DAMPING PROPERTIES OF SEQUOIA AND BIRCH UNDER SHOCK LOADING

To decrease mechanic effect on loads being transponed, shock load limiters (dampers) are being widely used today. Usually, the materials having «stress-strain» diagrams (a-E) of compression with a substantial ponion, where Õ=const, are used as dampers. Most widely used are dampers made of foam polystyrene having just the same compression diagram. Similar strain diagrams can be enlisted for some porous materials, timber under cross compression, perforated metallic crushers and some others. By selecting damper material, the level of transmitted to the protected object pressures can be varied from several to hundreds MPa Timber, as being widely used and featuring good technologic propenies together with low cost, becomes an attractive material to be used as the limiter of shock loads. This paper presents the results of stress - strain sequoia propenies (USA deliverable) and birch propenies (Volgo-Vyatski region) at dynamic (v=IOm/s) and quasistatic (v:: IO ... m/s) loading rates. The samples (0 2Sx2Smm) cut at 0, 5, IO, IS, 30, 45 and 90u angle relative to their fibre were tested on one-axis compression at -30, +20 and +65°C and fixed humidity (ro = 6-7%). Dynamic tests employed Kolsky method performed at the facility including Hopkinson's compound rod (Zukas et ai., I985). Sample loading was executed by trapezoidal pulsed pressure created by the explosive device. Samples were heated and cooled by special thermostates.