Dynamic Characteristics of Planar Deployable Structure Based on ScissorLike Element Using Influence Coefficient Method

In order to execute geometric analysis for planar deployable mechanism of scissors unit,the dynamic analysis model of scissor planar deployable structure is created based on the Cartesian coordinate system,the influence coefficient is acquired by means of the coordinate transformation,combining the D 'Alembert 's principle with Dynamic-Static method,the dynamic characteristic analysis is completed finally. Moreover,specific calculating examples are adopted to verify the effectiveness of proposed method,and the result shows that the movement of each component of scissors unit mechanism is more smooth during initial deployment stage,however,when the configuration angle θ of unit mechanism is approaching π,some comparative large variations would appear on movement parameters and hinge constraint force.

The Application of Ridge Regression in Dynamic Balancing of Flexible Rotors Based on Influence Coefficient Method

Based on the model structure of the influence coefficient method analyzed in depth by matrix theory ,it is explained the reason why the unreasonable and instable correction masses with bigger MSE are obtained by LS influence coefficient method when there are correlation planes in the dynamic balancing. It also presencd the new ridge regression method for solving correction masses according to the Tikhonov regularization theory, and described the reason why the ridge regression can eliminate the disadvantage of the LS method. Applying this new method to dynamic balancing of gas turbine, it is found that this method is superior to the LS method when influence coefficient matrix is ill-conditioned,the minimal correction masses and residual vibration are obtained in the dynamic balancing of rotors.

A General Calculating Method of Rotor’s Torsional Stiffness Based on Stiffness Influence Coefficient

In order to develop a general calculating rotor’s torsional stiffness based on stiffness influence coefficient for different rotor assembling, the calculation method of the torsional stiffness influence coefficient of equal thickness disc is researched in this paper at first. Then the torsional stiffness influence coefficient λ of equal thickness disc is fit to a binary curved face and a calculation equation is obtained based on a large quantity of calculating data, which lays the foundation for research on a general calculating method of rotor torsional stiffness. Thirdly a simplified calculation method for equivalent stiffness diameter of stepped equal thickness disc and cone disc in the steam turbine generators is suggested. Finally a general calculating program for calculating rotor’s torsional vibration features is developed, and the torsional vibration features of a verity of steam turbine rotors are calculated for verification. The calculating results show that stiffness influence coefficient λ of equal-thickness disc depends on parameters of B and H, as well as the stiffness influence coefficient λ;and discs with complex structure can be simplified to equal-thickness discs with little error by using the method suggested in this paper;error can be controlled within 1% when equivalent diameter of stiffness is calculated by this method.

Establishment of Constraint Relation of Robot Dynamics Equation Based on Kinematic Influence Coefficients Method

Due to the diversity of work requirements and environment,the number of degrees of freedom(DOFs)and the complexity of structure of industrial robots are constantly increasing.It is difficult to establish the accurate dynamical model of industrial robots,which greatly hinders the realization of a stable,fast and accurate trajectory tracking control.Therefore,the general expression of the constraint relation in the explicit dynamic equation of the multi-DOF industrial robot is derived on the basis of solving the Jacobian matrix and Hessian matrix by using the kinematic influence coefficients method.Moreover,an explicit dynamic equation with general constraint relation expression is established based on the Udwadia-Kalaba theory.The problem of increasing the time of establishing constraint relationship when the multi-DOF industrial robots complete complex task constraints is solved.With the SCARA robot as the research object,the simulation results show that the proposed method can provide a new idea for industrial robot system modeling with complex constraints.

