1 00:00:01,840 --> 00:00:07,520 Speaker 1: Welcome to Brainstuff, a production of iHeartRadio, Hey brain Stuff, 2 00:00:07,520 --> 00:00:11,040 Speaker 1: lor and Vogel Bomb. Here pop quiz in case you 3 00:00:11,080 --> 00:00:13,800 Speaker 1: didn't read this episode title, But what do a sheet 4 00:00:13,800 --> 00:00:15,960 Speaker 1: of paper being crushed into a ball and tossed into 5 00:00:16,000 --> 00:00:19,040 Speaker 1: a waste basket, The front end of a car forming 6 00:00:19,040 --> 00:00:22,960 Speaker 1: in a crash, and the Earth's crust gradually forming mountains 7 00:00:23,000 --> 00:00:27,680 Speaker 1: over millions of years all having common They're all undergoing 8 00:00:27,680 --> 00:00:31,720 Speaker 1: a physical process called crumpling, which occurs when a relatively 9 00:00:31,760 --> 00:00:34,800 Speaker 1: thin sheet of material, one with a thickness that's far 10 00:00:34,960 --> 00:00:37,680 Speaker 1: less than its length or its width, has to fit 11 00:00:37,880 --> 00:00:43,000 Speaker 1: into a smaller area. And while it's easy to imagine 12 00:00:43,040 --> 00:00:47,080 Speaker 1: crumpling as mere disarray, scientists who have studied crumpling have 13 00:00:47,159 --> 00:00:50,879 Speaker 1: discovered that it's anything but The crumpling turns out to 14 00:00:50,920 --> 00:00:56,320 Speaker 1: be a predictable, reproducible process governed by math. A recent 15 00:00:56,360 --> 00:00:59,360 Speaker 1: breakthrough at our understanding was described in a paper published 16 00:00:59,360 --> 00:01:02,880 Speaker 1: in Nature Communecations in twenty twenty one, in which researchers 17 00:01:02,920 --> 00:01:06,319 Speaker 1: describe a physical model for what happens when thin sheets 18 00:01:06,360 --> 00:01:12,120 Speaker 1: are crumpled, then unfolded, and recrumpled. For the article, this 19 00:01:12,160 --> 00:01:14,760 Speaker 1: episode is based on how Stuffwork. Spoke via email with 20 00:01:14,840 --> 00:01:18,960 Speaker 1: Christopher Ryecroft, the paper's corresponding author, who's Associate professor in 21 00:01:19,000 --> 00:01:21,880 Speaker 1: the John L. Paulson School of Engineering and Applied Sciences 22 00:01:21,920 --> 00:01:26,480 Speaker 1: at Harvard University. He said, from an early age, everyone 23 00:01:26,560 --> 00:01:28,920 Speaker 1: is familiar with crumpling a sheet of paper into a ball, 24 00:01:29,160 --> 00:01:32,399 Speaker 1: unfolding it, and looking at the complicated network of creases 25 00:01:32,440 --> 00:01:36,120 Speaker 1: that form on the surface. This seems like a random, 26 00:01:36,200 --> 00:01:39,639 Speaker 1: disordered process, and you might think it's difficult to predict 27 00:01:39,680 --> 00:01:43,280 Speaker 1: anything at all about what happens. Suppose now you repeat 28 00:01:43,280 --> 00:01:46,600 Speaker 1: this process, crumple the paper again and unfold it. You 29 00:01:46,640 --> 00:01:50,520 Speaker 1: will get more creases. However, you won't double the number 30 00:01:50,920 --> 00:01:54,520 Speaker 1: because the existing creases already weakened the sheet and allow 31 00:01:54,560 --> 00:01:59,200 Speaker 1: it fold more easily the second time around. That idea 32 00:01:59,320 --> 00:02:02,520 Speaker 1: formed the base of experiments performed several years ago by 33 00:02:02,520 --> 00:02:06,280 Speaker 1: another of the papers authors, former Harvard physicist Schumel M. 34 00:02:06,320 --> 00:02:10,600 Speaker 1: Rubinstein and his students. Rubinstein and his team crumpled a 35 00:02:10,639 --> 00:02:13,960 Speaker 1: thin sheet repeatedly and measured the total length of the 36 00:02:14,000 --> 00:02:18,920 Speaker 1: creases on that sheet, which they called mileage. Ryecroft said 37 00:02:19,360 --> 00:02:22,919 Speaker 1: they found that the growth of mileage is strikingly reproducible, 38 00:02:23,240 --> 00:02:26,040 Speaker 1: and each time the accrual of new mileage would get 39 00:02:26,040 --> 00:02:29,640 Speaker 1: a little less because the sheet is progressively getting weaker. 