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.

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.

Viscosity Models Based on Network Theory for Polymer Melts

2010 ◽  
Vol 129-131 ◽  
pp. 1244-1247
Author(s):  
Hai Hang Xu ◽  
Lei Zhong
Keyword(s):  
Experimental Data ◽  
Kinetic Equation ◽  
Constitutive Equation ◽  
Polymer Composites ◽  
Network Theory ◽  
Polymer Melts ◽  
Structure Parameter ◽  
Viscosity Models ◽  
Model Predictions ◽  
Good Agreement

New shear and extensional viscosity models based on Fredrickson kinetic equation coupled with Dewitt constitutive equation were established to predict viscosities of polymer melts. The experimental data of 125°C LDPE and LDPE filled with 35% glass beads reported from references were compared with the model predictions. The predictions showed good agreement with the measurements. The models are simple and easy to use. Because they contain no structure parameter, they are capable to describe the viscosities of pure polymer and polymer composites.

Macro/Meso/Micro Elastic-Viscoplastic Analysis of Plain-Woven Laminates Using Homogenization Theory

2014 ◽  
Vol 626 ◽  
pp. 365-371 ◽  
Author(s):  
Kohei Oide ◽  
Tetsuya Matsuda
Keyword(s):  
Experimental Data ◽  
Constitutive Equation ◽  
Glass Fiber ◽  
Present Method ◽  
Time Dependent ◽  
Homogenization Theory ◽  
Fiber Bundles ◽  
Woven Glass Fiber ◽  
Good Agreement

In this study, macro/meso/micro elastic-viscoplastic analysis of plain-woven laminates is conducted based on a homogenization theory for nonlinear time-dependent composites. For this, a plain-woven laminate is modeled with respect to three scales by considering the laminate as a macrostructure, fiber bundles (yarns) and a matrix in the laminate as a mesostructure, and fibers and a matrix in the yarns as a microstructure. Then, an elastic-viscoplastic constitutive equation of the laminate is derived by dually applying the homogenization theory for nonlinear time-dependent composites to not only the meso/micro but also the macro/meso scales. Using the present method, the elastic-viscoplastic analysis of a plain-woven glass fiber/epoxy laminate subjected to on-and off-axis loading is performed. It is shown that the present method successfully takes into account the effects of viscoplasticity of the epoxy in yarns on the elastic-viscoplastic behavior of the plain-woven GFRP laminate. It is also shown that the results of analysis are in good agreement with experimental data.

Creep Failure Simulations for 316H at 550°C

2012 ◽  
Author(s):  
Nak Hyun Kim ◽  
Yun Jae Kim ◽  
Catrin M. Davies ◽  
Kamran M. Nikbin ◽  
David W. Dean
Keyword(s):  
Experimental Data ◽  
Damage Model ◽  
Creep Damage ◽  
Inelastic Strain ◽  
Compact Tension ◽  
Creep Failure ◽  
Creep Ductility ◽  
Summation Rule ◽  
Creep Damage Model ◽  
Damage Summation

In this work a method to simulate failure due to creep is proposed using finite element damage analysis. The creep damage model is based on the creep ductility exhaustion concept. Incremental damage is defined by the ratio of incremental inelastic (plastic & creep) strain and multi-axial ductility. A simple linear damage summation rule is applied. When accumulated damage becomes unity, element stresses are reduced to almost zero to simulate progressive crack growth. The model is validated through comparison with experimental data on various sized compact tension, C(T), specimens of 316H stainless steel at 550 °C. The influence of the inelastic strain rate on the uniaxial ductility is considered. Good agreement is found between the simulated results and the experimental data.

