Title of Invention

A PROCESS FOR FRACTURING RE-ASSEMBLABLE COMPONENTS

Abstract

The subject is a process for fracturing re-assemblable components or their prematerials, the component the fracture being fractured by applying a fracturing force perpendicularly to the desired surface of fracture. A pressure force is applied to the component prior to the application of the fracturing force, the pressure force resulting in a tensile stress which is at its maximum perpendicular to the desired surface of fracture in the plane of this surface. The pressure force is such that the stress level generated thereby is below the yield point of the material of the component. The pressure force still acts on the component at the moment when the fracturing force is applied.

Full Text

The invention relates to a process for fracturing re-assemblable components or their prematerials. When separating components which are re-assemblable, the components being in their finished form or in a semifinished form, or being prematerials (intermediate products), fracturing has proven to be a preferred method in fields requiring high assembly precision combined with efficient manufacture, for example in the fields of internal combustion engines when separating the connecting-rod bearing cover from the connecting rod or the crankshaft bearing cover from the crankcase. The fracturing process is effected at different processing stages of the components, and always follows the same sequence in terms of the process technology involved. First of all, a notch is made in the part which is to undergo the fracture, the notch following the desired path of the fracture line completely or partly along the contour of the part. The notch can be made in many different ways, for which the information provided in the literature is exhaustive. The notch produced has the purpose of initiating the fracture path upon application of the forces effecting the fracture. The actual fracture is then effected such that a force is applied perpendicularly to the desired surface of fracture and splits the part at the desired point. In practice, however, it has been shown that the actual fracture path very often deviates from the desired fracture path. There are numerous causes of this. It can be due to the material itself; brittle cast materials are better suited to fracturing than ductile materials, as used for example in forged connecting rods. In addition to the material itself, internal stresses, impurities or inhomogeneities in the basic material can be the cause of an unsatisfactory fracture path. To favourably influence the fracture, it is known from DE 100 22 884, for example, to embrittle the fracture region with respect to the rest of the component by locally delimited heat treatment to effect a change in the structure which results in a local multiaxial state of stress. This embrittling can be achieved here in many different ways. In the case of enlarged laser-produced notches, as described for example in DE 196 17 4 02 Al, the material is melted along the desired fracture line and the melt is purged or vaporised so that a continuous notch or a line of successive blind holes is produced. The edge regions of the notch or holes embrittle to form appropriate structures since the heat moves very quickly from the very small melted region into the rest of the component. The multi-dimensional states of stress connected with the embrittling can result in microscopic hardening cracks which, although desirable, like the states of stress extend at various angles to the desired fracture line and, like these, cause the fracture line to "stray" when the fracture is initiated by the application of the fracturing force. To favourably influence the fracture, it is furthermore known from EP 0 661 125 Al to firstly apply a force to the component in the direction of the fracturing force which is to be applied at a later point, this prestressing force being below the yield point of the component to be separated. This enables the force required for the actual fracture to be minimised, thus setting the parameters for achieving the steepest possible build-up gradient of the actual fracturing force to be applied. Although the steep build-up gradient has a positive influence on the initiation of the fracture and the fracture path, owing to the fact that the static prestress acts on relatively large areas of the component, it cannot prevent the fracture line from straying unfavourably due to the causes described above. Starting from this prior art, it would be desirable to be able to provide a process for fracturing re-assemblable components or their prematerials which, on the one hand, largely prevents the actual fracture line from deviating from the desired path and, on the other, enables a prestress to be applied to the part which is to undergo the fracture in the direction of effect of the fracturing forces. In one aspect the present invention provides a process for fracturing re-assemblable components or their prematerials, the component which is to undergo the fracture being fractured by applying a fracturing force perpendicularly to the desired surface of fracture, characterised in that a pressure force is applied to the component prior to the application of the fracturing force, said pressure force resulting in a tensile stress which is at its maximum perpendicular to the desired surface of fracture in the plane of this latter, the pressure force being calculated such that the stress level generated thereby is still below the yield point of the material of the component, and the pressure force still acting on the component at the moment when the fracturing force is applied. In another aspect the invention provides a process for fracturing re-assemblable components or their prematerials, a notch effect being introduced into the component which is to undergo the fracture along at least part of the desired fracture line as a result of a mechanical and/or structure-changing influence on the component and the component then being fractured as a result of applying a fracturing force perpendicularly to the desired surface of fracture, characterised in that a pressure force is applied to the component prior to the application of the fracturing force, said pressure force resulting in a tensile stress which is at its maximum perpendicular to the desired surface of fracture in