Zhihong Du, Xinhua Ni, Xiequan Liu and Cheng Chen
According to the microstructural characteristics of composite ceramic, the strain field distribution regularity of triangular symmetrical composite eutectic is obtained from the…
Abstract
Purpose
According to the microstructural characteristics of composite ceramic, the strain field distribution regularity of triangular symmetrical composite eutectic is obtained from the stress field distribution regularity of three-phase element in composite ceramic. In allusion to the damage of composite eutectic, it is introduced as a variable in this paper with the aim to determine the strain field distribution regularity of triangular symmetrical composite eutectic with damage behavior.
Design/methodology/approach
On the basis of the relationship between strain field and fiber inclusions volume fraction, the strain field of composite eutectic is analyzed.
Findings
The strain field of composite ceramic is distinctly dependent on the fiber inclusions volume fraction, fiber diameter and damage behavior of composite eutectic by quantitative analysis. The strain in matrix parallel to eutectic is the maximum linear strain and the main factor for the damage and fracture of eutectics.
Originality/value
The foundation of the strength research of composite eutectic is laid.
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Xinhua Ni, Yunwei Fu, Xiequan Liu and Long Zhang
This paper aims to promote a strength model for TiC-TiB2 composite ceramic with non-ellipsoidal particles bridging. Based on the microstructure of TiC-TiB2 composite ceramic…
Abstract
Purpose
This paper aims to promote a strength model for TiC-TiB2 composite ceramic with non-ellipsoidal particles bridging. Based on the microstructure of TiC-TiB2 composite ceramic, equivalent average residual stress under particles interaction is calculated with the interact direct derivative estimate. Supposing the crack opening displacement keeps ellipsoidal under the TiB2 particles bridging, crack growth resistance curve is obtained.
Design/methodology/approach
Composite strength under R-cure with crack unstable propagation is calculated. Based on this model, influences of particles volume fraction, shape, size and other parameters on strength are analyzed.
Findings
Results indicated that calculated values are consistent to the tested data. Crack growth resistance increases with crack propagation and TiB2 volume fraction. The TiB2 particle does not pull-out entirely even ceramic fracture. Ceramic strength increases with the TiB2 particle volume fraction, the ratio of platelet diameter and thickness, and it reduces with particle thickness.
Originality/value
Supposing the crack open displacement keeps ellipsoidal under the TiB2 particles bridging, crack growth resistance curve is obtained.
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Jinfeng Yu, Xiequan Liu and Xinhua Ni
Composite ceramic has the excellent properties at normal and high temperatures, especially when the structure of the composite eutectic is triangular symmetrical. Obviously…
Abstract
Composite ceramic has the excellent properties at normal and high temperatures, especially when the structure of the composite eutectic is triangular symmetrical. Obviously, mechanical behavior and fracture properties of composite ceramic closely relates to the micro-structure of symmetrical triangular eutectic. In order to reveal the mechanical properties of eutectic composite ceramic, it is necessary to determine the intrinsic strength of triangular composite eutectic. Since the fiber and matrix of triangular symmetrical composite eutectic sharing a same covalent bond, the theoretical cohesion strength of symmetrical triangular eutectic was obtained by the combination-separation displacement of intrinsic bond. Basing on micro-structure plastic deformation before fracture of composite eutectic matrix, the dislocation pile-up model of eutectic composite ceramics was established. And then intrinsic bond fracture shear stress of triangular symmetrical composite eutectic was given by using the theory of dislocation pile-up. According to the macroscopic structure properties of triangular symmetrical composite eutectic and the distribution of stress field of composite eutectic, intrinsic strength of eutectic was obtained. The results shows that intrinsic strength of triangular symmetrical composite eutectic possessed clear size-dependence and the stress decreases with the increases of the diameter of fiber inclusions.
