Creation method of reference specimens with specified stress distribution

FIELD: metallurgy.

SUBSTANCE: plastic deformation is created on edges of a specimen. The following is used for creation of plastic deformations: local heating, rolling and combination of those methods of action; as a result, in the centre of the specimen a zone with uniform distribution of stress components appears, the signs and levels of which depend on the nature of action and can be found as per the measurement results of the specimen before and after the action.

EFFECT: improving accuracy of measurement results of mechanical stresses in steel structures.

2 cl, 2 dwg

 

The technical field

The invention relates to welding, in particular to methods of creating the stress in the metal samples mainly of carbon and low alloy steels, and can be used for calibration and validation of existing methods and equipment for determining the stress state in the metallic structure.

The level of technology

There are several experimental methods for the determination of stress state in metal structures: optical, strain, radiographic, magnetic, acoustic. The basis of all methods for the determination of mechanical stresses is the importance of the relationship between the internal stress and the measured parameters. The presence of such influencing factors as structure, temperature, heterogeneity of the stress state arising in the manufacture and during operation of structures that may be present at the same time, reduces the accuracy and reliability of results, leading to unacceptably large uncertainty evaluation stresses the ways specified above.

For debugging existing ways of fixing mechanical stresses and improve the reliability of their results necessary reference metal samples, in which it will be possible to create a stress state with the set is the component values. A known method of heat treatment at a high temperature tempering. After exposure at 600C and slow cooling voltage decreases to very low values ("Materials: Textbook for universities / Benassayag, Viglacera, Gay and other Publishing house of Moscow state technical University n.a. Bauman, 2008, str-155).

The disadvantage of this method is that it is possible to obtain samples only with zero stress.

The closest in technical essence and the achieved when using the result to the claimed invention is a method for calibration means determining mechanical stress, applying the samples, tie rod in discontinuous machines to the required values of mechanical stresses (Nasiakos the Use of electromagnetic acoustic pulse of ultrasound for control of mechanical stresses. // Log "welding and Diagnostics", 2010. No. 4. P.55-56).

The disadvantage of this method is that so hard to create complex multi-component stress state, moreover, by type of sample and the machine clear the type of the stress state. For testing of the device will preferably be such samples in appearance which the stress distribution in them cannot be set. Another disadvantage is that this method is suitable for use of the advantages to the public in the laboratory.

Disclosure of inventions

The problem to which the invention is directed to the method of improving the reliability of the results of measurements of mechanical stresses in metal structures experimental methods for determining the stress state.

The problem is solved in that the inventive method provides the effect on the edges of the manufactured sample (local heating, rolling rollers), causing the metal the formation of the plastic deformation, resulting in the centre of the sample area occurs with a uniform distribution component of stress, signs and levels which depend on the nature of the impact and can be found from the results of measurement of the sample before and after exposure, and this zone can be used for calibration and validation of existing methods of determining the stress state in the metallic structure.

The way to create mechanical stresses in the metal pattern includes the education of the plastic deformation in the metal as a result of the impact made on a sample of local heating and/or rolling of the rollers of its edges, which in the Central part of the sample occurs area with homogeneous complex stress state.

For accurate level measurement of the generated voltage before exposure to the sample is subjected from the case of long lasting start to remove previously present in it stresses then put the base measurement in zone 3 on the front and back sides of the sample and measure them with high accuracy. After treatment with heat and rollers again Oberau these bases and differential measurements calculated voltage on the formulas of theory of elasticity.

List of figures

To illustrate the method 1 schematically shows a reference pattern (top view)figure 2 - side view of collecting a reference sample.

The implementation of the invention

Figure 1 shows a sample 1, containing an area of plastic deformation 2 and zone with a homogeneous stress state 3.

Figure 2 shows the scheme by which to obtain in the Central part of the sample area with a homogeneous stress state 3, you need to create plastic deformation at the edges of the rolling rollers 4 and/or local heating of the edges of the heat source 5.

The proposed method is as follows. Depending on what sign the necessary voltage, tensile or compressive, select one of the ways of influencing the pattern: rolling or heat. To obtain the tensile stresses in zone 3 is used, the rolling zone 2 rollers 4. When rolling the metal is precipitated in thickness, resulting in its distribution in the longitudinal and transverse directions, and you receive the plastic deformation, which is oznikaet tensile stresses in the Central part of the sample 1. To obtain the compressive stresses in zone 3 produce local heating zone 2 heat source 5. At the same time in the heated zone 2 occur compressive stresses caused by the resistance of unheated part of the sample. These stresses reach the yield stress and lead to plastic deformation of the shortening in the heated zone 2. During cooling, the following occurs: the area experienced plastic deformation is reduced, and the remainder of the sample interferes with this reduction, which causes residual tensile stresses, reaching in zone 2 of the yield strength of the material. But since the sample is in equilibrium, then in zone 3 act residual compressive stresses to compensate for stretch in zone 2.

The ratio of voltage levels in zones 2 and 3 is inversely proportional to the ratio of sectional areas of these zones. To create a zone 3 biaxial stress state with different signs component may be combined rolling rollers 4 one edge of zone 2 and the heat of the heat source 5 other edges. For accurate level measurement of the generated voltage before exposure to the sample is subjected leave to withdraw previously present in it stresses, then put the base measurement in zone 3 on the front and back sides of the sample and measure them with high accuracy. After processing by heating and the role of the AMI again Oberau these bases and differential measurements calculated voltage on the formulas of theory of elasticity.

Thus, the method of creating the reference samples with known nature and level of the stress state can be used for areas with homogeneous stress state and calibration of existing methods of determining the stress state in the metallic structure.

1. A method of creating a reference sample with a given distribution of stresses, including the creation of plastic deformation in the resulting sample, characterized in that the plastic deformation creates on its edges, and to create plastic deformation apply local heating, rolling rollers and the combination of these techniques of influence, resulting in the centre of the sample area occurs with a uniform distribution component of stress, signs and levels which depend on the nature of the impact and can be found from the results of measurement of the sample before and after exposure.

2. The method according to claim 1, characterized in that before the exposure, the sample is subjected leave to withdraw previously present in it stresses, then put the base measurement on the front and back sides of the sample and measure them with high precision, after exposure to heat and/or rollers again Oberau these bases and differential measurements calculated voltage on the formulas of theory of elasticity.



 

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