Table of Content

25 September 2017, Volume 45 Issue 9

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Mechanical Engineering

Research Progress of Hydrodynamic Lubrication of Surface Texture

TANG Yong TANG Heng WAN Zhen-ping YUAN Wei LU Long-sheng LI Zong-tao

2017, 45(9):  1-11.  doi:10.3969/j.issn.1000-565X.2017.09.001

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Surface texturing is a technology to produce certain patterns of defined size,shapes and arrays on the surfaces of friction pairs,and it has been proven to be effective in enhancing the tribological performance of the friction pairs.As suitable geometrical parameters of surface texture can significantly improve the tribological performance of mechanical components,the optimal design of the surface texture under hydrodynamic lubrication has become the research focus of the scholars at home and abroad.In this paper,by analyzing the current researches on the surface texturing,the morphology and mechanism of the surface texture are introduced in detail.Then,the influences of the shape,direction,parameters,distribution,roughness of the surface texture as well as the velocity and the load on the hydrodynamic lubrication performance of the textured surface are discussed,and the state-ofthe- art research situation of the hydrodynamic lubrication theory of the surface texture is summarized.Finally,both the problems existing in current surface texturing and the development orientation are pointed out.

A Method to Construct Precise Geometric Model of Teeth Profile of Arbitrary Intersecting Line Gear

CHEN Yang-zhi CHEN Han-fei

2017, 45(9):  12-18.  doi:10.3969/j.issn.1000-565X.2017.09.002

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In order to construct a precise geometric model of the driving and driven teeth of arbitrary intersecting line gear ( LG) by using the 3D CAD software,the construction condition is discussed and obtained,which is that each of the cross-sections of the line teeth should be perpendicular to the corresponding contact line.Under this condition,the equation of the driven center curve is corrected,and then the profile equations of the driving and driven line teeth of arbitrary intersecting LG are deduced.Then,by using the 3D CAD software,a geometrical model of the LG is constructed,and a kinematical simulation is accomplished.The results prove the correctness of the proposed design method for the LG teeth profile.This method provides a geometric basis for the research on the elastic hydrodynamic lubrication theory of line gears.

Type Synthesis of Metamorphic Mechanism Based on Structure Realization of Metamorphic Joint

LIU Jiang-nan ZHANG Wen-bo

2017, 45(9):  19-25,33.  doi:10.3969/j.issn.1000-565X.2017.09.003

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Metamorphic mechanisms are characterized by variable topology structures,and there exists a great difficulty in the type synthesis of the mechanisms.In this paper,by analyzing the constraint variation features and structure realization patterns of metamorphic joints,a type synthesis method is proposed for the metamorphic mechanism.First,the arithmetic operation of constraint functions is adopted to describe the constraint variation features of the joints in three kinds of metamorphosis processes ( namely,the increase,removal and change of types) . Then, the structure design catalogues of metamorphic joints are established by summarizing and designing the structures of general metamorphic joints.On this basis,a source metamorphic mechanism is constructed by using a morphological matrix,and the metamorphic mechanism types are synthesized by solving the constraint variation features of metamorphic joints and by selecting suitable metamorphic structures.A case study shows that the proposed method can synthesize multiple types of the metamorphic mechanisms satisfying function demand,and it can improve the structure and property of the mechanisms.

A Ｒecursive Approach to Tolerance Analysis of Complex Assembly Based on Rigid Body Kinematics

DU Qun-gui ZHAI Xiao-chen WEN Qi YANG Wei-peng

2017, 45(9):  26-33.  doi:10.3969/j.issn.1000-565X.2017.09.004

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In the process of production,the errors of the components of an assembly are inevitable,that is to say,the assembly is actually a system with errors.Hence,it is of great importance to conduct the tolerance analysis of assemblies during the design phase.In this paper,on the basis of the actual geometrical and physical meaning of assemblies,the thought of building the nominal and actual local coordinate systems respectively at the nominal and actual positions of each variable feature is proposed,and in this way,a recursive model is constructed for the tolerance analysis of assemblies.Since the errors of geometrical dimension are usually small,the constructed recursive model is linearized according to the differential transformation of rigid body kinematics,and by taking a complex assembly with parallel dimension chains as an example,a linearized analytic equation of tolerance analysis is obtained.When the above-mentioned new approach is applied to a tolerance analysis,by establishing a common coefficient matrix for different complex assemblies,the calculation work can be reduced and the programming can be facilitated.At last,this paper elaborates on the application of the new approach by using an example.

