Verification of Alternative Criteria for Shakedown Evaluation Using Flat Head Vessel

2002 ◽  
Author(s):  
Seiji Asada ◽  
Norimichi Yamashita ◽  
Asao Okamoto ◽  
Isoharu Nishiguchi
Keyword(s):  
Finite Element ◽  
Plastic Strain ◽  
Evaluation Method ◽  
Three Dimensional ◽  
Evaluation Criteria ◽  
Strain Range ◽  
Element Analysis ◽  
Plastic Strain Range ◽  
Stress Evaluation ◽  
Elastic Shakedown

Alternative stress evaluation criteria suitable for Finite Element Analysis (FEA) proposed by Okamoto et al. [1] have been studied by the Committee on Three Dimensional Finite Element Stress Evaluation (C-TDF) in Japan. Thermal stress ratchet criteria in plastic FEA are now under consideration. Two criteria are proposed: evaluating variations in plastic strain increments and evaluating variations in the elastic core region. To verify the validity of these criteria, calculations were performed for several typical models in C-TDF [2]. This paper shows calculations and evaluation results of a Flat Head Vessel for shakedown. To study shakedown criteria for gross structural discontinuity, a flat head vessel is surveyed. The flat head vessel consists of a stiff flat head and a shell and is subjected internal pressure and thermal cycle. The elastic shakedown area and the plastic area are compared and plastic strain increments are surveyed. A shakedown evaluation method based on distribution of elastic-plastic strain range is proposed.

Verification of Alternative Criteria for Shakedown Evaluation Using 2-Dimensional and 3-Dimensional Nozzle Models

2002 ◽  
Author(s):  
Seiji Asada ◽  
Asao Okamoto ◽  
Isoharu Nishiguchi
Keyword(s):  
Finite Element ◽  
3D Model ◽  
Three Dimensional ◽  
Evaluation Criteria ◽  
Symmetric Model ◽  
Element Analysis ◽  
Stress Evaluation ◽  
Elastic Plastic ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Alternative stress evaluation criteria suitable for Finite Element Analysis (FEA) proposed by Okamoto et al. [1] have been studied by the Committee on Three Dimensional Finite Element Stress Evaluation (C-TDF) in Japan. Thermal stress ratchet criteria in plastic FEA are now under consideration. Two criteria are proposed: evaluating variations in plastic strain increments and evaluating variations in the elastic core region. To verify the validity of these criteria, calculations were performed for several typical models in C-TDF [2]. This paper shows calculations and evaluation results of 2-dimensional and 3-dimentinal nozzles for shakedown and Ke-factors, as defined by equation 2. Two models are used. One is a 2-dimensional (2D) axi-symmetric model of a typical nozzle. The other is a 3-dimantional (3D) model of the nozzle of which shell radius is half of 2-dimensional model. The primary and secondary stress, shakedown analyses using elastic-plastic FEA and Ke-factors which are directly calculated from elastic-plastic FE analyses are surveyed. The results show that the alternative criteria are applicable for those models. The analysis results of the 2D model show good relation to those of the 3D model.

Evaluation Criteria for Alternating Loads Based on Partial Inelastic Analyses

2002 ◽  
Author(s):  
Asao Okamoto ◽  
Yasuhiro Ohtake ◽  
Norimichi Yamashita
Keyword(s):  
Finite Element ◽  
Evaluation Method ◽  
Three Dimensional ◽  
Evaluation Criteria ◽  
Inelastic Behavior ◽  
Element Analysis ◽  
Plastic Strain Increment ◽  
Elastic Plastic ◽  
Stress Classification ◽  
Plastic Analysis

This paper discusses the evaluation criteria for alternating loads utilizing partial inelastic analyses and free from the stress classification. As finite element analysis becomes popular, it has been noticed by designers that in some cases the conventional stress classification does not work well. The stress classification itself had been engineered as a practical tool to evaluate the integrity of a structure by elastic analyses, which actually could have inelastic behavior. For example, primary stress limits were determined reflecting the stress level at collapse. Therefore, the problem concerning the stress classification can be solved recalling how it had been engineered. In other words, the key to solve the problem is the inelastic evaluation method corresponding to each stress category. From this point of the view, the application of the inelastic analyses becomes widely studied. Consequently, as for primary loads, it has been proven that the collapse load evaluation by Limit or Plastic Analysis is effective and practical for design analyses. On the other hand, as for the alternating loads, it is not sufficiently discussed how the alternative criteria should be without stress classification. In this paper, the following are discussed based on the calculation results in the Committee on Three Dimensional Finite Element Stress Evaluation in JPVRC. 1. Prerequisite of the elastic-plastic analysis for shakedown evaluation, and the evaluation criteria based on plastic strain increment and its distribution. 2. The advantage to use simplified elastic-plastic analysis method than to perform fully elastic-plastic analyses, and the calculation procedure for Ke factors to be used with. The associated code rules are proposed.

