共查询到20条相似文献,搜索用时 15 毫秒
1.
Baozhu sand particles with size between 75 μm and 150 μm were coated by resin with the ratio of 1.5 wt.% of sands. Laser sintering experiments were carried out to investigate the effects of laser energy density(E = P/v), with different laser power(P) and scanning velocity(v), on the dimensional accuracy and tensile strength of sintered parts. The experimental results indicate that with the constant scanning velocity, the tensile strength of sintered samples increases with an increase in laser energy density; while the dimensional accuracy apparently decreases when the laser energy density is larger than 0.032 J·mm^-2. When the laser energy density is 0.024 J·mm^-2, the tensile strength shows no obvious change; but when the laser energy density is larger than 0.024 J·mm^-2, the sample strength is featured by the initial increase and subsequent decrease with simultaneous increase of both laser power and scanning velocity. In this study, the optimal energy density range for laser sintering is 0.024-0.032 J·mm^-2. Moreover, samples with the best tensile strength and dimensional accuracy can be obtained when P = 30-40 W and v = 1.5-2.0 m·s^-1. Using the optimized laser energy density, laser power and scanning speed, a complex coated sand mould with clear contour and excellent forming accuracy has been successfully fabricated. 相似文献
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《中国铸造》2016,(5):335-341
High temperature compressive strength is one of the most important performances of resin sand; its value directly concerns the quality of castings. In order to seek the best testing method of resin sand high temperature compressive strength, a self-developed instrument was used to carry out experiments, and the sample shape and size were designed and studied. The results show that a hollow cylinder sample can reflect the strength difference of different resin sands better than a solid cylinder sample, and its data is stable. The experiments selected Φ20/5×30 mm as the size of the hollow cylinder samples. The high temperature compressive strengths of phenol-formaldehyde resin coated sand, furan resin self-setting sand, and TEA resin sand were each tested. For the resin sand used for cast steel and cast iron, 1,000 oC was selected as the test temperature; for the resin sand used for cast non-ferrous al oy, 800 oC was selected as the test temperature; and for all the resin sand samples, 1 min was selected as the holding time. This testing method can truthfully reflect the high temperature performance of three kinds of resin sand; it is reproducible, and the variation coefficients of test values are under 10%. 相似文献
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A numerical micromechanical method is adopted here to investigate the tensile strength of metal matrix composites (MMC) by
considering interface and matrix damage evolution. A cohesive zone model is employed to simulate the fiber/matrix interface
damage. The damage in the matrix, which characterizes microvoid nucleation, growth and coalescence, is described in term of
the Gurson-Tvergaard material model. These damage models are performed to a boundary value problem that involves a double
periodic array of elastic continuous fibers in the elastic-plastic matrix subjected to transverse loads. The main attempt
is made to investigate effects of interface strength and toughness on tensile strength of MMC. 相似文献
4.
基于分子动力学方法,建立了[100]、[110]、[111]三种常见沉积晶向的硬质合金基底金刚石涂层膜基界面模型。采用Morse势函数、Tersoff势函数以及LJ势函数相互耦合的方法,对模型原子间的相互作用进行了精确表征,借助分子动力学仿真软件Lammps对以上模型的力学性能进行了仿真分析。结果表明:沉积晶向为[100]的金刚石涂层膜基界面拉伸强度最大,[111]晶向次之,[110]晶向最小,并且弹性模量值随涂层晶向的变化规律与之趋同。 相似文献
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Water soluble cores(WSCs) have been widely applied in manufacture of complex metal components with hollow configurations or internal channels. However, the WSCs without any additons have low tensile strength and low humidity resistance. The purpose of this study is to prepare a water-soluble potassium carbonate sand core with addition of kaolin by the hot-temping method. The effects of kaolin on tensile strength, humidity resistance, fracture mechanism, as well as the gas evolution and collapsibility of WSCs were investigated. Results show that both the crystal morphology and the fracture mechanism of the inorganic salt are changed under the participation of kaolin, contributing to the increase of the tensile strength and the humidity resistance of the core. With the addition of 3wt.% kaolin, the tensile strength could be increased by a factor of 2, reached 1.50 MPa and the hygroscopic rate could be decreased by 14%, achieved 0.559%(after stored for 8 h), respectively. As the addition amount of kaolin increases from 0wt.% to 3wt.%, the main fracture mechanism changes from a adhesive to a cohesive fracture mechanism. The water-soluble potassium carbonate core obtained has the low gas evolution and excellent collapsibility, which makes it suitable for casting low melting metal with complex cavities and crooked channels. 相似文献
6.
