The material will be tested at as near 12 per cent moisture as is practicable.  The approximate weight of the air-dried specimens at 12 per cent moisture will be determined by measuring while green 20 per cent of the sticks to be air-dried and assuming their dry gravity to be the same as that of the specimens tested green.  This 20 per cent will be weighed as often as is necessary to determine the proper time of test.

Methods of Test

All tests will be made according to Circular 38 except in case of conflict with the instructions given below: 

Static bending:  The tests will be on specimens 2” X 2” X 30” on 28-inch span.  Load will be applied at the centre.

In all tests the load-deflection curve will be carried to or beyond the maximum load.  In one-third of the tests the load-deflection curve will be continued to 6-inch deflection, or till the specimen fails to support a 200-pound load.  Deflection readings for equal increments of load will be taken until well past the elastic limit, after which the scale beam will be kept balanced and the load read for each 0.1-inch deflection.  The load and deflection at first failure, maximum load and points of sudden change, will be shown on the curve sheet even if they do not occur at one of the regular load or deflection increments.

Impact bending:  The impact bending tests will be on specimens of the same size as those used in static bending.  The span will be 28 inches.

The tests will be by increment drop.  The first drop will be 1 inch and the increase will be by increments of 1 inch till a height of 10 inches is reached, after which increments of 2 inches will be used until complete failure occurs or 6-inch deflection is secured.

A 50-pound hammer will be used when with drops up to 68 inches it is practically certain that it will produce complete failure or 6-inch deflection in the case of all specimens of a species.  For all other species, a 100-pound hammer will be used.

In all cases drum records will be made until first failure.  Also the height of drop causing complete failure or 6-inch deflection will be noted.

Compression parallel to grain:  This test will be on specimens 2” X 2” X 8” in size.  On 20 per cent of these tests load-compression curves for a 6-inch centrally located gauge length will be taken.  Readings will be continued until the elastic limit is well passed.  The other 80 per cent of the tests will be made for the purpose of obtaining the maximum load only.

Compression perpendicular to grain:  This test will be on specimens 2” X 2” X 6” in size.  The bearing plates will be 2 inches wide.  The rate of descent of the moving head will be 0.024 inch per minute.  The load-compression curve will be plotted to 0.1 inch compression and the test will then be discontinued.

Hardness:  The tool shown in Fig. 43 (an adaptation of the apparatus used by the German investigator, Janka) will be used.  The rate of descent of the moving head will be 0.25 inch per minute.  When the penetration has progressed to the point at which the plate “a” becomes tight, due to being pressed against the wood, the load will be read and recorded.