共查询到19条相似文献,搜索用时 93 毫秒
1.
采用有限元方(Finite Element Method)对环氧树脂/聚氨酯(EP/PU)梯度材料在制备过程中产生的残余热应力进行了分析.详细讨论了梯度层数目对应力大小的影响.研究结果表明:当体系中EP和PU组成相同时,梯度材料缓和热应力的效果比双层材料显著.且梯度材料的热应力缓和效果随梯度层数增加而增加. 相似文献
2.
功能梯度材料残余热应力的大小及分布对其性能有效发挥及长期稳定使用有着较大的负面影响,为了尽可能充分发挥材料性能,增加材料的使用寿命,需尽可能减小残余应力以及使其合理分布.本文采用ANSYS有限元分析软件对不同叠层工艺参数的等离子体第一壁候选材料--SiC/C功能梯度材料(FGM)的残余热应力进行了数值模拟,获得了使热应力有效缓和的较适宜的工艺参数,对实际研发制备目标材料也可提供一些理论参照.相关结果表明,适量增加梯度叠层数及中间梯度层厚度可逐步有效缓和残余热应力,同时,针对本文今后应用的仍以炭材料为主体的炭基陶瓷保护层复合SiC/C FGM而言,纯SiC层厚度应取较小值,而叠层成分分布指数应取0.8~1.0为宜. 相似文献
3.
4.
以高密度聚乙烯(HDPE)为基体塑料,偶氮二甲酰胺与氧化锌复配物为发泡剂,过氧化二异丙苯(DCP)为交联剂,采用两步模压发泡法制备了HDPE/竹粉复合发泡材料,并研究了交联剂对复合材料密度和回弹性能、发泡性能、力学性能的影响。结果表明:当交联剂的添加质量分数为0.6%时,HDPE/竹粉复合发泡材料的密度达最小值,为0.054 g/cm~3;回弹率达最大值,为90.5%;当交联剂的添加质量分数为0.4%时,复合发泡材料的泡孔分布相对多而均匀,弯曲强度达最大值,为29.3 MPa,相比未发泡材料约低8.2%,冲击强度为6.8 k J/m~2,相比未发泡材料约低16%。 相似文献
5.
采用粉末冶金技术制备了梯度HA/Mg复合材料。研究了HA含量、HA梯度分布情况以及烧结温度对复合材料孔隙度、烧结收缩率和弯曲性能的影响,观察烧结产物的显微组织,并对复合材料的耐腐蚀性能进行测试。研究结果表明:随着梯度HA/Mg复合材料中间层HA含量的增加,梯度HA/Mg复合材料的烧结收缩率降低,孔隙度升高,抗弯强度降低。随着烧结温度的升高,梯度HA/Mg复合材料的烧结收缩率增大,孔隙度降低,抗弯强度增加。耐腐蚀性分析表明,与纯Mg相比,梯度HA/Mg复合材料具有更好的耐腐蚀性能。随着中间层HA含量的增加,腐蚀速率降低,溶液的pH增加缓慢。 相似文献
6.
研究了Al/Mg/Al三明治结构复合板的退火热处理工艺,探讨了退火温度、时间对复合界面和阻尼性能的影响。结果表明:退火使得Mg层中的孪晶及变形组织消失,晶粒明显长大,且可以促进Al-Mg界面原子的相互扩散。随着退火温度的升高,界面效应对复合板的阻尼性能影响由不利转变为有利,在250℃下随着退火时间的延长,复合板的阻尼性能有一定的提高。综合复合板的组织与性能要求,得到Al/Mg/Al复合板的最佳退火工艺为250℃×2h,在应变振幅为5×10~(-4)下复合板的阻尼值Q~(-1)达0.045。 相似文献
7.
《功能材料》2021,52(1)
利用微弧氧化法,在微弧氧化反应电解质中加入氟钛酸钾和GR/TiO_2粉末,在镁合金表面制备了MAO-GR/TiO_2涂层。采用SEM和FT-IR分别对GR/TiO_2粉末的表面形貌和结构进行了研究,用SEM、XRD和元素线扫描对MAO-GR/TiO_2涂层的表面形貌、相结构和元素分布进行了研究,用三电极技术对MAO-GR/TiO_2涂层的耐腐蚀性能进行了研究。结果表明,通过溶胶-凝胶法可将纳米TiO_2接枝到GO表面,生成GR/TiO_2粉末;MAO-GR/TiO_2涂层主要由Mg_2TiO_4相、Mg_3(PO4)_2相、Mg和MgO相组成;以界面为分界线,涂层一侧Ti、P和O元素高于基体一侧,基体一侧Mg元素高于涂层一侧;MAO-GR/TiO_2涂层的腐蚀电位为-0.723 V,腐蚀电流密度为8.96×10~(-8) A/cm~2,相比镁合金基体和MAO涂层,腐蚀电位提高了48.3%和36.7%,表明MAO-GR/TiO_2涂层可以显著提高镁合金基体的耐蚀性能。 相似文献
8.
