{"638619":{"#nid":"638619","#data":{"type":"event","title":"PhD Defense by Oliver Giraldo-Londo\u00f1o","body":[{"value":"\u003Cp\u003E\u003Cstrong\u003EPh.D. Thesis Defense Announcement\u003Cbr \/\u003E\r\nTopology optimization of single- and multi-material structures: From single-physics to multi-physics\u003Cbr \/\u003E\r\ndesigns\u003Cbr \/\u003E\r\nby\u003Cbr \/\u003E\r\nOliver Giraldo-Londo\u0026ntilde;o\u003C\/strong\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cbr \/\u003E\r\n\u003Cstrong\u003EAdvisor(s):\u003Cbr \/\u003E\r\nDr. Glaucio H. Paulino (CEE)\u003Cbr \/\u003E\r\nCommittee Members:\u003Cbr \/\u003E\r\nDr. Yang Wang (CEE), Dr. David Rosen (ME), Dr. Daniel W. Spring (The Equity Engineering Group, Inc.), Dr. Lucia\u003Cbr \/\u003E\r\nMirabella (Siemens Corporate Technology), Dr. Miguel Aguil\u0026oacute; (Sandia National Laboratories)\u003C\/strong\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cbr \/\u003E\r\n\u003Cstrong\u003ETopology optimization is a computational design method used to find the optimized geometry of materials or structures meeting\u003Cbr \/\u003E\r\nsome performance criteria while satisfying constraints applied either globally (as usual) or locally (a focus of this work). Topology\u003Cbr \/\u003E\r\noptimization can be used, for instance, to find lightweight structures that safely carry loads without failing. All you need is a\u003Cbr \/\u003E\r\ndesign objective (e.g., minimize the weight) and constraints (e.g., material strength) and, through a nonlinear programming\u003Cbr \/\u003E\r\ntechnique, the computer explores the solution space to find the optimized design. Despite the design freedoms afforded by\u003Cbr \/\u003E\r\ntopology optimization, its widespread adoption has primarily been hindered by the inability of current formulations to efficiently\u003Cbr \/\u003E\r\nhandle problems involving, for instance, multi-physics, multiple materials, and local material failure constraints. Thus, this thesis\u003Cbr \/\u003E\r\ncontributes to theoretical formulations, computer algorithms, and numerical implementations for topology optimization with an\u003Cbr \/\u003E\r\nemphasis on problems subjected to either global constraints (e.g., energy-type constraints) or local constraints (e.g., material\u003Cbr \/\u003E\r\nfailure constraints), and for applications involving single or multiple physical phenomena and single- or multi-material designs.\u003Cbr \/\u003E\r\nThis work can be divided into two parts. In the first part, we present a general multi-material formulation that can handle an\u003Cbr \/\u003E\r\narbitrary number of materials and volume constraints (i.e., global-type constraints), and any type of objective function. To handle\u003Cbr \/\u003E\r\nproblems with such generality, we adopt a special linearization of the original optimization problem using a non-monotonous\u003Cbr \/\u003E\r\nconvex approximation of the objective function written in terms of positive and negative components of its gradient. The outcome\u003Cbr \/\u003E\r\nis a scheme that updates the design variables associated with one constraint independently of the others, leading to an efficient,\u003Cbr \/\u003E\r\nparallelizable formulation. The new update scheme allows us to design multi-phase viscoelastic microstructures, thermoelastic\u003Cbr \/\u003E\r\nstructures, and structures subjected to general dynamic loading. In the second part of this thesis, we introduce an augmented\u003Cbr \/\u003E\r\nLagrangian formulation to solve problems with local stress constraints correctly\u0026mdash;a dilemma that has been unresolved thus far.\u003Cbr \/\u003E\r\nFirst, we create a formulation to solve stress-constrained problems both for linear and nonlinear structures and provide an\u003Cbr \/\u003E\r\neducational open-source code aiming to bridge the gap between research and education. Next, to extend the range of\u003Cbr \/\u003E\r\napplications to structures that can be made of materials other than ductile metals, we introduce a function that unifies several\u003Cbr \/\u003E\r\nclassical strength criteria to predict the failure of a wide spectrum of materials, including either ductile metals or\u003Cbr \/\u003E\r\npressure-dependent materials, and use it to solve topology optimization problems with local stress constraints. We then extend\u003Cbr \/\u003E\r\nthe framework to time-dependent problems and address stress-constrained problems for structures subjected to general\u003Cbr \/\u003E\r\ndynamic loading, in which the stress constraints are satisfied both in space (i.e., locally at every point of the discretized domain)\u003Cbr \/\u003E\r\nand time (i.e., throughout the duration of the dynamic event). Unlike most work in the literature, this augmented Lagrangian\u003Cbr \/\u003E\r\nframework leads to a scalable formulation that solves the optimization problem consistently with the local definition of stress and\u003Cbr \/\u003E\r\nhandles thousands or even millions of constraints efficiently. In summary, all components of this work are aimed to address\u003Cbr \/\u003E\r\ncritical challenges that have prevented topology optimization from being embraced as a practical design tool for\u003Cbr \/\u003E\r\nindustry-relevant applications.\u003C\/strong\u003E\u003C\/p\u003E\r\n","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":"","field_summary_sentence":[{"value":"Topology optimization of single- and multi-material structures: From single-physics to multi-physics designs "}],"uid":"27707","created_gmt":"2020-08-31 19:47:44","changed_gmt":"2020-08-31 19:47:44","author":"Tatianna Richardson","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2020-09-23T14:00:00-04:00","event_time_end":"2020-09-23T16:00:00-04:00","event_time_end_last":"2020-09-23T16:00:00-04:00","gmt_time_start":"2020-09-23 18:00:00","gmt_time_end":"2020-09-23 20:00:00","gmt_time_end_last":"2020-09-23 20:00:00","rrule":null,"timezone":"America\/New_York"},"extras":[],"groups":[{"id":"221981","name":"Graduate Studies"}],"categories":[],"keywords":[{"id":"100811","name":"Phd Defense"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[{"id":"1788","name":"Other\/Miscellaneous"}],"invited_audience":[{"id":"78761","name":"Faculty\/Staff"},{"id":"78771","name":"Public"},{"id":"174045","name":"Graduate students"},{"id":"78751","name":"Undergraduate students"}],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[],"email":[],"slides":[],"orientation":[],"userdata":""}}}