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21.
Elastic modulus measurements via laser-ultrasonic and knoop indentation techniques in thermally sprayed coatings 总被引:1,自引:0,他引:1
R. S. Lima S. E. Kruger G. Lamouche B. R. Marple 《Journal of Thermal Spray Technology》2005,14(1):52-60
Nondestructive techniques for evaluating and characterizing coatings were extensively demanded by the thermal spray community;
nonetheless, few results have been produced in practice due to difficulties in analyzing the complex structure of thermal
spray coatings. Of particular interest is knowledge of the elastic modulus values and Poisson’s ratios, which are very important
when seeking to understand and/or model the mechanical behavior or to develop life prediction models of thermal spray coatings
used in various applications (e.g., wear, fatigue, and high temperatures). In the current study, two techniques, laser-ultrasonics
and Knoop indentation, were used to determine the elastic modulus of thermal spray coatings. Laser-ultrasonics is a noncontact
and nondestructive evaluation method that uses lasers to generate and detect ultrasound. Ultrasonic velocities in a material
are directly related to its elastic modulus value. The Knoop indentation technique, which has been widely used as a method
for determining elastic modulus values, was used to compare and validate the measurements of the laser-ultrasonic technique.
The determination of elastic modulus values via the Knoop indentation technique is based on the measurement of elastic recovery
of the dimensions of the Knoop indentation impression. The approach used in the current study was to focus on evaluating the
elastic modulus of very uniform, dense, and near-isotropic titania and WC-Co thermal spray coatings using these two techniques.
Four different coatings were evaluated: two titania coatings produced by air plasma spray (APS) and high-velocity oxyfuel
(HVOF) and two types of WC-Co coatings, conventional and multimodal (nanostructured and microsized particles), deposited by
HVOF.
The original version of this article was published as part of the ASM Proceedings, Thermal Spray 2003: Advancing the Science and Applying the Technology, International Thermal Spray Conference (Orlando, FL), 5–8 May, 2003, Basil R. Marple and Christian Moreau, Eds., ASM International,
2003. 相似文献
22.
相变增韧陶瓷压痕开裂的力学分析 总被引:3,自引:3,他引:3
在相变增韧陶瓷中,压痕裂纹形成的原因除了因压痕导致塑性区体积变化产生的残余应力外,还与应力诱发相变导致塑性区体积膨胀而产生的附加应力或称相变应力有关。传统的压痕法和压痕-强度法忽略了相变应力对压痕开裂和试样断裂的贡献,所测得相变增韧陶瓷的断裂韧性数据往往偏低。 相似文献
23.
The nanoindenting method is based on the automatic measurement and recording of the force acting on the indenter (10−2-5 N) and the depth of indentation (10−2-200 μm). The scratch hardness or nanoscratching method is based on the continuous recording of resistance forces to movement
of the indenter impressed into the surface.
__________
Translated from Problemy Prochnosti, No. 4, pp. 132–139, July–August, 2006. 相似文献
24.
M. Tanaka K. Higashida H. Nakashima H. Takagi M. Fujiwara 《International Journal of Fracture》2006,139(3-4):383-394
Fracture toughness of silicon crystals has been investigated using indentation methods, and their surface energies have been
calculated by molecular dynamics (MD). In order to determine the most preferential fracture plane at room temperature among
the crystallographic planes containing the 〈001〉, 〈110〉 and 〈111〉 directions, a conical indenter was forced into (001), (110)
and (111) silicon wafers at room temperature. Dominant {110}, {111} and {110} cracks were introduced from the indents on (001),
(011) and (111) wafers, respectively. Fracture occurs most easily along {110}, {111} and {110} planes among the crystallographic
planes containing the 〈001〉, 〈011〉 and 〈111〉 directions, respectively. A series of surface energies of those planes were calculated
by MD to confirm the orientation dependence of fracture toughness. The surface energy of the {110} plane is the minimum of
1.50 Jm−2 among planes containing the 〈001〉 and 〈111〉 directions, respectively, and that of the {111} plane is the minimum of 1.19
Jm−2 among the planes containing the 〈011〉 direction. Fracture toughness of those planes was also derived from the calculated
surface energies. It was shown that the K
IC value of the {110} crack plane was the minimum among those for the planes containing the 〈001〉 and 〈111〉 directions, respectively,
and that K
IC value of the {111} crack plane was the minimum among those for the planes containing the 〈011〉 direction. These results are
in good agreement with that obtained conical indentation. 相似文献
25.
