A part of a machine is a beam with rectangle cross section to be subjected to a bending moment M. The cross-section dime

[answerhappygod]

A Part Of A Machine Is A Beam With Rectangle Cross Section To Be Subjected To A Bending Moment M The Cross Section Dime 1 (305.89 KiB) Viewed 33 times

A part of a machine is a beam with rectangle cross section to be subjected to a bending moment M. The cross-section dimensions are b=40 mm and t=20 mm. The material is Ti-6Al-4V titanium alloy with a yield strength σ0​=925MPa and a toughness KIC​=66MPam​. (a) A 12 mm slit (a narrow crack of a=12 mm ) is found at the edge. (See schematic drawing, not to scale, → ) If the applied moment M keeps increasing, the beam will fail. Determine whether this beam will fail first by brittle facture or by fully plastic yielding. Determine the magnitude of the applied moment M at failure. (b) Engineer Robin wants to remove the possibility of this beam to fail by fracture, so she drills a big hole (diameter d=6 mm ) in front of the cracktip, with the original cracktip just touching the hole, → With the circular hole now serving as the "cracktip" of this longer "crack" there is no sharp cracktip anymore. So, it loses the stress accentuation of the original sharp cracktip, and this "non-sharp crack" (a blunt notch) will not grow. Hence, with the stop-crack hole installed the beam will not fracture. If the applied moment M keeps increasing, the beam will fail. Determine the magnitude of the applied moment M at failure. \begin{tabular}{|l|l|l|l} \hline From Figure 8.13 of the textbook: \\ Stress intensity factor for edge crack in bending \end{tabular}