A Retrospective Assessment of Elastic-Plastic and Creep Deformation behavior in Structural Components Like Discs, Cylinders, and Shells

Creep deformation behavior of SA387Gr91Cl2 heat-resistant steel used for steam cooler has been investigated. Creep tests were carried out using flat creep specimens machined from the normalized and tempered plate at 973K with stresses of 100, 125 and 150MPa. The minimum creep rate and rupture time dependence on applied stress was analyzed. The analysis showed that the heat-resistant steel obey Monkman-Grant and modified Monkman-Grant relationships.

Download Full-text

Partitioned Cyclic Fatigue Damage Evolution Model for PB-Free Solder Materials

Volume 9: Eighth International Conference on Creep and Fatigue at Elevated Temperatures ◽

10.1115/creep2007-26306 ◽

2007 ◽

Author(s):

Leila J. Ladani ◽

A. Dasgupta

Keyword(s):

Fatigue Damage ◽

Creep Deformation ◽

Damage Evolution ◽

Evolution Model ◽

Micro Scale ◽

Elastic Plastic ◽

Constitutive Properties ◽

Free Solder ◽

Cyclic Damage ◽

Creep Deformations

This study presents an approach to predict the degree of material degradation and the resulting changes in constitutive properties during cyclic loading in viscoplastic materials in micro-scale applications. The objective in the modeling approach is to address the initiation and growth of distributed micro-damage, in the form of micro-cracks and micro-voids, as a result of cyclic, plastic and creep deformations of material. This study extends an existing micromechanics-based approach, developed for unified viscoplastic models [Wen, et al, 2001], which uses dislocation mechanics to predict damage due to distributed micro-scale fatigue crack initiation [Mura and Nakasone, 1990]. In the present study, the approach is extended to a partitioned viscoplastic framework, because the micro-scale mechanisms of deformation and damage are different for plastic and creep deformation. In this approach, the model constants for estimating cyclic damage evolution are allowed to be different for creep and plastic deformations. A partitioned viscoplastic constitutive model is coupled with an energy partitioning (E-P) damage model [Oyan and Dasgupta, 1992] to assess fatigue damage evolution due to cyclic elastic, plastic and creep deformations. Wen’s damage evolution model is extended to include damage evolution due to both plastic and creep deformations. The resulting progressive degradation of elastic, plastic and creep constitutive properties are continuously assessed and updated. The approach is implemented on a viscoplastic Pb-free solder. Dominant deformation modes in this material are dislocation slip for plasticity and diffusion-assisted dislocation climb/glide for creep. The material’s behavior shows a good correlation with the proposed damage evolution model. Damage evolution constants for plastic and creep deformation were obtained for this Pb-free solder from load drop data collected from the mechanical cycling experiments at different temperatures. The amount of cyclic damage is evaluated and compared with experiment.

Download Full-text

Creep in Ordered Nickel Base Alloys

MRS Proceedings ◽

10.1557/proc-39-279 ◽

1984 ◽

Vol 39 ◽

Cited By ~ 7

Author(s):

P. R. Strutt ◽

B. H. Kear

Keyword(s):

Creep Behavior ◽

Creep Deformation ◽

Crystallographic Orientation ◽

Deformation Behavior ◽

Strong Influence ◽

Deformation Mode ◽

Two Phase ◽

Effects Of Temperature ◽

Nickel Base ◽

Relative Creep

ABSTRACTThis paper examines the fundamentals of deformation behavior in ordered y′ (Ni3Al), β (NiAl) and β′ (Ni2AITi) phases, and specific two phase y/y′ and B/B′ alloys. The relative creep strengths of these ordered nickel-base alloys are discussed. Differences in creep behavior are explained in terms of the effects of temperature, crystallographic orientation and alloying on creep deformation mode. In particular, it is shown that trace additions of boron and carbon to y/y′ alloys, or deviations from stoichiometry in β′ -type alloys can exert a strong influence on creep behavior.

