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Smaller is Stronger !
Smaller is Stronger !
Mechanical testing of micropillars has now become a common practice to probe the mechanical properties of microscopic features (such as individual phases, precipitates etc.) in a material. While performing these micro-mechanical tests, such as micro-compression, micro-bending, micro-torsion, it has been commonly observed that when the pillar size becomes small they tend to become stronger. Sometimes such strengthening is immense - as high as 5-10 times than its bulk strength.
Useful for any practical application ?
Useful for any practical application ?
What if we exploit this phenomenon to our own benefit ? Is it possible to utilize such great strengthening to a practical use ?
We think it is possible. If we can fabricate arrays of micron-sized pillars of higher strength on a sheet surface systematically, the surface hardness/strength could be enhanced dramatically. Read more below to understand which industry can use such properties
Dent resistant body panels
Dent resistant body panels
We all have had the bad experience of getting dents on our vehicles body. We think the above work could find application in the improvement of dent-resistance of a sheet used for automotive outer panels. The sheets which are used in our car body are approximately 0.6 - 0.7 mm thick and need high yield strength to provide good resistance to permanent dents. Currently the grades used for car body have maximum yield strengths in the range of 300-500 MPa. If we could choose the micropillar size appropriately, the surface strength of these outer panels could be significantly enhanced (with a small tweak in the sheet metal forming route) without altering the grade of the material (so that it is economical).
Exploring dent resistance of micro-pillared sheets
Exploring dent resistance of micro-pillared sheets
Dent resistance test
In this work, we explored through a computational model using a gradient plasticity theory to capture the effect of the size on the maximum strengthening that could be achieved. One aspect that needs attention is that the total load bearing area is reduced due to micropillaring leading to an increased average stress on the surface for a given load. Hence a competition between the increased average stress on the surface and the strength enhancement due to size effect determines the dent resistance performance of the surface. This work explored the effect of such factors. Practical challenges exists in fabrication of such micron sized features on the sheet surface. However, we have patented a novel sheet forming method that can create such micro-texture on sheet metal surface.
Find out more about this in the articles given below.
A METHOD FOR IMPROVING YIELD STRENGTH OF A WORKPIECE, AN APPARATUS AND A WORKPIECE THEREOF. (USA 2023, Grant Number: 11821052, India 2019, Grant Number: 307439, Japan 2021, Grant Number: 10-2245033, South Korea 2021, Grant Number: 6992015)
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