Modeling of thickness effect on the creep properties of Ni-based superalloys

2017 ◽  
Vol 13 (3) ◽  
pp. 464-470 ◽  
Author(s):  
Xinmei Wang ◽  
Yao Wang ◽  
Xinzhong Wang
Keyword(s):  
Creep Behavior ◽  
Present Model ◽  
Thickness Effect ◽  
Specimen Thickness ◽  
Thin Wall ◽  
Thin Specimen ◽  
Creep Properties ◽  
Content Type ◽  
Oxidation Effect ◽  
Different Thickness

Purpose Specimen thickness has great influences on the creep behavior of single crystal Ni-based superalloys when it is less than 3.0 mm, which is known as thickness debit effect. Experiments have detected that oxidation can influence the microstructure of the Ni-based superalloys. Here, a model is proposed to bring in both the oxidation effect and void caused damage to account for the thickness debit effect. The paper aims to discuss these issues. Design/methodology/approach The model uses the simple Norton type creep relation to describe the creep rate evolution. The damage evolution caused by void is taken to be stress controlled. The load baring area changes are calculated with the consideration of oxidation and void evolutions. Findings Simulations on specimens with different thickness from 3.0 to 0.3 mm are carried out. The results show that the present model can reproduce the decrease of the creep strength with the decreases of the specimen thickness. The damage plays a major role in the creep behavior of the thick specimen. Both the damage and the oxidation are important for the thin specimen which should be paid attention to during the calculation of the creep response of the thin-wall turbine blade. Originality/value A model is proposed to account for the thickness debit effect on the creep behavior of Ni-based superalloys. Both oxidation influence and void caused damage are introduced. The simulation results show the capability of the model to reproduce the thickness debit effect.

Thickness Influence on the Creep Response of DD6 Ni-Based Single-Crystal Superalloy

2016 ◽  
Vol 35 (9) ◽  
pp. 871-880 ◽  
Author(s):  
Zhixun Wen ◽  
Haiqing Pei ◽  
Dongfan Li ◽  
Zhufeng Yue ◽  
Jingyun Gao
Keyword(s):  
Single Crystal ◽  
Oxide Thickness ◽  
Single Crystal Superalloy ◽  
Thickness Effect ◽  
Specimen Thickness ◽  
Thin Wall ◽  
Creep Life ◽  
Creep Response ◽  
Standard Specimens ◽  
Lower Temperature

AbstractThe effect of specimen thickness on the creep response of Ni-based single-crystal superalloy DD6 was investigated. With the thickness of 0.3 mm, 0.6 mm and 1.2 mm, a series of thin-wall specimens were tested in this paper respectively at 760℃, 980℃ and 1,100℃. Under the conditions of lower temperatures and higher stresses, the creep life of thin-wall specimens increases with the increase of δ, but it is almost equal under higher temperatures and lower stresses conditions. Compared with the standard specimens, an obvious reduction (about 60%) of creep life of the thin-wall specimens was found at 760℃, whereas it is almost the same at 980℃ and 1,100℃. Therefore, obvious thickness effect is prone to lower temperature and higher stress. The thickness effect is a comprehensive effect, which is caused by fracture mode, the degree of necking, the shape and quantity of creep cavities, oxide thickness, etc. Under each condition, an increased thickness resulted in increased creep strain to rupture.

scholarly journals Chemical Quantification of Atomic-Scale EDS Maps under Thin Specimen Conditions

2014 ◽  
Vol 20 (6) ◽  
pp. 1782-1790 ◽  
Author(s):  
Ping Lu ◽  
Eric Romero ◽  
Shinbuhm Lee ◽  
Judith L. MacManus-Driscoll ◽  
Quanxi Jia
Keyword(s):  
Atomic Scale ◽  
Specimen Thickness ◽  
Peak Width ◽  
Thin Specimen ◽  
Gaussian Peak ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
The Relationship ◽  
Chemical Quantification

AbstractWe report our effort to quantify atomic-scale chemical maps obtained by collecting energy-dispersive X-ray spectra (EDS) using scanning transmission electron microscopy (STEM) (STEM-EDS). With thin specimen conditions and localized EDS scattering potential, the X-ray counts from atomic columns can be properly counted by fitting Gaussian peaks at the atomic columns, and can then be used for site-by-site chemical quantification. The effects of specimen thickness and X-ray energy on the Gaussian peak width are investigated using SrTiO3 (STO) as a model specimen. The relationship between the peak width and spatial resolution of an EDS map is also studied. Furthermore, the method developed by this work is applied to study cation occupancy in a Sm-doped STO thin film and antiphase boundaries (APBs) present within the STO film. We find that Sm atoms occupy both Sr and Ti sites but preferably the Sr sites, and Sm atoms are relatively depleted at the APBs likely owing to the effect of strain.

