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A piping system stress analysis need to be re-performed for structural integrity assessment after reinforcement of a pipe with significant wall thinning. For efficient stress analysis, a one-dimensional beam element for the wall-thinned pipe with reinforcement needs to be developed. To develop the beam element, this work presents analytical equations for elastic stiffness of the wall-thinned pipe with reinforcement are analytically derived for axial tension, bending and torsion. Comparison with finite element (FE) analysis results using detailed three-dimensional solid models for wall-thinned pipe with reinforcement shows good agreement. Implementation of the proposed solutions into commercial FE programs is explained.

As a part of round robin analysis to develop a finite element elastic-plastic seismic analysis procedure for nuclear safety class 1 components, a series of parametric analyses was carried out on the simulated pressurizer surge line system model to investigate sensitivity of the analysis results to finite element analysis variables. The analysis on the surge line system model considered dynamic effect due to the seismic load corresponding to PGA 0.6 g and elastic-plastic material behavior based on the Chaboche combined hardening model. From the parametric analysis results, it was found that strains such as accumulated equivalent plastic strain and equivalent plastic strain are more sensitive to the analysis variables than von Mises effect stress. The parametric analysis results also identified that finite element density and ovalization option in the elbow elements have more significant effect on the analysis results than the other variables.

This paper suggests a fracture simulation method for SFR metallic fuel pin under accident condition. Two major failure mechanisms - creep damage and eutectic penetration - are implemented in the suggested method. To simulate damaged element, stress-reduction concept to reduce stiffness of the damaged element is applied. Using the proposed method, the failure size of cladding can be predicted in addition to the failure time and failure site. To verify the suggested method, Whole-pin furnace (WPF) test and TREAT-M test conducted at Argonne National Laboratory (ANL) are simulated. In all cases, predicted results and experimental results are overall in good agreement. Based on the simulation result, the effect of eutectic-penetration depth representing failure behavior on failure size is studied.

This paper proposes an elastic-plastic-based decoupling criterion that can be applied to the seismic analysis of large-scale complex piping systems in nuclear power plants under beyond design basis earthquakes. First, the existing elastic-based decoupling criteria for seismic analyses were critically reviewed. Next, the effect of plasticity on the decoupling criteria was investigated by considering the equivalent damping and stiffness reduction. Finally, the decoupling criterion considering plasticity was developed based on the changes resulting from existing decoupling criteria. The validity of the proposed decoupling criterion was confirmed through its application to an analysis of a real piping system.

This paper investigates the effect of the mesh density on reliability of XFEM stress intensity factor solutions using ABAQUS by comparing with the FE solutions using detailed crack-tip mesh. For analysis, a surface-cracked plate under mechanical and thermal loading is considered. Based on comparison, the requirements of mesh density in terms of the geometric dimension or of the enrichment radius are given.

The administration of mesenchymal stem cells (MSCs) was shown to attenuate overt as well as early diabetic nephropathy in rodents, but the underlying mechanism of this beneficial effect is largely unknown. Inflammation and mitochondrial dysfunction are major pathogenic factors in diabetic nephropathy. In this study, we found that the repeated administration of MSCs prevents albuminuria and injury to tubular epithelial cells (TECs), an important element in the progression of diabetic nephropathy, by improving mitochondrial function. The expression of M1 macrophage markers was significantly increased in diabetic kidneys compared with that in control kidneys. Interestingly, the expression of arginase-1 (Arg1), an important M2 macrophage marker, was reduced in diabetic kidneys and increased by MSC treatment. In cultured TECs, conditioned media from lipopolysaccharide-activated macrophages reduced peroxisomal proliferator-activated receptor gamma coactivator 1α (Pgc1a) expression and impaired mitochondrial function. The coculture of macrophages with MSCs increased and decreased the expression of Arg1 and M1 markers, respectively. Treatment with conditioned media from cocultured macrophages prevented activated macrophage-induced mitochondrial dysfunction in TECs. In the absence of MSC coculture, Arg1 overexpression in macrophages reversed Pgc1a suppression in TECs. These observations suggest that MSCs prevent the progression of diabetic nephropathy by reversing mitochondrial dysfunction in TECs via the induction of Arg1 in macrophages., Kidney disease: stem cells to the rescue Stem cells can halt the progression of kidney damage owing to diabetes by reducing inflammation and improving energy production in kidney cells. Eun Hee Koh at the University of Ulsan College of Medicine in Seoul, South Korea, and colleagues found that adult stem cells, known as mesenchymal stem cells (MSCs), derived from human umbilical cord blood had a protective effect on the kidneys of diabetic mice. Repeated administration of MSCs prevented the recruitment of pro-inflammatory cells into the kidney and increased the levels of arginase-1, a marker of cells with anti-inflammatory activity. Experiments in cells showed that MSCs stimulated the production of arginase-1 in that, in turn, were able to increase the production and activity of mitochondria in kidney cells. This study confirms an important role for MSCs in organ repair.

