Computational and Experimental Characterization of Indentation Creep

2003 ◽  
Vol 795 ◽  
Author(s):  
Ming Dao ◽  
Hidenari Takagi ◽  
Masami Fujiwara ◽  
Masahisa Otsuka
Keyword(s):  
Finite Element ◽  
Power Law ◽  
Constant Load ◽  
Dislocation Creep ◽  
Solid Solution Alloy ◽  
Indentation Creep ◽  
Creep Tests ◽  
Uniaxial Creep ◽  
Self Similar ◽  
Power Law Creep

ABSTRACT:Detailed finite-element computations and carefully designed indentation creep experiments were carried out in order to establish a robust and systematic method to accurately extract creep properties during indentation creep tests. Finite-element simulations confirmed that, for a power law creep material, the indentation creep strain field is indeed self-similar in a constant-load indentation creep test, except during short transient periods at the initial loading stage and when there is a deformation mechanism change. Self-similar indentation creep leads to a constitutive equation from which the power-law creep exponent, n, the activation energy for creep, Qc and so on can be evaluated robustly. Samples made from an Al-5.3mol%Mg solid solution alloy were tested at temperatures ranging from 573 K to 773 K. The results are in good agreement with those obtained from conventional uniaxial creep tests in the dislocation creep regime.

An investigation of the creep processes in tin and aluminum using a depth-sensing indentation technique

1992 ◽  
Vol 7 (3) ◽  
pp. 627-638 ◽  
Author(s):  
V. Raman ◽  
R. Berriche
Keyword(s):  
Stress Exponent ◽  
Constant Load ◽  
Indentation Creep ◽  
Depth Sensing ◽  
Creep Tests ◽  
Si Substrates ◽  
Uniaxial Creep ◽  
Rate Versus ◽  
Deformation Properties ◽  
Film Substrate

Constant load creep experiments were conducted using a depth-sensing indentation instrument with indentation depths in the submicron range. Experiments were conducted on polycrystalline Sn and sputtered Al films on Si substrates. The results show that the plastic depth versus time curves and the strain rate versus stress plots from these experiments are analogous to those obtained from conventional creep experiments using bulk specimens. The value of the stress exponent for Sn is close to the reported values from uniaxial creep tests. Tests on Al films showed that the stress exponent is dependent on the indentation depth and is governed by the proximity to the film/substrate interface. Load change experiments were also performed and the data from these tests were analyzed. It is concluded that indentation creep experiments may be useful in elucidating the deformation properties of materials and in identifying deformation mechanisms.

scholarly journals Nanoindentation Studies of Plasticity and Dislocation Creep in Halite

Geosciences ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 79 ◽  
Author(s):  
Christopher Thom ◽  
David Goldsby
Keyword(s):  
Strain Rate ◽  
Stress Exponent ◽  
Creep Behavior ◽  
Constant Load ◽  
Dislocation Creep ◽  
Indentation Creep ◽  
Creep Tests ◽  
Creep Flow ◽  
A Value ◽  
Flow Laws

Previous deformation experiments on halite have collectively explored different creep mechanisms, including dislocation creep and pressure solution. Here, we use an alternative to conventional uniaxial or triaxial deformation experiments—nanoindentation tests—to measure the hardness and creep behavior of single crystals of halite at room temperature. The hardness tests reveal two key phenomena: (1) strain rate-dependent hardness characterized by a value of the stress exponent of ~25, and (2) an indentation size effect, whereby hardness decreases with increasing size of the indents. Indentation creep tests were performed for hold times ranging from 3600 to 106 s, with a constant load of 100 mN. For hold times longer than 3 × 104 s, a transition from plasticity to power-law creep is observed as the stress decreases during the hold, with the latter characterized by a value of the stress exponent of 4.87 ± 0.91. An existing theoretical analysis allows us to directly compare our indentation creep data with dislocation creep flow laws for halite derived from triaxial experiments on polycrystalline samples. Using this analysis, we show an excellent agreement between our data and the flow laws, with the strain rate at a given stress varying by less than 5% for a commonly used flow law. Our results underscore the utility of using nanoindentation as an alternative to more conventional methods to measure the creep behavior of geological materials.

Creep Behaviour of Closed Cell Aluminium Foams from Stress Relaxation Tests

2009 ◽  
Vol 423 ◽  
pp. 131-136 ◽  
Author(s):  
B. Carcel ◽  
A.C. Carcel ◽  
P. Arrué
Keyword(s):  
Stress Relaxation ◽  
Power Law ◽  
Creep Behaviour ◽  
Solid Material ◽  
Constant Load ◽  
Creep Tests ◽  
Closed Cell ◽  
Power Law Exponent ◽  
Order Of Magnitude ◽  
Power Law Creep

