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.

Effect of Residual Stress or Plastic Deformation History on Fatigue Life Simulation of Pipeline Dents

2018 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Rick Wang
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Three Dimensional ◽  
Strain History ◽  
Deformation History ◽  
Stress Strain ◽  
Element Analysis ◽  
Fea Model

Mechanical dents often occur in transmission pipelines, and are recognized as one of major threats to pipeline integrity because of the potential fatigue failure due to cyclic pressures. With matured in-line-inspection (ILI) technology, mechanical dents can be identified from the ILI runs. Based on ILI measured dent profiles, finite element analysis (FEA) is commonly used to simulate stresses and strains in a dent, and to predict fatigue life of the dented pipeline. However, the dent profile defined by ILI data is a purely geometric shape without residual stresses nor plastic deformation history, and is different from its actual dent that contains residual stresses/strains due to dent creation and re-rounding. As a result, the FEA results of an ILI dent may not represent those of the actual dent, and may lead to inaccurate or incorrect results. To investigate the effect of residual stress or plastic deformation history on mechanics responses and fatigue life of an actual dent, three dent models are considered in this paper: (a) a true dent with residual stresses and dent formation history, (b) a purely geometric dent having the true dent profile with all stress/strain history removed from it, and (c) a purely geometric dent having an ILI defined dent profile with all stress/strain history removed from it. Using a three-dimensional FEA model, those three dents are simulated in the elastic-plastic conditions. The FEA results showed that the two geometric dents determine significantly different stresses and strains in comparison to those in the true dent, and overpredict the fatigue life or burst pressure of the true dent. On this basis, suggestions are made on how to use the ILI data to predict the dent fatigue life.

scholarly journals Numerical and experimental investigations of steel-concrete beams with thin-walled section

Vestnik MGSU ◽  
2019 ◽  
pp. 22-32
Author(s):  
Farit S. Zamaliev
Keyword(s):  
Experimental Data ◽  
Computer Simulation ◽  
Strain State ◽  
Concrete Beams ◽  
Concrete Structures ◽  
Stress Strain ◽  
Stress Strain State ◽  
Numerical Studies ◽  
Field Samples ◽  
Thin Walled

Introduction. Conducted is to the evaluation of the stress-strain state of the steel-concrete beams with thin-walled section. In recent times, steel-reinforced concrete structures have become widely used in civilian buildings (beams, slabs, columns). Thin-walled section have not found wide application in steel concrete structures, unlike steel structures. Presents the results of numerical studies of beams consisting of concrete, anchors and steel beams. Two investigating of the location of anchors are given. Numerical investigations are presented of steel-concrete beams with thin-walled section based on numerical studies. Testing procedure and test result are given. Results of calculations, comparison of numerical and experimental studies are presented. Materials and methods. For full-scale experiments, steel I-beams with filling of side cavities with concrete were adopted, screws are used as anchor ties, with varied both the lengths and their location (vertically and obliquely). As steel curved C-shaped steel profiles were used steel profiles from the range of the company “Steel Faces”. ANSYS software package was used for computer modeling. A total of 16 steel concrete beams were considered, for which the results of strength and stiffness evaluation were obtained in ANSYS. Results. The data of the stress-strain state of beams on the basis of computer simulation are obtained. The results are used for the production of field samples. Data of computer simulation are compared with the indicators of field experiments. Conclusions. The stress-strain state of steel-concrete structures was studied on the basis of numerical and experimental data. The proposed calculation method gives good convergence with the experimental data. Anchor connections made from self-tapping screws can be used in studies for modeling in steel-concrete beams structures and other anchor devices, ensuring the joint operation of concrete and steel profiles in structures.

scholarly journals Assessment of stress-strain state in cylindrical parts after transverse running with flat plates

2017 ◽  
Vol 2 (5) ◽  
pp. 38-43 ◽  
Author(s):  
Семен Зайдес ◽  
Semen Zaides ◽  
Дак Фам ◽  
Dac Pham
Keyword(s):  
Plastic Deformation ◽  
Strain State ◽  
Surface Plastic Deformation ◽  
Surface Plastic ◽  
Flat Plates ◽  
Stress Strain ◽  
Program Complex ◽  
Vertical Loading ◽  
Stress Strain State ◽  
Cylindrical Parts

For the deformation strengthening of parts like axles, pins, and bushes there is offered a method of surface plastic deformation based on blank rolling with flat plates. The method allows machining parts which do not have center holes. At transverse running a blank bending affected by transverse loading forces is excluded. With the aid of ANSYS program complex there is considered a change of a stress-strain state in cylindrical parts at transverse running. There are defined plastic and elastic cylinder deformations after loading. The distribution of residual stresses along cylinder section in the plane of vertical loading is obtained. The stress state of samples run with flat plates on equivalent stress is assessed. An efficient value of running at transverse running used as a basic parameter of surface plastic deformation is defined.

scholarly journals The Method of Reconstruction of Residual Stresses in a Prismatic Specimen with a Notch of a Semicircular Profile after Advanced Surface Plastic Deformation

2020 ◽  
Vol 20 (4) ◽  
pp. 478-492
Author(s):  
Vladimir P. Radchenko ◽  
◽  
Dmitry M. Shishkin ◽  
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Residual Stresses ◽  
Numerical Method ◽  
Stress Tensor ◽  
Stress Concentrator ◽  
Hardened Layer ◽  
Surface Plastic Deformation ◽  
Surface Plastic ◽  
Model Calculations

