Strain-gauge sensor

FIELD: measuring instrumentation.

SUBSTANCE: strain-gauge sensor includes loading element in the form of a hollow cylinder attached to the monitored object, pieso-optic converter converting tension value in stress-optical element attached in preloaded state into electrical signal, and signal processing unit. Optic axis of pieso-optic converter coincides with the cylinder axis and is perpendicular to measured deformation plane, loading element is a continuous hollow cylinder out of tensile material with wall thickness ensuring required elasticity of loading element in direction of deformations measured and determining sensitivity of strain-gauge sensor sealed at the ends and featuring hard lugs on the outside for attachment of the sensor to a monitored object and transmission of object deformation to stress-optical element.

EFFECT: enhanced functional capabilities of device.

9 cl, 14 dwg

 

The technical field

The invention relates to the control and measurement technology, in particular, to measure the strain (stress) in various designs through the polarization-optical converters and can be used in construction, transportation, industrial production, instrumentation.

The level of technology

It is known that piezooptical transducers used to measure deformations (strains)that have the greatest sensitivity in comparison with others, for example, piezoresistive transducers (Slesinger I.I. Piezooptical transducers. Measurement technology, 1985, No. 11, p.45-48) [1].

The closest in technical essence to the proposed strain sensor is a strain gauge (Patent No. 2454642 from 29.03.2011) [2]. The sensor consists of a load element is a hollow cylinder with four longitudinal through incisions that do not violate the integrity of the cylinder, and a photoelastic element piezooptical transducer is fixed in the cylinder so that the optical axis of piezooptical Converter coincides with the axis of the cylinder and perpendicular to the plane of the measured deformations. Photoelastic element is clamped by the cylinder wall, which provides sensometrics the th sensor as in compression, and stretching. Four longitudinal cross-section in the wall of the hollow cylinder load element also provide the effect of the initial power load on a photoelastic element in two mutually perpendicular directions.

The disadvantage of this strain gauge is that through incisions in the walls of the cylinder violate the integrity piezooptical transducer placed inside the cylinder, which will lead to the penetration of dust and moisture into the inverter. Making any additional constructions, sealing these incisions or not technological, or inevitably leads to an increased stiffness of the load element and, thereby, to the loss of sensitivity of the strain gauge.

Disclosure of inventions

The objective of the invention is to create a strain gauge, which provides a seal piezooptical Converter without compromising the sensitivity of the strain gauge.

The technical result is increased reliability and accuracy of measurement of deformation, increase lifetime.

The problem is solved due to the fact that in the known device, comprising a load element is a hollow cylinder, mounted on a controlled object, piezooptical Converter, conversions the store into an electrical signal the magnitude of stresses on the photoelastic element, which is enshrined in the notoriously loaded with the optical axis of piezooptical Converter coincides with the axis of the cylinder and perpendicular to the plane of the measured deformations and the block signal processing, according to the invention, the load element is a solid hollow cylinder made of elastic material with a wall thickness that provides the necessary elasticity of the load element in the direction of the measured deformations and determining the sensitivity of the strain gauge, which ends sealed, and with an outer side provided with a rigid protrusions arranged symmetrically relative to the axis of the cylinder, designed for mounting strain gauge on the test object and transmit the deformation of the object on a photoelastic element.

No cuts in the walls of the hollow cylinder, in which is placed piezooptical Converter, provides tightness of the Converter in the presence of tight caps on the ends of the cylinder. Load the element with piezooptical Converter is attached to the test object so that the axis piezooptical transducer is perpendicular to the plane of the measured deformations. The installation of the load element of the controlled object by using the hard protrusion is in the outer side wall of the cylinder, arranged symmetrically about the axis piezooptical Converter, which includes mounting holes. Hard tabs to ensure transmission of the deformation of the test object on a photoelastic element, with the cylinder walls do not significantly increase the rigidity in the direction of the measured deformations, due to the small thickness of the walls, and provide an efficient transfer of deformation on the photoelastic element. In addition, the small thickness of the cylinder wall provides flexibility of design, sufficient to secure a photoelastic element in the cylinder in an obviously loaded condition due to the fact that the external diameter of the photoelastic element exceeds the internal diameter of the space inside the hollow cylinder by an amount sufficient to mount a photoelastic element elasticity of the thin cylinder walls. When mounting a photoelastic element within a load element of the wall of the cylinder is elastically deformed due to the small wall thickness and elasticity of the material of the cylinder. After installation of the photoelastic element is clamped by the walls of the cylinder, enabling the strain gauge as in compression and in tension.

