预变形量和机械训练对形状记忆合金回复率的影响

利用废钢和生铁为原料,采用特殊保护剂,在大气中熔炼出Fe-Mn-Si-C形状记忆合金;利用应力诱发马氏体相变对Fe-Mn-Si-C合金实现形状记忆效应,探讨了预变形量和机械训练对Fe-Mn-Si-C合金回复率的影响规律.结果表明:在600℃的回复温度下,在一定的变形范围内,回复率随着预变形量的增大而降低;在机械训练过程中,合金的回复率随机械训练次数增加逐渐上升,训练超过一定次数后合金的回复率略有降低.     

Cr和RE对Fe-Mn-Si-C合金形状记忆效应影响规律

主要研究了Cr和RE及回火温度对Fe-Mn-Si-C合金形状记忆效应的影响规律.结果表明:形状回复率随Cr含量增加而增加,在Cr含量为10%wt.时形状回复率达到最大值98.75%;RE的加入使形状回复率呈现先减小后增加的特点.当加入RE0.1%wt.时,形状回复率明显降低,至最小值56.82%,超过0.1%wt.后,形状回复率迅速上升,至0.2%wt.后形状回复率趋于平稳;在预变形量和淬火温度相同的条件下,回火温度为500℃,Cr含量为10%wt.时,合金形状回复率最高可达98.75%;而回火温度为600℃,RE含量为0.2%wt.时,合金形状回复率可达98.66%.     

碳纤维增强聚苯乙烯形状记忆复合材料的弯曲性能

为了提高聚苯乙烯形状记忆聚合物的弯曲性能,制备了碳纤维增强聚苯乙烯形状记忆复合材料,并对其弯曲回复性能和弯曲性能进行了测试分析.结果表明:碳纤维增强聚苯乙烯形状记忆复合材料具有很好的形状回复性能,当回复时间在6 min以前其弯曲回复率高于聚苯乙烯的,最大回复率达98%;25℃时该复合材料承受的最大弯曲载荷约为聚苯乙烯的145%,达113 N,45℃时约为聚苯乙烯的108%,达39 N;塑性失效后复合材料的承载能力优于聚苯乙烯.     

叶片熔体输运过程拉伸形变速率的研究

叶片挤出机是一种基于拉伸流变的新型塑化输运设备,与常用塑料成型设备通过剪切力场来实现对聚合物及其填充体系的分散混合相比,拉伸流场具有更好的分散混合效果及较高的分散效率。通过分析叶片挤出机的结构特点,建立相应的物理模型,从理论上分析了聚合物在熔体输运阶段中拉伸形变速率的大小,得到拉伸形变速率在转角为0到/2过程中,轴向拉伸形变速率和周向拉伸形变速率大小相同,拉伸形变速率随转角呈现出抛物线变化,随着偏心距的增大而增大,随着挡板内径的增大而减小,随着转速的增大而增大;在转角为/2到过程中,轴向拉伸形变速率和周向拉伸形变速率大小也相同,拉伸形变速率随着转角的增大而逐渐减小,随着偏心距的增大而增大,随着挡板内径的增大而减小,随着转速的增大而增大。从而增大叶片结构单元的偏心距,减小挡板的内径尺寸以及在塑化加工过程中提高到适当的转速,有利于产生更强的拉伸作用。     

真空导入树脂模塑工艺对EKB1100/430LV复合材料纤维含量及力学性能的影响

通过真空导入树脂模塑工艺制备了EKB1100/430LV复合材料,研究了不同工艺参数对复合材料中玻璃纤维含量及力学性能的影响。结果表明:纤维含量随真空度的增大而增加,靠近树脂注入口区域的纤维含量较低,而真空抽口附近的纤维含量最高;复合材料的拉伸强度和压缩强度也随真空度的增大而增大;充模前对预成型体实施压缩可提高纤维含量;充模过程中溢流一定的树脂可提高弯曲强度和层间剪切强度。     

