摩擦对齿轮振动噪声影响的研究进展

围绕齿面摩擦引起的齿轮系统振动和噪声问题,从计入齿面摩擦的齿轮动力学模型、齿轮系统动态响应、齿轮摩擦噪声以及实验研究等方面,综述了近20年来齿轮振动噪声的研究现状和发展趋势。重点阐述了计入齿面摩擦的齿轮动力学研究的方式方法,总结了计入摩擦齿轮动力学的主要研究结论。最后就现有研究中存在的主要问题及研究方向提出了建议。     

舰船动力轴系冲击响应性能分析

摘 要：介绍了舰船轴系冲击激励的类型、基于有限元法建立的轴系冲击动力学模型以及基于有限元法在MATLAB平台上开发的舰船轴系动力学及冲击性能仿真平台(SHAFTFE)的基本功能,用SHAFTFE建立了一个包括推进轴系、推进电机和推进电机隔振器在内的整个动力轴系模型,计算了在不同冲击强度和动力轴系参数条件下整个动力轴系的冲击性能,分析了动力轴系的结构设计参数对动力轴系冲击性能的影响。结果表明,动力轴系在冲击作用下会出现较大的位移,因此在舰船动力轴系的设计中必须对轴系的冲击特性引起足够的重视,以增强整船的可靠性和生存能力。     

基于FEM和BEM法的大型立式齿轮箱振动噪声计算及测试分析

根据某大型立式行星传动齿轮箱的结构和安装特点,基于FEM法建立了该齿轮箱的和有限元模型,对其进行了振动模态分析,计算了其模态频率和稳态不平衡响应;基于BEM法建立了该齿轮箱的外声场边界元模型,导入了齿轮箱振动稳态不平衡响应结果作为声学边界条件,对辐射声场进行了数值计算和仿真分析。通过对齿轮箱进行现场振动和噪声测试分析,得到的测试结果与理论计算结果较为一致,表明了理论计算的可行性和准确性     

多齿轮耦合复杂转子系统的振动特性分析

本文探讨了多对齿轮耦合对齿轮转子系统动力学特性的影响程度,以压缩机转子系统为例,对整个耦合系统进行了安全校核。首先,基于有限元法,建立了通用的弯—扭—轴—摆斜齿轮耦合动力学分析模型,此模型中考虑了啮合刚度、方位角、啮合角、螺旋角以及主动轴转动方向对齿轮啮合刚度矩阵的影响;接着,对系统进行了固有特性分析,得到了系统的临界转速和安全裕度表;然后,基于模态叠加法,对系统进行了不平衡响应分析,对比了考虑齿轮啮合前后系统各位置处的不平衡响应变化曲线。研究结果表明,对于多对齿轮啮合的系统,齿轮间的耦合使系统之间的振动强烈,必须考虑齿轮耦合的影响,并且要结合固有特性以及瞬态响应分析来判断临界转速和振动峰值的大小。     

摩托车整车噪声分析与消声器改进

基于噪声声压、声强测试,分析声压频谱、声强与声功率分布,识别某摩托车噪声源,结果表明,发动机缸头处与排气管处对整车噪声贡献相当,考虑优化成本和改进的复杂程度,主要针对排气消声器改进。利用有限元仿真手段和试验对原发动机排气消声器空气动力学性能和声学性能进行了研究,提出了消声器改进方案,通过消声器功率损失测试、插入损失测试和整车通过噪声实验,结果表明,改进方案使整车通过噪声降低1-2dB。     

不同冲击速度条件下矩形巷道围岩变形-开裂过程数值模拟

利用自主开发的拉格朗日元与变形体离散元耦合的连续-非连续方法,开展了不同冲击速度条件下矩形巷道围岩变形-开裂过程的数值模拟研究。当岩石单元的应力满足剪切开裂判据时,考虑了应力脆性跌落效应,在此过程中,围压保持不变。为了检验该方法的正确性,开展了单轴压缩条件下岩样变形-开裂过程的数值模拟研究。针对矩形巷道围岩的计算表明:①冲击速度低时载荷-位移曲线呈单峰特点;冲击速度高时载荷-位移曲线呈多峰特点;②冲击速度低时围岩的开裂呈渐进性特点;冲击速度高时围岩的开裂呈间歇性特点,这与在冲击过程中围岩中过去形成的一种较为稳定的结构(拱)被打破,并在其外围形成了新的稳定结构(拱)有关;③在模型相同垂直方向位移时,冲击速度低时围岩两帮的开裂深度较大,这说明冲击速度低时应力的传递较为均匀,冲击速度低时的结果(例如,V形坑内岩石碎块涌入巷道)与围岩的片帮类似;冲击速度高时的结果(例如,岩石碎块的弹射现象)与岩爆类似。     

