scholarly journals Determination of fracture mechanics parameters J and C∗ by finite element and reference stress methods for a semi-elliptical flaw in a plate

2003 ◽  
Vol 80 (7-8) ◽  
pp. 565-571 ◽  
Author(s):  
F. Biglari ◽  
K.M. Nikbin ◽  
I.W. Goodall ◽  
G.A. Webster
Keyword(s):  
Finite Element ◽  
Fracture Mechanics ◽  
Reference Stress

Effects of Creep Deformation Model of Gr. 91 Steel at 600°C on Creep Fracture Mechanics Parameters

2017 ◽  
Author(s):  
Min-Gu Won ◽  
Nam-Su Huh ◽  
Hyeong-Yeon Lee ◽  
Woo-Gon Kim ◽  
Jae-Boong Choi
Keyword(s):  
Finite Element ◽  
Fracture Mechanics ◽  
Creep Deformation ◽  
Creep Model ◽  
Deformation Model ◽  
Secondary Creep ◽  
Creep Fracture ◽  
Reference Stress ◽  
Creep Region ◽  
Omega Model

The present paper investigates the effect of creep deformation model of Gr. 91 Steel at 600 °C on creep fracture mechanics parameters. Three types of creep deformation model were considered, i.e. Garofalo’s model and RCC-MRx model for primary-secondary creep region, and modified omega model for primary-secondary-tertiary creep region. The parameters for each creep deformation model were characterized from experiment results. Reference Stress (RS) method was used to estimate creep fracture mechanics parameters, C(t)-integral and COD rate for each creep model. Furthermore, elastic-creep finite element (FE) analyses were carried out to verify the results of RS method. Finally, the effect of creep deformation model was investigated by comparing the results of C(t)-integral and COD rate.

Research on Creep Fracture Mechanics Parameter by Reference Stress Method

2011 ◽  
Vol 189-193 ◽  
pp. 4383-4386
Author(s):  
Zhao Ji Hu ◽  
Ting Zhang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fracture Mechanics ◽  
Creep Crack Growth ◽  
Element Analysis ◽  
Creep Fracture ◽  
Creep Crack ◽  
Creep Coefficient ◽  
Reference Stress ◽  
Power Law Creep

Creep fracture mechanics parameter C* is used to relate the data of Creep crack initiation (CCI) and Creep crack growth (CCG). Reference stress method (RSM) can be used to explain the result of finite element analysis on evaluating structures, and it is widely used to design and assess of general structures. The result of C* is affected by the creep coefficient A and creep exponent n for power-law creep in solving creep fracture mechanics parameter C* though using RSM.

Approximate J Estimates for Circumferential Cracks in between Elbows and Attached Pipes

2007 ◽  
Vol 345-346 ◽  
pp. 521-524
Author(s):  
Tae Kwang Song ◽  
Chang Kyun Oh ◽  
Yun Jae Kim ◽  
Jong Sung Kim ◽  
Tae Eun Jin
Keyword(s):  
Finite Element ◽  
Fracture Mechanics ◽  
Closed Form ◽  
Limit Load ◽  
Small Strain ◽  
Straight Pipe ◽  
Popular Approach ◽  
Elastic Plastic ◽  
Reference Stress ◽  
Mechanics Analysis

The present work proposes a method for elastic-plastic fracture mechanics analysis of the circumferential through-wall crack in between elbows and attached straight pipes, subject to in-plane bending. Based on small strain finite element limit analyses, closed-form limit load solutions are given first. Then applicability of the reference stress based method to approximately estimate J is proposed. One interesting finding is that a popular approach to assume that the crack locates in the straight pipe could lead to significantly different assessment results.

