=Paper=
{{Paper
|id=Vol-2744/short39
|storemode=property
|title=Visualization of the Process of Processing Welds by a Deformation Wave (short paper)
|pdfUrl=https://ceur-ws.org/Vol-2744/short39.pdf
|volume=Vol-2744
|authors=Andrey Kirichek,Sergey Barinov,Alexandr Yashin
}}
==Visualization of the Process of Processing Welds by a Deformation Wave (short paper)==
https://ceur-ws.org/Vol-2744/short39.pdf
Visualization of the Process of Processing Welds by a
Deformation Wave*
Andrey Kirichek1[0000-0002-3823-0501], Sergey Barinov2 and
Alexandr Yashin3[0000-0002-3186-1300]
1 Bryansk State Technical University, 50 let Octyabrya Blvd. 7, 241035 Bryansk, Russia
avk57@yandex.ru
2 Murom Institute (branch) of Vladimir State University, Orlovskaya Str. 23, 602264 Murom,
Russia
box64@rambler.ru
3 Murom Institute (branch) of Vladimir State University, Orlovskaya Str. 23, 602264 Murom,
Russia
yashin2102@yandex.ru
Abstract. The aim of the paper is to obtain a unified finite element model of a
complex process, which makes it possible to obtain visual information related
to the influence of the welding process parameters on the results of the process
of wave strain hardening of the weld material. Modeling of sequentially execut-
ed technological processes of different physical nature - welding and hardening,
makes it possible to obtain more general and objective visual information about
the process as a whole. Modeling in the Ansys software package is performed
in stages, with the output of an earlier stage of modeling acting as the input data
of the subsequent stage. At the first stage, the problem of visualizing the pro-
cess of forming a weld is solved with the possibility of calculating temperature
fields, stress and strain fields during heating and cooling of the welded work-
piece. At the second stage, the calculated data is imported into the finite ele-
ment model of processing welds with a deformation wave. A finite element
model makes it possible to build microhardness maps for selected (dangerous)
sections and visually monitor the change in stresses and strains in welded
workpieces, depending on the technological modes of hardening by a defor-
mation wave. The obtained visual information allows for a qualitative and
quantitative assessment of the result of a complex process, which contributes to
an increase in the bearing capacity and performance of the product as a whole.
Keywords: Finite element model, Visualization, Welding, Wave strain harden-
ing, Temperature fields, Stress and strain fields.
Copyright © 2020 for this paper by its authors. Use permitted under Creative Com-
mons License Attribution 4.0 International (CC BY 4.0).
*
The reported study was funded by RFBR according to the research project No. 18-
38-20066.
2 A.Kirichek, S. Barinov, A. Yashin
1 Introduction
In the modern world, digital technologies are considered as a means of describing the
complete life cycle of a product - from design and manufacture to operation and dis-
posal. Science-intensive industries have been given a daunting task even before the
product and its constituent parts are put into production, to create, manufacture and
test mathematical models under operating conditions. The least developed from the
point of view of modeling are the technological processes of manufacturing parts. The
problems of their modeling are largely associated not only with a large number of
technological factors, but also with a change in the shape and size of a part during
processing, a continuously and dynamically changing stress-strain state of a product,
and the need to take into account thermal processes. The solution to the problem of
transferring information about the product during the transition from one operation to
another is also quite difficult. Since various software tools have been developed and
proposed to simulate different operations, the loss of some information is inevitable at
the stage of inter operational transition. The problem is especially acute for the trans-
fer of information between technological processes that differ in the physical nature
of the effects on the material of the original workpiece.
The aim of the paper is to obtain a unified finite element model of a complex pro-
cess, which makes it possible to obtain visual information related to the influence of
the welding process parameters on the results of the wave strain hardening (WSH)
process of the weld material. Modeling of interconnected sequentially executed tech-
nological processes of different physical nature - welding and hardening, makes it
possible to obtain more general and objective visual information about the process as
a whole. The known finite element models of the welding process do not imply the
modeling of subsequent effects on the weld [1-3]. The well-known means of modern
engineering analysis in most cases do not specialize in modeling fast shock processes
(lasting 10-7 ... 10-5 seconds), which is typical for WSH.
The essence of WSH [4] is wave loading of the processed material by shock pulses
with a given duty cycle, energy and duration. WSH has the ability to increase micro-
hardness and form compressive residual stresses at a depth of more than 10 mm. This
makes the use of the method promising for increasing the strength of welds. A finite
element model of a shock system with an intermediate link (waveguide), tested on
solid material, is known. It makes it possible to study the regularities of the influence
of the parameters of the shock system elements and the material of the loading medi-
um on the efficiency of the shock pulse energy transfer [5, 6], but does not allow us-
ing the results of modeling the welding process as initial information.
