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The Portable Instrument For The Control Of Residual Stresses
The instrument for the control of residual stresses

The measuring sensor







The instrument for the control of residual stresses is intended for indication the level of internal stresses in constructions from ferromagnetic steels and alloys:
- in welded constructions before and after welding (for any kind of welding);
- afterwelding machining of products (heat treatment, electrophysical machining, etc.);
- in details after any technological operations (forging, mechanical machining, etc.);
- at an estimation of quality of heat treatment of products, etc.
It is expedient to apply the instrument for nondestructive testing of products at repair and manufacturing of pipelines, tanks, constructions of a various configuration and sizes in machine building, shipbuilding, metallurgy and power engineering.

The Technological Principles.
The principle of operation of the instrument is based on the analysis of the information, gained as a result of multi-parameter measurement of dynamic magnetic characteristics (a remanent induction, a coercive force, magnetic permeability, the form of a hysteresis curve, etc.) of a material’ observed structure. Change of level of residual stresses (including ­microstresses of the II-sorts) is controlled through a combined parameter - relative change of the volume density of the magnetoelastic energy ΔWM/WM, connected with a transformation of metal­structure. The results of the measurements are given out in real time and represented on the display in the relative units. For unit value is accepted WM, measured on the sample after heat treatment (for obtaining the minimum residual stresses). The instrument is calibrated for each material, taking into account comprehensive tests of the samples by the methods of the destroying control and correlation between magnetic characteristics and mechanical properties of a steel.

Instrument design.
The design includes the panel (the electronic block) and the sensor with a cable.
Measurement is carried out by the sensor, which magnetic circuit is completed on a product for excitation in a material of a low-frequency electromagnetic field. The changes of the dynamic magnetic characteristics of the material are determined by the parameters of a magnetic stream. A place for sensor installation is flattened by polishing (a platform with the minimum sizes of 10 mm õ 25 mm). Indication of the quality of magnetic contact between the sensor and a product is provided­.
The device is equipped by microprocessor system, that is providing machining of the results of measurements, their relevance to results of comprehensive tests for various brands of steels, and definition the change of level for residual stresses through a combined parameter DWM/WM.. The results of the measurements are given out in real time and represented on the display in the relative units.
The power supply of the instrument is executed by the built-in accumulator (the control of voltage and a boost charge are provided).

Technical data:

Type of the instrument

Portable, for the not-destroying control

Sensor type
magneto-induction, differential
The square of cross-section of the sensor magnetic circuit of, mm
10 x 25
Length of a cable for sensor connection, m
1,0 – 1,5

Measuring range of residual stresses, relative unit

from 1 to 20

Controllable thickness of a material, mm

from 15,0
Time of measurement performance, not less, s


Quantity of controllable brands of steels, unit

The measuring digital display
indicator 2 x 14 symbols

Indication on the built-in display:

- in the sampling regime «Steel Quality»:

- in a measurement regime «Measuring»:

-brand of steel (is chosen)

- stability of magnetic contact of the sensor with a product;
- brand of steel;
- relative change of residual stresses.
Self-contained power supply, built-in
the accumulator
Continuous work time, hour
Voltage of the built-in accumulator, V
12 ± 1,2
The control of accumulator voltage
Overall dimensions, maximum, mm
160 x 155 x 250
Weight, maximum, kg

Remarks. The device is calibrated and programmed for 3 brands of the steels, specified by the Customer. Device calibrating is carried out on the samples of a welded joint, presented by the Customer.
The increase in number of controllable brands of steels (more than 3) is carried out under the special order.

Delivery complete set:
the panel (the electronic block), the measuring sensor, the cable for sensor connection, the charging block of the accumulator and the certificate.


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