Statistical Characterization of Dry Aggregate Strength Using Rupture Energy

Abstract

AbstractDry aggregate strength, s, is important in tillage studies. Weibull's brittle fracture model is a widely accepted statistical approach for analyzing variability in s. Tensile strength, T, is commonly used as the measure of s in Weibull's model. However, compression and shear also occur during tillage. Use of specific rupture energy, E, involves no assumptions regarding the mode of failure. Furthermore, E can be related to tillage draft energy. Information is lacking on the statistical characterization of s using E. Our objective was to compare the performance of E and T as measures of s in Weibull's model. We determined E and T simultaneously for 1400 air‐dry aggregates from five size classes and seven cropping‐tillage treatments on a loam soil. Weibull's model fit equally well using either T or E. Model parameters estimated using T (αT and βT) were significantly correlated with those estimated using E (αE and βE). A log‐log relationship was established between αE and αT, with an intercept of −5.01 and a slope of 1.16. The β values were related by the equation: βE = 0.69βT, indicating less variation in s as measured by T than as measured by E. The α parameter was more sensitive to size and cropping‐tillage effects than the β parameter. The αE resulted in a better discrimination between size classes and cropping‐tillage treatments than did the αT. The αE decreased with increasing aggregate size and decreasing tillage intensity. The use of E in Weibull's model is recommended for the statistical characterization of s in tillage studies.