Study on Peat-Forming Mechanism of Tropic and Sub-TropicTidal Flats

Tropic and sub-tropic tidal flats (generalised) are a kind of speific peat-forming environments. Taking the Mangrove tidal flats and mangrove pets in Hainan island as a example, the authors deeply study and discuss the peat-forming mechanism of tropic and sub-tropic tidal flats. The conclusions are as follows: intrusion accretiou of plant organic matter is more important ; the organic matter has accumulated witk high productivity, high return rate and high decompeition rate ;anaerobic bacterin play a more important role during early peatification ; sea level change is the fundameutal factor controlling the formation and evolution of tidal flat peat-forming environments; lagoon peat-flat and delta peat-flat are main types of tidal flat peat-forming euvironments ;tidal flat peat-forming environments are remarkably characterized by low-level and rabe properties.

Product Development of High Strength and Toughness Spring Flat Steel

With the continuous development of mechanical industry,higher requirements are put forward for the comprehensive properties of spring steel.The chemical composition and production process of spring flat steel are designed to meet the requirements of high strength and high toughness of spring flat steel,through the test,the product surface quality and internal quality all meet the national standards,the performance indicators to meet user requirements.

Simulation and Analysis of Spatial Weft Insertion Mechanism Considering Flexibility and Clearance

A 3D model of the spatial four-bar weft insertion mechanism was built with unigraphics NX(UG) according to the actual requirement,and dynamics simulation was carried out by importing the model into ADAMS.Without considering the clearance,the motion characteristic curve of the sword belt was generated through ADAMS combined with MATLAB.In this paper the hinge between the rod and the sector gear was selected as an example with different values of clearance,outputting the motion characteristic curve of the sword belt.Finite element analysis(FEA)was conducted,the flexible body was generated by importing the forked frame into ANSYS,and flexible dynamics simulation was carried out by importing the flexible body into ADAMS to replace the rigid rod.A comprehensive comparison of the output characteristics of the sword belt was conducted in the consideration of the clearance or flexible.Analysis of the force on the left hinge of the rod was carried out with the ADAMS post processing module.With the same clearance,considering the flexibility,amplitude of fluctuation of the force on the hinge increased obviously.

A Hand Prosthesis with an Under-Actuated and Self-Adaptive Finger Mechanism

One of the major problems faced by hand amputees is the unavailability of a lightweight and powered multi-functional hand prosthesis. Under-actuated finger designs play a key role to make the hand prosthesis lightweight. In this paper, a hand prosthesis with an under-actuated and self-adaptive finger mechanism is proposed. The proposed finger is capable to generate passively different flexion/extension angles for a proximal interphalangeal (PIP) joint and a distal interphalangeal (DIP) joint for each flexion angle of metacarpophalangeal (MCP) joint. In addition, DIP joint is capable to generate different angles for the same angle of PIP joint. Hand prosthesis is built on the proposed finger mechanism. The hand prosthesis enables user to grasp objects with various geometries by performing five grasping patterns. Thumb of the hand prosthesis includes opposition/apposition in addition to flexion/extension of MCP and interphalangeal (IP) joint. Kinematic analysis of the proposed finger has been carried out to verify the movable range of the joints. Simulations and experiments are carried out to verify the effectiveness of the proposed finger mechanism and the hand prosthesis.

Design and Kinematics Analysis of a Parallel Mechanism to be Utilized as a Luggage Door by an Analogy to a Four – Bar Mechanism

In this study, a luggage door mechanism to be used in commercial vehicles such as midibuses and buses is designed and analyzed. The mechanism is designed as a parallel hinged system. Velocities, rotational veloci- ties and rotational accelerations of selected points on the design are calculated. Furthermore, the experiment- tal model of the design is established and it is seen that the data taken from the model are compatible with the calculated results. The aim of this study is to design a mechanism with the minimal workspace so that the door can be utilized in narrow areas and the ergonomics of the luggage door is improved. Considering both commercial and passenger vehicle sales, vehicle interior and exterior trim features have an exceptionally important role in automotive industry, in addition to vehicle performance characteristics. In today’s compete- tive environment, parts used in a vehicle’s internal and external trim have to meet user demands in terms of ergonomics as well as aesthetics. Due to its similarity to a four-bar mechanism, kinematics analysis of the design was carried out based on a four-bar mechanism, which is used extensively in industry.

