scholarly journals The Numerical Analysis of the In-Plane Constraint Influence on the Behavior of the Crack Subjected to Cyclic Loading

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1764
Author(s):  
Jaroslaw Galkiewicz ◽  
Urszula Janus-Galkiewicz
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Cyclic Loading ◽  
Intensity Factor ◽  
Stress Intensity Factor Range ◽  
Cohesive Model ◽  
Paris Law ◽  
T Stress ◽  
Four Levels

The paper presents the influence of in-plane constraints defined by T-stress on the behavior of a crack subjected to cyclic loading. In the analysis, a modified boundary layer model approach was used in which the cohesive model was introduced. In the simulations, the constant maximum value of the stress intensity factor and four levels of T-stress were defined. The model was subjected to ten repeated stress cycles. Based on the results obtained, an analysis of the effect of the in-plane constraint on selected aspects of crack behavior was made. The strong influence of in-plane constraint applied in the model on the crack closure and the fatigue crack growth rate was proven. Since the in-plane constraint described the influence of geometry on the stress field surrounding the fatigue crack tip in real geometry, the results suggested that it is possible to create precise formulae connecting the level of the in-plane constraint with the effective stress intensity factor range and to incorporate the T-stress or Q-stress level in the Paris law.

Effect of Temperature on Fatigue Crack Growth in CPVC

2003 ◽  
Vol 125 (1) ◽  
pp. 71-77 ◽  
Author(s):  
Muhammad Irfan-ul-Haq ◽  
Nesar Merah
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Effect Of Temperature ◽  
Stress Intensity Factor Range ◽  
Crack Growth Behavior ◽  
Different Temperatures

This study addresses the effect of temperature on fatigue crack growth (FCG) behavior of CPVC. FCG tests were conducted on CPVC SEN tensile specimens in the temperature range −10 to 70°C. These specimens were prepared from 4-in. injection-molded pipe fittings. Crack growth behavior was studied using LEFM concepts. The stress intensity factor was modified to include the crack closure and plastic zone effects. The effective stress intensity factor range ΔKeff gave satisfactory correlation of crack growth rate (da/dN) at all temperatures of interest. The crack growth resistance was found to decrease with temperature increase. The effect of temperature on da/dN was investigated by considering the variation of mechanical properties with temperature. Master curves were developed by normalizing ΔKeff by fracture strain and yield stress. All the da/dN-ΔK curves at different temperatures were collapsed on a single curve. Crazing was found to be the dominant fatigue mechanism, especially at high temperature, while shear yielding was the dominant mechanism at low temperatures.

Mechanisms of Fatigue Crack Growth in WC-Co Cemented Carbides

2005 ◽  
Vol 297-300 ◽  
pp. 1120-1125 ◽  
Author(s):  
Myung Hwan Boo ◽  
Chi Yong Park
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Stress Ratio ◽  
Cemented Carbides ◽  
Stress Intensity Factor Range

In order to study the influence of stress ratio and WC grain size, the characteristics of fatigue crack growth were investigated in WC-Co cemented carbides with two different grain sizes of 3 and 6 µm. Fatigue crack growth tests were carried out over a wide range of fatigue crack growth rates covering the threshold stress intensity factor range DKth. It was found that crack growth rate da/dN against stress intensity factor range DK depended on stress ratio R. The crack growth rate plotted in terms of effective stress intensity factor range DKeff still exhibited the effect of microstructure. Fractographic examination revealed brittle fracture at R=0.1 and ductile fracture at R=0.5 in Co binder phase. The amount of Co phase transformation for stress ratio was closely related to fatigue crack growth characteristics.

scholarly journals Effect of Specimen Thickness and Stress Intensity Factor Range on Plasticity-Induced Fatigue Crack Closure in A7075-T6 Alloy

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 664
Author(s):  
Kenichi Masuda ◽  
Sotomi Ishihara ◽  
Noriyasu Oguma
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Crack Opening ◽  
Stress Intensity Factor Range ◽  
Radius Of Curvature ◽  
Specimen Thickness

