A Re-Examination of Failure Analysis and Root Cause Determination
A Re-Examination of Failure Analysis and Root Cause Determination
A Re-Examination of Failure Analysis and Root Cause Determination
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21Tensile Property TestingA tensile test specimen was machined from the broken shaft <strong>and</strong> tested in accordancewith the methods <strong>of</strong> ASTM A 370. The results are given below. The yield strength wasdetermined at 0.2% <strong>of</strong>fset. The shaft conformed to the tensile property requirements forthe German grade 30 NiMoCr8 steel for a section size between 160 <strong>and</strong> 250 mm.TENSILE PROPERTIES30 NiMoCr8Shaft(PSI) Shaft ( N / 2 mm ) 160-250mm__Yield Strength 134,100 924.5 700 N / 2 mm MINTensile Strength 151,800 1046.6 900-1100 N 2/ mm% Elongation in 2 Inches 17.5 17.5 12.0 MIN% <strong>Re</strong>duction <strong>of</strong> area 60.0 60.0 50.0 MINRockwell Hardness SurveyA cross section through the shaft diameter was cut adjacent to the crack <strong>and</strong> surfaceground to provide flat, parallel surfaces. Rockwell C scale hardness measurementswere made at 1 / 8 inch intervals across the shaft diameter. The results are plotted below.They show the hardness to be quite consistent across the shaft section.Hardness <strong>of</strong> Conveyor Drive ShaftRockwell C Hardness34.53433.53332.53231.53130.50 1 2 3 4 5 6Distance across shaft (inches)Impact Property Testing
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