Welding quality prediction method for ultrasonic continuous welding

Abstract

The invention provides a welding quality prediction method for ultrasonic continuous welding, and belongs to the technical field of thermoplastic composite welding. Comprising the steps of setting a weldment, determining the surface sound intensity energy of the weldment in the ultrasonic continuous welding process, determining the energy absorption rate of the weldment in the ultrasonic continuous welding process, determining the range of energy required by a weldment material, and establishing an ultrasonic continuous welding quality prediction model. In order to complete establishment of an ultrasonic continuous welding quality prediction model, the welding speed range needs to be determined, and then the welding quality corresponding to the welding speed is obtained. According to the method, the influence of the welding pressure on the sound wave velocity is fully considered, so that the accuracy of the model is remarkably improved, the influence of the energy of the welding radiation area on the temperature rise of the non-welded part is ensured to be brought into the quality prediction model in the welding process, the over-welding phenomenon is effectively improved, more accurate quality prediction is realized, and the welding quality is improved. And a more reliable control means is provided for the welding process.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermoplastic composite welding, and particularly relates to a method for predicting the welding quality of ultrasonic continuous welding. Background Art

[0002] Due to their low density, excellent mechanical properties, low processing cost, and recyclability, thermoplastic composites have been widely used in industrial fields such as the automotive industry, aerospace, and medical devices that pursue lightweight and high performance. However, due to the high viscosity of the thermoplastic composite matrix, the processing and forming size is limited, and more efficient connection technologies are required. Ultrasonic welding is a commonly used composite connection technology, which has the advantages of fast welding speed, high welding strength, good sealing performance, clean and pollution-free, and low cost.

[0003] However, with the wide application of thermoplastic composites in large composite structural parts such as carbon fiber vehicle bodies, carbon fiber vehicle chassis, carbon fiber trailers, and the middle section of aircraft fuselages, it is difficult to connect large-size joints in the above structural parts using traditional ultrasonic single-point static welding technology due to the limitation of the size of the welding head.

[0004] To solve the above problems, researchers in related fields have further carried out research on ultrasonic continuous welding. Ultrasonic continuous welding refers to the process in which, while ultrasonic welding is performed, the workpiece and the welding head continuously move relative to each other along the welding plane to form a continuous and complete weld seam.

[0005] Compared with the traditional ultrasonic single-point static welding process, during the ultrasonic continuous welding process, the sound intensity generated by the welding head acting on the material surface will generate a welding energy radiation area, which will lead to the accumulation of energy during the movement of the welding head. In addition, during the ultrasonic continuous welding process, the pressure applied by the welding head has a more significant impact on the welding quality. Compared with the fixed state of the welding head in single-point welding, the movement of the welding head will cause the material to deform, thereby generating a horizontal pressure. Therefore, the traditional ultrasonic single-point welding quality prediction method cannot be directly applied to continuous welding.

[0006] Therefore, during the ultrasonic continuous welding of current thermoplastic composites, due to the influence of the sound intensity radiation area caused by the movement of the welding head on the welding process, the energy distribution in the starting, steady-state, and termination stages of welding becomes uneven, making it difficult to predict the quality of ultrasonic continuous welding. Summary of the Invention

[0007] The problem to be solved by the present invention is to provide a method for predicting the welding quality of ultrasonic continuous welding that is efficient, simple, widely applicable, and capable of effective prediction.

