CONNECTING ELEMENT, REINFORCEMENT AND USE OF A CONNECTING ELEMENT

Abstract

A connecting element for the force- and/or form-fitting connection of a first component to a second component is provided, having a connecting portion having a shape memory material. Furthermore, a reinforcement and the use of the connecting element is provided.

Claims

1. A connecting element for force- and/or form-fitting connection of a first component to a second component, comprising a connecting portion having a shape memory material.

2. The connecting element as claimed in claim 1, wherein the shape memory material has an activation temperature above room temperature.

3. The connecting element as claimed in claim 1, wherein the shape memory material is magnetically activatable.

4. The connecting element as claimed in claim 1, wherein the shape memory material is an iron-based shape memory alloy.

5. The connecting element as claimed in claim 1, wherein the connecting portion is configured to receive a reinforcing element.

6. The connecting element as claimed in claim 1, wherein the connecting portion is sleeve-like.

7. The connecting element as claimed in claim 1, wherein the connecting portion has at least one cone.

8. The connecting element as claimed in claim 1, having cone slope (alpha) of at most 10.

9. The connecting element as claimed in claim 8, wherein the cone slope (alpha) is at least 0.1%.

10. The connecting element as claimed in claim 1, having a clamping force of an activated connecting portion that is greater than a tensile strength of at least one of the first and second components to be connected.

11. The connecting element as claimed in claim 1, wherein the connecting element is designed to connect, as the first component, a reinforcing element to the second component.

12. The connecting element as claimed in claim 1, wherein the connecting portion has a structured surface portion.

13. A reinforcement comprising a reinforcing element on which a connecting element as claimed in claim 1 is arranged.

14. A method of connecting a first component to a second component, the method comprising force- and/or form-fitting connection of the first component to the second component by a connecting element having an iron-based shape memory alloy.

15. The method of claim 14, wherein the connecting element comprises a connecting portion having the iron-based shape memory alloy.

16. The method of claim 14, including heating the iron-based shape memory alloy for activation to at least 100? C.

17. The method of claim 14, including physically activating the iron-based shape memory alloy.

18. The connecting element of claim 2, wherein the shape memory material has an activation temperature above 100? C.

19. The connecting element of claim 5, wherein the reinforcing element is a reinforcing bar.

20. The connecting element of claim 1, wherein the at least one cone is an internal cone.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0043] In the schematic drawing, exemplary embodiments of the invention are shown and explained in more detail in the following description.

[0044] FIG. 1 shows a schematic cross-sectional view of a connecting element before activation, into which two components to be connected to one another have been introduced;

[0045] FIG. 2 shows a schematic cross-sectional view of the connecting element with the two components after activation;

[0046] FIG. 3 shows a pressure/elongation diagram for illustrating the use of the connecting element, and

[0047] FIG. 4 shows a reinforcement.

DESCRIPTION OF THE EMBODIMENTS

[0048] In order to make it easier to understand the invention, the same reference signs are used in each case for identical or functionally corresponding elements in the following description of the figures.

[0049] FIG. 1 shows a schematic cross-sectional view of a connecting element 10 having a connecting portion 12. In this exemplary embodiment, the connecting portion 12 corresponds to the entire connecting element 10.

[0050] The connecting element 10 and thus also the connecting portion 12 are sleeve-like. Extending toward the two open ends of the connecting portion 12, internal cones 14 have been incorporated. The internal cones 14 have cone slopes alpha of about 2%.

[0051] The connecting portion 12 is made from an iron-based shape memory alloy, in particular of the FeMnSi type, particularly preferably of the FeMnSiCrNi type.

[0052] As is explained in more detail in connection with FIG. 3, the connecting portion 12 is pre-elongated in the state according to FIG. 1. In particular, the connecting portion 12 has been radially expanded. The expansion and thus pre-elongation can take place for example by means of conical punches (not illustrated in FIG. 1), which are pressed into the internal cones 14. Preferably, a lubricant is used in order for it to be possible, following the expansion and the associated partially plastic deformation of the connecting portion 12, to remove the punches from the connecting portion 12 again. The pre-elongation can in this case take place at a normal room temperature, for example 20? C.

[0053] Introduced into the internal cones 14 are a first component 16 and a second component 18 in order to be connected to one another. It is apparent that the components 16 and 18 each come into contact with the internal cones 14 and thus the connecting portion 12 in starting contact regions 20. On account of the conical design of the connecting portion 12, it is thus possible for very different kinds of components and in particular components with different sizes to be introduced into the connecting portion 12, such that the components can always come into contact internally with the connecting portion 12 radially or at least substantially radially in spite for example of different diameters.

[0054] The state according to FIG. 1 represents the state of the connecting element 10 at the start of the production of an at least force-fitting connection between the two components 16 and 18. In this case, the connecting element 10 and thus also the connecting portion 12 can be at a normal temperature, for example the prevailing ambient temperature, for example in the range between 5? C. and 25? C.

[0055] In order to establish a force-fit and, depending on the geometry of the components 18, optionally a form-fit between the two components 16 and 18, the iron-based shape memory material needs to be activated. In this exemplary embodiment, the iron-based shape memory alloy is activatable by heating starting from room temperature. In particular, it is necessary to heat the shape memory alloy above 100? C., for example to an activation temperature of 160? C.

