Pressure generation under deformation in a large-volume press

Deformation can change the transition pathway of materials under high pressure,thus significantly affects physical and chemical properties of matters.However,accurate pressure calibration under deformation is challenging and thereby causes relatively large pressure uncertainties in deformation experiments,resulting in the synthesis of complex multiphase materials.Here,pressure generations of three types of deformation assemblies were well calibrated in a Walker-type largevolume press(LVP)by electrical resistance measurements combined with finite element simulations(FESs).Hard Al_(2)O_(3) or diamond pistons in shear and uniaxial deformation assemblies significantly increase the efficiency of pressure generation compared with the conventional quasi-hydrostatic assembly.The uniaxial deformation assembly using flat diamond pistons possesses the highest efficiency in these deformation assemblies.This finding is further confirmed by stress distribution analysis based on FESs.With this deformation assembly,we found shear can effectively promote the transformation of C60 into diamond under high pressure and realized the synthesis of phase-pure diamond at relatively moderate pressure and temperature conditions.The present developed techniques will help improve pressure efficiencies in LVP and explore the new physical and chemical properties of materials under deformation in both science and technology.

Simulation of pressure effects on hot isostatic pressing of stainless steel powder

To investigate the effects of pressure on the hot isostatic pressing(HIP) process of a stainless steel powder,density distribution and deformation of the powder at four different applied pressure levels were predicted and compared by using finite element method(FEM).Constitutive relations of porous compacts during HIP process were derived based on the yield criterion of porous metal materials.Thermo-mechanical coupling calculations were carried out by the MSC.Marc.Densification mechanisms were studied through evolutions of relative density,equivalent plastic strain and equivalent viscoplastic strain rate for compacts.The simulation results were also compared with experimental data.The results show that the densification rate and final density of compacts increase dramatically with the increase in the applied pressure level when it is below 100 MPa during HIP process,and the creep for compacts evolves into steady stage with the improvement of density.

Experimental confirmation of physical metal penetration generation and press casting production considering molten metal's pressure control

This paper presents a technique for controlling the pressure of a molten metal when using a new type of iron casting method called sand mold press casting to realize high productivity and obtain high-quality products.The past test results using this method showed a casting yield of 90% to 95%,while conventional methods only show a casting yield of 60% to 70%.Although the press casting method does not require a sprue cup or runner channel casting defects such as metal penetration are often caused by the high pressure in the high-velocity pressing part of this casting process.Therefore,we proposed a pressure control method with a mathematical model of molten metal pressure,and with it we achieved experimental confirmation of the successful production of brake drums at different pressing temperatures.Results show that the proposed pressing control method can realize sound,penetration-free casting production.However,the theoretical analysis and design of this pressing process had not previously been studied sufficiently,and therefore this paper presents the theoretical design algorithm for the process as well as its experimental confirmation.

Effects of HIPing Pressure on Microstructures and Properties of TiAl Alloy

Blended elemental Ti 34%Al powders (mass fraction), containing 1.5%TiC, were hot isostatic pressed to prepare TiAl alloys. The effects of HIPing pressure on the sintered density, microstructure, constitutions phase were studied in details. The results show that the density of TiAl alloy increases repaidly with the increase of the HIPing pressure. At the same time, with the increase of pressure, the Ti 3Al phase in matrix disappears. TiC reacts with other substance, forming Ti 2AlC phase, which precipitates at grain boundaries. With the increase of hot isostatic pressing(HIPing) pressure, the shrinkage of the alloys increases, the fine spherical Ti 2AlC phase can meet together and forms a needle shape Ti 2AlC, and the amount of needle shaped Ti 2AlC phase increases. The composite material of TiAl containing C can be made easily by HIPing technology.

In-situ ultrasonic calibrations of pressure and temperature in a hinge-type double-stage cubic large volume press

Here,simultaneous in-situ calibration of pressures and temperatures was performed in a hinge-type second-stage cubic large volume press(LVP)up to 15 GPa and 1400 K by an acoustic travel-time approach.Based on the recently reported P-tSand P-T-tP-tSequations for Al2O3buffer rod,the cell pressures and temperatures in the chamber of LVP were insitu determined,in comparison with those by conventional off-line(or fixed-points)pressure calibration method and direct thermocouple measurement,respectively.It is found that the cell pressures of the LVP chamber are significantly reduced after annealing at simultaneous high pressures and high temperatures,owing to the stress relaxation as accumulate in the LVP chamber.This acoustic travel-time method is verified to be a good way for precise determination of thermal(cell)pressures at high temperature conditions,and is of great importance and necessity to conduct in-situ physical property measurements under extreme high P-T conditions,especially when the precious synchrotron x-ray/neutron diffraction beams are not available.

