scholarly journals A 3D Creep Model considering Disturbance Damage and Creep Damage and Its Application in Tunnel Engineering

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Geng-Feng Wang ◽  
Fan Sun ◽  
Xiao-Hui Xiong ◽  
Lei He ◽  
Ke-Hong Zhang
Keyword(s):  
Space Dimension ◽  
Creep Damage ◽  
Wave Theory ◽  
Creep Model ◽  
Time Dimension ◽  
Creep Tests ◽  
Railway Tunnel ◽  
Damage Theory ◽  
Term Creep

Based on the Kachanov damage theory and elastic wave theory, considering the long-term creep damage from time dimension and instantaneous disturbance damage from space dimension, we presented a 3D damage creep model and converted it to difference expressions in order to write into the finite difference software FLAC3D. Then, according to the results of creep tests, we conducted parameter inversion of our damage creep model with the help of the particle swarm optimization (PSO) method. Finally, the damage creep model was applied in a railway tunnel project in Yunnan to simulate the tunnel deformation. Compared with the Burgers model and the model considering only creep damage, our model which considers both creep damage and disturbance damage yielded more reasonable results.

Unified Viscoplastic Model Coupled With Damage for Evaluation of Creep-Fatigue of Grade 91 Steel

2017 ◽  
Author(s):  
Nazrul Islam ◽  
David J. Dewees ◽  
Tasnim Hassan
Keyword(s):  
Damage Mechanics ◽  
Creep Damage ◽  
Continuum Damage Mechanics ◽  
Creep Model ◽  
Damage Evaluation ◽  
Creep Fatigue ◽  
Grade 91 ◽  
Term Creep ◽  
Grade 91 Steel

A continuum damage mechanics (CDM) coupled unified viscoplasticity model has been developed to predict the creep-fatigue life of modified Grade 91 steel. A tertiary creep model termed MPC-Omega codified in Part 10 of API (and also implemented in the ASME BP&V Code for Grade 22V and more recently Grade 91 Steel) is also employed for creep damage evaluation. As MPC-Omega has a direct relationship with Larson-Miller parameter (LMP) coefficients, creep damage coefficients in the unified constitutive model (UCM) are tied with MPC-Omega coefficients in order to utilize WRC and API 579-1 Grade 91 creep rupture database. The model is validated against long-term creep, LCF, creep-fatigue and TMF experimental responses at T = 20–600°C.

Predicting the Time to Failure in Heavily Loaded Masonry Specimens with the Acoustic Emission Technique

2010 ◽  
Vol 133-134 ◽  
pp. 217-222 ◽  
Author(s):  
Els Verstrynge ◽  
Luc Schueremans ◽  
Dionys Van Gemert
Keyword(s):  
Acoustic Emission ◽  
Failure Time ◽  
Event Rate ◽  
Creep Damage ◽  
Time To Failure ◽  
Creep Tests ◽  
Strain Monitoring ◽  
Specimen Processing ◽  
Term Creep

This paper presents the results of a research project in which the knowledge on testing of creep damage in masonry and acoustic emission (AE) monitoring are combined. Results from different types of creep tests are combined to investigate whether AE monitoring could predict the failure time of the masonry specimens. In previous work, it was observed that the AE event rate is related to the time to failure of the specimen. Processing of the results of new tests enables to update the previously found relation between AE event rate and failure time and to indicate a confidence interval for predictions made with this model. Additionally, the question can be raised whether temporary monitoring could detect unstable damage accumulation and predict failure. Therefore, the results of long-term creep tests are analysed and compared with data from strain monitoring. The results indicate that in most cases, the failure can be predicted.

Modeling and Experimental Study of Long Term Creep Damage in Austenitic Stainless Steels

2013 ◽  
Vol 592-593 ◽  
pp. 83-86 ◽  
Author(s):  
Yi Ting Cui ◽  
Maxime Sauzay
Keyword(s):  
Grain Boundaries ◽  
Stainless Steels ◽  
Cavity Growth ◽  
High Stress ◽  
Austenitic Stainless Steels ◽  
Creep Damage ◽  
Future Generation ◽  
Creep Tests ◽  
Term Creep

