Dynamic Yield Loci of A Porous Visco-plastic Material by Using A lower Bound Approach

1996 ◽  
pp. 155-162 ◽  
Author(s):  
Zhuping Huang ◽  
Xi Yuan ◽  
Ren Wang ◽  
Jianguo Ning
Keyword(s):  
Lower Bound ◽  
Plastic Material ◽  
Dynamic Yield ◽  
Yield Loci

scholarly journals Lower Bound Yield Locus Calculations

1990 ◽  
Vol 12 (1-3) ◽  
pp. 89-101 ◽  
Author(s):  
William Hosford ◽  
Aitor Galdos
Keyword(s):  
Lower Bound ◽  
Upper Bound ◽  
Work Hardening ◽  
Stress Ratio ◽  
Yield Criterion ◽  
Yield Locus ◽  
Stress Strain ◽  
Strain Behavior ◽  
Yield Loci ◽  
The Hill

A lower-bound model for the deformation of work-hardening polycrystals is proposed. All grains are assumed to be loaded under the same stress and the stress–strain behavior is found by averaging the strains in all grains. The shapes of the yield loci have been calculated for textured metals which deform by {111} 〈110〉 slip (fcc) and by 〈111〉-pencil glide (bcc). As with the corresponding upper-bound models, the yield loci are best described by an anisotropic yield criterion with an exponent of 6 to 10 (instead of 2 as in the Hill theory). Also it is shown that a model of polycrystal deformation in which the grains are loaded to the same stress ratio (but not the same level of stresses) violates normality and is not a lower bound.

Lower Bound Methods in Elastic-Plastic Shakedown Analysis

2010 ◽  
Author(s):  
Wolf Reinhardt ◽  
Reza Adibi-Asl
Keyword(s):  
Lower Bound ◽  
Plastic Material ◽  
Shakedown Analysis ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Efficient Calculation ◽  
Asme Code ◽  
Elastic Shakedown ◽  
Plastic Shakedown

Several methods were proposed in recent years that allow the efficient calculation of elastic and elastic-plastic shakedown limits. This paper establishes a uniform framework for such methods that are based on perfectly-plastic material behavour, and demonstrates the connection to Melan’s theorem of elastic shakedown. The paper discusses implications for simplified methods of establishing shakedown, such as those used in the ASME Code. The framework allows a clearer assessment of the limitations of such simplified approaches. Application examples are given.

Foundation of Correlation Parameters for Eliminating Pulse Shape Effects on Dynamic Plastic Response of Structures

2005 ◽  
Vol 72 (2) ◽  
pp. 172-176 ◽  
Author(s):  
Q. M. Li ◽  
Norman Jones
Keyword(s):  
Lower Bound ◽  
Response Time ◽  
Pulse Shape ◽  
Theoretical Foundation ◽  
Plastic Material ◽  
Parameter Method ◽  
Two Dimensional ◽  
Plastic Response ◽  
Shape Effects ◽  
Correlation Parameters

The theoretical foundation of Youngdahl’s correlation parameters, which have been used to eliminate pulse shape effects in the dynamic plastic response of two-dimensional structural members, is studied in the present paper with the aid of bounds obtained for a rigid-plastic material. It is shown that Youngdahl’s empirical estimate for the structural response time is, in general, a lower bound on the actual response time. A lower bound expression is obtained for the maximum final displacement of a two-dimensional structural member when subjected to an axisymmetrically loaded transverse time-dependent pulse, which depends only on Youngdahl’s correlation parameters, and offers a theoretical foundation for the validity of Youngdahl’s correlation parameter method.

Shakedown Analysis of Nuclear Components Using Linear and Nonlinear Methods

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Dan Vlaicu
Keyword(s):  
Lower Bound ◽  
Plastic Material ◽  
Nonlinear Material ◽  
The Finite Element Method ◽  
Shakedown Analysis ◽  
Periodic Loading ◽  
Elastic Plastic Material ◽  
Compensation Approach ◽  
Elastic Shakedown ◽  
Loaded Structure

A cyclically loaded structure made of elastic-plastic material is considered as an elastic shakedown if plastic straining occurs in the first few cycles and the sequent response is wholly elastic. In this paper, the finite element method is used to develop upper and lower bound limits for the elastic shakedown of structures under periodic loading conditions. Linear methods using elastic compensation approach and the residual stress method derived from Melan’s theorem are used to generate the lower bound limit for the shakedown load, while the upper bound is found through a method derived from Koiter’s theorem. Furthermore, the results are compared with cycle-by-cycle method based on nonlinear material properties.

