• 专利附录
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    • 专利摘要:
    Method of manufacturing a part (1) with increased contact fatigue resistance characterized in that it comprises at least one step of making at least one hole (2) inside the part (1) in an area close to the contact surface (3) of the piece (1). The part (1) obtained has a contact fatigue strength at the contact surface (3) greater than a piece manufactured by means of prior art processes without the at least one inner hole (2). (Machine-translation by Google Translate, not legally binding)
    公开号:ES2684048A1
    申请号:ES201730434
    申请日:2017-03-28
    公开日:2018-10-01
    发明作者:Jesus VAZQUEZ VALEO；Jaime Dominguez Abascal；Carlos NAVARRO PINTADO；Diego ERENA GUARDIA
    申请人:Universidad de Sevilla；
    IPC主号:
    专利说明:

    MANUFACTURING PROCEDURE OF A PART WITH RESISTANCEINCREASED TO FATIGUE BY CONTACT D E S C R I P C I Ó N
    OBJECT OF THE INVENTION
    The present invention describes a method of manufacturing a piece with increased resistance to contact fatigue. The method comprises at least the realization of a hole inside the piece in an area close to the contact surface. BACKGROUND OF THE INVENTION
    A technique currently known for the improvement of fatigue resistance of metal components is, for example, the application of a coating on the part that modifies some or several of its surface properties. Some of these properties that can be modified are, for example, the coefficient of friction, hardness or fatigue resistance.
    Another solution of the prior art is the application of a heat treatment to the corresponding part of which the surface properties of the material are to be modified.
    Likewise, surface mechanical treatments can be applied to introduce residual compression stresses that also help improve fatigue resistance. In these cases the impact of small balls can be caused against the surface at high speed, the surface can be treated with laser, a roller can be applied with great force on the surface, etc.
    Another group of known solutions to increase the resistance of the metal parts of the contact pairs is to modify the geometry of the elements that form said contact pair. In this way, the stresses under the contact surfaces of both parts can be reduced. An example of this type of solutions includes the realization of a texturing on the contact surfaces so that instead of being smooth they have a certain texture or surface pattern. This known solution allows to reduce the tensions inside the piece but necessarily introduces tension concentrators on the surface. Thus, the most important technical problem associated with this solution is that cracks would start faster than they would then slow down. DESCRIPTION OF THE INVENTION
    The manufacturing process of a piece with increased resistance to contact fatigue is applicable to the manufacture of parts that will be part of a mechanical contact pair. Its applicability would be in any industrial sector where machines and structures with parts joined together by some kind of mechanical contact are used.
    Thus, the parts obtained by means of the proposed procedure can be used in any type of vehicle used in agriculture or transport, in wind turbines, in robots of food or textile factories, in bolted joints, etc.
    The objective of the present invention is to increase the resistance of the components of the machines or structures that suffer from contact fatigue. That is, the present invention aims to improve the fatigue resistance of parts of any contact pair.
    The phenomenon of contact fatigue occurs when the pieces are in contact, pressed together and there are also varying forces with time applied to them. This causes a friction between the surfaces of both pieces which produces wear and cracks. Such cracks can cause the part to break after a number of applied load cycles.
    The solution described here falls into the group of solutions that increase the resistance to contact fatigue of the pieces by modifying the geometry of some of these. Specifically, the modification of the geometry is carried out inside these pieces.
    In this case, the proposed procedure comprises the realization of at least one hole inside the part in an area close to the contact surface. The contact surface of the piece is understood as the surface that will be in contact with another piece, for example in a contact pair.
    Said contact surface is susceptible to the greatest stresses and deformations, and is therefore the part that can be subjected to a greater fatigue damage process. It is essential, in order to extend the useful life of the piece, that the stresses suffered near the contact surface are reduced. The hollow that is made inside the piece allows to delay the formation of cracks and even in some cases prevents the appearance of these.
    In no case does the at least one hole that is made in the piece protrude on the contact surface. That is to say, at first sight it is not possible to appreciate in the contact surface the holes made in the pieces obtained with the described procedure. The technical characteristic that the contact surface of the pieces obtained is smooth facilitates the assembly, operation of the machine or structure on which they are placed and the possible application of other treatments on the surface of the piece.
    Thus, with the process of the present invention the stresses and deformations due to mechanical contact in the pieces obtained are reduced and therefore it is possible to delay the onset and propagation of cracks caused by fatigue. As a result, the parts obtained with the process of the present invention have a longer shelf life. In some cases it is even possible to avoid the failure of the pieces.
