Failure of Compressible/Dilatant Geomaterials

1994 ◽  
Vol 47 (6S) ◽  
pp. S102-S106
Author(s):  
N. D. Cristescu
Keyword(s):  
Rock Mass ◽  
Constitutive Equation ◽  
Work Hardening ◽  
Transient Creep ◽  
Mining Engineering ◽  
Creep Failure ◽  
The Third ◽  
Instantaneous Failures ◽  
Ultimate Failure ◽  
Stationary Creep

The paper presents a general constitutive equation for geomaterials allowing to describe dilatancy and/or compressibility during transient and stationary creep. The constitutive equation also describes the instantaneous response of the geomaterial, work-hardening during transient creep, instantaneous failure and creep failure. The damage produced by dilatancy is used to formulate a criterion for creep failure. Thus ultimate failure may be involved in various ways, depending on the initial and boundary conditions and certainly on the constitutive equation. Typical mining engineering examples are given. First is discussed the creep closure of a deep vertical cylindrical cavern, various possible instantaneous failures, creep failure, and spreading of damage by dilatancy into the rock mass. Second example discusses the instantaneous failure and creep failure around a horizontal tunnel, and the location where damage by dilatancy is more pronounced. The third example presents the case of a rectangular-like shaped cavern.

ASME 1995 Nadai Lecture—Plasticity of Porous and Particulate Materials

1996 ◽  
Vol 118 (2) ◽  
pp. 145-156 ◽  
Author(s):  
N. D. Cristescu
Keyword(s):  
Experimental Data ◽  
Constitutive Equation ◽  
Model Prediction ◽  
Creep Damage ◽  
Mining Engineering ◽  
Creep Failure ◽  
Time Effects ◽  
Engineering Problems ◽  
Stationary Creep ◽  
Good Agreement

The paper discusses the formulation of constitutive equation for those materials for which the irreversible changes of the volume is also to be taken into account. These are mainly geomaterials, cement, powders of various kinds, ceramics, etc. Experimental evidence is first presented showing that the time effects on irreversible volumetric changes and failure are very important. The concept of compressibility/dilatancy boundary is further introduced. The general constitutive equation able to describe instantaneous response, transient and stationary creep, dilatancy and/or compressibility during creep, failure, creep damage and creep failure, is presented. Examples formulated for various materials are given. Comparison between model prediction and experimental data shows a very good agreement. A few examples of applications of the model to mining engineering problems are mentioned.

Identification of the constitutive equation by the indentation technique using plural indenters with different apex angles

2001 ◽  
Vol 16 (8) ◽  
pp. 2283-2292 ◽  
Author(s):  
Masatoshi Futakawa ◽  
Takashi Wakui ◽  
Yuji Tanabe ◽  
Ikuo Ioka
Keyword(s):  
Constitutive Equation ◽  
Yield Stress ◽  
Work Hardening ◽  
Indentation Technique ◽  
Work Hardening Coefficient ◽  
The Relationship ◽  
Stress Work ◽  
Hardening Coefficient ◽  
Depth Curve ◽  
Work Hardening Exponent

This paper describes a novel technique for determining the constitutive equation of elastic–plastic materials by the indentation technique using plural indenters with different apex angles. Finite element method (FEM) analyses were carried out to evaluate the effects of yield stress, work hardening coefficient, work hardening exponent, and the apex angle of indenter on the load–depth curve obtained from the indentation test. As a result, the characterized curves describing the relationship among the yield stress, work hardening coefficient, and the work hardening exponent were established. Identification of the constants of a constitutive equation was made on the basis of the relationship between the characterized curves and the hardness given by the load–depth curve. This technique was validated through experiments on Inconel 600 and aluminum alloy. The determined constitutive equation was applied to the FEM analyses to simulate the deformation including necking behavior under uniaxial tension. The analytical results are in good agreement with experimental results.