中科院深圳先进院制备出黑磷基光致形变复合材料

正中国科学院深圳先进技术研究院研究员喻学锋、副研究员阮长顺等成功制备出生物可降解的黑磷/聚氨酯复合物。该复合物可"植入"复杂形状记忆,在光照下展现多样形变。形状记忆材料是一类能够暂时固定在临时形状、受到外界刺激后回复到初始形状的智能材料,在柔性电子、生物医学等领域展现了越来越广的应用前景。开发可智能响应近红外光的生物可降解形状记忆材料,具有巨大的临床应用价值,但同时     

短纤维增强橡胶基密封复合材料纵向拉伸模量的研究

依据混合律,建立短纤维增强橡胶基密封复合材料纵向拉伸模量的理论预测模型,研究材料纵向拉伸模量随纤维长径比、体积含量以及温度变化的规律。结果表明:理论模型预测的纵向拉伸模量与试验结果较为一致;材料纵向拉伸模量与材料的诸多组分力学性能参数、细观结构参数以及温度有关;纵向拉伸模量随短纤维平均长径比和体积含量的增加而增加,随着温度的升高而减小。     

聚苯酯/玻璃纤维改性PTFE密封材料的热力学性能

采用动态热机械分析仪等手段分析研究聚苯酯/玻璃纤维/聚四氟乙烯(POB/GF/PTFE)密封材料的动态和静态热力学行为,考察不同含量的POB和GF对PTFE复合材料的储能模量、高温压缩-回复和蠕变性能的影响。结果表明,POB和GF的加入可显著提高PTFE复合材料的储能模量和热变形温度;在0~30%质量分数范围内,随着POB质量分数的增加,PTFE复合材料的压缩率和回复率均呈现下降趋势,而高温蠕变量则先降低后增大,然后又降低;在质量分数20%POB填充PTFE复合材料基础上,随着GF质量分数的增大,PTFE复合材料的压缩率、回复率和高温蠕变量均呈现先降低后增大,然后又降低的趋势。     

高分子材料拉伸形变取向对裂纹萌生及扩展的影响

应用电子拉伸机、扫描电镜和Ｘ光衍射仪对高密度聚乙烯和内烯材料的拉伸形变断裂行为进行了实验研究。结果表明，高分子材料冷拉形变量是在缩颈扩展阶段发生局部集中形变的累积量；拉伸取向主要是由局集形变贡献的，冷拉阶段的时间长短对取向度影响不大，并用Ｘ光衍射仪测定取向函数值进行了验证；材料在屈服阶段断裂时，其断裂部分一般总是发生在由弹性形变向塑性形变的转变处；一旦发生了塑变，沿外力方向产生了取向，则对裂纹萌生     

激光扫描速度对4D打印钛镍形状记忆合金相转变和超弹性的影响

通过调控激光扫描速度,运用4D打印技术制备出具有不同相转变温度和微观结构的钛镍形状记忆合金。结合XRD、DSC、SEM和循环压缩等分析方法研究了不同扫描速度对4D打印钛镍合金相组成、相转变、微观结构和超弹性的影响。结果表明,当激光扫描速度从80 mm/s到150 mm/s时,4D打印钛镍合金中马氏体相(B19’)含量减少,奥氏体相(B2)含量增加;马氏体转变开始温度(Ms)和奥氏体转变结束温度(Af)随激光扫描速度增加而降低。奥氏体状态下循环压缩试验结果表明:激光扫描速度为80mm/s时,4D打印钛镍合金具有良好的超弹性,10次循环压缩后稳定的可回复应变达到4.99%,高于目前文献报道的回复应变2.64%;激光扫描速度为150 mm/s时,在3次循环压缩后回复应变几乎保持在4.55%不变。     

