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A method of forced angular displacement loading based on ABAQUS software is proposed. In order to improve the efficiency of pretreatment, the type of model elements is selected as C3 D8 R and C3 D10 M suitable for contact analysis according to the structural characteristics of the threaded joints. In this method, the mechanical constraint is treated by balanced penalty function. The boundary conditions are established at the bolt head according to the way of obtaining the pretightening force in engineering. The pretightening force is defined by imposing a forced angular displacement on the rigid element. This method is simpler and more practical than other methods. Finally, the relationship between pretightening force and torsion is obtained by analyzing the thread connection structure of skirt plate lock with this method. The error between the results and the experimental results is within 8%, which is within the range of theoretical calculation. The validity of this method is proved.

CNT fibers are composed of millions of highly aligned CNTs. The mechanical properties of CNT fibers when passing through different intensities of currents were investigated experimentally. The experimental results show that the introduction of current can obviously reduce the modulus and breaking strength of the fibers. When the current passes through the fibers, an axial electro-contraction force is produced, the electro-contraction force is increased with the increase of current intensity, the electro-contraction force at 5mA is about 2.5mN. By stretching the fiber to the 2% strain axially, after 1000s of the stress relaxation, the load tends to be stable, then switch on current or increase the current intensity, it is found that the tension of the fiber is obviously decreased due to the decrease of the stress caused by the change of modulus is greater than the increase of electric-contraction force. Stretching the fiber axially to 2% strain when passing through a certain intensity of current, after the stress relaxation, the load tends to be stable, then the same intensity of AC current is passed through, the response of the electro-contraction force is very quick.When the AC current changes experience 400 cycles, electro-contraction force exhibits good change, which makes the CNT-fibers as a new type of electro-actuation material.

Flexible pressure and strain sensors have attracted increasing attention with the rapid development of medical and electronic interconnection.Ionic conductive hydrogels demonstrate more potential for flexible electronics sensors because of their excellent physicochemical properties such as biomimetic structures， suitable mechanical properties， and excellent biocompatibility. The classification， preparation methods， characteristics of ionic conductive hydrogels，and their applications in flexible pressure and strain sensors were reviewed. First， the sensing modes of ionic conductive hydrogels in pressure and strain sensors were introduced. Then， according to the different conductive principles， they were divided into three categories：metal ion hydrogels， ionic liquid hydrogels， and polyelectrolyte hydrogels. Their applications and research progress in pressure and strain sensors were systematically introduced from synthesis methods， performance characteristics，and improvement methods.Their potential application prospects and development trends were analyzed. The current challenges were summarized and prospects were made. It was believed that ionic conductive hydrogels still have great exploration space and application potential in intelligent flexible sensing.

MIG welding and ER5356 welding wire were used for butt welding of 7075 aluminum alloy with a thickness of 3 mm. The joint was subjected to T6 heat treatment after welding. The microstructure, mechanical properties and corrosion resistance of the joints were analyzed by optical microscope, X-ray diffraction, scanning electron microscope and energy spectrometer combined with room temperature stretching, microhardness and electrochemical corrosion. The results show that the molten pool flow brings Zn, Cu and other alloying elements in the molten part of the base metal into the weld, and precipitates MgZn2 and AlCuMg phases during the welding process, which become the basis for the heat treatment and strengthening of the weld. After heat treatment, most of the precipitated phase melts into the matrix to form solid solution+aging strengthening, the joint tensile strength increases by 20%, and the weld hardness increases by 18.4%, the corrosion resistance improves. However, due to the limited alloying element content flowing into the weld from the base metal, the difference in mechanical properties between the welding wire and the base metal and the heat-affected zone softening phenomenon cannot be eliminated.

The shape memory effect of alloy microwire with Fe replacing Ga based on Ni-Mn-Ga alloy microwire was analyzed. Ni-Mn-Ga-Fe alloy was prepared by vacuum tungsten arc melting furnace and the parent alloy was prepared by a high vacuum precision melt drawing equipment. The effects of Fe doping on the phase, the martensite transition behavior, and shape memory effect were studied by EDS, DSC, XRD and DMA. The results show that the Ni-Mn-Ga-Fe alloy microwire shows the mixed phase of tetragonal martensite phase and face-centered cubic austenitic phase. The step ordering heat treatment was used for the microwire. The microwire was treated by step-by-step step ordering heat treatment, the ordered heat treatment can effectively reduce the internal defects of the microwires, release the internal stress, refine the internal grains of the microwire, shrink the lattice volume, improve the compactness of the microwire, and make the martensite twin interface more straight and easier to move, and improve the elongation of the microwire.The one-way shape memory test of the prepared Ni-Mn-Ga-Fe alloy microwires is carried out at 258 K, after stretching to 350 MPa and unloading to 0 MPa. The strain recovery rate is 78.75% after the microwires are heated to the austenite state. The one-way shape memory test of the ordered heat-treated Ni-Mn-Ga-Fe alloy microwires is carried out at 289 K, and the strain recovery rate reaches 100%. The ordered heat-treated ternary Ni-Mn-Ga alloy microwire and Ni-Mn-Ga-Fe alloy microwire are stretched under constant stress at 126 MPa and 240 MPa, respectively. The two-way shape recovery ability of the two microwires can reach almost 100%, but the phase transition width of the alloy microwire during deformation, namely the elastic strain energy storage is more than that of the ternary alloy microwire. The addition of Fe makes the mechanical properties of the alloy microwires higher than that of the traditional ternary shape memory alloy microwire; compared with Ni-Mn-Ga alloy microwires, the martensitic transformation temperatures of Ni-Mn-Ga-Fe alloy microwires in as-prepared and heat-treated states increase by 6.0 K and 11.5 K respectively, and the thermal hysteresis decreases by 6.7 K and 1.5 K respectively. In practical applications, Ni-Mn-Ga-Fe shape memory alloy may be more widely used due to its small thermal hysteresis, high martensitic transformation temperature and large strain recovery rate.

The rapid traffic developments create demands for shallow four-line high-speed railway tunnels in weak soils, while construction technologies of such tunnels have yet to be reported. In this article, the construction schemes for a shallow four-line high-speed railway tunnel with a span of 26.3 m in weak tuff strata are investigated by numerical analysis and in-situ tests. First, 20 construction schemes of the shallow super-large span high-speed railway tunnel are proposed and simulated by the Finite Difference Method, including eight schemes for grade V rocks and 12 schemes for grades IV and III rocks. The mechanical response of grade V rock mass is simulated by the Bolt–Kelvin Mohr–Coulomb rheological model. The influence of construction method, rock grade, area, quantity, and excavation sequence of pilot tunnels on the rock deformation and the internal force of the primary support are comparatively explored. For further analysis, an 8 month field test was conducted to study the optimized effect of the construction scheme. Finally, a suggested construction method selection chart for super-large span tunnels in weak rocks (spans between 17 and 34 m) has been proposed. The research conclusion could provide a reference for building the super-large span tunnel in complex conditions.

