• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    A method for determining the fatigue strength of engine components including the steps of: - providing an engine component; - load at least a part of the motor component to a level below the ultimate limit of the motor component and measure the resulting deformation of the motor component; - determining at least one quantity on the basis of the applied load and the measured deformation; - providing a predetermined relationship between the measured fatigue strength of motor components and the at least one of the above-mentioned quantities determined from the ratio between applied load on motor components and deformation of motor components; - determining the fatigue strength of the supply motor component based on the at least one determined quantity and the predetermined relationship.
    公开号:SE1150078A1
    申请号:SE1150078
    申请日:2011-02-04
    公开日:2012-08-05
    发明作者:Fredrik Wilberfors
    申请人:Scania Cv Ab；
    IPC主号:
    专利说明:

    - loading at least a part of the motor component to a level below the ultimate limit of the motor component and measuring the resulting deformation of the motor component; - determining at least one quantity on the basis of the applied load and the measured deformation; - providing a predetermined relationship between measured fatigue strength of engine components and the at least one of the above-mentioned quantities determined from the ratio between applied load of engine components and deformation of engine components; determining the fatigue strength of the provided engine component based on the at least one determined quantity and the predetermined relationship.
    The method generally achieves a very high correspondence between the estimated and actual fatigue strength of engine components.
    Since the magnitude used to determine the engine component is determined at the ultimate limit of the engine components or below the fatigue limit, the fatigue strength is low load, typically with no risk of the engine component being destroyed. This enables a fast quality control with a high test frequency of engine components that are to be used in actual operation. The estimation of the fatigue strength of the engine components can be performed with high accuracy because it is based on quantities measured on the actual engine component instead of on reference details such as test rods manufactured together with the engine component.
    Preferably, the engine component consists of a cylinder head or an engine block for a heavy vehicle, preferably a truck.
    According to an alternative, the entire engine component is loaded. 10 15 20 25 30 According to an alternative, the motor component is loaded to a level below the fatigue limit of the motor component.
    According to one embodiment, the motor component is loaded by applying a force to the motor component by a force transmitting member engaging the motor component.
    Suitably the force is applied to the motor component by displacing the force transmitting means relative to the motor component, the deformation of the motor component being measured as the distance by which the force transmitting means has been displaced.
    According to an alternative, a test rod designed for tensile testing is cast together with the engine component or taken out of the engine component, thereby determining and the fatigue strength of the provided engine component. The breaking limit of the test rod is used to determine DEFINITIONS For the purposes of this application, "fatigue strength" means the amount of cyclic loads to which a component may be subjected before a predetermined value, including the amount of cracks formed in the component or the length of the cracks, is exceeded.
    "Fatigue limit" in this application refers to the maximum voltage that a component or parts of a component can be subjected to an infinite number of repeated times without cracks occurring in the component.
    The term “strength parameters” in this application refers to parameters that can be derived from a so-called tensile test curve that shows the relationship between stress and elongation in a test rod. Strength parameters are, for example, maximum voltage [Rm]; stress at total elongation 0.1% [Rt (0.1)]; stress at total elongation 0.2% [Rt (0,2)]; stress at total elongation 0.4% [Rt (0, 4)] § stress at 10 15 20 25 30 plastic elongation 0.1% [Rp (0.1)]; Stress at plastic elongation 0.2% [Rp (0.2)]; The slope of the stress-strain curve at 0 MPa [E0]; The slope of the stress-strain curve at 20 MPa [E20]; The slope of the stress-strain curve at 50 MPa [E50]; The slope of the stress-strain curve at 100 MPa [E100]; The slope of the stress-strain curve at 150 MPa [E150]; Total elongation at maximum voltage [Eight].
    DESCRIPTION OF FIGURES Figures 1a and 'lb: Schematic process of tensile test from steel and a gray iron.
    Figure 2: Diagram showing the relationship between fatigue strength of the cylinder head and the breaking point of the test rod.
    Figure 3: Diagram showing the relationship between fatigue strength of cylinder head and Eioo on test rod.
    Figure 4: Diagram showing the relationship between fatigue strength of cylinder head and breaking limit and Emo on test rod.
    Figure 5: Schematic view of a device for measuring deformation according to an embodiment of the method according to the invention.
    DESCRIPTION OF THE INVENTION Initially, the theoretical background of the invention will be briefly described with reference to Figures 1a and 1b.
    The strength of metallic materials can be described, for example, by stress-strain diagrams obtained by tensile testing of test rods. Figure 1a, schematically shows the process that the stress-strain diagram shows for many metallic construction materials, eg steel. Figure 1b shows the course of the stress-strain diagram for gray iron.