Numerical Uncertainty in Fluid Flow Calculations: Needs for Future Research

1993 ◽  
Vol 115 (2) ◽  
pp. 194-195 ◽  
Author(s):  
Ismail Celik
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Quality Control ◽  
Fluid Flow ◽  
Flow Problem ◽  
Future Research ◽  
Error Measures ◽  
Engineering Problems ◽  
Computational Fluid Dynamics Cfd ◽  
Good Agreement

Computational fluid dynamics (CFD) has established itself as a viable technique for performing research and solving engineering problems, and when used correctly, can give accurate results for many fairly complex problems. This success has led to an ever increasing number of journal publications, many code developers, and surprisingly many users in the industry. Commercial CFD packages are often marketed by claiming that a particular code can solve almost every fluid flow problem, while many users, both in industry and academia, stand aloof from quantitative error measures, instead being dazzled by colorful computer generated output. This is mostly due to insufficient education in the scientific computing discipline which often leads (intentional or not) to misuse and wrong conclusions. Every year, hundreds of papers are published in conference proceedings, and journals, on the advancement and application of CFD techniques. Whenever something is spawned in such large quantities it is very easy to lose sense of quality control. To assert quality, papers often end with a conclusion such as “good agreement is found between experiments and predictions” to which the readers have become so immune that it no longer has meaning. Unfortunately, very little information is provided about the numerical uncertainty and the experimental data are often treated as if they are 100 percent accurate.

scholarly journals Study on the Creep Damage Characteristics of Shale under the Combined Action of Osmotic Pressure and Disturbance Load

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Junguang Wang ◽  
Qingrong Yu ◽  
Bing Liang ◽  
Zhangqing Xuan
Keyword(s):  
Creep Test ◽  
Water Pressure ◽  
Creep Damage ◽  
Surrounding Rock ◽  
Seepage Water ◽  
Mining Engineering ◽  
Creep Failure ◽  
Disturbance Frequency ◽  
Combined Action

In the in situ modified fluidized mining engineering, the surrounding rock of the shaft wall is prone to creep instability damage under the action of disturbance and seepage water pressure, which seriously affects the stability of the surrounding rock of the deep in situ modified fluidized mining. In order to study the nonlinear creep damage and fracture characteristics of deep rocks under the combined action of seepage water pressure and disturbance load, a self-developed rock perturbation creep test rig under the action of seepage water pressure was used, and shale was used as the rock sample. In the method of staged loading, the rock uniaxial compression perturbation creep test under static axial pressure, different perturbation frequencies, and different seepage water pressures was carried out, and the creep characteristics of shale under the combined action of perturbation and seepage were studied. The results show that with the increase of seepage water pressure, the creep failure time of the rock decreases, and the ultimate strain value increases; with the increase of the disturbance frequency, the creep failure mode of the rock gradually transitions from shear failure to tension failure. When water pressure and disturbance load exist at the same time, rock creep is more sensitive to seepage water pressure; based on experimental results, a shale perturbation creep damage model considering the influence of seepage water pressure and disturbance frequency is established, and the model is verified. The research results have important theoretical significance for guiding the wellbore stability control of in situ modified fluidized mining engineering.

Creep Failure Behavior of Notched Structure in the Simulated Steam Turbine Rotor: Experimental and Damage Analysis

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Tian-Ye Niu ◽  
Cheng Gong ◽  
Jian-Guo Gong ◽  
Fu-Zhen Xuan
Keyword(s):  
Constitutive Equation ◽  
Steam Turbine ◽  
Contact Region ◽  
Creep Damage ◽  
Turbine Rotor ◽  
Failure Behavior ◽  
Creep Failure ◽  
Creep Tests ◽  
Blade Root ◽  
Evolution Behavior

Abstract Notched structures widely exist in steam turbine components in fossil power plant, e.g., the groove of the rotor, etc. Previous studies indicate that creep failures occur at the groove of the rotor or the adjacent regions. Thus, it is essential to study the creep failure behavior of the notched structures for the safe operation of the system. In this work, creep tests of the simulated steam turbine component have been conducted at the temperature of 605 °C, and the creep-damage constitutive equation is used to track the evolution behavior of creep strain and damage of this component. The influence of structural and loading configurations on creep failure behavior of the component is discussed. Results demonstrate that the shearing failure at the contact area between the blade root and the rotor is observed for the tested component, while the cracking at the groove of the rotor is not found. Creep-damage constitutive equation employed in this work could provide an adequate solution of the simulated component. Parametric studies indicate that creep crack initiation and creep failure of the simulated components may occur at the contact region (i.e., between the blade root and the rotor) and the groove of the rotor, which is closely related to structural and loading configurations of the components.