分段非线性轧机辊系系统的分岔行为研究

考虑轧机液压压下缸和平衡缸对辊系的约束影响,建立轧机辊系的分段非线性动力学模型。分别采用奇点稳定性理论和奇异性理论分析了该分段非线性系统在自治情况和非自治情况下的分岔特性,得到不同系统参数下的分岔形态。最后根据某轧机结构参数,模拟了轧机分段非线性辊系系统在不同的外部扰动下的局部分岔行为,发现随着外扰参数的变化该系统是周期运动、倍周期运动以及混沌等多种运动形态相互交替的复杂动力学系统,外部扰动参数的变化影响系统的运动形态,这为研究和抑制轧机辊系振动问题提供了理论参考。     

一种基于残周期正弦拟合的冲击峰值计算方法

针对半正弦冲击波形峰值幅度的计算,提出了一种基于残周期正弦曲线拟合的最小二乘计算方法,通过在脉冲测量波形中截取峰值附近近似于半正弦部分的峰值波形,使用残周期正弦曲线拟合方法计算获得冲击峰值幅度。它具有操作简捷易行、收敛性好的特点,并可以通过拟合残差有效值来判定拟合效果的优劣。该方法直接使用截取的峰值波形原始数据进行计算,不需要用滤波器对波形数据进行预处理,从而避免了冲击计量中常用的数字滤波给峰值计算结果带来的影响,可以获得更加客观准确的校准结果。通过在实际校准实验波形上的计算,并与以往计算方法进行了比较,验证了所述方法的有效性和切实可行性。     

基于位移的钢筋混凝土结构单层厂房易损性分析

通过按建筑结构抗震规范的规定构造加速度反应谱作为随机激励,构筑了我国四川地区典型钢筋混凝土结构单层厂房有限元模型,采用拟动力时程方法对结构的抗震性能进行了分析计算,得到了钢筋混凝土结构厂房的易损性曲线;同时,针对原型结构在地震作用下柱基础容易发生屈服破坏的情况,对原型结构基础采取了铅芯阻尼橡胶支座隔震加固措施,并对加固后的厂房结构进行了计算分析并得到了修正易损性曲线,通过对比得到结构在地基不失稳的前提下,在小震时发生中度以上损伤的概率非常小,在大震时随着承重结构进入塑性屈服发生中度以上的损伤概率开始逐渐变大,而且厂房结构纵横两个方向的易损性概率在大震时有差异,采取隔震加固措施后结构损伤概率明显减小。     

神经网络规则提取及其在转子故障诊断中的应用研究

利用神经网络进行智能诊断所获取的诊断知识难于解释和理解,因此限制了其在智能诊断中的进一步应用,基于此,本文研究了一种新的基于功能性观点的神经网络规则提取方法,介绍了连续属性离散、训练样本产生、神经网络训练、示例样本产生及规则提取等关键算法。并与其他方法进行了比较分析。最后,将方法应用于转子故障诊断,通过多功能转子故障模拟实验台获取故障实验样本,利用本文神经网络规则提取方法从故障样本中提取了诊断知识规则,并对其进行了解释,结果表明了方法的正确有效性。     

Ballistic behaviors of injection-molded honeycomb composite

The purpose of this study is to explore a new type of structure design and injecting material selection of the composite sandwich bulletproof system. A re-entrant hexagonal honeycomb with the negative Poisson’s ratio effect was designed. Thermoplastic polyurethanes (TPU), polypropylene (PP) and polycarbonate (PC) were chosen to inject into the re-entrant honeycomb structure by injection molding to form the composite sandwich layers. The total bulletproof system was later constructed with the boron carbide ceramic plates and aluminum alloy plates. The mechanical behaviors and energy absorption characteristics of different composite sandwich layers were investigated by quasi-static and dynamic compression tests. The dynamic responses of different structured layers were analyzed via numerical simulations in ANSYS/LS-DYNA, which employed 7.62 mm projectiles. The results indicated that the injection-molded composite sandwich layer shows excellent compressive strength and energy absorption capacity. The bulletproof performance of the injection-molded system has been greatly improved comparing with the non-injected molded system. Compared with TPU and PP, the composite injected with PC presents optimal penetration resistance.     

