金属反向挤压技术及其应用（3）

３ 反挤压的工艺特点３．１反向挤压的金属流动特点 如前所述,反向挤压时金属的变形区紧靠模面,高度＜０．３Ｄ筒。在变形后面金属不产生任何变形。变形区的形状近拟于圆筒状,筒底曲率半径很大,近似于直线。模面金属死区很薄．很难阻碍铸锭表面金属流入制品表面。 试验研究和测试分析表明,反向挤压时金属流动均匀,制品沿纵向和横向的变形比正向挤压时均匀,从而其组织和力学性能也比较均匀。因铸锭边部无剧烈的摩擦而产生的剪切变形,因此不易出现粗晶环缺陷。因死区较薄,铸锭表面可能直接流入制品表面,因而为了保证制品表面质量,…     

金属反向挤压技术及其应用（4）

３．４ 挤压工序分析及工艺参数的确定 （１）铸锭镦粗与梯度加热 在挤压筒中铸锭的两端部镦粗而中央部位未镦粗，从而使空气容易封入．这种状态必须避免。由于均热铸锭是可以从两端面镦粗的，所以当铸锭进行梯度加热使挤压模侧温度高时．有可能从一个方向进行镦粗。 梯度加热的效果计算 ａ．梯度加热的屈服应力分布 ｂ．屈服条件式 ｃ．轴向平衡－挤压垫侧） ｄ．中立位置 上述数值计算例示于图１７。因为铸锭的镦粗条件为σｒ＝σｙ，所以明确了在本例中只能是从一侧端面进行镦粗。如果减少铸锭长度，利用增加梯度加热程度的方法将使情况…     

挤压和锻造工艺对铍青铜棒材组织和性能的影响

文章以铍青铜半连续铸锭为原料,研究了挤压、锻造及锻造＋挤压工艺对铍青铜棒材组织和性能的影响。研究结果表明：由于挤压时铸锭内外层变形不均匀,导致沿断面上棒材的组织不均匀;在加工率相同条件下,锻造棒材的微观组织比挤压组织均匀,抗拉强度比挤压工艺的略低,但延伸率较高,而锻造＋挤压工艺对棒材组织改善最为明显,微观组织细小均匀,综合力学性能和内部组织最好。     

挤压工艺与模具结构对6005A轨道型材粗晶的影响

采用金相显微组织分析,研究了挤压工艺参数和模具结构对6005A轨道交通型材粗晶层厚度的影响。研究结果表明：适当降低挤压铸棒温度和挤压速度,即当铸锭温度为460～480℃、挤压速度为1.5～1.7 m/min时,能够减小粗晶层厚度;通过优化模具结构,增加前室面积并使前室与自由端形成一定角度,增大自由端供铝量,减小摩擦阻力和变形程度,能够有效地改善型材自由端粗晶层厚度。     

挤压温度和挤压比对6063铝合金导热性能的影响

研究了挤压温度和挤压比对6063铝合金组织及导热性能的影响。结果表明：通过挤压能有效地改善该合金的组织,使得强化相Mg2 Si均匀弥散分布在α-Al基体上。随着挤压温度的增大,材料的热导率下降。当挤压比小于50时,材料的热导率随着挤压比的增大而增大;当挤压比大于50时,材料热导率下降。当挤压比为50,挤压温度为380℃时,材料有最大热导率221.2 W/（m.K）。     

GH625合金管材热挤压成形工艺及组织演变的研究

利用卧式挤压机对GH625合金进行了管材热挤压试验,研究了挤压温度和挤压比对GH625合金管材挤压过程中的力能参数及挤压后管材不同部位的显微组织的影响.结果表明,随着挤压温度的降低和挤压比的升高,最大挤压力逐渐升高.管坯在固定挤压速度40 mm·s-1,预热温度为1150～1200℃和挤压比为3.46～4.10的条件下,可成功挤压出3种规格的GH625合金管材;挤压后的管材由于在挤压过程中发生了动态再结晶组织明显细化,管坯横向组织为等轴的动态再结晶晶粒和原始晶粒组成,纵向组织则由等轴的动态再结晶晶粒及被拉长的原始晶粒组成,呈条带状组织;挤压后管材的外壁、中心、内壁与管材的头部、中部与尾部在热挤压变形过程中,由于变形不均匀发生了不同程度的再结晶,因而存在不同程度的混晶组织.为消除混晶组织,结合设备能力与GH625合金的变形特征,可通过提高坯料挤压的变形温度和挤压比来控制变形的均匀性,并通过切头,去尾和对管材内壁进行少量机加工的方法,可获得具有完全动态再结晶组织的挤压管材.     

