Marine common rail pipe strength evaluation method

Abstract

The invention discloses a marine common rail pipe strength evaluation method. The method mainly solves the problems that a traditional empirical formula calculation method of the large-size common rail pipe is low in accuracy, time consumption is long when an overall model finite element is adopted for calculation, and a strength evaluation method of the parts is not clear. Comprising the following steps: S1, creating or intercepting a common rail pipe geometric model for calculation; s2, on the basis of the common rail pipe geometric model, a common rail pipe grid model for calculation is established, material attributes are given, and analysis steps are set; and when the set analysis steps are three steps, executing the following steps: S3: based on the common rail pipe grid model, performing strength calculation and evaluation in the common rail pipe strengthening process; s4, based on the common rail pipe grid model, performing strength calculation and evaluation after load unloading after the strengthening process; s5, on the basis of the common rail pipe grid model, common rail pipe strength calculation and evaluation are carried out in the working state after the load is unloaded; and when the strength of the common rail pipe is evaluated to be qualified in the steps S3-S5, the final strength of the common rail pipe is evaluated to be qualified, and otherwise, the common rail pipe is unqualified.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of diesel engine fuel system, and particularly relates to a marine common rail pipe strength evaluation method. BACKGROUND

[0002] The common rail pipe is one of the core components of the common rail type fuel injection system of a diesel engine, and has the characteristics of large inner diameter size and long axial distance in the common rail type fuel injection system of a marine diesel engine or other high-power diesel engines such as power generation and locomotive; the fuel pressure in the common rail pipe is high, up to 200 MPa or more, and since fuel needs to be provided to each cylinder of the engine, the common rail pipe is generally provided with multiple fuel outlets in the direction perpendicular to the axis, which makes the common rail pipe not a single hollow tubular structure; during the design stage, accurate strength evaluation of the common rail pipe is very important to ensure the safety and reliability of the fuel system. SUMMARY

[0003] Therefore, the application provides a marine common rail pipe strength evaluation method, which is characterized by the following steps:

[0004] The marine common rail pipe strength evaluation method comprises the following steps:

[0005] S1: creating or intercepting a common rail pipe geometric model for calculation;

[0006] S2: based on the common rail pipe geometric model, establishing a common rail pipe grid model for calculation and assigning material properties and setting analysis steps; when the set analysis steps are three steps, the following steps are executed:

[0007] S3: based on the common rail pipe grid model, performing common rail pipe strength calculation and evaluation during the strengthening process;

[0008] S4: based on the common rail pipe grid model, performing strength calculation and evaluation after load unloading after the strengthening process;

[0009] S5: based on the common rail pipe grid model, performing common rail pipe strength calculation and evaluation in the working state after load unloading;

[0010] When the common rail pipe strength is qualified in steps S3-S5, the final strength evaluation of the common rail pipe is qualified, otherwise it is not qualified;

[0011] when the set analysis steps are one step, the following steps are executed:

[0012] S6: Based on the common rail grid model, calculate and evaluate the strength of the common rail under working conditions.

[0013] Preferably, in step S1,

[0014] The common rail pipe geometric model includes a common rail pipe section, and the common rail pipe section at least includes a common rail pipe cavity, inlet and outlet oil passages, and a fillet of a connecting hole;

[0015] The common rail section is a certain solid part of the common rail along the axial direction, the inlet and outlet oil passages are connected to the inner cavity of the common rail, and the fillet of the intersection hole is a cambered transition structure at the connection between the inlet and outlet oil passages and the inner cavity of the common rail;

[0016] The distance L1 between the left end face of the common rail pipe section and the center line of the inlet and outlet oil passages is the product of a first preset typical value N1 and the diameter D of the common rail pipe inner cavity;

[0017] The distance L2 between the right end surface of the common rail pipe section and the center line of the inlet and outlet oil passages is the product of a second preset typical value N2 and the diameter D of the inner cavity.