Investigation into Pressure Drop Characteristics of Flow Channel in Hydraulic Valve Block for TBM

ZHANG Huai-liang PENG Ling ZHOU Jing-xing

2017, 45(9):  34-39,66.  doi:10.3969/j.issn.1000-565X.2017.09.005

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In view of the impact of strong vibration on the internal flow channels in hydraulic valve blocks during the tunneling process of tunnel boring machines ( TBM) ,the flow field simulation models of three typical flow channels of U-shape,Z-shape,V-shape under foundation vibration are constructed,and they are validated by experiments.Then,the influences of the vibration direction and intensity on the pressure drop characteristics of the typical flow channels are analyzed by simulations.The results indicate that the pressure drop of the flow channels in the hydraulic valve blocks under the foundation vibration fluctuates periodically with time,the fluctuation amplitude and mean value of the pressure drop increase with the amplification of the vibration intensity,and that,when the flow channels are placed in the hydraulic valve blocks,the vibration in the Y direction should be avoided in the Ushaped flow channel,the vibration in the X direction should be avoided in the Z-shaped flow channel,and the vibration in the Z direction should be avoided in the V-shaped flow channel.The conclusions can provide a theoretical basis for the structural design of hydraulic valve blocks under foundation vibration.

Design of an Automatic Control System for Magnetic Controlled Narrow-Gap TIG Arc Welding of Thick Plates

JIA Chuan-bao DU Yong-peng WU Chuan-song YUAN Xin

2017, 45(9):  40-46.  doi:10.3969/j.issn.1000-565X.2017.09.006

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In the investigation,first,an automatic control system of narrow-gap magnetic controlled tungsten inert gas ( TIG) arc welding for thick plates is designed,and the principle of avoiding the defect of incomplete penetration on side walls by adopting an alternatively-changed magnetic field to deflect welding arc towards left or right periodically is introduced.Next,by taking a programmable logic controller ( PLC) as the core and based on its characteristic,a control system is overall designed,and two independent arc length control systems are designed to keep the tungsten electrode exactly in the middle of the gap and at a relatively constant height.Then,a sensing and motion control system is designed and established,and effective protection of weld seam is realized by employing high-precision gas sensors to detect and control the actual flow rate of shielding gas and by implementing the realtime measurment and control of the distance between the shielding covering and the substrate.Finally,a suitable welding power source is selected and modified to realize a digital control,and a vision monitoring system for industry is set up.The results of welding experiments on thick titanium plates demonstrate that the designed automatic control system is reliable and stable,and it has the potentiality to be promoted in industry.

Food Science & Technology

Effects of Oxidation and Etherification Dual-Modification on Physicochemical Properties of Corn Starch

GAO Qun-yu DAI Gui-fang LI Hang WU Lei

2017, 45(9):  47-52.  doi:10.3969/j.issn.1000-565X.2017.09.007

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By taking the corn starches of different amylose contents as raw materials and by fixing the dosage of propylene oxide and sodium hypochlorite,an oxidation and etherification dual-modification was carried out so as to reveal the effects of the modification sequence on the physicochemical properties of the corn starches.Then,the modified corn starches were analyzed in terms of transparency and Brabender viscosity,and they were characterized by means of XRD.Experimental results show that ( 1) the carbonyl and carboxyl of the oxidized-hydroxypropylated starches have higher molar substitution degrees,while the hydroxypropyl of the hydroxypropylated-oxidized starches has a higher one; ( 2 ) the transparency of the oxidized-hydroxypropylated starches is higher than that of the hydroxypropylated-oxidized starches; ( 3) the peak viscosity of the hydroxypropylated-oxidized starches is higher than that of the oxidized-hydroxypropylated starches; ( 4) both the two kinds of modification do not change the crystal form of starch molecules; ( 5) the dual-modification is closely related to the modification order,and the first reaction plays a leading role; and ( 6) lower amylose content is beneficial to the oxidative modification,while higher amylose content is beneficial to the hydroxypropyl modification.

