ANALYSIS OF TEST EQUIPMENT FOR INVESTIGATION OF MATERIALS UNDER A STRONG LOAD APPLICATION

Abstract

An analysis of publications on this topic. It is established that in most literature sources the work of wood is shown only in the ascending branch of deformation, which is a false statement. The method of experimental studies of alder and spruce wood by axial compression along the fibers with a short-term load at standard humidity (by increasing displacements) is presented. The age of the wood was about 40 years. Experimental studies of such samples were performed on a modern STM- 100 test machine. 18 samples with a cross section of 30x30x120 mm were tested. Based on the experiment, complete deformation diagrams “stress σc - strain uc” were constructed and the main parameters were established: critical and residual strains, as well as their corresponding stresses. It is established that both diagrams have an ascending and descending branch, ie they work in both pre-critical and super-critical stages of work.
 The average critical deformations of alder wood uc,0,d = 0,00397, as well as the corresponding maximum stresses fc,0,d = 35,6 MPa, and spruce wood - uc,0,d = 0,00421 (fc,0,d = 38.1 MPa).
 Also, the average residual deformations for alder wood uc,fin = 0.277, and the corresponding stresses σc,fin = 3.9 MPa; for spruce wood uc,fin = 0.212, and stress - σc,fin = 3.6 MPa. 
 It is confirmed that deciduous and coniferous wood at standard humidity has an ascending and descending branch, ie works in the subcritical and supercritical stages of work.
 In the future it is necessary to conduct such experimental studies for other deciduous and coniferous species. In the future, determined mechanical characteristics experimentally, it is necessary to propose methods for finding and theoretical, which will give a complete picture of such materials.