scholarly journals Porosity Distribution Simulation and Impure Inclusion Analysis of Porous Crystal Layer Formed via Polythermal Process

Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1347
Author(s):  
Yingshuang Meng ◽  
Zhonghua Li ◽  
Xiangcun Li ◽  
Wu Xiao ◽  
Gaohong He ◽  
...  
Keyword(s):  
Growth Kinetic ◽  
Volume Fraction ◽  
Distribution Model ◽  
Crystal Layer ◽  
Porosity Distribution ◽  
Porosity Variation ◽  
Proposed Model ◽  
Porous Crystal ◽  
Crystal Settling ◽  
Crystal Particle

In this work, we investigated the porosity distribution and separation property of the porous crystal layer formed via the polythermal process. The proposed porosity distribution model, considering both the cooling profile and the crystal settling effect, provided simulative results that met the MRI analysis experimental results with suitable agreement. Significant porosity variation from the top to the bottom of the crystal layer (ϕ from 0.75 to 0.55 under rapid cooling profile) was detected. Meanwhile, the vertical supersaturation degree gradient induced by the fluid fluctuation could impact nucleation and crystal growth kinetic along with crystal particle settling. The resulting crystal layer possessed various impurity inclusion conditions. Under a moderate cooling profile (0.4 K·min−1), the volume fraction of closed pores against overall pores decreased from 0.75 to 0.36. The proposed model and experimental analysis approach were demonstrated to be helpful for porosity distribution simulation and impure inclusion analysis of layer crystallization.

Effects of Dispersed Al2O3 Particles on Sintering of LTCC

2008 ◽  
Vol 39-40 ◽  
pp. 375-380
Author(s):  
Ralf Müller ◽  
Stefan Reinsch ◽  
Markus Eberstein ◽  
Joachim Deubener ◽  
A. Thiel ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Al2o3 Particle ◽  
Model Composite ◽  
Heating Microscopy ◽  
Glass Crystal ◽  
Rate Controlled ◽  
Higher Temperature ◽  
Crystal Particle ◽  
Kinetics Of ◽  
Glass Viscosity

The sintering of Low Temperature Co-fired Ceramics prepared from alumoborosilicate glass- and Al2O3 powders of similar small particle size was studied by dilatometry, heating microscopy, microstructure analysis, glass- and effective viscosity measurements. The steric effect of Al3O3 inclusions was studied using a “non-reactive” model composite. With increasing Al3O3 volume fraction ( Φ ≤ 0.45), sintering decelerates and its final stage shifts to higher temperature. The attainable shrinkage is reduced as Al2O3 particle clusters bearing residual pores become more frequent. The kinetics of sintering could be described formally superposing the weighed contributions of differentially sized and randomly composed glass-crystal particle clusters and assuming a sintering rate controlled by the effective matrix viscosity, which increases with Φ and with progressive wetting of Al2O3 particles during densification. The “reactive” model composite shows significant dissolution of Al2O3 into the glass, which has two opposed effects on sintering: reducing Φ and increasing glass viscosity. For the present case ( Φ = 0.25), the latter effect dominates and sintering is retarded by Al2O3 dissolution. Crystallization of wollastonite starts after full densification. Dissolution of Al2O3 was found to promote the subsequent growth of anorthite.

Nondestructive Estimation of Fracture Toughness Using Instrumented Indentation Technique

2008 ◽  
Vol 385-387 ◽  
pp. 893-896
Author(s):  
Kyung Woo Lee ◽  
Hyun Uk Kim ◽  
Sang Wook Park ◽  
Jung Suk Lee ◽  
Kwang Ho Kim ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Damage Mechanics ◽  
Volume Fraction ◽  
Fracture Initiation ◽  
Continuum Damage Mechanics ◽  
Instrumented Indentation ◽  
Initiation Point ◽  
Indentation Technique ◽  
Proposed Model ◽  
Main Ideas

This study focused on the determination of fracture toughness by instrumented indentation technique. A theoretical model to estimate the fracture toughness of ductile materials is proposed and used to verify those results. Modeling of IIT to evaluate fracture toughness is based on two main ideas; the energy input up to characteristic fracture initiation point during indentation was correlated with material’s resistance to crack initiation and growth, and this characteristic fracture initiation point was determined by concepts of continuum damage mechanics. The estimated fracture toughness values obtained from the indentation technique showed good agreement with those from conventional fracture toughness tests based on CTOD. In addition, we confirmed that the proposed model can be also applied in the brittle material through modification of void volume fraction.

TSDT theory for free vibration of functionally graded plates with various material properties

2021 ◽  
Vol 8 (4) ◽  
pp. 691-704
Author(s):  
M. Janane Allah ◽  
◽  
Y. Belaasilia ◽  
A. Timesli ◽  
A. El Haouzi ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Volume Fraction ◽  
Equations Of Motion ◽  
Shear Deformation Theory ◽  
Functionally Graded ◽  
Third Order ◽  
Implicit Algorithm ◽  
Proposed Model ◽  
Graded Material ◽  
Composite Modeling

In this work, an implicit algorithm is used for analyzing the free dynamic behavior of Functionally Graded Material (FGM) plates. The Third order Shear Deformation Theory (TSDT) is used to develop the proposed model. In this contribution, the formulation is written without any homogenization technique as the rule of mixture. The Hamilton principle is used to establish the resulting equations of motion. For spatial discretization based on Finite Element Method (FEM), a quadratic element with four and eight nodes is adopted using seven degrees of freedom per node. An implicit algorithm is used for solving the obtained problem. To study the accuracy and the performance of the proposed approach, we present comparisons with literature and laminate composite modeling results for vibration natural frequencies. Otherwise, we examine the influence of the exponent of the volume fraction which reacts the plates "P-FGM" and "S-FGM". In addition, we study the influence of the thickness on "E-FGM" plates.

A study of the dielectric properties of PZT and PT ceramics depending on the lattice distortion

2005 ◽  
Vol 83 (5) ◽  
pp. 527-540 ◽  
Author(s):  
Duan -Ming Zhang ◽  
Xiang -Yun Han ◽  
Zhi -Hua Li ◽  
Zhi -Cheng Zhong ◽  
Wen -Sheng Yan ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Lattice Distortion ◽  
Volume Fraction ◽  
Structural Phase ◽  
Rhombohedral Phase ◽  
Point Of View ◽  
Distribution Model ◽  
Coexistence Region ◽  
Pzt Ceramics ◽  
Lattice Distortions

Depending on the lattice distortion, the dielectric properties of PZT and PT ceramics are studied from a structural phase transition point of view. The study involves a more profound physical process than the study of the relation between the dielectric properties and composition x. Two equations connecting the dielectric properties and the lattice distortions are established in the tetragonal and rhombohedral phase regions. In particular, the relation between the dielectric properties and the lattice distortion is investigated in the phase coexistence region of PZT ceramics using a phase statistical distribution model, and we determine the fitting value of the volume fraction of the tetragonal phase VT to composition x in the equation. All the fitting results indicate that our results are very consistent with the related experimental data for PZT and PT ceramics.PACS Nos.: 64.70.–p, 77.22.–d, 77.84.–s

A Three-Dimensional Load Sharing Model of Planetary Gear Sets Having Manufacturing Errors

2015 ◽  
Author(s):  
Nicholas D. Leque ◽  
Ahmet Kahraman
Keyword(s):  
Three Dimensional ◽  
Planetary Gear ◽  
Load Sharing ◽  
Distribution Model ◽  
Gear Mesh ◽  
Position Errors ◽  
Proposed Model ◽  
Manufacturing Errors ◽  
Manufacturing Tolerancing ◽  
Planetary Gear Sets

Planet-to-planet load sharing is a major design and manufacturing tolerancing issue in planetary gear sets. Planetary gear sets are advantageous over their countershaft alternatives in many aspects, provided that each planet branch carries a reasonable, preferably equal, share of the torque transmitted. In practice, the load shared among the planets is typically not equal due to the presence of various manufacturing errors. This study aims at enhancing the models for planet load sharing through a three-dimensional formulation of N-planet helical planetary gear sets. Apart from previous models, the proposed model employs a gear mesh load distribution model to capture load and time dependency of the gear meshes iteratively. It includes all three types of manufacturing errors, namely constant errors such as planet pinhole position errors and pinhole diameter errors, constant but assembly dependent errors such as nominal planet tooth thickness errors, planet bore diameter errors, and rotation and assembly dependent errors such as gear eccentricities and run-outs. At the end, the model is used to show combined influence of these errors on planet load sharing to aid designers on how to account for manufacturing tolerances in the design of the gears of a planetary gear set.

scholarly journals Numerical Investigation of Preload Process of Bolted Joint with Superelastic Shape Memory Alloy

Metals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 730
Author(s):  
Xiangjun Jiang ◽  
Yongkun Wang ◽  
Fengqun Pan ◽  
Ze Jing ◽  
Jin Huang ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Volume Fraction ◽  
Fe Modeling ◽  
Bolted Joint ◽  
Analysis Framework ◽  
Integration Algorithm ◽  
Applied Loading ◽  
Nonlinear Hysteresis ◽  
Proposed Model

A phenomenological constitutive model is developed to describe the uniaxial transformation ratcheting behaviors of the superelastic shape memory alloy (SMA) by employing a cosine–type phase transformation equation with the initial martensite evolution coefficient that can capture the feature of the predictive residual martensite accumulation evolution and the nonlinear hysteresis loop on a finite element (FE) analysis framework. The effect of the applied loading level on transformation ratcheting is considered in the proposed model. The evolutions of transformation ratcheting and transformation stresses are constructed as the function of the accumulated residual martensite volume fraction. The FE implementation of the proposed model is carried out for the numerical analysis of transformation ratcheting of the SMA bar element. The integration algorithm and the expression of consistent tangent modulus are deduced in a new form for the forward and reverse transformation. The numerical results are compared with those of existing models; experimental results show the validity of the proposed model and its FE implementation in transformation ratcheting. Finally, a FE modeling is established for a repeated preload analysis of SMA bolted joint.