Download Full-text

Creep Deformation Behavior and Microstructural Degradation During Creep of Pre-Strained 25Cr-20Ni-Nb-N Steel

Volume 9: Eighth International Conference on Creep and Fatigue at Elevated Temperatures ◽

10.1115/creep2007-26764 ◽

2007 ◽

Cited By ~ 1

Author(s):

Nobuhiko Saito ◽

Nobuyoshi Komai

Keyword(s):

Creep Rate ◽

Creep Deformation ◽

Deformation Behavior ◽

Minimum Creep Rate ◽

Strengthening Mechanism ◽

Creep Rupture ◽

Microstructural Degradation ◽

Solution Treated ◽

Long Time ◽

Strained Materials

The purpose of this study is to clarify the creep deformation behavior and microstructural degradation during creep of pre-strained 25Cr-20Ni-Nb-N steel (TP310HCbN), which has the highest creep strength among austenite stainless steels used for boiler tubes. The creep rupture strengths of the 20% pre-strained materials tested at 650°C under 210 MPa and 180 MPa were higher than those of solution-treated materials. However, the long time creep rupture strengths of the 20% pre-strained materials tested at 700°C and 750°C were lower than those of solution-treated materials. Thus, the creep strengths of the prestrained materials depend on test temperature and stress. Furthermore, the minimum creep rate of the 20% pre-strained materials and re-solution-treated materials tested at 650°C under 300MPa were 1.2 × 10−9 and 1.6 × 10−8 s−1, respectively. Thus, the minimum creep rate of the 20% pre-strained materials was lower than for re-solution-treated materials. The creep strengthening mechanism of the pre-strained materials at 650°C was considered to be that high-density dislocations were maintained until the late stage of creep. On the other hand, the creep rupture strengths of the 20% pre-strained materials were lower than those of solution-treated materials tested at over 700°C because of agglomeration and coarsening of precipitates and the recovery of dislocations.

Download Full-text

Advances in Ambient Temperature Creep Deformation Behavior of Two-Phase Titanium Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.475-479.779 ◽

2005 ◽

Vol 475-479 ◽

pp. 779-784 ◽

Cited By ~ 2

Author(s):

A. Jaworski ◽

Sreeramamurthy Ankem

Keyword(s):

Titanium Alloys ◽

Creep Deformation ◽

Deformation Behavior ◽

Creep Resistance ◽

Volume Fraction ◽

Beta Phase ◽

Two Phase ◽

Number Of Factors ◽

Strength Difference ◽

The Stability

In recent years, significant advances have been made in regard to the creep deformation behavior of two phase titanium alloys. It has been shown that the creep resistance depends on a number of factors, including the shape of the component phases, the strength difference between the phases, and the stability of the beta phase. For example, in two-phase materials with a similar volume fraction and morphology of phases, if the beta phase is less stable, then the creep resistance is lower. These developments will be reviewed and the reasons for such effects will be suggested.

Download Full-text

Large Deformation Behavior of Porous Polymer Materials With 3D Random Pore Structure: Experimental Investigation and FEM Modeling

Volume 12: Advanced Materials: Design, Processing, Characterization, and Applications ◽

10.1115/imece2019-11143 ◽

2019 ◽

Author(s):

Kanako Emori ◽

Tatsuma Miura ◽

Akio Yonezu

Keyword(s):