To provide regulatory elements for the regulation of metabolic fluxes in Saccharomyces cerevisiae cells and to control the efficient and precise expression of key genes at the transcriptional level in the cells, cloning and characterization studies of partial promoter elements of S. cerevisiae were carried out. The pRS41H-Promoter-EGFP expression vector was constructed using OE-PCR and enzymatic ligation using EGFP (enhanced green fluorescent protein) as the reporter gene. The relative strength and characterization of the S. cerevisiae promoters were characterized by measuring the fluorescence value of EGFP. The characterization results show that six new S. cerevisiae promoters are screened and cloned, namely PCBFI, PPAFI, PPOLI, PPOLII, PPOLIII and PRTFI, and their relative strengths are PPOLI>PPAFI>PPOLIII>PPOLII>PRTFI>PCBFI. Finally, the expression of promoter PPOLI in S. cerevisiae cells was investigated. It was found that PPOLI can continue to function in S. cerevisiae cells as they grow. This study provide a reference for the application of promoters in the regulation of metabolic flow homeostasis in chassis cells.

The 6061 aluminium alloy is a heat treatable reinforced aluminium alloy containing magnesium and silicon as its main alloying elements. It is commonly used in the aerospace and automotive industries due to its excellent mass to strength ratio and high thermal conductivity, but is particularly susceptible to the formation of coarse columnar crystals and thermal tearing, particularly during SLM processing.TiH2/AA6061 aluminium-based composite powders were prepared by the low-energy ball milling assembly modification method, and the titanium-containing 6061 aluminum alloy specimens were prepared by selective laser melting technique.The microstructure and mechanical properties of the samples with different TiH2 contents were systematically investigates. The results show that the addition of 1% TiH2 (mass fraction, the same below) results in the formation of a continuous equiaxed crystal zone at the alloy melt pool boundary, the average grain size decreases from 59.8 μm to 2.53 μm, and the coarse columnar grains and cracks inhibit, and with the addition of 1.5% TiH2, the coarse columnar grains of the SLM specimens inhibit completely and only a few small columnar grains exist. The microstructure transformation is attributed to the enhancement of the constituent undercooling by Ti elements and the in-situ reaction to form L12-Al3Ti nucleation particles, which form a coherent interface with the Al matrix and have a strong heterogeneous nucleation effect, thus significantly promoting the transformation from columnar to equiaxed crystals and grain refinement of the Al matrix. After selective laser melting, the tensile strength of 6061 aluminum alloy with 1% TiH2 addition is 274 MPa, the yield strength is 238 MPa, and the elongation after break is 18%.

In recent years, three-dimensional textile composites have been widely used in major national defense projects due to their excellent overall performance, rich structure, and net shape. Among them, the theoretical research of three-dimensional special-shaped textile composite materials is still far behind the application. Starting from the application of three-dimensional special-shaped textile composite material components, according to the typical characteristics of various components, the application status of three-dimensional special-shaped textile structural parts is summarized, and the main weaving process and weaving equipment development status of the three-dimensional special-shaped textile composite material preform were summarized. the research progress of the mechanical properties, meso-structure modeling and numerical simulation of 3D special-shaped textile composite materials from different levels at home and abroad were analyzed, and the key problems faced by the research of 3D special-shaped textile composite materials were put forward, aiming to provide support for the future applications of three-dimensional special-shaped textile composite materials.

Additive thin-walled parts have the characteristics of complex features and weak rigidity, which are prone to processing chatter vibration during the subsequent local feature milling and finishing. Therefore, this paper designed an electromagnetic magnetorheological damping fixture to semi-actively suppress processing vibration and improve processing quality. By simplifying the thin-walled part of the additive into a rectangular thin plate, considering the magneto-rheological fluid（MRF） excitation solidification damping characteristics, using the mode superposition method, the dynamic response model of the milling of the thin-walled part under the change of the magnetic induction intensity was obtained, and the fixture-workpiece system milling. The maximum error between the predicted value of dynamic response and the measured value is 21.4%. The feasibility and effectiveness of the method were verified through modal hammer percussion experiments and milling experiments, and the matching relationship between milling force, process parameters and magnetic induction intensity was fitted. Finally, the processing quality test of the typical samples was carried out. The processing flatness and roughness are increased by 80.0% and 80.3% respectively. The electromagnetic magneto-rheological damping fixture can effectively suppress the milling chatter, improve the processing stability of thin-walled parts, and improve the surface processing of the workpiece quality.

To study the stability of the over-pressure reinforcement effect of the copper tube at room temperature, the burst tests for the small diameter soft TP2 copper tube at room temperature during the natural aging time of 0, 6, 12 and 24 months were carried out respectively. These results indicated that: the mean of the measured burst pressure did not change significantly for small diameter soft TP2 copper bare tube and rifled tube at the same pretreatment pressure during the natural aging time of 0, 6, 12 and 24 months, respectively. The standard deviation was gradually smaller and the over-pressure strengthening effect was obvious. The measured burst pressure was different obviously for small diameter soft TP2 copper tube at the pretreatment pressure was 4.60 MPa and 16.50 MPa respectively during the same natural aging time, the mean was significantly larger and standard deviation was significantly smaller for measured burst pressure with the increase of pretreatment pressure, the results showed that pretreatment pressure had a great influence on strengthening effect, and higher pretreatment pressure could get better strengthening effect. The burst pressure conforms to the normal distribution for the same small diameter soft TP2 copper tube at the same over-pressure reinforcement during the natural aging time shall not exceed 24 months. Over-pressure reinforcement at room temperature was a suitable method to increase burst pressure of soft TP2 copper tube, and the method could be used in engineering.

Gradient nanostructured materials are regarded as a promising class of architectures with tunable mechanical properties, primarily dependent on the optimization of well-controlled fabrication parameters. In this paper, a microvariable-based constitutive model is incorporated into an integrated finite analysis technique. This approach correlates the fabrication parameters of surface mechanical grinding treatment (SMGT) with the corresponding measured mechanical properties of gradient structured (GS) materials, quantifying the relationship between process parameters, microstructure, and mechanical properties. Through theoretical prediction and experimental verification, it is observed that grain refinement, mechanical strength, and surface hardness are enhanced by increasing processing times and reducing path spacing. The yield stress of the fabricated GS material ranges from 126.8 MPa to 162.2 MPa, an increase of above 2.5 times compared to the original material, with a slight decrease in uniform elongation by a factor of 25.8 %, indicative of an excellent strength-ductility trade-off. The underlying mechanism for improved strength-ductility synergy is discussed, focusing on the importance of the tunable spatial distribution of grain size. This work sheds light on the potential application of gradient nanograined structures at an industrial scale and advances the fundamental understanding of strengthening mechanisms in gradient nanostructures.