the plane of this latter, the pressure force being calculated such that the stress level generated thereby is still below the yield point of the material of the component, and the pressure force still acting on the component at the moment when the fracturing force is applied. Advantageous features of the process are set forth in the dependent claims. In achieving the invention, it was assumed that those prestress components which have a positive influence on the fracture are those which are only effective in the desired surface of fracture and that, although the other states of stress associated with the conventional generation of the prestress also have to be generated in the part which is to undergo the fracture, they do not have a positive influence on the fracture path. It was therefore necessary to find a possible way of generating a tensile prestress which substantially only acts on the desired surface of fracture such that it is perpendicular thereto. Starting with this consideration, it was found that the desired tensile stress can be generated perpendicularly to the desired surface of fracture by applying a force to the part which is to undergo the fracture, said force resulting in a compressive or bending stress which is at its maximum in the plane of the desired surface of fracture. The desired tensile stress perpendicular to the fracture plane is produced as a result of the material-dependent cross-structure which, in the case of steel, is such that the transverse stress-to-longitudinal stress ratio is approximately 0.3. In the present case this means that, taking steel as the material used, the ratio of the compressive stress in the fracture plane to the tensile stress perpendicular thereto is 1:0.3. Apart from slight surface deformations, the force to be applied to the part here must not result in plastic deformation of the part which is to undergo the fracture and can be a statically or dynamically acting force. The advantage of the process according to the invention consists in that the maximum tensile stress generated in this way is located in the desired surface of fracture, which, on the one hand, generates a notch effect and, on the other, results in a prestress which acts perpendicularly to the desired surface of fracture and reduces the force required for the actual fracture, in turn setting the parameters for a high build-up gradient of the fracture force. Since, as mentioned above, the result of the tensile stress to be applied to the part which is to undergo the fracture corresponds to that of a notch effect, it is possible in suitable materials to completely or partly dispense with the introduction of notches and/or the generation of a notch effect through structural change. On the other hand, if the materials are very ductile materials with poor fracturing properties, when applying the known conventional notch effect described above the additional use of the process according to the invention enables the boundaries within which it is possible to effect the fracturing process to be considerably extended. The tensile stress which is to be applied according to the invention can be generated by pressure forces which act on the part in different ways in order to achieve the desired effect. It is thus possible to apply the pressure force by way of one or more sharp-edged wedges which act on the part along at least part of the desired fracture line. Here, the counter-pressure bearing can be formed by similar wedges opposite the wedges or even smooth bearing faces. The effect of the applied pressure force becomes increasingly favourable as the part of the desired fracture line acted upon by the pressure force increases. It is furthermore advantageously possible to apply the pressure force to the part which is to undergo the fracture by way of a shear arrangement. Here, the shear arrangement acts on the part such that the maximum compressive stress is in the plane of the desired surface of fracture. Here, the shear arrangement can act by means of mutually opposing shear edges which abut against the part along part of the peripheral line. A further simple and therefore advantageous possibility-consists in the pressure force being applied to the part which is to undergo the fracture by means of a bending arrangement. When applying a dynamic pressure force using one of the above-mentioned arrangements, this is to be effected such that the maximum tensile stress generated is achieved at substantially the same time as the maximum actual fracture force. Advantageous embodiments of the process according to the invention are explained in more detail below with reference to the drawings, in which: Fig. 1 illustrates a method of applying a pressure force by way of wedges; Fig. 2 illustrates a method of applying a pressure force by way of a shear arrangement; Fig. 3 illustrates a method of applying a pressure force by way of a three-point bending arrangement; and Fig. 4 illustrates a method of applying a pressure force by way of wedges, with slight simultaneous surface deformation. The fracturing process is explained below with reference to a test body which serves to simplify the illustration. The process according to the invention can, of course, be applied to other components suitable for fracturing. A preferred field of application here is the fracturing of bearing arrangements, e.g. connecting-rod bearings or crankshaft bearings for internal combustion engines. Figure 1 shows a side view of a component 1 which is to undergo the fracture. The fracture shall be effected here along the desired fracture line 3 . In order to achieve this, a pressure force is firstly exerted on the component 1 by way of two wedges 2a, 2b. The wedges 2a, 2b here lie with intermittent or extended contact against the desired fracture line 3, i.e. the peripheral line of the desired surface of fracture, by means of a sharp point or edge. They are arranged here facing each other on opposite sides of the component 1 so that the maximum compressive stress generated is in the plane of the desired surface of fracture, resulting in a tensile stress acting perpendicularly thereto. It is advantageous here if the part of the desired fracture line which is to be acted upon by the wedges 2a, 2b is as great as possible, measured over the total length of the desired fracture line 3. It is furthermore advantageous to let the