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冲击过程中能量匹配分析 总被引：1，自引：0，他引：1
颜祥山 《贵州教育学院学报》2001,12(2):16-17
简论了冲击过程中采用应力波方法分析能量匹配问题 ,得出 :冲击机械中入射应力波如满足理想波形时 ,从冲击对象反射回来的反射应力波能量达最小 ,冲击机械的能效达到最大值 相似文献
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高压水射流冲击下煤体初始失效机理研究有助于评价煤体损伤特征。以九龙矿2#煤层为研究对象,采用光滑粒子流体动力学(smoothed particle hydrodynamics, SPH)方法建立了水射流冲蚀煤体数值模型,结合von Mises理论分析了煤体在高压水射流冲击下内部应力分布及裂纹扩展特征,并基于Python编程图像处理技术量化表征了煤体内裂纹形成规律。研究结果表明：在射流冲击下煤体损伤演化过程分为3个典型区,即破碎区、初始裂纹形成区和裂纹扩展区。当射流接触煤体表面时,在水锤效应影响下煤体主要受剪应力作用形成破碎区;在初始裂纹形成区,煤体受到压剪应力及微小拉应力共同作用,初始裂纹萌生;随着水锤效应的消失,射流冲击引发的应力波导致煤体内部主要承受拉应力作用,形成裂纹扩展区。因此,在实际工程中可以通过实时监测射流冲击下煤体内部应力特征来判断其损伤程度。 相似文献
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冲击碰撞试验台在中应变率压缩试验中的应用 总被引：1，自引：0，他引：1
《实验室研究与探索》2015,(9)
选用以脉冲加速度作为激励的垂直冲击碰撞试验台进行中应变率压缩试验。针对缓冲材料在中应变率1~500 s-1的应力-应变曲线,介绍了垂直冲击碰撞试验台的工作原理,推导了缓冲材料试件的应力-应变曲线与输入脉冲加速度之间的关系。以常见的蜂窝纸板的动态压缩试验作为例子。试验表明,蜂窝纸板在动态压缩时的应力-应变曲线明显不同于在准静态压缩时的结果,同时证实了利用垂直冲击碰撞测试缓冲材料的中应变率压缩试验时,具有操作简单与易控制的优点。 相似文献
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采用有限元法分析铝金属空心球型闭孔泡沫材料的动态力学性能,研究了冲击速度、相对密度、基体材料的应变强化以及功能梯度对泡沫材料的平台应力和密实化应变能的影响。结果表明：泡沫材料的平台应力和密实化应变能均随着冲击速度、相对密度和应变强化的增加而增强;功能梯度模型在能量吸收方面表现出明显的优越性,即密度最大的一层作为冲击端、密度最小的一层作为固定端的梯度配置泡沫模型的能量吸收最大。 相似文献
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本文以地下工程开挖钻爆法为研究主体,深入分析了爆炸应力波传播及衰减规律,针对粉碎区和裂隙区分别构建了相应径向应力和切向应力的计算公式,并给出了粉碎区大致范围.分析认为爆炸应力波传播及衰减规律的研究关键是获取炮孔孔壁处冲击波波速、冲击波峰值压力和质点振动速度三个参数,未来提高爆炸应力波传播及衰减规律研究精度可从此三参数着手努力. 相似文献
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文章以同煤集团忻州窑矿为例,分析研究了冲击地压的成因,对浅埋深条件下坚硬顶板实施针对性爆破弱化处理,使煤层顶板集聚的能量得到有效释放,煤体与煤柱的应力和压力减小,冲击地压的频次与强度显著降低。为浅埋深坚硬顶板条件下冲击地压的防治探索出一条有效的途径。 相似文献
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建立了一种基于广义梁理论(GBT)的非线性显式动力梁有限元模型,该模型可用于等截面薄壁钢构件的冲击响应模拟.考虑冲击加载时的应变率强化及绝热升温引起的热软化效应,当前模型采用了一种修正的Cowper-Symonds率相关本构模型.用GBT截面变形模态构建单元截面位移场,因此新模型可考虑构件截面的畸变、屈曲及任意的翘曲剪切等局部效应.此外,用三次非均匀B样条基函数拟合各个GBT截面变形模态的幅值函数.用Kirchhoff薄板假设构造弯曲相关位移场.用Green-Lagrange应变张量和PK2应力分别描述材料点的应变和应力,假设各材料点处于平面应力状态.为了验证所提模型的有效性,给出了3组薄壁构件的冲击分析算例,将当前模型的结果和壳有限元(Ls-Dyna)分析结果进行了对比,结果表明:当前模型和壳有限元模型的位移解和应力解具有等效精度,但所提模型的计算效率更高,并具备更好的结构明晰性. 相似文献
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兰大奇 《河北能源职业技术学院学报》2002,2(2):55-56
冲击地压是一种严重威胁矿井生产的灾害，大部分发生在采准巷道。本文从采煤方法、煤体应力分布，支护强度及采动影响等几方面，对发生机理进行探讨，并提出防治措施。 相似文献
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冲击压实机冲击力及冲击能量的计算 总被引：5，自引：0，他引：5
冲击压实机广泛用于建筑行业．目前对具有特殊外形的冲击压实机冲击轮的动力特性研究的不多．根据冲量定理和动能定理，对冲击压实机的冲击力和冲击能进行研究．利用冲击轮的特殊外形，对地面产生大的冲击力和冲击能，通过理论计算，其结果与同吨位的振动压实机相比，冲击力提高十倍，冲击能效果明显，为压实机的设计及改进提供可靠的理论依据。 相似文献
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生命周期评估(LCA)是绿色产品设计的一项重要内容, 影响评估是LCA的重要阶段. 本文将各种排放物影响因子进行分类后, 应用灰色系统理论, 提出了影响评估灰类划分及其白化权函数, 对各影响类别进行了灰色聚类分析, 然后根据分析结果给出了分类影响指数的计算方法. 根据各影响类别的作用范围, 将影响类别按全球影响、区域影响、本地影响进行了分组, 并给出了分组影响指数以及总体影响指数的计算方法. 最后, 以设计中的3种材料钢、铝、工程塑料为例, 说明了以上方法在一类产品比较选择中的应用. 相似文献
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在冲击荷载作用下,钢框架结构的动态响应是一个复杂的非线性过程。运用ANSYS/LS-DYNA建立了钢框架的三维模型,对冲击荷载作用下钢框架的动态响应和破坏形态进行研究。采取多点积分算法,有效避免沙漏问题,保证计算结果精确。以冲击块与钢框架的碰撞冲击为例,研究了冲击速度、冲击块质量、冲击位置等参数对钢框架在横向冲击作用下动力响应的影响,并分析冲击荷载下钢框架的破坏形态。结果表明:冲击块的质量、速度、冲击位置的增加都会不同程度地加剧钢框架的动态响应;在冲击作用下,高应变主要出现在被冲击柱子的冲击区域、柱脚处和梁柱节点处;冲击荷载下钢框架的破坏形态为整个框架发生侧移,受冲击柱在冲击处翼缘出现局部屈曲,受冲击区域的截面发生弯扭,未受冲击柱出现倾斜。 相似文献
