Andrew Kustas of Sandia National Laboratories were able to improve the mechanical properties of magnetic alloys without changing their magnetic properties through microstructural refinement. This process has proven to be troublesome in the past.

Production of high-performance magnetic alloys and other intermetallics could prove particularly useful in aerospace and space exploration where materials must endure harsh environments including temperature extremes, shock, and vibration.

ECAE forces a bar of metallic or polymeric material at a 90-degree angle through a die channel. This process induces SPD without any changes in the cross-sectional area of the sample.

Originally the researchers at Sandia National Laboratories and Texas A&M worked together on a different topic involving shape memory alloys. They quickly realized the potential in combining the strengths of their respective facilities on an entirely new study and subsequently applied the experiences to magnetic alloys.

How extreme shocks deform a metal’s atomic structure

A new way to observe this deformation as it happens can help study a wide range of phenomena, from meteor impacts to high-performance ceramics used in armor, as well as how to protect spacecraft from high-speed dust impacts.

When hit by a powerful shock wave, materials can change their shape -- a property known as plasticity -- yet keep their lattice-like atomic structure. Now scientists have used the X-ray laser at the Department of Energy's SLAC National Accelerator Laboratory to see, for the first time, how a material's atomic structure deforms when shocked by pressures nearly as extreme as the ones at the center of the Earth.

The researchers said this new way of watching plastic deformation as it happens can help study a wide range of phenomena, such as meteor impacts, the effects of bullets and other penetrating projectiles and high-performance ceramics used in armor, as well as how to protect spacecraft from high-speed dust impacts and even how dust clouds form between the stars.

Deformation experiments reveal insight into material changes during shock compression

For the first time, scientists have reported in-situ diffraction experiments measuring deformation twinning at the lattice level during shock compression. The results were recently published in Nature by a team of researchers from Lawrence Livermore National Laboratory and collaborators from the University of Oxford, Los Alamos National Laboratory, the University of York and SLAC National Accelerator Laboratory.

Shock compression is a challenging area of study, as it combines extreme conditions, such as high pressures and temperatures, with ultrafast timescales. To simplify the problem, scientists often assume that solid materials behave like a fluid, flowing and changing their shape (plasticity) without resistance. Yet, as a solid, most materials also retain a lattice structure. As a material flows, changing shape, somehow the lattice must change as well while still maintaining the regular pattern of the lattice. The study of plasticity at a most fundamental level then rests on understanding how the lattice is changing while a material is deforming.

Dislocation-slip (where lattice dislocations are generated and move) and twinning (where sub-grains form with a mirror-image lattice) are the basic mechanisms of plastic deformation. Despite their fundamental importance to plasticity, diagnosing the active mechanism in-situ (during the shock) has been elusive. Previous research has studied the material after the fact (in "recovery"), which introduces additional complicating factors and has led to conflicting results.

POM Thermal Stability - How to Prevent Heat Deformation in High Temperatures

Understanding POM’s Thermal Limitations Polyoxymethylene (POM), commonly known as acetal or Delrin®, is a high-performance engineering thermoplastic prized for its excellent mechanical properties, dimensional stability, and low friction characteristics. However, when exposed to elevated temperatures, POM faces significant thermal stability challenges that engineers must address. Standard POM…