Roll fatigue damage calculation method considering contact fatigue damage and wear coupling

Abstract

The present application belongs to the technical field of metal rolling production, and particularly relates to a rolling fatigue damage calculation method considering coupling of contact fatigue damage and wear. The method comprises the following steps: step one, constructing a continuous damage mechanics model of rolling material; step two, constructing a rolling contact fatigue damage calculation model; step three, calculating unit damage; step four, constructing a wear amount calculation model of rolling material; step five, determining a wear coefficient through "strength-hardness" correlation; step six, calculating unit wear; and step seven, iterative calculation: after rolling body discretization, initial parameter assignment and iterative parameter setting are sequentially performed, iterative calculation in each interval is carried out according to the divided rolling service time interval, and a complete rolling fatigue damage of coupling contact fatigue damage and wear in a complete in-service period is iteratively calculated. The method solves the problems of excessive model simplification and ignored coupling effect in the existing evaluation method, and improves the calculation accuracy of rolling damage distribution.

Description

Technical Field

[0001] This invention belongs to the field of metal rolling production technology, specifically involving a method for calculating roll fatigue damage considering the coupling of contact fatigue damage and wear. Background Technology

[0002] Rolls are the core components for achieving plastic deformation of metals, and their service performance directly determines product precision, quality, and production efficiency. During long-term rolling, the surface of the rolls is subjected to the coupled effects of high-stress cyclic loads and sliding wear: on the one hand, the repeated contact stress between the rolls and the workpiece causes surface contact fatigue damage, manifested as the initiation and propagation of microcracks and material spalling; on the other hand, the relative sliding between the two and the abrasion of iron oxide scale lead to progressive surface wear, which not only shortens the roll life but also exacerbates stress concentration and accelerates fatigue damage.

[0003] Current roll fatigue damage assessment technology suffers from two major shortcomings, failing to meet the demands for high-precision monitoring and life prediction: First, the models are overly simplified. Traditional methods treat roll materials as homogeneous bodies, neglecting the gradient distribution of material properties and ignoring the dynamic process of material strength degradation under long-term cyclic loading. This leads to significant discrepancies between predicted and actual results, failing to provide accurate support for roll maintenance. Second, the coupling effect is ignored. Existing technologies treat fatigue damage and wear as independent processes, analyzing only a single factor without establishing a model of their interaction. In reality, wear alters the roll surface morphology and stress distribution, accelerating fatigue crack initiation; fatigue crack propagation, in turn, damages surface integrity, exacerbating wear. Existing methods lack effective consideration of this.

[0004] Therefore, developing a high-precision evaluation method that comprehensively considers the gradient distribution of material properties, strength degradation, and fatigue-wear coupling effect to achieve accurate prediction of roll damage accumulation is of great significance for optimizing maintenance strategies, extending service life, and reducing costs. It is a technical problem that urgently needs to be solved in the rolling field. Summary of the Invention

[0005] This invention provides a method for calculating roll fatigue damage that considers the coupling of contact fatigue damage and wear, which solves the problems of oversimplification of models and neglect of coupling effects in existing evaluation methods.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A method for calculating roll fatigue damage considering the coupling of contact fatigue damage and wear includes the following steps:

[0008] Step 1: Construct a progressive damage mechanical model for the roll material:

[0009] ,

[0010] In the formula, The degree of damage at a radial depth y from the surface of the roll after N load cycles; The stress amplitude that causes fatigue damage to the roll material; For the damage stress of the roll material; is a material constant for the roll, obtained through contact fatigue testing; y is the radial depth.

[0011] Step 2: Construct a calculation model for roll contact fatigue damage:

[0012] ,

[0013] In the formula, This refers to the stress required to resist contact fatigue damage in the rolls. The damage degree of the unit at a radial depth y from the roll surface after N load cycles; The orthogonal shear stress amplitude of the roll cross section; The coordinates are perpendicular to the y-direction and tangent to the axial cross-section of the roll.