扁平大空间船舶火灾烟气控制试验研究

为有效控制扁平大空间船舶火灾烟气蔓延,研究大尺度火灾过程中的油池质量损失速率、舱室温度分布、隔热效率和烟气控制效果。利用尺寸为30 m×24 m×2.3 m的模拟舱,在0.35、0.55和0.70 m等3种不同挡烟垂壁高度和机械通风条件下开展试验。结果表明:挡烟垂壁高度增加,油池质量损失速率峰值减小;挡烟垂壁高度对舱室上层烟气温度的影响比对下层气体温度的影响更明显,1.4 m以上空间温度峰值明显下降,而1.4 m以下空间温度峰值无明显变化。顶棚平均温度和隔热效率随挡烟垂壁高度增加而下降。随挡烟垂壁高度增加,火源区与非火源区同时控烟模式隔热效率从28.2%提升至50.8%,火源区单独控烟模式隔热效率从29.4%提升至54.7%。

三沙湾潮滩涨落潮和大小潮冲淤特征及其动力机制

潮滩不同尺度的变化规律一直是地表过程研究的核心之一。利用声学多普勒流速仪(ADV)、温盐深(CTD)、光学后向散射浊度计(OBS)对三沙湾潮滩涨落潮和大小潮冲淤及动力变化进行了高精度的观测。结果发现,潮周期内,潮滩冲淤呈现涨潮初期冲刷-落潮末期淤积-中间时段稳定的特征,涨潮初期水深<1 m的30 min内平均冲刷4.05 mm,落潮末期水深<1 m的30 min内平均淤积3.72 mm,中间时段动态稳定;大小潮周期内,呈现中潮到小潮平均淤积3.4 mm,小潮到大潮平均冲刷8.2 mm的特征。通过流速、紊动能、水深、悬沙浓度等因子与冲淤的相关性分析发现,潮周期内,流速和紊动能的增减决定涨潮初期冲刷和落潮末期淤积的变化;大小潮周期内,涨潮冲刷大于落潮淤积的特性决定了大潮到小潮阶段的冲刷,涨潮冲刷小于落潮淤积决定了小潮到大潮阶段的淤积。涨落潮周期和大小潮潮周期的冲淤机制为潮滩动力地貌和动力沉积学研究提供了一定的参考。

空间站舱段平转式转位方案设计与验证

根据我国空间站实验舱在转位前后对天/地指向不变的任务需求,提出舱段平转式转位方案,设计基于转位机构的舱段转位实现方案。转位期间,空间站组合体采用重力梯度被动稳定姿态飞行,解决姿态主动停控时空间站稳定指向的难题。通过设计选取合适的转位任务窗口,确保转位全程测控链路畅通、光照充足,以提高任务安全性和可靠性。地面试验和在轨实验舱转位任务实施,全面验证了空间站舱段平转式转位方案的正确性。

FLAT-PRO深水合成基钻井液恒流变作用机理研究

目前,适应于深水、超深水作业的FLAT-PRO恒流变合成基钻井液体系由于其良好的恒流变特性、抗污染能力及储层保护性,已在中国南海成功应用近10井。但是近年来,所钻遇的地层越来越复杂,要求的温度范围和密度范围越来越高,这需要对合成基钻井液恒流变机理有更清楚的认识。文章旨在FLAT-PRO恒流变合成基钻井液体系的基础上,对体系恒流变机理进行研究。体系中的核心处理剂流型调节剂通过氢键作用插入有机土层间,扩大层间距并促进其片层在油中高度分散,温度越高,插入有机土层间的流型调节剂分子越多,补偿由于温度升高导致的粘度降低,从而形成具有温度响应的网架结构。

Quantitative analysis of the morphing wing mechanism of raptors: Analysis methods, folding motions, and bionic design of Falco Peregrinus

