This paper discusses the modeling of residual stresses in fracture problems. Historically, residual stress effects in fracture have focused on the crack driving force, so that solely opening mode residual stresses are assumed to influence fracture. However, residual stresses can effect all components of stress at the crack-tip, and can thereby alter crack-tip constraint and influence material t...

A numerical model for rolling contact fatigue has been developed using finite element method and the Tanaka-Mura micromechanical to calculate crack threshold. Two different approaches are compared: macroscopic modeling mesoscopic which considers a Voronoi polycrystalline geometry. Smooth dented surface contacts considered methods computing shear stress compared. It is shown that length scale co...

The aim of this article is to investigate how the stress triaxiality affects plastic deformation behavior high-density polyethylene using an approach combining experiments and micromechanics-based modeling. stress-strain along with cavitation damage accumulation are experimentally quantified under well-controlled transversal response hourglass-shaped tensile specimens different curvature radii ...

Abstract Architected piezoelectric composites (PCs) have recently gained interest in designing transducers and nondestructive testing devices. The current analytical modeling approach cannot be readily applied to design architected periodic PCs exhibiting elastic anisotropy activity. This study presents a micromechanical (MM)-model based finite element (FE) framework predict the electromechanic...

In the present work, damage propagation in thermoplastic composite laminates subjected to quasi-static tensile loading was numerically simulated using different models. The simulation performed commercial finite element suite LS-Dyna, where various material models were evaluated based on their ability simulate behavior. More specifically, Tsai-Wu failure criteria (MAT_055), progressive modeling...

OF DOCTORAL DISSERTATION HELSINKI UNIVERSITY OF TECHNOLOGY P.O. BOX 1000, FI-02015 TKK http://www.tkk.fi Author Mika Petteri Koskenvuori Name of the dissertation Microelectromechanical resonators for frequency reference and frequency conversion applications Manuscript submitted 07.12.2007 Manuscript revised 03.03.2008 Date of the defence 04.04.2008 Monograph Article dissertation (summary + orig...

A 10-MHz series resonant micromechanical resonator oscil-lator has been demonstrated using a custom-designed, single-stage, zero-phase-shift sustaining amplifier together with a clamped-clamped beam micromechanical resonator, designed with a relatively large width of 40 µm to achieve substantially lower series motional resistance R x and higher power handling than previous such devices. Using a...

Micromechanical RF filters and reference oscillators based on recently demonstrated vibrating on-chip micromechanical resonators with Q’s >10,000 at 1.5 GHz, are described as an attractive solution to the increasing count of RF components (e.g., filters) expected to be needed by future multi-band wireless devices. With Q’s this high in on-chip abundance, such devices might also enable a paradig...