Method for evaluating fatigue life of ship body welded joint after shot peening and related equipment

Abstract

The application provides a shot peening reinforced ship body welding joint fatigue life evaluation method and related equipment, and belongs to the technical field of structure fatigue life evaluation. The method comprises the following steps: obtaining an initial S-N curve corresponding to a target ship body welding joint before shot peening reinforcement; determining a fatigue performance influence coefficient introduced after shot peening reinforcement by analyzing fatigue performance data of sample welding joints before and after shot peening reinforcement, wherein the sample welding joints are welding joints with the same material and shape as the target ship body welding joint; correcting the initial S-N curve according to the fatigue performance influence coefficient to obtain a corrected S-N curve; and evaluating the fatigue life of the target ship body welding joint after shot peening reinforcement according to the equivalent structural stress variation range of the target ship body welding joint after shot peening reinforcement and the corrected S-N curve, thereby improving the precision of the fatigue life evaluation of the ship body welding joint after shot peening reinforcement.

Description

Technical Field

[0001] This invention relates to the field of structural fatigue life assessment technology, specifically to a method and related equipment for assessing the fatigue life of welded joints in a ship hull after shot peening. Background Technology

[0002] With the widespread application of shot peening technology in the shipbuilding industry, it has proven effective in improving the fatigue life of ship structures as a life-extending technique. However, accurately quantifying the specific degree to which shot peening enhances the fatigue life of ship structures has become a key research issue.

[0003] Traditional fatigue assessment methods, such as stress-based finite element analysis and hot spot stress methods, have been widely used in fatigue assessment of shipbuilding structures, but they have certain limitations and uncertainties when dealing with fatigue problems of welded joints. These methods often fail to accurately reflect the actual impact of shot peening on fatigue life. Summary of the Invention

[0004] In view of this, it is necessary to provide a method and related equipment for assessing the fatigue life of welded joints of hulls after shot peening, so as to solve the technical problem that it is difficult to accurately quantify the specific improvement of the fatigue life of hull structure by shot peening, resulting in low accuracy of fatigue life assessment of welded joints of hulls after shot peening.

[0005] To address the aforementioned technical problems, in a first aspect, the present invention provides a method for evaluating the fatigue life of welded joints in a ship hull after shot peening, comprising:

[0006] Obtain the initial SN curve of the target hull weld node before shot peening;

[0007] By analyzing the fatigue performance data of the sample welded nodes before and after shot peening, the fatigue performance influence coefficient introduced after shot peening is determined. The sample welded nodes are welded nodes with the same material and shape as the target hull welded nodes.

[0008] The initial SN curve is corrected based on the fatigue performance influence coefficient to obtain the corrected SN curve;

[0009] The fatigue life of the target hull weld joint after shot peening is evaluated based on the range of equivalent structural stress change of the target hull weld joint after shot peening and the modified SN curve.

[0010] In one possible implementation, the fatigue performance data includes residual pressure, and the fatigue performance influence coefficient includes a residual stress influence coefficient; the step of determining the fatigue performance influence coefficient introduced after shot peening by experimentally analyzing the fatigue performance data of the sample weld joints before and after shot peening includes:

[0011] The residual stress distribution of the sample weld joints before and after shot peening was measured experimentally.

[0012] Based on fracture mechanics theory and fatigue material theory, the residual stress influence coefficient is calculated in conjunction with the residual stress distribution.

[0013] In one possible implementation, the fatigue performance data includes hardness, and the fatigue performance influence coefficient includes a surface hardening influence coefficient; the step of determining the fatigue performance influence coefficient introduced after shot peening by experimentally analyzing the fatigue performance data of the sample weld joints before and after shot peening includes:

[0014] The surface hardness of the sample weld nodes before and after shot peening was measured experimentally.

[0015] Based on the theory of material hardening and fatigue materials, the surface hardening influence coefficient is calculated in conjunction with the surface hardness.

[0016] In one possible implementation, the fatigue performance data includes surface roughness, and the fatigue performance influence coefficient includes a surface roughness influence coefficient; the step of determining the fatigue performance influence coefficient introduced after shot peening by experimentally analyzing the fatigue performance data of the sample weld joints before and after shot peening includes:

[0017] The surface roughness of the sample weld joints before and after shot peening was measured experimentally.

[0018] Based on the relationship between surface coefficient and fatigue limit, the surface roughness influence coefficient is calculated in conjunction with the surface roughness.

[0019] In one possible implementation, the step of calculating the surface roughness influence coefficient based on the relationship between the surface coefficient and the fatigue limit, combined with the surface roughness, includes:

[0020] Determine the ratio between the first surface roughness of the sample weld node before shot peening and the second surface roughness after shot peening;

[0021] Based on the relationship between the surface coefficient and the fatigue limit, the ratio is calculated to obtain the surface roughness influence coefficient.

[0022] In one possible implementation, the step of determining the range of equivalent structural stress change of the target hull weld joint after shot peening includes:

[0023] The maximum and minimum equivalent stress of the target hull weld node after shot peening are determined by measurement. The maximum and minimum equivalent stresses are the equivalent stresses of the first and second regions of the target hull weld node, respectively. The first region is the region where the sum of membrane stress and bending stress is maximized, and the second region is the region where the sum of membrane stress and bending stress is minimized.