High-strength aluminum alloys (2××× and 7×××, etc.) are widely used in aerospace, automobile and other fields because of their high specific strength and good machinability. With the development of high thrust-weight ratio engine and automobile lightweight technology, the demand for lightweight structural materials is increasing. Meanwhile, parts also present the "thin-walled, hollow and composite" tendency gradually, and the traditional processing methods of high-strength aluminum alloy are increasingly difficult to meet the requirements. As a common metal additive manufacturing (AM) technology, selective laser melting (SLM) is a great potential manufacturing technology for complex parts. SLM is expected to become an emerging technology to expand the application of high-strength aluminum alloys. However, due to their poor casting and welding properties, high-strength aluminum alloys easily produce the periodic hot cracks and coarse columnar grains during SLM, leading to unsatisfactory mechanical properties. Grain refinement is the key to overcome the inherent hot-tearing crack of SLMed high-strength aluminum alloys. The research progress in microstructure and mechanical property control of SLMed high-strength aluminum alloys in recent years was reviewed. The mechanical properties of alloys with different compositions were summarized. Importantly, the main strategies to suppress hot-crack formation in SLMed high-strength aluminum alloys were highlighted, including optimization of SLM process parameters and grain refinement by microalloying or addition of nanoparticles. It was pointed out that the main issue of SLMed high-strength aluminum alloys was the change of alloy composition on the comprehensive properties and heat treatment process was still unclear. The development trends were forecasted, such as designing new high-strength aluminum alloys and evaluating their comprehensive performances, using post-treatment process and other means to further improve the comprehensive performances of the alloys, and designing special grain refiners for SLM and investigating refinement mechanism.

Continuous drive friction welding technology was used to weld pure aluminum 1060/Q235 low carbon steel dissimilar material joints, and two cycles (30 d/60 d) thermoelectric coupling test (static load 392 N +high temperature 300 ℃+DC 60 A) was carried out. The effect of thermoelectric coupling on the microstructure, mechanical properties and interface growth of the welded joints of aluminum/steel dissimilar materials was studied. The results show that the thickness of the intermetallic compounds (IMCs) layer in the radial direction of the original joint interface is uneven, and there is no obvious IMCs formation in the central area. After 30 days of thermoelectric coupling, an IMCs layer with a width of 0.3-0.5 μm at the center of the interface is formed and dispersed from the steel side to the aluminum side in granular form, the overall tensile fracture is in the thermally affected zone of the aluminum base metal. After 60 days of thermoelectric coupling, a corrosion groove appears between the IMCs layer and the steel side, and the IMCs are broken, there are no cracks on the steel side, a large number of cracks and voids from the IMCs layer to the aluminum base metal are formed on the aluminum side, segregation of components occurs at the weld and crack tip, the overall tensile fracture is at the weld. The speed of interfacial corrosion and failure rate is proportional to the thickness of the interface IMCs layer, namely vcenter < v1/2R < v2/3R. Due to the uneven structure of the original joint interface and the difference in the growth rate of the structure at different positions of the interface during the thermoelectric coupling test, the boundary line of different fracture morphologies appears at the 2/3R position of the joint interface after thermoelectric coupling. The inner side of 2/3R is dominated by quasi-cleavage fracture, and the outer side of 2/3R is the combined result of dimple fracture and quasi-cleavage fracture.

In view of the fatigue failure of the transmission shaft in advance, the study of the stress state and life is carried out. Through the analysis of the actual measured load, the cause of the fatigue failure of the drive shaft in advance is the inconsistent output load of the left and right splines. The finite element model of the transmission shaft is established by using finite element software, and the maximum stress at the root of the right tooth of the transmission shaft is obtained, which is the weak part of the transmission shaft. The response surface method and genetic algorithm are used to optimize the structural parameters of the transmission shaft（tooth root fillet, spline transition arc, and arc groove depth）. After optimization, the stress of the weak part of the transmission shaft tooth root is reduced by 28.3%. The fatigue life of the transmission shaft is increased by five times, and the reliability is higher. Finally, the fatigue test is carried out on the scaled down sample. The test result shows that the life of the drive shaft is doubled. The effectiveness of the optimization method is verified through experiments, and the method has certain reference significance for the optimization of shaft parts in the future.

In order to explore the effects of material properties, filling density, support structure and other parameters on mechanical properties and strength characteristics of 3 D printed products, an optimization design method of 3 D printed configuration based on strength requirements was proposed. The mechanical properties of the products were obtained through the simulation calculation of the finite element structure strength and the comparative analysis of the tensile test of the characteristic samples. The tensile strength of 3 D printed products with different internal structures has great differences when the packing density is the same. In theoretical analysis and experimental test, the tensile strength of concentric structures is higher, while that of folded lines and spirals is lower. The results have guiding significance for in-depth analysis of the relationship between the strength of 3 D printing parts and the filling structure, and provide research data support for the optimization design of 3 D printing parameters based on strength demand.

In view of the blindness and contingency of the trial cutting method in traditional processing of spiral bevel gears, this paper proposes a processing adjustment method of designing grinding wheel section according to the curvature of the tooth surface. Firstly, the spiral bevel gear is simulated by CATIA to build a high-precision cutting model. In ABAQUS, the finite element analysis of the cutting model is carried out, and the contact spots are extracted. Then, according to the analysis results of the cutting model, the curvature and node offset of the tooth surface are calculated for contact area adjustment. Finally, the grinding wheel section is designed according to the cutter section and the offset of the tooth surface, which is called in the virtual grinding. The analysis results show that the contact performance and transmission performance of the gear after curvature adjustment are greatly improved, which indicates that the tooth surface curvature adjustment is realized by adding the grinding process, and it is in line with the actual process flow. It provides a new research method for transmission error optimization and contact area correction of spiral bevel gear system.

