A simulation method for simulating shot peening of structural components with projectiles obliquely incident

Abstract

The present invention proposes a simulation method for simulating shot peening strengthening of a structural member with an inclined projectile impact. The number of projectiles at saturation shot peening is calculated based on the crater diameter obtained from the finite element simulation of a single projectile impact and the saturation shot peening coverage rate; a calculation method for residual stress at different projectile incident angles and projectile incident velocities is established, and the residual stress along the depth direction of the projectile impact area when the projectile is obliquely incident is calculated based on the residual stress along the depth direction of the projectile impact area when the projectile is vertically incident; a calculation method for residual stress in the area of multiple projectile impacts is established, and the residual stress along the depth direction of the projectile impact area during multiple projectile impacts is calculated based on the residual stress along the depth direction of the projectile impact area at different projectile incident velocities and projectile incident angles; the residual stress under different shot peening conditions is introduced into the structural member model in the form of initial stress, and thus the finite element simulation of the shot peening strengthening deformation of the structural member with an inclined projectile impact is carried out.

Description

Technical Field

[0001] The present invention relates to the technical field of finite element simulation of shot peening, and specifically to a simulation method for simulating shot peening of a structural member with inclined projectile incidence. Background Art

[0002] Shot peening is a surface treatment method that can effectively improve the fatigue life of workpieces and improve the surface integrity of workpieces, and is widely used in military and civilian fields such as aviation, aerospace, shipbuilding, and automobiles. The shot peening process is a special process in which a large number of projectiles impact the surface of a workpiece, causing elastic-plastic deformation of the material on the surface layer of the workpiece to introduce residual compressive stress, and under the action of the residual compressive stress, the workpiece is bent and extended to form the required shape. In order to reduce the number of tests and lower the research and development costs, using the finite element numerical analysis method to analyze the shot peening process has become an important research means. The shot peening process not only involves the impact process of a large number of projectiles, but also involves the deformation of parts during the shot peening process. It is currently very difficult to simulate its strengthening process according to the actual projectile impact situation. Therefore, simulating the shot peening process by an equivalent method has become a feasible approach.

[0003] The Chinese patent "A finite element simulation method for shot peening deformation based on ABAQUS" with the publication number CN104866652 established a finite element model of uniform projectile impact, and wrote the residual stress distribution results obtained by simulation into the shot peening finite element model in the form of an equivalent load to obtain the deformation of the part under a given initial stress. The projectile impact simulation was carried out by the dynamic analysis solver of the finite element analysis software ABAQUS, the initial stress was defined by the subroutine SIGINI in the finite element analysis software, and the springback calculation was carried out by the static analysis solver of the finite element analysis software ABAQUS. The Chinese patent "A numerical simulation method for shot peening process considering projectile random effects" with the publication number CN109359365 considered the random effects of projectiles when establishing the projectile generation algorithm, and the generated projectiles were given different projectile sizes, projectile velocity magnitudes and projectile directions, which was more in line with the projectile situation in the actual shot peening process. However, in the method of the above patent, the simulation of shot peening deformation when the projectile is inclined to enter is not considered, nor is the secondary impact effect of the rebounding projectile on the part considered. Summary of the Invention

[0004] In order to overcome the deficiencies in existing shot peening strengthening simulation technologies, this paper proposes a simulation method for simulating shot peening strengthening of structural components with inclined projectile incidence. The number of projectiles during saturation shot peening is calculated based on the crater diameter obtained from finite element simulation of single-projectile impact and the saturation shot peening coverage rate; the residual stress in the depth direction of the projectile impact area during inclined projectile incidence is calculated based on the residual stress in the depth direction of the projectile impact area when the projectile is vertically incident; the residual stress in the depth direction of the projectile impact area during secondary projectile impact is calculated based on the residual stress in the depth direction of the projectile impact area at different projectile incidence velocities and projectile incidence angles; the residual stresses under different shot peening conditions are introduced into the structural component model in the form of initial stresses, and thus the finite element simulation of shot peening strengthening deformation of structural components with inclined projectile incidence is carried out.

[0005] The technical solution adopted by the present invention to solve its technical problems is: a simulation method for simulating shot peening strengthening of structural components with inclined projectile incidence, which is characterized by including the following contents:

[0006] First step, establish a distributed finite element model of projectile impact in the finite element analysis software ABAQUS. The model includes a representative unit model of the structural component and a projectile model. There is a layer of infinite elements on each of the side and bottom surfaces of the representative unit model of the structural component. The projectile model is a 1 / 2 rigid body model. The number of projectiles is calculated based on the diameter of the crater and the saturation shot peening coverage rate; the projectile incidence velocity is input in the way of general predefined field, and the residual stress in the depth direction of the projectile impact area is obtained after the simulation is completed.

