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Experimental research on the critical conditions and critical equation of chip splitting when turning a C45E4 disc workpiece symmetrically with a high-speed steel double-edged turning tool

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Advances in Manufacturing 2022年第2期10卷 159-174页

作者： Ming-Xian Xu Liang-Shan Xiong Bao-Yi Zhu Ling-Feng Zheng Kai Yin School of Mechanical Science and Engineering Huazhong University of Science and TechnologyWuhan 430074People's Republic of China

Chip splitting is a natural chip separation phenomenon that can significantly reduce cutting energy *** reveal its occurrence mechanisms,a method for obtaining its critical conditions through cutting experiments and establishing its critical equation is proposed in this *** on previous research results regarding the relationship between chip removal interference and chip splitting,the control variables that affect chip splitting are identified by analyzing a geometric model of the cutting process.A total of 366 experiments on turning a C45E4 disc workpiece with a high-speed steel double-edged turning tool based on the dichotomy method were conducted and 51 experimental data on chip splitting critical conditions were *** these experimental data,a critical equation expressed by a finitedegree polynomial with a cutting thickness equal to the other control variables was *** analyzing the critical surface,it was determined that chip splitting followed a law in which the smaller the cutting thickness and the larger the absolute value of the negative rake angle,edge angle,and edge inclination of the tool,the more likely chip splitting was to *** a verification experiment,it was determined that the derived critical equation could accurately predict the occurrence of 95.24%of chip *** was also determined that the occurrence of chip splitting led to a cliff-like drop in the specific total cutting force with a maximum drop of 51.23%.This research lays a foundation for the rational utilization of chip splitting in tool structure parameter design and cutting parameter energy saving optimization.

关键词： Chip splitting critical conditions critical equation Cutting force Experimental research Doubleedged turning tool symmetrical transverse cutting

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critical firing conditions for titanium alloys by molten droplet ignition

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Corrosion Communications 2023年第3期11卷 33-43页

作者： Lin Chen Yu Dong Yun-Qi Tong Mei-Jun Liu Guan-Jun Yang State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and Engineering Xi'an Jiaotong University

Reliable service of indispensable titanium alloys in aeroengines is limited by titanium fire with unclear critical *** this study,critical conditions in the form of parameter phase diagrams for secondary burning were determined by molten droplet *** element analysis（FEA） reveals that the molten droplet size（R0）,relative oxygen content（Pr）,and initial temperature（T0） significantly affect titanium fire following power exponential *** addition,Prand T0affect ablation synergically,and a unified empirical relationship for critical ablation of titanium alloy is ***,the critical T0of a typical TC4 alloy under 20%Pris higher than 973 K,which explains the reliable service performance of TC4 alloy at ≤ 873 K in compressors in commerical air *** addition,the critical empirical conditions are consistent with the FEA results,and the deviation occurs due to oxidation at T0≥ 673 ***,the ablated TC4 alloy can be divided into five characteristic zones,and loose and porous oxide scales are formed at the front of the titanium *** present study points the way towards long-lifetime services of TC4 alloys through sound titanium fire protection strategies.

关键词： Titanium fire Ablation Molten droplet ignition critical conditions Scaling law

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Thermal explosion of a reactive gas mixture at constant pressure for non-uniform and uniform temperature systems

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Defence Technology（防务技术） 2022年第10期18卷 1842-1851页

作者： Saad A.El-Sayed Mechanical Power Engineering Dept.Zagazig University ZagazigAlshrkiaEgypt

In this study,the approximate and exact solutions for the stationary-state of the solids model with neglecting reactant consumption for both non-uniform and uniform temperature systems were applied on gas ignition under a constant pressure *** criticality conditions for a slab,an infinite cylinder,and a sphere are determined and discussed using dimensionless temperatures under constant ambient and surface temperatures for a non-uniform temperature *** solution for a Semenov model with convection heat loss was also *** solution of the Semenov problem for constant volume or density as a solid and constant pressure were *** critical parameterδis calculated and compared with those of Frank-Kamenetskii solution *** validation of the calculated ignition temperatures with other exact solution and experimental results were *** relation between critical parameters form Semenov and *** solution was introduced.

