Spatial Constitutive Modeling of AA7050-T7451 with Anisotropic Stress Transformation.

The mechanical properties of anisotropic materials are generally characterized based on the orthotropy or transverse isotropy. However, the two-dimensional plane stress problems cannot comprehensively characterize the anisotropy of materials. In this study, based on the theory of elasticity and the transformation of the three-dimensional space coordinate system, combined with the projection relationship of the Cauchy stress tensor of an arbitrary section, the transformation relationship of the elastic modulus, shear modulus, and stress-strain between the orthogonal and load coordinate systems are obtained. The orthotropic Johnson-Cook (JC) constitutive model of AA7050-T7451 aluminum alloy is modified by fitting, and the constitutive relationship at any spatial angle is theoretically calculated by combining the obtained spatial coordinate transformation matrix. The generated spatial constitutive model is verified and modified through experiments. The results demonstrate that the theoretical mechanical properties and the modified spatial constitutive model can accurately reflect the effect of the spatial angle on the material stress distribution.

Study on the Material Removal Mechanism of Ultrasonic Elliptical Vibration Cutting of Medical ß Titanium Alloy.

For new medical ß titanium implants, the surface micro texture processing technology is a difficult problem. To solve this problem, a new method of ultrasonic elliptical vibration cutting (UEVC) is adopted in this paper. The mechanism of material removal in ultrasonic elliptical vibration cutting is explored for different cutting paths. By means of simulation and experimentation, the material removal mechanism of ultrasonic elliptical vibration cutting medical ß titanium alloy is revealed with respect to the aspects of cutting deformation, stress distribution, force and thermal variation, and chip formation mechanism. The results show that: (1) The cutting temperature and cutting force in the UEVC process obey the law of periodic change, and the maximum point of cutting force appears ahead of the maximum point of cutting temperature. (2) The material removal process of UEVC is a "press-shear-pull" composite cutting process. The tool squeezes the material to form the chips. Under the action of high temperature, the material is removed by adiabatic shear. (3) The difference of UEVC paths will affect the removal mode of materials and form different surface morphology. (4) For different cutting paths, compressive stress is distributed at the lowest point of the machining pit, and tensile stress is distributed at the protrusion position.

Analysis of gas-solid two-phase flow and structure optimization of mobile shot blasting machine recovery device.

To address the problem of low efficiency of recycling process waste by gas-solid two-phase flow of the shot blasting machine recycling device, a method and structure by increasing the negative pressure value and optimizing the outlet pipe position are proposed. Computational fluid dynamics (CFD), discrete element method (DEM) and discrete phase model (DPM) were used to study the waste recovery efficiency at different pressure outlet conditions and outlet pipe locations. The validity of the model was verified by velocity tests at the outlet and inlet compared with simulations. The effect of particle size and particle generation rate on solid particle recovery efficiency was further investigated by analyzing the flow field distribution of the recovery unit. The results show that the maximum velocity of the gas phase in the recovery device increases with the increase of the absolute value of the outlet pressure, when the outlet pressure is -6500 Pa, the maximum velocity is 67.59 m/s. When the absolute value of the outlet pressure is greater than 6000 Pa, a small amount of steel shot particles is discharged from the recovery bin under the action of the outlet pressure, resulting in the loss of steel shot particles. After the outlet pipe position optimization, the steel shot particle recovery efficiency increased by 10% and the waste particle recovery efficiency increased by 18.9%.

Complete mitochondrial genome of the guava fruit fly, Bactrocera correcta (Diptera: Tephritidae).

Bactrocera correcta (Diptera: Tephritidae) is one of the most serious pest insects in south China and surrounding Southeast Asian countries. The family Tephritidae includes over 4257 species distributed worldwide, so the complete mitochondrial genome would be helpful for bio-identification, biogeography and phylogeny. The B. correcta genome consists of 15 936 bp. Annotation indicated that the structure and orientation of 13 protein-coding genes (PCGs), 22 tRNA and 2 rRNA sequences were typical of, and similar to, the ten closely related tephritid species. The nucleotide composition shows heavily biased toward As and Ts accounting 73.2% and exhibits a slightly positive AT skew, which is similar to other known tephritid species and other insects. The phylogenetic tree indicated the presence of three distinct families (Tephritidae, Muscidae, Drosophilidae) in Order Diptera.

The complete mitochondrial genome of the melon fly Bactrocera cucurbitae (Diptera: Tephritidae).

The mitochondrial genome of Bactrocera cucurbitae, a representative of the Tephritid family, was completely sequenced for the first time. The B. cucurbitae genome is a double-stranded circular molecule of 15,825 bp long, including the entire set of the 37 genes. The 72.9% A+T content and 0.047 AT-skew are within the range of the known dipteran genomes. Comparative analyses showed that dipteran mitochondrial protein-coding genes present complex evolutionary patterns. Some of the codon families were strongly biased towards J-strand. The mitochondrial ATP8 of B. cucurbitae exhibited a faster substitution rate than other genes. Cox1 is the slowest evolving protein and could be considered as a potential phylogenetic marker.