临床试验中中心效应的评价及处理方法

探讨多中心临床试验中, 中心效应的评价与处理方法, 采用Breslow-Day 检验对有效率的中心间差异进行评价, 采用CMH 方法对组间有效率及疗效等级进行分析, 采用logistic 回归方法对中心效应及有效率或疗效等级同时进行评价。结果提示,Breslow-Day 检验只能对有效率的中心间差异进行评价, 而不能对疗效等级的中心差异进行评价, CMH方法不能同时考虑其它协变量的影响。     

树脂板多点热成形数值模拟与实验研究

介绍了树脂板多点热成形的原理,选择具有良好综合性能的聚甲基丙烯酸甲酯(PMMA)和聚碳酸酯(PC)为研究对象,测试了其玻璃态转变温度。建立了树脂板多点热成形有限元模型,得到了球形面和鞍面件多点热成形的数值模拟结果,结果表明多点热成形技术可以实现PMMA、PC等树脂板三维曲面件的高精度成形。进行了PMMA板球面件和PC板鞍面件多点热成形实验,结果表明实验件的轮廓形状较好、壁厚分布较均匀,验证了树脂板多点热成形技术的可行性和实用性。对树脂板多点热成形实验结果和数值模拟结果进行对比分析,结果表明,在合理的偏差及测量误差范围内,实验结果与数值模拟结果吻合较好,验证了树脂板多点热成形数值模拟的正确性。     

组建小直径管坯生产基地探讨

论述了传统管坯的生产工艺以及采用水平连铸生产小直径管坯存在的问题,提出了采用连铸大方坯、CC-HDR生产小直径管坯的方案,论证了其在技术经济效益上优于用钢锭轧制的轧制坯。     

铁素体/马氏体双相钢的组织及性能

采用金相显微镜、SEM等试验方法,研究了中碳铁素体/马氏体双相钢的组织及性能。结果表明:在785~800℃淬火,起始组织为铁素体加珠光体的A型组织钢和起始组织为马氏体的B型组织钢随两相区淬火温度的升高强度升高;原始组织不同两相区淬火后钢的组织及性能不同,经785℃×30 min淬火的B型组织钢强度明显高于A型组织钢,经800℃×30 min淬火的B型组织钢伸长率和断面收缩率高于A型组织钢;785℃保温10 min淬火的B型组织钢相比于A型组织钢奥氏体化过程加速,钢的强度及塑性均好于A型组织钢;两相区淬火具有双相组织的钢具有连续屈服和快速应变硬化现象及低的屈强比,785℃×30 min两相区处理的钢与调质处理的钢相比塑性低但强度明显提高,785℃×10 min两相区处理的B型组织钢强度略低于调质钢,但塑性略有增加。     

一种新型振动下料机的PLC控制

在分析了新型振动下料机采用继电器－接触器控制方式存在不足的基础上，指出了对其进行PLC控制的必要性。分析了该振动下料机的基本构成及工作原理，建立了相应的液压系统。针对下料机正常工作对控制系统要求，确定了PLC的输入量及输出量，建立了PLC控制的硬件接线图，编制了相应的梯形图控制软件。大量实验验证了该控制方案的可行性和实用性。     

板材冲压自动拆垛上料技术

介绍了在板材冲压加工中，板材上下料机构的结构种类、性能和应用特点。     

The Influence of Thermomechanical Treatment of TRIP Steel on its Final Microstructure

Higher demands are currently being made on material properties and their combinations, for example, high strength steel with good cold formability. With increasing strength, material formability generally worsens, but with some kinds of steels, for example, with TRIP steel, it is possible to obtain an excellent combination of strength and ductility. However, these materials are interesting not only for use as sheets but also for other applications. Semi-products with thin walls represent the best way of further extending TRIP steels into the bulk forming area. This trend supposes that suitable technological conditions will be found and the process for a chosen production procedure will be optimized. The model optimization of the process for TMT with incremental deformations was experimentally carried out on a thermomechanical simulating machine. Microstructures obtained by the model treatment were analyzed by means of optical and electron microscopy.     

