An ahp-based diesel engine body-cylinder head joint surface seal failure evaluation method and system

Abstract

The present application relates to a kind of diesel engine body-cylinder cover joint surface sealing failure evaluation method and system based on AHP, method includes: based on the key influence parameter of the core characterization parameter of body-cylinder cover joint surface sealing performance, AHP evaluation model is constructed;Based on the AHP evaluation model, judgment matrix is constructed, and consistency check is carried out;Based on the judgment matrix after consistency check, the weight of index is calculated;Body-cylinder cover combination structure finite element model is constructed, and finite element simulation is carried out;Simulation data are normalized, the weight of index determined in combination with AHP evaluation model, calculate comprehensive sealing performance index, according to the size quantization evaluation sealing failure risk of index, the performance of different schemes is sorted out.The present application provides clear direction for sealing structure optimization design, effectively reduce sealing failure probability, improve engine reliability.

Description

Technical Field

[0001] This invention relates to the field of diesel engine sealing performance evaluation technology, and in particular to a method and system for evaluating the sealing failure of the diesel engine block-cylinder head mating surface based on AHP. Background Technology

[0002] As diesel engines develop towards higher power density and higher burst pressure, the sealing environment at the engine block-cylinder head mating surface becomes increasingly demanding. Seal failure in this area typically manifests as air leakage, water leakage, or oil leakage, directly impacting the engine's power, fuel economy, and reliability. Current mainstream research on diesel engine sealing is as follows: 1. Finite element analysis of sealing characteristics: By establishing finite element models, parameters such as contact pressure and stress distribution of the seal are calculated to evaluate the sealing effect. For example, Dong Hongquan et al. established a finite element analysis model of the cylinder head gasket sealing characteristics of a diesel engine combustion chamber and evaluated the sealing effect of the combustion chamber after power enhancement by using contact pressure; Yang Dongya et al. used the maximum contact stress and the maximum von Mises stress as evaluation indicators and obtained the optimal parameters of the sealing structure through response surface optimization.

[0003] 2. Study on single-target sealing performance: Research focuses on a single influencing factor or a single evaluation objective. For example, Heming Cheng et al. studied the influence of working pressure and preload ratio of rubber O-rings on contact stress, and Yi Ma et al. constructed a transient thermo-mechanical coupling model of rubber seals to analyze the contact width and maximum contact pressure during dynamic processes.

[0004] 3. Traditional multifactor analysis method: Some studies attempt to consider the influence of multiple factors, but lack systematic quantitative assessment models, fail to clarify the relative importance weight of each factor, and are unable to achieve a comprehensive quantitative ranking of multiple objectives.

[0005] Existing technologies have significant shortcomings: they focus primarily on performance analysis of a single objective and have not yet established a quantitative sealing failure assessment model with multiple objectives (multiple criteria). They are unable to accurately quantify core indicators such as contact stress, contact stress uniformity, and contact width, as well as the weights of each influencing parameter. This results in highly subjective and inaccurate assessment results, making it difficult to effectively support the positive design of sealing structures and the prediction of failure risks. Summary of the Invention

[0006] Existing diesel engine block-cylinder head mating surface sealing performance evaluation methods lack multi-objective, quantitative failure assessment models. These models fail to accurately quantify the weights of core criteria and influencing parameters, resulting in low accuracy, high subjectivity, and difficulty in effectively predicting sealing failure risks. This invention aims to propose an AHP-based diesel engine block-cylinder head mating surface sealing failure assessment method and system. By constructing a hierarchical assessment model and clarifying the weights and priorities of each indicator, and combining finite element simulation data, it achieves accurate quantitative assessment of sealing failure, providing support for the optimized design of sealing structures.

[0007] To achieve the above objectives, the present invention provides the following solution: A method for assessing the seal failure of the diesel engine block-cylinder head mating surface based on AHP includes: Based on the core characterization parameters and key influencing parameters of the sealing performance of the engine block-cylinder head mating surface, an AHP evaluation model is constructed. Based on the AHP evaluation model, a judgment matrix is ​​constructed, and a consistency check is performed; Calculate the indicator weights based on the judgment matrix after consistency verification; Construct a finite element model of the engine block-cylinder head composite structure and perform finite element simulation. The simulation data is normalized, and the index weights determined by the AHP evaluation model are combined to calculate the comprehensive sealing performance index. The risk of sealing failure is quantitatively assessed based on the index size, and the performance ranking of different schemes is achieved.

[0008] Optionally, the AHP evaluation model includes: a target layer, a criterion layer, and an indicator layer; The target layer is: the failure of the seal at the joint surface of the diesel engine block and cylinder head. The criteria layer includes three core physical quantities: contact stress, contact stress uniformity, and contact width. The indicator layer includes: bolt preload, burst pressure, fluororubber hardness, bolt preload sequence, gas pad thickness, and gas pad elastic modulus.

[0009] Optionally, based on the AHP evaluation model, a judgment matrix is ​​constructed, and a consistency check is performed, including: According to the 1-9 scaling method, judgment matrices for the target layer-criteria layer and the criteria layer-indicator layer are constructed respectively. The eigenvectors and the maximum eigenvalue are calculated by the product root method, and consistency is tested. The eigenvectors are the preliminary weight vectors that reflect the relative importance of each evaluation indicator, i.e., the factors of the criteria layer or indicator layer, and their elements correspond to the relative priority proportion of each indicator in the judgment matrix.

[0010] Optionally, based on the judgment matrix after the consistency test, the calculation of the indicator weights includes: After passing the consistency test, the feature vector is normalized to obtain the weights of the criterion layer and the index layer, and to clarify the priority of each factor's influence on sealing failure.

[0011] Optionally, constructing a finite element model of the engine block-cylinder head composite structure and performing finite element simulations includes: A finite element model of the engine block-cylinder head composite structure was constructed, and material properties, contact relationships, and load conditions were set. Through simulation, contact stress, contact stress uniformity, and contact width data under different schemes were extracted.

[0012] A diesel engine block-cylinder head mating seal failure assessment system based on AHP includes: Model building module: used to build AHP evaluation model based on the core characterization parameters and key influencing parameters of the sealing performance of the engine block-cylinder head mating surface; The matrix construction module is used to construct a judgment matrix based on the AHP evaluation model and perform consistency checks. The indicator calculation module is used to calculate indicator weights based on the judgment matrix after consistency verification. The simulation module is used to build a finite element model of the engine block-cylinder head composite structure and perform finite element simulation. The sealing failure assessment module is used to normalize simulation data, calculate the comprehensive sealing performance index by combining the index weights determined by the AHP assessment model, quantify the sealing failure risk based on the index size, and achieve performance ranking of different schemes.

[0013] Optionally, the AHP evaluation model includes: a target layer, a criterion layer, and an indicator layer; The target layer is: the failure of the seal at the joint surface of the diesel engine block and cylinder head. The criteria layer includes three core physical quantities: contact stress, contact stress uniformity, and contact width. The indicator layer includes: bolt preload, burst pressure, fluororubber hardness, bolt preload sequence, gas pad thickness, and gas pad elastic modulus.

[0014] Optionally, in the matrix construction module: Based on the 1-9 scaling method, judgment matrices for the target layer-criteria layer and the criterion layer-indicator layer are constructed respectively. The eigenvectors and the largest eigenvalue are calculated by the product root method, and consistency checks are performed.

[0015] Optionally, in the indicator calculation module: After passing the consistency test, the feature vector is normalized to obtain the weights of the criterion layer and the index layer, and to clarify the priority of each factor's influence on sealing failure.

[0016] Optionally, in the simulation module: A finite element model of the engine block-cylinder head composite structure was constructed, and material properties, contact relationships, and load conditions were set. Through simulation, contact stress, contact stress uniformity, and contact width data under different schemes were extracted.

[0017] The beneficial effects of this invention are as follows: This invention constructs an AHP hierarchical evaluation model comprising a target layer, a criterion layer, and an index layer. It integrates three core criteria: contact stress, contact stress uniformity, and contact width. By employing the 1-9 scaling method and consistency checks, it accurately quantifies the weights of each index. Combined with finite element simulation data, it achieves multi-objective quantitative evaluation of sealing performance. This not only solves the problems of single-objective evaluation and subjective judgment bias in existing technologies, but also accurately predicts the sealing failure risk of different schemes. The process is clear and highly operable, applicable to complex sealing systems such as high-power-density diesel engines. It provides a clear direction for the optimized design of sealing structures, effectively reduces the probability of sealing failure, and improves engine reliability. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a diesel engine block-cylinder head mating surface seal failure assessment method based on AHP according to an embodiment of the present invention; Figure 2 This is a hierarchical structure diagram of the diesel engine block-cylinder head mating surface sealing evaluation model according to an embodiment of the present invention; Figure 3 This is a judgment matrix diagram of the target layer - criterion layer (AC) and the criterion layer - index layer (C1-D, C2-D, C3-D) in an embodiment of the present invention; Figure 4 This is a schematic diagram of the CAD model (cross-sectional view) and finite element mesh model of the engine block-cylinder head combined structure according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the contact stress of the cylinder head gasket in an embodiment of the present invention; Figure 6 This is a polar coordinate diagram of the circumferential distribution of contact stress in oil holes, water holes, and air holes according to an embodiment of the present invention. Figure 7 This is a bar chart showing the average contact stress at each hole location in an embodiment of the present invention. Figure 8This is a schematic diagram illustrating the normalization and evaluation results of different schemes in this embodiment of the invention. Figure 9 This is a schematic diagram illustrating the index layer normalization and evaluation results of different schemes in embodiments of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1 As shown in the figure, this embodiment proposes a method for assessing the seal failure of the diesel engine block-cylinder head mating surface based on AHP, including: Based on the core characterization parameters and key influencing parameters of the sealing performance of the engine block-cylinder head mating surface, an AHP evaluation model is constructed. Based on the AHP evaluation model, a judgment matrix is ​​constructed, and a consistency check is performed; Calculate the indicator weights based on the judgment matrix after consistency verification; Construct a finite element model of the engine block-cylinder head composite structure and perform finite element simulation. The simulation data is normalized, and the index weights determined by the AHP evaluation model are combined to calculate the comprehensive sealing performance index. The risk of sealing failure is quantitatively assessed based on the index size, and the performance ranking of different schemes is achieved.

[0023] Furthermore, an AHP evaluation model was constructed, consisting of three layers: the target layer, the criterion layer, and the indicator layer. The target layer is "diesel engine block-cylinder head mating surface seal failure"; the criterion layer selects three core physical quantities: contact stress, contact stress uniformity, and contact width; the indicator layer includes six parameters: bolt preload, burst pressure, fluororubber hardness, bolt preload sequence, gas cushion thickness, and gas cushion elastic modulus. Among these, contact stress, contact stress uniformity, and contact width are the core characterization parameters of the engine block-cylinder head mating surface seal performance, while the six parameters—bolt preload, burst pressure, fluororubber hardness, bolt preload sequence, gas cushion thickness, and gas cushion elastic modulus—are the key influencing parameters.

[0024] Furthermore, based on the AHP evaluation model, a judgment matrix is ​​constructed, and consistency checks are performed, including: Based on the 1-9 scale method, combined with expert experience and engineering practice, judgment matrices for the target layer-criteria layer and the criteria layer-indicator layer are constructed respectively. The eigenvectors and the largest eigenvalue are calculated by the product root method, and consistency checks are performed (CR<0.10 is considered qualified).

[0025] Specifically, in the AHP evaluation model of this embodiment, the eigenvector is a preliminary weight vector reflecting the relative importance of each evaluation indicator (criteria layer or indicator layer factor), and its elements correspond to the relative priority proportion of each indicator in the judgment matrix. After eigenvector normalization, the final weight of each indicator can be directly obtained, which is the core intermediate parameter for quantifying the importance of the indicators.

[0026] This embodiment uses the product root method to calculate the eigenvectors of the judgment matrix. The specific steps are as follows: (1) Calculate the product of the elements in each row of the judgment matrix: Let the judgment matrix be... ( (where the number of indicators is ), multiply the elements in each row: (2) Calculate the product of each row. The right root: , to obtain the initial feature vector ; (3) Normalization: Divide each element of the initial feature vector by the sum of all elements to obtain the normalized feature vector. ,in, This vector represents the initial weight of each indicator.

[0027] Furthermore, based on the judgment matrix after the consistency check, the index weights are calculated as follows: After passing the consistency test, the feature vector is normalized to obtain the weights of the criterion layer and the index layer, and to clarify the priority of each factor's influence on sealing failure.

[0028] Furthermore, a finite element model of the engine block-cylinder head composite structure is constructed, and finite element simulation is performed, including: A finite element model of the engine block-cylinder head composite structure was constructed, and material properties, contact relationships, and load conditions were set. Through simulation, contact stress, contact stress uniformity, and contact width data under different schemes were extracted.

[0029] Figure 2 This diagram illustrates the hierarchical structure of the diesel engine block-cylinder head mating surface sealing evaluation model. Figure 3 The judgment matrix diagrams of the target layer-criteria layer (AC) and the criteria layer-indicator layer (C1-D, C2-D, C3-D) are shown. Figure 4 The CAD model (section view) and finite element mesh model of the engine block-cylinder head assembly structure are displayed. Figure 5 A schematic diagram of cylinder head gasket contact stress is shown; Figure 6 The polar coordinate diagrams of the circumferential distribution of contact stress in oil holes, water holes, and air holes are displayed. Figure 7 A bar chart showing the average contact stress at each hole location is presented. Figure 8 The results of criterion-level normalization and evaluation for different schemes are presented. Figure 9 The results of index level normalization and evaluation for different schemes are presented. Figure 2 Clearly define the hierarchical structure of the evaluation model; Figure 3 This serves as the core basis for weight calculation; Figure 4-7 Displaying finite element models and simulation data; Figures 8-9 This is a quantitative result for the assessment of seal failure.

[0030] The following study uses a V10 high-strength diesel engine as the research object and employs the method of this embodiment to evaluate seal failure.

[0031] Construct an AHP evaluation model: The target layer is "diesel engine block-cylinder head mating surface seal failure"; the criteria layer is contact stress (C1), contact stress uniformity (C2), and contact width (C3); the index layer is bolt preload (d1), burst pressure (d2), fluororubber hardness (d3), bolt preload sequence (d4), gas cushion thickness (d5), and gas cushion elastic modulus (d6).

[0032] Constructing the judgment matrix and consistency check: Construct judgment matrices AC, C1-D, C2-D, and C3-D according to the 1-9 scaling method. Calculate the results using the product root method: the largest eigenvalue of matrix AC is 3.038, CR=0.0328; the largest eigenvalue of matrix C1-D is 6.318, CR=0.0513; both satisfy the consistency requirement of CR<0.10.

[0033] Weights were calculated as follows: After normalization, the weights of the criterion layer were C1=0.637, C2=0.258, and C3=0.105; the total weights of the indicator layer were d1=0.278, d3=0.197, d4=0.169, d5=0.154, d6=0.086, and d2=0.058.

[0034] Finite element simulation: A finite element model of the combined structure was established. The body material was AlSi7Mg-T6, the cylinder head was GJV-300, and the cylinder head gasket rubber ring adopted the Mooney-Rivlin hyperelastic model (C10=1.5, C01=0.4). Bolt preload was applied, and the sealing parameters of 6 schemes were extracted (e.g., Scheme 6: contact stress 21.00MPa, uniformity 0.15, contact width 3.10mm).

[0035] Comprehensive evaluation: After normalizing the sealing parameters and calculating the comprehensive performance index based on weights, the ranking of the criteria layer is as follows: Scheme 6 (1.00) > Scheme 3 (0.80) > Scheme 1 (0.40) > Scheme 5 (0.28) > Scheme 2 (0.21) > Scheme 4 (0.15). The ranking of the index layer is consistent, verifying the effectiveness of the model. Scheme 4 has the highest risk of seal failure due to low bolt preload (110kN), low rubber hardness (63HA), and high burst pressure (26MPa); Scheme 6 has the best parameter combination and the lowest risk of failure.

[0036] This embodiment also proposes a diesel engine block-cylinder head mating surface seal failure assessment system based on AHP, including: Model building module: used to build AHP evaluation model based on the core characterization parameters and key influencing parameters of the sealing performance of the engine block-cylinder head mating surface; The matrix construction module is used to construct a judgment matrix based on the AHP evaluation model and perform consistency checks. The indicator calculation module is used to calculate indicator weights based on the judgment matrix after consistency verification. The simulation module is used to build a finite element model of the engine block-cylinder head composite structure and perform finite element simulation. The sealing failure assessment module is used to normalize simulation data, calculate the comprehensive sealing performance index by combining the index weights determined by the AHP assessment model, quantify the sealing failure risk based on the index size, and achieve performance ranking of different schemes.

[0037] Furthermore, the AHP evaluation model includes: target layer, criterion layer, and indicator layer; The target layer is: failure of the seal at the joint surface of the diesel engine block and cylinder head; The criteria layer includes three core physical quantities: contact stress, contact stress uniformity, and contact width. The indicator layer includes: bolt preload, burst pressure, fluororubber hardness, bolt preload sequence, gas pad thickness, and gas pad elastic modulus.

[0038] Furthermore, in the matrix construction module: Based on the 1-9 scaling method, judgment matrices for the target layer-criteria layer and the criteria layer-indicator layer are constructed respectively. The eigenvectors and the largest eigenvalue are calculated by the product root method, and consistency checks are performed.

[0039] Furthermore, in the indicator calculation module: After passing the consistency test, the feature vector is normalized to obtain the weights of the criterion layer and the index layer, and to clarify the priority of each factor's influence on sealing failure.

[0040] Furthermore, in the simulation module: A finite element model of the engine block-cylinder head composite structure was constructed, and material properties, contact relationships, and load conditions were set. Through simulation, contact stress, contact stress uniformity, and contact width data under different schemes were extracted.

[0041] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for assessing the seal failure of the diesel engine block-cylinder head mating surface based on AHP, characterized in that, include: Based on the core characterization parameters and key influencing parameters of the sealing performance of the engine block-cylinder head mating surface, an AHP evaluation model is constructed. Based on the AHP evaluation model, a judgment matrix is ​​constructed, and a consistency check is performed; Calculate the indicator weights based on the judgment matrix after consistency verification; Construct a finite element model of the engine block-cylinder head composite structure and perform finite element simulation. The simulation data is normalized, and the index weights determined by the AHP evaluation model are combined to calculate the comprehensive sealing performance index. The risk of sealing failure is quantitatively assessed based on the index size, and the performance ranking of different schemes is achieved.

2. The method for assessing the sealing failure of the diesel engine block-cylinder head mating surface based on AHP according to claim 1, characterized in that, The AHP evaluation model includes: target layer, criterion layer, and indicator layer; The target layer is: the failure of the seal at the joint surface of the diesel engine block and cylinder head. The criteria layer includes three core physical quantities: contact stress, contact stress uniformity, and contact width. The indicator layer includes: bolt preload, burst pressure, fluororubber hardness, bolt preload sequence, gas pad thickness, and gas pad elastic modulus.

3. The method for assessing the seal failure of the diesel engine block-cylinder head mating surface based on AHP according to claim 2, characterized in that, Based on the AHP evaluation model, a judgment matrix is ​​constructed, and consistency checks are performed, including: Based on the 1-9 scaling method, judgment matrices for the target layer-criteria layer and the criteria layer-indicator layer are constructed respectively. The eigenvectors and the largest eigenvalue are calculated by the product root method, and consistency is tested. The eigenvectors are the preliminary weight vectors that reflect the relative importance of each evaluation indicator, i.e., the criteria layer or indicator layer factors, and their elements correspond to the relative priority proportion of each indicator in the judgment matrix.

4. The method for assessing the sealing failure of the diesel engine block-cylinder head mating surface based on AHP according to claim 2, characterized in that, Based on the judgment matrix after consistency verification, the index weights are calculated as follows: After passing the consistency test, the feature vector is normalized to obtain the weights of the criterion layer and the index layer, and to clarify the priority of each factor's influence on sealing failure.

5. The method for assessing the seal failure of the diesel engine block-cylinder head mating surface based on AHP according to claim 1, characterized in that, Constructing a finite element model of the engine block-cylinder head composite structure and performing finite element simulations includes: A finite element model of the engine block-cylinder head composite structure was constructed, and material properties, contact relationships, and load conditions were set. Through simulation, contact stress, contact stress uniformity, and contact width data under different schemes were extracted.

6. A diesel engine block-cylinder head mating surface seal failure assessment system based on AHP for implementing the method as described in any one of claims 1-5, characterized in that, include: Model building module: used to build AHP evaluation model based on the core characterization parameters and key influencing parameters of the sealing performance of the engine block-cylinder head mating surface; The matrix construction module is used to construct a judgment matrix based on the AHP evaluation model and perform consistency checks. The indicator calculation module is used to calculate indicator weights based on the judgment matrix after consistency verification. The simulation module is used to build a finite element model of the engine block-cylinder head composite structure and perform finite element simulation. The sealing failure assessment module is used to normalize simulation data, calculate the comprehensive sealing performance index by combining the index weights determined by the AHP assessment model, quantify the sealing failure risk based on the index size, and achieve performance ranking of different schemes.

7. The diesel engine block-cylinder head mating surface seal failure assessment system based on AHP according to claim 6, characterized in that, The AHP evaluation model includes: target layer, criterion layer, and indicator layer; The target layer is: the failure of the seal at the joint surface of the diesel engine block and cylinder head. The criteria layer includes three core physical quantities: contact stress, contact stress uniformity, and contact width. The indicator layer includes: bolt preload, burst pressure, fluororubber hardness, bolt preload sequence, gas pad thickness, and gas pad elastic modulus.

8. The diesel engine block-cylinder head mating surface seal failure assessment system based on AHP according to claim 7, characterized in that, In the matrix construction module: Based on the 1-9 scaling method, judgment matrices for the target layer-criteria layer and the criterion layer-indicator layer are constructed respectively. The eigenvectors and the largest eigenvalue are calculated by the product root method, and consistency checks are performed.

9. The diesel engine block-cylinder head mating surface seal failure assessment system based on AHP according to claim 7, characterized in that, In the indicator calculation module: After passing the consistency test, the feature vector is normalized to obtain the weights of the criterion layer and the index layer, and to clarify the priority of each factor's influence on sealing failure.

10. The diesel engine block-cylinder head mating surface seal failure assessment system based on AHP according to claim 7, characterized in that, In the simulation module: A finite element model of the engine block-cylinder head composite structure was constructed, and material properties, contact relationships, and load conditions were set. Through simulation, contact stress, contact stress uniformity, and contact width data under different schemes were extracted.

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