{"108061":{"#nid":"108061","#data":{"type":"news","title":"Model Analyzes Shape-Memory Alloys for Use in Earthquake-Resistant Structures","body":[{"value":"\u003Cp\u003ERecent earthquake damage has exposed the vulnerability of\nexisting structures to strong ground movement. At the Georgia Institute of\nTechnology, researchers are analyzing shape-memory alloys for their potential\nuse in constructing seismic-resistant structures.\u003C\/p\u003E\n\n\u003Cp\u003E\u201cShape-memory alloys exhibit unique characteristics that you\nwould want for earthquake-resistant building and bridge design and retrofit\napplications: they have the ability to dissipate significant energy without\nsignificant degradation or permanent deformation,\u201d said \u003Ca href=\u0022http:\/\/www.ce.gatech.edu\/people\/faculty\/891\/overview\u0022 target=\u0022_blank\u0022\u003EReginald DesRoches\u003C\/a\u003E, a professor\nin the \u003Ca href=\u0022http:\/\/www.ce.gatech.edu\/\u0022 target=\u0022_blank\u0022\u003ESchool of Civil and Environmental Engineering\u003C\/a\u003E at Georgia Tech.\u003C\/p\u003E\n\n\u003Cp\u003EGeorgia Tech researchers have developed a model that\ncombines thermodynamics and mechanical equations to assess what happens when\nshape-memory alloys are subjected to loading from strong motion. The researchers\nare using the model to analyze how shape-memory alloys in a variety of\ncomponents -- cables, bars, plates and helical springs -- respond to different loading\nconditions. From that information, they can determine the optimal\ncharacteristics of the material for earthquake applications.\u003C\/p\u003E\n\n\u003Cp\u003EThe model was developed by DesRoches, \u003Ca href=\u0022http:\/\/www.me.gatech.edu\/\u0022 target=\u0022_blank\u0022\u003ESchool of Mechanical\nEngineering\u003C\/a\u003E graduate student Reza Mirzaeifar, School of Civil and Environmental\nEngineering associate professor \u003Ca href=\u0022http:\/\/www.ce.gatech.edu\/people\/faculty\/421\/overview\u0022 target=\u0022_blank\u0022\u003EArash Yavari\u003C\/a\u003E, and School of Mechanical Engineering\nand \u003Ca href=\u0022http:\/\/www.mse.gatech.edu\/\u0022 target=\u0022_blank\u0022\u003ESchool of Materials Science and Engineering\u003C\/a\u003E professor \u003Ca href=\u0022http:\/\/www.me.gatech.edu\/faculty\/gall.shtml\u0022 target=\u0022_blank\u0022\u003EKen Gall\u003C\/a\u003E.\u003C\/p\u003E\n\n\u003Cp\u003EA paper describing the thermo-mechanical model was published\nonline Feb. 3 in the \u003Cem\u003E\u003Ca href=\u0022http:\/\/dx.doi.org\/10.1016\/j.ijnonlinmec.2012.01.007\u0022\u003EInternational\nJournal of Non-Linear Mechanics\u003C\/a\u003E\u003C\/em\u003E. This research was supported by the\nTransportation Research Board IDEA program.\u003C\/p\u003E\n\n\u003Cp\u003ETo improve the performance of structures during earthquakes,\nresearchers around the world have been investigating the use of \u201csmart\u201d\nmaterials, such as shape-memory alloys, which can bounce back after\nexperiencing large loads. The most common shape-memory alloys are made of metal\nmixtures containing copper-zinc-aluminum-nickel, copper-aluminum-nickel or\nnickel-titanium. Potential applications of shape-memory alloys in bridge and\nbuilding structures include their use in bearings, columns and beams, or\nconnecting elements between beams and columns. But before this class of\nmaterials can be used, the effect of extreme and repetitive loads on these\nmaterials must be thoroughly examined.\u003C\/p\u003E\n\n\u003Cp\u003E\u201cFor standard civil engineering materials, you can use\nmechanics to look at force and displacement to measure stress and strain, but\nfor this class of shape-memory alloys that changes properties when it undergoes\nloading and unloading, you have to consider thermodynamics and mechanics,\u201d explained\nYavari.\u003C\/p\u003E\n\n\u003Cp\u003EThe Georgia Tech team found that the generation and\nabsorption of heat during loading and unloading caused a temperature gradient\nin shape-memory alloys, which caused a non-uniform stress distribution in the\nmaterial even when the strain was uniform.\u003C\/p\u003E\n\n\u003Cp\u003E\u201cShape-memory alloys previously examined in detail were\nreally thin wires, which can exchange heat with the ambient environment rapidly\nand no temperature change is seen,\u201d said Mirzaeifar. \u201cWhen you start to examine\nalloys in components large enough to be used in civil engineering applications,\nthe internal temperature is no longer uniform and needs to be taken into\naccount.\u201d\u003C\/p\u003E\n\n\u003Cp\u003ETo predict the internal temperature distribution of\nshape-memory alloys under loading-unloading cycles, which could then be used to\ndetermine the stress distribution, the researchers developed a model that used\nthe surface thermal boundary conditions, diameter and loading rate of the alloy\nas inputs.