Physical and tribological properties of PTFE micropowder-filled EPDM rubber

The physical and tribological properties of ethylene-propylene-diene-rubber (EPDM) filled with polytetrafluoroethylene (PTFE) micropowders, i.e. MP1100 and MP1200 having chemically similar but distinctive microstructural morphology have been investigated. EPDM-PTFE micropowder blends filled with MP1200 having a solid granular structure, showed poor tensile strength and elongation at break but significantly improved tribological properties. It attained both the lowest steady-state friction coefficient and specific wear rate. However, EPDM-PTFE blends containing a fine agglomerated PTFE micropowder of MP1100 showed enhanced physical properties. Its increasing tensile strength and elongation at break with PTFE micropowder loading compared to MP1200-filled EPDM blend was essentially due to its characteristic morphology, which enhanced its dispersion and compatibility with EPDM. It showed specific wear rate similar to MP1200-filled EPDM but resulted in high friction coefficient. Scanning electron microscopy (SEM) of the PTFE micropowders and the corresponding PTFE micropowder-filled EPDM blends suggest that agglomerates morphology, dispersion and interfacial compatibility with EPDM are the key factors influencing physical and tribological properties of these compounds.     

Tribological testing of peroxide-cured EPDM rubbers with different carbon black contents under dry sliding conditions against steel

The friction and sliding wear behaviors of peroxide-cured ethylene/propylene/diene rubbers (EPDM) were studied against steel counterparts under dry conditions. The carbon black (CB; N347 type) content of the EPDM rubbers was varied between 0 and 60 parts per hundred parts rubber (phr). For their tribotesting, different test configurations, viz. pin(steel)-on-plate(rubber) (POP) and roller(steel)-on-plate(rubber) (ROP), were used and their oscillation wear behavior (fretting) studied, too. The EPDM rubbers were characterized using dynamic-mechanical thermal analysis (DMTA), hardness, tensile and tear tests. The coefficient of friction (COF), volume loss and specific wear rate of the EPDM rubbers were determined. It was found that with increasing CB content all above characteristics were reduced. However, the COF and wear parameters strongly depended on the related test configuration. The wear mechanisms were concluded by inspecting the worn surfaces in scanning electron microscope (SEM) and discussed.     

面向驱动桥壳再制造的磁记忆无损检测

为研究汽车驱动桥壳再制造的金属磁记忆检测,选用510L钢拉伸试样,分析了塑性应变不同阶段磁记忆信号的变化规律;以材料拉伸试验为基础,针对废旧驱动桥壳进行磁记忆损伤检测及变形量检测,得到了桥壳变形量与磁记忆信号特征值的关系。结果表明,随着应变量的增大,拉伸试样表面磁记忆信号法向分量Hp(y)由斜线、无异变峰变化为反转且出现过零点,磁记忆信号法向分量梯度Kmax早期缓慢增大,颈缩时出现快速增大;桥壳的变形检测显示,桥壳变形量与Kmax存在量化关系,当桥壳发生较大变形时,梯度Kmax发生突变,磁记忆检测可为再制造损伤评估提供依据。     

聚丙烯（PP）冷压变形行为研究

采用镦粗变形对结晶型PP进行3种变形速度和4种变形程度的冷压变形实验,实验结果表明,镦粗变形的几何变形模式及其极限伸长率的几何性质与单向拉伸完全不同,但PP的屈服应力随变形速度增大而提高的现象与许多材料单向拉伸屈服应力相似。与此同时,冷压镦粗PP的延性大变形属于“类塑性”性质,其性质和数值与聚合物及其结构和变形回弹相关。虽然PP冷压镦粗后的回弹率很大,但回弹随变形速度提高而减小,因此为了研发聚合物锻造技术,需要提高变形速度或采用加热措施,或改用闭式锻造变形模式。     

新型铜基记忆合金(CuAlMnX)机械性能测试

新型铜基记忆合金（CuAlMnX）在经过布氏硬度测试、拉伸试验、超弹性回复性能测试、超弹状态下的疲劳寿命这4项机械性能的测试后。证实其综合机械性能已达到企业标准,断裂韧性优于NiTi形状记忆合金,弹性回复率、塑性等性能均优于已见报道的其它铜基记忆合金。     

