CN108871671A - A kind of introducing device of any residual stress of plane - Google Patents

Abstract

A device for introducing arbitrary residual stress in a plane, including a base body, a loading assembly, a load sensor, a movable fixture and a fixed pressing piece. In the opening where the lead wires of the load sensor are drawn out, a platform for supporting the sample and a connecting portion constraining two ends of the sample are arranged inside the base body; the load sensor is equipped with a connected load display, and the load sensor is arranged on the The inside of the substrate is connected with the loading assembly and the movable fixture respectively. The invention can generate uniform, arbitrary combination of tension and compression, and directly readable residual stress inside the sample, so that the introduced residual stress can be used as an agreed reference value to directly test the accuracy and reliability of the residual stress detection technology.

Description

A Device for Introducing Arbitrary Residual Stress in a Plane

technical field

The invention relates to the field of testing devices for mechanical properties of materials, in particular to a device for introducing arbitrary residual stress on a plane.

Background technique

Residual stress refers to the stress that exists inside the object in a balanced state when there is no external force, and its root cause is the non-uniform deformation inside the object. In mechanical manufacturing (such as welding), remanufacturing (such as surface strengthening) and service processes (such as pressure vessels), due to mechanical, thermal, chemical and other factors, residual stress inevitably exists on the surface of workpieces or structures. Residual stress will significantly affect the service performance of materials and workpieces, such as fracture, fatigue, corrosion resistance, etc., so it needs to be accurately measured. Existing non-destructive testing techniques for residual stress are relatively abundant, including nano-indentation method, X-ray method, neutron diffraction method and so on. In order to regularly test and calibrate the above-mentioned residual stress detection technology, a standard sample with a known residual stress state is required or a residual stress introduction device is used to generate known stress inside the sample to simulate the residual stress. Generally, it is difficult to obtain standard samples with known residual stress state, and the cost is high; in contrast, the method of generating residual stress by means of residual stress introduction device is more reliable and easy to implement, and the cost is lower, which can be used for a long time.

The current residual stress introduction device mainly generates stress through bending and tension and compression. For the bending method, residual stress can be introduced inside the sample through three-point bending or four-point bending, but the stress distribution on different thicknesses of the sample is different, which requires the measurement of the bending curvature, position in the thickness direction and elasticity of the sample Modulus, etc. to calculate the residual stress state at different locations. Since the residual stress state inside the sample is obtained indirectly through calculation, its accuracy and reliability are not high. For the tension-compression method, a uniform residual stress can be introduced inside the sample by stretching or compressing, but the existing devices mainly introduce one-dimensional residual stress (tensile stress or compressive stress) through uniaxial tension and compression, and cannot produce tensile stress. In-plane arbitrary residual stresses of compressive stress combinations. Therefore, it is necessary to design a device that introduces arbitrary residual stress in a plane through a combination of biaxial tension and compression to obtain specimens with richer residual stress states.

Contents of the invention

In order to overcome the difficulties and high cost of the existing residual stress standard sample preparation, the insufficient precision of the bending residual stress introduction device and the incomplete data volume of the uniaxial tension and compression residual stress introduction device, the present invention proposes a planar arbitrary residual stress introduction The device can generate uniform, arbitrary combination of tension and compression and directly readable residual stress inside the sample, so that the introduced residual stress can be used as the agreed reference value to directly test the accuracy and reliability of the residual stress detection technology.

The technical solution adopted by the present invention to solve its technical problems is:

A device for introducing arbitrary residual stress on a plane, including a base body, a loading assembly, a load sensor, a movable fixture and a fixed pressure piece. In order to lead out the opening of the load sensor lead, the base body is provided with a platform for supporting the sample and a connecting part that constrains two ends of the sample;

The load sensor is equipped with a connected load indicator, the load sensor is arranged inside the base body, and is connected to the loading assembly and the movable fixture respectively;

There are two sets of loading components, which are tensile stress applying components and compressive stress applying components, which are connected to the load sensor through the circular threaded holes at both ends of the base body, and are used to apply transverse and longitudinal tension to the sample respectively. stress or compressive stress;

The movable clamp is located inside the base body and is used for clamping the sample along the transverse direction and the longitudinal direction.