Effects of Third Invariant of Deviatoric Stress Tensor on Transient Creep of Thick-Walled Tubes

1974 ◽  
Vol 96 (3) ◽  
pp. 207-213 ◽  
Author(s):  
S. Murakami ◽  
Y. Yamada
Keyword(s):  
Mild Steel ◽  
Stress Tensor ◽  
Equivalent Stress ◽  
Transient Creep ◽  
Deviatoric Stress ◽  
The Third ◽  
Third Invariant ◽  
Stress Functions ◽  
Thin Walled ◽  
Deviatoric Stress Tensor

Creep theories with the effect of the third invariant of the deviatoric stress tensor and their accuracy as applied to practical problems are discussed. Constitutive equations for transient creep are first formulated by assuming creep potentials of the Prager-Drucker and the Bailey-Davis type together with the associated equivalent stress functions. Strain-hardening and time-hardening hypotheses are assumed. Experimental results hitherto reported for thin-walled tubes are discussed according to these equations. Then, the creep of a thick-walled tube of mild steel is analyzed and compared with experiments.

Transient creep behaviour of Ni3Al polycrystals

2000 ◽  
Vol 646 ◽  
Author(s):  
Tomas Kruml ◽  
Birgit Lo Piccolo ◽  
Jean-Luc Martin
Keyword(s):  
Strain Rate ◽  
Yield Point ◽  
Work Hardening ◽  
Creep Behaviour ◽  
Constant Strain Rate ◽  
Transient Creep ◽  
Peak Temperature ◽  
Creep Tests ◽  
Repeated Stress ◽  
Deformation Parameters

ABSTRACTRepeated creep tests were used for measuring various constant strain-rate deformation parameters. The results are consistent with those of repeated stress relaxations, although the precision is lower for creep in the present case. The small yield point observed in reloading after the transient is directly related to the amount of exhausted mobile dislocations, i.e. it originates from multiplication processes. During the transient test (180s total), the total exhaustion rate of mobile dislocations can be as high as 99%. It exhibits a maximum at the same T (about 500 K) as the work hardening. This supports the validity of a model which considers the work-hardening peak temperature to correspond to the stress under which incomplete Kear-Wilsdorf locks yield.

A Mechanical Model for TRIP Sheet Steel Forming

2011 ◽  
Vol 221 ◽  
pp. 21-26
Author(s):  
Ti Kun Shan ◽  
Li Liu
Keyword(s):  
Constitutive Equation ◽  
Strain Hardening ◽  
Uniaxial Tension ◽  
Work Hardening ◽  
Trip Steel ◽  
Mechanical Model ◽  
Sheet Steel ◽  
Stress Triaxiality ◽  
Transformation Rate ◽  
Stress Strain Relation

An enhanced elastic-plastic constitutive equation taking into account strain induced transformation and its effect on work hardening of TRIP steel during deformation are investigated. The transformation rate relies on the stress triaxiality. The strain hardening of the TRIP steel takes on parabola shape because of the austenite changed to the martensite during straining. The physical model is verified by comparing with the stress-strain relation of the uniaxial tension experiment. The results showed that the steel keeps a high hardening potential which retards the onset of necking and a good formability thanks to the martensitic strain-induced transformation and the subsequent austenite hardening.

Shape of creep curves in frozen soils and polycrystalline ice

1987 ◽  
Vol 24 (4) ◽  
pp. 623-629 ◽  
Author(s):  
Anatoly M. Fish
Keyword(s):  
Constitutive Equation ◽  
Creep Strain ◽  
Failure Time ◽  
Frozen Soil ◽  
Time To Failure ◽  
Secondary Creep ◽  
Creep Failure ◽  
Creep Tests ◽  
Creep Curves ◽  
Polycrystalline Ice

A new method was developed for determining creep parameters, particularly the time to failure, from a single linear plot in which an individual creep curve forms a straight line for primary and tertiary creep. Secondary creep is considered to be a principal point on this line that predetermines the onset of failure. The times to failure can be predicted even when creep tests are not complete by extrapolating information obtained for primary creep. Based upon T. H. Jacka's test data, prediction of creep strain was evaluated using the constitutive equation of A. M. Fish for entire creep and compared with the modified Sinha equation of M. F. Ashby and P. Duval for attenuating creep as well as with models for primary and secondary creep. It is shown that the shape of the creep curves, and thus the creep parameters, varies with stress, temperature, and other factors. Hence, a family of creep curves cannot be described by a constitutive equation with a single set of creep parameters that do not take into account these variations without loss in the accuracy of the creep strain calculations. Key words: frozen soil, polycrystalline, ice, creep, failure, time to failure, attenuation, constitutive modelling.

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