wedges 2a, 2b act on the fracture line 3 at points where, owing to the structural features, a deviation of the actual fracture line from the desired fracture line 3 is to be expected or has been established in tests. The pressure forces can be applied by means of the wedges 2a, 2b such that both wedges 2a, 2b act on the component with the same force by way of a drive (not illustrated) . It is, of course, also possible to actively apply the force by way of the drive of only a first wedge 2a, whilst the second wedge 2b serves as a passive abutment. It is likewise conceivable to replace the second wedge 2b serving as an abutment with a bearing face (not illustrated) serving as an abutment, or to transfer the function of the abutment to a clamping means (not illustrated) for the component. For the following examination of the force and stress ratios on the component 1, it is assumed that a respective force F1 and F1' is applied to the component 1 by way of the two wedges 2a, 2b. The forces F1 and F1' result in a compressive stress distribution 4' in the component 1, which is likewise shown in Fig. 1 (sigma = stress) . The maximum of the compressive stress distribution 4' is achieved in the plane in which the forces F1, F1' act, i.e. in the desired surface of fracture. The tensile stress generated by way of the compressive stress and acting perpendicularly thereto follows the tensile stress distribution 4 and here represents, on the one hand, a load on the component 1 which corresponds to the effect of a notch in the direction of the desired surface of fracture and, on the other, a load whereof the effect corresponds to a prestress on the component 1 in the direction perpendicular to the desired surface of fracture, as would be generated by hypothetical forces F2, F2' with the difference that the hypothetical forces F2, F2' would generate this state of stress in the entire component 1 and not only in a small region of the component in the immediate vicinity of the desired surface of fracture. In the arrangement described above, the fracturing procedure proceeds in such a way that the forces F1, F1' are firstly applied to the component 1 which is to undergo the fracture along part of the fracture line 3 by means of the wedges 2a, 2b. Under this state of stress, the actual fracturing forces F3, F3' are then applied to the component 1 perpendicularly to the desired surface of fracture and these split the component 1 into the parts la, lb along the fracture line 3 . As a result of the state'-of stress in the region of the desired surface of fracture, starting cracks which initiate the fracture form such that they follow the maximum stress, which can substantially prevent the surface of fracture straying into other regions of the component 1. The state of stress of the component 1 during the fracturing procedure moreover reduces the forces necessary for the fracture which, as described above, can be used to increase the build-up rate of the forces F3, F3' . Deviating from the sequence described above, the forces F1, F1' can also be applied to the component 1 in a dynamic procedure during the fracturing procedure, i.e. at the same time as the fracturing forces F3, F3' . Care should be taken here to ensure that the forces" F1, F1' and the fracturing forces F3, F3' achieve the maximum level effecting the fracture at substantially the same time. Another possibility for applying a compressive stress to the component which is to undergo the fracture in the region of the surface of fracture is illustrated in Fig. 2. A shear arrangement comprising two shear jaws 5a, 5b and an abutment 5c acts on the component 1 with its shear edges 6a, 6b extending along part of the fracture line 3, which here also corresponds to the peripheral line of the desired surface of fracture. Acting on the shear jaws 5a, 5b are forces F4, F4' which generate a compressive stress in the component 1, which is at its maximum in the region of the desired surface of fracture. The effects of the tensile stress generated by way of the compressive stress are the same as those described in connection with Fig. 1: on the one hand, the notch effect in the fracture plane; on the other, the prestress perpendicular to the fracture plane. There is also no difference between the fracturing procedure itself and that described in connection with Fig. 1, so that it is possible to refer to these parts of the description. Analogously to the situation already described with reference to Fig. 1, it is also possible to apply the shear forces F4, F4' statically or dynamically here. In addition to generating the desired state of stress by way of a pure compressive stress, as illustrated in Figures 1 and 2, it is also possible to achieve the corresponding effect by way of a bending arrangement. In this regard, Figure 3 illustrates an arrangement which, by way of example, has the component 1 subjected to a three-point bending load. Here, a pressure force F5 acts, in the direction of the plane of the desired surface of fracture by way of a sharp-edged wedge 7a which acts on the component 1 along part of the fracture line 3. On the side of the component 1 which is opposite the wedge 7a, two wedge-shaped bearing elements 7b, 7c are each arranged on either side of the fracture line 3 at an equal spacing therefrom and act on the component 1 with counter forces F5', F5" to the pressure force F5. The force ratios produce a bending stress in the component 1, whereof the maximum extends opposite the sharp-edged wedge 7a and centrally between the wedge-shaped bearing elements 7b, 7c along a line 8 which is perpendicular to the plane of the drawing in Fig. 3. The bending stress results in a tensile stress which acts perpendicularly to the desired surface of fracture and, like the bending stress, achieves its maximum along the line 8. The fracturing procedure itself proceeds here such that a bending stress, and with this a tensile stress, is firstly applied to the component 1 by way of the sharp-edged wedge 7a as a result of the pressure force F5 and the wedge-shaped bearing elements 7b, 7c. As described above, the maximum tensile stress is located in the line 8. If, under this state of stress, the actual fracturing forces F3, F3' , which, like the tensile stress, act perpendicularly to the surface of fracture, are now applied to the component 1, a crack, which develops along the surface