Blank optimization method for machining deformation control of long beam type parts

Abstract

The application discloses a blank optimization method for machining deformation control of long-beam-like parts, which comprises the following steps: S1, selecting samples on different blanks, and detecting initial residual stress of the samples along the thickness direction; S2, calculating the strain energy density of the blank, and providing a blank machining safety evaluation standard based on the strain energy density; S3, establishing a solving function of the minimum deformation of the part, analyzing the minimum deformation of the part after machining of all the remaining blanks, and removing the blanks with the minimum deformation greater than the machining tolerance of the part; S4, selecting the blank with the minimum thickness from the remaining blanks meeting the condition that the minimum deformation is greater than the machining tolerance of the part; and S5, selecting the blank corresponding to the batch with the minimum deformation fluctuation of the part at different positions from the batches of different blanks as the optimized blank, and providing the position of the part corresponding to the minimum deformation of the part in the blank. The application has the advantage of improving the manufacturing yield of the part.

Description

Technical Field

[0001] This invention belongs to the field of residual stress processing deformation control technology, specifically relating to a method for selecting the best blank for processing deformation control of long beam parts. Background Technology

[0002] Integral structural components are widely used in the aerospace industry, but the frequent occurrence of machining deformation is a prominent problem that has long plagued the aerospace manufacturing industry, leading to direct economic losses and a large waste of resources.

[0003] Initial residual stress in the blank is one of the most significant factors leading to deformation. Many scholars have conducted extensive research on the relationship between initial residual stress and machining deformation, focusing on analyzing and controlling the deformation caused by initial residual stress. Control methods for machining deformation have been established based on initial residual stress. However, due to the current international situation, a large amount of imported materials have been replaced by domestically produced materials. From a machining performance perspective, compared to imported materials, domestically produced materials exhibit unstable initial residual stress distributions in the blank state for different grades and batches, specifically manifested as different initial residual stress distributions at different thicknesses. Therefore, current machining deformation control methods cannot completely solve the machining deformation problem of domestically produced materials. To address the machining deformation caused by the unstable initial residual stress distribution in domestically produced blanks, a blank optimization method for controlling machining deformation of long beam-type parts is proposed. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art.

[0005] Therefore, this invention proposes a method for selecting the best blank for controlling the deformation during machining of long beam-type parts. This method has the advantage of improving the yield rate of parts manufacturing.

[0006] A preferred method for controlling deformation during machining of long beam-type parts according to an embodiment of the present invention includes the following steps:

[0007] S1. Select samples from different blanks and test the initial residual stress along the thickness direction of the samples;

[0008] S2. Based on the initial residual stress of the test sample, calculate the strain energy density of the blank, propose a blank processing safety evaluation standard based on strain energy density, and classify the blank into no deformation risk, low deformation risk and high deformation risk.

[0009] S3. Establish a theoretical analysis model for machining deformation based on the initial residual stress of the blank, and establish a solution function for the minimum deformation of the part. Analyze the minimum deformation of the part after machining all remaining blanks, and remove blanks with a minimum deformation greater than the machining tolerance of the part.

[0010] S4. Further, select the blank with the smallest thickness from the remaining blanks that satisfy the minimum deformation amount being greater than the part machining tolerance;

[0011] S5. Among the remaining blanks that satisfy the minimum deformation amount greater than the part machining tolerance, there are different production batches. Further optimization is carried out. Among these different batches of blanks, the blanks of the batch with the smallest fluctuation in the deformation amount of the part at different positions are selected as the preferred blanks. The position of the part in the blank corresponding to the minimum deformation amount of the part is provided as a reference for the machining process planning.

[0012] According to one embodiment of the present invention, in S2, the safety evaluation criterion sets the strain energy density to be less than 1 KJ / m. 3 At this time, there is no risk of deformation; the strain energy density is greater than 2 kJ / m. 3 At this time, there is a high risk of deformation; the strain energy density is between 1 KJ / m². 3 and 2KJ / m 3 At this stage, blanks with low deformation risk are excluded first; blanks with high deformation risk are excluded in this step.

[0013] According to one embodiment of the present invention, in S4, the blank that satisfies the minimum deformation amount being greater than the part machining tolerance should have a front and back allowance of ≥2mm.