ANALYSIS OF FORMING PRESSURE AND INSIDE DIAMETER VARIATION IN THIN WALL TUBE PRESS EXPANSION

The forming pressure is calculated by utilizing the slab method and the variation principles and influence factors of inside diameter in thin wall tube press expansion are analyzed.The results of theoretical analysis are well agree with the experiments.The conclusion is valuable to product quality control in the actual manufacturing.

Function of large-volume high-pressure apparatus at SECUF

Pressure allows the precise tuning of a fundamental parameter, the interatomic distance, which controls the electronic structure and virtually all interatomic interactions that determine material properties. Hence, pressure tuning is an effective tool in the search for new materials with enhanced properties. To realize pressure tuning on matter, large-volume press （LVP） apparatuses have been widely used not only to synthesize novel materials but also to implement the in situ measurement of physical properties. Herein, we introduce the LVP apparatuses, including belt-type, cubic anvil, and 6-8 type multi-anvil, that will be constructed at the Synergetic Extreme Condition User Facility （SECUF） at Jilin University. Typically, cell volumes of 1000 mm3 can be obtained at 20 GPa in a belt-type apparatus that is significantly larger than that obtained in a 6-8 type multi-anvil apparatus at the same pressure. Furthermore, the in situ measurement of physical prop- erties, including thermological, electrical, and mechanical behaviors, is coupled to these LVP apparatuses. Some typical results of both synthetic experiments and in situ measurements obtained from the LVP apparatuses are also reviewed.

Compressive behavior of NiAl/(Cr,Mo)Hf alloy prepared by high-pressure die casting and hot isostatic pressing

The NiAl-28Cr-5.85Mo-0.15Hf alloy was prepared by high-pressure die casting (HPDC) and subsequent hot isostatic pressing(HIP), and tested for compressible strength and fracture behavior at 300-1 373 K. The results show that the elevated temperature 0.2% compressible yield strength as well as the room-temperature compressible fracture strain of as-HIP alloy are larger than those of the same alloy prepared by directional solidification (DS). It suggests that the fine structures with a homogeneous distribution of fine Cr (Mo) and Hf-rich phase created by high-pressure die casting lead to these improvements.

Influence of twist extrusion process on consolidation of pure aluminum powder in tubes by equal channel angular pressing and torsion

In comparison with the conventional equal channel angular pressing（ECAP） process,a comprehensive study of influence of twist extrusion（TE） process on consolidating pure aluminum powder in tubes（PITs） by equal channel angular pressing and torsion（ECAPT） was conducted via three-dimensional（3D） finite element simulation,experimental investigation and theoretical analysis.Simulation results revealed that during the consolidation of aluminum powder particles by ECAPT,TE process played a significant role of back pressure.Due to the torsional shear and high hydrostatic pressure exerted by twist channel,both the magnitude and homogeneity of the effective strain were increased markedly.After one pass of ECAPT process using a square channel with an inner angle of 90° and a twist slope angle of 36.5° at 200℃,commercial pure aluminum powder particles were successfully consolidated to nearly full density.Simulation and experimental results showed good agreement.In the microstructure observations,grains were greatly refined.At the same time,porosities were effectively eliminated by shrinking in size and breaking into small ones.Microhardness test indicated that strain distribution of ECAPT-processed billet was more homogeneous with respect to the ECAP-processed one.All these improvements may be attributed to the extreme intense shear strain induced during ECAPT and the increase in self-diffusion coefficient of aluminum due to the back pressure exerted by TE process.

EX-PRESS青光眼引流器植入术治疗开角型青光眼

目的：EX-PRESS青光眼引流器植入术治疗开角型青光眼的临床疗效和安全性。方法：回顾经视力、眼压、房角镜、眼底、视野等检查确诊为开角型青光眼患者40例47眼。患者年龄6～73（平均39.9±16.5）岁，最佳矫正视力0.01～0.60，眼压18～65mmHg。给予3种以上降眼压药物控制不理想，行EX-PRESS青光眼引流器植入术。术后1，3d； 1wk进行眼压、裂隙灯检查。比较治疗前后最佳矫正视力、眼压的临床资料，观察其疗效及安全性。结果：术前平均视力0.26±0.29，术后1wk平均视力0.24±0.22，平均视力稍有下降，但无统计学意义（t=1.56，P=0.13）。术前平均眼压36.62±14.01mmHg，术后1，3d； 1wk平均眼压分别为10.04±5.77，9.59±4.93，9.47±3.06mmHg。EX-PRESS青光眼引流器植入术后1，3d； 1wk的眼压均较治疗前明显降低（F=157.20，P〈0.05）。除5眼术后1d眼压〈5mmHg，所有患者在治疗过程中及术后1wk均未见明显眼部或全身不良反应。结论：EX-PRESS青光眼引流器植入术治疗开角型青光眼是安全有效的，术中及术后风险低、并发症少。