Raptors can change the shape and area of their wings to an exceptional degree in a fast and efficient manner,surpassing other birds,insects,or bats.Some researchers have focused on the functional properties of muscle skeletons,mechanics,and flapping robot design.However,the wing motion of the birds of prey has not been measured quantitatively,and synthetic bionic wings with morphing abilities similar to raptors are far from reality.Therefore,in the current study,a 3D suspension system for holding bird carcasses was designed and fabricated to fasten the wings of Falco Peregrinus with a series of morphing postures.Subsequently,the wing skeleton of the falcon was scanned during extending motions using the computed tomography(CT)approach to obtain three consecutive poses.Subsequently,the skeleton was reconstructed to identify the contribution of the forelimb bones to the extending/folding motions.Inspired by these findings,we propose a simple mechanical model with four bones to form a wing-morphing mechanism using the proposed pose optimisation method.Finally,a bionic wing mechanism was implemented to imitate the motion of the falcon wing—divided into inner and outer wings with folding and twisting motions.The results show that the proposed four-bar mechanism can track bone motion paths with high fidelity.

铝合金轨道车辆不同枕梁结构的焊接变形机理及差异性分析

铝合金轨道车辆的枕梁焊接强度要求高,焊接热输入量大,焊后变形严重。为探讨铝合金轨道车辆不同枕梁结构在焊接过程中的变形机理及其差异性,采用两种典型的枕梁结构——A型(中间盖板与筋板拼焊)和B型(中间整体型材)进行了详细的焊接试验。试验包括单件组焊、调修矫形、加工和底架组焊四个步骤,每个步骤后均进行严格的尺寸测量,以监测和分析变形情况。试验结果为:用A型枕梁结构单件组焊后平面度7~9.4 mm,经调修矫形与一次加工完毕组焊至底架之后平面度3~4.9 mm,中心孔偏差1.4~3 mm,空气簧中心孔偏差1~1.9 mm,为满足转向架机构装配需求需要进行二次加工。B型枕梁结构单件组焊后平面度4~5.3 mm,经调修矫形与一次加工完毕组焊至底架之后平面度2 mm以下,中心孔偏差在0.15 mm以下,空气簧中心孔偏差在0.1 mm以下,能够满足转向架机构装配需求,无需再进行二次加工。研究表明,采用中间整体型材的B型枕梁结构在焊接变形控制方面显著优于采用中间盖板与筋板拼焊的A型结构。

缺气保用轮胎静态力学性能分析

以相同花纹的255/45ZRF18缺气保用轮胎和255/45ZR18普通轮胎为研究对象,分析不同负荷和充气压力下轮胎静负荷性能和静态力学特性。结果表明:与普通轮胎相比,充气压力为290 kPa,负荷为700,875和1050 kg时,缺气保用轮胎径向刚性更大,肩部受力更为集中;充气压力为170 kPa,负荷为875 kg时,缺气保用轮胎压力分布更均衡,接地印痕形状矩形比依然稳定。

空间布平板结构力学性能研究

空间布平板结构作为一新型充气结构因其高强度、轻量化以及出色的可设计性,在土木工程领域可应用于屋面板、围护结构和桥梁等,展现出广泛的应用前景。但是目前空间布平板结构的研究较少,缺乏一种简单高效的计算方法。对此建立了一种适用于空间布平板结构在弯曲下的力学模型,并利用包含内压的二维三节点铁木辛柯梁单元进行非线性有限元分析,使用MATLB编写相应的有限元程序对其荷载位移曲线和褶皱荷载进行预测。最终对空间布平板结构进行四点弯曲试验,验证理论的正确性。结果表明该力学模型可以预测空间布平板结构的全过程力学行为。

The Effects of Farmyard Manure and Mulch on Soil Physical Properties in a Reclaimed Coastal Tidal Flat Salt-Affected Soil