[0008] To solve the above technical problems, the technical solution adopted by the present invention is: A method for predicting the welding quality of ultrasonic continuous welding, comprising the following steps: S1. Setting of the workpieces: Place the workpieces on the base. The workpieces include an upper plate and a lower plate. The welding head of the welder acts on the surface of the workpieces. During the ultrasonic continuous welding process, the sound intensity generated by the welding head generates welding energy acting on the workpieces to weld the upper plate and the lower plate. S2. Determine the sound intensity energy on the surface of the workpiece 2 during the ultrasonic continuous welding process I b : In the formula, I f is the sound intensity energy of the radiation area on the surface of the workpiece; I 0 is the sound intensity energy of the ultrasonic oscillation area under the welding head; Among them, I 0 is: In the formula, f is the welder frequency, A 0 is the welder amplitude, c 0焊头 is the sound speed of the sound wave in the non-pressure state of the welding head, ρ 焊头 is the density of the welding head; Among them, I f is: In the formula, p(r) is the sound intensity energy attenuation curve of the radiation area on the surface of the workpiece; R is the radiation radius of the radiation area on the surface of the workpiece; r is any position within the radiation radius R; Among them, p(r) is: In the formula, p 1, p 2… p n are the fitting curve polynomial coefficients; X is the maximum energy of the radiation area on the surface of the workpiece; n is the fitting order; S3. Determine the energy absorption rate of the workpiece during the ultrasonic continuous welding process W : In the formula, I Li is the sound intensity energy after i cycles; S is the welding area; n总 is the total number of cycles; Among them, the Kelvin-Voigt model is used to characterize the sound intensity energy i after I Li cycles: In the formula, I z is the total energy entering the upper plate; x 1 is the thickness of the upper plate, x 2 is the thickness of the lower plate, i is the number of acoustic wave cycles; λ is the viscous damping; is the acoustic wave reflection coefficient between the welded part and the base; is the acoustic wave reflection coefficient between the welded part and the sonotrode; Among them, I z is: In the formula, is the acoustic wave transmission coefficient between the sonotrode and the welded part; S4. Determine the energy required for the welded material Q total range: In the formula, Q total is the energy required for the welded material; Q melting is the energy required for the welding material to reach the melting temperature; Q decomposition is the energy required for the welding material to reach the decomposition temperature; S5. Establish a prediction model for ultrasonic continuous welding quality: In order to establish a prediction model for ultrasonic continuous welding quality, it is necessary to determine the welding speed range, and then obtain the welding quality corresponding to the welding speed; In the formula: v is the welding speed, d is the welding distance.

[0009] Furthermore, in step S2, c 0焊头 is: In the formula, E 焊头 is the Young's modulus of the sonotrode.

[0010] Furthermore, in step S2, R is: In the formula, a is the long side of the rectangular welding head, b is the short side of the rectangular welding head, f(θ) is the factor of the sound field scattering effect, representing the function of the sound wave propagation direction θ in the sound field, and the scattering coefficient can be used to represent the scattering effect in the sound field.

[0011] Furthermore, in step S3, the sound wave reflection coefficient and the sound wave transmission coefficient between each structure remain unchanged during each cycle. Therefore, the following sound wave reflection coefficient and sound wave transmission coefficient are calculated based on the sound wave reflection coefficient and the sound wave transmission coefficient in the first cycle; The sound wave reflection coefficient and the sound wave transmission coefficient between each structure are respectively ： In the formula, is the sound wave reflection coefficient between the welding head and the welded part; is the sound wave transmission coefficient between the welded part and the base; ρ 焊件 is the density of the welded part; ρ 基座 is the density of the base; c 0基座 is the sound velocity in the base under the condition of no pressure; is the sound velocity in the compressed welded part.

[0012] Furthermore, the value of is the same as the value of

[0013] Furthermore, in step S4, Qtotal is: In the formula, Q heating is the energy required for the temperature rise of the welded part material, Q m is the energy required for the melting of the welding material, m is the mass of the welding material, C p is the specific heat capacity of the welding material, ΔT is the temperature rise of the welding material, L is the latent heat of fusion of the welding material; In the formula, ΔT melting is the temperature rise of the welding material reaching the melting temperature; ΔT decomposition is the temperature rise of the welding material reaching the decomposition temperature; ΔQ is the endothermic decomposition of the welded part.

[0014] Due to the adoption of the above technical solution, the present invention has the following beneficial effects: The present invention studies the sound intensity energy in the ultrasonic oscillation area under the welding head, the influence of the welding pressure on the sound velocity of the sound wave, the influence of the energy radiation area on the sound intensity energy of the surface of the welded part, and the energy attenuation mode of the sound intensity.