热挤压对FGH96镍基粉末高温合金微观组织的影响

研究了热挤压温度、挤压比、挤压速度、挤压前预处理对FGH96镍基粉末高温合金微观组织的影响规律,确定了获得晶粒尺寸小于10 μm的超塑性细晶组织的热挤压方法。研究结果表明,热等静压后FGH96合金发生了再结晶,实现了粉末的完全致密化成形,但晶粒大小极不均匀,且存在明显的原始颗粒边界(PPB)缺陷。采用热挤压前预处理工艺在确保合金晶粒不长大的同时,又可使γ'相粗化,显著降低热挤压变形抗力。随着挤压温度的升高,合金晶粒尺寸呈长大趋势。挤压温度为1 080 ℃时,获得平均晶粒小于10 μm的完全再结晶超塑性组织,挤压温度继续升高,晶粒尺寸将明显长大。随着挤压比的增大,挤压载荷明显增大,采用大于6∶1的挤压比,有利于获得平均晶粒小于10 μm的完全再结晶超塑性组织。载荷随热挤压速度的升高而增大,在保证合金组织为细晶的条件下,应尽量选择较低的挤压速度。由于在热挤压过程中合金已发生了完全的动态再结晶,未观察到明显的取向,力学性能测试结果也表明沿着挤压方向和垂直于挤压方向的性能相当,说明不同挤压方向的微织构对性能没有明显影响。     

6063铝合金型材挤压堵模的成因及其对策

从6063铝合金铸锭、挤压工艺条件、模具、金属的不均匀变形等方面分析了型材挤压时发生堵模现象的原因,提出了具体防止措施.     

高体积分数SiCp/Al复合材料杯形件高温反挤压成形

将无压浸渗制备出的高体积分数SiCp/Al复合材料,通过高温反挤压方式成形杯形件.研究了在高温反挤压过程中复合材料的流变规律,利用扫描电镜(SEM)观察分析了高温反挤压参数对杯形件组织的影响.结果表明:在基体熔点以上,高体积分数SiCp/Al复合材料呈黏流体状态,颗粒与基体形成固-液混合体;高体积分数SiCp/Al复合材料高温反挤压变形后,基体仍保持连续,SiC颗粒在压力作用下发生转动、重排,部分颗粒破碎,颗粒分布均匀性较好;当变形温度较低、挤压速度较大时,颗粒易破碎,SiCp/Al复合材料杯形件内部颗粒尺寸不均匀,杯形件内角处颗粒尺寸较小;当变形温度较高、挤压速度较小时,杯形件内部颗粒尺寸均匀.     

工艺参数对IN690合金管材热挤压出口温度的影响

结合等温压缩实验获得的IN690合金本构关系,建立了该合金管热挤压过程的有限元模型,该模型考虑了坯料与模具的热传导、对流换热及摩擦功与塑性功的热转换.模拟结果表明:坯料在变形区附近温度开始升高,进入变形区内急剧升高,且在模孔出口靠近芯棒处温度达到最高,芯棒附近的温度大于挤压筒附近的温度;填充挤压阶段结束时出现最大温升.分析得到了工艺参数对出口温度的影响规律:挤压速度越大,出口温度越高,速度过慢将会使出口温度下降严重;坯料预热温度越高,出口温升越小;当摩擦因数小于0.04时,摩擦因数对出口温度影响很小,但摩擦因数大于0.1时出口温度明显升高.     

Performance appraisal for groups: Models and methods for assessing group processes and outcomes for development and evaluation.

This paper guides consulting psychologists in how to help managers and group leaders assess group members' reactions, behaviors, and performance. The results may be used for development in improving group performance and for evaluation in making decisions about group members' pay and assignments. Individual and group-level measures of conditions (pressures and opportunities), input, process, and outcomes are considered. The paper discusses who seeks group assessment, the multiple purposes of assessment, models of group process to guide assessment, what is assessed and when, methods for assessment, and who contributes to the assessment process. Implications for inculcating a culture of assessment and continuous learning within groups and organizations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Casual attributions for success and failure for psychiatric rehabilitees and college students

College students and psychiatric rehabilitees performed a manual dexterity task in which consistent success or failure was maipulated over four consecutive task trials. Contrasting predictions for the use of casual attributions (luck, task difficulty, effort, and ability) following Trial 1 and Trial 4 for the two populations were derived from Heider's balance theory and "naive theory of action". Consistent with native theory, students who succeeded and rehabilitees who succeeded used unstable attributions only college students who failed used stable attributions to account for these trial outcomes, whereas students who failed and rehabilitees who failed made significant changes in their attributional patterns from Trial 1 to Trial 4. Results are discussed regarding intervention with psychiatric rehabilitees and other groups with severe achievement difficulties.     