[0007] Second step, calculate the residual stress in the depth direction of the projectile impact area during inclined projectile incidence based on the residual stress in the depth direction of the projectile impact area when the projectile is vertically incident. The calculation method for the residual stress in the depth direction of the projectile impact area during inclined projectile incidence is:

[0008]

[0009] where k is the correction coefficient; θ is the projectile incidence angle; v is the projectile incidence velocity, unit m / s; σ(v 0° ,0°,h) is the residual stress at a depth of h in the projectile impact area when the projectile incidence velocity is v 0° and the projectile incidence angle is 0°, unit MPa; σ(v,θ,h) is the residual stress at a depth of h in the projectile impact area when the projectile incidence velocity is v and the projectile incidence angle is θ, unit MPa.

[0010] Step 3: Calculate the residual stress along the depth direction of the area repeatedly struck by the projectiles based on the residual stress along the depth direction of the impact area of the projectiles at different projectile incident velocities and projectile incident angles; the repeated striking of the projectiles means that the reflected projectile impacts on the area that has already been struck by the projectile, that is, the reflection velocity of the projectile becomes the new incident velocity; the calculation method for the residual stress along the depth direction of the area repeatedly struck by the projectiles is as follows:

[0011]

[0012] where α is an empirical coefficient with a value range of 2.3 to 5; σ n is the residual stress after the projectile impacts the structural member for n times, with the unit of MPa; σ i (v, θ, h) is the residual stress corresponding to the projectile incident angle and projectile incident velocity when the projectile impacts the structural member for the i-th time, with the unit of MPa; n is the total number of times the structural member is struck by the projectile. When n = 1, it means that the reflected projectile impacts on the area that has not been struck by the projectile.

[0013] Step 4: Introduce the residual stress under different shot peening conditions into the structural member model in the form of the initial stress, and conduct a finite element simulation of the shot peening strengthening deformation of the projectile obliquely incident on the structural member.

[0014] Furthermore, the diameter of the crater is obtained from the finite element simulation of a single projectile impact. The finite element simulation of a single projectile impact is the finite element simulation carried out in Step 1 after setting the number of projectiles to one.

[0015] Furthermore, the calculation method for the number of projectiles calculated from the saturated shot peening coverage rate is as follows:

[0016]

[0017] where n represents the number of projectiles; d represents the diameter of the crater, with the unit of mm; S represents the area of the projectile impact region, with the unit of mm2; η represents the shot peening coverage rate, and takes the value of 200% for saturated shot peening.

[0018] Furthermore, the correction coefficient k is calibrated through saturated shot peening tests, and the calculation method is as follows:

[0019]

[0020] where M exp is the bending moment obtained from the test, with the unit of N·mm; M sim is the bending moment obtained from the simulation, with the unit of N·mm.

[0021] Further, introducing the residual stresses under different shot peening conditions into the structural member model in the form of initial stresses is realized through the subroutine SIGINI in the finite element analysis software ABAQUS. The structural member model adopts a shell element composite layer model, and the finite element simulation of the shot peening deformation of the projectile obliquely incident on the structural member is carried out by the static analysis solver of the finite element analysis software ABAQUS for rebound calculation.

[0022] Beneficial effects

[0023] The present invention proposes a simulation method for simulating the shot peening strengthening of a projectile obliquely incident on a structural member. The number of projectiles at saturation shot peening is calculated according to the crater diameter obtained from the finite element simulation of a single projectile impact and the saturation shot peening coverage rate; a calculation method for residual stresses under different projectile incident angles and projectile incident velocities is established, and the residual stresses in the depth direction of the projectile impact area when the projectile is obliquely incident are calculated based on the residual stresses in the depth direction of the projectile impact area when the projectile is vertically incident; a calculation method for the residual stresses in the area of multiple projectile strikes is established, and the residual stresses in the depth direction of the projectile impact area during multiple projectile strikes are calculated based on the residual stresses in the depth direction of the projectile impact area under different projectile incident velocities and projectile incident angles; the residual stresses under different shot peening conditions are introduced into the structural member model in the form of initial stresses, and the finite element simulation of the shot peening deformation of the projectile obliquely incident on the structural member is carried out accordingly. Description of the drawings

