scholarly journals The effect of surface plastic hardening technology, residual stresses and boundary conditions on the buckling of a beam

2020 ◽  
pp. 87-98
Author(s):  
V P Radchenko ◽  
O S Afanaseva ◽  
V E Glebov
Keyword(s):  
Residual Stresses ◽  
Boundary Conditions ◽  
Hardened Layer ◽  
Surface Plastic ◽  
Straight Line ◽  
Calculated Profile ◽  
Inhomogeneous Temperature ◽  
Inhomogeneous Temperature Field ◽  
Plastic Hardening ◽  
Initial Strains

The complex influence of the surface plastic hardening technology, residual stresses, and boundary conditions on the bending of a hardened beam of EP742 alloy was performed. A phenomenological method of restoring the fields of residual stress and plastic deformations performed by its experimental verification in the particular case of ultrasonic hardening is given. The correspondence of the calculated and experimental data for the residual stresses is observed. For assess the influence of the formed residual stresses on convex cylinders, the calculation methods are used for initial strains based on using analogies between the initial (residual) plastic strains and temperature strains in an inhomogeneous temperature field. This allowed us to reduce the consideration of the problem to the problem of thermoelasticity, which was further solved by numerical methods. The effect of four types of boundary conditions for fixing the ends of the beams (rigid fastening and articulation of the ends and ribs in various combinations, cantilever) on the shape and size of the bending of the beam 10×10×100 mm after ultrasonic hardening is studied in detail. It was found that the minimum deflection is observed with a hard seal of both ends of the beam. The effect of the thickness of the beam, which varied from 2 to 10 mm, on their buckling under the same distribution of residual stresses in the hardened layer was studied, and the nonlinear nature of the increase in the deflection boom with decreasing thickness for all types of boundary conditions was established. It is shown that under all boundary conditions, the curvature along the length of the beam practically does not change, therefore it can be considered constant. The consequence of this is the preservation of the hypothesis of flat sections after the hardening procedure, which is confirmed by the calculated profile of the beam section in plane symmetry, close to a straight line. The influence of the anisotropy of surface plastic hardening on the buckling of the beam was found to be significant, which can serve as the basis for choosing the optimal hardening procedure. The performed parametric analysis of the task is presented in the form of graphical and tabular information on the results of the calculations.

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.

A Neutron Diffraction Investigation of Residual Stresses in Rail Ends after Severe Deformation of Rail Surfaces

2014 ◽  
Vol 777 ◽  
pp. 213-218 ◽  
Author(s):  
Chandrahas Rathod ◽  
David Wexler ◽  
Vladimir Luzin ◽  
Paul Boyd ◽  
Manicka Dhanasekar
Keyword(s):  
Neutron Diffraction ◽  
Residual Stresses ◽  
Vertical Plane ◽  
Surface Plastic Deformation ◽  
Primary Component ◽  
Rolling Contact ◽  
Surface Plastic ◽  
Stress Evolution ◽  
Test Rig ◽  
Complex Deformation

Insulated rail joints (IRJs) are a primary component of the rail track safety and signalling systems. Rails are supported by two fishplates which are fastened by bolts and nuts and, with the support of sleepers and track ballast, form an integrated assembly. IRJ failure can result from progressive defects, the propagation of which is influenced by residual stresses in the rail. Residual stresses change significantly during service due to the complex deformation and damage effects associated with wheel rolling, sliding and impact. IRJ failures can occur when metal flows over the insulated rail gap (typically 6-8 mm width), breaks the electrically isolated section of track and results in malfunction of the track signalling system. In this investigation, residual stress measurements were obtained from rail-ends which had undergone controlled amounts of surface plastic deformation using a full scale wheel-on-track simulation test rig. Results were compared with those obtained from similar investigations performed on rail ends associated with ex-service IRJs. Residual stresses were measured by neutron diffraction at the Australian Nuclear Science and Technology Organisation (ANSTO). Measurements with constant gauge volume 3x3x3 mm3 were carried in the central vertical plane on 5mm thick sliced rail samples cut by an electric discharge machine (EDM). Stress evolution at the rail ends was found to exhibit characteristics similar to those of the ex-service rails, with a compressive zone of 5mm deep that is counterbalanced by a tension zone beneath, extending to a depth of around 15mm. However, in contrast to the ex-service rails, the type of stress distribution in the test-rig deformed samples was apparently different due to the localization of load under the particular test conditions. In the latter, in contrast with clear stress evolution, there was no obvious evolution of d0. Since d0 reflects rather long-term accumulation of crystal lattice damage and microstructural changes due to service load, the loading history of the test rig samples has not reached the same level as the ex-service rails. It is concluded that the wheel-on-rail simulation rig provides the potential capability for testing the wheel-rail rolling contact conditions in rails, rail ends and insulated rail joints.