用折线法确定避雷针保护范围的防雷漏洞与改进

用现行折线法确定避雷针高度为h的保护范围,由于没有考虑h的有效保护范围的影响,单支h及两支等高h之间的保护范围均存在防雷漏洞。分析了这些防雷漏洞,并对折线法进行了改进:设h=30 m时h在0.5h高度处的有效保护半径为r_(h/2)=15 m,h的圆锥体及圆台体保护范围的地面有效保护半径分别为r_(01)=30 m,r_(02)=45 m,推导出当h>30 m时,h对圆锥体的保护角α′及h在任意高度处的保护半径r_(x)的计算公式;取D<2r_(01)或D<2r_(02)限制两支等高h的针间距离,按h_(0)=r_(01)或h_(0)=r_(02)为半径的圆弧确定两支等高h的针间保护范围。改进后随着h的增高,α′减小,r_(h/2)、r_(01)、r_(02)保持不变,单支h的保护范围被拉高变窄,单支h及两支等高h之间的保护范围均在h的有效保护范围之内,有效堵住了折线法的防雷漏洞。

考虑表面多尺度几何特征的三维多层结构接触响应研究

航空发动机叶盘结构服役于高温、高转速的恶劣环境,使得叶片与轮盘非连续界面之间的涂层接触力学行为复杂,影响整体动力学性态.本文基于三维弹性理论建立了一种基于多层半空间体的接触模型,研究多层结构粗糙表面间的接触响应规律.采用数学解析形式将粗糙表面形貌分解为微观、介观和宏观多层级几何轮廓,引入Papkovich-Neuber势函数(P-N势函数),结合傅里叶积分变换法和影响系数法,构建了多层接触的边值问题,应用共轭梯度算法得到接触频响函数解.通过典型多层接触问题的解析解和有限元结果对比,验证了模型的可靠性;进一步研究了不同弹性模量、泊松比及摩擦系数下层内的应力场、位移场变化规律,为研究涂层系统表面粗糙界面的接触响应提供了一种可行而有效的方法.

径向来流畸变对燃气轮机压气机叶片颤振特性的影响研究

为分析来流畸变对燃气轮机压气机颤振特性的影响,建立了径向畸变的入口来流总压模型,基于影响系数法研究了不同相位角和不同畸变强度的径向来流总压畸变对压气机流场特征及气弹稳定性的影响。结果表明:相位角为90°和180°的径向来流总压畸变会使危险工况下的气动阻尼最小值有所增大,气弹稳定性提升;相位角为180°的径向来流总压畸变可以在所有叶间相位角下提高压气机的气弹稳定性;相位角为0°和270°的径向来流总压畸变均会提高压气机发生颤振的风险,需要尽量避免。

带低屈服点钢耗能梁段高强钢框筒结构的结构影响系数和位移放大系数研究

在传统钢框筒结构的部分裙梁跨中处设置LYP225低屈服点钢耗能梁段,其余构件采用Q460高强度钢材,提出带低屈服点钢耗能梁段高强钢框筒结构(HSS-FTS-LSL)。在地震作用下耗能梁段发生剪切屈服耗散地震能量,梁、柱等构件由于采用高强钢从而保持弹性或部分进入塑性阶段。为了研究HSS-FTS-LSL的结构影响系数和位移放大系数,以楼层数、耗能梁段长度及布置方式为变量,按照我国规范设计了3组共8个HSS-FTS-LSL算例,并且考虑高阶振型的影响,采用分布侧向力调整法对各算例进行了Pushover分析,基于改进的能力谱法计算了8个算例的结构影响系数和位移放大系数,分析了结构层数、耗能梁段长度及布置方式对结构性能系数的影响并给出了建议取值。最后,根据提出的HSS-FTS-LSL抗震设计反应谱对其中一个结构算例进行重设计,并对重设计前后两个算例结构进行弹塑性分析,对比了二者的抗震性能以及用钢量,验证了本文提出的HSS-FTS-LSL结构影响系数建议值的合理性。

