Structural Engineering Research Projects

  • Meshfree Method for Impact and Penetration Modeling

    Figure 1. Micro-crack informed damage model
    Figure 1. Micro-crack informed damage model

    Figure 2. Meshfree multiscale modeling of bullet penetration through concrete walls
    Figure 2. Meshfree multiscale modeling of bullet penetration through concrete walls

    Professor J. S. Chen

    Professor J. S. Chen and his students are working with the U.S. Army Engineer Research and Development Center to develop a micro-crack informed damage model and multiscale reproducing kernel particle method (RKPM) formulation to model impact and penetration into brittle materials. By developing a semi-Lagrangian stabilized nodal integration formulation, key phenomena such as multi-body contact, material fragmentation, and large material flow are accurately modeled. The multiscale formulation provides a critical link between microstructure failure and macroscale damage (Fig. 1), leading to improved modeling of material softening and failure, which is crucial in penetration events (Fig. 2). Similar numerical techniques have also been applied to metal forming and earth-moving simulations that are difficult to be modeled by the mesh based finite element methods.

  • Sources of Error in Finite Element Simulations of Effects of Blasts on the Human Brain

    Professor Petr Krysl

    Recent military conflicts have resulted in an increase in the number of blast related traumatic brain injuries. The present project examines the mechanical effects in a brain impinged upon by a blast wave as simulated by a finite element coupled fluid-solid framework. Various sources of errors were assessed and conclusions are (a) the least important source of error was the assumption of linear kinematics and linear constitutive equation; (b) the discretization error was significant, and controlling it will remain a challenge; and (c) the most significant source of error was found to be the uncertainty of the input parameters (experimental variability) and the lack of knowledge of the detailed micro-mechanics of deformation of the brain tissues under conditions of blast loading.

    In collaboration with Mark W. Bondi, Samuel R. Ward, and Lawrence R. Frank, UCSD/VA San Diego Healthcare System. Project was supported by Dr. Frank Stone and Dr. Ernie Young at the Chief of Naval Operations, Environmental Readiness Division

    Photo: Acoustic pressure (red positive, blue negative) in the cortex. (Snapshots spaced ~0.035 ms).

  • Optimal Damage Detection and Prognosis Vis Elastic Stress Wave Scattering

    Professor Michael Todd

    Ultrasonic guided wave interrogation using both coherent-phase arrays and sparse arrays (sparsity defined as arrays whose average sensor-to-sensor distance is significantly longer than the interrogating wavelengths) has evolved into a very active research area. This research focuses on the detection, classification, and prognosis of damage using elastic waves as the interrogation mechanism.

    The novel approach in this work is the embedding of stochastic models to account for uncertainty of model/physical parameters, in order to derive an optimal detection process that supports predictive modeling with quantified uncertainty. Research is focusing on maximum likelihood estimates for detecting and localizing small scatterers (holes, asymmetric cracks) in metallic plate-like structures. Detection is accomplished using generalized likelihood ratio test (GLRT) and Bayesian detectors in conjunction with a broadband beamformer to estimate the arrival angle of scattered waveforms. 

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