Ductile Fracture Behaviour of Class 2 and 3 LWR Piping and Its Implications for Flaw Evaluation Criteria

2007 ◽  
Vol 120 ◽  
pp. 85-94 ◽  
Author(s):  
Naoki Miura ◽  
Katsumasa Miyazaki ◽  
Masakazu Hisatsune ◽  
Kunio Hasegawa ◽  
Koichi Kashima
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Evaluation Method ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Evaluation Criteria ◽  
Element Analysis ◽  
Reference Stress ◽  
Class 1 ◽  
Fracture Tests

To achieve a rational maintenance program for aged Light Water Reactor components, it is important to establish and to improve the flaw evaluation criteria. The current flaw evaluation criteria such as ASME Boiler and Pressure Vessel Code Section XI are focused on Class 1 piping which usually shows relatively higher toughness. On the other hand, flaw evaluation criteria suitable for Class 2, 3 piping with moderate-toughness are also required because some Class 2, 3 piping systems are as important to plant safety analysis as Class 1 piping. In this study, both analytical and experimental studies were conducted to provide the evaluation method of fracture loads for acceptance criteria for Class 2, 3 piping. Pipe fracture tests by four-point bending were conducted on circumferentially cracked carbon steel pipes with moderate-toughness. The Net-Section Collapse criterion overpredicted experimental maximum loads for through-wall-cracked pipes, which suggested the necessity of Z-factor. Three-dimensional finite element analysis and simplified analysis based on the reference stress method were conducted to complement the limited pipe fracture tests. It was ascertained that the reference stress method always gave moderately conservative fracture loads compared with the finite element analysis and pipe fracture tests as well. Z-factor for Class 2, 3 piping was then derived and formulated using the reference stress method. Z for Class 2, 3 piping was affected by radius-to-thickness ratio, and was higher than Z for Class 1 piping in the present codes.

The Comparison of the Criteria for Ratcheting in ASME VIII-2 and Methods Given by C-TDF

2020 ◽  
Author(s):  
Liping Wan ◽  
Wangping Dong
Keyword(s):  
Finite Element ◽  
Plastic Strain ◽  
Engineering Design ◽  
3D Structure ◽  
Three Dimensional ◽  
Element Analysis ◽  
Finite Element Software ◽  
Elastic Core ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Abstract Ratcheting assessment by elastic-plastic stress analysis is presented in ASME VIII-2, paragraph 5.5.7. There are three criteria. The first one is strict in engineering design. It’s hard for most of structures to satisfy it. If the plastic strain in the structure is zero, it means that the material is not fully utilized and maybe the structure is unreasonable. Therefore, the second and third criteria are used much more. The first one and the third one can be observed directly and judged accurately by the finite element analysis results. The second one demands an elastic core in the primary-load-bearing boundary. It could be easily observed when the structure is axisymmetric, but hard to judge in the 3D structure. Okamoto in Committee on Three Dimensional Finite Element Stress Evaluation (C-TDF) has studied two thermal stress ratchet criteria: evaluating variations in the plastic strain increments and evaluating variations in the elastic core region, which can accurately assess ratcheting. Recent years, based on the criteria above, more researches have been performed by engineers not only from C-TDF but from all over the world. In this work, several two-dimensional structures and three-dimensional structures under particular load and displacement boundaries are performed by using finite element software ANSYS, aiming to compare the similarities and differences between the criteria in ASME VIII-2, 5.5.7.2 and those given by C-TDF. The assessment of these structures presented in this work will help engineers understand the realization of the criteria and methods in engineering design, especially how to utilize the results from ANSYS.

