Comparative investigation of strength and plastic instability in Cu/Au and Cu/Cr multilayers by indentation

2009 ◽  
Vol 24 (3) ◽  
pp. 728-735 ◽  
Author(s):  
Y.P. Li ◽  
X.F. Zhu ◽  
J. Tan ◽  
B. Wu ◽  
W. Wang ◽  
...  
Keyword(s):  
Layer Thickness ◽  
Mechanical Response ◽  
Plastic Instability ◽  
Comparative Investigation ◽  
Individual Layer ◽  
Confining Effect ◽  
Significant Difference ◽  
Deformation Instability ◽  
Interface Structures ◽  
Constituent Layer

The mechanical response to indentation (including nano- and microindentation) has been investigated in Cu/Au and Cu/Cr multilayers with respective layer thickness ratios of 1:1 and 2:1, and individual layer thickness ranging from nanometer to submicrometer scale. It was found that the Cu/Cr multilayer has higher strength than the Cu/Au multilayer, although both multilayers have close Hall–Petch slope. Examination of indentation-induced deformation behavior shows that the Cu/Cr multilayer exhibits higher resistance to plastic deformation instability than the Cu/Au multilayer. Theoretical analysis indicates that the significant difference in mechanical response originates from the constituent layer configuration and interface structures, which impose distinguishing confining effect on dislocation activity.

Ocular surface analysis: A comparison between the LipiView® II and IDRA®

2020 ◽  
pp. 112067212096903
Author(s):  
Jeong Min Lee ◽  
Young Joon Jeon ◽  
Kook Young Kim ◽  
Kyu-Yeon Hwang ◽  
Young-A Kwon ◽  
...  
Keyword(s):  
Observational Study ◽  
Layer Thickness ◽  
Surface Analysis ◽  
Ocular Surface ◽  
Random Order ◽  
Meibomian Gland ◽  
Lipid Layer ◽  
Cross Sectional ◽  
Single Visit ◽  
Significant Difference

Purpose: To compare the lipid layer thickness (LLT), meibomian gland (MG) dropouts, and blinking pattern determined by the analysis of images acquired from the LipiView® II (LVII) and the IDRA® Ocular surface analyzer. Methods: A cross-sectional single-visit observational study was conducted. The LLT (minimum, maximum, and average), percentages of MG dropouts, and partial blink rates (PBR) were taken from both eyes of 47 participants using LVII and IDRA. Both devices were used to image the inferior eyelid of each participant in a random order. Results: Forty-seven participants (mean age 56.77 ± 14.47 (21–79) years, 66% female) completed the study. There was no significant difference in LLT between the two devices. A significant difference in percentages of MG dropouts was obtained between the LVII (36.51 ± 17.53) and the IDRA (45.36 ± 21.87), p = 0.003). There was also a significant difference in PBR between the LVII (0.51 ± 0.37) and the IDRA (0.23 ± 0.27), p < 0.001). Conclusion: No significant difference in LLT was obtained between LVII and IDRA. IDRA had a significantly lesser percentage of MG dropout and a higher PBR compared to LVII. These results indicate that these devices should not be used interchangeably for the evaluation of MG dropouts and PBR.

Effects of Elevated Temperature Annealing on the Structure and Hardness of Copper/niobium Nanolayered Films

2005 ◽  
Vol 20 (8) ◽  
pp. 2046-2054 ◽  
Author(s):  
A. Misra ◽  
R.G. Hoagland
Keyword(s):  
Grain Size ◽  
Elevated Temperature ◽  
Layer Thickness ◽  
Vacuum Annealing ◽  
Thermally Stable ◽  
Morphological Stability ◽  
Individual Layer ◽  
Individual Layer Thickness ◽  
Equiaxed Grain