[0015] First of all, by fully considering the influence of the welding pressure on the sound wave velocity, the present invention accurately quantifies the propagation velocity of the ultrasonic wave, thereby significantly improving the accuracy of the model. This optimization makes the analysis of the ultrasonic continuous welding process more perfect, ensures the continuous stability of the welding quality, and effectively improves the problem of unstable welding prediction results.

[0016] Secondly, the present invention considers the welding radiation area during the welding process, ensures that the influence of the energy in this area on the temperature rise of the unwelded part is incorporated into the quality prediction model, thereby effectively improving the over-welding phenomenon caused by not considering the energy in the welding area, achieving more accurate quality prediction, and providing a more reliable control means for the welding process.

[0017] In addition, the Kelvin-Voigt model of the present invention allows the viscous damping to be adjusted according to the frequency change. By introducing the viscous damping component, the dynamic behavior of complex materials is more finely depicted, which is more in line with the viscoelastic characteristics of the materials during the ultrasonic welding process, thereby further improving the accuracy of the model.

[0018] Furthermore, the present invention also has excellent flexibility, and its design can adapt to the welding requirements under different working conditions, ensuring that the accuracy of the welding quality prediction is not affected when predicting during the welding process of different materials.

[0019] At the same time, the present invention can determine the appropriate range of welding parameter selection by inputting the material parameters of the welded part and the welding machine parameters (including the welding speed), and obtain the welded joint with the corresponding welding quality, thereby solving the problem of poor welding quality caused by not knowing the appropriate welding parameters. The present invention is applicable to various welding heads and materials with different shapes and has a wide range of applications. Brief Description of the Drawings

[0020] The present invention will be specifically described below with reference to the accompanying drawings and in combination with examples. The advantages and implementation manners of the present invention will become more obvious. The content shown in the accompanying drawings is only used for the explanation of the present invention and does not constitute any limitation to the present invention. In the drawings: Figure 1 It is a schematic diagram of the ultrasonic continuous welding quality prediction process of the present invention.

[0021] Figure 2 It is a schematic diagram of the deformation of the welded part after the welding head of the present invention presses on the welded part.

[0022] In the figure: 1. Welding head; 2. Welded part; 3. Base; 21. Upper plate; 22. Lower plate. Specific implementation manner

[0023] As Figure 1 shown, a welding quality prediction method for ultrasonic continuous welding of the present invention includes the following steps: S1. Setting of the welded part 2: Place the welded part 2 on the base 3. The welded part 2 includes an upper plate 21 and a lower plate 22; The welding head 1 of the welding machine acts on the surface of the welded part 2. During the ultrasonic continuous welding process, the sound intensity generated by the welding head 1 will generate welding energy acting on the welded part 2 to weld the upper plate 21 and the lower plate 22.

[0024] S2. Determine the sound intensity energy on the surface of the welded part 2 during the ultrasonic continuous welding process I b : In the formula, I f is the sound intensity energy of the radiation area on the surface of the welded part; I 0 is the sound intensity energy of the ultrasonic oscillation area under the welding head; Among them, I 0 is: In the formula, f is the welding machine frequency, A 0 is the welding machine amplitude, c 0焊头 is the sound velocity of the sound wave in the non-pressure state of the welding head, ρ 焊头 is the density of the welding head; Since the calculation formula of the sound velocity is: In the formula, c is the sound velocity of the sound wave in the material, E is the Young's modulus of the material, ρis the density of the material; Therefore, c 0焊头 is: In the formula, E 焊头 is the Young's modulus of the sonotrode; Among them, I f is: In the formula, p(r) is the sound intensity energy attenuation curve of the radiation area on the surface of the welded part; R is the radiation radius of the radiation area on the surface of the welded part; r is any position within the radiation radius R; Among them, p(r) is: In the formula, p 1, p 2… p n are the polynomial coefficients of the fitting curve; X is the maximum energy of the radiation area on the surface of the welded part; n is the number of fitting times.

[0025] Among them, R is: In the formula, a is the long side of the rectangular sonotrode, b is the short side of the rectangular sonotrode, f(θ) is the factor of the sound field scattering effect, representing the function of the sound wave propagation direction θ in the sound field, and the scattering effect in the sound field can be represented by the scattering coefficient.