Further, the fixed pressing piece is "back" type, and is used to fix the sample on the supporting platform of the base.

The tensile stress application assembly includes a force nut and a feed screw, the feed screw is connected to the load sensor and passes through a threaded hole at one end of the substrate; the force nut is located on the feed screw , is threadedly connected with the feed screw; the tensile stress is applied to the sample by tightening the force nut.

The compressive stress application assembly includes a force applying screw and a connecting head. The left end of the connecting head is flat, and the right end is threadedly connected with the load sensor. The right end of the screw is designed as a truncated cone, and the surface of the truncated cone is in plane contact with the left end of the connecting head. The pressure generated by rotating the force-applying screw acts on the connecting head to apply compressive stress to the sample.

Both the movable fixture and the base body are processed with diamond-shaped joints to match the diamond-shaped joints at the four ends of the sample, and the ends of the sample are provided with through holes, and the four ends of the sample can be fixed by screws.

Preferably, the opening is a "U"-shaped opening.

The connecting portion is a pit.

The inside of the base body is provided with a groove serving as a moving guide rail of the movable fixture. The movable fixture is located in the corresponding groove guide rail of the base body and moves in the groove guide rail.

The beneficial effects of the present invention are mainly reflected in: the device can ensure that the sample is in a bidirectional stress state, the stress state in the middle test area of the sample is uniform and stable, and can generate residual stress of any combination of tension and compression in the plane; Dual-purpose, two test loading conditions of tensile stress and compressive stress can be realized by simply replacing the tensile stress applying component and the compressive stress applying component, and the operation is simple; the device is integrated in design and simple in structure, and the residual stress introduced on the sample is controlled by the load sensor Obtained by direct measurement, accurate and reliable; this device is equipped with a guide rail for the movement of the movable fixture, so that the direction of the force applied during the loading process is strictly parallel to the guide rail, stable and accurate; the sample of this device is provided with a through hole, and the sample can be fixed by screws On the substrate, the end of the sample is designed as a rhombus, which can be stretched or compressed; this device presses a fixed pressure piece on the sample, which plays a secondary role in fixing the sample and prevents the sample from warping under force. Curved deformation will affect the measurement accuracy.

Description of drawings

Fig. 1 is the schematic diagram of residual stress introducing device of the present invention;

Fig. 2 is that the drawing stress of the present invention applies schematic diagram;

Fig. 3 is a schematic diagram of applying compressive stress in the present invention;

Figure 4 shows the area to be tested with residual stress applied.

Among them, 1-substrate, 2-load sensor, 3-applying nut, 4-feed screw, 5-movable fixture, 6-sample to be tested, 7-positioning screw, 8-pressing piece, 9-fixing screw, 10-connector, 11-force screw, 12-guide rail, 13-area to be tested.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

Referring to FIGS. 1 to 4 , a device for introducing arbitrary residual stress in a plane includes a base 1 , two sets of loading components, a load sensor 2 , a movable fixture 5 and a pressing piece 8 . The base body 1 is "L" shaped, with threaded through holes at both ends, a platform for supporting the sample 6, a diamond-shaped interface for fixing the sample 6, and a guide rail 12 for keeping the movable fixture 5 moving in parallel. The base body 1 is mainly used for installing and supporting accessories of various parts, and has a positioning function.

The loading assembly is connected to the load sensor 2 through a threaded through hole at one end of the base body 1 , and is used to apply transverse and longitudinal tensile stress and compressive stress to the test sample 6 .

The movable clamp 5 is located inside the base body 1, and is used to clamp the sample 6 to be tested in the horizontal and vertical directions and to act on the sample 6 by the force applied by the conductive loading assembly. The movable clamp 5 is located in the corresponding guide rail 12 of the base body 1, and Movement in guide rail 12.