[0024] The range of stress variation in the equivalent structure is determined based on the maximum and minimum equivalent stress.

[0025] In one possible implementation, the step of correcting the initial SN curve based on the fatigue performance influence coefficient to obtain a corrected SN curve includes:

[0026] The target parameters in the initial SN curve are corrected based on the fatigue performance influence coefficient, and the target parameters include the range of stress structure variation.

[0027] Secondly, the present invention also provides a device for evaluating the fatigue life of welded joints in a ship hull after shot peening, comprising:

[0028] The acquisition unit is used to acquire the initial SN curve of the target hull weld node before shot peening.

[0029] The determination unit is used to analyze the fatigue performance data of the sample welded nodes before and after shot peening through experiments, and to determine the fatigue performance influence coefficient introduced after shot peening. The sample welded nodes are welded nodes with the same material and shape as the target hull welded nodes.

[0030] The correction unit is used to correct the initial SN curve according to the fatigue performance influence coefficient to obtain the corrected SN curve;

[0031] The evaluation unit is used to evaluate the fatigue life of the target hull weld joint after shot peening based on the range of equivalent structural stress change of the target hull weld joint after shot peening and the modified SN curve.

[0032] Thirdly, the present invention also provides an electronic device, including a memory and a processor, wherein the memory is used to store a program;

[0033] The processor, coupled to the memory, is used to execute the program stored in the memory to implement the steps in the fatigue life assessment method for welded joints of hull after shot peening as described in any of the above implementations.

[0034] Fourthly, the present invention also provides a computer-readable storage medium for storing a computer-readable program or instruction, which, when executed by a processor, can implement the steps in the fatigue life assessment method for welded joints of hulls after shot peening as described in any of the above implementations.

[0035] The beneficial effects of this invention are:

[0036] The fatigue life assessment method for ship hull weld joints after shot peening provided by this invention obtains the initial SN curve of the target ship hull weld joint before shot peening, providing a "zero-treatment" baseline for the fatigue life of the weld joint, which is used to compare the performance improvement after shot peening. By experimentally analyzing the fatigue performance data of sample weld joints before and after shot peening, the fatigue performance influence coefficient introduced after shot peening is determined. The sample weld joints are weld joints with the same material and shape as the target ship hull weld joints, eliminating systematic errors caused by material and geometric differences, thus enabling precise quantification of the contribution of shot peening to fatigue life. Based on the fatigue performance influence coefficient, the initial... The SN curve is corrected to obtain a modified SN curve, which can intuitively reflect the fatigue strength gain brought about by shot peening. In addition, the fatigue performance influence coefficient is combined with the dimensionless characteristic of the fatigue performance influence coefficient. While maintaining the compatibility of the SN curve correction specification, the fatigue life prediction error is controlled within the allowable range of engineering, which significantly improves the quantitative evaluation accuracy of the shot peening effect of the hull weld joint. Based on the equivalent structural stress change range of the target hull weld joint after shot peening and the modified SN curve, the fatigue life of the target hull weld joint after shot peening is evaluated, which improves the accuracy of fatigue life evaluation of the hull weld joint after shot peening. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0038] Figure 1 This is a schematic flowchart of an embodiment of the fatigue life assessment method for welded joints of a ship hull after shot peening provided by the present invention.

[0039] Figure 2 A schematic diagram of a longitudinal girder through-cabin node model of a certain type of aluminum alloy ship hull provided by the present invention;

[0040] Figure 3The residual stress distribution curves along the depth direction of the heat-affected zone of the sample after shot peening with a shot peening intensity of 0.175 mmA under different cycle periods provided by the present invention.

[0041] Figure 4 Hardness distribution curves along the depth direction of the heat-affected zone of the sample after shot peening with a shot peening intensity of 0.175 mmA under different cycle periods provided by the present invention.

[0042] Figure 5 A schematic diagram showing the surface roughness of 5083 aluminum alloy before and after shot peening with a shot peening intensity of 0.175 mmA, provided by the present invention.

[0043] Figure 6 A schematic diagram of an embodiment of the fatigue life assessment device for welded joints of a ship hull after shot peening provided by the present invention;

[0044] Figure 7 A schematic diagram of an embodiment of the electronic device provided by the present invention. Detailed Implementation

[0045] 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 a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0046] In the description of the embodiments of the present invention, unless otherwise stated, "multiple" means two or more. "And / or" describes the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0047] The terms "first," "second," etc., used in the embodiments of this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a technical feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature.

[0048] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0049] The execution subject of the fatigue life assessment method for welded joints of hull after shot peening in this application embodiment can be the fatigue life assessment device for welded joints of hull after shot peening provided in this application embodiment, or different types of electronic devices such as server equipment, physical host, or user equipment (UE) that integrate the fatigue life assessment device for welded joints of hull after shot peening. The fatigue life assessment device for welded joints of hull after shot peening can be implemented in hardware or software. The UE can be a terminal device such as a smartphone, tablet computer, laptop computer, handheld computer, desktop computer, or personal digital assistant (PDA).

[0050] This invention provides a method and related equipment for assessing the fatigue life of welded joints in a ship hull after shot peening, which will be described below.