Careful soil management is important for the soil quality and productivity improvement of the reclaimed coastal tidal flat saline land in northern Jiangsu Province, China. Farmyard manure（ FYM） and mulch applications, which affect soil characteristics and plant significantly, are regard as an effective pattern of saline land improvement. As a conventional management in the study region, FYM and mulch are used for the amendment of the new reclaimed tidal flat regularly, but little is known about their effects on soil physical properties functioning. A study was conducted on a typical coastal tidal flat saline land, which was reclaimed in 2005, to evaluate the effects of FYM, polyethylene film mulch（PM）, straw mulch（SM）, FYM combined with PM（FYM＋PM）, FYM combined with SM（FYM＋SM）, on soil hydraulic properties and soil mechanical impedance. CK represented conventional cultivation in study area without FYM and mulch application and served as a control. The experiment, laid out in a randomized complete block design with three replications, was studied in Huanghaiyuan Farm, which specialized in the agricultural utilization for coastal tidal flat. Result showed that capillary water holding capacity（CHC）, saturated water content（SWC）, saturated hydraulic conductivity（ Ks） and bulk density（BD）, cone index（CI） were affected significantly by the FYM and mulch application, especially in the 0-10 cm soil layer. FYM and mulch management increased CHC, SWC and Ks over all soil depth in the order of FYM＋SM〉FYM＋PM〉FYM〉SM〉PM〉CK. With the contrary sequence, BD and CI decreased significantly; however, FYM and mulch application affected BD and CI only in the upper soil layers. CHC, SWC and Ks decreased significantly with the increasing of soil depth, BD and CI, and a significant liner equation was found between CHC, SWC, Ks and BD, CI. With the highest CHC（38.15%）, SWC（39.55%）, Ks（6.00 mm h-1） and the lowest BD（1.26 g cm-3） and CI（2.71 MPa）, the combined management of FYM and SM was recommend to be an effective method for the melioration of reclaimed coastal tidal flat saline soil.

Mechanical Properties of QFP Joints Soldered with SnAgCu and SnPb Solders

With the development of lead-free solder alloys, the investiagtion focusing on the relibility of lead-free solders are essential. Since the reliability database of lead-free solder joints needs to be further supplied, the creep behavior of SnAgCu soldered joints on Quad Flat Package （QFP） devices under thermo cycling load are studied in this paper, compared to conventional SnPb solder, by finite element simulation based on Garofalo-Arrhenius creep model. Meanwhile, the mechanical properties of SnAgCu and SnPb soldered joints in the pitches of QFP devices are also carried out by means of tensile test. The results indicate that the values of strain and stress of SnAgCu soldered joints were all smaller than those of SnPb under thermal cycling, and the tensile strength of the joints soldered with SnAgCu solder was higher than that of SnPb, which means the reliability of the joints soldered with SnAgCu solder is better than SnPb soldered joints. As the fracture surface morphology of the soldered joints compared, SnAgCu soldered joint presented ductile fracture, while the fracture mechanism of SnPb solder joints displayed both brittle and ductile fracture. Above all, the experimental results is in accord with that of simulation, which will provide guidance for reliability study and application of lead-free solders.

Friction self-piercing riveting(F-SPR)of aluminum alloy to magnesium alloy using a flat die

Friction self-piercing riveting(F-SPR)process based on a pip die has been invented to solve the cracking problems in riveting high-strength and low-ductility light metals,such as magnesium alloys,cast aluminum,and 7 series aluminum alloys.In this paper,in order to solve quality issues caused by the misalignment between rivet and pip-die in F-SPR,a flat-die based F-SPR process was proposed and employed to join 1.27 mm-thick AA6061-T6 to 3 mm-thick AZ31B.The results indicate that a 1.0 mm die distance is effective to avoid rivet upset and insufficient flaring.As the feed rate increases,the heat input in the whole process decreases,resulting in a larger riveting force,which in turn increases both the bottom thickness and interlock amount.Besides,solid-state bonding,including Al-Mg intermetallic compounds(IMCs),Al-Mg mechanical mixture,and Al-Fe atom interdiffusion was observed at the joint interfaces.The upper Al layer was softened,but the lower Mg layer was hardened,and both sheets exhibited a narrowed affected region with the increase of feed rate,while the rivet hardness shows no obvious change.Three fracture modes appeared accompanying the variations in lap-shear strength and energy absorption as the feed rate increased from 2 mm/s to 8 mm/s.Finally,the F-SPR process using a flat die was compared to those using a pip die and a flat bottom die to show the advantage of flat die on coping with the misalignment problem.

