水下金刚石绳锯机切割动力学特性研究

水下金刚石绳锯机是一种柔性切割工具,其安全、环保,近年来发展非常迅速。绳锯机切割过程中的振动不仅会影响切割效率,而且会降低其使用寿命,进而会影响水下作业施工。文中简要介绍了绳锯机构成,分析了其切割系统的动力学特性,建立了动力学方程,求解方程从而获得以串珠绳锯张力变化描述的纵向振动特性。并进一步分析了串珠绳横向振动特性,结合绳锯机切割系统的实际参数,进行了仿真及试验研究。结果表明:纵向和横向振动会发生一定的耦合,当实际切割频率接近系统的共振频率时,串珠绳锯会发生较大的振动,引发一系列不良的后果,必须通过调节参数,避免这种现象的发生。     

水下金刚石绳锯机切割管道特性参数研究

水下金刚石绳锯机是近年发展起来的一种清洁环保的水下作业机械。介绍了其构成及工作原理。分析了单个串珠切割过程中的受力,针对管道的切割,建立了其力学模型,通过对模型的分析,获得了绳锯切割过程中串珠所受压力的计算公式。为使串珠绳锯在切割过程中能够实现一定的周向自转,需预先在串珠绳锯上施加一定的扭矩,得出了相应的计算关系式。搭建了水下绳锯机试验系统,对串珠绳锯切割过程中的特性进行了试验研究。结果表明:试验结果比较符合相应的理论,该结果为水下绳锯机切割过程参数的进一步合理优化选择提供了依据。     

金刚石绳锯振动信号检测与分析

研究了金刚石绳锯机在锯切花岗石时串珠绳的振动。通过高精度位移传感器采集串珠绳振动信号,并通过零均值化、坏点剔除及消除线性趋势项等一系列方法对检测信号进行了分析处理,利用相同加工条件下均方根值的稳定性对信号的数据处理方法进行了验证。处理前,三组信号的均方根值最大差值为11.91 mm,误差率高达79.27%。经过处理后,三组信号均方根值的最大误差率控制在1.3%以内,证明了信号处理方法的可行性及有效性。试验为绳锯加工过程中振动信号的采集和分析搭建了较好的平台,并为信号的进一步分析和处理提供依据。     

海洋废弃平台桩基拆除绳锯机多扰动定位夹紧力研究

海洋废弃平台桩基拆除绳锯机是一种复杂的机电设备,夹紧力的选择,直接关系到绳锯机的安全稳定工作。分析了桩基夹紧时的截面弯矩和变形量,得到了废弃平台桩基失稳临界力计算方法。利用有限元法分析了桩基夹紧时的变形和受力。采用非线性模型求解出了不同失稳临界力条件下的夹紧瓣夹紧力。实验表明,满足桩基不同失稳临界力条件下,绳锯机夹紧装置的夹紧力能够保证绳锯机安全工作。该结果为绳锯机的水下可靠性工作打下了一定基础。     

水下绳锯机切割油气管道锯切参数优化研究

水下绳锯机是一种快速发展的清洁环保切割工具,在水下油气管道出现问题时,可以采用其切割维修。水下切割的成本很高,要求绳锯机在工作中不更换绳锯的前提下高效完成切割,这就要求对管道切割过程中的参数进行优化。文中通过三因素三水平两指标的正交实验方法,得出了绳锯机切割过程中,不同截面位置处的切割速度、进给速度和串珠绳张紧力的最佳组合值。水下切割实验表明,该结果达到了预期目标,从而为绳锯机的水下切割最佳控制提供了一定的基础。     

海洋废弃平台桩基拆除绳锯机夹紧力的研究

介绍废弃平台桩基拆除水下绳锯机的组成和工作原理。对夹紧装置进行力学模型简化,从理论上证明绳锯机夹紧装置能够满足形封闭条件,可以使绳锯机稳定地固定在平台桩基上。分析绳锯机夹紧时的受力情况,根据最小值原理得出了绳锯机夹紧力求解的数学模型。按照水下绳锯机的实际工况对夹紧力进行求解,该结果为绳锯机的夹紧装置结构设计和液压系统设计提供理论依据。     

锯切参数对串珠绳振动特性的影响

利用六个激光位移传感器对锯切加工花岗石过程中串珠绳的振动进行跟踪,利用MATLAB软件分析采集来的振动信号,从频率和幅值两个方面来研究锯切过程对串珠绳振动的影响.试验结果表明,串珠绳在非切削过程中的振动信号含有多个主频率,但是进入切削过程后,其主要振动频率为串珠的冲击频率.切削过程的振动信号幅值比非切削过程中振动信号的...     

海洋废弃平台桩基拆除绳锯机液压系统可靠性研究

海洋废弃平台桩基拆除绳锯机是一种近年发展起来的新型水下切割机具,液压系统为其提供动力。可靠的液压系统是绳锯机安全、稳定工作的保障。设计了绳锯机液压系统,分析了液压系统的可靠性理论,得到了废弃平台桩基拆除绳锯机液压系统逻辑图。根据绳锯机的具体水下工作环境和条件,研究并计算了其液压系统可靠性,为绳锯机的安全稳定工作打下了一定基础。实验表明,绳锯机液压系统可靠性满足设计要求。     

海洋废弃平台桩基拆除绳锯机驱动系统控制研究

伴随着海洋油气田多年的开采,越来越多的废弃平台需要分解处理,切割是非常重要的一道工序。平台水下桩基切割可以采用绳锯机来完成,考虑到桩基的直径较大,研发的绳锯机切割框架包含4个绳轮,其中驱动轮为相邻两个。为了安全高效切割,必须使两个驱动轮保持同步。建立驱动轮同步工作的动力学模型,提出同步耦合控制方法。结合绳锯机的实际结构,对控制方法进行仿真分析和实验研究。结果表明:该控制方法能够满足绳锯机的水下切割要求,为绳锯机的高效稳定工作打下了一定理论基础。     

水下绳锯机切割参数分析优化

海洋工程中,出于维修需求或者环保要求,需要进行水下切割,切割作业可以采用绳锯机完成。水下绳锯机是一种柔性磨削切割机械,具有可切割多种材质、清洁环保的特点。合适的切割参数是保证绳锯机安全、高效工作的前提。分析了绳锯机切割过程中的影响因素,以质量功能配置为基础,引入欧式范数的分析方法,对绳锯机几组切割参数进行了优化选择,获取了合理的切割参数。经实验证明,为绳锯机切割过程的优化提供了一定的理论基础。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。