Breakage functions of particles of four different materials subjected to uniaxial compression

Particle breakage is a common problem in the conveying and handling of particulate solids. The phenomenon of particle breakage has been studied by experiments by a number of researchers in order to describe the process of breakage by mathematical functions. The development of comminution functions that can suitably describe the breakage behavior of granular materials can lead to a significant improvement in the design and efficiency of particulate solids handling equipment. The present study focuses on developing the strength distribution and the breakage functions of particles of four different materials subjected to uniaxial compressive loading. Single particles were compressed until fracture in order to determine their strength distribution and the fragments were investigated to determine their size distribution. The parameters of logistic function and breakage function were obtained by curve-fitting of the functions to the strength distribution and size distribution of the fragments respectively. These functions were then implemented in the BGU-DEM code which was used to carry out Discrete Element Method (DEM) simulations on single particle breakage by compression. The simulations produced a similar mass distribution of fragments to the breakage function obtained from the experimental data

Can scalable design of wings for flapping wing micro air vehicle be inspired by natural flyers?

Lift production is constantly a great challenge for flapping wing micro air vehicles (MAVs). Designing a workable wing, therefore, plays an essential role. Dimensional analysis is an effective and valuable tool in studying the biomechanics of flyers. In this paper, geometric similarity study is firstly presented. Then, the pw−AR ratio is defined and employed in wing performance estimation before the lumped parameter is induced and utilized in wing design. Comprehensive scaling laws on relation of wing performances for natural flyers are next investigated and developed via statistical analysis before being utilized to examine the wing design. Through geometric similarity study and statistical analysis, the results show that the aspect ratio and lumped parameter are independent on mass, and the lumped parameter is inversely proportional to the aspect ratio. The lumped parameters and aspect ratio of flapping wing MAVs correspond to the range of wing performances of natural flyers. Also, the wing performances of existing flapping wing MAVs are examined and follow the scaling laws. Last, the manufactured wings of the flapping wing MAVs are summarized. Our results will, therefore, provide a simple but powerful guideline for biologists and engineers who study the morphology of natural flyers and design flapping wing MAVs