N. Sivaneri

Elastic-plastic crack-tip-field numerical analysis integrated with moire interferometry

A novel method of integrating displacement field measurements from high-sensitive moire interferometry with the finite element method is introduced for the elastic-plastic fracture mechanics problems. The measured displacements normal to the crack in a fatigue-precracked specimen are input to a finite element model along a near-field boundary. In this paper the analysis is done for a power-law strain hardening material. The near-field region is discretized using 8-noded isoparametric quadrilateral elements. A validation procedure indicates that just the uy-displacement (normal to the crack) as input is sufficient for an edge-cracked specimen whereas a center-cracked specimen requires both ux- and ux-displacement inputs. Results are obtained in the form of J-integral evaluations, HRR fields, and plastic zones. A significant CPU time saving is achieved when compared with the load-input case. Also the results indicate the existence of HRR field under large scale yielding.

Numerical solutions of transonic flows by parametric differentiation and integral equation techniques

The paper discusses results of an exploratory study of the advantages obtained by combining integral equation methods with the method of parametric differentiation in the treatment of transonic flow problems. In the proposed method, the nonlinear unsteady transonic flow equation for small perturbations is transformed into a linear equation by the use of the method of parametric differentiation. The linear equation is split into a pair of weakly coupled partial differential equations by writing the transformed perturbation potential as the sum of a steady component and an unsteady component. The solution of the steady equation as an integral equation is based on Oganas treatment (1978). As a test case, the formulation is applied to predict the steady transonic flow over a nonlifting parabolic-arc airfoil.

Multimodeling strategy for assessment of complex mechanical systems

Abstract Engineering modeling plays an important role in the overall design process for a complex mechanical and/or structural system, yet the development and generation of a suitable finite element model for the static, dynamic, or thermal analysis of the system is one of the most tedious and time consuming tasks in engineering analysis. Enormous amounts of resources (human and computational) are dedicated and lost to the development of complex mathematical models that do not accomplish the function they are intended to fulfill, namely to produce reliable results. This paper presents a strategy for complex system modeling using the application of finite element modeling techniques. In this approach, the model reflects the objective of the analysis and its associated attributes. Said attributes indicate the type of analysis required, the type of loading and boundary conditions, the type of geometry and the environment for the analysis, including hardware, software, and time-frame resources. To illustrate this strategy, the paper concludes by presenting a model of a flexible internal combustion engine system based on the Stiller-Smith mechanism, in which a combination of solid, beam, and gap elements is used to represent an entire, three-dimensional system. The model presented is used to produce elastodynamic response needed for system design.