Fatigue life of filled natural rubbers used in isolators is very dispersive owing to many uncertainties such as loads and temperature. Conventional crack initiation methods and crack propagation methods to determine fatigue life of rubbers are insufficiently to characterize the phenomenon; thus, probabilistic methods are desired in practical engineering. Based on the test data of uniaxial tensile fatigue experiment of rubbers, the cumulative distribution function and probability density function of residual fatigue life corresponding to two typical probability distribution models of three parameters Weibull distribution（3 PWD） and logarithmic normal distribution（LND） were derived and applied to the prediction of residual life reliability, in order to determine the minimum required under different probability distribution model of sample number and working condition number. The results showed that 3 PWD was more suitable to characterize the probability distribution of rubber fatigue life. The minimum values of the number of rubber fatigue test samples and the number of working conditions are distributed between 4 and 6. The log mean should be preferred for subsequent fatigue analysis when determining the median life. The research can provide guidance for the anti-fatigue design and test of rubber vibration isolators.

The stitched foam-core sandwich composites with different stitching methods and stitch density were manufactured using vacuum assisted resin infusion (VARI) molding process. The effect of stitching parameters on their flatwise tensile, three-point flexural, core shear and climbing drum peel properties was investigated. The results show that although stitching makes flatwise tensile strength and core shear strength of foam-core sandwich composites to decrease obviously, it can improve flexural properties as well as substantially enhance climbing drum peel properties. Modified lock stitch method is better than tufting stitch method. Properly increasing stitch space has certain positive effect for mechanical properties, but it is not conducive to the enhancement of climbing drum peel properties. For modified lock stitched foam-core sandwich composites with the stitch density of 30 mm×10 mm, flatwise tensile strength and core shear strength are reduced by 14.75% and 24.79%, respectively, whereas flexural strength and average peel strength are respectively increased by 7.96% and 80.78% compared to those of unstitched foam-core sandwich composites.

As the lightest metal structural materials, magnesium and its alloys have great potential to achieve lightweight products in the future. However, magnesium has a high corrosion sensitivity, and the magnesium hydroxide film formed on the surface is loose and porous with little protection, which leads to its application being limited. How to improve the corrosion resistance of magnesium has become a worldwide problem that restricts its application. Alloying is one of the ways to radically improve the corrosion resistance of magnesium alloys. In this paper, the corrosion mechanisms of pure magnesium and the mechanisms of alloying elements on the corrosion performance of magnesium alloys are described in terms of the influence of alloying elements on the corrosion resistance of magnesium and its alloys. In addition, protection mechanisms produced by alloying elements on magnesium alloys were compiled, and the protection mechanisms and corresponding characteristics of beneficial elements on magnesium alloys were summarized. This can provide some reference for the development of new magnesium alloys and the improvement of the corrosion resistance of magnesium alloys. In addition, this paper contributes to a better understanding of the corrosion behavior of magnesium alloys. At present, there is no magnesium alloys can be as good as aluminum alloys or stainless steels corrosion resistance, so the development of corrosion-resistant magnesium alloys needs further research. This paper provides a theoretical basis for the interaction between elements in magnesium alloys, which can provide ideas for the development of new corrosion-resistant magnesium alloys. The synergy between the elements will have a significant impact on the design, process and performance of new corrosion resistant magnesium alloys, and as the research progresses, it is expected that new corrosion-resistant magnesium alloys similar to "stainless steel" will be constructed.

Ethylene-vinyl alcohol copolymer/nylon 6 (EVOH/PA6) composites were prepared by a melt blending method. The processing rheological properties of EVOH/PA6 composites were studied by advanced capillary rheometer and rotational rheometer. The relationship between viscosity and shear rate ($\mathop \gamma \limits^.$) of EVOH/PA6 composites were fitted by power law model, and the relationship between viscosity and temperature of composites were described by Arrhenius equation. The results show that the EVOH/PA6 composites are pseudoplastic fluid. Apparent viscosity (ηa) and non Newtonian constant (n) of EVOH/PA6 composites are all enhanced with the increasing contents of EVOH. In the angular frequency (ω) scan range, the storage modulus (G'), loss modulus (G″), and complex viscosity |η*| of EVOH/PA6 composites are enhanced by the addition of EVOH. Han curve, cole-cole curve and scanning electron microscope (SEM) study show that EVOH and PA6 have good compatibility. Furthermore, EVOH/PA6 composite forms a microphase separation structure when containing 15% (mass fraction) EVOH.

The preparation of 7×××series aluminum alloy by selective laser melting technology (SLM) is hindered by hot tearing. Novel ZrH2 modified 7075 composite powders were prepared by the low-energy ball milling technology. Zirconium-containing 7×××series aluminum alloy was then prepared by the SLM process. The microstructure and mechanical properties of the samples with different ZrH2contents (0.5%, 1.0%, 1.5%, mass fraction, the same below) were systematically investigated. The results show that the addition of ZrH2 can significantly reduce hot tearing and change the microstructure. When 1.5% ZrH2 is added, the hot tearing is completely eliminated and the grain microstructure is entirely composed of fine equiaxed grains. The transition of columnar grains to equiaxed grains is attributed to the in-situ formation of L12-Al3Zr which provides numerous nucleation positions for solidification. After T6 heat treatment, the tensile strength, yield strength and elongation of SLMed sample are (550±10), (490±5) MPa and (12±1)%, respectively. Fractography analysis shows a large number of dimples on the fracture surface after tensile testing, indicating ductile fracture mode.

Shallow urban tunnels with super-large sections in weak soils may experience much more devastating seismic hazards than conventionally deep tunnels in seismically vulnerable areas. This study investigates the seismic response and isolation technology for the largest comprehensive urban pipe gallery in the Xiong’an New Area, Hebei Province, China, using seismic simulation. First, the engineering background, static-seismic model, dynamic motions, and measuring points of the numerical simulation are introduced. Then, using the finite difference method to explore seismic behaviors of the super-large comprehensive urban pipe gallery under strong earthquake excitations are explored. The indexes including the deformation, the stress, the internal force, and the safety factor of segments are analyzed. Meanwhile, the aseismic effects of three proposed isolation schemes (namely, the cushion scheme, the partial buffer layer, and the integral buffer layer), which are proposed to be employed in the super-large comprehensive urban pipe gallery, are explored comparatively. The result shows that the integral buffer layer presents the most dramatic seismic isolation effect (97.85%), followed by the partial buffer layer (22.58%), and the cushion (15.07%). The integral buffer layer scheme is recommended to be employed in the seismic design for the present super-large pipe gallery. These conclusions can give scientific guidance for the seismic design of the super-large urban tunnels.

