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dc.rights.licenseRestricted to current Rensselaer faculty, staff and students. Access inquiries may be directed to the Rensselaer Libraries.
dc.contributorDe, Suvranu
dc.contributorAnderson, Kurt S.
dc.contributorZeghal, Mourad
dc.contributorZhang, Lucy T.
dc.contributor.authorPanneerselvam, Karthikeyan
dc.date.accessioned2021-11-03T09:24:58Z
dc.date.available2021-11-03T09:24:58Z
dc.date.created2021-07-08T15:40:45Z
dc.date.issued2019-05
dc.identifier.urihttps://hdl.handle.net/20.500.13015/2677
dc.descriptionMay 2019
dc.descriptionSchool of Engineering
dc.description.abstractPhysically realistic modeling of flexible rod-like objects, such as cables, hair, threads, is important in applications including virtual surgical suturing, automotive cable design, tethered space-walk simulations, gaming, computer graphics, and animation. Realistic real-time simulation of such objects poses challenges related to computational efficiency, preserving accuracy with varied constraints, loads, loading rates, and collision interactions.
dc.description.abstractThe smooth dynamic formulation equipped with elastic-viscoplastic constitutive model and the collision detection and response algorithms are applied to model the suture thread in a virtual suturing simulator to demonstrate the applicability of the model in a virtual interactive simulation environment. Several surgical suturing tasks are simulated to elucidate the efficacy of the simulator. The deformation behavior of the suture thread under different manipulations of needle and tools is validated against similar manipulations with the real suture. The comparison of deformation behavior and collision handling in the knot tightening process shows good correlation with the experimental observations while the force involved in tightening a knot shows a nonlinear increase as seen in the experiments.
dc.description.abstractSelf-collision and interaction of rods with rigid objects such as rigid shafts and tessellated surface meshes are treated using a new continuous collision detection (CCD) algorithm, which offers robustness and efficiency over the existing algorithms. A new collision response algorithm that can handle acute curvature of the rods coupled with large sliding is developed for computationally demanding applications such as surgical suturing. Further, several collision simulations demonstrate the applicability of the model for real-world applications.
dc.description.abstractThe dynamic formulation is further enhanced to model the rate dependent plastic effects of the rod through a novel moment-curvature based elasto-visco-plastic constitutive model. The plastic curvature is defined as a uniformly varying field in contrast to localized lumped plasticity, suitable for simulation of objects that undergo uniform plastic deformation such as a cable or suture thread. The constitutive relations are developed based on the smooth moment-curvature fields using yield criterion and plastic/visco-plastic flow rule. With the Bishop Frame field as reference, the material curvatures are defined using twist degree of freedom, enabling tracking the plastic fields with scalar twist thereby eliminating slopes as DOF. The constitutive model is integrated into the CSD formulation enabling efficient elasto-visco-plastic simulation at interactive rates. Uniform curvature bending test and moment relaxation test are performed to study the convergence behavior of the model. Several real-world tests involving contact are performed to demonstrate the applicability of the model in interactive simulations.
dc.description.abstractIn this thesis, we have developed a Constrained spline dynamics (CSD) method for interactive simulation of rod-like objects. The CSD is a constraint-based model for simulating the elastodynamics of rod-like objects using spline discretization with material points as degrees of freedom (DOF). The geometry of the rod and its kinematics in three-dimensional space are described using a novel smooth discretization that enables the use of the rod’s centerline co-ordinates as DOF. To achieve this, interpolating shape functions using B-splines are developed, which offers the benefits of B-splines basis in addition to Kronecker delta property. Moreover, by enforcing uniform arc-length parametrization, high accuracy is achieved with few discretization points in modeling bend, twist, and bend-twist coupling. The formulation eliminates slopes or rotational director frames as DOF resulting in high accuracy-to-cost ratio, a crucial parameter in real-time computing. An efficient algorithm to simulate the elastodynamics of rods under a range of loading rates is developed from Hamilton’s principle with bending and twisting energies represented as compliant constraints using the smooth discretization. The bend-twist coupled behavior is modeled using the concept of holonomy of curves utilizing the smooth and accurate curvature and bi-normal vector fields. The model is verified by comparing predictions with analytical problems. The validation of bending behavior with a standard benchmark test shows superior rate of convergence when compared to methods of smooth discretization that uses slopes or director frames as DOF, demonstrating computational efficiency and, hence, reinforcing the suitability for real-time simulation. The elastodynamic behavior of rods is verified with analytical results of free and forced vibrations of beams.
dc.language.isoENG
dc.publisherRensselaer Polytechnic Institute, Troy, NY
dc.relation.ispartofRensselaer Theses and Dissertations Online Collection
dc.subjectMechanical engineering
dc.titleConstrained spline dynamics
dc.typeElectronic thesis
dc.typeThesis
dc.digitool.pid180528
dc.digitool.pid180529
dc.digitool.pid180530
dc.rights.holderThis electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.
dc.description.degreePhD
dc.relation.departmentDept. of Mechanical, Aerospace, and Nuclear Engineering


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