Ex-press青光眼引流钉植入术治疗难治性青光眼的疗效分析

目的：探讨Ex-press青光眼引流钉植入术治疗难治性青光眼的临床疗效与安全性。方法：回顾性分析行Ex-press青光眼引流钉植入术治疗的难治性青光眼患者22例23眼。观察术前及术后1wk,1、2、3、6mo,1a的视力、眼压及并发症发生情况。结果：所有患者均随访至1a。完全成功率为52%（12眼）,部分成功率22%（5眼）,总成功率74%。术前平均眼压为40.59±11.11mmH g（1mmH g=0.133k Pa）,术后1wk,1、2、3、6mo,1a的平均眼压分别为10.30±5.07、12.23±4.03、13.87±4.62、16.52±6.09、18.35±7.06、19.65±8.26mmH g。术后各时间点眼压与术前眼压相比均有统计学意义（P〈0.01）。术后患者视力较术前提高,差异有统计学意义（P〈0.01）。23眼中3眼出现少量前房出血,分别于术后4~7d自行吸收;2眼出现一过性低眼压,密切观察8~10d后眼压〉6mmH g;1眼术后1mo出现渗出性脉络膜脱离,给予局部使用激素后于术后37d复位。所有患者均未出现其他并发症。结论：Ex-press青光眼引流钉植入术治疗难治性青光眼安全有效。

EX-PRESS青光眼引流钉植入术和小梁切除术治疗原发性开角型青光眼的临床观察

目的：与小梁切除术对比，观察EX-PRESS青光眼引流钉植入术治疗原发性开角型青光眼的有效性和安全性。方法对药物不能控制的原发性开角型青光眼患者进行手术，随机分为EX-PRESS青光眼引流钉植入术组和小梁切除术组，每组术中均联合使用丝裂霉素。收集术前，术后1 d，2周，1，3，6，12个月的视力、眼压等基本数据。结果评价主要为平均眼压和术后并发症的发生率。手术完全成功的标准为：在不使用任何降眼压药物的情况下，眼压控制在5～18 mmHg或比基线眼压下降20％。结果28例原发性开角型青光眼患者共32只眼纳入研究，每组各14例。 EX-PRESS青光眼引流钉植入组术前平均眼压（34．5±5．6） mmHg，小梁切除术组术前平均眼压（33．8±6．8） mmHg。两组比较无差异（ P ＞0．05）。术后1年两组平均眼压分别为（12．6±4．5） mmHg和（11．5±4．6） mmHg。两组比较无差异（ P ＞0．05）。术后随访1年，完全成功者EX-PRESS青光眼引流钉植入组占69％，小梁切除术组占56％。相对成功者两组分别占87％和81％。两组比较无差异（ P ＞0．05）。在手术时间和并发症发生率上两组比较无明显统计学差异。结论对于原发性开角型青光眼患者，巩膜瓣下植入EX-PRESS青光眼引流钉装置安全、有效。

基于AMESim的超高压气动吹除阀仿真与实验研究

介绍一种带压差控制的超高压气动吹除阀及其工作原理。运用AMESim气动元件设计库建立吹除阀仿真模型,对其动态特性进行系统的分析研究,并进一步探究主阀阀芯节流孔孔径、控制阀弹簧预压缩量、气源压力、舷外海水压力等参数对吹除阀吹除性能的影响。最后,对吹除阀的性能进行实验研究。研究结果表明:吹除阀的工作性能平稳,响应灵敏,压差控制精度高;气源压力、舷外海水压力对吹除阀压差控制性能没有影响,但提高气源压力或降低舷外海水压力能够有效提高吹除效率;通过改变节流孔孔径与控制阀弹簧预压缩量,可以调节吹除阀压差控制范围。

