scholarly journals Generalized Relaxation Behavior of Rock Under Various Loading Conditions Using a Constant Linear Combination of Stress and Strain

2021 ◽  
Vol 9 ◽  
Author(s):  
Hailong Zhang ◽  
Yang Tang ◽  
Seisuke Okubo ◽  
Shoujian Peng ◽  
Cancan Chen
Keyword(s):  
Linear Combination ◽  
Control Method ◽  
Relaxation Behavior ◽  
Time Dependent ◽  
Feedback Signal ◽  
Failure Behavior ◽  
Stress And Strain ◽  
Loading Conditions ◽  
Underground Structures ◽  
Dependent Behavior

Time-dependent behavior has been demonstrated to be an essential factor in determining the long-term stability of underground structures. Creep and relaxation experiments are commonly used to investigate time-dependent behavior by subjecting rock to constant stress and strain. However, both stress and strain of in-situ rock masses are likely to change with time, a phenomenon known as generalized relaxation that has not been thoroughly investigated. In this study, a newly proposed control method with a constant linear combination of stress and strain as a feedback signal is used in compression and tension tests to investigate generalized relaxation behaviors of rocks. The results showed that the stress and strain of generalized relaxation are dependent on values of α, which represented generalized relaxation direction. The isochronous curves are enclosed within stress–strain curves of different loading conditions. The variation of stress (∆σ) and strain (∆ε) increases with increasing stress level and decreases with increasing confining pressure. Also, ∆σ and ∆ε in region II are smaller than in regions I and III. Furthermore, by performing brittle rock tests, complete generalized relaxation curves are obtained; three stages are observed, which are similar to conventional creep and relaxation behavior. Finally, the time and generalized relaxation failure behavior of Class I and Class II rock are discussed. The study is a valuable resource for gaining a comprehensive understanding of the time-dependent behavior of rocks and improving the stability and safety of underground structures.

scholarly journals Loading-Rate Dependency of Young’s Modulus for Class I and Class II Rocks

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Hailong Zhang ◽  
Seisuke Okubo ◽  
Cancan Chen ◽  
Yang Tang ◽  
Jiang Xu
Keyword(s):  
Young’S Modulus ◽  
Loading Rate ◽  
Young's Modulus ◽  
Underlying Mechanism ◽  
Time Dependent ◽  
Rate Dependency ◽  
Underground Structures ◽  
Dependent Behavior ◽  
Rate Of Increase ◽  
Variable Compliance

Understanding the time-dependent behavior of rocks is important for ensuring the long-term stability of underground structures. Aspects of such a time-dependent behavior include the loading-rate dependency of Young’s modulus, strength, creep, and relaxation. In particular, the loading-rate dependency of Young’s modulus of rocks has not been fully clarified. In this study, four different types of rocks were tested, and the results were used to analyze the loading-rate dependency of Young’s modulus and explain the underlying mechanism. For all four rocks, Young’s modulus increased linearly with a tenfold increase in the loading rate. The rocks showed the same loading-rate dependency of Young’s modulus. A variable-compliance constitutive equation was proposed for the loading-rate dependency of Young’s modulus, and the calculated results agreed well with measured values. Irrecoverable and recoverable strains were separated by loading-unloading-reloading tests at preset stress levels. The constitutive equations showed that the rate of increase in Young’s modulus increased with the irrecoverable strain and decreased with increasing stress. The increase in the irrecoverable strain was delayed at high loading rates, which was concluded to be the main reason for the increase in Young’s modulus with an increasing loading rate.

Development of Creep Test Method for Thermoplastic Fiber-Reinforced Polymer Composite Tubes Under Pure Hoop Loading Condition

2019 ◽  
Author(s):  
Hai G. M. Doan ◽  
Hossein Ashrafizadeh ◽  
Pierre Mertiny
Keyword(s):  
Creep Behavior ◽  
Axial Loading ◽  
Test Method ◽  
Image Correlation ◽  
Fiber Reinforced Polymer ◽  
Time Dependent ◽  
Loading Conditions ◽  
Fiber Reinforced ◽  
Reinforced Polymer ◽  
Dependent Behavior

Abstract Piping made from thermoplastic fiber reinforced polymer composites (TP-FRPCs) is receiving increasing attention in the oil and gas industry. Creep and time-dependent behavior is one of the main factors defining the service life of TP-FRPC structures. The lifetime and time-dependent behavior of TP-FRPC structures can be predicted using simulation tools, such as finite element analysis, to aid in the design optimization by modeling the long-term behavior of the material. Composite material time-dependent properties are required inputs for such models. While there is previous research available on creep testing of TP-FRPCs in laminate geometry, such tests may not enable accurate determination of the composite properties due to edge effects. On the other hand, coupons with tubular geometry not only provide improved load distribution between the fibers and matrix with minimal end effects, they also enable certain loading conditions experienced during typical piping operations such as internal pressure. In this study, a testing method to capture the creep behavior of tubular TP-FRPC specimens subjected to multi-axial loading conditions was developed. Tubular coupons were prototyped by an automated tape placement process. Strain was measure using digital image correlation technique and strain gauges. The development of the test setup forms the foundation for further testing of tubular TP-FRPC coupons at different multi-axial loading conditions. As a preliminary test, the creep behavior of a TP-FRPC tube subjected to pure hoop stress condition was evaluated using the developed testing process.

