A novel strategy for developingα+βdual-phase titanium alloys with low Young's modulus and high yield strength

In this study,a novel strategy for developingα+βdual-phase titanium alloys with low Young's modulus and high yield strength was proposed,and a Ti-15Nb-5Zr-4Sn-1 Fe alloy was developed through theoretical composition design and microstructure manipulation.After hot-rolling and subsequent annealing,a high volume fraction of ultrafine grainedαphase embedded in metastableβ-matrix was formed in the microstructure as intended.Consequently,this alloy exhibits both low Young's modulus(61 GPa)and high yield strength(912 MPa).The experimental results prove that the proposed strategy is appropriate for developing titanium alloys with superior yield strength-to-modulus ratio than those of conventional metallic biomedical materials.Present study might shed light on the research and development of advanced biomedical titanium alloys with low Young's modulus and high yield strength.

A New Elasticity and Finite Element Formulation for Different Young's Modulus When Tension and Compression Loadings

This paper presents a new elasticity and finite element formulation for different Young's modulus when tension and compression loadings in anisotropy media. The case studies, such as anisotropy and isotropy, were investigated. A numerical example was shown to find out the changes of neutral axis at the pure bending beams.

NANOINDENTATION OF THIN-FILM-SUBSTRATE SYSTEM DETERMINATION OF FILM HARDNESS AND YOUNG'S MODULUS

In the present paper,the hardness and Young's modulus of film-substrate systems are determined by means of nanoindentation experiments and modified models.Aluminum film and two kinds of substrates,i.e.glass and silicon,are studied.Nanoindentation XP Ⅱ and continuous stiffness mode are used during the experiments.In order to avoid the influence of the Oliver and Pharr method used in the experiments,the experiment data are analyzed with the constant Young's modulus assumption and the equal hardness assumption.The volume fraction model(CZ model)proposed by Fabes et al.(1992)is used and modified to analyze the measured hardness.The method proposed by Doerner and Nix(DN formula)(1986)is modified to analyze the measured Young's modulus.Two kinds of modified empirical formula are used to predict the present experiment results and those in the literature,which include the results of two kinds of systems,i.e.,a soft film on a hard substrate and a hard film on a soft substrate.In the modified CZ model,the indentation influence angle,(?), is considered as a relevant physical parameter,which embodies the effects of the indenter tip radius, pile-up or sink-in phenomena and deformation of film and substrate.

EFFECT OF DISPERSION OF MICA IN MATRIX ON YOUNG'S MODULUS OF MICA FILLED POLYETHYLENE

The correlation between Young's modulus of mica-filled high density polyethylene (HDPE), low density polyethylene(LDPE) and the state of dispersion of plasma-treated mica in the polymer matrices was studied. The modulus and the number average diameter of mica aggregates in matrix were determined with tensile testing and image analysis respectively. The interface structure of the filler/matrix and the bulk structure of matrix were examined through the dielectric spectrometry, differential scanning calorimetry (DSC) and dynamic viscoelastic spectrometry. The results show that the Young's modulus of the filial polyethylene depends to a great extent upon the state of dispersion of filler in matrix, but it is independent of the interface structure and bulk structure. The better the dispersion, the higher the Young's modulus.

Anomalies in Young's modulus behavior after annealing in polycrystalline SmS

In this paper,the dependencies of Young's modulus and attenuation decrement on samarium sulfide polycrystals(SmS)under various annealing temperatures are studied by the piezoelectric ultrasonic composite oscillator technique at a frequency of 100 kHz in the temperature range of 80-300 K.A decrease in Young's modulus with an increase of the annealing temperature due to the texturing of the material was revealed.At the same time,attenuation peaks were observed at temperatures about 90 and 125 K,presumably due to Niblett-Wilks and Bordoni relaxations.

