An Investigation on Multiple Axial Surface PWSCC Growth Behaviors in Primary Alloy 600 Components Using the PWSCC Initiation Model and Damage Mechanics Approach

2014 ◽  
Author(s):  
Jong-Sung Kim ◽  
Eun-Ju Heo ◽  
Jun-Young Jeon ◽  
Yun-Jae Kim
Keyword(s):  
Damage Mechanics ◽  
Assessment Method ◽  
Alloy 600 ◽  
Surface Cracks ◽  
Collinear Crack ◽  
Parallel Cracks ◽  
Element Size ◽  
Study Results ◽  
Axial Surface ◽  
Penetration Time

The paper proposes a new numerical method to predict the growth behavior of the multiple PWSCCs in the primary alloy 600 components. The method based on the PWSCC initiation model and macroscopic phenomenological damage mechanics approach can induce same results irrespective of the element size. The assessment method was verified comparing with the previous study results. The verified method was applied to collinear and parallel axial surface cracks. As a result, for the collinear crack, the penetration times of the collinear cracks are earlier than those of the single cracks, and the penetration time increases with increasing the space between two cracks. For the parallel crack, the penetration times of the parallel cracks are later than those of the single cracks, and the penetration time increases with decreasing the space between two cracks.

Ductile Failure Simulation to Predict Burst Pressures of Steam Generator Tubes With Multiple Axial Cracks

2013 ◽  
Author(s):  
Han-Sang Lee ◽  
Nak Hyun Kim ◽  
Yun-jae Kim ◽  
Jong Sung Kim ◽  
Jin Weon Kim
Keyword(s):  
Steam Generator ◽  
Stress Reduction ◽  
Damage Model ◽  
Ductile Failure ◽  
Thin Plates ◽  
Alloy 600 ◽  
Surface Cracks ◽  
Failure Simulation ◽  
Steam Generator Tubes ◽  
Axial Surface

This paper a new simple numerical method to predict burst pressures of Alloy 600 steam generator tubes with multiple through-wall cracks, based on the stress-modified fracture strain damage model with stress reduction technique. To validate the new method, simulated results using the proposed method are compared with thirty-on published test data of Alloy 600 thin plates and tubes with single or multiple through-wall cracks. Simulated results showing that predicted loads are within 10% of experimentally-measured ones for all cases considered. Moreover, a parametric study is performed to investigate the interaction effect of two axial surface cracks in Alloy 600 steam generator tubes under internal pressure.

scholarly journals Assessment of Lacrimal Duct Patency in Patients Undergoing Endoscopic Medial Maxillectomy

2021 ◽  
Vol 10 (2) ◽  
pp. 245
Author(s):  
Andrzej Sieśkiewicz ◽  
Tomasz Łysoń ◽  
Marek Rogowski ◽  
Marek Bielecki ◽  
Ewa Gindzienska-Sieskiewicz ◽  
...  
Keyword(s):  
Assessment Method ◽  
Test Results ◽  
Functional Disorders ◽  
Lacrimal Duct ◽  
Assessment Tests ◽  
Number Of Patients ◽  
Study Results ◽  
Assessment Techniques ◽  
Medial Maxillectomy ◽  
Comparison Of The Results

Purpose: The risk of epiphora after medial maxillectomy with lacrimal duct transection is difficult to assess. The data available in the literature are inconclusive due to various operating techniques used by the authors of medical publications, different additional procedures aimed at improving tear drainage after maxillectomy, and a variety of lacrimal duct patency assessment techniques. The aim of our work was to assess the anatomical and functional patency of lacrimal ducts after medial maxillectomy without performing additional procedures to improve tear drainage as well as comparison of the results obtained with different assessment tests. Materials and methods: 21 patients who underwent medial maxillectomy in the years 2016–2019 were assessed for discomfort and epiphora based on patients’ own reports and basic clinical examination, lacrimal duct rinse test, the Munk score, and a modified endoscopic Jones I test. Results: Gradually increasing the sensitivity of the assessment method resulted in an increase in the number of patients with potential tear drainage disorders, starting from 0% in the rinsing test, 4.8% self-reported tearing complaints, 14.3% Munk score, and 19% modified endoscopic Jones I test. Conclusions: The study results revealed that a small fraction of patients tend to report epiphora as a consequence of medial maxillectomy themselves. Subtle functional disorders, which are not particularly bothersome to patients, are more common. More sensitive lacrimal duct patency tests reveal more cases of tear drainage disorders. The results of studies assessing the incidence of epiphora after medial maxillectomy appear to depend on the type of test used.

