Archives: Events

Title:

Large Deformation Analysis of Composites & Functionally Graded Shells: Recent  Developments

Abstract:

In this lecture a high-order spectral/hp continuum shell finite element for the numerical simulation of the finite deformation mechanical response of elastic shell structures is discussed.  The shell element is based on a modified first-order shell theory using a 7-parameter expansion of the displacement field.  The seventh parameter is included to allow for the thickness stretch, and fully three-dimensional constitutive equations are used.  The finite element coefficient matrices and force vectors are evaluated numerically using appropriate high-order Gauss-Legendre quadrature rules and the virtual work statement is further integrated numerically through the shell thickness at each quadrature point of the mid-surface; hence no thin-shell approximations are imposed in the numerical implementation.  For laminated composite shells, we introduce a user prescribed vector field (defined at the nodes) tangent to the shell mid-surface.  This discrete tangent vector allowes for simple construction of the local bases associated with the principal orthotropic material directions of each lamina.  As a result, we were free to employ skewed and/or arbitrarily curved elements in actual finite element simulations.  Through the numerical simulation of carefully chosen benchmark problems, it is shown that the developed shell element is insensitive to all forms of numerical locking and severe geometric distortions.

 

 

About the Speaker:

Prof. J.N. Reddy is a Distinguished Professor and holder of the Oscar S. Wyatt Endowed Chair in Mechanical Engineering at Texas A&M University. Dr. Reddy is most well known for his research in the development of higher-order theories of plates and shells. His shear deformation plate and shell theories and their finite element models and penalty finite element models of fluid flows have been implemented into finite element computer programs like ABAQUS, NISA, and HyperXtrude. Dr. Reddy earned numerous awards and honors. He is a member of the National Academy of Engineering and fellow of the Indian National Academy of Engineering. Click here for downloadable flyer.

Faculty Host:Prof. Somnath Ghosh, 203 Latrobe, 410-516-7833, [email protected]

For more information, please contact Khairul Bariah Abd Majid PhD, 410-516-5033, [email protected]

 

Title:

On Marriage of Finite Element and Numerical Integration Techniques for Reliable Recovery of Inter-laminar Stresses in Composites

Abstract:

Professor Tarun Kant has contributed very significantly in fundamental research work in development of C_o higher order beam/plate/shell theories. Most modern structures are made of advanced laminated composite and sandwich materials to exploit their high degree of anisotropy and inhomogeneity across the thickness to reduce weight without sacrificing strength, integrity and durability.  In addition, to achieve optimum performance they are made of functionally graded materials (FGMs) that have continuously varying volume fractions of constituents to provide the desired functionality.  Due to the inhomogeneity in material properties, accurately modeling and designing these structures is very challenging, and has been intensely researched in the last four decades across the world and Professor Kant has made seminal contributions in this area, for which he is renowned internationally. Two dimensional (2D) plate/shell theories are developed to approximate deformation fields in real three dimensional (3D) structures that have one dimension much smaller than the other two dimensions.  Thus, some information in lost in this transformation of modeling of 3D structures with 2D approximate plate/shell theories. However, for designing them one needs accurate knowledge of stresses developed in the structure.  Professor Kant’s recent efficient and clever technique to accurately recover these stresses (e.g., see “A general partial discretization methodology for interlaminar stress computation in composite laminates, Computer Modeling in Engineering & Science 17(2), 135-161, 2007”) by the marriage of finite element (FE) and numerical integration (NI) techniques is considered to be first of its kind in the realm of elasto-statics by his peers.

About the Speaker:

Professor Kant received his BSc degree from the University of Allahabad, his BTech (Hons) in civil engineering from the Indian Institute of Technology Bombay (IIT Bombay) and MTech in civil engineering with specialization in structural engineering from the Indian Institute of Technology Kanpur (IIT Kanpur). He spent about one and a half year in a consulting engineering firm in Mumbai before joining IIT Bombay on 20 Jan 1971 as a Lecturer. He earned his PhD degree while working as a Lecturer from IIT Bombay. He was selected as an Assistant Professor in 1978 and a Professor in 1986. He has held the positions of the Dept. Head (2000-2002), the Dean (Planning) of the Institute (2001-2003), the Chairman of the prestigious Joint Entrance Examination (JEE-1998) and the Chairman of the Central Library (1995-1999) with great distinction. The Institute appointed him as an Institute Chair Professor from 31^st December 2009. Professor Kant was elected a Fellow of the Indian National Academy of Engineering (INAE) in 1999, a Fellow of the Indian Academy of Sciences (IASc) in 2004, a Fellow of the Indian National Science Academy (INSA) in 2007 and a Fellow of the National Academy of Sciences, India (NASI) in 2011. He is the first and only civil engineer in the country to get elected to all the four national academies. He is a recipient of the Burmah-Shell Best Paper Prize. He was awarded the 1979 Jawaharlal Nehru Memorial Trust (U.K) Scholarship and the 1992-’93 European Commission (EC) Senior Faculty Exchange Fellowship, both by the Government of India. IIT-Bombay, on 13 March 2007, conferred the 2006 Professor H.H. Mathur Award for Excellence in Research in Applied Sciences in recognition of his outstanding work in the area of Mechanics of Composite Materials and Structures. He also received the 2009 Khosla National Award for his life time achievement in the field of engineering. He is also a recipient of the 2010 IIT Bombay Research Paper Award. IIT Bombay, on 4^th April 2012, conferred on him the 2011 Life Time Achievement Award. ICCS17 (17^th International Conference on Composite Structures, Porto, Portugal, 17-21 June 2013) honoured him by calling him a legend and recognized him as a pioneer in initiating a new direction in mechanics of composites. Very recently he received the APACM Senior Scientist Award of the Asia Pacific Association of Computational Mechanics (APACM) on 12 December 2013 during APCOM2013 in Singapore and the ICCES (International Conference on Computational and Experimental Engineering and Sciences) Lifetime Achievement Medal in Reno, Nevada, USA on 20-24 July 2015 for making seminal contributions to composite materials and to the education of generations of students in India. He occupies the position of an Institute Chair Professor in the Department of Civil Engineering at IIT Bombay and has teaching and research experience of 48 years.  He was a visiting professor at University of Wales, Swansea (1979-’82), University of Cambridge (1993) and University of California, Los Angeles (2005).

