scholarly journals Analysis of Test System Misalignment in the Creep Test

1982 ◽  
Vol 104 (4) ◽  
pp. 280-284
Author(s):  
Han C. Wu ◽  
T. P. Wang
Keyword(s):  
Creep Strain ◽  
Creep Test ◽  
Test System ◽  
Neutral Axis ◽  
Strain Level ◽  
Initial Strain ◽  
Creep Tests ◽  
Test Sheet ◽  
Creep Stress ◽  
Creep Time

An analysis of test system misalignment is presented for the creep test. Sheet type rectangular 1100-0 aluminum specimens are used for discussion. It is found that the creep strain at the geometric centerline of the specimen is different than that at the neutral axis. However, this difference in the creep strain decreases with time. Generally, the effect of misalignment decreases with creep time. Creep tests conducted with long pullrods and large initial strain level (high creep stress) will tend to minimize the effect of misalignment.

scholarly journals The Effect of Test System Misalignment in the Dynamic Tension Test

1982 ◽  
Vol 104 (4) ◽  
pp. 285-290
Author(s):  
Han C. Wu ◽  
T. P. Wang ◽  
M. C. Yip
Keyword(s):  
Plastic Strain ◽  
Strain Rate ◽  
Constant Strain Rate ◽  
Test System ◽  
Tension Test ◽  
Neutral Axis ◽  
Dynamic Tension ◽  
Test Sheet

An analysis of test system misalignment is presented for dynamic tension test. Sheet type rectangular 1100-0 aluminum specimens are used for discussion. For a constant strain rate tension test, the strain rate is constant only on the neutral axis of the specimen. The lower the strain rate is, the more significant the misalignment errors become. The neutral axis will shift away from the centerline of the specimen as the plastic strain increases. But, it will reach a limit and will not completely move back to the centerline.

scholarly journals Microstructural Characterization of Alloy 617 Crept Into the Tertiary Regime

2015 ◽  
Author(s):  
Thomas M. Lillo ◽  
Richard N. Wright
Keyword(s):  
Image Analysis ◽  
Creep Strain ◽  
Void Formation ◽  
Microstructural Characterization ◽  
Low Energy ◽  
Creep Tests ◽  
Alloy 617 ◽  
Creep Stress ◽  
Creep Strains

The dislocation structure and area fraction of creep voids in Alloy 617 were characterized following creep tests interrupted at total creep strains ranging from 2–20%. A range of creep temperatures (750–1000°C) and initial creep stresses (10–145 MPa) produced creep test durations ranging from 1 to 5800 hours. Image analysis of optical photomicrographs on longitudinal sections of the gage length was used to document the fraction of creep porosity as a function of creep parameters. In interrupted creep tests performed at 750°C, minimal levels of creep porosity were found even in samples crept to ∼20% total creep strain. At 1000°C, creep porosity was negligible below total creep strains of 10% and increased thereafter with increasing total creep strain. Also, creep porosity increased with decreasing creep stress for a given total creep strain. TEM performed on the gage sections did not reveal significant creep void formation on grain boundaries or in the grains at the sub-micron level. However, dislocation boundaries exhibited extensive dislocation rearrangement and dislocation-dislocation reactions. It was concluded that the onset of tertiary creep did not result from creep void formation and more likely arose due to the formation of low energy dislocation substructures.

CREEP CHARACTERISTICS OF CHALK MARL UNDER UNIAXIAL AND CONFINED COMPRESSION STATE STRESS

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Nuri Al-Mohamadi
Keyword(s):  
Creep Strain ◽  
Stress Level ◽  
Axial Strain ◽  
Confined Compression ◽  
Creep Tests ◽  
Creep Stress ◽  
State Of Stress ◽  
Uniaxial Creep ◽  
Creep Characteristics ◽  
State Stress

This paper studies the time-dependent deformation of chalk marl under uniaxial state of stress in a specially built creep rigs, and confined compression stress state. The tests carried out include: six uniaxial creep tests with vertical and lateral deformation measurements, at different stress levels which lasted for 75 to 268 days, six oedometer creep tests under different stress intensities and different loading conditions which lasted for 80 to 250 days. All tested samples were trimmed from 113 mm diameter cores. For uniaxial tests 0.5% axial strain occurred almost instantaneously in the first series subjected to a stress level of 80%. In the second series subjected to a stress level of 40%, the average initial strain was 0.25% which indicate clearly their stress level dependency. After 75 to 150 days creep period, the measured average creep strain was 0.33% for the first series, which represents 57% of the consolidation strain. For series 2 the average creep strain = 0.26%, which represents 54% of the consolidation strain. This implies that the proportional creep ratio Cr = (Et-E1) / E1 is independent of the applied stress level, where Et strain at any time t, E1 strain at one day. For 1-D creep tests E1 and the proportional strain (Et-E1) are not affected significantly by the intensity of applied creep stress, while both of them are highly influenced by the method of load application. From these results, it can be concluded that creep deformation constitutes an important part of the total deformation of chalk marl.