\u003C\/p\u003E\n\n\u003Cp\u003EThe team included ambient conditions in the model because\nshape-memory alloys for seismic applications could operate in a variety of\nenvironments -- such as water if used in bridge structures or air if used in\nbuilding structures -- which would produce different rates of heat transfer. The\nresearchers used a thermal camera to record the variation in surface\ntemperature of shape-memory alloys experiencing loading and unloading.\u003C\/p\u003E\n\n\u003Cp\u003EUsing their model, the researchers were able to accurately\npredict internal temperature and stress distributions for shape-memory alloys. The\nmodel results were verified with experimental tests. In one test, they found\nthat a shape-memory alloy loaded at a very slow rate had time to exchange the\nheat created with the ambient environment and exhibited uniform stress. If it was\nloaded very rapidly, it did not have enough time to exchange the heat, leading\nto a non-uniform stress distribution.\u003C\/p\u003E\n\n\u003Cp\u003E\u201cOur analytical solutions are exact, fast and capable of simulating\nthe complicated coupled thermo-mechanical response of shape-memory alloys\nconsidering temperature changes and loading rate dependency,\u201d said Mirzaeifar.\u003C\/p\u003E\n\n\u003Cp\u003EIn future work, the researchers plan to examine more\ncomplicated shapes and the effects of combination loading -- tension, bending\nand torsion -- to optimize shape-memory alloys for earthquake applications.\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cem\u003EThis project is\nsupported by the Transportation Research Board of the National Academies (Award\nNo. NCHRP-147). The National Academies has rights to the data and the content\nis solely the responsibility of the principal investigators and does not\nnecessarily represent the official views of the National Academies.\u003C\/em\u003E\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003E\nGeorgia Institute of Technology\u003Cbr \/\u003E\n75 Fifth Street, N.W., Suite 314\u003Cbr \/\u003E\nAtlanta, Georgia  30308  USA\u003C\/strong\u003E\n\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cstrong\u003EMedia Relations\nContacts:\u003C\/strong\u003E Abby Robinson (abby@innovate.gatech.edu; 404-385-3364) or John\nToon (jtoon@gatech.edu; 404-894-6986)\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cstrong\u003EWriter: \u003C\/strong\u003EAbby\nRobinson\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003ERecent earthquake damage has exposed the vulnerability of\nexisting structures to strong ground movement. At Georgia Tech, researchers are\nanalyzing shape-memory alloys for their potential use in constructing\nseismic-resistant structures.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Georgia Tech researchers are analyzing shape-memory alloys for their potential use in constructing seismic-resistant structures."}],"uid":"27206","created_gmt":"2012-02-09 11:02:50","changed_gmt":"2016-10-08 03:11:40","author":"Abby Vogel Robinson","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2012-02-09T00:00:00-05:00","iso_date":"2012-02-09T00:00:00-05:00","tz":"America\/New_York"},"extras":[],"hg_media":{"108021":{"id":"108021","type":"image","title":"Shape-memory alloy temperature","body":null,"created":"1449178188","gmt_created":"2015-12-03 21:29:48","changed":"1475894725","gmt_changed":"2016-10-08 02:45:25","alt":"Shape-memory alloy temperature","file":{"fid":"194009","name":"u_temp_hires.jpg","image_path":"\/sites\/default\/files\/images\/u_temp_hires_0.jpg","image_full_path":"http:\/\/tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/u_temp_hires_0.jpg","mime":"image\/jpeg","size":139408,"path_740":"http:\/\/tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/u_temp_hires_0.jpg?itok=d4bfHtKq"}}},"media_ids":["108021"],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"145","name":"Engineering"},{"id":"135","name":"Research"}],"keywords":[{"id":"23471","name":"Arash Yavari"},{"id":"594","name":"college of engineering"},{"id":"1400","name":"Construction"},{"id":"5770","name":"Earthquake"},{"id":"9575","name":"Ken Gall"},{"id":"1692","name":"materials"},{"id":"23461","name":"Reginald DesRoches"},{"id":"167864","name":"School of Civil and Environmental Engineering"},{"id":"167535","name":"School of Materials Science and Engineering"},{"id":"167377","name":"School of Mechanical Engineering"},{"id":"169458","name":"shape-memory alloy"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EAbby Robinson\u003Cbr \/\u003E\nResearch News and Publications\u003Cbr \/\u003E\n\u003Ca href=\u0022mailto:abby@innovate.gatech.edu\u0022\u003Eabby@innovate.gatech.edu\u003C\/a\u003E\u003Cbr \/\u003E\n404-385-3364\u003C\/p\u003E","format":"limited_html"}],"email":[],"slides":[],"orientation":[],"userdata":""}}}