搅拌头组织对其使用寿命的影响

利用拉长晶粒和再结晶两种组织搅拌头对X70管线钢进行搅拌摩擦焊,通过使用寿命试验、拉伸试验和冲击试验,研究了搅拌头组织不同对其使用寿命和焊接接头力学性能的影响,结合硬度测量、金相组织观察和扫描电镜分析探究了其影响机理。结果表明:两种组织搅拌头焊接接头的力学性能相当,均因焊缝金属中出现马氏体组织而使强度升高、塑性和韧性下降;再结晶组织搅拌头焊后其本身组织产生变形,出现晶粒间缺陷使其使用寿命低于拉长晶粒搅拌头,两种搅拌头焊接过程中磨损机理均为磨料磨损。

西安市青少年正常(牙合)软组织X线头影测量研究——第一部分:Burston软组织分析法

早期的X线头影测量研究主要局限于硬组织,但是近年来软组织X线头影测量越来越多地受到各国学者的重视,认为软组织X线头影测量是硬组织X线头影测量必不可少的研究。本文以西安市112名正常(牙合)儿童为研究对象,利用电子计算机作为测量统计手段,得出了Burston软组织分析法的全部测量项目的正常值,以供临床参考。

游离腓骨头复合组织瓣重建儿童内踝骨及皮肤缺损的护理

儿童内踝骨及皮肤缺损临床较为少见，治疗方法复杂，常采用一期皮瓣封闭创面，二期植骨等多次手术治疗，且效果不佳。2005—06～2011-10笔者所在科行游离腓骨头复合组织瓣重建儿童内踝骨及皮肤缺损13例，现将护理报告如下。

负压封闭引流联合头皮帽状腱膜下软组织扩张皮瓣转移修复大面积头皮缺损28例临床分析

目的探讨负压封闭引流（VSD）联合头皮帽状腱膜下软组织扩张皮瓣转移在治疗大面积头皮缺损中的临床疗效。方法自2012年始，采用头皮缺损区域行VSD联合头皮帽状腱膜下软组织扩张皮瓣转移治疗各种类型大面积头皮缺损28例（男20例，女8例，年龄25～65岁），头皮缺损区先行清创后安装VSD行持续负压吸引，同时根据头皮缺损的情况置入软组织扩张器于头皮帽状腱膜下层形成扩张皮瓣，II期扩张皮瓣转移修复头皮缺损区。结果本组患者经VSD及头皮帽状腱膜下层软组织扩张后，均成功扩张皮瓣转移修复头皮缺损，疗效满意。结论VSD联合头皮帽状腱膜下软组织扩张皮瓣转移是修复较大面积头皮缺损的有效临床治疗方案。

TC4/72Ag-28Cu钎焊组织及Ti-Cu化合物生长机理研究

在钎焊温度 1 1 0 3K一定的条件下 ,分析了钎焊时间对 TC4 / 72 Ag-2 8Cu/ TC4钎焊接头组织及分布形态的影响。研究表明 :钎焊时间较短 ,扩散到界面的 Ti、Cu在冷却过程中通过共析转变形成了 Ti2 Cu化合物 ;钎焊时间大于某一临界值 ,由于母材中 Ti大量向钎缝中溶解及在界面 Cu相对浓度的降低 ,使钎缝中 Cu全部固溶在 Ti中 ,最终 Ti2 Cu化合物消失。在此基础上提出了临界钎焊时间的概念。

超细氧化物颗粒对Sn-58Bi钎料组织及性能影响

研究了分别添加1%Al2O3、Fe2O3、SiO2、TiO2超细粉末对Sn-58Bi共晶钎料的润湿性、钎焊接头微观组织及力学性能影响.结果表明,氧化物粉末的添加对钎料熔点影响不大,但钎料润湿性及钎焊接头剪切强度明显提高;明显细化钎焊接头基体组织及界面金属间化合物颗粒大小,并且界面金属间化合物层厚度也有一定减薄;另外,可抑制钎焊时焊点表面Bi的氧化,因此焊点表面光亮度也有明显提高.

