Tae Jin Chung

Hybrid Full-Field Stress Analysis Around Holes in Tensile-Loaded Plates by Phase-Shifting Photoelasticity

A hybrid stress determination around circular and elliptical holes utilizing photoelastic phase-shifting and nonlinear least-squares methods is presented. The method was demonstrated by calculating fringe orders of distant points along straight lines using 8-step phase-shifting method. The data was used to evaluate the coefficients in the complex stress functions for hybrid analysis. Tangential stresses around the boundary of the holes were obtained using conformal mapping technique. Different number of terms in a power-series representation of the complex type stress function was tested to qualitatively observe the effects of varying stress field. Actual fringes were related with the reconstructed and sharpened fringes along with the change in the number of terms, m. Good agreement was obtained when m in stress functions was equal to nine. At high stress concentration, the result obtained from the hybrid method agrees with FEM by two and five percent for circular and elliptical hole, respectively. The results show that the established numericalexperimental method for stress analysis is considerably reliable.

Application of P1-nonconforming Element for Shell Structure of Incompressible Materiel

This research focused on solving volumetric locking problem of shell structure of incompressible material. Degenerated solid-shell elements are widely applied on curved structure. But, volumetric locking will take place when the structure is made of incompressible material, such as rubber. Due to Poisson’s locking free property of P1-nonconforming element, it is employed to solve volumetric locking problem of shell structure. Furthermore, the study on shell structure is extended to topology optimization design. To verify the volumetric locking free of P1-nonconforming element on shell structure of incompressible material, some structures are studied by different elements. Comparing with the utilization of high order elements to solve volumetric locking problems, P1-nonconforming elements can save calculation time and reduce the numerical cost.

The Response Characteristics of Various Impact Patterns on the Smart Bumper of Automotives

In this paper, a pendulum system is constructed to perform the fundamental research which is concentrated on the various frequency patterns of impact-object simulation tests. We confirmed the application possibility for the method of discriminable pattern recognition whether impact-object is human-like or not via frequency analysis using smart sensors. Therefore a specific experimental data are compared and analyzed with the obtained database within a short time period. The impact analysis system, which is based on the above processing, can be developed and then used to recognize the impact information measured by smart sensors.

Automobile body continuous-variable-based discrete thickness optimization for maximizing natural frequency

Thickness optimization of an automobile body is presented. The thicknesses of plates making-up the monocoque body of an automobile are employed as design variables for optimization and the objective is to increase the first torsional and bending natural frequencies. By allotting one design variable to each plate of the body, compared to previous works based on element-wise design variables, design space of optimization was reduced to a large extent. Considering manufacturability of the optimized thicknesses, a straightforward thickness discretization scheme considering design sensitivities and employing a subsequent reduced optimization problem is formulated. With the optimized thicknesses, the car body maintained its weight with around 6 Hz frequency increase compared to the initial design.