Modeling in the Ansys software package is performed in stages, with the output of
an earlier stage of modeling acting as the input data of the subsequent stage. The
choice of Ansys is based on the high reliability of the data obtained and a wide range
of multidisciplinary calculation modules, combined on one platform. The use of a
single platform greatly facilitates data exchange when solving multidisciplinary prob-
lems without loss of accuracy in calculations. In a complex formulation in relation to
the indicated processes, the problem is solved for the first time.
Visualization of the Process of Processing Welds by a Deformation Wave 3
2 Visualization of the process of processing welds by a
deformation wave
The development of a finite element model of the process of processing welds by a
deformation wave consisted of two stages.
At the first stage, using the previously obtained data, a finite element model of the
weld was created. For this, in the "Transient Thermal" module, in the "Geometry"
section, the geometry of the welded specimen was created, and the weld was divided
into face and root elements (Fig. 1). In the "Engineering Data" section, the properties
of the processed material such as: yield stress, strength, density, thermal expansion
coefficient, Young's modulus, Punson's coefficient, thermal conductivity, specific
heat, tangential modulus, etc., were set. Some physical and mechanical properties
were determined depending on the temperature. Further, a finite element mesh was
formed in the welded workpiece. To solve thermal problems, the mesh was assigned
the "Explicit" type. The elements of the weld were heated using the heat flow set by
the “Heat Flow” function. The procedure for determining the value of the required
heat flux during welding is presented in various sources, for example [7]. A heat flux
value was assigned to each element of the weld. For the front and root welds, the heat
flux values are different, this is due to the specifics of welding material with a thick-
ness of more than 10 mm. Then, the boundary value of convection "Convection" was
assigned to all surfaces of the welded workpiece. It created the condition for all sur-
faces of the welded workpiece to come into contact with "standing" air. The task set-
up was completed by setting the calculation parameters - "Analysis Setting", in which
the number of calculation steps was set. In the problem, each element of the weld was
heated in one calculation step, and in addition to the calculation, two more steps were
added. They recorded the process of stopping heating, and set the time during which
the workpiece cools after welding. The result of the calculation in the Transient
Thermal module was to obtain the temperature fields of the welded workpiece heating
and cooling, which were then transferred to the “Static Structural” module to obtain
thermal deformations that occur in the product after welding.
The geometry of the welded product and the material model were transferred to the
“Static Structural” module from the “Transient Thermal” module (Fig. 1). The finite
element mesh was re-formed. The “Fixed Support” boundary condition was assigned
to the ends of the welded workpiece. It secures the edges of the workpiece in space.
The boundary condition "Frictionless Support" was applied to the bottom of the weld-
ed workpiece to ensure its normal restraint, with freedom in the tangential direction.
The “Imported Load” function was used to import temperature fields from the “Tran-
sient Thermal” module. The adjustment of the calculation parameters "Analysis Set-
ting" was carried out in the same way as in the "Transient Thermal"module, which is
necessary for adequate transmission and use in the calculation of temperature fields in
time. After solving the problem in the "Static Structural" module, it became possible
to assess the stresses and strains that occur in the workpiece after welding.
The second stage was the combination of the data obtained as a result of modeling
a weld with a strain wave hardening model into a single finite element model of the
process of processing welds with a strain wave. For this, the “Transient Structural”
4 A.Kirichek, S. Barinov, A. Yashin
module was used. Import from the previous calculations of the values of stresses and
strains, the geometry of the workpiece changed as a result of welding, was carried out
using the "External Data" and "Mechanical Model" modules, respectively (Fig. 1).
In the "Transient Structural" module (Fig. 1), to the previously created geometry of
the weld, one more body is added - a rod roller, through which the impact energy is
communicated to the processed surface of the welded workpiece. Preparation for the
calculation of the "Transient Structural" module began with setting the contact in the
"Connectoins" section, in which the contact type was defined as "Frictional" and the
friction coefficient value was set. To simplify the organization of contact settings
between bodies, the “Contact Tool” function was created and enabled. The direct
transfer of weld stresses to the “Transient Structural” module was performed using
the “Imported Initial Stress” function. Restriction of the roller movement along one of
the axes was set by the introduction of the Displacement boundary condition. Fas-
tening of the edges of the welded workpiece in space was ensured by the "Frictionless
Support" boundary condition, which was applied to the ends of the workpiece. The
movement of the workpiece in the process of wave strain hardening was carried out
using the "Velocity" function, which provided the setting of the kinematic speed of
the workpiece movement in the selected direction.
The law of deformation of the welded workpiece by the roller was set using the
"Force" function, which reflected the change in the impact force over time. The type
of dependence was determined from previously solved contact problems based on the
finite element model of a shock system with an intermediate link [2, 3]. As a result, a
shock impulse was modeled, the shape of which was described by the dependence of
the impact force on time. The resulting shock impulse had decay and rise fronts, and,
depending on the shock system parameters, could have a tail section providing a
higher efficiency of the impact process. Thus, using the previously developed model
of the impact system with an intermediate link, based on the specified parameters of
the impact system and the properties of the processed material, the law of force varia-
tion for one impact in time was determined. The resulting dependence was used later
in the "Transient Structural" module for a given number of strokes.
