A weak rigid structure welding stress deformation regulation and control device and method based on multi-medium composite cooling and ultrasonic vibration

Abstract

The application discloses a kind of weak rigid structure welding stress deformation regulation and control equipment and method based on multi-medium composite cooling and ultrasonic vibration, including ultrasonic vibration system, water mist cooling system, liquid nitrogen cooling system, welding system and infrared temperature measurement system.It is characterized in that control power, alternating current frequency and cooling coefficient three factors adjust welding heat input, ultrasonic vibration and effect of cooling along with welding, water mist and liquid nitrogen cooling are cooperated to realize the cooling along with welding to workpiece.When the rocket tank section structure is carried out friction stir welding, the hollow ultrasonic device is cooperated with the internal welding head to apply ultrasonic vibration to the melting area, and when switched to laser welding head, laser beam passes through the hollow area inside the ultrasonic device and acts on the rib.The application reduces residual stress and deformation after welding by regulating and controlling the matching coefficient of welding heat input-ultrasonic vibration-cooling medium and precise input, realizes the regulation and control of weak rigid structure welding stress and deformation.

Description

Technical Field

[0001] This invention relates to a device and method for controlling welding stress and deformation of weakly rigid structures based on multi-medium composite cooling and ultrasonic vibration, belonging to the field of welding stress and deformation control. Background Technology

[0002] Welding not only meets the requirements for weight reduction in aircraft structures, but also significantly reduces manufacturing costs by replacing integral forged components with segmented welded structures. However, laser welding involves localized heating of the workpiece to high temperatures, and the highly concentrated transient heat input generates significant internal stress during the welding process. Simultaneously, the accumulation of heat input leads to substantial deformation of the welded components, resulting in uneven stress distribution within the welded structure. While friction stir welding is used to connect the cylindrical sections of rocket propellant tanks, laser welding can be used to connect the internal wall panels and ribs. Because friction stir welding and laser welding produce different deformation effects on the cylindrical sections, affecting safety and lifespan during service, reducing residual stress and controlling post-weld deformation during laser welding and friction stir welding are pressing technical problems that need to be addressed.

[0003] Currently, traditional methods such as applying external fields after welding, including vibration impact and roller straightening, are mainly used to correct deformation. However, these methods cannot fundamentally eliminate warping deformation; rather, the warping deformation of the welded component is relatively transferred after being subjected to external force. The fundamental reason for warping deformation in welded structures is that the residual compressive stress in the welded component exceeds the critical instability stress of the structure, causing structural instability and subsequent welding deformation. Therefore, the core of controlling the deformation of welded structural components is to reduce the residual compressive stress at the source, which requires deformation control during the welding process. During welding, methods such as in-process gas cooling and in-process ultrasonic excitation are often used to control welding deformation. The cooling effect and the acoustic flow effect of ultrasound both reduce the residual compressive stress in the component, thus reducing the amount of welding warping deformation. However, the extent to which the residual stress is reduced after welding and the degree of control over post-weld deformation can only be qualitatively controlled, and precise regulation of the deformation of complex structural components cannot be achieved.

[0004] To address the aforementioned issues, it is essential to implement innovative designs for controlling stress and deformation based on existing welding equipment in order to more accurately control residual stress and post-weld deformation, and to save on factory production costs. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention utilizes the coordinated operation of a welding system, an ultrasonic vibration system, and a multi-medium cooling system. By adjusting the ratio coefficients and precise input of welding heat input, ultrasonic vibration, and cooling media, the stress and deformation of the workpiece can be controlled. This invention provides a device and method for controlling the welding stress and deformation of weakly rigid structures based on multi-medium composite cooling and ultrasonic vibration. Friction stir welding is used for the connection between rocket propellant tank sections, while laser welding is used for the ribs on the wall panels. Water mist and liquid nitrogen are used to apply different cooling effects to both sides of the weld, precisely controlling residual stress after welding, reducing the degree of workpiece deformation, improving the forming quality and mechanical properties of the workpiece, effectively increasing the yield of qualified welded workpieces, and saving factory time and costs.