[0026] S3. Determine the energy absorption rate of the welded part during continuous ultrasonic welding W : In the formula, I Li is the sound intensity energy after i cycles; S is the area of the welding area; n 总 is the total number of cycles; Among them, the Kelvin-Voigt model is used to characterize the sound intensity energy i after I Li cycles: Wherein, I z is the total energy entering the upper plate; x 1 is the thickness of the upper plate, x 2 is the thickness of the lower plate, i is the number of acoustic wave cycles; λ is the viscous damping; is the acoustic wave reflection coefficient between the welded part and the base; is the acoustic wave reflection coefficient between the welded part and the welding head; Wherein, I z is: Wherein, is the acoustic wave transmission coefficient between the welding head and the welded part; Since the acoustic wave reflection coefficient and the acoustic wave transmission coefficient between the structures remain unchanged during each cycle, the following acoustic wave reflection coefficient and acoustic wave transmission coefficient are calculated based on the acoustic wave reflection coefficient and acoustic wave transmission coefficient of the first cycle; Then, the acoustic wave reflection coefficient and the acoustic wave transmission coefficient between the structures of the present invention are respectively ： Wherein, is the acoustic wave reflection coefficient between the welding head and the welded part; is the acoustic wave transmission coefficient between the welded part and the base; ρ 焊件 is the density of the welded part; ρ 基座 is the density of the base; c 0基座 is the sound velocity of the acoustic wave in the unpressurized state of the base; is the sound velocity in the compressed welded part.

[0027] Wherein, the value of is the same as the value of

[0028] S4. Determine the energy required for the welded part material Q total range: Wherein, Q total is the energy required for the welded part material; Q melting is the energy required for the welding material to reach the melting temperature; Qdecomposition The energy required for the welding material to reach the decomposition temperature; Among them, Qtotal is: In the formula, Q heating is the energy required for the temperature rise of the welded part material, Q m is the energy required for the melting of the welding material, m is the mass of the welding material, C p is the specific heat capacity of the welding material, ΔT is the temperature rise of the welding material, L is the latent heat of fusion of the welding material.

[0029] S5. Establish a quality prediction model for ultrasonic continuous welding: To establish a quality prediction model for ultrasonic continuous welding, it is necessary to determine the welding speed range, and then the welding quality corresponding to the welding speed can be obtained; In the formula: v is the welding speed, d is the welding distance.

[0030] Example: In the continuous welding process selected in this example, the amplitude of the ultrasonic continuous welding machine A 0 = 0.00008 m, the welding machine frequency f = 20000 HZ, the welding pressure H = 2 MPa, the temperature range of the welded part material ΔT is 220~320 °C (in this example, the temperature rise for the melting of the welded part material ΔTmelting is 220 °C, and the temperature rise for the decomposition of the welded part material ΔTdecomposition is 320 °C), the welded part material is 30% carbon fiber reinforced nylon 66, the material of the welding head 1 is 7075 aluminum alloy, the base material is 45 steel, the pressure coefficient of the welded part material α = 0.42, the specific heat capacity of the welding material Cp = 1250 J / (kg·°C), the mass of the welded part m = 0.00381 kg, the thickness of the welded part is 2 mm, the welding distance d = 100 mm, the welding area S = 0.0003837 m2, the latent heat of fusion of the welded part material L = 200000 J / kg, the endothermic heat for the decomposition of the welded part ΔQ = 210 kJ / kg, the viscous damping λ of the welded part = 0.0026.

[0031] S1. Setting of the workpieces: Place the workpiece 2 on the base 3. The workpiece 2 includes an upper plate 21 and a lower plate 22. The welding head 1 of the welder acts on the surface of the workpiece 2. During the continuous ultrasonic welding process, the sound intensity generated by the welding head 1 generates welding energy that acts on the workpiece 2 to weld the upper plate 21 and the lower plate 22.

[0032] S2. Determining the sound intensity energy on the surface of the workpiece 2 during the continuous ultrasonic welding process I b : In the formula, I f is the sound intensity energy of the radiation area on the surface of the workpiece; I 0 is the sound intensity energy of the ultrasonic oscillation area under the welding head; In order to obtain the sound intensity energy 0 of the ultrasonic oscillation area under the welding head 1 I 0, it is necessary to calculate the sound speed under the condition of no pressure c 0焊头 , and the sound speeds of the sound waves in the welding head 1, the workpiece 2, and the base 3 under the condition of no pressure can be calculated respectively according to the sound speed calculation formula under the condition of no pressure c 0焊头 , c 0焊件 and c 0基座 , that is In this embodiment, the Young's modulus of the welding head material E welding head = 72 GPa, the density of the welding head material under the condition of no pressure ρ welding head = 2810 kg / m3, the Young's modulus of the workpiece material E workpiece = 2.7 GPa, the density of the workpiece material under the condition of no pressure ρ workpiece = 1270 kg / m3, the Young's modulus of the base material E base = 282.6 GPa, the density of the base material under the condition of no pressure ρ base = 7850 kg / m2. Substitute each parameter respectively, and the following can be calculated: c 0welding head = 5061.9 m / s, c 0workpiece = 1458.1 m / s, c 0base = 6000 m / s.

[0033] Therefore, the sound intensity energy in the ultrasonic oscillation region under the welding head 1 can be solved by the following formula I 0: In the formula, f is the welding machine frequency, A 0 is the amplitude of the welding machine; Substitute the parameters of this embodiment and calculate to get I 0 = 2π 2 × 20000 2 × 0.00008 2 × 2810 × 5061.9 = 7.1876×10 8 W / m 2 ; As Figure 2 shown, the welded part material is compressed under the action of the pressure of the welding head 1. In order to obtain the sound intensity energy in the radiation region on the surface of the welded part 2 I f , it is necessary to calculate the radiation radius R of the radiation region according to the welding parameters, which can be solved by the following formula: In the formula, a is the long side of the rectangular welding head, b is the short side of the rectangular welding head, f(θ) is the factor of the sound field scattering effect, representing the function of the sound wave propagation direction θ in the sound field, and the scattering effect in the sound field can be represented by the scattering coefficient.

[0034] For the sake of simplifying the calculation result, assume that the sound field distribution is uniform. At this time f(θ) = 1, then the above formula can be written as: In this embodiment, the size of the rectangular welding head is 12 mm × 15 mm, that is a = 15mm, b = 12mm, so the calculation result is R = 13.5831 mm.

[0035] Determine the sound intensity energy attenuation curve in the radiation region on the surface of the welded part according to the energy attenuation data p(r) , simulate the material relaxation and creep according to the Maxwell model, and fit the experimental data of the material combination by using the Prony series (data source: Study on the Creep Behavior of Nylon 6 / Montmorillonite Composite Materials). The parameters are shown in Table 1 as follows: Table 1 Experimental data of material combination fitted by Prony series

[0036] In the table, J 0 is the transient creep compliance,t 1 is the first delay time, t 2 is the second delay time, t 3 is the third delay time, A 1 is the coefficient of the first exponential decay term, A 2 is the coefficient of the second exponential decay term, A 3 is the coefficient of the third exponential decay term.