Plastic Deformation ◽

Pore Structure ◽

Creep Deformation ◽

Deformation Behavior ◽

Superposition Principle ◽

Critical Role ◽

Test Sample ◽

Porous Polymer ◽

Polymer Materials ◽

Polymeric Membrane

Abstract This study investigates the deformation behavior of porous polymer materials with 3D random pore structure. The test sample has sub-micron-sized pores with an open cellular structure, which plays a critical role for water purification. The base polymer is PVDF (polyvinylidene difluoride). First, the surface and cross section of the sample are observed using FESEM to investigate the microstructure (cell size and geometry of the cell ligament, etc). Next, uni-axial tensile loading is carried out for polymeric membrane and it is found that the membranes underwent elasto-plastic deformation. In order to establish a numerical model, finite element metod (FEM) is employed. Using a software of Surface Evolver, 3D random pore structure is created in the representative volume element (RVE). The established computational model can predict both elastic deformation and plastic deformation. Furthermore, viscoplastic deformation behavior (i.e. time-dependent deformation and creep deformation) is investigated, experimentally and numerically. In particular, creep compliance is measured, and we investigate the effect of applied loading on creep deformation behavior. Using the time–temperature–stress superposition principle (TTSSP), we obtain a new master curve, which covers higher stress level, and successfully establish an FEM model of creep deformation of the test sample. The present model enables the prediction of the macroscopic and microscopic deformation behavior of the porous materials, by taking into account of 3D random pore structure.

Download Full-text

Creep Deformation Analyses for Grade 91 Steels Considering Heat-to-Heat Variation

Volume 6A: Materials and Fabrication ◽

10.1115/pvp2018-85058 ◽

2018 ◽

Author(s):

Haruhisa Shigeyama ◽

Yukio Takahashi ◽

John Siefert ◽

Jonathan Parker

Keyword(s):

Creep Strain ◽

Creep Deformation ◽

Deformation Behavior ◽

Power Plants ◽

Primary Creep ◽

Heat Resistant ◽

Large Heat ◽

Reasonable Prediction ◽

Materials Used ◽

Grade 91

In order to evaluate creep life of heat-resistant materials used in power plants, it is important to estimate variation of stress distribution caused by creep deformation appropriately. For achieving this, creep strain equations which can express the creep deformation behavior with good accuracy are indispensable. Additionally, a lot of heat-resistant steels show large heat-to-heat variations in creep properties. Therefore, it is also important to take into account of the heat-to-heat variations in the creep analyses. In this study, existing creep strain equations for Grade 91 steel were applied to six heats with a variety of creep strength and creep deformation behavior. Furthermore, some modification was made in order to obtain better agreement with test data in primary creep stage. It was found that reasonable agreements were obtained between the measured creep deformation behavior and predictions obtained by these equations only by changing creep rupture property depending on the particular heats. This suggests that reasonable prediction for creep deformation can be made even for the materials lacking the information of creep deformation as long as their rupture properties are known.

Download Full-text

Long-Term Settlement of High Concrete-Face Rockfill Dam by Field Monitoring and Numerical Simulation

Advances in Civil Engineering ◽

10.1155/2020/8898433 ◽

2020 ◽

Vol 2020 ◽

pp. 1-17

Author(s):

Xinjie Zhou ◽

Xinjian Sun ◽

Junxing Zheng ◽

Haoyuan Jiang ◽

Yongye Li ◽

...

Keyword(s):

Finite Element ◽

Creep Deformation ◽

Deformation Behavior ◽

Finite Element Software ◽

Rockfill Materials ◽

Stress And Deformation ◽

Long Term Performance ◽

Term Performance ◽

Concrete Face

High concrete-face rockfill dams (CFRDs) with heights of over 100 m have been quickly developed in recent years. The self-weight of rockfill materials causes creep deformation of the dam body. However, the creep analysis method of high CFRDs in finite element software is few, and sometimes, it can also not reflect the long-term performance of high CFRDs well. Therefore, it is necessary to carry out the secondary development in finite element software. This study developed a subroutine that can run in Finite Element Method (FEM) platform ABAQUS to simulate long-term creep deformation behavior of the rockfill materials more accurately. Then, a displacement back-analysis for parameters, based on the Xujixia high CFRD project, is performed by the neural network response surface method (BP-MPGA/MPGA). Remarkable agreements are observed between simulation and field monitoring results. The calibrated FEM model is used to predict stress and deformation behavior of the Xujixia high CFRD after three years of operation period. The result indicates that rockfill creep deformation has a significant impact on stress and deformation of the high CFRD during the operation. This research may predict long-term performance using FEM in the design stage for high CFRDs.

Download Full-text