of fracture and therefore the fracture line 3, is initiated along the line 8, i.e. in the region of the maximum bending stress and therefore the maximum tensile stress, the state of the maximum bending stress and therefore the tensile stress following the apex of the crack and thus being reinforced so that the crack always extends along the maximum stress, as a result of which the crack can be substantially prevented from straying. It goes without saying that, in connection with the bending arrangement described above, it is also possible to apply the pressure force F5 and the counter forces F5' and F5" dynamically to the component 1. It is also true here that this has to take place such that the bending stress generated by way of the arrangement described, and therefore the resulting tensile stress, achieves its maximum at substantially the same time as the maximum fracturing forces F3, F3' applied to the component 1. To supplement the fracturing process described above, it is of course also possible, in conjunction therewith, to apply the procedure, known per se, of providing notches along the desired fracture line. The notches here are generated in the component which is to undergo the fracture in the known manner, e.g. by melting the surface using a laser beam, by-mechanical notching, by changing the structure etc., and promote the fracturing process, particularly also of ductile materials such as ductile steels which are used for example in forged connecting rods. The generation of the notches described above can also be advantageously achieved with the arrangement described in connection with Fig. 1 in that, when applying the pressure forces F1, F1', these are calculated such that, as shown in Fig. 4, the sharp edges 9a, 9b of the wedges 2a, 2b penetrate into the surface of the component 1 so that, in addition to the desired state of stress, a notch which promotes the initiation of the crack is also produced. As mentioned above, the above-described examples of fracturing procedures using the inventive process are merely explanatory. Using known means and procedures, the person skilled in the art is able to apply, or adapt, the process to all conceivable fracturing circumstances. WE CLAIM 1." A process for fracturing a re-assemblable component (1) along a desired surface of fracture, the component (1) being fractured by applying a fracturing force perpendicularly to the desired surface of fracture, wherein a pressure force (Fx to F6' ) is applied to the component (1) prior to the application of the fracturing force (F3, F3' ) , the said pressure force (Fx to F6' ) resulting in a tensile stress which is at its maximum perpendicular to the desired surface of fracture in the plane of this surface, the pressure force (Fi to F6' ) being such that the stress level generated thereby is below the yield point of the material of the component (1) , characterised in that the pressure force (Fi to F6' ) is applied to the component (1) by means of wedges (2a, 2b) or shear jaws (5a, 5b) which simultaneously act with intermittent or extended contact at the peripheral line of the desired surface of fracture with a sharp point or edge, in each case directed towards each other on opposite sides of the desired surface of fracture, and wherein the pressure force (Fi to F6' ) still acts on the component (1) at the moment when the fracturing force (F3, F3' ) is applied. 2. A process as claimed in claim 1, wherein a notch effect is firstly introduced into the component (1) along at least part of the desired fracture line (3) as a result of a mechanical and/or structure-changing influence on the component (1) and the component (1) is then fractured. 3. A process as claimed in claim 1 or 2, wherein the part of the desired fracture line (3) which is to be acted upon by the wedges (2a, 2b) or shear jaws (5a, 5b) is as great as possible, measured over the total length of the desired fracture line (3) . 4. A process as claimed in any preceding claim, wherein the pressure force (Fi to F6' ) is applied to the component (1) by a static pressure load, the pressure force (Fi to F6' ) acting on the component (1) in the plane of the surface of fracture and/or parallel thereto. 5. A process as claimed in any preceding claim, wherein the pressure force {F1 to F6' ) is applied to the component (1) by a dynamic pressure load, the pressure force {F± to Fs' ) acting on the component (1) in the plane of the surface of fracture and/or parallel thereto and reaching a maximum at substantially the same time as the fracturing force (F3, F3' ) . 5. A process as claimed in any preceding claim, wherein the pressure force is applied to the component by way of at least one sharp-edged wedge along at least part of the peripheral line of the desired surface of fracture, a counter-pressure bearing being provided by a similar wedge, which is opposite the sharp-edged wedge and acts on the peripheral line of the desired surface of fracture, or by a bearing face, or as a result of clamping the component. 6. A process as claimed in any preceding claim, wherein the pressure force (Fx to Fe' ) is applied to the component (1) by a shear arrangement (5a, 5b, 5c) comprising the shear jaws (5a, 5b) , and wherein a first bearing face of the shear arrangement (5a, 5b, 5c) acts on the component (1) such that it lies with a shear edge (6a) along part of the peripheral line of the desired surface of fracture and extends in the direction of a first end of the component (1) and, opposite this first bearing face, a second bearing face of the shear arrangement (5a, 5b, 5c) acts on the component such that it lies with a shear edge (6b) along part of the peripheral line of the desired surface of fracture and extends in the direction of a second end of the component (1), and the component (1) is secured against tilting so that the shear arrangement (5a, 5b, 5c) generates a compressive stress in the plane of the desired surface of fracture and, with this, a tensile stress acting perpendicularly thereto. 7. A process as claimed in any preceding claim, wherein the pressure force (Fi to F6' ) is such that at least one of the sharp-edged wedges (2a, 2b) penetrates into the surface of the component (1). 8. A process for fracturing a re-assemblable component, substantially as described with reference to Figure 1, Figure 2, Figure 3, or Figure 4 of the accompanying drawings.