    In general, Figure 1a shows a first area I where low forces act on the test rod. In this region, the distance between the atoms in the material increases without changing their relative order. If the force is removed, the test rod regains its original dimensions. The test rod is thus elastically deformed. This area is usually called the linear-elastic area. Applying a higher force to the test rod increases the tension in the material. When the stress passes the so-called yield strength II, the atomic plane begins to slide over each other and a demanding deformation is created in the material. The material continues to be plastically deformed in the area designated III in Figure 1a if the force is further increased. At a certain tension, the so-called breaking limit IV, a waist begins to form in the test rod. If more force is applied to the test rod, it will eventually come off at Vifigur la.
    Figure 1b schematically describes a stress-strain diagram for a cast iron of the gray iron type, the same designations as in Figure 1a are used. The course of the stress-strain diagram for gray iron differs from the general stress-strain diagram described in Figure 1a in that gray iron does not have a linear-elastic region at the beginning of the stress-strain curve.
    Furthermore, the elongation of the gray iron before fracture, about 1%, is significantly shorter than the elongation of eg steel, typically 20%. Figure 1b shows that the gray iron begins to deform plastically immediately when a load is placed on the material. The reason for this deformation behavior is assumed to be that the graphite scales in the gray iron function as stress concentrations. The perlite matrix of gray iron is plasticized locally around the tips of the graphite scales and with increasing load cracks form between the graphite scales. Gray iron thus, unlike, for example, steel, does not have an area with linear elastic behavior. If the gray iron test rod is further loaded, the breaking limit IV of the material is passed where the test rod comes off.
    Since gray iron is plastically deformed even at low loads, several strength parameters can be calculated from the lower part of the gray iron tensile curve.
    This is because both the initial slope of the curve and the amount of plastic deformation are strongly linked to the graphite structure and the nature of the matrix of the gray iron.
    As mentioned in the introduction, tensile samples are often used on test rods cast together with gray iron components to ensure the quality of cast components. In the known methods, the ultimate strength of the test bar is determined by a tensile test based on the fatigue strength of the component based on predetermined relationships. the breaking limit is then estimated from the cast between measured breaking limit of test rods and measured fatigue strength of cast components.
    However, it has been found that the expected fatigue strength of actual always satisfactory with the predicted fatigue strength that the cast iron component does not conform corresponds to the breaking limit of the test rod.
    A study has shown that test rods of gray iron that are manufactured in the same way and of the same gray iron type do indeed have essentially the same breaking limit, but that the stress-strain curve for the different materials can have different processes. The reason for this is believed to be, for example, variations in the composition of the grass iron or variations in the manufacturing process of the test rods, eg the nucleation potential of the base iron, inoculum type or inoculation method.
    A further study has shown that in addition to the yield strength, more strength parameters, which can be deduced from the stress-strain curve, are important in predicting fatigue strength of cast gray iron components. The course of the stress-strain curve strongly influences the magnitude of these parameters and variations in the course of the curve therefore have a great influence on how accurately the fatigue strength can be predicted in the components based on the strength parameters.
    An experiment carried out in connection with the above-mentioned study has shown that a very good agreement is achieved between the estimated and actual fatigue strength of the finished gray iron component if the estimate of the fatigue strength is based on strength parameters determined in the initial area of the tensile test curve. That is, in an area where the load of the gray iron test bar is below this, the strength parameters are determined: the breaking limit of the test bar. In range, for example, the following Rt (0.1), ie the stress at total elongation can be 0.1%.
    E (0) i.e. the slope of the stress-strain curve at stress 0 MPa.
    E (50) i.e. the slope of the stress-strain curve at a stress of 50 MPa.
    E (100) i.e. the slope of the stress-strain curve at a stress of 100 MPa.
    In the experiment, in a first step, seven series each with 10 available Cylinder Heads were produced using methods intended for series production. Cylinder heads of a commercial grass iron alloy.
    A sample rod with a waist diameter of 8 mm was then taken from each cylinder head. The test bar was subjected to a tensile test in a 100Kn servo-hydraulic tractor of the MTS brand. The tensile test was performed at room temperature with controlled displacement and at a speed of 0.05 mm / s. An MTS 634.11 F-24 extensometer was used to collect the data. The measurement length was 25 mm and the data collection frequency 10 Hz.
    The cylinder heads were mounted in a test rig and then subjected to cyclic fatigue testing until cracks could be detected in the cylinder heads.
    From the collected data for each test rod, the breaking limit Rm and E1oo- The determined breaking limit was then compared with the measured fatigue strength for each series of cylinder heads. Figure 2 shows in a diagram the correspondence between the yield strength and the fatigue strength. A linear relationship was established between the measured breaking limit Rm of the test rods and the fatigue strength of the cylinder heads. From the relationship, the RZ value was calculated. The RZ value that 10 15 20 25 30 indicates how well the relationship corresponds to reality can vary between 0 and 1, where 1 means that the relationship is perfectly adapted to reality. The RZ value for the relationship in Figure 3 is 0.83.