Effect of Intermetallic Compounds on the Thermomechanical Fatigue Life of Three-Dimensional Integrated Circuit Package Microsolder Bumps: Finite Element Analysis and Study

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Soud Farhan Choudhury ◽  
Leila Ladani
Keyword(s):  
Fatigue Life ◽  
Integrated Circuits ◽  
Integrated Circuit ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Strain Range ◽  
Bulk Solder ◽  
Element Analysis ◽  
Plastic Strain Range ◽  
Inelastic Strains

Currently, intermetallics (IMCs) in the solder joint are getting much attention due to their higher volume fraction in the smaller thickness interconnects. They possess different mechanical properties compared to bulk solder. Large volume fraction of IMCs may affect the mechanical behavior, thermomechanical and mechanical fatigue life and reliability of the solder interconnects due to very brittle nature compared to solder material. The question that this study is seeking to answer is how degrading IMCs are to the thermomechanical reliability of the microbumps used in three-dimensional (3D) integrated circuits (ICs) where the microsolder bumps have only a few microns of bond thicknesses. Several factors such as “squeezed out” solder geometry and IMC thickness are studied through a numerical experiment. Fatigue life is calculated using Coffin–Manson model. Results show that, though undesirable because of high likelihood of creating short circuits, squeezed out solder accumulates less inelastic strains under thermomechanical cyclic load and has higher fatigue life. The results show that with the increase of IMCs thickness in each model, the inelastic strains accumulation per cycle increases, thus decreasing the fatigue life. The drop in fatigue life tends to follow an exponential decay path. On the other hand, it was observed that plastic strain range per cycle tends to develop rapidly in Cu region with the increase in IMC thickness which calls for a consideration of Cu fatigue life more closely when the microbump contains a higher volume fraction of the IMCs. Overall, by analyzing the results, it is obvious that the presence of IMCs must be considered for microsolder bump with smaller bond thickness in fatigue life prediction model to generate more reasonable and correct results.

Effects of Local Peak Stress Distribution on the Ratchet Limit

2002 ◽  
Author(s):  
Nobuyoshi Yanagida ◽  
Masaaki Tanaka ◽  
Norimichi Yamashita ◽  
Yukinori Yamamoto
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Plastic Strain ◽  
Equivalent Stress ◽  
Equivalent Plastic Strain ◽  
Peak Stress ◽  
Element Analysis ◽  
Stress Evaluation ◽  
Elastic Plastic ◽  
Plastic Analysis

Alternative stress evaluation criteria suitable for Finite Element Analysis (FEA) proposed by Okamoto et al. [1],[2] have been studied by the Committee on Three Dimensional Finite Element Stress Evaluation (C-TDF) in Japan. Thermal stress ratchet criteria in plastic FEA are now under consideration. Two criteria are proposed: (1) Evaluating variations in plastic strain increments, and (2) Evaluating the width of the area in which Mises equivalent stress exceeds 3Sm. To verify of these criteria, we selected notched cylindrical vessel models as prime elements. To evaluate the effect of the local peak stress distribution on these criteria, cylindrical vessels with a semicircular notch on the outer surface were selected for this analysis. We used two notch configurations for our analysis, and the stress concentration factor for the notches was set to 1.5 and 2.0. We conducted elastic-plastic analysis to evaluate the ratchet limit. Sustained pressure and alternating enforced longitudinal displacements which causes secondary stress were used as parameters for the elastic-plastic analysis. We found that when no ratchet was observed, the equivalent plastic strain increments decreased and the area in which Mises equivalent stress exceeds 3Sm are below the certain range.

Mechanical Analysis and Strength Evaluation of KEY COMPONENTS Tripod of SNUBBING UNIT

2013 ◽  
Vol 477-478 ◽  
pp. 303-306
Author(s):  
Min Luo ◽  
Fa Cheng Li ◽  
Ting Ting Zhao ◽  
Ting Ting Xu ◽  
Jiu Bao Liu ◽  
...  
Keyword(s):  
Finite Element ◽  
Evaluation Method ◽  
Complex Structure ◽  
Three Dimensional ◽  
Safety Evaluation ◽  
Mechanical Analysis ◽  
Analysis Model ◽  
Element Analysis ◽  
Strength Evaluation ◽  
Three Dimensional Finite Element

Tripod is the key components of snubbing unit, its strength directly affect the normal work of snubbing unit. Considering the structure and force characteristics of key components tripod of snubbing unit, three-dimensional finite element analysis model of tripod is established. By using the finite element method, mechanical analysis of tripod is conducted and safety evaluation is finished by adopting the stress classification and introducing analysis design standard of pressure vessel. The results show that key components tripod of snubbing unit are safe and reliable under the maximum lifting force and the maximum downward force. It provides theory evidence for snubbing unit design. The safety evaluation method provides effective evaluation methods for complex structure strength evaluation.

