Interfacial reactions and bending strength of SiC/A356/FeNi50 composite fabricated by gas pressure infiltration

The SiC/A356/FeNi50 composite was fabricated by gas pressure infiltration. The interfacial region of the SiC/A356/FeNi50 composite consisted of FeNi50 reaction layer, A1 reaction layer and A1 alloy matrix. The main intermetallic compounds were （Fe,Ni）a（A1,Sih3 and （Fe,Ni）2（A1,Si）5 at the A1 reaction layer and FeNi50 reaction layer, respectively. The bending behavior versus different infiltration temperatures and holding times was also investigated. The bending strength at 670 ~C was the highest and close to the bending strength of A1 alloy （223 MPa）, and 46% of SIC/A356. The brittle intermetallic compounds existing at the interface induced the decreasing of the bending strength. The pores were reduced by adequate heating time due to the homogeneous temperature of preform, which was beneficial to improve the bending strength of the composite.

Influence of Characteristics on Bending Strength of Layered Steel Fiber Reinforced Concrete

The influence of two main characteristics of steel fiber, the aspect ratio （Df） and volume fraction （ρf）, on the bending strength of Layered Steel Fiber Reinforced Concrete （LSFRC） is investigated by using orthogonal test. Via the variance analysis on the experimental results and trend analysis on the two characteristics, Df is found significantly related to the bending strength of LSFRC. The influence ratio is 63.3%. The bending strength of LSFRC increases if Df increases, makes better when Df reaches 100. ρf has ordinary influence on the bending strength of LSFRC. The influence ratio is 29.2%. Other characteristics, such as the shape of steel fiber and the mix proportion, have less influence. The best ρf contributing to the bending strength of LSFRC is 1.5 %. If ρf is greater than 1.5%, it has negative influence on the bending strength of LSFRC. So, ρf makes a limited contribution to the bending strength of LSFRC.

Relationships among Preparative Technique,Phase Composition and Bending Strength of Bauxite Porcelain

Bauxite porcelain can be sintered to make its bending strength reach 179Mpa by using sintered bauxite, clay and potash feldspar and albite as the main raw materials in oxidation atmosphere under the normal pressure. XRD, SEM and so on are utilized to study the relationships between factors like the composition of ingot, reduction particle size and heat insulating time at sintering temperature and the phase composition, microstructure and bending strength of ceramic body. The results show that the main phases in bauxite porcelain are corundum, mullite and glass, and the mullite is composed of two parts： primary mullite formed by clay conversion and secondary mullite whiskers precipitating from high temperature melt. The bending strength of ceramic body can be improved by enhancing the content of sintered bauxite in the formula： the smaller the particle size of the ceramic body is, the higher the bending strength will be. The high-temperature heat insulating technique is beneficial to the precipitation of certain quantitative secondary mullite whiskers so as to remarkably improve the strength of glass phase and ceramic body.

Bending strength and fracture surface topography of natural fiber-reinforced shell for investment casting process

In order to improve the properties of silica sol shell for investment casting process, various contents of cattail fibers were added into the slurry to prepare a fiber-reinforced shell in the present study. The bending strength of fiber-reinforced shell was investigated and the fracture surfaces of shell specimens were observed using SEM. It is found that the bending strength increases with the increase of fiber content, and the bending strength of a green shell with 1.0 wt.% fiber addition increases by 44% compared to the fiber-free shell. The failure of specimens of the fiber-reinforced green shell results from fiber rupture and debonding between the interface of fibers and adhesive under the bending load. The micro-crack propagation in the matrix is inhibited by the micro-holes for ablation of f ibers in specimens of the f iber-reinforced shell during the stage of being fired. As a result, the bending strength of specimens of the fired shell had no significant drop. Particularly, the bending strength of specimens of the fired shell reinforced with 0.6wt.% fiber reached the maximum value of 4.6 MPa.

Enhanced Thermal Conductivity and Bending Strength of Graphite Flakes/aluminum Composites Via Graphite Surface Modification

The effect of graphite surface modification on the thermal conductivity(TC) and bending strength of graphite flakes/Al composites(Gf/Al) prepared by gas pressure infiltration were investigated. Al3 Ni and Al4C3 phase may form at the interface in Ni-coated Gf/Al and uncoated Gf/Al composites, respectively, while the Al-Cu compound cannot be observed in Cu-coated Gf/Al composites. The Cu and Ni coatings enhance TC and the bending strength of the composites in the meantime. TC of Cu-coated Gf/Al composites reach 515 Wm^-1·K^-1 with 75 vol% Gf, which are higher than that of Ni-coated Gf/Al. Meanwhile, due to Al3 Ni at the interface, the bending strength of Ni-coated Gf/Al composites are far more than those of the uncoated and Cu-coated Gf/Al with the same content of Gf. The results indicate that metal-coated Gf can effectively improve the interfacial bonding between Gf and Al.

