Al2O3陶瓷表面加工残余应力的研究

讨论了四种不同的工艺对Al2O3-TiC复相陶瓷进行表面处理,以改变其表面残余应力分布状态。利用扫描电子显嫩镜(SEM)观察试样的表面形貌;采用非破坏性的X射线衍射sin^2ψ法,对不同工艺条件下的残余应力进行了测试研究。结果表明：在本研究条件下,经平面磨处理后．试样表面赴于拉应力状态;经工具磨处理后,试样表面处于压应力状态;经抛光处理后,残余应力值均有所减小。这对于提高陶瓷材料的强度和耐磨性具有重要的意义。     

Experimental Investigation of White Layer Thickness on EDM Processed Silicon Steel Using ANFIS Approach

Since the white layer thickness influences the surface quality of the machined specimens using electrical discharge machining process, the prediction of su     

钢制压力容器焊接残余应力测试分析

应用小孔释放法对系列钢制压力容器手弧焊接接头的焊接残余应力进行测试 ,讨论了焊接残余应力的分布规律及其相关影响因素 ,对加载法消除焊接残余应力的效果进行了初步的验证。结果表明 ,焊接接头的应力不均匀性和不确定性是影响钢制压力容器安全性的关键 ,采用加载法可以有效地改善这种非均匀应力分布状况。     

螺旋钢管残余应力分析研究

螺旋钢管因其制造工艺成熟、成本较低,是流体输送管道主要使用的一种钢管。目前普遍采用连续成型,埋弧焊接的方法制造螺旋钢管。成型方法有内承式和外抱式两种。由于这两种成型方法一般都是不足量成型,钢管制造后有很大的残余应力,降低了钢管的承压能力。经过理论分析,给出了不足量成型时钢管的残余应力计算公式,并通过实际测量内承式成型的螺旋钢管的残余应力,验证了本文给出的残余应力计算公式的正确性,对螺旋钢管的制造与应用具有指导作用。     

Residual Stress Analysis of Commercial Float Glass Using Digital Photoelasticity

Residual stresses are generated in float glass at the time of manufacturing due to thermal gradients created during the cooling process. The quantification of these residual stresses is important in glass industries as they affect their cutting quality. Photoelasticity can be used for residual stress analysis of glasses, as glass exhibits stress-induced birefringence. In this study, a methodology involving carrier fringes in conjunction with digital photoelasticity is used to quantify the residual stress in float glass. The results are verified by six-step phase-shifting technique (a subset of ten-step phase-shifting method) using an automatic polariscope. Finally, to demonstrate the utility of the proposed method, the residual stress is measured in float glasses of different thicknesses. A method for approximate estimation of residual stress which does not require sophisticated digital image acquisition and processing systems is also reported.     

Residual Stress and Microstructural Evolution in Tantalum Oxide Coatings on Silicon Nitride

Due to its coefficient of thermal expansion (CTE) and phase stability up to 1360°C, tantalum oxide (Ta₂O₅) was identified and investigated as a candidate environmental barrier coating for silicon nitride-based ceramics. Ta₂O₅ coatings were plasma sprayed onto AS800, a silicon nitride ceramic from Honeywell International, and subjected to static and cyclic heat treatments up to 1200°C in air. Cross-sections from coated and uncoated substrates were polished and etched to reveal the effect of heat treatments on microstructure and grain size. As-sprayed coatings contained vertical cracks that healed after thermal exposure. Significant grain growth that was observed in the coatings led to microcracking due to the anisotropic CTE of Ta₂O₅. High-energy X-ray diffraction was used to determine the effect of heat treatment on residual stress and phases. The uncoated substrates were found to have a surface compressive layer before and after thermal cycling. Coating stresses in the as-sprayed state were found to be tensile, but became compressive after heat treatment. The microcracking and buckling that occurred in the heat-treated coatings led to stress relaxation after long heat treatments, but ultimately would be detrimental to the function of the coating as an environmental barrier by affording open pathways for volatile species to reach the underlying ceramic.     

焦炭塔冷却过程中残余应力产生原因及数值分析

由于焦炭塔是在冷热循环的条件下工作的,所以在焦炭塔冷却的过程中产生的残余应力对塔体的变形也产生很大的影响,对此进行了理论上的解释说明和数值分析。由计算结果得知,导致焦炭塔腰鼓变形的主要因素是焦炭塔简体周向残余应力过大,产生较大的塑性变形。     

低成本制备氮化硅材料的研究

采用工业用纯净水作分散介质,制备了氮化硅陶瓷试样。并对试样进行了力学性能的测试,结果表明其常温力学性能指标略低于用酒精作分散介质材料的试样,断裂韧性为6.42MPa·m~(1/2),硬度为1522kgf·mm~(-2),证明了这种材料在常温下是可以使用的。     

磨加工及残余应力对氮化硅陶瓷强度的影响

利用X-射线衍射方法测量了经不同磨削的氮化硅陶瓷表面残余应力及其对抗弯强度的影响。结果表明，磨削工艺所引入的残余应力是拉应力，对陶瓷抗弯强度有显著降低。     

材料种类对夹芯注射制品残余应力的影响

采用Moldflow公司MPI软件中的Co-injection分析模块,对夹芯注射成型过程进行动态模拟分析；揭示不同材料种类组合对夹芯注射成型过程中残余应力的影响规律。结果发现,夹芯注射体系中两种物料相容性的好坏对芯/壳层界面处残余应力的分布有较大影响,芯层为结晶型材料时会导致残余应力有较大的跃迁。     