[0014] Step 3: Calculate unit damage: Divide the entire fatigue process into several equally spaced cycles. Within each cycle, the evolution rate of contact fatigue damage at different radial depths y at each node of the roll is:

[0015] ,

[0016] In the formula, i represents the i-th cycle; j represents the j-th axial discrete unit of the roll body length direction discretization; Let y be the damage degree at the radial depth y from the surface in the j-th axial discrete element during the i-th cycle. The number of load cycles within an equally spaced cycle period;

[0017] During the i-th cycle, the increment of contact fatigue damage at different radial depths y from the surface for each axial discrete element j is:

[0018] ,

[0019] In the formula, The number of load cycles within an equally spaced cycle period;

[0020] Step 4: Construct a calculation model for the wear of the roll material:

[0021] ,

[0022] In the formula, s is the slip ratio factor between the rolls, and d is the diameter of the roll used to calculate wear. The wear coefficient of the roll material is determined experimentally; H is the hardness ratio of the rolls in contact with each other. This represents the maximum contact stress.

[0023] Step 5: Determine the wear coefficient through the "strength-hardness" correlation:

[0024] ,

[0025] In the formula, The initial wear coefficient is determined experimentally. It is a function of hardness;

[0026] Step 6: Calculate unit wear: Discretize the roll body length direction into j axial discrete units. The j-th axial discrete unit is in the i-th cycle. Wear under secondary load cycles Represented as:

[0027] ,

[0028] In the formula, Let y be the wear coefficient of the material at the radial depth y from the surface of the j-th axial discrete element in the i-th cycle. The maximum contact stress of the j-th axial discrete element in the i-th cycle;

[0029] Step 7, Iterative Calculation: After discretizing the roll body, assigning initial parameters, and setting iterative parameters, iterative calculations are performed one by one according to the divided roll service time intervals. The coupled contact fatigue damage and wear fatigue damage of the roll are calculated iteratively for a complete on-machine service cycle.

[0030] .

[0031] Preferably, in step one, fatigue strength performance data of the roll material at different depths along the radial depth y of the roll are first obtained to form a raw dataset of "radial depth-damage resistance stress"; then, an interpolation function is used to mathematically describe the raw dataset to obtain the damage resistance stress of the roll material. The function expression:

[0032] ,

[0033] In the formula, The damage resistance stress is located at the point where the radial depth y of the roll from the surface approaches infinity. The stress at y=0 on the roll surface is the damage resistance stress. The attenuation coefficient is obtained experimentally. y Radial depth;

[0034] Then, the damage resistance stress of the roll material is further increased. By incorporating the continuous damage mechanical model of roll materials, a continuous damage mechanical model of roll materials is obtained.

[0035] Preferably, in step two, based on contact mechanics theory, the orthogonal shear stress amplitude of the roll cross section is obtained by first combining the elastic deformation and non-uniform load distribution during the contact process between the roll and the workpiece. :

[0036] ,

[0037] In the formula, This represents the maximum orthogonal shear stress at the roll cross-section. The minimum orthogonal shear stress of the roll cross section;

[0038] Then, the orthogonal shear stress amplitude of the roll cross section is... The radial depth y is introduced into the continuous damage mechanics model of the roll material to construct a calculation model for roll contact fatigue damage.

[0039] Preferably, in step four, the wear height calculation formula for the axial discrete element is obtained by combining the wear calculation model of the axial discrete element:

[0040] ,

[0041] In the formula, Let be the stress on the contact area caused by the load on the j-th axial discrete element of the contact deformation region; The adhesive wear coefficient; This is the sliding distance;

[0042] Replacing the maximum contact stress in the contact deformation area, the formula for calculating wear height changes to:

[0043] ,

[0044] In the formula, H The hardness ratio of the contacting rolls;

[0045] During the rolling process, the rolls and the workpiece undergo relative rolling and sliding motion. The slip ratio factor s between the rolls is introduced into the calculation formula of the wear height of the axial discrete unit of the roll, and finally a calculation model of the wear amount of the roll material is constructed.

[0046] Preferably, in step six, due to the change in roller profile, the contact stress... Reconstructed as:

[0047] ,

[0048] ,

[0049] In the formula, denoted as , where is the normal contact stress distribution on the contact surface of the two elastic bodies; 'a' is the contact half-width of the two contacting rolls corresponding to the axial discrete element j. , R2 represents the radius of the two parallel cylindrical elastic bodies under plane strain conditions. When the roll is in contact with the workpiece, R2 can be taken as infinite. E1 and E2 are the elastic moduli of the two cylinders. , Let be the Poisson's ratio of the two cylinders.

[0050] Preferably, in step five, the intensity function of the axial discrete element is first constructed. :

[0051] ,

[0052] In the formula, The tensile strength of the roll surface; The coefficient is determined experimentally;

[0053] Then the intensity function Convert to hardness function :

[0054] ,

[0055] In the formula, Vickers hardness, i.e.:

[0056] ,

[0057] In the formula, c is determined experimentally;

[0058] Then Substituting into the wear coefficient formula, we obtain the initial wear coefficient that varies with radial depth y.

[0059] Preferably, when calculating the contact fatigue damage of the rolls, the entire service life of the rolls is divided into several consecutive equally spaced cycles. Each cycle corresponds to a certain number of load cycles. After the wear calculation for the i-th cycle is completed, the axial discrete element j will generate wear. Then the initial damage degree at the start of the damage calculation for the (i+1)th cycle is: And after the i-th cycle of the calculation is completed Residual strength at depth As the initial intensity for the (i+1)th cycle, it is substituted into the wear calculation formula for iteration.

[0060] Compared with the prior art, the present invention has the following advantages:

[0061] This invention establishes a calculation model for roll contact fatigue damage distribution that simultaneously considers performance gradient distribution, strength degradation, and the coupling of contact fatigue damage and wear. Based on Archard's wear model, a calculation model for wear amount considering performance gradient distribution and strength degradation is established. Combining the service characteristics of rolls in "on-the-machine service - on-the-machine wear", the coupled accumulation of contact fatigue damage and wear is calculated iteratively, and the damage distribution and residual strength are corrected. This realizes the dynamic coupling interaction simulation of fatigue damage and wear, significantly improving the calculation accuracy of damage distribution, and is suitable for roll life management under complex working conditions.

[0062] For the first time, the dynamic interaction between fatigue damage and wear was integrated, and realistic simulation of service behavior was achieved through iterative calculations. Based on material property gradient modeling and dynamic correction of strength degradation, as well as the coupling of contact fatigue damage and wear, the calculation accuracy of roll damage distribution was significantly improved.

[0063] Combining the core characteristics of "on-machine service and on-machine wear" existing simultaneously, accumulating synchronously, and influencing each other during the service life of rolling mill rolls, this paper addresses the coupling relationship among three factors: "the physical removal effect of wear on the damaged layer," "the material strength degradation effect caused by damage accumulation," and "the reconstruction effect of roll profile changes on the contact stress field, thus affecting contact fatigue damage and wear accumulation." Through a closed-loop iterative system of "unit damage and unit wear calculation → overall roll profile correction → contact stress reconstruction → unit parameter update," this paper achieves dynamic coupling analysis of damage, wear, and roll profile during the service life of rolling mill rolls. The final output includes a quantitative relationship containing the number of iterations N, corrects the damage distribution and residual strength, and accurately calculates the contact fatigue damage accumulation of rolling mill rolls during their service life. Attached Figure Description

[0064] Figure 1 This is a schematic diagram of the performance gradient distribution of the present invention;

[0065] Figure 2 This is a schematic diagram of the damage distribution of different damage layers predicted by the present invention, wherein (a) is the damage distribution of different damage layers of roller P, and (b) is the damage distribution of different damage layers of roller J.

[0066] Figure 3 This is a schematic diagram of the hardness distribution of each roller obtained by actual measurement in this invention, wherein (a) is the hardness distribution of roller P after it is removed from the machine, and (b) is the hardness distribution of roller J after it is removed from the machine. Detailed Implementation

[0067] To further illustrate the technical solution of the present invention, the present invention will be further described below through embodiments.

[0068] This embodiment provides a method for calculating roll fatigue damage considering the coupling of contact fatigue damage and wear, including the following steps:

[0069] Step 1: Construct a progressive damage mechanical model for roll materials: based on the gradient distribution characteristics of the roll cross-section strength properties, such as... Figure 1 As shown, fatigue strength performance data of roll material at different depths along the radial depth y of the roll are first obtained by the stratified sampling test method, forming the original dataset of "radial depth-damage resistance stress".

[0070] Subsequently, an interpolation function was used to mathematically describe the original dataset, yielding the damage resistance stress of the roll material. The function expression:

[0071] ,

[0072] In the formula, The damage resistance stress at the point where the radial depth y of the roll from the surface approaches infinity is given by MPa. The damage resistance stress at y=0 on the roll surface is expressed in MPa. The attenuation coefficient is obtained experimentally. In practical applications, it needs to be obtained based on the actual material test data due to the material and heat treatment process. y Radial depth;

[0073] Then, the damage resistance stress of the roll material is further increased. Introducing a progressive damage mechanics model for roll materials In this process, a progressive damage mechanical model for the roll material is obtained:

[0074] ,

[0075] In the formula, The damage degree at the radial depth y from the surface of the roll after N load cycles is between 0 and 1, where 0 indicates that the roll material is not damaged and 1 indicates that the roll material is completely damaged. The stress amplitude that causes fatigue damage to the roll material, expressed in MPa; For the damage stress of the roll material; y is the material constant of the roll, obtained through contact fatigue testing; y is the radial depth.

[0076] Step 2: Constructing a calculation model for roll contact fatigue damage: Based on contact mechanics theory, and considering actual working conditions such as elastic deformation and non-uniform load distribution during the contact process between the roll and the workpiece, the orthogonal shear stress amplitude of the roll cross section is obtained. :

[0077] ,

[0078] In the formula, This represents the maximum orthogonal shear stress at the roll cross-section. The minimum orthogonal shear stress of the roll cross section;

[0079] Then, the orthogonal shear stress amplitude of the roll cross section is... The radial depth y is introduced as a variable in the continuous damage mechanics model of the roll material to construct a calculation model for roll contact fatigue damage:

[0080] ,

[0081] In the formula, The contact fatigue damage resistance stress of the roll represents the roll material's ability to resist damage accumulation. It is measured through a contact fatigue test and is measured in MPa. Let L be the damage degree of the element at a radial depth y from the surface of the roll after N load cycles. In the initial state, the stress distribution of the contact stress field sub-model is determined by the initial roll profile L0 before the roll is installed. The orthogonal shear stress amplitude of the roll cross section; The coordinates are perpendicular to the y-direction and tangent to the axial cross-section of the roll.

[0082] Step 3: Calculate unit damage: Divide the entire fatigue process (the total number of roll stress cycles within one rolling cycle) into several equally spaced cycles. Within each cycle, the contact fatigue damage evolution rate at different radial depths y of each node of the roll is:

[0083] ,

[0084] In the formula, i represents the i-th cycle; j represents the j-th axial discrete unit of the roll body length direction discretization; Let y be the damage degree at the radial depth y from the surface in the j-th axial discrete element during the i-th cycle. The number of load cycles within an equally spaced cycle period;

[0085] During the i-th cycle, the increment of contact fatigue damage at different radial depths y from the surface for each axial discrete element j is:

[0086] ,

[0087] In the formula, This represents the number of load cycles within an equally spaced cycle period, i.e., the number of cycles between the coupling iteration interval of contact fatigue damage and wear.

[0088] Step 4: Construct a wear calculation model for the roll material: Based on Archard's wear theory, establish a wear model for the roll material under sliding contact conditions:

[0089] ,

[0090] In the formula, K is the probability of generating abrasive particles; L is the sliding distance; n The normal load is H; H is the hardness ratio of the phase-contact rolls.