水下夹芯复合空腔结构声学特性计算方法研究

建立了水下夹芯复合空腔结构入射声波模型,运用刚性管中声波传播特性和声固耦合边界条件,提出了一种声学特性有限元计算方法。通过与钢制和橡胶中间层解析解,以及单层夹芯复合结构和夹芯舵结构传递矩阵法、试验结果比较,验证了计算方法对均质层的有效性。通过与经典文献周期空腔覆盖层结构空气背衬和水背衬条件下计算结果进行比较,本文计算方法与经典方法吻合较好,同时兼顾了结构整体弯曲振动对声学性能的影响。通过分析周期阵列边界条件对夹芯复合空腔结构的声学特性影响,补充验证了本文计算方法的可行性。     

树状分形结构夹芯板动态冲击特性研究

目的 探究一种新型树状分形结构夹芯板的动态冲击特性。方法 采用Ansys Workbench建立有限元模型,选用真空注型用聚氨酯(PU)弹性体材料制备1阶分形结构夹芯板试样进行动态冲击实验,验证模型可靠性;仿真分析该结构在不同分形阶数(n)下的动态冲击特性,并与常见中空型和三角型夹芯板对比。结果 模型平均误差约为7.25%;相同条件下,2阶TFS模型的比能量吸收(SEA)分别比0阶、1阶的提高了16.71%和0.23%。平均压溃力(FS)分别比0阶、1阶提高了27.76%和11.66%。与中空型夹芯板和三角型夹芯板对比,1阶分形夹芯板动态缓冲特性较优。结论 树状分形结构应用于缓冲包装中,可以表现出优良的吸能效率,为包装设计提供了一种新思路。     

“Segment-wise model” for theoretical simulation of barely visible indentation damage in composite sandwich beams: Part II – Experimental verification and discussion

When localized transverse loading is applied to a sandwich structure, the facesheet locally deflects and the core crushes. A residual dent induced by the core crushing significantly degrades the mechanical properties of the sandwich structure. In a previous paper, the authors established a “segment-wise model” for theoretical simulation of barely visible indentation damage in honeycomb sandwich beams with composite facesheets. Honeycomb sandwich beam was divided into many segments based on the periodic shape of the honeycomb and complicated through-thickness characteristics of the core were integrated into each segment. In this paper, the new model is validated by experiments using specimens with different types of honeycomb cores. In addition, the damage growth mechanism under indentation load was clarified from the viewpoint of the reaction force from the core to the facesheet. The applicability of the model to other types of core materials is also discussed.     

Development of a satellite structure with the sandwich T-joint

In this study, a monocoque satellite structure composed of many composite sandwich panels, which consist of two carbon fiber/epoxy composite faces and an aluminum honeycomb core, was designed to reduce structural mass and to improve static and dynamic structural rigidity. To join composite sandwich panels with T-shape joints, a new I-shape side insert, which was fixed inside the composite sandwich panel edge with film adhesive, was suggested. The composite sandwich panels were assembled with bolts using the through-the-thickness insert and the I-shape side insert. The flatwise tensile and compressive tests of the composite sandwich panels were performed with respect to the bonding pressure between the composite face and the aluminum honeycomb core to achieve an optimal bonding pressure. To investigate the joint characteristics of the composite faces and the I-shape side insert, cleavage peel tests were performed with respect to the bonding thickness. Also, a finite element model of the composite sandwich T-joint with the I-shape side insert was developed from experimental results of the impulse response tests and composite sandwich T-joint static tests. From the finite element analysis, the structural reliability of the monocoque composite sandwich satellite structure was verified.     