Quantity of external protrusions may be two (the angle between the projections relative to the axis of the cylinder 180 degrees), four (the angle between adjacent high is upama 90 degrees) or more.

Having four outer edges, small wall thickness of the hollow cylinder and the rigidity of the protrusions provide the effect of the initial power load on a photoelastic element in two mutually perpendicular directions. This, in turn, preserves the distribution of stress in the photoelastic element when the deformations caused by temperature changes, both the cylinder and the controlled object, which, in turn, provides a temperature independent signal.

Photoelastic element may have the shape of a cylinder or truncated cone.

The greatest efficiency of transmission of deformation in a photoelastic element is achieved in design, providing the location of the photoelastic element at the level of the surface of the test object.

Seat photoelastic element may be formed by protrusions on the inner surface of the cylinder at fixing external hard tabs. In case of implementation of a photoelastic element in the form of a truncated cone, the protrusions form a tapered hole whose axis coincides with the axis of the cylinder, and the cone angles of the hole and the cone photoelastic element are the same and equal to the Morse taper, and the average diameter of a photoelastic element exceeds the average diameter of the hole by an amount sufficient for fastening by Provost the walls of the cylinder.

The protrusions on the inner surface of the cylinder provide a stress concentration on a photoelastic element in two mutually perpendicular directions, which increases the sensitivity of the sensor. For higher stress concentration on a photoelastic element, the protrusions may be in the form of ribs with the reduced area of contact with the photoelastic element.

As the material of the load element can be used alloyed tempered steel.

As a photoelastic material element can be used, for example, fused silica, having a high damage threshold in compression, which provides a high dynamic range measurements of deformations and reliability of the sensor.

To improve the reliability of fastening of a load element for the controlled object on the outer protrusions may be made of the teeth lying in the same plane in contact with the surface of the test object.

In some cases, to measure voltages, for example, in a reinforced concrete beam, a more convenient way of mounting the load element is its anchoring within the mounting holes, made in the controlled object, which can be either end-to-end, and deaf. In this embodiment, sensor design the outer surface of the protrusions of the hollow cylinder is made in videonasa Morse. Mounting hole in the object under test can take the form of a cylinder or cone Morse, the average diameter mounting holes must be equal to the average diameter of the cone Morse load element.

The rationale put signs

As the cylinder is solid, without cuts, the tightness piezooptical Converter is provided by the manufacturer sealed caps closing the ends of the cylinder, and the small wall thickness of the cylinder does not increase the rigidity in the direction of the measured strain.

As a photoelastic element is initially compressed, the sensor with the same sensitivity works both in compression and in tension. In the case of four rigid protrusions, a photoelastic element, due to the elasticity of the walls of the cylinder is clamped in two mutually perpendicular directions lying in a plane parallel to the plane of the measured deformations. The deformation of the test object that occur along any of these areas leads to anisotropic compression or stretching of the photoelastic element that, in turn, causes the output signal piezooptical Converter is proportional to the deformation. When you change the same temperature as the cylinder, and the controlled object photoelastic element is compressed or once imaeda isotropic, that does not rotate the polarization vector of the source of polarized light beam when passing through the photoelastic element. This provides temperature readings independent strain gauge.

Due to the proposed placement piezooptical Converter within a load element representing a continuous hollow cylinder with a thin elastic walls, sealed the ends, and the method of its attachment to the controlled object is achieved by sealing piezooptical Converter, greatly extending the validity period of the sensor without compromising the sensitivity of the strain gauge.

Thus, the proposed set of characteristics that defines the design of the strain gauge, allows to achieve the stated technical result: ensure tightness piezooptical Converter, improve life, improve the reliability and accuracy of measurement of the deformation of the test object.

Description strain gauge

The description of the device illustrated by figures 1, 2, 3, 4, 5.

Figure 1 shows the design of the strain gauge with a photoelastic element made in the form of a solid cylinder, where 1 is the load element (solid cylinder), 2 - external lugs with mounting about what holes (two, four or more), 3 - a photoelastic element. The ends of the cylinder 1 is hermetically closed by a lid 4. On the inner walls of the cylinder load element is made projections 5, also forming a cylindrical surface (footprint) for fastening a photoelastic element, and the axis of the photoelastic element and the axis of the cylinder seats are the same. Due to the elasticity of the walls of the cylinder, a photoelastic element is clamped in the X direction (in the case of the two outer projections) or in two mutually perpendicular directions X and Y (in the case of four or more outer projections). Piezooptical Converter is located inside the cylinder so that its optical axis 6 coincides with the axis of the cylinder. To improve the reliability of fastening of a load element 1 to the controlled object 7 on the outer protrusions 2 are made of the teeth 8.

