Stress Singularity at the Free Surface of a Dynamically Growing Crack

1990 ◽  
Vol 57 (1) ◽  
pp. 112-116 ◽  
Author(s):  
Peter Gudmundson ◽  
So¨ren O¨stlund
Keyword(s):  
Free Surface ◽  
Crack Front ◽  
Isotropic Material ◽  
Stress Singularity ◽  
Crack Tip ◽  
Finite Element Program ◽  
Linear Elastic ◽  
Growing Crack ◽  
Element Program ◽  
Tip Velocity

The stress singularity at the intersection between the crack front and the free surface of a dynamically growing crack in a linear elastic isotropic material has been numerically evaluated by an especially developed finite element program. The singularity parameter (λ), defined by σ ~ Rλ−1, is presented as a function of the crack-tip velocity and the angle (β) between the crack front and the free surface. The angle (β) at which the singularity (λ) equals 0.5 was found to be 101 deg almost independently of the crack-tip velocity.

Anisotropic Modeling of Granular Bases in Flexible Pavements

1997 ◽  
Vol 1577 (1) ◽  
pp. 18-26 ◽  
Author(s):  
Erol Tutumluer ◽  
Marshall R. Thompson
Keyword(s):  
Flexible Pavements ◽  
Triaxial Tests ◽  
Anisotropic Model ◽  
Wheel Load ◽  
Finite Element Program ◽  
Linear Elastic ◽  
Element Program ◽  
Stress Dependent ◽  
Repeated Load Triaxial ◽  
Simple Stress

A new cross-anisotropic model is proposed to predict the performance of granular bases in flexible pavements. A cross-anisotropic representation has different material properties (i.e., elastic modulus and Poisson’s ratio) assigned in the horizontal and vertical directions. Repeated-load triaxial tests with vertical and lateral deformation measurements can be used to establish these anisotropic properties. Simple stress-dependent granular material models, obtained from analysis of the laboratory test data, are used in a nonlinear finite element program, named GT-PAVE, to predict pavement responses. The horizontal and shear stiffnesses are typically found to be less than the vertical. The nonlinear anisotropic approach is shown to account effectively for the dilative behavior observed under the wheel load and the effects of compaction-induced residual stresses. The main advantage of using a cross-anisotropic model in the base is the drastic reduction or elimination of significant tensile stresses generally predicted by isotropic linear elastic layered programs.

A Material Model for Prediction of Fatigue Damage and Degradation of CFRP Materials

2017 ◽  
Vol 742 ◽  
pp. 740-744 ◽  
Author(s):  
Jörg Hohe ◽  
Monika Gall ◽  
Hannes Gauch ◽  
Sascha Fliegener ◽  
Zalkha Murni binti Abdul Hamid
Keyword(s):  
Fatigue Damage ◽  
Low Cycle Fatigue ◽  
Damage Model ◽  
Material Model ◽  
Finite Element Program ◽  
Damage Evolution Equation ◽  
Brittle Damage ◽  
Linear Elastic ◽  
Element Program ◽  
Definition Of

Objective of the present study is the definition of a material model accounting for fatigue damage and degradation. The model is formulated as a brittle damage model in the otherwise linear elastic framework. A stress driven damage evolution equation is derived from microplasticity considerations. The model is implemented as a user-defined material model into a commercial finite element program. In a comparison with experimental data in the low cycle fatigue regime, a good agreement with the numerical prediction is obtained.

The solution of viscous incompressible jet and free-surface flows using finite-element methods

1974 ◽  
Vol 65 (1) ◽  
pp. 189-206 ◽  
Author(s):  
R. E. Nickell ◽  
R. I. Tanner ◽  
B. Caswell
Keyword(s):  
Surface Tension ◽  
Finite Element ◽  
Free Surface ◽  
Transient Flow ◽  
Reynolds Numbers ◽  
Free Surface Flows ◽  
Stick Slip ◽  
Finite Element Program ◽  
Viscous Forces ◽  
Element Program

We discuss the creation of a finite-element program suitable for solving incompressible, viscous free-surface problems in steady axisymmetric or plane flows. For convenience in extending program capability to non-Newtonian flow, non-zero Reynolds numbers, and transient flow, a Galerkin formulation of the governing equations is chosen, rather than an extremum principle. The resulting program is used to solve the Newtonian die-swell problem for creeping jets free of surface tension constraints. We conclude that a Newtonian jet expands about 13%, in substantial agreement with experiments made with both small finite Reynolds numbers and small ratios of surface tension to viscous forces. The solutions to the related ‘stick-slip’ problem and the tube inlet problem, both of which also contain stress singularities, are also given.