Behaviour of glued fibre composite sandwich structure in flexure: Experiment and Fibre Model Analysis

The behaviour of glued composite sandwich beams in flexure was investigated with a view of using this material for structural and civil engineering applications. The building block of this glue-laminated beam is a new generation composite sandwich structure made up of glass fibre reinforced polymer skins and a high strength phenolic core material. A simplified Fibre Model Analysis (FMA) usually used to analyse a concrete beam section is adopted to theoretically describe the flexural behaviour of the innovative sandwich beam structure. The analysis included the flexural behaviour of the glued sandwich beams in the flatwise and the edgewise positions. The FMA accounted for the non-linear behaviour of the phenolic core in compression, the cracking of the core in tension and the linear elastic behaviour of the fibre composite skin. The results of the FMA showed a good agreement with the experimental data showing the efficiency and practical applications of the simplified FMA in analysing and designing sandwich structures with high strength core material.     

纸蜂窝夹芯复合板材静态缓冲性能研究

目的为了新型纸蜂窝夹芯复合板材在运输包装中的推广应用,对新型泡状纸蜂窝夹芯复合板和纸蜂窝夹芯复合平板的缓冲性能和吸能特性进行研究。方法主要通过静态压缩实验,研究不同芯高的纸蜂窝结构类板材的应力-应变曲线、总能量吸收图、单位体积能量吸收图和缓冲系数-应变曲线,分析结构和芯高对板材静态压缩性能的影响。结果数据表明同种芯高的板材,纸蜂窝夹芯复合平板的应力峰值稍高;纸蜂窝夹芯复合平板的能量吸收、单位体积能量吸收最好;泡状纸蜂窝夹芯板由于泡结构的作用,缓冲性能大大增强。结论纸蜂窝夹芯复合平板的平压强度最好,而泡状纸蜂窝夹芯复合板的缓冲性能优于同等结构的蜂窝纸板,2种板材都有很好的应用前景。     

Flexural properties of sandwich beams consisting of air plasma sprayed alloy 625 and nickel alloy foam

Sandwich structures are considered as viable engineering constructions due to their unique structural, physical, and mechanical properties. An investigation of the mechanical characteristics of sandwich structures suitable for high temperature application is presented. A process has developed to produce high temperature sandwich structures by depositing alloy 625 skins on Ni alloy foam cores using air plasma spraying (APS). The experimental investigation consisted of fabrication of sandwich structures and testing of mechanical performance of sandwich specimens under flexural loading conditions. The responses of the as-fabricated sandwich structure to heat treatment were investigated. The strength of the sandwich structure was significantly increased after heat treatment. The influence of skin thickness on mechanical behavior of sandwich structures was examined by performing four-point bending test on sandwich samples with skin thicknesses of 0.5 and 0.1 mm. The larger the skin thickness, the higher the strength of the sandwich beams. Comparison between the results of four-point bending tests on sandwich structures with different skin thicknesses will help us to understand the effect of skin thickness on the failure mechanism of sandwich structures.

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含流道微桁架夹层面板隔热性能评估方法

本文详细探讨了含流道的微桁架夹层面板内部复杂的传热机制,并基于简化假设,提出了一种评估该结构隔热性能的解析模型,建立了该类新型一体化主动冷却热防护结构的隔热性能快速评估方法。通过与Fluent软件详细的数值模拟结果对比,验证了评估方法的有效性。该研究为新结构的实际应用提供了理论基础。     

多级三角形格栅夹芯板力学分析

为了提高点阵复合材料结构的轻质高强力学特征,尤其提高其抗屈曲性能,设计了一种新型的多级三角形格栅夹芯板结构。根据等效连续介质力学方法提出了多级三角形格栅夹芯板的等效计算理论,预测了拉伸主导型多级三角形格栅夹芯板结构的等效弹性模量以及等效抗弯刚度。分析了侧压条件下多级三角形格栅夹芯板的弹性屈曲载荷和强度破坏模式。在理论模型的基础上绘制了侧压条件下多级三角形格栅夹芯板结构的失效模式图,指出了结构破坏模式与多级三角形格栅夹芯板尺寸之间的对应关系。研究表明:具有工字型截面的多级三角形格栅夹芯板结构相比于传统矩形截面格栅结构具有更高的抗弯刚度和弹性屈曲载荷,是一种性能更加优越的轻质高强点阵结构。