scholarly journals Predicting bending creep of laminated veneer lumber (LVL) sengon (Paraserianthes falcataria) beams from initial creep test data

2018 ◽  
Vol 195 ◽  
pp. 02028
Author(s):  
Achmad Basuki ◽  
Ali Awaludin ◽  
Bambang Suhendro ◽  
Suprapto Siswosukarto
Keyword(s):  
Test Data ◽  
Creep Test ◽  
Ultimate Load ◽  
Beam Deflection ◽  
Creep Model ◽  
Secondary Creep ◽  
Test Results ◽  
Creep Tests ◽  
Paraserianthes Falcataria ◽  
Laminated Veneer Lumber

This paper presents the results of creep tests of Laminated Veneer Lumber Sengon (LVL Sengon) beams, aiming to determine the creep factor and to establish the prediction beam deflection based on the initial creep test data. The LVL Sengon beams have a cross section of 40 mm by 80 mm and a clear span length of 2,000 mm, they were loaded at midspan for three different stress levels: 30%, 40%, and 50% of the ultimate load within 30, 60, and 90 days. Each loading level consists of four repetitive beams where one beam was wrapped with a plastic sheet. The test results showed that for 90 days the bending creep test can not determine the secondary creep yet. Curve fitting of bending creep test data indicated that the parameters of the Modified Burger creep model of the first 30 days can be accurately used to predict the beam deflection curve up to 60 and 90 days of loading.

Modelling and Data Interpretation of Small Punch Creep Testing

2011 ◽  
Author(s):  
R. Li ◽  
T. H. Hyde ◽  
W. Sun ◽  
B. Dogan
Keyword(s):  
Large Deformation ◽  
Test Data ◽  
Creep Test ◽  
Creep Model ◽  
Test Results ◽  
Creep Tests ◽  
Creep Properties ◽  
Small Punch ◽  
Draft Code ◽  
Uniaxial Creep

The small punch testing (SPT) technique has been proposed for use in determining the creep properties of materials for which only a very small volume of material is available. A draft code of practice on SPT has been produced. However it is not, as yet, generally accepted that the data obtained from small punch tests can be directly related to those which would be obtained from conventional uniaxial creep tests. For this reason, the development of techniques suitable for the interpretation of SPT data has become very important. In this paper, a set of uniaxial creep test data has been characterised in such a way as to gain an improved understanding of the correlation between the data from small punch tests and corresponding uniaxial creep tests. Finite element (FE) analyses of small punch creep tests, using a damage mechanics based creep model, have been performed. The effect of large deformation on the determination of material properties for a creep damage model, has been investigated to take into account the large deformation nature of small punch tests. An equivalent stress, σeq, proposed by the draft code, was used to relate the SPT results to the corresponding uniaxial creep test results. A preliminary assessment of the use of small punch test results, in determining creep properties, has been presented, which includes comparisons of the failure life and equivalent minimum strain rate results obtained from SPTs with the corresponding uniaxial creep test data. Future work related to the interpretation of SPT is briefly addressed.

Creep Properties Assessment of Materials by a Small Cantilever Beam Specimen

2018 ◽  
Author(s):  
Fakun Zhuang ◽  
Shantung Tu ◽  
Guoshan Xie ◽  
Shanshan Shao ◽  
Luowei Cao
Keyword(s):  
Cantilever Beam ◽  
Creep Test ◽  
Uniaxial Stress ◽  
Test Method ◽  
Creep Model ◽  
Beam Specimen ◽  
Secondary Creep ◽  
Creep Tests ◽  
Creep Properties ◽  
Uniaxial Creep

Small specimen creep test techniques have been widely applied in the creep properties assessment of materials for the equipment in-service. In order to acquire the creep data accurately and conveniently, the creep test method with small cantilever beam specimens is proposed. On the basis of Norton-Bailey creep law, analytical creep model for the cantilever beam specimen is derived. With this model, the load can be converted to equivalent uniaxial stress and the displacement rate can be converted to equivalent uniaxial strain rate. The creep properties of Cr-Mo steel are assessed by the cantilever beam specimens creep tests. And the creep parameters are evaluated, which are compared to the uniaxial creep parameters. The results show that parameters obtained from the cantilever beam tests correspond reasonably well with those from uniaxial tests. It proves that the primary and secondary creep properties can be assessed by the cantilever beam specimen tests.

