In the modern body structure, about 3,000 solder joints are to be completed. In order to ensure the welding quality, a chiseling method is usually adopted (followed by visual inspection), but this method requires more time, and it must be reshaped after the parts are deformed, and the cost incurred by the company is higher. After an attempt, ultrasonic technology is more efficient for non-destructive testing of resistance spot welding, and it can almost identify various defective solder joints.
Body spot welding quality monitoring
At present, resistance spot welding is still the most widely used method in the body connection process. Therefore, major auto manufacturers pay great attention to the quality of resistance spot welding. In general, car body spot welding quality monitoring can be divided into three parts: prevention, control and inspection.
Prevention refers to taking measures to prevent the occurrence of substandard solder joints before resistance spot welding. Usually, the main measure is daily monitoring of welding equipment. For example, regularly check the welding parameters to ensure that the set value meets the process requirements; regularly measure the actual welding pressure, actual current and energization time to ensure that the output value is consistent with the set value; regularly measure the resistance value of the secondary circuit, especially The resistance value of the non-inductive cable (if split transformer structure is used) is used to ensure the normal power-on capability of the welding system. Since solder joints are made by welding equipment, only the proper monitoring of the state of the welding equipment can prevent the occurrence of substandard solder joints.
Control refers to the process of resistance spot welding, the application of corresponding technology for online monitoring to ensure that unqualified solder joints are discovered in time. At present, the main method is to monitor the output current of each welding (may be primary current or secondary current) through a welding controller. Once it is lower than the set range, it will promptly alarm to avoid the occurrence of unacceptable solder joints. In addition, newer technologies monitor the dynamic resistance during the welding process to determine if the solder joints are acceptable. In this way, after each welding is completed, we can detect unsatisfactory solder joints in time and take measures.
Inspection refers to the destructive and non-destructive inspection of solder joints that have been completed to achieve the purpose of eliminating substandard solder joints. The destructive inspection is to inspect the solder joints of the entire vehicle body one by one. It is comprehensive and all unqualified solder joints can be found. However, the body after inspection can only be scrapped, and the sampling frequency is low, which is not conducive to the timely detection of problems. Non-destructive inspections are routine inspections of vehicle body welds. The traditional methods are visual inspections and chisels. Generally, some typical solder joints are selected and have certain limitations. The application of ultrasonic non-destructive testing technology can make up for this limitation, and along with the promotion and development of this technology, it can also gradually replace the existing destructive inspection, thereby further reducing the cost of the vehicle manufacturer.
Ultrasonic nondestructive testing
1. Background
In the modern body structure, approximately 3,000 solder joints are to be completed. In order to ensure the quality of welding, a chiseling method is usually adopted (followed by visual inspection), which requires more time for inspection, and it must be reshaped after the parts are deformed. In addition, chiseling has certain limitations, such as solder joints that cannot be achieved by the chisel, solder joints with high surface quality requirements, and solder joints of some high-strength steels. Destructive inspection of the entire body or part of the subassembly takes a lot of costs.
After trying, other non-destructive inspection methods are not suitable for resistance spot welding, such as infrared, X-ray and eddy current testing. The use of ultrasonic technology for non-destructive testing of resistance spot welding with high efficiency, almost all kinds of defective solder joints can be identified. Therefore, ultrasonic NDT is an effective and reliable technique for resistance spot welding.
2. Principle
Spot welding ultrasonic inspection method is from the final interface of the welded structure multiple reflection detection and reflection of the parts of the middle echo (Figure 1). For correct solder joints and defective solder joints, there is a difference between the length of the echo series reflected from the full thickness, the signal attenuation, and the amplitude and position of the intermediate echo, thereby identifying the defective solder joint. The effective diameter of the ultrasonic beam should be equal to the diameter of the melting point.
Fig. 1 Ultrasonic transmission
3. Quality determination
There is a certain relationship between the echo pattern obtained by ultrasonic testing and the defects of solder joints (see Figure 2).
Figure 2 Relationship between defects and waveforms
4. Application conditions
The application of ultrasonic testing can sometimes be affected by the actual state of the solder joint (Figure 3), resulting in reduced accuracy of the test results.
Figure 3 ultrasonic testing application conditions
5. Detection system
As a relatively complete system, the application of ultrasonic detection technology can be divided into three steps: (1) using a database to establish a measurement plan; (2) using professional software for testing; and (3) performing statistical analysis and outputting a report.
6. Testing equipment
At present, there are three main types of ultrasonic testing equipment used in OEMs (Figure 4): laptops + portable measuring devices; portable ones; desktops + measuring devices.
Figure 4 Detection equipment types
As an advanced non-destructive testing method, ultrasonic solder joint quality inspection has received more and more attention. Traditional chiseling and destructive inspection methods coupled with advanced ultrasonic inspection methods are combined to form the main method of car body welding quality. In order to ensure the welding quality of its own brand, Shanghai Automotive Group Co., Ltd. established a relatively complete welding quality control system including ultrasonic testing technology, and the destructive inspection solder joint qualification rate reached more than 99%.
Cylinder is the place where the fuel-air mixture is compressed and burned to convert chemical energy to heat and mechanical energy to make the bike go. Just like in any other internal combustion engine. The engine might have only one cylinder or many. More than four is rare, though.The cylinder is fired by a spark plug which creates a spark electrically from the battery .
It is the cylinder in an engine where the combustion takes place-..in vehicle the cylinder is just above the transmission. think of it as a syringe. the piston moves up and compresses the air fuel mixture and as a result combustion takes place. the piston is then pushed down. this up and down motion of the piston rotates the crankshaft which is connected to the transmission which transmits power to the wheels. there are various configurations of cylinders in an engine. in vehicle have single cylinder, parallel twin, v twin, L twin, inline 4, inline 3, inline 6, v4, flat twin. similarly in cars you get inline 3, inline4, inline6 , v6, v8, v10, w12. the number represents the no. of cylinders and the letter or prefix represents the configuration.
Cylinder
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