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Dynamic material properties of wood subjected to low-velocity impact

 
: Polocoser, T.; Kasal, B.; Stöckel, F.; Li, X.

:

Materials and structures 51 (2018), Nr.3, Art. 71, 16 S.
ISSN: 0025-5432
ISSN: 1359-5997
Englisch
Zeitschriftenaufsatz
Fraunhofer WKI ()
wood; impact; intermediate strain rates; design factors; validation; duration of load

Abstract
This article studied the effects of low-velocity impact on the failure stresses and stiffness using a pendulum test. The specimens were of variable depth (20, 30, and 40 mm), a width of 50 mm, length of 650 mm, and span-length of 480 mm. The smallest specimen depth was similar to specimen sizes tested in the literature used to create the duration of load curve, while the largest specimen depth are considered structural size specimens. The impact was predicted using a numerical approach with Euler–Bernoulli beam, as well as Timoshenko beam theory, with a plastic contact law. The models were validated for impact from a low release-angle (where the beam remained elastic), but could use improvement for the force prediction at a high incidence velocity. The measured force signals were used as forcing functions to obtain the dynamic failure stresses for all of the evaluated specimens, and the Timoshenko–Goens–Hearmon Method to derive the dynamic E. The resulting strain rates ranged from 9.11 × 10⁻⁵ s⁻¹ for the quasi-static specimens up to 25 s⁻¹ for the greatest incidence velocity. The results from this study suggest different duration of load factors than the Madison Curve, influencing the design of structures subjected to dynamic loading.

: http://publica.fraunhofer.de/dokumente/N-497050.html