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

Abstract

The invention belongs to the technical field of metal rolling production, and particularly relates to a roller fatigue damage calculation method considering contact fatigue damage and wear coupling, which comprises the following steps of: 1, constructing a roller material continuous damage mechanical model, 2, constructing a roller contact fatigue damage calculation model, and 3, calculating unit damage. The method comprises the following steps of 1, dividing roller service time intervals, 2, dividing roller service time intervals, 4, constructing a roller material abrasion loss calculation model, 5, determining an abrasion coefficient through'strength-hardness' association, 6, calculating unit abrasion, and 7, carrying out iterative calculation: carrying out roller body discretization, initial parameter assignment and iterative parameter setting in sequence, and then calculating unit abrasion according to the divided roller service time intervals. And carrying out iterative calculation in the intervals one by one, and carrying out iterative calculation to obtain coupling contact fatigue damage and worn roller fatigue damage in a complete on-machine service cycle. According to the method, the problems of excessive model simplification and neglected coupling effect in an existing evaluation method are solved, and the calculation precision of roller damage distribution is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal rolling production, and particularly relates to a rolling fatigue damage calculation method considering contact fatigue damage and wear coupling. BACKGROUND

[0002] Rolling is the core component to realize metal plastic deformation, and its service performance directly determines product precision, quality and production efficiency. In the long-term rolling process, the surface of the roll is subjected to the coupling effect of high stress cyclic load and sliding wear: on the one hand, the contact stress of the roll and the rolled piece repeatedly acts, causing surface contact fatigue damage, which is manifested as micro-crack initiation, propagation and material spalling; on the other hand, the relative sliding between the two and the grinding of the oxide scale lead to progressive wear of the surface, which not only shortens the service life of the roll, but also aggravates stress concentration and accelerates fatigue damage.

[0003] There are two key deficiencies in the current rolling fatigue damage evaluation technology, which cannot meet the needs of high-precision monitoring and life prediction: first, the model is oversimplified, the traditional method regards the rolling material as a homogeneous body, without considering the gradient distribution of the material performance of the roll, and ignoring the dynamic process of material strength degradation under long-term cyclic load, resulting in significant deviation between the predicted results and the actual situation, and unable to provide accurate support for roll maintenance; second, the coupling effect is ignored, the existing technology regards fatigue damage and wear as independent processes, only analyzes a single factor, and does not establish a mutual interaction model. In practice, wear changes the surface topography and stress distribution of the roll, accelerating the initiation of fatigue cracks; fatigue crack propagation also destroys the surface integrity, aggravating wear, and the existing method lacks effective consideration of this.

[0004] Therefore, it is of great significance to develop a high-precision evaluation method that comprehensively considers the gradient distribution of material performance, strength degradation and fatigue-wear coupling effect, to realize accurate prediction of rolling damage accumulation, optimize maintenance strategy, prolong service life and reduce cost, which is a technical problem to be solved in the rolling field. SUMMARY

[0005] The application provides a rolling fatigue damage calculation method considering contact fatigue damage and wear coupling to solve the problems of oversimplified model and ignored coupling effect in the existing evaluation method.

[0006] To achieve the above purpose, the application adopts the following technical scheme:

[0007] The rolling fatigue damage calculation method considering contact fatigue damage and wear coupling comprises the following steps:

[0008] Step 1, build a continuous damage mechanics model of rolling material:

[0009] ,

[0010] wherein, is the damage degree of the unit at the radial depth y from the surface of the roll after N loading cycles; is the stress amplitude leading to fatigue damage of the roll material; is the damage resistance stress of the roll material; is the constant of the roll material, which is obtained by contact fatigue test; y is the radial depth;

[0011] Step two, constructing the calculation model of the contact fatigue damage of the roll:

[0012] ,

[0013] wherein, is the contact fatigue damage resistance stress of the roll; is the damage degree of the unit at the radial depth y from the surface of the roll after N loading cycles; is the normal shear stress amplitude of the cross section of the roll; is the coordinate perpendicular to the y direction and tangent to the axial cross section of the roll;

