Defining the limits to long-term nano-indentation creep measurement of viscoelastic materials

2018 ◽  
Vol 70 ◽  
pp. 297-309 ◽  
Author(s):  
X.D. Hou ◽  
N.M. Jennett
Keyword(s):  
Indentation Creep ◽  
Viscoelastic Materials ◽  
Nano Indentation ◽  
Creep Measurement

scholarly journals High-Temperature Nano-Indentation Creep of Reduced Activity High Entropy Alloys Based on 4-5-6 Elemental Palette

Entropy ◽  
2020 ◽  
Vol 22 (2) ◽  
pp. 230 ◽  
Author(s):  
Maryam Sadeghilaridjani ◽  
Saideep Muskeri ◽  
Mayur Pole ◽  
Sundeep Mukherjee
Keyword(s):  
Stress Exponent ◽  
Creep Resistance ◽  
Nuclear Reactors ◽  
Indentation Creep ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Nano Indentation ◽  
Creep Stress ◽  
Plastic Deformation Behavior ◽  
Reduced Activity

There is a strong demand for materials with inherently high creep resistance in the harsh environment of next-generation nuclear reactors. High entropy alloys have drawn intense attention in this regard due to their excellent elevated temperature properties and irradiation resistance. Here, the time-dependent plastic deformation behavior of two refractory high entropy alloys was investigated, namely HfTaTiVZr and TaTiVWZr. These alloys are based on reduced activity metals from the 4-5-6 elemental palette that would allow easy post-service recycling after use in nuclear reactors. The creep behavior was investigated using nano-indentation over the temperature range of 298 K to 573 K under static and dynamic loads up to 5 N. Creep stress exponent for HfTaTiVZr and TaTiVWZr was found to be in the range of 20–140 and the activation volume was ~16–20b3, indicating dislocation dominated mechanism. The stress exponent increased with increasing indentation depth due to a higher density of dislocations and their entanglement at larger depth and the exponent decreased with increasing temperature due to thermally activated dislocations. Smaller creep displacement and higher activation energy for the two high entropy alloys indicate superior creep resistance compared to refractory pure metals like tungsten.

Corelation of Results of Creep and Micro-Indentation Creep for PP-Copo

2014 ◽  
Vol 606 ◽  
pp. 233-236
Author(s):  
Martin Reznicek ◽  
Martin Ovsik ◽  
David Manas ◽  
Adam Skrobak ◽  
Michal Stanek ◽  
...  
Keyword(s):  
Material Properties ◽  
Test Material ◽  
Indentation Creep ◽  
Comparison Of Methods ◽  
Depth Sensing ◽  
Indentation Method ◽  
Material Development ◽  
Term Creep ◽  
Micro Indentation

This article deals with the comparison of methods for measuring the creep behavior of filled polypropylene. Creep was measured by two methods, using the micro-indentation method (Depth Sensing Indentation - DSI) and the standard long-term creep test at elevated temperature. Results of this article show the feasibility of these two methods to replace each other and thus shorten the length of the testing material development with evaluation whether the test material is better or worse than the previous. Using the DSI method we can evaluated other material properties at the same time, which may be an important contributor in determining an appropriate application of the material. Mixtures of polypropylene with different kinds and levels of filling were selected for the comparison.

Indentation Creep Analysis of Amorphous Nitrogen-Containing Carbon Films

1997 ◽  
Vol 505 ◽  
Author(s):  
Daisuke Tanaka ◽  
Shigeo Ohshio ◽  
Hidetoshi Saitoh
Keyword(s):  
Mechanical Properties ◽  
Nitrogen Content ◽  
Carbon Film ◽  
Rate Sensitivity ◽  
Carbon Films ◽  
Indentation Creep ◽  
Diamond Like Carbon ◽  
Nano Structure ◽  
Nano Indentation ◽  
Creep Analysis

ABSTRACTAn indentation creep analysis has been performed to investigate micro-mechanical properties of amorphous nitrogen-containing carbon films. Using results of the slope of the time-displacement relation of creep procedure, the strain rate sensitivity exponent m is obtained. The m value of 0.004 was obtained for diamond-like carbon film without nitrogen. In contrast, those were found to be in the range between 0.009 and 0.101 for nitrogen-containing carbon films. These slightly increased with increasing the nitrogen content of the films. We present results that indicate that the nano-indentation creep technique enables clarification of the nano-structure of nitrogen-containing carbon films.