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Nataliya Perevoshchikova, Jordan Rigaud, Yu Sha, Martin Heilmaier, Barrie Finnin, Elena Labelle and Xinhua Wu
The Ni-based superalloy IN-738 LC is known to be susceptible to porosity and different types of cracking during the build-up process and, thus, challenging to manufacture using…
Abstract
Purpose
The Ni-based superalloy IN-738 LC is known to be susceptible to porosity and different types of cracking during the build-up process and, thus, challenging to manufacture using selective laser melting (SLM). Determining a feasible set of operating parameters for SLM of nickel-based superalloys involves new approach to experimental design based on the Doehlert method that assists in determining an optimal (feasible) set of operating parameters for SLM of IN-738 LC powder alloy.
Design/methodology/approach
The SLM parameters are evaluated in terms of their effectiveness in obtaining the microstructure with a porosity content of <0.5 per cent and without micro-cracking. The experimental approach is exemplified with the Doehlert matrix response variable, relative density, by comparing Archimedes method with microstructural assessments of pores and cracks from image analysis. The effect of heat treatment (HT) and hot isostatic pressing (HIP) on the microstructure of the SLMed IN-738 LC powder alloy has been examined and the consequential tensile response characterised.
Findings
By using optimised process parameters (low heat input, medium scanning speed and small hatching distance) which provides medium energy density, samples of IN-738 LC with a macroscopic porosity <0.5 per cent and free of micro-cracks can be manufactured by SLM. The results indicate that HIP of SLMed material did not lead to a noticeable effect on mechanical properties compared to HT of SLMed material suggesting that the level of both porosity and crack density might be already below the detection limit for the mere heat-treated material.
Originality/value
SLM processing parameters (power, scan speed, hatching distance) for IN-738 LC were successfully optimised after only 14 experiments using Doehlert design. Two independent methods, Archimedes method and image analysis, were used in this study to assess relative density of SLM-produced samples with sets of processing parameters showing coherency in prediction with predicted response by Doehlert design.
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In modern China, sports and nationalism always have close connection, and nationalism is the important reason for the promotion of Chinese sports. However, the relationship…
Abstract
In modern China, sports and nationalism always have close connection, and nationalism is the important reason for the promotion of Chinese sports. However, the relationship between Chinese sports and nationalism in globalised China could be much more examined by academics, as well as its influencing factors. This chapter selects the Beijing 2008 Olympic Games as the context and representative three Chinese sports heroes in the period of globalisation to study. The findings show that in some extent, Beijing 2008 Olympic Games and three Chinese sports heroes represent the national image of China in the globalised world, also bearing the burden of washing away historical humiliation and pursuing national glory. Furthermore, it is manifested that China have a complex nationalism in the process of hosting the 2008 Olympic Games. Under the influence of mass media, market economy and sports professionalisation, nationalism still exists in Chinese sports, but people gradually start to reflect on the ‘Juguo Tizhi’, the traditional Chinese sports system and the concept of ‘winning glory for the nation’. The relationship between Chinese nationalism and sports shows the important implications of rapid Chinese sports development.
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Due to climate change and an increasing concentration of the world’s population in vulnerable areas, how to manage catastrophe risk efficiently and cover disaster losses fairly is…
Abstract
Purpose
Due to climate change and an increasing concentration of the world’s population in vulnerable areas, how to manage catastrophe risk efficiently and cover disaster losses fairly is still a universal dilemma.
Methodology
This paper applies a law and economic approach.
Findings
China’s mechanism for managing catastrophic disaster risk is in many ways unique. It emphasizes government responsibilities and works well in many respects, especially in disaster emergency relief. Nonetheless, China’s mechanism which has the vestige of a centrally planned economy needs reform.
Practical Implications
I propose a catastrophe insurance market-enhancing framework which marries the merits of both the market and government to manage catastrophe risks. There are three pillars of the framework: (i) sustaining a strong and capable government; (ii) government enhancement of the market, neither supplanting nor retarding it; (iii) legalizing the relationship between government and market to prevent government from undermining well-functioning market operations. A catastrophe insurance market-enhancing framework may provide insights for developing catastrophe insurance in China and other transitional nations.
