Dataset for: Notch aspect ratio orders the mode I fracture toughness of granite in four-point bending
Description
This dataset supports a four-point bending (4PB) study on how the notch aspect ratio a0/t controls the mode I fracture toughness K_IC of granite. Twenty-one beams were sawn from a single Sesame White granite plate (L x W x B = 350 x 75 x 50 mm) and tested to failure at a constant saw-kerf width t = 2 mm over eight nominal notch depths a0 = 0, 5, 10, 23, 30, 40, 45 and 55 mm (a0/W = 0-0.73, a0/t = 0-27.5). The dataset contains (i) the reduced per-specimen quantities for all 21 beams, (ii) the group statistics, one-way ANOVA, regression parameters and the Welch t-tests reported in the manuscript, and (iii) the raw synchronous records of every beam: time, load, cross-head displacement and crack-mouth opening. Note on the displacement channel: the displacement recorded in the raw curves is the cross-head displacement of the testing machine and contains roughly 92 % of the load-train compliance and the initial take-up. The work of fracture W_tot and the specific fracture energy G_f derived from it are therefore relative indices, valid for comparing specimens within this batch only; they must not be read as material fracture energies. See README_data.txt for full column definitions and unit conventions. --------------------------------- time_s Time, s load_N Applied load, N crosshead_disp_mm Cross-head displacement, mm (machine + specimen; NOT crack opening) CMOD_mm Clip-gauge opening across the notch mouth, mm surface_strain_ch4 Surface strain gauge channel; not connected for this batch (zeros) Geometry and unit conventions ----------------------------- L x W x B = 350 x 75 x 50 mm, outer span S = 300 mm, loading rollers 100 mm apart, kerf width t = 2 mm constant. Units are mm-N-MPa throughout: stress in N/mm2 = MPa, energy in N*mm = 1e-3 J. Important note on displacement and energy ----------------------------------------- The displacement channel is the cross-head displacement and contains roughly 92 % of the load-train compliance and initial take-up. The work of fracture W_tot and the specific fracture energy G_f derived from it are therefore RELATIVE indices that are valid for comparing specimens within this batch; they must not be interpreted as material fracture energies. Please cite the accompanying manuscript when using these data.
Files
Steps to reproduce
Specimen preparation All specimens were cut from a single Sesame White granite plate. Beam geometry: L x W x B = 350 x 75 x 50 mm, outer support span S = 300 mm, loading rollers 100 mm apart (pure-bending segment L_r = 100 mm). A single saw cut of constant kerf width t = 2 mm was introduced at mid-span to eight nominal depths a0 = 0, 5, 10, 23, 30, 40, 45 and 55 mm, giving 21 beams in total. Testing Tests were run in four-point bending on a SANS SHT4605 servo-hydraulic frame (600 kN capacity, 0.5 % accuracy class) under displacement control at 0.5 mm/min. Each curves/<specimen>.csv holds the raw synchronous record: time_s, load_N, crosshead_disp_mm and CMOD_mm. The surface-strain channel was not connected for this batch and is identically zero. Reduction to K_IC K_IC was computed from the peak load P_max with the four-point bending (pure-bending) stress intensity factor for a single-edge-notched beam: K = F(alpha) * sigma * sqrt(pi * a_e), alpha = a_e / W F(alpha) = sqrt(2*tan(pi*alpha/2)/(pi*alpha)) * (0.923 + 0.199*(1 - sin(pi*alpha/2))^4) / cos(pi*alpha/2) with the bending moment of the four-point bend M = 50 * P (N*mm for P in N), the extreme-fibre stress sigma = 6 * M / (B * W^2) (MPa), and the effective crack length a_e = a0 + 1 mm, i.e. half the kerf width t = 2 mm. Units are mm-N-MPa throughout; K follows in MPa*mm^0.5 and is divided by sqrt(1000) to give MPa*m^0.5. Files - TableS1_per_specimen.csv per-specimen reduced quantities (21 rows) - TableS2_group_statistics.csv n, mean, sd, CV, 95 % CI, min, max - TableS3_ANOVA.csv one-way ANOVA of the main response quantities - TableS4_regression_parameters.csv fitted parameters, standard errors, 95 % CI, R2, RMSE - Table3_Welch_t_tests.csv Welch two-sided t-tests of the notch-depth segments - curves/<specimen>.csv raw records of the 21 beams