The loss of imprinting of MEST has been linked to certain types of cancer by promoter switching. However, MEST-mediated regulation of tumorigenicity and metastasis are yet to be understood. Herein, we reported that MEST is a key regulator of IL-6/JAK/STAT3/Twist-1 signal pathway-mediated tumor metastasis. Enhanced MEST expression is significantly associated with pathogenesis of breast cancer patients. Also, MEST induces metastatic potential of breast cancer through induction of the EMT-TFs-mediated EMT program. Moreover, MEST leads to Twist-1 induction by STAT3 activation and subsequently enables the induction of activation of the EMT program via the induction of STAT3 nuclear translocation. Furthermore, the c-terminal region of MEST was essential for STAT3 activation via the induction of JAK2/STAT3 complex formation. Finally, MEST is required for metastasis in an experimental metastasis model. These observations suggest that MEST is a promising target for intervention to prevent tumor metastasis.

Lagrangian-based meshless CFD methods have recently been developed and are being gradually applied to various research areas. In nuclear engineering, the meshless methods are gaining attention in modeling natural disasters and severe accident phenomena, such as tsunami, molten corium behaviors, etc., because of its flexible computational domain and effective treatment of non-linear deformations. This paper introduces recent progress and on-going activities in Lagrangian-based CFD code development at Seoul National University (SNU). The code, named SOPHIA, is based on the smoothed particle hydrodynamics (SPH) method, one of the best-known meshless numerical methods, based on a Lagrangian framework that can easily handle various types of physics because of its simplicity in expressing and solving mathematical equations. The SOPHIA code currently incorporates basic conservation equations and various physical models, including fluid flow, heat transfer, turbulence, multi-phase, phase change, elastic solid, diffusion and so on. To handle multi-phase, multi-component, and multi-resolution flows simultaneously, the SOPHIA code formulates density and continuity equations based on the normalized-density form, which has been recently developed and is proposed in the current study. The SOPHIA code also adapts CUDA GPU architectures for parallelization and performance improvement. Based on the benchmark calculations, the parallelized GPU code shows much higher computational speed by two orders of magnitude compared to the single CPU code for 1.0 million particles. This paper summarizes the overall features of the SOPHIA code, including governing equations, algorithms, and parallelization methods, along with some benchmark simulations.

Interstitial lung disease (ILD) is the most common lung manifestation in patients with Sjögren syndrome (SJS) and is associated with poor outcomes. This study aimed to investigate the long-term clinical course and prognostic factors in patients with SJS-ILD. Clinical data and high-resolution computed tomography (HRCT) images of 62 patients with primary SJS-ILD were retrospectively analyzed (biopsy-proven cases, n = 16). The mean patient age was 59.8 years; 83.9% of the patients were females, and 38.7% showed a usual interstitial pneumonia (UIP) pattern on HRCT. The median follow-up period was 61.5 months. During follow-up, 15 patients (24.2%) died, 7 (11.3%) experienced acute exacerbation (AE), and 27 (43.5%) progressed. The 1-, 3- and 5-year survival rates were 93.5%, 85.8%, and 81.1%, respectively. Age (hazard ratio [HR]: 1.158, P = 0.003), C-reactive protein (CRP) level (HR: 1.212, P = 0.045), FVC (HR: 0.902, P = 0.005), and a UIP pattern on HRCT (HR: 4.580, P = 0.029) were significant prognostic factors in multivariable Cox analysis. In conclusion, death, AE, and ILD progression occurred in 25%, 10%, and 50% of the patients with SJS-ILD, respectively. Older age, higher CRP level, lower FVC, and a UIP pattern on HRCT indicated poor prognosis.

This study designed a specimen that simulates the deformation and failure behaviors of the piping components in nuclear power plants (NPPs) under excessive seismic loads beyond the design basis, and conducted ultimate-strength tests using this specimen at room temperature (RT) and 316 °C. SA312 TP316 stainless steel (SS) and SA508 Gr.3 Cl.1 low-alloy steel (LAS) were used in the experiments. Displacement-controlled cyclic loads with constant and random amplitudes of load-line displacement (LLD) were applied as input loads. A set of input cyclic loads consisted of 20 cycles, and the LLD amplitudes of the cyclic load were determined to induce the maximum membrane plus bending stress intensity of 6–42Sm on the specimen, where Sm is the allowable design stress intensity. Multiple sets of input cyclic loads, with increasing amplitude of LLD, were applied to the specimen until cracking initiated. The results demonstrate that the simulated specimen adequately showed the ratcheting deformation and fatigue-induced cracking of piping components under displacement-controlled excessive seismic loads. In addition, samples of both materials failed under displacement-controlled cyclic load levels that were several times higher than those of the design basis earthquake (DBE). The SA316 TP316 SS had greater resistance to failure under large-amplitude cyclic loads than did SA508 Gr.3 Cl.1 LAS. For both materials, resistance to failure was lower at 316 °C than at RT. This study confirmed that the evaluation procedure of the ASME design code predicted the fatigue failure of specimens very conservatively under large-amplitude cyclic loads simulating displacement-controlled excessive seismic loads.