Determination of Charge Coefficient of Piezoelectric Films Using a Combined Finite Element Model and Dynamic Loading Technique

2020 ◽  
Vol 835 ◽  
pp. 229-242
Author(s):  
Oboso P. Bernard ◽  
Nagih M. Shaalan ◽  
Mohab Hossam ◽  
Mohsen A. Hassan
Keyword(s):  
Finite Element ◽  
Dynamic Loading ◽  
Material Properties ◽  
Accurate Determination ◽  
Substrate Material ◽  
Experimental Results ◽  
Piezoelectric Composite ◽  
Piezoelectric Film ◽  
Piezoelectric Charge

Accurate determination of piezoelectric properties such as piezoelectric charge coefficients (d33) is an essential step in the design process of sensors and actuators using piezoelectric effect. In this study, a cost-effective and accurate method based on dynamic loading technique was proposed to determine the piezoelectric charge coefficient d33. Finite element analysis (FEA) model was developed in order to estimate d33 and validate the obtained values with experimental results. The experiment was conducted on a piezoelectric disc with a known d33 value. The effect of measuring boundary conditions, substrate material properties and specimen geometry on measured d33 value were conducted. The experimental results reveal that the determined d33 coefficient by this technique is accurate as it falls within the manufactures tolerance specifications of PZT-5A piezoelectric film d33. Further, obtained simulation results on fibre reinforced and particle reinforced piezoelectric composite were found to be similar to those that have been obtained using more advanced techniques. FE-results showed that the measured d33 coefficients depend on measuring boundary condition, piezoelectric film thickness, and substrate material properties. This method was proved to be suitable for determination of d33 coefficient effectively for piezoelectric samples of any arbitrary geometry without compromising on the accuracy of measured d33.

scholarly journals Stiffness Estimation and Equivalence of Boundary Conditions in FEM Models

2021 ◽  
Vol 11 (4) ◽  
pp. 1482
Author(s):  
Róbert Huňady ◽  
Pavol Lengvarský ◽  
Peter Pavelka ◽  
Adam Kaľavský ◽  
Jakub Mlotek
Keyword(s):  
Boundary Condition ◽  
Finite Element ◽  
Boundary Conditions ◽  
Model Updating ◽  
Element Model ◽  
Computational Time ◽  
Stiffness Coefficients ◽  
First Case ◽  
Numerical Approaches

The paper deals with methods of equivalence of boundary conditions in finite element models that are based on finite element model updating technique. The proposed methods are based on the determination of the stiffness parameters in the section plate or region, where the boundary condition or the removed part of the model is replaced by the bushing connector. Two methods for determining its elastic properties are described. In the first case, the stiffness coefficients are determined by a series of static finite element analyses that are used to obtain the response of the removed part to the six basic types of loads. The second method is a combination of experimental and numerical approaches. The natural frequencies obtained by the measurement are used in finite element (FE) optimization, in which the response of the model is tuned by changing the stiffness coefficients of the bushing. Both methods provide a good estimate of the stiffness at the region where the model is replaced by an equivalent boundary condition. This increases the accuracy of the numerical model and also saves computational time and capacity due to element reduction.

Determination of collapse moment of different angled pipe bends with initial geometric imperfection subjected to in-plane bending moments

2021 ◽  
pp. 095440622199640
Author(s):  
Manish Kumar ◽  
Pronab Roy ◽  
Kallol Khan
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Circular Cross Section ◽  
Initial Imperfection ◽  
Bend Angle ◽  
Bending Moments ◽  
Element Analysis ◽  
Geometric Imperfection ◽  
Initial Geometric Imperfection

From the recent literature, it is revealed that pipe bend geometry deviates from the circular cross-section due to pipe bending process for any bend angle, and this deviation in the cross-section is defined as the initial geometric imperfection. This paper focuses on the determination of collapse moment of different angled pipe bends incorporated with initial geometric imperfection subjected to in-plane closing and opening bending moments. The three-dimensional finite element analysis is accounted for geometric as well as material nonlinearities. Python scripting is implemented for modeling the pipe bends with initial geometry imperfection. The twice-elastic-slope method is adopted to determine the collapse moments. From the results, it is observed that initial imperfection has significant impact on the collapse moment of pipe bends. It can be concluded that the effect of initial imperfection decreases with the decrease in bend angle from 150∘ to 45∘. Based on the finite element results, a simple collapse moment equation is proposed to predict the collapse moment for more accurate cross-section of the different angled pipe bends.

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