• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.2
• /
• pp.475-485
• /
• 1995

In this study, statistical analysis of fatigue data which had obtained from respective 24 fatigue crack, was examined for SiC whisker reinforced aluminium 6061 composite alloy (SiC$_{w}$/A16061) and aluminium 6061 alloy. SiC volume fraction in composite alloy is 25%. The analysis results stress intensity factor range and 0.1 mm fatigue crack initiation life for SiC$_{w}$/A16061 composite & A16061 matrix are the log-normal distribution. And regression analysis by linear model, exponential model and multiplicative model were performed to find out the relationship between fatigue crack growth rate(da/dN) and stress intensity for find out the relationship between fatigue crack growth rate(da/dN) and stress intensity factor range(.DELTA.K) in the SiC$_{w}$/A16061 composite and examine the applicability of Paris' equation to SiC$_{w}$A16061 composite. Also computer simulation was performed for fatigue life prediction of SiC$_{w}$/A16061 composite using the statistical results of this study.udy.

• Nuclear Engineering and Technology
• /
• v.51 no.7
• /
• pp.1805-1815
• /
• 2019

While nickel-based alloys have been widely used for power plants due to corrosion resistance and good mechanical properties, during the last couple of decades, failures of nuclear components increased gradually. One of main degradation mechanisms was primary water stress corrosion cracking at dissimilar metal welds of piping and reactor head penetrations. In this context, precise estimation of welding effects became an important issue for ensuring reliability of them. The present study deals with a series of finite element analyses and crack growth rate evaluation of Alloys 690/152. Firstly, variation of residual stresses and equivalent plastic strains was simulated taking into account welding of a cylindrical block. Subsequently, extraction and pre-cracking of compact tension (CT) specimens were considered from different locations of the block. Finally, crack growth curves of the alloys and heat affected zone were developed based on analyses results combined with experimental data in references. Characteristics of crack growth behaviors were also discussed in relation to mechanical and fracture parameters.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.337-340
• /
• 2005

The effect of residual stress on fatigue crack growth was investigated in terms of finite element analysis. Simulations were performed on a CT specimen in plane strain. An interface-cohesive element that accounts for damage accumulation due to fatigue along the notch direction has been used. Numerical results show that fatigue crack growth rate slows down when compressive residual stress field exists in front of the crack tip.

• Computers and Concrete
• /
• v.8 no.3
• /
• pp.327-341
• /
• 2011

Three-dimensional graphic objects created by MATLAB are exported to the AUTOCAD program through the MATLAB handle functions. The imported SAT format files are used to produce the finite element mesh for MSC.PATRAN. Based on the Monte-Carlo random sample principle, the material heterogeneity of cement composites with randomly distributed fibers is described by the WEIBULL distribution function. In this paper, a concept called "soft region" including micro-defects, micro-voids, etc. is put forward for the simulation of crack propagation in fiber-reinforced cement composites. The performance of the numerical model is demonstrated by several examples involving crack initiation and growth in the composites under three-dimensional stress conditions: tensile loading; compressive loading and crack growth along a bimaterial interface.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.29 no.2
• /
• pp.152-161
• /
• 1993

This paper deals with the effect of spatial distribution of material properties on its statistical characteristics and numerical estimation method of reliability of fatigue sensitive structures with respect to the fatigue crack growth. A method is proposed to determine experimentally the probability distribution functions of material parameters of Paris law. da/dN=C(ΔK/K sub(0) ) super(m), using stress intensity factor controlled fatigue tests. The result with a high tensile strength steel shows that the distribution of the parameter m is approximately normal and that of 1/C, is a 3-parameter Weibull. The main result obtained are : (1) The theoretical autocorrelation of the resistance, 1/C, to fatigue crack growth are almost same for different lengths. (2) The variance decreases with the increasing a averaging length. When spatial correlation length is very small. the variane decreases significantly were the averaging length. (3) The probability distribution of load cycles or the number for a crack to reach a certain length can be estimated using these functions by simulation of non-Gaussian(expecially Weibull) Stochastic Process.