Figure 2 shows the design of the strain gauge with a photoelastic element 3 made in the form of a cone Morse, the protrusions 5 on the inner surface of the cylinder load element also form a Morse taper, with the optical axis 6 photoelastic element 3 coincides with the axis of the cylinder.

Figure 3 shows the design of the strain gauge with a photoelastic element 3 made in the form of a cone Morse, on the inner surface of the cylinder load element, the protrusions 5 are made in the form of a child who R with the reduced area of contact with a photoelastic element 3, forming a Morse taper for mounting a photoelastic element 3.

Figure 4 shows the design variant strain gauge with a load element 1, whose outer surface of outer projections made in the form of a cone Morse for mounting within the mounting holes in the object under test 7.

Figure 5 shows the design of the strain gauge, in which a photoelastic element 3 is located at the level of the surface of the test object 7.

Description of the device

Strain gauge works as follows.

A load element 1 is fixed on the surface of the investigated object 7 through the outer projections 2 with mounting holes and teeth 8 or by means of a cone Morse inside mounting holes made in the test object 7. Warp tension or compression that occurs in a controlled object in the X direction (in the case of two outer projections) or X and Y (in the case of four or more exterior protrusions), transferred to the cylinder 1 through the attachment. Deformation of the walls of the cylinder is transmitted to the photoelastic element 3, which leads to additional compression (+Δσx,y) or stretching (-Δσx,y) photoelastic element, where Δσx,y- change the value of the voltage in a photoelastic element in the X or y direction.

As a result, in piezooptical PR is the education there is an additional phase difference of ±Δ between mutually perpendicular polarization components of the beam, passed through a photoelastic element, which leads to the change of the electric signal at the output of the photodetector piezooptical Converter, which is recorded, processed by the processing unit of the signal and is displayed on the display panel.

Used sources of information

1. Slesinger I.I. Piezooptical transducers. Measurement technology, 1985, No. 11, p.45-48.

2. Patent No. 2454642 from 29.03.2011.

1. Strain gauge comprising a load element is a hollow cylinder, mounted on a controlled object, and piezooptical Converter that converts into an electrical signal the magnitude of stresses on the photoelastic element, which is fixed in the notoriously loaded with the optical axis of piezooptical Converter coincides with the axis of the cylinder and perpendicular to the plane of the measured deformations, and the processing unit of the signal, wherein the load element is a solid hollow cylinder made of elastic material with a wall thickness that provides the necessary elasticity of the load element in the direction of the measured deformations and determining the sensitivity of the strain gauge, which ends sealed, and with outer side provided with a rigid protrusions arranged symmetrical relative to the positive axis of the cylinder, designed for attaching a strain gauge to the test object and transmit the deformation of the object on a photoelastic element.

2. The sensor according to claim 1, wherein the photoelastic element made in the form of a cylinder, has an external diameter greater than the diameter of the seats formed by projections on the inner walls of the hollow cylinder load element by an amount sufficient to mount a photoelastic element due to the elasticity of the walls of the cylinder.

3. The sensor according to claim 1, wherein the photoelastic element is designed in the shape of a truncated cone, and on the inner surface of the cylinder load element has protrusions for attaching a photoelastic element, forming a conical hole, the axis of which coincides with the axis of the cylinder and with the axis of the photoelastic element, and the angles of the cone holes and cone photoelastic element are the same and equal to the Morse taper.

4. The sensor according to claim 2 or 3, characterized in that the protrusions may be in the form of ribs with the reduced area of contact with the photoelastic element.

5. The sensor according to claim 1, characterized in that the hard outer protrusions load element have the mounting holes for fastening to the controlled object.

6. The sensor according to claim 5, characterized in that to increase the reliability of fastening of a load element on Nar is the author of the protrusions made of the teeth, in contact with the controlled object and lying in the same plane.

7. The sensor according to claim 1, wherein the load element provided with external projections, the outer surface of which forms a cone is equal to the Morse cone and the axis of which coincides with the axis of the hollow cylinder.

8. The sensor according to claim 7, characterized in that the average diameter of the cone Morse formed the outer surface of the outer projections of the cylinder equal to the average diameter of the mounting holes in the test object.

9. The sensor according to claim 1, characterized in that the attaching point of the photoelastic element provides its placement on a level surface of the test object.



 

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