Incorporation of Strain Hardening Effect Into Simplified Limit Analysis

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
P. S. Reddy Gudimetla ◽  
R. Adibi-Asl ◽  
R. Seshadri
Keyword(s):  
Lower Bound ◽  
Strain Hardening ◽  
Limit Load ◽  
Element Analysis ◽  
Active Volume ◽  
Limit Loads ◽  
Reference Volume ◽  
Perfectly Plastic ◽  
Tangent Method ◽  
Elastic Perfectly Plastic

In this paper, a method for determining limit loads in the components or structures by incorporating strain hardening effects is presented. This has been done by including a certain amount of the strain hardening into limit load analysis, which normally idealizes the material to be elastic perfectly plastic. Typical strain hardening curves such as bilinear hardening and Ramberg–Osgood material models are investigated. This paper also focuses on the plastic reference volume correction concept to determine the active volume participating in plastic collapse. The reference volume concept in combination with mα-tangent method is used to estimate lower-bound limit loads of different components. Lower-bound limit loads obtained compare well with the nonlinear finite element analysis results for several typical configurations with/without crack.

Incorporation of Strain Hardening Effect Into Limit Load Analysis

2010 ◽  
Author(s):  
P. S. Reddy Gudimetla ◽  
R. Adibi-Asl ◽  
R. Seshadri
Keyword(s):  
Strain Hardening ◽  
Limit Load ◽  
Active Volume ◽  
Limit Loads ◽  
Reference Volume ◽  
Perfectly Plastic ◽  
Tangent Method ◽  
Novel Method ◽  
Typical Strain ◽  
Load Analysis

In this paper a novel method for finding out limit loads in the components or structures by incorporating strain hardening effects is presented. This has been done by including certain amount of the strain hardening into limit load analysis, which normally idealizes the material to be perfectly plastic. The typical strain hardening curves including bilinear hardening and Ramberg-Osgood material models are investigated. The paper also concentrates on plastic reference volume correction concept to find the active volume participating in plastic collapse. The reference volume concept in combination with mα-Tangent method is used to estimate the lower bound limit load of different components.

Local Limit-Load Analysis Using the mβ Method

2006 ◽  
Vol 129 (2) ◽  
pp. 296-305 ◽  
Author(s):  
R. Adibi-Asl ◽  
R. Seshadri
Keyword(s):  
Lower Bound ◽  
Upper Bound ◽  
Local Limit ◽  
Limit Load ◽  
Element Analysis ◽  
Limit Loads ◽  
Linear Elastic ◽  
Reference Volume ◽  
Component Design ◽  
Load Analysis

Several upper-bound limit-load multipliers based on elastic modulus adjustment procedures converge to the lowest upper-bound value after several linear elastic iterations. However, pressure component design requires the use of lower-bound multipliers. Local limit loads are obtained in this paper by invoking the concept of “reference volume” in conjunction with the mβ multiplier method. The lower-bound limit loads obtained compare well to inelastic finite element analysis results for several pressure component configurations.

Limit Load Estimate Using Reference Volume Approach

2010 ◽  
Author(s):  
P. S. Reddy Gudimetla ◽  
R. Seshadri ◽  
Munaswamy Katna
Keyword(s):  
Lower Bound ◽  
Limit Load ◽  
Limit Loads ◽  
Volume Correction ◽  
Reference Volume ◽  
Tangent Method ◽  
Novel Methods ◽  
Volume Method ◽  
General Component

In this paper two novel methods (elastic reference volume method and plastic reference volume method) for reference volume correction while finding out limit loads in the components or structures are presented. These reference volume correction concepts are used in combination with mα-Tangent method to obtain the lower bound limit load of general component or structure.