Viscosity model for pure gases at atmospheric conditions

The production processes for petroleum gases use a broad range of simulation packages to reduce the capital, time, and cost associated with actual recovery and pipeline transportation. The viscosity model is an important component of these packages. In this study, two simple-to-use empirical models are presented for predicting the viscosity of petroleum gases: the three-parameter Yaws equation; and the correlation of Miadonye-Clyburn. New values were obtained for the constants in Yaws’ equation for various hydrocarbon gases. Alternatively, the Yaws equation has been extended to cover nonhydrocarbon gases, some for the first time, and new values were derived for the constants for these gases. The results obtained with the new constants were compared with the viscosity predictions from both the Yaws and the Miadonye-Clyburn correlations. For four petroleum gases and two nonhydrocarbon gases at temperatures from 100 to 1500 K, the models gave viscosity predictions with overall average absolute deviations of 0.30 and 0.75% for the Yaws correlation with new constants, and 1.17 and 2.7% for the Miadonye-Clyburn correlation for viscosity predictions based on one viscosity value. Both models are simple to incorporate in design and simulation packages, and are accurate within the limits of experimental errors for the viscosities of petroleum gases.     

Self-assembling molecules as corrosion inhibitors for 1050 aluminum

Whether it contains hexavalent chromium, chromium (VI), or simply Cr(VI), chromating has been largely used for surface preparation of aluminum aimed at corrosion protection due to its effectiveness and easy application. The most used among these processes are those that contain toxic and carcinogenic substances, which generate environmental backlash concerning the disposal of used baths with toxic elements. The high costs involved in the treatment of the disposal solutions prior to being discarded, besides the increasing restrictions concerning the environment, have encouraged research in the search for alternatives with lower toxicities than chromating processes but with high effectiveness for corrosion protection. Surface treatments with alkane diphosphonate molecules (ADM) have been investigated as potential substitutes for chromating. However, their effectiveness in the corrosion protection of aluminum alloys still needs further investigation. In the present study, the corrosion resistance of 1050 aluminum with various surface treatments was investigated by electrochemical techniques and salt spray testing. The corrosion performance of 1050 aluminum samples with a surface treatment that consisted of immersion in ADM was compared with that of the same alloy chromated by immersion in baths of Cr(III) or Cr(VI). The results showed that surface treatment with ADM was effective on samples that had been exposed to boiling water for oxide growth prior to treatment with ADM. The results also showed the superior corrosion performance for samples with the oxide-hydroxide + ADM surface treatment compared to those with both chromating treatments, either with Cr(III) or with Cr(VI). Cr(III) chromating treatment also provided better corrosion performance than chromating with Cr(VI), suggesting that both surface treatments (oxide-hydroxide + ADM and Cr(III)) are potential candidates for substitution for Cr(VI)-containing processes. However, for effective corrosion protection, the ADM treatment has to be carried out on surfaces previously exposed to treatments that favor oxide growth.     

适于镀锌钢板激光焊接的CO2激光切割

研究适合于裁焊板生产的板坯切割的技术方案，重点讨论了CO2激光切割。采用氮气辅助激光切割，氧气辅助激光切割，铣切和普通剪切方法进行了镀锌钢板的切割。研究表明，氮气辅助CO激光切割方正度较好，切口质量符合裁焊板拼接间隙小于0．1mm的要求。激光切割时，由于热影响范围小，镀锌钢板切口边缘镀锌层烧损范围小，整个切缝无宏观残余形变。氮气辅助CO2激光切割具有切割速度快，质量好的优点，适合于进行裁焊板的板坯切割。     

Application of the R-functions method to visioplastic analysis in metal forming

This study is concerned with visioplastic analysis of metal forming processes with help of the R-functions method. The method in conjunction with the flow function and stress function methods is used to construct kinematically admissible velocity fields and statically admissible stress fields for regions with complicated boundary shapes. Application of such fields for approximation of the experimentally obtained information allows to determine mechanically correct strain and stress distribution for steady and non-steady-state problems in axisymmetric and plane-strain metal forming processes.     