在钢基体(EUROFER、F82H、CLAM、316L)上喷涂钨涂层已成为制备面向等离子体材料的一个重要方法.为了防止钨涂层与钢基体间由于材料热膨胀不匹配而开裂失效,采用热应力缓和型功能梯度涂层是一种行之有效的解决方案.利用有限元分析软件(ANSYS 10.0)分析了梯度涂层厚度对W/316L功能梯度涂层残余应力的影响.模拟结果表明,纯钨层厚度确定时,制备厚的梯度涂层可降低残余应力.当顶层厚度为1mm、梯度涂层厚度为100~200μm时,将产生较大的轴向应力,制备涂层时应当避免此厚度范围.此模拟结果可为该涂层设计和制备提供理论依据和指导. 相似文献
9.
采用有限元方法分析了钛合金TC4表面分别溅射沉积的4种医用陶瓷涂层Ta2O5、Nb2O5、ZrO2和TiO2的残余热应力分布情况,并以Ta2O5涂层为例,研究涂层的厚度与结构对残余热应力最大值的影响。结果表明,4种氧化物涂层的残余热应力都表现为拉应力,且应力最大值均位于涂层/基体结合界面的外边缘,其中残余热应力最大值最大的是Ta2O5涂层(32.2 MPa),其次是Nb2O5(19.7 MPa)和ZrO2涂层(10.2 MPa),最小是TiO2涂层(1.03 MPa)。当涂层厚度由1 μm增加到4 μm时,Ta2O5涂层的残余热应力最大值呈现先减小后增大的变化趋势,其中涂层厚度为2.5 μm时的残余应力最大值最小。对于不同结构的Ta 相似文献
10.
设计了Y-TZP/LZAS微晶玻璃功能梯度涂层,使用有限元软件分析了成分分布指数、梯度层数目和梯度层厚度等参数对涂层/基体界面残余热应力的影响。结果表明:功能梯度材料的最佳成分梯度指数为m=1;涂层最佳层数为3-5层;涂层最佳厚度为1-1.5 mm;涂层表层主要分布为径向压应力;在涂层/基体界面的边缘区域应力集中较为严重;涂层/基体界面处的径向应力、轴向应力和剪切应力与成分分布指数、梯度层数目和梯度层厚度有密切的关系。用涂搪法制备了梯度涂层,用X射线衍射法(XRD)测试了涂层表面残余应力,验证了有限元结果的准确性。 相似文献
11.
The SiCw/6061Al composites were fabricated by squeeze casting method. Varia-tions of thermal residual stresses with quenching temperature, cooling manner, aging time and thethermal-cold cycle process in thin specimens,and the distributions of thermal residual stresses alongthe distances from the surface and changes with heating temperatnres in thick specimens were stud-ied by means of X-ray diffraction (XRD). The effects of residual stresses on the mierostructure, di-mensional stability and age-hardening behavior were studied by SEM, TEM observations, and tensiletest. The results showed that there existed macrostress, microstress and thermal mismatch stress inSiCw/Al compo-site,and the presence of microstress and thermal mismatch stress has no influenceon the measurement of macrostress, but the macrostress can affect the measured value of thermalmismatch stress. Thermal res dual stress induced during the composite fabrication process, will be further in-creased when the composite were subjected to the e 相似文献
12.
13.
14.
