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1.
往复式切割器传动机构运动动力学分析 总被引：2，自引：0，他引：2
油菜收获机割台损失主要由割台振动与割刀切割损失两部分形成,而割台上的往复式切割器工作时的惯性冲击力是造成其振动损失的主要因素之一。为降低油菜联合收割机割台损失,本文对油菜联合收割机上往复式切割器传动机构进行了运动动力学分析,建立了该机构运动动力学模型,分析了各主要构件的运动加速度,得到了求解机构中各运动副之间约束力的方程组,并对方程组进行了求解,得到了主要构件的惯性力表达式。在此基础上分析了惯性力的影响因素。其研究结论为降低往复式切割器惯性冲击力的影响,降低割台振动,优化结构提供了理论依据。 相似文献
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以新建四川省盐源县平川铁矿黄草坪尾矿库为工程背景,通过堆坝模型试验与室内土工试验,获得尾矿坝干滩面几何特征、颗粒分布规律及尾矿力学性质。基于离散元理论,采用PFC 2D数值模拟软件进行双轴试验,与土工试验结果对比,得到尾矿细观力学参数,并分析尾矿坝颗粒接触力分布、颗粒位移与坝体结构变形特征。结果显示：1)初期坝中颗粒间接触力较大,形成的力链大致呈45°倾斜向上;坝体尾矿颗粒接触力随着埋深的增加而增大,在基岩凸起处接触力较大且集中。2)初期坝颗粒位移不明显,堆积坝少数尾矿颗粒沿坡面向下滚动,具有较大位移;尾矿堆积坝存在较为典型的滑移面,滑移面上部区域颗粒位移较大。3)初期坝结构变化不明显,尾矿堆积坝中靠近初期坝内坡面附近结构变形显著。 相似文献
3.
为了分析卧式青核桃脱皮机中刀片及刀片安装板等核心关键部件的结构强度和力学性能,通过设计和计算确定了刀片及刀片安装板的结构参数,采用UG三维模型软件,创建了刀片及刀片安装板的分析模型,并通过ANSYS有限元分析软件对刀片及刀片安装板进行了静力学分析和模态分析。结果表明：刀片及刀片安装板既可以实现对青核桃的输送功能,又可以实现刀片对青皮的切割作用;刀刃边缘位置的变形最大,最大值为0.509 mm;刀片折弯位置的应力和应变值最大,最大值出现在0°刀片的折弯位置,最大值为114.7 MPa;在工作过程中最大等效应力远小于材料的屈服强度,刀片及刀片安装板的模态分析前三阶固有频率分别为466.99、1 206.8、2 199.7 Hz,而机构的工作频率远小于所分析零部件的固有频率,刀片及刀片安装板的结构能够满足强度和刚度要求,且工作过程中不会出现共振问题,这为研制卧式青核桃脱皮机链板输送机构提供了理论依据。 相似文献
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针对目前位移传感器很难直接测得木结构或木构件在转动中产生较大绝对水平位移的问题,研制了量程为±500 mm的电阻应变式位移传感器（WD位移传感器）,应用正交试验法分析WD位移传感器的影响因素,并对其进行设计与制作,拟合了传感器在不同量程下应变位移的分段函数关系,通过计算得出了WD位移传感器的6种静态参数指标。试验结果表明,WD位移传感器克服了传统电阻应变式位移传感器量程小的问题,解决了木结构或木构件发生非直线运动很难直接测得绝对水平位移的问题,且各静态参数指标良好。 相似文献
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以重庆东水门大桥—千厮门大桥渝中区连接隧道为研究对象,基于UDEC软件建立离散元数值模拟分析模型,研究了城区连拱隧道施工引起的地表沉降,上部建筑物基础沉降及倾斜,新建隧道下方已有轨道六号线的变形、受力特征,并将监测数据与数值模拟进行对比分析。结果表明,连拱隧道左侧隧道上导坑施工引起的隧道拱顶沉降和基础沉降量最大,经计算上部建筑物基础最大沉降量为3.81 mm,最大倾斜量为0.02%,建筑物基础沉降量和倾斜在规范许可范围之内;隧道施工引起的地层损失使得轨道六号线左拱肩向上隆起,六号线弯矩分布规律和其变形形态基本一致,弯矩最大值位于左拱肩部位,最大值为238 kN·m;数值模拟计算结果与监测数据量值相当,变形趋势基本一致;采用UDEC软件可以准确地计算出隧道开挖过程中节理的存在对隧道周围建筑物变形的影响。 相似文献
