arms(at the bottom of the blade)in tension. When the mixer is running, the rotational forces further add to the tensile loads on the inside radii of the shoulders Fig 7 Ice cream mixer blade as manufactured (left) and assembled to spindle(right) Analysis of the failed mixer blades revealed multiple fatigue crack origins on the inside radii of the bends at the bottom shoulders(Fig. 8). Metallographic examination of the arm materials revealed additional problems with the configuration the shoulders on the arms were cold bent. introducing tensile residual stresses on the inside radii of the shoulders and creating a localized area of fatigue susceptibility due to the inherent notch sensitivity of cold-formed 300 series stainless steel B Fig. 8 Fracture surface of failed ice cream mixer blade. arrows indicate fatigue crack origins.13× Clearly, the physical root cause is the design of the mixer blade, which defined two bend that contained tensile residual stresses, tensile assembly stresses, and a notch-sensitive microstructure that added to the normal operating rotational and vibratory stresses. The net effect was a reduction in the life of the blade causing loss of function Corrective-action recommendations included the addition of a stand-off washer between the wavy washer and the bottom shoulders of the blade, or modification of the shape of the wavy washer to prevent contact with the blade shoulders as assembledarms (at the bottom of the blade) in tension. When the mixer is running, the rotational forces further add to the tensile loads on the inside radii of the shoulders. Fig. 7 Ice cream mixer blade as manufactured (left) and assembled to spindle (right) Analysis of the failed mixer blades revealed multiple fatigue crack origins on the inside radii of the bends at the bottom shoulders (Fig. 8). Metallographic examination of the arm materials revealed additional problems with the configuration: the shoulders on the arms were cold bent, introducing tensile residual stresses on the inside radii of the shoulders and creating a localized area of fatigue susceptibility due to the inherent notch sensitivity of cold-formed 300 series stainless steel. Fig. 8 Fracture surface of failed ice cream mixer blade. Arrows indicate fatigue crack origins. 13× Clearly, the physical root cause is the design of the mixer blade, which defined two bend areas that contained tensile residual stresses, tensile assembly stresses, and a notch-sensitive microstructure that added to the normal operating rotational and vibratory stresses. The net effect was a reduction in the life of the blade causing loss of function. Corrective-action recommendations included the addition of a stand-off washer between the wavy washer and the bottom shoulders of the blade, or modification of the shape of the wavy washer to prevent contact with the blade shoulders as assembled