An Equivalent Creep Crack Growth Model for Probabilistic Life Prediction of Plastic Pipe Materials

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Yuhao Wang ◽  
Tishun Peng ◽  
Ernest Lever ◽  
Yongming Liu
Keyword(s):  
Experimental Data ◽  
Crack Growth ◽  
Growth Model ◽  
Life Prediction ◽  
Creep Crack Growth ◽  
Creep Damage ◽  
Crack Size ◽  
Initial Crack ◽  
Local Geometry ◽  
Crack Growth Model

Abstract Life prediction in energy infrastructure such as gas pipelines is important to maintain the integrity of such systems. This paper explores a life prediction model for polyethylene materials in natural gas distribution pipelines under creep damage. The model uses a power law equation to describe the crack growth rate and an asymptotic solution for the stress intensity factor (SIF) calculation considering local geometry variations. The SIF solution considers the effect of stress concentration introduced by common damages in pipes such as rock impingement and slit. An effective initial crack size model is proposed for the life prediction of plastic pipes considering the intrinsic initial defect. Large loading-induced plastic deformation is included by a correction factor in the crack growth model. The model is calibrated and validated using experimental data on Aldyl-A pipes with different types of damage. Due to the stochastic nature of the crack growth process, uncertainty quantification is performed, and Monte Carlo (MC) simulation is used to estimate the failure probability. The predicted probabilistic life distributions under different loading conditions are compared with the experimental data. Some conclusions and future work are drawn based on the proposed study and experimental validation.

Experimental Investigation on Stochastic Crack Growth Model of GH4133B at Fatigue-Creep

2009 ◽  
Author(s):  
Dianyin Hu ◽  
Rongqiao Wang
Keyword(s):  
Experimental Data ◽  
High Temperature ◽  
Crack Growth ◽  
Room Temperature ◽  
Deterministic Model ◽  
Hold Time ◽  
Testing Machine ◽  
Crack Size ◽  
Long Distance ◽  
Crack Growth Model

Experiments on the fatigue crack growth have shown great dispersancy. Study on stochastic crack growth of material at room temperature has been widely performed. However, probabilistic model for crack growth at fatigue-creep has been little investigated due to the complexity of the deterministic model for crack growth at fatigue-creep as well as the time-consuming and the difficulty of the experiments. Traditional crack measurement such as direct current and alternating current electrical potential technique, compliance method is limited for circuit interference at large crack, especially when the temperature is higher than 500°C. Experimental system to achieve real-time FCCG detection at high temperature is established by introducing a long-distance microscope with high magnification and resolution from distances of 15cm to 35cm. The experimental setup consists of a dynamic testing machine, a machine controller, a temperature controlled box, a long-distance microscope and a high temperature furnace from room temperature to 1000°C. Then the fatigue-creep crack growth (FCCG) rate tests on thirty compact tension (CT) specimens made of GH4133B material at 600°C are carried out. The reason for choosing the GH4133B Ni-based superalloy is owing to its popularity in use for the turbine disc of the aero-engine. The tests are conducted on a 100KN capacity servo-hydraulic closed-loop machine employed trapezoidal load with hold time at upon peak load. Based on the crack growth models used for room temperature, the deterministic model for FCCG rate considering the parameters including temperature, hold time is established through comparison of the analytical results with the experimental data. Then the stochastic FCCG model for GH4133B is proposed and the probability of random to reach a specified crack size can be obtained as well as the distribution function of crack size at the service time. Through comparison between the analytical and experimental results, it’s found that the probabilistic FCCG model can fit the experimental data well. Once the stochastic FCCG model is established, it can be used for the probabilistic damage tolerance design of the turbine components made of GH4133B material.

Fatigue crack growth prediction model under variable amplitude loading conditions

2021 ◽  
pp. 105678952199873
Author(s):  
Menghan Li ◽  
Xin Liu ◽  
Zhenguo Li ◽  
Yingbo Zhang
Keyword(s):  
Crack Growth ◽  
Life Prediction ◽  
Stress Ratio ◽  
Crack Size ◽  
Model Parameters ◽  
Remaining Life ◽  
Variable Loading ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Crack Growth Model

Crack size prediction under variable amplitude loading is a very complex process, which is also important for life prediction in engineering. A crack growth model considering different stress ratio for fatigue remaining life prediction is proposed in this paper. The model utilizes stress ratio to describe the variable loading sequences, which makes the calculation greatly simplified. The rain-flow method is utilized to characterize the load sequence effects under variable amplitude loading. In addition, particle filter is utilized to estimate the model parameters describing the crack growth. Finally, case study indicates that the proposed approach is efficient in predicting crack growth and fatigue remaining life.