Based on the excellent chelating ability of phytic acid (PA), Ag+, Cu2+, Fe3+, and Zn2+, were used to chelate with PA, and deposited on the surface of layered double hydroxides (LDHs) to form core-shell structure, so as to improve the interfacial compatibility between layered clay and polymer matrix. Surface coated LDHs (LDHs@PA-M) loaded with different metal ions were prepared. The micromorphology of LDHs@PA-M loaded with different metal ions was studied and applied in the strengthening modification of poly(ε-caprolactone) (PCL). The results show that PA can form stable and uniform nano-coatings with Ag+ and Cu2+on the surface of LDHs. With the excellent antibacterial activity of Ag+ and Cu2+, the antibacterial rates of LDHs@PA-Ag+ and LDHs@PA-Cu2+ against Escherichia coli (E.coli) both exceed 99.99%. Compared with pure PCL, the tensile strength and elongation at break of LDHs@PA-Cu2+/PCL nanocomposites (mass fraction of LDHs@PA-Cu2+ is 1%) increase by 30.7% and 33.3%, reaching 40.9 MPa and 816%, respectively. The enhancement of mechanical properties for LDHs@PA-Cu2+/PCL nanocomposites is the most remarkable. The antibacterial rate of LDHs@PA-Cu2+/PCL and LDHs@PA-Ag+/PCL nanocom-posites against E.coli both exceed 99.99%. It shows excellent antibacterial activity, which expands the application of layered clay/bio-based polymer nanocomposites in the field of active packaging.

For the wave cylinder,three wavelength models were established. The large eddy simulation method is used to analyze the flow characteristics of wave members with convection angle under high Reynolds number. The velocity and pressure distribution laws of wave members with different wavelengths were investigated,and characteristics about time-domain and frequency-domain of the circumferential pressure coefficient,drag and lift were discussed. The results show that the larger the surface inclination,the higher the surface pressure variation. The smaller the wavelength is,the larger the resistivity of the member and the main peak ranges. According to the characteristics of flow fields,a wave member with a spatial AOA of λ/Dm=3. 26 obtains better drag and vibration reductions,compared λ/Dm= 5. 5,λ/Dm= 3. 26 and λ/Dm= 2. 24. These findings are vitally significant and valuable for researches and applications about flow characteristics of wave cylinder.

The tower is the main bearing component of wind turbine,and its performance directly affects the service life and safety of wind turbine. The 2 MW wind turbine tower structure optimization was researched,with the tower quality was taken as the optimization objective,the natural frequency,stress and height was taken as the constraint conditions,and the diameter,wall thickness,pitch length was taken as control variables. The tower structure was optimized by simulation and checked by analytical solution. The results show that the optimized tower has reduced weight 4. 21% and increased natural frequency,the maximum stress position obtained by simulation is the same but 22. 3% larger than the analytical,the analytical first order natural frequency is 18% larger than the simulation. This optimization method has certain practicability and engineering application value,and is suitable for popularization and application.

In order to provide the basis for selecting suitable design formula of pressure equipment strength,and to establish the reliability method of pressure equipment strength design,the ratio of the flat winding vessel burst pressure actual value to the formula calculated value was considered as a random variable. applied mathematical statistics and probability theory,the validity and homogeneity of random variables statistical samples were discussed,the random variables distribution law was analyzed,the comparison method of random variables distribution parameters was constructed. The evaluation index and method of formulas engineering adaptability were established from two aspects of precision and stability. Taking 15 sets of flat winding simulation vessel burst pressure measured data and 5 sets of flat winding industrial scale vessel burst pressure measured data as examples,the distribution laws and parameters of the random variables corresponding to four burst pressure calculation formulas were analyzed and compared,the engineering adaptability of the corresponding formula was evaluated. The researching results show that:（ 1） When the confidence of both sides was 99%,4 formulas corresponding random variables statistical samples are effective and homogeneous; if the significance was 0. 05,the 3 random variables are basically accorded with normal distribution,when the confidence of both sides was 98%,the value interval of distribution parameters are obtained.（ 2） Of the three random variables that basically fit the normal distribution,there is no significant difference in the distribution parameters of two random variables,but there is significant difference with the distribution parameters of the other one.

In order to solve the problem that the MEMS accelerometer used the external ballistic information measurement cannot withstand the high overload during projectile launching and is easy to cause damage to the device,a low-range capacitive accelerometer with high overloading resistance was designed. Platforms modeled on the bridge fender structure were placed at the end of the beam where the stress was relatively large and easy to be broken by impact. The structure can absorb a part of the energy during an impact with its own deformation,thereby reducing the deformation of the sensor itself. The finite element simulation results indicated that the stress of the proposed accelerometer under the condition of 30 000 g overload was reduced from 994. 88 MPa to 70 MPa. Therefore,the possibility of device damage and fracture was greatly reduced,which meets the design expectations of improving the sensor’s anti-overload capability.

To provide a basis for selecting formulas or extending their applied ranges,applying probability theory and mathematical statistics,a comparison and evaluation method of formula stability and precision was established. Based on the study that the ratio of actual burst pressure to the formula calculated value was basically in accordance with the normal distribution random variables, comparing and evaluation the formula stability from the variation coefficient of distribution parameters fluctuation range,comparing and evaluation the formula precision from the distribution parameters value interval contact ratio.When the bilateral confidence was 98% and in the applied range of the formula,the stability and precision of Mid-diameter formula,Tresca formula,Faupel formula and Rheological stress formula were compared and evaluated. The researching results shown that:（ 1） It is the basic conditions for selecting formulas or extending their applied ranges that stability and precision not reduced.（ 2） For pressure-bearing single-layer cylinder,the applied range of the Mid-diameter formula for measured burst pressure specified by the standard,it can be extended from no more than 105 MPa to no more than 329. 6 MPa,the stability of the Mid-diameter formula is obviously improved and the precision is not reduced. The applied range of the Tresca formula for measured burst pressure specified by the standard,it can be extended from between 91. 0 MPa and 300 MPa to no more than329. 6 MPa,the stability of the Tresca formula is obviously improved and the precision is not reduced. If the measured burst pressure was not exceed 329. 6 MPa,the stability and precision is no significant difference between the Mid-diameter formula and the Tresca formula. When the applied range of the Rheological stress formula for measured burst pressure was not less than 220 MPa,and the applied range of the Faupel formula for measured burst pressure was not less than 250 MPa,the precision of the two formulas is not significantly different,and the stability of Rheological stress formula is obviously better than Faupel formula.For Mid-diameter or Tresca formula with measured burst pressure not exceeding 329. 6 MPa,and for Rheological stress formula with measured burst pressure not less than 220 MPa,the stability of Mid-diameter or Tresca formula is obviously better than the Rheological stress formula,and the precision is higher than the Rheological stress formula.（ 3） For flat steel ribbon wound pressure vessel with measured burst pressure was not exceed 209. 7 MPa,the precision and stability of Mid-diameter formula is lower than that of four predictor formulas of burst pressure for pressure-bearing single-layer cylinder.

The aim of the present work is to upgrade the functionality and environmental friendliness of polypropylene (PP) by means of a blending technique. The influence of the metal pigment on the odor, volatile organic compounds (VOC) and metal texture of PP, and the effects of the extractant, adsorbent and processing technology on the odor and VOC of PP composites were studied systematically. It was found that metallic pigment significantly increased the VOC, odor, metallic texture and MFR of PP, and reduced the impact strength and elongation at break. The adsorbent and extractant can effectively reduce the VOC and odor of the PP composites. When the adsorbent and extractant contents were 0.5 and 5 wt%, respectively, the maximum reduction in the VOC and odor reached 73.6% and 1 level, respectively. When the extractant and adsorbent were used at the same time, the method of adding extractant and adsorbent from the main and the secondary feeding port respectively was significantly superior to the method of adding the extractant and adsorbent from the main feeding port together in reducing the odor and VOC of PP composites, which displayed a good synergistic effect.

The bioactive coatings were prepared on the surface of Ti6Al4V by micro-arc oxidation in the electrolyte system consist of CaSiO3, Na2SiO3·9H2O, EDTA-2Na, K2HPO4·3H2O and the electrical parameters were fixed at 400 V, 600 Hz, 15%, 10 min with constant voltage mode. The value of concentration of CaSiO3 and Na2SiO3·9H2O were changed, and the range of change was 0.0835-0.15 mol/L and 0-0.06 mol/L respectively. Structural properties and microstructure of bioactive coating fabricated by micro-arc oxidation were detected by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), electrochemical workstation, eddy current thickness profiler, scratch tester and Image-Pro Plus 6.0. The effects of CaSiO3 and Na2SiO3·9H2O concentrations on the bioactive coating were studied. The results show that thickness, roughness, micropore diameter and porosity, calcium phosphate ratio gradually increase and corrosion resistance, bond strength gradually deteriorate with the increase of CaSiO3 concentration. Micropore diameter and porosity first grow larger and then become smaller, thickness,roughness,calcium phosphate ratio and bond strength gradually increase and corrosion resistance becomes better first and then deteriorates with the increase of Na2SiO3·9H2O concentration. The performance of the coating is the best when the concentrations of calcium silicate and sodium silicate are 0.15 mol/L and 0.015 mol/L, respectively.

A strategy based on grafting organocatalytic units as side-chain on the organic linkers, a TEMPO radical decorated terphenyl-dicarboxylic acid linker was synthesized. By employing acetic acid as modulator, TEMPO radical decorated UiO-68-TEMPO nanocrystals were synthesized by using H2tpdc-TEMPO as organic linker and ZrOCl2 as metal source under solvothermal conditions. UiO-68-TEMPO are monodispersed nanocrystals with side in the range of 800-1200 nm, with high BET areas (up to 1320 m2/g), and contain a large number of TEMPO radicals as evidenced by solid-state EPR spectrum. UiO-68-TEMPO nanocrystals enable selective oxidation of a broad range of alcohols, including primary aromatic alcohols, secondary aromatic alcohols, and heterogeneous atomic alcohols, with high efficiency and selectivity. The catalytic activity of UiO-68-TEMPO nanocrystals remains 75% after catalysis for four cycles. Finally, a plausible catalytic mechanism for the oxidation of benzyl alcohol by UiO-68-TEMPO was proposed, that is the TBN co-catalyst produces NO2/NO redox mediator, which enables the oxidation of TEMPO radicals to oxoammonium cations by O2, and finally oxidize benzyl alcohol to benzaldehyde.

The basic structure, working principle, and the development process and research status of resistive random access memory (RRAM) were outlined. Material systems, including dielectric materials, electrode materials, and substrate materials, as well as broad trends and recent researches of flexible RRAM were summarized; the performance characteristics of flexible RRAM, including storage performance and mechanics performance, were analyzed. The significance and challenge of developing flexible RRAM were explicated. Problems existing in this area and possible approaches to the problems were also put forward. It was concluded that the highly conductive stretchable electrode and the steadily stored stretchable dielectric are primary direction in the future.

Tribological properties of oleic acid modified natural serpentine ultrafine mineral powders as lubricating oil additive were investigated by a reciprocating sliding wear tester. The effects of the four factors including load, reciprocating frequency, sliding time and concentration of serpentine on the properties of serpentine additive were analyzed. Results indicate that the anti-wear and friction-reducing properties of the base oil are significantly improved by the addition of the modified serpentine powders. The order that affects the friction-reducing performance of the serpentine additive is:concentration, reciprocating frequency, load, sliding time, and the optimal tribological conditions are 100 N, 5 Hz, 180 min, 0.5%(mass fraction). While that affects the anti-wear property is:load, concentration, reciprocating frequency, sliding time, and the optimal conditions are 100 N, 50 Hz, 180 min, 0.3%. Serpentine minerals forms a tribofilm consisting of various oxides, graphite and organic compounds on the friction surface, which is the key to improving anti-wear and friction-reducing properties.

The basic principles and methods of infrared radiation and infrared stealth technology were discussed in this paper. It was found that flexible regulation of multi-band spectrum was the key to realize infrared stealth compatible with radar stealth, laser stealth and visible light stealth. The research status of traditional infrared stealth materials were summarized and the bottleneck of their development was clarified. Furthermore, the design idea, research basis and development advantages of infrared stealth metamaterials with spectral tailoring function were proposed. We reviewed the research status and development trend of the infrared stealth compatible with radar stealth, infrared stealth with infrared radiation window and infrared stealth compatible with laser and visible light.

Due to its unique optical and electrical properties, p-type metal oxide materials stannous oxide has been favored by more and more people in various fields such as catalysis, sensing and optoelectronic devices.This paper focuses on the research and application of stannous oxide in thin film transistors. As a core component of display driver panels, thin film transistors play an important role in the display.The research progress of p-type stannous oxide thin film transistors was summarized in this paper, which includes the analysis of the microcosmic properties of stannous oxide, the preparation of stannous oxide thin film materials and the fabrication methods of transistors. By introducing the crystal and electronic structure of stannous oxide in details, the microcosmic regul-ation mechanism of the properties of tin oxide was discussed. Through the preparation of stannous oxide materials and the research and application of the devices, the problems of low current-to-switch ratio faced by stannous oxide thin film transistors were analyzed and their prospects in the direction of the complementary metal-oxide-semiconductor devices were put forward, in order to provide a refere-nce for the preparation of p-type metal oxide thin film transistors which are stable and eco-friendly.