[0014] According to one embodiment of the present invention, in S1, the method for detecting the initial residual stress is as follows: a sample is selected from each of the four sides of the blank, and the blank is cut in its entirety along the thickness direction to facilitate the detection of the initial residual stress in the entire thickness direction of the blank. The initial residual stress is measured using the crack compliance method. The principle of the crack compliance method is to introduce a crack on the surface of the sample through processing means such as wire cutting, thereby releasing the stress in the material. During the test, the depth of the crack gradually increases. By recording the strain changes at the measurement points caused by multiple cuts, the residual stress distribution along the depth direction is then calculated.

[0015] According to one embodiment of the present invention, in S1, when measuring the initial residual stress using the crack compliance method, a crack is introduced by wire electrical discharge machining (EDM), with a kerf width of approximately 0.2 mm. The electrode wire is selected from... In the test, the crack depth of the molybdenum wire cut was 1 mm each time. The KD7016 static strain gauge was selected for strain measurement and recording. The instrument accuracy was 5±10-6ε.

[0016] According to one embodiment of the present invention, in S2, the strain energy density u is calculated as follows:

[0017]

[0018] Where t is the blank thickness, E is the elastic modulus, ν is Poisson's ratio, and σ x It is the stress distribution in the rolling direction, σ y It is a lateral stress distribution.

[0019] According to one embodiment of the present invention, to obtain more accurate results by considering the anisotropy of materials, the method for calculating the strain energy density u is as follows:

[0020]

[0021]

[0022] u = u x +u y ;

[0023] Among them, u x u is the strain energy density in the rolling direction. y The strain energy density is in the transverse direction.

[0024] According to one embodiment of the present invention, in S3, the method for analyzing the minimum deformation of the machined part is as follows:

[0025] Define the equivalent blank internal stress σ in the rolling direction eq For: σ eq =σ r -νσ t ;

[0026] Where, σ r It is the distribution of internal stress in the blank along the rolling direction, σ t It is the distribution of internal stress in the blank along the transverse direction, where ν is Poisson's ratio, and the length direction of the blank is the rolling direction;

[0027] bending deformation of the part w final for:

[0028] Where A is the cross-sectional region where the final part is located, and I X and These are the moment of inertia and center of mass of the final part, respectively, and L is Young's modulus and workpiece length;

[0029] For a specific part, based on the actual working conditions, among all possible final deformation amounts from all process options, the minimum deformation amount is used as the evaluation index, and the objective function is set as: min w final , i = 1, 2, ..., n;

[0030] Among them, w final (i) represents the minimum deformation corresponding to the i-th process scheme.

[0031] The beneficial effect of this invention is that it calculates the strain energy density of the blank by detecting the initial residual stress at different thickness locations of the blank, thereby obtaining the strain energy density of the entire blank. Based on the strain energy density, the blank is evaluated, which can characterize the deformation risk of the part after processing. This allows for the classification of blanks before part processing, thereby improving the yield of the processed part.

[0032] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention.

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0034] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0035] Figure 1 This is a schematic diagram illustrating the relationship between strain energy density and deformation risk in this invention;

[0036] Figure 2 This is a schematic diagram of the machining deformation analysis structure for long beam-type parts according to the present invention;

[0037] Figure 3 This is a schematic diagram of the component structure of the present invention;

[0038] Figure 4 This is a schematic diagram of the initial residual stress distribution of 20mm blanks from different batches according to the present invention;

[0039] Figure 5 This is a schematic diagram of the initial residual stress distribution of 30mm blanks from different batches according to the present invention;

[0040] Figure 6 This is a schematic diagram showing the deformation of the part of the present invention as a function of position in blanks of different thicknesses and batches. Detailed Implementation

[0041] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0042] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, features defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0043] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0044] The preferred method for controlling the deformation of long beam-type parts according to an embodiment of the present invention is described in detail below with reference to the accompanying drawings.

[0045] like Figure 1-6 As shown, the preferred method for controlling the deformation of a long beam-type part during machining according to an embodiment of the present invention includes:

[0046] A method for selecting the best blank for controlling deformation during machining of long beam-type parts, comprising the following steps:

[0047] S1. Select samples from different blanks and test the initial residual stress along the thickness direction of the samples;

[0048] In S1, the initial residual stress detection method involves taking samples from all available aluminum alloy sheet blanks of different grades, batches, and thicknesses. If the part grade has been specified in the design phase, only aluminum alloy sheet blanks of the same grade but different batches and thicknesses need to be measured. Specifically, the initial residual stress detection method involves selecting a sample from each of the four sides of the blank and cutting the entire blank along its thickness direction to detect the initial residual stress along the entire thickness direction. The initial residual stress measurement uses the crack compliance method. The principle of the crack compliance method is to introduce a crack on the surface of the sample through processing methods such as wire cutting, thereby releasing the stress in the material. During the test, the depth of the crack gradually increases. By recording the strain changes at the measurement points caused by multiple cuts, the residual stress distribution along the depth direction is then calculated.