Static Radical Stiffness and Contact Behavior of Nonpneumatic Mechanical Elastic Wheel

Conventional pneumatic tires exhibit disadvantages such as puncture,blowout at high speed,pressure maintenance,etc.Owing to these structural inevitable weaknesses,non?pneumatic tires have been developed and are investigated.A non?pneumatic mechanical elastic wheel(NPMEW)is introduced and investigated as a function of static radical stiffness characteristics and contact behavior.A bench test method is utilized to improve the riding comfort and the traction traffic ability of NPMEW based on tire characteristics test rig,and the static radical stiffness characteristics and the contact behavior of NPMEW are compared with that of an insert supporting run?flat tire(ISRFT).The vertical force?deformation curves and deformed shapes and contact areas of the NPMEW and ISRFT are obtained using a set of vertical loads.The contact behavior is evaluated using extracted geometrical and mechanical feature parameters of the two tires.The results indicate that the NPMEW appears to exhibit considerably high radical stiffness,and the numerical value is dependent on the mechanical characteristic of the flexible tire body and hinge units.NPMEW demonstrates more uniform contact pressure than ISRFT within a certain loading range,and it can efficiently mitigate the problem of stress concentration in ISRFT shoulder under heavy load and enhance the wear resistance and ground grip performances.

Non-pneumatic mechanical elastic wheel natural dynamic characteristics and influencing factors

Non-pneumatic tire appears to have advantages over traditional pneumatic tire in terms of flat proof and maintenance free.A mechanical elastic wheel(MEW) with a non-pneumatic elastic outer ring which functions as air of pneumatic tire was presented.The structure of MEW was non-inflatable integrated configuration and the effect of hinges was accounted for only in tension. To establish finite element model of MEW, various nonlinear factors, such as geometrical nonlinearity, material nonlinearity and contact nonlinearity, were considered. Load characteristic test was conducted by tyre dynamic test-bed to obtain force-deflection curve. And the finite element model was validated through load characteristic test. Natural dynamic characteristics of the MEW and its influencing factors were investigated based on the finite element model. Simulation results show that the finite element model closely matched experimental wheel. The results also show that natural frequency is related to ground constraints, material properties, loads and torques. Influencing factors as above obviously affect the amplitude of mode of vibration, but have little effect on mode of vibration shape. The results can provide guidance for experiment research, structural optimization of MEW.

Mechanical properties of QFP micro-joints soldered with lead-free solders using diode laser soldering technology

Soldering experiments of quad flat package(QFP) devices were carried out by means of diode laser soldering system with Sn-Ag-Cu and Sn-Cu-Ni lead-free solders, and competitive experiments were also carried out not only with Sn-Pb eutectic solders but also with infrared reflow soldering method. The results indicate that under the conditions of laser continuous scanning mode as well as the fixed laser soldering time, an optimal power exists, while the optimal mechanical properties of QFP micro-joints are gained. Mechanical properties of QFP micro-joints soldered with laser soldering system are better than those of QFP micro-joints soldered with IR reflow soldering method. Fracture morphologies of QFP micro-joints soldered with laser soldering system exhibit the characteristic of tough fracture, and homogeneous and fine dimples appear under the optimal laser output power.

RELIABILITY-BASED ANALYSIS AND SYNTHESIS OF MECHANICAL ERROR FOR PATH GENERATING LINKAGES

A reliability-based analysis approach to mechanical error in path generating linkages is pre- sented . The reliability index is taken as a measure for the deviation of the actual path of a coupler point from the desired one. A reliability-based synthesis procedure of the mechanical error for path generating linkages to allocate optimal tolerances and clearances is developed. A four-bar path generating mechanism is considered for numerical illustration.