共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
薄壁球壳受刚性平面压缩的连续变形测量 总被引:1,自引:0,他引:1
建立了非接触光学测量实验系统,对薄壁球壳受刚性平面压缩的连续变形及失稳行为进行了实验研究。实验以理想弹塑性材料制成的薄且壁厚均匀的乒乓球为压缩对象,采用透明石英玻璃板作为刚性平面,用相机透过玻璃板采集清晰的散斑图像。然后利用具有非接触、全场、高精度等优点的三维数字图像相关(3D-DIC)技术对与刚性平面接触的乒乓球表面的连续变形进行直接测量,同时利用二维数字图像相关技术结合压力传感器得到对应的力-位移关系。实验研究表明,基于3D-DIC方法测量三维表面变形场,实现了对受刚性平面压缩的乒乓球表面从局部压平阶段到轴对称屈曲阶段,进而演化到非轴对称屈曲阶段等力学行为的可视化。实验结果表明,对乒乓球半径的测量精度可达0.5%,利用Abaqus有限元方法得到的结果与实验结果非常吻合,验证了所提方法的有效性。 相似文献
3.
4.
两步压入法--薄膜力学性能的可靠测量方法 总被引:17,自引:2,他引:17
提出了采用力学探针测量薄膜力学性能的两步压入法.该方法通过大载荷压入展示基体变形对薄膜硬度的影响,从而选择不影响基体变形的小载荷测出薄膜的硬度和弹性模量.对高速钢基片上的TiN硬质薄膜,单晶硅片上的金属Ni薄膜和(Ti,Al)N/VN纳米多层膜的测量表明,两步压入法能够测出各种性质薄膜的力学性能,并且具有准确可靠的特点.此外,两步法对(Ti,Al)N/VN纳米多层膜的力学性能的测量表明,该体系的纳米多层膜存在硬度和弹性模量异常升高的超硬、超模量效应. 相似文献
5.
6.
针对机械密封运转过程中平均膜厚的变化规律,采用重构分形接触模型表征端面形貌,结合机械密封泄漏率预测模型,建立了平均膜厚预测模型。使用Mathematica软件对给定工况下机械密封的泄漏率和平均膜厚进行理论计算,分析不同参数条件下泄漏率和平均膜厚的变化趋势。研究表明:当分形维数较小时,尺度系数减小、材料系数增大和端面比载荷增大均可使平均膜厚减小,但材料系数变化对平均膜厚数值的影响幅度较小,而尺度系数和材料系数减小、端面比载荷增大可导致泄漏率降低;当分形维数大于1.69时,机械密封端面比载荷和材料性能参数对泄漏率和平均膜厚的影响可忽略不计。 相似文献
7.
为增强基于Ag膜光纤表面等离子体共振(SPR)传感器的抗氧化能力,可将Au膜镀于Ag膜表面。利用TFCalc软件对不同厚度Ag膜和Au-Ag复合膜的光纤SPR传感特性进行理论仿真研究。仿真结果表明:光纤SPR吸收峰显著依赖于Ag膜厚度,当Ag膜厚度由40nm逐渐增加到80nm时,共振吸收峰的半峰全宽逐渐减小,且共振波长随Ag膜厚度的增大而减小,共振波长变化范围较小,仅为7nm左右;Au膜的引入对共振吸收峰反射率影响不大,不同厚度Au-Ag复合膜的SPR共振波长随Au膜厚度的增大而增大。 相似文献
8.
Jung-Eun Lee Hyun-Joon Kim Dae-Eun Kim 《Journal of Mechanical Science and Technology》2010,24(1):97-101
Thin film coatings are commonly utilized to prevent wear, modify surface properties, and manipulate the frictional behavior
of various mechanical systems. The behavior of a coating has a direct effect on the life as well as performance of the system.
However, the coating itself is subject to damage, and the quality of the coating is related to the adhesion characteristics
between the coating and the substrate. Therefore, a quantitative assessment of the adhesion properties of thin film is important
to guarantee the reliability of not only the thin film but also the mechanical system. In this study, ramp loading scratch
tests were performed to assess the adhesion characteristics of Ag and ZnO thin films coated on a silicon wafer. Silver thin
film, deposited by sputtering, and ZnO thin film, fabricated by a sol-gel method, were used as scratch specimens. Scratch
tests using a diamond tip were performed with a continuously increasing normal force. During the scratch test, the normal
and frictional forces were monitored to assess the integrity of the film. The Benjamin and Weaver model commonly used for
obtaining the horizontal force during the scratching of films coated on a substrate showed large discrepancies with the experimental
results. In this work, the model was modified with a plowing term to minimize the difference between the experimental and
theoretical results. Using the modified model, the experimental results could be predicted with an accuracy of about 10%. 相似文献
9.
10.
采用射频磁控溅射法沉积了Si1-xGex薄膜,研究了溅射气压、衬底温度对薄膜结构、厚度、表面形貌、表面成分及光吸收性能的影响。结果表明:薄膜均为微晶结构且相组成不随溅射气压和衬底温度的改变而改变;随着溅射气压升高,薄膜结晶性能降低,升高衬底温度使其结晶性能提高;随气压或温度的升高,薄膜厚度均先增大后减小,在1.0Pa或400℃达到最大值;随温度的升高,薄膜表面团簇现象消失并变得平整致密,气压为8.0Pa时,表面有孔洞和沟道;随气压升高,薄膜中锗含量降低,光吸收强度减小,光学带隙增大;衬底温度的变化对光学带隙影响不大。 相似文献
11.
