Method of welding a weld stud to a workpiece and of checking the strength of the welded joint

Abstract

A method of welding a weld stud to a workpiece and of checking the strength of the welded joint includes the steps of providing a tool, a workpiece, and a weld stud, the weld stud including a shank and a polygonal shaped head; welding the weld stud onto the workpiece; applying the tool to the polygonal shaped head section of the stud; applying a predetermined test torque to the weld stud with the tool; and checking the welded joint for satisfactory acceptance of the test torque.

Claims

1. A method of welding a weld stud to a workpiece and of checking the strength of the welded joint, wherein the method includes the steps: providing a tool, a workpiece, and a weld stud, the weld stud comprising: a shank; a flange axially adjoining the shank, the flange projects radially relative to the shank and defines a polygon shaped outer circumference; an annular section axially adjoining the flange and including an axially facing and radially extending annular weld surface; and the annular section and the flange comprise a head section, and the polygonal shape of the flange extends over the annular section up to its axially facing annular weld surface; welding the weld stud onto the workpiece by drawn-arc stud welding; applying the tool to the polygonal shaped head section of the stud; applying a predetermined test torque to the weld stud with the tool; and checking the welded joint for satisfactory acceptance of the test torque.

2. A method of welding a weld stud to a workpiece and of checking the strength of the welded joint according to the steps of claim 1, wherein the steps of applying the tool, applying the predetermined torque, and checking the welded joint are performed immediately after the step of welding the weld stud onto the workpiece.

3. A method of welding a weld stud to a workpiece and of checking the strength of the welded joint according to the steps of claim 1, wherein the steps of applying the tool, applying the predetermined torque, and checking the welded joint are performed during a body-in-white phase of a production process.

4. A method of welding a weld stud to a workpiece and of checking the strength of the welded joint according to the steps of claim 1, wherein the steps of applying the tool, applying the predetermined torque, and checking the welded joint are performed before a further processing step.

5. A method of assembling a fastening arrangement onto a workpiece, wherein the method includes the steps: providing a torque application tool, a workpiece, and fastening element; providing a weld stud, the weld stud comprising; a shank; a flange axially adjoining and projecting radially from the shank; an annular section axially adjoining the flange and including an axially facing and radially extending annular welding surface which is weldable to the workpiece; and wherein the annular section directly adjoins the flange, and the annular section and the flange form a head section, and the head section includes a polygonal shaped outer perimeter and the polygonal shape outer perimeter extends over the annular section up to its axially facing annular weld surface; welding the weld stud onto the workpiece by drawn-arc stud welding; applying the tool to the polygonal shaped head section of the stud; applying a predetermined test torque to the weld stud with the tool; checking the welded joint has absorbed the test torque without damage; and fixing the fastening element to the weld stud.

6. A method of assembling a fastening arrangement onto a workpiece according to the steps of claim 5, wherein the steps of applying the tool, applying the predetermined torque, and checking the welded joint are performed immediately after the step of welding the weld stud onto the workpiece.

7. A method of assembling a fastening arrangement onto a workpiece according to the steps of claim 5, wherein the steps of applying the tool, applying the predetermined torque, and checking the welded joint are performed during a body-in-white phase of a production process.

8. A method of assembling a fastening arrangement onto a workpiece according to the steps of claim 5, wherein the steps of applying the tool, applying the predetermined torque, and checking the welded joint are performed before a further assembly step.

9. A method of assembling a fastening arrangement onto a workpiece according to the steps of claim 5, wherein the step of fixing the fastening element to the weld stud is performed before the welding step.

10. A method of assembling a fastening arrangement onto a workpiece according to the steps of claim 5, wherein the step of fixing the fastening element to the weld stud is performed after the welding step.

11. A method of assembling a fastening arrangement onto a workpiece according to the steps of claim 5, wherein the step of fixing the fastening element to the weld stud includes the step of locking the fastening element against rotation by engaging the fastening element to the polygon shaped head section.

12. A method of assembling a fastening arrangement onto a workpiece according to the steps of claim 5, wherein the step of fixing the fastening element to the weld stud includes the step of securing the fastening element in a predetermined correct position by engaging the fastening element to the polygon shaped head section.

13. A method of assembling a fastening arrangement onto a workpiece according to the steps of claim 5, wherein the fastening element is a plastic clip.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) Exemplary embodiments of the invention are shown in the drawing and described in more detail below. In the drawing:

(2) FIG. 1 shows a partly sectioned side view of a stud according to an embodiment of the invention;

(3) FIG. 2 shows a view of the stud of FIG. 1 from the front; and

(4) FIG. 3 shows a fastening arrangement with a workpiece and a stud according to FIGS. 1 and 2 welded onto the workpiece.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

(5) An embodiment of a stud according to the invention is designated generally by 10 in FIGS. 1 and 2.