As study on the burst pressure probability distribution of single-layer cylindrical vessels is a basic work,the establishment of pressure vessels reliability design method was carried out to build precision evaluation system of pressure vessel strength calculating formula. The burst pressure probability distribution of single-layer cylindrical vessel was analyzed by using the hypothesis test method in the mathematical statistics theory,based on 84 sets measured burst pressure data of single-layer cylindrical vessel. Research results indicated that:（ 1） Based on the engineering practice of Chinese standard,the application range of the formula can be divided into the 3 groups according to the design pressure which are no exceeding 35 MPa,between35 MPa and 100 MPa,and no more than 100 MPa,respectively;（ 2） According to the relationship between design pressure and burst pressure,the actual burst pressure of the formula application range sample was no more than 105. 5 MPa,between 91. 0 MPa and 329. 6 MPa,and no more than 329. 6 MPa,respectively;（ 3） When the significance was 0. 05,the ratio of the samples measured burst pressure and mid-diameter formula and Tresca formula calculated values is 6 random variables with the normal distribution.（ 4） When the 2-sides confidence was 98%,the distribution parameters value range of 6 random variables were obtained respectively.

The microstructure of as-cast Mg-6Zn-xCe alloy was investigated by optical microscope (OM), X-ray diffraction (XRD), scanning election microscopy (SEM), energy dispersive spectrometer (EDS), transmission electron microscopy (TEM)and the changing rule of thermal conductivity with the content of Ce was investigated using the flash method. The results show that Mg-6Zn alloy is mainly composed of α-Mg and Mg7Zn3 phases. The ternary phase Ce5 (Mg,Zn)41 which is mainly distributed between grain boundaries and dendrites appears in the alloy after the addition of the rare earth element Ce, and the appearance of ternary phase has an inhibitory effect on Mg7Zn3 phase. The content of eutectic structure is increased by the addition of Ce, and the distribution continuity is improved with the increase of Ce content. The thermal conductivity of the alloy is decreased with the increase of Ce content, which may be caused by the increase of volume fraction, more continuous distribution of eutectic structure in the alloy, the enhanced electron scattering, the extended electron conduction paths and the increased thermal resistance, ultimately the thermal conductivity of the alloy is reduced.

7075 aluminum alloy butt welding was carried out by TIG welding with self-made 7075 wire. The effects of different currents on the microstructure and mechanical properties of the joint before and after heat treatment were studied. Before heat treatment, the strength and elongation of the joint are 274.84 MPa and 6.3%, which are determined by the presence of a large number of second phase precipitates with different shapes. After heat treatment, the tensile strength and elongation are increased to 511.75 MPa and 13.76%. Since most of the second phase has been dissolved, the grain size becomes the decisive factor. The fine grain size and more sufficient recrystallization degree make the mechanical properties of the low-current joint better.

Free radical-cationic hybrid UV-curable resin applied to UV-cured 3D printing was developed with epoxy resin (EPON828) and polyurethane acrylate (RJ429) as photosensitive prepolymers. The influences of types, ratios and dosages of free radical and cationic photoinitiators on photocuring kinetics, mechanical properties and prototyping precision of hybrid UV-curing resin were investigated. The results show that cationic photoinitiator Gencure 842 and free radical photoinitiator Doracur 1173 are the most appropriate hybrid photoinitiators, with an optimum mass ratio of 0.75:1 and mass fraction of 6%. The optimum mass ratio of EPON828 and RJ429 is determined as 1:1, and the viscosity of the developed resin is 50.5Pa·s. The tensile strength, impact strength, volume shrinkage and warpage of UV-cured resin items are 6.60MPa, 8.28kJ·m-2,-3.986% and 3.62%, respectively. The hybrid UV-curing resin can basically satisfy the requirements of UV-cured 3D printing.

The binding energies, electronic structures and mechanical properties of M doped in α-Fe(N) system were investigated by using first principle calculations, where M represents Ti, V, Cr, Mn, Co,and Ni. The results show that Ti and V occupy preferentially the corner of α-Fe(N) unit cell, Cr and Mn occupy preferentially the body-centered position of the cell, the structure is the most stable when Co and Ni are not adjacent to the N atom. The doped elements Ti and V strengthen the stability of α-Fe(N); Cr, Mn and Ni have an opposite effect; Co does not affect the stability. The metallic and ionic bonds coexist in the doped systems. The bonding orbitals are created by the interaction of M3d, Fe4s3p3d and N2p. Compared with the pure α-Fe system, the material rigidity is stronger for doped systems. The calculation results show that the elastic modulus E,shear modulus G and bulk modulus B of α-Fe(N)-V are the maximum. It reveals that doped V can significantly improve the overall mechanical properties of steel and it is the most effective nitrogen fixing element. It is consistent with the experimental results of high nitrogen steel smelting.

The iron salts (ferric and ferrous salts) play a critical role for the synthesis of morphology and size controllable, and highly crystalline MIL-100(Fe). The use of ferrous salt results in octahedral, highly crystalline MIL-100(Fe) with high surface areas. In contrast, the use of ferric salt only results in smaller Fe-BTC metal-organic polymers with low crystallinity. The crystal structure, morphology, photo-absorption property, absorption and photocatalytic-degradation properties of MIL-100(Fe) and Fe-BTC toward RhB, were fully characterized by XRD, SEM, FT-IR, UV-Vis DRS, and UV-Vis spectroscopy. The results indicate that the slow oxidation of Fe2+ to Fe3+ is key to the synthesis of highly crystalline MIL-100(Fe) since this process facilitates the formation of μ3-OFe(Ⅲ)O6, which is inorganic secondary building unit (SBU) of MIL-100(Fe). When FeCl3 used as iron source, the fast dynamic reaction of Fe3+ with BTC3- is not beneficial to the formation of μ3-OFe(Ⅲ)O6 SBU; therefore, Fe-BTC nanoparticle polymer is obtained. The smaller size of Fe-BTC nanoparticless, and meso-/macroporous structure in the aggregated nanoparticle surface, which facilitates the diffusion of RhB as well as the photodegradated forms. Fe-BTC shows better absorption capacity and photocatalytic activity toward RhB compared to MIL-100(Fe).

Pre-strain on austenitic stainless steel was a method in order to obtain good mechanical properties,the pre-strain effect evaluation was the basis of improving the production process of the steel. Applying the theory of probability and mathematical statistics,the evaluation system of pre-strain effect was established: the pre-strain effect on the mechanical properties parameter standard deviation was evaluated,using F-distribution; the pre-strain effect on the mechanical properties parameter mean value was evaluate,using t-distribution. For example of pre-strain effect on austenitic stainless steel S30408,based on the effective tensile test data at liquid nitrogen temperature,and the bilateral confidence was 99%,the effect of 9%-prestrain on the steel was evaluated: 1) 9%-pre-strain significantly increases the yield strength of steel S30408,and the standard deviation is basically unchanged; 2) for steel S30408 tensile strength,9%-pre-strain is no effect on the mean and the standard deviation.

