scholarly journals Time-dependent craze zone growth at a crack tip in polymer solids

Polymer ◽  
2004 ◽  
Vol 45 (10) ◽  
pp. 3519-3525 ◽  
Author(s):  
Wen-Bo Luo ◽  
Ting-Qing Yang ◽  
Xia-Yu Wang
Keyword(s):  
Crack Tip ◽  
Time Dependent ◽  
Craze Zone ◽  
Zone Growth

Modeling of Stiffness Reduction of Vibration Conveyor Springs Subjected to Ultra High Cyclic Loading under High Humidity

2011 ◽  
Vol 471-472 ◽  
pp. 975-980
Author(s):  
Takahiko Yoshi ◽  
Kazuya Okubo ◽  
Toru Fujii
Keyword(s):  
Crack Propagation ◽  
Creep Deformation ◽  
Crack Tip ◽  
Time Dependent ◽  
High Humidity ◽  
Humidity Condition ◽  
Stiffness Reduction ◽  
Carbon Fiber Cloth ◽  
Plate Spring ◽  
High Humidity Condition

Significant stiffness reduction of the plate spring due to delaminations around the interwoven cloths could be prevented by using CFRTP (carbon fiber cloth and Polyethylene Terephthalate (PET)) rather than that by using CFRP (carbon fiber cloth and epoxy), when ultra high cyclic loading was applied to the plate spring under high humidity condition. To explain the result, the prediction model of stiffness reduction was introduced considering time-dependent crack propagation accompanying with creep deformation around the crack tip. Stiffness reduction of CFRP under high humidity condition was not only determined by cyclic crack propagation but also by time-dependent crack propagation accompanying with creep deformation around the crack tip. It was found that CFRTP was effective material of the plate springs on vibration conveyer for the uses under high humidity condition to prevent significant stiffness reduction, where the crack propagation accompanying with creep deformation should be prevented around the crack tip.

Strip-Yield Modeling of Load-Time-Temperature Effects on Crack Growth in Engine Materials

2020 ◽  
Author(s):  
James C. Newman ◽  
Rani Sullivan
Keyword(s):  
Stress Relaxation ◽  
Crack Growth ◽  
Test Data ◽  
Crack Front ◽  
Crack Tip ◽  
Time Dependent ◽  
Yield Model ◽  
Linear Superposition ◽  
Strip Yield Model ◽  
Creep Deformations

Abstract Plastic and creep deformations around a crack front and in the wake of a moving crack under cyclic loading are implemented into the life-prediction code, FASTRAN (a strip-yield model). Creep deformations are modeled by stress relaxation around the crack-tip location, since the crack-front material is under displacement control due to the surrounding elastic material. Sinusoidal and trapezoidal loading are considered. A modified linear superposition model was used to compute the cyclic- and time-dependent damage, which was based on the stress-intensity-factor concept for creep-brittle materials. Application of the modified strip-yield model was made on two sets of test data on Inconel-718 alloy. The environments were laboratory air or helium gas. From the literature, the “environment” had been shown to be a major contributor to damage magnitudes. Thus, the time-dependent crack-growth constants were selected to match the test data. In addition, the effects of a small overload on time-dependent damage, and the effects of stress relaxation and varying temperatures on crack-opening stresses and cyclic crack-tip-opening displacements, were studied.

Fracture mechanics in design and service: ‘living with defects’ - Subcritical crack growth: fatigue, creep and stress corrosion cracking

1981 ◽  
Vol 299 (1446) ◽  
pp. 31-44 ◽  
Keyword(s):  
Stress Corrosion ◽  
Crack Growth ◽  
Stress Corrosion Cracking ◽  
Crack Extension ◽  
Subcritical Crack Growth ◽  
Practical Interest ◽  
Crack Tip ◽  
Corrosion Cracking ◽  
Time Dependent ◽  
Crack Advance

Subcritical crack growth can occur under steady or varying loads. In the former it is precipitated by specific environmental conditions that encourage the operation of time-dependent processes controlling crack advance. These include aggressive environments leading to stress corrosion cracking, or elevated temperature conditions leading to creep cavitation. The result is a time-dependent maintenance of a sharp crack profile during crack extension. Under varying loads such a sharp profile is readily achieved by plastic deformation on load reduction. Net crack advance in fatigue therefore occurs in each load cycle by this blunting-resharpening process, and empirical crack growth laws reflect this physical basis. Parameters such as K and J, which define crack tip deformation, are useful for correlating fatigue crack growth. In that they define crack tip stress-strain fields under load, they also partly describe crack advance for steady load creep and stress corrosion cracking. In particular they can define a threshold state for crack extension by all three processes. Under varying loads, if fatigue conditions are combined with an aggressive or high-temperature environment the description of crack growth can be complex. These areas of corrosion fatigue and creep fatigue are of considerable current practical interest.