We investigated the effects of elevated temperature vacuum annealing on the morphological stability and hardness of self-supported, textured, polycrystalline Cu–Nb nanolayered films with individual layer thickness varying from 15 to 75 nm. Films with layer thickness greater than approximately 35 nm are found to resist layer pinch-off and spheroidization even after long annealing times at 700 °C, while films with layer thickness ∼15 nm exhibit layer pinch-off and evolve into an equiaxed grain microstructure. Nanoindentation measurements indicate almost no change in hardness after annealing for films that retain the layered morphology, in spite of the increase of in-plane grain dimensions. Significant decreases in hardness are noted for films that develop a coarsened equiaxed grain microstructure after annealing. The mechanism that leads to the development of a thermally stable nanolayered structure is analyzed. Also, the relative effects of in-plane grain size and layer thickness on the multilayer hardness are discussed.

scholarly journals Cracking and Toughening Mechanisms in Nanoscale Metallic Multilayer Films: A Brief Review

2018 ◽  
Vol 8 (10) ◽  
pp. 1821 ◽  
Author(s):  
Qing Zhou ◽  
Yue Ren ◽  
Yin Du ◽  
Dongpeng Hua ◽  
Weichao Han
Keyword(s):  
Fracture Toughness ◽  
High Strength ◽  
Plastic Instability ◽  
Multilayer Films ◽  
Fracture Mechanisms ◽  
Toughening Mechanisms ◽  
Individual Layer ◽  
Practical Applications ◽  
Mechanical Responses ◽  
The Individual

Nanoscale metallic multilayer films (NMMFs) have captured scientific interests on their mechanical responses. Compared with the properties of monolithic films, multilayers possess unique high strength as the individual layer thickness reduces to the nanoscale, which is benefited from the plentiful hetero-interfaces. However, NMMFs always exhibit a low fracture toughness and ductility, which seriously hinders their practical applications. While there have been reviews on the strengthening and deformation mechanisms of microlaminate, rapid developments in nanotechnology have brought an urgent requirement for an overview focused on the cracking and toughening mechanisms in nanoscale metallic multilayers. This article provides an extensive review on the structure, standard methodology and fracture mechanisms of NMMFs. A number of issues about the crack-related properties of NMMFs have been displayed, such as fracture toughness, wear resistance, adhesion energy, and plastic instability. Taken together, it is hoped that this review will achieve the following two purposes: (1) introducing the size-dependent cracking and toughness performance in NMMFs; and (2) offer a better understanding of the role interfaces displayed in toughening mechanisms. Finally, we list a few questions we concerned, which may shed light on further development.

Nanoindentation properties of compression-moulded ultra-high molecular weight polyethylene

2003 ◽  
Vol 217 (5) ◽  
pp. 357-366 ◽  
Author(s):  
S P Ho ◽  
L Riester ◽  
M Drews ◽  
T Boland ◽  
M LaBerge
Keyword(s):  
Molecular Weight ◽  
Elastic Modulus ◽  
High Molecular Weight ◽  
Mechanical Response ◽  
Total Joint Replacement ◽  
Scanning Calorimetry ◽  
Nanomechanical Properties ◽  
Significant Difference ◽  
Ultra High Molecular Weight ◽  
Penetration Depths

This paper investigates the elastic modulus and hardness of untreated and treated compression-moulded ultra-high molecular weight polyethylene (UHMWPE) tibial inserts of a total knee replacement (TKR) prosthesis. Investigations were carried out at a nanoscale using a Nanoindenter™ at penetration depths of 100, 250 and 500 nm. The nanomechanical properties of surface and subsurface layers of the compression-moulded tibial inserts were studied using the untreated UHMWPE. The nanomechanical properties of intermediate and core layers of the compression-moulded tibial insert were studied using the cryoultrasectioned and etched UHMWPE treated samples. The cryoultrasectioning temperature (-150°C) of the samples was below the glass transition temperature, Tg(-122± 2°C), of UHMWPE. The measurement of the mechanical response of crystalline regions within the nanostructure of UHMWPE was accomplished by removing the amorphous regions using a time-varying permanganic-etching technique. The percentage crystallinity of UHMWPE was measured using differential scanning calorimetry (DSC) and the Tg of UHMWPE was determined by dynamic mechanical analysis (DMA). Atomic force microscopy (AFM) was used to assess the effect of surface preparation on the samples average surface roughness, Ra. In this study, it was demonstrated that the untreated UHMWPE samples had a significantly lower ( p<0.0001) elastic modulus and hardness relative to treated UHMWPE cryoultrasectioned and etched samples at all penetration depths. No significant difference ( p > 0.05) in elastic modulus and hardness between the cryoultrasectioned and etched samples was observed. These results suggest that the surface nanomechanical response of an UHMWPE insert in a total joint replacement (TJR) prosthesis is significantly lower compared with the bulk of the material. Additionally, it was concluded that the nanomechanical response of material with higher percentage crystallinity (67 per cent) was predominantly determined by the crystalline regions within the semi-crystalline UHMWPE nanostructure.