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建立增速齿轮箱动力学分析有限元模型,利用Lanczos法求得齿轮系统的振动模态;以齿轮副时变啮合刚度激励、齿面综合误差激励和轮齿啮合冲击激励为内部作用激励,采用直接积分法求得箱体表面节点的动态响应。选取箱体上12个主要结构参数作为动力学性能优化的设计变量,齿轮箱体积为状态变量,以齿轮箱表面振动加速度的均方根值最小为动力学性能优化的目标函数,利用零阶与一阶优化算法求得最优设计变量。结果表明：优化前后箱体均不产生共振,且满足静力学条件;优化后目标函数减小37.5%,箱体各计算点的振动响应均有较大幅度的减小,最大减小量为54%。 相似文献
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以桥面板等高性能混凝土板式构件为研究对象，通过实验测试了板式构件不同截面厚度位置处早期收缩分布情况，探讨混凝土早期收缩变形与温度、湿度发展过程。结果表明，混凝土板式构件的内部厚度方向不同位置处的相对湿度随龄期都呈现逐渐减小趋势，并呈现两阶段特征，同时，混凝土板式构件早期收缩变形厚度方向不同步，导致板式构件表面产生拉应力，当拉应力大于当时混凝土的抗拉强度时，混凝土表面就会出现浅层裂缝，这与实际工程中发现的板式构件表面开裂情况相吻合。混凝土板式构件早期收缩变形与相同配合比混凝土的早期自由收缩变形进行比较，引入相对约束度并建立了混凝土板式构件早期收缩变形的预测模型，并验证了该模型的准确性，其特点是能预测高性能混凝土板式构件不同截面厚度位置的早期收缩变形，对控制混凝土桥梁板式结构的早期收缩裂缝具有实际意义。 相似文献
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大型渠道水荷载加载过程中渠床变形特性 总被引：1，自引：1，他引：0
为了研究改建后的大型渠道在首次加荷过程中产生的沉降位移量是否会对灌溉设计产生较大影响,笔者基于大型梯形渠道弧形底混凝土防渗渠加荷与卸荷过程中变形观测原位试验,分析了改建后的大型渠道在首次加荷与卸荷过程中渠床的变形特性。结果表明：改建后的大型渠道在首次加荷与卸荷过程中,会发生一个较大的弹性变形及塑性变形,渠道在垂向上的沉降量与回弹量的大小随外荷载不断变化具有一定特征;改建后的大型渠道在首次加荷过程中产生的沉降位移量与渠底以下非饱和土壤的厚度有较大关系;由于渠道在首次加荷与卸荷过程中在垂向上有较大的沉降量,则为满足灌溉条件,应在渠道的设计与施工中采取一定的必要措施。 相似文献
10.
单层柱面网壳抗连续倒塌性能 总被引：1，自引：0，他引：1
研究了不同荷载布置形式、支承方式条件下,单层柱面网壳的抗连续倒塌性能和倒塌破坏模式,采用基于构件承载能力的敏感性评价指标,分析了初始缺陷、压杆失稳等因素对杆件、节点敏感性指标的影响。结果表明,当采用四边支承时,满跨均布荷载起控制作用,跨中节点为敏感构件,与之相邻斜杆为关键构件;当采用纵向两边支承时,半跨均布荷载起控制作用,杆件和节点的敏感性指标在1/3跨处最大,支座处最小。当考虑初始缺陷时,杆件、节点重要性系数分别增大了41%和53%;当考虑压杆失稳时,杆件和节点重要性系数分别增大了45%和62%。通过对关键构件进行加强,可以优化该类结构的抗连续倒塌性能。 相似文献
11.