Ti对Mo-Ti合金拉伸强度及显微组织的影响 总被引:1,自引:1,他引:1
采用粉末冶金方法制备Mo-Ti合金,研究合金元素添加方式及添加量对材料拉伸强度和显微组织的影响。结果表明,添加Ti112粉末所制备的合金的拉伸强度及相对密度均较添加纯Ti粉末的合金高,当添加量(质量分数)为0.8%时合金拉伸强度最高。显微组织分析结果表明,一部分Ti固溶到Mo基体,提高材料的拉伸强度,另一部分则与Mo及合金中的氧结合形成MoxTiyOz复合氧化物第二相粒子,起到细化晶粒及净化晶界的作用。 相似文献
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《Acta Materialia》2007,55(8):2791-2803
We investigate with first-principles density functional theory (DFT) the adhesion of the Al2O3(0 0 0 1)/NiAl(1 1 0) interface as a model for the thermally grown oxide/bond coat alloy interface in thermal barrier coatings. We find that the clean interface has an ideal work of adhesion of 0.66 J m−2. We predict that S impurities reduce interfacial adhesion significantly, due to a reduction in cross-interface bonds. The presence of Pt alters the interface adhesion only slightly, while Hf dopants dramatically increase adhesion via formation of strong Hf–O bonds, as expected from Hf’s open-shell character. We discuss the implications of these predictions, which are consistent with experimental observations of the effects of S, Pt, and Hf on the lifetime of thermal barrier coatings. 相似文献
8.
In this study,the 24 h tensile strength of new type acetone-urea-formaldehyde furan resin (nitrogen content 3%) was investigated by uniform design optimization.Four independent variables such as acetone:formaldehyde molar ratio (mol/mol),solution pH value,reaction temperature (℃) and reaction time (min) were considered in the experiments.U13(134) uniform design was employed and the equation of 24 h tensile strength model was obtained after 13 experimentations.The 24 h tensile strength was optimized by apply... 相似文献
9.
《International Journal of Cast Metals Research》2013,26(6):376-382
AbstractThe compaction behaviour of green sand was studied to assess the applicability of the Cooper–Eaton equation under conditions close to those of real foundry operations. The results indicate that the Cooper–Eaton equation describes the behaviour reasonably well, allowing prediction of the pressure required to achieve sand moulds of reasonable density. A corresponding distinct element method numerical simulation was also attempted. The study contributes useful information to the understanding of green sand compaction. It is clear that spherical sand is preferable to improve filling behaviour and that the gap between mould wall and pattern must be sufficiently large to avoid prevent weak sand compaction. 相似文献
10.
Effects of ultrasonic treatment on microstructure and tensile strength of AZ91 magnesium alloy 总被引:1,自引:0,他引:1
In this study, the effects of ultrasonic treatment on microstructural features and tensile strength of AZ91 magnesium alloy were investigated. AZ91 melts were subjected to ultrasonic waves of different power levels for 5 min using an ultrasonic device with frequency of about 20 kHz and maximum power of 600 W and cast in sand moulds. The results showed that ultrasonic treatment of the melt prior to casting had a significant effect on the size and sphericity of α-Mg dendrites as well as on the size, continuity, sphericity and distribution of intermetallic particles formed during cooling and solidification of the alloy. Increasing the applied ultrasonic power resulted in smaller, more rounded and better distributed grains and particles. The microstructural effects were mainly attributed to the cavitation and streaming phenomena which took place during ultrasonic treatment in the melt. Tensile strength of the alloy was significantly improved by ultrasonic treatment of the melt. Discontinuity and refinement of Mg17Al12 particles in the ultrasonically treated samples is thought to be the main reason for this improvement. The paper also examines different possible mechanisms responsible for microstructural modification of different phases under ultrasonic treatment conditions. 相似文献
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为了更好的理解热障涂层的失效机理,文中运用ABAQUS有限元软件来分析热障涂层的失效情况,使用内聚力单元和扩展有限元(XFEM)两种方法研究热障涂层TGO界面开裂与陶瓷涂层(TC)和氧化层(TGO)内随机裂纹的萌生与扩展,研究竖直裂纹与水平裂纹的关系.结果表明,热障涂层TGO界面的开裂首先出现在TGO/TBC波谷处.陶瓷涂层和氧化层内随机裂纹的萌生同样发生在TGO/TBC波谷处.竖直裂纹的存在可以抑制水平裂纹的萌生与扩展,且其在TGO/TBC波谷处的扩展长度比在TGO/TBC波峰处的扩展长度更长,说明TGO/TBC波谷区域是个危险区域,在此区域容易引发裂纹的萌生与扩展. 相似文献
13.