Time-Dependent Cyclic Deformation and Failure Behavior and Its Damage Coupled Simulation for Solder Alloy 63Sn-37Pb

2005 ◽  
Vol 297-300 ◽  
pp. 881-886 ◽  
Author(s):  
Xianjie Yang ◽  
Qing Gao
Keyword(s):  
Solder Alloy ◽  
Failure Criterion ◽  
Cyclic Deformation ◽  
Cyclic Strain ◽  
Cyclic Stress ◽  
Time Dependent ◽  
Failure Behavior ◽  
Deformation And Failure ◽  
Viscoplastic Model ◽  
Dependent Behavior

The tests of 63Sn-37Pb under cyclic strain and stress were conducted to investigate the material’s time-dependent behavior. A damage-coupled viscoplastic model and its failure criterion are proposed. The prediction of the proposed viscoplastic model implies that the model can describe the cyclic strain and cyclic stress ratcheting behavior, and the fatigue lives very well.

scholarly journals Correlation of Structural Ceramic Time Dependent Failure Data

1986 ◽  
Author(s):  
Lewis R. Swank
Keyword(s):  
Stress Rupture ◽  
Time Dependent ◽  
Failure Behavior ◽  
Flexural Stress ◽  
Failure Data ◽  
Dependent Behavior ◽  
Structural Applications ◽  
Rupture Data ◽  
Dependent Failure ◽  
Fast Fracture

Today there is a rapidly growing interest in the use of ceramics for structural applications. In applying structural ceramics it is necessary to estimate the time dependent failure behavior of the material. An analytical method is required to utilize flexural fast fracture and stress rupture data to predict the time dependent behavior of complex structures. This paper proposes an empirical equation to correlate the data. The proposed equation is applied to flexural and spin disk data. The flexural data correlate reasonably well. The spin disk data correlate well if the assumption is made that the stress in the flexural stress rupture specimens of the data base are those of steady state creep.

Time-dependent behavior of nitric oxide excited states under the effect of electron impact

2021 ◽  
Vol 28 (2) ◽  
pp. 024503
Author(s):  
Mohammed amin Ferdi ◽  
Abdelaaziz Bouziane ◽  
Mourad Djebli
Keyword(s):  
Nitric Oxide ◽  
Electron Impact ◽  
Excited States ◽  
Time Dependent ◽  
Dependent Behavior

Time-dependent behavior of retaining piles during pre-excavation dewatering in multi-layered saturated soils

2021 ◽  
Vol 137 ◽  
pp. 104300
Author(s):  
Yi Chong Cheng ◽  
Ri Hong Zhang ◽  
Kui Hua Wang ◽  
Zhi Yong Ai
Keyword(s):  
Time Dependent ◽  
Saturated Soils ◽  
Dependent Behavior

Consideration of Environmentally Assisted Fatigue in Austenitic Stainless Steel: Calculation and Practical Application

2012 ◽  
Author(s):  
Sven H. Reese ◽  
Johannes Seichter ◽  
Dietmar Klucke
Keyword(s):  
Primary Circuit ◽  
Stress And Strain ◽  
Loading Conditions ◽  
Practical Application ◽  
Circuit Component ◽  
Detailed Assessment ◽  
The Mean ◽  
Fatigue Evaluation ◽  
Assessment Procedures

The influence of LWR coolant environment to the lifetime of materials has been discussed recent years. Nowadays the consideration of environmentally assisted fatigue is under consideration in Codes and Standards like ASME and the German KTA Rules (e.g. Standard No. 3201.2 and Standard No. 3201.4) by means of so called attention thresholds. Basic calculation procedures in terms of quantifying the influence of LWR coolant environment by the Fen correction factor were proposed by Higuchi and others and are given in NUREG/CR-6909. This paper deals with the application of the proposed assessment procedures of ANL and the application to plant conditions. Therefore conservative assessment procedures are introduced without assuming the knowledge of detailed stress and strain calculations or temperature transients. Additionally, detailed assessment procedures based on Finite-Element calculations, respecting in-service temperature measurements including thermal reference transients and complex operational loading conditions are carried out. Fatigue evaluation of a PWR primary circuit component is used in order to evaluate the influence of plant like conditions numerically. Conclusions regarding the practical application are drawn by means of comparing the ANL approach considering laboratory conditions, conservative assessment procedures for the determination of cumulative fatigue usage factors of plant components and detailed assessment procedures. Plant like loading conditions, complex component geometries, loading scenarios and reference temperature transients shall be taken into account. Practical issues like the determination of the mean temperature or the strain rate have to be considered adequately.

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