[0091] If the roll is discretized into j equally spaced axial discrete elements along its length, then the wear calculation model for each axial discrete element is as follows:

[0092] ,

[0093] In the formula, V(j) is the wear volume on the i-th unit of the roller contact area, and K abr p(j) is the adhesive wear coefficient; p(j) is the inter-roll contact stress on the j-th unit of the inter-roll contact area. Where H is the relative sliding distance between the contact points, and H is the hardness ratio of the contacting rolls;

[0094] According to the principle of volume equivalence, the volume of roll material removed from the rolls during the rolling process is the volume of wear. Therefore:

[0095] ,

[0096] In the formula, A is the contact area between the rolls, and h is the wear height of the roll.

[0097] Based on the wear calculation model of the axial discrete element, the formula for calculating the wear height of the axial discrete element is obtained:

[0098] ,

[0099] In the formula, Let be the stress on the contact area caused by the load on the j-th axial discrete element of the contact deformation region; The adhesive wear coefficient; This is the sliding distance;

[0100] Replacing the maximum contact stress in the contact deformation area, the formula for calculating wear height changes to:

[0101] ,

[0102] In the formula, H The hardness ratio of the contacting rolls;

[0103] During the rolling process, there is relative rolling and sliding motion between rolls and between rolls and the workpiece. A slip factor s between rolls is introduced into the formula for calculating the wear height of the axial discrete unit of the rolls, ultimately constructing a model for calculating the wear amount of the roll material.

[0104] ,

[0105] In the formula, s is the slip ratio factor between the rolls, and d is the diameter of the roll used to calculate wear. The wear coefficient of the roll material is determined experimentally; H is the hardness ratio of the rolls in contact with each other. This represents the maximum contact stress.

[0106] Step 5: Determine the wear coefficient through the "strength-hardness" correlation: First, construct the strength function of the axial discrete element. :

[0107] ,

[0108] In the formula, The tensile strength of the roll surface; The coefficient is determined experimentally;

[0109] Then the intensity function Convert to hardness function :

[0110] ,

[0111] In the formula, Vickers hardness, i.e.:

[0112] ,

[0113] In the formula, c is determined experimentally;

[0114] Then Substituting into the wear coefficient formula, we obtain the initial wear coefficient that varies with radial depth y.

[0115] ,

[0116] In the formula, The initial wear coefficient is determined experimentally. This is a hardness function.

[0117] Step 6: Calculate unit wear: Discretize the roll body length direction into j axial discrete units. The j-th axial discrete unit is in the i-th cycle. Wear under secondary load cycles Represented as:

[0118] ,

[0119] In the formula, Let y be the wear coefficient of the material at the radial depth y from the surface of the j-th axial discrete element in the i-th cycle. This represents the maximum contact stress of the j-th axial discrete element in the i-th cycle.

[0120] Due to the change in roller shape, contact stress Reconstructed as:

[0121] ,

[0122] ,

[0123] In the formula, denoted as , where is the normal contact stress distribution on the contact surface of the two elastic bodies; 'a' is the contact half-width of the two contacting rolls corresponding to the axial discrete element j. , R2 represents the radius of the two parallel cylindrical elastic bodies under plane strain conditions. When the roll is in contact with the workpiece, R2 can be taken as infinite. E1 and E2 are the elastic moduli of the two cylinders, in MPa. , Let be the Poisson's ratio of the two cylinders.

[0124] Step 7, Iterative Calculation: After discretizing the roll body, assigning initial parameters, and setting iterative parameters, iterative calculations are performed one by one according to the divided roll service time intervals. The coupled contact fatigue damage and wear fatigue damage of the roll are calculated iteratively for a complete on-machine service cycle.

[0125] .

[0126] Considering the simultaneous existence and accumulation of "in-machine service - in-machine wear" in the service life of roll materials, this paper takes into account the coupled effects of wear on damage layer removal and strength degradation caused by damage during in-machine service, thus affecting wear performance. The paper iteratively calculates the coupled accumulation of contact fatigue damage and wear, and corrects the damage distribution and residual strength, specifically including:

[0127] Discretization modeling of the roll body: The roll body is uniformly discretized into j-axis discrete elements along the roll axis, denoted as element j (j=1,2,...,m). The element width is determined based on the workpiece width and the effective contact length of the roll body.