Bulging Factor for Axial Surface Cracks in Pipes

2014 ◽  
Author(s):  
Do-Jun Shim ◽  
Gery Wilkowski
Keyword(s):  
Surface Crack ◽  
Maximum Pressure ◽  
Surface Cracks ◽  
Correction Factors ◽  
Constant Depth ◽  
Dugdale Model ◽  
Crack Driving Force ◽  
Actual Surface ◽  
Secant Equation ◽  
Axial Surface

The bulging factor for an external constant-depth axial surface crack in a pipe was calculated by 3D FE simulations. This was done in a manner consistent with Folias’s original work for the axial through-wall-cracked pipe bulging factor (MT), but was evaluated in the elastic to full-plastic conditions. The results demonstrated that the actual surface-cracked pipe bulging factor is considerably lower than the bulging factor empirically derived by Maxey/Kiefner (Mp) back in the 1970s. Based on the results of the present study, it is suggested that Mp function in the Ln-Secant equation is not truly a bulging factor for axial surface crack. Rather it is an empirically developed equation with many correction factors embedded in it to apply the Dugdale model for prediction of maximum pressure of axial surface-cracked pipes. However, due to this empiricism, this method becomes invalid (or overly conservative) when it is applied in predicting the crack-driving force using the J-based Ln-Secant equation.

Further Development of the Nonlocal Damage Model of Rousselier for the Transition Regime of Fracture Toughness and Different Stress States

2014 ◽  
Author(s):  
Sarah Gehrlicher ◽  
Michael Seidenfuss ◽  
Xaver Schuler
Keyword(s):  
Fracture Toughness ◽  
Damage Mechanics ◽  
Damage Model ◽  
Nonlocal Damage ◽  
Brittle Transition ◽  
Mechanics Model ◽  
Element Size ◽  
Transition Area ◽  
Ductile To Brittle Transition ◽  
Stress States

In nuclear power engineering failure has to be excluded for components with high safety relevance. Currently, safety assessments mainly use fracture mechanics concepts. Especially in the transition region of fracture toughness where limited stable crack extension may appear before cleavage fracture the currently applied methods are limited. This Paper deals with the development and verification of a closed concept for safety assessment of components over the whole range from the lower shelf to the upper shelf of fracture toughness. The results of classical used local damage mechanics models depend on the element size of the numerical model. This disadvantage can be avoided using an element size depending on microstructure. With high stress gradients and small crack growth rates usually smaller elements are required. This is in conflict with an element size depending on microstructure. By including the damage gradient as an additional degree of freedom in the damage mechanics model the results depend no longer at the element size. In the paper damage mechanics computations with a nonlocal formulation of the Rousselier model are carried out for the evaluation of the upper transition area. For the prediction of fracture toughness from the ductile to brittle transition area the nonlocal Rousselier model is coupled with the Beremin model. Thus ductile crack growth and failure by brittle fracture can be described in parallel. The numerical prediction of the behaviour of fracture toughness specimens (C(T)-specimens and SE(B)-specimens with and without side grooves) and the experimental results are highly concordant. The load displacement behavior of the specimens and the developed crack front from the ductile to brittle transition area can be well calculated with the nonlocal damage model. The instability in relation to temperature calculated with the coupled damage mechanics model predicts the variations of the experimental results very well. For further application of the nonlocal Rousselier model experiments and numerical calculations of specimens with different stress states and multi-axiality are carried out. Modified fracture toughness specimens like CTS-specimens (compact tension shear specimens) are taken to investigate the applicability of the nonlocal damage model of Rousselier to mixed mode fracture.

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