带加强层的钢框架-支撑结构受力性能分析

1引言目前在水泥厂的窑尾塔架设计中通常采用钢结构体系,相对于混凝土结构而言,钢结构建筑刚度较小,在水平荷载(风或地震作用)作用下,建筑物往往由于顶部水平位移过大而不能满足规范设计要求。为解决此问题,沿建筑高度方向间隔一定楼层设置水平加强层是一种既经济、又有效的手段[1-2]。     

扁平钢带错绕式压力容器钢带两端焊接残余应力的研究

扁平钢带错绕式压力容器已成功应用于80 MPa级高压储氢容器,同时更高压力的储氢容器正在研制之中。随着该类容器工作压力的不断提高,以及在储氢苛刻条件下的应用,绕带层两端的焊接缺陷(残余应力)已经成为影响容器整体性能的不可预测的因素。对一工作压力为98 MPa的储氢容器研究了其钢带两端焊缝处的残余应力。盲孔法测量数据表明,各钢带两端焊接处应力差异很大,部分应力较大的地方在残余应力的影响下极易产生疲劳裂纹,甚至局部屈服。     

焊接电流对Q235钢焊接接头残余应力的影响

对12 mm厚Q235试板进行手工电弧焊试验研究。采用3种不同焊接电流参数对3组试板进行焊接,以研究不同焊接电流下焊接接头所产生的残余应力。3组试板均采用双面焊。分别对正面填充焊和盖面层焊采用155 A、165 A、175 A三种焊接电流。焊完后采用残余应力测试方法对焊接接头进行分析。研究结果表明,Q235钢在175 A电流下焊接接头残余应力比165 A电流下大,155 A电流下最小。随着焊接电流的增大,焊接残余应力升高。     

Effect of Relative Humidity on Repetitive Impact Behavior of Machined Silicon Nitride

Silicon nitride is a promising candidate material to replace metallic valves in internal combustion engines. Its attractive mechanical properties relative to conventional alloys are expected to lead to reduced valve wear. As valves operate under combined conditions of impact and sliding contact, the durability of Si₃N₄ under a repetitive 45° impact was studied to assess the performance of these materials as valves. A significant effect of relative humidity on the impact behavior of Si₃N₄ was noticed. Humid conditions resulted in a significant increase in impact wear resistance. This increase appears to be related to the differences in fracture modes under humid versus dry conditions. A possible mechanism for the observed humidity effects in Si₃N₄ is advanced to explain the change in fracture modes. Increased impact resistance is expected to be a useful property for valve materials, as engine atmospheres contain significant amounts of water vapor resulting from the combustion reactions.     

表面处理对氮化硅陶瓷力学性能的影响

采用X射线衍射应力分析的sin2ψ法计算了Si3N4陶瓷试样的残余应力，并分别测量了表面处理前后Si3N4试样的力学性能。结果表明，经平面磨削后的Si3N4试样表面残余应力为拉应力，而抛光处理可适当降低残余应力。两种方法都使试样抗弯强度降低。     

注塑件残余应力数值模拟分析及工艺优化

基于Moldflow软件模拟研究了注塑件厚度方向上残余应力分布规律,采用正交实验设计考察了熔体温度、模具温度、注射时间和保压压力等工艺参数对注塑件平面上残余应力均值和极差的影响。结果表明,注塑件厚度方向残余应力表现出拉-压-拉的三区域分布,平面上残余应力均值和极差受保压压力影响最大,其次为注射时间和熔体温度,模具温度影响最小。最佳注射工艺组合的数值计算和试验结果比较发现,残余应力变化趋势相似,对于生产实际有重要的指导意义。     

Direct and Residual Effects of Water Deficit Stress,Different Sources of Silicon and Plant-Growth Promoting Bacteria on Silicon Fractions in the Soil

Silicon - Silicon (Si) and plant growth promoting bacteria (PGPB) can effectively reduce the negative effects of water deficit stress and augment plant growth. Few studies have simultaneously...     

Determination of Residual Stress Profile Using a Strain Gage Technique

A simple beam theory analysis is presented for the determination of residual stress patterns in beams or plates using a strain gage technique. The analysis is valid for a general stress distribution which need not be symmetric with respect to the neural axis. The experimental approach consists of attaching a strain gage on the surface of a beam or a plate and then grinding off the other side. The recorded strain vs thickness ground off data can be used to determine the corresponding stress profile.     

Predicting Failure Stress of Silicon Nitride Ceramics Using Microfocus Radiography

Microfocus projection radiography was used to evaluate nondestructively a large quantity of silicon nitride modulus-of-rupture test bars. Quantitative data (size, shape, and location) on major naturally occurring voids in rejected bars were determined from radiographs. Failure stress prediction was attempted using a fracture mechanics model and nondestructive evaluation data and compared to actual failure stress.     

液化石油气钢瓶残余应力测试分析

采用钻孔法对液化石油气钢瓶的残余应力进行测试,并分析了环焊缝、角焊缝和封头位置的残余应力分布特性与钻孔法测试残余应力的适用性,为开展液化石油气钢瓶出厂残余应力抽样检测提供借鉴。