The obtained mechanical characteristics of the steel are as follows: proportional limit [[sigma].
Since automatic couplers in railway carriages are loaded with varying forces and those as shown above cause stresses exceeding the proportional limit, therefore to investigate the cyclical properties of the material stress, limited loading was chosen during which strains are unlimited and proceed freely, so damage modes depend on loading level.
Following increasing levels of bending load, beyond the proportional limit
, the acoustic velocity decreased.
The values for the stress at proportional limit
and maximum crushing strength collected in the longitudinal direction appeared to decrease with the solvent treatments, however, the differences between the treatments were not statistically significant when compared by analysis of variance.
From these two series of tests, it appears that at 90 degrees the increase of the friction coefficient doesn't change the proportional limit
Since two stress-strain relations were measured from one test specimen, two Young's moduli, two proportional limit
stresses, and one compressive strength were obtained.
The shear modulus, shear stress at the proportional limit
, and shear strength were determined by a similar procedure to that in the +45[degrees]/-45[degrees] off-axis tension test.
Measurement of Young's modulus, proportional limit
stress, and bending strength
The results were interpreted in terms of joint stiffness as well as three limit states: proportional limit
, 5 percent offset yield load, and ultimate load.
A 50 percent decrease in wave velocity may indicate the presence of moderate decay and corresponds with a 60 percent decrease in elastic modulus and a 40 percent decrease in compression perpendicular-to-the-grain stress at the proportional limit
Tension parallel to grain properties, maximum strength, fiber stress at proportional limit
, and MOE of the seven red oak species investigated in the green and 12 percent MC conditions are shown in Table 2.
MOE = modulus of elasticity; MOR = modulus of rupture; FSPL = fiber stress at proportional limit