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The present paper reports results of analysis of the strength and strain properties of birch wood at different loading rates, sample temperatures, and angles of orientation of fibers relative to the direction of loading. Dynamic tests (v = 10 m/sec) In engineering practice dealing with pulsed loads, dampers of shock loads have been widely used. They are most frequently used in transportation of freight of various types to decrease the effect of transportation loads, including loads leading to a failure. In most cases, the dampers are materials whose compression by tens of percent proceeds at a practically constant stress (a = const). Such materials are, for example, low-density foam plastics and tubular (in axial compression) and perforated crushers made of metals [1--4]. By choosing a damper material, it is possible to vary the level of transmitted pressure from units (low-density foam plastic) to hundreds and thousands of megapascals (tubular and perforated crushers made of metals).The deformation of wood under transverse compression is similar in character to the deformation of foam polystyrene [5, 6]. The availability of wood and the great variety of wood species with considerably different mechanical properties make wood an attractive material for use as a damper of shock loads.Cylindrical test samples (diameter and height 25 mm) having different orientation of their axes relative to the fibers were manufactured from the central board of a birch (Volgn--Vyatskii region). In order that the moisture content of the wood be constant (6--7%), the dried samples were hermetically packaged in a thin (0.02 ram) polyethylene film, in which they were then tested. The initial density of the samples ps varied from 540 to 710 kg/m 3.Dynamic tests of samples (v = 10 m/sec) under uniaxial compression were conducted by the Kol'skii method on a setup with a Hopkinson compound rod [7]. A diagram of the measuring test complex is shown in Fig. 1. A loading pulse of a nearly rectangular shape with an amplitude of 0.2 9 106 N and duration of 200 psec was generated by an explosive loading device, which contains charge 4 of a liquid explosive (LE) with a mass of 0.75 g, a damping system (steel impactor 5 and perforated crusher 6), and massive supporting disk 2. Explosion was localized in protective reinforced chamber 1. Initiation of the LE charge was performed by spark discharger 3 to which a high-voltage pulse from explosive setup 13 was supplied [8].In tests at lower (-30~ and elevated (+650C) temperatures, samples 11 were previously held at the required temperature in thermostat 10. The time of holding the samples in the thermostat was not less than 1 h to equalize the temperature over the volume. The signal from strain gauges 9 was recorded by strain station Institute of Experimental Physics, Sarov 607190.

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