Strain-based and energy-based model are proposed for the evaluation of very-low cycle fatigue life considering multi-axial stress states. In the strain-based model, based on void growth and shrinkage, the void shrinkage ratio is proposed as a function of the plastic strain range. The energy-based model is developed by considering stress triaxiality in the relationship between fatigue life and fracture strain energy. For validation, two models are determined using smooth and notched bar tensile test and best-fit fatigue life curves of SA508 Gr.3 and TP316L. Fatigue lives predicted by both models are within 85% of experimental values in all cases.

OBJECTIVES There is an increasing need for grading with small endoscopic ultrasound-guided fine needle aspiration biopsy (EUS-FNAB) specimens for the proper diagnosis and therapy selection of patients with unresectable pancreatic neuroendocrine tumors (PanNET). However, our understanding of EUS-FNAB specimen grading is limited compared with surgically resected specimens. METHODS We retrospectively determined Ki-67 labeling index (LI) of 33 matched EUS-FNAB and surgically resected PanNETs with digital image analyzer. Pairwise grades between the matched biopsy and surgically resected PanNET specimens were compared. RESULTS The mean Ki-67 LI was higher in surgically resected PanNET specimens (5.5%) than in biopsy specimens (3.2%; P = 0.022). There was moderate agreement between the Ki-67 LI grades when individually evaluated matched biopsy and resected specimen pairs were compared (κ value = 0.62; P < 0.0001). However, discordance was noted in 6 cases (18%), and all of them were either grade 2 or 3 in resected PanNETs. CONCLUSIONS Although Ki-67 LI grading of EUS-FNAB specimens may be concordant with that of matched surgically resected specimens in a large proportion of the PanNET cases, Ki-67 LI grading of EUS-FNAB specimens should be carefully applied in clinical practice because of the possibility of grading underestimation with grade 2 to 3 PanNET cases.

Tumor heterogeneity is an important concept when assessing intratumoral variety in vascular phenotypes and responses to antiangiogenic treatment. This study explored spatiotemporal heterogeneity of vascular alterations in C6 glioma mice during tumor growth and antiangiogenic treatment on serial MR examinations (days 0, 4, and 7 from initiation of vehicle or multireceptor tyrosine kinase inhibitor administration). Transvascular permeability (TP) was quantified on dynamic‐contrast‐enhanced MRI (DCE‐MRI) using extravascular extracellular agent (Gd‐DOTA); blood volume (BV) was estimated using intravascular T2 agent (SPION). With regard to region‐dependent variability in vascular phenotypes, the control group demonstrated higher TP in the tumor center than in the periphery, and greater BV in the tumor periphery than in the center. This distribution pattern became more apparent with tumor growth. Antiangiogenic treatment effect was regionally heterogeneous: in the tumor center, treatment significantly suppressed the increase in TP and decrease in BV (ie, typical temporal change in the control group); in the tumor periphery, treatment‐induced vascular alterations were insignificant and BV remained high. On histopathological examination, the control group showed greater CD31, VEGFR2, Ki67, and NG2 expression in the tumor periphery than in the center. After treatment, CD31 and Ki67 expression was significantly suppressed only in the tumor center, whereas VEGFR2 and α‐caspase 3 expression was decreased and NG2 expression was increased in the entire tumor. These results demonstrate that MRI can reliably depict spatial heterogeneity in tumor vascular phenotypes and antiangiogenic treatment effects. Preserved angiogenic activity (high BV on MRI and high CD31) and proliferation (high Ki67) in the tumor periphery after treatment may provide insights into the mechanism of tumor resistance to antiangiogenic treatment.

This work presents finite element ductile tearing simulation and experimental validation of a piping system with a circumferential surface cracked (SC) A106 Gr. B pipe under simulated seismic loading condition. The damage model for simulation is based on the multiaxial fracture strain energy. The parameters in the damage model are determined from tensile and fracture toughness test results under the monotonic loading condition. For the system dynamic time history analysis, the Rayleigh damping model is employed. For cyclic constitutive equations, two models were considered to confirm its sensitivity. Predicted crack initiation and ductile tearing agree well with the experimental results.

