Pressure sensor matrix for indirect measurement of grip and push forces exerted on a handle

To date, a large part of workers is exposed to vibrations (23% in Europe) which can negatively impact on their health. This work discusses the importance of measuring grip and push forces in the context of hand-arm vibration tests, bearing in mind the state-of-art of current standards. It proposes a method for indirect measurement of coupling forces using a matrix of polymeric pressure capacitive sensors and discusses the model used for defining these quantities. The matrix of pressure sensors is wrapped around the tool handle and the acting forces, exchanged with the handle, are derived from the pressure values measured by the matrix. Calibration is presented and the effect of curvature is discussed. The work continues with the experimental validation of the model proposed for push force measurements carried out through lifting tests using known masses with a cylindrical handle. An experimental correction coefficient is defined in correlation to the type of grip. The method for measuring the push force, thus corrected, is assessed by means of push force tests on an instrumented handle. Finally the experimental data are analysed in order to assess the uncertainty of the proposed method for measuring the push force, highlighting the contribution of the different sources of uncertainty. The proposed measurement method allows to measure the push and the grip force (known influencing quantities for the measurement of the hand-arm vibration) during tool test and without modifying the handles.     

磁流变阻尼器抑制转子系统振动试验

针对大型旋转机械通过临界转速时振动过大及运行中故障频发等问题,搭建转子试验台,模拟启停机过程和碰摩、不对中故障。不改变原有支撑形式,安装自主设计的磁流变阻尼器,在不停机的情况下,试验研究阻尼器抑制转子通过临界转速时振动过大及各类故障振动。试验结果表明,阻尼器可以有效抑制转子系统临界转速附近的振动,降幅在60%以上;转子发生碰摩或不对中故障时,阻尼器可以降低其高倍频振动。     

Relations between asphaltene content,viscosity reduction rate of heavy oil and ultrasonic parameters

Ultrasonic treatment could decrease the viscosity of heavy oil and previous study on had focused on one heavy oil sample and involved less on the influence of asphaltene content. This study examined the effect of asphaltene content on viscosity reduction rate by ultrasonication. A comparison on samples with various asphaltene content and vibration parameter was made. The results showed that the optimal vibration frequency might decrease as the asphaltene content increased, whereas the optimal vibration intensity and the optimal treatment time were suggested to be enlarged. A semi-quantitative correlation was matched, which helped for numerical simulation about ultrasonic treatment.     

Preliminary results of hand arm vibration (HAV) exposures of chipping hammer operators in tropical weather: Analysis of exposures and protective gloves

Objectives of this study are to analyze the HAV exposures of chipping hammer operators from field measurements and to investigate the potential of various types of gloves in reducing the exposures. HAV exposures of twelve male operators were measured at four different operating conditions: bare hand, wearing normal workman gloves, wearing heavy workman gloves and wearing vibration reducing gloves. From the measurements, 8 h exposure values were determined and assessed against standards. The total vibration values were determined and effectiveness in vibration attenuation by gloves was compared. It was found that all most all operators, HAV exposure levels exceeded the exposure action value (EAV) and about 83% of the operators exceeded the exposure limit values (ELV). A reduction in the total vibration magnitude was observed with protective gloves: 8.3% with normal workman gloves, 14.6% with heavy workman gloves and 40% with vibration-reducing gloves. To confirm the effectiveness of the vibration reducing gloves, further field investigations are required with simultaneous measurements by considering parameters affecting HAV (i.e., hand forces and postures).     

轧机垂直系统动力学参数辨识

 针对轧机垂直系统动力学参数可信度不足等问题，提出一种基于实测数据的改进粒子群算法辨识轧机垂直系统动力学参数的方法。首先,将轧机垂直系统刚度和阻尼考虑成达芬振子和范德波尔振子，构建轧机垂直系统非线性动力学模型，并对粒子群算法进行改进；然后，通过数值仿真算例辨识得到系统在感染噪声和不含噪声时的动力学参数，验证了该算法的有效性；最后，以现场某轧机垂直系统为研究对象，基于现场实测数据，应用该算法进行辨识，得到了轧机垂直系统动力学参数估计，通过实测位移、速度和加速度信号分别与辨识后的位移、速度和加速度信号进行对比，证明该方法辨识轧机垂直系统动力学参数结果可靠，具有一定的工程应用价值。     

