玻纤含量对玻纤增强聚丙烯拉伸性能的影响

采用不同玻纤含量的标准拉伸试样,应用试验方法,通过玻纤含量对玻纤增强PP复合材料的拉仲性能进行比较,找出了实现最佳抗拉强度的玻纤含量。     

日本制成碳纤维增强石膏模具

为弥补现有高强度石膏模具的不足，日本近来成功研制出碳纤维增强石膏模具，为陶瓷泥浆浇注成型提供了一种性能更完满的高强度模具。石膏模具是陶瓷生产中重要的辅助工具，在注浆成型中普遍采用。由于普通石膏模具强度低，使用寿命短，逐渐被高强度石膏所替代。目前常用的高强度石膏模具主要以高强度石膏为基材，外掺水泥、树脂或以天然纤维、玻璃纤维为增强材料。经使用证明，这些高强度石膏模具的强度虽有改善，但还存在以下缺陷：(1)对以高强度石膏为基材的外掺水泥模具，因自身基体吸水性差，坯体脱模强度低，易变形，影响成品质量。(2)…     

超声检测法确定受损伤复合材料的力学性能

应用超声探伤法对不同损伤程度的玻纤(玻璃纤维)增强复合材料进行了测试,并将测试过的试件作了力学性能分析,从而建立起超声波穿透材料时的衰减值与材料轴向刚度与强度之间的关系。该方法可用于对使用了一段时间以后的复合材料构件进行强度评估。     

管材向外翻卷变形机理的研究

圆管在模具上受轴向压缩，翻转并非唯一的变形模式，还有如失稳、撕裂、扩口、卷曲等多种变形模式。本文应用能量观点分析了管材向外翻卷变形过程，提出了周向变形能增量控制管端翻卷变形的规律，并用实验加以验证，这为有效地控制翻管变形提供了理论依据。     

冷型热阻角对HCCM水平连铸BFe10-1-1管材周向组织和力学性能均匀性的影响

提出在结晶器冷型底部设置气隙热阻以提高热冷组合铸型(HCCM)水平连铸BFe10-1-1管材周向组织和力学性能均匀性的方法,研究热阻角对连铸传热行为、管材周向组织和力学性能均匀性的影响。结果表明:未设置热阻时,管材上部和下部组织均由"V"形柱状晶组成,侧部组织为与轴向呈夹角29°~36°的柱状晶,周向的柱状晶形貌和数量分布不均匀,其周向不同部位的抗拉强度和断后伸长率差异较大。当热阻角为8°~32°时,随热阻角的增大,管材柱状晶组织与轴向的夹角减小,周向组织和力学性能的均匀性提高。在本实验条件下,BFe10-1-1管材HCCM水平连铸结晶器冷型底部设置合理的热阻角为32°。冷型底部设置热阻使管材周向传热及凝固区周向温度场分布更为均匀,这是管材周向组织和力学性能均匀性提高的主要原因。     

小口径TA18航空钛合金管材织构测定与分析

利用X射线衍射极图测量技术,对国内试制的Φ6mm的TA18(Ti-3Al-2.5V)合金冷轧管材的织构类型进行研究。并测量了国外同直径的商用航空管材的织构类型和强度,与国产的管材进行了对比分析。采用管材减薄展平法解决了形状对X射线衍射强度影响无法修正的困难,实现了对管材织构的精确测定。结果表明:国产管材的织构类型与进口管材基本相似,主织构的(0002)面与管材径向夹角均为24°,晶向[1010]与管轴向平行。但是织构的强度差别很大,进口管材的织构强度是国产管材的2倍以上。提高织构强度及减小离散程度是改善国产管材性能的一个重要方向。     

基于响应曲面法的玻纤增强PBT激光透射焊接工艺参数优化

对玻纤增强聚对苯二甲酸丁二醇酯（PBT）复合材料进行平顶光束激光透射焊接工艺参数优化，选取焊接工艺参数（激光功率、焊接速度、玻纤含量）为影响因素，选择焊接质量（焊缝抗剪强度、焊缝宽度）为响应值。通过方差分析表和残差概率图验证了模型的准确性，并探究不同焊接工艺参数组合对焊接质量的交互影响。结果表明，增大激光功率、提高焊接速度和增加玻纤含量，焊缝抗剪强度先升高后下降；降低激光功率，提高焊接速度，焊缝宽度下降；增大玻纤含量，焊缝宽度先增大后减小。焊接速度对焊缝抗剪强度影响较大，玻纤含量对焊缝宽度影响较大。分别以最佳焊接质量和最小焊接成本为目标确定了玻纤复合材料的最优焊接工艺参数。     