The stress-strain state in a surface-hardened bar (beam) with a stress concentrator of the semicircular notch type is investigated. A numerical method for calculating the residual stresses in the notch region after an advanced surface plastic deformation is proposed. The problem is reduced to the boundary-value problem of fictitious thermoelasticity, where the initial (plastic) deformations of the model are simulated by temperature deformations in an inhomogeneous temperature field. The solution is constructed using the finite element method. For model calculations, experimental data on the distribution of residual stresses in a smooth beam made of EP742 alloy after ultrasonic mechanical hardening were used. The effect of the notch radius and beam thickness on the nature and magnitude of the distribution of the residual stress tensor components in the region of the stress concentrator is studied. For the normal longitudinal component of the residual stress tensor, which plays an important role in the theory of high-cycle fatigue, it was found that if the radius of a semicircular notch is less than the thickness of the hardened layer (area of material compression), an increase (in modulus) of this component of residual stresses occurs in the smallest section of the part (in the volume immediately adjacent to the bottom of the concentrator). If the depth of the notch is greater than the thickness of the hardened layer, then a decrease (in magnitude) of this value is observed in comparison with a smooth hardened sample. It is shown that in a reinforced notched beam, the deflection value due to induced self-balanced residual stresses is less than in a smooth beam. Experimental verification of the developed numerical method is done for a surface-hardened smooth beam made of EP742 alloy.

scholarly journals Numerical Study of Stress-Strain State of Workpiece in Contact Problem of Surface Mandrel Drilling

2021 ◽  
Vol 20 (3) ◽  
pp. 259-267
Author(s):  
N. S. Sivtsev ◽  
V. V. Tarasov
Keyword(s):  
Plastic Deformation ◽  
Friction Coefficient ◽  
Contact Interaction ◽  
Computational Experiment ◽  
Strain State ◽  
Numerical Study ◽  
Surface Plastic Deformation ◽  
Surface Plastic ◽  
Stress Strain ◽  
Stress Strain State

In recent years, the economic factor has played an increasingly important role in the selection of technologies for manufacturing machine parts with specified values of normalized parameters of geometric accuracy and quality of working surfaces. As applied to surface plastic deformation processes, this is noticeably manifested in the search for effective friction control methods in the “tool – workpiece” pair, which ultimately determines the distribution pattern and the magnitude of stresses and strains in the workpiece and the tool. It is not possible to obtain a rigorous analytical solution to the problem of establishing a connection between surface conditions, friction, and the stress-strain state of the contacted bodies. In this regard, the construction of mathematical models comes to the fore, the solution of which is possible by numerical methods. The paper presents the results of a numerical study (computational experiment) of a finite-element model of workpiece deformation under various conditions of contact interaction and friction by one of the methods of surface plastic deformation – surface mandrel drilling. The friction coefficient has been chosen as the criterion for assessing the conditions of contact interaction and friction. It is shown that a change in the friction coefficient in the process of surface mandrel has no noticeable effect on the formation of a stress field in the deformable workpiece both in the axial, and in the radial and circumferential directions. At the same time, with an increase in the value of the friction coefficient in the “tool – workpiece” pair and with the associated increase in the force of mechanical resistance to deformation of the workpiece, their growth is observed. A computational experiment has confirmed the presence of non-contact deformations of the workpiece and tool during surface mandrel drilling, as well as  as a decrease in the value of residual deformations in the workpiece with a decrease in the coefficient of friction. Balance assessment of contact surface displacements in the workpiece (the inner surface of the hole to be machined) and the tool (mandrel) has shown that the deformations of the tool in the elastic region can lead to a significant decrease in the real tightness of surface mandrel drilling.

TECHNOLOGY OF COMBINED ELECTROMECHANOULTRASONIC TREATMENT OF SURFACE LAYERS OF MACHINE PARTS

2020 ◽  
Vol 2 ◽  
pp. 26-33
Author(s):  
V.R. EDIGAROV
Keyword(s):  
Plastic Deformation ◽  
Surface Layer ◽  
Residual Stresses ◽  
Ultrasonic Treatment ◽  
Mechanical Treatment ◽  
Surface Plastic Deformation ◽  
Surface Plastic ◽  
Surface Layers ◽  
Machine Parts ◽  
Acoustic Treatment

The technology of combined electro–mechanical–acoustic treatment is presented, which is a combination of electro–mechanical treatment and surface plastic deformation by ultrasonic treatment. Microhardness and residual stresses in strengthened EMUzO surface layer of machine parts investigated.

Dressing of shafts by surface plastic deformation with elastic bending of a billet at machining process

2020 ◽  
pp. 62-66
Author(s):  
G.V. Muratkin ◽  
V.A. Sarafanova
Keyword(s):  
Plastic Deformation ◽  
Strain State ◽  
Residual Deformation ◽  
Surface Plastic Deformation ◽  
Machining Process ◽  
Surface Plastic ◽  
Stress Strain ◽  
Elastic Bending ◽  
Stress Strain State ◽  
Accuracy Stress

A method for dressing of non-rigid parts by surface plastic deformation is proposed, which is based on a change in the stress-strain state of the billet during finishing and hardening processing. Keywords non-rigid shaft, dressing, surface plastic deformation, technological residual deformation, accuracy, stress. [email protected]

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