发夹式换热器管束流致振动数值模拟研究

运用计算流体力学方法,采用ANSYS CFX软件对发夹式换热器的壳侧流场进行了三维数值模拟。流场计算中采用多孔介质模型对管束区域进行简化,分析了壳侧流场的速度分布,结果表明:直管段部分的流体湍流强度大于弯管段,且外层管束所在区域为高流速区,受流体冲刷严重。结合流场信息,通过功率谱生成随机激振力,采用ABAQUS软件模拟计算了湍流激振下管束的振动响应,结果显示管束的面外均方根位移远大于面内位移,且弯管部分的振动位移最大。该研究结果可为发夹式换热器的性能分析和优化设计提供参考和依据。     

YC12VC型高速柴油机发火顺序的分析研究

基于AVL-EXCITE软件搭建了YC12VC发电用高速柴油机轴系动力学模型,其模拟值与试验值吻合性较好,验证了该模型可以较好地模拟不同工况条件下轴系的运动情况。基于平衡性和均匀发火等原则,设计了8种不同的发火顺序,并针对轴承受力、轴承润滑、轴系扭振和转速不均匀性开展影响规律研究。结果表明:通过发火顺序的优化,在保证最大主轴承负荷和最小油膜厚度满足设计要求的前提下,标定工况下的曲轴扭振总振幅从0.465°降低到0.259°,转速不均匀系数从0.018降低到0.009。     

考虑流固耦合的管道机器人冲击环焊缝过程动力学建模与分析

以管道机器人（Pipeline inspection gauge，PIG）为载体的内检测技术是保障油气管道安全运输的重要手段。针对管内高压流体作用下，管道机器人在冲击管内环焊缝过程中产生的动力学行为突变问题。建立了管道周向受限空间中基于Kelvin弹簧阻尼的管道机器人密封盘等效动力学模型，结合管道机器人本体建立了多体系管道机器人动力学模型；详细推导了管道机器人轴向振动微分方程，以及管内流体的流动方程；并使用Matlab/Simulink与Adams进行流固耦合仿真，作为重要的工艺参数之一，研究了管道机器人速度改变时，其在冲击环焊缝过程中的动力学响应情况。结果表明：所建立的密封盘及管道机器人动力学模型能够很好地表征密封盘在管道轴向、径向以及周向的力学特性；运行速度越快，管道机器人通过环焊缝引起的轴向振动越剧烈，冲击振动越明显；而垂向和俯仰振动现象随运动速度增大而显著减弱。     

Vibration suppression for monopile and spar‐buoy offshore wind turbines using the structure‐immittance approach

Offshore wind turbines have the potential to capture the high‐quality wind resource. However, the significant wind and wave excitations may result in excessive vibrations and decreased reliability. To reduce vibrations, passive structural control devices, such as the tuned mass damper (TMD), have been used. To further enhance the vibration suppression capability, inerter‐based absorbers (IBAs) have been studied using the structure‐based approach, that is, proposing specific stiffness‐damping‐inertance elements layouts for investigation. Such an approach has a critical limitation of being only able to cover specific IBA layouts, leaving numerous beneficial configurations not identified. This paper adopts the newly introduced structure‐immittance approach, which is able to cover all network layout possibilities with a predetermined number of elements. Linear monopile and spar‐buoy turbine models are first established for optimisation. Results show that the performance improvements can be up to 6.5% and 7.3% with four and six elements, respectively, compared with the TMD. Moreover, a complete set of beneficial IBA layouts with explicit element types and numbers have been obtained, which is essential for next‐step real‐life applications. In order to verify the effectiveness of the identified absorbers with OpenFAST, an approach has been established to integrate any IBA transfer functions. It has been shown that the performance benefits preserve under both the fatigue limit state (FLS) and the ultimate limit state (ULS). Furthermore, results show that the mass component of the optimum IBAs can be reduced by up to 25.1% (7,486 kg) to achieve the same performance as the TMD.     

A novel hybridized metaheuristic technique in enhancing the diagnosis of cross-sectional dent damaged offshore platform members

Offshore jacket platforms are widely used for oil and gas extraction as well as transportation in shallow to moderate water depth. Tubular cross-sectional elements are used to construct offshore platforms. Tubular cross sections impart higher resistance against hydrodynamic forces and have high torsional rigidity. During operation, the members can be partially or fully damaged due to lateral impacts. The lateral impacts can be due to ship collisions or through the impact of falling objects. The impact forces can weaken some members that influence the overall performance of the platform. This demonstrates an urgent need to develop a framework that can accurately forecast dent depth as well as dent angle of the affected members. This study investigates the use of an adaptive metaheuristics algorithm to provide automatic detection of denting damage in an offshore structure. The damage information includes dent depth and the dent angle. A model is developed in combination with the percentage of the dent depth of the damaged member and is used to assess the performance of the method. It demonstrates that small changes in stiffness of individual damaged bracing members are detectable from measurements of global structural motion.