[0128] Initial parameter assignment:

[0129] Initial unit damage : The rolls had no service damage before they started working, so the cumulative damage at all units j and at all radial depths y is set to 0;

[0130] Initial cell wear : The rolls had no service wear before they started working, so the radial wear at all units j and at all radial depths y was assigned a value of 0;

[0131] Counter k: Initial number of coupled calculations k=0, the 0th iteration is the initial state;

[0132] Combining the theory of material microstructure dynamics, quantitatively correlate unit damage Along with changes in hardness, the impact of strength degradation on subsequent damage calculations is characterized. When contact fatigue damage in the roll material accumulates to a certain extent, the mechanical properties of the roll material will degrade, that is:

[0133] ,

[0134] In the formula, The elastic modulus of the roll during the i-th cycle is expressed in MPa. This is the elastic modulus when the roll is damaged, expressed in MPa.

[0135] After discretizing the roll body, assigning initial parameters, and setting iterative parameters, iterative calculations are carried out one by one according to the divided roll service time intervals. During the calculation of each interval, the unit parameters need to be updated. The iterative calculations include the damage accumulation caused in the previous service time interval, the residual strength at different depths in the cross section caused by the damage accumulation, the wear amount of the roll unit corresponding to this service interval, and the roll diameter at the corresponding position of the worn unit. Then, the damage, the residual diameter of the cross section corresponding to the unit position after wear, and the residual strength distribution of the cross section are substituted into the damage calculation, damage accumulation calculation, and wear amount calculation model of the next service interval.

[0136] During the iteration process, when calculating the contact fatigue damage of the rolls, the entire service life of the rolls is divided into several consecutive equally spaced cycles. Each cycle corresponds to a certain number of load cycles. In the wear calculation of the i-th cycle, the strength parameter of element j adopts the remaining strength at the initial moment of the cycle and obtains the corresponding hardness, thereby determining the wear coefficient of the cycle.

[0137] After the wear calculation for the i-th cycle is completed, element j will generate radial wear. Therefore, the damage calculation formula for the (i+1)th unit needs to update the damage distribution of unit j. The initial damage degree at the start of the (i+1)th cycle damage calculation is then... And after the i-th cycle of the calculation is completed Residual strength at depth As the initial intensity for the (i+1)th cycle, it is substituted into the wear calculation formula for iteration.

[0138] The load cycle occurs within the (i+1)th cycle. The damage to unit j after that is .

[0139] This process is repeated iteratively to calculate the coupled contact fatigue damage and wear fatigue damage of the rolls during a complete in-machine service cycle.

[0140] This embodiment calculates and verifies the fatigue damage distribution of the intermediate roll of a certain brand of 20-roll mill.

[0141] Technical solution: The invention is programmed using mathematical programming software to calculate and analyze the fatigue damage of the intermediate roll of a 20-roll mill. As the main roll for shape adjustment, the fatigue damage of the intermediate roll has a significant impact on the rolling quality.

[0142] Implementation process:

[0143] 1. Model programming: Based on the iterative model, a damage accumulation calculation program is implemented using mathematical programming software.

[0144] 2. Determination of core parameters:

[0145] (1) Material property gradient distribution: The property gradient distribution is described by fitting an interpolation function based on experimentally measured hardness gradient data;

[0146] (2) Cyclic load parameters: rolling force, rotational speed, and contact stress level.

[0147] (3) Material parameters: m=13, =5778MPa.

[0148] (4) Parameters of the loop jump algorithm: The maximum damage increment for each loop cycle is set to 0.1, and the critical damage degree D c Set it to 0.99.

[0149] 3. Selection of research subjects:

[0150] (1) P roller: cone length 255mm, lateral displacement 0mm;

[0151] (2) J roller: crown 0mm;

[0152] Selection criteria: As the core shape control rolls of the rolling mill, fatigue damage of these two rolls directly affects the rolling quality.

[0153] 4. Damage distribution calculation:

[0154] The fatigue damage distribution at three depths—the surface layer, 0.2 mm from the surface layer, and 0.6 mm from the surface layer—was calculated using a fatigue damage accumulation calculation program for both P-roll and J-roll. The predicted damage distribution is as follows: Figure 2 As shown.