(6) The stud 10 has a shank 12, adjoining which in the axial direction is a flange 14. Adjoining the flange 14 in the axial direction is an annular section 16, within which a recess 17 of circular cross section is located.

(7) A longitudinal axis of the stud 10 is shown at 18.

(8) A front annular surface 19 is formed on the front end of the annular section 16. The recess 17 extends from the front annular surface 19 up to the flange 14.

(9) On the whole, the flange 14 and the annular section 16 form a head section 20, the outer circumference of which has a polygonal shape 22, in the present case an octagonal shape.

(10) A coarse thread 24 is formed on the shank 12. The stud 10 has an overall length L. The axial length of the head section 20 is designated by K in FIG. 1. The axial length of the flange section is designated by F in FIG. 1. An outside diameter of the head section 20 is designated by D, and an inside diameter of the recess 17 is designated by A.

(11) The ratio of the axial length F of the flange 14 to the axial length K of the head section 20 is within the range of 3/10 to 5/10, in the present case approximately within the range of 4.5/10.

(12) The ratio of the inside diameter A of the recess 17 to the outside diameter D of the head section 20 is within the range of 5/10 to 8/10, preferably within the range of 6/10 to 7/10.

(13) The ratio of the axial length K of the head section 20 to the overall length L of the stud 10 is within the range of 1/10 to 4/10, preferably within the range of 1.5/10 to 3/10. In the present case the ratio is about 2/10.

(14) The front annular surface 19 extends in the radial direction. The inner circumference of the annular section 16 is of circular design in cross section.

(15) FIG. 3 shows a fastening arrangement 30 according to the invention, said fastening arrangement 30 having a stud 10 of the type shown in FIGS. 1 and 2, said stud 10 being welded onto a workpiece 32. The workpiece 32 is a metal sheet, preferably made of the same material as the stud 10 or of a material similar to that of the stud 10. The workpiece 32 has a thickness W which is less than 1.0 mm, in particular less than 0.8 mm. In the present case the thickness W is about 0.6 mm.

(16) As indicated schematically in FIG. 3, the stud 10 is suitable for fixing a plastic fastening element or clip 34, as is known per se in the prior art. The clip 34 may contain, for example, a receptacle 36 for a component 38. The component 38 may be, for example, a cable or a cable harness, a brake line or a fuel line.

(17) In this case, the clip 34 bears on that side of the flange 14 which points toward the shank 12, as shown in FIG. 3.

(18) In the field of vehicle technology, the clip 34 is fastened to the stud 10 as a rule in an assembly area. In this case, the body shell of the vehicle is produced and the workpiece 32 including the stud 10 is as a rule already painted, such that the requisite attachments can be carried out. The stud 10 is welded onto the workpiece 32 beforehand in a body-in-white phase.

(19) Directly after the body-in-white phase and before further processing steps, it is preferably checked whether the welded joint between the stud 10 and the workpiece 32 has sufficient strength.

(20) In this case, during the body-in-white phase or before the assembly phase, a torque T is exerted on the stud 10 about the longitudinal axis 18 by means of a tool 40 (indicated schematically in FIG. 3). In the process, the tool 40 acts on the head section 20 provided with the polygonal shape. The torque T that is applied in this case is a predetermined torque which a stud 10 correctly welded to the workpiece 32 can absorb without damaging the welded joint and/or the stud 10.

(21) In addition, the polygonal shape of the head section 14 enables mounted components or plastic fastening elements (clips 34), given the provision of suitable receptacles, to be able to act on the polygonal shape 22 in order to permit anti-rotation locking or adjustment in the correct position.

(22) The stud 10 can generally be used universally. It may be provided with or without a pre-completed plastic part (for example welding of the stud 10 to the workpiece, wherein the plastic fastening element is already pre-fitted on the stud 10, as is advantageous, for example, in underbody fastening).

(23) In this embodiment, care should possibly be taken to ensure that the pre-fitted plastic fastening element leaves at least part of the polygonal shape 22 of the head section 20 free in order to still be able to exert the test torque in the body-in-white phase.

(24) Furthermore, the stud 10 can also be welded onto a workpiece 32 without pre-fitted plastic part, as described above. A plastic fastening element such as a clip 34 can then be fastened thereto, for example in an assembly area.

(25) The stud 10 is preferably welded on by arc welding with drawn arc. In the process, the annular surface 19 is set down on the workpiece 32. An electric pilot current is then switched on. The stud 10 is then lifted again from the workpiece 32, in the course of which an arc is struck. After that, if need be a cleaning current is switched on (not absolutely necessary). Finally, a welding current which is markedly higher than the pilot current is switched on, the energy being sufficient in order to fuse the front annular surface 19 and a corresponding mating surface on the workpiece 32. Finally, the stud 10 is lowered again onto the workpiece 32, in the course of which the molten pools fuse together. The welding current is then switched off. The complete molten pool solidifies, and the stud 10 is integrally connected to the workpiece 32.

(26) Although exemplary embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.