Shot peening technology in shot peening treatment for aviation manufacturing

As a surface strengthening process, shot peening has a long history dating back to 2700 BC. According to records, blacksmiths at the time had realized that metal that was hammered in a cold state could become harder. Europeans in the Middle Ages found in the use of horse-drawn sedans that the same leaf springs that had been sand-blown on the surface had a significantly longer service life. These are just people's initial understanding of shot peening. After entering the 20th century, people began to use metal particles to shot peened the roots of springs and large gears.

Especially in the 1940s, a large number of researchers began to make a lot of research and exploration in the shot peening process, and their understanding of the shot peening process was raised to a higher level, thus promoting and expanding the application of this process. range. Lockheed Martin engineer Jim Boerger was inspired by shot peening Almen test pieces and created an advanced forming technology in modern aircraft manufacturing-shot peening technology.

The basic principle of shot peening is to use high-speed projectiles (diameter 1-6mm) to hit the surface of the metal sheet, causing the impacted surface and the underlying metal material to plastically deform and extend, thereby gradually causing the sheet to protrude toward the sprayed surface. Bending deformation in both directions.

The main advantages of shot peening technology are:

1) The process equipment is simple and does not require forming molds, so the parts manufacturing cost is low, and the adaptability to the size of the parts is strong;

2) After the shot peening is formed, residual compressive stress is formed on the upper and lower surfaces along the thickness direction of the part (as shown in the figure below), so while the part is formed, the fatigue resistance of the part can also be improved;

3) Both single-curvature parts and complex double-curvature parts can be formed.

It is precisely based on these advantages that shot peening technology has been widely used in the manufacture of integral siding parts in aerospace and other fields. The United States took the lead in the use of shot peening technology to manufacture integral wing panels on the "Constellation" aircraft. Since the mid-1950s, shot peening technology began to set foot on the historical stage of aviation manufacturing, including civil military aircraft wings and fuselages. Forming of parts such as siding, etc.

In recent years, with the increasing requirements of modern aircraft for overall aerodynamic performance and the rapid development of computer technology, the research and development of shot peening technology have been greatly promoted, and prestressed shot peening technology and digital shot peening technology have emerged. , New shot peening forming/strengthening technology, etc., greatly expanding the processing capacity and application range of shot peening forming technology.

1. Prestressed shot peening forming

After entering the 1980s, supercritical wing has become an important symbol of aircraft advancement. The integral wall panels that make up the wing have also appeared complex saddle-shaped and torsion characteristics, and the ribbed structure has increased significantly. Traditional shot peening of such parts is difficult to meet the required deformation. For this reason, prestressed shot peening technology has been paid attention. Prestressed shot peening is a forming method in which elastic deformation force is applied to the slab with the aid of a prestressed fixture before forming, and then shot peening is performed on it. Under the same conditions, the forming limit of prestressed shot peening is 2-3 times that of free shot peening. At the same time, prestressed shot peening can effectively control the additional bending deformation along the shot peening route. The application of this technology further promotes shot peening. The development of forming technology.

At present, prestressed shot peening technology has been applied in the manufacture of supercritical wing integral wall panels. Canadian NMF company adopts prestressed shot peening technology for Israeli Galaxy aircraft wing ribbed integral wall panels. The application of prestressed shot peening technology avoids the adverse effects on fatigue life caused by the use of mechanical bending to form such parts.

Of course, it is necessary to design and manufacture special prestressed fixtures to apply prestress to the parts. The design of prestressed fixtures must be simple, portable, easy to operate, and coordinate with the shot blasting equipment used. Therefore, further research on the simple and easy prestress loading method and the use of finite element method to analyze and accurately determine the size of the applied prestress to ensure that the part is completely within the elastic deformation range under the prestress will be the prestress shot peening technology. Development trend.

2. Digital shot peening technology

Digital shot peening forming technology, as the name suggests, is to use digital technology to analyze the digital process geometry information of parts, select and optimize shot peening process parameters, simulate and control the shot peening process, and digitally inspect the shape of the formed part. , The digital management of the shot peening process files and programs of the parts, etc., so as to realize the advanced forming technology-CNC spraying, which describes the parts and the whole process of shot peening in the form of digital quantities, and manages the data formed at each stage in a unified manner. pill.

3. Automated shot peening technology

The implementation of automated shot peening technology can now be divided into three stages, namely conceptual design and analysis stage, pre-production (development) stage and production stage.

In the conceptual design and analysis stage, the process of shot peening is mainly analyzed and evaluated for the CAD model of the part, and the initial shot peening process plan and forming process parameters are formulated, and the corresponding requirements are formulated for the user's equipment and personnel conditions. ; In the pre-production stage, the process is mainly optimized through the shot peening test of the test piece, and the relevant process control files and procedures are generated. At the same time, the user's equipment is required to be upgraded and adjusted. In addition, the parts can also be carried out in parallel at this stage. Design changes and perfection; in the production stage, by calling the relevant parts control program that has been formulated, automatic shot peening can be realized, and the technical training of relevant personnel can be completed at the same time.

Through the 3 stages described above, users can establish an automated shot peening technology system. When new product development is needed in the future, they only need to perform offline programming and then transfer the relevant data and programs to the user's equipment. Carry out the process of automatic shot peening and carry out processing and forming.

Transfer from Aviation Manufacturing Network