Strength Prediction for Jute Polyester Composite for Transverse Fiber Reinforcement

2007 ◽  
Vol 561-565 ◽  
pp. 799-802
Author(s):  
A.A. Shaikh ◽  
S.A. Channiwala
Keyword(s):  
Volume Fraction ◽  
Jute Fiber ◽  
Strength Prediction ◽  
Transverse Reinforcement ◽  
Weight Saving ◽  
Transverse Fiber ◽  
Proposed Model ◽  
Polyester Composite ◽  
The Right ◽  
Effective Contribution

The composites are very useful in present era due to weight saving and economy of construction by tailoring material to structural application. In order to save the crop from extinction and to ensure a reasonable return to the farmers, non-traditional outlets have to be explored for the jute fiber. Jute fiber due to its adequate tensile strength and good specific modulus enjoys the right potential for usage in composites. In the present work the experimentations were conducted for the strength of composite by varying volume fraction of fiber in the range of 12 % to 42 %. The tensile strengths of specimen were measured as per ASTM D 3039-76, and the amount of voids fraction is measured to evaluate actual contributing volume fraction of fiber and volume fraction of matrix. The prediction of strength is proposed by considering efficiency terms f η and m η representing effective contribution of fiber and matrix and an additional efficiencies t1 η and t 2 η representing effectiveness from fiber and matrix for transverse reinforcement case. The results are also compared with FEM results obtained using standard package ANSYS and IDEAS. The results obtained by experiments are observed to be within 0.9 % with developed model and 2.85 % and 3.21 % with ANSYS and IDEAS simulated results. The deviation of proposed model is observed under predictive for experimental data available in literature while the experimental results obtained in present work is also found to be on lower side to that of available predictive models from literature.

Study on Constitutive Model of Weibull Distribution of Cement-Soil Uniaxial Stress Conditions

2012 ◽  
Vol 184-185 ◽  
pp. 810-817
Author(s):  
Zhi Nang Yu ◽  
Xin Jiang Song
Keyword(s):  
Constitutive Model ◽  
Weibull Distribution ◽  
Random Variable ◽  
Uniaxial Stress ◽  
Distribution Model ◽  
Proposed Model ◽  
Soil Stress ◽  
Uniaxial Compressive Test ◽  
Cement Soil ◽  
Nonlinear Elastic

According to the results of cement-soil uniaxial compressive test, consider cement-soil stress-strain relations as a continuous random process, the function of random variable obeys Weibull distribution, and introduce generalized hooke′s law in order to establish Weibull distribution of cement-soil constitutive model, solve the softening problem that a variety of incremental nonlinear elastic models cannot reflect the cement-soil. This paper discussed the parameter character of Weibull distribution model of cement-soil, presented the solving method of parameters of cement-soil Weibull distribution constitutive model, verified by results of test, revealed the rationality of the model and shows that the proposed model is more convenient than other model, have widely application value.

scholarly journals Dynamic compaction of granular materials

2013 ◽  
Vol 469 (2160) ◽  
pp. 20130214 ◽  
Author(s):  
N. Favrie ◽  
S. Gavrilyuk
Keyword(s):  
Sound Velocity ◽  
Granular Materials ◽  
Granular Media ◽  
Volume Fraction ◽  
Entropy Inequality ◽  
Yield Limit ◽  
Basic Principles ◽  
Proposed Model ◽  
Embedded Model ◽  
Von Mises

An Eulerian hyperbolic multiphase flow model for dynamic and irreversible compaction of granular materials is constructed. The reversible model is first constructed on the basis of the classical Hertz theory. The irreversible model is then derived in accordance with the following two basic principles. First, the entropy inequality is satisfied by the model. Second, the corresponding ‘intergranular stress’ coming from elastic energy owing to contact between grains decreases in time (the granular media behave as Maxwell-type materials). The irreversible model admits an equilibrium state corresponding to von Mises-type yield limit. The yield limit depends on the volume fraction of the solid. The sound velocity at the yield surface is smaller than that in the reversible model. The last one is smaller than the sound velocity in the irreversible model. Such an embedded model structure assures a thermodynamically correct formulation of the model of granular materials. The model is validated on quasi-static experiments on loading–unloading cycles. The experimentally observed hysteresis phenomena were numerically confirmed with a good accuracy by the proposed model.

Research on Workstation-Oriented Production Logistics Optimization of Chinese Discrete Manufacturing Enterprises

2013 ◽  
Vol 834-836 ◽  
pp. 1751-1757
Author(s):  
Li Jiang ◽  
Hong Yan Wang
Keyword(s):  
Distribution Model ◽  
Just In Time ◽  
Improved Genetic Algorithm ◽  
New Thought ◽  
Production Logistics ◽  
Manufacturing Enterprises ◽  
Proposed Model ◽  
Discrete Manufacturing ◽  
Mode A

To optimize the production logistics in discrete manufacturing enterprises, we put forward a new thought of workstation-oriented production logistics for the solution of low picking efficiency and high delivery cost of JIT (Just in Time) mode. A distribution model is constructed to minimize the total distribution time in workshop. An improved genetic algorithm is designed to solve the proposed optimization model. Finally, a case study is presented to demonstrate the feasibility and validity of the proposed model.

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