Shot peening, as a surface strengthening process, dates back to 2700 BC. According to records, the blacksmith at the time had realized that in the cold state, the metal hit by a hammer can become harder. Medieval Europeans found in the use of horse-drawn cars that the same leaf springs, which have been treated with sandblasting on the surface, have a significantly longer service life. At the beginning of the 20th century, people began to use metal particles to peening the roots of springs and large gears.

After the efforts of a large number of researchers in the 1940s, everyone's understanding of the shot peening process has been raised to a higher level, thereby promoting and expanding the application scope of this process. Lockheed Martin's engineer Jim Boerger was inspired by shot peening Almen test strips and pioneered an advanced forming technology in modern aircraft manufacturing, shot peening.

The basic principle of shot blasting is: using a high-speed projectile (diameter 1 ~ 6mm) to hit the surface of the metal sheet, so that the impacted surface and the underlying metal material are plastically deformed and extended, so that the sheet gradually protrudes toward the sprayed surface. From the two-way bending deformation (as shown).

There are different types of shot peening according to different classification methods: according to different shot peening areas, they are divided into single-sided shot peening and double-sided shot peening; according to the driving method of projectile speed, shot peening is divided into centrifugal shot peening. Forming, pneumatic shot peening, and ultrasonic shot peening; according to whether an external load is applied to the part in advance during shot peening, shot peening is divided into free state shot peening and prestressed shot peening.

The advantages of shot peening are very significant. First of all, the process does not require a forming mold, and the process equipment is simple. It can save a lot of mold design and manufacturing time, greatly shorten the production preparation cycle and cost, and can quickly and flexibly respond to design changes. It is particularly suitable for large sizes and relatively flat shapes. Parts. Secondly, the length of the parts to be formed is not limited by the size of the equipment (the length can reach more than 35m). As long as the plant site allows, the machine tool guide can be lengthened arbitrarily to accommodate large parts of any length. Again, shot peening helps to extend the fatigue life and corrosion resistance of the material.

It is based on these advantages that shot peening technology has been widely used in the manufacture of integral wall panel parts in aerospace and other fields. The United States first used the shot peening method to manufacture the entire wing wall panel on the Constellation aircraft. From the mid 1950s, shot peening technology has become the main forming of wing, fuselage and other wall plate parts for civil military aircraft. means. In the 1980s, the supercritical wing became an important symbol of the advanced nature of the aircraft. The overall wall panels that make up the wing appeared complicated saddle-shaped and torsional features, and the ribbed structure increased significantly. For such parts, traditional shot peening is difficult to meet the required deformation. For this reason, prestressed shot peening technology has been valued. Prestressed shot peening is a method of applying elastic deformation force to a slab before forming by shot peening and then shot peening the same. Under the same conditions, the forming limit of pre-stressed shot peening is 2 to 3 times that of free shot peening. At the same time, pre-stressed shot peening can also effectively control additional bending deformation along the direction of the shot peening route. The application of this technology further promotes shot peening. Development of forming technology.

With the advent of the information age, the rapid development of computer technology has promoted the research and development of shot peening technology, followed by digital shot peening technology, which opened a new era of shot peening technology. Digital shot peening is an advanced forming technology that describes the entire process of the part and its shot peening in digital form, and uniformly manages the data formed at each stage. A successful example is the automatic shot peening technology proposed by the German KSA company. Over the years, KSA has established a cooperative relationship with Airbus. In the early days, it manufactured A310 fuselage panels for Airbus. In 2001, it shot-blasted and shaped the A380 laser welded fuselage panels. The most advanced CNC shot peening equipment in the shot peening room in the world at that time.

At present, the shot blasting process is widely used in the forming of the wing integral wall panels of large and medium passenger aircraft (including all Airbus and Boeing passenger aircraft series currently in operation) and transport aircraft. Therefore, the shot peening of the large-scale wing integral wall panel is one of the core technologies for large-scale aircraft wing manufacturing. This technology has been monopolized by a few companies such as the United States Boeing and Metal Improvement Company and European Airbus, and has been implemented in other countries. Technology blockade. With the continuous improvement of large aircraft design requirements, shot peening technology has experienced the application process of the entire wall panel from single curvature to complex double curvature, from unribbed to ribbed. Bring new challenges and opportunities to shot peening technology.

Looking into the future, the development of shot peening technology will show the following characteristics: First, the shot peening objects and equipment are large, such as shot peening of large and complex overall wall panels and large overall structures. They require large shot peening equipment and corresponding shot peening. technology. Secondly, the external structure of shot peening panels is becoming more and more complicated, that is, based on the shape, structure and shape of existing shot peening components, it is more complicated and requires a greater amount of shot peening deformation. Thirdly, the shot blasting process is intelligent, which frees manpower from the complicated shot peening process to the greatest extent, and improves the quality and efficiency of shot peening. The development of modern technology has made it possible to realize the gradual realization of the blasting process intelligently. Finally, new types of shot peening methods continue to emerge. Among them, the development and application of double-sided shot peening technology, laser shot peening technology, ultrasonic shot peening technology, and high-pressure water shot peening technology have received extensive attention and attention.

Little bullets change not only the shape of parts, but also the development of modern aircraft manufacturing technology. With the rapid progress of aerospace manufacturing, the development and application prospects of shot peening technology are bright, and the technical and economic market is broad. It will occupy an irreplaceable position in the overall siding manufacturing.