[0051] Figure 1 This is a schematic flowchart of an embodiment of the fatigue life assessment method for welded joints in a ship hull after shot peening provided by the present invention, as shown below. Figure 1 As shown, the fatigue life assessment method for welded joints in a ship hull after shot peening includes:

[0052] S101. Obtain the initial SN curve of the target hull welding node before shot peening.

[0053] The target hull welding node refers to the hull welding node that requires fatigue life assessment after shot peening. For example, it could be the longitudinal girder penetration node of a certain type of aluminum alloy hull. Figure 2 The image shown is a schematic diagram of a longitudinal rib through-cabin node model for a certain type of aluminum alloy ship hull.

[0054] The S&P / SN curve is used to describe the fatigue life of a material or structure under different stress levels. In the fatigue assessment of welded joints in ship hulls, the initial S&P / SN curve is used to describe the stress variation range of a target ship hull welded joint that has not undergone shot peening under cyclic loading. ΔS s The relationship between the number of failure cycles N and the number of failure cycles is usually expressed in power law form:

[0055]

[0056] in, C d and h These are material constants, obtained by fitting standard fatigue test data.

[0057] Specifically, for welded joints, based on fracture mechanics theory and through numerous fatigue test results of welded joints, SN curves applicable to different types of welded joints under the same material have been summarized. The initial SN curve before shot peening can be obtained according to the material and shape of the target hull welded node, providing a "zero-treatment" baseline for fatigue life of the hull welded node, which can be used to compare the performance improvement after shot peening.

[0058] S102. By analyzing the fatigue performance data of the sample welded nodes before and after shot peening through experiments, the fatigue performance influence coefficient introduced after shot peening is determined. The sample welded nodes are welded nodes with the same material and shape as the target hull welded nodes.

[0059] Among them, the sample welding nodes are welding nodes with the same material and shape as the target ship hull welding nodes, and can be divided into two groups of samples: samples that have not been shot peened and samples that have been shot peened.

[0060] Fatigue performance data includes fatigue performance data before and after shot peening. This data can be obtained by conducting constant amplitude fatigue tests on two sets of samples. The fatigue performance data characterizes data related to fatigue testing, such as the number of cycles N, residual stress data, hardness data, and surface roughness data for different stress variation ranges ΔS.

[0061] The fatigue performance influence coefficient characterizes the amplification factor of fatigue strength after shot peening relative to that without shot peening.

[0062] Specifically, by conducting group fatigue tests on sample welded joints before and after shot peening, recording stress-life (SN) fatigue performance data, and comparing and analyzing the fatigue performance data, a fatigue performance influence coefficient is derived. This coefficient allows for the quantification of the specific improvement in the fatigue life of the hull structure caused by shot peening, enabling the correction of the initial SN curve. Understandably, this embodiment eliminates systematic errors caused by material / geometric differences by experimentally analyzing the fatigue performance data of sample welded joints before and after shot peening, thus enabling precise quantification of the contribution of shot peening to fatigue life.

[0063] S103. The initial SN curve is corrected according to the fatigue performance influence coefficient to obtain the corrected SN curve.

[0064] Specifically, parameters in the initial SN curve, such as the range of equivalent structural stress variation, can be corrected based on the fatigue performance influence coefficient. This allows for the generation of a corrected SN curve after dimensionless conversion of the equivalent structural stress variation range in the initial SN curve. Understandably, since the fatigue performance influence coefficient quantifies the specific improvement in the fatigue life of the hull structure after shot peening, correcting the initial SN curve based on the fatigue performance influence coefficient enables the corrected SN curve to directly reflect the fatigue strength gain brought about by shot peening. Furthermore, by utilizing the dimensionless nature of the fatigue performance influence coefficient, while maintaining the compatibility of the SN curve correction specifications, the fatigue life prediction error is controlled within the allowable engineering range, significantly improving the quantitative evaluation accuracy of the shot peening effect on hull weld joints.

[0065] In one specific implementation, the fatigue performance influence coefficient includes the residual stress influence coefficient. k r Surface hardening influence coefficient k h Surface roughness influence coefficient k s Let's take an example to illustrate:

[0066] To more intuitively illustrate the relationship between the fatigue performance influence coefficient and the initial SN curve, the initial SN curve expression is first transformed into a double logarithmic form, as follows:

[0067]

[0068]

[0069] Furthermore, let's assume the modified SN curve expression for shot peening is as follows:

[0070]

[0071] Based on extensive SN curve data provided by industry associations such as AMSE, IIW, and DNV, it is shown that for nodes of the same material and similar structural form, the slope is usually a fixed value. Based on the principle of equal slopes, assuming m1=m2=m, when both the modified SN curve and the initial SN curve are at their fatigue limits, then:

[0072]

[0073] The fatigue strength relationship between the welded joints of the sample before and after shot peening can be expressed by the following formula:

[0074]

[0075] Therefore:

[0076] In the formula: σ sp The fatigue strength after shot peening; σ 0 represents the fatigue strength before shot peening.

[0077] In summary, the expression for the corrected SN curve after shot peening is as follows:

[0078]

[0079] Therefore, the modified SN curve is a parallel line with a constant slope and an overall leftward shift, which intuitively reflects the fatigue strength gain brought about by shot peening.

[0080] S104. Based on the range of equivalent structural stress change of the target hull weld joint after shot peening and the modified SN curve, evaluate the fatigue life of the target hull weld joint after shot peening.

[0081] The equivalent structural stress variation range is the range by which the stress at a certain point or region in the structure changes from the minimum value to the maximum value under fatigue load.

[0082] Specifically, by substituting the equivalent structural stress variation range into the modified SN curve, the fatigue life can be calculated. Understandably, since the modified SN curve utilizes dimensionless coefficients for correction and can accurately quantify the specific improvement in fatigue life of the hull structure caused by shot peening, the fatigue life can be calculated directly by substituting the equivalent structural stress variation range into the modified SN curve. This assessment method is simple and accurate, improving the precision of fatigue life assessment.

[0083] In summary, the fatigue life assessment method for ship hull weld nodes after shot peening provided in this embodiment of the invention obtains the initial SN curve of the target ship hull weld node before shot peening, providing a "zero-treatment" baseline for the fatigue life of the weld node, which is used to compare the performance improvement after shot peening. By experimentally analyzing the fatigue performance data of the sample weld node before and after shot peening, the fatigue performance influence coefficient introduced after shot peening is determined. The sample weld node is a weld node with the same material and shape as the target ship hull weld node, eliminating systematic errors caused by material and geometric differences, thereby accurately quantifying the contribution of shot peening to fatigue life. Based on the fatigue performance influence coefficient, the initial... The initial SN curve is corrected to obtain a modified SN curve, which can intuitively reflect the fatigue strength gain brought about by shot peening. Furthermore, by combining the fatigue performance influence coefficient, which is dimensionless, the fatigue life prediction error is controlled within the allowable engineering range while maintaining the compatibility of the SN curve correction specifications. This significantly improves the quantitative evaluation accuracy of the shot peening effect on hull weld nodes. Based on the equivalent structural stress change range of the target hull weld node after shot peening and the modified SN curve, the fatigue life of the target hull weld node after shot peening is evaluated, improving the accuracy of fatigue life assessment of hull weld nodes after shot peening.

[0084] In some embodiments of the present invention, the fatigue performance data includes residual pressure, and the fatigue performance influence coefficient includes residual stress influence coefficient; step S102 includes:

[0085] S201. The residual stress distribution of the sample weld joints before and after shot peening is measured experimentally.

[0086] S202. Based on fracture mechanics theory and fatigue material theory, calculate the residual stress influence coefficient in conjunction with the residual stress distribution.

[0087] The residual stress distribution includes the residual stress distribution before and after shot peening. The residual stress influence coefficient reflects the effect of the residual compressive stress introduced by shot peening on fatigue life.

[0088] Fracture mechanics theory focuses on the formation and propagation of cracks within materials. Residual compressive stress can inhibit crack propagation, thereby improving the fatigue life of materials. Materials fatigue theory describes the performance degradation and eventual failure of materials under cyclic loading, and residual compressive stress has a significant impact on the initiation and propagation of fatigue cracks. Therefore, based on fracture mechanics and materials fatigue theories, this paper determines the residual stress influence coefficient and considers the impact of the physical mechanism by which residual stress inhibits crack propagation on the fatigue life of materials.

[0089] Specifically, based on fracture mechanics theory and fatigue material theory, the residual stress distribution before and after shot peening is compared and analyzed, and the residual stress influence coefficient is calculated. By accurately determining the residual stress influence coefficient, the fatigue life of the material after shot peening can be predicted more accurately, thereby optimizing the design and improving the reliability of the structure.

[0090] In one specific implementation, the residual stress influence coefficient k r The specific quantitative analysis methods are as follows:

[0091] For the SN curve, the improvement in fatigue life can be regarded as a scaling effect on the stress range. Based on this premise, a mean stress correction curve with similar function is derived. Referring to the Dietmann curve, it can be expressed as:

[0092]

[0093] In the formula: σ a The stress amplitude before correction; σ -1 The fatigue limit is when the stress ratio R = -1; σ m The average stress before correction; σ u This represents the tensile strength of the material, i.e., the residual stress distribution before shot peening.

[0094] If the peak value of the residual compressive stress after relaxation and stabilization is... σ rr Consider it as the average stress under shot peening, that is, the residual stress distribution after shot peening, and assume... σ a This is the fatigue limit at this point, and its relationship with σ -1 The ratio is the residual stress influence coefficient. k r Under this premise, we can obtain:

[0095]

[0096]

[0097] Substituting the residual stress distribution before and after shot peening into the above formula, the residual stress influence coefficient is calculated. k r The residual stress influence coefficient was achieved. k r Precise quantitative calculations.

[0098] In some embodiments of the present invention, the fatigue performance data includes hardness, and the fatigue performance influence coefficient includes a surface hardening influence coefficient; step S102 includes:

[0099] S301. The surface hardness of the sample weld joints before and after shot peening is measured experimentally.

[0100] S302. Based on the material hardening theory and fatigue material theory, calculate the surface hardening influence coefficient in conjunction with the surface hardness.

[0101] Surface hardness includes the surface hardness before and after shot peening. The surface hardening influence coefficient reflects the impact of shot peening-induced surface hardening on fatigue life.

[0102] Hardening theories, including work hardening (cold work hardening) and phase transformation hardening, explain the mechanism of increased surface hardness in materials. Fatigue material theory, particularly regarding the influence of surface treatment on fatigue crack initiation and propagation, provides the theoretical basis. Therefore, based on material hardening theory and fatigue material theory, the surface hardening influence coefficient is determined, considering the physical mechanism by which surface hardness increases the yield threshold and its impact on material fatigue life.

[0103] Specifically, based on the theories of material hardening and fatigue materials, the surface hardness before and after shot peening is compared and analyzed, and the surface hardness influence coefficient is calculated. By accurately determining the surface hardening influence coefficient, the fatigue life of the material after shot peening can be predicted more accurately, thereby optimizing the design and improving the reliability of the structure.

[0104] In one specific implementation, the surface hardening influence coefficient k h The specific quantitative analysis methods are as follows:

[0105] When considering the actual effect of hardness on a specimen, similar to the calculation principle of the residual stress influence coefficient, it is necessary to base it on a stable value after a certain number of cycles to avoid overestimating its strengthening effect. The modified Goodman formula proposed by Arakawa et al. demonstrates that the hardness of a material exhibits an approximately linear relationship with its yield strength, tensile strength, and other mechanical parameters, as shown in the following formula:

[0106]

[0107]

[0108] In the formula: HV SP To determine the surface hardness after shot peening. HV virgin The surface hardness is before shot peening.

[0109] Substituting the surface hardness before and after shot peening into the above formula, the surface hardening influence coefficient is calculated. k h The surface hardening influence coefficient was achieved. k h Precise quantitative calculations.

[0110] In some embodiments of the present invention, the fatigue performance data includes roughness, and the fatigue performance influence coefficient includes a surface roughness influence coefficient; step S102 includes:

[0111] S401. The surface roughness of the sample weld joints before and after shot peening is measured experimentally.

[0112] S402. Based on the relationship between the surface coefficient and the fatigue limit, calculate the surface roughness influence coefficient in conjunction with the surface roughness.

[0113] Surface roughness includes the surface roughness before and after shot peening. The surface roughness influence coefficient reflects the impact of surface roughness changes caused by shot peening on fatigue life.

[0114] The relationship between surface coefficient and fatigue limit, proposed by Buch, characterizes the impact of variations in surface roughness on the fatigue performance of a sample. Therefore, based on this relationship, a surface roughness influence coefficient is determined, considering the physical mechanism of stress concentration effects caused by surface roughness on the material's fatigue life.

[0115] Specifically, based on the relationship between surface coefficient and fatigue limit, the surface roughness before and after shot peening is compared and analyzed, and the surface roughness influence coefficient is calculated. By accurately determining the surface roughness influence coefficient, the fatigue life of the material after shot peening can be predicted more accurately, thereby optimizing the design and improving the reliability of the structure.

[0116] In one specific implementation, the surface roughness influence coefficient k s The specific quantitative analysis methods are as follows:

[0117] The relationship between the surface coefficient and fatigue limit proposed by Buch can be used to characterize the effect of changes in sample surface roughness on its fatigue performance. The surface coefficient can be expressed by the following formula:

[0118]

[0119] In the formula: C S For surface coefficient, σ dsThe fatigue strength is defined as the fatigue strength of any surface condition without surface polishing. σ d The fatigue strength is the result of fine polishing.

[0120] Due to surface coefficient C S With the surface roughness parameter maximum profile height R z Relatedly, as surface roughness increases, both the surface coefficient and fatigue limit decrease. According to... C S With R z The relationship and its negative correlation are determined using the surface roughness influence coefficient. k s The formula for assessing local fatigue strength is as follows:

[0121]

[0122] In the formula: R ZSP The surface roughness after shot peening. R ZNP This represents the surface roughness before shot peening.

[0123] Substituting the surface roughness before and after shot peening into the above formula, the surface roughness influence coefficient is calculated. k s The surface roughness influence coefficient was achieved. k s Precise quantitative calculations.

[0124] It is worth noting that, after determining the residual stress influence coefficient... k r Surface hardening influence coefficient k h Surface roughness influence coefficient k s Then, the quantified value of the influence coefficient is returned to the initial SN curve to correct the initial SN curve.

[0125] In some embodiments of the present invention, step S402 includes:

[0126] S501. Determine the ratio between the first surface roughness of the sample weld node before shot peening and the second surface roughness after shot peening.

[0127] S502. Based on the relationship between the surface coefficient and the fatigue limit, the ratio is calculated to obtain the surface roughness influence coefficient.

[0128] Specifically, based on the relationship between the surface coefficient and the fatigue limit, the ratio between the first surface roughness and the corresponding second surface roughness after shot peening is calculated by taking the square root of a preset number of times to obtain the surface roughness influence coefficient. Since the calculation method is based on the relationship between the surface coefficient and the fatigue limit to determine the ratio, the accuracy of the surface roughness influence coefficient calculation is improved.

[0129] In one specific implementation, the cube root of the ratio of the first surface roughness to the second surface roughness can be used as the surface roughness influence coefficient.

[0130] In some embodiments of the present invention, the step of determining the range of equivalent structural stress change of the target hull weld joint after shot peening includes:

[0131] S601. The maximum equivalent stress and minimum equivalent stress of the target hull weld node after shot peening are determined by measurement, wherein the maximum equivalent stress and minimum equivalent stress are the equivalent stresses of the first region and the second region of the target hull weld node, respectively. The first region is the region that maximizes the sum of membrane stress and bending stress, and the second region is the region that minimizes the sum of membrane stress and bending stress.

[0132] S602. Determine the range of stress variation of the equivalent structure based on the maximum equivalent stress and the minimum equivalent stress.

[0133] Based on the results of membrane stress, bending stress, and structural stress, the range of structural stress variation can be calculated using the following formula:

[0134]

[0135] =

[0136]

[0137]

[0138]

[0139]

[0140] In the formula: ∆Ss is the equivalent structural stress variation range, in MPa; For structural stress, These are the maximum equivalent stress and the minimum equivalent stress, respectively; For membrane stress; σ b is the bending stress; fy is the force per unit length on the welding line; m xt is the torque per unit length on the welding line; t is the plate thickness in mm; n is the crack propagation index; r is the ratio of bending stress to structural stress.

[0141] Specifically, the difference between the maximum and minimum equivalent stress is determined as the range of equivalent structural stress variation.

[0142] In some embodiments of the present invention, step S103 includes:

[0143] S701. Based on the fatigue performance influence coefficient, the target parameters in the initial SN curve are corrected, and the target parameters include the stress structure variation range.

[0144] Specifically, by correcting the stress structure variation range in the initial SN curve based on the fatigue performance influence coefficient, fatigue performance influence parameters such as the residual stress influence coefficient can be improved. k r Surface hardening influence coefficient k h Surface roughness influence coefficient k s Perform the product calculation to obtain k r 》 k h k s Then divide the range of stress structure variation in the initial SN curve by k r 》 k h k s This allows for the correction of the initial SN curve.

[0145] In one specific embodiment, the process of evaluating the fatigue life of longitudinal girder penetration nodes of 5083 aluminum alloy hulls using the evaluation method of this application is as follows:

[0146] Referring to the average master signal-to-noise ratio (SN) curve for aluminum alloy welded joints provided by ASME, it can be expressed by the following formula:

[0147]

[0148]

[0149] In the formula: C d and h The values ​​are 3495.13 and 0.27712, respectively.

[0150] like Figure 3As shown, the residual stress distribution curves along the depth direction of the heat-affected zone of the sample after shot peening with an intensity of 0.175 mmA under different cycle periods are presented. N in the figure represents the cycle period corresponding to the curve. Figure 3 As can be seen, significant residual stress relaxation occurred in the first 5000 cycles; however, after more than 5000 cycles, the residual stress relaxation behavior became less pronounced. The peak residual compressive stress after relaxation stabilization... σ rr Considering the average stress under shot peening, the influence coefficient of residual compressive stress can be obtained under this premise:

[0151]

[0152] like Figure 4 The figure shows the hardness distribution curves along the depth direction of the heat-affected zone of the sample after shot peening with an intensity of 0.175 mmA under different cycle cycles. It can be seen that the hardness exhibits relaxation behavior similar to residual stress. In the first 5000 cycles, the surface hardness of the sample showed a relatively obvious relaxation phenomenon. After more than 5000 cycles, the relaxation behavior became less obvious. Therefore, the surface hardening influence coefficient is:

[0153]

[0154] like Figure 5 The figure shows the surface roughness results of 5083 aluminum alloy before and after shot peening with an intensity of 0.175 mmA. The surface roughness remains largely unchanged with fatigue loading, but shot peening significantly increases it. Furthermore, the surface roughness influence coefficient decreases with increasing surface roughness. Under shot peening with an intensity of 0.175 mmA, the surface roughness influence coefficient is:

[0155]

[0156] According to the modified SN curve:

[0157]

[0158]

[0159]

[0160]

[0161]

[0162]

[0163] The main SN curve expression after shot peening is corrected as follows:

[0164]

[0165] Based on the results of membrane stress, bending stress, and structural stress, the range of structural stress variation can be calculated using the following formula:

[0166]

[0167] =

[0168]

[0169]

[0170]

[0171]

[0172] In this embodiment, the plate thickness t = 4 mm; the crack propagation index n = 3.6.

[0173] Using the modified SN curve after shot peening, the fatigue life of a 5083 aluminum alloy longitudinal rib through-barrel joint model under shot peening with a shot peening intensity of 0.175 mmA and a maximum cyclic load of 126 MPa was predicted, and the prediction was compared with the fatigue life results obtained from experiments. Table 1 shows the fatigue life prediction results of the modified SN curve after shot peening. s Compared with fatigue life test results N ex and its relative error result δs:

[0174] Table 1 Fatigue life prediction and test results

[0175]

[0176] As can be seen from Table 1, the fatigue life prediction results evaluated using the modified SN curve in this embodiment are close to the test average life, verifying the reliability of the method. At the same time, the predicted life of this method is smaller than the test average life. This more conservative prediction result can improve the survival rate of the evaluated target and provide a scientific basis for ship structure design and maintenance.

[0177] To better implement the fatigue life assessment method for welded joints of hulls after shot peening in this embodiment of the invention, based on the existing method, correspondingly, as follows: Figure 6 As shown, this embodiment of the invention also provides a fatigue life assessment device for welded joints of a ship hull after shot peening. The fatigue life assessment device 600 for welded joints of a ship hull after shot peening includes:

[0178] Acquisition unit 601 is used to acquire the initial SN curve of the target hull welding node before shot peening.

[0179] The determination unit 602 is used to analyze the fatigue performance data of the sample welded node before and after shot peening through experiments, and to determine the fatigue performance influence coefficient introduced after shot peening. The sample welded node is a welded node with the same material and shape as the target hull welded node.

[0180] The correction unit 603 is used to correct the initial SN curve according to the fatigue performance influence coefficient to obtain the corrected SN curve;

[0181] Evaluation unit 604 is used to evaluate the fatigue life of the target hull weld joint after shot peening based on the equivalent structural stress variation range of the target hull weld joint after shot peening and the modified SN curve.

[0182] The fatigue life assessment device 600 for welded joints of hull after shot peening provided in the above embodiments can realize the technical solutions described in the embodiments of the fatigue life assessment method for welded joints of hull after shot peening. The specific implementation principles of each module or unit can be found in the corresponding content in the embodiments of the fatigue life assessment method for welded joints of hull after shot peening, and will not be repeated here.

[0183] like Figure 7 As shown, the present invention also provides an electronic device 700. The electronic device 700 includes a processor 701, a memory 702, and a display 703. Figure 7 Only some components of the electronic device 700 are shown, but it should be understood that it is not required to implement all the components shown, and more or fewer components may be implemented instead.

[0184] In some embodiments, processor 701 may be a central processing unit (CPU), microprocessor, or other data processing chip, used to run program code stored in memory 702 or process data, such as the fatigue life assessment method for welded joints of ship hulls after shot peening in this invention.

[0185] In some embodiments, processor 701 may be a single server or a group of servers. The server group may be centralized or distributed. In some embodiments, processor 701 may be local or remote. In some embodiments, processor 701 may be implemented on a cloud platform. In one embodiment, the cloud platform may include a private cloud, public cloud, hybrid cloud, community cloud, distributed cloud, internal cloud, multi-cloud, etc., or any combination thereof.

[0186] In some embodiments, memory 702 may be an internal storage unit of electronic device 700, such as a hard disk or memory of electronic device 700. In other embodiments, memory 702 may also be an external storage device of electronic device 700, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc. equipped on electronic device 700.

[0187] Furthermore, the memory 702 may include both internal storage units of the electronic device 700 and external storage devices. The memory 702 is used to store application software and various types of data installed on the electronic device 700.

[0188] In some embodiments, display 703 may be an LED display, a liquid crystal display, a touch-sensitive liquid crystal display, or an OLED (Organic Light-Emitting Diode) touchscreen. Display 703 is used to display information from electronic device 700 and to display a visual user interface. Components 701-703 of electronic device 700 communicate with each other via a system bus.

[0189] In one embodiment, when the processor 701 executes the fatigue life assessment program for welded joints of the hull after shot peening in the memory 702, the following steps can be implemented:

[0190] Obtain the initial SN curve of the target hull weld node before shot peening;

[0191] By analyzing the fatigue performance data of the sample welded nodes before and after shot peening, the fatigue performance influence coefficient introduced after shot peening is determined. The sample welded nodes are welded nodes with the same material and shape as the target hull welded nodes.

[0192] The initial SN curve is corrected based on the fatigue performance influence coefficient to obtain the corrected SN curve;

[0193] The fatigue life of the target hull weld joint after shot peening is evaluated based on the range of equivalent structural stress change of the target hull weld joint after shot peening and the modified SN curve.

[0194] It should be understood that when the processor 701 executes the fatigue life assessment program for the welded joints of the hull after shot peening in the memory 702, in addition to the functions mentioned above, it can also perform other functions, as can be found in the description of the corresponding method embodiments above.

[0195] Furthermore, this embodiment of the invention does not specifically limit the type of electronic device 700 mentioned. Electronic device 700 can be a mobile phone, tablet computer, personal digital assistant (PDA), wearable device, laptop computer, or other portable electronic device. Exemplary embodiments of portable electronic devices include, but are not limited to, portable electronic devices running iOS, Android, Microsoft, or other operating systems. The aforementioned portable electronic device can also be other portable electronic devices, such as a laptop computer with a touch-sensitive surface (e.g., a touch panel). It should also be understood that in some other embodiments of the invention, electronic device 700 may not be a portable electronic device, but rather a desktop computer with a touch-sensitive surface (e.g., a touch panel).

[0196] Accordingly, this application also provides a computer-readable storage medium for storing computer-readable programs or instructions. When the programs or instructions are executed by a processor, they can implement the steps or functions in the fatigue life assessment method for welded nodes of ship hulls after shot peening provided in the above-described method embodiments.

[0197] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware (such as a processor, controller, etc.), and the computer program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0198] The fatigue life assessment method and related equipment for welded joints of ship hulls after shot peening provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for evaluating the fatigue life of welded joints in a ship hull after shot peening, characterized in that, include: Obtain the initial SN curve of the target hull weld node before shot peening; By experimentally analyzing the fatigue performance data of sample weld nodes before and after shot peening, the fatigue performance influence coefficient introduced after shot peening is determined. The sample weld nodes are weld nodes with the same material and shape as the target hull weld nodes. The fatigue performance data includes residual stress, hardness, and roughness. The fatigue performance influence coefficient includes residual stress influence coefficient, surface hardening influence coefficient, and surface roughness influence coefficient. Specifically, the determination of the fatigue performance influence coefficient introduced after shot peening by experimentally analyzing the fatigue performance data of sample weld nodes before and after shot peening includes: The residual stress distribution of the sample weld joints before and after shot peening was measured experimentally. Based on fracture mechanics theory and fatigue material theory, the residual stress influence coefficient is calculated in conjunction with the residual stress distribution. The surface hardness of the sample weld nodes before and after shot peening was measured experimentally. Based on the theory of material hardening and fatigue materials, the surface hardening influence coefficient is calculated in conjunction with the surface hardness. The surface roughness of the sample weld joints before and after shot peening was measured experimentally. Based on the relationship between surface coefficient and fatigue limit, the surface roughness influence coefficient is calculated in conjunction with the surface roughness. The initial SN curve is corrected based on the fatigue performance influence coefficient to obtain the corrected SN curve; The fatigue life of the target hull weld joint after shot peening is evaluated based on the range of equivalent structural stress change of the target hull weld joint after shot peening and the modified SN curve.

2. The method for evaluating the fatigue life of welded joints in a ship hull after shot peening as described in claim 1, characterized in that, The calculation of the surface roughness influence coefficient based on the relationship between the surface coefficient and the fatigue limit, combined with the surface roughness, includes: Determine the ratio between the first surface roughness of the sample weld node before shot peening and the second surface roughness after shot peening; Based on the relationship between the surface coefficient and the fatigue limit, the ratio is calculated to obtain the surface roughness influence coefficient.

3. The method for evaluating the fatigue life of welded joints in a ship hull after shot peening as described in claim 1, characterized in that, The steps for determining the range of equivalent structural stress changes at the target hull weld joints after shot peening include: The maximum and minimum equivalent stress of the target hull weld node after shot peening are determined by measurement. The maximum and minimum equivalent stresses are the equivalent stresses of the first and second regions of the target hull weld node, respectively. The first region is the region where the sum of membrane stress and bending stress is maximized, and the second region is the region where the sum of membrane stress and bending stress is minimized. The range of stress variation in the equivalent structure is determined based on the maximum and minimum equivalent stress.

4. The method for evaluating the fatigue life of welded joints in a ship hull after shot peening according to claim 1, characterized in that, The step of correcting the initial SN curve based on the fatigue performance influence coefficient to obtain the corrected SN curve includes: The target parameters in the initial SN curve are corrected based on the fatigue performance influence coefficient, and the target parameters include the range of equivalent structural stress variation.

5. A device for assessing the fatigue life of welded joints in a ship hull after shot peening, characterized in that, include: The acquisition unit is used to acquire the initial SN curve of the target hull weld node before shot peening. The unit is used to determine the fatigue performance influence coefficient introduced after shot peening by experimentally analyzing the fatigue performance data of sample welded nodes before and after shot peening. The sample welded nodes are welded nodes with the same material and shape as the target hull welded nodes. The fatigue performance data includes residual stress, hardness, and roughness. The fatigue performance influence coefficient includes residual stress influence coefficient, surface hardening influence coefficient, and surface roughness influence coefficient. The determination of the fatigue performance influence coefficient introduced after shot peening by experimentally analyzing the fatigue performance data of sample welded nodes before and after shot peening includes: The residual stress distribution of the sample weld joints before and after shot peening was measured experimentally. Based on fracture mechanics theory and fatigue material theory, the residual stress influence coefficient is calculated in conjunction with the residual stress distribution. The surface hardness of the sample weld nodes before and after shot peening was measured experimentally. Based on the theory of material hardening and fatigue materials, the surface hardening influence coefficient is calculated in conjunction with the surface hardness. The surface roughness of the sample weld joints before and after shot peening was measured experimentally. Based on the relationship between surface coefficient and fatigue limit, the surface roughness influence coefficient is calculated in conjunction with the surface roughness. The correction unit is used to correct the initial SN curve according to the fatigue performance influence coefficient to obtain the corrected SN curve; The evaluation unit is used to evaluate the fatigue life of the target hull weld joint after shot peening based on the range of equivalent structural stress change of the target hull weld joint after shot peening and the modified SN curve.

6. An electronic device, characterized in that, It includes a memory and a processor, wherein the memory is used to store programs; The processor, coupled to the memory, is used to execute the program stored in the memory to implement the steps in the fatigue life assessment method for welded joints of hull after shot peening as described in any one of claims 1 to 4.

7. A computer-readable storage medium, characterized in that, Used to store computer-readable programs or instructions, which, when executed by a processor, can implement the steps in the fatigue life assessment method for welded joints of hulls after shot peening as described in any one of claims 1 to 4.

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