Creep Behavior Study for Carbon Fiber Nano-Composites

2014 ◽  
Vol 626 ◽  
pp. 502-511
Author(s):  
Yi Luen Li ◽  
Tsung Yu Chou ◽  
Ming Yuan Shen ◽  
Wei Jen Chen ◽  
Chin Lung Chiang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Epoxy Resin ◽  
Creep Strain ◽  
Resin Composites ◽  
Test Results ◽  
Creep Tests ◽  
Electrical Conductivities ◽  
The Matrix ◽  
Creep Time ◽  
Epoxy Resin Composites

The surface modification of carbon nanotubes (CNTs) has been recently observed to influence the distribution of CNTs in epoxy resin and the mechanical properties and electrical conductivities of these CNTs. Accordingly, the treatment of CNTs to with organic acids to oxidize them generates functional groups on the surface of CNTs. This investigation studies the consequent enhancement of the mechanical properties and electrical conductivities of CNTs. The influence of adding various proportions of CNTs to the epoxy resin on the mechanical properties and electrical conductivities of the composites thus formed is investigated, and the strength of the material is tested at different temperatures.The test results also indicate that mechanical strength and electrical conductivity increase with the amount of CNTs added to the composites. Different coefficients of expansion of the matrix, fiber and CNTs, are such that overexpansion of the matrix at high temperature results in cracking in it.Moreover, the creep behaviors of carbon fiber (CF) /epoxy resin thermosetting composites and CNTs/CF/ epoxy resin composites were tested and analyzed at different stresses, orientations of fiber, temperatures and humidities. The creep exhibits only two stages-primary creep and steady-state creep. The effects of creep stress, creep time, and humidity on the creep of composites that contain various proportion of CNTs were investigated at various temperatures.Additionally, increasing the number of cycles in cyclic creep tests at room temperature resulted in a decrease in creep strain even at a high temperature of 55°C. Possible room temperature creep mechanisms have been proposed and discussed. With increasing number of creep tests, the creep strain decreased due to strain hardening which occurred during creep. Creep strain is believed to increase with applied stress, creep time, humidity, temperature and degree of the angle θ between the orientation of fiber and the direction of the applied stress.Finally, the test results of creep strain of CF/epoxy resin composites and CNTs/CF/epoxy resin composites tested under various conditions can be smoothly fitted by the fitting curves of Findley power law.

Mudstone Creep Test and Numerical Stimulation of Casing Loads in Deep Well

2011 ◽  
Vol 383-390 ◽  
pp. 1684-1690
Author(s):  
Zhi Qian Xu ◽  
Xiang Zhen Yan ◽  
Fan Bu
Keyword(s):  
Creep Test ◽  
Element Model ◽  
Test System ◽  
Oil Well ◽  
Test Results ◽  
Deep Well ◽  
Numerical Stimulation ◽  
Creep Time ◽  
The Finite Element Model

In this paper, a creep test was carried out for simulating the creeping of the core of the mudstone under condition of deep formation subsurface conditions by MTS-810 test system, the creep rule and the characteristic parameters of the mudstone formation were obtained from the experiments. According to the test results, the finite element model for casings load calculation was established, and the calculation program was also written. With the program, the casing load of one western oil well was calculated in mudstone formation. The numerical simulation results show that the casing load has a relationship with phase angle θ and creep time, and the casing load is 10% greater than the stress in situ.

Creep Behavior and Mechanical Properties of Carbon Fiber Nano-Composites

2011 ◽  
Vol 338 ◽  
pp. 156-165
Author(s):  
Yi Luen Li ◽  
Ming Yuan Shen ◽  
Wei Jen Chen ◽  
Chin Lung Chiang ◽  
Ming Chuen Yip
Keyword(s):  
Mechanical Properties ◽  
Epoxy Resin ◽  
Creep Strain ◽  
Room Temperature ◽  
Resin Composites ◽  
Test Results ◽  
Creep Tests ◽  
The Matrix ◽  
Creep Time ◽  
Epoxy Resin Composites

