Crack Roughness in the 2D Random Threshold Beam Model

We study the scaling of two-dimensional crack roughness using large scale beam lattice systems. Our results indicate that the crack roughness obtained using beam lattice systems does not exhibit anomalous scaling in sharp contrast to the simulation results obtained using scalar fuse lattices. The local and global roughness exponents ($\zeta_{loc}$ and $\zeta$, respectively) are equal to each other, and the two-dimensional crack roughness exponent is estimated to be $\zeta_{loc} = \zeta = 0.64 \pm 0.02$. Removal of overhangs (jumps) in the crack profiles eliminates even the minute differences between the local and global roughness exponents. Furthermore, removing these jumps in the crack profile completely eliminates the multiscaling observed in other studies. We find that the probability density distribution $p(\Delta h(\ell))$ of the height differences $\Delta h(\ell) = [h(x+\ell) - h(x)]$ of the crack profile obtained after removing the jumps in the profiles follows a Gaussian distribution even for small window sizes ($\ell$).Comment: 8 pages, 6 figure

Analytical, experimental and numerical study of a graded honeycomb structure under in-plane impact load with low velocity

Given the significance of energy absorption in various industries, light shock absorbers such as honeycomb structure under in-plane and out-of-plane loads have been in the core of attention. The purpose of this research is the analyses of graded honeycomb structure (GHS) behaviour under in-plane impact loading and its optimisation. Primarily, analytical equations for plateau stress and specific energy are represented, taking power hardening model (PHM) and elastic–perfectly plastic model (EPPM) into consideration. For the validation and comparison of acquired analytical equations, the energy absorption of a GHS made of five different aluminium grades is simulated in ABAQUS/CAE. In order to validate the numerical simulation method in ABAQUS, an experimental test has been conducted as the falling a weight with low velocity on a GHS. Numerical results retain an acceptable accordance with experimental ones with a 5.4% occurred error of reaction force. For a structure with a specific kinetic energy, the stress–strain diagram is achieved and compared with the analytical equations obtained. The maximum difference between the numerical and analytical plateau stresses for PHM is 10.58%. However, this value has been measured to be 38.78% for EPPM. In addition, the numerical value of absorbed energy is compared to that of analytical method for two material models. The maximum difference between the numerical and analytical absorbed energies for PHM model is 6.4%, while it retains the value of 48.08% for EPPM. Based on the conducted comparisons, the numerical and analytical results based on PHM are more congruent than EPPM results. Applying sequential quadratic programming method and genetic algorithm, the ratio of structure mass to the absorbed energy is minimised. According to the optimisation results, the structure capacity of absorbing energy increases by 18% compared to the primary model

Aerostructural Optimization of Nonplanar Lifting Surfaces

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83557/1/AIAA-44727-830.pd

Chemotypes and geographic distribution of the Fusarium graminearum species complex

The Fusarium graminearum species complex (FGSC) consists of phylogenetically distinct pathogenic species. Isolates from various regions display genetic variety worldwide. Three type B trichothecene chemotypes have been identified within the FGSC: nivalenol, 3-deoxynivalenol and 15-deoxynivalenol. The variations in morphological, genetic and virulence traits of FGSC fungi can be attributed mainly to their geographic boundaries. The geographic range of host plants, type of farming system and weather conditions also influence the prevalence of FGSC taxa. The geographic distribution of FGSC members may reflect not only their chemotype but also adaptive traits. While 15-acetyl-deoxynivalenol (15-ADON) chemotype is prevalent in most of Europe, the 3-acetyl-deoxynivalenol (3-ADON) chemotype has achieved greater prevalence in parts of North America. The Asian species F. asiaticum has spread into new territories. Isolates of F. asiaticum have been identified in North America and Europe, and the species has recently been reported to be infecting cereal crops in South America. The occurrence of numerous members of the FGSC in those regions and the introduction of F. asiaticum into new areas raise significant food safety concerns and indicate the need for monitoring mycotoxin concentrations in harvested grain