Applications of Limit Load Analyses to Assess the Structural Integrity of Pressure Vessels

2005 ◽  
Author(s):  
Richard C. Biel ◽  
Chris Alexander
Keyword(s):  
Lower Bound ◽  
Structural Integrity ◽  
Plastic Material ◽  
Limit Load ◽  
Pressure Vessels ◽  
Analysis Model ◽  
External Pressures ◽  
Buckling Resistance ◽  
Engineered Systems ◽  
Elastic Plastic Material

With advances in computational modeling techniques, limit load methods are gaining wider acceptance as a tool for determining the structural integrity of pressure vessels. The objective of a limit load analysis is to size a vessel or structure considering nonlinear methods such as elastic-plastic material properties and non-linear strain-displacement relations. Case studies are presented in this paper that feature external pressures, gravity, and wind loads. The technique applies an appropriate initial magnitude for each load type and uses the analysis model to increase the load until a lower bound is calculated. The lower bound value is determined by incrementally increasing the load until convergence is not possible then the results are extracted. This paper presents how limit load techniques were used to address the structural integrity of four engineered systems including the structural stability of a corroded tower under wind and vacuum loads, determining the pressure capacity of a pressure vessel, analysis of a subsea vessel under high external pressures, and the remaining buckling resistance of a dented subsea flowline. The paper highlights the application of limit load techniques using criteria detailed in WRC 464.

A lower bound approach to the yield loci of porous materials

1989 ◽  
Vol 5 (3) ◽  
pp. 237-243 ◽  
Author(s):  
Sun Yi ◽  
Wang Duo
Keyword(s):  
Lower Bound ◽  
Porous Materials ◽  
Yield Loci

Lower Bound Methods in Elastic-Plastic Shakedown Analysis

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Wolf Reinhardt ◽  
Reza Adibi-Asl
Keyword(s):  
Lower Bound ◽  
Plastic Material ◽  
Material Behavior ◽  
Shakedown Analysis ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Efficient Calculation ◽  
Asme Code ◽  
Elastic Shakedown ◽  
Plastic Shakedown

Several methods were proposed in recent years that allow the efficient calculation of elastic and elastic-plastic shakedown limits. This paper establishes a uniform framework for such methods that are based on perfectly-plastic material behavior, and demonstrates the connection to Melan's theorem of elastic shakedown. The paper discusses implications for simplified methods of establishing shakedown, such as those used in the ASME Code. The framework allows a clearer assessment of the limitations of such simplified approaches. Application examples are given.

Microplasticity Predictions of r-Values and Yield Loci of Low Carbon Sheet Steels Deforming by Pencil Glide

1979 ◽  
Vol 3 (3) ◽  
pp. 191-214 ◽  
Author(s):  
S. L. Semiatin ◽  
P. R. Morris ◽  
H. R. Piehler
Keyword(s):  
Lower Bound ◽  
Upper Bound ◽  
Carbon Steels ◽  
Distribution Functions ◽  
Interstitial Free ◽  
Low Carbon ◽  
Sheet Steels ◽  
Interstitial Free Steel ◽  
Carbon Sheet ◽  
Yield Loci

The plastic deformation of low carbon sheet steels has been analyzed using microplasticity models and Hill's theory of anisotropic continuum plasticity. The analytical methods used to determine the crystallite stress states which must be generated for the isostress (lower-bound) and isostrain (upper-bound) cases are briefly discussed and then applied to predict yield loci for three cold-rolled, annealed low-carbon steels (enameling iron, aluminum-killed steel, and interstitial-free steel) whose textures were characterized by crystallite orientation distribution functions. While measured r-values correlate best with upper-bound yield loci predictions for enameling iron, those for the aluminum-killed steels show better agreement with lower-bound yield loci predictions. In the case of the interstitial-free steel, measured r-values could not be accounted for by either upper- or lower-bound predictions. The yield loci measurements and predictions are reviewed in the context of Hill's continuum theory.

Masonry: the brittle or plastic material?

2019 ◽  
pp. 22-28
Keyword(s):  
Plastic Material ◽  
Experimental Studies ◽  
Point Of View ◽  
Plastic Properties ◽  
Plastic Deformations ◽  
Base Materials ◽  
Stress States ◽  
Creep Deformations ◽  
Structural Point

The results of experimental studies of masonry on the action of dynamic and static (short-term and long-term) loads are presented. The possibility of plastic deformations in the masonry is analyzed for different types of force effects. The falsity of the proposed approach to the estimation of the coefficient of plasticity of masonry, taking into account the ratio of elastic and total deformations of the masonry is noted. The study of the works of Soviet scientists revealed that the masonry under the action of seismic loads refers to brittle materials in the complete absence of plastic properties in it in the process of instantaneous application of forces. For the cases of uniaxial and plane stress states of the masonry, data on the coefficient of plasticity obtained from the experiment are presented. On the basis of experimental studies the influence of the strength of the so-called base materials (brick, mortar) on the bearing capacity of the masonry, regardless of the nature of the application of forces and the type of its stress state, is noted. The analysis of works of prof. S. V. Polyakov makes it possible to draw a conclusion that at the long application of the load, characteristic for the masonry are not plastic deformations, but creep deformations. It is shown that the proposals of some authors on the need to reduce the level of adhesion of the mortar to the brick for the masonry erected in earthquake-prone regions in order to improve its plastic properties are erroneous both from the structural point of view and from the point of view of ensuring the seismic resistance of structures. It is noted that the proposal to assess the plasticity of the masonry of ceramic brick walls and large-format ceramic stone with a voidness of more than 20% is incorrect, and does not meet the work of the masonry of hollow material. On the basis of the analysis of a large number of research works it is concluded about the fragile work of masonry.

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