Initial stresses in reinforced and filled polymers

Stresses in flex spline/gear cup in harmonic drives with involute toothed gear pair and conventional strain wave generating cam are analyzed using finite element method in ANSYS® environment and experiments. The most innovative part of this investigation is establishing the evidence of secondary contacts and probable load shared by those contacts experimentally over the finite element analysis. Aiming at the performance improvement of gearing in harmonic drives, with involute toothed gear pair, the investigations are carried out through the following analyses. (a) Initial stresses in flex gear cup due to cam insertion only. (b) Stresses in flex gear cup at no load in fully assembled harmonic drive components i.e. flex gear, ring gear, and strain wave generating cam. (c) Stresses in flex gear cup at full load passing through the two pitch points, i.e. the intersection points of ring gear pitch circle, flex gear pitch curve, and major axis on both sides. Finally, (d) stresses in flex gear cup at full load distributed over all possible primary and secondary contacts, in proportion to their contact intensities. Recorded strains of the flex-gear cup while the cam being rotated showed very good agreement with the results obtained by finite element analysis with proper modeling of loading.

Download Full-text

Dynamic problems of the mechanics of the brittle fracture of materials with initial stresses for moving cracks. 1. Problem statement and general relationships

International Applied Mechanics ◽

10.1007/bf02700871 ◽

1998 ◽

Vol 34 (12) ◽

pp. 1175-1186 ◽

Cited By ~ 12

Author(s):

A. N. Guz’

Keyword(s):

Brittle Fracture ◽

Initial Stresses ◽

Dynamic Problems ◽

Problem Statement ◽

Fracture Of Materials

Download Full-text

Migration and Settling of Particulates in Filled Epoxies

Volume 1: Fora, Parts A, B, C, and D ◽

10.1115/fedsm2003-45780 ◽

2003 ◽

Author(s):

Lisa Mondy ◽

Rekha Rao ◽

Eric Lindgren ◽

Amy Sun ◽

Robert Lagasse ◽

...

Keyword(s):

Particle Concentration ◽

Particle Migration ◽

Polymerization Reaction ◽

Temperature Dependent ◽

Filled Polymers ◽

Post Test ◽

Manufacturing Applications ◽

Microscopy Data ◽

Suspension Model ◽

Epoxy Systems

Manufacturing applications for filled polymers include encapsulation of microelectronics and injection molding of composite parts. Predictive tools for simulating these manufacturing processes require knowledge of time- and temperature-dependent rheology of the polymer as well as information about local particle concentration. The overall system rheology is highly dependent on the particle concentration. The local particle concentration can change due to gravity, convection and shear-induced migration. For the epoxy systems of interest, an extent of reaction can be used to track the degree of cure. We couple the curing model with a diffusive flux suspension model [Zhang and Acrivos 1994] to determine the particle migration. This results in a generalized Newtonian model that has viscosity as a function of temperature, cure and concentration. Using this model, we examine settling of the particulate phase in both flowing and quiescent curing systems. We focus on settling in molds and flow in wide-gap counter-rotating cylinders. The heat transfer, including the exothermic polymerization reaction, must be modeled to achieve accurate results. The model is validated with temperature measurements and post-test microscopy data. Particle concentration is determined with x-ray microfocus visualization or confocal microscopy. Agreement between the simulations and experimental results is fair.

Download Full-text

Surface Wave Speed of Functionally Graded Magneto-Electro-Elastic Materials with Initial Stresses

Journal of Theoretical and Applied Mechanics ◽

10.2478/jtam-2014-0016 ◽

2014 ◽

Vol 44 (3) ◽

pp. 49-64 ◽

Cited By ~ 5

Author(s):

Li Li ◽

P. J. Wei

Keyword(s):

Surface Wave ◽

Boundary Conditions ◽

Elastic Material ◽

Short Circuit ◽

Equations Of Motion ◽

Open Circuit ◽

Functionally Graded ◽

Initial Stresses ◽

Shear Surface ◽

Traction Boundary Conditions

Abstract The shear surface wave at the free traction surface of half- infinite functionally graded magneto-electro-elastic material with initial stress is investigated. The material parameters are assumed to vary ex- ponentially along the thickness direction, only. The velocity equations of shear surface wave are derived on the electrically or magnetically open circuit and short circuit boundary conditions, based on the equations of motion of the graded magneto-electro-elastic material with the initial stresses and the free traction boundary conditions. The dispersive curves are obtained numerically and the influences of the initial stresses and the material gradient index on the dispersive curves are discussed. The investigation provides a basis for the development of new functionally graded magneto-electro-elastic surface wave devices.

Download Full-text

Modeling the Initial Stresses in Prestressed Concrete Members under Torsion

Structures Congress 2010 ◽

10.1061/41130(369)162 ◽

2010 ◽

Cited By ~ 3

Author(s):

Chyuan-Hwan Jeng ◽

Hao-Jan Chiu ◽

Cho-Sheng Chen

Keyword(s):

Prestressed Concrete ◽

Initial Stresses ◽

Concrete Members

Download Full-text

Fundamentals of generalized rigidity matrices for multi-layered media

Bulletin of the Seismological Society of America ◽

10.1785/bssa0730030749 ◽

1983 ◽

Vol 73 (3) ◽

pp. 749-763

Author(s):

Maurice A. Biot

Keyword(s):

Plane Strain ◽

Initial Stress ◽

Three Dimensional ◽

Layered Media ◽

Mathematical Structure ◽

Irreversible Thermodynamics ◽

Initial Stresses ◽

General Context ◽

Viscoelastic Media ◽

Linear Irreversible Thermodynamics

abstract Rigidity matrices for multi-layered media are derived for isotropic and orthotropic layers by a simple direct procedure which brings to light their fundamental mathematical structure. The method was introduced many years ago by the author in the more general context of dynamics and stability of multi-layers under initial stress. Other earlier results are also briefly recalled such as the derivation of three-dimensional solutions from plane strain modes, the effect of initial stresses, gravity, and couple stresses for thinly laminated layers. The extension of the same mathematical structure and symmetry to viscoelastic media is valid as a consequence of fundamental principles in linear irreversible thermodynamics.

Download Full-text