Dynamic Flexural Modulus and Low-Velocity Impact Response of Supercomposite^TMLaminates with Vertical Z-Axis Milled Carbon Fiber Reinforcement

In work reported here, the dynamic properties and low-velocity impact response of woven carbon/epoxy laminates incorporating a novel 3D interlaminar reinforcement concept with dense layers of Z-axis oriented milled carbon fiber SupercompositeTM prepregs, are presented. Impulse-frequency response vibration technique is used for non-destructive evaluation of the dynamic flexural modulus (stiffness) and loss factor (intrinsic damping) of woven carbon/epoxy control and SupercompositeTM laminates. Low-velocity punch-shear tests were performed on control and SupercompositeTM laminates according to ASTM D3763 Standard using a drop-weight impact test system. Control panels had all layers of 3K plain woven carbon/epoxy prepregs, with a dense interlaminar reinforcement of milled carbon fibers in Z- direction used in designing the SupercompositeTM laminate—both having same areal density. Impulse-frequency response vibration experiments show that with a 50% replacement of woven carbon fabric in control panel with milled carbon fibers in Z direction dynamic flexural modulus reduced 25% - 30% (loss in stiffness) and damping increased by about the same 25% - 30%. Low-velocity punch-shear tests demonstrated about 25% reduction in energy absorption for SupercompositeTM laminates with the replacement of 50% woven carbon fabric in control panel.

Shear modulus and damping ratio of sand-granulated rubber mixtures

Recycled waste tires when mixed with soil can play an important role as lightweight materials in retaining walls and embankments, machine foundations and railroad track beds in seismic zones. Having high damping characteristic, rubbers can be used as either soil alternative or mixed with soil to reduce vibration when seismic loads are of great concern. Therefore, the objective of this work was to evaluate the dynamic properties of such mixtures prior to practical applications. To this reason, torsional resonant column and dynamic triaxial experiments were carried out and the effect of the important parameters like rubber content and ratio of mean grain size of rubber solids versus soil solids(D50,r/D50,s) on dynamic response of mixtures in a range of low to high shearing strain amplitude from about 4×10-4% to 2.7% were investigated. Considering engineering applications, specimens were prepared almost at the maximum dry density and optimum moisture content to model a mixture layer above the ground water table and in low precipitation region. The results show that tire inclusion significantly reduces the shear modulus and increases the damping ratio of the mixtures. Also decrease in D50,r/D50,s causes the mixture to exhibit more rubber-like behavior. Finally, normalized shear modulus versus shearing strain amplitude curve was proposed for engineering practice.

Effect of B_4C on Oxidation Resistance of Low-Carbon MgO-C Materials

B4C was added into the low-carbon MgO-C materials in order to improve the oxidation resistance. The results show adding 0. 3wt% B4C can get the best oxidation resistance and adding 0. 2 wt% B4C can get the highest hot modulus of rupture. Altogether, adding 0. 2wt% B,C into the low-carbon MgO-C materials can get better oxidation resistance and hot strength.

Effect of Mild-calcined Coal Gangue Additionon Hot Strength and Refractoriness Under Loadof Ultra Low Cement Castablesin Al_2O_3-SiO_2 System

This work explored the way to improve hot modulus q/＇ rupture （HMOR） and refractoriness under load （RUL） by adding mild-calcined coal gangue （MCG） in Al2O3 -SiO2 ultra low cement （ULC） castables, making use of the in-situ effect of the MCG during heating-up. The influence of respective additions of 5%, 10% and 1.5% of the MCG powders calcined at 700℃ was investigated on HMOR at 1400 ℃ and RUL of the castables. With increased addition of the MCG, HMOR and RUL become significantly enhanced. At 10% of the MCG addition, HMOR reaches 3 MPa, as compared to 0. 3 MPa in the case of no MCG addition. RUL of the specimens dried at 110 ℃for 24 h can be increased by some 270 ℃ with 10% of the MCG addition. RUL 0.11 the specimens preheated at 1 500℃ for 3 h maintains the growth trend with the MCG addition increasing. The microstructure of the heated castable samples was investigated by means of SEM. The in-situ formed needle-like and interlaced mullite in the matrix is contributive to the tmprovement.

Low embankment dynamic response under vehicle traffic loads in arid-oasis areas

The use of low embankments is of significant concern for ecological protection in aridoasis areas.Based on the project of Sansha Expressway located in Kashgar City,Xinjiang,China,physical model tests were conducted in this study to investigate the dynamic response of the low embankment as per the effects of road structure,load amplitude,load frequency,load cycle,and moisture content.The dynamic stress is shown to increase with load amplitude while the dynamic elastic modulus decreases with load amplitude under short-term loading.The load frequency slightly influences the soil’s dynamic behavior;higher frequencies can improve the dynamic elastic modulus of the subgrade soil.The moisture content has greater influence on the mechanical properties of the subsoil than that of subgrade layer.The subgrade bears the majority of the traffic load as the stress dissipates to 37%of the whole value on its surface.The number of load cycles has the greatest effect on the dynamic response among the influencing factors tested.The dynamic elastic modulus with the type of long-term dynamic loading is only 40%-52%of that with static loading across the entire depth range.The dynamic stress shows significant accumulation with load cycles over the long-term dynamic loading test and becomes stable after 8×10~4 cycles of loading.An equation is established to quantify the cumulative dynamic stress in the low embankment under long-term dynamic loading conditions.

The Effect of Nano-Alumina Particles Generated in Situ in the Matrix of Ultralow and No Cement 85 wt%Al_(2)O_(3) Refractory Castables

Advanced high alumina refractory castables of ultra-low and to cement types, are well-known because of their ability on developing similar and/or superior thermal and mechanical properties. Following the recent trend of including nanoparticles in refractory castables, in this work, it is presented a novel way to obtain the benefit effects on the thermal and mechanical properties, promoted by the development in situ, of alumina’s nanoparticles in the matrix of castable (85 wt% Al2O3). The alumina nanoparticles were originated in situ after firing, due to the pyrolysis and oxidation of an aqueous resin, produced by the Pechini process. The resin played a double role, one as mixing liquid vehicle and the other as the aluminum oxide nanoparticles precursor. The results indicate a strong increase in flexural strength and elastic modulus as well as leading to a higher residual strength after thermal shock.

低弹模混凝土防渗墙材料参数统计特性及相关分布模型

为获取低弹模混凝土防渗墙渗透系数、弹模和抗压强度3个材料参数的统计特性及相关分布模型,基于2座土石坝的检测数据,根据赤池信息准则(AIC)识别材料参数的最优分布类型及相关分布模型的最优Copula函数、Bootstrap方法模拟识别结果的统计不确定性。结果表明,抗压强度、渗透系数和弹模分别服从极值Ⅰ型、对数正态、威布尔或极值Ⅰ型分布,变异系数均值分别为0.17、0.40、0.11;抗压强度与渗透系数、弹模与抗压强度、弹模与渗透系数之间的Pearson相关系数均值分别为-0.79、0.67、-0.55,最优Copula函数分别为Plackett Copula、Gaussian Copula、Gaussian Copula。研究结果可为低弹模混凝土防渗墙的渗流和强度可靠度计算提供参考。

高模低缩型聚酯工业丝凝聚态结构与应用特性的关联机制

高模低缩(HMLS)型聚酯工业丝的凝聚态结构对其在特定应力和受热条件下应用特性的影响尚不明确。对3种HMLS聚酯工业丝的蠕变、应力松弛、热收缩等性能进行测试,通过广角X射线衍射等方法对其凝聚态结构进行研究,分析结晶度、晶区和非晶区取向以及晶粒尺寸等参数与HMLS聚酯工业丝应用特性的关联性。结果表明,结晶度和非晶区取向度的协同作用对HMLS聚酯工业丝的蠕变、应力松弛和热收缩性能有重要影响。HMLS2的高结晶度抑制了应力作用和热收缩过程中分子链的滑移,适中的非晶区取向度减少了分子链的收缩解取向。HMLS2在60%的平均断裂载荷作用下蠕变回复率高达83.98%,60 s的应力松弛率为14.65%,195℃热处理后强度损失仅为8%,抗蠕变和热稳定性均较好。

空心玻璃微珠低密度水泥有效弹性模量计算与分析

空心玻璃微珠低密度水泥是典型的高水灰比、低胶凝相、多掺杂的多相多层次非均质复合材料,在弹性阶段其宏观力学性能由细观、微观乃至纳观尺度下的组成与结构决定。为探究材料的细微观结构对宏观力学性能的影响,在细微观力学框架下,基于Mori-Tanaka法、自洽法和四相模型,建立了考虑界面与微珠相互作用的微珠-低密度水泥弹性模量的多尺度均匀化理论模型,根据实验验证结果进行了影响因素拓展和分析。结果表明:水泥养护龄期越长,其弹性模量越高,但随着时间增长,弹性模量增大的趋势逐渐放缓,到28 d时趋于平稳;ITZ(界面过渡区)厚度是水泥弹性模量的重要影响因素,厚度的增加会使水泥的弹性模量极大地减小;微珠的密度与弹性模量共同影响水泥的弹性模量。

超声剪切波弹性成像评价不同针刺取穴法干预慢性非特异性腰痛患者临床研究

目的观察不同针刺取穴法干预慢性非特异性腰痛(CNLBP)患者腰骶部多裂肌的杨氏模量值,根据其差异性为超声剪切波弹性成像(SWE)评价CNLBP的临床应用提供理论依据。方法将64例患者随机分为观察组(32例)和对照组(32例)。其中对照组给予常规针刺配穴干预,观察组在对照组的基础上根据本地五运六气配穴针刺干预。各组每日治疗1次,连续治疗6 d后休息1 d,共治疗2周。观察两组患者干预前后及治疗结束4周后(随访期)的日本骨科协会腰椎功能评分(JOA)、视觉模拟疼痛评分(VAS)。应用SWE评价两组患者干预前后双侧腰骶部多裂肌(俯卧位)杨氏模量值。比较两组患者干预前后血清β-内啡肽(β-EP)水平。结果治疗后,两组患者多裂肌杨氏模量值均较治疗前降低(P<0.05),组间对比差异无统计学意义(P>0.05);两组血清β-EP水平较治疗前均升高(P<0.05),观察组高于对照组(P<0.05);两组患者JOA评分较治疗前均升高(P<0.05),观察组高于对照组(P<0.05);两组患者VAS评分均较治疗前降低(P<0.05),组间对比差异无统计学意义(P>0.05)。随访时,两组患者JOA评分较治疗前均升高(P<0.05),观察组高于对照组(P<0.05);VAS评分较治疗前降低(P<0.05),组间对比差异无统计学意义(P>0.05)。结论SWE可为临床CNLBP针刺治疗方案提供评价依据。运气理论指导下的取穴针刺能够降低腰骶部多裂肌杨氏模量值,上调血清β-EP水平,改善患者临床症状,疗效优于常规针刺。

Photoacoustic elastography based on laser-excited shear wave

Elastography can be used as a diagnostic method for quantitative characterization of tissue hardness information and thus,differential changes in pathophysiological states of tissues.In this study,we propose a new method for shear wave elastography(SWE)based on laser-excited shear wave,called photoacoustic shear wave elastography(PASWE),which combines photoacoustic(PA)technology with ultrafast ultrasound imaging.By using a focused laser to excite shear waves and ultrafast ultrasonic imaging for detection,high-frequency excitation of shear waves and noncontact elastic imaging can be realized.The laser can stimulate the tissue with the light absorption characteristic to produce the thermal expansion,thus producing the shear wave.The frequency of shear wave induced by laser is higher and the frequency band is wider.By tracking the propagation of shear wave,Young’s modulus of tissue is reconstructed in the whole shear wave propagation region to further evaluate the elastic information of tissue.The feasibility of the method is verified by experiments.Compared with the experimental results of supersonic shear imaging(SSI),it is proved that the method can be used for quantitative elastic imaging of the phantoms.In addition,compared with the SSI method,this method can realize the noncontact excitation of the shear wave,and the frequency of the shear wave excited by the laser is higher than that of the acoustic radiation force(ARF),so the spatial resolution is higher.Compared to the traditional PA elastic imaging method,this method can obtain a larger imaging depth under the premise of ensuring the imaging resolution,and it has potential application value in the clinical diagnosis of diseases requiring noncontact quantitative elasticity.

环氧固封式大容量高频变压器温度-应力场分布与优化

环氧固封式高频变压器采用环氧材料实现设备整体绝缘,可大幅降低设备体积,有效提高功率密度。大容量高频变压器内部温度分布不均,环氧树脂热应力分布集中致使整机开裂,导致绝缘失效。文中以10 kV高压大容量环氧固封式高频变压器为研究对象,建立了温度仿真模型和应力计算模型;获得了在额定运行工况下高频变压器热应力分布,其热应力主要集中在铁芯和绕组之间的环氧层;提出了降低局部热应力方法:通过材料改性提升环氧树脂导热系数降低高频变压器热点温度,可降低铁芯和绕组之间环氧树脂应力,安全系数由0.965提高至1.035;通过添加玻璃纤维增强材料和应力缓冲层双重措施,可大幅度降低应力集中区域材料弹性模量,降低内部最大应力,安全系数由1.035提高至2.691。研制了10 kV/200 kVA样机,通过–30~120℃高低温冲击试验,验证了其抗开裂性能和降低热应力方法的有效性。

低水胶比水泥浆体静动态流变行为的经时变化

基于浆体流动度、静态屈服应力以及小振幅振荡模式下储能模量,研究不同水胶比以及减水剂用量对浆体静动态流变行为经时变化的影响机制,探讨低水胶比浆体的静动态流变行为。研究结果表明:通过调整减水剂用量获得的初始流动度相同但水胶比不同的浆体,流动性经时变化存在显著的差异。极低水胶比浆体的流动性经时损失更为显著;但高减水剂用量时,浆体的流动性经时损失较小。基于静态屈服应力和储能模量G′表征了浆体静态流变行为的发展,发现颗粒胶体作用力和水化产物的桥接作用共同决定了浆体微观结构强度发展。低水胶比浆体的静态屈服应力和储能模量随时间延长增长更加显著。增加减水剂用量,可增大颗粒间距,抑制早期水化,有利于延缓颗粒网络强度发展。影响静动态流变行为内在机制的不同导致了浆体的静动态性能经时变化存在显著差异,其中水化产物的桥接作用是关键因素。

HMLS涤纶工业丝生产工艺探讨

以特性黏数为1.12~1.14 dL/g的大有光增黏聚对苯二甲酸乙二醇酯(PET)切片为原料,采用日本TMT公司纺丝设备生产1670 dtex/480 f高模低缩型(HMLS)涤纶工业丝,探讨了原料PET切片的特性黏数、螺杆温度、无风区高度、冷却工艺、拉伸工艺对HMLS涤纶工业丝性能的影响。结果表明:控制PET切片特性黏数在1.12~1.14 dL/g时,可确保无油丝特性黏数在0.95~0.97 dL/g;生产HMLS涤纶工业丝时,选择微孔环形分布的喷丝板,合适的螺杆温度为280~290℃,无风区高度为50 mm,采用低温冷却工艺可确保丝束能承受高的卷绕速度和较大的拉伸力;与低温冷却高温拉伸工艺相比,采用低温冷却低温拉伸工艺生产的HMLS涤纶工业丝的断裂强度略高,断裂伸长率较低,且浸胶后帘子线强力保持率高,但毛丝率要明显高于低温冷却高温拉伸工艺。

高模量碳纤维复合材料管件高低温交变环境结构稳定性研究

针对高模量碳纤维复合材料管件高低温交变环境下截面变形、分层问题,基于纤维混杂思路,在其大角度差铺层之间增设单层超薄(0.02 mm)无碱玻璃纤维平纹布,仿真分析表明,该玻璃纤维平纹布的加入,有效缓解了碳纤维大角度铺层之间的热膨胀失配,降低了层间应力。高低温交变试验结果印证了仿真分析的正确性,经过液氮温度(-196℃)至+150℃共六个高低温交变循环后,层间设置玻璃纤维平纹布的管件试件截面结构保持完整,几何尺寸未发生变化。单向板弯曲对比试验表明,超薄玻璃纤维平纹布的加入不仅起到了层间增韧效果,且对结构的弯曲性能无明显影响,这得益于超薄玻璃纤维平纹布的低模量与极小的厚度占比(1.6%)。