Effects of occlusal scheme on All-on-Four abutments, screws and prostheses: A three-dimensional finite element study

2020 ◽  
Author(s):  
Nurullah Türker ◽  
Hümeyra Tercanlı Alkış ◽  
Steven J Sadowsky ◽  
Ulviye Şebnem Büyükkaplan
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Good Prognosis ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Group Function ◽  
Occlusal Contact ◽  
Maximum Deformation ◽  
Contact Points ◽  
Von Mises

An ideal occlusal scheme plays an important role in a good prognosis of All-on-Four applications, as it does for other implant therapies, due to the potential impact of occlusal loads on implant prosthetic components. The aim of the present three-dimensional (3D) finite element analysis (FEA) study was to investigate the stresses on abutments, screws and prostheses that are generated by occlusal loads via different occlusal schemes in the All-on-Four concept. Three-dimensional models of the maxilla, mandible, implants, implant substructures and prostheses were designed according to the All-on-Four concept. Forces were applied from the occlusal contact points formed in maximum intercuspation and eccentric movements in canine guidance occlusion (CGO), group function occlusion (GFO) and lingualized occlusion (LO). The von Mises stress values for abutment and screws and deformation values for prostheses were obtained and results were evaluated comparatively. It was observed that the stresses on screws and abutments were more evenly distributed in GFO. Maximum deformation values for prosthesis were observed in the CFO model for lateral movement both in the maxilla and mandible. Within the limits of the present study, GFO may be suggested to reduce stresses on screws, abutments and prostheses in the All-on-Four concept.

Towards Predicting Relative Belt Edge Endurance With the Finite Element Method

1990 ◽  
Vol 18 (4) ◽  
pp. 216-235 ◽  
Author(s):  
J. De Eskinazi ◽  
K. Ishihara ◽  
H. Volk ◽  
T. C. Warholic
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Three Dimensional ◽  
The Finite Element Method ◽  
Shear Deformations ◽  
Element Analysis ◽  
Vertical Loading ◽  
Predicted Values ◽  
Element Method

Abstract The paper describes the intention of the authors to determine whether it is possible to predict relative belt edge endurance for radial passenger car tires using the finite element method. Three groups of tires with different belt edge configurations were tested on a fleet test in an attempt to validate predictions from the finite element results. A two-dimensional, axisymmetric finite element analysis was first used to determine if the results from such an analysis, with emphasis on the shear deformations between the belts, could be used to predict a relative ranking for belt edge endurance. It is shown that such an analysis can lead to erroneous conclusions. A three-dimensional analysis in which tires are modeled under free rotation and static vertical loading was performed next. This approach resulted in an improvement in the quality of the correlations. The differences in the predicted values of various stress analysis parameters for the three belt edge configurations are studied and their implication on predicting belt edge endurance is discussed.

Torsional Analysis of a Steel Cord-Rubber Tire Belt Structure

1996 ◽  
Vol 24 (4) ◽  
pp. 339-348 ◽  
Author(s):  
R. M. V. Pidaparti
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Composite Structures ◽  
Three Dimensional ◽  
Element Model ◽  
Torsional Stiffness ◽  
Element Analysis ◽  
Rubber Belt ◽  
Steel Cord ◽  
Torsional Analysis

Abstract A three-dimensional (3D) beam finite element model was developed to investigate the torsional stiffness of a twisted steel-reinforced cord-rubber belt structure. The present 3D beam element takes into account the coupled extension, bending, and twisting deformations characteristic of the complex behavior of cord-rubber composite structures. The extension-twisting coupling due to the twisted nature of the cords was also considered in the finite element model. The results of torsional stiffness obtained from the finite element analysis for twisted cords and the two-ply steel cord-rubber belt structure are compared to the experimental data and other alternate solutions available in the literature. The effects of cord orientation, anisotropy, and rubber core surrounding the twisted cords on the torsional stiffness properties are presented and discussed.

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