40 00:02:32,320 --> 00:02:36,440 Speaker 1: That finding stumped the physics community, hence the more recent research. 41 00:02:37,080 --> 00:02:39,720 Speaker 1: A Ryecraft said, we found that the way to make 42 00:02:39,800 --> 00:02:43,080 Speaker 1: progress was not to focus on the creases themselves, but 43 00:02:43,160 --> 00:02:46,400 Speaker 1: rather to look at the undamaged facets that are outlined 44 00:02:46,440 --> 00:02:50,680 Speaker 1: by the creases. Houstuffworks also spoke by email with the 45 00:02:50,720 --> 00:02:54,120 Speaker 1: more recent papers lead author Yovanna A. And Jyevic, a 46 00:02:54,280 --> 00:02:59,280 Speaker 1: Harvard doctoral candidate. She said, in the experiment, thin sheets 47 00:02:59,280 --> 00:03:02,519 Speaker 1: of mylar, a thin film that crumples similarly to paper, 48 00:03:02,800 --> 00:03:06,800 Speaker 1: were systematically crumpled several times, developing some new creases with 49 00:03:06,880 --> 00:03:11,200 Speaker 1: each repetition. In between crumples, the sheets were carefully flattened 50 00:03:11,240 --> 00:03:14,760 Speaker 1: and their height profiles scanned using an instrument called a profilometer. 51 00:03:15,480 --> 00:03:18,440 Speaker 1: The profilometer makes measurements of the height map across the 52 00:03:18,480 --> 00:03:21,120 Speaker 1: surface of the sheet, which allows us to calculate and 53 00:03:21,280 --> 00:03:27,800 Speaker 1: visualize the locations of creases as an image. Because creasing 54 00:03:27,919 --> 00:03:31,760 Speaker 1: can be messy and irregular, it generates noisy data that 55 00:03:31,840 --> 00:03:34,400 Speaker 1: can be tough for computer automation to make sense of. 56 00:03:35,120 --> 00:03:38,440 Speaker 1: To get around that problem, Andreavic hand traced the crease 57 00:03:38,480 --> 00:03:42,760 Speaker 1: patterns on twenty four sheets using a tablet, PC, Adobe illustrator, 58 00:03:42,840 --> 00:03:47,120 Speaker 1: and photoshop. That meant hand recording twenty one thousand, one 59 00:03:47,240 --> 00:03:53,200 Speaker 1: hundred and ten facets in total. Thanks to Andreevic's labors 60 00:03:53,240 --> 00:03:57,040 Speaker 1: and image analysis, the researchers could analyze how many facets 61 00:03:57,080 --> 00:04:01,040 Speaker 1: of different sizes were created as the crumpling progress. They 62 00:04:01,120 --> 00:04:05,400 Speaker 1: found that the size distributions could be explained by fragmentation theory, 63 00:04:05,720 --> 00:04:08,760 Speaker 1: which looks at how objects are ranging from rocks and 64 00:04:08,840 --> 00:04:12,800 Speaker 1: glass shards to volcanic debris and icebergs, break up into 65 00:04:12,840 --> 00:04:18,800 Speaker 1: small pieces over time. Ryecroft said that same theory can 66 00:04:18,839 --> 00:04:22,359 Speaker 1: accurately explain how the facets of the crumpled sheet break 67 00:04:22,440 --> 00:04:25,960 Speaker 1: up over time as more creases form. We can also 68 00:04:26,040 --> 00:04:29,279 Speaker 1: use it to estimate how the sheet becomes weaker after crumpling, 69 00:04:29,640 --> 00:04:33,640 Speaker 1: and thereby explain how the accumulation of mileage slows down. 70 00:04:34,520 --> 00:04:37,000 Speaker 1: This allows us to explain the mileage results and the 71 00:04:37,040 --> 00:04:40,839 Speaker 1: logarithmic scaling that we're seen in the twenty eighteen study. 