非手术方法治疗成人反患者软组织疗效分析研究

目的:对比非手术方法治疗成人反患者矫治前后软组织的头影测量分析结果,从而确定此种方法的疗效。方法:选用常规拔除前磨牙方法,利用标准方丝弓矫治技术辅以多曲方丝弓技术治疗恒牙期骨性Ⅲ类错畸形患者15例。通过软组织头影测量分析方法,比较治疗前后患者侧貌变化。结果:①软组织改善明显,侧貌更接近正常。②NLA平均减少9.50°,LLL平均减少2.85°,ULP平均增大1.30°,LLP平均减少2.30°,H角平均增大2.10°。③H线与软组织侧面的关系,鼻点-H线(mm)平均减少3.00mm,鼻唇沟-H线(mm)平均增加2.10mm,下唇突点-H线(mm)平均减少1.95mm,颏唇沟-H线(mm)平均增加1.75mm。结论:非手术方法治疗成人反患者,从软组织角度来看,可取得相对满意疗效。

应用垂线参考平面图法进行面部头影测量分析的初步探讨

目的 :建立一个强调前后向指标的软组织头影测量分析法。方法 :在垂直于自然水平面并经过软组织鼻下点的垂线参考平面建立后 ,13个垂直间距及 5个软组织突距分别从 6 6个中国年轻正常 (33名男性 ,33名女性 )的头颅侧位片中获得。结果 :在性别二态性比较上看 ,男性组比女性组多数指标有显著增大的绝对值 ,但在某些测量项目上 ,如G -VL ,NT -VL ,As-VL ,ULA -VL ,B -Bs ,Pog -Pos等间距男女无显著性差异。结论 :女性在软组织发育有关的项目上 ,并没有表现出比男性明显的弱势。另外 。

基于磁共振电阻抗成像技术的3维脑病变检测仿真

为避免成像物体在核磁共振成像系统(MRI)实际操作中的旋转难题,基于微分进化思想提出了一种3维磁共振电阻抗成像算法(MREIT),并采用单方向磁感应强度"测量值"在3维真实头模型上进行了仿真验证研究。结果表明:该算法可以对病变的真实头模型进行阻抗图像重构,且计算值和理论值之间的相对误差<5%,具有较高的成像精度和空间分辨率;实时调整参数因子以适应算法,可以缩短重构时间,加快算法收敛性。因此改进后的算法具有很好收敛性,且成像质量较高,在临床应用上具有一定的可行性。

Microstructure and mechanical properties of dissimilar pure copper/1350 aluminum alloy butt joints by friction stir welding

The dissimilar friction stir welding of pure copper/1350 aluminum alloy sheet with a thickness of 3 mm was investigated. Most of the rotating pin was inserted into the aluminum alloy side through a pin-off technique, and sound welds were obtained at a rotation speed of 1000 r/min and a welding speed of 80 mm/min. Complicated microstructure was formed in the nugget, in which vortex-like pattern and lamella structure could be found. No intermetallic compounds were found in the nugget. The hardness distribution indicates that the hardness at the copper side of the nugget is higher than that at the aluminum alloy side, and the hardness at the bottom of the nugget is generally higher than that in other regions. The ultimate tensile strength and elongation of the dissimilar welds are 152 MPa and 6.3%, respectively. The fracture surface observation shows that the dissimilar joints fail with a ductile-brittle mixed fracture mode durin~ tensile test.

Effect of joining temperature on microstructure and properties of diffusion bonded Mg/Al joints

The joining of AZ31B Mg alloy to 6061 Al alloy was investigated at different joining temperatures by vacuum diffusion bonding method. The microstructures of Mg/Al dissimilar joints were studied by means of optical microscopy （OM）, scanning electron microscopy （SEM） and energy dispersive X-ray （EDX）. The results show that the thickness of each layer in the diffusion zone increases with the increase of joining temperature, and the microstructure changes obviously. At joining temperature of 440 °C, the diffusion zone is composed of Mg2Al3 layer and Mg17Al12 layer. At joining temperatures of 460 and 480 °C, the diffusion zone is composed of Mg2Al3 layer, Mg17Al12 layer, eutectic layer of Mg17Al12 and Mg-based solid solution. The width of high-hardness zone in the joint increases with increasing joining temperature, and the micro-hardnesses at different locations in the diffusion zone are significantly different. The joining temperature of 440 °C offers the highest tensile strength of 37 MPa, and the corresponding joint exhibits brittle fracture at the intermetallic compound layer of Mg17Al12.

