共查询到18条相似文献,搜索用时 734 毫秒
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煤矿用全液压钻机动力头主要采用液压驱动和齿轮传动相结合的方式,其中,齿轮传动的振动烈度直接影响着动力头的输出能力,成为了设计中必须考虑的重要问题。以ZYWL-2600R型松软煤层螺旋钻机为研究对象,在齿轮副的单自由度扭转振动模型基础上,以啮合线上的振动加速度为优化目标,建立了动力头齿轮副的动态优化设计模型,并借助Matlab优化工具箱和GUI工具开发了优化设计程序的图形界面,求解了齿轮振动最小的宏观设计参数,为钻机“高速”动力头的动态优化设计提供了参考。结果表明,优化后齿轮副的时变啮合刚度显著提高,有效改善了齿轮传动的振动特性。 相似文献
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利用人工振动技术增加石油产量的机理之一是地层的机械共振作用。提出了一种简化的地层模型,并将其转化为一个双自由度有阻尼振动系统。研究了各种不同厚度的地层的振幅与振动频率的关系、共振频率与固有频率的关系以及品质因素 Q 对地层振幅和共振频率的影响,得出有意义的结论。 相似文献
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采用三维建模软件SolidWorks建立轻便岩心钻机的动力头三维几何模型,并导入有限元分析软件ANSYS Workbench中,得到有限元模型;利用有限元分析法,分别分析动力头内关键零部件的动态特性等机械性能要求;分析齿轮在钻进过程中啮合时的受力变形情况,证明齿轮满足强度、刚度等机械性能要求,并分析齿轮间接触区域的接触情况;模拟钻探工程中提下钻、加压钻进、减压钻进3种工况,分析主轴的受力变形情况,为主轴设计提供一定的依据;分析箱体在提下钻、钻进工况下的受力变形,证明箱体具有良好的刚度、强度,并对箱体进行模态分析,得出箱体固有频率,验证箱体的动态性能。 相似文献
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深部地质钻探时,钻杆受力条件复杂,振动形式多变且剧烈。为认识钻杆的动力学特征,减少钻杆失效风险,提高钻进效率,建立了仅考虑纵向振动和扭转振动耦合作用下的深部地质钻杆动力学分析模型,并推导了钻杆固有振动频率公式,在此基础上,借助ANSYS软件进行仿真分析。研究成果表明:在纵向(扭转)振动下,随着模态阶数的增加,钻杆的轴向(角)位移变化越来越复杂;随着模态阶数的增加,钻杆的固有频率呈现线性增加;在相同模态阶数条件下,随着深度的增加,固有频率逐渐降低,但其降幅逐渐减小;当激振频率与钻柱纵向(扭转)振动固有频率相近时,钻杆的轴向(角)位移达到极值。 相似文献
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避共振是工程抗震设计中的重要课题,目前在边坡工程中鲜见这方面的研究。本文运用有限元法研究了边坡在双向地震作用下的共振规律及其固有频率。研究结果表明:边坡虽然有多阶固有频率,但只有前三阶固有频率处共振峰明显,其中尤以第一阶频率处的共振峰值最为突出,其他频率处则无明显共振现象;边坡在双向地震作用下的共振响应存在垂直放大和临空面放大作用;阻尼越大共振峰值越小,共振曲线越平缓;对影响边坡固有频率的主要因素进行深入研究,通过回归分析建立了边坡固有频率的经验公式,经检验该公式的计算误差较小。 相似文献
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《Atmósfera》2014,27(3):273-286
The temporal behavior of the annual frequency of heat and cold waves observed between 1961 and 2010 is established for the Spanish Central Plateau and for the two sub-areas in it. The series of daily maximum and minimum temperature anomalies for the working areas were calculated from the daily data concerning temperature anomalies. The thresholds of these series of anomalies, determined by the P10 and P90 percentiles values, were obtained. Heat waves occur when there are two or more consecutive days on which the maximum and minimum temperature anomalies are simultaneously greater than the values of the thresholds obtained for the P90 percentile. The heat waves that affected the Spanish Central Plateau and the two sub-areas during the period of time considered were identified and their monthly and annual frequencies were obtained. Likewise, a cold wave is considered to have occurred when there are two or more consecutive days on which the maximum and minimum temperature anomalies are simultaneously lower than the thresholds established by the corresponding P10 percentiles. The cold waves occurring in the study area were identified and their monthly and annual frequencies in the study period were established. According to the results, the months with highest number of heat waves between 1961 and 2010 were May (25 waves) and June (23 waves). Trend analysis of the series of annual frequencies indicates that there was an increasing trend towards the occurrence of heat waves, with a confidence level greater than 99%. The linear model established indicates that an increase had occurred in the frequency of heat waves in the