Bending Strength and Fracture Behavior of Ni50Mn29Ga21 Alloy with Terbium

The bending strength and fracture behaviors of Ni50Mn29Ga21 alloy with terbium were investigated.The results show that the bending strength of the alloy is increased dramatically with the increase of terbium content.The fracture appearance of the sample without terbium is dominated by grain boundary fracture,while that with terbium is dominated by cleavage fracture with the increase of terbium content.Moreover,the grains are refined obviously and the oxygen content is decreased after adding terbium.

SIZE EFFECT ON THE BENDING AND TENSILE STRENGTH OF MICROMACHINED POLYSILICON FILMS FOR MEMS

The bending strength of microfabricated polysilicon beams was measured by beam bending using a nanoindenter. Also, the tensile strength of microfabricated polysilicon thin ?lms was measured by tensile testing with a new microtensile test device. It was found that the bending strength and tensile strength of polysilicon microstructures exerts size e?ect on the size of the specimens. In such cases, the size e?ect can be traced back to the ratio of surface area to volume as the governing parameter. A statistical analysis of the bending strength for various specimen sizes shows that the average bending strength of polysilicon microcantilever beams is 2.885 ± 0.408 GPa. The measured average value of Young’s modulus, 164 ± 1.2 GPa, falls within the theoretical bounds. The average fracture tensile strength is 1.36 GPa with a standard deviation of 0.14 GPa, and the Weibull modulus is 10.4 -11.7, respectively. The tensile testing of 40 specimens on failure results in a recommendation for design that the nominal strain be maintained below 0.0057.

The Influence of Mineral Admixtures on Bending Strength of Mortar on the Premise of Equal Compressive Strength

The influence of mineral admixtures on bending strength of mortar on the premise of equal compressive strength was investigated. Three mineral admixtures （fly ash, ground granulated blast-furnace slag and steel slag） were used. The adding amount of mineral admixture in this study ranges from 22.5% to 60%, and the water-to-binder ratio ranges from 0.34 to 0.50. With equal compressive strength, different mortars can be arranged in such a descending order with their bending strength： cement-fly ash mortar, cement mortar, cement-GGBS mortar, and cement-steel slag mortar. With the same compressive strength, the higher the steel slag content and water-to-binder ratio, the lower the bending strength of mortars. However, the effect of mineral mixture content and water-to-binder ratio on the bending strength of cement-fly ash mortar and cement-GGBS mortar is far inconspicuous.

Numerical Simulation on Dynamic Bending Strength of Three-Graded Concrete Beam Based on Meso-Mechanics

To study the bending strength of mass concrete under dynamic loading, the pure bending zone of three-graded concrete beam is considered as a three-phase composite composed of matrix, aggregate and interface between them on meso-level. Dynamic constitutive model considering strain-rate strengthening effect and damage softening effect is adopted to describe the cocrete and meso-element's damage. The failure mechanisms of beam under impact loading, triagle wave load, dynamic load coupling with initial static loading were simulated by using displacement-controlled FEM. Furthermore, stress-strain curve of the specimens and their dynamic bending strength were obtained. The results obtained from numerical simulation agreed well with experimental data.

The Relationship of Microstructure, Density and Bending Strength Properties of Blighia sapida

Wood anatomical structures of various tree species help identify the wood. The characteristics and composition of these structures affect their utilisation. In this work, the microstructure of Blighia sapida a lesser-known Ghanaian hardwood species using light microscope and scanning electron microscope (SEM) was studied. The relationship between the microstructure and some physical properties such as density, and bending strength were also studied. The anatomical features studied were fibre length, double fibre wall thickness, fibre proportion, vessel diameter and proportion, rays and axial parenchyma proportions. It was observed that the use of SEM in studying the anatomical or ultra-structural aspects of wood gives a clearer understanding of the features and structures found in wood. Anatomical features such as presence of crystals and absence of axial parenchyma in Blighia sapida are reported in the work. The study also established that Blighia sapida had a low water uptake even though it had vessel distribution of 12 vessels/mm2. Having not very distinct axial parenchyma may have accounted for the low water uptake. The presence of occluded pits could also account for the low water uptake and the fibre wall thickness may also account for a medium bending strength of 62.8 N/mm2 at 12% moisture content.

