ITERATIVE GLOBAL-LOCAL APPROACH TO CONSIDER THE EFFECTS OF LOCAL ELASTO-PLASTIC DEFORMATIONS IN THE ANALYSIS OF THIN-WALLED MEMBERS

2017 ◽  
Vol 15 (2) ◽  
pp. 143-173
Author(s):  
R. Emre Erkmen ◽  
Ali Saleh
Keyword(s):  
Local Approach ◽  
Plastic Deformations ◽  
Thin Walled

Limit Dependences in Stability Calculations With Account for Physical Nonlinearity

2016 ◽  
Vol 33 (2) ◽  
pp. 157-160
Author(s):  
J. Rutman ◽  
V. Ulitin
Keyword(s):  
Critical State ◽  
Physical Nonlinearity ◽  
Solution Algorithm ◽  
Stability Calculation ◽  
Plastic Deformations ◽  
Thin Walled Structures ◽  
Calculated Stress ◽  
Thin Walled ◽  
Deformation Stress ◽  
Proportionality Limit

AbstractStability of bars, plates, shells, and other thin-walled structures in conditions of small physical nonlinearity is considered, when stresses exceed the proportionality limit, the amount of deformations being limited. Shanley's concept is used. The critical state is determined by means of some limit dependences. In a large number of cases, when creating efficient highly-stressed constructions, limited plastic deformations are allowed in them. When analysing stability in the critical state, the calculated stresses turn out to exceed the proportionality limit and the Young's modulus of elasticity turns out to be greater than the tangent modulus corresponding to the calculated stress on the diagram “deformation-stress”. The objective of this work is to show that stability calculation beyond the proportionality limit is reduced to the analysis of some limit dependences as well as to develop a general solution algorithm for similar problems.

scholarly journals The method of reconstruction of residual stresses and plastic deformations in thin-walled pipelines in the delivery state and after bilateral vibro-shock surface hardening with a shot

2020 ◽  
pp. 123-133
Author(s):  
V. P Radchenko ◽  
V. Ph Pavlov ◽  
T. I Berbasova ◽  
M. N Saushkin
Keyword(s):  
Experimental Data ◽  
Plastic Deformation ◽  
Residual Stresses ◽  
Strain Tensor ◽  
Anisotropy Parameter ◽  
Surface Plastic ◽  
Phenomenological Method ◽  
Stress Strain ◽  
Plastic Deformations ◽  
Thin Walled

We suggest the phenomenological method of reconstructing the fields of residual stresses and plastic deformations in thin-walled cylindrical tubes made of Х18N10Т steel in the delivery state and after a simultaneous bilateral surface plastic hardening by the vibration-shot blasting of the surface with beads on a special vibrating stand. A cylindrical container filled with three-millimeter beads was attached to it. The tubes were 50 % filled with one-millimeter beads, and they were placed inside the container. The axis of the tube and the container coincided. The space between the tube and the container was 80 % filled with beads. The vibrational frequency of the stand was 18.5 KHz, the hardening time was 20 minutes. The tube in the container was rotated to ensure uniform hardening. We determined the experimental values of residual stresses σθ and σ z in the surface layers using the method of rings and strips with the procedure of the layer-by-layer electrochemical picking of the hardened layers. For this purpose, the experimentally measured values of the beam-strip deflection and the angular opening of the cut ring (changing the diameter) were used. The hardening anisotropy parameter which relates the axial and circumferential components of plastic deformation was introduced into the mathematical model. In solving the stated problems the hypotheses of plastic incompressibility of the material, the absence of secondary plastic deformations of the material in the compression region of the surface layer, as well as the hypothesis of flat sections and straight radii were used. We described the method aimed at solving this type of boundary value problems of reconstructing stress-strain states, which makes it possible to determine the missing component σ r and all the components of the tensor of residual plastic deformations (off-diagonal components of the tensors of stresses and deformations were not considered). The method of reconstructing the stress-strain state is universal, because it has shown its operability both in determining the technological fields of residual stresses, as well as the irreversible strains in the samples in the delivered state after mechanical operations, and after bilateral surface plastic deformation. The adequacy of the calculated data was verified, which was obtained using the phenomenological method of reconstructing the stress and strain fields of the experimental data for the samples in the delivery state and after hardening. The correspondence of the calculated and experimental data was matched. The numerical values are given for the anisotropy parameter connecting the circumferential and axial irreversible strains, for samples, in the delivery state, its numerical value is 0.1, and, for the hardened samples, it is 4.2. This indicates a significant anisotropy of the distribution of the axial and circumferential components of the residual strain tensor. It has been established that the compressive residual stresses are observed in the delivery state in the region adjacent to the inner surface, and the tensile stresses are observed in the layer on the outer surface. Only compressive stresses are observed in both regions after hardening, which significantly exceed in module similar stresses for the samples in the delivery state. The main results are illustrated by the tabular data and the corresponding diagrams of the distribution of residual stresses along the depth of the hardened layer.