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转子叶轮-定子触碰故障的分析与辨识 总被引：1，自引：0，他引：1
基于航空涡轮发动机和工业透平机中的转子叶轮定子间触碰故障背景 ,以力学建模为指导搭建了两类简支型的转子定子触碰故障实验台架 ,考察了转子定子间正常无触碰、早期尖锐型轻微触碰、中期半尖锐型触碰、晚期平钝型触碰 4种状态时转子振动位移的时域轨迹 ,观测到了早期尖锐型轻微触碰时伴生的混沌现象 .采用FFT方法对上述 4种状态试验数据的频率结构作了分析 ,结果表明当出现三分频以下 (包括三分频 )的分频特征时可以初步判断叶片发生了早期触碰 ,而当转子振动位移的频谱图中仅存有两分频分量甚至轴频分量时 ,叶片 -转子间的触碰故障已相当严重了 . 相似文献
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王向远 《商丘师范学院学报》2003,19(6):5-9
“影响研究”就是在“传播研究”所能提供的事实非常有限的条件下，提出文学影响的假说，并在此基础上对作家作品进行细致地分析和研究。在这个问题上，笔者不同意韦勒克等人关于“影响研究”“甚至不可能完整地研究一部艺术品”的看法，认为“影响研究”有三个阶段或三个层次：第一，提出“影响”的假说；第二，为论证影响假说而对具体作家作品进行分析，其中包括对主题、题材与情节的分析、对典型人物的解剖、对艺术手法艺术风格的对比等等，从而看出影响是否存在，如何存在，如何表现；第三，指出影响接受者如何超越影响，即“超影响”的研究，亦即研究影响的范围与限度、影响与独创的关系。 相似文献
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Thorsten Gruber 《Journal of Marketing for HIGHER EDUCATION》2013,23(2):165-177
Increasingly, academics have to demonstrate that their research has academic impact. Universities normally use journal rankings and journal impact factors to assess the research impact of individual academics. More recently, citation counts for individual articles and the h-index have also been used to measure the academic impact of academics. There are, however, several serious problems with relying on journal rankings, journal impact factors and citation counts. For example, articles without any impact may be published in highly ranked journals or journals with high impact factor, whereas articles with high impact could be published in lower ranked journals or journals with low impact factor. Citation counts can also be easily gamed and manipulated, and the h-index disadvantages early career academics. This paper discusses these and several other problems and suggests alternatives such as post-publication peer review and open-access journals. 相似文献
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Yong-wei Wang Jun Wang Chong Yao Qiu-jun Lu 《Journal of Zhejiang University. Science. B》2009,10(12):883-889
The impact force response of a peach impacting on a metal flat-surface was considered as nondestructive determination of firmness. The objectives were to analyze the effect of firmness, drop height, fruit mass, and impact orientation on the impact force parameters, and to establish a relationship between the impact force parameter and firmness. The effect of fruit firmness, drop height and fruit mass on the impact force parameters (coefficient of restitution, percentage of energy absorbed, and coefficient of force-time) was evaluated. The study found that the coefficient of restitution, percentage of energy absorbed, and force-time impact coefficient were significantly affected by fruit ripeness, but not affected by drop height, impact position (fruit cheek), and mass. The percentage of absorbed energy increased with ripeness, while the force-time impact coefficient and coefficient of restitution decreased with ripeness. Relationships were obtained between the three impact characteristic parameters (force-time impact coefficient, coefficient of restitution, and percentage of energy absorbed) and peach firmness using a polynomial model (R~2=0.932), S model (R~2=0.910), and exponential model (R~2=0.941), respectively. 相似文献