[0018] Preferably, the size of the fillet of the connecting hole is R0.3-R1.0, the value range of the first preset typical value N1 is 0.7≤N1≤3, and the value range of the second preset typical value N2 is 0.7≤N2≤3.

[0019] Preferably, in step S2, the common rail grid model at least includes a grid model of the common rail section;

[0020] The material property of the common rail pipe section is at least an elastic-plastic constitutive model including deformation data of the plastic zone;

[0021] The grid model of the common rail pipe section adopts a second-order tetrahedral grid, the number of grid layers along the circumferential direction of the fillet at the intersection hole fillet is ≥2, and the grid transition rate is ≤1.5.

[0022] Preferably, step S3 includes:

[0023] S31, applying equivalent loads to both end surfaces of the common rail pipe segment grid model according to the strengthening process pressure and the sealing area between the common rail pipe and the end cover;

[0024] S32, applying a pressure load to the surface of the common rail inner cavity, the surfaces of the oil inlet and outlet passages, and the surface of the fillet of the intersection hole, wherein the value of the applied pressure load is equal to the value of the strengthening process pressure;

[0025] S33 , performing finite element calculation to extract the equivalent stress value and the equivalent plastic strain value of the common rail pipe section, and performing strength assessment using the extracted equivalent stress value and the equivalent plastic strain value.

[0026] Preferably, step S33 includes:

[0027] S331: If the maximum equivalent stress value is greater than or equal to the material yield strength, compare whether the maximum equivalent plastic strain value is less than the ratio of the material's elongation after fracture to a first preset safety factor; if so, the common rail strength at this stage is considered qualified, and step S4 is executed; if not, the common rail strength during the strengthening process is considered unqualified;

[0028] S332: If the maximum equivalent stress value is less than the material yield strength, compare whether the maximum equivalent stress value is less than the ratio of the material yield strength to the second preset safety factor; if so, it is considered that the strength of the common rail pipe at this stage is qualified, and then execute step S4; if not, it is considered that the strength of the common rail pipe during the strengthening process is unqualified.

[0029] Preferably, step S4 includes:

[0030] S41, canceling the equivalent loads applied to both end surfaces of the common rail pipe segment grid model, and canceling the pressure loads applied to the surface of the common rail pipe inner cavity, the surfaces of the inlet and outlet oil passages, and the surface of the fillet of the intersection hole;

[0031] S42, performing finite element calculation to extract the equivalent stress value of the common rail pipe section and perform common rail pipe strength assessment;

[0032] If the extracted maximum equivalent stress value is greater than or equal to the ratio of the material yield strength to the fourth preset safety factor, the common rail pipe strength at this stage is considered unqualified, otherwise it is qualified.

[0033] Preferably, step S5 includes:

[0034] S51, applying equivalent loads to both end surfaces of the common rail pipe segment grid model according to the pressure in the working state and the sealing area between the common rail pipe and the end cover;

[0035] S52, applying a pressure load to the surface of the common rail inner cavity, the surfaces of the oil inlet and outlet passages, and the surface of the fillet of the intersection hole, wherein the value of the applied pressure load is equal to the value of the pressure in the working state;

[0036] S53, performing finite element calculation, extracting the equivalent stress of the common rail pipe section and performing common rail pipe strength assessment; if the extracted maximum equivalent stress is greater than or equal to the ratio of the material yield strength to the fifth preset safety factor, the common rail pipe strength at this stage is considered unqualified, otherwise it is qualified.

[0037] Preferably, the value range of the first preset safety factor, the second preset safety factor, the fourth preset safety factor, the fifth preset safety factor and the sixth preset safety factor is 1-3.