Framework for Competency and Capability Assessment for Resource Allocation

This paper proposes a decision process that engineering organizations can use to make human resource allocation decisions. This type of systematic approach will assist organizations in determining accurate predictions of their strengths and weaknesses and enable them to determine optimum resource allocations. In addition, identifying strategic core competencies followed by identification of organizational and individual capabilities necessary to fulfill the needs of these core competencies will optimize human resource allocations. The proposed framework can complement and improve on available methods for identifying sourcing strategies with a goal of “rightsizing” organizations. Assessment of organizational competencies and capabilities can provide the necessary rationale behind human resource allocation and outsourcing decisions. Using the proposed framework presented in this paper would, therefore, assist companies in optimizing human resource allocation decisions.     

Scales for sex experience for males and females.

Tested 83 male and 101 female unmarried undergraduates on scales containing a range of heterosexual experiences. 2 12-item scales, one for males and one for females, were developed. Coefficients of reproducibility were .97 for both males and females, and the rank-order correlation between the ordering of items in male and female scales was .95. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adrenocortical carcinoma: surgery and mitotane for treatment and steroid profiles for follow-up

Adrenocortical carcinoma (ACC) is a rare disease with a poor prognosis. It has been difficult to establish a strict treatment program for ACC, and better treatment alternatives and diagnostic tools must be sought. Even though surgery is the treatment of choice, the role of surgery in advanced disease has been questioned. Eighteen consecutive patients were treated at our unit over a 22-year period (1975-1997). All patients underwent surgery and were followed by our protocol, which includes urinary steroid profiles, clinical examinations, analysis of steroid hormones, and radiologic investigations. Twelve patients received mitotane with drug concentration measurements to deliver an effective, nontoxic dose. The median duration of mitotane treatment was 12 months. Few side effects were observed. Four patients with low-stage tumors underwent second-look operations with no pathologic findings. Five patients were subjected to repeat operations, and the mean duration of the disease-free interval before repeat surgery for these patients was 59 months. There was a significant positive correlation between the disease-free interval and the observed survival after repeat surgery. Eleven patients with intentionally curative surgery had their urinary steroid profiles tested several times postoperatively. For five patients preoperative urine samples were also available. Steroid profiles indicated recurrent disease despite normal radiologic findings in two of these five patients. The follow-up ranged from 6 weeks to 24 years. The predicted 5-year survival was 58% according to the Kaplan-Meier method. We conclude that monitoring serum concentrations of mitotane makes long-term treatment possible with few side effects; steroid profile analysis can be used for early detection of tumor recurrence; and repeat surgery for recurrence is of value for patients with long disease-free intervals.     

Rationale for cigarette smoking and for mentholation preference in cocaine- and nicotine-dependent outpatients

The effects of sauna exposure on sperm movement characteristics and other semen parameters were evaluated using computer-assisted sperm analysis (CASA). A significant (p < 0.01) decrease in average path velocity (VAP), curvilinear velocity (VCL) and amplitude of lateral head displacement (ALH) was found after exposure to sauna for 2 weeks. The altered parameters returned to their original values within 1 week after cessation of sauna exposure. Mean values for semen volume, sperm count, percentage motility, sperm morphology and sperm penetration assay (SPA) were not statistically different during and after sauna, when compared to the corresponding control values. The results suggest that increasing scrotal temperature by sauna causes a reversible decrease in sperm movement parameters.     

阳极精炼及浇铸的作业方式与金隆扩产方案的选择

结合世界上主要铜冶炼厂回转式阳极炉和圆盘浇铸的作业方式,分析了不同作业方式在金隆扩产改造中应用的可行性。根据金隆扩产的产量规模、目前的作业水平、将来操作改善的可能,对各种改造方案进行了论证,提出了优化的改造方案。根据阳极精炼和圆盘浇铸作业技术发展趋势的分析,提出了未来金隆阳极精炼和圆盘浇铸的优化作业方式,并指出了达到优化作业目标需要解决的主要问题。     

卷取机转动惯量测量计算的新方法

在铝带（ 箔） 冷轧机等设备的卷取机张力控制系统中,动态补偿环节需要准确的转动惯量,本文介绍一种采用最小二乘方法计算卷取或开卷机转动惯量的新方法。这种方法能在很大程度上消除因手工绘制曲线和电机空载电流偏小等因素引起的转动惯量测量计算误差。