This paper presents ductile fracture simulation using the GTN (Gurson-Tvergaard-Needleman) model of through-wall cracked STPT410 carbon steel pipe test under pure bending. Three issues related to practical application are addressed; (i) how to determine the parameters in the GTN model from fracture toughness data, (ii) how to incorporate the element-size effect to the GTN model and (iii) the effect of the crack-tip mesh design on determination of the GTN model parameters. It is found that determined values of the parameters depend on the crack-tip mesh design and the finite element size used in simulation. The split of the crack tip element into two makes parameter determination easier and gives better simulation results, but is difficult to apply to three-dimensional surface crack problems.

This paper proposes burst pressure estimation equations for steam generator tubes with multiple axial surface cracks, based on the local collapse load approach concept. The proposed equations are for a single axial surface crack, two collinear axial surface cracks and two non-aligned axial surface cracks. The proposed equations are validated against experimental tube burst test results. Predicted burst pressures agree well with the experimental results, suggesting validity of the proposed equations to estimate burst pressures for multiple axial surface cracks.

In this study, fatigue assessment was performed to evaluate fatigue lifetime of the buried natural gas pipe repaired using a composite material sleeve. Lap shear tensile and shear fatigue tests were firstly carried out in order to determine mechanical properties and to establish a damage model. Then from the test results, the damage model of the composite material sleeve was determined, based on stiffness reduction phenomenon due to adhesive damage. Via finite element damage analysis using the damage model and a structural stress/fracture mechanics approach presented in ASME B&PV Code Sec. VIII Div. 2, delamination behavior, burst pressure of the damaged pipe and fatigue lifetime of the damaged pipe after occurrence of the delamination are investigated. As results, it is confirmed that damage of the adhesive did not significantly affect the fatigue lifetime of the buried natural gas pipe even when delamination between composite layers due to adhesive damage occurred around corroded damage of the pipe.

// In Ja Park 1 , Soyeon An 5 , Sang-Yeob Kim 3, 4 , Hye Min Lim 4 , Seung-Mo Hong 2 , Mi-Ju Kim 4 , Yun Jae Kim 4 and Chang Sik Yu 1 1 Department of Colon and Rectal Surgery, University of Ulsan College of Medicine and Asan Medical Center, Seoul, Korea 2 Department of Pathology, University of Ulsan College of Medicine and Asan Medical Center, Seoul, Korea 3 Department of Convergence Medicine, University of Ulsan College of Medicine and Asan Medical Center, Seoul, Korea 4 Asan Institute for life sciences, Asan Medical Center, Seoul, Korea 5 Department of Pathology, Incheon St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Incheon, Korea Correspondence to: Chang Sik Yu, email: csyu@amc.seoul.kr Sang-Yeob Kim, email: sykim3yk@amc.seoul.kr Keywords: rectal cancer, preoperative chemoradiotherapy, responsiveness, immune infiltrates Received: April 04, 2017 Accepted: July 14, 2017 Published: July 25, 2017 ABSTRACT We evaluate whether the tumor immune infiltrate (TIL) could be used for prediction of responsiveness to preoperative chemoradiotherapy (PCRT) in rectal cancers. Using formalin-fixed paraffin-embedded slides of pretreatment biopsies, co-stain for CD4, CD8, CD274 (PD-L1), FOXP3, cytokeratin, and DAPI was performed with Opal multi staining kit (Perkin-Elmer, Waltham, MA). Multispectral imaging and digital analysis to visualize and quantify specific immune infiltrates were performed using the Vectra imaging system (Perkin-Elmer). The density (number of cells per mm 2 ) and proportion of total TILs and specific cell types in the stroma were calculated by inForm ™ 2.2.1 software (Perkin-Elmer). The density and proportion of total TILs and specific cell types in the stroma were calculated by inForm ™ 2.2.1 software (Perkin-Elmer, Waltham, MA). Patients were classified as group with total regression (TR, n = 25) and group with residual disease (near total, moderate, and minimal regression, RD, n = 50). The mean density of T cell infiltration and CD274 (PD-L1)+ lymphocyte were significantly higher in TR ( p = 0.005, p = 0.001). The proportion of CD4+ lymphocyte (p=0.042) and CD274 (PD-L1)+ lymphocyte ( p = 0.002) were different between 2 groups. The TR group has lower CD4+ and higher CD274 (PD-L1)+ proportions than RD group. The ratio among CD4+, CD8+, CD274 (PD-L1)+, FOXP3+ T cell was different between groups. TR group showed lower CD4/ CD274 (PD-L1) ( p = 0.007), CD8/ CD274 (PD-L1) ( p = 0.02), and FOXP3/ CD274 (PD-L1) ( p = 0.003) ratio than RD group. The determination of the immune infiltrate in biopsies before treatment could be a valuable information for the prediction of responsiveness to PCRT.