管材斜连轧过程的运动学分析及实验研究

介绍了生产无缝管材的斜连轧工艺的变形过程。以建立了连续斜轧关系后受穿孔段轧辊及轧管段轧辊共同作用的管材为研究对象,采用理论分析方法,建立了轧辊与管材间的运动学关系,获得了满足变形协调关系的穿孔段出口与轧管段入口间管材的速度方程。在斜连轧实验机组上进行了实验研究,采用单一变量控制法,分析了轧管段轧辊转速对斜连轧过程及轧后管材质量的影响。实验结果表明:当穿孔段工艺参数不变时,轧管段轧辊转速对能否顺利完成连续斜轧轧制的影响较大;当转速为174 r·min~(-1)时,由于轴向和周向的速度协调,可实现顺利轧制;当转速为168 r·min~(-1)时,由于轴向速度不协调,出现堆钢现象;当转速为182 r·min~(-1)时,由于周向速度不协调,出现扭转现象。     

基于RBFNN的FRPP复合管材缠绕成型性能预测

以玻纤增强聚丙烯(FRPP)复合管材缠绕成型性能及其关联的成型过程参数为对象,基于留一法交叉检验的手段,采用径向基神经网络(RBFNN)建模的方法研究了FRPP复合管材缠绕成型性能预测模型。结果表明,预测层间剪切强度、环向拉伸强度时,分别存在的一种RBFNN模型的检验最大相对误差≤0.001%。对学习好的RBFNN模型进行敏感度分析表明,玻纤增强聚丙烯(FRPP)复合管材缠绕成型性能及其关联的成型过程参数之间的关系为高度非线性关系。性能最好的工艺参数分析说明所建立的模型是可靠的。     

高密度聚乙烯燃气管材及其对接接头力学行为的研究

对高密度聚乙烯管材及其对接接头在不同温度下的基本力学行为进行了测试。试验结果发现随着试验温度的降低，HDPE以及对接接头的强度逐渐提高，最大断裂伸长率(应变)则逐渐下降。而且其断裂形式也有相应的变化，并且对于整个管件而言，对接接头及其附近区域仍可能是易发生断裂的薄弱环节。该结果对高密度聚乙烯管材进行其它方面的深入研究具有深远的意义。     

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管环拉伸试验是国际上应用于重要结构钢管的主要工艺试验方法之一,为了建立管环拉伸性能评价体系,采用了自行设计的管环拉伸模具,对不同尺寸和材料的钢管进行了管环拉伸试验,通过对拉伸曲线的分析,提出了管环拉伸后屈服强度、抗拉强度以及伸长率的评价方法,并进行了检测结果的稳定性分析.结果表明:提出的评价方法可有效适用于不同尺寸和材质的钢管,试验结果稳定可靠,研究成果对中国进出口钢管的质量把关具有极其重要的意义.     

圆柱螺旋弹簧的正断/切断型疲劳断裂模式与提高其疲劳断裂抗力的途径

结合承受扭转切应力和轴向正应力圆柱体的受力分析,讨论了圆柱螺旋弹簧发生的正应力断裂,纵向以及横向切应力断裂等3种疲劳断裂模式。结果指出,喷丸引入的残余正应力(即应力强化机制)只影响正应力而不影响纵/横向切应力断裂模式的疲劳强度(寿命)。但喷丸引起表面形变层内的组织结构改性(即组织结构强化机制)却能提高所有3种断裂模式的疲劳断裂抗力。     

Compression tests of carbon steel ball mould for casting

Abstract

In this study, the carbon steel boll mould that has merit of the metal mould and the sand mould was produced. Steel balls were heated and joined to produce the steel ball mould. The compressive strength was measured for the strength of the mould. The compression specimen was manufactured after putting steel balls into the carbon vessel and heating to join. The compression specimen was 10 mm in diameter and about 10 mm in height. The influence of the diameter of the steel ball and temperature of heating on the strength of the steel ball mould was examined. The compressive strength decreased as the ball diameter became large. Steel balls were oxidised and joined by heating. Melted aluminium was cast into the carbon steel ball mould. The macrostructure of the solidified specimen was observed.     

PP-R管件注射模浇注系统设计与CAE分析

针对管件生产中出现的熔接痕问题 ,通过理论分析和计算 ,认为浇注系统设计不当是产生熔接痕的主要原因 ,进而应用CAE软件进行分析 ,通过优化浇口位置将熔接痕减到最小 ,据此设计制造的模具满足管件产品的质量要求 ,同时该方法也为提高PP_R管件模具的质量提供了可靠的技术保证。     

热处理对高强度捆带钢的组织和性能的影响

实验室研究了一种高强捆带钢的热处理工艺、组织和性能的关系.结果表明:含031%C-0.23%Si-1.43%Mn的冷轧板,经735～745℃的两相区迅速淬火+470℃中温同火后可达到1100 MPa以上的抗拉强度和10%以上的伸长率,用此工艺生产的捆带钢比传统的铅浴等温淬火工艺具有更高的强度.     