    Preferably the manufacturing process is carried out by additive manufacturing (also known as 3D printing), although depending on the geometry of the piece to be manufactured it is possible to apply other types of manufacturing techniques. With the additive manufacturing technique, the piece is generated layer by layer. Each layer has a thickness of a few tens of microns which allows the formation of at least one hole in the interior of the piece precisely. Likewise, this type of manufacturing ensures the correct positioning of the gaps inside the piece. DESCRIPTION OF THE DRAWINGS
    To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, according to a preferred example of practical implementation thereof, a set of drawings is attached as an integral part of said description. where, for illustrative and non-limiting purposes, the following has been represented:
    Figure 1a.- Shows a view of the contact surfaces of two pieces of a contact pair where one of said parts comprises a plurality of gaps below the contact surface.
    Figure 1b.- Shows a view of the contact surfaces of two pieces of a contact pair where both parts comprise a plurality of gaps below the contact surface.
    Figure 2.- Shows a view of the two pieces of a contact pair in which the geometric parameters that define the position and size of a hole in the contact pair have been represented.
    Figure 3.- Shows a graph in which the equivalent voltage of von Mises, ıVM, dimensioned with the maximum normal surface pressure, p0, has been represented for a contact pair of the state of the art and a contact pair in which one of the pieces comprises a gap below the surface. PREFERRED EMBODIMENT OF THE INVENTION
    An example of parts of the present invention is described below with the aid of Figures 1 to 3.
    A method of manufacturing a piece (1) of increased contact fatigue resistance is proposed, which comprises a step of making at least one hole (2) inside the piece. Preferably, the manufacturing process comprises at least one stage of additive manufacturing of the piece.
    With the invention a piece is achieved in which the stress / strain fields have been redistributed. This delays the appearance of cracks and therefore improves the life of the parts and their resistance to contact fatigue.
    Figure 1a shows a contact pair in which one of the pieces, in this case the interior, has been manufactured including a hole in its interior as described. As can be seen in this example, six holes (2) have been made inside the piece (1), in an area close to the contact surface (3).
    Preferably, when a part (1) obtained with the process of the invention is used in a contact pair, said part (1) must be the one that is subjected to higher tensions, or it must be the part that by design has a higher requirement of fatigue resistance, or that piece of the contact pair that allows, for some design reason, to make holes inside.
    In figure 1b two pieces (1) obtained by the process of the present invention are shown. In this case both pieces (1) form a contact pair. As can be seen, in this example six holes (2) have been made inside each piece.
    When one or both pieces (1) in a contact pair comprise more than one hole
    (2) inside, the maximum of the tension of concentrations in the contact surface (3) can be decreased by choosing the position, size and number of holes well. Despite the fact that the gaps (2) themselves generate a concentration of stresses, the decrease in stresses on the contact surface (3) of the piece (1) compensates for the increase in the concentration of stresses inside.
    The embodiment in which the manufacturing process comprises the realization of several gaps (2) inside the piece (1), allows the pieces (1) obtained to be used in cases where the assembly of a pair of contact of which said part (1) is part, admits some error in the mounting position.
    The contact zone between two pieces of a contact pair is considered to be the area along which the contact surfaces of the pieces that form it contact. In figure 2 the half-width of the contact area (-a, a) between both pieces of the contact pair has been indicated. In a preferred embodiment, in the stage of making at least one hole (2) inside the part (1), the hole is made in an area close to the end of the contact area (-a, a) . This is because at the ends of the contact areas (-a, a) of the parts in a contact pair is where the highest tensions occur. In figure 2 it can be seen where a hole (2) made according to this embodiment would be positioned.
    The effect that is achieved with the gap (2) is to make the area of the piece (1) in which the highest tensions occur due to contact with the other part of a contact pair. This reduces the tensions in the most critical area of the contact pair. By decreasing tensions in the most critical area, the cracks take longer to start and may even appear but not continue to grow and therefore not break the piece.
    With respect to the embodiment in which the manufacturing process comprises at least one stage of additive manufacturing, as the layers that make up a piece so manufactured are of thicknesses of a few tens of microns, small gaps (2) can be easily generated inside the piece (1). This embodiment also allows a very precise control of the position of the at least one hole (2) inside the part (1).
    To check the influence of at least one hole (2) on at least one of the pieces
    (1) In the life of a contact pair, calculation methods based on multiaxial fatigue can be used. For this, finite element programs are used in which a modeling of the contact pair with the forces acting on each piece is introduced. When modeling is performed, the gaps (2) of each of the pieces (1) are taken into account and the results obtained from the stress / strain fields are compared with the results obtained for the same contact pair of the state of the technique, that is, in which the pieces do not include internal gaps.