Little is known about the characteristics and clinical implications of specific subsets of intragraft natural killer (NK) cells in kidney transplant recipients. We analyzed 39 for-cause renal transplant biopsies performed at our center from May 2015 to July 2017. According to histopathologic reports, 8 patients (20.5%) had no rejection (NR), 11 (28.2%) had T cell-mediated rejections (TCMR) only, and 20 (51.3%) had antibody-mediated rejection (ABMR). NK cells were defined as CD3–CD56+ lymphocytes that are positive for CD57, CD49b, NKG2A, or KIR. The density of NK cells was significantly higher in the ABMR group (2.57 ± 2.58/mm2) than in the NR (0.12 ± 0.22/mm2) or the TCMR (0.25 ± 0.34/mm2) group (P = 0.002). Notably, CD56+CD57+ infiltrates (2.16 ± 1.89) were the most frequently observed compared with CD56+CD49b+ (0.05 ± 0.13), CD56+NKG2A+ (0.21 ± 0.69), and CD56+KIR+ (0.15 ± 0.42) cells in the ABMR group (P P = 0.025). In conclusion, CD56+CD57+ infiltrates are a major subset of NK cells in kidney transplant recipients with ABMR and NK cell infiltration is significantly associated with graft failure post-transplant.

In this paper, allowable bending moments for circumferential inner surface cracked pipes are evaluated. ASME Boiler and Pressure Vessel code Section XI, “Rules for Inspection of Nuclear Power Plant Components” provides analytical evaluation procedures. Analytical evaluation methods based on the failure mechanism are provided in nonmandatory Appendix C and those based on failure assessment diagram are given in nonmandatory Appendix H. Allowable bending moments are evaluated using both appendices and compared with experiments. Conservativeness is compared quantitatively between both methods by normalizing allowable bending moments with experimental maximum moments.

When discrete multiple flaws are in the same plane, and they are close to each other, it can be determined whether they are combined or standalone in accordance with combination rules provided by fitness-for-service (FFS) codes. However, specific criteria of the rules are different among these FFS codes. On the other hand, plastic collapse bending stresses for stainless steel pipes with two circumferential similar flaws were obtained by experiments, and the prediction procedure for collapse stresses for pipes with two similar flaws was developed analytically. Using the experimental data and the analytical procedure, plastic collapse stresses for pipes with two similar flaws are compared with the stresses in compliance with the flaw combination criteria. It is shown that the calculated plastic collapse stresses based on the flaw combination criteria are significantly different from the experimental and analytical stresses.

This paper presents a numerical method to simulate ductile tearing in cracked components under high strain rates using finite element damage analysis. The strain rate dependence on tensile properties and multiaxial fracture strain is characterized by the model developed by Johnson and Cook. The damage model is then defined based on the ductility exhaustion concept using the strain rate dependent multiaxial fracture strain concept. The proposed model is applied to simulate previously published three cracked pipe bending test results under two different test speed conditions. Simulated results show overall good agreement with experimental results.

This technical note presents the effect of elastic-plastic properties on calculated time-dependent C ( t ) and J ( t ) values. This is investigated via systematic elastic-plastic-creep finite element (FE) analysis. Three different stress-strain curves are used, having essentially the same plastic properties at large strains but different tensile data near the 0.2% proof (yield) strength. It is found that the plastic property in stress-strain curve affects the FE C ( t ) values only at short times (within approximately 20% of the redistribution time). The plastic property affects the initial J values at time t = 0 but not the rate of change of J ( t ) with time.

In this study, the plastic influence functions, h 1 , for estimates of J -integral of a pipe with a complex crack were newly proposed based on the systematic 3-dimensional (3-D) elastic-plastic finite element (FE) analyses by using Ramberg-Osgood (R-O) relation, in which global bending moment, axial tension and internal pressure were considered as loading conditions. Based on the present plastic influence functions, the GE/EPRI-type J -estimation scheme for complex-cracked pipes was suggested, and the results from the proposed J -estimation were compared with the FE results using both R-O fit parameters and actual tensile data of SA376 TP304 stainless steel. The comparison results demonstrate that although the proposed scheme provided sensitive J estimations according to fitting ranges of R-O parameters, it showed overall good agreements with the FE results using R-O relation. Thus, the proposed engineering J prediction method can be utilized to assess instability of a complex crack in pipes for R-O material.

This paper presents a numerical method using FE damage analysis to simulate ductile tearing in CT specimen under low cycle fatigue loading conditions. To define a cyclic material properties, the nonlinear kinematic hardening model is adopted. The damage model is defined based on the ductility exhaustion concept using the multi-axial fracture strain energy concept. The proposed model is then applied to simulate two cyclic fracture toughness tests with different R-ratios. Simulated results show overall good agreement with experimental results.

