Material Composition Distribution Research Articles

MEMS-based portable confocal Raman spectroscopy rapid imaging system.

Aiming at the miniaturization and rapid imaging requirements of a portable confocal Raman system, a MEMS-based portable confocal Raman spectroscopy rapid imaging method is proposed in this study. This method combines the dual 2D MEMS mirror scanning method and the grid-by-grid scanning method. The dual 2D MEMS mirror scanning method is used for the miniaturization design of the system, and the grid-by-grid scanning method is used for rapid imaging of Raman spectroscopy. Finally, the rapid imaging and miniaturization design of a portable confocal Raman spectroscopy system are realized. Based on this method, a portable confocal Raman spectroscopy rapid imaging system with an optical probe size of just 98m m×70m m×40m m is constructed. The experimental results show that the imaging speed of the system is 45 times higher than that of the traditional point-scan confocal Raman system, and the imaging speed can be further improved according to the requirements. In addition, the system is used to swiftly identify agate ore, and the material composition distribution image over a 126µm 2×126µm 2 region is obtained in just 16min. This method provides a new solution for the rapid imaging and miniaturization design of the confocal Raman system, as well as a new technical means for rapid detection in deep space exploration, geological exploration, and field detection.

Influence of oxygen content on melt pool dynamics in metal additive manufacturing: High-fidelity modeling with experimental validation

In the metal additive manufacturing process, the exposure to oxygen and its incorporation into the melt pool are usually deemed unfavorable, but cannot be completely eliminated. Yet, the understanding of this inevitable process remains limited. This work aims to shed light on the effect of oxygen content on melt pool dynamics through multiphysics thermal-fluid flow simulations of the laser powder bed fusion process. Our simulations reveal that oxygen sources from the powder, base plate and oxygen absorption from the atmosphere influences the melt pool dynamics. Although changes in oxygen content barely affect melt pool dimensions, they induce huge differences in the melt pool dynamics and the corresponding material composition distribution within the melt pool. Moreover, our model further clarifies and explains observed experimental phenomena. We demonstrate that the melt pool flow characteristics are responsible for the formation of oxygen-rich streaks observed in experiments regardless of inward or outward Marangoni circulation, while previous experimental studies attributed that to the outward circulation. Additionally, we show that sulfur content minimizes the effect of oxygen on Marangoni flow in iron alloys, and thus leads to the apparent consistency of surface roughness for additively manufactured iron alloys. This work is a fundamental development towards modeling for additive manufacturing under reactive atmospheres and provides unprecedented details on the effects of oxygen on melt pool dynamics. Consequently, this work can further offer practical guidance on powder reuse and adjusting manufacturing parameters for reused powders, thereby improving the sustainability of additive manufacturing.

Stress Analysis of Solid Oxide Fuel Cell Electrodes Using Functional Gradient Materials

The differences in material properties of different components of solid oxide fuel cells cause high stresses during sintering and operation, functional gradient material electrodes are expected to alleviate this problem. In this study, electrodes with three different material compositions are compared with electrodes using conventional materials, and the residual and thermal stresses are calculated by applying functional gradient materials to single-sided and double-sided electrodes, respectively, and the results are analyzed with the optimization goal of minimizing the stresses to find the optimal functional gradient material composition distribution. The study shows that the functional gradient material electrode can significantly reduce the interfacial stress and alleviate the local stress concentration. When using functional gradient materials for one side of the electrode, a specific material component distribution can reduce the residual stress and thermal stress on the other side, but the stresses may increase on the local side of the electrode. The interfacial stress between layers can be reduced to a maximum of 0.1 MPa when a functional gradient material with a quadratic linear distribution of components is used for both sides of the electrodes. This study has implications for the fabrication of functional gradient materials for SOFC electrodes.