A. P. S. Selvadurai A. Shirazi 《International journal for numerical methods in engineering》2005,63(14):2017-2039
A flat rigid elliptical anchorage located in a damage‐susceptible fluid‐saturated poroelastic medium is subjected to an in‐plane load, which induces a pure translation in the plane of the anchor. This paper develops computational estimates for the time‐dependent displacement of the disc anchor for the classical problem that involves Biot consolidation and compares the results with situations where the porous skeleton can experience micro‐mechanical damage that leads to an alteration in both its elasticity and fluid transport characteristics. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
26.
Test results for different high-strength steel specimens in static and impact tension and compression over a wide range of strain rates were summarized. These data were used to calculate the generalized deformation curve. The calculations based on this curve were compared with the experimental data on impact indentation with the conical indenter to evaluate the applicability of this method for studying the behavior of metals at high strain rates. 相似文献
27.
28.
《Journal of Nuclear Science and Technology》2013,50(4):575-579
Part of the Fuel Cycle R&D (FCRD) initiative in the USA is to investigate materials for high dose application. While mechanical testing on large samples delivers direct engineering data, these types of tests are only possible if enough sample material and required hot cell capabilities are available. Smallscale materials testing methods in addition to large-scale materials testing allows insight on the same specimen and direct probing into areas of interest which are not accessible otherwise. In order to establish an empirical and research-based relationship between small-scale and large-scale materials testing, several different mechanical testing techniques were conducted on the same specimen irradiated in the Swiss spallation source irradiation program (STIP) at the Swiss spallation source (SINQ) at the Paul Scherrer Institute (PSI) up to a dose of 19 dpa. It is shown that the yield strength measured by tensile testing, microcompression testing and microhardness testing all show the same trend. In addition, focused ion beam (FIB)-based techniques also are used to produce local electrode atom probe (LEAP) samples. This procedure allows cutting samples of such a small size that no radioactivity on the prepared sample can be measured. 相似文献
29.
Fatou Ndoye Muhammad Sulaiman Yousafzai Giovanna Coceano Serena Bonin Giacinto Scoles Oumar Ka 《International Journal of Optomechatronics》2016,10(1):53-62
We studied the lateral forces arising during the vertical indentation of the cell membrane by an optically trapped microbead, using back focal plane interferometry to determine force components in all directions. We analyzed the cell-microbead interaction and showed that indeed the force had also lateral components. Using the Hertz model, we calculated and compared the elastic moduli resulting from the total and vertical forces, showing that the differences are important and the total force should be considered. To confirm our results we analyzed cells from two breast cancer cell lines: MDA-MB-231 and HBL-100, known to have different cancer aggressiveness and hence stiffness. 相似文献
30.
Robert F. Cook 《Journal of the American Ceramic Society》2018,101(4):1684-1695
The strengths of four brittle materials―cordierite glass ceramic, fused silica, silicon, and polycrystalline alumina were measured after exposure to weakly corrosive water and moderately corrosive buffered HF (BHF) solution. Exposure to water did not alter the strengths in subsequent inert strength tests and decreased the strengths in reactive strength tests. Exposure to BHF increased the strengths in both tests, but only after an incubation exposure time. Prior to the incubation time, the BHF had the same effect as water, suggesting that the bond rupture kinetics were unaffected. Examination of strength‐controlling indentation flaws after the incubation time showed clear corrosive effects on the flaw geometry indicative of reductions in the indentation residual stress fields. The implication is that moderately corrosive environments increase the strength or lifetime of a brittle component by reducing the crack driving force via flaw alteration and do not, as perhaps expected, decrease the strength or lifetime through enhanced chemical reactivity. 相似文献