Does grinding toe really improve fatigue strength?

The welding technology of German MAN Marine diesel engine is adopted to improve the fatigue strength of welding seam by grinding toe for low speed diesel engine frame.  Without proper grinding, welds cannot achieve the fatigue strength calculated for design, which may result in structural defects during use.  Grinding toes has two advantages for fatigue strength:

 (1) Remove toe defects that may cause fatigue cracks;

 (2) To achieve a smooth and coordinated transition between plate and welding surface, so as to eliminate local stress concentration.

 The grinding position requirements of MAN drawings are mainly in the following positions: free end of the machine base;  The welding seam of the connection between the main bearing seat and the upper panel of the frame;  Weld joint between main bearing seat and floor plate (if sometimes);  The chassis supports the floor plate.  Frame output end;  The chassis supports the floor plate.

 Therefore, when the diesel engine base is completed for inspection, attention should be paid to whether the grinding of the corresponding welding toe (position, size, etc.) meets the requirements of the technical drawings of the patent party, and MT inspection should be carried out on the appearance surface of the welding seam after grinding.

 In addition, for the method of using grinding weld toe to eliminate fatigue stress, some domestic scholars do the research, experiment and theoretical calculation of the finite element analysis method of the theoretical calculation results show that reduce the weld toe Angle, increase the transition arc radius, can slow down the weld toe in the change of the cross section shape, improve coal toe of stress concentration;  Thickness makes the stress concentration factor increases "the four welding tee joint spacing form (grinding springtails, convex circle, concave round, flat shape) and the finite element model was established, through the calculation and experiment show that tee joint weld toe part of fatigue fracture of danger, planar weld toe is a better form of T joint weld toe.  Convex arcs are the worst.