1 exactly where this proportional limit
falls, but the expanded view in Fig.
The difference lies in the attempt to use equations developed for materials that have a proportional limit
on materials that do not have a true proportional limit
and not considering the properties of copper strain hardening.
Therefore, there is a concern that bending properties, including Young's modulus, proportional limit
stress, and bending strength, cannot be evaluated appropriately by the conventional bending tests.
To simplify the calculations, it was taken, that cyclic proportional limit
For high loads, stress and strain exceed proportional limit
and elastic plastic strain occurs.
As long as the stress does not exceed a metal's proportional limit
, the energy induced in the part by the applied force is stored as recoverable, or elastic, energy, and the part returns to its original dimensions with negligible permanent deformation when the force is released.
It was anticipated that as the wood was loaded over and above the proportional limit
, the permanent damage could be detected via acoustic velocity measurement.
While strains at yield typically range from 3% to 10% for most thermoplastics, the strain at the proportional limit
rarely exceeds 1% and for many materials it is less than 0.
Samples of southern yellow pine outer bark and wood were tested in compression to determine values for modulus of elasticity, stress at proportional limit
, and maximum crushing strength.
This work is a part of a larger research effort to establish a usable computer program for the design of all timber to timber and timber to steel joint stiffness and proportional limit
The compressive properties such as Young's modulus, proportional limit
stress, and compressive strength were obtained from the stress-strain relation.
Several uniaxial tension tests of the specimens with the off-axis angles of+45[degrees]/-45[degrees], 45[degrees], 15[degrees], and 20[degrees] were conducted, and the shear properties such as shear modulus, shear stress at the proportional limit
, and shear strength were obtained from the shear stress/shear strain relation.