Numerical investigation into effect of self-healing composite microcapsules thickness and diameter on their failure strength

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Raj Kumar Pittala ◽  
Satish Ben B. ◽  
Syam Kumar Chokka ◽  
Niranjan Prasad
Keyword(s):  
Matrix Composite ◽  
Polymer Matrix ◽  
Shell Thickness ◽  
Polymer Matrix Composite ◽  
Thickness Effect ◽  
Failure Strength ◽  
Self Healing ◽  
Content Type ◽  
Reinforced Polymer ◽  
Healing Agent

Purpose Microcapsule-embedded autonomic healing materials have the ability to repair microcracks when they come into contact with the crack by releasing the healing agent. The microcapsules with specific shape and thickness effect in releasing healing agent to the cracked surfaces. Thus, the purpose of this paper is to know the load bearing capacity of the self-healing microcapsules and the stresses developed in the material. Design/methodology/approach In the present study, self-healing microcapsule is modelled and integrated with the polymer matrix composite. The aim of the present study is to investigate failure criteria of Poly (methyl methacrylate) microcapsules by varying the shell thickness, capsule diameter and loading conditions. The strength of the capsule is evaluated by keeping the shell thickness as constant and varying the capsule diameter. Uniformly distributed pressure loads were applied on the capsule-reinforced polymer matrix composite to assess the failure strength of capsules and composite. Findings It is observed from the results that the load required to break the capsules is increasing with the increase in capsule diameter. The failure strength of microcapsule with 100 µm diameter and 5 µm thickness is observed as 255 MPa. For an applied load range of 40–160 N/mm2 on the capsules embedded composite, the maximum stress developed in the capsules is observed as 308 MPa. Originality/value Failure strengths of microcapsules and stresses developed in the microcapsule-reinforced polymer composites were evaluated.

Effect of the CMT advanced process combined with an active cooling technique on macro and microstructural aspects of aluminum WAAM

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Felipe Ribeiro Teixeira ◽  
Fernando Matos Scotti ◽  
Ruham Pablo Reis ◽  
Américo Scotti
Keyword(s):  
Electrical Signal ◽  
Management Technique ◽  
Marginal Effect ◽  
Thin Wall ◽  
Cold Metal Transfer ◽  
Content Type ◽  
Active Cooling ◽  
Cold Metal ◽  
Wire Arc Additive Manufacturing ◽  
Cooling Technique

Purpose This paper aims to assess the combined effect of the Cold Metal Transfer (CMT) advanced process and of a thermal management technique (near immersion active cooling [NIAC]) on the macro and microstructure of Al wall-like preforms built by wire arc additive manufacturing (WAAM). As specific objective, it sought to provide information on the effects of the electrode-positive/electrode-negative (EP/EN) parameter in the CMT advanced process fundamental characteristics. Design/methodology/approach Initially, bead-on-plate deposits were produced with different EP/EN ratios, still keeping the same deposition rate, and the outcomes on the electrical signal traces and bead formation were analyzed. In a second stage, the EP/EN parameter and the layer edge to water distance (LEWD) parameter from the NIAC technique were systematically varied and the resultant macro and microstructures compared with those formed by applying natural cooling. Findings Constraints of EP/EN setting range were uncovered and discussed. The use of the NIAC technique favors the formation of finer grains. For a given EP/EN value, a variation in the NIAC intensity (LEWD value) showed marginal effect on grain size. When the EP/EN parameter effect is isolated, i.e. for a given LEWD setting, it was observed that an increase in the EP/EN level favors coarser grains. Originality/value Both the EP/EN parameter and the use of an active cooling technique (NIAC) might be used, even in combination, as effective tools for achieving proper macro and microstructure in WAAM of thin wall builds.