Optimal Design of Functionally Graded Parts

Several additive manufacturing processes are capable of fabricating three-dimensional parts with complex distribution of material composition to achieve desired local properties and functions. This unique advantage could be exploited by developing and implementing methodologies capable of optimizing the distribution of material composition for one-, two-, and three-dimensional parts. This paper is the first effort to review the research works on developing these methods. The underlying components (i.e., building blocks) in all of these methods include the homogenization approach, material representation technique, finite element analysis approach, and the choice of optimization algorithm. The overall performance of each method mainly depends on these components and how they work together. For instance, if a simple one-dimensional analytical equation is used to represent the material composition distribution, the finite element analysis and optimization would be straightforward, but it does not have the versatility of a method which uses an advanced representation technique. In this paper, evolution of these methods is followed; noteworthy homogenization approaches, representation techniques, finite element analysis approaches, and optimization algorithms used/developed in these studies are described; and most powerful design methods are identified, explained, and compared against each other. Also, manufacturing techniques, capable of producing functionally graded materials with complex material distribution, are reviewed; and future research directions are discussed.

Optimal three-dimensional design of functionally graded parts for additive manufacturing using Tamura–Tomota–Ozawa model

Although some conventional manufacturing technologies are capable of producing functionally graded materials, only a few additive manufacturing processes are able to build functionally graded materials with complex distribution of material composition. To exploit this unique advantage, we have developed a new methodology capable of optimization of material distribution for three-dimensional parts for any given conditions. Representation of material distribution was done through a new technique by extending the nonuniform rational basis spline surfaces to four-dimensional space. Mori–Tanaka, Levin, and Tamura–Tomota–Ozawa models were employed for the estimation of effective material properties of functionally graded structures. Subroutines were developed in a commercial finite element software to enable the analysis of parts made from functionally graded material. A constrained particle swarm optimization method was selected and implemented to optimize the material composition distribution taking into account the additive manufacturing limitations. As a case study, the material distribution optimization of a functionally graded femur bone plate under thermomechanical loading was considered. The objective was to maximize the safety factor; i.e. the ratio of local yield strength of the functionally graded plate over the von Mises stress. The results showed significant improvement compared to nonoptimal part and demonstrated the efficacy of the proposed methodology.

Monitoring and control of multiple fraction laws with ring based composite structure

In present article, utilizing the Love shell theory with volume fraction laws for the cylindrical shells vibrations provides a governing equation for the distribution of material composition of material. Isotopic materials are the constituents of these rings. The position of a ring support has been taken along the radial direction. The Rayleigh-Ritz method with three different fraction laws gives birth to the shell frequency equation. Moreover, the effect of height- and length-to -radius ratio and angular speed is investigated. The results are depicted for circumferential wave number, length- and height-radius ratios with three laws. It is found that the backward and forward frequencies of exponential fraction law are sandwich between polynomial and trigonometric laws. It is examined that the backward and forward frequencies increase and decrease on increasing the ratio of height- and length-to -radius ratio. As the position of ring is enhanced for clamped simply supported and simply supportedsimply supported boundary conditions, the frequencies go up. At mid-point, all the frequencies are higher and after that the frequencies decreases. The frequencies are same at initial and final stage and rust itself a bell shape. The shell is stabilized by ring supports to increase the stiffness and strength. Comparison is made for non-rotating and rotating cylindrical shell for the efficiency of the model. The results generated by computer software MATLAB.

Microstructural and mechanical properties of Al-Cu functionally graded materials fabricated by powder metallurgy method

In the present work, four dissimilar-layered volume fraction of Al-Cu functionally graded materials were fabricated by using powder metallurgy. The volume fraction of Cu (0, 5, 10 and 15 wt%) powder mixture was hot pressed with a pressure of 400 MPa and sintered at 550 0C for 3 h as layer by layer. The mechanical and microstructural properties shows the material composition distribution of two-layered FGMs varies gradually. The properties such as density and hardness of FGMs was carried out in order to compare with homogeneous mixture of Non-FGM samples. A complete characterization of the microstructural graphs of FGMs achieved using Optical Microscope, Back scattered electron Mode, scanning electron microscopy and XRD analysis. The results shows an improved in micro-mechanical properties of the Al-Cu FGMs based on material selection and sintering temperature as well as dwell time.