We propose a primary water stress corrosion cracking (PWSCC) initiation model of Alloy 600 that considers the stress triaxiality factor to apply to finite element analysis. We investigated the correlation between stress triaxiality effects and PWSCC growth behavior in cold-worked Alloy 600 stream generator tubes, and identified an additional stress triaxiality factor that can be added to Garud's PWSCC initiation model. By applying the proposed PWSCC initiation model considering the stress triaxiality factor, PWSCC growth simulations based on the macroscopic phenomenological damage mechanics approach were carried out on the PWSCC growth tests of various cold-worked Alloy 600 steam generator tubes and compact tension specimens. As a result, PWSCC growth behavior results from the finite element prediction are in good agreement with the experimental results.

In this article, a semi-analytical method to estimate elastic follow-up factor as input to estimate the transient creep C( t) parameter under secondary loading is presented and validated against finite element results for a cracked two-bar structure under constant displacement loading. Predicted values of C( t) agree well with the finite element results for both elastic-creep cases and for elastic-plastic cases with the same creep and plastic hardening exponents. For elastic-plastic-creep cases with different creep and plastic hardening exponents, the proposed method gives good predictions at long time but can under- or over-predict C( t) at short time.

In this paper, numerical ductile tearing simulation results are compared with six circumferential through-wall and surface cracked pipes made of two materials (SA-333 Gr. 6 and A106 Gr. B carbon steels), performed at Battelle. For simulation, a model using a simplified fracture strain model is employed, by analysing tensile data of the material. By comparing experimental J-R data with FE simulation results, the damage model dependent on the element size is determined based on the ductility exhaustion concept. The model is used to simulate ductile tearing behaviour of six circumferential through-wall and surface cracked pipes. In all cases, simulated results agree well with experimental load, crack length and crack mouth opening displacement versus load line displacement data.

The plastic influence functions for calculating fully plastic Crack opening displacement (COD) of complex-cracked pipes were newly proposed based on systematic 3-dimentional (3-D) elastic-plastic Finite element (FE) analyses using Ramberg-Osgood (R-O) relation, where global bending moment, axial tension and internal pressure are considered separately as a loading condition. Then, crack opening analyses were performed based on GE/EPRI concept by using the new plastic influence functions for complex-cracked pipes made of SA376 TP304 stainless steel, and the predicted CODs were compared with FE results based on deformation plasticity theory of tensile material behavior. From the comparison, the confidence of the proposed fully plastic crack opening solutions for complex-cracked pipes was gained. Therefore, the proposed engineering scheme for COD estimation using the new plastic influence functions can be utilized to estimate leak rate of a complex-cracked pipe for R-O material.

A method to simulate ductile tearing in large-scale pipes using finite element analysis is proposed, based on the stress-modified fracture strain model. An element-size-dependent critical damage model is also introduced in damage simulations. The damage model and associate parameters are determined from tensile and fracture toughness test data. The method is applied to simulate five bending tests of circumferential cracked carbon steel pipes. Simulated results agree overall well with two through-wall cracked pipe test data, but consistently over-predict the maximum loads for three surface cracked pipe tests. Advantages of the proposed method in practical application is briefly discussed.

This paper presents equations for estimating the crack tip characterizing parameters C(t) and J(t), for general elastic-plastic-creep conditions where the power-law creep and plasticity stress exponents differ, by modifying the plasticity correction term in published equations. The plasticity correction term in the newly proposed equations is given in terms of the initial elastic-plastic and steady-state creep stress fields. The predicted C(t) and J(t) results are validated by comparison with systematic elastic-plastic-creep FE results. Good agreement with the FE results is found.

This paper characterizes the elastic-plastic-creep crack-tip stress fields under load and displacement control. The stress field has been calculated from finite element (FE) transient creep analysis under each load control condition and displacement control condition. Varying the magnitude of initial step load is considered to investigate the influence of plasticity to creep. Both same stress exponent and different stress exponent in power-law creep and plasticity were considered. In the displacement control condition, elastic-follow-up factor is estimated by comparing FE results with existing formula. This paper proposes an equation to predict crack-tip stress fields under transient creep using a modification of the existing formula and verifies the proposed equation by comparing with FE results.

The mα-tangent method is a simple way to estimate limit load for mechanical components. The method is based on a linear elastic finite element analysis to estimate the limit loads. Present work reports limit loads for branch pipe junctions under internal pressure and in-plane bending which is determined by ma-tangent method. All results are compared with published closed-form solutions and also FE results. The FE results can be found by small-strain three-dimensional finite element (FE) limit load analyses using elastic–perfectly plastic materials. Various branch pipe geometries are considered to verify the accuracy of the ma-tangent method.

This paper propose estimation equations of transient C(t)-integrals for general material properties where plastic and creep stress exponent are different under load and displacement control. The new equations are made by modifying the plasticity correction term in the existing equations. The modified plasticity corrections term is expressed in terms of initial elastic-plastic and steady state creep stress fields. For validation, elastic-plastic-creep finite element analysis are performed. FE results are compared with predicted C(t) results using proposed equations. Good agreement with FE results is found even when plastic and creep stress exponents are different.

