Advanced Materials Research Vol. 500

Abstract: The mechanism of micro-milling modeling for aluminum alloy 7050-T745 is to be investigated, and a finite element model for micro-milling that reflects the actual state of the three-dimensional micro-milling is built by adopting the software of ABAQUS/Explicit. Experiment is conducted to verify the validation of the model. Simulated chip morphology in different cutting parameters agrees to the experimental results very well. Based on the FE model, cutting stresses, equivalent plastic strains, temperatures distribution and cutting forces are obtained and analyzed. This provides a good method to investigate the micro milling principles.

Abstract: ntroducing the machining-ability of the surface of hydrogenated cylindrical shells blank, and the analysis showed that one of the main macroscopic factors which caused the tool to be broken early was forging defect. According to researching on both failure mechanisms and rules of the heavy-duty turning tools fracture, the conclusions that the dynamic load led into the crack then made the tool to be broken could be drawn. Then, the finite element simulation was utilized to analyze the tools working state under dynamic load condition, and the simulation results verified the correctness of the conclusion. For improving production efficiency and providing a reference for the prediction of tool breakage, finally, the critical time model of tool breakage under the condition of dynamic cutting was built, and the measures of preventing tools premature failure were developed.

Abstract: Accuracy of cutting simulation model mostly depends on whether its material constitutive equation describes workpiece physical property under cutting state. It is necessary to research on the constitutive properties of cutting material in the high strain state of temperature. In this paper high strength steel GCr15 is used as a research object under the high speed cutting state. By FEM Johnson-cook constitutive model in Hopkinson Experiment is simulated, and the sensitivity of constant on constitutive model is also analyzed. Also influence of temperature on workpiece material stress and strain is revealed. The result provides reference for Johnson-cook model parameters of high strength steel GCr15, and it provides theory basis of material properties analysis in cutting state as well.

Abstract: nconel718 is particle reinforced metal matrix composites widely applied in important fields. To evaluate the impact of particles on the machined subsurface in Inconel718 during high-speed machining operation, a multi-scale orthogonal cutting finite element (FE) model is established. A cohesive element technique is adopted to predict particle crack initiation process. The multi-scale FE model is validated with experimental data in terms of cutting forces and chip morphology. The simulation reveals that particle has a great influence on surface roughness and the feed force when particles are located in the sub-surface within the depths of 30μm, and the cutting process has less effect on the particle crack initiation when the particles in the depths of more than 40μm or deeper. The interaction effects generated from particle sizes in the same depth are investigated on the cutting process and particle crack initiation.

Abstract: A bellows expansion joint of a refinery cracked within a year of use. Analysis was carried out based on the investigation of the working conditions and environments. Through the macroscopic analysis, chemical components analysis, microstructure analysis and SEM analysis, we drew some conclusions. The high-temperature sulfur corrosion led to the failure directly, while the direct reason was the extra load applied on the joint which was caused by the unreasonable support structure. Preventive measures were proposed at last.

Abstract: The paper is devoted to the numerical stability of fractional delay differential equations with non-smooth coefficients using the Chebyshev collocation method. In this paper, based on the Grunwald-Letnikov fractional derivatives, we discuss the approximation of fractional differentiation by the Chebyshev polynomial of the first kind. Then we solve the stability of the fractional delay differential equations. Finally, the stability of the delayed Mathieu equation of fractional order is examined for a set of case studies that contain the complexities of periodic coefficients, delays and discontinuities.

Abstract: The paper deals with the numerical stability analysis of fractional delay differential equations with non-smooth coefficients using the Lagrange collocation method. In this paper, based on the Grunwald-Letnikov fractional derivatives, we discuss the approximation of fractional differentiation by the Lagrange polynomial. Then we study the numerical stability of the fractional delay differential equations. Finally, the stability of the delayed Mathieu equation of fractional order is studied and examined by Lagrange collocation method.

Abstract: Currently, deep brain stimulation (DBS) is one of the most effective surgical treatments of treating serious stubborn resistance movement disorders (such as Parkinson's disease, essential tremor and dystonia, etc.). The nerve probe has been greatly favored by the authorities and scientists with the respect to the role it acted as the main brain stimulation tool. This article mainly introduces the materials of brain stimulated micro-electrode, the matched specifications and the evaluation on the compound functions in the developing course. The application prosperity and its development trendy will also be included with the intention to help people gain more systematic acknowledgement on the electrodes for deep brain stimulation.

Abstract: The large flywheel energy storage system requires very high radial tensile strength of the flywheel rim, for the sake of the ultimate strength requirement, multilayer flywheel rim structure of carbon fiber/glass fiber hybrid composite is employed in the paper. Both stress calculation and FEM analysis show that rational densign of the layer thickness and the hybrid ratio of carbon fiber to glass fiber can reduce radial strength requirement of rim material, especially for large flywheel energy storage system.

Abstract: Geometry constraint and physical constraint change because the structure is complex, tonnage is large, and assembly load is complex on heavy duty machine tool, assembly relation is changed for repeated assembly, then, the assembly accuracy reproducibility and assembly accuracy retentivity decline, which results in the decrease of assembly reliability. According to this problem, the interaction of geometry constraint and physical constraint is discussed in this paper, the influence factors of assembly accuracy reproducibility and assembly accuracy retentivity are respectively analyzed, the establishing, demolition and re-establishing of assembly relation effects assembly accuracy reproducibility, and evolution of assembly relation with time effects assembly accuracy retentivity, which are respectively revealed. Using margin method to evaluate assembly accuracy reliability, the criterion and evaluation method of assembly accuracy reliability is proposed, in order to provide reliable and quantitative criterion for assembly process design, and reasonably set safety margin of geometry constraint and physical constraint, form reliable assembly process, realize that the assembly accuracy is controlled and improved by assembly.