阅读说明：本技术 建立普旋凸缘起皱预测模型的方法 (Method for establishing general rotation flange wrinkling prediction model ) 是由 詹梅 高鹏飞 陈淑婉 马飞 张洪瑞 于 2019-09-30 设计创作，主要内容包括：本发明公开了建立普旋凸缘起皱预测模型的方法,基于塑性成形理论和普旋力学特征,建立凸缘最大周向压应力模型；基于极限理论,结合普旋中凸缘皱波特征,建立凸缘临界周向压应力模型；建立普旋过程中凸缘稳定的力学条件；建立临界起皱状态下普旋参数间关系；本发明综合考虑凸缘在普旋过程中的周向收缩和在旋轮力作用下的周向弯曲建立普旋中凸缘起皱预测模型,能够真实反映凸缘在实际生产中的成形特点。本发明通过理论计算法建立凸缘最大周向压应力模型与临界周向压应力模型,避免了进行过程繁杂、耗时耗材的板坯普旋试验及有限元模拟,使起皱预测结果免于受到有限元建模形式和计算精度的影响,准确、快速地预测普旋中的凸缘起皱缺陷。(The invention discloses a method for establishing a general rotation flange wrinkling prediction model, which is based on a plastic forming theory and general rotation mechanics characteristics, and establishes a flange maximum circumferential compressive stress model; based on a limit theory, establishing a flange critical circumferential compressive stress model by combining the characteristics of flange corrugation in the common spin; establishing a stable mechanical condition of the flange in the normal rotation process; establishing a relation between common rotation parameters in a critical wrinkling state; the invention comprehensively considers the circumferential shrinkage of the flange in the common rotation process and the circumferential bending under the action of the spinning wheel force to establish a flange wrinkle prediction model in the common rotation, and can truly reflect the forming characteristics of the flange in the actual production. According to the method, the maximum circumferential compressive stress model and the critical circumferential compressive stress model of the flange are established by a theoretical calculation method, the slab general rotation test and finite element simulation which are complicated in process and time-consuming and consumable are avoided, the wrinkling prediction result is free from the influence of a finite element modeling form and calculation precision, and the flange wrinkling defect in the general rotation is accurately and quickly predicted.)

1. The method for establishing the general rotation flange wrinkling prediction model is characterized by comprising the following steps of:

s1, establishing a maximum circumferential compressive stress model of a flange based on a plastic forming theory and a general rotation mechanics characteristic;

s2, establishing a flange critical circumferential compressive stress model based on a limit theory and combined with the characteristics of flange corrugation in the normal spin;

s3, establishing a stable mechanical condition of the flange in the normal rotation process;

and S4, establishing a relation between the ordinary rotation parameters in a critical wrinkling state.

2. A method of developing a prophy flange corrugation prediction model according to claim 1, wherein:

establishing a maximum circumferential compressive stress model of the flange based on a plastic forming theory and a common rotation mechanics characteristic:

wherein K is the material strain strengthening coefficient, n is the material hardening index, sigma_θmaxIs the maximum circumferential compressive stress of the flange, epsilon_θmaxIs the maximum circumferential compressive strain at the flange outer edge in the normal rotation process, and when the rotating wheel path is straight lines, epsilon_θmaxThe analytical solution of (a) is expressed as:

wherein R is₀Is the radius of the core mold, b₀The initial slab radius, f the feed ratio of the wheel, α the half cone angle of the linear wheel path, and n' the mandrel parameters.

3. A method of developing a prophy flange corrugation prediction model according to claim 2, wherein:

based on a limit theory, combining with the characteristics of the flange wrinkle wave in the ordinary spin, establishing a flange critical circumferential compressive stress model:

wherein σ_SMaterial yield stress, t slab thickness, α₀Is the instantaneous half-cone angle of the spinning wheel path.

4. A method of developing a prophy flange corrugation prediction model according to claim 3, wherein: establishing a mechanical condition for stabilizing the flange in the normal rotation process:

σ_θmax≤σ_θcr(4)。

5. a method of developing a prophy flange wrinkling prediction model according to claim 4, wherein: establishing a relation between common rotation parameters under a critical wrinkling state:

wherein epsilon_θcrCritical buckling condition, circumferential compressive strain at the outer edge of the flange, and when the spinning wheel path is straight line,. epsilon_θcrThe analytical solution of (a) is expressed as:

wherein, n'_crIs the mandrel parameter in the critical wrinkling state.