Inner and outer pressure forming of nickel based super-alloy thin-walled part with variable diameter sections

A novel forming method of nickel based super-alloy thin-walled part with variable diameter sections was proposed by using inner and outer pressure with the visco-elasto-plastic pressure-carrying medium at room temperature, and the principle of the method was provided. Experiments and FE simulations were carried out to analyze the deformation characteristics for the part with larger variable diameter ratio （35%）. The results show that visco-elasto-plastic pressure-carrying medium can meet the requirements of the room-temperature deformation condition for nickel based super-alloy sheet. The inner and outer pressure forming with the visco-elasto-plastic pressure-carrying medium can meet the requirements of dimensional accuracy for the thin-walled part with variable diameter sections. The thinning of wall-thickness is less than 4%. This method provides a new approach for near-net shape forming of nickel based super-alloy thin-walled parts with variable diameter sections.     

大型龙门式五轴加工中心仿真系统在UGNX7．5上的建立和应用

对数控编程计算机碰撞仿真加工系统进行分析和研究。通过在UGNX7．5中进行二次开发,研究了在UGNX7．5中开发五轴数控机床切削仿真加工环境,并以T35龙门五轴联动加工中心为例,详细介绍了在UGNX7．5中对大型龙门结构的数控五轴加工中心机床的切削仿真加工系统进行开发的方法与过程,开发了T35在UGNX7．5中的碰撞仿真加工系统。T35机床的仿真系统,对在其上加工的复杂零件刀具路径及机床运动可以进行精确的模拟加工,真实地反映和再现实际的加工过程,大大减少了机床的试切时间,提高了CAM程序的安全性和可靠性,降低了产品研发的成本。     

固溶处理对316H不锈钢中厚板晶粒度的影响

将300 mm厚316H不锈钢电渣锭锻造坯轧制成50 mm厚钢板,选取晶粒度为5、6、7和9级的原始晶粒,进行了1000 ℃固溶60 min和120 min、1050 ℃固溶30 min和60 min、1100 ℃固溶20、40和60 min。结果表明,获得晶粒均匀的完全再结晶热轧态组织是获得晶粒均匀固溶态组织的必要条件,热轧态混晶或者有部分再结晶的组织,通过固溶处理不能获得晶粒均匀的固溶态组织。热轧态晶粒均匀的钢板,通过合理匹配固溶温度与时间,晶粒能够均匀长大,厚度为20~50 mm的316H不锈钢中厚板合理的固溶制度为1050 ℃保温30~60 min,1100 ℃保温20~40 min,可根据热轧态组织及用户需求调整固溶时间获得理想的晶粒度级别。     

Size effects on flow stress of C3602 in cylinder compression with different lubricants

Micro parts are more difficult to be formed than macro parts because of size effects. The size effects on the flow stress of copper alloy C3602 with different lubricants were studied. Specimens were heat treated at 350°C for 1 h and 700°C for 3 h in nitrogen atmosphere, respectively. The initial diameters of the specimens were varied from 5 to 1 mm with a height-to-diameter ratio h ₀/D ₀ = 1.5. Cylinder compression was carried out in the lubrication condition with talc powder, without lubricant, with petroleum jelly, and with vegetable oil. The experiment was carried out at room temperature on a universal testing machine INSTRON 5569 with a strain rate of $ \dot \varepsilon $ \dot \varepsilon = 0.0025 /s. The results show that with the same lubricant, the yield strength decreases with a decrease in specimen size for the specimens annealed at 350°C for 1 h; however, it increases with a decrease in specimen size for the specimens annealed at 700°C for 3 h. The yield strength decreases with an increase in grain size. The influences of lubricants on yield strength become larger with miniaturization of the specimens.     

