斜角切削过程的三维热—弹塑性有限元分析

基于大变形理论和虚功原理,建立了斜角切削加工过程的三维热-弹塑性有限元模型。分析和研究了涉及切削加工有限元模拟的关键技术。采用通用有限元求解器ABAQUS/Explicit对斜角切削过程进行了有限元模拟,分析了切削过程中切屑的形成过程及其形貌、三维切削力的变化情况,以及应力、应变、切削温度和已加工表面残余应力的分布规律。通过与试验数据的比较,证明了所建立有限元模型的正确性。斜角切削过程的三维热—弹塑性有限元模拟研究为铝合金高速切削加工的工艺参数优化、刀具几何参数的合理选择提供了参考。

基于弹塑性理论的高速铣削表面粗糙度力学建模

基于分子—机械摩擦理论,提出了已加工表面残留高度的力学模型。并根据热—弹塑性大变形理论,对材料的流动应力方程(非线性)进行了分析,推导出了材料的应变硬化、应变率和温度与切削变形应力增量的关系,研究了不同材料(45钢和3Cr2Mo模具钢)已加工表面残留高度的实验结果,分析了材料物理性能对加工表面粗糙度的影响。

Fabrication of flatten grooved-sintered wick heat pipe

With the rapid rising of heat flux and reduction of heat dissipating space of microelectronic devises, flattened sintered heat pipe has become an ideal conducting element of use in the electronic cooling field. A manufacturing technology named phase change flattening process is presented to fabricate the flattened grooved-sintered wick heat pipe （GSHP for short）. Deformation geometry of flattened GSHP and the elasto-plastic deformation of flattening process are analyzed theoretically and verified by experiments. The results show that the vapor pressure inside sintered heat pipe during flattening process is determined by the saturated vapor pressure equation; the width and vapor area of flattened heat pipe change greatly as the flattening proceeds; the maximum equivalent strain distributes at the interface between wick and vapor in the fiat section; the buckling phenomenon can be well eliminated when the flattening temperature reaches 480 K; phase change flattening punch load increases with flattening temperature and displacement.

Pyrolysis-Gas Chromatography/Mass Spectrometry for Microstructure and Pyrolysis Pathway of Polyester-Polyether Multiblock Copolymer

The composition and sequence distribution of monomeric units in polyester polyether multiblock copolymer were studied by pyrolysis? gas chromatography (PGC) and pyrolysis gas chromatography/mass spectrometry (PGC/MS). PGC was applied to study the F t curve of the multiblock copolymer and PGC/MS was used to separate and identify the pyrolyzates. DTA experiment was used to study the decomposition temperature. The results show that the beginning point of elastomer’s decomposition was about 300?℃ and the decomposition temperature of most of the sample was 550?℃. Many pyrolyzates were produced because of the breaking of weak bonds in the sample. The possible microstructure was verified and the pyrolysis pathway of the copolymer was investigated.

Stress distribution and its influencing factors of bottom-hole rock in underbalanced drilling

The underbalanced drilling has been widely used due to its advantages of high drilling efficiency and low cost etc., especially for hard formation drilling. These advantages, however, are closely related to the stress state of the bottom-hole rock; therefore, it is significant to research the stress distribution of bottom-hole rock for the correct understanding of the mechanism of rock fragmentation and high penetration rate. The stress condition of bottom-hole rock is very complicated while under the co-action of overburden pressure, horizontal in-situ stresses, drilling mud pressure, pore pressure and temperature etc. In this paper, the fully coupled simulation model is established and the effects of overburden pressure, horizontal in-situ stresses, drilling mud pressure, pore pressure and temperature on stress distribution of bottom-hole rock are studied. The research shows that： in air drilling, as the well depth increases, the more easily the bottom-hole rock is broken; the mud pressure has a great effect on the bottom hole rock. The bigger the mud pressure is, the more difficult to break the bottom-hole rock; the max principle stress of the bottom-hole increased with the increasing of mud pressure, well depth and temperature difference. The bottom-hole rock can be divided into 3 regions respectively according to the stress state, 3 direction stretch zone, 2 direction compression area and 3 direction compression zone; the corresponding fragmentation degree of difficulty is easily, normally and hardly.

Fractal model of thermal elasto-plastic contact of rough surfaces

Without considering the influence of heat,existing fractal contact models are not applicable to analyze the contacts when the temperature changes.For this problem,the normal load model and the normal stiffness model of thermal elasto-plastic contact of rough surfaces are developed respectively in this paper.The proposed model is based on the normal contact mechanics model of fractal theory of anisotropic and thermal elasto-plastic contact theory which can be used to characterize the rough surface thermodynamic properties.Then the validity of the model is verified.Finally,the influence of main parameters on the total normal load and the whole normal stiffness of thermal elasto-plastic contact at the interface is analyzed by contact simulation.The results show that the total normal load of thermal elasto-plastic contact increases with the increases of temperature.The whole normal stiffness of thermal elasto-plastic contact increases with increasing coefficient of linear expansion,scale factor,temperature difference or fractal dimension,but decreases with increasing fractal roughness.This model expands basic theory and applications of traditional models,and can be used to calculate and analyze the contacts when the temperature changes.