Backward and forward rotating of FG ring support cylindrical shells

In this research work, the analytical rotating vibration for functionally graded shell with ring supports are restricted to some volume fraction laws based on Rayleigh-Ritz technique. The frequencies of functionally grade cylindrical shells have been investigated for the distribution of material composition of material with two kinds of material. Stability of a cylindrical shell depends highly on these aspects of material with ring supports. The frequency behavior is investigated with fraction laws versus circumferential wave number, length-to-radius and height-to-radius ratios. The frequencies are higher for higher values of circumferential wave number. The frequency first increases and gain maximum value with the increase of circumferential wave mode. Moreover, the effect of angular speed is also investigated. It is examined that the backward and forward frequencies increases and decreases on increasing the ratio of height- and length-to-radius ratios.

Numerical simulation of O<sub>2</sub>/CO<sub>2</sub> combustion in large cement precalciner

The cement industry is the second largest source of CO2 emissions after the power industry. The greenhouse effect caused by CO2 is increasing nowadays, so CO2 emission reduction is urgent, the cement precalciner kiln O2/CO2 combustion technology has great application value in CO2 emission reduction. This paper selects 3200 t/d TTF cement precalciner as the research object, and Tianhe-2 supercomputer is used to carry out massive parallel CFD numerical simulation. Numerical simulation was used to study on the effects of pulverized coal combustion mixed air with pulverized coal combustion mixed O2/CO2 on velocity field, temperature field, material composition distribution and NO x concentration distribution. The results show that the O2/CO2 combustion technology has similar velocity field distribution and raw material decomposition ratio when compared with the conventional air combustion, and it will not affect the operation of the precalciner. Besides, the over-temperature zone in the precalciner is reduced, the temperature-brushing phenomenon is effectively alleviated, and the NO x concentration at the outlet reduced greatly from 995 to 96 mg/m3, so that the post-treatment De-NO x process can be removed to reduce investments. Furthermore, the nearly pure high-concentration CO2 in the flue gas is easy to be captured and reused, alleviating the greenhouse effect.

Active Layer Thickness Effect on the Behavior of Electrodes Based on Lithium Iron Phosphate

The effect of the active layer thickness (the amount of active material per unit area of the electrode) on the behavior of electrodes based on lithium iron phosphate was first studied by methods of galvanostatic cycling and cyclic voltammetry. When considering the electrode as a system with doubly distributed parameters (distribution of material composition along the individual LiFePO4 grain radius and distribution of the process along the depth of the active layer), it was concluded that the distribution of the process over the depth of the active layer is much more pronounced than in the bulk of individual grains of lithium iron phosphate. It is assumed that such conclusion will be valid for electrodes from other materials.

Computer-aided design–computer-aided engineering associative feature-based heterogeneous object modeling

Conventionally, heterogeneous object modeling methods paid limited attention to the concurrent modeling of geometry design and material composition distribution. Procedural method was normally employed to generate the geometry first and then determine the heterogeneous material distribution, which ignores the mutual influence. Additionally, limited capability has been established about irregular material composition distribution modeling with strong local discontinuities. This article overcomes these limitations by developing the computer-aided design–computer-aided engineering associative feature-based heterogeneous object modeling method. Level set functions are applied to model the geometry within computer-aided design module, which enables complex geometry modeling. Finite element mesh is applied to store the local material compositions within computer-aided engineering module, which allows any local discontinuities. Then, the associative feature concept builds the correspondence relationship between these modules. Additionally, the level set geometry and material optimization method are developed to concurrently generate the geometry and material information which fills the contents of the computer-aided design–computer-aided engineering associative feature model. Micro-geometry is investigated as well, instead of only the local material composition. A few cases are studied to prove the effectiveness of this new heterogeneous object modeling method.