Analysis of Domain Switching Zone Near a Crack Tip in Piezoceramics

1999 ◽  
Author(s):  
I. Chang ◽  
C. T. Sun
Keyword(s):  
Stress Field ◽  
Electric Field ◽  
Applied Electric Field ◽  
Domain Switching ◽  
Piezoelectric Materials ◽  
Crack Tip ◽  
Finite Element Program ◽  
Poling Direction ◽  
Element Program ◽  
Switching Criterion

Abstract In this paper, a finite element program in conjunction with domain switching criterion was developed to analyze domain wall switching and its effect on the near tip stress field in piezoelectric materials containing a crack. Domain switching zones in the vicinity of the crack tip corresponding to various combined electric and mechanical loads were obtained. It is found that the size, shape and mode (90° or 180° switching) of domain switching zone near the crack tip depend on the direction as well as magnitude of the applied electric field. For a positive electric field (same as the poling direction), 90° domain switching occurs behind the crack tip, and the zone increases as the applied positive electric field increases. If the applied electric field is negative, then a 180° domain switching zone appears ahead of the crack tip while a 90° domain switching zone exists behind the tip. Moreover, the stress field near the crack tip is found to be significantly affected by the domain switching.

Finite Element Simulations of Free Surface Flows With Surface Tension in Complex Geometries

2002 ◽  
Vol 124 (3) ◽  
pp. 584-594 ◽  
Author(s):  
Gang Wang
Keyword(s):  
Surface Tension ◽  
Finite Element ◽  
Free Surface ◽  
Surface Force ◽  
Free Surface Flows ◽  
Complex Geometries ◽  
Finite Element Program ◽  
Surface Flows ◽  
Static Contact ◽  
Element Program

The finite-element program, ANSYS/FLOTRAN, has been enhanced at Release 5.7 to predict free surface flows with surface tension in complex geometries. The two-dimensional incompressible Navier-Stokes and energy equations are solved in both Cartesian and axisymmetric coordinate systems. At Release 5.6, the free surface capabilities have been incorporated into ANSYS/FLOTRAN using the CLEAR-VOF algorithm. The main contribution of this work is to implement a surface tension model into ANSYS/FLOTRAN to study free surface flows with surface tension in complex geometries. Both normal and tangential components of surface tension forces are modeled at the interface through a continuum surface force (CSF) model. This new algorithm is first validated with two model problems: a droplet in equilibrium and an oscillating droplet. For the first problem, the computed pressure value is compared with the theoretical value, whereas for the second problem, the oscillation frequency is compared with both the analytical solution and experimental data. The computer program is then applied to thermocapillary flows in two types of trapezoidal cavities to investigate the interesting flow and heat transfer characteristics. Systematic calculations are performed to study the influence of Marangoni number, capillary number and static contact angle on Marangoni convection.

Analysis of Ultimate Load-Bearing Capacity of Long-Span CFST Arch Bridges

2011 ◽  
Vol 90-93 ◽  
pp. 1149-1156 ◽  
Author(s):  
Yang Liu ◽  
Da Wang ◽  
Yi Zhou Zhu
Keyword(s):  
Bearing Capacity ◽  
Failure Modes ◽  
Ultimate Load ◽  
Elastic Buckling ◽  
Load Bearing Capacity ◽  
Finite Element Program ◽  
Load Bearing ◽  
Linear Elastic ◽  
Long Span ◽  
Element Program

