整舱浮筏隔振系统功率流理论与试验研究

采用FEM和SEA方法计算整舱浮筏隔振系统传递的功率流，初步分析整舱浮筏隔振系统功率流传递特性。用间接方法测量了整舱浮筏隔振系统的功率流传递，分析整舱浮筏功率流理论计算和试验结果之间的关系及功率流的传递规律，说明采用FEM＋SEA方法计算整舱浮筏隔振系统的功率流隔振效果在工程上是可行的。     

复杂耦合隔振系统的实用解研究

针对工程实际中的复杂柔性耦合系统 ,本文对建立在柔性基础 弹性浮筏上的隔振系统应用子系统导纳法进行分析 ,推导了耦合系统动态功率流传递计算公式。在研究中 ,将浮筏和基础的基频与被隔振机组固有频率之比作为特性参数 ,对系统在不同频率比下的传递特性进行了计算研究 ;针对计算结果 ,分析了浮筏的弹性和基础的柔性对耦合系统的传递功率流的影响 ,给出了可以将基础或浮筏当作刚体来处理的弹性变化范围。     

复杂结构安装频率对传递功率流影响

针对工程实际中弹性浮筏复杂隔振系统 ,建立了柔性基础上机组多扰源弹性浮筏耦合隔振系统动力学普遍模型 ,给出了系统动态特性结构化分析方法。根据工程中两机组浮筏隔振系统功率流数值计算结果 ,着重探讨了复杂结构安装频率及隔振器阻尼对支承结构柔性及传递功率流影响     

吸振器在浮筏隔振系统中的应用

针对工程中广泛应用的浮筏隔振装置,建立柔性基础复杂激励作用下多维耦合浮筏隔振系统的动力学模型。由于浮筏隔振系统在低频范围内减振效果欠佳,为改善浮筏隔振系统的隔振性能,把吸振器引入到浮筏系统。利用子结构导纳综合法分别建立带有动力吸振器、自调谐吸振器和主动式自调谐吸振器的浮筏隔振系统动力学模型。以功率流为指标,研究单频激励下吸振器对浮筏系统功率流传递特性的影响。最后分析多频激励下带有自调谐吸振器的浮筏隔振系统的功率流传递特性。以传递到基础的功率流为目标函数,分析主动式自调谐吸振器在多频激励下的减振效果。仿真结果表明,吸振器对浮筏具有良好的低频隔振效果,吸振器类型不同与安装方式不同对传递到基础的功率流有不同程度的抑制效果。     

多源激励下浮筏隔振系统导纳功率流研究

建立了浮筏隔振系统的振子力学统计分析模型，使用导纳功率流的方法研究了隔振系统的振动响应和振动功率流特性，并通过数值方法分析了筏体和隔振器参数变化对传递到基础结构功率流的影响。分析结果表明：增大基础厚度、减小系统中耦合元件的耦合刚度和增大筏体质量可以有效控制系统的传递功率流。     

空间复杂激励下柔性耦合系统振动功率流传递特性研究

本文针对现代工业中的动力设备的振动和噪声控制问题 ,建立六维空间单层[1] [2 ] 弹性浮筏的多机组隔振理论分析计算模型 ,导出了弹性浮筏传递功率流的表达式 ,从振动能量传输的角度来评价浮筏系统隔振效果 ,绘制了功率谱曲线 ,揭示机组的质量 ,筏架阻尼等结构参数以及各个方向的力和力矩对功率流传递的影响 ,给出了浮筏设计中结构参数选择的一般准则。     

浮筏隔振系统多维耦合振动特性分析

针对工程中的浮筏隔振装置,建立了柔性基础上复杂激励多维耦合隔振系统动力学模型。考虑隔振支撑多维波动效应,运用子结构导纳法推导了耦合系统动态传递方程及功率流表达式,给出了系统的功率流谱。数值模拟计算表明,复杂激励隔振系统在低频域出现多个共振峰,在高频域基础的弯曲共振模态及隔振器驻波效应使得系统功率流提高。减小隔振器刚度能明显降低系统功率流但也使驻波效应提前。增加筏体质量可明显降低系统功率流。     

基于子结构模型的平置式浮筏隔振系统功率流传递特性分析

针对大型船用浮筏隔振系统的声学优化设计问题,从振动能量传递角度出发,研究浮筏隔振系统各子结构参数变化对系统隔振性能的影响,分析振动能量由设备机脚经浮筏隔振系统传至基础的传递规律。采用子结构导纳综合法,建立基于弹性基础的多激励源多自由度浮筏隔振系统动力学模型,通过仿真分析不同子结构参数条件下浮筏系统振动功率流传递特性和变化规律。仿真结果表明:平置式浮筏系统中隔振器刚度、机组和筏体质量、弹性基础板厚度等结构参数对传入基础的功率流影响较大,减小隔振器刚度、增加机组设备、增加筏体质量、增大基础板厚度均可有效降低传入基础的振动能量。     

浮筏及双层隔振装置隔振性能计算与分析

浮筏隔振是从传递路径上控制舰艇机械噪声的重要措施之一。为分析浮筏隔振装置的性能及筏架上设备激励相位差的影响,并与双层隔振装置的效果进行对比,本文基于导纳理论建立了设备-浮筏-安装基座系统的动力学分析模型,对泵组小型浮筏隔振装置进行了数值计算与分析。结果表明,在中高频段,浮筏隔振装置的效果主要取决于设备-上层隔振器、筏架-下层隔振器系统的垂向刚体振动固有频率ω1、ω2,故筏架上单台设备运行时其隔振效果与同固有频率ω1、ω2的双层隔振装置基本一致,而在低频段浮筏隔振装置效果略好;筏架上设备激励的相位差对中高频段传递到基座的振动功率流及振级落差几乎没有影响,但对低频段的振动传递及隔振性能有一定影响。     

水泵机组浮筏隔振系统研究

结合某换热站水泵机组振动与噪声控制工程,分析水泵机组噪声源特性,根据引入双层隔振理论出浮筏隔振设计方案.应用功率流法推导多扰动源浮筏隔振系统的动力传递特性,探讨结构参数变化对隔振效的影响.应用结果证明本设计方案切实可行.     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...