scholarly journals Growth and Mechanical and Tribological Characterization of Multi-Layer Hard Carbon Films

1996 ◽  
Vol 438 ◽  
Author(s):  
J. Ager ◽  
I. Brown ◽  
O. Monteiro ◽  
J. A. Knapp ◽  
D. M. Follstaedt ◽  
...  
Keyword(s):  
Layer Thickness ◽  
Carbon Films ◽  
Vacuum Arc ◽  
Individual Layer ◽  
Implantation Damage ◽  
Film Hardness ◽  
Sublayer Thickness ◽  
Pin On Disk ◽  
Tribological Characterization ◽  
20 Nm

AbstractVacuum-arc deposition is used to deposit multilayer carbon films by modulating the sample bias during deposition. The effect of varying the sublayer thickness in multilayer films consisting of alternating layers of “hard” (68.4 GPa, -100 V bias) and “soft” (27.5 GPa, -2000 V bias) was investigated. Films consisting of equal thickness layers of hard and soft material and an individual layer thickness varying from 10 to 35 nm were deposited. Mechanical property measurements were obtained by finite element modeling of nanoindentation load-displacement curves. The film hardness values were about 20% below the average of the component layers and relatively independent of the layer thickness. TEM investigation revealed deterioration of the multilayer structure when the sublayer thickness was below 15 nm due to implantation damage of the hard layers caused by the energetic C+ ions of the soft layers (-2000 V bias) deposited over them. Pin-on-disk wear tests show that the wear rate drops when sublayer thickness is decreased below 20 nm and remains constant with further decreases in the layer thickness.

Tribological Properties of Ni/Cu Multilayers

2007 ◽  
Vol 561-565 ◽  
pp. 2451-2454 ◽  
Author(s):  
Tomoya Hattori ◽  
Yoshihisa Kaneko ◽  
Satoshi Hashimoto
Keyword(s):  
Layer Thickness ◽  
Sliding Wear ◽  
Nickel Coating ◽  
Copper Substrate ◽  
Total Thickness ◽  
Individual Layer ◽  
Hardness Tests ◽  
Plastic Deformation Process ◽  
Electrodeposited Nickel ◽  
20 Nm

Sliding wear and hardness tests in Ni/Cu multilayers electrodeposited on polycrystalline copper substrate were carried out. The multilayers had a total thickness of 5 μm and an individual layer thickness from 5 to 100 nm. Hardness of the multilayers measured with a nanoindentation tester was found to be dependent on layer thickness. The multilayer with the layer thickness of 20 nm showed the highest value among them. It was found that the wear resistances of all the multilayers tested were higher than that of an electrodeposited nickel coating. It was also revealed that the specific wear rate of multilayers decreased with decreasing the layer thickness although the highest hardness was attained at the 20 nm layer thickness. Scanning ion microscope observation showed that the subsurface area kept the layered structure of nickel and copper even after sliding wear. The multilayer had plasticity sufficient to accommodate deformation coming from the sliding wear, because fine grains peculiar to severe plastic deformation process were formed near the worm surface.

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