Originality
First, this paper analyzes China’s mechanism for managing catastrophic disaster risks and China’s approach which emphasizes government responsibilities will shed light on solving how to manage catastrophe risk efficiently and cover disaster losses fairly. Second, this paper starts a broader discussion about government stimulation of developing catastrophe insurance and this framework can stimulate attention to solve the universal dilemma.
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To modernize budgeting system is a challenge issue in many developing countries. To some scholars (Schick, 1998a, 1998b; Ma, 2009a), developing countries must first put into place…
Abstract
To modernize budgeting system is a challenge issue in many developing countries. To some scholars (Schick, 1998a, 1998b; Ma, 2009a), developing countries must first put into place basic budgetary controls before moving to more advanced models of budgeting. This approach of “basic first,” however, is questioned by others (e.g., Andrew, 2006). Drawing on China's recent budget reforms, this essay reconfirms the validity of the “basics first” approach. In China, budget reform since 1999 has begun to install budgetary controls for state finance, leading to an enhancement of budgeting capacity and financial accountability. However, governments at the same time have begun to be plagued by the unexpected problem of delays in spending and the accumulation of significant underexpenditures. Contrary to what many people may believe, we contend that this somewhat odd problem arises not because the new budgeting system has exercised too much control but rather because the new system is not yet effective in exerting budgetary controls.
Songtao Qu, Qingyu Shi, Gong Zhang, Xinhua Dong and Xiaohua Xu
This study aims to address the problem of low-temperature wave soldering in industry production with Sn-9Zn-2.5 Bi-1.5In alloys and develop qualified process parameters. Sn–Zn…
Abstract
Purpose
This study aims to address the problem of low-temperature wave soldering in industry production with Sn-9Zn-2.5 Bi-1.5In alloys and develop qualified process parameters. Sn–Zn eutectic alloys are lead-free solders applied in consumer electronics due to their low melting point, high strength, and low cost. In the electronic assembly industry, Sn–Zn eutectic alloys have great potential for use.
Design/methodology/approach
This paper explored developing and implementing process parameters for low-temperature wave soldering of Sn–Zn alloys (SN-9ZN-2.5BI-1.5 In). A two-factor, three-level design of the experiments experiment was designed to simulate various conditions parameters encountered in Sn–Zn soldering, developed the nitrogen protection device of waving soldering and proposed the optimal process parameters to realize mass production of low-temperature wave soldering on Sn–Zn alloys.
Findings
The Sn-9Zn-2.5 Bi-1.5In alloy can overcome the Zn oxidation problem, achieve low-temperature wave soldering and meet IPC standards, but requires the development of nitrogen protection devices and the optimization of a series of process parameters. The design experiment reveals that preheating temperature, soldering temperature and flux affect failure phenomena. Finally, combined with the process test results, an effective method to support mass production.
Research limitations/implications
In term of overcome Zn’s oxidation characteristics, anti-oxidation wave welding device needs to be studied. Various process parameters need to be developed to achieve a welding process with lower temperature than that of lead solder(Sn–Pb) and lead-free SAC(Sn-0.3Ag-0.7Cu). The process window of Sn–Zn series alloy (Sn-9Zn-2.5 Bi-1.5In alloy) is narrow. A more stringent quality control chart is required to make mass production.
Practical implications
In this research, the soldering temperature of Sn-9Zn-2.5 Bi-1.5In is 5 °C and 25 °C lower than Sn–Pb and Sn-0.3Ag-0.7Cu(SAC0307). To the best of the authors’ knowledge, this work was the first time to apply Sn–Zn solder alloy under actual production conditions on wave soldering, which was of great significance for the study of wave soldering of the same kind of solder alloy.
Social implications
Low-temperature wave soldering can supported green manufacturing widely, offering a new path to achieve carbon emissions for many factories and also combat to international climate change.
Originality/value
There are many research papers on Sn–Zn alloys, but methods of achieving low-temperature wave soldering to meet IPC standards are infrequent. Especially the process control method that can be mass-produced is more challenging. In addition, the metal storage is very high and the cost is relatively low, which is of great help to provide enterprise competitiveness and can also support the development of green manufacturing, which has a good role in promoting the broader development of the Sn–Zn series.