The results of research on the stabilization of the geometric dimensions of large hull blocks obtained using welded joints are presented. The connection between the change in the construction geometry and the modes of strengthening by vibration effects caused by controlled electromagnetic pulses with the imposition of an electric field is shown. The ways of controlling multiple mechanical impulses to strengthen the surface layer and equalize the internal stresses of the mating parts are shown, which allows reducing errors after welding. Developed methodology for designing a combined technological process for pulse stabilization of the geometry of workpieces.
In [1,2] it is shown that one of the ways to stabilize the size of cast and welded workpieces is pulse combined electromagnetic processing, which does not require the creation of thermal sections and is successfully used for processing large-sized parts in small and medium-sized businesses .It is known from [3,4] that controlled pulse effects can reduce the level of surface stresses and equalize their level to a value that excludes warping of products during processing and operation .
Magnetic pulse surface treatment has a lot in common with vibration shock hardening , but it can significantly simplify the technological process, since it is performed without the use of mechanical vibrators, the installation of which causes great difficulties when installing on complex-contoured surfaces. In addition, this method allows for local processing of product sections, which significantly expands the area of manufacturing large-sized parts, since many machine-building enterprises of small and medium-sized businesses do not have their own thermal sites for metal annealing, and performing such operations on the side is associated with additional transport costs, lengthening the technological cycle, and the need to re-equip their own production with control tools and personnel of performers.
Magnetic pulse stabilization of the workpiece geometry.
The essence of the magnetopulse method is sufficiently fully disclosed in  and shown in (Figure 1)
1. charging device; 2. capacitor Bank; 3. capacitor Winding;4. Billet. The charger 1 (Figure 1) contains a rectifier of the current supplied to the capacitor Bank 2.in which, at the beginning of the discharge, energy is accumulated sufficient to de-form the workpiece 4, but not exceeding the value of the beginning of the plastic flow of the workpiece material. Next, it is placed on the windings of the exciter 3, where a changing magnetic field is formed, causing the appearance of electromagnetic forces (shown by the arrows in the Figure.1), the control of which allows you to create a vibration of the workpiece and ensure the redistribution of residual stresses in it in the areas adjacent to the welding sites.
The principal difference between the technology of magnetoimpulse stabilization of stresses in the surface layer of the workpiece from a similar process of their formation [3,4] is the use of a control criterion ,according to which the limit value of the electromagnetic force must be lower than the yield strength of the workpiece material 4 (RISU-nok1).Since part of the pulse energy is converted to heat, which affects the deformation of the workpiece, the criterion record uses a coefficient that reduces the calculated value of this force by 15-20%, which should be taken into account when calculating technological modes magnetic pulse process. The efficiency of using magnetic pulse processing to stabilize the properties of workpieces depends on the level of
manufacturability  and the quality of surface preparation in the
same way .
The initial data for the design of the technological process
of magnetic pulse processing, which provides stabilization of
internal stresses of large-sized welded structures, is information
about the geometry, properties of the material of the workpieces,
methods of their production, processing modes, the degree of
development of the vibration process, availability of personnel and
equipment of the production. The effectiveness of the developed
technological process is evaluated by the stability of obtaining the
required accuracy and performance characteristics of products at
all stages of the CALS technology. With regard to the processing
necessary to justify the choice of parameters considered in the
study of the mechanism of magnetic-pulse processing scheme
of an agent according to [3,4], to identify areas of detail which
require vibrostability voltages. This should be reflected in the
technical documentation, where recommendations should be
included installation instructions sources of vibration on the
When working out the manufacturability should be taken into
1. The possibility of direct force action on the workpiece of
the vibration exciter. Violation of this condition can cause shock
loads on the tool and its destruction.
2. Take into account the limitations that ensure the safety
of the workpiece during processing, for which use the results on
the rigidity of the workpiece under the action of pulses obtained
at the stage of development of a new process, and periodically
monitor the state of technological discipline in the serial
production of products.
3. Use modes adapted to the final indicators for the
specified accuracy of the workpieces. Thus, the experience of
vibration stabilization of welded structures has shown that
the process can be performed in several transitions: at the first
stage, which takes about half of the processing time, the greatest
calculated vibration amplitude of the treated area is applied. At
the next transitions, the mode is gradually softened. Here, the
control is performed by the processing time and the value of the
amplitude of vibrations of the workpiece section.
The stage of work on the equipment includes the preparation
of installation bases, where standard elastic machine supports are
used for this purpose, which are selected taking into account the
mass and geometry of the parts to be processed. The number of
supports (at least 3) depends on the size and shape of the support
surface of the workpiece. When working out the processing
modes, adjust the frequency of vibrations, preferably until a stable
resonant amplitude value appears. The range from 50 to 100 Hz
is used as the base for tuning, which does not cause technological
Control of the processing mode can be performed by changing
the current supplied to the vibrator. However, with an increase in
the size of the part, this indicator decreases and when changing
less than 12-15 %, it becomes not a reliable indicator for control.
Therefore, the process is controlled by the processing time that is
set during setup, taking 60 minutes as the initial value for large
workpieces and reducing this figure during debugging mode with
an interval of 5-10 minutes. Acceptance control of processing
quality is performed based on the results of measuring the
size of the part at the base points after stabilization of residual
stresses. The operation is usually performed selectively on the
first processed part from the batch. on coordinate measuring
Figure 2 shows the results of measuring residual stresses in
the process of magnetic pulse processing, where the stability of
their value is estimated by the average value of the unevenness
of residual stresses (Δσ ) at the welding site in the workpiece from
the time (τ ) of magnetic pulse processing. The index 1 shows the
non-uniformity of residual stresses in the welded structure of the
milling machine stand made of steel 3 with dimensions of 100
X 600 X 950 mm with the calculated placement of 4 vibration
exciters. The workpiece was placed on a table with a stable gap.
Index 2 (Figure 2) shows information about a steel frame with a
length of 2200 mm after arc welding.
Analysis of materials in Figure2 shows that depending on
the shape, dimensions, position of welds, the main para-metertime
management of the process of magnetic-pulse treatment –
should work with real samples and re-results of comprehensive
measurements to clarify the processing time increases with
increase in size of the parts. In this case, for a smaller part, the
minimum processing time is about 20 minutes, and for a larger
frame-more than 40 minutes.
Figure 3 shows the operating modes of stabilization of the
rack shown in Figure 2 under index 1. For a time of τ =20 min
(Figure 2), the vibration frequency (f) should be maintained in
the range of 55-65 Hz and preferably in a resonant mode. For
the same processing duration, the vibration amplitude (A) at the
processing site is set according to Figure 3. Measurements of the
processed parts (Figure 3) showed that stable dimensions can be
obtained for metal-cutting machines with a welded stand at an
optimal (preferably resonant) pulse frequency and oscillation
amplitude of 0.5-0.7 mm. If the resonant frequency exceeds the
recommended range, then set the frequency required for this and
specify the modes according to the calculated dependencies and
graphs of the type shown in (Figures 2 & 3).
The study of the mechanism of magneto-pulse stabilization
of large-sized welded parts and the experience of operating
mobile installations using the proposed technology have shown
the feasibility of using the process in flexible structures used in
industrial enterprises of small and medium-sized businesses and
in the repair of technological equipment in the absence of funds
for heat treatment of large-sized parts.
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