scholarly journals Time Dependent Crack Initiation and Growth in Ceramic Matrix Composites

1997 ◽  
Author(s):  
Matthew R. Begley ◽  
Brian N. Cox ◽  
Robert M. McMeeking
Keyword(s):  
Crack Growth ◽  
Crack Tip ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Matrix Cracking ◽  
Time Dependent ◽  
Small Scale ◽  
Matrix Composites ◽  
Fine Grained ◽  
Growth Initiation

Matrix cracking in ceramic matrix composites with fine grained fibers at high temperatures will be governed by fiber creep, as relaxation of the fibers eliminates crack tip shielding. Using a time dependent bridging law which describes the effect of creeping fibers bridging a crack in an elastic matrix, crack growth initiation and history have been modeled. For a stationary crack, crack tip stress intensity factors as a function of time are presented to predict incubation times before subcritical crack growth. Two crack growth studies are reviewed: a constant velocity approximation for small-scale bridging, and a complete velocity history analysis which can be used to predict crack length as a function of time. The predictions are summarized and discussed in terms of identifying various regimes of crack growth initiation, subcritical growth, and catastrophic matrix cracking.

scholarly journals Synergism Between Fatigue and Cyclic-Stress Corrosion-Cracking

2020 ◽  
Author(s):  
Meryl Hall, Jr
Keyword(s):  
Stress Corrosion ◽  
Crack Growth ◽  
Stress Corrosion Cracking ◽  
Crack Tip ◽  
Cyclic Stress ◽  
Corrosion Cracking ◽  
Time Dependent ◽  
Stress Cycles ◽  
Cycle Dependent ◽  
Crack Growth Rates

For 50 years, researchers have considered how time-dependent environmental effects can be included in cycle-dependent corrosion fatigue (CF) crack growth rate (CGR) models. Common assumptions are that cycle- and time-dependent contributions are separable, operate in parallel, are non-interacting and that total environmental CGR can be obtained by linear summation of cycle-dependent fatigue and time-dependent (SCC) CGRs. However, considered here are data and analyses that show that environmental CGRs may be greater than predicted by superposition models. A phenomenological model is developed to quantify the effect of crack-tip strain-rate due to fatigue stress-cycles on electrochemical activity at a crack tip and thereby synergistically increase crack growth rates by a cyclic-stress corrosion-cracking (C-SCC) mechanism.

Correlation Analysis Between Time-Dependent Creep Crack-Tip Stress and Constraint Effect on Creep Crack Initiation Time

2020 ◽  
Author(s):  
Seung-Ho Lee ◽  
Hyun-Woo Jung ◽  
Yun-Jae Kim ◽  
Kamran Nikbin ◽  
Robert A. Ainsworth
Keyword(s):  
Crack Initiation ◽  
Correlation Analysis ◽  
Creep Crack Growth ◽  
Crack Tip ◽  
Compact Tension ◽  
Time Dependent ◽  
Initiation Time ◽  
Constraint Effect ◽  
Creep Crack ◽  
Crack Tip Stress

Abstract In this study, to qualify the constraint effect on creep crack initiation, the correlation analysis between proposed constraint parameter Q’ using time-dependent creep crack-tip stress and creep crack initiation time variable Ai was performed. Ai implies the influence of constraint effect on creep crack initiation. The procedure to calculate the Ai and the Q’-parameter was presented. To evaluate various status of constraint effect, creep crack growth tests for twenty-one compact tension specimens of Type 316H stainless steel at 550°C were investigated. The results of correlation analysis explain the reason for the different initiation time at the same C* level in respect of constraint effect.

Time-dependent flow of solute atoms near a crack tip

1978 ◽  
Vol 12 (3) ◽  
pp. 249-254 ◽  
Author(s):  
Y.T. Chou ◽  
R.S. Wu ◽  
R.P. Wei
Keyword(s):  
Crack Tip ◽  
Time Dependent ◽  
Solute Atoms ◽  
Dependent Flow

Time dependent crack tip enrichment for dynamic crack propagation

2009 ◽  
Vol 162 (1-2) ◽  
pp. 33-49 ◽  
Author(s):  
Thomas Menouillard ◽  
Jeong-Hoon Song ◽  
Qinglin Duan ◽  
Ted Belytschko
Keyword(s):  
Crack Propagation ◽  
Crack Tip ◽  
Time Dependent ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack
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