[0037] Input the Prony series into the Abaqus software for energy field simulation to obtain energy decay data. The fitting data is as follows: r = [0, 0.49958, 0.999161, 1.49874, 1.99832, 2.49791, 2.99749, 3.49707, 3.99665, 4.49623, 4.99581, 5.49539, 5.99497, 6.49455, 6.99413, 7.49372, 7.9933, 8.49288, 8.99246, 9.49204, 9.99162, 10.4912, 10.9908, 11.4904, 11.9899, 12.4895, 12.9891, 13.4887, 13.9883, 14.4878, 14.9874]; X = [14.6002, 14.476, 14.3243, 14.1339, 13.8931, 13.5985, 13.2499, 12.8548, 12.4208, 11.9588, 11.4761, 10.9797, 10.4728, 9.95716, 9.43304, 8.90007, 8.33299, 7.76235, 7.18801, 6.60854, 6.01974, 5.41536, 4.78726, 4.12831, 3.43979, 2.73587, 2.04816, 1.41964, 0.8979, 0.517273, 0.277685]; where, r is the radiation radius R at any position within the range; n is the number of fitting times; p 1, p 2… p n are the polynomial coefficients of the fitting curve; X is the maximum energy value in the radiation area on the surface of the welded part; The least-squares fitting is performed using the fit function in Matlab (since the fifth-degree polynomial is computationally simple and has a good fitting effect, the fifth-degree polynomial fitting is selected in this embodiment) to obtain the sound intensity energy attenuation curve of the radiation area on the surface of the welded part. p(r) ; Therefore, the sound intensity energy in the radiation area on the surface of the welded part I f , can be calculated by the following formula: Calculated: In summary, after obtaining the sound intensity energy I 0 in the ultrasonic oscillation area under the welding head 1 and the sound intensity energy If in the radiation area on the surface of the welded part 2, the sound intensity energy Ib on the surface of the welded part 2 can be obtained: Obtained I b = 1.4632×10 9 W / m 2 .

[0038] S3. Determine the energy absorption rate of the welded part during continuous ultrasonic welding W : To calculate the energy absorption rate W of the welded part, it is necessary to calculate the sound intensity energy i after I Li cycles and introduce the Kelvin-Voigt model to characterize it: In the formula, I z is the total energy entering the upper plate; x 1 is the thickness of the upper plate, x 2 is the thickness of the lower plate, i is the number of acoustic wave cycles; λ is the viscous damping; is the acoustic wave reflection coefficient between the welded part and the base; is the acoustic wave reflection coefficient between the welded part and the welding head; Among them, in the formula i the expression of is: In the formula, ε is the cycle accuracy, and the prediction model accuracy is different under different values of it, ; is the acoustic wave transmission coefficient between the welding head and the welded part; is the acoustic wave reflection coefficient between the welded part and the base at the first cycle; is the acoustic wave reflection coefficient between the welded part and the welding head during the second cycle; is the acoustic wave reflection coefficient between the welded part and the base during the second cycle; is the acoustic wave reflection coefficient between the welded part and the welding head during the third cycle; and so on.

[0039] Since the acoustic wave reflection coefficient and the acoustic wave transmission coefficient between the structures remain unchanged during each cycle, the acoustic wave reflection coefficient and the acoustic wave transmission coefficient in the formula are calculated based on the acoustic wave reflection coefficient and the acoustic wave transmission coefficient of the first cycle; that is 、 are both equal to ; 、 and are equal, and so on.

[0040] Among them, the value of is the same as the value of the value of is the same as the value of

[0041] When i = 1, the acoustic intensity energy I L1 after 1 cycle is: When i = 2, the acoustic intensity energy I L2 after 2 cycles is: When i = 3, the acoustic intensity energy I L3 after 3 cycles is: By analogy, it can be obtained that I L4 、 I L5 … I Li 。

[0042] It can be seen that the acoustic intensity energy i after I Li cycles is related to the total energy I z entering the upper plate and the acoustic wave reflection coefficient F 。

[0043] Therefore, it is necessary to first calculate the sound velocity ; Substitute into the calculation to obtain c 1焊件 = 1799.9 m / s; The acoustic wave anti-transmission coefficient between the sonotrode 1 and the work piece 2 (i.e., the upper layer plate 21 of the sonotrode 1 and the work piece 2) can be solved by the following formula: In the formula, is the acoustic wave reflection coefficient between the sonotrode and the work piece; is the acoustic wave transmission coefficient between the work piece and the base; ρ 焊件 is the density of the work piece; is the sound velocity in the compressed work piece.

[0044] Substitute the parameters of this embodiment into the calculation, and we get: The anti-transmission coefficient between the work piece 2 and the base 3 (i.e., the lower layer plate 22 of the work piece 2 and the base 3) can be solved by the following formula: In the formula, ρ 基座 is the density of the base; c 0基座 is the sound velocity of the acoustic wave in the unpressurized state of the base.