关键词： Thermal explosion Approximate solution critical conditions Distributed and uniform temperature systems

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Mechanism of brittle-ductile transition of a glass-ceramic rigid substrate

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International Journal of Minerals,Metallurgy and Materials 2011年第2期18卷 229-233页

作者： Yu-li Sun Dun-wen Zuo Hong-yu Wang Yong-wei Zhu Jun Li Jiangsu Key Laboratory of Precision and Micro-manufacturing Technology College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

The hardness, elastic modulus, and scratch resistance of a glass-ceramic rigid substrate were measured by nanoindentation and nanoscratch, and the fracture toughness was measured by indentation using a Vickers indenter. The results show that the hardness and elastic modulus at a peak indentation depth of 200 nm are 9.04 and 94.70 GPa, respectively. These values reflect the properties of the glass-ceramic rigid substrate. The fracture toughness value of the glass-ceramic rigid substrate is 2.63 MPa？m1/2. The material removal mechanisms are seen to be directly related to normal force on the tip. The critical load and scratch depth estimated from the scratch depth profile after scratching and the friction profile are 268.60 mN and 335.10 nm, respectively. If the load and scratch depth are under the critical values, the glass-ceramic rigid substrate will undergo plastic flow rather than fracture. The formula of critical depth of cut described by Bifnao et al. is modified based on the difference of critical scratch depth

关键词： brittle-ductile transition critical conditions glass ceramics nanoindentation nanoscratch

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Mechanism of Downcutting Erosion of Debris Flow over a Movable Bed

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Journal of Mountain Science 2015年第1期12卷 243-250页

作者： Pan Hua-li Huang Jiang-cheng Ou Guo-qiang Key Laboratory of Mountain Hazards and Earth Surface Process Institute of Mountain Hazards and Environment CAS Asian International Rivers Center Yunnan University

The phenomenon of debris flow is intermediate between mass movement and solid transport. Flows can be sudden, severe and destructive. Understanding debris flow erosion processes is the key to providing geomorphic explanations, but progress has been limited because the physical-mechanical properties, movement laws and erosion characteristics are different from those of sediment-laden flow. Using infinite slope theory, this research examines the process and mechanism of downcutting erosion over a moveable bed in a viscous debris flow gully. It focuses specifically on the scour depth and the critical slope for viscous debris flow,and formulas for both calculations are *** scour depth and the critical conditions of downcutting erosion are related to debris flow properties(sand volume concentration and flow depth) and gully properties(longitudinal slope,viscous and internal friction angle of gully materials,and coefficient of kinetic friction). In addition, a series of flume experiments was carried out to characterize the scouring process of debris flows with different properties. The calculated values agreed well with the experimental data. These theoretical formulas are reasonable, and using infinite slope theory to analyze down cutting erosion from viscous debris flow is feasible.

关键词： Debris flow Down cutting erosion Infinite slope theory critical conditions Flumeexperiments

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Factors driving riverbed scouring and sedimentation in the Bayangaole to Toudaoguai reaches of the Upper Yellow River

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Journal of Geographical Sciences 2016年第9期26卷 1305-1320页

作者： HOU Suzhen WANG Ping GUO Yan HU Tian Yellow River Institute of Hydraulic Research Yellow River Conservancy Commission Zhengzhou 450003 China Key Laboratory of Yellow River Sediment Research Ministry of Water Resources Zhengzhou 450003 China

The Inner Mongolia reaches of the Yellow River face problems of severe sedimen- tation caused by a variety of complex factors. The sedimentation process in those reaches has been characterized using the sediment balance method, and the key factors affecting the process have been analyzed using the correlation analysis method. The results show that during the period 1952-2012 the Bayangaole （Bayan Gol） to Toudaoguai reaches in Inner Mongolia have undergone successive processes of accumulative sedimentation, then relative balance, and then accumulative sedimentation once again. The total annual sedimentation is 12.0341×108 m^3, of which accumulations from July to October account for 95.1% and the reaches from Sanhuhekou to Toudaoguai account for 98.5%. The main factor affecting scouring and sedimentation of the Bayangaole to Sanhuhekou reaches is the combined water and sediment condition. The critical conditions for equilibrium are an incoming sediment co- efficient 〈 0.007 kg·s·m^-6 and a flow discharge 〉 700 m^3·s^-1. The main factor affecting scouring and sedimentation of the Sanhuhekou to Toudaoguai reaches is the incoming sediment from the tributaries on the south bank and the combined water and sediment condition of the main stream. The critical conditions of the main stream for maintaining equilibrium status are a flow discharge of the main stream exceeding 800 m^3·s^-1 and a comprehensive incoming sediment coefficient 〈 0.005 kg^-3·m^-6. The incoming sediment from the tributaries has little impact on the main stream when the annual sediment load is less than 0.1 ×10^8 t. The incoming sediment coefficient of the main stream and the incoming sediment from the tributaries both play vital roles in the riverbed evolution of the Inner Mongolia reaches, but the latter contributes the most.

关键词： Inner Mongolia Yellow River riverbed evolution sedimentation quantity incoming sediment coefficient critical conditions

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