Faculty Host:Prof. Somnath Ghosh, 203 Latrobe, 410-516-7833, [email protected]

For more information, please contact Khairul Bariah Abd Majid PhD, 410-516-5033, [email protected]

 

The AFOSR 2015 Annual Grantees’/Contractors’ Meeting for Mechanics of Multifunctional Materials and Microsystems Program was successfully held in Dayton, Ohio.

Prof Ghosh and his students,  Shu Guo and Reza Yaghmaie attended this meeting and presented their work.

 

The Air Force Office of Scientific Research (AFOSR), the basic research directorate for the Air Force Research Laboratory (AFRL), provides grants to university scientists, contracts to industry and funding for DoD laboratories. The aim of this meeting is to review and evaluate the progress of the grant awardees.

Professor Somnath Ghosh will be presenting his work to the organization by giving a talk entitled, “Image-Based Modeling of Polycrystalline Metallic Materials”. He is also invited to attend the Advisory Panel Meeting.

 

 

Title:

Multi-Scale Modeling of Microstructurally Small Fatigue Cracks in Aluminum Alloy from Synchrotron-Based Measurements

Abstract:

Advancing the state of materials design and high-fidelity structural prognosis will require a synergistic coupling between multi-scale experimental characterization and numerical modeling approaches. This talk describes recent efforts to couple synchrotron-based measurements of microstructurally small fatigue cracks with multi-scale modeling (mesoscale to macroscale) using 3D finite-element simulations. Ex-situ techniques are employed to characterize fatigue-crack propagation within the microstructure of an aluminum alloy. The experimental characterization involves X-ray tomography along with near-field high-energy X-ray diffraction microscopy (HEDM), which provides a 3D map of the grain morphologies and orientations adjacent to fatigue-crack surfaces. The experimental data are then used to digitally reconstruct and model the measured polycrystalline volume and fatigue-crack morphologies as a way to reproduce the observed crack evolution and thereby compute response fields in the neighborhood of observed crack fronts. Cracks are represented explicitly through the underlying geometry of the finite-element mesh. A concurrent multi-scale modeling technique is employed, whereby a model of the measured polycrystalline volume is embedded within a model of the global fatigue specimen. The mesoscale and macroscale regions are modeled using crystal plasticity and von Mises plasticity, respectively.  The simulation results will be used to inform quantitative relationships among local, microstructure-sensitive fields and the variability of 3D crack-growth rates.

About the Speaker:

Dr. Ashley Spear is an Assistant Professor of Mechanical Engineering at the University of Utah and the Director of the Multi-Scale Mechanics & Materials Laboratory. She specializes in 3D deformation, fatigue, and fracture in polycrystalline aluminum by coupling diffraction-based characterization with crystal-plastic finite-element modeling. She received her Ph.D. in Civil Engineering from Cornell University, where she was a member of the Cornell Fracture Group and an NSF Graduate Research Fellow. She is a recent recipient of the Young Investigator Award from the Air Force Office of Scientific Research. Click Here for Downloadable Seminar Flyer.

Faculty Host:Prof. Somnath Ghosh, 203 Latrobe, 410-516-7833, [email protected]

For more information, please contact Khairul Bariah Abd Majid PhD, 410-516-5033, [email protected]

 

 

 

Professor Somnath Ghosh was invited to speak at the 2015 ASM Spring Symposium, at the Material Prediction / Modeling Session. The event was held at GE Global Research Center (GRC), in Niskayuna, New York. The title of his talk was ‘Multi-Scale Crystal Plasticity FE Models for Predicting Fatigue in Polycrystalline Metals and Alloys‘.

 

Click here about the 2015 Spring Symposium

 

Prof. Somnath Ghosh who is the current President of USACM, gave a Semi-Plenary lecture on Tuesday, July 28^th, at 1:00 pm.

The title of his talk is, ‘Computational Mechanics in Advancing the Integrated Computational Materials Science & Engineering (ICMSE) Initiative for Metals & Alloys’.