[0049] In S1, when measuring the initial residual stress using the crack compliance method, a crack is introduced by wire electrical discharge machining (EDM), with a kerf width of approximately 0.2 mm. The electrode wire used is... In the test, the crack depth of the molybdenum wire cut was 1 mm each time. The KD7016 static strain gauge was selected for strain measurement and recording. The instrument accuracy was 5±10-6ε.

[0050] S2. Based on the initial residual stress of the test sample, calculate the strain energy density of the blank, propose a blank processing safety evaluation standard based on strain energy density, and classify the blank into no deformation risk, low deformation risk and high deformation risk.

[0051] In S2, the strain energy density u is calculated as follows:

[0052]

[0053] Where t is the blank thickness, E is the elastic modulus, ν is Poisson's ratio, and σ x It is the stress distribution in the rolling direction, σ y It is a lateral stress distribution.

[0054] If we consider the anisotropy of materials and obtain more accurate results, the method for calculating the strain energy density u is as follows:

[0055]

[0056]

[0057] u = u x +u y ;

[0058] Among them, u x u is the strain energy density in the rolling direction. yThe strain energy density is in the transverse direction.

[0059] In S2, the safety evaluation standard sets the strain energy density to be less than 1 kJ / m³. 3 At this time, there is no risk of deformation; the strain energy density is greater than 2 kJ / m. 3 At this time, there is a high risk of deformation; the strain energy density is between 1 KJ / m². 3 and 2KJ / m 3 At this stage, blanks with low deformation risk are excluded first; blanks with high deformation risk are excluded in this step.

[0060] like Figure 1 As shown, when the strain energy density of the blank is less than 1 KJ / m, it can be expected that the final part will not have a significant deformation risk, i.e., it is set as no deformation risk; when the strain energy density is greater than 2 KJ / m, the part will have a significant deformation risk, i.e., it is set as high deformation risk; when the strain energy density is between 1 KJ / m and 2 KJ / m, the part has a possible deformation risk, i.e., it is set as low deformation risk; among them, blanks with low deformation risk can be set as alternative blanks.

[0061] S3. Establish a theoretical analysis model for machining deformation based on the initial residual stress of the blank, and establish a solution function for the minimum deformation of the part. Analyze the minimum deformation of the part after machining all remaining blanks, and remove blanks with a minimum deformation greater than the machining tolerance of the part.

[0062] For aerospace long beam parts, a rapid evaluation model for the final deformation of the part during machining is established. When the part is a beam with a uniform cross-section, the length, width, and height of the blank are L, B, and H, respectively; σ r It is the distribution of internal stress in the blank along the rolling direction, σ t This represents the distribution of internal stress in the blank along the transverse direction, where ν is Poisson's ratio and the length direction of the blank is the rolling direction. A1 and A2 represent the distances from the sidewall of the part to the boundary of the blank and from the bottom of the part to the bottom of the blank, respectively. The deformation of long beam-type parts is mainly bending deformation along the length direction, with smaller torsional and other deformation values. To accurately analyze the bending deformation in the rolling direction caused by internal stress, the equivalent internal stress σ in the blank in the rolling direction is defined. eq For: σ eq =σ r -νσ t ;

[0063] When analyzing the bending deformation of a long beam, one end of the beam is fixed and the other end is hinged; furthermore, the part can be simplified as a simply supported beam, and the deformation is characterized by the maximum deflection value of the bending deformation. The final bending deformation w of the part... fina l is:

[0064] Where A is the cross-sectional area where the final part is located. X and These are the moment of inertia and center of mass of the final part, respectively, and L is Young's modulus and workpiece length.

[0065] For beams with stiffeners and beams with variable cross-sections, the equivalent cross-sectional stiffness of the parts needs to be calculated before using the above method for calculation.

[0066] For a specific part, based on the actual working conditions, among all possible final deformation amounts from all process options, the minimum deformation amount is used as the evaluation index, and the objective function is set as: min w final , i = 1, 2, ..., n;

[0067] Among them, w final (i) represents the minimum deformation corresponding to the i-th process scheme.

[0068] S4. Further, select the blank with the smallest thickness from the remaining blanks that satisfy the minimum deformation amount being greater than the part machining tolerance;

[0069] In S4, the blank that satisfies the minimum deformation amount being greater than the part machining tolerance should have a front and back allowance of ≥2mm.