Documents:

717-DEL-2005-Abstract-(01-09-2011).pdf

717-del-2005-abstract.pdf

717-DEL-2005-Claims-(01-09-2011).pdf

717-del-2005-Claims-(21-05-2013).pdf

717-del-2005-claims.pdf

717-DEL-2005-Correspodence Others-(04-01-2012).pdf

717-DEL-2005-Correspondence Others-(01-09-2011).pdf

717-DEL-2005-Correspondence Others-(16-02-2012).pdf

717-DEL-2005-Correspondence Others-(24-08-2011).pdf

717-del-2005-Correspondence Others-(28-07-2011).pdf

717-del-2005-Correspondence-Others-(21-05-2013).pdf

717-del-2005-correspondence-others.pdf

717-DEL-2005-Description (Complete)-(01-09-2011).pdf

717-del-2005-description (complete).pdf

717-del-2005-drawings.pdf

717-DEL-2005-Form-1-(01-09-2011).pdf

717-del-2005-form-1.pdf

717-del-2005-form-18.pdf

717-DEL-2005-Form-2-(01-09-2011).pdf

717-del-2005-form-2.pdf

717-DEL-2005-Form-3-(16-02-2012).pdf

717-DEL-2005-Form-3-(24-08-2011).pdf

717-del-2005-form-3.pdf

717-del-2005-form-5.pdf

717-del-2005-gpa.pdf

717-DEL-2005-Petition-137-(04-01-2012).pdf