Creep behaviour of closed cell aluminium foams and transitions from power law to power law breakdown (PLB) creep regimes are investigated from results of stress relaxation tests (SRT) carried out on Alporas foams with densities between 0.20 to 0.32 g/cm3. Tests were carried out at temperatures between 200°C and 300°C and stress relaxation was measured from the collapse stress under compression of the foams. Under similar foam density, temperature and stress conditions, the values of strain rate calculated from SRT tests were of the same order of magnitude than those previously reported in the literature from conventional constant load creep tests. Under stress values close to the collapse stress, the creep mechanism seems to follow a PLB regime, with values of the power law exponent n=10-17, much higher than those corresponding to the power law creep in the solid material (n=4.4-6.5) and with activation energy values close to Q = 150 KJ/mol. Having in mind the limitations of available creep models for closed cell foams and the need for additional experimental results, the use of SRT testing would offer advantages for the assessment of the high temperature behaviour of aluminium foams, due to its lower testing times and reduced experimental effort.

scholarly journals Nanoindentation creep testing: Advantages and limitations of the constant contact pressure method

2021 ◽  
Author(s):  
Christian Minnert ◽  
Karsten Durst
Keyword(s):  
Contact Pressure ◽  
Constant Load ◽  
Indentation Creep ◽  
Creep Tests ◽  
Creep Properties ◽  
Pressure Method ◽  
Ultrafine Grained ◽  
Uniaxial Creep ◽  
Power Law Exponent ◽  
Properties Of Materials

AbstractDifferent loading protocols have been developed in the past to investigate the creep properties of materials using instrumented indentation testing technique. Recently, a new indentation creep method was presented, in which the contact pressure is kept constant during the creep test segment, similar to the constant stress applied in a uniaxial creep experiment. In this study, the results of constant contact pressure creep tests are compared to uniaxial and constant load hold indentation creep experiments on ultrafine grained Cu and CuAl5. The constant contact pressure method yields similar stress exponents as the uniaxial tests, down to indentation strain rates of 10–6 s−1, whereas the constant load hold method results mainly in a relaxation of the material at decreasing applied pressures. Furthermore, a pronounced change in the power law exponent at large stress reductions is found for both uniaxial and constant contact pressure tests, indicating a change in deformation mechanism of ultrafine grained metals. Graphical abstract

Elastic Follow-Up Factor for Cruciform Plate Under Bi-Axial Loading

2011 ◽  
Author(s):  
Kuk-Hee Lee ◽  
Yun-Jae Kim ◽  
Robert A. Ainsworth ◽  
David Dean ◽  
Tae-Eun Jin
Keyword(s):  
Finite Element ◽  
Power Law ◽  
Analytical Solutions ◽  
Axial Stress ◽  
Axial Loading ◽  
Finite Element Analyses ◽  
Structural Discontinuity ◽  
Stress States ◽  
Power Law Creep

This paper derives analytical solutions of the elastic follow-up factor for power-law creeping cruciform plates under bi-axial displacements to investigate the effect of multi-axial stress states on elastic follow-up behaviors. Validity of the proposed solutions is checked against the results from finite element analyses using power-law creep material. Based on proposed solutions, effects of the biaxiality, geometry, Poisson’s ratio and creep exponent on elastic follow-up factors are discussed. Present results show that the elastic follow-up factor for structure with structural discontinuity can be significantly affected by the multi-axial stress states.

Finite Element Modeling of Diamond Indentation Creep in MgO

2011 ◽  
Vol 393-395 ◽  
pp. 106-109
Author(s):  
Jin Hua Hu ◽  
Leslie Henshall
Keyword(s):  
Activation Energy ◽  
Finite Element ◽  
Flow Stress ◽  
Low Temperature ◽  
Single Crystal ◽  
Creep Model ◽  
Dislocation Creep ◽  
Indentation Creep ◽  
Low Temperature Creep ◽  
Shear Flow Stress

The modified dislocation creep model and the power law breakdown creep model were proposed to be used in the indentation creep deformation analyses for single crystal MgO at low temperature varying from 293K to 873K. A FE indentation creep modeling procedure was proposed and implemented. The activation energy and the shear flow stress for low temperature creep in single crystal MgO were predicted based on the analytical indentation creep analyses.

Finite Element Simulation for Creep Response of Strengthened Wood/PVC Composite

2013 ◽  
Vol 747 ◽  
pp. 261-264 ◽  
Author(s):  
T. Pulngern ◽  
K. Preecha ◽  
Narongrit Sombatsompop ◽  
V. Rosarpitak
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Power Law ◽  
High Carbon Steel ◽  
Creep Model ◽  
Element Analysis ◽  
Creep Response ◽  
Element Simulation ◽  
Before And After ◽  
Power Law Creep

This paper investigates the finite element simulation to predict the creep response of Wood/PVC (WPVC) composite members before and after strengthening by using high carbon steel (HCS) flat bar strip adhered to the tension side. The creep parameters based on power law models of WPVC composites and the HCS flat bars were determined experimentally. Then, the nonlinear finite element analysis (FEA) software of ABAQUS was applied to predict the creep behaviors of composite members using the obtained experimentally creep parameters of individual component of WPVC composites and HCS flat bars. Good correlation between finite element simulation and experimental results are obtained for all cases. ABAQUS software with power law creep model show good potential for prediction the creep response of WPVC composites before and after strengthening.

Sign in / Sign up

Export Citation Format

Share Document