Jack Chessa - Academia.edu (original) (raw)

Papers by Jack Chessa

Bulletin of the American Physical Society, Apr 13, 2013

Mechanics of Advanced Materials and Structures, 2013

The thermal residual stress and associated effects in TiN coatings with planar and nonplanar surf... more The thermal residual stress and associated effects in TiN coatings with planar and nonplanar surface roughness on silicon (100) substrates were analyzed using both analytical and finite element (FE) modeling. The effect of growth temperature (Ts), thickness, and the modulus of elasticity on the stress evolution in TiN coatings is reported. The results indicate that the variable thermal stress in the TiN coatings is due to the existence of both positive and negative temperature gradients and thus the resultant existence of disparity of the coefficient of thermal expansion between the substrate and the coating.

Frontiers in Bioengineering and Biotechnology

Bioprinting is an emerging technique used to layer extrudable materials and cells into simple con... more Bioprinting is an emerging technique used to layer extrudable materials and cells into simple constructs to engineer tissue or arrive at in vitro organ models. Although many examples of bioprinted tissues exist, many lack the biochemical complexity found in the native extracellular matrix. Therefore, the resulting tissues may be less competent than native tissues—this can be especially problematic for tissues that need strong mechanical properties, such as cardiac or those found in the great vessels. Decellularization of native tissues combined with processing for bioprinting may improve the cellular environment for proliferation, biochemical signaling, and improved mechanical characteristics for better outcomes. Whole porcine hearts were decellularized using a series of detergents, followed by lyophilization and mechanical grinding in order to produce a fine powder. Temperature-controlled enzymatic digestion was done to allow for the resuspension of the decellularized extracellular...

Overview of level set method. Synergism of XFEM and level set method. Application to Stefan probl... more Overview of level set method. Synergism of XFEM and level set method. Application to Stefan problems. Application to free surface problems. Summary, conclusions and future work.

The public reporting burden for this collection of information is estimated to average 1 hour per... more The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to the Department of Defense, Executive Service Directorate (0704-0188). Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION. 1. REPORT DATE (DD-MM-YYYY) 06/23/2009 2. REPORT TYPE Final DATES COVERED (From To) 9/30/2005-12/31/2008 4. TITLE AND SUBTITLE Computational Design of Zr02-Si02 Coatings for Oxidation of ZrB2/Z...

Additive manufacturing in space has been recognized as one of the required technologies for space... more Additive manufacturing in space has been recognized as one of the required technologies for space colonization and deep space exploration. The current state of the art indicates that efforts are being done to achieve 3D (Three Dimensional) printing in space, in particular, inside the International Space Station (ISS) in a controlled environment. However, no spacecraft has performed additive manufacturing tasks in open outer space subject to the vacuum, reduced gravity and the extreme temperatures. In this work, a 1U small satellite, nicknamed Orbital Factory II (OFII) will perform a technological demonstration of 3D printing of conductive material. The small satellite features a 3D printing 2-DOF gantry table mechanism that will deposit conductive ink and simulate repairing of a solar cell. The material to 3D print was selected based on bulk resistivity, viscosity and amount of conductive particles, as well as curing time and low outgassing. Up to date, vacuum test has determined th...

Couri, 2012

Parallel architectures in computer systems are powerful tools for processing enormous amounts of ... more Parallel architectures in computer systems are powerful tools for processing enormous amounts of information. The results of this research will illustrate their optimal usage by evaluating the scalability of the code Abaqus in the cases of domain decomposition and loop parallelization architectures. The scalability was analyzed using concomitant variation having the DoF (Degrees of Freedom) and CPU (Central Processing Unit) numbers as the variables. Abaqus jobs with less than 100,000 DoF showed similar scalability than that of jobs with more than 500,000. These results contradict the original hypothesis which proposed that small jobs would show poor scalability and vice versa. Another evaluation will be realized with jobs containing more than 1,000,000 DoF to determine if scalability is actually related to the number of DoF

Thesis (Ph. D., Mechanical Engineering)--Northwestern University, 2003.

Computer Methods in Applied Mechanics and Engineering, 2006

We describe a method for fluid-structure interaction with the interface and free surfaces defined... more We describe a method for fluid-structure interaction with the interface and free surfaces defined by level sets. The fluid is treated by an Eulerian mesh whereas the solid or structure by a Lagrangian mesh. The level set method provides a compact framework for writing the weak form and for developing and computing the discretized equations. Lagrange multiplier methods and penalty methods are used to couple the fluid and structure. Results are presented for a few compressible fluid problems representative of high pressure waves.

Ceramics International, 2014

ABSTRACT Titanium nitride (TiN,) coatings were grown by magnetron sputtering onto Si(100) substra... more ABSTRACT Titanium nitride (TiN,) coatings were grown by magnetron sputtering onto Si(100) substrates by varying time of deposition to produce coatings with variable thickness (d(TiN)) in the range of 20-120 nit. TiNx coatings were characterized by studying their structure, composition, and mechanical properties. Nuclear reaction analysis (NRA) combined with Rutherford backscattering spectrometry (RBS) analyses indicate that the grown coatings were stoichiometric TiN. Grazing incidence X-ray diffraction (GIXRD) measurements indicate that the texturing of TiN coatings changes as a function of d(TiN). The (111) and (002) peaks appear initially; (111) becomes intense while (002) disappears with increasing d(TiN). Dense, columnar grain structure was evident for all the coatings in electron microscopy analyses. The residual stress for TiN coatings with d(TIN)similar to 120 nm was 1.07 GPa in compression while thinner samples exhibit higher values of stress.

Some minor changes made, like adding the files to the release.