基于等效原则、相似理论，考虑三维地震动作用下振动台试验中原型结构隔震层的简化，并对模型结构隔震层进行系统研究。针对不同高宽比隔震结构，提出完全等效简化方法和部分等效简化方法，包括隔震垫等效、模型支座参数及坐标确定、相似关系确定等。利用不同高宽比隔震结构振动台试验，结合有限元数值模拟，进行方法验证。理论推导与数值模拟证明简化方法具有良好的准确性，且在误差允许范围内，简化后的隔震层所获得的加速度、速度、位移等动力特性与简化前相同，可以用于振动台试验模型设计。 相似文献
12.
The response properties of displacement and stress of tunnel support structure are discussed in detail under the action of horizontal earthquake acceleration(Ya),longitudinal earthquake acceleration(Za) and horizontal-longitudinal earthquake acceleration(YZa).This discussion is based on an analysis of the surrounding rock-support structure-earthquake interaction,adoption of an ADINA nonlinear finite element and construction mechanics,and transient dynamic time domain analysis of a large cross section tunnel.Results of analysis show that:(1) Horizontal earthquake acceleration has important influence on horizontal displacement,maximum principal stress,acceleration and velocity.(2) Longitudinal earthquake acceleration has important influence on longitudinal displacement,effective stress,maximum and minimum principal stress,maximum shear stress,acceleration and velocity.(3) When Ya=0.191g and 0.440g or Za=0.141g and their combined action,the initial support of tunnel would be damaged and the local lining would have partial damage.(4) When Ya=0.440g or Za=0.326g and their combined action,the lining of tunnel would be damaged.(5) When Ya=0.880g or l Za=0.652g,the support structure of tunnel would have severe damage. 相似文献
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The digital image displacement measurement technology and finite element data smooth were applied in the soil slope shaking table test. The displacement field and strain field were obtained from the whole vibration process. And the seismic failure mode and failure mechanism were discussed as well. The results show the deformation of soil slope increases gradually; there is shear failure from slope middle to toe and tension-shear failure at the top of slope; there forms deep arc-shaped slip surface when the slope model fails. The generalized curvature of displacement time-hisrory curve is used to judge whether the slope seismic failure is feasible. 相似文献
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In order to better understand the seismic performance of the hybrid structure, numerical analysis and shaking table model testing were conducted on a real tall building constructed in Beijing. The nonlinear analytic model of the structure was established with the aid of PERFORM-3D program, and the elastoplastic time-history analysis was performed. From displacement responses and energy dissipation of the entire structure, and deformations and plastic hinge forming condition of components, the response features under different earthquake levels were obtained. Based on the predetermined allowable limits of performance indices, the seismic performance of the structure was evaluated. In the mean time, the numerical analysis results were compared with test results. Both of test results and numerical analysis results indicate that the hybrid structure has good seismic performance. 相似文献
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Based on dynamic time history analysis, dynamic response behavior of an un supported tunnel through fault zone which was simulated by interface and solid elements was studied under uniform input earthquake wave excitation. The analyses of response behaviors, including displacement difference, acceleration magnification, and plastic zones and so on, were carried out when earthquake wave excitation was input along transverse, longitudinal and vertical of tunnel respectively. The results show that simulation method for fault zone is effective; the earthquake causes obvious displacement difference at fault zone and surrounding rock contacting part. The maximal displacement difference reaches to 51.8mm under transverse uniform input earthquake wave excitation. And the displacement difference under vertical and longitudinal is only 44.3% and 23.1% of the transverse value, respectively; the acceleration magnification in fault zone is significantly greater than that in surrounding rock. Shear failure zone appears at the fault zone and surrounding rock contacting part, and it is especially prominent under input longitudinal earthquake wave excitation. It is proposed that fault zone has significantly influence on the dynamic performance of tunnel. The fault zone and the transitional zones are the control zones of seismic design when tunnel passes through fault zone, thus, the study on the anti seismic measures should be further strengthened. 相似文献
16.