A Hydrolyzing Method of Neutral Sugar in Sugar Beet Pectin and Their Quantitative Analysis

YU Shu-juan WANG Zhi-ming GUO Xiao-ming LI Tai-hong AI Chao GUO Xiao-bing

2017, 45(9):  53-59.  doi:10.3969/j.issn.1000-565X.2017.09.008

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In order to determine the variety and contents of the neutral sugar in sugar beet pectin ( SBP) ,a twostep hydrolysis method was proposed for the SBP.In the method,the neutral sugar in the SBP were sequentially hydrolyzed by using pectinase and trifluoroacetic acid ( TFA) .First,the SBP was degraded into the fractions of smaller relative molecular mass by pectinase.Second,the neutral sugar attached to the SBP were liberated into solution by TFA.Among three commercial pectinases,Rapidase C80 was selected as the objective pectinase because of its lower endogenous monosaccharide content and better hydrolyzing activity.It is found that the optimal hydrolysis parameters of C80 are 50℃,pH 5 and 15 h.Moreover,the effects of the TFA concentration,the temperature and the hydrolysis duration on the hydrolysis of the neutral sugar were further investigated.By compromising the hydrolysis rate and the degradation rate of the neutral sugar,suitable TFA concentration,temperature and hydrolysis duration were respectively determined to be 1mol /L,110℃ and 4 h.The HPAEC analysis results show that the proposed method has a good effect in achieving rhamnose through hydrolysis,and it exhibits a good stability and a high repeatability,which means that this method can be used to quantitatively analyze the neutral sugar in the SBP.

Modification of Physicochemical Properties of Soy Protein Isolate by Soybean Soluble Polysaccharide

QI Jun-ru CAO Jing CHENG Meng WENG Jing-yi ZHANG Xi YANG Xiao-quan

2017, 45(9):  60-66.  doi:10.3969/j.issn.1000-565X.2017.09.009

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Soy protein isolate ( SPI ) -soybean soluble polysaccharide ( SSPS) conjugates ( SSC) were prepared through a Maillard reaction at 60℃ for seven days with a relative humidity of 79%.Then,the product was separated into two components ( namely,SC45 and SC65) on the basis of their solubility at pH4. 5 ( near the isoelectric point of the SPI) and pH6. 5 ( neutral condition) respectively.Finally,the two components were characterized through SDS-PAGE and were analyzed in terms of turbidity,particle size and Zeta potential.The results show that ( 1) the graft of a higher relative molecular mass forms after the reaction,and each subunit in the 7S and 11S of the SPI is involved in the glycation reaction; ( 2) the graft degrees of the two components are respectively up to 41. 79% and 36. 75%; ( 3) in acid conditions,the turbidity of SC45 is significantly lower than that of SC65,meaning that SC45 has a better solubility near the isoelectric point and can effectively reduce the self-aggregation of the protein; and ( 4) the stability of the SSC depends on the steric hindrance caused by the hydrophilic side chains of the SSPS.