Experimental study on the causes of cracking of high-strength steel during bending

This paper studies the chemical composition, tensile properties, inclusions, metallogrophic structure, and other such parameters to identify the causes of cracking during the bending of high-strength steel. The results show that the major causes of cracking are the original transverse cracks or holes on the surface of the slab and the presence of scales rolled into the cracks or holes. Cold fracturing from such defects is rare, and can be eleminated by enhancing the control of the steelmaking process and by mechanical clean-up of the surface cracks and holes in the slab.

板厚对UHPC薄板抗弯性能的影响

薄壁薄板结构是超高性能混凝土(UHPC)一个重要应用,而厚度减小会影响到钢纤维的取向和分布,并直接影响力学性能,如抗弯性能等。对5~50 mm UHPC薄板的抗弯性能进行研究,并通过三维视频显微镜和图像法研究由厚度引起的纤维分布取向变化,发现板厚大于20 mm后所能承受的破坏荷载快速增加,但抗弯强度随板厚减小而增加,纤维取向性(沿长度方向)也逐渐增强,尤其是对厚度为5~10 mm的薄板。抗弯强度变化主要取决于钢纤维取向性和厚度因子,而后者对超薄板影响较大。

熔压温度对光纤面板抗弯强度的影响

光纤面板在微光夜视、空间探测、核诊断、医学诊疗等领域有着广泛的应用,在使用过程中对强度有一定要求,目前缺少相关研究,本文研究了熔压温度对光纤面板x、y、z三个方向抗弯强度的影响,采用三点弯曲法测试光纤面板的抗弯强度。结果表明:熔压温度为660℃时,二次复丝之间熔合不充分,存在间隙,光纤面板抗弯强度较低,x、y、z方向抗弯强度分别为107、93、114 MPa;熔压温度为670℃时,二次复丝之间间隙消除,但依然存在界面,抗弯强度有所提升,x、y、z方向抗弯强度分别为110、109、125 MPa;熔压温度为680℃时,二次复丝充分熔合,此时光纤面板抗弯强度在x、z方向满足复合材料混合定律,分别为123、127 MPa,y方向芯玻璃作为增强相对皮玻璃起到增强作用,抗弯强度为113 MPa。本文研究对提高光纤面板强度以满足装管和使用需求具有重要意义。

牡蛎壳微粉改性水泥基复合材料性能及微观结构研究

以牡蛎壳粉部分替换传统水泥基材料,在实现牡蛎壳废物利用的同时可有效降低建材成本。利用牡蛎壳粉作为普通硅酸盐水泥掺合料,探讨其不同掺杂量及不同粉磨方式对水泥胶砂强度及安定性的影响,确定了牡蛎壳粉的适宜添加量,并用XRD、SEM及EDS等测试分析手段表征不同掺量下胶凝试块的结构及性能变化。实验结果表明,牡蛎壳的球磨方式对水泥胶砂强度有明显影响,掺加湿法球磨牡蛎壳粉的胶凝材料的强度高于相应的掺加干法球磨的样品。牡蛎壳粉的掺加量为5%时,试样的抗压强度和抗折强度分别达到49.2 MPa和7.55 MPa,显著高于未掺加的空白样品。通过安定性实验制得的试样经过预养、沸煮之后,表面均光滑、无裂纹,体积无明显膨胀或收缩,表明掺杂牡蛎壳粉的胶凝材料安定性良好。微观结构表征结果显示牡蛎壳粉在水泥胶凝材料中独立存在,主要起惰性填充作用。利用牡蛎壳微粉部分替代水泥基材料是可行的,既可以改善水泥基材料综合性能,又能节约材料成本、减少环境污染,具有良好的应用前景。

黏结剂喷射制备陶瓷型芯抗弯强度、尺寸精度及表面质量影响因素的研究进展

黏结剂喷射因具有低成本和可控性优势而在陶瓷型芯的制备中得到广泛的应用,但制备陶瓷型芯的抗弯强度、尺寸精度和表面质量一般较低,而这些不足可以通过改变制备工艺参数来进行改进。综述了粉末、黏结剂、成形工艺和后处理工艺这4个方面的参数对陶瓷型芯抗弯强度、尺寸精度和表面质量的影响,提出了提高黏结剂喷射制备陶瓷型芯抗弯强度、尺寸精度和表面质量的未来发展方向。