形状记忆合金双程弯曲驱动器的设计及试验

为解决变体机翼中蒙皮大变形与承载力之间的矛盾,同时满足光顺性及疲劳寿命的要求,提出了一种以形状记忆合金板为驱动元件的双程弯曲驱动器。基于形状记忆效应及材料力学弯曲理论,通过对驱动器变形过程中的力学特性进行分析,推导出双程弯曲驱动器的设计理论,再利用热成形法与反变形训练法制备出驱动器样件并进行了变形性能测试。研究结果表明：依据推导出的理论所设计的形状记忆合金双程弯曲驱动器的变形量与试验结果一致;随着加热温度的升高,驱动器的挠度及输出力逐渐增大,直至达到最大值;随着回复弹簧钢板厚度的增大,驱动器的最大挠度及最大输出力减小,加热变形响应速度减慢,但冷却回复响应速度加快;经过循环激励后,驱动器的变形效果稳定。     

一种仿章鱼腕足柔性模块的设计与运动控制

针对软体机器人由于刚度太低且是连续变形,故很难进行运动控制的问题,提出一种由形状记忆合金弹簧驱动的柔性机械臂。机械臂由３Ｄ打印制造而成,内部嵌入３个线性霍尔传感器,用于测量柔性臂弯曲运动。通过压缩补偿计算可以精确控制弯曲运动。实验结果表明,该柔性机械臂可以以较高精度进行三维运动。     

过氧化二异丙苯和酚醛树脂对HDPE/GTR共混物的原位反应性增容

采用过氧化二异丙苯(DCP)和热塑性酚醛树脂(HY-2045)在未添加催化剂时实现了对高密度聚乙烯(HDPE)/废旧轮胎胶粉(GTR)共混物的原位反应性增容, 并研究了其对共混物的微观形貌、 应力-应变曲线、 动态力学性能和结晶性能的影响. 扫描电镜结果显示, 共混物橡塑界面处有大量的纤维状物质同时嵌入到基体相和分散相中, 使得共混物的界面强度得到显著增加, 从而获得较好的综合力学性能. 差式扫描热量(DSC)和X射线衍射(XRD)测试结果表明, 原位增容后的共混物的结晶度显著降低, 致使其明显的拉伸屈服现象消失. 由于反应型增容剂DCP和HY-2045使得共混物在界面处形成化学交联, 尽管其结晶度有所降低, 但是其拉伸强度和断裂伸长率还是得到了显著的增加. 另外, 动态力学性能测试表明, 增容后的HDPE/GTR共混物中GTR相的玻璃化转变峰变宽, 玻璃化转变温度升高.     

Characteristics of metal magnetic memory signals of different steels under static tension

To study the characteristics of metal magnetic memory (MMM) signals of different steels during tensile test, static tension tests were applied to 30 pieces of Q235 and 16MnR base metal and welded specimens. During the various deformation periods, MMM signals are tested, and micrometallographic is observed. Furthermore, the derivative of magnetic intensity (dH_p/dx) is analyzed by mathematical and statistical methods to study the macro and micro corresponding relationships and difference among magnetic signals. Results show that despite the different magnetic intensity (H_p) curves of different materials, their dH_p/dx patterns in the yielding and necking stages are the same; welded specimens have the similar magnetic signal curves with their base metal, and the welded structure does not interfere with its H_p distribution; different materials have their unique zero point (H_p＝0) before being fractured, which is independent of the fracture location; there is a direct relationship between the intragranular slip and the changes of magnetic signals, which indicates the uneven plastic deformation.     

Determination of the Drucker-Prager parameters of polymers exhibiting pressure-sensitive plastic behaviour by depth-sensing indentation

This paper presents a method to determine the Drucker-Prager parameters of pressure-dependant elastic-perfectly plastic polymeric materials by means of the depth-sensing indentation technique. This is achieved via an inverse analysis of the load-displacement data resulting from two tests performed with Berkovich and spherical tips. The well-posedness and the effective range of application of the proposed method are carefully assessed first. Then the method is tested for two elasto-plastic materials with mild initial strain-hardening (HDPE and PMMA), and the results are compared to those measured using conventional tensile and compression tests. It is found that the pressure-sensitivity indices can be accurately predicted, while the yield stress predictions in tension and compression fall within the non-linear portion of the uniaxial stress-strain curves, i.e., inside the region where plastic deformation begins.