Effect of tribological parameters on sliding wear and friction coefficient which relates to preload loss in tapered roller bearing

2019 ◽  
Vol 71 (1) ◽  
pp. 61-73 ◽  
Author(s):  
Ayush Jain ◽  
Abhishek Singh ◽  
Arendra Pal Singh
Keyword(s):  
Sliding Wear ◽  
Roller Bearing ◽  
Wear Test ◽  
Thickness Effect ◽  
Surface Parameters ◽  
Content Type ◽  
Tapered Roller Bearing ◽  
Tapered Roller ◽  
Tribological Parameters ◽  
Ball On Disc

Purpose This paper aims to study the sliding wear and coefficient of friction (COF) using “ball on disc” tribometer. Discs of bearing steel were subjected to different tribological parameters such as heat treatment (through hardening and case hardening), sliding speed, sliding distance and micro-geometry of the functional ball and disc point contact. Results obtained from tribometer were correlated with the preload loss in tapered roller bearing. Preload loss is subjected to wear rate pattern with respect to the internal geometry and micro-geometry of functional surfaces of the tapered roller bearing, caused by internal resistance between roller large ends sliding against cone supporting face. This confirms the optimum geometry and physical/mechanical property of the tapered roller bearing, which makes the use of these bearings under the demanding application in the automotive industry such as differential gears and installation of pinions of differential gears in power transmissions or wheels. Design/methodology/approach The paper opted for an exploratory study using the design of experiments with full factorial method. The approach was to do ball on disc sliding wear test and correlate that sliding wear with preload loss in tapered roller bearing. Findings The paper provides the limit of preload loss in tapered roller bearing. Research limitations/implications Because of the chosen research approach, the research lacks the effect of environmental conditions such as temperature and relative humidity and lube film thickness effect on wear test. It also lacks the validation part with actual preload loss on tapered roller bearings. Above work is included in future scope of work. Practical implications This paper includes the recommendation for surface parameters which can increase the bearing life by reducing the preload loss in tapered roller bearing. Social implications This paper includes the recommendation for surface parameters for bearing manufacturing industries. Originality/value This paper provides the relation between sliding wear and preload loss in tapered roller bearing.

Modelling of a Phase Change Material melting process heated from below using spectral collocation methods

2014 ◽  
Vol 24 (3) ◽  
pp. 697-734 ◽  
Author(s):  
Jean Batina ◽  
Serge Blancher ◽  
Tarik Kouskou
Keyword(s):  
Heat Flux ◽  
Energy Storage ◽  
Phase Change ◽  
Phase Change Material ◽  
Textile Industry ◽  
Present Model ◽  
Good Accuracy ◽  
Content Type ◽  
Energy Equations ◽  
Change Material

Purpose – Mathematical and numerical models are developed to study the melting of a Phase Change Material (PCM) inside a 2D cavity. The bottom of the cell is heated at constant and uniform temperature or heat flux, assuming that the rest of the cavity is completely adiabatic. The paper used suitable numerical methods to follow the interface temporal evolution with a good accuracy. The purpose of this paper is to show how the evolution of the latent energy absorbed to melt the PCM depends on the temperature imposed on the lower wall of the cavity. Design/methodology/approach – The problem is written with non-homogeneous boundary conditions. Momentum and energy equations are numerically solved in space by a spectral collocation method especially oriented to this situation. A Crank-Nicolson scheme permits the resolution in time. Findings – The results clearly show the evolution of multicellular regime during the process of fusion and the kinetics of phase change depends on the boundary condition imposed on the bottom cell wall. Thus the charge and discharge processes in energy storage cells can be controlled by varying the temperature in the cell PCM. Substantial modifications of the thermal convective heat and mass transfer are highlighted during the transient regime. This model is particularly suitable to follow with a good accuracy the evolution of the solid/liquid interface in the process of storage/release energy. Research limitations/implications – The time-dependent physical properties that induce non-linear coupled unsteady terms in Navier-Stokes and energy equations are not taken into account in the present model. The present model is actually extended to these coupled situations. This problem requires smoother geometries. One can try to palliate this disadvantage by constructing smoother approximations of non-smooth geometries. The augmentation of polynomials developments orders increases strongly the computing time. When the external heat flux or temperature imposed at the PCM is much greater than the temperature of the PCM fusion, one must choose carefully some data to assume the algorithms convergence. Practical implications – Among the areas where this work can be used, are: buildings where the PCM are used in insulation and passive cooling; thermal energy storage, the PCM stores energy by changing phase, solid to liquid (fusion); cooling and transport of foodstuffs or pharmaceutical or medical sensitive products, the PCM is used in the food industry, pharmaceutical and medical, to minimize temperature variations of food, drug or sensitive materials; and the textile industry, PCM materials in the textile industry are used in microcapsules placed inside textile fibres. The PCM intervene to regulate heat transfer between the body and the outside. Originality/value – The paper's originality is reflected in the precision of its results, due to the use of a high-accuracy numerical approximation based on collocation spectral methods, and the choice of Chebyshev polynomials basis in both axial and radial directions.