Combined Tension-Torsion Tests for Aluminum Alloy 2S-O

1952 ◽  
Vol 19 (4) ◽  
pp. 496-500
Author(s):  
Aris Phillips
Keyword(s):  
Aluminum Alloy ◽  
Plastic Flow ◽  
Experimental Results ◽  
Plastic Deformations ◽  
Circular Tubes ◽  
Thin Walled ◽  
Stress Ratios ◽  
Theory Of Plastic Flow

Abstract In this paper ten combined tension-torsion tests with thin-walled circular tubes of aluminum alloy 2S-O are described. All specimens were loaded with variable stress ratios. It has been found that the theory of plastic flow represents the experimental results with much greater accuracy than does the theory of plastic deformations.

scholarly journals Seismic design of pallet racking systems

1983 ◽  
Vol 16 (4) ◽  
pp. 291-305
Author(s):  
B. J. Brown
Keyword(s):  
New Zealand ◽  
Seismic Design ◽  
Shaking Table ◽  
Performance Criteria ◽  
Building Structures ◽  
Shaking Table Tests ◽  
Capacity Design ◽  
Plastic Deformations ◽  
Design Requirements ◽  
Thin Walled

Modern industrial pallet racking systems in use in
 New Zealand are adaptions of overseas design, using thin 
walled cold formed sections. These sections are not generally considered suitable for plastic deformations, or resistance to seismically induced loadings. This paper reviews full scale shaking table tests reported by Rack Manufacturers Institute, Pittsburg, (R.M.I.) in 1980, and comments on the applicability of the results to the seismic design philosophy embodied in
 NZS 4203. Seismic performance criteria (not strictly the same as for building structures) are proposed, and design approaches suggested that will enable the capacity design requirements of NZS 4203 to be considered, while keeping with the cold formed sections traditionally used for pallet rack construction.

scholarly journals Calculation of thin-walled axisymmetrically loaded structures of the AIC taking into account FEM-based physical nonlinearity

2020 ◽  
Vol 17 ◽  
pp. 00199
Author(s):  
Arsen Dzhabrailov ◽  
Anatoly Nikolaev ◽  
Natalya Gureeva
Keyword(s):  
Finite Element ◽  
Comparative Analysis ◽  
Shell Structure ◽  
Deformation Theory ◽  
Physical Nonlinearity ◽  
Plastic Deformations ◽  
Conjugation Conditions ◽  
Elastic Plastic ◽  
Theory Of Plasticity ◽  
Thin Walled

The article describes an algorithm for calculating an axisymmetrically loaded shell structure with a branching meridian, taking into account elastic-plastic deformations when loading based on the deformation theory of plasticity without assuming that the material is incompressible during plastic deformations. The correct relations which determine the static conjugation conditions of several revolution shells in the joint assembly are used. A comparative analysis of finite element solutions is presented for various options plasticity matrix development at the loading stage.

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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