China Pavilion for Expo 2010 Shanghai is designed with peculiar style and special structural system. The main structure is composed of four concrete tubes with steel-concrete composite floors. It is designed with a shape of inverted trapezoid in elevation. The fundamental vibration mode of this structure is a torsional mode due to the special shape with greater moment of inertia in upper floor, which exceeds the limit value stipulated in Chinese code. The seismic analysis of prototype is carried out by ANSYS program to evaluate its overall seismic performance and improve the structural design. At the same time, shaking table tests of a 1/27-scale structural model are conducted. It is faund that although the first mode is torsional, the torsional responses are not so large, which agrees well with the results of shaking table tests. Both the test results and calculation results demonstrate that the designed structural system satisfies the seismic damage patterns and meets the pre-defined performance objectives. Based on the test results, suggestions for improving design are also put forward. 相似文献
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To know well the impact on the deformation of underground diaphragm wall caused by soil excavation, centrifugal model tests reflecting Shanghai soft soil creep effects were designed, and finite element was used to calculate the deformation of underground diaphragm wall caused by different excavation timeline, sequence and width based on the top down construction method in the deep and large foundation pit of Shanghai Expo axis underground complex project. Centrifuge model tests and monitoring data indicate that the results of numerical calculation are approximately close to the horizontal displacement of the underground diaphragm wall measured in site, which reflects the deformation behavior of excavation. The results show that remained berm and middle plate have good control over the deformation of underground diaphragm wall. Most part of underground diaphragm wall deformation caused by soil creep occurs after the remained berm is excavated. So in order to decrease the deformation of underground diaphragm wall, it would be useful to conduct plate structures as soon as the remained berm is excavated. The excavation width of remained berm in the north part is less than that in the south part. It will be advisable to finally excavate the remained berm where there are protected objects nearby. 相似文献
18.
The advantage of blade-offset rotary vane compressor is analyzed, and its kinematic model is established through simplifying the vane motion to the circle center movement of the main vane arc by using equidistant curve envelope principle. Then, the relationship between the displacement, velocity, acceleration of blade and the angle of rotor is obtained. Finally, based on the theory obtained, the simulation is also carried out. Results show this method can avoid complex process for finding the contact point, which meanwhile has good solving accuracy. Because of the differences on kinematic characteristics, the blade kinematic analysis for blade-cardiac cannot be simply used for the blade-offset one, and the kinematic and dynamic characteristics of cylinder profile cannot be shown by the simplified analysis. However, the scientific theory calculation method for the kinematic analysis of blade-offset rotary vane compressor put forward provides a reliable theoretical basis for the innovation of multi-stage combination cylinder profile with high volumetric efficiency and compression ratio, and also broadens the design theory of the rotary vane compressor. 相似文献
19.
Simulation of regulatory driving cycle for motorcycle on the engine test bench 总被引：1，自引：0，他引：1 
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下载免费PDF全文 Dynamic performance test methods and experiments of motorcycle engine are investigated. The models of clutch, transmission and brake are simulated by changing the resistance torque imposed by the dynamometer to the engine and with the moment of inertia and road resistance data, the model of a 125 mL motorcycle is established on the dynamic engine test bench. On this basis, the road tests are simulated with models of different inertial mass. Compared with the experiments on the drum tester, the results show that when the inertial mass is set to 1.1 times the datum mass of the motorcycle, the deviations of its maximum speed, sliding distance and acceleration time are no more than 3% and the fuel consumption of 100 km is no more than 5% except the speed of 35 km/h. Through driver operational model, the effect of different gear change models on vehicle acceleration performance is studied. Finally, the regulatory driving cycle for motorcycle is implemented on the dynamic bench and the measurements show that it has high ability to accurately control speed. 相似文献
20.
Accurately predicting the residual displacement of reinforced concrete (RC) structures after an earthquake is of great significance in post-earthquake structural performance evaluation and control. To study the residual deformation of the structure, seismic time-history responses of single degree-of-freedom (SDOF) systems with different parameters were analyzed. Based on the analytical results, simplified models for estimating the likely residual deformations of structures characterized by Takeda and Kinematic hysteretic models were proposed respectively, and the residual deformation was found to be sensitive to hysteretic characteristics, stiffness ratio of structures, peak ground acceleration (PGA), as well as maximum elasto-plastic deformation. A case study for RC single-column bridge pier was provided to illustrate the process of residual deformation calculation and post-earthquake performance evaluation by using the proposed methods. Calculation results indicate that the residual deformation of the single-column pier characterized by the Takeda model often is much larger than that of columns characterized by the Kinematic model. 相似文献