[0045] Substitute the parameters of this embodiment into the calculation, and we get: On the other hand, calculate the total energy entering the upper layer plate I z : The calculation result is I z = 6.9815×10 8 W / m 2 ; Solve for the number of acoustic wave cycles according to the anti-transmission coefficient i , take the cycle accuracy ε = 0.1, and the calculated number of acoustic wave cycles i = 2; The total energy I z entering the upper layer plate, and the number of acoustic wave cycles iSubstitute the reflection coefficients of each sound wave and calculate the sound intensity energy after i cycles I Li , and obtain the total energy absorbed by the welded part: ∑ I Li = I L1 + I L2 = 1362129.7546 W / m 2 Finally, determine the energy absorption rate of the welded part W , which can be calculated by the following formula: In the formula, I Li is the sound intensity energy after i cycles; S is the area of the welding area; n 总 is the total number of cycles; Substitute the total energy absorbed by the welded part ∑ I Li and the area of the welding area S into it, and calculate the energy absorption rate of the welded part W = 522.6492 W.

[0046] S4. Determine the energy required for the welded part material Q total range: In the formula, Q total is the energy required for the welded part material; Q melting is the energy required for the welding material to reach the melting temperature; Q decomposition is the energy required for the welding material to reach the decomposition temperature; Among them, Qtotal is: In the formula, Q heating is the energy required for the welded part material to increase in temperature, Q m is the energy required for the welding material to melt, m is the mass of the welding material, C p is the specific heat capacity of the welding material, ΔT is the temperature increase of the welding material, L is the latent heat of fusion of the welding material; Wherein, ΔT melting is the temperature rise of the welding material reaching the melting temperature; ΔT decomposition is the temperature rise of the welding material reaching the decomposition temperature; ΔQ is the endothermic decomposition of the weldment.

[0047] Substituting the parameters of this embodiment and calculating, we get: Then the energy required for the welding material Q total ranges from 1809.75 J to 3276.6 J.

[0048] S5. Establish a prediction model for ultrasonic continuous welding quality: The entire continuous welding process considers welding pressure, acoustic wave reflection and transmission, acoustic wave transmission loss, and the number of acoustic wave cycles.

[0049] To establish the prediction model for ultrasonic continuous welding quality, it is necessary to determine the welding speed range, and then the welding quality corresponding to the welding speed can be obtained; Wherein: v is the welding speed, d is the welding distance.

[0050] Calculated to obtain v ranges from 15.951 mm / s to 28.8796 mm / s.

[0051] Therefore, in this embodiment, when the welding speed v > 28.8796 mm / s, the welding quality is a virtual weld, which will cause insufficient fusion of the joint and cannot form a stable welded joint. When the welding speed is v < 15.951 mm / s, the welding quality is an over-weld, which will cause a large number of pores at the joint, thus affecting the joint quality. While when 15.951 mm / s ≤ v ≤ 28.8796 mm / s, the welding quality is a normal weld, the joint is evenly fused, a stable welded joint can be formed and the joint quality is high.

[0052] In summary, under the relevant welding parameters given in the present invention, the prediction model for ultrasonic continuous welding quality can be established according to the above steps, and further infer the influence of different welding speed ranges on the quality of the welded joint, so as to realize the prediction of the quality of the welded joint of the weldment at different welding speeds.

[0053] The embodiments of the present invention have been described in detail above. However, the above content is only the preferred embodiments of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope covered by the present invention.