Fatigue crack growth experiments are performed using A7075-T6 compact tension (CT) specimens with various thicknesses t (1–21 mm). The stress intensity factor at the crack opening level Kop is measured, and the effects of t and the stress intensity factor range ΔK on Kop are investigated. In addition, the change in Kop value due to specimen surface removal is investigated. Furthermore, we clarify that the radius of curvature of the leading edge of the fatigue crack decreases as t becomes thinner. Using the three-dimensional elastoplastic finite element method, the amount of plastic lateral contraction (depression depth d) at the crack tip after fatigue loading is calculated quantitatively. The following main experimental results are obtained: In the region where ΔK is 5 MPam1/2 or higher, the rate of fatigue crack growth da/dN at a constant ΔK value increases as t increases from 1 to 11 mm. The da/dN between t = 11 and 21 mm is the same. Meanwhile, in the region where ΔK is less than 5 MPam1/2, the effect of t on da/dN is not observed. The effects of t and ΔK on the da/dN–ΔK relationship are considered physically and quantitatively based on d.

Development of Surface Crack Analysis Program and its Application to Some Practical Problems

2011 ◽  
Author(s):  
Masaki Shiratori ◽  
Masaki Nagai ◽  
Naoki Miura
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Surface Crack ◽  
Surface Stress ◽  
Structural Components ◽  
Paris Law

The authors have developed a software system called “SCANP™” by which users can analyze residual lives of surface-cracked structural components such as pressure vessels and their piping systems due to fatigue or SCC. The basic concept is based upon an influence function method by which the stress intensity factor “K” of a surface crack can be calculated for arbitrarily distributed surface stresses on the cracked surface. The authors and his group have developed a great number of database of “Kij”, the influence coefficient of the stress intensity factor, for many different types of surface-cracked structural components. The database is installed into the SCANP and the K-values for one of these cracks against an arbitrarily distributed surface stress can be calculated easily through the algorithm of superposition of the surface stress and the corresponding Kij data. The fatigue crack propagation can be simulated by integrating the Paris’ law, and it is easy to estimate the residual fatigue lives up to the leakage. Further, residual lives due to SCC, stress corrosion cracking, can be simulated by following the algorithm described in the JSME Standard. In this paper it is demonstrated how the SCANP works by applying it to some practical industrial problems such as fatigue crack and SCC crack propagations into welded residual stress field, and fatigue crack propagation initiated from double-surface cracks. In the latter case the simulation was compared with the experimental results in order to evaluate the validity of the developed system. It was found that the scatter of the material data describing the Paris’ law is far larger than the errors in estimating K-values, and therefore, the choice of these material data is very important when a user wants to use this program effectively. In order to use the developed program correctly, the authors have organized “SCANP User Meeting” where only the members can use the program. In the User Meeting the users give presentations about how they applied SCANP to analyze practical problems, and discuss about the validity of the modeling, and the computed results. In this paper some of these activities will be described, and the problem of verification, validation and uncertainty quantification is discussed.

Influences of the Factors on Fatigue Crack Growth Retardation Behavior due to Multiple Overloads

2006 ◽  
Vol 306-308 ◽  
pp. 121-126
Author(s):  
Seon Jin Kim ◽  
Seok Hwan Ahn ◽  
Yu Sik Kong ◽  
Sang Woo Kwon
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Growth Retardation ◽  
Stress Intensity Factor Range ◽  
Specimen Thickness ◽  
Crack Growth Retardation

Constant K fatigue crack growth tests were performed by applying an intermediate multiple overloads for S45C steel. The purpose of this study is to investigate effects of specimen thickness at various baseline stress intensity factor range levels (Kb), the application position of the overload (a/W) and the application frequency of the overload (OLHz) on fatigue crack growth retardation behavior. The principal results are summarized as follows. The number of retardation cycles for the constant baseline stress intensity factor level (Kb ) decreases with increasing specimen thickness. The normalized number of retardation cycles ( Nd / Nc ) decreases with increasing specimen thickness. But, at Kb = 45 MPa(m)1/2, the cycle increases with increasing specimen thickness.

Sign in / Sign up

Export Citation Format

Share Document