Thermoelastoplastic Deformation Analysis of Electromechanical Equipments under Electrocaloric Shock

A coupled thermomechanical model is presented to investigate the thermoelastoplastic deformation mechanism of electromechanical equipments under the condition of electrocaloric shock. In the coupling model, differentiating from the previous analyzing viewpoint that looked upon deformation work as additional heat source, temperature-field equation is established by considering the weakening role of deformation work on the intensity of internal heat source; in the process of setting up displacement-field equation, G-derivative of nonlinear functional is introduced into the traditional theory of elastoplastic finite deformation to simplify the expression of structural stiffness; stress-field equation is constructed by using the least square method to improve the stress solution obtained by constitutive equation. The presented model is converted into finite element program to simulate deforming process of 3-D structures with temperature-dependent material properties. As an example, thermal deformation analysis of Shanghai metro cars’ brake resistor is performed and compared with experimental results for illustrating the validity of the presented model.

Numerical Simulation of New Friction Welded Joints

In developing the new friction welding technology, the thermal elastic-plastic stress analysis by the finite element method was carried out to seek the suitable welding conditions such as the friction pressure, the friction speed and the upset pressure. The results obtained are as follows： Heat transfer to the specimens and the intermediate material during friction process was made clear; The operational conditions such as the rotation number of the intermediate material and the friction pressure to reach the liquidus in the interface could be estimated; Further, as the overhang length near the interface is well related to the joint efficiency, we tried to obtain the operational conditions by numerical analysis to acquire a certain length of the overhang length near the interface.

Henriksen and Flora （1999） Revisited A Literature Review on Third-Person Effects and Children/Adolescents＊

In this literature review on TPE （third-person effects） and the behavioral consequences on children, the research questions posed are how the body of knowledge has evolved since the first empirical evidence of TPE among children and what knowledge gaps that remain. The traceable developments are two： （1） Compared to the vast amount of articles on TPE in general, the 5 9 identified on the topic of children are few and two thirds actually focus on adolescents/young adults rather than children. The reason put forward for studying younger children is the urge to prevent risky behavior through media literacy programs or pro-social advertisements; and （2） The studies have not primarily addressed results to support occurrence of TPE among children. Rather they support parental TPE or among the adolescents that TPE and reverse TPE occur due to certain kind of media content. The discussion on knowledge gaps that remain follow three themes： （1） Differentiations between self and others are in psychological studies implied to occur among children between the ages of 3-4 years old, yet no study address how children develop TPE; （2） There is a tendency to follow the more general development within TPE research with the renewed interest in behavioral consequences. But the primary behavioral consequence studied in TPE in general and within studies of TPE and children is support for censorship. Few studies address ＂real＂ behavioral consequences like parental mediation; and （3） There is also a need for more theoretically coherent research on the importance of social distance.

Preparation of Thermoplastic Elastomer from Polypropylene-SIR 10 Rubber Blends with Addition of Dicumil Peroxide as Initiator and Divinylbenzene as a Crosslinker

Preparation of thermoplastic elastomer of Polypropylene-SIR 10 rubber blends with addition of DCP （dicumil peroxide） as initiator and DVB （divinylbenzene） as a crosslinker has been done. Blends of Polypropylene-SIR 10 rubber with variation of weight 60/40 （w/w）, 50/50 （w/w） and 40/60 （w/w） with variation concentration of DCP and DVB 1 phr, 2 phr and 3 phr were mixed into internal mixer at temperature 180 ℃. Then, the blends were pressed at 185 ℃ and specimen were molded according to the ASTM D638. The characterization were carried out based on tensile strength testing, crosslink percentage, morphology surface analysis with SEM and fungtional group analysis with FTIR （Fourier Transform Infra Red）. The result showed that the blends of Polypropilene-SIR 10 rubber 60/40 （w/w） with 2 phr DCP and 1 phr DVB posses a higher tensile strength with value 1.37 Kgf/mm2 and value of elongation at break 17.58%, and value of percentage crosslink 82.4%. The result of morphology test with SEM showed that the blend was well homogenous. Spectra analysis with FT-IR has shown physical interaction among components of the blends.