6. A method of developing a prophy flange wrinkling prediction model according to claim 5, wherein: the use method of the established propulsive model for the flange wrinkling in the pronation comprises the following steps:

1) respectively substituting given plate blank material parameters, geometric parameters and normal rotation process parameters into a flange maximum circumferential compressive stress model formula (1) and a critical circumferential compressive stress model formula (3), comparing the obtained flange maximum circumferential compressive stress with the critical circumferential compressive stress, and if the flange maximum circumferential compressive stress reaches or is greater than the critical value, considering that unstable wrinkling occurs to the flange in the normal rotation; if the maximum circumferential compressive stress of the flange is smaller than the critical value, the common-rotation middle plate blank is considered to be successfully formed;

2) and calculating the wrinkling moment of the plate blank or the limit parameter value capable of being successfully formed according to the relation (5) between the ordinary rotation parameters in the critical wrinkling state.

7. A method for establishing a predictive model of purl flange wrinkling according to claim 6 wherein, in use, the minimum half cone angle of the slabs with the minimum half cone angle is most formed and the maximum half cone angle of the slabs with the maximum half cone angle is least formed by comparing the maximum half cone angles of the slabs with different steel grades and different geometric dimensions of series.

Technical Field

The invention relates to the field of sheet forming processing, in particular to a method for establishing and using a flange wrinkling prediction model in a common spin, which is mainly used for judging unstable wrinkling of a flange in the common spin, evaluating the forming performance of the flange, acquiring a formable domain of a plate blank and providing theoretical guidance for the design of forming parameters and a spinning wheel path in the common spin.

Background

The spinning of the metal sheet is local plastic deformation processes, the local plastic deformation of the plate blank clamped by the tail top and the mandrel is generated by the force of a spinning wheel, the local plastic deformation gradually expands to the whole plate blank along with the high-speed rotation of the mandrel and the feeding motion of the spinning wheel, the spinning process of the metal sheet plays an important role in the manufacturing of aviation, aerospace and civil products due to the unique advantages of small forming force, high forming performance and the like.

At present, three methods for predicting the general spinning wrinkling are provided, namely a geometric visual method, a spinning pressure method and a theoretical analytical method, wherein the geometric visual method represents the fluctuation condition of the flange through the average value and the standard deviation of the axial fluctuation of the outer edge of the spinning flange, and the spinning pressure method judges the wrinkling moment according to the spinning pressure oscillation amplitude.

Disclosure of Invention

Aiming at the limitations of the conventional common-spin flange wrinkling prediction method, the invention provides an establishment and use method of common-spin flange wrinkling prediction models, which is used for rapidly and accurately judging the wrinkling defects of the common-spin flange and effectively evaluating the forming performance of a plate blank.

The invention is realized by adopting the following technical scheme: the method for establishing the pre-rotation flange wrinkling prediction model is realized by the following steps,

s1, establishing a maximum circumferential compressive stress model of a flange based on a plastic forming theory and a general rotation mechanics characteristic:

wherein K is the material strain strengthening coefficient, n is the material hardening index, sigma_θmaxIs the maximum circumferential compressive stress of the flange, epsilon_θmaxFor maximum circumferential compressive strain at the flange outer edge during pronation, when the spinning wheel path is straight lines, ε_θmaxThe analytical solution of (a) is expressed as:

wherein R is₀Is the radius of the core mold, b₀Is the initial radius of the slab, f is the feed ratio of the rotary wheel, α is the linear rotationThe wheel path half cone angle, n' is the mandrel parameter.

S2, based on a limit theory and in combination with the characteristics of the flange wrinkle wave in the normal spin, establishing a flange critical circumferential compressive stress model:

wherein σ_sMaterial yield stress, t slab thickness, α₀Is the instantaneous half-cone angle of the spinning wheel path.

S3, establishing a stable mechanical condition of the flange in the normal rotation process:

σ_θmax≤σ_θcr(4)

s4, establishing a relation between the ordinary rotation parameters under a critical wrinkling state:

wherein epsilon_θcrWhen the rotor path is straight line, ε_θcrThe analytic solution of (d) can be expressed as:

wherein, n'_crIs the mandrel parameter in the critical wrinkling state.

The use method of the established propulsive model for the flange wrinkling in the pronation comprises the following steps:

1) respectively substituting the given plate blank material parameters, the given geometric parameters and the given ordinary rotation process parameters into a flange maximum circumferential compressive stress model (formula (1)) and a critical circumferential compressive stress model (formula (3)), comparing the obtained flange maximum circumferential compressive stress with the critical circumferential compressive stress, and if the flange maximum circumferential compressive stress reaches or is greater than the critical value, considering that the flange in the ordinary rotation is unstable and wrinkled; if the maximum circumferential compressive stress of the flange is less than its critical value, the slab is considered to be successfully formed in the normal spin.