Plastic Response Estimation in Repeated Elastic Analyses for Strain Hardening Material Model

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
S. L. Mahmood ◽  
R. Adibi-Asl ◽  
C. G. Daley
Keyword(s):  
Strain Hardening ◽  
Strain Energy ◽  
Plastic Material ◽  
Limit Load ◽  
Material Model ◽  
Element Analysis ◽  
Hardening Material ◽  
Linear Elastic ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic

Simplified limit analysis techniques have already been employed for limit load estimation on the basis of linear elastic finite element analysis (FEA) assuming elastic-perfectly-plastic material model. Due to strain hardening, a component or a structure can store supplementary strain energy and hence carries additional load. In this paper, an iterative elastic modulus adjustment scheme is developed in context of strain hardening material model utilizing the “strain energy density” theory. The proposed algorithm is then programmed into repeated elastic FEA and results from the numerical examples are compared with inelastic FEA results.

Reference Volume Consideration in the mα-Tangent Method Based Linear Elastic Analysis

2011 ◽  
Author(s):  
R. Adibi-Asl ◽  
M. M. Hossain ◽  
S. L. Mahmood ◽  
P. S. R. Gudimetla ◽  
R. Seshadri
Keyword(s):  
Finite Element ◽  
Rapid Determination ◽  
Limit Load ◽  
Elastic Analysis ◽  
Element Analysis ◽  
Limit Loads ◽  
Linear Elastic ◽  
Reference Volume ◽  
Tangent Method

Limit loads for pressure components are determined on the basis of a single linear elastic finite element analysis by invoking the concept of kinematically active (reference) volume in the context of the “mα-tangent” method. The resulting technique enables rapid determination of lower bound limit load for pressure components by eliminating the kinematically inactive volume. This method is applied to a number of practical components with different percentages of inactive volume. The results are compared with the corresponding inelastic finite element results, or available analytical solutions.

A Global Limit Load Solution for Plates With Embedded Elliptical Cracks Under Combined Tension and Bending

2008 ◽  
Author(s):  
Rongsheng Li ◽  
Zhiming Fang ◽  
Lihua Liang ◽  
Zengliang Gao ◽  
Yuebao Lei
Keyword(s):  
Limit Load ◽  
Elliptical Crack ◽  
Three Dimension ◽  
Element Analysis ◽  
Limit Loads ◽  
Rectangular Crack ◽  
Perfectly Plastic ◽  
The Difference ◽  
Elastic Perfectly Plastic ◽  
Elliptical Cracks

A global limit load solution is obtained in this paper for an embedded elliptical crack in a plate under combined tension and bending, based on the net-section collapse principle. The limit load solution is compared with three-dimension finite (3-D) element analysis limit load solution and the global limit load solution of a plate with an embedded rectangular crack. The limit load solution developed in this paper is conservative and close to the elastic-perfectly-plastic FE solutions. It is suitable for the estimation of the limit load. By comparison, it can be observed that the limit load of an embedded elliptical crack is larger than that of a rectangular crack. The difference between limit loads of these two cracks is negligible as the ratio of the depth to length of the crack is close to zero, however, the difference gets distinct as the ratio increases. The rectangular solutions are accurate enough as the ratio is less than 0.5 in engineering applications, and the elliptical solutions are more appropriate to the calculated limit load when the ratio is larger than 0.5.

Limit Load Analysis of Cracked Components Using the Reference Volume Method

2006 ◽  
Vol 129 (3) ◽  
pp. 391-399 ◽  
Author(s):  
R. Adibi-Asl ◽  
R. Seshadri
Keyword(s):  
Elastic Modulus ◽  
Three Dimensional ◽  
Local Limit ◽  
Limit Load ◽  
Multiple Cracks ◽  
Element Analysis ◽  
Limit Loads ◽  
Integrity Assessment ◽  
Reference Volume ◽  
Volume Method

Cracks and flaws occur in mechanical components and structures, and can lead to catastrophic failures. Therefore, integrity assessment of components with defects is carried out. This paper describes the Elastic Modulus Adjustment Procedures (EMAP) employed herein to determine the limit load of components with cracks or crack-like flaw. On the basis of linear elastic Finite Element Analysis (FEA), by specifying spatial variations in the elastic modulus, numerous sets of statically admissible and kinematically admissible distributions can be generated, to obtain lower and upper bounds limit loads. Due to the expected local plastic collapse, the reference volume concept is applied to identify the kinematically active and dead zones in the component. The Reference Volume Method is shown to yield a more accurate prediction of local limit loads. The limit load values are then compared with results obtained from inelastic FEA. The procedures are applied to a practical component with crack in order to verify their effectiveness in analyzing crack geometries. The analysis is then directed to geometries containing multiple cracks and three-dimensional defect in pressurized components.