When applying tensile stress, the tensile stress application assembly includes a force nut 3 and a feed screw 4, which are threadedly matched, wherein the feed screw 4 is connected to the load sensor 2 and passes through the threaded through hole at one end of the base body 1; the force nut 3 The outer contour of one end is designed to be tapered, and it is located on the feed screw 4. It can rotate freely without applying force, and has the function of support and positioning; by tightening the force nut 3, the pulling force generated by the movement of the feed screw 4 acts on the load sensor 2 and the movable fixture 5 connected to it, apply tensile stress to the sample 6.

When compressive stress is applied, the compressive stress applying assembly includes a force applying screw 11 and a connector 10, wherein the left end of the connector 10 is a plane, and the right end is screwed to the load sensor 2, and the force applying screw 11 passes through the threaded through hole at one end of the substrate 1, and The base body 1 is threaded, and the right end of the force applying screw 11 is designed as a truncated cone. 5, thereby applying compressive stress to sample 6.

Any combination of tensile stress and compressive stress applied to the sample 6 can be realized by replacing the loading components at both ends of the matrix 1 .

The device of the present invention integrates the loading assembly, the load sensor 2, the movable fixture 5, and the sample to be tested 6 into the base body 1, wherein the loading assembly adopts a thread feeding method to tighten or compress the sample to be tested 6, and the external force nut 3 The contour adopts a truncated cone to have a better centering effect; the conversion of tensile stress and compressive stress can be realized by replacing the tensile stress applying component and the compressive stress applying component, and the operation is simple. The load sensor 2 is a mature commercial product, and its force value is displayed by a supporting digital display instrument. One end of the load sensor 2 is threadedly connected to the loading assembly, and the other end is connected to the movable fixture 5, so that the current load can be measured in real time when the test sample 6 is tested for tensile stress and compressive stress. The movable fixture 5 is connected with the sample 6 to be tested to coordinate the elongation (or compression) deformation of the sample, and it is located in the guide rail 12. During the loading process, the movable fixture always keeps moving in a straight line to ensure that the loading direction is accurate and reliable. The four ends of the sample 6 to be tested are designed as diamond-shaped joints, which can be used for both tension and compression, and the movable fixture 5 and the base 1 are provided with diamond-shaped pits matching the ends of the sample 6 to be tested.

The usage method of the present invention:

Referring to Fig. 2, when applying tensile stress, first install the four end joints of the sample 6 to be tested in the diamond-shaped pits of the substrate 1 and the movable fixture 5, and the bottom of the sample 6 to be tested needs to be in contact with the substrate 1 when placed. The inner support platform is fully contacted. The force applying nut 3 is connected with the feed screw 4 , the force apply nut 3 is fitted on the outside of the threaded hole at the end of the base body 1 , and the feed screw 4 is fixedly connected to the load sensor 2 . After adjusting the leveling of the sample 6 to be tested, the positioning screw 7 passes through the through hole at the end of the sample to fix the sample on the base 1 and the movable fixture 5, and then place the "back" type pressing piece 8 on the sample 6 to be tested , the fixing screw 9 presses and fixes the pressing piece 8 on the test sample 6 through the holes at the four ends of the pressing piece 8, and plays a role of secondary fixing of the test sample to avoid the occurrence of warping. Rotate the force applying nut 3, during the rotation, clamp the feed screw 4 to ensure that it does not rotate relative to the load sensor 2, and load the sample 6 to be tested to a predetermined tension value by detecting the load display.

When compressive stress is applied, refer to Figure 3, install the sample 6 to be tested on the substrate 1 and the movable fixture 5 sequentially according to the installation method of applying tensile stress, and use the fixed pressing piece 8 for secondary fixation, and the movable fixture 5 is installed on the substrate 1 In the guide rail 12, and connected with the load sensor 2. The connecting head 10 is threadedly connected with the load sensor 2, the force applying screw 11 passes through the hole at the end of the base body 1 and is threadedly matched with the base body 1, the conical surface end of the force applying screw 11 is in flat contact with the left end of the connecting head 10, and the force applying screw 11 is rotated A pressure is generated to act on the plane of the connecting head 10 to realize the compression of the sample 6, and the test sample 6 is loaded to a predetermined pressure value by detecting the load display.