异步轧制AZ31镁合金板材在退火处理中的组织性能演变

研究了异步轧制AZ31镁合金板材经200～350 ℃退火30～120 min后的组织性能演化.在试验条件下,AZ31镁合金板材在200 ℃退火时,随保温时间的延长,组织的均匀程度和晶粒尺寸没有明显变化;在300 ℃退火30 min,基本完成再结晶过程,获得均匀细小的等轴晶,保温时间增加到60 min时,部分再结晶晶粒长大;在350 ℃退火30 min和60 min,均在完成再结晶的同时晶粒长大;300 ℃退火30 min后AZ31镁合金板材的综合性能较好,室温抗拉强度为315 MPa,伸长率为33.0%.     

楔块锁模空心枝形件闭式挤压模具设计

因空心枝形件形状所致,其挤压成形无法采用上模插入下模的闭式锻模结构.本文论述了空心枝形件闭式挤压工艺,给出了空心枝形件闭式挤压新型模具结构和设计要点.该模具采用楔块锁紧上凹模与下凹模对合结构,锻件在两个凹模和两个凸模形成的封闭模腔中挤压成形,生产的锻件无飞边.     

An orthotropic ductile damage model for visco-plastic materials

Numerical modelling of bulk forming processes has to identify the conditions that may result in unsatisfactory products. In ductile materials, damage may occur with the micro void nucleation at the site of second phase particles and inclusions in the plastic or visco-plastic matrix and then with the micro void growth. In this work an isotropic ductile damage model is extended to load cases with successive tensile and compressive steps and with pure deviatoric stress state. The constitutive equations satisfy the Clausius-Duhem inequality for negative or positive voids volume fraction rate. The constitutive parameters are identified with the Rice and Tracey model modified for a sphere initially filled with a soft or a hard inclusion. Axisymmetric geometries are considered for remote strain fields without distortion. A plane cell and a 3D unit cell are analysed numerically for the deviatoric strain state and various combined deviatoric and volumetric deformations.     

Modelling immersion corrosion of structural steels in natural fresh and brackish waters

The multi-phase mean-value model previously proposed for modelling the marine immersion corrosion of low carbon and low alloy structural steels is examined for application to fresh and brackish waters. Use is made of field data for brackish and fresh waters available in the literature, supplemented with data or estimates for water temperature, pH, hardness and nutrient levels. It is shown that the data exhibits consistency with the model and that it is a function of average water temperature. Corrosion in brackish and fresh waters corrosion depends on water hardness, pH and nutrient levels, with higher pH levels and lower water hardness associated with higher aerobic levels of corrosion but these are not significant for anaerobic corrosion. In the anaerobic phases 3 and 4 of the model, the available data and associated trends are interpreted as showing that elevated levels of nutrients produce higher rates of corrosion. Conversely, these phases showed very low rates of corrosion for fresh waters with very low nutrient levels. Consistent with basic corrosion theory and with laboratory observations, salinity by itself is not a clear distinguishing characteristic. The model provides a new approach to interpreting the available data for corrosion in fresh and brackish waters. It permits plausible explanations for previous apparently inconsistent observations for corrosion in brackish waters. Finally, it reinforces the need for full and detailed reporting of corrosion testing programs, including details of precise timing, location, orientation and environmental conditions including means and variations in water temperatures, DO, salinity, pH, water hardness, carbonates and various nutrients.     

Embedded atom potential calculation of the Al–Pb immiscible alloy system

Embedded atom method (EAM) potentials for the Al–Pb immiscible alloy system were calculated along with some properties for f.c.c. Al, Pb and thermodynamic data for Al–Pb alloys. The calculated results for Al and Pb pure metals are in general agreement with the experimental values. The heat of solution for Pb in Al with our Al–Pb cross-potential was calculated and the result is close to that of ab initio calculated value. With the calculated heat of solution the solubility for Pb in Al after mechanical alloying was also calculated and the result is about 0.19 at.% Pb.