Energy Levels and Electromagnetic Transition of 90-94mo Nuclei Using Ibm-1

2020 ◽  
pp. 149-152
Keyword(s):  
Experimental Data ◽  
Transition Probability ◽  
Energy Levels ◽  
Dynamical Symmetry ◽  
Interacting Boson Model ◽  
Excitation Energies ◽  
Electromagnetic Transition ◽  
Boson Model ◽  
Energy States ◽  
Good Agreement

The energy states for the J , b , ɤ bands and electromagnetic transitions B (E2) values for even – even molybdenum 90 – 94 Mo nuclei are calculated in the present work of "the interacting boson model (IBM-1)" . The parameters of the equation of IBM-1 Hamiltonian are determined which yield the best excellent suit the experimental energy states . The positive parity of energy states are obtained by using IBS1. for program for even 90 – 94 Mo isotopes with bosons number 5 , 4 and 5 respectively. The" reduced transition probability B(E2)" of these neuclei are calculated and compared with the experimental data . The ratio of the excitation energies of the 41+ to 21+ states ( R4/2) are also calculated . The calculated and experimental (R4/2) values showed that the 90 – 94 Mo nuclei have the vibrational dynamical symmetry U(5). Good agreement was found from comparison between the calculated energy states and electric quadruple probabilities B(E2) transition of the 90–94Mo isotopes with the experimental data .

Predicting the Effect of Tire Tread Pattern Design on Thick Film Wet Traction

1977 ◽  
Vol 5 (1) ◽  
pp. 6-28 ◽  
Author(s):  
A. L. Browne
Keyword(s):  
Experimental Data ◽  
Network Design ◽  
Thick Film ◽  
Digital Computer ◽  
Analytical Tool ◽  
Design Practice ◽  
Pattern Design ◽  
Performance Results ◽  
Good Agreement

Abstract An analytical tool is presented for the prediction of the effects of changes in tread pattern design on thick film wet traction performance. Results are reported for studies in which the analysis, implemented on a digital computer, was used to determine the effect of different tread geometry features, among these being the number, width, and lateral spacing of longitudinal grooves and the angle of zigzags in longitudinal grooves, on thick film wet traction. These results are shown to be in good agreement with experimental data appearing in the literature and are used to formulate guidelines for tread groove network design practice.

A New Condition of Formation and Stablity of All Crystalline Systems in a Good Agreement with Experimental Data

2015 ◽  
Vol 11 (3) ◽  
pp. 3224-3228
Author(s):  
Tarek El-Ashram
Keyword(s):  
Experimental Data ◽  
Brillouin Zone ◽  
Electron Concentration ◽  
Free Electron ◽  
Lattice Point ◽  
Valence Electron ◽  
Fermi Gas ◽  
Valence Electron Concentration ◽  
Fermi Sphere ◽  
Good Agreement

In this paper we derived a new condition of formation and stability of all crystalline systems and we checked its validity andit is found to be in a good agreement with experimental data. This condition is derived directly from the quantum conditionson the free electron Fermi gas inside the crystal. The new condition relates both the volume of Fermi sphere VF andvolume of Brillouin zone VB by the valence electron concentration VEC as ;𝑽𝑭𝑽𝑩= 𝒏𝑽𝑬𝑪𝟐for all crystalline systems (wheren is the number of atoms per lattice point).

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