- #1

Rich76

- 25

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stress = force x length / (width x (depth x depth))

Stress ("outer fibers at midpoint"), (MPa)

Force ("load at a given point on the load deflection curve"), (N)

Length ("Support span"), (mm)

Width ("Width of test beam"), (mm)

Depth ("Depth or thickness of tested beam"), (mm)

Source: https://en.wikipedia.org/wiki/Four-point_flexural_test

Plugging in the numbers from this youtube video (four-point test of reinforced concrete):

Force = 42000 N (failure point)

Length = 3000 mm

Width = 152 mm

Depth = 269 mm

stress = 42000 x 3000 / (152 x (269 x 269))

stress = 11.45572 MPaI have two questions:

1. Is the math correct (I'm assuming "failure point" is "the load at a given point on the load deflection curve")?

2. What does a flexural stress of 11.45572 MPa mean? 11.45572 MPa "outer fibers at midpoint"?