Analysis of Thick-Walled Pipeline Elements Operating in Creep Conditions

2015 ◽  
Vol 712 ◽  
pp. 63-68
Author(s):  
Przemysław Osocha ◽  
Bohdan Węglowski
Keyword(s):  
Finite Element ◽  
Test Data ◽  
Creep Test ◽  
Power Plants ◽  
Steam Pressure ◽  
Creep Model ◽  
Creep Process ◽  
Fe Model ◽  
Element Analysis ◽  
Wide Range

In some coal-fired power plants, pipeline elements have worked for over 200 000 hours and increased number of failures is observed. The paper discuses thermal wear processes that take place in those elements and lead to rupture. Mathematical model based on creep test data, and describing creep processes for analyzed material, has been developed. Model has been verified for pipeline operating temperature, lower than tests temperature, basing on Larson-Miller relation. Prepared model has been used for thermal-strength calculations based on a finite element method. Processes taking place inside of element and leading to its failure has been described. Than, basing on prepared mathematical creep model and FE model introduced to Ansys program further researches are made. Analysis of dimensions and shape of pipe junction and its influence on operational element lifetime is presented. In the end multi variable dependence of temperature, steam pressure and element geometry is shown, allowing optimization of process parameters in function of required operational time or maximization of steam parameters. The article presents wide range of methods. The creep test data were recalculated for operational temperature using Larson-Miller parameter. The creep strain were modelled, used equations and their parameters are presented. Analysis of errors were conducted. Geometry of failing pipe junction was introduced to the Ansys program and the finite element analysis of creep process were conducted.

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 Testing Technique for Remnant Life Assessment

2014 ◽  
Vol 592-594 ◽  
pp. 739-743 ◽  
Author(s):  
J. Ganesh Kumar ◽  
K. Laha ◽  
M.D. Mathew
Keyword(s):  
Creep Test ◽  
Rupture Life ◽  
Life Assessment ◽  
Test Results ◽  
Creep Tests ◽  
Testing Technique ◽  
Creep Properties ◽  
Small Punch ◽  
Miniature Specimens ◽  
Deflection Rate

Small punch creep (SPC) testing technique is a material non-intensive testing technique for evaluating creep behavior of materials using miniature specimens. It can be used for remnant life assessment (RLA) studies on components in service, by scooping out limited material for testing without impairing the strength of component. In order to ensure the reliability of use of SPC technique for RLA, it is necessary to establish sound database on SPC properties of the material before putting into service. In this investigation, SPC technique was used to evaluate creep properties of 316LN stainless steel using specimens of size 10 x 10 x 0.5 mm. SPC tests were conducted in load controlled mode at 923 K and at various loads. SPC curves clearly exhibited primary, secondary and tertiary creep stages. The minimum deflection rate increased and rupture life decreased with an increase in applied load. Like in conventional creep test results, the minimum deflection rate obeyed Norton’s power law and Monkman-Grant relationship. SPC test was correlated with corresponding conventional creep test. Good correlation was established between creep rupture life values evaluated from SPC tests and conventional creep tests.

Creep Model Based on Theta Projection and Omega Method for Predicting the Creep Behavior of Alloy

2007 ◽  
Vol 353-358 ◽  
pp. 533-536
Author(s):  
Bong Min Song ◽  
Jong Yup Kim ◽  
Joon Hyun Lee
Keyword(s):  
Creep Behavior ◽  
Constant Load ◽  
Control Mode ◽  
Creep Model ◽  
Test Results ◽  
Creep Data ◽  
Creep Tests ◽  
Omega Method ◽  
Improved Model ◽  
Term Creep

Creep testing of Alloy 718 has been carried out at various loads in the temperature range near 650°C in constant load control mode in order to understand how to predict the creep behavior including tertiary creep. The test results have been used for evaluating the existed models, such as Theta projection and Omega method that have been widely used for predicting long term creep strain and rupture time. After determining variables and material parameters of each method with the test results, estimated creep data from each model have been compared with the each measured creep data from the creep tests. The root cause of the discrepancy between estimated and measured data has been analyzed in order to improve the existed methods. The reliability of the improved model has been evaluated in relation to creep data.

scholarly journals Creep Resistance of VM12 Steel

2016 ◽  
Vol 61 (3) ◽  
pp. 1635-1640 ◽  
Author(s):  
A. Zieliński ◽  
G. Golański ◽  
J. Dobrzański ◽  
M. Sroka
Keyword(s):  
Functional Properties ◽  
Creep Test ◽  
Creep Resistance ◽  
Practical Aspect ◽  
Test Results ◽  
Creep Tests ◽  
Steam Parameters ◽  
Term Creep ◽  
Long Term Impact

Abstract This article presents selected material characteristics of VM12 steel used for elements of boilers with super- and ultra-critical steam parameters. In particular, abridged and long-term creep tests with and without elongation measurement during testing and investigations of microstructural changes due to long-term impact of temperature and stress were carried out. The practical aspect of the use of creep test results in forecasting the durability of materials operating under creep conditions was presented. The characteristics of steels with regard to creep tests developed in this paper are used in assessment of changes in functional properties of the material of elements operating under creep conditions.

Bending Creep of High-Temperature Dried Spruce Timber

Holzforschung ◽  
2003 ◽  
Vol 57 (1) ◽  
pp. 95-100 ◽  
Author(s):  
C. Bengtsson ◽  
R. Kliger
Keyword(s):  
High Temperature ◽  
Relative Humidity ◽  
Low Temperature ◽  
Creep Test ◽  
Raw Material ◽  
Drying Methods ◽  
Test Results ◽  
Creep Tests ◽  
Free Shrinkage ◽  
Creep Deformations

Summary In this paper, bending creep test results from high-temperature (HT) dried Norway Spruce timber are presented. The results are compared with creep tests of conventional low-temperature (LT) dried timber. The HT drying was performed at 115°C and the LT drying was performed at 70°C. The creep tests were performed in a varying climate with 20°C and 30–90% relative humidity. A total number of 24 specimens, 45 × 70 × 1100 mm, were loaded in bending during approximately 240 days. Both the HT-dried and the LT-dried material were cut from the same four trees to have as equal raw material as possible for the two drying methods. The results show smaller bending creep deformations of HT-dried timber (approximately 30%) as compared to the LT-dried timber. The variation in magnitude of creep for HT-dried timber was equal to or smaller than for LT-dried timber. Additionally, the variation in deformation between the moisture cycles was smaller for HT-dried timber. These observations indicate a less pronounced mechano-sorptive effect for HT-dried timber. The free shrinkage in the grain direction was significantly smaller for the HT-dried material than for the LT-dried material.

A Finite Element Study of Friction Effect in Four-Point Bending Creep Test

2003 ◽  
Author(s):  
Young Suk Kim ◽  
Don R. Metzger
Keyword(s):  
Finite Element ◽  
Test Data ◽  
Creep Test ◽  
Contact Point ◽  
Simulation Studies ◽  
Creep Tests ◽  
Contact Conditions ◽  
Creep Properties ◽  
Four Point Bending ◽  
Bend Tests

Creep tests are often performed in four-point bending and the stress distribution in the bending specimen is nonlinear, so creep properties are estimated from bend creep test data. However, getting creep properties from bending creep tests is often doubted because of uncertainties from contact point shift and frictional effect between loading pin and specimen in four-point bending creep tests. Finite element simulations of the four-point bending creep tests were performed with geometric models which include contact conditions. It was found from simulation studies that friction in the bend tests can cause error in the estimation of creep properties, but when no friction was applied in simulations the creep properties were well predicted from bend test data.

scholarly journals Creep Strain Analysis and an Improved Creep Model of Granite Based on the Ratio of Deviatoric Stress-Peak Strength under Different Confining Pressures

2021 ◽  
Author(s):  
Li Qian ◽  
Jianhai Zhang ◽  
Xianliang Wang ◽  
Yonghong Li ◽  
Ru Zhang ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Creep Behavior ◽  
Viscosity Coefficient ◽  
Deviatoric Stress ◽  
Peak Strength ◽  
Creep Model ◽  
Secondary Creep ◽  
Creep Tests ◽  
Underground Powerhouse ◽  
Confining Pressures

Abstract Creep refers to the deformation of rock with time under long-term applied stress, which occur in most underground engineering. The creep behavior of granite in Shuang jiangkou underground powerhouse in Western Sichuan Province, China, was studied by creep tests. Based on test results, a new parameter DPR, the ratio of deviatoric stress to peak strength, is proposed. DPR is found to be a key parameter to describe creep parameters such as instantaneous elastic modulus, creep elastic modulus, and viscosity coefficient of rock under different confining pressures. Creep tests show that instantaneous elastic modulus increases with the increase of DPR. Creep elastic modulus increases when DPR changes from 0.54 to 0.7004, but decreases when DPR is from 0.7004 to 0.88, indicating fractures in rock closes firstly and then new fractures are generated. The viscosity coefficient of the rock increases first and then decreases with the increase of DPR, and when DPR = 0.7171, viscosity coefficient is maximum, indicating the time for rock to reach stability is the longest in creep tests. By introducing DPR and confining pressure into creep model, which interconnect creep parameters in a unified expression, an improved generalized Kelvin creep model is proposed which can accurately describe the primary and the secondary creep behavior of granite under given deviatoric stresses and confining pressures.

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