聚丙烯腈纤维调控水泥基充填材料凝结硬化与力学性能研究

利用聚丙烯腈(PAN)纤维调控水泥基充填材料,对水泥基充填材料的凝结硬化时间、抗压强度、黏结强度、抗弯强度和抗拉强度进行了分析,研究了不同纤维掺量(0.5%、1%、1.5%)和不同长径比(100、200、300)的聚丙烯腈纤维对水泥基充填材料力学性能的影响。结果表明:当PAN纤维掺量为1.5%时,较CM组(不掺PAN纤维)的初凝和终凝时间分别降低了11.1%和5.7%;PAN纤维水泥基充填材料的抗压强度随着PAN纤维含量增加而降低。与CM组相比,当PAN纤维体积含量为0.5%、1.0%和1.5%时,抗压强度分别下降了13.0%、3.7%和7.4%;纤维掺量为1%、长径比为200的水泥基充填材料的抗弯强度较CM组增加了78.6%,增幅最大。水泥基充填材料的黏结强度和抗弯强度先增加,然后随着PAN体积掺量和长径比增加而降低;随着PAN纤维掺入,水泥基充填材料的抗拉强度有所提高,与CM组相比,PAN纤维水泥基充填材料的抗拉强度提高了36.4%~418.2%。

加工因素对HDPE基木塑复合材料静曲强度的影响

为了研究木塑复合材料加工因素对复合材料力学性能的影响,采用正交实验法以静曲强度为评价标准,利用极差分析和方差分析法分析了螺杆转速、造粒温度、偶联剂质量分数和木粉含量等加工因素对力学指标静曲强度影响的顺序及各因素的最佳水平,确定了木塑复合材料静曲强度的各加工因素的最佳参数组合;系统地分析了各加工参数对木塑复合材料力学性能指标静曲强度的影响。结果表明,影响木塑复合材料静曲强度的主要加工因素由大到小依次为偶联剂质量分数>木粉含量>转速>造粒温度;得到最佳静曲强度的加工因素参数组合为转速150 r/min、造粒温度145℃、偶联剂质量分数为5%、木粉含量为60%;木粉含量及偶联剂质量分数对材料的静曲强度具有显著性影响,转速和造粒温度对材料静曲强度影响的显著性较低,其中,随着偶联剂含量的增加,静曲强度呈明显上升的趋势;当木粉含量从30%增大至70%时,材料的静曲强度呈先增加后减小的趋势。

正硅酸锂氚增殖材料结构改性及机械性能研究

三元锂陶瓷可作为聚变堆候选固态氚增殖材料。其中,硅酸锂(Li_(4)SiO_(4))锂密度较高,释氚性能良好。然而,Li_(4)SiO_(4)烧结较为困难,力学性能亟待改善。针对这一问题,研究提出通过中子倍增元素Pb、Zr添加的方式,调控陶瓷烧结特性及微细结构,以提高陶瓷致密度、改善机械性能。向前驱体溶液中以硝酸铅[Pb(NO_(3))_(2)]形式添加2 wt.%、5 wt.%和8 wt.%Pb元素,通过微波辅助溶液燃烧合成法得到陶瓷粉体。X射线衍射分析显示,陶瓷中Pb的有效成分为PbO。当向陶瓷中添加2 wt.%Pb元素后,陶瓷的致密度有所提高。在氧气氛围下,经1273 K烧结后相对致密度可达90%。对陶瓷的抗弯强度进行了测试,结果显示Pb添加可在一定程度上改善陶瓷的机械性能。因而,PbO虽然能够改善陶瓷的烧结致密化过程,但难以显著提高Li_(4)SiO_(4)的力学性能。向Li_(4)SiO_(4)添加10 wt.%ZrO_(2)后,Zr主要以Li_(2)ZrO_(3)形式存在。陶瓷晶粒得到明显细化,陶瓷的相对致密度为86.19%,其抗弯强度与致密度成正向关系。在此基础上,制备了Li_(4)SiO_(4)-10 wt.%ZrO_(2)微球,其抗压溃力可达40.76 N。

圆形截面钢管混凝土受弯构件塑性发展系数的双因素计算模型研究

为了综合考虑截面几何和材料特性对圆形截面钢管混凝土(CFST)受弯构件抗弯强度的影响,选择截面厚径比和材料强度比作为自变量,研究建立了圆CFST受弯构件截面塑性发展系数的二元函数计算表达,并建立了截面抗弯强度计算模型。首先在确定厚径比和强度比取值范围的基础上,设计1 656个圆CFST受弯构件的数值模型,利用纤维模型法计算确定每个构件的截面抗弯强度和塑性发展系数。然后选择截面钢管壁厚与外径之比、钢管强度与核心混凝土强度之比作为自变量,通过回归分析建立圆CFST构件的截面塑性发展系数的二元函数表达式,据此提出了圆CFST构件截面抗弯强度的计算模型。最后通过与试验数据、现行设计规范和研究文献中不同计算模型进行对比分析,验证了建立的圆形截面钢管混凝土受弯构件的截面塑性发展系数和抗弯强度计算模型具有更高的精度和适用性。