[0070] S5. Among the remaining blanks that satisfy the minimum deformation amount greater than the part machining tolerance, there are different production batches. Further optimization is carried out. Among these different batches of blanks, the blanks of the batch with the smallest fluctuation in the deformation amount of the part at different positions are selected as the preferred blanks. The position of the part in the blank corresponding to the minimum deformation amount of the part is provided as a reference for the machining process planning.

[0071] For each candidate blank, a corresponding machining deformation theoretical analysis model is established. Specifically, a program is written in MATLAB to calculate the position of the part in the blank and the minimum deformation value corresponding to the minimum deformation amount, using the position of the part in the blank as a variable. It is then determined whether the calculated minimum deformation value exceeds the allowable tolerance δ of the part. If it exceeds the tolerance, the blank is discarded. Among the remaining qualified blanks, the blank with the smallest thickness (with a front and back allowance ≥ 2mm) is selected. This selection takes into account both economy and machining safety. Furthermore, among the blanks of different batches with the smallest thickness, the blank with the smallest fluctuation in deformation amount at different positions is selected as the preferred blank. The position of the part in the blank corresponding to the minimum deformation amount is provided as a reference for machining process planning.

[0072] Example 1, Figure 3For the schematic diagram of the part structure, four types of blanks were selected. Blanks 1 and 2 are 20mm thick plates from two different batches; blanks 3 and 4 are 30mm thick plates from two different batches. All blanks are domestically produced AA6061-T651 aluminum alloy pre-stretched plates. After solution heat treatment, the blanks are stretched to a certain amount to relieve stress, and then artificially aged. No further straightening is performed on the material after stretching. The material properties of the blanks are as follows: elastic modulus 68.9 GPa, yield strength 240 MPa, Poisson's ratio 0.33, density 2.75 kg / m³. -3 .

[0073] Samples were taken from four blanks, and the initial residual stress distribution of each blank was measured using the crack compliance method. The final residual stress distribution along the thickness direction is shown in the figure. Figure 4-5 As shown.

[0074] The total energy density of the four blanks was analyzed. The total energy densities of blanks 1, 2, 3, and 4 were 1.42 KJ / m³, 1.52 KJ / m³, 1.65 KJ / m³, and 1.69 KJ / m³, respectively. All four blanks had energy densities less than 2 KJ / m³.

[0075] All of these can be used as alternative blanks.

[0076] A machining deformation analysis model was established. During the analysis, the position of the part in the blank was defined to move up and down in units of 1 mm. Since the residual stress values ​​of the blank of the same thickness are consistent, for the study of bending deformation, it was set that the part is located in the middle position in the left and right directions of the blank in each case.

[0077] Figure 6 The figure shows the deformation of the part in different batches of blanks with varying thicknesses, depending on the part's position within the blank. As can be seen from the figure, the minimum deformation of the part in all four blanks is close to zero, meeting the machining tolerance requirements. Among the four candidate blanks, the 20mm thick blank is preferred because the part height is 12mm, with a 4mm allowance in both directions, meeting the minimum allowance requirement. Among the two 20mm thick blanks, blank 1 shows the smallest fluctuation in deformation at different positions. Therefore, considering all these factors, blank 1 is selected as the optimal blank.

[0078] In summary, since the initial residual stress value of domestically produced blanks is in the thickness direction, detecting the initial residual stress at different thickness locations of the blank can provide a comprehensive understanding of the initial residual stress value of the sample, thereby obtaining the strain energy density of the entire blank. Factors affecting the final deformation of the part include the fluctuation of stress distribution within different blanks, the part structure, and the part's position within the blank. In the manufacturing process, the part structure is already determined; therefore, only the selection of the blank and the part's position within it can be optimized. In other words, by understanding the strain energy density of the blank, the minimum deformation and its value within the blank can be calculated. The strain energy density reveals the global stress level of the blank, and based on strain energy... Density is used to evaluate blanks, which can characterize the deformation risk of parts after processing. By numerically judging whether the blank exceeds the allowable tolerance value of the part, the yield rate of part production can be predicted before production. It can be determined whether the blank can be manufactured according to the requirements of the finished part, and the optimal blank for manufacturing the part can be found. If it exceeds the tolerance value, it means that the blank is not suitable for manufacturing the part and is discarded. However, the blank has not undergone part processing in this process, reducing unnecessary production costs. At the same time, the blank can be used for other purposes, reducing the waste of blanks. Dividing blanks into multiple grades can help users make appropriate choices based on their cost budget when selecting blank manufacturers and blank thicknesses before producing parts.

