Yield Criteria for the Elastic-Plastic Design of Tubesheets With Triangular Penetration Pattern

2000 ◽  
Vol 123 (1) ◽  
pp. 118-123 ◽  
Author(s):  
Wolf D. Reinhardt
Keyword(s):  
Finite Element ◽  
Biaxial Loading ◽  
Yield Criterion ◽  
Equivalent Stress ◽  
Yield Function ◽  
Second Order ◽  
Element Analysis ◽  
Yield Criteria ◽  
Elastic Plastic ◽  
Symmetry Properties

To perform an elastic-plastic finite element analysis of a tubesheet, the anisotropic stiffness and yield properties of the perforated region are represented by an equivalent solid plate. Traditional anisotropic yield criteria (like Hill’s criterion) do not give accurate predictions under general biaxial loading because they neglect the plastic compressibility of the perforated material. A compressible-anisotropic second-order yield criterion is derived which can model both the actual out-of-plane and in-plane behavior. Using an equivalent stress vector, the in-plane symmetry properties of the second-order compressible model are examined for a triangular penetration pattern. Generally, the tubesheet symmetry is not precisely reflected by this model. Additional planes of symmetry can be introduced with a higher-order yield function. A fourth-order yield function with the required symmetry properties is presented which is in excellent agreement with the response of a finite element, elastic-plastic model of a tubesheet ligament under in-plane biaxial loading.

The Finite Element Analysis on the Compression Splicing Position of Strain Clamp in Guy Tower

2014 ◽  
Vol 680 ◽  
pp. 249-253
Author(s):  
Zhang Qi Wang ◽  
Jun Li ◽  
Wen Gang Yang ◽  
Yong Feng Cheng
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Distribution ◽  
Finite Element Model ◽  
Equivalent Stress ◽  
Element Model ◽  
Element Analysis ◽  
Elastic Plastic ◽  
The Finite Element Analysis

Strain clamp is an important connection device in guy tower. If the quality of the compression splicing position is unsatisfied, strain clamp tends to be damaged which may lead to the final collapse of a guy tower as well as huge economic lost. In this paper, stress distribution on the compressible tube and guy cable is analyzed by FEM, and a large equivalent stress of guy cable is applied to the compression splicing position. During this process, a finite element model of strain clamp is established for guy cables at compression splicing position, problems of elastic-plastic and contracting are studied and the whole compressing process of compressible position is simulated. The guy cable cracks easily at the position of compressible tube’s port, the inner part of the compressible tube has a larger equivalent stress than outside.

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.

An Elastic-Plastic-Creep Finite Element Analysis for Small Punch Creep Test Specimens

2006 ◽  
Author(s):  
Xiang Ling ◽  
Yangyan Zheng ◽  
Zhengmai Qian
Keyword(s):  
Finite Element ◽  
Creep Test ◽  
Equivalent Stress ◽  
Creep Damage ◽  
Flow Rule ◽  
Element Analysis ◽  
Small Punch ◽  
Elastic Plastic ◽  
Plastic Creep ◽  
Small Punch Creep Test

An elastic-plastic-creep finite element model, incorporating a Von Mises plastic flow rule and a creep damage equation, was established based on the small punch creep test on Cr5Mo steel specimens at 550 °C and three different loads. Finite element analyses were performed to examine the variation of the central creep deflection and the creep strain with time and the evolution of creep damage. The sensitivity of the creep deflection and equivalent stress at the centre on the disc to mesh size is discussed. Numerical results presented in this paper confirm that the creep damage at the central part is high. The stress gradients are highest near the centre area of the specimen (from 0 to 1 mm). Therefore, accurate stress and strain can be obtained using refined meshes near the specimen center and coarse meshes in other places. The test results are in agreement with those of the numerical simulation and three different stages appearing in the curve of creep deflection, which are quite similar to those observed in conventional creep tests.

Efficient Tubesheet Design Using Repeated Elastic Limit Analysis Technique

2000 ◽  
Vol 123 (2) ◽  
pp. 197-202 ◽  
Author(s):  
W. D. Reinhardt ◽  
S. P. Mangalaramanan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Lower Bound ◽  
Limit Analysis ◽  
Yield Criterion ◽  
Elastic Analysis ◽  
Collapse Load ◽  
Element Analysis ◽  
Simple Method ◽  
Yield Criteria

Conventional analysis of tubesheets in nuclear steam generators involves elastic analysis of a solid plate with equivalent properties. It has recently been recognized that alternate design techniques such as inelastic finite element analysis would lead to substantial cost reductions in material and manufacturing. Due to the anisotropy, arriving at yield criteria for an equivalent solid tubesheet is more complicated than for an isotropic solid. In addition, applying plastic finite element analysis in design is significantly more complex and time-consuming than elastic analysis. This paper proposes a relatively simple method to perform tubesheet collapse analysis. An anisotropic yield criterion is applied in conjunction with the classical lower-bound theorem of limit analysis and repeated elastic analyses involving elastic modulus modification. Two yield criteria are examined, namely Hill’s yield criterion and a recently suggested compressible fourth-order yield function. The collapse load predictions of the lower-bound equivalent solid methods are compared with the elastic-plastic finite element collapse load of the equivalent solid and of the actual perforated tubesheet.