72 00:04:40,920 --> 00:04:43,960 Speaker 1: We believe that the fragmentation theory provides a perspective on 73 00:04:44,000 --> 00:04:47,120 Speaker 1: the problem and is especially useful to model the accumulation 74 00:04:47,200 --> 00:04:52,520 Speaker 1: of damage over time. But okay, let's back up a second. 75 00:04:53,080 --> 00:04:56,000 Speaker 1: Why do some objects crumple in the first place, as 76 00:04:56,040 --> 00:04:59,239 Speaker 1: opposed to simply breaking apart into a lot of little pieces. 77 00:05:00,279 --> 00:05:02,920 Speaker 1: It has to do with how flexible a material is. 78 00:05:03,520 --> 00:05:06,559 Speaker 1: Things like paper and milar are very easy to bend, 79 00:05:06,920 --> 00:05:09,719 Speaker 1: so they're not very likely to break when you apply pressure, 80 00:05:10,320 --> 00:05:13,400 Speaker 1: But things like rock and glass don't bend easily, so 81 00:05:13,600 --> 00:05:18,760 Speaker 1: force can make them break. Andreevic explained a crumpling and 82 00:05:18,800 --> 00:05:22,680 Speaker 1: breaking are quite distinct processes, but there are some similarities 83 00:05:22,720 --> 00:05:26,800 Speaker 1: we can recognize. For example, both crumpling and breaking are 84 00:05:26,800 --> 00:05:30,960 Speaker 1: mechanisms of relieving stress and a material. The idea of 85 00:05:31,040 --> 00:05:34,640 Speaker 1: creases protecting other regions of a sheet from damage refers 86 00:05:34,680 --> 00:05:38,400 Speaker 1: to damage being localized to very narrow ridges in the sheet. 87 00:05:39,279 --> 00:05:42,160 Speaker 1: In fact, the sharp vertices and ridges that form when 88 00:05:42,160 --> 00:05:45,799 Speaker 1: a sheet crumples are localized regions of stretching in the sheet, 89 00:05:46,160 --> 00:05:51,120 Speaker 1: which are energetically unfavorable. As a result, the sheet minimizes 90 00:05:51,240 --> 00:05:55,520 Speaker 1: those costly deformations by confining them to very narrow regions, 91 00:05:55,720 --> 00:05:59,760 Speaker 1: protecting the rest of the sheet as much as possible. Furthermore, 92 00:06:00,120 --> 00:06:02,760 Speaker 1: your research showed that the more a sheet is crumpled, 93 00:06:03,200 --> 00:06:07,479 Speaker 1: the more it resists further compression, so that increasingly more 94 00:06:07,600 --> 00:06:11,480 Speaker 1: force is required to compress it. The ridges seem to 95 00:06:11,560 --> 00:06:14,920 Speaker 1: line up and act as pillars that increase the strength 96 00:06:15,000 --> 00:06:20,080 Speaker 1: of the crumpled sheet. There's still a lot that needs 97 00:06:20,120 --> 00:06:23,719 Speaker 1: to be learned about crumpling. For example, it's not clear 98 00:06:23,760 --> 00:06:27,240 Speaker 1: whether different types of crumpling of using a cylindrical piston, 99 00:06:27,320 --> 00:06:29,960 Speaker 1: for example, rather than your hand it results in a 100 00:06:30,040 --> 00:06:34,240 Speaker 1: different type of crease pattern. A Ryecroft said, we'd like 101 00:06:34,279 --> 00:06:39,280 Speaker 1: to understand how general our findings are. In addition, researchers 102 00:06:39,320 --> 00:06:41,760 Speaker 