Setting up the “Analysis Setting” calculation parameters was reduced to turning on
the “Auto Time Stepping” function and choosing the principle of calculating steps
after a specified time, indicating the minimum and maximum time for calculating one
step. After solving the problem, in the "Transient Structural" module it becomes pos-
sible to assess stresses, deformations, displacements, temperatures, etc. If it is neces-
sary to study any other parameters or their combinations, they are activated before
starting the calculation in the "Analysis Setting" or written in the command line.
As an example of using the developed technique, a unified finite element model of
processing welds with a deformation wave was created. So the welded product con-
sisted of two steel plates of 40X grade with dimensions of 150 * 70 * 10 mm (Fig. 2).
Welding was carried out in two passes, semi-automatic, with the current strength of
the root and face seam, respectively, 185 and 130A. The deposited material is steel
40X grade. Cutting the edges of welded workpieces was done in accordance with
GOST 5264-80. WSH modes are: impact energy 70 J; overlap coefficient K = 0.3; rod
roller tool 40 mm long and 10 mm in diameter.
Visualization of the Process of Processing Welds by a Deformation Wave 5
Fig. 1. Modular diagram of the model
As an example, seven impacts of the tool on the surface of the welded workpiece
were modeled. The adequacy of the data obtained as a result of modeling was estab-
lished on the basis of its comparison with experimental data obtained under similar
conditions. In the model of the welded workpiece, the microhardness distribution map
in the surface layer before and after the WSH was compared, the sizes of individual
indentations and the distribution of the hardness map under them were estimated. The
values obtained as a result of modeling correspond to the results of the experiment
with a confidence level of 0.95.
Fig. 2. Schematic model
Figures 3 and 4 show the distribution of residual stresses in welds before and after
WSH. The data obtained indicate a decrease in the magnitudes of tensile stresses (data
with a plus sign) and their transition to compressive stresses (data with a minus sign),
on average, in depth by 8 mm.
Summing up the work done, it should be noted that:
- at the first stage, the problem of visualizing the process offorming a weld with the
possibility of calculating temperature fields, stress and strain fields during heating and
cooling of the welded workpiece is solved;
- at the second stage, the calculated data are imported into the finite element model
of processing welds with a deformation wave;
- a unified finite element model makes it possible to build microhardness maps for
selected (dangerous) sections and visually track the change in stresses and strains in
6 A.Kirichek, S. Barinov, A. Yashin
welded workpieces, depending on the technological modes of hardening by a defor-
mation wave.
The obtained visual information allows for a qualitative and quantitative assess-
ment of the result of a complex process, which contributes to an increase in the bear-
ing capacity and performance of the product as a whole.
Fig. 3. Distribution of residual stresses in the sample after welding
Fig. 4. Distribution of residual stresses in the welded specimen after WSH
3 Acknowledgments
The reported study was funded by RFBR according to the research project No. 18-38-
20066.
References
1. Pronin, A.: Development of methods for assessing the performance of circular welds of
gas pipelines of compressor stations: dissertation ... Candidate of technical sciences:
25.00.19., Ukhta (2009).
2. Porowski, J., O’Donnell, W., et al.: Use of the mechanical stress improvement process to
mitigate stress corrosion cracking in BWR piping system. Nuclear Engineering and Design
124, 91-100 (1990).
Visualization of the Process of Processing Welds by a Deformation Wave 7
3. Bilenko, G., Morgunov E., Korobov Yu.: Computer modeling of the stress state of a weld-
ed joint made of stainless steel 03X18H9M3, performed by multi-pass orbital welding.
Welding and diagnostics: collection of reports of the international forum, p. 35 (2015).
4. Kirichek, A., Soloviev, D., Lazutkin, A.: Technology and equipment for static-impulse
processing by surface plastic deformation. M.: Mechanical engineering (2004).
5. Kirichek, A., Barinov, S., Ryzhkova, M., Yashin, A.: Visualizing the process of forming a
shock pulse in the deformation zone. CEUR Workshop Proceedings 2485, pp. 265-267
(2019).
6. Kirichek, A., Barinov, S., Yashin, A., Konstantinov, A.: Study of the influence of cross
section sizes of the rod shock system on the efficiency of shock pulse energy transfer to
the deformation center. Applied Mathematics, Computational Science and Mechanics:
Current Problems IOP Conf. Series: Journal of Physics: Conf. Series 1479, 012067 (2020).
7. Vasiliev K., Vill V., Volchenko V., and others: Welding in mechanical engineering:
Handbook in 4 volumes. Mechanical Engineering, Moscow (1978-1979).