Forging shape is generated under the action of external force. Therefore, correct calculation of deformation force is the basis for selecting equipment and performing mold calibration. Stress and strain analysis inside the deformed body is also indispensable for optimizing the process and controlling the microstructure of the forging.
There are four main methods for analyzing the deformation force. Although the principal stress method is not very strict, it is relatively simple and intuitive, and the total pressure and the stress distribution on the contact surface between the workpiece and the tool can be calculated. The slip line method is strict for the plane strain problem of forgings, and the stress distribution for high part local deformation is relatively straightforward, but the scope of application is narrow. The upper limit method can give an overestimated load, and the upper limit element can also predict the shape change of the workpiece during deformation. The finite element method can not only give the external load and the shape change of the workpiece, but also give the internal stress and strain distribution. The disadvantage is that the computer has more machine time, especially when it is solved by elastoplastic finite element, it needs a large computer capacity. The machine is longer. Recently, there has been a trend to analyze problems using a joint approach, for example, using the upper bound method for rough calculations and finite element calculations at key locations.
Reducing friction not only saves energy but also increases mold life. One of the important measures to reduce the friction of the product due to the uniform deformation is to use lubrication. The lubricant used is different due to the different methods of forging and the difference in working temperature. Glass lubricants are mostly used in high temperature alloys and titanium alloy forging. For hot forging of steel, water-based graphite is a widely used lubricant. For cold forging, due to the high pressure, it is often necessary to carry out phosphate or oxalate treatment before forging.