1: want to learn more about the actual mechanisms of how 103 00:06:41,839 --> 00:06:44,880 Speaker 1: creases form and to be able to take measurements during 104 00:06:44,880 --> 00:06:48,560 Speaker 1: the process rather than just examining the end result. A 105 00:06:48,640 --> 00:06:52,440 Speaker 1: Ryecraft explained. To get around this, we're currently developing a 106 00:06:52,480 --> 00:06:55,960 Speaker 1: three D mechanical simulation of a crumpled sheet, which can 107 00:06:56,000 --> 00:06:59,960 Speaker 1: allow us to observe the entire process already our simulation 108 00:07:00,080 --> 00:07:02,360 Speaker 1: and can create creased patterns that are similar to those 109 00:07:02,400 --> 00:07:04,800 Speaker 1: seen in the experiment, and it provides us with a 110 00:07:04,880 --> 00:07:11,520 Speaker 1: much more detailed view of the crumpling process. But all right, 111 00:07:12,080 --> 00:07:16,400 Speaker 1: why does crumple theory matter? Gaining insights about crumpling is 112 00:07:16,440 --> 00:07:19,560 Speaker 1: potentially really important to all sorts of things in our 113 00:07:19,680 --> 00:07:23,920 Speaker 1: modern world. Ryecroft said, if you're using a material in 114 00:07:24,000 --> 00:07:28,560 Speaker 1: any structural capacity, it is critical to understand its failure properties. 115 00:07:29,240 --> 00:07:32,600 Speaker 1: In many situations, it's important to understand how materials will 116 00:07:32,600 --> 00:07:37,760 Speaker 1: behave under repeated loading. For example, aircraft wings vibrate up 117 00:07:37,760 --> 00:07:41,000 Speaker 1: and down many thousands of times over their lifetime. Our 118 00:07:41,040 --> 00:07:43,600 Speaker 1: study of repeated crumpling can be viewed as a model 119 00:07:43,640 --> 00:07:47,560 Speaker 1: system for how materials are damaged under repeated load. We 120 00:07:47,680 --> 00:07:50,720 Speaker 1: expect that some core elements of our theory about how 121 00:07:50,760 --> 00:07:54,680 Speaker 1: materials are weakened by fractures increases over time may have 122 00:07:54,800 --> 00:08:02,160 Speaker 1: analogs in other material types, and sometimes crumpling might actually 123 00:08:02,200 --> 00:08:07,680 Speaker 1: be utilized technologically. For example, crumpled graphene sheets have been 124 00:08:07,720 --> 00:08:13,840 Speaker 1: suggested as a possibility for making high performance electrodes for batteries. Really, 125 00:08:13,920 --> 00:08:17,480 Speaker 1: crumple theory provides insights into all sorts of phenomena, from 126 00:08:17,600 --> 00:08:21,440 Speaker 1: how insects wings unfold to how DNA packs into a 127 00:08:21,520 --> 00:08:24,680 Speaker 1: cell nucleus, all of which could be used to build 128 00:08:24,760 --> 00:08:32,600 Speaker 1: more efficient machines. In the future. Today's episode is based 129 00:08:32,640 --> 00:08:35,000 Speaker 1: on the article crumple theory. We can learn a lot 130 00:08:35,040 --> 00:08:37,680 Speaker 1: from how paper crumples on how stuffworks dot com, written 131 00:08:37,679 --> 00:08:40,200 Speaker 1: by Patrick J. Higer. Brain Stuff is production of by 132 00:08:40,240 --> 00:08:42,480 Speaker 1: Heart Radio in partnership with how stuffworks dot Com and 133 00:08:42,600 --> 00:08:45,920 Speaker 1: is produced by Tyler Klang. For more podcasts on iHeartRadio, 134 00:08:46,160 --> 00:08:49,199 Speaker 1: visit the iHeartRadio app, Apple Podcasts, or wherever you listen 135 00:08:49,240 --> 00:09:00,960 Speaker 1: to your favorite shows.