[0014] Step three, calculating the damage of the unit: dividing 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:

[0015] ,

[0016] wherein, 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 of the j-th axial discrete unit at the radial depth y from the surface in the i-th cycle period; is the number of loading cycles in the equal-interval cycle period;

[0017] In the i-th cycle period, the damage degree increment of each axial discrete unit j at different radial depths y from the surface is:

[0018] ,

[0019] wherein, is the number of loading cycles in the equal-interval cycle period;

[0020] Step four, constructing the calculation model of the wear amount of the roll material:

[0021] ,

[0022] wherein, s is the sliding rate factor between the rolls, d is the diameter of the roll for which the wear amount is calculated, is the wear coefficient of the roll material, which is determined by experiment; H is the hardness ratio of the contacting rolls; is the maximum contact stress;

[0023] Step five, determining the wear coefficient by the "strength-hardness" correlation:

[0024] ,

[0025] wherein, is the initial wear coefficient, which is calibrated by experiment; is the hardness function;

[0026] Step six, calculating the unit wear: discretize the roll barrel length direction into j axial discrete units, the jth axial discrete unit in the ith cycle period is the wear amount under the ith cycle period and jth axial discrete unit is expressed as:

[0027] ,

[0028] wherein, is the wear coefficient of the material at the radial depth y of the jth axial discrete unit in the ith cycle period; is the maximum contact stress of the jth axial discrete unit in the ith cycle period;

[0029] Step seven, iterative calculation: after discretizing the roll barrel, assigning the initial parameters and setting the iterative parameters, the iterative calculation is carried out in the divided service time interval of the roll, and the coupled contact fatigue damage and wear of the roll in the whole in-service period are iteratively calculated:

[0030] .

[0031] Preferably, in the step one, first, the fatigue strength performance data of the roll material at different depths along the radial depth y of the roll is obtained to form an original data set of "radial depth-anti-damage stress"; then the original data set is mathematically described by using an interpolation function to obtain a functional expression of the anti-damage stress of the roll material:

[0032] ,

[0033] wherein, is the anti-damage stress of the roll at the radial depth y tending to infinity; is the anti-damage stress of the roll at the surface y=0; is the attenuation coefficient, which is measured by experiment; y is the radial depth;

[0034] Rolling mill roll material damage stress The continuous damage mechanics model of the roll material is obtained by introducing the roll material continuous damage mechanics model.

[0035] Preferably, in the step two, based on the contact mechanics theory, the elastic deformation and the uneven distribution of load in the process of the roll contacting with the rolled piece are combined to obtain the roll section orthogonal shear stress amplitude :

[0036] ,

[0037] In the formula, is the maximum orthogonal shear stress of the roll section; is the minimum orthogonal shear stress of the roll section;

[0038] The roll section orthogonal shear stress amplitude is introduced into the continuous damage mechanics model of the roll material as a variable of the radial depth y, and the roll contact fatigue damage calculation model is constructed.

[0039] Preferably, in the step four, the wear height calculation formula of the axial discrete unit is obtained by combining the wear amount calculation model of the axial discrete unit.

[0040] ,

[0041] In the formula, is the stress of the load on the contact area of the jth axial discrete unit in the contact deformation area; is the adhesive wear coefficient; is the sliding distance;

[0042] The wear height calculation formula is changed to:

[0043] , In the formula, H is the hardness ratio of the contacting rolls;

[0044] In the rolling process, the rolls and the rolls 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 to finally construct the wear amount calculation model of the roll material.

[0045] Preferably, in the step six, since the roll shape is changed, the contact stress is reconstructed as:

[0046] ,

[0047] ,

[0048] 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; , respectively, the radii of the two parallel cylindrical elastic bodies in the plane strain state, when the roll is in contact with the rolled piece, R2 can be taken as infinity; E1, E2 are the elastic moduli of the two cylindrical bodies; , are the Poisson's ratios of the two cylindrical bodies.