A Kinetic Model of Extracting Polysaccharides from Hemerocallis citrina by Combining Rectangular High Pulsed Electrical Field with Ultrasound

LU Hai-qin LI Yi-hua LI Dong-mei YANG Ｒi-fu HANG Fang-xue ZHANG Li-chao FAN Xiao-dan

2017, 45(9):  67-73,87.  doi:10.3969/j.issn.1000-565X.2017.09.010

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On the basis of the Fick's second law,a kinetic model was constructed to describe the extraction of Hemerocallis citrina polysaccharides in a rectangular high pulsed electrical field with ultrasound.Then,the changes of the extraction yield with time at different ultrasound powers and electric voltages were measured and as a result,the constructed kinetic model was verified.Finally,the corresponding kinetic parameters were obtained.The results show that the constructed kinetic model can well reflect the effective diffusion coefficient and the function relationship between the ultrasound power and the electric voltage in the extraction process,and the correlation between the experimental values and the predicted ones is comparatively obvious ( r2 = 0. 9286) .The construction of the kinetic model and the solution of the parameters help to design and improve the high pulsed electric field extraction technology with ultrasound.

Preparation of D-Isoascorbyl Oleate and It Structural Characterization

LIU Guo-qin WANG Ling-li LIU Xin-qi

2017, 45(9):  74-80.  doi:10.3969/j.issn.1000-565X.2017.09.011

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D-isoascorbyl oleate ( IAO) was synthesized by using non-aqueous lipizyme 435 as the biocatalyst and oleic acid as the acyl donor,and the yield of the product was quantified by means of HPLC.Then,the factors influencing the synthesis of IAO were screened by single factor tests,and a Box-Behnken model between the IAO yield and the screened factors ( namely,reaction time,temperature,and molecular sieve dosage) was constructed by means of JMP software.Consequently,this model was used to optimize the synthesis conditions of IAO through the response surface methodology.Finally,the structure of the synthesized IAO was characterized by means of FTIR and NMR.The results showed that,under the optimal conditions,that was,when a oleic acid-to-D-isoascorbyl acid molar ratio of 3∶ 1,a lipase dosage of 3%,an oleic acid concentration of 0. 6mol /L,a reaction temperature of 53. 3℃,a molecular sieve dosage of 150 g /L and a reaction time of 21. 3 h,the predicted IAO yield and the tested one was 78. 40% and ( 74. 65 ± 1. 50) %，respectively,which indicated oleic acid was introduced into the sn-6-hydroxy group of D-isoascorbic acid,and therefore the synthesized IAO was mainly D-isoascorbic acid-6- oleate.

Identification of a Bacillus coagulans and Production of High Optical Purity L-Lactic Acid via Synchronous Saccharifying Fermentation

LIU Dong-mei ZHOU Quan-xing ZHOU Jin-song

2017, 45(9):  81-87.  doi:10.3969/j.issn.1000-565X.2017.09.012

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A Bacillus coagulans ( BCS 13002) isolated from pickle was identified by using 16S RNA and on the basis of physiology and biochemistry,and the effects of carbon source and neutralizer on the production of L-lactic acid were analyzed.Then,the fed-batch fermentation with glucose and the synchronous saccharifying fermentation ( SSF) with corn starch were respectively carried out at 5L fermentation tanks.The results show that ( 1) glucose is a kind of ideal carbon source,while xylose and corn starch are not beneficial to the production of L-lactic acid; ( 2) as a kind of neutralizer,NaOH is better than Ca( OH) ₂ and CaCO₃ ; ( 3) through the fed-batch fermentation with glucose in a tank,the L-lactic acid content reaches up to 115. 86 g /L with a sugar acid conversion ratio of about 82. 31%,and MnSO₄·H₂O and MgCl₂·6H₂O play a special role in the fermentation; and ( 4) through the synchronous saccharifying fermentation with corn starch,the L-lactic acid content reaches up to 123. 3 g /L,with a sugar acid conversion ratio of 70. 03 % and an optical purity of L-lactic acid of more than 99. 8%.