Induction brazing – old process with potential innovations

The practical strength of line pipe steel has extended to X80 or greater. The line pipes of X80 grade have been commercialised successfully and now the development and evaluation of X100 and X120 grade line pipes are being conducted.

The effect of boron addition on the toughness and microstructure of seam weld metal was investigated in tensile strength range from 700 to 1100 MPa. Two types of weld metal were employed in this study. Type A weld metal was produced by boron added flux. The boron content in type A weld metal was around 30 ppm. Type B weld metal was produced by boron free flux. The boron content in type B weld metal was 15 ppm or less. In a tensile strength range less than 800 MPa, type B weld metal had lower absorbed energy than type A because of grain boundary ferrite formation. In a tensile strength range of 800 MPa or more, type B weld metal had greater absorbed energy than type A. In this tensile strength range, some of the acicular ferrite is replaced with bainite or bainite/martensite and the absorbed energy decreases with increase of tensile strength. And the type B weld metal had more amounts of acicular ferrite and greater absorbed energy than type A in this tensile strength range.     

Process design of high-strength bolt of fully pearlitic high-carbon steel

In this study, fully pearlitic high-carbon steel, known as a higher delayed fracture strength material, with an ultimate tensile strength of 1410 MPa was used for manufacturing a high-strength M8 bolt. Softening behavior was observed by a compression test of the material. The tensile strength of the material was measured after application of several drawings. On the basis of these test results, two multi-stage manufacturing processes were designed by a knowledge-based expert system in order to develop a high-strength bolt using either the upsetting mode or the extrusion mode for the second preform. The load requirement and possible defect formation during the process were predicted by employing a rigid-viscoplastic finite element analysis. When the second preform was made in a laboratory experiment according to the process design on the basis of the upsetting mode, the specimens cracked at the flange in the final stage of forming. However, the bolt was successfully manufactured using the second preform obtained using the extrusion mode and showed extended tool life in the laboratory test. Finally, the manufactured bolt was confirmed via experiments to have tensile strength of 1600 MPa and delayed fracture strength.     

热型连铸Al-1%Si合金线材的试验分析

通过在自行研发的水平式热型连铸设备上制备Al-1％Si合金线材的试验研究，分析型口温度、连铸速度及冷却能力等工艺参数对铸锭表面质量的影响，提出了制备Al-1％Si合金的优化工艺参数。同时，利用本试验制备的Al-1％Si合金线材和传统铸造多晶Al-1％Si线材作试样，分析两者的室温拉伸性能。结果表明，热型连铸制备的Al-1％Si合金线材和传统铸造多晶Al-1％Si线材相比，屈服强度提高41．4％，屈强比提高37．8％，伸长率提高49．1％，并具有良好的导电性能。     

Influences of process parameters on tensile strength of friction stir welded cast A319 aluminium alloy joints

Fusion welding of cast A319 (Al-Si-Cu) alloy will lead to many problems including porosity, micro-fissuring, and hot cracking. Friction Stir Welding (FSW) can be used to weld A319 alloy without these defects. In this investigation, an attempt has been made to study the effect of FSW process parameters on the tensile strength of A319 alloy welded joints. Joints were made using different combinations of tool rotation speed, welding speed, and axial force, each at four levels. The quality of weld zone was analyzed using macrostructure and microstructure analysis. Tensile strength of the joints were evaluated and correlated with the weld zone microstructure. The joint fabricated with a 1200 rpm tool rotation speed, 40 mm/min welding speed, and 4 kN axial force showed superior tensile strength compared with the other joints.     

Multi-objective optimization of friction stir welding parameters using desirability approach to join Al/SiCp metal matrix composites

Silicon carbide particulate (SiC_p) reinforced cast aluminium (Al) based metal matrix composites (MMCs) have gained wide acceptance in the fabrication of light weight structures requiring high specific strength, high temperature capability and good wear resistance. Friction stir welding (FSW) process parameters play major role in deciding the performance of welded joints. The ultimate tensile strength, notch tensile strength and weld nugget hardness of friction stir butt welded joints of cast Al/SiC_p MMCs (AA6061 with 20% (volume fraction) of SiC_p) were investigated. The relationships between the FSW process parameters (rotational speed, welding speed and axial force) and the responses (ultimate tensile strength, notch tensile strength and weld nugget hardness) were established. The optimal welding parameters to maximize the mechanical properties were identified by using desirability approach. From this investigation, it is found that the joints fabricated with the tool rotational speed of 1370 r/min, welding speed of 88.9 mm/min, and axial force of 9.6 kN yield the maximum ultimate tensile strength, notch tensile strength and hardness of 265 MPa, 201 MPa and HV114, respectively.