[0049] Preferably, in the step five, the strength function of the axial discrete element is first constructed :

[0050] ,

[0051] wherein, is the tensile strength of the roll surface; is a coefficient, which is determined by experiment;

[0052] The strength function is then converted into the hardness function :

[0053] ,

[0054] wherein, is the Vickers hardness, that is:

[0055] ,

[0056] wherein, c is determined by experiment;

[0057] The is substituted into the wear coefficient formula to obtain the initial wear coefficient varying with the radial depth y.

[0058] Preferably, when the roll contact fatigue damage calculation is performed, the entire service period of the roll is divided into a plurality of continuous equal-interval cycle periods , each cycle period corresponds to a plurality of load cycle times ; when the wear calculation of the i-th cycle period is completed, the axial discrete element j will generate a wear amount , then the initial damage degree at the beginning of the damage calculation of the i+1-th cycle period is , and the remaining strength at the depth y after the calculation of the i-th cycle period is completed is taken as the initial strength of the i+1-th cycle period, which is substituted into the wear amount calculation formula for iteration.

[0059] Compared with the prior art, the present application has the following advantages:

[0060] The application establishes a rolling contact fatigue damage distribution calculation model considering the performance gradient distribution and strength degradation and the coupling of contact fatigue damage and wear; based on Archard's wear model, a wear amount calculation model considering the performance gradient distribution and strength degradation is established; the coupling accumulation of contact fatigue damage and wear is iteratively calculated combined with the service characteristics of the rolling "in-service-in-wear", and the damage distribution and residual strength are corrected, the dynamic coupling interaction simulation of fatigue damage and wear is realized, the calculation accuracy of damage distribution is significantly improved, and the rolling life management under complex working conditions is suitable.

[0061] The dynamic interaction of fatigue damage and wear is integrated for the first time, and the real simulation of service behavior is realized through iterative calculation. Based on the modeling of material performance gradient and dynamic correction of strength degradation, the coupling of contact fatigue damage and wear, the calculation accuracy of rolling damage distribution is significantly improved.

[0062] Combined with the core characteristics of the simultaneous existence, synchronous accumulation and mutual influence of "in-service-in-wear" of the rolling during in-service, the mutual coupling relationship of the "wear physical removal effect on the damage layer", the "material strength degradation effect caused by damage accumulation" and the "reconstruction effect of contact stress field caused by roll shape change and then affecting the contact fatigue damage and wear accumulation", through the closed-loop iterative system of "element damage and element wear calculation→overall roll shape correction→contact stress reconstruction→element parameter update", the dynamic coupling analysis of damage, wear and roll shape during the service period of the rolling is realized, and finally the quantitative relationship containing the iteration number N is output, the damage distribution and residual strength are corrected, and the contact fatigue damage accumulation of the rolling during in-service is accurately calculated. BRIEF DESCRIPTION OF DRAWINGS

[0063] Figure 1 It is a performance gradient distribution diagram of the application;

[0064] Figure 2 It is a damage distribution diagram of different damage layers predicted by the application, wherein (a) is the damage distribution of different damage layers of P roll, and (b) is the damage distribution of different damage layers of J roll;

[0065] Figure 3 It is a hardness distribution diagram of each roll actually measured, wherein (a) is the hardness distribution of P roll after getting off the machine, and (b) is the hardness distribution of J roll after getting off the machine. DETAILED DESCRIPTION

[0066] In order to further illustrate the technical scheme of the application, the application will be further described below through examples.

[0067] The rolling fatigue damage calculation method considering the coupling of contact fatigue damage and wear of the application comprises the following steps:

[0068] Step one, build a continuous damage mechanics model of roll material: with the gradient distribution characteristics of roll cross-section strength performance as the core basis, as shown in the figure, first, through the layered sampling test method, the roll material fatigue strength performance data at different depths along the radial depth y of the roll is obtained, forming the "radial depth-anti-damage stress" original data set. Figure 1

[0069] Subsequently, the original data set is described by an interpolation function, and the function expression of the anti-damage stress of the roll material is obtained:

[0070] ,

[0071] In the formula, is the anti-damage stress of the roll when the radial depth y of the roll from the surface tends to infinity, with the unit of MPa; is the anti-damage stress of the roll at the surface y=0, with the unit of MPa; is the attenuation coefficient, which is measured by experiment, and in actual application, it needs to be obtained according to the actual material test fitting data due to the material and heat treatment process; y is the radial depth;

[0072] The anti-damage stress of the roll material is introduced into the continuous damage mechanics model of the roll material , and the continuous damage mechanics model of the roll material is obtained:

[0073] ,

[0074] In the formula, is the damage degree of the roll at the radial depth y from the surface after N times of load cycles, with the value between 0 and 1, 0 indicating that the roll material is not damaged, and 1 indicating that the roll material is completely damaged; is the stress amplitude that causes fatigue damage of the roll material, with the unit of MPa; is the anti-damage stress of the roll material; is the constant of the roll material, which is obtained by contact fatigue test; y is the radial depth.

[0075] Step two, build a roll contact fatigue damage calculation model: based on the theory of contact mechanics, first, combined with the actual working conditions such as elastic deformation and non-uniform distribution of load in the process of roll and rolled piece contact, the maximum orthogonal shear stress amplitude of roll cross-section is obtained:

[0076] ,

[0077] In the formula, is the maximum orthogonal shear stress of the roll cross-section; ​The minimum orthogonal shear stress of the roll section;

[0078] The orthogonal shear stress amplitude of the roll section The roll material continuous damage mechanics model is introduced as a variable of the radial depth y, and a roll contact fatigue damage calculation model is constructed:

[0079] ,

[0080] In the formula, The roll contact fatigue damage stress is the ability of the roll material to resist damage accumulation, which is measured by a contact fatigue test, and the unit is MPa; The damage degree of the unit at a radial depth y from the roll surface after N load cycles is determined by the stress distribution of the contact stress field sub-model in the initial state, and the stress distribution of the roll before installation is determined by the initial roll shape L0. The orthogonal shear stress amplitude of the roll section The coordinate perpendicular to the y direction and tangent to the axial section of the roll.

[0081] Step three, calculate the unit damage: divide the entire fatigue process (the total number of stress cycles of the roll in one machine cycle) into several equal interval cycles, and in each cycle, the contact fatigue damage evolution rate of each node of the roll at different radial depths y is:

[0082] ,

[0083] In the formula, i represents the i-th cycle; j represents the j-th axial discrete unit in the length direction of the roll body; The damage degree of the j-th axial discrete unit at a radial depth y from the surface in the i-th cycle is: The number of load cycles in the equal interval cycle;

[0084] In the i-th cycle, the contact fatigue damage degree increment of each axial discrete unit j at different radial depths y from the surface is:

[0085] ,

[0086] In the formula, The number of load cycles in the equal interval cycle, that is, the number of contact fatigue damage and wear coupling iteration interval cycles.

[0087] Step four, build a wear amount calculation model of the roll material: according to the Archard wear theory, a wear model of the roll material under sliding contact conditions is established:

[0088] ,

[0089] where K is the probability of generating abrasive particles; is the sliding distance; L n is the normal load; H is the hardness ratio of the contacting rolls;

[0090] The roll is discretized into j equidistant axial discrete units along the length of the roll body, and the wear amount calculation model of each axial discrete unit is:

[0091] ,

[0092] where V(j) is the wear volume on the i-th unit of the inter-roll contact area, K abr is the adhesive wear coefficient; p(j) is the inter-roll contact stress on the j-th unit of the inter-roll contact area; is the relative sliding distance of the contact point, H is the hardness ratio of the contacting rolls;

[0093] According to the principle of volume equivalence, the volume of the roll material removed from the roll during rolling production is the volume of wear, so:

[0094] ,

[0095] where A is the inter-roll contact area of the roll, and h is the wear height of the roll.

