|Title of Invention||
"A DEVICE FOR THE MESUREMENT OF RESIDUAL STRESSES ON-LINE DURING WELDING OPERATION"
|Abstract||The invention relates to a device for the measurement of on - line weld residual stress and a control signal proportional to the magnitude of residual stress is available continously during the operation as an analogue voltage output and this can be fed to a servo control device/ for control of various weld parameters viz. weld current/ speed of welding etc. A VDU for monitoring and an on - line printer provides a hard copy of the results of residual stresses.|
|Full Text||This invention relates to a device for the measurement of residual stresses on-line during welding operations.
Manufacturing process like welding, casting, forgings, and involving heat, produces residual stresses due to the inherent nature of the process. Unless special treatments are given to the manufactured part, these stresses act in combination with operational stresses thereby leading to early failures. The conventional system used for the measurement of the residual stresses comprises very expensive and one-time usuable residual stress strain rosettes in association with expensive hole drilling system.
There are disadvantages associated with the conventional system. One of the main disadvantage is that the conventional system facilitates measurement of the residual stress after a considerable time of the completion of welding operation which is a lengthy and time consuming system.
Another disadvantage is that specialized expert personel are required for fixing the sensors and for interpretation of the measured data.
Yet another disadvantage is that by the use of such conventional system only final stress state can be measured and the measurements from the start to the end of the welding operation are not possible.
Still another disadvantage is that due to the factors as stated above/ residual stress measurement has been an expensive proposition/ and therefore is being restricted to very important situations.
Welding processes are utilized in extremely diverse and wide ranging industries. Any attempt at reducing the complexity of residual stress measurement by developing simpler technique and taking remedial measures like heat input control and wel di ng fixtures for reducing the levels of locked-in stresses due to the process itself will immensely benefit the large number of industries where welding is used.
Therefore the main object of the present invention is to provide a simple and cost effective device for on - line measurements of residual stresses during welding operation.
Another object of the present invention is to provide a device/system for providing measurements many times at a preselected threshold temperature value during the welding operation.
Yet another object of the present invention is to provide a device for" the measurement of residual stresses on-line during the welding operation/ which is an easy and not a time consuming system.
Further object's" and advantages of this invention will be more apparent from the ensuing description.
At the outset of the description which follows, it is to be understood that the ensuing description only illustrates a particular form of this invention. However, such a particular form is only an exemplary embodiment, and without intending to imply any limitation on the scope of this invention. Accordingly, the description is to be understood as an exemplary embodiment and teaching of the invention and not intended to be taken restrictively.
According to this invention there is provided a device for the measurement of residual stresses on-line during welding operation comprising a plurality of sensors provided for sensing the temperature being connected to a data acquisition and singal conditioning means provided for converting the thermal signals into computer reliable signals, said means being connected to a computer through an interface and provided for storing the information and for providing the print-out of the measured residual stresses and a VDU being provided so as to control and monitoring and servo control device connected to said computer and provided for controlling various weld parameters.
The nature of the invention, its objectives and further advantages residing in the same will be apparent from the following description made with reference to non limiting exemplary illustrative embodiments of the constituents of the system of the invention represented in the accompanying drawings.
Fig. 1 is a block diagram of the on line weld
residual stress measurement system. Reference is invited
# to this figure which is a schematic representation of an
embodiment of the system and particularly represents the
principle employed in the system of the invention to identify
residual stresses in components during welding. The on-line
weld residual stress measurement system comprises of a
personal computer (11) containing in it a plugged-in data
acquisition card for acquiring temperature data from tempera
ture sensors (5) and a signal conditioning device (6) for
converting the analogue temperature signals into voltage
of appropriate magnitude. Resident in the computer memory
is a specially written computer programme for converting the
thermal data/ measured by temperature sensors (5) into
residual stresses. A video display unit (12) enables the
graphical output (16) of the computed residual stresses to
be seen. A control signal (7) proportional to the magnitude
of residual stress is available as an analogue voltage
output and this can be fed to a servo control- device (10),
for control of various weld parameters viz./ weld current/
speed of welding etc.- An on-li neprinter provides a hard
copy of the results of residual stresses.
Fig. 2 shows the procedures involved prior to the
measurements. The temperature sensors (5) are mounted on
the job surface near the zone of welding (2). The leads from t
sensor are connected directly to electronic signal
conditioning equipment (6). The measurement system is switched
on and the welding operations are carried out on the job.
At the end of welding operation and after the job (1) has cooled to the ambient temperature/ residual stress can be displayed on the monitor by appropriate control functions on the personal computer keyboard (1). Also during the operation itself, the variation of residual stress can bo seen on the video display
unit (12) of the device.
Fig. 3 gives a typical output of residual stress variation
(14) during the welding operation.
In accordance with the present invention a plurality
of sensors are provided for sensing the temperature of the job
to be welded and during the welding operation. The sensors are
generally in the form of thermo couples (5). Resistance temperatur
devices or temperature mapping cameras are also used.Its numbers
depends on the form and shape of the job. TTiermo generates signals in terms of DC voltage corresponding to the
temperature it is sensing. The analogue temperature signals
are then converted by the signal conditioning device (6) into
voltage of appropriate magnitude for the computer (11) to
convert—this thermal data into residual stress. A specially
written computer programme also generates a control signal (7)
proportional to the magnitude of residual stress in the form of an
analogue voltage output which is fed into a servio control device
(10) for control of various weld parameters viz/ weld current/ speed of welding etc. Thus controlling the magnitude of residual stress automatically at optimum level.
Print out (14) is obtained as and when required from the on-line printer provided.
Thus it is seen that by using the device of the present invention the residual stress during the welding operation can be measured from the begining to end at a low cost and effective manner.
1. A device for the measurement of residual stresses on-line during welding operation comprising a plurality of sensors 5 provided for sensing the temperature being connected to a data acquisition and singal conditioning means 6 provided for converting the thermal signals into computer reliable signals, said means being connected to a computer 11 through an interface 8 and provided for storing the information and for providing the print-out of the measured residual stresses and a VDU 12 being provided so as to control and monitoring and servo control device 10 connected to said computer 11 and provided for controlling various weld parameters.
2. A device as claimed in claim 1 wherein said sensors for sensing the temperature are selected from thermo-couples, resistance temperature devices, temperature mapping cameras.
3. A device for the measurement of residual stresses on-line during welding operation substantially as herein described and illustrated in the drawings.
|Indian Patent Application Number||570/DEL/1995|
|PG Journal Number||31/2009|
|Date of Filing||29-Mar-1995|
|Name of Patentee||BHARAT HEAVY ELECTRICALS LIMITED|
|Applicant Address||BHEL HOUSE, SIRI FORT,NEW DELHI-110 049.INDIA.|
|PCT International Classification Number||G01L 1/00|
|PCT International Application Number||N/A|
|PCT International Filing date|