Effect of Material Property Difference on the Creep Behavior of Bending Specimen

2019 ◽  
Vol 795 ◽  
pp. 375-382 ◽  
Author(s):  
Fa Kun Zhuang ◽  
Shan Tung Tu ◽  
Guo Shan Xie ◽  
Luo Wei Cao
Keyword(s):  
Stress Exponent ◽  
Material Property ◽  
Creep Behavior ◽  
Bending Test ◽  
Creep Properties ◽  
Tension And Compression ◽  
Beam Bending ◽  
Testing Techniques ◽  
Metal Materials ◽  
State Stress

The application of small specimen testing techniques in the evaluation of creep properties of materials in-service arise. In order to acquire the creep data accurately and conveniently, the bending test with small beam specimens has been proposed and validated for the metal materials. Initially, the fact that material behaves different creep rates under tension and compression is ignored for simplification. Thus, the effect of material property difference on the creep behavior of bending specimen is analyzed in the present paper. On the basis of Norton creep law, the deformation behavior of three type’s specimens under tension and compression is theoretically described. Assumed different creep exponents and constants, finite element models of these beam bending specimens are established. The creep response is simulated. Meanwhile, the effect of material property under different stress state is further investigated. The results show that the stress exponent has a significant effect on the creep curves. Usually, the stress exponent can be evaluated based on the displacement rate or strain rate. However, if large discrepancy of creep properties under tension and compression exits, it will yield disparate results for the steady-state stress exponent. It is suggested that the stress exponent determined solely by bending test should be accepted with a certain degree of reliability, especially for the non-metal materials.

The Effect of Specimen Thickness on the Tearing Energy of a Gum Vulcanizate

1989 ◽  
Vol 62 (5) ◽  
pp. 850-862 ◽  
Author(s):  
Kenneth A. Mazich ◽  
K. N. Morman ◽  
F. G. Oblinger ◽  
T. Y. Fan ◽  
P. C. Killgoar
Keyword(s):  
Finite Element ◽  
Laboratory Experiments ◽  
Pure Shear ◽  
Thickness Effect ◽  
Specimen Thickness ◽  
J Integral ◽  
Shear Specimen ◽  
Standard Specimens ◽  
Finite Element Calculations ◽  
Tearing Energy

Abstract We have examined the effect of thickness on the critical tearing energy of a simple gum vulcanizate of SBR in pure shear. Laboratory experiments and finite-element calculations agree that the tearing energy that is measured with a pure-shear specimen increases with the thickness of the specimen. Laboratory measurements indicate that the deformation for crack growth in a pure-shear specimen increases with the thickness of the specimen. Finite-element calculations show that the energy available for release at a given deformation also increases with thickness in the range from t=1.4 mm to t=14 mm. Experiments show that the crtical tearing energy varies linearly with thickness in the range t=0.7 mm to t=2.7 mm. The effect of thickness on the tearing energy was also studied by calculating the J-integral at various points of the crack through the thickness of the pure-shear specimen. In general, the J-integral calculated at the surface of the specimen can be higher than the J-integral calculated at the center of the specimen for specimens that are sufficiently thick. The thickness effect measured in this work suggests that the “critical tearing energy” obtained from standard laboratory specimens may not be a true material property. For this reason, critical tearing energy that is measured on standard specimens may not be generally applied to predict failure in arbitrary elastomeric components.

How to measure knowledge management: dimensions and model

VINE ◽  
2015 ◽  
Vol 45 (1) ◽  
pp. 107-125 ◽  
Author(s):  
Mariano García-Fernández
Keyword(s):  
Knowledge Management ◽  
Literature Review ◽  
Design Methodology ◽  
Present Model ◽  
Content Type ◽  
Proposed Model ◽  
The Creation ◽  
And Storage ◽  
Practical Implications

Purpose – The aims of this paper are: to identify the dimensions of knowledge management (KM), and to propose a model for KM that will be useful for future researchers in carrying out KM measurement. Design/methodology/approach – The paper is based on a literature review of theoretical and empirical contributions to KM. Findings – The results obtained show that the creation, transfer and storage, and implementation and use are dimensions of the concept of KM. On the basis of these dimensions, this study proposes a model integrating these dimensions and operationalizes it using selected items, so that future researchers may carry out measurements using the proposed model. Practical implications – The study implies that companies and researchers use a smaller time in theoretical checks and can devote to measurements which develop improvements. Originality/value – The present model differs from other, previous models in that it integrates various approaches to the study of KM.

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