铁路车辆用LZ50钢车轴裂纹的形成机理

铁路车辆用车轴经锻造及机械加工后,在其表面常发现纵向裂纹,造成车轴报废。采用光学显微镜、扫描电子显微镜、能谱仪、维氏硬度计等分析手段,对LZ50钢车轴表面裂纹形成的机理进行了研究。发现车轴微裂纹的形成可有两种机理:一是车轴钢坯中的显微缩松在锻造时被轧扁但未完全弥合所致;二是由车轴钢坯中的氧化铝类夹杂物在锻造时形成裂纹源,导致车轴微观组织脆性穿晶断裂。     

Brain Tumor Auto-Segmentation on Multimodal Imaging Modalities Using Deep Neural Network

Due to the difficulties of brain tumor segmentation, this paper proposes a strategy for extracting brain tumors from three-dimensional Magnetic Resonance Image (MRI) and Computed Tomography (CT) scans utilizing 3D U-Net Design and ResNet50, taken after by conventional classification strategies. In this inquire, the ResNet50 picked up accuracy with 98.96%, and the 3D U-Net scored 97.99% among the different methods of deep learning. It is to be mentioned that traditional Convolutional Neural Network (CNN) gives 97.90% accuracy on top of the 3D MRI. In expansion, the image fusion approach combines the multimodal images and makes a fused image to extricate more highlights from the medical images. Other than that, we have identified the loss function by utilizing several dice measurements approach and received Dice Result on top of a specific test case. The average mean score of dice coefficient and soft dice loss for three test cases was 0.0980. At the same time, for two test cases, the sensitivity and specification were recorded to be 0.0211 and 0.5867 using patch level predictions. On the other hand, a software integration pipeline was integrated to deploy the concentrated model into the webserver for accessing it from the software system using the Representational state transfer (REST) API. Eventually, the suggested models were validated through the Area Under the Curve–Receiver Characteristic Operator (AUC–ROC) curve and Confusion Matrix and compared with the existing research articles to understand the underlying problem. Through Comparative Analysis, we have extracted meaningful insights regarding brain tumour segmentation and figured out potential gaps. Nevertheless, the proposed model can be adjustable in daily life and the healthcare domain to identify the infected regions and cancer of the brain through various imaging modalities.     

翅片管换热器过冷管设计对系统性能影响研究

试验对比研究在翅片管换热器底部设置1根U形管过冷、2根并联U形管过冷、2根串联U形管过冷的过冷效果,测试数据表明用2根U形管串联进行过冷的效果最好。当把2根铜管串联用于过冷时,对R22制冷剂在B工况测试条件下,与没有过冷相比,过冷度增加了1．1℃,能效比高出0．33W／W,提高了8．25％;对R410A制冷剂在B工况测试条件下,与没有过冷相比,过冷度增加了2．0℃,能效比高出0．10W／W,提高了2．69％。     

钎缝间隙对TC4与Ti3Al-Nb合金钎焊接头组织的影响

采用50Ti-20Zr-20Ni-10Cu粉末钎料对Ti3Al-Nb(Ti-13Al-24Nb)(质量分数)合金与TC4合金(Ti-6Al-4V)进行真空钎焊,通过SEM、EDS电子探针及拉伸试验,研究不同钎缝间隙的钎焊接头的显微组织及性能特征。结果表明,钎缝间隙对钎焊接头的组织及性能有较大影响,当钎缝间隙增大时,钎焊接头的组织变得复杂,在接头中既形成了共晶组织又形成了化合物带,这种组织特征会显著降低接头的强度。     

脉冲激光沉积Ti50Ni36Cu14薄膜的成分均匀性

采用脉冲激光沉积(PLD)技术制备了Ti50Ni36Cu14合金薄膜.研究表明,PLD合金薄膜的成分与沉积距离(基片/靶间距)、激光脉冲频率有较大关系.当沉积距离(D)为20～30mm时,可获得成分均匀稳定的合金薄膜;当其它条件相同,激光脉冲频率(F)为5Hz时,合金薄膜与靶成分更为接近.采用PLD技术制备的Ti50Ni36Cu14合金薄膜成分均匀性较好,同时与磁控溅射薄膜相比PLD薄膜的平均成分更加接近靶体.采用本工艺获得的Ti50Ni36Cu14薄膜的平均成分为47.53at.%Ti、38.90 at.% Ni和13.57 at.%Cu.     

Cytotoxicity of titanium dioxide nanoparticles differs in four liver cells from human and rat

Titanium dioxide (TiO₂) nanoparticles (NPs) are the important nanoscale components of composites. Although TiO₂ NPs and their related nanocomposites have been widely used in industrial and medical applications, the adverse effects of TiO₂ nanomaterials have not been well studied. Here, we investigated the cytotoxicity of TiO₂ NPs in vitro using four liver cell lines: human hepatocellular carcinoma cell line (SMMC-7721), human liver cell line (HL-7702), rat hepatocarcinoma cell line (CBRH-7919) and rat liver cell line (BRL-3A). We checked cell viability, cell morphology, and the levels of reactive oxygen species (ROS) and glutathione (GSH) after TiO₂ exposure at varying concentrations (0.1–100 μg/mL) and different exposure periods of time (12–48 h). Compared to the NP-free control, all four cell lines exposed to TiO₂ NPs showed cytotoxicity in a dosage-dependent and time-dependent manner, which was associated with the changes of cell viability and cell morphology, increased intercellular ROS levels, and decreased intracellular GSH levels. Further, we observed that carcinomatous liver cells and human liver cells exhibited more tolerance to TiO₂ NPs exposure for 24 h, compared to normal liver cells and rat liver cells, respectively. The results indicate that the in vitro cytotoxicity induced by NPs should be assessed with great caution before the use of nanocomposites and that there is a need to standardize the cytotoxicity testing procedure of nanoscale components in composites when using different cell lines.     

基于Elber型方程的随机疲劳长裂纹扩展概率模型

拓展有效应力强度因子范围的概念为因子范围与门槛值之差,导出了Elber型方程并建立了他的随机疲劳长裂纹扩展概率模型。同时考虑了数据分散性规律和试样数量两方面对概率的影响。模型分别由存活概率、置信度和联合存活概率—置信度下的裂纹扩展率—应力强度因子范围关系曲线组成。在因子范围服从对数正态分布下,应用线性回归技术和极大似然法建立了模型参数的测定方法。通过对LZ50车轴钢试验数据的分析,考察了模型的效果,揭示出模型对数据的拟合精度良好,能合理地预测中高应力强度因子范围的长裂纹稳定扩展和低应力强度因子范围趋于门槛值的概率规律。     

RE2B轴磁粉探伤产生废品的原因分析

综合分析了LZ50提速车轴坯的磁探裂纹的原因,并提出解决措施和方案。     

CSP热轧50CrV4带钢普通球化退火工艺

系统研究了球化退火温度及保温时间对CSP热轧50CrV4带钢组织与性能的影响。研究结果表明:在730~770℃的温度范围内球化退火4~18h时,随着退火温度的提高,碳化物粒径先缓慢增大后迅速降低,球化率逐渐增大;随着保温时间的延长,碳化物粒径逐渐增大,730及750℃时,球化率先增大后降低;770℃时球化率逐渐降低。当退火温度为770℃,保温时间为4h时,球化效果最佳,球化率为90.6%,碳化物平均粒径为0.29μm,硬度为202.8HV。