带血管蒂腓骨头复合组织瓣修复儿童内踝缺损的初步研究

目的探讨以带血管蒂腓骨头复合组织瓣修复儿童内踝骨及皮肤软组织缺损的方法及近期疗效。方法2008年11月-2011年1月,收治8例内踝骨及皮肤软组织缺损患儿。男5例,女3例;年龄2~9岁,平均4.6岁。机器绞伤2例,车轮绞伤6例。内踝完全缺损,软组织缺损范围为3.5 cm×3.0 cm^7.0 cm×4.5 cm。受伤至入院时间2~8 h,平均4.5 h。以带血管蒂腓骨头复合组织瓣行骨及软组织修复重建,其中5例复合组织瓣携带腓骨头周围皮肤,3例创面过大(>5 cm×4 cm),采用内踝上皮瓣修复软组织缺损。供区2例直接缝合,6例植皮修复。结果术后带血管蒂腓骨头复合组织瓣及内踝上皮瓣均顺利成活,创面均Ⅰ期愈合。供区1例植皮出现局部坏死吸收;其余植皮均顺利成活,切口均Ⅰ期愈合。8例均获随访,随访时间10个月~3年,平均22个月。皮瓣颜色及弹性良好。患儿双下肢等长,其中6例无关节内、外翻畸形;2例术后1年出现进行性踝关节内翻。5例踝关节屈伸功能恢复正常,3例轻度受限;水平侧方及前后移动均与健侧无差别。术后10个月按美国矫形足踝协会(AOFAS)足踝功能评价标准评定,获优5例,良3例。X线片示踝穴间隙与健侧发育基本同步,6例内踝骨骺无早闭及骨桥形成,2例于术后1年出现骨桥。结论带血管蒂腓骨头复合组织瓣修复儿童内踝骨及皮肤软组织缺损近期疗效满意,重建的内踝可随患儿生长同步发育,但远期疗效有待进一步随访观察。

Formation, microstructure and mechanical properties of double-sided laser beam welded Ti-6Al-4V T-joint

The T-joints of Ti?6Al?4V alloy were manufactured by double-sided synchronized laser beam welding with the homologous filler wire. The formation, microstructure and mechanical properties of welded joints as well as the correlations of each other were investigated. The results indicate that the quality of weld seams is good without defects such as discontinuity, beading, visible cracks or porosity, which is linked to the steady molten pool behavior and droplet transition. The morphologies of the heat affected zone (HAZ) located on the skin and stringer are disparate. The microstructure of the HAZ and fusion zone (FZ) is mainly comprised of acicular martensiticα′ phases. The microhardness of the HAZ and FZ is higher than that of the base metal (BM) and reaches a maximum value at the HAZ near FZ on the stringer. The tensile specimens along the skin and stringer fractured at the BM with ductile fracture surfaces.

Effects of germanium additions on microstructures and properties of Al-Si filler metals for brazing aluminum

A series of Al?Si?Ge filler metals were studied for brazing aluminum. The microstructures and properties of the filler metals were investigated systematically. The results show that the liquidus temperature of Al?Si?Ge filler metals drops from 592 to 519 °C as the content of Ge increases from 0 to 30% (mass fraction). As the content of Ge increases, bright eutectic Ge forms. However, as the Ge content exceeds 20%, the aggregation growth of the eutectic structure tends to happen and coarsened primary Si?Ge particle forms, which is detrimental to the properties of alloys. The Al?10.8Si?10Ge filler metal has good processability and wettability with the base metal Al. When this filler metal is used to braze 1060 aluminum, the complete joint can be achieved. Furthermore, the shear strength test results show that the fracture of brazed joint with Al?10.8Si?10Ge filler metal occurs in the base metal.

Prediction of vulnerable zones based on residual stress and microstructure in CMT welded aluminum alloy joint

Numerical simulation and experimental results were employed for the identification of the most vulnerable zones in three-pass cold-metal-transferring （CMT） welded joint. The residual stress distribution in the joint was predicted by finite element （FE） method, while the structural morphology of distinctive zones was obtained through metallographic experiments. The highest principal stress made the symmetric face of the joint most sensitive to tensile cracks under service conditions. Whereas, the boundaries between the weld seam and the base plates were sensitive to cracks because the equivalent von Mises stress was the highest when the first interpass cooling was finished. The third weld pass and the inter-pass remelted zones exhibited the modest mechanical performances as a result of the coarse grain and coarse grain boundary, respectively. The most vulnerable zones were regarded to be the crossed parts between the zones identified by numerical and experimental methods.