抗VEGF联合Ex-press青光眼引流器植入治疗新生血管性青光眼

目的:观察玻璃体腔注射抗VEGF联合Ex-press青光眼引流器植入术对新生血管性青光眼的临床疗效。方法:回顾性分析我院收治的新生血管性青光眼患者20例20眼,15眼行玻璃体腔注射抗VEGF及Ex-press青光眼引流器植入联合PPV术,术中行全视网膜光凝术。另5眼行玻璃体腔注射抗VEGF及Ex-press青光眼引流器植入术,术后7d行全视网膜光凝。分别观察20例患者术中及术后并发症情况,以及术后1wk,1、3、6mo后的视力、眼压、虹膜新生血管消退情况。结果:治疗前平均眼压为47±5.6mmHg,治疗后1wk,1、3、6mo时平均眼压分别为13.4±3.6、15.3±4.2、16.9±5.3、18.7±6.9mmHg,治疗后各随访时间点眼压较治疗前差异具有统计学意义(P<0.05)。Ex-press青光眼引流器植入术术中及术后并发症主要有早期浅前房、引流管阻塞,经适当治疗后均恢复。滤过泡瘢痕化8眼,但眼压稳定在正常范围。结论:玻璃体腔注射抗VEGF联合Ex-press青光眼引流器植入术可以有效治疗新生血管性青光眼,降低新生血管性青光眼患者的眼压。

超声乳化联合EX-PRESS引流钉植入治疗难治性开角型青光眼合并白内障

目的:观察超声乳化联合EX-PRESS引流钉植入治疗难治性开角型青光眼合并白内障的疗效。方法:选取难治性开角型青光眼合并白内障患者共66例67眼。试验组采用超声乳化吸除联合EX-PRESS引流钉植入术,对照组采用超声乳化吸除联合小梁切除术。术前进行BCVA、IOP检查;观察并发症、手术时间,术后观察视力、眼压、滤过泡改变;随访时间为术后1d,1wk,1、6mo,1a。结果:试验组手术时间为23.26±2.00min,对照组手术时间为31.73±2.17min,两组间有差异(t=16.68,P<0.01)。试验组术后发生浅前房和滤过泡瘢痕化者各1眼;对照组术后发生低眼压3眼,前房出血和脉络膜脱离各1眼,滤过泡瘢痕化者5眼。滤过泡Kronfeld分型无差异(Z=-0.775,P=0.438)。两组干预因素及时间对患者术后眼压均有影响(F组间=8.67,P组间<0.01;F时间=127.58,P时间<0.01;F组间×时间=7.5,P组间×时间<0.01)。干预因素对患者术后视力无影响,两组术后视力同术前相比均有差异(F组间=0.35,P组间=0.55;F时间=34.92,P时间<0.01;F组间×时间=0.38,P组间×时间=0.86)。结论:超声乳化联合EX-PRESS引流钉植入治疗难治性开角型青光眼合并白内障安全有效、手术时间短,可作为一种常规青白联合手术方式。

Ex-press微型引流器植入联合深层巩膜切除术治疗难治性青光眼

目的:探讨Ex-press微型引流器植入联合深层巩膜切除术治疗难治性青光眼的临床疗效。方法:收集2014-01/11难治性青光眼患者24例30眼,施行Ex-press微型引流器(P-50)植入联合深层巩膜切除术。术后随访12mo,分析术前及术后疼痛感、眼压、视力、并发症等情况。结果:术后随访期间所有患者眼痛症状均缓解。术前平均眼压为51.15±2.60mmHg,末次随访时平均眼压15.11±2.51mmHg,术后眼压与术前相比,差异有统计学意义(P<0.05)。术后视力有提高者8眼,无显著改变者22眼。术后前房出血2眼(7%),1wk后出血吸收。结论:Ex-press微型引流器植入联合深层巩膜切除术是治疗难治性青光眼相对安全、有效的方法,能显著降低眼压,减少患者痛苦,且并发症少。

Ex-Press房水引流物植入术治疗新生血管性青光眼临床观察

目的评价Ex-Press房水引流物植入术治疗新生血管性青光眼的有效性和安全性。方法 2014年5月至2017年6月在北京同仁医院确诊为新生血管性青光眼并行ExPress房水引流物植入术的患者23例(23眼),术后随访12个月,观察术前、术后患者的眼压、降眼压药物种类及术后并发症情况。结果 23例患者术前眼压为(39.0±4.2)mm Hg(1 k Pa=7.5 mm Hg);术后1个月、3个月、6个月、12个月眼压分别为(12.8±0.7)mm Hg、(15.5±0.9)mm Hg、(18.4±1.0)mm Hg、(20.6±2.5)mm Hg,与术前相比差异均有统计学意义(均为P<0.05)。至末次随访时,手术完全成功17眼(73.9%),条件成功1眼(4.3%),总手术成功率78.3%。术前使用抗青光眼药物(3.3±0.9)种,术后12个月为(0.2±0.5)种。术后浅前房3眼、前房积血1眼、高眼压7眼。结论 Ex-Press房水引流物植入术安全、有效、并发症少,可作为新生血管性青光眼患者的手术治疗方式之一。