An AIEgens and exonuclease Ⅲ aided quadratic amplification assay for detecting and cellular imaging of telomerase activity

Monitoring telomerase activity with high sensitive and reliable is of great importance to cancer analysis. In this paper, we report a sensitive and facile method to detect telomerase activity using AIEgens mod- ified probe （TPE-Py-DNA） as a fluorescence reporter and exonuclease llI （Exo lIl） as a signal amplifier. With the aid of telomerase, repeat units （TrAGGG）n are extended from the end of template substrate oligonucleotides （TS primer） that form duplex DNAs with TPE-Py-DNA. Then, Exo llI catalyzes the diges- tion of duplex DNAs, liberating elongation product and releasing hydrophobic TPE-Py. The released hydrophobic TPE-Py aggregate together and produce a telomerase-activity-related fluorescence signal. The liberated product hybridizes with another TPE-Py-DNA probe, starting the second cycle. Finally, we obtain the target-to-signal amplification ratio of 1 ：N2. This strategy exhibits good performance for detecting clinical urine samples （distinguishing 15 cancer patients＇ samples from 8 healthy ones） and checking intracellular telomerase activity （differentiating cell lines including HeLa, MDA-MB-231, MCF-7, A375, HLF and MRC-5 from the cells pretreated with telomerase-related drug）, which shows its potential in clinical diagnosis as well as therapeutic monitoring of cancer.

Aggregation-enhanced emission and efficient electroluminescence of conjugated polymers containing tetraphenylethene units

Tetraphenylethene (TPE) is a popular luminogen characterized by aggregation-induced emission and has been widely used to construct solid-state emissive materials. In this work, two thermally stable polymers (P1 and P2) consisting of TPE conjugated to the 2,7-positions of fluorene and carbazole, respectively, are synthesized and characterized. Both polymers are weakly fluorescent in solutions but show greatly enhanced emission as the aggregate formation, presenting an aggregation-enhanced emission feature. Two kinds of polymer light-emitting diodes are fabricated utilizing P1 and P2 as emitters (EML) (device I: ITO/PEDOT:PSS (45 nm)/PVK:EML (1:1 wt%, 55 nm)/TPBI (38 nm)/Ca:Ag; device II: ITO/PEDOT:PSS (45 nm)/ PVK:OXD-7:EML (3:1:3 wt%, 55 nm)/TPBI (38 nm)/Ca:Ag). The device II of P2 shows the best performances, affording a maximum luminance of 6500 cd/m 2 and a high peak efficiency of 2.11 cd/A.

One-step preparation of branched PEG functionalized AIE-active luminescent polymeric nanoprobes

The synthesis of amphiphilic aggregation-induced emission （ALE） dyes based organic nanoparticles has recently attracted in- creasing attention in the biomedical fields. These AlE dyes based nanoparticles could effectively overcome the aggregation caused quenching effect of conventional organic dyes, making them promising candidates for fabrication of ultrabright organic luminescent nanomaterials. In this work, AIE-active luminescent polymeric nanoparticles （4-NH2-PEG-TPE-E LPNs） were facilely fabricated through Michael addition reaction between tetraphenylethene acrylate （TPE-E） and 4-arm-poly（ethylene glycol）-amine （4-NH2-PEG） in rather mild ambient. The 4-NH2-PEG can not only endow these AlE-active LPNs good water dispersibility, but also provide functional groups for further conjugation reaction. The size, morphology and luminescent prop- erties of 4-NH2-PEG-TPE-E LPNs were characterized by a series of techniques in detail. Results suggested that these AlE-active LPNs showed spherical morphology with diameter about 100-200 nm. The obtained 4-NH2-PEG-TPE-E LPNs display high water dispersibility and strong fluorescence intensity because of their self assembly and AlE properties of TPE-E. Biological evaluation results demonstrated that 4-NH2-PEG-TPE-E LPNs showed negative toxicity toward cancer cells and good fluorescent imaging performance. All of these features make 4-NHz-PEG-TPE-E LPNs promising candidates for biolog- ical imaging and therapeutic applications.

Construction of deep-blue AIE luminogens with TPE and oxadiazole units

In this paper, two AIE-active luminogens (Oxa-pTPE and Oxa-mTPE) constructed from tetraphenylethene and oxadiazole units were successfully synthesized and their thermal, optical and electronic properties were investigated. By linking TPE to the oxadiazole core through meta-or para-position, the intramolecular conjugation is effectively controlled. Thanks to the intelligent molecular design and specific AIE feature, when fabricated as emissive layers in non-doped OLEDs, they exhibit blue or deep-blue emission with CIE coordinates of (0.17, 0.23) and (0.15, 0.12), and good efficiencies with ηC, max and ηP, max up to 1.52 cd A-1 and 0.84 Im W-1 , shedding some light on the construction of deep-blue AIE fluorophores.