Elastic-Plastic Solutions for Open-End Thick Walled Cylinders Subjected to Internal and External Pressures

2008 ◽  
Author(s):  
R. D. Dixon ◽  
E. H. Perez
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Yield Criterion ◽  
External Pressure ◽  
Plastic Collapse ◽  
Elastic Instability ◽  
Element Analysis ◽  
Collapse Pressure ◽  
Elastic Plastic ◽  
External Pressures

Available theoretical solutions for the collapse pressure of open-end thick walled cylinders based on the Vo n Misses yield criterion are very limited. The known elastic-plastic theoretical solutions are primarily based on the Tresca yield criterion. So far, little study has been devoted to fairly thick open-end cylinders under external pressure. This can be performed by finite element analysis that considers material plasticity. In this paper the authors propose the use of simple formulae for the solution of the collapse internal and external pressures of open-end cylinders. The proposed formulae provide excellent agreement with finite element results obtained by the authors. Also criterion is provided for the interaction of elastic instability and plastic collapse of open-end cylinders subjected to external pressure.

Yield Criterion for Thin Perforated Plates With Square Penetration Pattern

2004 ◽  
Vol 126 (2) ◽  
pp. 169-178
Author(s):  
A. Bhattacharya ◽  
V. Venkat Raj
Keyword(s):  
Finite Element ◽  
Fourth Order ◽  
Yield Criterion ◽  
Pure Shear ◽  
Second Order ◽  
Plane Stress Condition ◽  
Element Analysis ◽  
Perforated Plates ◽  
Order Polynomial ◽  
Solid Plate

Second and fourth order polynomials describing the yield criterion for perforated plates with square penetration pattern were developed following the methodology shown by Hill (1950) and later by Reinhardt (2001) for triangular penetration pattern. The inadequacy of Hill’s (1950) criterion to describe the yield surface of the equivalent solid plate was observed by Reinhardt (2001). Unlike in the case of triangular penetration pattern, the second-order polynomial satisfies the uniqueness of yield stresses after symmetric rotation in the case of square penetration pattern, even though the second order polynomial is incomplete as it cannot satisfy the yield criterion for pure shear. However, the fourth order polynomial is found to satisfy the symmetry and boundary conditions arising from biaxial loadings completely and shows closer agreement with the finite-element results obtained by the authors as compared to the second-order polynomial. Some of the finite-element results were compared with the experimental results of Litewka (1991) and the agreement between them was found to be satisfactory. The effect of out-of-plane stresses have not been considered in the present investigation as these are found to be negligible in case of thin perforated plates, for which plane stress condition was assumed in the finite element analysis.

Effect of Defect on Elastic/Plastic and Creep Behavior of Bone: A Finite Element Study

2007 ◽  
Author(s):  
A. Ajdari ◽  
P. K. Canavan ◽  
H. Nayeb-Hashemi ◽  
G. Warner
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Trabecular Bone ◽  
Fatigue Loading ◽  
Dimensional Structure ◽  
Plastic Behavior ◽  
Element Analysis ◽  
Elastic Plastic ◽  
Local Bone ◽  
Osteoporotic Vertebral Fractures

Three-dimensional structure of trabecular bone can be modeled by 2D or 3D Voronoi structure. The effect of missing cell walls on the mechanical properties of 2D honeycombs is a first step towards understanding the effect of local bone resorption due to osteoporosis. In patients with osteoporosis, bone mass is lost first by thinning and then by resorption of the trabeculae [1]. Furthermore, creep response is important to analyze in cellular solids when the temperature is high relative to the melting temperature. For trabecular bone, as body temperature (38 °C) is close to the denaturation temperature of collagen (52 °C), trabecular bone creeps [1]. Over the half of the osteoporotic vertebral fractures that occur in the elderly, are the result of the creep and fatigue loading associated with the activities of daily living [2]. The objective of this work is to understand the effect of missing walls and filled cells on elastic-plastic behavior of both regular hexagonal and non-periodic Voronoi structures using finite element analysis. The results show that the missing walls have a significant effect on overall elastic properties of the cellular structure. For both regular hexagonal and Voronoi materials, the yield strength of the structure decreased by more than 60% by introducing 10% missing walls. In contrast, the results indicate that filled cells have much less effect on the mechanical properties of both regular hexagonal and Voronoi materials.

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