Austenitic Stainless Steels (SSs) are presently being investigated as appropriate candidates for structural components for the future Generation IV nuclear reactors. Austenitic SSs of different grades will operate at high temperature and suffer low stress loading for decades. At the laboratory, austenitic SSs have been subjected to creep tests at various stresses and temperatures between 500°C to 700°C, up to nearly 50·103h. Interrupted creep tests show an acceleration of the reduction in cross-section only during the last 15% of creep lifetime which may be called macroscopic necking. The modeling of necking using a modified Norton power-law allows lifetime predictions in agreement with experimental data up to a few thousand hours only. And the experimental results show that, the extrapolation of the 'stress lifetime curves obtained at high stress leads to large overestimations of lifetimes at low stress. After FEGSEM observations, these overestimates are mainly due to additional intergranular cavitation along grain boundaries. The modeling of cavity growth by vacancy diffusion along grain boundaries coupled with continuous nucleation proposed by Riedel has been carried out. Lifetimes for long term creep are rather correctly predicted with respect to experimental lifetimes. The lifetime curves predicted by either the necking model or the creep cavity one cross each other, defining transition times of five to ten thousand hours for temperatures between 600°C and 700°C, in agreement with experimental curves.

scholarly journals Study on creep performance of launch canister under long-term storage

2019 ◽  
Vol 43 (2) ◽  
pp. 199-208 ◽  
Author(s):  
Cun-Gui Yu ◽  
Tong-Sheng Sun ◽  
Guang-Yuan Xiao
Keyword(s):  
Residual Deformation ◽  
Bottom Layer ◽  
Tensile Creep ◽  
Creep Model ◽  
Model Parameters ◽  
Creep Tests ◽  
Software Environment ◽  
Long Term Storage ◽  
Term Storage

In this paper, the creep performance of a multi-barrel rocket launch canister under long-term stacking storage is studied. Based on the Bailey–Norton model, a creep model for the frame material of a launch canister was established. Constant stress tensile creep tests under different stress levels at room temperature were carried out on the frame materials of the launch canister and the creep model parameters were obtained by test data fitting. The three-dimensional finite element model of the launch canister was established in the ABAQUS software environment and the creep deformation of the launch canister after long-term stacking storage was studied. The results indicated that the bottom layer of the launch canister frame presented an extended residual deformation when the stacking storage solution with the original support pad was used. Therefore, a position adjustment program of the support pad was put forward. The residual deformation of the launch canister frame after long-term storage could be significantly reduced, thus the performance requirements for the launch canister are guaranteed.

Modified Dyson Continuum Damage Model for Austenitic Steel Alloy

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Seok Jun Kang ◽  
Hoomin Lee ◽  
Jae Boong Choi ◽  
Moon Ki Kim
Keyword(s):  
Damage Model ◽  
Life Time ◽  
Continuum Damage ◽  
Creep Life ◽  
Creep Tests ◽  
Continuum Damage Model ◽  
Thermal Plant ◽  
Uniaxial Creep ◽  
Term Creep

Ultrasuper critical (USC) thermal plants are now in operation around the globe. Their applications include superheaters and reheaters, which generally require high temperature/pressure conditions. To withstand these harsh conditions, an austenitic heat-resistant HR3C (ASME TP310NbN) steel was developed for metal creep resistance. As the designed life time of a typical thermal plant is 150,000 h, it is very important to predict long-term creep behavior. In this study, a three-state variable continuum damage model (CDM) was modified for better estimation of long-term creep life. Accelerated uniaxial creep tests were performed to determine the material parameters. Also, the rupture type and microstructural precipitation were observed by scanning electron microscopy. The creep life of HR3C steel was predicted using only relatively short-term creep test data and was then successfully verified by comparison with the long-term creep data.

Microstructures of Grade 91 Steels Under Long-Term Creep Conditions

2018 ◽  
Author(s):  
Kenji Kako ◽  
Susumu Yamada ◽  
Masatsugu Yaguchi ◽  
Yusuke Minami
Keyword(s):  
Remaining Life ◽  
Martensitic Steels ◽  
Creep Data ◽  
Creep Life ◽  
Creep Tests ◽  
Microstructural Observation ◽  
Type Iv ◽  
Grade 91 ◽  
Term Creep

Type IV damage has been found at several ultra-supercritical (USC) plants that used high-chromium martensitic steels in Japan, and the assessment of the remaining life of the steels is important for electric power companies. The assessment of the remaining life needs long-term creep data for over 10 years, but such data are limited. We have attempted to assess the remaining life by creep tests and by microstructural observation of Grade 91 steels welded pipes which were used in USC plants for over 10 years. Following the results of microstructural observation of USC plant pipes, we find that microstructures, especially distribution of MX precipitates, have large effect on the creep life of Grade 91 steels.