Thermal Residual Stresses in Bonded Repairs 总被引:1,自引:0,他引:1
The number of ageing aircraft is increasing and will further increase considerably in the near future. The control of damage by inspection and repair becomes therefore more and more important. The bonded repair method proved to be a cost-effective way to repair damage. However, this method has some disadvantages. One of them is the introduction of thermal residual stresses in the repair, due to the mismatch in coefficients of thermal expansion between the skin material and the repair material. Two analytical models are available to determine these residual stresses in the repairs, i.e., the Wang–Rose model and the Van Barneveld–Fredell model. A new computer program CalcuRep2000 [1] is being developed. This computer program will be used to calculate the stresses in bonded repairs, and is developed by the US Air Force in co-operation with the faculty of Aerospace Engineering of Delft University of Technology in The Netherlands. For this program an analytical model, which is able to calculate the thermal stresses in a bonded repair accurately, is essential. This paper describes how the most adequate analytical model was identified by comparison with Finite Element (FE) analysis. Two repair configurations were distinguished: The test specimen, i.e., bonded repair specimens used for fatigue tests in laboratories, and the in-field specimen, i.e., a realistic repair. The difference between both repair configurations is that a test specimen is free to expand during curing while in a realistic repair configuration expansion is partly prevented by the cooler surroundings of the heated area. The analytical model of Van Barneveld and Fredell proved to be the most accurate one. The results of this model agree with the results of the FE model of the test specimen and the in-field specimen. The Wang–Rose model calculates the thermal residual stresses accurately in the case of a test specimen, but the stresses calculated in the case of an in-field specimen are less accurate. No useful experimental data are available in literature from measurements of thermal residual strains on bonded repairs. Therefore experiments were conducted to measure thermal residual strains in bonded repairs. The same repair configurations were used for these experiments. The results obtained with the experiments are compared with FE results. Finally, the temperature distribution calculated by the analytical models is compared with the temperature distribution measured during the experiments of the in-field specimen. The influence on the thermal residual stresses of a different temperature field is discussed here, using the FE results. 相似文献
15.
采用机械合金化的方法在AZ31镁合金表面涂覆SiO2(Mg)涂层。通过XRD、显微硬度计、扫描电镜等测试手段对表面涂层的微观形貌结构、涂层的显微硬度进行分析,利用电化学工作站对涂覆前后的AZ31镁合金的耐蚀性能进行检测。结果表明:SiO2涂层被成功地涂覆到AZ31镁合金表面;同时,随着球磨时间的增加,涂层的显微硬度呈增加趋势,且随着球料比的增加,显微硬度亦增加,最高达到370.6HV,较基体提高了15.2%;涂层的厚度也呈现先增加后趋于稳定的趋势,但球磨时间过长,涂层内部出现裂纹;当球料比为15:1、球磨时间为15 h时,所制备涂层厚度为148μm,涂层致密且与基体结合较好;所对应的自腐蚀电流密度较基体降低了一个数量级,对应的腐蚀电压提高了6.5%,耐腐蚀性能得到明显改善。 相似文献
16.
以环氧树脂R368-1/硼纤维复合材料为研究对象,采用柱体单胞结构,建立了三维有限元分析模型。考虑试样加工制备过程和常温使用时的温度差,对残余应力分布特点和应力水平进行了讨论,给出了应力分布云图和应力沿径向的分布规律。进一步考察了纤维体积分数、温度差和附加界面层对残余应力分布的影响,结果表明,基体主要受拉伸应力作用,纤维主要受压缩应力作用,纤维体积分数增加和附加界面层有助于改善复合材料中残余应力的分布,试样制备温度的升高对纤维中应力的增加具有较大影响。 相似文献
17.
18.
镁合金/环氧聚氨酯涂层体系的耐腐蚀性能 总被引:1,自引:0,他引:1
环氧聚氨酯(ER/PU)涂层具有良好的电绝缘性、耐腐蚀性以及与金属基体的附着力,能够有效地阻挡或缓解Cl-,NO3-,SO2-4,H2O和O2等对镁合金基材的侵蚀,提高镁合金的耐腐蚀性能.为此,采用附着力、铅笔硬度测试,浸泡、失重法、盐雾及电化学试验等方法研究了聚氨酯(PU)涂层及环氧聚氨酯(ER/PU)涂层对镁合金的腐蚀保护效果及机理.结果表明,2种涂层体系都显著提高了镬合金的耐腐蚀性能,与基材附着良好、且硬度高,但后者效果更好. 相似文献
19.
镁合金表面Ni-P-纳米SiC复合化学镀层的耐腐蚀性能 总被引:3,自引:0,他引:3
为了提高AZ91D镁合金的应用性能,将纳米SiC引入Ni-P镀液,采用化学镀的方法制备了Ni-P-纳米SiC复合镀层,研究了Ni-P-纳米SiC镀层的孔隙率、盐雾性能以及阳极极化曲线,并与Ni-P化学镀层的耐蚀性进行了对比.结果表明:Ni-P-纳米SiC镀层均匀、致密,纳米SiC在镀层表面呈弥散分布;当纳米SiC浓度为4 g/L时,复合镀层的孔隙率最小,为1个/cm,耐蚀时间(90 h)明显长于Ni-P镀层(60 h),腐蚀电位为-0.58 V,略高于Ni-P镀层(-0.59 V). 相似文献