Comments on “a model for nano-indentation creep”

1995 ◽  
Vol 32 (1) ◽  
pp. 139-144 ◽  
Author(s):  
Fuqian Yang ◽  
J.C.M. Li
Keyword(s):  
Indentation Creep ◽  
Nano Indentation

Generalized criterion of the long-term strength of viscoelastic materials

1976 ◽  
Vol 11 (5) ◽  
pp. 678-681
Author(s):  
Yu. Ya. Bart ◽  
V. P. Trifonov ◽  
A. B. Kozachenko ◽  
N. I. Malinin
Keyword(s):  
Term Strength ◽  
Viscoelastic Materials

scholarly journals High-Temperature Nano-Indentation Creep Behavior of Multi-Principal Element Alloys under Static and Dynamic Loads

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 250 ◽  
Author(s):  
Maryam Sadeghilaridjani ◽  
Sundeep Mukherjee
Keyword(s):  
Stress Exponent ◽  
Dynamic Loads ◽  
Dislocation Creep ◽  
Indentation Creep ◽  
Principal Element ◽  
Dislocation Glide ◽  
Nano Indentation ◽  
Plastic Deformation Behavior ◽  
Structural Applications ◽  
Static And Dynamic Loads

Creep is a serious concern reducing the efficiency and service life of components in various structural applications. Multi-principal element alloys are attractive as a new generation of structural materials due to their desirable elevated temperature mechanical properties. Here, time-dependent plastic deformation behavior of two multi-principal element alloys, CoCrNi and CoCrFeMnNi, was investigated using nano-indentation technique over the temperature range of 298 K to 573 K under static and dynamic loads with applied load up to 1000 mN. The stress exponent was determined to be in the range of 15 to 135 indicating dislocation creep as the dominant mechanism. The activation volume was ~25b3 for both CoCrNi and CoCrFeMnNi alloys, which is in the range indicating dislocation glide. The stress exponent increased with increasing indentation depth due to higher density and entanglement of dislocations, and decreased with increasing temperature owing to thermally activated dislocations. The results for the two multi-principal element alloys were compared with pure Ni. CoCrNi showed the smallest creep displacement and the highest activation energy among the three systems studied indicating its superior creep resistance.

scholarly journals Microstructure and Relative Humidity Effects on Long-Term Indentation Creep Properties of Calcium Carbonate Cement

2018 ◽  
Author(s):  
Jesús Rodríguez-Sánchez ◽  
Qing Zhang ◽  
Dag Kristian Dysthe
Keyword(s):  
Elastic Modulus ◽  
Calcium Carbonate ◽  
Relative Humidity ◽  
Indentation Creep ◽  
Amorphous Calcium Carbonate ◽  
Creep Properties ◽  
Carbonate Cement ◽  
Creep Modulus ◽  
Term Creep

This paper addresses the effect of both microstructure and relative humidity on the long-term creep properties of sustainable calcium carbonate (CaCO3) cements. Those can be prepared by mixing amorphous calcium carbonate and vaterite with water. A larger starting amount of vaterite, XV, within the mixture design gives a higher elasticity and resistance to the specimens due to the larger overall bridging area within the newly formed calcite crystals. Regarding creep properties for a given relative humidity, the amplitude of creep strain decreases with XV, and makes the relation between the elastic modulus, E, and hardness, H, of the samples to be linear with the contact creep modulus, C. On the other hand, for a given composition, the amplitude of creep increases with the relative humidity, making the contact creep modulus, Ci, to rise exponentially with the elastic modulus, E, and hardness, H, of the specimens. The most probable creep mechanisms for this kind of cement seem to be a combination of microcraking in the early stages and dissolution and reprecipitation of calcite in the long-term (also known as pressure solution theory). The presence of water in pores with increasing relative humidity might enhance the local dissolution of calcite, and hence the creep amplitude.

Sign in / Sign up

Export Citation Format

Share Document