Finite Element Simulation of Laser Beam Welding Induced Residual Stresses and Distortions in a T-Joint Configuration for Aeronautic Structures

2009 ◽  
Author(s):  
Muhammad Zain-ul-abdein ◽  
Daniel Ne´lias ◽  
Jean-Franc¸ois Jullien ◽  
Dominique Deloison
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Laser Beam ◽  
Boundary Conditions ◽  
Laser Beam Welding ◽  
Temperature Fields ◽  
Heat Transfer Analysis ◽  
Small Scale ◽  
Joint Configuration ◽  
Simulation Results

Laser beam welding has found its application in the aircraft industry for the fabrication of fuselage panels in a T-joint configuration. However, the inconveniences like distortions and residual stresses are inevitable consequences of welding. The effort is made in this work to experimentally measure and numerically simulate the distortions induced by laser beam welding of a T-joint with industrially used thermal and mechanical boundary conditions on the thin sheets of aluminium 6056-T4. Several small scale experiments were carried out with various instrumentations to establish a database necessary to verify the simulation results. Finite element (FE) simulation is performed with Abaqus and the conical heat source is programmed in FORTRAN. Heat transfer analysis is performed to achieve the required weld pool geometry and temperature fields. Mechanical analysis is then performed with industrial loading and boundary conditions so as to predict the distortion and the residual stress pattern. A good agreement is found amongst the experimental and simulation results.

scholarly journals STABILITY OF A VISCOUS INCOMPRESSIBLE CONDUCTING LIQUID LAYER OF A CYLINDRICAL SHAPE IN AN INHOMOGENEOUS TEMPERATURE FIELD AND A MAGNETIC FIELD OF A VACUUM ARC CURRENT THROUGH IT

2021 ◽  
pp. 91-97
Author(s):  
O.L. Andrieieva ◽  
B.V. Borts ◽  
А.F. Vanzha ◽  
I.М. Korotkova ◽  
V.I. Tkachenko
Keyword(s):  
Magnetic Field ◽  
Temperature Field ◽  
External Magnetic Field ◽  
Fluid Layer ◽  
Vacuum Arc ◽  
Cylindrical Shape ◽  
Conducting Liquid ◽  
Inhomogeneous Temperature ◽  
Inhomogeneous Temperature Field ◽  
Arc Current

Convective mass transfer in a cylindrical viscous incompressible conductive fluid layer in an inhomogeneous temperature field and in the external magnetic field of the vacuum arc current through it is theoretically investigated in this work. For a horizontal layer of a viscous, incompressible, conducting liquid of a cylindrical shape, located in a temperature field inhomogeneous in height and in an external magnetic field of a vacuum arc current flowing through it, the original equations are written. These equations consist of linearized equations for small velocity perturbations, small deviations from the equilibrium values of temperature, pressure, and magnetic field strength. The considered boundary value problem is solved for the case of free boundaries. Comparison of the experimental data with theoretical calculations made it possible to determine the rotation velocity of the steel melt during vacuum arc melting.

Analysis of High-Speed Rotating Disks With Variable Thickness and Inhomogeneity

1994 ◽  
Vol 61 (1) ◽  
pp. 186-191 ◽  
Author(s):  
Kai-Yuan Yeh ◽  
R. P. S. Han
Keyword(s):  
High Speed ◽  
Elevated Temperatures ◽  
Rotating Disk ◽  
Rotating Disks ◽  
Analytic Expressions ◽  
Inhomogeneous Temperature ◽  
Inhomogeneous Temperature Field ◽  
Thermoelastic Stresses ◽  
Shrink Fit ◽  
Annular Disks

A rotating disk with varying thickness and inhomogeneity, and subjected to a steady, inhomogeneous temperature field is analyzed. To handle the arbitrary profile, the disk is discretized into a series of uniform annular disks possessing constant material properties and then solved by the step-reduction method. Analytic expressions for thermoelastic stresses are given, and based on these results, the formulation is extended to include the calculation of shrink fit, the solving of the inverse problem for equistrength rotating disks, and the computations of plastic stresses and creep at elevated temperatures.

Sign in / Sign up

Export Citation Format

Share Document