5_68 - 5.68 A 100-mm-wide by 8-mm-thick steel bar is...

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Unformatted text preview: 5.68 A 100-mm-wide by 8-mm-thick steel bar is transmitting an axial tensile load of 3,000 N. After the load is applied, a 4mm-diameter hole is drilled through the bar, as shown in Fig. P5.68. The hole is centered in the bar. (a) Determine the stress at point A (on the edge of the hole) in the bar before and after the hole is drilled. (b) Does the axial stress at point B on the edge of the bar increase or decrease as the hole is drilled? Explain. Comment [TAP1]: (a) σA = 3.75 MPa (before); σA = 11.29 MPa (after) (b) σB decreases Fig. P5.68 Solution (a) Stress at point A: Before hole is drilled: P 3,000 N σA = = = 3.75 MPa A (100 mm)(8 mm) After hole is drilled: d 4 mm = = 0.04 D 100 mm σA = Ans. ∴ K ≅ 2.89 PK (3,000 N)(2.89) = = 11.29 MPa Anet (100 mm − 4 mm)(8 mm) (b) Stress at point B: The axial stress at point B decreases. Since the average stress changes very little with the introduction of the small hole and since the stress at A is larger than the average stress, the axial stress far from the hole must be less than the average stress. Ans. ...
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This note was uploaded on 02/09/2012 for the course MECHANICAL EM217 taught by Professor Joyce during the Spring '11 term at Naval Academy.

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