In recent years, it has been observed that surface modification of carbon nanotubes（CNTs）influences on CNT’s distribution among epoxy resin and affects the mechanical properties of CNTs. Accordingly, the treatment of CNTs to with organic acids to oxidize them generates functional groups on the surface of CNTs. This investigation studies the consequent enhancement of the mechanical properties of CNTs. The influence of adding various proportions of CNTs to the epoxy resin on the mechanical properties of the composites thus formed is investigated, and the strength of the material is tested at different temperatures. The creep behaviors of carbon fiber (CF) /epoxy resin thermosetting composites and CNTs/CF/ epoxy resin composites were tested and analyzed at different stresses, orientations of fiber, temperatures and humidities. The creep exhibits only two stages- primary creep and steady-state creep. The effects of creep stress, creep time, and humidity on the creep of composites that contain various proportion of CNTs were investigated at various temperatures. Additionally, increasing the number of cycles in cyclic creep tests at room temperature resulted in a decrease in creep strain even at a high temperature of 55°C. Possible room temperature creep mechanisms have been proposed and discussed. With increasing number of creep tests, the creep strain decreased due to strain hardening which occurred during creep. Creep strain is believed to increase with applied stress, creep time, humidity, temperature and degree of the angle θ between the orientation of fiber and the direction of the applied stress. Moreover, the test results of creep strain of CF/epoxy resin composites and CNTs/CF/epoxy resin composites tested under various conditions can be smoothly fitted by the fitting curves of Findley power law. Finally, the test results also indicate that mechanical strength increase with the amount of CNTs added to the composites. Different coefficients of expansion of the matrix, fiber and CNTs, are such that overexpansion of the matrix at high temperature results in cracking in it. An SEM image of the fracture surface reveals debonding and the pulling out of longitudinal fibers because of poor interfacial bonding between fiber and matrix, which reduce overall strength.

scholarly journals Creep Strain and Permeability Evolution in Cracked Granite Subjected to Triaxial Stress and Reactive Flow

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Fan Zhang ◽  
Jianjian Zhao ◽  
Dawei Hu ◽  
Qian Sheng ◽  
Jianfu Shao
Keyword(s):  
Acid Solution ◽  
Strain Rate ◽  
Creep Strain ◽  
Alkaline Solution ◽  
Confining Pressure ◽  
Creep Strain Rate ◽  
Reactive Flow ◽  
Secondary Creep ◽  
Creep Tests ◽  
Creep Stage

Fluid flow and fluid-rock interaction mainly take place in fracture network, consequently resulting in deformation and permeability variation of rock and deterioration of the wellbore performance. Mechanical-reactive flow coupling creep tests are performed on cracked granite under various confining pressures and acid and alkaline solution flows. The testing results show that the confining pressure and solution pH significantly influence the creep deformation, creep strain rate, and permeability. A primary creep stage and secondary creep stage are observed in all creep tests in this study; notably, the sample under a confining pressure of 10 MPa and acid solution injection undergoes creep failure for over 2700 hours. The acid solution has a more obvious influence on the creep behavior than that of the alkaline solution. With an increase in confining pressure, the total creep strain and creep strain rate in the samples gradually decrease during the injection of either solution. The permeability of the samples injected with either solution gradually deceases during the testing process, and this deceasing rate increases with the confining pressure. The scanning electron microscopy observations on the crack surfaces after the creep tests show that the surfaces of the fractures injected with the acid solution are smooth due to the dissolution of the matrix, while those injected with the alkaline solution include voids due to the dissolution of quartz. These experimental results could improve the understanding of the long-term transport and mechanical behaviors of wellbore.

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.

Small Punch Creep Properties of Heat Affected Zones of Reduced Activation Ferritic Steel

2008 ◽  
Author(s):  
Taichiro Kato ◽  
Shin-Ichi Komazaki ◽  
Yutaka Kohno ◽  
Hiroyasu Tanigawa
Keyword(s):  
Base Metal ◽  
Creep Test ◽  
Ferritic Steel ◽  
Electron Beam Welding ◽  
High Stress ◽  
Creep Rupture ◽  
Creep Tests ◽  
Creep Properties ◽  
Small Punch ◽  
Uniaxial Creep

The small punch (SP) creep test was carried out at the temperatures of 823∼923 K by using a further miniaturized specimen, namely, TEM disk-type specimen (φ 3.0×t0.25 mm). The tests were applied to the fine grain heat affected zone (FGHAZ), tempered HAZ (THAZ) and base metal (BM), respectively, which were removed from the joint of the reduced activation ferritic steel welded by an electron beam welding, in order to investigate the creep properties of such local regimes. The results obtained from the SP creep test were correlated with those of uniaxial creep tests using the base metal (BM) and welded joint (WJ). Experimental results revealed that there were no large differences between the SP creep rupture strengths of the FGHAZ and THAZ and that of the BM at the relatively high load levels. This result was in good agreement with the fact that the uniaxial creep strength of the WJ was almost coincident with that of the BM at the relatively high stress levels. In addition, the ratio of load (P) to stress (σ), which gave same rupture time, was calculated by using the creep rupture data of the BMs. As a result, the ratio was determined to be 0.43, resulting in the following equation; P = 0.43 σ.

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