[0155] 5. Model Validation:

[0156] (1) Verification logic:

[0157] Contact fatigue leads to increased roller body hardness, with the damage peak area corresponding to the hardness peak area; in comparison... Figure 2 The predicted damage distribution shown is... Figure 3 The hardness distribution is shown as measured after rolling for 240 kilometers.

[0158] (2) Verification results:

[0159] Figure 2 The results show that the peak axial damage of both rolls P and J is located in the middle of the roll body; Figure 2 As shown in (a) and (b), the roll damage distribution map output by the present invention is consistent with the field measurement results in terms of damage amplitude, location and depth distribution, and is significantly better than the traditional homogeneous model and the model that does not consider wear and assumptions.

[0160] Figure 3 In the measured hardness distribution, the measured peak positions of fatigue hardening of P roll and J roll completely coincide with the damage peak calculated by the method proposed in this invention.

[0161] Furthermore, by Figure 3 The field-measured hardness distribution shown in (a) and (b) has peak positions that are similar to those in (b). Figure 2 The damage peak positions in the data completely overlap, thus quantitatively verifying that the present invention can significantly improve the calculation accuracy of roll damage distribution.

[0162] 6. Verification Conclusion:

[0163] The consistency between the damage distribution and the hardness distribution verifies the correctness of the model in this invention.

[0164] Contents not described in detail in this specification are prior art known to those skilled in the art. Although illustrative specific embodiments of the invention have been described above to facilitate understanding by those skilled in the art, it should be understood that the invention is not limited to the scope of the specific embodiments. Various modifications are readily apparent to those skilled in the art as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of this invention are protected.

Claims

1. A method for calculating fatigue damage of a roll considering coupling of contact fatigue damage and wear, characterized by, The method comprises the following steps: Step one, constructing a continuous damage mechanics model of the roll material: ， wherein is the damage at the radial depth y of the roll surface after N load cycles; is the stress amplitude that causes fatigue damage of the roll material; is the damage resistant stress of the roll material; is a constant of the roll material, determined by contact fatigue testing; and y is the radial depth. Step two, constructing a contact fatigue damage calculation model of the roll: ， In the formula, is the contact fatigue damage stress of the roll; is the damage degree of the unit at the radial depth y from the roll surface after N times of load cycles; is the normal shear stress amplitude of the roll cross section; is the coordinate perpendicular to the y direction and tangent to the axial cross section of the roll. Step three, calculating the unit damage: divide the whole fatigue process into several equal-interval cycle periods, and in each cycle period, the contact fatigue damage evolution rate of each node of the roll at different radial depths y is: ， In the formula, i represents the i-th cycle period; j represents the j-th axial discrete unit discretized in the length direction of the roll body; is the damage degree at the radial depth y from the surface in the i-th cycle period in the j-th axial discrete unit; is the number of load cycles in the equal-interval cycle period; In the i th cycle period, the contact fatigue damage degree increment of each axial discrete unit j at different radial depths y from the surface is: ， In the formula, N is the number of load cycles within an equidistant cycle period. Step four, constructing a wear amount calculation model of the roll material: ， where s is a sliding ratio factor between the rolls, d is the diameter of the roll for which the wear is calculated, is the wear coefficient of the roll material, determined experimentally; H is the hardness ratio of the rolls in contact; is the maximum contact stress; Step five, determining the wear coefficient through the "strength-hardness" correlation: ， wherein is the initial wear coefficient, calibrated from experiments; is the hardness function; Step six, calculate the unit wear: the length direction of the roll body is discretized into j axial discrete units, the jth axial discrete unit is in the ith cycle period Wear amount under secondary load cycle is expressed as: ， wherein is the wear coefficient of the material at the radial depth y from the surface for the jth axial discrete unit in the ith cycle; is the maximum contact stress of the jth axial discrete unit in the ith cycle. Step seven, iterative calculation: after the roll body discretization, initial parameter assignment, and iterative parameter setting are sequentially performed, the iterative calculation is carried out in the intervals according to the divided service time intervals of the roll, and the coupled contact fatigue damage and wear of the roll in a complete in-service period is iteratively calculated: 。 2. The method of roll fatigue damage calculation considering coupling of contact fatigue damage and wear according to claim 1, characterized in that, In the step one, firstly, the fatigue strength performance data of the roll material at different depths along the roll radial depth y is obtained, forming a "radial depth-damage resistant stress" original data set; then the original data set is mathematically described by using an interpolation function, obtaining a function expression of the damage resistant stress of the roll material ​ ， wherein is the damage resistant stress for a radial depth y approaching infinity of the roll surface; is the damage resistant stress at the roll surface at y = 0; is the decay coefficient, determined experimentally; y is the radial depth; Further damage resistant stress for roll materials The continuous damage mechanics model of roll materials is obtained by introducing the continuous damage mechanics model of roll materials.