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Tina Cook Jonathan Boote Nicola Buckley Sofia Vougioukalou Michael Wright 《Educational Action Research》2017,25(4):473-488
Action research has been characterised as systematic enquiry into practice, undertaken by those involved, with the aim changing and improving that practice: an approach designed to have impact. Whilst much has been written about the process and practice of ‘researching’, historically ‘impact’ has been somewhat taken for granted. In recent years, however, the impact of all forms of research has become the focus of interest with many funding bodies now demanding that researchers not only articulate the prospective impact of their work, but what kinds of evidence will be proffered to demonstrate that impact. This has raised questions for action researchers, not about whether their work has an impact, but what form that impact takes, how it is recognised and by whom. This paper focuses on difficulties researchers find in both articulating the impact of participatory research and demonstrating links between such forms of research and impact. We draw on discussions about the notion of impact with authors that have self-reported and published their work as participatory. These discussions revealed that not only were there difficulties in clarifying the participatory dimension of their research but that whilst authors were able to discuss particular impacts of their work, articulating and evidencing that impact was often absent from their published papers. This paper offers insights into some of issues and barriers those who undertake participatory research face in explicating, for the external audience (and indeed sometimes for ourselves), the impact of this action-based form of enquiry. 相似文献
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Despite the growing debate about scholarly impact, an analysis of the onto-epistemic grammar underlying impact has remained absent. By taking a different analytical approach to examining impact, we interrogate the concept through the lens of decolonial thought. We offer an empathetic review of the impact scholarship and illuminate the limits of the modern imaginary that circumscribe critiques of impact in the literature, making visible the Eurocentric and provincial horizons of modern reason underlying these critiques and impact in general. Drawing on ?ūnyatā ontological perspective, we seek to articulate from modernity imaginary’s edges and suggest imagining and being otherwise. We argue that the question of scholarly impact is intimately structured by and connected to the modern subject’s desire for ontological security. 相似文献