After the applied tensile stress or compressive stress is stable, the device is placed on the residual stress test bench for experiments. After the required data is measured, the loading component is adjusted to another required stress value, and the experiment process is repeated for different Test experiments on specimens under stress.

After the experiment is completed, the residual stress of the sample is obtained through corresponding calculation, and compared with the applied standard stress, the calculation process is verified and corrected. The device for introducing arbitrary residual stress in the plane proposed by the invention can generate uniformly distributed stress on the surface of the sample area to be tested by applying force in both directions. The structure of the device is simple, the stress state is stable, and it can be used as a standard stress introduction device for the inspection of residual stress test.

The content described in the embodiments of this specification is only an enumeration of the implementation forms of the inventive concept. The protection scope of the present invention should not be regarded as limited to the specific forms stated in the examples. The protection scope of the present invention also includes those skilled in the art. Equivalent technical means conceivable according to the concept of the present invention.

Claims (8)

1. a kind of introducing device of any residual stress of plane, it is characterised in that：The introducing device includes matrix, load group Part, load transducer, floating holder and fixed tabletting, described matrix are " L " type, and both ends of the surface offer round thread through-hole, two A side offers the opening for drawing load transducer conducting wire, and described matrix is internally provided with the platform peace treaty of support sample The interconnecting piece of beam sample two of them end；

The load transducer is arranged inside described matrix equipped with connected load display, the load transducer, and It is connected respectively with charging assembly and floating holder；

The charging assembly has two sets, and respectively tensile stress applies component and compression applies component, passes through described matrix both ends Round thread through-hole be connected with the load transducer, answered for applying horizontal and vertical tensile stress or pressure to sample respectively Power；

The floating holder is located inside described matrix, for by sample transversely with longitudinal clamping.

2. a kind of introducing device of any residual stress of plane as described in claim 1, it is characterised in that：The fixed tabletting For " returning " type, for sample to be fixed on to the support platform of described matrix.

3. a kind of introducing device of any residual stress of plane as claimed in claim 1 or 2, it is characterised in that：The drawing is answered Force applying assembly includes that force nut and feed screw, the feed screw are connected with the load transducer, and pass through described The threaded hole of matrix one end；The force nut is located on the feed screw, is threadedly coupled with feed screw；It is applied by tightening Power nut applies tensile stress to sample.

4. a kind of introducing device of any residual stress of plane as claimed in claim 1 or 2, it is characterised in that：The pressure is answered Force applying assembly includes force screw rod and connector, and the connector left end is plane, and right end is threadedly coupled with load transducer, The force screw rod passes through the hole of described matrix one end, cooperates with matrix screw thread, and force screw rod right end is designed as frustum, frustum platform Face and connector left end plane contact act on connector by the pressure that rotation force screw rod generates, apply pressure to sample and answer Power.

5. a kind of introducing device of any residual stress of plane as claimed in claim 1 or 2, it is characterised in that：The activity Fixture and matrix process diamond shape interface, match with the diamond shape connector of four ends of sample, and sample end is provided with through-hole, Four ends of the fixed sample of screw can be passed through.

6. a kind of introducing device of any residual stress of plane as claimed in claim 1 or 2, it is characterised in that：The opening For U-typed opening.

7. a kind of introducing device of any residual stress of plane as claimed in claim 1 or 2, it is characterised in that：The connection Portion is diamond shape pit.

8. a kind of introducing device of any residual stress of plane as claimed in claim 1 or 2, it is characterised in that：Described matrix Inside is equipped with the groove for serving as floating holder motion guide rail, and the floating holder is located in the respective slot guide rail of described matrix, It is moved in grooved rail.