The effects of drawing on the structure and mechanical properties of a Co-based metallic glass under tension were thoroughly investigated. Surface changes induced by drawing, including removal of surface flaws, surface chemical homogenization and generation of compressive residual stress tend to increase the fracture strength, whilst open volumes created during drawing, particularly nano-voids, are likely to soften the wires. Initially, the surface changes are decisive factors, but as drawing proceeds, the open volumes gradually become dominant, yielding a maximum fracture strength in the wires with an area reduction ratio of 22%. Moreover, it was found that the fracture strength reliability was enhanced by the drawing, which is due not only to the surface perfection but also to the increase of plastic deformation capability, manifested by the decrease in the activation energy of individual shear transformation zones. Our results imply that the drawing technique could be a promising approach to continuously producing small-sized glassy wires with improved overall properties. 相似文献
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Joining is one of the key technologies for industrial products. Nearly all goods need to be joined during their production
development process. An innovative joining method such as a metal hook and loop fastener offers new possibilities for the
design and functionality of a product. In contrast to a synthetic hook and loop fastener, a metal fastener combines the advantage
of a fast assembling or disassembling with the characteristics of a metal joining. The outstanding benefits of the metal hook
and loop fastener are temperature and acid resistance. Additionally, features such as shock or sound absorbance can be realized.
In this paper, we present the development and characterization of a metal hook and loop fastener. The cohesion of the joining
is analyzed by cross tension tests as well as by shearing tests. To draw conclusions from the design of the joining partners,
the joining patches are analyzed by neutron μ-CT and compared with force measurements. 相似文献
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为了研究Al-Mg-Si系合金热处理制度和合金成分对力学性能的影响规律,采用人工神经网络(artificial neural network, ANN)和遗传算法(genetic algorithm, GA)相结合的方法,构建了Al-Mg-Si系合金强度预测模型(ANN-GA模型)。通过单因素和双因素分析,研究了合金元素含量和热处理工艺参数对铝合金抗拉强度的影响规律。结果表明,随着Si含量的增加,铝合金的抗拉强度呈现先降低后升高的趋势;随着Mg含量的增加、Cu含量的增加或者Fe含量的减少,铝合金的抗拉强度整体上呈现升高的趋势。双因素分析更能反映输入参数对铝合金抗拉强度的影响。Mg/Si比、Mg+Si总量和时效时间对Al-Mg-Si系合金力学性能的影响显著。铝合金的硬度随时间的变化趋势与ANN-GA模型的计算结果一致,峰值时效时间为29 h,相对误差为11.86%。 相似文献
19.
《中国铸造》2019,(3)
To develop a high performance gray cast iron with high tensile strength and thermal conductivity,multivariable analysis of microstructural effects on properties of gray cast iron was performed. The concerned parameters consisted of graphite content,maximum graphite length,primary dendrite percentage and microhardness of the matrix. Under the superposed influence of various parameters,the relationships between thermal conductivity and structural characteristics become irregular,as well as the effects of graphite length on the strength. An adaptive neuro-fuzzy inference system was built to link the parameters and properties. A sensitivity test was then performed to rank the relative impact of parameters. It was found that the dominant parameter for tensile strength is graphite content,while the most relative parameter for thermal conductivity is maximum graphite length. The most effective method to simultaneously improve the tensile and thermal conductivity of gray cast iron is to reduce the carbon equivalent and increase the length of graphite flakes. 相似文献