Author: John Edward PopePublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
A Three-dimensional Model of Fatigue Crack Growth Incorporating Crack Closure
Author: John Edward PopeModeling of Three-Dimensional Effects on Fatigue Crack Closure Processes in Small-Scale Yielding
Author: RH. DoddsPublisher:
ISBN:
Category : Contact
Languages : en
Pages : 19
Book Description
In ductile metals, plasticity-induced closure of fatigue cracks often retards significantly measured crack growth rates in the Paris regime and contributes strongly to the observed R-ratio effect in experimental data. This work describes a similarity scaling relationship based on the 3D small-scale yielding framework wherein the thickness, B, defines the only geometric length-scale of the model. Dimensional analysis suggests a scaling relationship for the crack opening loads relative to the maximum cyclic loads (Kop/Kmax) governed by the non-dimensional load parameter ̄K=Kmax/?0 ?B, i.e., a measure of the in-plane plastic zone size normalized by the thickness. Both Kop and Kmax refer to remotely applied values of the mode I stress-intensity factor. Large-scale, 3D finite element analyses described here demonstrate that Kop/Kmax values vary strongly across the crack front in thin sheets but remain unchanged when Kmax, B, and ?0 vary to maintain ̄K = constant. The paper also includes results to demonstrate that the scaling relationship holds for non-zero values of the T-stress (which affect the Kop/Kmax values) and for an overload interspersed in the otherwise constant amplitude cycles. The present results focus on R = Kmin/Kmax = 0 loading, although the scaling relationship has been demonstrated to hold for other R > 0 loadings as well. The new similarity scaling relationship makes possible more realistic estimates of crack closure loads for a very wide range of practical conditions from just a few analyses of the type described here.
Prediction of Fatigue Crack-growth Patterns and Lives in Three-dimensional Cracked Bodies
Author: Three-Dimensional Aspects of Fatigue Crack Closure
Author: A. F. GrandtPublisher:
ISBN:
Category :
Languages : en
Pages : 205
Book Description
This final report summarizes progress on a basic research effort to determine three-dimensional aspects of the relationship between applied load and fatigue crack face separation. The research was motivated by the well known crack closure phenomenon, which indicates that naturally occurring fatigue cracks are physical held shut (or propped open) at zero load, so that crack surfaces do not separate in a linear elastic manner. Although prediction of fatigue crack opening behavior is of fundamental importance to many aspects of crack growth, relatively little is known about the three-dimensional character of closure. The research employed experimental and numerical procedures to develop predictive techniques for this important aspect of crack closure. Optical interference was used to measure crack opening in transparent polymer specimens, along with conventional crack opening and back face strain techniques for measuring crack closure. A numerical algorithm was developed to predict opening loads in surface flawed plates, and was compared with the experimental results. Keywords: Crack propagation, Cracking(Fracturing).
Advanced Three-dimensional Simulations and Cohesive Modeling of Fatigue Crack Growth
Author: Ani UralA Three-dimensional Investigation of Steady-state Fatigue Crack Closure Behavior for Through-thickness and Part-through Flaws
Author: Suvendoo Kumar RayThree-dimensional Aspects of Plasticity-induced Fatigue Crack Closure
Author: Mechanics of Fatigue Crack Closure
Author: Wolf ElberPublisher: ASTM International
ISBN: 0803109962
Category : Fracture mechanics
Languages : en
Pages : 671
Book Description
Simulating Fatigue Crack Growth in Spiral Bevel Pinion
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 50
Book Description
New results for predicting crack trajectory and fatigue life for a spiral bevel pinion using the Finite Element Method (FEM) are reported. The predictions presented are based on linear elastic fracture mechanics combined with the FEM, incorporating plasticity induced fatigue crack closure and moving gear tooth loads. The analyses were carried out using a parallel FEM solver, which calculates stress intensity factors using equivalent domain J-integral method. Fatigue life predictions were made based on a modified Paris model incorporating crack closure. To obtain a more detailed understanding of the contact between a cracked pinion tooth in mesh with an uncracked gear tooth, three-dimensional contact analyses were performed on a spiral bevel gear set incorporating a crack. The goal in carrying out these analyses was to capture the redistribution of contact loads due to crack growth. Results of these analyses showed the expected trend of decreasing tooth loads carried by the cracked tooth with increasing crack length. It was also showed that this decrease in contact loads bad an impact on the stress intensity factor values and therefore would also affect the crack trajectory and fatigue life predictions.
Author: