Prediction method for unidirectional tensile stress of heterogeneous forge piece
Through the heterogeneous performance gradient coefficient, the yield strength and tensile strength of the heterogeneous forging are predicted by formula I and II, and the problems of inaccurate and inconsistent tensile performance testing of forgings in the prior art are solved, and the accurate prediction of the unidirectional tensile stress of the heterogeneous forgings is achieved.
Patent Information
- Application Number
- CN202510000573.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-02
- Publication Date
- 2025-07-25
AI Technical Summary
The prior art cannot accurately predict the unidirectional tensile stress of heterogeneous forgings, and traditional methods have problems such as incomplete performance testing, large fluctuations, and lack of unified prediction methods on large forgings.
Through the heterogeneous performance gradient coefficient, the yield strength and tensile strength of the heterogeneous forging are predicted using formulas I and II, and considering the tissue differences between the forging from the surface to the core, a method for prediction of the unidirectional tensile stress of the heterogeneous forging is provided.
Accurate prediction of tensile stress of heterogeneous forgings is achieved, reducing fluctuations in performance tests, suitable for forgings of different sizes, and providing a theoretical model with good consistency.
Smart Images
Figure CN120372120A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of material property testing, and particularly relates to a method for predicting unidirectional tensile stress of heterogeneous forgings. Background Art
[0002] With the development of fields such as energy, automobiles, and aerospace, the number of major equipment involved is increasing day by day. The key load-bearing components of these equipment are mainly manufactured by forging processes, such as hydraulic turbine blades, front axles of heavy-duty trucks, and aircraft landing gears. These components directly affect the normal operation of the equipment.
[0003] According to the basic assumptions of material mechanics, that is, the material is continuous, homogeneous, and isotropic, these components are all treated as homogeneous structures in design. However, the assumption that the structure is homogeneous does not conform to the actual situation: after forging and heat treatment of forgings, the material shows a non-uniform structure from the surface to the inside; after annealing of forgings, there is a completely or partially decarburized layer on the surface of the forgings due to decarburization and burning loss, which is inconsistent with the structure of the core; after quenching of forgings, due to the problem of material hardenability, the surface structure is harder and has higher strength, and the core structure is inconsistent with the surface structure because it is not completely quenched.
[0004] At present, the measurement method of the tensile properties of large forgings is to take samples at key positions on the forgings, and it is required that the tensile samples are at a certain distance from the surface, and the tensile properties of local samples are detected to characterize the tensile properties of the entire component. For example, the front axle of an automobile is a core component of the automobile and also a typical representative of forgings. When testing the tensile properties of the front axle of an automobile, generally 4 key points are selected, the sampling depth is 12 mm from the surface, tensile samples are prepared, and the tensile strength is detected. However, this prediction method can only detect local properties, does not consider the influence of different tissue parts on the surface and the core on the tensile properties, and cannot accurately characterize the tensile properties of forgings.
[0005] Therefore, the traditional method has the following problems. 1. Using the test data of several key points to represent the overall performance, the data collection is incomplete and the performance test is inaccurate; 2. The size of the sample is restricted by the overall size of the component. When the overall size of the component is too large or too small, the tensile samples are all non-standard samples, and the performance test fluctuates greatly; 3. When processing parts of different sizes with the same process, it is necessary to measure the tensile properties separately, and there is no unified and simple prediction method. Summary of the Invention
[0006] The purpose of the present invention is to provide a method for predicting unidirectional tensile stress of heterogeneous forgings, and the prediction method provided by the present invention can accurately predict the tensile stress of forgings.
[0007] In order to achieve the above purpose, the present invention provides the following technical solutions:
[0008] The present invention provides a method for predicting the unidirectional tensile stress of a heterogeneous forging, comprising the following steps:
[0009] Substitute the radius of the heterogeneous forging into Equation I to obtain the yield strength of the heterogeneous forging; substitute the radius of the heterogeneous forging into Equation II to obtain the tensile strength of the heterogeneous forging.
[0010]
[0011] In the formula, is the yield strength, with the unit of MPa; σ s0 is the yield strength of the homogeneous region of the core properties of the heterogeneous forging, with the unit of MPa; r is the radius of the heterogeneous forging, with the unit of mm; r0 is the radius of the homogeneous region of the core properties of the heterogeneous forging, with the unit of mm; k1 is the slope of the change in the yield strength of the heterogeneous forging, with the unit of MPa / mm; σ b is the tensile strength, with the unit of MPa; σ b0 is the tensile strength of the homogeneous region of the core properties of the heterogeneous forging, with the unit of MPa; k2 is the slope of the change in the tensile strength of the heterogeneous forging, with the unit of MPa / mm.
[0012] Preferably, the shape of the heterogeneous forging is a bar.
[0013] Preferably, the heterogeneous forging is an automotive front axle.
[0014] Preferably, the radius of the heterogeneous forging is 3 mm to 100 mm.
[0015] The present invention provides a method for predicting the unidirectional tensile stress of a heterogeneous forging. Through the heterogeneous performance gradient coefficient (change slope), the present invention accurately predicts the tensile stress of the forging, which is used for the design, simulation, and structural optimization of the forging, and solves the problems of inconvenient measurement and inaccurate prediction of the tensile properties of large forgings. Moreover, the prediction method provided by the present invention has small fluctuations in the performance test of the unidirectional tensile stress of the heterogeneous forging, is not affected by the part size, can quantitatively and qualitatively characterize the mechanical properties of the unidirectional tensile stress with a unified and accurate theoretical model, has simple steps, a short performance test period, and good consistency. Brief Description of the Drawings
[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.
[0017] Figure 1Process flow chart of the prediction method for unidirectional tensile stress of heterogeneous forgings provided by the present invention;
[0018] Figure 2 Schematic diagram of the fitting relationship between the performance (yield strength or tensile strength) P of the specimen and the radius of the specimen. Detailed implementation mode
[0019] The present invention provides a prediction method for unidirectional tensile stress of heterogeneous forgings, including the following steps:
[0020] Substitute the radius of the heterogeneous forging into Equation I to obtain the yield strength of the heterogeneous forging; substitute the radius of the heterogeneous forging into Equation II to obtain the tensile strength of the heterogeneous forging;
[0021]
[0022] In the formula, is the yield strength, with the unit of MPa; σ s0 is the yield strength of the homogeneous region of the core performance of the heterogeneous forging, with the unit of MPa; r is the radius of the heterogeneous forging, with the unit of mm; r0 is the radius of the homogeneous region of the core performance of the heterogeneous forging, with the unit of mm; k1 is the change slope of the yield strength of the heterogeneous forging, with the unit of MPa / mm; σ b is the tensile strength, with the unit of MPa; σ b0 is the tensile strength of the homogeneous region of the core performance of the heterogeneous forging, with the unit of MPa; k2 is the change slope of the tensile strength of the heterogeneous forging, with the unit of MPa / mm.
[0023] In the present invention, the shape of the heterogeneous forging is preferably a bar; the heterogeneous forging is preferably a front axle of an automobile; the heterogeneous forging is divided into a homogeneous region of core performance and a non - homogeneous region according to homogeneity.
[0024] In the present invention, the radius of the heterogeneous forging is preferably 3 mm to 100 mm, and specifically can be 5 mm, 10 mm, 20 mm, 40 mm, 60 mm, 80 mm or 100 mm.
[0025] In the present invention, the mechanism of Equation I and Equation II is exemplified as follows: The non - homogeneous region of the heterogeneous forging is stratified from the surface to the core, and the yield strength or tensile strength of each layer is detected; then the yield strength and tensile strength of each layer are fitted to obtain the change slope k1 of the yield strength σ s and the change slope k2 of the tensile strength σ b ; then the change slopes k1 and k2 are substituted into the yield strength formula and the tensile strength formula, and the total force on the cross - section is obtained by integration, and divided by the cross - sectional area to obtain Formula I and Formula II of the present invention.
[0026] The present invention stratifies the non-uniform region of the heterogeneous forging from the surface to the core, and detects the yield strength or tensile strength of each layer. The present invention has no special requirements for the preparation method of the heterogeneous forging. In a specific embodiment of the present invention, the preparation method of the heterogeneous forging is preferably: heating 42CrMo and then performing quenching, tempering and shot peening in sequence; the heating is preferably intermediate frequency induction heating; the heating temperature is preferably 1150 °C; the quenching temperature is preferably 850 °C; the tempering temperature is preferably 615 °C.
[0027] In the present invention, the number of layers of the stratification is preferably 3 to 4 layers; the thickness of a single layer of the stratification is preferably less than 1.5 mm, and specifically can be 1 mm.
[0028] In the present invention, the detection of the yield strength of each layer is preferably: preparing and processing a plate-shaped tensile specimen, and detecting the yield strength of each layer of specimen (denoted as σ s1 , σ s2 , σ s3 or σ s1 , σ s2 , σ s3 , σ s4 ).
[0029] In the present invention, the detection of the tensile strength of each layer is preferably: preparing and processing a plate-shaped tensile specimen, and detecting the tensile strength of each layer of specimen (denoted as σ b1 , σ b2 , σ b3 or σ b1 , σ b2 , σ b3 , σ b4 ).
[0030] After detecting the yield strength or tensile strength of each layer, the present invention respectively fits the yield strength and tensile strength of each layer with the radius as the abscissa, and obtains the change slope k1 of the yield strength σ s and the change slope k2 of the tensile strength σ b . The fitting results of the yield strength and tensile strength in the present invention are as Figure 2 shown. According to the fitting relationship curve, the change slope k1 of the yield strength σ s and the change slope k2 of the tensile strength σ b are obtained.
[0031] After obtaining the change slope k1 of the yield strength σ s and the change slope k2 of the tensile strength σ b , by integration, calculate the sum of the forces on the cross-section, and divide by the cross-sectional area to obtain Formula I and Formula II of the present invention.
[0032] In the present invention, the yield strength formula is as shown in Formula III:
[0033]
[0034] Wherein, σ s is the yield strength, with the unit of MPa; σ s0 is the yield strength of the homogeneous region of the core properties of the heterogeneous forging, with the unit of MPa; r is the radius of the heterogeneous forging, with the unit of mm; r0 is the radius of the homogeneous region of the core properties of the heterogeneous forging, with the unit of mm; k is the performance gradient coefficient of the heterogeneous forging, with the unit of MPa / mm; x is the distance from the center of the circle, with the unit of mm.
[0035] In the present invention, the tensile strength formula is as follows:
[0036]
[0037] Wherein, σ b is the tensile strength, with the unit of MPa; σ b0 is the tensile strength of the homogeneous region of the core properties of the heterogeneous forging, with the unit of MPa.
[0038] Formula I and Formula II in the present invention are as follows:
[0039]
[0040] Wherein, σ s is the yield strength, with the unit of MPa; σ s0 is the yield strength of the homogeneous region of the core properties of the heterogeneous forging, with the unit of MPa; r is the radius of the heterogeneous forging, with the unit of mm; r0 is the radius of the homogeneous region of the core properties of the heterogeneous forging, with the unit of mm; k1 is the change slope of the yield strength of the heterogeneous forging, with the unit of MPa / mm; σ b is the tensile strength, with the unit of MPa; σ b0 is the tensile strength of the homogeneous region of the core properties of the heterogeneous forging, with the unit of MPa; k2 is the change slope of the tensile strength of the heterogeneous forging, with the unit of MPa / mm; x is the distance from the center of the circle, with the unit of mm.
[0041] In order to further illustrate the present invention, the solutions of the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but they should not be construed as limiting the protection scope of the present invention.
[0042] Example 1
[0043] A heterogeneous bar with a radius of 5 mm is divided into 3 layers at 3 mm, 4 mm, and 5 mm from the inside to the outside of the heterogeneous bar to make specimens, and then the yield strength, tensile strength of each layer of specimens, as well as the yield strength and tensile strength of the whole heterogeneous bar are detected. The results are shown in Table 1.
[0044] Table 1 Yield Strength Test Results of Example 1
[0045] Project 3mm 4mm 5mm Overall Yield strength / MPa 759.00 673.23 648.15 682.31 Tensile strength / MPa 938.88 909.41 833.36 910.23
[0046] Based on the test results in Table 1, the yield strength gradient change of the heterogeneous bar in this example can be obtained, specifically as shown in Equation V:
[0047] σ s = 759 - 55.67(r - 3) Equation V;
[0048] In Equation V, k1 = -55.67.
[0049] Substitute r = 5 and r0 = 3 into Equation I, and we get It only differs by 5.57% from the overall yield strength result in Table 1, with good agreement.
[0050] Based on the test results in Table 1, the tensile strength gradient change of the heterogeneous bar in this example can be obtained, specifically as shown in Equation VI:
[0051] σ s = 938.88 - 52.76(r - 3) Equation VI;
[0052] In Equation VI, k2 = -52.76.
[0053] Substitute r = 5 and r0 = 3 into Equation I, and we get σ = 902.30 MPa, which only differs by 0.87% from the overall tensile strength result in Table 1, with good agreement.
[0054] From the above examples, it can be seen that the prediction method provided by the present invention can accurately predict the tensile properties of heterogeneous forgings, with good prediction agreement.
[0055] Although the above examples have described the present invention in detail, they are only a part of the embodiments of the present invention, not all embodiments. Other embodiments can be obtained based on this example without creative efforts, and these embodiments all fall within the protection scope of the present invention.
Claims
1. A method for predicting the unidirectional tensile stress of a heterogeneous forging, characterized in that Including the following steps: Substitute the radius of the heterogeneous forging into Equation I to obtain the yield strength of the heterogeneous forging; substitute the radius of the heterogeneous forging into Equation II to obtain the tensile strength of the heterogeneous forging. In the formula, is the yield strength, with the unit of MPa; σ s0 is the yield strength of the homogeneous region of the core properties of the inhomogeneous forging, with the unit of MPa; r is the radius of the heterogeneous forging, in mm; r0 is the radius of the region with uniform properties at the core of the heterogeneous forging, in mm; k1 is the slope of the yield strength change of the heterogeneous forging, in MPa / mm; σ b is the tensile strength, in MPa; σ b0 is the tensile strength of the region with uniform properties at the core of the heterogeneous forging, in MPa; k2 is the slope of the tensile strength change of the heterogeneous forging, in MPa / mm.
2. The prediction method according to claim 1, wherein The shape of the heterogeneous forging is a bar.
3. The prediction method according to claim 1 or 2, characterized in that, The heterogeneous forging is an automotive front axle.
4. The prediction method according to claim 1 or 2, characterized in that, The radius of the heterogeneous forging is 3 mm to 100 mm.