Due to the loss of constraint, shallow cracked specimens can ‘absorb’ more energy than deeply cracked specimens commonly used to define the critical value to fracture and therefore exhibit a higher fracture toughness. The increase in energy absorption allows a reduction in the inherent conservatism when assessing components in low constraint conditions. This study addresses the benefit of using shallow cracked SE(T) fracture toughness specimens in fitness for service (FFS) assessment of defects under low constraint conditions, e.g. blunt defects or shallow cracks. Tearing resistance curves (J-R curves) have been constructed by means of a virtual test framework to determine crack initiation and propagation for shallow cracked SE(T) specimens and parametric notched C(T) specimens. The effect of constraint level on J-R curves is compared. It is observed that most of the blunted C(T) specimens analysed exhibit the same or a lower toughness value than that of a shallow cracked SE(T) specimen. The results are used to show how reduced conservatism can be made in defect assessment of blunt defects or in cases in which reduced constraint conditions can be demonstrated.

In this paper, the effect of plastic models on initial C(t) and J(t) values was investigated. Plastic material properties used in this research are based on three different plastic models. One model consists of one-term equation, which is similar to Ramberg-Osgood equation and was used as a reference model in this research. Another model is composed of two-term equations and the other model is consist of three-term equations. FE results of these two models were used for comparison. Elastic-plastic-creep finite element analysis were performed for SE(B) specimen. FE results were analyzed through normalizing C(t) and J(t) values of two-term and three-term models by those of the reference model. It is confirmed that different plastic models contribute to the difference only in early stage of C(t) and J(t).

This paper compares a combined plastic and creep damage model with only creep damage model by simulating creep crack growth of P91. The previous model considered only creep damage is extended to consider effect of plastic damage to creep crack growth. The damage model is based on the stress-modified fracture strain model using the ductility exhaustion concept. Also, creep fracture strain depending on the strain rate is considered. Total damage is defined simply through linear addition of plastic and creep damage. When the accumulated damage becomes unity, all stress components at the finite element gauss point are reduced to a small value to simulate failure. Finite element damage analysis results using previous and proposed model are compared with experimental data for P91. The proposed model gives a better agreement with the experimental data compared with the previous model.

In this paper, the feasibility study to develop strain-based seismic design criteria applicable for the components of nuclear power plants are carried out as an alternative rule to the current stress-based criteria. To do this, two acceptance criteria are investigated through the detailed example of an application for the surge line nozzles in a nuclear steam supply system, which are known as one of the seismic fragile components in nuclear power plants. These strain-based seismic design criteria are primarily to prevent two types of failure modes, such as a ductile fracture and a cyclic fatigue-induced damage due to continuous large amplitude cyclic loads during seismic event. Through the example problem, the required procedures are described step-by-step with calculations of an accumulated plastic strain, triaxiality factor by the elasto-plastic seismic analysis using the finite element method. For a precise inelastic seismic analysis, the Chaboche kinematic and Voce isotropic hardening material parameters are identified by the test data and used for an inelastic material model. The results by the strain-based criteria are compared with those by the ASME (American Society of Mechanical Engineers) stress-based design criteria for a service level D limits. From the study, it is expected that the strain-based seismic design method investigated in this paper will be beneficial for the nuclear components, especially when the design basis earthquakes are large enough to cause severe plastic strains at a critical location.

This paper reviews the definition of elastic follow-up starting with that used in creep assessments and seeking parallel definitions for the treatment of combined primary and secondary loadings in fracture assessments. Methods for estimating the elastic follow-up factor for secondary stresses acting alone in cracked structures are then presented. It is shown that elastic follow-up factors can be estimated from elastic-plastic estimates of J for high secondary stress and are weakly dependent on elastic-plastic material properties. Potential methods for estimating J under combined primary and secondary loadings, using the elastic follow-up factor evaluated for secondary stresses acting alone, are then presented. The applicability of these methods is examined in part 2 of this paper by comparison with detailed finite element calculations.

Rationale and Objectives Variation in tissue damage after cerebral ischemia/reperfusion (I/R) can cause uncertainty in stroke-related studies, which can be reduced if the damage can be predicted early after ischemia by measuring the apparent diffusion coefficient (ADC). We investigated whether ADC measurement in the acute phase can predict permanent cerebral I/R injury. Materials and Methods The middle cerebral artery occlusion model was established using the intraluminal suture method to induce 60 minutes of ischemia followed by reperfusion in rats. T2-weighted images and diffusion-weighted images were obtained at 30 minutes and 24 hours after ischemia. Neuronal cell survival was assessed by neuronal nuclei (NeuN) immunofluorescence staining. The correlation between relative ADC (rADC) values at 30 minutes and I/R injury at 24 hours after ischemia was analyzed. Magnetic resonance imaging results were confirmed by histologic analysis. Results The correlation between rADC values at 30 minutes and 24 hours was strong in the ischemic core and peri-infarct region but moderate in the anterior choroidal and hypothalamic region. Histologic analysis revealed that the correlation between rADC values at 30 minutes and the number of NeuN-positive cells at 24 hours was strong in the ischemic core and peri-infarct region but moderate in the anterior choroidal and hypothalamic region. Furthermore, there was a strong positive correlation between the sum of rADC values of three regions at 30 minutes and the infarct volume at 24 hours. Conclusion ADC measurement in the acute phase can predict permanent cerebral I/R injury and provide important information for the evaluation of ischemic stroke.

In this paper, the combination rule for circumferential multiple-cracked pipe assessment is investigated using finite element damage analysis. The FE damage analysis based on the stress-modified fracture strain model is validated against limited fracture test data of two circumferential surface cracked pipes. Then systematic parametric study is performed using FE damage analysis for symmetrical surface cracked pipes. Failure bending stresses are calculated using the combination rule and the net-section collapse load approach for single crack provided in ASME BPV Code. It is found that predicted failure bending stress using the combination rule might be non-conservative when the distance between two cracks is short. To overcome the problem, a new combination criterion based on crack dimensions is proposed and compared with numerical data.

In this paper, a method to predict ductile fracture under low cyclic loading condition is proposed. Then it is compared with test results of surface cracked pipes which is conducted by Battelle Institute. A&F nonlinear kinematic hardening model is adopted to describe material behavior under cyclic loading condition and energy-based damage model is applied to simulate ductile crack growth. The energy-based damaged model is depending on multi-axial fracture strain energy. To apply this model, two parameters should be determined from tensile and C(T) test results under monotonic loading condition. One is multi-axial fracture strain energy Wf and the other is critical damage value ωc. From the determined damaged model, it is enable to simulate surface cracked pipe tests under low cyclic loading condition.

The refinement of the piping integrity assessment methods has emerged as a priority issue, in response to heightened concerns about the beyond design basis accident following several events. The compliance change in structures may have a significant influence on the fracture estimation. For instance, the deformation of a crack in the piping system may result in a decrease of the applied moment at the cracked section. To consider these effects, the authors have developed the general formula for prediction of the effective applied moment at circumferential cracked section based on the elastic beam theory. Using the developed formula, one can evaluate the extent of the load reduction at a crack position due to the change in compliance. This paper aims to expand the applicability of the formula for dynamic loading conditions. By conducting the time history analysis using FE model accompanying the comparisons with the piping system experiment results, it was confirmed that the formula is also available for dynamic loading conditions. It is expected that the proposed formula can be implemented in sthe piping integrity assessment to consider the restraint effect.

The loss of imprinting of MEST has been linked to certain types of cancer by promoter switching. However, MEST-mediated regulation of tumorigenicity and metastasis are yet to be understood. Herein, we reported that MEST is a key regulator of IL-6/JAK/STAT3/Twist-1 signal pathway-mediated tumor metastasis. Enhanced MEST expression is significantly associated with pathogenesis of breast cancer patients. Also, MEST induces metastatic potential of breast cancer through induction of the EMT-TFs-mediated EMT program. Moreover, MEST leads to Twist-1 induction by STAT3 activation and subsequently enables the induction of activation of the EMT program via the induction of STAT3 nuclear translocation. Furthermore, the c-terminal region of MEST was essential for STAT3 activation via the induction of JAK2/STAT3 complex formation. Finally, MEST significantly increases the breast cancer’s ability to metastasize from the mammary gland to the lung. These observations suggest that MEST is a promising target for intervention to prevent tumor metastasis.

This paper estimates the time-dependent crack-tip stress fields under elastic-plastic-creep conditions. We perform Finite-Element (FE) transient creep analyses for a Single-Edge-notched-Bend (SEB) specimen. We investigate the effect of the initial plasticity on the transient creep by systematically varying the magnitude of the initial step-load. We consider both the same stress exponent and different stress exponent in the power-law creep and plasticity to determine the elastic-plastic-creep behaviour. To estimation of the crack-tip stress fields, we compare FE analysis results with those obtained numerically formulas. In addition, we propose a new equation to predict the crack-tip stress fields when the creep exponent is different from the plastic exponent.

In this paper, we estimate the time-dependent C(t) integrals under elastic-plastic-creep conditions. Finite- element (FE) transient creep analyses have been performed for single-edge-notched-bend (SEB) specimens. We investigate the effect of the initial plasticity on the transient creep by systematically varying the magnitude of the initial step load. We consider both the same stress exponent and different stress exponents in the power-law creep and plasticity to elastic-plastic-creep behavior. To estimate the C(t) integrals, we compare the FE analysis results with those obtained using formulas. In this paper, we propose a modified equation to predict the C(t) integrals for the case of creep exponents that are different from the plastic exponent.