Spanish plateau of the order of 0.6 waves every 10 years. Regarding cold waves, these were detected in each month of the year and their frequency ranged between eight and 16 events per year. The months with lowest number of cold waves were April (nine), July (eight) and August (nine), and the months with the highest number were March, May, June and October, with 16 cold waves. The years with the highest number of cold waves were 1969, 1971 and 1977, with seven cases. In the other years the annual rate was between one and six. Trend analysis of the series of annual frequencies indicated that there was a decreasing frequency of cold waves, at the confidence level of 99%. When a linear model was considered for the Spanish Central Plateau a decreasing frequency of the cold waves of the order of 0.54 waves in every 10 years was observed from 1961 to 2010. 相似文献
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岩爆孕育过程中所记录的微震事件波形本身就包含着丰富的前兆信息。基于深埋隧洞微震波的衰减特征,修正了最大有效振幅,将相对有效振幅和最大有效频率作为频谱分析参数。TBM和钻爆法不同开挖方式下诱发的即时型岩爆孕育过程的频谱演化特征基本一致,有如下特征:(1)无岩爆发生时,每日最大释放能量微震事件频谱对应的相对有效振幅的量级为10-6 m/s及以下,而最大有效频率则多大于300 Hz;(2)中等岩爆发生前,相对有效振幅的量级维持在10-5 m/s,最大有效频率则介于200~300 Hz;(3)强烈岩爆发生前,微震事件对应相对有效振幅的量级增长并保持在10-4 m/s,最大有效频率则基本在200 Hz以下;(4)对于一个完整的即时型岩爆孕育过程,当岩爆发生时,相对有效振幅增至最大,同时最大有效频率降至最低。微震信号的频谱演化特征可为即时型岩爆发生时间及等级的预警提供参考和依据。 相似文献
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针对目前参数估计方法存在稀遇洪水频率设计值偏大的问题,提出采用基于数值次序统计量期望值的适线法计算洪水频率设计初始值;针对目前参数估计方法存在常遇洪水频率设计值偏小的问题,提出采用周文德公式修正目前频率设计偏小的情形,计算洪水频率设计修正值;针对目前传统方法计算洪水频率设计值抽样误差大的问题,提出采用基于数值次序统计量标准差的方法计算洪水频率设计保证值。定量分析表明,提出的基于数值次序统计量期望值的优化适线法具有良好的无偏性和有效性;寸滩站洪水频率设计修正值大于频率设计初始值,且两者偏差随着频率减小而减小;寸滩站洪水频率设计保证值明显大于修正值。 相似文献
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现行分期设计洪水模式估算的分期设计洪水值均小于或等于年最大设计值,达不到规定的防洪标准。采用Gumbel-Hougaard Copula函数描述两个分期的分期最大洪水之间的相关性结构,并构造边缘分布为P-Ⅲ分布的分期最大洪水联合分布,建立分期最大洪水与年最大洪水的关系式,讨论分期设计洪水频率与防洪标准应满足的关系,探讨能够满足防洪标准的新的分期设计洪水模式。应用示例表明,新模式主汛期设计值相对年最大设计值小幅度增加,而非主汛期设计值则小于年最大设计值,既满足不降低防洪标准的要求又能够起到优化设计洪水的作用,为分期设计洪水研究提供了一条新的思路。 相似文献
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海平面的变化是旋回性沉积作用的重要控制因素。在克拉通盆地滨海平原沉积背景中,海岸线附近的沉积环境受海平面变化影响最为明显,旋回性沉积作用易留下证据。而在远离海岸线的内陆或滨外较深水地区,海平面变化一般难以引起沉积环境的明显变化,因而其旋回性的沉积作用不甚明显。反映在旋回的数量上,海岸线附近的旋回数目比远离海岸线地区的旋回数目要多得多。海岸线附近一般是最有利的聚煤场所,所以某一时期的旋回频率曲线中的峰值所在地区即是该时期聚煤中心所在位置。在三级海平面变化范围内,从低位、海侵到高位层序组,旋回峰值区会随着海平面的变化而变化,据此我们可以识别聚煤中心的迁移规律。依据高分辨率层序地层学原理,本文将贵州西部晚二叠世含煤岩系划分为3个三级复合层序及15个四级层序,每个三级复合层序中又分为低位、海侵和高位层序组,在此基础上,进一步建立了不同层序组及不同复合层序的旋回频率曲线,并根据其峰值的位置分析了相应聚煤中心的变化。 相似文献
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The problem of selecting the optimum operating frequency of a scatterometer, used for remote sensing of sea surface wind speed
has been addressed by applying the criteria of maximum sensitivity of backscattering coefficient to wind speed as well as
its correlation with wind speed. The backscattering coefficient values for sea surface were computed by the two-scale scattering
theory. To compute the atmospheric transmittance, 753 clear sky atmospheres over Indian Ocean were used. While the correlation
coefficient was uniform (0.94) throughout the frequency range of 1 to 30GHz, only frequencies above 5GHz were found sensitive
enough to yield a wind speed accuracy of ±2msec−1 and better, the accuracy improving with frequency. 相似文献