Fatigue of Aluminum-Alumina-Chrome Carbide Composite Coating

2002 ◽  
Author(s):  
Maksim Kireitseu ◽  
L. Yerakhavets ◽  
Ion Nemerenco
Keyword(s):  
Composite Coatings ◽  
Crack Arrest ◽  
Fatigue Properties ◽  
Surface Cracks ◽  
Crack Driving Force ◽  
Deformation And Failure ◽  
In Situ Experiments ◽  
Fatigue And Fracture

In this paper fatigue and fracture of the Al-Al2O3-CrC, coatings have been investigated by in situ experiments performed in a scanning electron microscope. More importantly, micromechanical models using arrays of internal or surface cracks have been developed. The models provide mechanics of deformation and failure for the coating. The models also reveal the role of overloading in crack arrest, which may well be exploited in the safe design of toughened ceramics against fatigue. Initial overloads prior to cyclic loading are found to reduce significantly the crack driving force in post-overload fatigue crack growth. It expected that pre-service overloading has a great potential for improving the fatigue properties of composite coatings based on oxide ceramics and chrome carbide.

Nanoindentation Technique at Investigating of Aluminum Oxide - CrC Nanoparticles Composite Coating

2002 ◽  
Vol 740 ◽  
Author(s):  
Maksim V. Kireitseu
Keyword(s):  
Composite Coating ◽  
Fracture Resistance ◽  
Composite Coatings ◽  
Load Rating ◽  
Alumina Layer ◽  
Nanostructured Composite ◽  
Nanoindentation Technique ◽  
In Situ Experiments ◽  
Fatigue And Fracture

ABSTRACTIn this paper fatigue and fracture of Al-Al2O3-CrC nanostructured composite coatings was investigated by nanoindentation technique and in-situ experiments performed by a scanning electron microscope to permit examination of freshly exposed surfaces. Crystallography and morphological textures were characterized and fracture resistance was measured. CrC layer improves fracture resistance of alumina layer. CrC layer produced by pyrolitic deposition (CVD) may effectively heal pores and defects of alumina layer. It resulted in high load rating of the composite coating. Experiments reveal that in all cases, the detection of an acoustic signal corresponded to the appearance of a circular cracks seen on surface; in a very few cases, examination of surface after detection of a signal revealed presence of two ring cracks. Degree of toughening associated with crack healing is determined by a number of healed defects and an effectiveness of an individual healing.

scholarly journals The Role of Electron Microscopy in Materials Science

1982 ◽  
Vol 35 (6) ◽  
pp. 727 ◽  
Author(s):  
PB Hirsch
Keyword(s):  
Electron Microscopy ◽  
Materials Science ◽  
Optical Techniques ◽  
Bulk Properties ◽  
In Situ Experiments ◽  
Powerful Means ◽  
Appropriate Scale ◽  
Powerful Electron

The properties of the materials in a component or a device depend on structure and composition often on a scale of 10-10 to 10-6 m. Electron microscopy and microanalytical techniques provide a powerful means for determining the structure and composition on the appropriate scale, lead to an understanding of basic mechanisms, and by correlation or in situ experiments to explanations of bulk properties. Examples are given of the application of a variety of powerful electron optical techniques to a number of materials problems.

scholarly journals The trophic biology of the holothurian <i>Molpadia musculus</i>: implications for organic matter cycling and ecosystem functioning in a deep submarine canyon

2010 ◽  
Vol 7 (8) ◽  
pp. 2419-2432 ◽  
Author(s):  
T. Amaro ◽  
S. Bianchelli ◽  
D. S. M. Billett ◽  
M. R. Cunha ◽  
A. Pusceddu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Ecosystem Functioning ◽  
Submarine Canyon ◽  
Gut Contents ◽  
Digestion Rate ◽  
In Situ Experiments ◽  
Total Digestion ◽  
Organic Matter Cycling

Abstract. Megafaunal organisms play a key role in ecosystem functioning in the deep-sea through bioturbation, bioirrigation and organic matter cycling. At 3500 m water depth in the Nazaré Canyon, NE Atlantic, very high abundances of the infaunal holothurian Molpadia musculus were observed. To quantify the role of M. musculus in sediment cycling, sediment samples and holothurians were collected using an ROV and in situ experiments were conducted with incubation chambers. The biochemical composition of the sediment (in terms of proteins, carbohydrates and lipids), the holothurians' gut contents and holothurians' faecal material were analysed. In the sediments, proteins were the dominant organic compound, followed by carbohydrates and lipids. In the holothurian's gut contents, protein concentrations were higher than the other compounds, decreasing significantly as the material passed through the digestive tract. Approximately 33±1% of the proteins were digested by the time sediment reached the mid gut, with a total digestion rate equal to 67±1%. Carbohydrates and lipids were ingested in smaller amounts and digested with lower efficiencies (23±11% and 50±11%, respectively). As a result, the biopolymeric C digestion rate was on average 62±3%. We estimated that the population of M. musculus could remove approximately 0.49±0.13 g biopolymeric C and 0.13±0.03 g N m−2 d−1 from the sediments. These results suggest that M. musculus plays a key role in the benthic tropho-dynamics and biogeochemical processes in the Nazaré Canyon.