2) And (4) calculating the wrinkling moment of the plate blank or the limit parameter value of successful forming according to the relation (formula (5)) between the ordinary rotation parameters under the critical wrinkling state.

When the forming machine is used, the limit half cone angles of the slabs of series with different steel grades and different geometric dimensions, which can be successfully formed, are compared, the forming performance of the slab with the minimum limit half cone angle is the best, and the forming performance of the slab with the maximum limit half cone angle is the worst.

The method is suitable for general spinning forming with various types of spinning wheel paths.

Compared with the prior art, the invention has the following advantages:

1) the invention comprehensively considers the circumferential shrinkage of the flange in the common rotation process and the circumferential bending under the action of the spinning wheel force to establish a flange wrinkle prediction model in the common rotation, and can truly reflect the forming characteristics of the flange in the actual production.

2) According to the method, the maximum circumferential compressive stress model and the critical circumferential compressive stress model of the flange are established by a theoretical calculation method, the slab general rotation test and finite element simulation which are complicated in process and time-consuming and consumable are avoided, the wrinkling prediction result is free from the influence of a finite element modeling form and calculation precision, and the flange wrinkling defect in the general rotation is accurately and quickly predicted.

Drawings

FIG. 1 is a generalized spin forming diagram of a 1mm thick slab under a straight spinning wheel path, with consideration of wrinkling defects.

FIG. 2 is a sample of a 1060 aluminum alloy pronation test of a 1mm thick slab: (a) a half cone angle of 60 DEG and (b) a half cone angle of 70 deg.

Fig. 3 is a linear spinning wheel path limiting half cone angle for different material hardening indices.

Detailed Description

The model for predicting the wrinkle of the convex edge in the normal spin established by the invention can be used for successfully predicting the wrinkle defect of the convex edge in the normal spin, effectively evaluating the forming performance of the model and reasonably guiding the design of the normal spin process.

The method for establishing the pre-rotation flange wrinkling prediction model is realized by the following steps,

s1, establishing a maximum circumferential compressive stress model of a flange based on a plastic forming theory and a general rotation mechanics characteristic:

wherein K is the material strain strengthening coefficient, n is the material hardening index, sigma_θmaxIs the maximum circumferential compressive stress of the flange, epsilon_θmaxFor maximum circumferential compressive strain at the flange outer edge during pronation, when the spinning wheel path is straight lines, ε_θmaxThe analytical solution of (a) is expressed as:

wherein R is₀Is the radius of the core mold, b₀The initial slab radius, f the feed ratio of the wheel, α the half cone angle of the linear wheel path, and n' the mandrel parameters.

S2, based on a limit theory and in combination with the characteristics of the flange wrinkle wave in the normal spin, establishing a flange critical circumferential compressive stress model:

wherein σ_sMaterial yield stress, t slab thickness, α₀Is the instantaneous half-cone angle of the spinning wheel path.

S3, establishing a stable mechanical condition of the flange in the normal rotation process:

σ_θmax≤σ_θcr(4)

s4, establishing a relation between the ordinary rotation parameters under a critical wrinkling state:

wherein epsilon_θcrWhen the rotor path is straight line, ε_θcrThe analytic solution of (d) can be expressed as:

wherein, n'_crIs the mandrel parameter in the critical wrinkling state.

The use method of the established propulsive model for the flange wrinkling in the pronation comprises the following steps:

1) respectively substituting the given plate blank material parameters, the given geometric parameters and the given ordinary rotation process parameters into a flange maximum circumferential compressive stress model (formula (1)) and a critical circumferential compressive stress model (formula (3)), comparing the obtained flange maximum circumferential compressive stress with the critical circumferential compressive stress, and if the flange maximum circumferential compressive stress reaches or is greater than the critical value, considering that the flange in the ordinary rotation is unstable and wrinkled; if the maximum circumferential compressive stress of the flange is less than its critical value, the slab is considered to be successfully formed in the normal spin.

2) And (4) calculating the wrinkling moment of the plate blank or the limit parameter value of successful forming according to the relation (formula (5)) between the ordinary rotation parameters under the critical wrinkling state.

When the forming machine is used, the limit half cone angles of the slabs of series with different steel grades and different geometric dimensions, which can be successfully formed, are compared, the forming performance of the slab with the minimum limit half cone angle is the best, and the forming performance of the slab with the maximum limit half cone angle is the worst.

The method is suitable for general spinning forming with various types of spinning wheel paths.