    An embodiment is described below in which a piece (1) of a contact pair with a single recess (2) has been manufactured in an area close to the contact surface (3) and close to the end of the area of contact (a, -a) between both pieces of the contact pair.
    In this case a contact pair has been studied in which one of the pieces comprises at least one cylindrical surface that is in contact with the contact surface (3) of a piece (1) made with the method of the invention and whose behavior has resembled a semi-plane. Both the contact piece with a cylindrical surface and the piece whose behavior has resembled a semi-plane have been assumed under conditions of flat deformation.
    In this example, a compression load, N, and subsequently a tangential oscillatory load, Q, are applied to the part comprising the cylindrical contact surface (3), so that a contact fatigue test is reproduced. The ratio of both charges must meet that Q <μN so that there is no overall slip between the two pieces of the contact pair, but relative micrometric partial slips.
    Figure 2 shows the geometric parameters described whose values are shown in the following table (Table 1). For the realization of the test it has been considered that both pieces of the contact pair are made of steel and have an elastic and linear behavior. The geometric parameters are:
    a: is the half-width of the contact area between both pieces of the contact pair.
    c: is the half-width of the adhesion zone (this being an area in which there are no relative displacements between both surfaces of the contact pair).
    A: it is the radius of the cylindrical surface of the piece of the pair that comprises a cylindrical surface and that in this case is the one that applies the force on the other piece.
    l: is the vertical distance from the contact surface (3) of the part (1) (semi-flat) to the center of the hole.
    b: is the horizontal distance between the central point of contact between the surfaces of both pieces and the center of the hole.
    A: It is the radius of the hole.N and Q: are the normal and tangential contact loads applied respectively.
    Table 1: Experimental geometric parameters for conducting a contact fatigue test.
    AND ȣμ NQRrlb
    210GPa 0.30.68500 N / mm170 N / mm10 mm0.138 mm0.322 mm0.23 mm
    5 Figure 3 shows the equivalent voltage values of von Mises, dimensioned with the maximum normal pressure p0 on the contact surface (3) of a contact pair of the state of the art and a contact pair in the that one of the pieces (1) has been manufactured with the process of the present invention according to the geometric parameters previously described and represented in Table 1.
    The values represented in the plot with dashed lines correspond to the tension suffered in the contact pair comprising a part (1) manufactured with the process of the present invention. The values represented in the continuous line graph correspond to the voltage suffered in a contact pair of the state of
    15 the technique without interior gaps under the surface of any of the pieces.
    As can be seen in the graphs, a reduction of the tension greater than 50% is achieved in the area near the contact edge in which the gap has been included. Thus the resistance of the contact torque against the stresses is increased
    20 contact fatigue.
    权利要求:
    Claims (2)
    [1]
     R E I V IN D I C A C I O N E S
    1.- Method of manufacturing a piece with increased contact fatigue resistance characterized in that it comprises at least one stage of making at least one hole (2) inside the piece (1) in an area close to the surface of contact (3) of the piece (1).
    [2]
    2. Manufacturing process according to claim 1 characterized in that it comprises at least one stage of additive manufacturing of the piece.
     FIG.1a
    FIG.1b
     FIG. 2 
    FIG. 3
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    同族专利:
    公开号 | 公开日
    WO2018178418A1|2018-10-04|
    ES2684048B1|2019-07-17|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    WO2012024215A2|2010-08-16|2012-02-23|National Oilwell Varco, L.P.|Reinforced stators and fabrication methods|
    US9216524B1|2012-08-14|2015-12-22|Timothy H. Cook|Low density subsea buoyancy and insulation material and method of manufacturing|
    法律状态:
    2018-10-01| BA2A| Patent application published|Ref document number: 2684048 Country of ref document: ES Kind code of ref document: A1 Effective date: 20181001 |
    2019-07-17| FG2A| Definitive protection|Ref document number: 2684048 Country of ref document: ES Kind code of ref document: B1 Effective date: 20190717 |
    优先权:
    申请号 | 申请日 | 专利标题
    ES201730434A|ES2684048B1|2017-03-28|2017-03-28|MANUFACTURING PROCEDURE OF A PIECE WITH RESISTANCE INCREASED TO FATIGUE BY CONTACT|ES201730434A| ES2684048B1|2017-03-28|2017-03-28|MANUFACTURING PROCEDURE OF A PIECE WITH RESISTANCE INCREASED TO FATIGUE BY CONTACT|
    PCT/ES2018/000026| WO2018178418A1|2017-03-28|2018-03-23|Method for producing a part with increased contact fatigue resistance|
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