[0006] This invention is achieved through the following technical solution:

[0007] A device for controlling the welding stress and deformation of weakly rigid structures based on multi-medium composite cooling and ultrasonic vibration, characterized in that it includes an ultrasonic vibration system, a water mist cooling system, a liquid nitrogen cooling system, a welding system, and an infrared temperature measurement system;

[0008] The welding system is used to weld workpieces and includes a six-axis robot, a welding head, and a worktable. The welding head includes a laser welding head and a friction stir welding head, and the welding head can be switched by a rotating device to perform laser welding and friction stir welding. The infrared temperature measurement system is used to measure the temperature of the workpiece in real time during the welding process and transmit the data to a computer. It includes an infrared thermal imaging thermometer and a support frame.

[0009] The liquid nitrogen cooling system is used to cool the weld area at low temperature during the welding process. It includes a gas-cooled automatic welding torch, a ventilation hose, a liquid nitrogen cooling tank, a U-shaped copper pipe, and an argon cylinder. The gas-cooled automatic welding torch is fixed to the right side of the welding head by a tight fit with an L-shaped metal plate bolt. The water mist cooling system cools the workpiece by spraying water mist onto the weld area. It includes a cooling sprayer, a ventilation hose, a water hose, a regular gas cylinder, and a water tank. The cooling sprayer is fixed to the left side of the welding head by magnetic attraction. The water mist cooling system and the liquid nitrogen cooling system work together to form a multi-media cooling system. The ultrasonic vibration system is used to apply ultrasonic vibration to the molten area during the welding process. It includes a cylinder, a spring, and a hollow ultrasonic device.

[0010] The welding system, ultrasonic vibration system and multi-medium cooling system work together to adjust the ratio coefficient and precise input of welding heat input, ultrasonic vibration and cooling medium between the systems. This establishes a response surface of three factors, namely power, AC frequency and cooling coefficient, and residual stress value and post-weld deformation, thereby enabling the control of residual stress and deformation of the welded workpiece.

[0011] Preferably, when the ultrasonic vibration system is working, air enters the cylinder to drive the piston to move, thereby compressing the spring to ensure that the ultrasonic vibration head is always in contact with the workpiece surface;

[0012] Preferably, the friction stir welding head is located inside the hollow ultrasonic device, and the two work together to apply ultrasound during the friction stir welding process; another hollow ultrasonic device is installed below the laser welding head, and the laser beam passes through its hollow area to act on the workpiece, and the two work together to apply ultrasound during the laser welding process; the intensity of the ultrasonic vibration is controlled by adjusting the value of the AC frequency f.

[0013] Preferably, the equipment can be used for welding the cylindrical sections of rocket propellant tanks. The circumferential seam between the sections is welded by a friction stir head, and the rotating device is switched to a laser welding head for laser welding of the ribs on the inner wall of the section. During the friction stir welding and laser welding processes, multi-medium cooling and ultrasound work together on the welded area to control the overall deformation of the section.

[0014] Preferably, the equipment can also be used for welding large and complex curved surface structures, including but not limited to rocket shells, satellite shells, etc.

[0015] Preferably, the water inlet and air inlet of the cooling sprayer are connected to the water tank and ordinary gas cylinder respectively, and the water mist flow rate is controlled by the gas flow rate adjustment knob and the liquid flow rate adjustment knob. Before the test begins, a pre-test should be conducted to adjust the position of the knobs to ensure a suitable water mist flow rate.

[0016] Preferably, an infrared thermal imaging thermometer is used to monitor the temperature at a point 1 cm from the center of the weld on the workpiece, and the temperature is uploaded to the software to generate a thermal cycle curve. The cooling coefficient during the welding process is defined as C.

[0017]

[0018] In the formula, T0 represents the peak temperature at the measurement point under conditions of no water mist and liquid nitrogen cooling during the welding process, T C This indicates the peak temperature at the measurement point after cooling with water mist and liquid nitrogen.