Materials Science & Technology

Structure Performance of Calcium Silicate Board /Fiber-Reinforced Foamed Concrete Sandwich Panel Under Compression

YU Qi-jun LIN Qiu-wang LI Fang-xian WEI Jiang-xiong ZHANG Tong-sheng HU Jie

2017, 45(9):  88-95.  doi:10.3969/j.issn.1000-565X.2017.09.013

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Foamed concrete sandwich panels were prepared by using calcium silicate boards as the skin layer and fiber-reinforced foamed concrete as the core material.Then,the influence of the polypropylene fiber dosage and the core material density on the structure performance of the prepared sandwich panels under compression was investigated,and the stress-strain curve equations were established through the regression analysis of compressive stressstrain curves.The results show that ( 1) as the fiber dosage in the core material increases from 0 to 2 kg /m³,the crack number of the core material decreases,while the compressive strength and the compressive toughness index increase respectively by 76. 08% and 30. 03%; ( 2) as the core material density increases from 400 kg /m³ to 600 kg /m³,the failure mechanism of the prepared sandwich panels gradually changes from single damage to overall destruction,with a greater increase in the compressive strength but a smaller increase in the compressive toughness index; ( 3) the stress-strain curves of the prepared sandwich panels can be divided into four stages,namely,elastic strain,stress hardening,strain softening and failure; ( 4) the peak strain increases with the increase of the fiber dosage,while the core material density has less effect on the peak strain; and ( 5) interface cracks and a delamination phenomenon may occur in the prepared sandwich panels under compression.

Evaluation of Deterioration of Cement Paste Under Coupled Effects of Organic Acids and Scour

YIN Su-hong LI Rong HU Jie HUANG Hao-liang

2017, 45(9):  96-101,109.  doi:10.3969/j.issn.1000-565X.2017.09.014

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The deterioration of cement paste exposed to artificial organic acid solution involved in biological metabolism and a scour of 2m/s was evaluated,in terms of the erosion depth,the decrease of calcium hydroxide content and the loss of mass per unit area of sample surface.The acceleration of deterioration of cement paste caused by the scour of solution was investigated by comparing to the deterioration under static immersion.The results show that ( 1) the erosion depth and the loss of mass per unit area of sample surface under the coupled effects of organic acids and scour are 2. 72 times and 3. 77 times those in static organic acid solutions,respectively; ( 2) the coupled effects of the organic acids and the scour significantly accelerate the deterioration of cement paste; and ( 3) the loss of mass per unit area of sample surface fully reflects the chemical erosion effect of the organic acids and the physical effect of the scour,meaning that this index is suitable to evaluate the deterioration of cement-based materials.

Reaction Mechanism of Compensating Shrinkage of Inorganic Polymer Pastes by Using Reactive MgO

YANG Yong-min LI Zhao-heng ZHANG Tong-sheng YIN Su-hong WEI Jiang-xiong CHEN Xiao-wen YU Qi-jun

2017, 45(9):  102-109.  doi:10.3969/j.issn.1000-565X.2017.09.015

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In order to compensate the shrinkage of inorganic polymer pastes uniformly and quickly,reactive MgO powders were evenly dispersed in the inorganic polymer pastes,and the deformation,mechanical property,microstructure and component of the inorganic polymer pastes doped with the reactive MgO were investigated.The results indicate that,when the dosage of the reactive MgO is 6%,the chemical shrinkage,autogenous shrinkage and drying shrinkage of the inorganic polymer pastes decrease respectively by 10. 7% at 28d,72. 1% at 7d and 20. 0% at 28 d,which means that the shrinkage of the inorganic polymer pastes in a hardening process is effectively compensated by the reactive MgO,In addition,after the reaction of the reactive MgO with the water in a high-alkalinity liquid-phase environment,fine wormlike Mg( OH) ₂ crystal forms and causes a uniform expansion in the inorganic polymer pastes,which refines the pore size of the inorganic polymer pastes and enhances their compressive strength,so that the compensation of the reactive MgO for the shrinkage of the inorganic polymer pastes is accomplished.

