Anindya Deb

Analysis of orthotropically modeled stiffened plates

Abstract In the past, formulations for technically orthotropic plates appear to have been based only on Kirchhoffs assumptions for the classical thin plate theory. In the present paper, the authors have studied a formulation applicable to eccentrically stiffened plates based on the Reissner-Mindlin plate theory. Due to the formidability of the 10th-order governing equations of this formulation in yielding closed form analytical solutions, recourse has been taken to the finite element method. The range of validity of the orthotropic model, so dependent upon the proximity of stiffeners, has been assessed and demarcated by comparison with a more general discrete plate-beam model using the techniques of dimensional analysis. Finally, results arc presented for the geometrically non-linear orthotropic plate and comparisons are made with the work of earlier investigators to highlight the fact that the degree of eccentricity of stiffeners is an important factor to be taken into account, in addition to the volumetric ratio between plate and stiffeners.

Vehicle front impact safety design using a hybrid methodology

Computer-aided engineering (CAE), based on techniques like finite element modeling and analysis, can be considered as the backbone for designing complex systems such as automobiles. However, for highly nonlinear problems such as automotive crashworthiness and occupant safety design, a major problem is posed in terms of computational efficiency, modelling efforts, and model quality. For a design engineer, thus, judicious employment of various tools such as statistical regression analysis, lumped parameter modeling, and detailed finite element-based simulation can be the key for achieving an optimised design in a competitive design cycle. The current study highlights a hybrid methodology resulting from the application of these various techniques in an integrated manner for front impact safety design of vehicle platforms. In particular, new regression models are presented and the hybrid approach is demonstrated with an aluminium-intensive vehicle using LS-DYNA for detailed frontal US-NCAP analysis.

The matrix method: a powerful technique in dimensional analysis

Abstract Dimensional analysis has proved to be a most useful engineering tool, and various techniques have been developed since the 19th century. Of these, the matrix method can be considered to be the most systematic approach for obtaining a set of dimensionless parameters from a group of relevant variables. In the present paper, an organized mathematical formulation, not previously reported in the literature, is presented. Other methods of implementation are also described for the sake of completeness. The elegance and efficiency of the matrix method, when the number of variables increases, is demonstrated with the help of a suitable example.

Effectiveness of Countermeasures in Upper Interior Head Impact

Trim covers made of impact resistant polymers on vehicle interior sheet metal can contribute to reduction of HIC(d) (Head Injury Criterion, dummy) during headform impact. Airgap between trim and interior sheet metal can also induce deceleration of striking headform before it forces trim to contact sheet metal surface. As evidenced from laboratory component testing, situations may arise where additional protective measures may need to be incorporated between trim and sheet metal in order to attain acceptable levels of HIC(d). Two such alternatives in the form of energy-absorbing foam, and trim with molded collapsible stiffeners are discussed in this paper. The effectiveness of these countermeasures is evaluated through nonlinear finite element analysis, and favorable comparison with laboratory results is reported. (A) For the covering abstract see IRRD 893297.