Comparison between Three-point and Four-point Flexural Tests

COMPARISON BETWEEN THREE-POINT AND FOUR-POINT FLEXURAL TESTS 2 TO DETERMINE WOOD STRENGTH OF EUCALYPTUS SPECIMENS 3 Paulo Ricardo Gherardi HEIN*, Loïc BRANCHERIAU 4 *Corresponding author: [email protected] 5 Received: September 21, 2016 6 Accepted: January 24, 2018 7 Posted online: January 25, 2018 8 9 ABSTRACT 10 11 Comparison between flexural wood strength values obtained from three-point and four-point 12 bending tests in wood were only reported in few previous works, but remains unclear. Thus, 13 the aim of this study was to determine the relationship between wood strength (MOR) 14 obtained by 4-point and 3-point bending tests in Eucalyptus. Two or three specimens were cut 15 from the same scantling (thus considered as twin) and submitted to flexural vibration tests. 16 Then 190 wood specimens were tested by 4-point bending tests and 138 twin specimens were 17 submitted to 3-point bending tests. Wood strength determined from 3-point bending test 18 presented significantly higher mean value (76.8 MPa) than that from 4-point bending test 19 (73.0 MPa). A linear regression for converting MOR from 3-point to 4-point bending test was 20 proposed for these Eucalyptus specimens: MOR4p = 0.889 × MOR3p + 5.14 in MPa (R2=0.74). 21 The correlation of MOR in 3-point bending with density was higher (R2=0.57) than in 4-point 22 bending (R2=0.45). The correlations between dynamic elastic moduli and moduli of rupture 23 were similar (circa R2=0.57 for MOR3p and R2=0.65 for MOR4p). 24