Fluorescence Properties of Tunable Luminescence Color CMC-Tb /Eu Nano Complexes Synthesized via Microwave-Assisted Heating

YE Jun LIANG Wei-peng XIONG Jian

2017, 45(9):  110-117.  doi:10.3969/j.issn.1000-565X.2017.09.016

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A series of novel tunable luminescence color CMC ( Carboxymethyl Cellulose) -Tb /Eu nano complexes were synthesized via the coprecipitation reaction with microwave-assisted heating.Then,the morphology,structure,fluorescence properties and energy transfer characteristic of the synthesized nano complexes were investigated by means of SEM-EDS,TEM,XPS,UV-Vis,PL spectra and decay lifetime.The results show that ( 1) as compared with CMC,there exist more cracks on the surface of the synthesized CMC-Tb /Eu nano complexes; ( 2) in the nano complexes,small solid particles cluster on the surface of CMC,and the average size of the particles is 75 ～ 98 nm; ( 3) the O atoms in —OH,—COO^- and —COC— of the molecular chain of CMC bond with Tb3 + or Eu³⁺ in the synthesized nano complexes ionically and covalently; ( 4) CMC is the main energy acceptor,and in the energy transfer between CMC and Tb or between CMC and Eu,the efficiency of transferring energy from CMC to Tb3 + is higher than that to Eu³⁺ ; ( 5) under a 350 nm excitation,the ⁵D₄→ ⁷F₅ ( 544 nm) and ⁵D₄→ ⁷F₆ ( 489 nm) transitions of Tb³⁺ appear in the emission spectrum of CMC-Tb /Eu; ( 6) the two peaks respectively locating at around 589 nm and 616 nm result from the overlapping of the transitions ( ⁵D₄ →⁷F₃ and ⁵D₄ →⁷F₄ ) of Tb³⁺ and the transitions ( ⁵D₀ →⁷F₁ and ⁵D₀ →⁷F₂ ) of Eu³⁺ ,respectively; and ( 7) the tunable luminescence color is realized.The intensity change of ⁵D₄ →⁷F₅ of Tb³⁺ and the luminescence lifetime change of the synthesize nano complexes demonstrate that the energy transfer of Tb( Ⅲ)→ Eu( Ⅲ) exists in the synthesized nano complexes.

Preparation and Properties of Composite Paper-Based Supercapacitors with Nanocellulose

CHEN Gang LIN Dong-han FANG Zhi-qiang

2017, 45(9):  118-127.  doi:10.3969/j.issn.1000-565X.2017.09.017

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Nanocellulose ( NFC ) /reduced graphene oxide ( RGO) ( NR) and NFC /RGO/ polyaniline ( PANI) ( NRP) paper-based electrodes were prepared by means of the ultrasonic irradiation of a suspension of nanocellulose,reduced graphene oxide ( RGO) and polyaniline ( PANI) and vacuum filtration.Meanwhile,the relationship between the carboxyl content of NFC and the electrical properties of the electrodes as well as that between the carboxyl content of NFC and the mechanical properties of the electrodes was discussed,so as to achieve composite paper- based electrodes of better electrochemical properties.Finally,by taking polyving akohol /sulfuric acid ( PVA/ H₂SO₄ ) as the electrolyte,two composite paper-based supercapacitors named NRS and NRPS were prepared respectively with NRand NRP.The results show that ( 1) by controlling the ratio of NFC,RGO and PANI,hydrophilic NFC can effectively decrease the restacking between RGO and PANI,meanwhile,the hydrophilic properties of NFC can effectively improve the diffusion of electrolyte ions; ( 2) increasing the carboxyl content of NFC helps to enhance the combination of composite materials,thus improving the electrical properties and mechanical properties of the composite paper-based electrodes; and ( 3) when the mass ratio of NFC,RGO and PANI is 5∶ 3∶ 3 and the current density is 0. 5A/g,the NRPS paper-based supercapacitor is of a specific capacitance of 305 F /g,and 98. 3% of the specific capacitance is retained after 1000 charge-discharge cycles,which means that this supercapacitor is of better electrochemical cycle stability.

Analysis on Thermal Performance of Carbon Fiber Coating

LI Jing LI Xue LIU Ye-ming WU Shao-ru

2017, 45(9):  128-134.  doi:10.3969/j.issn.1000-565X.2017.09.018

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As the working temperatures of electronic modules directly affect their service life and stability,the corresponding heat emission problem should be solved,so as to ensure their working reliability.Radiant coatings are effective in cooling electronic modules.In the investigation,a new type of composite radiant coating was prepared with carbon fibers as the main thermal conductive fillers and an acrylic-amino resin system as the matrix.Then,by means of the single factor method，the effect of the content of carbon fibers on the heat dispersion of the coating was discussed.The results show that，as the content of carbon fibers increases,the heat dispersion and heat conduction coefficient of the coating both tend to increase firstly and then decrease,and that,when the mass fraction of carbon fibers is 12. 3%,the coating achieves a best heat dispersion effect and exhibits an excellent comprehensive performance,specifically,the adhesion,hardness and heat conduction coefficient of the coating are respectively 1st grade,grade H and 1. 61 W/( m·K) ) .Furthermore,the surface structure of the coating was characterized by means of SEM,and the thermal conductivity was measured.Finally,the mechanism of the heat conduction was also explored.It is found that the addition of carbon fibers into the coating causes a kind of heat-transfer channel for fast heat conduction to form,and there exists an optimal dosage of carbon fibers.Specifically,due to the packing phenomenon and anisotropy of carbon fibers,excessive carbon fibers will cause the heat dispersion effect to degrade.

Evolution of Corrosion Products of Carbon Steels and Galvanized Steel in Simulated Marine Atmosphere

GAO Yan HUANG Yin-hui MENG Xiao-bo LIAO Yong-li LI Ｒui-hai

2017, 45(9):  135-141.  doi:10.3969/j.issn.1000-565X.2017.09.019

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In order to investigate the evolution of the composition and form of steel corrosion products with time in simulated marine atmosphere,Q235,Q345 and galvanized Q235 steels were exposed in neutral salt spray boxes for 2,6,24,48,144,240,360h.Then,the corrosion rates were calculated via the weight loss method,and the corrosion products were characterized by means of XRD and SEM.The results show that ( 1) the corrosion kinetics curves of the three kinds of steels follow the bilogarithmic equation; ( 2) the galvanized Q235 steel has a much lower corrosion rate than Q235 and Q345 steels,while the corrosion rate of Q235 steel is close to that of Q345 steel; ( 3) the corrosion products forming on Q235 and Q345 steels are mainly α-FeOOH,β-FeOOH,γ-FeOOH and Fe₃O₄ ,and the change rules of these products with the spraying time are different; ( 4) different corrosion products exhibit different topographic characteristics,specifically,γ-FeOOH ,β-FeOOH and less reported Fe₃O₄ are respectively flower-like,cotton ball-like and spinelle-like; and ( 5) as compared with the two kinds of carbon steels,the galvanized Q235 steel has a more compact rust layer.

Adjusting Method of Multi-Point Flexible Stretch-Bending Forming Die Head of Profiles

LIANG Ce ZHAO Hong-wei LI Yi LIANG Ji-cai

2017, 45(9):  142-146.  doi:10.3969/j.issn.1000-565X.2017.09.020

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In order to increase the manufacturing accuracy of the multi-point flexible three-dimensional stretch-bending forming parts of profiles and to determine die-head adjusting parameters quickly and precisely,the intersection of the horizontal axis and the vertical axis in the die unit is defined as the shape-controlling point during the multipoint die rotation forming process according to the geometric relationship between the die head and the profile forming shape.Meanwhile,the curve composited by the shape controlling points in the horizontal direction is defined as the horizontal shape-adjusting line.Then,the relationship between the shape-controlling points in the vertical direction and the adjusting curve of the forming parts is further investigated,and the calculation formulas of the deformation parameters for the die-head shape-adjusting forming process are derived.This method simplifies the adjusting process,and it is of broad applicability.