A process analysis method for influencing the reliability risk points of the combustion chamber shell strength

Abstract

The application provides a process analysis method for influencing a risk point of a combustion chamber shell strength reliability, which comprises the following steps: firstly, calculating the outer diameter size and the inner diameter size of the shell, calculating the upper limit deviation size of the inner diameter according to the upper limit deviation size of the outer diameter processing process, calculating the lower limit deviation size of the inner diameter according to the lower limit deviation size of the outer diameter processing process, comparing the upper limit deviation size of the inner diameter and the lower limit deviation size of the inner diameter with the design minimum wall thickness respectively, judging whether they all meet the requirements, and determining that there is a risk point influencing the strength reliability if any of them does not meet the requirements. The application can determine the position of the risk point and the specific deviation from the design state, and give technical improvement suggestions, so that the design structure is more scientific, rigorous and reliable, hidden dangers are eliminated, and the strength reliability of product design is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of structural process analysis, and relates to a risk point process analysis method. BACKGROUND

[0002] The shell structure of a solid rocket engine combustion chamber is usually formed by connecting pieces and a cylinder after welding and heat treatment, and must have certain strength requirements. Among them, the wall thickness size is a key control element, which can ensure the working safety of the engine. In the forming process of the combustion chamber shell, in order to improve the material utilization rate, the cylinder is usually formed by spinning process to ensure the wall thickness and shape and position tolerances, but this method has relatively large dispersion of the outer diameter size of the machined parts. Therefore, in order to ensure the welding quality and control the radial misalignment of the connecting piece and the cylinder welding part, the outer diameter of the connecting piece is processed to match the cylinder. The inner surface of the connecting piece is composed of a straight section and an ellipsoidal surface, the long axis vertex of the ellipsoidal surface is connected with the straight section, and the outer surface is formed by offsetting a certain wall thickness size from the inner surface. The basic structure is shown in Figure 1

[0003] The main problems of this design structure are:

[0004] 1) The process forming process has a great influence on the design;

[0005] 2) There are weak points in the structure, and stress concentration points may occur during the working process of the engine, affecting the safety in use;

[0006] 3) The risk is strong and it is difficult for general designers to find or pay attention to it. SUMMARY

[0007] In order to overcome the shortcomings of the prior art, the present application provides a risk point process analysis method for affecting the strength reliability of the combustion chamber shell, which can determine the position of the risk point and the specific deviation from the design state, and give technical improvement suggestions, so that the design structure is more scientific, rigorous and reliable, the hidden danger is eliminated, and the strength reliability of product design is improved.

[0008] The technical solution adopted by the present application to solve its technical problems comprises the following steps:

[0009] 1) Calculate the outer diameter size Wherein is the measured value of the outer diameter size of the cylinder, and the matching size requirement is

[0010] 2) Calculate the inner diameter size A0, A0 上偏差 =A1 上偏差 -2*A2 下偏差 , A0 下偏差 =A1 下偏差 -2*A2 上偏差 , wherein​ The wall thickness size is A2±0.05 mm, and the inner diameter size is

[0011] 3) The upper deviation limit size of the inner diameter is calculated according to the upper deviation limit size of the outer diameter machining process, and the lower deviation limit size of the inner diameter is calculated according to the lower deviation limit size of the outer diameter machining process; the upper deviation limit size of the inner diameter and the lower deviation limit size of the inner diameter are compared with the design minimum wall thickness respectively, and it is judged whether both meet the requirements, if any one does not meet the requirements, it is judged that there is a risk point affecting the strength reliability.

[0012] The actual measured value of the outer diameter size of the cylinder The vehicle matching size requirement is The outer diameter size A1=A

[0013] The wall thickness size is A2±0.05 mm, and the inner diameter size is

[0014] According to the upper deviation limit size of the outer diameter machining process, the outer diameter is (A+0.5) mm, and the wall thickness is the lower deviation (A2-0.05) mm, then the upper deviation limit size of the inner diameter is (A-2*A2) mm+0.6 mm; the theoretical diameter of the top point of the long axis of the inner type surface is (A-2*A2) mm, then it is judged that the inner diameter and the outer diameter at the connection part of the straight section and the ellipsoidal surface all appear step differences, the outer diameter is offset by +0.5 / 2=0.25 mm relative to the ellipsoidal surface, the inner diameter is offset by +0.6 / 2=+0.3 mm relative to the ellipsoidal surface, that is, the straight section is upward relative to the ellipsoidal surface, and the wall thickness at the connection part is (A2-0.3) mm, which does not meet the design minimum wall thickness (A2-0.05) mm requirement.

[0015] According to the lower deviation limit size of the outer diameter machining process, the outer diameter is (A-0.2) mm, and the wall thickness is the upper deviation (A2+0.05) mm, then the lower deviation limit size of the inner diameter is (A-2*A2) mm-0.3 mm; it can be judged that the inner diameter and the outer diameter at the connection part of the ellipsoidal surface and the straight section all appear step differences, the outer diameter of the straight section is offset by-0.2 / 2=-0.1 mm relative to the ellipsoidal surface, the inner diameter is offset by-0.3 / 2=-0.15 mm relative to the ellipsoidal surface, that is, the straight section is downward relative to the ellipsoidal surface, and the wall thickness at the connection part is (A2-0.1) mm, which does not meet the design minimum wall thickness (A2-0.05) mm requirement.

[0016] If the wall thickness requirement of step 3) is not met, the structure is improved and optimized, the inner type surface is divided into a cylinder section and a cone section, and a conical surface transition is adopted between the two sections.

[0017] The beneficial effects of the present application are:

[0018] (1) The influence of process on the design structure

[0019] According to the process characteristics of the forming process, a new process analysis method is provided.

[0020] (2) Eliminate technical risks

[0021] It can analyze and mine the weak points and risk points of the design structure, and prevent or eliminate design defects.

[0022] (3) Provide basis for design optimization

[0023] Through process analysis and calculation, the specific situation of the actual product deviating from the design condition can be determined, providing a reference for design optimization.

[0024] (4) Has promotional value

[0025] The analysis method and calculation process can be used in similar structures, providing risk control points that may affect the strength reliability for design and process personnel, especially for the structure design of aerospace product parts, which can effectively improve the design process and reliability of the product. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a theoretical design diagram;

[0027] Figure 2 is a forming process flowchart;

[0028] Figure 3 is a forming process flowchart structure;

[0029] Figure 4 is a size chain relationship diagram;

[0030] Figure 5 is an outer diameter deviation diagram;

[0031] Figure 6 is an outer diameter deviation diagram;

[0032] Figure 7 is a structure diagram of a certain type of connector;

[0033] Figure 8 is a size chain relationship diagram of the embodiment;

[0034] Figure 9 is an outer diameter deviation diagram of the embodiment;

[0035] Figure 10 is an outer diameter deviation diagram of the embodiment;

[0036] Figure 11 is an improved outer diameter deviation diagram;

[0037] Figure 12 is an improved outer diameter deviation diagram. DETAILED DESCRIPTION

[0038] The present application is further illustrated in conjunction with the accompanying drawings and examples, which include but are not limited to the following examples.

[0039] In view of the defects of the prior art, the technical problem to be solved by the present application is to determine the risk points through process analysis and calculation, and eliminate technical risks.

[0040] To achieve the above-mentioned purpose, the present application provides a process analysis method and a calculation method.

[0041] (1) Analysis of the forming process

[0042] The connecting piece is mostly machined by numerical control lathe, and the process flow of the forming process is as shown in Figure 2 , and the structure is as shown in Figure 3 .

[0043] (2) Analysis and calculation of the forming process

[0044] 1) Outer diameter size

[0045] The specific calculation is as follows:

[0046] The outer diameter size precision of the cylinder is generally (A±0.3) mm according to the industry standard, and the outer diameter size of the connecting piece is generally required to be (wherein A is the actual measured value of the outer diameter size of the cylinder), and the outer diameter size of the connecting piece is calculated as

[0047] 2) Inner diameter size

[0048] According to the sequence of the process flow of the forming process, the size chain (wall thickness, outer diameter, inner diameter) is constructed, wherein the open loop is the wall thickness size (A2±0.05) mm and the outer diameter size A1, and the closed loop is the inner diameter size A0, as shown in Figure 3 . The calculation process is as follows:

[0049] A0 A0max =A1 A1max -2*A2 A2min =(A+0.5)-{2*(A2-0.05)}=(A-2*A2) +0.6

[0050] A0 A0min =A1 A1min -2*A2 A2max =(A-0.2)-{(2*A2+0.05)}=(A-2*A2) -0.3

[0051] Therefore, the inner diameter size is:

[0052]

