Process for fabricating a moldboard blade

A process for forming a moldboard blade for a grader by inducing beneficial residual stresses during fabrication. This increases the strength of the blade without adding additional material and weight. The blade is first bowed towards its supporting structure surface. The supporting structure is welded to the blade and the blade is released. The blade is then bent in the opposite direction towards its working surface and released. The blade is then checked to determine if it is straight. If the blade is not straight it is bent again until it is straight.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention is directed to a process of forming a moldboard blade by 
inducing beneficial residual stresses in the blade, thereby increasing 
strength of the blade without adding additional material and weight. 
2. Description of the Prior Art 
In fabricating a moldboard blade for a grader, the assignee of the present 
invention currently mounts the blade on a welding fixture and bows the 
blade slightly in the direction of the soon to be mounted supporting 
structure. The supporting structure is then welded to the backside of the 
blade. The blade is then released from the fixture and because of the 
thermal stresses induced in the blade during welding, the blade 
straightens out and is ready to be mounted on a grader. 
SUMMARY 
It is an object of the present invention to form a moldboard blade of 
greater strength without additional weight by inducing beneficial residual 
stresses in the blade and also strain hardening the blade during 
fabrication. 
A grader moldboard blade of the present invention is first bowed in the 
direction of the supporting structure. This bowing is greater than the 
amount of bowing recovered by the thermal stresses induced in the blade 
when welding the supporting structure to the blades. The supporting 
structure is welded to the blade after it is bowed. The blade is then 
released and the blade recovers only a portion of the bow curvature. The 
blade is then bent in the opposite direction past its intended shape. The 
blade is then released and compared to the final desired shape. The blade 
may then be bent again to reach the correct configuration.

DETAILED DESCRIPTION 
FIG. 1 illustrates an articulated motor grader 10 comprising a front frame 
12 and a rear frame 14. The front frame is supported by wheels 16 and the 
rear frame is supported by tandem wheels 18. The rear frame 14 houses the 
engine and transmission of the motor grader. The front frame 12 supports 
moldboard circle assembly 20 which is used to manipulate the position of 
the moldboard blade 22. The moldboard blade 22 is supported from the 
grader moldboard circle assembly by supporting structure 24. 
As illustrated in FIG. 2, moldboard blade 22 comprises a concave blade 
member 25 having a working surface 27 and a support structure surface 29. 
The working surface 27 faces the primary working direction for the 
moldboard blade. Longitudinal channels 26 are welded to the support 
structure side of the blade member 25. The ends of these channels are 
enclosed by plates 28 which are also welded to the channels and the 
moldboard. Elongated mounting rails 30 are welded to each of the channels. 
These mounting rails are interconnected by cross member 32 which is welded 
to these rails. Cross member 32 is provided with an aperture 34 which is 
coupled to the side shift assembly of the circle assembly. The moldboard 
blade illustrated if FIGS. 2-4 is of a relatively conventional 
configuration. The process of fabricating the moldboard blade as discussed 
below induces beneficial residual stresses in the blade and strain hardens 
the blade so that it better resists deformation during the grading 
operation. This process is illustrated in FIGS. 5-9. 
The first step comprises placing an unbent blade member 25 on a welding 
fixture (not shown) and bowing the blade in the direction of its 
supporting structure, as illustrated in FIG. 6. This bowing is greater 
than what is currently done to overcome thermal stresses during the 
welding process. The bowing maybe accomplished by restraining the ends of 
the blade member to prevent their upward movement. Then a hydraulic 
cylinder having a working face conforming to the working surface of the 
blade member may be positioned towards the center of the blade member. The 
hydraulic cylinder is driven upwardly so as to form the bow illustrated in 
FIG. 6. 
The channels 26 and rails 30 are then welded to the bowed blade member. 
After welding, the moldboard is released from the fixture. Because of the 
thermal stresses induced in the moldboard during welding, the moldboard 
tends to straighten. However, the moldboard still maintains its curved 
configuration as shown in FIG. 7 when released. 
The moldboard blade is then placed in another fixture or press and bent in 
the opposite direction. The moldboard is bent past its desired shape which 
with a grader moldboard is a straight configuration, as illustrated in 
FIG. 8. This bending induces beneficial residual stresses in the moldboard 
so that it will resist bending from loads coming from the primary working 
direction and contacting the working side of the moldboard blade during 
grading operations. This bending is accomplished in a manner similar to 
that used to bow the blade member. The ends of the blade are restrained 
from moving downwardly and a hydraulic cylinder or press having a working 
face conforming to the support structure side of the moldboard blade 
presses the middle of the moldboard blade downwardly, as illustrated in 
FIG. 8. 
After releasing the moldboard blade from this bending operation, the 
moldboard blade is compared to its desired shape, which in the case of a 
grader moldboard blade is straight. If the moldboard blade is still 
slightly bowed, the moldboard blade can be bent again under greater 
pressure. The moldboard blade is again released and compared with its 
desired shape. This process can be repeated until the desired shape is 
reached. It is important to note however, that the moldboard blade should 
not be subjected to pressures which bend the moldboard blade so that it 
exceeds its desired shape and must be rebent in the opposite direction. 
Bending the moldboard blade in the opposite direction reduces or 
eliminates the beneficial residual stresses formed in the moldboard blade. 
The beneficial residual stresses formed in the moldboard blade are in 
direct relation to the force used to bend the moldboard blade to its 
desired shape, (i.e. greater force produces more beneficial stresses). In 
addition to these beneficial residual stresses the moldboard blade has 
also undergone strain hardening which further contributes to the strength 
of the newly formed blade. 
The above described process should not be limited to the above described 
embodiment, but should be limited solely by the claims that follow.