The Effect of a Stringer on the Stress in a Cracked Sheet

1965 ◽  
Vol 32 (1) ◽  
pp. 59-66 ◽  
Author(s):  
Robert Greif ◽  
J. L. Sanders
Keyword(s):  
Integral Equation ◽  
Tensile Stress ◽  
Plane Stress ◽  
Complex Variable ◽  
Concentration Factor ◽  
Stress Singularity ◽  
Maximum Load ◽  
Great Distance ◽  
Variable Approach ◽  
Finite Crack

An infinite stringer is assumed to be continuously attached to a sheet along a line perpendicular to a finite crack. At a great distance from the crack, the sheet is under a uniform tensile stress parallel to the stringer. The plane-stress solution for this problem is carried out by using the complex variable approach of Muskhelishvili to derive an integral equation which is then solved numerically on the IBM 7090 computer. In particular, the effect of the stringer on the strength of the stress singularity at the crack tip, and the maximum load-concentration factor in the stringer are found.

High-Fidelity AeroAcoustic Optimization Tool for Flexible Rotors

2020 ◽  
Author(s):  
Li Wang ◽  
Boris Diskin ◽  
Leonard V. Lopes ◽  
Eric J. Nielsen ◽  
Elizabeth Lee-Rausch ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Complex Variable ◽  
High Performance ◽  
Computational Cost ◽  
Geometric Constraints ◽  
General Level ◽  
High Fidelity ◽  
Variable Approach ◽  
Multidisciplinary Analysis ◽  
Tightly Coupled

A high-fidelity multidisciplinary analysis and gradient-based optimization tool for rotorcraft aero-acoustics is presented. Tightly coupled discipline models include physics-based computational fluid dynamics, rotorcraft comprehensive analysis, and noise prediction and propagation. A discretely consistent adjoint methodology accounts for sensitivities of unsteady flows and unstructured, dynamically deforming, overset grids. The sensitivities of structural responses to blade aerodynamic loads are computed using a complex-variable approach. Sensitivities of acoustic metrics are computed by chain-rule differentiation. Interfaces are developed for interactions between the discipline models for rotorcraft aeroacoustic analysis and the integrated sensitivity analysis. The multidisciplinary sensitivity analysis is verified through a complex-variable approach. To verify functionality of the multidisciplinary analysis and optimization tool, an optimization problem for a 40% Mach-scaled HART-II rotor-and-fuselage configuration is crafted with the objective of reducing thickness noise subject to aerodynamic and geometric constraints. The optimized configuration achieves a noticeable noise reduction, satisfies all required constraints, and produces thinner blades as expected. Computational cost of the optimization cycle is assessed in a high-performance computing environment and found to be acceptable for design of rotorcraft in general level-flight conditions.

Scattering of a shear horizontal wave by a circular cavity in a piezoelectric bi-material strip based on guided wave theory

2020 ◽  
Vol 25 (4) ◽  
pp. 968-985 ◽  
Author(s):  
Hui Qi ◽  
Meng Xiang ◽  
Jing Guo
Keyword(s):  
Integral Equation ◽  
Electric Fields ◽  
Concentration Factor ◽  
Scattering Problem ◽  
Reference Value ◽  
Wave Theory ◽  
Guided Wave ◽  
Circular Cavity ◽  
Two Phase ◽  
Shear Horizontal

The scattering problem of a shear horizontal guided wave in a piezoelectric bi-material strip is analysed by means of the "mirror method," the Green’s function method and guided wave theory. A harmonic out-of-plane line-source force is applied at the junction of two-phase materials. Then, the bi-material strip is divided into two parts, and a pair of in-plane electric fields and a pair of counter-planar forces are applied to the vertical boundary. According to the boundary conditions, the Fredholm integral equation of the first kind is established by using the conjunction method. By effectively truncating the integral equation, the integral equation is simplified to an algebraic equation. The electric field intensity concentration factor and dynamic stress concentration factor around the circular cavity are obtained. The research content of this article is of great reference value in non-destructive testing, providing a reference for the judgement of the reliability of a piezoelectric bi-material strip.

Stress in an elastic hump: the effects of glacier flow over elastic bedrock

1975 ◽  
Vol 344 (1637) ◽  
pp. 157-173 ◽  
Keyword(s):  
Plane Stress ◽  
Complex Variable ◽  
Analytic Solution ◽  
Rational Functions ◽  
Fortran Program ◽  
Stress Fields ◽  
Infinite Domain ◽  
Principal Directions ◽  
Glacier Flow ◽  
Principal Strains

Stress fields in an isotropic elastic semi-infinite domain with a humped contour subjected to applied tractions are obtained for plane strain or plane stress conditions. Domains mapped conformally onto the half-plane by a class of rational functions are considered and a complex variable method is used to determine an analytic solution. A general Fortran program has been constructed to determine stresses, principal directions, principal strains, and maximum shear tractions at specified points.

An Integral Equation Approach to the Semi-Infinite Strip Problem

1973 ◽  
Vol 40 (4) ◽  
pp. 948-954 ◽  
Author(s):  
G. D. Gupta
Keyword(s):  
Integral Equation ◽  
Singular Integral Equation ◽  
Singular Integral ◽  
Laminate Composite ◽  
Integral Transform ◽  
Stress Singularity ◽  
Infinite Strip ◽  
Integral Equation Approach ◽  
Fixed End ◽  
Integral Transform Technique

A semi-infinite strip held rigidly on its short end is considered. Loads in the strip at infinity (far away from the fixed end) are prescribed. Integral transform technique is used to provide an exact formulation of the problem in terms of a singular integral equation. Stress singularity at the strip corner is obtained from the singular integral equation which is then solved numerically. Stresses along the rigid end are determined and the effect of the material properties on the stress-intensity factor is presented. The method can also be applied to the problem of a laminate composite with a flat inclusion normal to the interfaces.

Representation of Finite Cracks by Dislocation Pileups: An Application to Atomic Simulation of Fracture

1995 ◽  
Vol 408 ◽  
Author(s):  
Vijay Shastry ◽  
Diana Farkas
Keyword(s):  
Displacement Field ◽  
Anisotropic Body ◽  
Interatomic Interaction ◽  
Elastic Displacement ◽  
Mode I ◽  
Multiple Cracks ◽  
Atomic Simulation ◽  
Variable Approach ◽  
Finite Crack ◽  
Eam Potential

AbstractThe elastic displacement field solution of a semi-infinite crack in an anisotropic body, calculated using a complex variable approach due to Sih and Liebowitz, is usually used by atomistic simulations of fracture. The corresponding expression for the displacement field of a finite crack is numerically cumbersome since it involves multiple square roots of complex numbers. In this study, displacement field of the crack is calculated by superposing the displacements of dislocations in an equivalent double pileup, equilibrated under mode I conditions. An advantage of this method is its extensibility to atomistic studies of more complex systems containing multiple cracks or interfaces. The pileup representation of the finite crack is demonstrated as being equivalent to its corresponding continuum description using the example of a double ended crack in α-Fe, loaded in mode I. In these examples, the interatomic interaction in α-Fe is described by an empirical embedded atom (EAM) potential.

Sign in / Sign up

Export Citation Format

Share Document