[0024] Figure 1 is a flowchart of a simulation method for simulating the shot peening strengthening of a projectile obliquely incident on a structural member;

[0025] Figure 2 is a schematic diagram of the representative unit model of the structural member and the projectile model in the embodiment of the present invention;

[0026] Figure 3 is the average residual stress diagram in the depth direction of the projectile impact area corresponding to a projectile incident angle of 0° and a projectile incident velocity of 50 m / s in the embodiment of the present invention;

[0027] Figure 4 is the cross-sectional contour diagram of the double-reinforced structural member model in the embodiment of the present invention;

[0028] Figure 5 is the simulation result diagram of the shot peening strengthening deformation of the double-reinforced structural member with the projectile obliquely incident on the structural member in the embodiment of the present invention;

[0029] In the figure: 1. Representative unit model of the structural member; 2. Projectile model; 3. Region 3; 4. Region 4; 5. Region 5; 6. Region 6; 7. Cross-section of the double-reinforced structural member model; 8. Double-reinforced structural member model. Specific implementation manners

[0030] The following further describes in detail the embodiments of the present invention in conjunction with the accompanying drawings and embodiments.

[0031] First step, establish a distributed finite element model of projectile impact in the finite element analysis software ABAQUS. The model includes a representative unit model 1 of the structural member and a projectile model 2, as Figure 2 shown. Add an infinite element layer on the side and bottom surfaces of the representative unit model of the structural member. The element type of the representative unit model of the structural member is C3D8R, and the element type of the infinite element region is CIN3D8. The projectile model is a 1 / 2 rigid body model, and the number of projectiles is calculated according to the diameter of the crater and the saturation shot peening coverage rate. Fix the bottom surface of the representative unit model of the structural member, set the normal contact relationship between the projectile model and the representative unit model of the structural member as hard contact, and set the tangential friction coefficient to 0.2. Input the projectile incident velocity in the way of general predefined field, and obtain the residual stress along the depth direction in the projectile impact area after the simulation is completed;

[0032] In this embodiment, the J-C constitutive model is adopted, with a material density of 2770 kg / m3, an elastic modulus of 72.6 GPa, a Poisson's ratio of 0.33, an initial yield stress A of 369 MPa, a material strain hardening modulus B of 684 MPa, a hardening index n of the material of 0.73, and a material strain rate hardening coefficient C of 0.0083.

[0033] In this embodiment, the projectile flow rate is 10 kg / min, the projectile diameter is 3.175 mm, and the shot peening pressure is 0.5 MPa. Substitute into the formula for calculating the average projectile incident velocity:

[0034]

[0035] In the formula, p is the shot peening air pressure, unit MPa; m is the projectile flow rate, unit kg / min; d is the projectile diameter, unit mm;

[0036] Conduct a single projectile impact finite element simulation according to the calculated projectile incident velocity. In the single projectile impact finite element simulation, the projectile incident angle is 0°, and the diameter of the crater obtained after the simulation is completed is 1.12 mm.

[0037] In this embodiment, the projectile impact area in the distributed projectile impact finite element simulation is 2 mm × 2 mm. Substitute the crater diameter and the projectile impact area into the formula to calculate the number of projectiles at saturation shot peening:

[0038]

[0039] Among them, n represents the number of projectiles; d represents the diameter of the crater, unit mm; S represents the area of the projectile impact area, unit mm2; η represents the shot peening coverage rate, taking a value of 200% at saturation shot peening;

[0040] According to the calculated number of projectiles and the projectile incident velocity during saturation peening, a uniform projectile impact finite element simulation of perpendicular projectile incidence is carried out. After the simulation is completed, the residual stress in the depth direction of the projectile impact area is obtained. In order to more accurately describe the value of the residual stress, the average value of the residual stress at the same thickness layer in the projectile impact area is used as the measure of the residual stress at this thickness, as Figure 3 shown.

[0041] In the second step, the bending moment value obtained from the known test is 1785 N·mm; the bending moment value calculated according to the average residual stress in the depth direction of the projectile impact area is 1650 N·mm, that is, the simulated bending moment is 1650 N·mm. Substitute into the formula to calculate the correction factor:

[0042]

[0043] where, M exp is the bending moment obtained from the test, in units of N·mm; M sim is the bending moment obtained from the simulation, in units of N·mm;

[0044] In this embodiment, the projectile incident angle is 45°, the projectile incident velocity is 50 m / s, and a single projectile impact simulation of inclined projectile incidence is carried out according to the peening parameters. After the simulation is completed, the projectile reflection velocity is 27 m / s and the reflection angle is 56.2°.

[0045] Calculate the residual stress in the depth direction of the projectile impact area when the projectile is inclined to impact according to the residual stress in the depth direction of the projectile impact area when the projectile is vertically incident; substitute the projectile incident angle and the projectile incident velocity into the formula to obtain the residual stress in the depth direction of the projectile impact area when the projectile is inclined to impact:

[0046]

[0047] where, k is the correction factor; θ is the projectile incident angle; v is the projectile incident velocity, in units of m / s; σ(v 0° , 0°, h) is the residual stress at a depth of h in the projectile impact area when the projectile incident velocity is v 0° and the projectile incident angle is 0°, in units of MPa; σ(v, θ, h) is the residual stress at a depth of h in the projectile impact area when the projectile incident velocity is v and the projectile incident angle is θ, in units of MPa;

[0048] In this embodiment, the residual stress represented by σ(50, 0°, h) is as Figure 3As shown in the figure. When the projectile incident angle is 45° and the projectile incident velocity is 50 m / s and they are substituted into the above calculation method, the residual stress in the depth direction of the projectile impact area is 0.54σ(50, 0°, h); when the projectile incident angle is 33.8° and the projectile incident velocity is 27 m / s and they are substituted into the above calculation method, the residual stress in the depth direction of the projectile impact area is 0.22σ(50, 0°, h).

[0049] Step 3: Calculate the residual stress in the depth direction of the area repeatedly struck by the projectile according to the residual stress in the depth direction of the projectile impact area under different projectile incident velocities and projectile incident angles; the repeated striking of the projectile means that the reflected projectile impacts on the area that has already been struck by the projectile, that is, the reflected velocity of the projectile becomes the new incident velocity; the calculation method for the residual stress in the depth direction of the area repeatedly struck by the projectile is as follows:

[0050]

[0051] where α is an empirical coefficient, and its value range is 2.3 - 5; σ n is the residual stress after the projectile strikes the structural member n times, with the unit of MPa; σ i (v, θ, h) is the residual stress corresponding to the projectile incident velocity and projectile incident angle when the projectile strikes the structural member for the i-th time, with the unit of MPa; n is the total number of times the structural member is struck by the projectile. When n takes the value of 1, it means that the reflected projectile impacts on the area that has not been struck by the projectile;

[0052] In this embodiment, α is taken as 3 and n is taken as 2. In the area of the projectile's second strike in this embodiment: the projectile incident angle during the first projectile strike is 0°, and the projectile incident velocity is 50 m / s; the projectile incident angle during the second projectile strike is 33.8°, and the projectile incident velocity is 27 m / s. Substituting into the above calculation method, the residual stress in the depth direction of the area of the projectile's second strike is as follows:

[0053]

[0054] Step 4: Introduce the residual stress under different shot peening conditions into the structural member model 8 in the form of initial stress, and perform finite element simulation on the shot peening strengthening deformation of the projectile obliquely incident on the structural member; introducing the residual stress under different shot peening conditions into the double-reinforced structural member model 8 in the form of initial stress is realized through the subroutine SIGINI in the finite element analysis software ABAQUS. The double-reinforced structural member model 8 adopts a shell element composite layer model. The finite element simulation on the shot peening strengthening deformation of the projectile obliquely incident on the structural member is carried out through the static analysis solver of the finite element analysis software ABAQUS for springback calculation.

[0055] In this embodiment, the structural member model 8 is a double-reinforced structure, and the structural member model is as Figure 5 shownFigure 4 It is a sectional contour diagram of the model. The cross-section 7 of the double-reinforcement structural member model includes regions 3, 4, 5, and 6, and its sectional contour diagram is as follows Figure 4 shown. The shot peening parameters on the upper and lower sides of region 3 and the upper and lower sides of region 4 of the cross-section 7 of the double-reinforcement structural member model are a shot peening incident velocity of 50 m / s and a shot peening incident angle of 0°; the shot peening parameters on the lower side of region 5 of the cross-section 7 of the double-reinforcement structural member model are a shot peening incident velocity of 50 m / s and a shot peening incident angle of 0°; the shot peening parameters on the left and right sides of region 6 of the cross-section 7 of the double-reinforcement structural member model are a shot peening incident velocity of 50 m / s and a shot peening incident angle of 45°. The shot peening projectiles hitting region 6 rebound and then hit regions 4 and 5 again. That is, the shot peening incident angle at the second shot peening impact on the upper side of region 4 is 33.8° and the shot peening incident velocity is 27 m / s, and the shot peening incident angle on the upper side of region 5 is 33.8° and the shot peening incident velocity is 27 m / s. Introduce the residual stresses under the above different shot peening conditions into the shell element model of the structural member, and carry out the simulation of shot peening strengthening deformation of the structural member with inclined shot peening incidence. The results obtained after the simulation are as follows Figure 5 shown.

