CEE300_Lab_4_worksheet
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University of Notre Dame *
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300
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Apr 3, 2024
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CEE 300 / TAM 324: Lab 4 Notch Sensitivity Worksheet Lab section: Student name: General note: use space as needed. The answer length is not suggested by the space. Include sample calculations where applicable. All figures and tables MUST be formatted as outlined in Lab 0 lecture – including captions. Q1 (15 pts). Complete Table 1 and plot load vs. deflection for all materials tested. Table 1—Notched bending specimen data Measurement or property Material Quantity Symbol Units 1045 HR Steel 6061 Aluminum PMMA Sharp Round Sharp Round Compr. Tension Initial data Overall beam height H mm Notch depth d mm Net beam height at notch h mm Notch radius r mm Beam thickness w mm Moment of inertia I
mm
4
Upper span U mm Lower span L mm Support moment arm a
L
U
2
mm Strength Apparent yield load P
y
kN Maximum load P
max kN Reason for stopping test — —
Detail of fracture surface or final shape — — Derived quantities Apparent yield strength
y E MPa Modulus of rupture in bending R
B MPa 1045HR Steel Plot: 6061 Aluminum Plot: PMMA Plot:
Q2 (5 pts). For the PMMA specimen, first recall the value of the modulus of rupture as determined previously in the Bending and Torsion Tests lab for an unnotched specimen, and then compute the modulus of rupture for the notched specimen (with the notch loaded in tension), based on the current failure load and the net section of height h
. Complete Table 2. Then deduce the value of the stress concentration factor K
t for your geometry using Eqn. (3) in lab manual. Table 2—Comparison of unnotched and notched bending results Measurement or property Material 1045 Steel 6061 Aluminum PMMA Quantity Symbol Units Sharp Round Sharp Round Compr Tension Derived properties (from unnotched bend tests—Lab 3) Yield strength
y
MPa Modulus of rupture in bending R
B MPa Nature of fracture surface — — Derived properties (from notched bend tests) Apparent yield strength
y E MPa Predicted yield strength
y P MPa Modulus of rupture in bending R
B MPa Nature of fracture surface — — Stress concentration factor K
t
—
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Q3 (5 pts). From the load–deflection plots for steel and aluminum, calculate the experimentally obtained apparent yield strength
’
yE
. Compare these values with
y values obtained for the same materials in Labs 1, 2, and 3. Comment on the differences, if any. How did the notch affect the material? Explain. Answers: Q4 (5 pts). Derive Eqn. (7), describing briefly the reasoning involved. Substitute the value
= 0.3 into this expression and compare the relative values of
’
yP and
y . Does this reasoning assist in explaining “notch strengthening” if in fact it was observed in the lab? Explain briefly. Answers: