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采用热弹塑性有限元方法,在考虑了材料性能参数随温度变化和界面反应层的情况下,计算了陶瓷/金属钎焊接头残余应力的大小和分布。通过计算发现:陶瓷/金属接头在冷却过程中产生的径向应力和剪应力对接头的影响较小。而在陶瓷表面的边缘接近焊缝的位置产生了最大的轴向拉应力,它影响接头的载荷承受能力,并且由于40Cr的屈服强度比45钢的高,计算出的Si3N4/40Cr接头的应力峰值比Si3N4/45钢的高。陶瓷/钎料和陶瓷/金属的界面反应层虽然薄,但它也是影响陶瓷/金属接头残余应力大小和分布的一个重要因素。另外,选择合适的钎料层、中问层和钎焊压力都可以有效地减小残余应力的峰值。 相似文献
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采用有限元数值模拟方法研究了用AgCuTi钎料并添加Kovar中间层对氧化铝陶瓷/不锈钢进行钎焊连接接头残余应力的分布情况,分析接头形式对残余应力的影响.结果表明,采用等壁厚直接对接接头时,接头最大等效应力高达600 MPa以上,而将不锈钢壁厚减半后再进行对接时,接头最大等效应力可以降低近200 MPa;两种情况下最大等效应力均出现在靠近连接界面的陶瓷中,断裂易在此位置发生.考查了各应力分量对最终残余应力的贡献,结果显示轴向应力和剪切应力在靠近界面的陶瓷侧有较大残余拉应力是造成接头强度降低的主要因素. 相似文献
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玻璃和金属焊接接头由于设计不合理,将致使接头存在较大的焊接残余应力,会严重削弱接头强度.应用顺次耦合有限元热应力计算方法,对平板玻璃和金属在真空条件下的钎焊过程进行了数值模拟,分析了玻璃、金属、钎料厚度、钎焊压力和钎焊温度等因素对应力集中区域残余应力的影响,并观察了焊接接头拉伸断裂后的形貌特征.结果表明,金属厚度增加会增大残余应力,并且其对残余应力影响最显著;钎焊压力和钎焊温度的增加可以降低残余应力;玻璃和钎料厚度对残余应力的影响不大;焊接接头的拉伸断裂区域位于玻璃和金属焊接接头界面贴近玻璃一侧. 相似文献
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孟普 《金刚石与磨料磨具工程》2013,(5):57-60
针对Ni-Cr合金钎焊金刚石冷却过程中产生较大残余应力的问题,利用有限元软件ANSYS建立金刚石六-八面体模型进行模拟分析。结果表明:残余应力在金刚石中心轴线和金刚石与钎料界面垂直方向上变化明显;最大残余应力出现在金刚石六-八面体尖角与钎料界面结合处;金刚石在钎料中包埋深度不同,残余应力最大值不同,包埋深度为60%时,工具性能较好。激光拉曼光谱对钎焊金刚石接头中残余应力测试结果与有限元数值模拟结果相符,误差小于10%。 相似文献
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不锈钢板翅结构钎焊残余应力及其影响因素 总被引:2,自引:0,他引:2
利用有限元软件ABAQUS,对不锈钢板翅结构在真空钎焊过程中产生的残余应力进行有限元分析,讨论钎缝间隙,隔板厚度、翅片内距、翅片内高,翅片厚度、钎焊温度、翅片层数、材料匹配程度以及压力对残余应力的影响.计算结果表明,由于镍基钎料和不锈钢母材力学性能的不匹配,在钎焊接头中产生了较大的残余应力.钎角处应力集中且状态复杂,成为最薄弱环节.钎缝间隙、隔板厚度、翅片内距、翅片厚度、材料匹配程度以及压力是残余应力的主要影响因素,钎焊温度、翅片层数以及翅片内高对残余应力的影响不大. 相似文献
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以复相陶瓷、纤维增强陶瓷基复合材料以及热电材料为例,从钎料成分设计、钎缝界面组织调控、接头残余应力缓解以及钎焊接头性能评测等角度,讨论了近年来发表的研究成果. 结果表明,在钎料中添加活性元素以及对母材表面改性的方法,能够有效改善钎料润湿性和界面结合强度;对于界面元素扩散以及母材过渡溶解的问题,可以设计制备复合钎料或阻隔层进行解决;接头残余应力的大小受材料热膨胀系数差异的影响较大,目前已提出了多孔中间层、梯度复合层以及母材表面机械加工等多种创新方法,但研究成果的应用仍停留在小尺寸样件,对于缓解大尺寸接头的残余应力问题仍有待解决. 最后对相关研究方向进行了总结和展望,期望推动航空航天构件连接的发展进程. 相似文献
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C. Jiménez K. Mergia N. V. Moutis X. A. Azpiroz Ch. Wilhelmi Th. Speliotis S. Messoloras 《Journal of Materials Engineering and Performance》2012,21(5):683-689
Cf/SiC ceramic composites have been brazed to Nimonic alloys using TiCuAg filler metal. In order to improve wettability and
to provide compatibility between ceramic and metal, the Cf/SiC surface was metallized through the deposition of a chromium layer. Subsequent heat treatments were carried out to develop
intermediate layers of chromium carbides. Excellent wetting of both the composite ceramic and the metal from the filler metal
is observed in the fabricated joints. Shear tests show that failure occurs always within the ceramic material and not at the
joint. In the filler region depletion of Ti and formation of Ag and Cu rich regions are observed. At the Cf/SiC-filler interface a layered structure of the filler metallic elements is observed. Titanium interacts with the SiC matrix
to form carbides and silicides. 相似文献
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X. Hernandez C. Jiménez K. Mergia P. Yialouris S. Messoloras V. Liedtke C. Wilhelmi J. Barcena 《Journal of Materials Engineering and Performance》2014,23(8):3069-3076
In view of aerospace applications, an innovative structure for joining a Ti alloy to carbon fiber reinforced silicon carbide has been developed. This is based on the perforation of the CMC material, and this procedure results in six-fold increase of the shear strength of the joint compared to the unprocessed CMC. The joint is manufactured using the active brazing technique and TiCuAg as filler metal. Sound joints without defects are produced and excellent wetting of both the composite ceramic and the metal is observed. The mechanical shear tests show that failure occurs always within the ceramic material and not at the joint. At the CMC/filler, Ti from the filler metal interacts with the SiC matrix to form carbides and silicides. In the middle of the filler region depletion of Ti and formation of Ag and Cu rich regions are observed. At the filler/Ti alloy interface, a layered structure of the filler and Ti alloy metallic elements is formed. For the perforation to have a significant effect on the improvement of the shear strength of the joint appropriate geometry is required. 相似文献
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Jianming Gong Wenchun Jiang Qinshan Fan Hu Chen S.T. Tu 《Journal of Materials Processing Technology》2009,209(4):1635-1643
This paper presents a finite element modelling of brazed residual stress in a stainless steel plate-fin structure applied to recuperators in microturbines. The effects of nine influence factors on residual stress are investigated. The results show that the brazed joint creates large residual stresses due to the mechanical properties mismatching between base metal and filler metal. Strength in the middle joint is affected mainly by longitudinal stress. The residual stress gradient around the interface between base metal and filler metal is very large, which can have a great effect on interface strength. The material mismatching, brazing gap, pressure loading, fin pitch, fin thickness, fin height and plate thickness significantly affect the residual stress distribution, while the brazing temperature and the number of fin layers have little impact on residual stress. This work provides a reference for optimizing the brazing procedure and decreasing the residual stress for stainless steel plate-fin structures. 相似文献
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采用自制不同形态的Al-Si-Mg-Cu-Ti钎料对70% SiCp/Al复合材料进行了半固态加压反应钎焊,阐述了该焊接方法的内涵,分析了接头组织性能. 结果表明,填充粉末钎料时,钎缝组织为铝合金基体、深灰色环状和块状Ti7Al5Si12和块状Ti;填充片状钎料时,钎缝组织为铝合金基体和短棒状Ti7Al5Si12. 接头界面结合情况是影响接头性能的主要因素. 填充粉末钎料时,钎料与母材结合充分,原子扩散通道多,接头界面结合好,没有明显分界线,接头力学性能好,抗剪强度达92.1 MPa,断口属于韧脆混合断口;填充片状钎料时,界面处有明显分界线,接头力学性能差,抗剪强度为43.9 MPa,断口为脆性断口. 相似文献
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ZrO2 and 40Cr steel were brazed by inserting buffer Ni,4J33,Ti and Cu separately. The chemical composition of 4J33 and Ni will damage the wetting property of Ag66Cu30Ti4 filler metal to ceramic and hinder the interface reaction between the active filler metal and Zr O2, so ZrO2/40Cr steel can not be bonded. Cu and Ti can efficiently release the residual stresses in the ceramic without injuring the wettabilty of filler metal, so the high joining strength can be obtained by inserting Cu and Ti. 相似文献
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以ABAQUS软件为平台,开发了用于模拟多层多道焊接头温度场、残余应力和焊接变形的热-弹-塑性有限元计算方法. 利用所开发的计算方法对板厚为16 mm的Q345钢平板对接接头的温度场、应力场和变形进行了数值模拟. 采用试验方法测量了对接接头的残余应力和角变形. 试验结果与数值结果比较吻合,验证了所开发方法的有效性. 结果表明,在板厚相同的条件下角变形和横向收缩随着焊接层数的增多有增大的趋势;焊缝附近的纵向拉伸应力区域分布范围随焊接层数的增加略有减小;焊接层数对纵向残余应力的峰值影响较小. 相似文献