Claims

1. A simulation method for simulating shot peening of a structural member with obliquely incident projectiles, characterized in that The following contents are included: 1-1 Establish a distributed projectile impact finite element model in the finite element analysis software ABAQUS. The model includes a representative unit model of the structural component and a projectile model. There is an infinite element layer on each of the side and bottom surfaces of the representative unit model of the structural component. The projectile model is a 1 / 2 rigid body model. The number of projectiles is calculated based on the diameter of the crater and the saturation shot peening coverage rate. The projectile incident velocity is input in the form of a general predefined field. After the simulation is completed, the residual stress in the depth direction of the projectile impact area is obtained. 1-2 Calculate the residual stress in the depth direction of the projectile impact area when the projectile is obliquely incident based on the residual stress in the depth direction of the projectile impact area when the projectile is vertically incident. The calculation method for the residual stress in the depth direction of the projectile impact area when the projectile is obliquely incident is as follows: where k is the correction coefficient; θ is the projectile incident angle; v is the projectile incident velocity, in m / s; σ(v 0° , 0°, h) is the residual stress at a depth of h in the projectile impact area when the projectile incident velocity is v 0° and the projectile incident angle is 0°, in MPa; σ(v, θ, h) is the residual stress at a depth of h in the projectile impact area when the projectile incident velocity is v and the projectile incident angle is θ, in MPa; 1-3 Calculate the residual stress in the depth direction of the projectile multi-strike area based on the residual stress in the depth direction of the projectile impact area under different projectile incident velocities and projectile incident angles. The projectile multi-strike means that the projectile after reflection impacts on the area that has already been impacted by the projectile, that is, the reflection velocity of the projectile becomes the new incident velocity. The calculation method for the residual stress in the depth direction of the projectile multi-strike area is as follows: Among them, α is an empirical coefficient, and its value range is 2.3 to 5; σ n is the residual stress after the nth projectile impacts the structural member, with the unit of MPa; σ i (v, θ, h) is the residual stress corresponding to the projectile incident angle and the projectile incident velocity when the ith projectile impacts the structural member, with the unit of MPa; n is the total number of times the structural member is impacted by the projectile. When n takes the value of 1, it means that the projectile after reflection impacts the area that has not been impacted by the projectile. 1-4 Introduce the residual stress under different shot peening conditions into the structural component model in the form of initial stress, and thus perform a finite element simulation of the shot peening strengthening deformation of the projectile obliquely incident on the structural component.

2. The simulation method for simulating shot peening of a structural member with obliquely incident projectiles according to claim 1, characterized in that, The diameter of the crater is obtained from the finite element simulation of single projectile impact. The finite element simulation of single projectile impact is the finite element simulation carried out in 1-1 after setting the number of projectiles to one.

3. The simulation method for simulating shot peening of a structural member with obliquely incident projectiles according to claim 1, characterized in that, The calculation method for obtaining the number of projectiles calculated from the saturation shot peening coverage rate is as follows: Wherein, n represents the number of projectiles; d represents the diameter of the crater, in mm; S represents the area of the projectile impact area, in mm 2 ; η represents the shot peening coverage rate, and takes a value of 200% during saturation shot peening.

4. The simulation method for simulating shot peening of a structural member with obliquely incident projectiles according to claim 1, characterized in that, The correction coefficient k is calibrated through saturation shot peening tests. The calculation method is as follows: Among them, M exp is the bending moment obtained from the test, with the unit of N·mm; M sim is the bending moment obtained from the simulation, with the unit of N·mm.

5. The simulation method for simulating shot peening of a structural member with obliquely incident projectiles according to claim 1, characterized in that, The introduction of the residual stress under different shot peening conditions into the structural component model in the form of initial stress is realized through the subroutine SIGINI in the finite element analysis software ABAQUS. The structural component model adopts a shell element composite layer model. The finite element simulation of the shot peening strengthening deformation of the projectile obliquely incident on the structural component is carried out by the static analysis solver of the finite element analysis software ABAQUS for springback calculation.

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