In this paper is discussed the effect of the physical characteristics of substrate surfaces on the lubrication properties of thin films at nanometre scale. Different coatings with different surface energies have been formed on the surface of a steel ball by means of plasma assisted sedimentation (PAS). The ball was put in a pure rolling system in point contact, where the lubricant film is measured by relative optical interference intensity (ROII). Experimental results show that the film thickness is closely related to the substrate surface energy when the film is in the nanometre scale, and that the combined surface roughness in the contact region is closely related to the liquid lubricant film thickness and the contact pressure. The thinner the film and the higher the contact pressure, the smaller will be the combined surface roughness. Lastly, the relationship between critical film thickness and its influencing factors is discussed. 相似文献
12.
为研究在弹流润滑状态下表面形貌对亚表层特性的影响,利用激光加工方法获得2种微凹坑型织构表面形貌,通过将实测的表面形貌坐标输入弹流润滑数值计算程序得到油膜压力和膜厚分布;以对应工况的油膜压力作为表面法向压应力,利用Rabinowicz经验公式算出剪切应力;将表面法向压应力和切向剪应力叠加后对弹流润滑界面亚表层特性进行仿真研究。结果表明:表面织构使亚表层应力分布发生显著改变;微凹坑直径、卷吸速度对亚表层应力的大小与分布有不同的影响;亚表层变形在摩擦过程中呈现随深度增加先缓慢减小后快速下降的规律,研究结果将为通过表面形貌设计改善轴承等零件受力状况提供理论支持。 相似文献
13.
Silver was sputter deposited on a glass with a thin film thickness ranging from 10 to 80 nm. Scanning tunnelling microscopy was used to study the morphology of the obtained Ag–glass surfaces and to estimate the surface roughness. An equation for the surface roughness of the thin film was evaluated using parameters related to the thin film features: the surface roughness of the substrate, the compressibility of the thin film and the film thickness. The experimental results were fitted using the evaluated equation, and the conditions favouring lower or higher surface roughness were analyzed. 相似文献
14.
Rwei -Ching Chang Feng -Yuan Chen PaoHsiang Yang 《Journal of Mechanical Science and Technology》2007,21(10):1739-1744
Photo resist thin films have mainly been used and investigated for versatile applications of micro electronic mechanical systems
because of its outstanding aspect ratio and attainable film thickness. An accurate structure properties derived from validated
material characterization is required in engineering applications. In this work, dynamic responses of photo resist thin films
are tested by a nanoindentation in association with a dynamic mechanical analysis, where the thin film is coated on a silicon
wafer by spin coating. The results show that the storage modulus of the photo resist thin film remains constant at the beginning
and then increases as the indentation depth increases. Meanwhile, the loss modulus increases as the indentation depth increases.
Varying the film thickness shows that the substrate effect plays an important role in determining the dynamic properties of
thin films. However, the results agree well with the bulk material when the amplitude of nanoindentation is relatively small.
It illustrates the dynamic mechanical analysis can be an efficient method to characterize the viscoelastic properties of thin
films, but proper attention on the test parameters is needed. 相似文献
15.
16.
17.
Tong-Bou Chang Wen-Yu Yeh Go-Long Tsai 《Journal of Mechanical Science and Technology》2009,23(12):3399-3406
This study performs a theoretical investigation into the problem of two-dimensional steady filmwise condensation flow on a
horizontal tube with suction effects at the tube surface. An effective suction function is introduced to model the effect
of the wall suction on the thickness of the liquid condensate film. The local condensate film thickness and the local Nusselt
number are then derived using a simple series numerical method. The results show that the Nusselt number varies as a function
of the Jakob number Ja, the Rayleigh number Ra, and the suction parameter Sw. It is found that the wall suction effect has a significant influence on the heat transfer performance. An analytical solution
is derived for the mean Nusselt number for the case in which the wall suction effect is ignored. Finally, a closed-form correlation
is presented for the mean Nusselt number subject to a wall suction effect. 相似文献
18.
19.
Feng -Yuan Chen Rwei -Ching Chang 《Journal of Mechanical Science and Technology》2007,21(10):1471-1476
In this paper, the imperfect tip effect of the Ti film on Si substrate on nanoindentation with Berkovich probe tip was investigated
with the finite element method (FEM). In the literature, we found the effects of tip deformation and tip radius on nanoindentation
were investigated frequently, but the imperfect centerline of tip has never been studied. In this work, at first, the Ti film
on Si substrate was conducted with a high-resolution nanomechanical test. The Young’s modulus of Ti films can be obtained
by using the Oliver and Pharr method while the nanoindentation depth is smaller than 20% of the film thickness for avoiding
the substrate effect. Second, the FEM was employed to determine the yield stress of thin films because it cannot be found
from nanoindentation. Finally, the load-depth of nanoindentation was compared between the experimental data and numerical
results. The results show while choosing the suitable yield stress of films, the load-depth curves of numerical simulation
were very close to the experimental curves with the imperfect effect being ignored. Moreover, it is concluded while the imperfect
angles of tip were considered that the larger imperfect angles |θ
x
| orθ
x
, the smaller displacement on nanoindentation. 相似文献
20.
Pengwan CHEN Zhongbin ZHOU Shaopeng MA Qinwei MA Fenglei HUANG 《Frontiers of Mechanical Engineering》2011,6(3):292
In this work, a pre-cracked semi-circular shaped explosive simulant was loaded using a split Hopkinson pressure bar (SHPB). A high-speed camera was used to capture the deformation and fracture process of the specimen in situ. The digital images were processed using the digital image correlation (DIC) method. Next, full displacement and strain fields were obtained. The displacement vector field shows that the specimen fractured under tensile stress action. The strain field can be used to predict the crack propagation. Results show that the method of combined DIC and SHPB is effective to study the dynamic deformation and fracture behavior of explosive simulants. In addition, the specimen was loaded using a drop weight. The fracture toughness of the specimen was preliminary measured. 相似文献