PMMA“鸟巢”工艺品注塑工艺分析与模具设计

针对以中国国家体育场“鸟巢”为原型设计的聚甲基丙烯酸甲酯工艺品,通过塑件结构及注塑工艺分析,设计了一套具有瓣块式收缩型芯与摆钩式二次分型机构的注塑模具。该模具可以顺利实现“鸟巢”工艺品的注塑与脱模,并为其他中小型中空塑件的模具设计提供一套高效、切实可行的设计方案。     

脱β层厚度对CVD涂层硬质合金性能的影响

通过对WC-TiC-(Ta,Nb)C-Co硬质合金在1 300～1 380℃的渗氮气氛处理和随后的脱N烧结制得了不同脱β层厚度的合金基体,通过化学气相沉积(CVD)工艺制成从内到外依次为TiN/MT-TiCN/Al2O3/TiN的涂层硬质合金。采用光学显微镜、扫描电镜和能谱仪、抗弯(TRS)和切削试验对合金基体涂层前后的组织特征与性能进行了研究。结果表明,随着脱β层厚度的增加,试样涂层前后的抗弯强度均增加,在厚度达到20μm以上时,增加不明显。CVD涂层硬质合金可转位刀片的抗冲击性能也有相应的规律,而耐磨性则基本上保持一致。     

手机天线注射模设计

介绍了手机天线的模具设计和成形工艺,对于既要保持产品原有品质性能,又有外观要求的此类模具设计,提出了嵌件设计和浇口设置方法及与立式注塑机配套使用的特殊模具结构。经实际验证,可进行批量生产,生产效率大大提高,质量稳定可靠,符合设计要求。     

带金属嵌件的汽车接插件注塑成型工艺分析

采用Moldflow软件对产品进行注塑分析,以得到带金属嵌件的汽车接插件最佳注塑工艺条件.在分析中,首先得到能充填满型腔的工艺参数,然后利用正交试验研究熔体温度、模具温度、保压控制、充填速度和速度/压力切换点等工艺参数对制件质量指标如注射压力、缩痕深度、最大流动前沿温度、冷却时间、顶出时的体积收缩率、零件质量（重量）的影响,发现熔体温度和速度/压力切换点两个因素对塑件质量影响最大.最后,在最优工艺条件下,塑件的翘曲变形在充许的范围内.     

螺旋插入件式管状换热器在大型加热炉上的应用

设计、制造并使用换热效率高、使用寿命长的换热器是提高加热炉燃烧效率、燃烧稳定性、加热炉节能效果的重要措施。本文将分析、讲述螺旋插入件式管状换热器的换热和设备工作原理以及在攀钢热轧板厂加热炉上的使用情况。     

插入件换热器传热系数的数值分析

对插入件换热器的传热面积、传热系数及其结构尺寸进行了数值计算,分析了各初始条件对传热系数的影响并绘制了曲线.模拟结果表明,在其他初始条件不变时,传热系数与各初始条件呈线性,指数或幂函数关系.     

The Influence of Intravaginal Gestagens Treatment on the Morphological Features and Endometrial Steroid Hormone Receptors Content during Anestrus Type II in Dairy Cattle

Background: Gestagens are the most widely used therapy in anestrus type II. The aim of this research is to evaluate the effectiveness of the vaginal progesterone inserts therapy in anestrus type II in cows. Methods: The study was conducted on 33 cows. Progesterone (PR) and estrogen (ER) receptors expression in endometrium was assessed on a molecular level based on mRNA tissue expression. Additionally, blood 17ß-estradiol and progesterone levels were evaluated. Results: A decrease in mRNA expression of A and B PR and ER α was noted in treated and untreated animals. In the treated group, an increase of ERß mRNA expression was observed, while a decreased was found in untreated animals. There was increased PR, ERα and ß expression in endometrial tissue in treated cows, and decreased expression of these factors in untreated cows. In the treated group, recurrence of ovarian cyclicity was noted in 52% of animals and pregnancy was obtained in 34.8% of them, while in the untreated group, recurrence did not occur. In the control group, spontaneous recurrence of ovarian cyclicity was not observed. An increase of PR expression was correlated with increased proliferation of endometrial cells. Conclusions: It seems likely that the endometrium is well developed and ready for placentation after removing the exogenous source of progesterone and preventing the recurrence of cyclicity of ovaries.     

Rapid manufacturing of plastic aspheric optical lens

This paper presents a new process to rapid manufacture the plastic aspheric optical lens. A bridge tooling was developed for fabricating the mold inserts of an aspheric lens using silicone rubber materials. Epoxy‐based composites were used to fabricate mold inserts of an aspheric optical lens. Z‐axis shrinkage error was investigated after plastic injection molding and compensated to the designed aspheric lens. In comparison with conventional method for fabricating a pair of mold inserts of a new plastic lens, a cost reduction of 75.02% and a time saving of 77.78% can be achieved. The deformation improvement percentage is about 92.48%. This technology can be used to compensate the z‐axis deformation efficiently due to shrinkage error of plastics in molding aspheric lens. Aspheric optical lens can be produced rapidly and cost‐effectively.     

Characterisation and Assessment of Load Response, Failure and Fatigue Phenomena in Sandwich Structures Induced by Localised Effects: A Review

Abstract:  The objective of the paper is to provide an overview of the mechanical effects, which determine the occurrence and severity of localised bending effects in sandwich structures, and to provide a survey of the available structural sandwich models, with special emphasis on their ability to describe local bending effects. The presentation includes a brief survey of the various structural models, including classical, 'first-order shear', 'high-order' and continuum mechanics-based models. Moreover, the paper focuses on and addresses the experimental characterisation and assessment of local effects in sandwich structures based on realistic engineering practice, examples including sandwich panels with core materials of different stiffness (core junctions), sandwich plates with inserts and junctions between sandwich panels of different curvature. The issues of general load response (global and local) as well as failure and fatigue of such sandwich structures subjected to out-of-plane and in-plane loads are discussed in some detail, with the inclusion of recent theoretical and experimental results.