• Journal of the Korean Society of Safety
• /
• v.22 no.2 s.80
• /
• pp.15-21
• /
• 2007

Fine grained Al-5083 alloy produced by equal channel angular pressing (ECAP) at $120^{\circ}C$ was tested for investigating mechanical properties and crack growth propagation behavior. Also, FEM stress and strain analysis for the samples during ECAP were investigated, using a plastic deformation analysis software DEFORM 2-D. Coarse grained as-received samples exhibited UTS of 255.6MPa with a elongation to failure of 34.4%. By contrast, the ECAPed fine grained samples exhibited UTS of 362.0MPa with a elongation to failure of 12.9%. Fatigue crack growth resistance and threshold of fine grained samples were lower than that of as-received coarse grained samples. The higher fatigue crack growth rate in the fine grained ECAPed samples may partially arise from small roughness closure effect due to smoother fracture surfaces.

• Computers and Concrete
• /
• v.24 no.4
• /
• pp.283-293
• /
• 2019

The limited availability of raw materials and increasing service demands for pavements pose a unique challenge in terms of pavement design and concrete material selection. The self-compacting rubberized concrete (SCRC) can be used in pavement design. The SCRC pavement slab has advantages of excellent toughness, anti-fatigue and convenient construction. On the premise of satisfying the strength, the SCRC can increase the ductility of pavement slab. The aim of this investigation is proposing a new method to predict the crack growth and flexural capacity of large-scale SCRC slabs. The mechanical properties of SCRC are obtained from experiments on small-scale SCRC specimens. With the increasing of the specimen depth, the bearing capacity of SCRC beams decreases at the same initial crack-depth ratio. By constructing extended finite element method (XFEM) models, crack growth and flexural capacity of large-scale SCRC slabs with different fracture types and force conditions can be predicted. Considering the diversity of fracture types and force conditions of the concrete pavement slab, the corresponding test was used to verify the reliability of the prediction model. The crack growth and flexural capacity of SCRC slabs can be obtained from XFEM models. It is convenient to conduct the experiment and can save cost.

• Journal of the Korean Society of Safety
• /
• v.15 no.4
• /
• pp.15-19
• /
• 2000

The exact estimation of the ductile crack growth in a thin sheet would be needed in part of the commercial transport aircraft industry fields. A 2-dimensional elastic plastic finite element analysis was carried out to simulate a stable crack extension in a thin sheet 2024 aluminium alloy. Two kinds of crack modeling were used to evaluate curves of the stable crack extension. And then CTOA(crack tip opening angle) and CTED(crack tip energy density) were calculated in order to determine whether they can be used as useful crack extension criterions in a thin sheet. Results indicate that stable crack extension behaviors were simulated well and CTED is more admirable even though CTOA also is reasonable as a criterion for a stable crack extension in a thin 2024 aluminium alloy sheet.

• Proceedings of the KSME Conference
• /
• 2005.11a
• /
• pp.124.2-124.2
• /
• 2005

• Journal of the Korean Society for Precision Engineering
• /
• v.15 no.10
• /
• pp.113-119
• /
• 1998

Ship structures and aircraft structures are consisted of thin sheet alloy, so it is very important to understand the characteristics of fatigue crack propagation of that material and to establish the data base. The data for fatigue crack propagation behavior scatter very much even under identical experimental conditions with constant loading. The behavior of fatigue crack propagation under regular and irregular cyclic loadings is known to be highly affected by complicated factors such as plastic zone developed at the vicinity of crack tip and reduction of cross sectional area. In this paper, the controlled stress amplitude and overload fatigue crack propagation tests have been conducted to investigate the effect of varying factors such as plastic zone size near the crack tip and area reduction factor (AF) on the fatigue crack propagation behavior A better simulation of fatigue crack propagation behavior is found to be obtainable by using Wheeler and Willenborg models with AF effect.