[0019] Preferably, the U-shaped copper tube is placed in a liquid nitrogen cooling tank. The inlet and outlet of the U-shaped copper tube are connected to an argon cylinder and a gas-cooled automatic welding torch respectively through a ventilation hose. Two-thirds of the length of the U-shaped copper tube is immersed in liquid nitrogen to ensure that the protective gas is fully cooled in the liquid nitrogen tank.

[0020] Preferably, the ventilation hose (51) is covered with a layer of vacuum insulation cotton to prevent the cooled gas from liquefying due to the influence of room temperature.

[0021] A method for operating a welding stress and deformation control device for weakly rigid structures based on multi-medium composite cooling and ultrasonic vibration, characterized in that the device can be used for rocket propellant tank structures, and includes the following steps:

[0022] Step 1: Place the two cylindrical sections to be welded on the support, align the welding points of the two sections, and mechanically constrain them around the perimeter.

[0023] Step 2: Before starting the welding work, open the argon gas cylinder valve, control the argon shielding gas flow rate to 15-35 L / min, and set the angle between the nozzle of the gas-cooled automatic welding torch and the horizontal direction to 30°. Open the ordinary gas cylinder valve, control the working pressure of the water mist outlet to ≥0.2 MPa, and set the angle between the water mist outlet direction and the horizontal direction to 45°. Conduct a preliminary experiment by using an infrared thermal imaging thermometer to monitor the temperature at a point near the weld and generate a thermal cycle curve. Calculate the cooling coefficient C0 at this point using the formula for the cooling coefficient C.

[0024] Step 3: Input the stirring needle rotation speed N0 into the computer, input an AC voltage with frequency f0 into the piezoelectric ceramic transducer, and then perform stir friction welding on the circumferential seam between the two cylindrical sections.

[0025] Step 4: After the circumferential weld is completed, use the rotating device to switch to the laser welding head, input the appropriate power P0 into the computer, and then perform laser welding on the ribs on the inner wall panel of the cylinder section.

[0026] Step 5: Design experiments based on four variables: C, N, P, and f. Use resistance strain gauges and a 3D scanning machine to measure the deformation and stress of each welded component. Use response surface methodology to solve for the optimal stress and deformation region at which C is calculated. R N R P R and f R This allows for the control of workpiece stress and deformation.

[0027] The present invention has the following advantages:

[0028] This invention discloses a device and method for controlling the welding stress and deformation of weakly rigid structures based on multi-medium composite cooling and ultrasonic vibration. During the welding of rocket propellant tank structures, after connecting the various cylindrical sections through friction stir welding, a laser head is switched and laser welding of the reinforcing ribs is performed. Water mist cooling and liquid nitrogen cooling are used together as the cooling method during welding. Ultrasonic vibration assists the welding process and acts in real-time on the welding melting zone, reducing stress concentration in the workpiece after welding. Adjusting the ratio coefficient of welding heat input, ultrasonic vibration, and cooling medium between the systems reduces the plastic deformation zone of the workpiece during welding, lowers stress concentration at the weld, reduces the degree of deformation of the workpiece after welding, and results in a joint with high strength and good quality after welding. Attached Figure Description

[0029] To more clearly illustrate the apparatus of the present invention, exemplary embodiments will be described below with reference to the accompanying drawings, wherein:

[0030] Figure 1 A schematic diagram of the overall structure of a welding stress and deformation control device for weakly rigid structures based on multi-medium composite cooling and ultrasonic vibration;

[0031] Figure 2 A schematic diagram of the friction stir welding head and ultrasonic vibration head structure of a weak rigid structure welding stress deformation control device based on multi-medium composite cooling and ultrasonic vibration;

[0032] Figure 3 This is a schematic diagram of the rotating device used to switch welding heads;

[0033] Figure 4 This is a schematic diagram of the cooling sprayer device in a water mist cooling system.

[0034] Figure 5 This is a schematic diagram of a hollow ultrasonic device.

[0035] In the picture:

[0036] 1-Laser welding head, 2-Friction stir welding head, 3-Rotating device;

[0037] 4-Infrared thermal imaging thermometer, 41-Support frame;

[0038] 5-Gas-cooled automatic welding torch, 51-Gas hose, 52-Liquid nitrogen cooling tank, 53-Argon gas cylinder;

[0039] 6-Cooling sprayer, 61-Ventilation hose, 62-Water hose, 63-Ordinary gas cylinder, 64-Water tank, 65-Water inlet, 66-Air inlet, 67-Gas flow rate adjustment knob, 68-Liquid flow rate adjustment knob;

[0040] 7-Cylinder, 8-Spring, 9-Hollow ultrasonic device, 91-Ultrasonic vibrating head, 10-Cylinder section, 11-Firming plate. Detailed Implementation

[0041] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention and not the entire structure.

[0042] like Figure 1As shown, this example provides a device and method for controlling the stress and deformation of weak rigid structure welding based on multi-medium composite cooling and ultrasonic vibration, including an ultrasonic vibration system, a water mist cooling system, a liquid nitrogen cooling system, a welding system and a tooling system. Before the welding test begins, the gas cylinder valve is opened and the gas flow rate is adjusted. The corresponding power and other parameters are set on the computer according to the specific workpiece. The cooling sprayer and the liquid nitrogen cooling tank are respectively used to perform water mist cooling and liquid nitrogen cooling on the workpiece in the welding process. The U-shaped copper tube is placed in the liquid nitrogen cooling tank. The inlet and outlet of the U-shaped copper tube are connected to the argon gas cylinder and the gas-cooled automatic welding gun respectively through the ventilation hose. Two-thirds of the length of the U-shaped copper tube is immersed in liquid nitrogen, so as to ensure that the protective gas is fully cooled in the liquid nitrogen tank. The ventilation hose (51) is covered with a layer of vacuum insulation cotton to prevent the cooled gas from being affected by the temperature difference. When the welding test begins, the water mist cooling system, the liquid nitrogen cooling system and the welding system are turned on by the program control of the robot teaching device. The ultrasonic vibration system works by the vibration head through an external voltage-frequency power supply.

[0043] Specifically, see Figure 2 The friction stir welding head is located inside the hollow ultrasonic vibrating head. During the welding process, the welding is carried out through the cooperation of a cylinder and a spring. See [link / reference needed]. Figure 5 To ensure that the ultrasonic vibrating head always acts on the workpiece surface, the ultrasonic waves and the friction stir welding head work together on the molten area during the welding process, applying ultrasonic vibrations around the molten pool. This includes a piezoelectric ceramic transducer, a transmission rod, and an ultrasonic vibrating head. During the welding process, by providing appropriate frequency and voltage to the piezoelectric ceramic transducer and transmitting it through the transmission rod, the ultrasonic vibrations are ensured to be evenly distributed around the molten area.

[0044] During the welding of the rocket propellant tank structure, after the circumferential seam of the friction stir welded cylinder section is joined, a rotating device is used; specifically, see [link to details]. Figure 3 After switching to the laser welding head, laser welding of the internal ribs of the cylinder section is carried out.

[0045] Specifically, see Figure 4 The water inlet and air inlet of the cooling sprayer are connected to the water tank and ordinary gas cylinder respectively through water hose and air hose. The water mist flow rate is controlled by the gas adjustment knob and the liquid adjustment knob. Before the test begins, a pre-test is conducted to adjust the position of the knobs to ensure a suitable water mist flow rate.

[0046] Application example: A rocket propellant tank section with a diameter of 3.8m was selected and subjected to ultrasonic-assisted friction stir welding and laser welding under multi-medium cooling.

[0047] Specific steps:

[0048] 1. Place the two cylindrical sections to be welded on the support, align the welding points of the two sections, and mechanically constrain them around the perimeter.

[0049] 2. Before the welding test begins, open the argon gas cylinder valve and control the argon shielding gas flow rate to approximately 20 L / min. Set the nozzle of the gas-cooled automatic welding torch to a 30° angle with the horizontal direction. Open the ordinary gas cylinder valve and control the water mist outlet working pressure to 0.4 MPa, with the water mist outlet direction at a 45° angle with the horizontal direction. Conduct a preliminary experiment by using an infrared thermal imaging thermometer to monitor the temperature at a point near the weld and generate a thermal cycle curve. Calculate the cooling coefficient C0 at this point using the formula for the cooling coefficient C.

[0050] 3. Input the stirring needle rotation speed N = 900 rpm into the computer, input an AC voltage with a frequency of f = 38 MHz into the piezoelectric ceramic transducer, and then perform stir friction welding on the circumferential seam between the two cylindrical sections.

[0051] 4. After the circumferential weld is completed, use the rotating device to switch to the laser welding head, set the laser power P=900W in the computer, and then perform laser welding on the ribs on the inner wall panel of the cylinder section;

[0052] 5. Design experiments based on four variables: C, N, P, and f. Use resistance strain gauges and a 3D scanning machine to measure the deformation and stress of each welded component. Use response surface methodology to solve for the optimal stress and deformation region at which C is calculated. R N R P R and f R This allows for the control of workpiece stress and deformation.

[0053] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, based on the concept of the present invention, there will be changes in specific implementation methods and application scope. The content of this specification should not be construed as a limitation of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A device for controlling welding stress and deformation of weakly rigid structures based on multi-medium composite cooling and ultrasonic vibration, characterized in that... It includes an ultrasonic vibration system, a water mist cooling system, a liquid nitrogen cooling system, a welding system, and an infrared temperature measurement system; The welding system is used to weld workpieces and includes a six-axis robot, a welding head and a worktable; the welding head includes a laser welding head (1) and a friction stir welding head (2), and the welding head can be switched by a rotating device (3) to perform laser welding and friction stir welding; the infrared temperature measurement system is used to measure the temperature of the workpiece in real time during the welding process and transmit the data to a computer, including an infrared thermal imaging thermometer (4) and a support frame (41). The liquid nitrogen cooling system is used to cool the weld area at low temperature during the welding process. It includes an air-cooled automatic welding torch (5), a ventilation hose (51), a liquid nitrogen cooling tank (52), a U-shaped copper pipe, and an argon gas cylinder (53). The air-cooled automatic welding torch (5) is fixed to the right side of the welding head (2) by a tight fit with an L-shaped metal plate bolt. The water mist cooling system cools the workpiece by spraying water mist onto the weld area. It includes a cooling sprayer (6), a ventilation hose (61), a water hose (62), a regular gas cylinder (63), and a water tank (64). The cooling sprayer is fixed to the left side of the welding head by magnetic attraction. The water mist cooling system and the liquid nitrogen cooling system work together to form a multi-media cooling system. The ultrasonic vibration system is used to apply ultrasonic vibration to the molten area during the welding process. It includes a cylinder (7), a spring (8), and a hollow ultrasonic device (9). The welding system, ultrasonic vibration system, and multi-medium cooling system work together to adjust the ratio coefficients and precise inputs of welding heat input, ultrasonic vibration, and cooling medium between the systems. This establishes a response surface between four factors—cooling coefficient C, stirring pin speed N, power P, and AC frequency f—and residual stress and post-weld deformation, thereby enabling the control of residual stress and deformation of the welded workpiece. The ultrasonic vibration system uses air entering the cylinder (7) to drive the piston, thereby compressing the spring (8) to ensure that the ultrasonic vibration head (91) is always in contact with the workpiece surface; The friction stir welding head (2) is located inside the hollow ultrasonic device, and the two work together to apply ultrasound during the friction stir welding process; another hollow ultrasonic device is installed below the laser welding head, and the laser beam passes through the hollow area inside it to act on the workpiece, and the two work together to apply ultrasound during the laser welding process; the strength of the ultrasonic vibration is controlled by adjusting the value of f. The weak rigid structure welding stress deformation control equipment can be used for welding the rocket tank structure cylinder section (10). First, the circumferential seam between each cylinder section is welded by the friction stir head. Then, the rotating device is switched to the laser welding head to laser weld the ribs (11) on the inner wall of the cylinder section. During the friction stir welding and laser welding process, the welding cooling and ultrasonic waves work together on the welded part to control the overall deformation of the cylinder section.

2. The stress and deformation control device for welding weakly rigid structures based on multi-medium composite cooling and ultrasonic vibration according to claim 1, characterized in that... The equipment can also be used for welding large and complex curved structures, including rocket shells and satellite shells.

3. The stress and deformation control device for welding weakly rigid structures based on multi-medium composite cooling and ultrasonic vibration according to claim 1, characterized in that... The water inlet (65) and air inlet (66) on the cooling sprayer are connected to the water tank and the ordinary gas cylinder, respectively. The water mist flow rate is controlled by the gas flow rate adjustment knob (67) and the liquid flow rate adjustment knob (68). Before the test begins, a preliminary experiment is conducted to adjust the position of the knobs to ensure a suitable water mist flow rate.

4. The stress and deformation control device for welding weakly rigid structures based on multi-medium composite cooling and ultrasonic vibration according to claim 1, characterized in that... The temperature at a point 1 cm from the center of the weld on the workpiece is monitored using an infrared thermal imaging thermometer, and the data is uploaded to software to generate a thermal cycle curve. The cooling coefficient during the welding process is defined as C. In the formula, T0 represents the peak temperature at the measurement point under conditions of no water mist and liquid nitrogen cooling during the welding process, T C This indicates the peak temperature at the measurement point after cooling with water mist and liquid nitrogen.

5. The stress and deformation control device for welding weakly rigid structures based on multi-medium composite cooling and ultrasonic vibration according to claim 1, characterized in that... The U-shaped copper tube is placed inside the liquid nitrogen cooling tank. The inlet and outlet of the U-shaped copper tube are connected to the argon cylinder and the gas-cooled automatic welding torch respectively through ventilation hoses. Two-thirds of the length of the U-shaped copper tube is immersed in liquid nitrogen to ensure that the protective gas is fully cooled in the liquid nitrogen tank.

6. The stress and deformation control device for welding weakly rigid structures based on multi-medium composite cooling and ultrasonic vibration according to claim 1, characterized in that... The ventilation hose (51) is covered with a layer of vacuum insulation cotton to prevent the cooled gas from liquefying due to the influence of room temperature.

7. The operating method of the stress and deformation control device for welding weakly rigid structures based on multi-medium composite cooling and ultrasonic vibration according to claim 1, characterized in that... This device can be used in rocket propellant tank structures, employing the following steps: Step 1: Place the two cylindrical sections to be welded on the support, align the welding points of the two sections, and mechanically constrain them around the perimeter. Step 2: Before starting the welding work, open the argon gas cylinder valve, control the argon shielding gas flow rate to 15-35 L / min, and set the angle between the nozzle of the gas-cooled automatic welding torch and the horizontal direction to 30°. Open the ordinary gas cylinder valve, control the working pressure of the water mist outlet to ≥0.2 MPa, and set the angle between the water mist outlet direction and the horizontal direction to 45°. Conduct a preliminary experiment, using an infrared thermal imaging thermometer to monitor the temperature at the measurement point and generate a thermal cycle curve. Calculate the cooling coefficient C0 at this time using the formula for the cooling coefficient C. Step 3: Input the stirring needle rotation speed N0 into the computer, input an AC voltage with frequency f0 into the piezoelectric ceramic transducer, and then perform stir friction welding on the circumferential seam between the two cylindrical sections. Step 4: After the circumferential weld is completed, use the rotating device to switch to the laser welding head, input the appropriate power P0 into the computer, and then perform laser welding on the ribs on the inner wall panel of the cylinder section. Step 5: Design experiments based on four variables: C, N, P, and f. Use resistance strain gauges and a 3D scanning machine to measure the deformation and stress of each welded component. Use response surface methodology to solve for the optimal stress and deformation region at which C is calculated. R N R P R and f R This allows for the control of workpiece stress and deformation.

Images