[0096] Combined with the wear amount calculation model of the axial discrete unit, the wear height calculation formula of the axial discrete unit is obtained:

[0097] ,

[0098] where is the stress of the load on the contact area on the j-th axial discrete unit of the contact deformation area; is the adhesive wear coefficient; is the sliding distance;

[0099] The wear height calculation formula is changed by replacing the maximum contact stress of the contact deformation area:

[0100] , where H is the hardness ratio of the contacting rolls;

[0101] During rolling, the rolls and the rolls, and the rolls and the rolled piece are in relative rolling motion. In the wear height calculation formula of the axial discrete unit of the roll, the sliding rate factor s of the inter-roll is introduced, and finally the wear amount calculation model of the roll material is constructed:

[0102] ,

[0103] where s is the 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 by experiment; H is the hardness ratio of the contacting rolls; is the maximum contact stress.

[0104] Step five, determination of the wear coefficient by the "strength-hardness" correlation: first, the strength function of the axial discrete element is constructed :

[0105] ,

[0106] where is the tensile strength of the roll surface; is a coefficient, determined by experiment;

[0107] The strength function is then converted into the hardness function :

[0108] ,

[0109] where is the Vickers hardness, i.e.

[0110] ,

[0111] where c is determined by experiment;

[0112] The wear coefficient formula is then substituted by to obtain the initial wear coefficient as a function of the radial depth y

[0113] ,

[0114] where is the initial wear coefficient, calibrated by experiment; is the hardness function.

[0115] Step six, calculation of the element wear: the roll barrel length is discretized into j axial discrete elements, the wear of the jth axial discrete element in the ith cycle period under the ith cycle period is expressed as:

[0116] ,

[0117] where is the wear coefficient of the material of the jth axial discrete element at the radial depth y from the surface in the ith cycle period; is the maximum contact stress of the jth axial discrete element in the ith cycle period.

[0118] ​Due to the change of roll shape, the contact stress Reconstruction:

[0119] ,

[0120] ,

[0121] In the formula, is the normal contact stress distribution on the contact surface of the two elastic bodies; a is the contact half-width of the two contact rolls corresponding to the axial discrete unit j; , R1 and R2 are the radii of the two parallel cylindrical elastic bodies in the plane strain state, and R2 takes infinity when the roll is in contact with the rolled piece; E1 and E2 are the elastic moduli of the two cylinders, with units of MPa; , μ1 and μ2 are the Poisson's ratios of the two cylinders.

[0122] Step seven, iterative calculation: after the roll body discretization, initial parameter assignment and iterative parameter setting, the iterative calculation in the interval is carried out one by one according to the divided roll service time interval, and the coupled contact fatigue damage and wear of the roll in the whole service period is iteratively calculated:

[0123] .

[0124] Considering the characteristics of the simultaneous existence and accumulation of "in-service service-in-service wear" of the roll material during in-service service, considering the mutual coupling effect of the damage layer removal caused by wear and the strength degradation caused by damage during in-service service, the coupling accumulation of contact fatigue damage and wear is calculated by iteration, and the damage distribution and residual strength are corrected, which specifically includes:

[0125] Roll body discretization modeling: the roll body is uniformly discretized into j axial discrete units along the roll axis, denoted as unit j, (j=1, 2,..., m), and the unit width is determined according to the roll piece width and the effective contact length of the roll body;

[0126] Initial parameter assignment:

[0127] Initial unit damage : Before the roll starts to work, there is no service damage, so the cumulative damage degree of all units j and all radial depths y is assigned to 0;

[0128] Initial unit wear : Before the roll starts to work, there is no service wear, so the radial wear amount of all units j and all radial depths y is assigned to 0;

[0129] Counter k: initial coupling calculation times k=0, the 0th iteration is the initial state;

[0130] Quantitative correlation unit damage based on material microstructure dynamics theory The influence of hardness change and strength degradation on subsequent damage calculation is characterized. When the contact fatigue damage of the roll material accumulates to a certain extent, the mechanical properties of the roll material will degrade, i.e.