Model Building of Backup Roller Diameter Effect Rate in 4-High Mill

Software for calculating the strip profile in 4-high hot rolling mill was developed using influence coefficient method. Regularity of backup roller diameter effect rate was studied systematically using the software. The results show that backup roller diameter effect rates decrease versus the increase of strip width, increase significantly versus the increase of backup roller diameter and obscurely increase versus the increase of reduction. The difference between backup roller diameter effect rate and it is reference value increases versus strip width increasing. When backup rollers diameter is set to be 1.64 m and strip width is 1.85 m, the error of strip profile calculated using the model of backup roller diameter effect rate reference value will be 3.55μm. Based on the results, reference values of roller diameter effect rate and six power polynomial fitting coefficients of modification coefficients were determined considering coherent parameters. The high precision model of backup roller diameter effect rate was established. When the model is used to predict strip profile, the accuracy is less than 5.0 μm.

Dimensional Variation Modeling of Aircraft Compliant Part Assembly Considering Clamping Force Change

Compliant parts are widely applied to aircraft structures.Due to the ease of deformation of compliant parts in assembly,the prediction of assembly variation is especially important for assembly quality control.A dimensional variation model considering the clamping force change in assembly is proposed based on the method of influence coefficient(MIC).First,the assembly process is decomposed into several steps including positioning,clamping,joining,and spring-back.Then,the force-displacement relationship is formulated according to the varied force conditions on the parts in each assembly step.Finally,two examples are illustrated to validate the proposed assembly variation model.The results show the impact of clamping force change is significant on the assembly variation,and the proposed model can predict the assembly variation more accurately than the referred method without clamping force correction at the over-constrained locating points of fixture.

Residual Value Balance Method for Large Flexible Rotors

A Large balancing weight may be obtained by calculation, when the ordinary influence coefficient method is used. In this paper, a new residual value balance method is recommended. The fundamental idea of the new method is on the principle of getting the minimized weight on condition that the vibration values at various points are less than the admitted ones. Experimental results show that this method is effective for balancing the insensitive rotor and rotors with special dynamic characteristics.

钢结构精细化抗震设计方法综述

相较于传统的钢结构抗震设计方法,采用钢结构精细化抗震设计方法时,地震作用效应取值与结构的延性发生更为明确的关联,且板件、构件、结构的分类基于延性,力学概念更为清晰。详细介绍了结构影响系数的计算方法,构件抗震验算方法,板件、构件和结构的分类,并介绍了不同钢结构体系的屈服机制、验算方法以及钢结构抗震性能化设计方法。

影响随机噪声CCA法勘探的关键因素试验研究

随机噪声观测技术的潜在应用前景已被众多学者公认,但由于噪声源复杂、观测方式特殊等因素,导致随机噪声勘探法仍处于探索阶段。为推动随机噪声勘探法的实际应用,本文通过现场试验数据,计算了不同采样率、采样时长、台阵半径和不同应用场景中随机噪声的Fourier谱、功率谱密度和相关系数,分析了不同应用场景的信号特征,研究了不同因素对探测结果的影响规律,以期解决城市环境中常规物探方法难于开展或根本无法开展的难题。结果表明不同应用场景中,随机噪声呈现出不同的有效频带,详细了解这一特征有助于指导施工设计;采样率会影响观测精度,试验证实在满足采样定理的前提下采用较高的采样率能够获得更好的测量结果;较短的采样时长仍能获得高质量噪声数据,但受限于随机噪声复杂性,需要通过现场试验获得最佳采样时长;更小台阵半径仍能保证随机噪声的时空平稳性,有利于拓展随机噪声勘探法的应用领域。