3. The method of roll fatigue damage calculation considering coupling of contact fatigue damage and wear according to claim 1, characterized in that, In the second step, based on the contact mechanics theory, the elastic deformation and the non-uniform distribution of load in the process of the contact between the roller and the rolled piece are combined to obtain the normal shear stress amplitude of the roller section : ， wherein is the maximum orthogonal shear stress of the roll cross section; is the minimum orthogonal shear stress of the roll cross section; Again, the cross shear stress amplitude of the roll section The roll contact fatigue damage calculation model is constructed by introducing the roll material continuous damage mechanics model as the variable of the radial depth y.

4. The method of roll fatigue damage calculation considering coupling of contact fatigue damage and wear according to claim 1, characterized in that, In the step four, the wear height calculation formula of the axial discrete unit is obtained in combination with the wear amount calculation model of the axial discrete unit: ， wherein is the stress on the jth axial discrete element in the contact deformation zone on the load per contact area; is the coefficient of adhesive wear; is the sliding distance; The wear height calculation formula is changed to: ， wherein H H is the hardness ratio of the contacting rolls. In the rolling process, the roll and the roll, and the roll and the rolled piece are relatively rolling and sliding, and the sliding rate factor s of the rolls is introduced into the wear height calculation formula of the axial discrete unit of the roll, and finally the wear amount calculation model of the roll material is constructed.

5. The method for calculating the fatigue damage of a roll considering the coupling of contact fatigue damage and wear according to claim 4, characterized in that, In the step six, due to the roll type change, the contact stress is reconfigured as: ， ， wherein is the normal contact stress distribution on the two elastic contact surfaces; a is the contact half-width of the two contact rolls corresponding to the axial discrete element j element; , are the radii of the two parallel cylindrical elastic bodies in the plane strain state, and R2 can be taken as infinity when the roll is in contact with the rolled piece; E1 and E2 are the elastic moduli of the two cylindrical bodies; , are the Poisson's ratios of the two cylindrical bodies.

6. The method of roll fatigue damage calculation considering coupling of contact fatigue damage and wear according to claim 1, characterized in that, In the step five, the strength function of the axial discrete unit is constructed first : ， wherein is the tensile strength of the roll surface; is a coefficient, determined experimentally; The strength function is again converted into a hardness function :​ ， wherein is the Vickers hardness, i.e. ， In the formula, c is determined by experiment; Again Substituting the wear coefficient formula, the initial wear coefficient varying with the radial depth y is obtained.

7. The method of roll fatigue damage calculation considering coupling of contact fatigue damage and wear according to claim 1, characterized in that, In the calculation of the contact fatigue damage of the roll, the whole service period of the roll is divided into several continuous equal-interval cycle periods , each cycle period corresponds to a number of load cycle times . When the wear calculation of the i-th cycle is completed, the axial discrete unit j generates a wear amount Then, the initial damage degree at the start of the damage calculation of the i+1-th cycle is And the remaining strength at the depth of the i-th cycle after the calculation is completed The remaining strength at the depth of the i-th cycle after the calculation is completed As the initial strength of the i+1-th cycle, the wear amount calculation formula is substituted and iterated.

Images