Results of Impact Tests to Compare the Pendulum Impact and Toughness Test Methods.

摘要

Two types of single-blow impact machines are in common use for testing small, clear specimens of wood. These are the simple pendulum impact machine, as embodied in the Amsler testing machine, and the Forest Products Laboratory toughness machine, which employs a linked chain operating over a drum at the axis of a pendulum. Previous studies have shown that results of tests with different sizes of specimens with any one machine are not directly convertible in unit energy values from one size to the other. In the interest of unifying test procedures, the same size specimen used for the pendulum impact (2 centimeters square in cross section) was adopted for the toughness test method. An extensive series of tests was made on matched material to determine the comparability of results by the two methods. The data show that, while each provides good comparative data among species and between other variables in test conditions, the pendulum impact method afforded generally lower average results than the Forest Products Laboratory toughness test method. The average differences ranged from 4 to 27 percent. It does not appear from these data than an accurate conversion factor can be established to translate test values from one test method into directly comparable results of the other, even when the same size specimen is used. As a very broad, general approximation, however, average values from the pendulum impact method can be estimated as about 15 percent lower than values obtained by the toughness test method for comparable material.