????????????The front axle assembly of an automobile is also called a driven axle. It is a mechanism for transmitting vertical, longitudinal, and lateral forces acting on the work machine by the road surface. The driven wheels mounted on the front axle, in addition to supporting part of the vehicle weight, also play a guiding role.
???????The general stress condition of the front axle is large in the vertical and horizontal directions. When the working machine is stationary, the driven bridge is like a simply supported beam. The fulcrums at both ends are directly above the tire grounding center. The weight of the working machine acts on the connection between the beam and the frame. At this time, the driven bridge mainly bears the bending moment, and the I-beam is more reasonable. However, the driven axle is equipped with a brake. When the working machine brakes, it also has the function of bearing torque. In this case, it is more reasonable to use a round or rectangular cross-section beam. Considering the above factors comprehensively, variable-section beams can be used according to the structure and strength requirements.
???????The determination of the front axle load is caused by the change of the weight of the work machine, the road condition, the travel speed, the work condition and other factors when the work machine runs straight or brakes on the horizontal road. For example, if the working machine is driving on a rough and uneven road, the load is much larger than that of a straight and constant speed driving on a flat road, and it is mostly an impact load. At present, for the strength design of the front axle, its calculated load is often obtained through the following three severe working conditions:
???????Process requirements: Because the front axle assembly of the car bears a large part of the total weight of the car, and the stress situation is also very complicated, it is a very important part in the front axle. And for the main method of producing front beams at present, the processing technology we adopt is forging. Now the commonly used forging methods are free forging, die forging and tire die forging. Because the shape of the front axle is more complicated, and its requirements for mechanical performance and service life are higher, we adopted the method of die forging for the front axle. Die forging is a processing method that places the heated blank in the forging die cavity and forces the blank to deform to obtain forgings under the effect of forging pressure. When the blank is deformed, the flow of metal is restricted and guided by the die cavity, thus Obtain a forging that is consistent with the shape of the die bore.
????????For die-forged parts, generally meet the following principles:
1) The forgings should have a reasonable parting surface to meet the convenience of mold making, the metal is easy to fill the mold cavity, the forgings are easy to release the mold and reduce the requirements of remaining blocks.
2) The non-machined surface on the forgings perpendicular to the parting surface should be designed with a structural slope.
3) On the premise of meeting the requirements for use, the shape of the forgings should be simplified, especially the structures such as thin slices, high ribs, and high platforms should be avoided.
4) Narrow grooves, deep grooves, deep holes, and porous structures should be avoided as much as possible to facilitate mold manufacturing and extend mold life.
????????The front axle we designed must pay attention to the following problems during the forging process:
1) Die forging slope
???????In order to facilitate the filling of the die cavity with metal and the removal of the forging from the die cavity, the forging surface perpendicular to the parting surface on the forging must have an additional slope. This slope is called the die forging slope. The slope of the outer wall of the forging is called the outer die forging slope, and the design of the front axle assembly of the light truck on the inner wall.
?2) Fillet radius
???????The intersection of all faces on the forging must be rounded. The function of the rounded corner of the forging (the rounded corner of the protruding part in the die cavity) is to reduce the frictional resistance of the metal flow during forging, to avoid the tearing of the forging or the breaking of the fiber structure, reduce the wear of the die, and increase the service life. The function of the rounded corner of the forging (the rounded corner of the concave part in the die cavity) is that the metal is easy to fill the die cavity to avoid cracking caused by stress concentration during the heat treatment or forging process of the die.
??????????The front beam also needs to be heat treated. The purpose is to adjust the hardness and facilitate cutting; eliminate internal stress and prevent deformation during cutting; uniform structure and refine grain. The forgings of the front beam are annealed and normalized. If the hardness is still high after normalizing, high temperature tempering treatment can be added, the tempering temperature is about 560 ~ 660 ℃.