scholarly journals Time Blast Wave Theory for the Expansion of the Universe

2021 ◽  
Author(s):  
G K Jarvis
Keyword(s):  
Blast Wave ◽  
Space Dimension ◽  
High Redshift ◽  
Wave Theory ◽  
Time Dimension ◽  
Expansion Time ◽  
Expansion Of The Universe ◽  
Time Away ◽  
The Universe ◽  
Strong Agreement

Abstract A new theory is presented and tested that time itself is the phenomenon that causes the expansion of the universe and that without expansion, time would simply not be. The model of the theory accurately matches observed cosmological luminosity data consequently accurately describing the observed expansion of the universe. The theory implies that the universe exploded outwards within the dimension of time with all particles expanding from this event within a time blast sphere. Each space dimension is wrapped around the time dimension and every object that is gravitationally separate within the time blast-wave will progress on their own time trajectory of time away from time zero. This has the effect that all objects will expand or move apart as the time sphere expands. We observe distant, and therefore historic, objects on a spiral timeline. We have modelled the theory and shown strong agreement with luminosity observations both at low and high redshift without the need for a cosmological constant thus indicating that the universe is not accelerating in its expansion. The model in fact predicts it is decelerating. The theory also predicts that the unperturbed speed of time expansion will impose a limit on the universe in terms of the fastest speed possible and the speed that light must always travel at. With this limit and as no object can ever be stationary in the time dimension, but that faster and heavier objects will expand less, the theory consequently leads us to explain why special and general relativity occur. Gravity can be explained by the clumping of matter into the dimension of time causing a localised slowing of expansion subsequently causing time dilation and thus resulting in an attractive force with other objects. By this theory, black holes are not singularities but are simply dimples on the time blast wave front.

Influence of service ageing on polyester-reinforced polyvinyl chloride-coated fabrics reported through mathematical material models

2018 ◽  
Vol 89 (8) ◽  
pp. 1472-1487
Author(s):  
Krzysztof Zerdzicki ◽  
Pawel Klosowski ◽  
Krzysztof Woznica
Keyword(s):  
Polyvinyl Chloride ◽  
Constitutive Models ◽  
Uniaxial Tensile ◽  
Creep Tests ◽  
Material Models ◽  
Material Parameters ◽  
Coated Fabric ◽  
Coated Fabrics ◽  
Term Creep

In this paper the coupled service (constructional tension) and environmental (sunlight, rainfalls, temperature variations) ageing influence on the polyester-reinforced polyvinyl chloride (PVC)-coated fabric VALMEX is studied. Two cases of the same fabric have been analyzed: one USED for 20 years on the real construction of the Forest Opera in Sopot (Poland), and one kept as a spare material (NOT USED). The following tests have been conducted: uniaxial tensile, biaxial tensile and long-term creep tests. The obtained results have been used for the parameter identification of the piecewise non-linear, Burgers and Bodner–Partom models. Next, the analysis of the influence of environmental conditions on the parameters of these models has been made. It has been concluded that some parameters are more and the others are less sensitive to the exposure to environmental and mechanical conditions. The change of material parameters for fill threads (due to larger deformation) is higher. The obtained results may be useful in the durability evaluation of the textile membranes reinforced with polyester threads and PVC coated. All the constitutive models with the identified parameters may be used for the numerical analysis of structures made of fabrics at the service beginning and after long-term usage.

An Experimental Study on the Creep of FRC Sub-Base for Pavement Using a New Testing Device

2013 ◽  
Vol 639-640 ◽  
pp. 493-497
Author(s):  
Woo Tai Jung ◽  
Sung Yong Choi ◽  
Young Hwan Park
Keyword(s):  
Creep Test ◽  
Strain Curve ◽  
Hydraulic Pressure ◽  
Slight Variation ◽  
Test Results ◽  
Creep Tests ◽  
Loading Device ◽  
Permanent Load ◽  
Term Creep

The hydraulic loading device commonly used for creep test necessitates continuous recharge of the hydraulic pressure with time and is accompanied by slight variation of the permanent load at each recharge. Therefore, accurate test results cannot be obtained for long-term creep tests requiring time-dependent behavioral analysis during more than 6 months. This study conducts creep test as part of the analysis of the long-term characteristics of fiber-reinforced lean concrete sub-base of pavement. The creep test is executed using the new load-amplifier device not a conventional loading device. Since the results of the preliminary verification test on the new creep test device show that constant permanent load is applied without significant variation, it can be expected that more accurate measurement of the creep will be possible in a long-term compared to the conventional hydraulic device. In addition, the creep test results of sub-base specimens reveal the occurrence of large instantaneous elastic strain, differently from the strain curve observed in ordinary concrete, as well as the occurrence of small creep strain leading to low creep coefficient.

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