Claims

1. A method for predicting the welding quality of ultrasonic continuous welding, characterized in that: It includes the following steps: S1. Setting of the welded part: Place the welded part on the base. The welded part includes an upper plate and a lower plate; The welding head of the welder acts on the surface of the welded part. During the ultrasonic continuous welding process, the sound intensity generated by the welding head will generate welding energy acting on the welded part to weld the upper plate and the lower plate; S2. Determine the surface sound intensity energy of the workpieces during continuous ultrasonic welding I b : In the formula, I f is the sound intensity energy of the radiation area on the surface of the welded part; I 0 is the sound intensity energy in the ultrasonic oscillation area under the welding head; S3. Determine the energy absorption rate of the workpieces during continuous ultrasonic welding W : Wherein, I Li is the sound intensity energy after i cycles; S is the area of the welding region; n 总 is the total number of cycles; Among them, the Kelvin-Voigt model is used to characterize the sound intensity energy after i cycles of I Li as follows: Wherein, I z is the total energy entering the upper plate; x 1 is the thickness of the upper plate, x 2 is the thickness of the lower plate, i is the number of acoustic wave cycles; λ is the viscous damping; is the acoustic wave reflection coefficient between the welded part and the base; is the acoustic wave reflection coefficient between the welded part and the welding head; Among them, I z is as follows: In the formula, is the acoustic wave transmission coefficient between the welding head and the welded part; S4. Determine the energy required for the welding material Q total Range: Wherein, Q total is the energy required for the weldment material; Q melting is the energy required for the welding material to reach the melting temperature; Q decomposition is the energy required for the welding material to reach the decomposition temperature; S5. Establishing a prediction model for the quality of ultrasonic continuous welding: In order to establish a prediction model for the quality of ultrasonic continuous welding, it is necessary to determine the welding speed range and then obtain the welding quality corresponding to the welding speed; In the formula: v is the welding speed, d is the welding distance.

2. The welding quality prediction method for ultrasonic continuous welding according to claim 1, characterized in that: In step S2, I 0 is: In the formula, f is the welder frequency, A 0 is the welder amplitude, c 0焊头 is the sound velocity of the acoustic wave in the non-pressure state of the welding head, ρ 焊头 is the density of the welding head; Among them, I f is as follows: In the formula, p(r) is the sound intensity energy attenuation curve of the radiation area on the surface of the welded part; R is the radiation radius of the radiation area on the surface of the welded part; r is any position within the radiation radius R. Among them, p(r) is: In the formula, p 1, p 2… p n are the polynomial coefficients of the fitting curve; X is the maximum value of the energy in the radiation area of the weldment surface; n is the fitting order.

3. The method for predicting the welding quality of ultrasonic continuous welding according to claim 2, wherein: In step S2, c 0焊头 is as follows: wherein, E 焊头 is the Young's modulus of the welding head.

4. The method for predicting the welding quality of ultrasonic continuous welding according to claim 1, wherein: In step S2, R is: In the formula, a is the long side of the rectangular welding head, b is the short side of the rectangular welding head, f(θ) is the factor of the sound field scattering effect, representing the function of the sound wave propagation direction θ in the sound field.

5. The method for predicting the welding quality of ultrasonic continuous welding according to claim 1, characterized in that: In step S3, the acoustic wave reflection coefficient and the acoustic wave transmission coefficient between each structure remain unchanged during each loop. Therefore, both the acoustic wave reflection coefficient and the acoustic wave transmission coefficient are calculated based on the acoustic wave reflection coefficient and the acoustic wave transmission coefficient of the first loop; the acoustic wave reflection coefficient and the acoustic wave transmission coefficient between each structure are respectively ： Wherein, is the acoustic wave reflection coefficient between the welding head and the workpiece; is the acoustic wave transmission coefficient between the workpiece and the base; ρ 焊件 is the density of the workpiece; ρ 基座 is the density of the base; c 0基座 is the sound velocity of the acoustic wave in the unpressurized state of the base; is the sound velocity in the compressed workpiece.

6. The welding quality prediction method for ultrasonic continuous welding according to claim 5, wherein: The value of is the same as 7. The method for predicting the welding quality of ultrasonic continuous welding according to claim 1, wherein: In step S4, Q total is: Wherein, Q heating is the energy required for the temperature rise of the welded part material, Q m is the energy required for the melting of the welding material, m is the mass of the welding material, C p is the specific heat capacity of the welding material, ΔT is the temperature rise of the welding material, L is the latent heat of fusion of the welding material; In the formula, ΔT melting is the temperature rise when the welding material reaches the melting temperature; ΔT decomposition is the temperature rise when the welding material reaches the decomposition temperature; ΔQ is the endothermic decomposition of the welded part.

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