超大跨扁平地下洞室围岩分级方法探讨

为解决20~70 m超大跨洞室围岩分级难题,提出在初步分级阶段采用面积加权平均法确定围岩基本质量指标、在详细分级阶段增加跨度影响修正系数的超大跨扁平洞室围岩分级方法,跨度影响修正系数值根据洞室稳定系数与围岩基本质量指标和洞室跨度之间的关系来确定。采用三维数值模拟和强度折减法,通过模拟洞室的开挖全过程,计算Ⅰ—Ⅳ级围岩中20~70 m跨度洞室的稳定系数,分析得出洞室稳定系数与围岩基本质量指标和跨度之间的经验公式。结果表明:1)当跨度由20 m增大至70 m后,洞室稳定系数减小了46.54%~50.67%;2)当洞室跨度相同时,围岩基本质量指标越小,洞室稳定性越差。定义跨度影响修正系数为洞室稳定系数偏离基准跨度(20 m)洞室稳定系数的相对偏离度与基准跨度洞室稳定系数级差的比值。跨度影响修正系数取值范围为0~1.0,跨度增大对围岩稳定性的最不利影响相当于围岩级别降低1级。

一种基于轮胎不平衡量动力学解算与标定方法

针对轮胎不平衡量进行两面性平衡简化,建立了轮胎不平衡量的动力学模型,给出了在该系统模型下不平衡量大小的解算方法。提出了基于黑箱理论下的双面影响系数法,建立起一种数学理论计算模型,对轮胎平衡测试系统进行了标定。多次实验数据结果表明,相比直接求解法,采用该方法有效的消除了系统自身的误差影响以及各种振动、噪音信号的干扰,减少了量标定过程的复杂度,提高了轮胎动平衡机系统的测量精度,保证了动平衡测试的准确性与稳定性。

大型灌区农作物灌溉水经济价值估算及影响因素分析

以云南省石屏大型灌区为例,通过效益分摊系数法和剩余价值法分析了灌区内农作物灌溉水经济价值和影响因素,发现经济作物和水果的灌溉水经济价值高于粮食作物,同时建议在灌区规划时推荐采用效益分摊系数法计算效益,结果可指导类似灌区规划,助力于高标准现代化灌区建设。

基于整体模型的塔器框架基础的抗震分析

自支撑塔器包含落地式基础与框架式基础两种结构,框架式基础的抗震分析比较复杂,是抗震设计中的一个难点。对于框架式基础,常规方法中,采用框架支撑的塔器和支撑框架通常解耦分析,塔器与框架基础分别单独进行抗震分析,计算模型均未能充分反映塔器与框架的组合结构振动特性,与工程实际差别较大。文章建立塔器与框架的整体组合结构模型,考虑了框架、塔器的质量和刚度沿高度方向的分布,经对比分析,基于整体模型计算的地震作用小于常规简化方法,符合工程实际,能有效优化框架抗震设计与塔器抗震设计。

现场动平衡技术在密封结构试验器减振中的应用

某航空发动机密封结构试验器在更换试验转接段和密封对象件后,由于转子不平衡导致振动超限。本文基于现场动平衡原理和影响系数法,通过振动测试仪、激光式转速传感器、振动加速度传感器,对某试验对象件进行现场动平衡,在保持安装精度不变的情况下,提高轴系的平衡精度,平衡转速下振动幅值降低77.6%,确保试验正常运行。该方法可适用于同类型试验器的减振、排故。

基于动平衡的电机轴质量定心系统研究

提出基于动平衡理论的质量定心系统。以双面动平衡法测算电机轴不平衡量,以质量定心原理建立不平衡量与质心偏移量的关系,通过解算得到质心偏移量,数据通过TCP/IP网络通信发送给可编程逻辑控制器PLC控制加工中心去重加工。结果表明,电机轴经过质量定心系统去重后,剩余不平衡量达到0.04~0.06 g,与有质量定心机的质量定心系统相比,该系统成本更低,数据传输距离远,传输干扰小,数据更准确。

一种双级动叶可调轴流风机的动平衡方法

根据影响系数动平衡方法,提出一种适用于刚性短转子的改进双面影响系数动平衡方法。该方法适用于运行在临界转速以下、同方向测点振动相位相同,且振动数值差距较小的刚性短转子。通过振动测试,分析了双级动叶可调轴流风机振动数值增大的故障原因。应用该方法对风机进行动平衡处理,验证了该方法的有效性,同时减少风机的启停次数,节约检修时间。