Comparison of Elastic and Plastic Reference Volume Approaches

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
P. S. Reddy Gudimetla ◽  
Munaswamy Katna
Keyword(s):  
Limit Load ◽  
Nonlinear Finite Element ◽  
Empirical Methods ◽  
Element Analysis ◽  
Volume Correction ◽  
Adjustment Procedure ◽  
Reference Volume ◽  
Tangent Method ◽  
Proper Estimation ◽  
Volume Method

For finding out reliable limit load multipliers in pressure vessel components or structures using simplified limit load methods, proper estimation of reference volume is important. In this paper, two empirical methods namely elastic reference volume method (ERVM) and plastic reference volume method (PRVM) for reference volume correction are presented and compared. These reference volume correction concepts are used in combination with mα-tangent method and elastic modulus adjustment procedure to achieve converged limit load multiplier solution. These multipliers are compared with nonlinear finite element analysis results and are found to be lower bounded. Elastic reference volume method is the simplest method for reference volume correction when compared to plastic reference volume method.

Integral Mean of Yield Criterion in Design and Fitness for Service Assessment

2008 ◽  
Author(s):  
R. Adibi-Asl ◽  
R. Seshadri
Keyword(s):  
Lower Bound ◽  
Variational Formulation ◽  
Yield Criterion ◽  
Hot Spot ◽  
Corrosion Damage ◽  
Limit Load ◽  
Assessment Procedure ◽  
Limit Loads ◽  
Reference Volume ◽  
Volume Method

Mura’s variational formulation for determining limit loads, originally developed as an alternative to classical methods, is extended further by allowing the pseudo-elastic distributions of stresses to lie outside the yield surface provided they satisfy the “integral mean of yield” criterion. Consequently, improved lower-bound and upper-bound values for limit loads are obtained. The mα estimation limit load method, reference volume method and the fitness for service assessment procedure (including corrosion damage and thermal hot spot damage), are all applications and extensions of the “integral mean of yield” criterion.

scholarly journals An Elastic-Perfectly Plastic Flow Model for Finite Element Analysis of Perforated Materials

2000 ◽  
Vol 123 (3) ◽  
pp. 265-270 ◽  
Author(s):  
D. P. Jones ◽  
J. L. Gordon ◽  
D. N. Hutula ◽  
D. Banas ◽  
J. B. Newman
Keyword(s):  
Plastic Flow ◽  
Fourth Order ◽  
Flow Model ◽  
Limit Load ◽  
Outer Edge ◽  
Triangular Array ◽  
Element Analysis ◽  
Perfectly Plastic ◽  
Fea Model ◽  
Elastic Perfectly Plastic

This paper describes the formulation of an elastic-perfectly plastic flow theory applicable to equivalent solid (EQS) modeling of perforated materials. An equilateral triangular array of circular penetrations is considered. The usual assumptions regarding geometry and loading conditions applicable to the development of elastic constants for EQS modeling of perforated plates are considered to apply here. An elastic-perfectly plastic (EPP) EQS model is developed for a fourth-order collapse surface which is appropriate for plates with a triangular array of circular holes. A complete flow model is formulated using the consistent tangent modulus approach based on the fourth-order function. The EPP-EQS method is used to obtain a limit load solution for a plate subjected to transverse pressure and fixed at the outer edge. This solution is compared to a solution obtained with an EPP-FEA model in which each penetration in the plate is modeled explicitly. The limit load calculated by the EPP-EQS model is 6 percent lower than the limit load calculated by the explicit model.

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