A PROJECT FOR AUTOMATICALLY STRAIGHTENING WORKS
IN SHIPBUILDING AND OTHER BRANCHES
Peter Seyffarth1 and Oleg V. Makhenko2
1
SLV Mecklenburg-Vorpommern GmbH, Germany, Rostock
2
The Paton Welding Institute, Ukraina, Kiev
1. Introduction
Straightening an reworking after welding contents about 30 % of working time in
welded constructions. Sometimes the reworking time is higher than the welding time.
This fact needs at first a package of measures to avoid weld distortions. But besides
the need to use low heat input the specialists have to develop methods to decrease the
waste of time for reworking. This is possible to manage with new computer aided
simulation programs for estimation and pre-calculation of pre-bending. Another way to
manage the problem is to calculate the coordinates and the value of heat input for
automatically straightening works.
In this paper are described both of the possibilities developed in the SLV MecklenburgVorpommern in Rostock/Germany together with the Paton-Institute Kiev/Ukraina.
2. Beam production
To improve the productivity and the accuracy of welded
beams the laser welding technique is more an more in
use especially for high alloyed steels with very
complicated geometry, fig. 1 and 2.
Fig. 1: Laser welded beam with unconventional geometry
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Fig. 2: Design of laser welded beams
The driving forces for this development are the need to use large beams, made of
stainless steel, which are not available for structural steelwork. Also the reduced costs
achieved by reduced weight, reduced stocks and “Just in Time”-production are driving
forces. For the enterprises these facts give an improved competitiveness by improved
and more consisted quality. Furthermore the deep narrow welds from one side, the low
heat input in the material and following the low thermal distortion, the high production
rates and
process flexibility are
advantages of
laser techniques. Also
the component
design opportunities
are enhanced,
fig. 3.
Fig. 3: Clamping devices for laser welding of beams
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At the other hand, there are disadvantages, too. Close fitting and well clamped joints
are required, to avoid the so called gap breathening which occurred. Accurate beam
alignment is also necessary, because the narrow weld easily miss the joint line if not
accurately positioned. Precise beam manipulation equipment is necessary and the total
equipment and operation costs are high.
Therefore there is a need to calculate by computer simulation the following points:

Kinetics of distortion

Mechanical forces at clamping

Temperature field during welding

Residual stresses after welding

Prebending and straightening parameters.
By the help of the results of computation it is possible to prebend the beams before
welding to get after welding and cooling a straight profile, if the equipment design allows
prebending. With the same program it is possible, too, to design improved clamping
devices The clamps must be very strong and heavy, if the distances between the clamps
are very narrow. With increasing distances between the clamps the number of clamps is
less and the forces on the clamps are lower. This fact allows to design cheaper clamps
with less mass, but the distortion of
the welded beam would be higher in
this case. Therefore the estimation of
the mechanical forces at clamping
and the kinetics of distortion is a tool
to optimise the clamping design and
the accuracy of the beam too.
Fig. 4 shows the mask for the data
input and fig. 5 gives a snapshot of
the kinetics of distortion during
welding.
Fig. 4: Data input in the program “BEAMS”
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The calculation gives very adequate results as it is shown in table 1.
Deflection after Welding
Calculation
Measurement
Z-direction
17,63 mm
18,0 mm
Y-direction
15,98 mm
16,5 mm
Tab. 1: Comparison between calculated and measured distortion of a 6 m beam
The final results of the computer simulation program BEAMS are the following:

Methods of clamping can be calculated

Clamping forces can be calculated

Longitudinal shrinkage can be calculated

Seam tracking can be delivered

Production can be optimised.
3. Sandwich panel production
Sandwich panels, fig. 6, have a lot of advantages for ships, bridges, parking houses and
Fig. 6: Sandwich-panel for decks and walls in shipbuilding or parking houses
so on. The main advantages are shown in fig. 7:
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Fig. 7: Advantages of laser welded sandwich panels
There is a need to calculate
the distortion in case of very
large panels because of the
very thin upper and lower
plate in the sandwich
construction and the large
range in the construction.
This is possible by the help of
the computer – aided
program “CASSETTA”.
Fig. 8 shows the data input
mask.
Fig. 8: Data input to calculate deformation and prebending for sandwich panels
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Fig. 5: Kinetic of distortion of a 4 m long beam at various steps of welding time,
calculated by the program BEAMS
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4.
Project of automatic straightening of plates
In a big copper production plant is a need for automatic straightening of catode plates.
There are working 60 000 plates to collect copper an their surface by catodic refining. It
is a high economical loss, if the plates are deformed and therefore the copper
production efficiency is decreasing. A automatically working equipment was proposed
to solve the problem of the high number of plates which must be straightening and is
now under construction. The basic steps of automatically straightening are the
following:

Automatically measurement of the deformed surface
topography

Link and transfer of the surface data to the straightening
program

Calculation of the numbers, coordinates and the values of heat
input

Link and transfer of the computed data to heat input machine

Fulfilling the operation

Finally automatic measurement of evenness and the accuracy
of plates.
The program based on the simply Gauss distribution of heat around a heat spot and is
computed as an one dimensional problem in direction of the radius. The principle of the
calculation program is to minimize the deformed plate surface by shrinkage around the
heat spots to achieve evenness of the plate.
The program allows to
estimate the stresses and the
strains around the heating
spot at every time during
heating and cooling depending
on the power of heating, on
the diameter of heating spot
and in connection with this as
a function of energy intensity,
fig. 9.
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Fig. 9: Data input mask
The distribution of temperature and of stresses and strains in radius and tangential
direction are shown in fig. 10, and the final number and coordinates of heat spots in fig.11
Fig. 10: Calculation of temperature, strains and stresses
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Fig. 11: Number and distribution of heating spots for straightening
5. Conclusion
There was developed a certain number of computer aides programs to simulate
deformation of welded constructions. An effective way to achieve constructions with a
high accuracy and in a very short time is the use of automatically straightening
process.
By the help of this program it needs no more than 10 minutes to straightening a plate
with the dimensions 1200 x 1200 x 3,25 made of high alloyed steels from the first
measurement up to the last finally measurement to guarantee the evenness of the
plate.
In this way the use of computer aided simulation programs increases the productivity
and efficiency of production processes.
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