[0131] ,

[0132] In the formula, is the elastic modulus of the roll in the i th cycle, with units of MPa; is the elastic modulus of the roll when damage occurs, with units of MPa.

[0133] After completing the roll body discretization, initial parameter assignment, and iterative parameter setting, the iterative calculation in each interval is carried out according to the divided roll service time interval. Unit parameter updating is required during each interval calculation. The damage accumulation caused by the previous service time interval and the residual strength at different depths of the cross section, the wear amount of the roll unit corresponding to this service interval, and the roll diameter at the corresponding position of the unit after wear are calculated before the iteration. Then, the residual diameter of the corresponding cross section and the residual strength distribution of the cross section after the damage and wear of the corresponding unit position in the previous interval are substituted into the damage calculation, damage accumulation calculation, and wear amount calculation model of the next service interval.

[0134] During the iteration process, when the contact fatigue damage of the roll is calculated, the entire service period of the roll is divided into several continuous equal-interval cycle periods , and each cycle period corresponds to a certain number of load cycles . In the wear calculation of the i th cycle period, the strength parameter of unit j uses the residual strength at the initial moment of the cycle period, and the corresponding hardness is obtained, and then the wear coefficient of the cycle period is determined.

[0135] When the wear calculation of the i th cycle period is completed, unit j will produce a radial wear amount Therefore, the damage degree distribution of unit j needs to be updated in the damage calculation formula of the i+1 th unit, and the initial damage degree at the beginning of the damage calculation of the i+1 th cycle period is , and the residual strength at the depth of after the calculation of the i th cycle period is as the initial strength of the i+1 th cycle period, which is substituted into the wear amount calculation formula for iteration.

[0136] After the load cycle times in the i+1 th cycle period, the damage of unit j is .

[0137] So the iteration, iterative calculation of a complete in-service coupling contact fatigue damage and wear of the roll fatigue damage.

[0138] This embodiment calculates and verifies the fatigue damage distribution of the intermediate roll of a certain brand of 20-roll mill.

[0139] Technical scheme: The fatigue damage of the intermediate roll of the 20-roll mill is calculated and analyzed by programming the program using mathematical programming software. The intermediate roll of the mill is the main shape adjusting roll, and its fatigue damage has a significant impact on the rolling quality.

[0140] Implementation process:

[0141] 1. Model programming: Based on the iterative model, the damage accumulation calculation program is realized by using mathematical programming software.

[0142] 2. Core parameter determination:

[0143] (1) Material performance gradient distribution: The hardness gradient data is measured by experiment, and the interpolation function is fitted to describe the performance gradient distribution;

[0144] (2) Cycle load parameters: rolling force, rotating speed, contact stress level.

[0145] (3) Material parameters: m=13, =5778MPa.

[0146] (4) Cycle jump algorithm parameters: the maximum damage degree increment of each cycle is set to 0.1, and the critical damage degree D c is set to 0.99.

[0147] 3. Selection of research object:

[0148] (1) P roll: taper length 255mm, transverse displacement 0mm;

[0149] (2) J roll: crown 0mm;

[0150] Selection basis: As the core shape control roll of the mill, the fatigue damage of the two will directly affect the rolling quality.

[0151] 4. Damage distribution calculation:

[0152] The fatigue damage distribution of P roll and J roll at three depths of surface layer, 0.2mm from surface layer and 0.6mm from surface layer is calculated by using the fatigue damage accumulation calculation program, and the predicted damage distribution is shown in Figure 2 .

[0153] 5. Model verification:

[0154] (1) Verification logic:

[0155] 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.

[0156] (2) Verification results:

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 6. Verification Conclusion:

[0161] The consistency between the damage distribution and the hardness distribution verifies the correctness of the model in this invention.

[0162] 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 roll fatigue damage calculation method considering coupling of contact fatigue damage and wear according to claim 1, characterized by, 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 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