Based on the theory of rigid-flex coupled multi-body system dynamics,systematic research has conducted on transmission system of a coal winning machine’s cutting part. By using the software of Recur Dyn,the model was established including transmission gears,drive shaft and bearing. Considering the flexible characteristics of drive shaft,the rigid-flexible coupled model was built.Transmission system of a coal winning machine’s cutting part was simulated dynamics analysis before contact parameter setting on the parts of transmission system. The working process of shearer transmission system was described intuitively and dynamically. Results showed that 11 th gear mesh together is the biggest,11272634. 4 N.4 th. The maximum strain,measured at the axes of 4,is 0. 081. It reveals the difference of Gear meshing force curve and its frequency-domain information between Rigid-flexible coupling system and Stiff systems. Results provide a basis for optimum design of the transmission system and prediction of fatigue life.

Strip steel vibrations is inevitable in the rolling process of tandem mill, and the coupled model between elastoplastic body of strip steel and main drive system directly affects the overall dynamic performance of rolling mill. According to the movement mechanism of strip steel and main drive system, the main drive system was simplified to a two-degree-of-freedom discrete model and the strip steel was simplified to an axially moving Euler beam, the coupled vibration mechanical model of transverse and longitudinal vibrations of strip steel and torsional vibration of main drive system was established. Then, the nonlinear vibration differential equations of the coupled model were derived with Hamilton’s principle. The modified iteration method and the Kantorovich averaging method were used to solve the differential equations. Finally, by using the Matlab simulation, the influence of torsional vibration fundamental frequency of main drive system on strip steel vibration characteristics was discussed. The results can enrich the theoretical achievements on vibration of rolling mill, and it is valuable for transforming theoretical results into engineering applications.

In order to study the influence of thermal deformation of the cycloid ball meshing pair on dynamic performance of the precision ball transmission, the thermal deformation of contact point of the cycloid ball meshing pair was analyzed by the Green function method, and the influence of system parameters on thermal deformation was analyzed. According to the angle deformation of the planetary disk caused by thermal deformation of meshing pair, the expression of the meshing stiffness coefficient was derived, the factors affecting variation of the meshing stiffness coefficient were analyzed. The finite element single tooth model of meshing pair was established, the finite element simulation of thermal deformation of meshing pair was analyzed by thermal structure coupling. The results show that the thermal deformation of the epicycloid groove is higher than that of the hypocycloid groove, the maximum thermal deformation occurs in the vicinity of 1/3 tooth height of the epicycloid groove, the thermal meshing stiffness coefficient is approximately sinusoidal in a small range, the parameters of system have great influence on the thermal deformation and the thermal meshing stiffness coefficient. This study provides a theoretical basis for the thermal dynamic analysis of precision ball transmission.

Due to the complicated structure of the loop-type compound epicyclic gear system, the torque and power relationship between the basic components in the system is complex and variable, forming a variety of power flow types. In order to quickly judge the power flow type of the system during the design process, a composite lever analysis method is proposed. Based on the lever model of a single epicyclic gear train, combined with the structural characteristics of the coupled system, used the superposition principle, a composite lever model reflecting the characteristics of the loop system is established. Then the application method of this model during analyze the characteristics of single loop system is introduced. This composite lever model is found to intuitively reflect the speed, torque and power relationship among the basic components, and then derive the power flow type of the single loop system. The values of the above characteristics can also be calculated by the force arms of the model that reflect the characteristic parameters of the epicyclic gear systems. On this basis, the application of this method in the power flow analysis of dual-loop system is introduced, which provides a new idea for the analysis of multi-loop system.

During the process of combined rotor modularization amplification or reduction,due to the size effect,the law of the influence of microcrack expansion on the dynamic performance of the combined rotor with different sizes is not clear.Dimensional analysis method of similarity theory was used to introduce the "size effect"existing in the process of microcrack expansion. And taking the prototype,2. 3-fold scale model and 1. 3-fold scale-up model of a heavy duty gas turbine combined rotor as the research objects,the combined rotor natural frequency drift were analyzed in the case of initial microcracks varying with combined rotor size. The results show that there is comparatively large deviation when using the ordinary Paris formula to analyze the natural frequency drift of the different size combined rotors caused by microcrack expansion. There is a certain correlation between the change of dynamic performance and the size of combined rotor considering microcracks.

In order to increase the burst pressure of copper pipe,save the copper material under the premise of guaranteeing safety,overpressure enhancement of TP2 copper tube was tested at room temperature,the relationship between the burst pressure of copper tube and the pretreatment pressures was studied,the changes of TP2 material tensile strength was analyzed. Based on28 groups burst test of TP2 copper tubes under different pretreatment pressure at room temperature,studies have shown that: 1)If the enhancement pretreatment pressure of TP2 copper tube is equal to the yield pressure,the thermal effect of copper tubes brazing should be improved,copper tube burst pressure and TP2 material tensile strength should be strengthened to a certain extent. 2) Compared with non overpressure enhancement at room temperature,for the burst pressure and the tensile strength of TP2 copper tube used appropriate pressure pretreatment,the means of copper tube burst pressure and the TP2 material tensile strength are increased significantly,the standard deviation and coefficient of variation are decreased significantly,and the precision is improved obvious. For the burst pressure and the tensile strength of TP2 copper tube,the fluctuation range of the average,standard deviation and coefficient of variation are smaller,and the stability is become well.

To improve flame retardant properties of polypropylene,the brominated epoxy resin (BEO) and nano-Sb2O3 were added into polypropylene by using a high energy ball milling technique. Flame retardant properties of polypropylene composites were evaluated by UL94 vertical combustion tests and limit oxygen index (LOI). The surface morphology of combustion products of composites was characterized by scanning electron microscopy(SEM) and the flame-retardant mechanism of flame retardant additives acting on the polymer matrix was studied by using thermo gravimetric analysis(TGA) and Fourier transform infrared (FT-IR) spectroscopy. The results show that the reaction between modified nano-Sb2O3 and BEO can prolong residence of the halogens in the combustion area, resulting in more hydroxyl and hydrogen radicals are replaced by the bromine radicals. When the content of modified nano-Sb2O3 is 7% (mass fraction, the same below) and that of BEO is 21%, the nano-Sb2O3/BEO/PP composite has excellent flame retardant performance with 28.6% of LOI value and V-0 of UL94 grade of vertical combustion.