scholarly journals In Situ Experiments To Reveal the Role of Surface Feature Sidewalls in the Cassie–Wenzel Transition

Langmuir ◽  
2014 ◽  
Vol 30 (50) ◽  
pp. 15162-15170 ◽  
Author(s):  
René Hensel ◽  
Andreas Finn ◽  
Ralf Helbig ◽  
Sebastian Killge ◽  
Hans-Georg Braun ◽  
...  
Keyword(s):  
Surface Feature ◽  
In Situ Experiments

Finite Element Model of a Cell Incorporating Cell Membrane, Cytoskeletal Structure and Intracellular Fluid Pressure

2002 ◽  
Author(s):  
Vidyashankar Venkatesan ◽  
Nilay Mukherjee
Keyword(s):  
Finite Element ◽  
Compressive Loading ◽  
Fluid Pressure ◽  
Element Model ◽  
Structural Components ◽  
Element Analysis ◽  
In Situ Experiments ◽  
A Cell

Compressive loading is intrinsic to certain tissues in our body like articular cartilage and bone (1). In situ experiments in cartilage suggest that chondrocytes can undergo significant deformation due to compressive loading on the tissue (2). In situ and isolated cell experiments have concluded that cells are quite resilient to compressive loading, aspiration etc. and exhibit a moduli in the range of 0.6 to 2 kPa (3). However, few studies have attempted to understand the compressive behavior of cells in terms of its structural components. The structural components of a cell consist of a membrane and a dense network of at least three elements (actin, microtubules and intermediate filaments). Using finite element analysis techniques we wanted to explore the role of these structural components in determining the ability of the cell to withstand compression.

scholarly journals Influence of condensation domains on activity and specificity of adenylation domains

2021 ◽  
Author(s):  
Janik Kranz ◽  
Sebastian L. Wenski ◽  
Alexnder A. Dichter ◽  
Helge B. Bode ◽  
Kenan A. J. Bozhueyuek
Keyword(s):  
Structural Features ◽  
Peptide Synthetases ◽  
In Situ Experiments ◽  
The Subject ◽  
New Perspective ◽  
Condensation Domain

Many clinically used natural products are produced by non-ribosomal peptide synthetases (NRPSs), which due to their modular nature should be accessible to modification and engineering approaches. While the adenylation domain (A) plays the key role in substrate recognition and activation, the condensation domain (C) which is responsible for substrate linkage and stereochemical filtering recently became the subject of debate - with its attributed role as a "gatekeeper" being called into question. Since we have thoroughly investigated different combinations of C-A didomains in a series of in vitro, in vivo, and in situ experiments suggesting an important role to the C-A interface for the activity and specificity of the downstream A domain and not the C domain as such, we would like to contribute to this discussion. The role of the C-A interface, termed 'extended gatekeeping', due to structural features of the C domains, can also be transferred to other NRPSs by engineering, was finally investigated and characterised in an in silico approach on 30 wild-type and recombinant C-A interfaces. With these data, we not only would like to offer a new perspective on the specificity of C domains, but also to revise our previously established NRPS engineering and construction rules.

scholarly journals Effect of unsteady wind on drifting snow: first investigations

2002 ◽  
Vol 2 (3/4) ◽  
pp. 129-136 ◽  
Author(s):  
J.-L. Michaux ◽  
F. Naaim-Bouvet ◽  
M. Naaim ◽  
M. Lehning ◽  
G. Guyomarc’h
Keyword(s):  
Wind Tunnel ◽  
Numerical Models ◽  
Wind Gust ◽  
Strong Wind ◽  
Blowing Snow ◽  
Wind Tunnel Experiments ◽  
Drifting Snow ◽  
In Situ Experiments

Abstract. Wind is not always a steady flow. It can oscillate, producing blasts. However, most of the current numerical models of drifting snow are constrained by one major assumption: forcing winds are steady and uniform. Moreover, very few studies have been done to verify this hypothesis, because of the lack of available instrumentation and measurement difficulties. Therefore, too little is known about the possible role of wind gust in drifting snow. In order to better understand the effect of unsteady winds, we have performed both experiments at the climatic wind tunnel at the CSTB (Centre Scientifique et Technique des Bâtiments) in Nantes, France, and in situ experiments on our experimental high-altitude site, at the Lac Blanc Pass. These experiments were carried out collaboratively with Cemagref (France), Météo-France, and the IFENA (Switzerland). Through the wind tunnel experiments, we found that drifting snow is in a state of permanent disequilibrium in the presence of fluctuating airflows. In addition, the in situ experiments show that the largest drifting snow episodes appear during periods of roughly constant strong wind, whereas a short but strong blast does not produce significant drifting snow.  Key words. Drifting snow, blowing snow, gust, blast, acoustic sensor

The role of second phase particles and grain boundaries on recrystallization: Quasi-in situ experiments and modeling in U-10Mo alloy system

2021 ◽  
pp. 153445
Author(s):  
Jacqueline I. Reeve ◽  
Benjamin J. Schuessler ◽  
William E. Frazier ◽  
David P. Field ◽  
Vineet V. Joshi
Keyword(s):  
Grain Boundaries ◽  
Alloy System ◽  
Second Phase ◽  
Second Phase Particles ◽  
In Situ Experiments
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