[0053] (3) Process analysis

[0054] Based on process analysis and calculation, the outer diameter, wall thickness, and inner diameter of the connector are respectively... (A2±0.05)mm, (A-2*A2) Calculated based on the upper deviation of the limit dimensions during the outer diameter machining process, the outer diameter is taken as (A+0.5) mm, and the wall thickness is taken as the lower deviation as (A2-0.05) mm. Therefore, the upper deviation of the limit dimensions of the inner diameter is (A-2*A2) mm + 0.6 mm. The major axis (b) of the ellipsoid equation is generally designed according to the theoretical dimension (A-2*A2) / 2 mm, that is, the theoretical diameter of the vertex of the major axis of the inner surface is (A-2*A2) mm. It can be determined that at the junction of the straight section and the ellipsoidal surface, both the inner and outer diameters show a step difference. The outer diameter offset relative to the ellipsoidal surface is +0.5 / 2 = 0.25 mm, and the inner diameter offset relative to the ellipsoidal surface is +0.6 / 2 = +0.3 mm. That is, the straight section moves up relative to the ellipsoidal surface, and the wall thickness at the junction is (A2-0.3) mm, which does not meet the design minimum wall thickness requirement of (A2-0.05) mm. For example... Figure 4 As shown.

[0055] Calculating based on the lower deviation of the limit dimension during the outer diameter machining process, with the outer diameter taken as (A-0.2) mm and the wall thickness as the upper deviation as (A2+0.05) mm, the lower deviation dimension of the inner diameter limit is (A-2*A2) mm-0.3 mm. It can be determined that a step difference occurs in both the inner and outer diameters at the junction of the ellipsoid and the straight section. The outer diameter of the straight section is offset relative to the ellipsoid by -0.2 / 2 = -0.1 mm, and the inner diameter is offset relative to the ellipsoid by -0.3 / 2 = -0.15 mm. That is, the straight section shifts downward relative to the ellipsoid, and the wall thickness at the junction is (A2-0.1) mm, which does not meet the design minimum wall thickness requirement of (A2-0.05) mm. Figure 5 As shown.

[0056] In summary, based on process analysis and calculations using technological methods, this type of structural design has risk points that could affect strength and reliability.

[0057] Taking a certain type of connector structure as an example, the structure is as follows: Figure 7 As shown, the wall thickness is 2.5mm ± 0.1mm, and the equation of the inner ellipsoid is X. 2 / 104 2 +Y 2 / 254 2 =1. To ensure welding strength and control welding misalignment, the outer diameter of the connector is required to be... The vehicle is designed to be matched with a cylinder outer diameter of 513mm. The vehicle size requirements are as follows: ( (This refers to the actual dimensions of the cylinder).

[0058] (1) Calculation process

[0059] 1) Outer diameter size

[0060] The specific calculation is as follows:

[0061] The outer diameter size of the cylinder is The size requirement of the vehicle is The outer diameter size of the connecting piece is

[0062] 2) Inner diameter size

[0063] According to the processing sequence, the size chain open loop is the wall thickness size (A2) and the outer diameter size (A1), and the closed loop is the inner diameter size (A0), as shown in Figure 8 The calculation process is as follows:

[0064]

[0065]

[0066] The inner diameter size is:

[0067]

[0068] (2) Process forming process

[0069] The specific processing steps are:

[0070] ① The outer diameter of the cylinder is matched with the vehicle to ensure the size of 20mm;

[0071] ② Process the straight section of the inner surface, ensure the wall thickness size of 2.5mm±0.1mm and the depth size of 35mm;

[0072] ③ Process the inner type ellipsoid surface according to the equation; process the inner type surface cone, determine the cone angle according to the actual size of the inner diameter, and connect with the ellipsoid long axis;

[0073] ④ Process the outer surface, ensure the wall thickness size of 2.5mm±0.05mm.

[0074] ⑤ After welding and heat treatment, process the outer diameter (shelf position).

[0075] (3) Process analysis

[0076] Through process analysis and calculation, the outer diameter, wall thickness and inner diameter size of the connecting piece are respectively 2.5mm±0.1mm, According to the upper deviation calculation of the limit size of the outer diameter processing process, the outer diameter is The wall thickness is 2.4mm, and the upper limit deviation size of the inner diameter is Therefore, it can be judged that the inner diameter and the outer diameter at the connection between the straight section and the ellipsoidal surface have step differences, the outer diameter is offset by +0.4 / 2=0.2mm relative to the ellipsoidal surface, the inner diameter is offset by +0.6 / 2=+0.3mm relative to the ellipsoidal surface, that is, the straight section is upward relative to the ellipsoidal surface, and the wall thickness at the connection is 2.5-0.3=2.2mm, which does not meet the requirement of the minimum wall thickness 2.4mm. As shown in Figure 9 .