Finite Element Damage Analyses for Predictions of Creep Crack Growth

2010 ◽  
Author(s):  
Chang-Sik Oh ◽  
Nak-Hyun Kim ◽  
Sung-Hwan Min ◽  
Yun-Jae Kim
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Crack Growth ◽  
Damage Mechanics ◽  
Creep Crack Growth ◽  
Creep Damage ◽  
Simulation Method ◽  
Creep Tests ◽  
Creep Ductility ◽  
Creep Crack

This paper provides the virtual simulation method for creep crack growth test, based on finite element (FE) analyses with damage mechanics. Creep tests of smooth bars are used to quantify the constants of creep constitutive equation. The reduction of area resulting from creep tests of smooth and notched bar is adopted as a measure of creep ductility under multiaxial stress conditions. The creep ductility exhaustion concept is adopted for calculating creep damage, which is defined as the ratio of creep strain to the multiaxial creep ductility. To simulate crack propagation, fully damaged elements are forced to have nearly zero stresses using user-defined subroutine UHARD in the general-purpose FE code, ABAQUS. The results from 2D or 3D FE analyses are compared with experimental data of creep crack growth. It is shown that the predictions obtained from this new method are in good agreement with experimental data.

Predicting the Crack Growth Behavior in a Filled Elastomer

2006 ◽  
Vol 3-4 ◽  
pp. 273-278
Author(s):  
C.T. Liu ◽  
M. Yen ◽  
H.K. Ching
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Length ◽  
Crack Growth ◽  
Growth Model ◽  
Initial Crack ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Initial Crack Length ◽  
Crack Growth Model

In this study, single-edge cracked uniaxial specimens with an initial crack length of 0.1 in. or 0.3 in. and wedge-shaped sheet specimens with an initial crack length of 0.3 in were tested at a constant displacement rate of 50 in/min under 1000 psi confining pressure. The specimens were made of a highly filled polymeric material, containing 86% by weight of hard particles embedded in a rubbery matrix, which was made of polybutadiene-acrylic acid-acrylonitrile rubber. The uniaxial crack growth data were used to develop a crack growth model, relating crack growth rate da/dt and Mode I stress intensity factor KI. The developed crack growth model was used to predict the crack growth behavior in the wedge-shaped specimen. The results of the analysis indicated that the predicted crack growth rate compared well with the experiment

Analysis of Crack Growth in a 3D Voronoi Structure: A Model for Fatigue in Low Density Trabecular Bone

2002 ◽  
Vol 124 (5) ◽  
pp. 512-520 ◽  
Author(s):  
A. M. Makiyama ◽  
S. Vajjhala ◽  
L. J. Gibson
Keyword(s):  
Fatigue Life ◽  
Relative Density ◽  
Trabecular Bone ◽  
Crack Growth ◽  
Three Dimensional ◽  
Crack Size ◽  
Initial Crack ◽  
Low Density ◽  
Cycle Fatigue ◽  
Crack Growth Model

Both creep and crack growth contribute to the reduction in modulus associated with fatigue loading in bone. Here we simulate crack growth and subsequent strut failure in fatigue in an open-cell, three-dimensional Voronoi structure which is similar to that of low density, osteoporotic bone. The model indicates that sequential failure of struts leads to a precipitous drop in modulus: the failure of 1% of the struts leads to about a 10% decrease in modulus. A parametric study is performed to assess the influence of normalized stress range, relative density, initial crack size, crack shape and cell geometry on the fatigue life. The fatigue life is most sensitive to the relative density and the initial crack length. The results lead to a quantitative expression for the fatigue life associated with crack growth. Data for the fatigue life of trabecular bone are compared with the crack growth model described in this paper, as well as with a previous model for creep of a three-dimensional Voronoi structure. In our models, creep dominates the fatigue behavior in low cycle fatigue while crack growth dominates in high cycle fatigue, consistent with previous observations on cortical bone. The large scatter in the trabecular bone fatigue data make it impossible to identify a transition between creep dominated fatigue and crack growth dominated fatigue. The parametric study of the crack growth model indicates that variations in relative density among specimens, initial crack size within trabeculae and crack shape could easily produce such variability in the test results.

Fatigue life prediction based on an equivalent initial flaw size approach and a new normalized fatigue crack growth model

2016 ◽  
Vol 69 ◽  
pp. 15-28 ◽  
Author(s):  
J.A.F.O. Correia ◽  
S. Blasón ◽  
A.M.P. De Jesus ◽  
A.F. Canteli ◽  
P.M.G.P. Moreira ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Model ◽  
Life Prediction ◽  
Flaw Size ◽  
Fatigue Life Prediction ◽  
Crack Growth Model

The Fatigue Life Prediction Methodology Based on the Unigrow Model

2015 ◽  
Author(s):  
Sergey Bogdanov ◽  
Semyon Mikheevskiy ◽  
Grzegorz Glinka
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Model ◽  
Crack Problem ◽  
Crack Size ◽  
Engineering Structure ◽  
Time Required ◽  
Crack Growth Model ◽  
Total Life

This paper is concerned with the problem of prediction of the total life of an engineering structure based on the fatigue crack growth model. The life of an engineering component is generally modeled as a combination of the time required for a crack to initiate and then the time required for crack to propagate till the final fracture. Unfortunately the crack initiation size is a vaguely defined parameter. In order to overcome this ambiguity it is proposed to model the total life of an engineering structure by using the UniGrow fatigue crack growth model with assumption of the intrinsic material parameter ρ* as an initial crack size. The method to overcome the small crack problem in fatigue crack modeling is presented as well. The proposed model was successfully used to predict fatigue lives of misaligned cruciform welded joints under a constant amplitude loading. Results from the analysis and experiment are in a good agreement.

Sign in / Sign up

Export Citation Format

Share Document