[0038] The beneficial effects of the present invention are:

[0039] Taking into account the typical characteristics of marine common rails, a segmented model of the common rail is calculated, and weak points such as intersection holes are included in the calculation. This greatly reduces the calculation scale and time for the entire common rail. Furthermore, the marine common rail strength assessment method provided by the present invention includes strength assessments of the common rail under different states, such as reinforcement, unloading, and operation, and takes into account the influence of the equivalent tensile load at the end of the common rail. This load is generally not negligible in marine common rails with larger inner diameters, thus improving the accuracy of the calculation.

[0040] The above technology of the present invention can be used not only for strength evaluation of common rail tubes in marine high-pressure common rail systems, but also for strength evaluation of common rail tubes in high-power diesel engine common rail systems in other industries such as the power and locomotive industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic diagram of the structure of marine common rail components;

[0042] Figure 2 Schematic diagram of a flow chart of a method for evaluating the strength of a marine common rail pipe in an embodiment of the present invention;

[0043] Figure 3 It is a structural diagram of the common rail pipe geometric model intercepted in S1;

[0044] Figure 4 It is a structural diagram of the common rail pipe grid model in S2;

[0045] Figure 5 Schematic diagram of the load and boundary condition settings for the finite element model in S3;

[0046] Figure 6 is the equivalent stress cloud diagram calculated in S3;

[0047] Figure 7 is the equivalent plastic strain cloud diagram calculated in S3;

[0048] Figure 8 is the equivalent stress cloud diagram calculated in S4;

[0049] Figure 9 is the equivalent stress cloud diagram calculated in S5;

[0050] Description of reference numerals:

[0051] 1- common rail pipe, 2- end cover, 3- bracket, 10- common rail pipe section, 101- common rail pipe cavity, 102- inlet and outlet oil channels, 103- intersection hole fillet, 31- bracket bottom surface, 32- mounting hole. DETAILED DESCRIPTION

[0052] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0053] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0054] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0055] In the present invention, unless otherwise specified, directional words such as "up" and "down" are generally used with respect to the directions shown in the drawings, or with respect to the vertical, perpendicular or gravity directions; similarly, for ease of understanding and description, "left" and "right" are generally used with respect to the left and right shown in the drawings; "inside" and "outside" refer to the inside and outside relative to the outline of each component itself, but the above directional words are not used to limit the present invention.

[0056] The common rail pipe is one of the core components of the high-pressure common rail fuel injection system, and its main function is to accumulate and distribute high-pressure fuel. Figure 1 The figure shows the structure of a typical common rail pipe for marine or high-power diesel engines. The common rail pipe components mainly include the common rail pipe 1, end cover 2, bracket 3, and other parts. Due to the large fuel injection volume required by marine diesel engines, unlike automotive common rail pipes, this type of common rail pipe 1 has a longer axial length. The common rail pipe 1 and end cover 2 are usually machined separately and then assembled together.

[0057] In this embodiment, both ends of the common rail pipe 1 are provided with end caps 2 and connected by screws. Therefore, the connection between the two ends of the common rail pipe 1 and the end caps 2 will have a sealing requirement for the high-pressure fuel medium in the pipe. The sealing structure between the end caps 2 and the common rail pipe 1 can adopt any of a variety of types such as spherical-conical surface, arc-conical surface, plane-plane, etc. In this embodiment, the end caps 1 and the common rail pipe 2 adopt a arc-conical surface sealing structure, and it is assumed that the sealing area of ​​the sealing structure is S seal , the sealing diameter is D1.

[0058] Reference Figure 1 The common rail pipe 1 is provided with an inner cavity 101 in the middle thereof, and the inner cavity 101 is used to store high-pressure fuel. The inner cavity 101 can be cylindrical or in other shapes. In this embodiment, the inner cavity 101 is a cylindrical structure. Figure 1Multiple inlet and outlet oil passages 102 are sequentially defined along the axis of the common rail 1 at varying intervals. These passages 102 are radially arranged and communicate with the inner cavity 101. These passages primarily deliver high-pressure fuel to and from the common rail 1. Furthermore, a bracket 3 is disposed externally on the common rail 1. Bracket 3 is a block-shaped structure with a central hole. In this embodiment, the bottom surface 31 of bracket 3 is a flattened surface with mounting holes 32 defined therein for securing the common rail 1 to the diesel engine.

[0059] For marine common rail pipes, stress concentration will occur around the intersection hole between the inlet and outlet oil channels 102 and the inner cavity 101 under the action of high-pressure fuel, thus becoming a structural weak point of the common rail pipe 1. Considering that the axial dimension of the common rail pipe is relatively long and the characteristic dimension of the intersection hole is relatively small compared to the overall dimension of the common rail pipe, the calculation scale of modeling the entire common rail pipe is large, time-consuming, and even difficult to perform.

[0060] Therefore, a method for evaluating the strength of a marine common rail pipe is proposed in the embodiment of the present application. Figure 2 As shown, the specific steps include:

[0061] S1: Create or intercept the common rail geometry model for calculation.

[0062] In this embodiment, a portion of the common rail pipe 1 is cut along the axis of the common rail pipe 1, which is called the common rail pipe section 10. Figure 3 As shown, the common rail segment 10 and the bracket 3 are used together as the common rail geometric model for calculation. The common rail geometric model includes at least the common rail segment 10, and the bracket 3 is not essential within the scope of the present invention. In this embodiment, the bracket 3 is used as a carrier for applying the displacement boundary condition to eliminate the rigid body displacement of the model. This is merely a specific example of the implementation of the present invention. However, those skilled in the art will readily understand that subsequent modeling and calculation can be performed only on the common rail segment 10, and the calculation can also be completed by applying the displacement boundary condition to the common rail segment 10.

[0063] like Figure 3 The common rail pipe section 10 at least includes a common rail pipe inner cavity 101, an inlet and outlet oil channel 102, and a fillet 103 of the intersection hole at the intersection of the two. It is worth noting that the fillet 103 of the intersection hole here is broad within the scope of the embodiment of the present invention, including other arc surface transition structures such as circular arc and elliptical arc. In the embodiment of the present invention, an arc structure is adopted for convenience.

[0064] As attached Figure 3As shown, in this embodiment, the diameter of the common rail tube cavity 101 is set to D, and the distances between the axis of the inlet and outlet oil passages 102 and the left and right end surfaces of the intercepted common rail tube section 10 are L1 and L2, respectively. L1=L2 is not strictly required, but it is preferred to ensure that the ratios of L1, L2, and D are within a certain range, for example, L1 / D=N1 and L2 / D=N2. It is recommended that 0.7≤N1≤3 and 0.7≤N2≤3. In this embodiment, N1=N2=2 is selected.

[0065] In addition, in this embodiment, considering that the common rail pipe section 10 and the bracket 3 have a good planar symmetrical structure, half of them are also cut off for subsequent finite element calculations.

[0066] In the embodiment of the present application, the common rail pipe geometric model intercepted in step S1 can also be recreated according to the requirements using a variety of modeling software, or created using the geometric modeling function of finite element software.

[0067] S2: Based on the common rail geometry model, a common rail mesh model is established for calculation, and material properties are assigned to it and analysis steps are set.

[0068] In this embodiment, the common rail pipe geometric model is imported into the finite element analysis software ANSYS to establish a common rail pipe mesh model for calculation, including:

[0069] Material properties are assigned to the common rail pipe section 10, and the material model is at least an elastic-plastic model that includes deformation data in the plastic zone. In this embodiment, the material model specifically adopts a bilinear elastic-plastic model. 930 MPa is set as the material yield point, that is, the critical stress value at which the material transitions from elastic deformation to plastic deformation. The true strain corresponding to 1080 MPa is set to 0.11.

[0070] As for the material properties of the bracket 3, since it is not the focus, only the linear elastic material properties are set.

[0071] The grid of the common rail pipe section 10 is a second-order tetrahedron grid. At the intersection hole fillet 103, the grid is set to 4 layers along the circumferential direction of the fillet, and the grid transition rate is set to 1.4. Figure 4 shown.

[0072] Contact is set between the common rail pipe section 10 and the bracket 3. The contact property is a Coulomb friction model. It can also be set to a binding contact.

[0073] A fixed constraint is applied to the mounting hole of the common rail bracket 3 .

[0074] In some embodiments of the present application, after completing step S2, the number of calculation and analysis steps is set to 3, i.e., steps S3-S5 are executed. It is worth noting that to perform the common rail strength calculation and evaluation at different stages in subsequent steps S3-S5, different analysis steps can be sequentially created within the common rail grid model, with different loads set within each analysis step to represent the different stages of the common rail. For ease of comparison and understanding, in embodiments of the present invention, the load setting process for different analysis steps is placed within steps S3-S5. This does not necessarily require resetting the model after completing step S3. In other words, the model setup for all stages can be completed simultaneously within the common rail grid model, with subsequent evaluations only requiring separate evaluations.

[0075] S3: Based on the common rail grid model, the strength calculation and evaluation of the common rail strengthening process are performed.

[0076] At different stages of the common rail pipe, since the end cover 2 is subjected to the pressure of the medium in the pipe, an equivalent load must be applied to both end surfaces of the common rail pipe section 10. The equivalent load can be the equivalent force F eq Or equivalent pressure P eq , calculated according to formula (1) and formula (2):

[0077] F eq =P·S seal (1)

[0078]

[0079] Among them, F eq For equivalent effect, N; S seal is the sealing area between the common rail pipe 1 and the end cover 2, mm 2 ;P eq is the equivalent pressure, MPa; S1 is the cross-sectional area of ​​the left and right end surfaces of the common rail pipe section 10, mm 2 ; P is the medium pressure in the common rail pipe 1 at different stages, MPa; If a line seal is used between the common rail pipe 1 and the end cover 2, assuming the seal diameter is D1 (unit: mm), then:

[0080]

[0081] In this embodiment, the sealing diameter D1 of the common rail pipe 1 and the end cover 2 is 40 mm, and the medium pressure P during the common rail pipe strengthening process is 250 MPa. According to formula (1), the equivalent force F applied to the left and right end surfaces of the common rail pipe section 10 can be calculated as follows: eq =314000N. Since a symmetrical model is used, the equivalent force F is loaded in the finite element model. eq =157000N, as attached Figure 5 shown.

[0082] During the strengthening process, the surface of the common rail tube cavity 101, the surface of the oil inlet and outlet channel 102, and the rounded surface of the intersection hole 103 are all subjected to the action of the high-pressure medium. A pressure load P = 250MPa is applied to the above surfaces. Figure 5 shown.

[0083] Perform finite element calculations and extract the results of the corresponding analysis step, including equivalent stress values, equivalent plastic strain values, etc. Focus on the equivalent stress values ​​and equivalent plastic strain results around the fillet 103 of the intersection hole. Since stress concentration usually occurs there, the equivalent stress peak value and the equivalent plastic strain peak value are both located at this structure.

[0084] The equivalent stress value and the equivalent plastic strain value of the common rail pipe section 10 in the strengthening stage are calculated.

[0085] If the maximum equivalent stress value is greater than or equal to the material yield strength, compare whether the equivalent plastic strain value is less than the ratio of the material's elongation after fracture to the first preset safety factor; if so, the common rail pipe strength at this stage is considered qualified, and step S4 is executed; if not, the common rail pipe strength during the strengthening process is considered unqualified;

[0086] If the maximum equivalent stress value is less than the ratio of the material yield strength to the second preset safety factor, the common rail pipe strength at this stage is considered qualified. a32 The recommended value is between 1 and 3.

[0087] See attached Figure 6 and Figure 7 In this embodiment, the first preset safety factor S a31 The recommended value is between 1 and 3. In this embodiment, it is specifically 1, and the elongation of the material is 0.12. It can be seen that the maximum equivalent stress is 969.96MPa> the material yield strength (930MPa), and the maximum equivalent plastic strain is 0.00248<the elongation of the material / S a31 =0.12, indicating that the strength of the common rail pipe section is qualified during the strengthening stage.

[0088] S4: Based on the common rail grid model, the strength calculation and evaluation after load unloading are performed after the strengthening process.

[0089] In this embodiment, since there is no pressure load within the common rail pipe 1 after load unloading, the equivalent forces applied to the left and right end surfaces of the common rail pipe segment 10 are set to 0. The pressure loads on the surfaces of the common rail pipe lumen 101, the inlet and outlet oil passages 102, and the intersection hole fillet 103 are also set to 0. In other words, the equivalent loads applied to the end surfaces of the common rail pipe segment mesh model are canceled, as are the pressure loads applied to the surfaces of the common rail pipe lumen 101, the inlet and outlet oil passages 102, and the intersection hole fillet 103.

[0090] If the extracted maximum equivalent stress value is greater than or equal to the ratio of the material yield strength to the fourth preset safety factor, the common rail pipe strength at this stage is considered unqualified, otherwise it is qualified.

[0091] The equivalent stress cloud diagram obtained by extraction is attached. Figure 8 , the maximum equivalent stress is 351.29 MPa, still located at the corner 103 of the intersection hole, and the fourth preset safety factor S in this embodiment a4 Specifically, take 1, the maximum equivalent stress < material yield strength / S a4 =930MPa, indicating that the strength of the common rail pipe is qualified at this stage.

[0092] S5: Based on the common rail grid model, the strength of the common rail is calculated and evaluated in the working state after load unloading.

[0093] In this embodiment, in the working state, the medium (fuel) pressure in the common rail pipe 1 is 150 MPa. According to formula (1), the equivalent force F applied to the left and right end surfaces of the common rail pipe section 10 can be calculated as eq It is 188400N. Due to the symmetrical model, the equivalent force is 94200N in the finite element model, and a pressure load of 150MPa is applied to the surface of the common rail tube cavity 101, the surface of the inlet and outlet oil channels 102, and the surface of the intersection hole fillet 103.

[0094] Extract the equivalent stress cloud diagram of the common rail pipe section 10. See the attached Figure 9 In this embodiment, the fifth preset safety factor S a5 Taking the value as 1, it can be seen that the maximum equivalent stress is 582.78MPa < material yield strength / S a5 =930MPa, based on which it is judged that the strength of the common rail pipe at this stage is qualified.

[0095] In summary, after strength assessment of the common rail pipe in the three stages of strengthening, unloading and working status, all of them are qualified, so the final conclusion is that the strength of the common rail pipe is qualified.

[0096] When a common rail pipe has multiple opening structures, that is, the structural parameters of the oil inlet and outlet passages 102 and the intersection hole fillet 103 are inconsistent, it is only necessary to repeat steps S1 to S5 of the present invention for similar structures with different structural parameters.

[0097] In other embodiments of the present application, after completing step S2, the number of calculation and analysis steps is set to 1, that is, step S6 is executed to calculate and evaluate the strength of the common rail pipe in the working state based on the common rail pipe grid model.

[0098] Step S6 includes:

[0099] S61, applying equivalent loads to both end surfaces of the common rail pipe segment grid model according to the pressure in the working state and the sealing area between the common rail pipe 1 and the end cover 2;

[0100] S62, applying a pressure load on the surface of the common rail inner cavity 101, the surface of the oil inlet and outlet passages 102, and the surface of the intersection hole fillet 103, wherein the value of the applied pressure load is equal to the pressure in the working state;

[0101] S63, perform finite element calculation, extract the equivalent stress value and equivalent plastic strain value of the common rail pipe section 10 and perform common rail pipe strength assessment; specifically: if the maximum equivalent stress value is greater than or equal to the material yield strength, compare whether the equivalent plastic strain value is less than the ratio of the material's elongation after fracture to the sixth preset safety factor; if so, it is considered that the common rail pipe strength at this stage is qualified; if not, it is considered that the common rail pipe strength is unqualified; if the maximum equivalent stress value is less than the material yield strength, compare whether the maximum equivalent stress value is less than the ratio of the material yield strength to the fifth preset safety factor; if so, it is considered that the common rail pipe strength is qualified; if not, it is considered that the common rail pipe strength is unqualified.

[0102] The sixth preset safety factor S a6 The recommended value range is 1 to 3.

[0103] It will be understood by those skilled in the art that the present invention can also be used to guide the design of common rail pipe structural parameters. For example, for different inlet and outlet oil channel diameters and intersection hole fillet radius parameters, the rationality of the parameters can be evaluated according to the present invention, and thus the above process is also within the scope of the present invention.

[0104] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referenced to each other.

[0105] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they become aware of the basic creative concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0106] It should also be noted that, in this document, the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are for the purpose of facilitating the description of the present invention and simplifying the description, rather than indicating or implying that the devices or components referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention. In addition, relational terms such as "first" and "second" are used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any actual relationship or order between these entities or operations, nor should they be understood as indicating or implying relative importance. Moreover, the terms "comprises", "includes" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device comprising a series of elements does not include those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or terminal device comprising the element.

[0107] The technical solutions provided by the present invention have been described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is intended only to facilitate understanding of the present invention, and the contents of this specification should not be construed as limiting the present invention. Furthermore, those skilled in the art will appreciate that various modifications may be made to the specific implementation methods and scope of application according to the present invention. It is not necessary and impossible to exhaustively enumerate all implementation methods herein, and any obvious variations or modifications derived therefrom remain within the scope of protection of the present invention.

Claims

1. A method for evaluating the strength of a marine common rail pipe, characterized in that: The following steps are involved: S1: Create or intercept the common rail geometry model for calculation; S2: Based on the common rail geometry model, create a common rail mesh model for calculation, assign material properties, and set analysis steps. If the analysis step set is three, execute: S3: Based on the common rail grid model, the strength calculation and evaluation of the common rail strengthening process are performed; S4: Based on the common rail grid model, the strength calculation and evaluation after load unloading are carried out after the strengthening process; S5: Based on the common rail grid model, the strength of the common rail is calculated and evaluated in the working state after load unloading. If the common rail pipe strength is assessed as qualified in steps S3-S5, the final strength of the common rail pipe is assessed as qualified, otherwise it is unqualified; or When the analysis step is set to one, execute: S6: Based on the common rail grid model, calculate and evaluate the strength of the common rail under working conditions.

2. The marine common rail strength assessment method according to claim 1, characterized in that: In step S1, The common rail pipe geometric model comprises a common rail pipe section (10), wherein the common rail pipe section (10) at least comprises a common rail pipe inner cavity (101), an inlet and outlet oil passage (102), and a connecting hole fillet (103); The common rail pipe section (10) is a certain solid part of the common rail pipe (1) along the axial direction, the inlet and outlet oil passages (102) are connected with the common rail pipe inner cavity (101), and the intersection hole fillet (103) is a cambered transition structure at the connection point between the inlet and outlet oil passages (102) and the common rail pipe inner cavity (101); The distance L1 between the left end face of the common rail pipe section (10) and the center line of the inlet and outlet oil passage (102) is the product of a first preset typical value N1 and a diameter D of the common rail pipe inner cavity (101); The distance L2 between the right end surface of the common rail pipe section (10) and the center line of the inlet and outlet oil passage (102) is the product of a second preset typical value N2 and the diameter D of the inner cavity (101).

3. A marine common rail strength assessment method according to claim 2, characterized in that: The size (103) of the fillet of the intersection hole is R0.3~R1.0, the value range of the first preset typical value N1 is 0.7≤N1≤3, and the value range of the second preset typical value N2 is 0.7≤N2≤3.

4. A marine common rail strength assessment method according to claim 2, characterized in that: In step S2, the common rail grid model includes at least a grid model of the common rail section; The material properties of the common rail pipe section (10) are at least an elastic-plastic constitutive model including deformation data of the plastic zone; The grid model of the common rail pipe section (10) adopts a second-order tetrahedral grid, the number of grid layers along the circumferential direction of the fillet at the intersection hole fillet (103) is ≥2, and the grid transition rate is ≤1.

5.

5. A marine common rail strength assessment method according to claim 1, characterized in that: Step S3 includes: S31, applying equivalent loads to both end faces of the common rail section grid model according to the pressure during the strengthening process and the size of the sealing area between the common rail pipe (1) and the end cover (2); S32, applying a pressure load to the surface of the common rail tube inner cavity (101), the surface of the inlet and outlet oil passages (102), and the surface of the intersection hole fillet (103), wherein the value of the applied pressure load is equal to the value of the strengthening process pressure; S33, performing finite element calculation to extract the equivalent stress value and equivalent plastic strain value of the common rail pipe section (10), and performing strength assessment using the extracted equivalent stress value and equivalent plastic strain value.

6. A marine common rail strength assessment method according to claim 5, characterized in that: Step S33 includes: S331: If the maximum equivalent stress value is greater than or equal to the material yield strength, compare whether the maximum equivalent plastic strain value is less than the ratio of the material's elongation after fracture to a first preset safety factor; if so, the common rail strength at this stage is considered qualified, and step S4 is executed; if not, the common rail strength during the strengthening process is considered unqualified; S332: If the maximum equivalent stress value is less than the material yield strength, compare whether the maximum equivalent stress value is less than the ratio of the material yield strength to the second preset safety factor; if so, it is considered that the strength of the common rail pipe at this stage is qualified, and then execute step S4; if not, it is considered that the strength of the common rail pipe during the strengthening process is unqualified.

7. A marine common rail strength assessment method according to claim 6, characterized in that: Step S4 includes: S41, canceling the equivalent loads applied to both end surfaces of the common rail pipe segment grid model, and canceling the pressure loads applied to the surface of the common rail pipe inner cavity (101), the surface of the inlet and outlet oil passages (102), and the surface of the intersection hole fillet (103); S42, performing finite element calculation, extracting the equivalent stress value of the common rail pipe section (10) and performing common rail pipe strength evaluation; If the extracted maximum equivalent stress value is greater than or equal to the ratio of the material yield strength to the fourth preset safety factor, the common rail pipe strength at this stage is considered unqualified, otherwise it is qualified.

8. A marine common rail strength assessment method according to claim 6, characterized in that: Step S5 includes: S51, applying equivalent loads to both end surfaces of the common rail pipe section grid model according to the pressure in the working state and the size of the sealing area between the common rail pipe (1) and the end cover (2); S52, applying a pressure load to the surface of the common rail tube inner cavity (101), the surface of the inlet and outlet oil passages (102), and the surface of the intersection hole fillet (103), wherein the value of the applied pressure load is equal to the value of the pressure in the working state; S53, performing finite element calculation, extracting the equivalent stress of the common rail pipe section (10) and performing common rail pipe strength evaluation; if the extracted maximum equivalent stress is greater than or equal to the ratio of the material yield strength to the fifth preset safety factor, the common rail pipe strength at this stage is considered unqualified, otherwise it is qualified.

9. A marine common rail strength assessment method according to claim 8, characterized in that: The value range of the first preset safety factor, the second preset safety factor, the fourth preset safety factor, the fifth preset safety factor and the sixth preset safety factor is 1-3.

Images