[0056] The iron-based shape memory alloy is also electrically conductive. Therefore, an activation device 22, which is only schematically illustrated in FIG. 1, can be electrically connected to the connecting element 10 and in particular to the connecting portion 12 formed from the iron-based shape memory alloy. The activation device 22 has a power source, for example a rechargeable battery, in particular a lithium-based rechargeable battery. It is designed to allow an electric current, preferably a pulse of current with a duration in the region of seconds or a few minutes, to flow in the connecting portion 12 connected to it. In this way, the iron-based shape memory alloy can be heated until it is activated. The activation device 22 is also designed to automatically switch off after the activation temperature is reached, for example by means of a temperature sensor and/or by means of monitoring the current generated and the electric voltage applied, such that overheating is avoided. Following activation, the activation device 22 can be detached from the connecting element 10 again.

[0057] The connecting portion 12 can preferably be internally lined, in particular in the region of the internal cones 14, with an insulating coating 24, for example an electrically insulating varnish. The current generated by the activation device 22 thus flows only through the connecting element 10 and in particular through the iron-based shape memory alloy contained therein.

[0058] On reaching the activation temperature, the iron-based shape memory alloy is activated such that it tends to deform into its target geometry, in this case the state prior to pre-elongation of the connecting portion 12.

[0059] The connecting element 10 and in particular the connecting portion 12 thus start to radially shrink until they reach the state according to FIG. 2.

[0060] It is apparent from FIG. 2, in which again a schematic cross-sectional view is depicted, that the connecting portion 12 comes into contact with the components 16 or 18, respectively, as a result of its shrinkage in the region of clamping contact regions 26. Depending on the original spacing of the inner side of the connecting portion 12 or of the internal cones 14, clamping pressures Pk are developed in the process. In this exemplary embodiment, the clamping pressures Pk can be up to 500 MPa. In FIG. 2, a triangle symbolically illustrates that the clamping pressures Pk increase linearly or at least substantially linearly toward the inside and thus no local stress peaks occur, which could damage the components 16 or 18.

[0061] Thus, the components 16 and 18 are each connected to the connecting portion 12 by clamping and thus also to one another at least by way of a force-fit.

[0062] If the components 16 and/or 18 do not have smooth surfaces, for example have ribbed surfaces, one or more rear engagements of the connecting portion 12 can occur to some extent, such that, depending on the components 16 and/or 18 to be connected, form-fits can also be formed in addition to the force-fits.

[0063] FIG. 3 will now be used to explain in more detail the use of the connecting element 10, which has an iron-based shape memory alloy, for the force- and/or form-fitting connection of the two components 16 and 18.

[0064] In the diagram according to FIG. 3, the stresses p prevailing in the shape memory material are plotted versus its relative elongation 1%.

[0065] Starting from the non-pre-elongated, non-prestressed shape memory material (point 0), the shape memory material, and in particular thus the sleeve-like connecting portion 12 (FIG. 1), is pre-elongated by means of the conical punches. The sleeve-like connecting portion 12 is thus elongated radially until it achieves a maximum relative elongation 1% at the point a. Now, the punches are removed. As a result, spring-back in the order of magnitude of up to about 1%, preferably of up to 0.5%, occurs, such that a pre-elongation in the order of magnitude in the region of about 2.5% to 6.5% remains.

[0066] Then, the components 16 and 18 (FIG. 1) are introduced into the connecting portion 12 until they come into contact with the connecting portion 12 according to the point b, at least in the starting contact regions 20 (FIG. 1). It should be noted that the spring-back does not result in complete regression of the elongation.

[0067] Subsequently, the shape memory material is activated by heating at least up to the activation temperature, for example up to 160? C. The shape memory material thus tends, on the basis of its inherent shape memory effect, to pass back into the initial state and thus also the target state according to point 0.

[0068] It is prevented from returning entirely, however, on account of the components 16 and 18. Depending on the original distance between the respective portion along the components 16 and 18 and the connecting portion 12, a partial reduction in the relative elongation 1% occurs, with the result that the connecting portion 12 fits snugly against the respective component 16 or 18. Depending on the extent of residual relative elongation 1%, different clamping pressures Pk (FIG. 2) arise, which, at most, corresponding here to the point b, can amount for example to up to 500 MPa depending on the shape memory material. The points c, d accordingly represent states with a lower residual relative elongation 1% and accordingly lower clamping pressures Pk.

[0069] In this state, i.e. substantially the state according to FIG. 2, the components 16 and 18 are thus fixed to the connecting element 10 with sufficiently high clamping pressures Pk overall and thus securely connected to one another. Sufficiently high clamping pressures Pk can be considered in particular to be clamping pressures Pk, the surface integral of which over the clamping contact regions 28 corresponds to a clamping force at which the component 16 or 18 in question is fixed to the connecting element 10 with a retaining force which corresponds at least to a breaking force, in particular a tensile breaking force, of the component 16 or 18. This can mean that the connection at least between the connecting element 10 and the component 16 or 18 exhibits greater tensile strength than the component 16 or 18 itself.

[0070] Finally, FIG. 4 shows a reinforcement 28. The reinforcement 28 is designed to reinforce a concrete part to be produced. It has a multiplicity of components in the form of rod-like reinforcing bars, of which, by way of example, a first component 16 and a second component 18 are labeled with reference signs.

[0071] The components, i.e. the reinforcing bars, are connected to one another by connecting elements, of which again, by way of example, one connecting element 10 is provided with a reference sign. These connecting elements substantially correspond in terms of structure and function to the connecting elements 10 described above in relation to FIG. 1, FIG. 2 and FIG. 3. They have, for example, the special feature of being cruciform. In this example, they can thus connect up to four different components to one another by means of their four open ends by way of force- and/or form-fits.

[0072] Overall, the reinforcement 28 thus has a matrix-like structure