P50型与P200型Ex-PRESS引流器植入术对开角型青光眼疗效及安全性的随机对照研究

背景 目前国外对Ex-PRESS引流器植入术治疗开角性青光眼的临床应用效果已有报道,在中国临床上使用的Ex-PRESS引流器有内径分别为50μm和200μm的P50型和P200型,但2种类型引流器的临床效果是否有所不同,目前国内外报道较少. 目的 对比观察P50型与P200型Ex-PRESS引流器植入术治疗开角型青光眼的早期临床疗效和安全性. 方法 采用随机对照临床研究设计,纳入2012年3月至2013年4月在广州军区武汉总医院行Ex-PRESS引流器植入术的开角型青光眼患者69例80眼,采用随机数字表法将患者分为基线特征匹配的2个组,分别实施P50型Ex-PRESS引流器植入术（35例40眼）和Ex-PRESS引流器植入术（34例40眼）,比较2个组患者的病种构成比、最佳矫正视力恢复时间、理论住院天数、手术前后的眼压变化及并发症的发生情况.结果 P50组和P200组术眼手术前后眼压平均下降幅度分别为（21.19±11.22）和（24.35±12.27）mmHg（1 mmHg=0.133 kPa）,差异无统计学意义（t=-1.201,P＞0.05）.P50组患者的理论住院天数和最佳矫正视力恢复时间分别为（3.65±0.92）d和（2.85±0.95）d,明显少于P200组的（4.90±0.81）d和（3.40±0.96）d,差异均有统计学意义（t=-6.444,P＜0.01;t=-2.584,P＜0.05）.P50组和P200组术眼术后并发症发生率分别为6.06％和25.00％,差异有统计学意义（x2=9.800,P＜0.05）,P50组术眼发生低眼压和浅前房的跟数少于P200组.结论 P50型和P200型Ex-PRESS引流器植入术对开角性青光眼的降眼压作用接近,与P200型Ex-PRESS引流器植入术比较,P50型Ex-PRESS引流器植入后早期患者的视力恢复快,并发症的发生率低.

Ex-press青光眼引流器治疗难治性青光眼12例临床研究

目的分析和探讨Ex-press青光眼引流器治疗难治性青光眼的治疗效果。方法将2013年1月~2016年1月我院应用Ex-press青光眼引流器治疗难治性青光眼12例(16眼)作为研究对象,观察患者术后的视力改善情况、眼压变化情况、并发症情况。结果术后1周,手术完全成功率93.75%(15眼);随访满1年,完全成功率50%(8眼),部分成功率25%(4眼),总成功率75%。12例难治性青光眼患者术后1个月、12个月的视力分别较术前显著提高,12例难治性青光眼患者术前平均眼压(51.3±9.1)mm Hg,术后1个月眼压为(12.34±3.22)mm Hg,术后12个月的眼压为(15.11±3.28)mm Hg,分别与术前比较差异有统计学意义(P<0.05)。术后发生前房积血1眼、一过性低眼压2眼、引流钉入口虹膜堵塞1眼、脉络膜脱离1眼。结论 Ex-press青光眼引流器治疗难治性青光眼可以明显改善患者术的视力,效的控制眼压、并发症少,值得推广和应用。

EX-PRESS引流钉植入术对POAG患者角膜内皮细胞及眼压的影响

目的:评价EX-PRESS引流钉植入术对原发性开角型青光眼(POAG)患者角膜内皮细胞及眼压的影响。方法:前瞻性临床研究。收集2016-05/2017-12在我院行EX-PRESS引流钉植入术的原发性开角型青光眼患者32例38眼,随访至术后24mo,观察中央、鼻侧、颞侧、上方、下方5个方位的角膜内皮细胞密度、眼压及最佳矫正视力情况,并观察前房深度及引流钉与虹膜、角膜的位置情况及手术疗效。结果:手术前后,本组患者5个方位的角膜内皮细胞密度和最佳矫正视力均无明显变化(P>0.05),但术后各时间点眼压均较术前明显降低(P<0.05)。术后24mo,本组患者手术完全成功率为66%,条件成功率为21%,失败率为13%,手术失败的主要原因为滤过泡包裹。本组患者术中和术后随访期间均未出现前房完全消失;术后1眼出现浅前房,5眼引流钉与虹膜面相贴,余32眼引流钉均位于虹膜与角膜内皮之间,位置良好。结论:EX-PRESS引流钉植入术对POAG患者角膜内皮细胞无明显影响,且能有效控制眼压,是治疗原发性开角型青光眼的安全有效的方法。