    In Figure 3, the Emo and fatigue strength have been plotted for each series of cylinder head / test rod. Here, too, a linear relationship was calculated between the Emo values and the fatigue strength_ The Rz value of the relationship is 0.92, which shows that there is a very good agreement between Emo and fatigue strength calculated with the relationship. Figure 3 thus shows that better correspondence is achieved between actual and predicted fatigue strength when the predicted values are based on strength parameters that are below the yield strength than when they are based only on the yield strength.
    In Figure 4, the measured fatigue strength and the predicted fatigue strength have been plotted against each other in a predicted fatigue strength was determined from both E100 and the yield strength according to the relationship below: diagram. The predicted fatigue strength = 0.2129 + 3,473-10'3-E (100) + 1,759-10 '3_R The line drawn in Figure 4 shows how good the correspondence is between measured and predicted fatigue strength.
    As can be seen from the R2 value, 0.95, the concordance increases even more if several strength parameters are added to the connection.
    Analogously to the above studies, the invention is based on the fact that suitable quantities can be obtained from a curve which describes the relationship between a low load directly on an engine component and measured deformation of the material in the engine component. The quantities can then be used to predict with high accuracy the fatigue strength of engine components.
    According to the method according to the invention, a connection is first established, i.e. predetermined, between fatigue strength of motor components and quantities which are determined from the ratio between applied load and the resulting deformation of the motor component material at low load.
    First, a number of engine components are manufactured, such as three series of ten engine components each. Both This is done as follows: series with the number of series and the number of engine components in each series can be varied. Each series is manufactured in a separate casting process to provide sufficiently high variation. Thereafter, each motor component, or part of each motor component, is subjected to a low load. The load, eg a force applied to the motor component, must be so low that the stresses resulting in the motor component do not exceed the breaking point or fatigue limit that the component in question is assumed to be able to withstand. The person skilled in the art can relatively easily assume which loads a current component can withstand, for example based on experience.
    To ensure that the component does not break during the load, it is appropriate to, for example, load the component to a maximum of 50% of the breaking limit.
    In the event that only a part of the engine component is loaded and that part is not subjected to loads during operation, even higher loads can be selected during the test.
    Loading of the engine component and measurement of the resulting deformation of the engine component can take place in the manner specified below, see Figure 5. 10 15 20 25 30 ”IO Figure 5 shows an engine component 1, in this case an engine block having cavities for cylinders 2. Two power transmissions means 3, for example two rods, are lowered into each cylinder hole 2. Respective force transmitting means 3 are connected to a hydraulic device 4 which is arranged to move the force transmitting means laterally in force F hydraulic device 4 on each force transmitting means, direction from each other. One is then laid off, the power transmitting means being displaced laterally along the center line of the engine block.
    Due to the displacement of the force-transmitting means, the motor component is deformed, i.e. the material of the motor component is deformed.
    The forces F are gradually increased to a predetermined value, for example until the voltage in the motor block amounts to 15% of the assumed breaking limit of the motor block. After each increase of the force F, the resulting displacement of the force transmitting means is measured. This displacement can, for example, be measured as the distance d that each force-transmitting member has moved in the direction away from its starting point at the beginning of the load (marked Figure 5). the motor component is deformed by the applied force. The applied force dashed in the Displacement d gives a measure of how much and the resulting displacement is then plotted in a diagram and from the slope of the diagram different quantities can be calculated. A suitable quantity is, for example, the slope of the force / displacement curve at an applied force as 50% of it generates stresses in the component which amount to fatigue strength assumed for the engine block.
    The actual fatigue strength of each engine component is then determined by cyclic fatigue testing until a predetermined value due to cracks has passed or the engine component breaks. This can be done with standardized methods.
    A relationship is established between fatigue strength and the magnitude determined from the ratio between the force of the motor components / deformation of the component at low load. 10 15 20 25 30 11 The relationship can be, for example, a table, an equation or a diagram between the measured fatigue strength of engine components and the quantity determined from engine components. The relationship can, for example, be obtained from a linear regression the ratio between measured force / deformation of which is adapted to the measured values. The connection is stored, for example, in a non-volatile electronic memory in a computer from which it can be retrieved if necessary.
    The accuracy of the relationship between measured fatigue strength of engine components and the magnitude determined from the ratio of measured force / deformation of the engine components can be improved by performing additional fatigue tests. It is also possible to improve adding observations and experiences from the actual outcome in the field. the accuracy of the joint further by using the joint The bond developed above is then used in the method according to the invention to estimate the fatigue strength of additional engine components which are manufactured, for example, in current industrial production. This is done as follows: In a first step, a motor component is manufactured by casting a gray iron material.