In order to study the ultimate load-bearing capacity of the long-span concrete-filled steel tubular (CFST) arch bridge with fly-bird-type, the ANSYS finite element program was used to establish its special model, and to study ultimate load-bearing capacity of this bridge with three different methods. The constitutive relation factors of concrete-filled steel tubular was taken into consideration including confining effect ultimate load coefficients, failure modes, and load-displacement curves of this bridge under different cases. The result indicate that the ultimate load-bearing capacity of the bridge can meet the requirement, all of its failure modes is out-plane, the two methods, linear elastic buckling analysis and only geometric nonlinearity analysis, will over high estimate ultimate load-bearing capacity of this bridge, and linear elastic buckling method cannot reflect real failure mode of this structure. In order to correctly estimate the ultimate load-bearing capacity of the bridge structure, the effect of geometric and material double nonlinearity couldn’t be neglected.

A Method to Calculate Pack Ice Driving Forces

1995 ◽  
Vol 117 (2) ◽  
pp. 145-150
Author(s):  
E. Evgin ◽  
C. Zhan ◽  
R. M. W. Frederking
Keyword(s):  
Driving Forces ◽  
Stress Distributions ◽  
Nonlinear Analyses ◽  
Creep Equation ◽  
Finite Element Program ◽  
Linear Elastic ◽  
Pack Ice ◽  
Short Period ◽  
Stress Levels ◽  
Element Program

A method is proposed to calculate pack ice driving forces. In order to develop the method, stress distributions in a circular ice floe are calculated for various boundary loading conditions. The analysis is carried out using a special-purpose finite element program in which Sinha’s creep equation is used to model the behavior of ice. Charts relating pack ice driving forces to stresses in the ice floe are produced for both linear elastic and creep equations for ice behavior. The results indicate that, for a short period of loading time and at low stress levels, a linear elastic analysis can be used to calculate the pack ice driving forces. However, when the stress levels in the ice floe are high or the time span of load application is long, linear and nonlinear analyses produce much different values for pack ice driving forces.

Stresses Near the End of an Internal Electrode in Multilayer Electrostrictive Ceramic Actuators

1994 ◽  
Vol 360 ◽  
Author(s):  
Xiao-Yan Gong
Keyword(s):  
Finite Element ◽  
Electric Field ◽  
Electric Displacement ◽  
Electrical Coupling ◽  
Stress Singularity ◽  
Stress Difference ◽  
Finite Element Program ◽  
Coupling Problem ◽  
Internal Electrode ◽  
Element Program

AbstractStresses near the end of an internal electrode in a multilayer electrostrictive ceramic actuator are studied in detail. A finite element program capable of overcoming two major difficulties is developed. The program solves both the mechanical and electrical coupling problem and the nonlinear electric field and electric displacement relationship for these materials. Results indicate that the stress difference between the coupled and the uncoupled cases can only be distinguished when a stress singularity is present. Tensile stresses are found both in front, and behind, the end of an internal electrode. The magnitude of the stresses is predetermined by the material constants.

Finite-Element Analysis of Portland Cement Concrete Pavements with Cracks

1997 ◽  
Vol 1568 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Jeffery R. Roesler ◽  
Lev Khazanovich
Keyword(s):  
Finite Element ◽  
Crack Depth ◽  
Stress Singularity ◽  
Element Model ◽  
Concrete Pavements ◽  
Portland Cement Concrete ◽  
Element Analysis ◽  
Finite Element Program ◽  
Spring Element ◽  
Element Program

It was verified that finite-element modeling could be successfully used to analyze concrete pavements with partial-depth cracks. An existing finite-element program, ILLI-SLAB, was modified (ILSL97) to allow for partial-depth crack analysis. To model a partial-depth crack, a special line spring element was added to the finite-element code. The line spring elements mimic the behavior of a crack by acting as a rotational hinge between two continuous slabs. By using available fracture mechanics techniques, a relationship was derived between the amount of moment load transfer across a crack and the crack depth. This analytical solution was then used to formulate the element stiffness matrix for the line spring element. The deflections predicted by the new finite-element program are correct, but the stresses in the vicinity of the crack tip needed to be corrected to match the stress singularity zone in front of cracks. Several example problems were used to verify the proposed finite-element model, and an example of a typical highway loading condition was analyzed.

Sign in / Sign up

Export Citation Format

Share Document