[0079] During blank production, the same blank selection method for controlling deformation during the processing of long beam-type parts can be used to classify blanks by grade, so as to improve the pass rate of blanks upon delivery.

[0080] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0081] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for selecting the optimal blank for controlling deformation during machining of long beam-type parts, characterized in that, Includes the following steps: S1. Select samples from different blanks and test the initial residual stress along the thickness direction of the samples; S2. Based on the initial residual stress of the test sample, calculate the strain energy density of the blank, propose a blank processing safety evaluation standard based on strain energy density, and classify the blank into no deformation risk, low deformation risk and high deformation risk; the safety evaluation standard sets the strain energy density to be less than 1 KJ / m³ as no deformation risk. When the strain energy density is greater than 2 kJ / m³, there is a high risk of deformation. When the strain energy density is between 1 KJ / m³ and 2 KJ / m³, the deformation risk is low; in this step, blanks with high deformation risk are first excluded. S3. Establish a machining deformation theoretical analysis model based on the initial residual stress of the blank, and establish a solution function for the minimum deformation of the part. Analyze the minimum deformation of the part after machining all remaining blanks, and discard blanks whose minimum deformation exceeds the part machining tolerance. Blanks whose minimum deformation exceeds the part machining tolerance should have a front and back allowance ≥ 2mm. The method for analyzing the minimum deformation of the machined part is as follows: Define the equivalent blank internal stress in the rolling direction for: ; in, It is the distribution of internal stress in the blank along the rolling direction. It is the distribution of internal stress in the blank along the transverse direction. It is Poisson's ratio, and the length direction of the blank is the rolling direction; Bending deformation of parts for: ; in, It is the cross-sectional area where the final part is located. and These are the moment of inertia and center of mass of the final part, respectively. Given Young's modulus and workpiece length; For a specific part, based on the actual working conditions, among all possible final deformation amounts from all process options, the minimum deformation amount is used as the evaluation index to set the objective function: ; in, This represents the minimum deformation corresponding to the i-th process scheme; S4. Further, select the blank with the smallest thickness from the remaining blanks that satisfy the minimum deformation amount being greater than the part machining tolerance; S5. Among the remaining blanks that satisfy the minimum deformation amount greater than the part machining tolerance, there are different production batches. Further optimization is carried out. Among these different batches of blanks, the blanks of the batch with the smallest fluctuation in the deformation amount of the part at different positions are selected as the preferred blanks. The position of the part in the blank corresponding to the minimum deformation amount of the part is provided as a reference for the machining process planning.

2. The method for selecting the best blank for controlling deformation during machining of long beam-type parts according to claim 1, characterized in that, In S1, the method for detecting initial residual stress is as follows: a sample is selected from each of the four sides of the blank, and the entire blank is cut along its thickness direction to facilitate the detection of initial residual stress along the entire thickness direction of the blank. The initial residual stress is measured using the crack compliance method. The principle of the crack compliance method is to introduce a crack on the surface of the sample through processing means such as wire cutting, thereby releasing the stress in the material. During the test, the depth of the crack gradually increases. By recording the strain changes at the measurement points caused by multiple cuts, the residual stress distribution along the depth direction is then calculated.

3. The method for selecting the best blank for controlling deformation during machining of long beam-type parts according to claim 2, characterized in that, In S1, when measuring the initial residual stress using the crack compliance method, a crack was introduced by wire electrical discharge machining (EDM) with a kerf width of 0.2 mm. The electrode wire was Ø0.18 mm molybdenum wire. In the test, the crack depth was 1 mm for each cut. A KD7016 static strain gauge was used for strain measurement and recording. The instrument's accuracy... .

4. The method for selecting the best blank for controlling deformation during machining of long beam-type parts according to claim 3, characterized in that, In S2, strain energy density The calculation method is as follows: ； Where t is the thickness of the blank. For elastic modulus, Poisson's ratio, It is the stress distribution in the rolling direction. It is a lateral stress distribution.

5. The method for selecting the best blank for controlling deformation during machining of long beam-type parts according to claim 4, characterized in that, If we consider the anisotropy of materials, we can obtain more accurate results, such as strain energy density. The calculation method is as follows: ； ； ； in, The strain energy density is in the rolling direction. The strain energy density is in the transverse direction.

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