 C. Dumont

C. Dumont reported a 1939 experimental study of stress around a circular hole in an aluminum-alloy plate under out-of-plane bending. The primary NACA record retains that exact initial-only name and lists an Aluminum Company of America affiliation.^[ref]

Dumont measured plate deflection and strain for two loads. The largest hole-edge stresses were tangential at the ends of the transverse diameter. The reported maximum was 1.59 times a computed net-section stress and 1.85 times the computed stress for an otherwise solid plate subjected to the same bending forces.^[ref]

Those ratios demonstrate why a stress concentration factor requires a stated denominator. For an original numerical illustration, stipulate a local peak $37\mathrm{MPa}$. Reference stresses $37/1.85=20.0\mathrm{MPa}$ and $37/1.59\approx 23.27\mathrm{MPa}$ then reproduce the two ratios for the same peak. These invented stresses illustrate normalization; they are not recovered loads or stresses from Dumont's experiment.

The bending result is also distinct from the factor three in the in-plane tensile Kirsch equations. Geometry, stress components and boundary loading differ. Dumont's comparison of strain and deflection provided complementary local and overall observations rather than assuming a universal circular-hole amplification.

For a linear-elastic model, doubling the load at fixed geometry doubles both strain and deflection. Taking measurements at more than one load can therefore test proportionality. Agreement at two loads alone would not establish fatigue life or the onset of yielding. This explains the value and the limits of the experiment without expanding the initial C. or assigning an unverified biography.