The Study on Innovation Model Characteristics and Function Enhancement of “Leading Grain Enterprises+Farmers” in New Circumstances——an Investigation and Analysis on Major Grainproducing Areas in Hubei Province

ln the context of comprehensively deepening the reform, and integration of three The first, second and third industry sectors in rural areas, the research took major grain-producing areas in Hubei as an example, analyzed dominant grain in-dustrialization models “leading grain enterprises＋farmers”, and revealed its character-istics, advantages, and approaches for function reinforcement. The research is so meaningful, practical y or in future.

Microstructure and high-temperature mechanical properties of laser beam welded TC4/TA15 dissimilar titanium alloy joints

The microstructure evolution and high-temperature mechanical properties of laser beam welded TC4/TA15 dissimilar titanium alloy joints under different welding parameters were studied.The results show that the weld fusion zone of TC4/TA15 dissimilar welded joints consists of coarsenedβcolumnar crystals that contain mainly acicularα’martensite.The heat affected zone is composed of the initialαphase and the transformedβstructure,and the width of heat affected zone on the TA15 side is narrower than that on the TC4 side.With increasing temperature,the yield strength and ultimate tensile strength of the TC4/TA15 dissimilar welded joints decrease and the highest plastic deformation is obtained at 800°C.The tensile strength of the dissimilar joints with different welding parameters and base material satisfies the following relation(from high to low):TA15 base material>dissimilar joints>TC4 base material.The microhardness of a cross-section of the TC4/TA15 dissimilar joints reaches a maximum at the centre of the weld and is reduced globally after heat treatment,but the microhardness distribution is not changed.An elevated temperature tensile fracture of the dissimilar joints is located on the side of the TC4 base material.Necking occurs during the tensile tests and the fracture characteristics are typical when ductility is present in the material.

Wettability, microstructure and properties of 6061 aluminum alloy/304 stainless steel butt joint achieved by laser-metal inert-gas hybrid welding-brazing

Laser-metal inert-gas(MIG)hybrid welding-brazing was applied to the butt joint of 6061-T6 aluminum alloy and 304 stainless steel.The microstructure and mechanical properties of the joint were studied.An excellent joint-section shape was achieved from good wettability on both sides of the stainless steel.Scanning electron microscopy,energy-dispersive spectroscopy and X-ray diffractometry indicated an intermetallic compound(IMC)layer at the 6061-T6/304 interface.The IMC thickness was controlled to be^2μm,which was attributed to the advantage of the laser-MIG hybrid method.Fe3Al dominated in the IMC layer at the interface between the stainless steel and the back reinforcement.The IMC layer in the remaining regions consisted mainly of Fe4Al13.A thinner IMC layer and better wettability on both sides of the stainless steel were obtained,because of the optimized energy distribution from a combination of a laser beam with a MIG arc.The average tensile strength of the joint with reinforcement using laser-MIG hybrid process was improved to be 174 MPa(60%of the 6061-T6 tensile strength),which was significantly higher than that of the joint by traditional MIG process.

Experimental Study on Tissue Ablation with Novel Microwave Probe

Objective: To validate a newly designed microwave probe capable of producing larger volume of ablated lesions in ex vivo swine livers. Methods: A novel microwave probe was developed and tested in ex vivo specimens of swine liver. Group A was not given saline infusion under power output 50 W. Group B, C, D under power output 90 W were tested respectively according to the condition of no saline infusion (group B), 5 min preinfusion (5 ml saline, group C), preinfusion and continuous infusion (at the rate of 1 ml/min, group D) using the novel probe. The sizes of the microwave-induced lesions were evaluated and the volume of the tissue destruction qualified. Results: The approximate volumes of the microwave-induced lesions were (16.48±3.86) cm3, (28.86±6.15) cm3, (34.11±5.86) cm3, (40.50±10.88) cm3, respectively (P<0.01). Preinfusion and continuous infusion (group D) created more spherical lesions than only preinfusion (group C). Conclusion: The newly-developed microwave probe increased the volume of coagulation necrosis, created a more spherical lesion under the power output of 90 W, and might achieve the effective treatment of larger neoplasm with a single application of microwave energy.