    In a second step, at least one quantity is determined from the ratio between force / deformation at low load of the motor component or a part of the motor component. This quantity is thus of the same kind as that on which the predetermined relation is based. The determination of this quantity takes place as described above by the motor component being loaded during its During the motor component, the deformation of the motor component and from the assumed breaking limit or fatigue limit is measured. the load of the ratio between applied force and deformation is determined by a quantity. In a third step, a predetermined relationship provided according to the OVan is provided.
    In a fourth step, the fatigue strength of the manufactured engine component is estimated based on the magnitude determined from the relationship between force / deformation of and the applied engine component predetermined relationship. This can be done in several different ways.
    If the predetermined relationship is a linear curve that is adapted to the observed fatigue strength of engine components and measured from the ratio between force / deformation of the manufactured fatigue strength is read from the linear curve. quantities determined engine components then the engine component The connection can also be taken from a table or non-volatile memory.
    In the described embodiments, the engine component may consist of, for example, an engine block or a cylinder head for a heavy vehicle, for example a truck. However, it should be understood that the predetermined relationship should be based on the same type of fatigue strength to be estimated. engine component as the engine component in which a specific embodiment of the invention has been described in detail. This has been done for illustrative purposes and not for the purpose of limiting the invention. It is obvious that various changes and modifications may be made to the invention within the scope of the appended claims.
    For example, a test rod can be cast together with the engine component, and then broken loose. The test rod can also be taken directly from the manufactured engine component, for example by milling. Tensile tests can then be performed on the test rod and the results therefrom, for example the breaking point, can be used in the method according to the invention to predict the fatigue strength of the engine component 13. However, this presupposes that the predetermined relationship includes saturations from test rods.
    权利要求:
    Claims (7)
    [1]
    Method for determining the fatigue strength of motor components of gray iron, characterized by comprising the steps of: - providing a motor component; - load at least a part of the motor component to a level below the ultimate limit of the motor component and measure the resulting deformation of the motor component; - determining at least one quantity on the basis of the applied load and the measured deformation; - providing a predetermined relationship between the measured fatigue strength of motor components and the above-mentioned at least one quantity determined from the ratio between the applied load on motor components and the deformation of motor components; determining the fatigue strength of the provided engine component based on the at least one determined quantity and the predetermined relationship.
    [2]
    The method according to claim 1, wherein the engine component consists of a cylinder head or an engine block for a heavy vehicle, preferably a truck.
    [3]
    The method of any of claims 1 or 2, wherein the entire engine component is loaded.
    [4]
    The method according to any one of claims 1 to 3, wherein the motor component is loaded to a level below the fatigue limit of the motor component.
    [5]
    The method according to any one of claims 1 to 4, wherein the motor component is loaded by applying a force to the motor component by a force transmitting means engaging the motor component. 10 15 15
    [6]
    The method according to claim 5, wherein the force is applied by displacing the force transmitting means relative to the motor component, the deformation of the motor component being measured as the distance by which the force transmitting means has been displaced.
    [7]
    The method according to any one of claims 1 to 6, wherein a test rod designed for tensile testing is cast together with the engine component or removed from the engine component, the breaking limit of the test rod being determined and used to determine the provided fatigue strength of that engine component.
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    同族专利:
    公开号 | 公开日
    WO2012105895A1|2012-08-09|
    EP2671062A1|2013-12-11|
    US20130291647A1|2013-11-07|
    CN103339487A|2013-10-02|
    CN103339487B|2014-11-05|
    BR112013017526A2|2016-10-25|
    SE535595C2|2012-10-09|
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    法律状态:
    2016-10-04| NUG| Patent has lapsed|
    优先权:
    申请号 | 申请日 | 专利标题
    SE1150078A|SE535595C2|2011-02-04|2011-02-04|Method for determining fatigue strength of engine components|SE1150078A| SE535595C2|2011-02-04|2011-02-04|Method for determining fatigue strength of engine components|
    PCT/SE2012/050090| WO2012105895A1|2011-02-04|2012-01-31|Method for determining fatigue strength of engine components|
    EP12742549.4A| EP2671062A1|2011-02-04|2012-01-31|Method for determining fatigue strength of engine components|
    CN201280007310.5A| CN103339487B|2011-02-04|2012-01-31|Method for determining fatigue strength of engine components|
    US13/979,776| US20130291647A1|2011-02-04|2012-01-31|Method for determining fatigue strength of engine components|
    BR112013017526A| BR112013017526A2|2011-02-04|2012-01-31|method for determining fatigue strength of engine components|
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