Effect of Material Composition Distribution on the Electro-thermal Response of a Non-uniform Functionally Graded Metal Line under a Direct Current Field

The effect of material composition distribution on the electro-thermal response of a thin, non-uniform functionally graded metal (FGM) line is investigated under a direct current field. The distribution of material composition along the FGM line is expressed in terms of a general power-law function of space variable, which, in turn, suggests the corresponding distributions of material properties involved. The governing differential equations associated with the electro-thermal problem are derived in terms of variable electrical resistivity and thermal conductivity of the material. The solution of the coupled boundary-value problem is then obtained numerically using finite-difference technique. The electro-thermal response of the FGM line is obtained for different composition profiles and environmental conditions, which are discussed in light of comparison with those of individual constituent metal lines.

Investigation of the presence of metal droplets after pulsed InN and GaN epitaxial growth using atomic force microscopy and nanoindentation

The purpose of this study was to detect the presence of excess Ga- or In-metal on the surface of GaN or InN epitaxial layers, using AFM11AFM, atomic force microscopy. and nanoindentation. We ascertain that in this case AFM phase-contrast images could not be used for actual material composition distribution mapping due to the large topography variation of the surface. Force spectroscopy on droplets shows observable hysteresis between approach and retraction curves as well as the presence of adhesion forces on the retraction curves. This indicates the presence of compliant material – Ga- or In-metal in our case. Etching away these droplets with HCl solution confirmed their metallic consistence. The presence of In-metal is confirmed by XRD22XRD, X-ray diffraction. measurements on the InN sample with the presence of the (101)In reflection plane peak, which disappears after etching. The method becomes extremely useful for detection of Ga-metal which cannot be detected by XRD. We have also observed that this technique is also able to identify the situation where a metal droplet is partially nitrided on the droplet surface, so that it cannot be removed by etching, a situation where the droplets presence might not otherwise be observed by phase-contrast measurements, or by other techniques.

Optimisation of material composition of functionally graded materials based on multiscale thermoelastic analysis

This paper presents a method for optimisation of the material composition of functionally graded materials (FGMs) for thermal stress relaxation. This method consists of a multiscale thermoelastic analysis and a genetic algorithm. In the presented method, location-dependent unit cells representing the microstructures of two-phase FGMs are created using morphology description functions, and the homogenised material properties and microscale thermal stresses are computed using the asymptotic expansion homogenisation method. Thermal stress relaxation effects at the microscale in the FGMs are quantitatively evaluated, being reflected for the optimisation computation of the material composition. Numerical calculations are performed for a functionally graded infinite plate subjected to prescribed surface temperatures, and it is demonstrated that the optimisation with the knowledge of specific microstresses in FGMs results in not only a different trend of material composition distribution but also a different critical location for material failure from those obtained by conventional optimisation without the knowledge of the microstresses.

Thermal Residual Stresses in One-Directional Functionally Graded Plates Subjected to In-Plane Heat Flux

This study carries out the transient thermal residual stress analyses of functionally graded clamped plates for different in-plane material compositions and in-plane heat fluxes. The heat conduction and Navier equations representing the two-dimensional thermoelastic problem were discretized using the finite-difference method, and the set of linear equations were solved using the pseudo singular value method. Both in-plane temperature distributions and the heat transfer period were affected considerably by the compositional gradient. The type of in-plane heat flux had a minor effect on the temperature profile, but on the heat transfer period. The high stress levels appeared in the ceramic-rich regions. The normal and equivalent stresses exhibited a sharp change in the plates with ceramic-rich as well as metal-rich compositions, and the concentrated on a narrow ceramic layer. A smooth stress variation was achieved through the graded region with a balanced composition of ceramic and metal-phases, and the stress discontinuities disappeared. The in-plane shear stress was negligible. The equivalent stress exhibited a linear temporal variation for both constant and sinusoidal heat fluxes, but a nonlinear variation for the exponential heat flux. In case the heat flux is applied along the metal edge (metal-to-ceramic plate) instead of the ceramic edge, the displacement and stress components exhibited similar distributions to those of a ceramic-to-metal plate but in the opposite direction. As a result, the distribution of in-plane material composition affects only normal stress distributions, whereas the peak stress levels occur in the ceramic-rich regions. Since the normal stresses concentrate along a narrow ceramic layer for ceramic-rich or metal-rich compositions, a balanced in-plane material composition distribution of ceramic and metal would be useful to avoid probable local ceramic fracture or damage.