[0077] According to the calculation of the lower deviation of the limit size in the outer diameter processing process, the outer diameter is taken as The wall thickness is taken as the upper deviation 2.6mm, and the limit lower deviation size of the inner diameter is Therefore, it can be judged that the inner diameter and the outer diameter at the connection between the straight section and the ellipsoidal surface have step differences, the outer diameter is offset by -0.4 / 2=-0.2mm relative to the ellipsoidal surface, the inner diameter is offset by -0.6 / 2=-0.3mm relative to the ellipsoidal surface, that is, the straight section is downward relative to the ellipsoidal surface, and the wall thickness at the connection is 2.5-0.2=2.3mm, which does not meet the requirement of the minimum wall thickness 2.4mm. As shown in Figure 10 Through process analysis and calculation, the design structure still has a risk point.

[0078] (4) Improvement measures or suggestions

[0079] According to the deviation of the design technical state based on the process analysis and calculation results, and considering the strength reliability, the structure can be improved and optimized, the inner type surface is divided into two parts of the cylinder section and the cone section, the taper transition is adopted, all size deviations can be contained to affect the key wall thickness size of the design, the reliability of the product design is improved, the design defects are eliminated, and the working strength requirement is met.

[0080] The effect after improvement is shown in Figure 11 , 12 .

Claims

1. A method of process analysis affecting the reliability risk points of the strength of a combustion chamber shell, characterized by, Comprise the following steps: 1) Calculate the outside diameter dimension where is the measured value of the outside diameter dimension of the cylinder, and the required dimension of the vehicle is 2) Calculate inner diameter dimension A0, A0 上偏差 = A1 上偏差 - 2 * A2 下偏差 , A0 下偏差 = A1 下偏差 - 2 * A2 上偏差 where is the wall thickness dimension; 3) Calculate the upper limit of the inner diameter deviation size according to the upper limit of the outer diameter machining process size, and calculate the lower limit of the inner diameter deviation size according to the lower limit of the outer diameter machining process size; compare the upper limit of the inner diameter deviation size and the lower limit of the inner diameter deviation size with the designed minimum wall thickness respectively, and judge whether they meet the requirements, if any of them does not meet the requirements, it is determined that there is a risk point affecting the strength reliability.

2. The process analysis method for affecting the risk point of the reliability of the strength of the combustion chamber housing according to claim 1, characterized by, If the wall thickness requirement of step 3) is not met, the structure is improved and optimized, the inner surface is divided into two parts of cylinder segment and cone segment, and a conical transition is adopted between the two parts.

3. The process analysis method for affecting the risk point of the reliability of the strength of the combustion chamber housing according to claim 1, characterized by, The measured value of the outer diameter size of the barrel The size requirement for the vehicle is The outer diameter size 4. The method of claim 3, wherein, The wall thickness dimension is A2 ± 0.05 mm, and the inner diameter dimension is 5. The method of claim 4, wherein, According to the upper limit of the outer diameter machining process size, the outer diameter is (A+0.5) mm, the wall thickness is (A2-0.05) mm, then the upper limit of the inner diameter deviation size is (A-2*A2) mm+0.6 mm; the theoretical diameter of the long axis top point of the inner surface is (A-2*A2) mm, then it is judged that the inner diameter and the outer diameter at the junction of the straight section and the ellipsoidal surface appear step difference, the outer diameter is offset by +0.5 / 2=0.25 mm relative to the ellipsoidal surface, the inner diameter is offset by +0.6 / 2=+0.3 mm relative to the ellipsoidal surface, that is, the straight section moves upward relative to the ellipsoidal surface, and the wall thickness at the junction is (A2-0.3) mm, which does not meet the designed minimum wall thickness (A2-0.05) mm requirement.

6. The method of claim 4, wherein, According to the lower limit of the outer diameter machining process size, the outer diameter is (A-0.2) mm, the wall thickness is (A2+0.05) mm, then the lower limit of the inner diameter deviation size is (A-2*A2) mm-0.3 mm; it can be judged that the inner diameter and the outer diameter at the junction of the ellipsoidal surface and the straight section appear step difference, the outer diameter of the straight section is offset by-0.2 / 2=-0.1 mm relative to the ellipsoidal surface, the inner diameter is offset by-0.3 / 2=-0.15 mm relative to the ellipsoidal surface, that is, the straight section moves downward relative to the ellipsoidal surface, and the wall thickness at the junction is (A2-0.1) mm, which does not meet the designed minimum wall thickness (A2-0.05) mm requirement.

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