THE DEVELOPMENT OF HETEROGENEOUS OBJECT DESIGN FOR RAPID PROTOTYPING

Rapid Prototype (RP) manufacturing has been widely used in many industries, including prototype fabrication, product assembly testing, mechanism interference testing, and rapid tooling. Researchers have been focusing on the RP applications for functional part fabrication in recent years. One of the most challenging research topics in RP is Rapid Prototype fabrication, particularly with graded material objects. Graded material means that the material's composition is changed according to the area of the object. The graded material object model includes the typical part geometric information and the heterogeneous material information that forms a more complicated object model. This research developed a heterogeneous object model, which was implemented on a software program. Results show that the heterogeneous model contains material grading information as well as geometry information. Two examples are included for the material composition distribution at the end of this paper.

Switching reliability improvement of phase change memory with nanoscale damascene structure by Ge 2 Sb 2 Te 5 CMP process

Phase change memory with nanoscale damascene structure was successfully fabricated by Ge2Sb2Te5 (GST) film chemical mechanical polishing (CMP) process. An ultra-smooth surface reduced the GST/TiN contact resistance, and more homogeneous GST material composition distribution caused by the damascene structure made GST sheet resistance steady. Thus, switching reliability of the device was improved greatly compared with that of the device without CMP process owing to the reduction of device resistance fluctuation.

1153 傾斜機能型電波吸収体の電磁場-熱連成効果と熱応力解析(G03-5 材料力学(5)力学挙動1,21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

Functionally graded (FG) type electromagnetic (EM) wave absorbers have been proposed for the improvement in absorption performance and material strength. In this study, coupling effects on the performance of the FG type EM wave absorbers and thermal stresses in the absorbers are investigated. The coupling effects of electromagnetic field and temperature field related with the heat generation due to high power injection and temperature-dependency of electromagnetic properties are analyzed by weak-coupling method based on the iterative use of the analytical solutions for each field. The thermal stress field is also analyzed for a thin plate with arbitrary nonhomogeneous properties and temperature-dependent thermal and electromagnetic properties. Numerical calculations are carried out for the FG type EM wave absorbers composed of epoxy resin and conductive titanium oxide. The magnitude of electric field, temperature field and thermal stress field is evaluated. The effects of material composition distribution, high power injection and heat condition on the absorption performance and thermal stress are then discussed. The significance of the coupling effects and the thermal stress analysis is revealed.

Optimum material composition design for thermal stress reduction in FGM lathe bit

Abstract Nowadays, many attempts to apply the concept of functionally graded material (FGM) to major industrial parts are intensively being in progress. A FGM lathe bit is one of such applications, in which a dual-phase graded region is inserted between shank and tip in order to enforce the material composition continuity. The severe thermal stress concentration that has been occurred near the tip–shank interface in traditional lathe bits could be significantly relaxed if the material composition distribution in the graded region is appropriately tailored. This paper is concerned with the optimum design of the material composition distribution in lathe bit to minimize the thermal stress level. Illustrative numerical results as well as theoretical formulations are presented. The optimum distribution greatly reduces the global and local thermal stress levels and the optimization scheme shows the robustness and the high convergence rate.

傾斜機能平板の熱曲げ曲率から材料組成分布を同定する逆問題解析 : 物性値の温度依存性を考慮した場合(OS3-8 先進材料の機能性発現,OS3 先端機能性構造材料の力学的挙動に関する数理解析とマルチスケールアナリシスへの進展)

傾斜機能平板の熱曲げ曲率から材料組成分布を同定する逆問題解析 : 物性値の温度依存性を考慮した場合(OS3-8 先進材料の機能性発現,OS3 先端機能性構造材料の力学的挙動に関する数理解析とマルチスケールアナリシスへの進展)