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1.
本文以声阻探伤法的“机械振动”理论来解释金属胶接蜂窝结构面板上小凹坑处的讯号“异常”现象,说明了小凹坑处的声阻探伤“等效圆板”的弹性模量,泊松比,板厚,板径等都已改变,故决定声阻探伤讯号大小的工件“等效弹簧常数”完全可能与脱粘区的“等效弹簧常数”相等,从而导致二者的声阻探伤讯号相同。对小凹坑处的检测除应辅以其他手段外,建议先试行改变声阻探杆激励频率的办法,因这样有可能区分二者的差别。  相似文献   

2.
本文以声阻探伤法的“机械振动”理论来解释金属胶接蜂窝结构面板上小凹坑处的讯号“异常”现象,说明小凹坑处的声阻探伤“等效圆板”的弹性模量、泊松比、板厚、板径等都已改变,故决定声阻探伤讯号大小的工件“等效弹簧常数”完全可能与脱粘区的“等效弹簧常数”相等,从而导致二者的声阻探伤讯号相同。对小凹坑处的检测除应辅以其他手段外,建议先试行改变声阻探杆激励频率的办法,因这样有可能区分二者的差别。  相似文献   

3.
1.前言 随着飞机使用寿命的延长,对飞机胶接构件的质量也提出了更高的要求。胶接构件的质量主要指两个方面,一是胶接剂与被胶接件表面的粘接质量;一是胶接剂自身的内聚质量。目前国内对胶接结构的层板和蒙皮-蜂窝芯胶接质量的检测方法,主要是敲击、目视、谐振胶接仪、声阻仪等。一般说来这些方法具有原理可靠、轻便等特点。不足之处是多为手工操作,受人为因素影响大,灵敏度和可靠性不够理想。  相似文献   

4.
利用频响函数法辨识栓接结合部等效动力学参数时,由于实验测量、噪声干扰及数值运算(矩阵求逆)等所致误差,使辨识结果出现不适定性。为避免此问题的产生,使辨识结果能真实反映栓接结合部动态特性,提出新的辨识方法。建立含栓接结合部的整体结构有限元模型,据栓接结合部不同等效刚度与等效阻尼与整体结构归一化频率关系,确定栓接结合部等效刚度与等效阻尼的取值范围,并取该范围的平均值为初值,以实验与仿真整体结构频响函数误差最小为目标确定栓接结合部等效刚度与等效阻尼值。通过实验研究及与文献[16]结果比较表明,采用该方法可达准确辨识栓接结合部等效参数之目的。  相似文献   

5.
为了无损检测金属胶接结构的胶接强度.我组在六二五所、七二一厂、武汉无线电元件厂的大力协助下,参考国内外有关仪器于一九六六年十二月研制成松花江-Ⅸ型胶接质量检查仪(图1)。松花江-Ⅸ型胶接质量检查仪是一种按“换能器谐振法”进行工作的超声波探伤设备。“换能器谐振法”是资本土义国家探伤的主要办法。一九五一年荷兰 Fokker(弗克)皇家飞机工厂在美国麻省工学院 H.G.Albert  相似文献   

6.
文章论述了现代战机机体上复合材料胶接结构的超声检测技术.该技术以声阻法为原理,对相应的超声检测系统进行了设计.据此系统可以检测复合材料脱粘伤等缺陷形式,并且可以定性评估缺陷损伤程度.在实际应用中,已经验证了该方法的可行性、可靠性和准确性.  相似文献   

7.
李翔  王皓  陈力奋 《振动与冲击》2012,31(9):113-117
结合频响函数的性质,采用目标频带内各模态峰值响应的 -范数作为整体响应水平的衡量指标,将等效目标函数的灵敏度表示为固有频率和振型灵敏度的函数,进而采用基于梯度的迭代方法求解,实现结构在宽频激励下的整体动响应优化,该方法适合于多频带的响应控制。此外,在频带响应优化模型的基础上,提出了通过增加频率约束,使之能应用于密集频率结构,避免迭代过程中的密频和重频现象。最后通过桁架截面优化和形状优化的数值算例,表明了本文提出方法的合理性和有效性。  相似文献   

8.
通过对两栋基础隔震建筑在环境激励下的振动测试,运用随机子空间识别法和有理分式多项式法分别识别了结构的模态频率、振型和模态阻尼比。识别结果表明在环境激励下,基础隔震结构的基本频率远大于设计计算多遇地震工况下的基本频率;等效黏滞阻尼比很小,与未隔震结构的阻尼比相当,可以将基础隔震结构视为经典的比例阻尼系统。进一步以其中一栋为研究对象,以识别的模态参数作为修正基准,采用多目标优化的方法反演了环境激励下隔震层的实际水平等效刚度,结果表明其值为多遇地震下计算刚度取值的10.9倍。最后,基于反演的实际隔震层的水平等效刚度对结构的初始有限元模型进行了修正,并对修正后的模型进行了数值分析,分析结果与实际测试结果的对比表明修正后的模型可以更好地反映基础隔震结构在环境激励下的动力特性。  相似文献   

9.
徐建新  乔新 《工程力学》1996,(A01):229-232
针对复合材料补片胶接修补损伤金属结构中存在的残余热应力,本文充分考虑了周期结构对胶接修补区域的约束作用,系统地分析了胶接修补结构中残余应力大小以及残余热应力对结构静强度和疲劳寿命的影响,所得结果将为实际结构的胶接修补提供依据。  相似文献   

10.
变摩擦TMD特性和简谐激励控制效果的研究   总被引:2,自引:1,他引:1  
提出一种变正压力式变摩擦装置,通过改变摩擦面正压力实现摩擦力随系统位移增大而增大。将其用于TMD能有效克服常摩擦TMD摩擦力不可变的缺点。采用一阶谐波平衡法推导了变摩擦系统的等效阻尼比和等效频率,分析了系统各参数对其等效阻尼比和等效频率的影响,通过与经典阻尼单自由度系统的比较探讨了单自由度变摩擦系统的频率响应特性。从理论和试验两个方面研究了简谐激励下变摩擦TMD对单自由度主结构振动控制的特点。分析结果表明,变摩擦TMD的频率响应特性与经典阻尼TMD类似,二者都能有效减小主结构频率响应曲线的峰值,试验结果验证了变摩擦TMD在简谐激励下的有效性  相似文献   

11.
In this paper, the effect of silica nanoparticles (nano-silica) on the bonding strength of reinforced adhesive joints was experimentally studied in five concentrations. A two-part epoxy-based adhesive (Araldite 2015) was used to bond the adherends as well as silica nanoparticles for strengthening purposes. Nano-silica was added into the adhesive by 1, 1.5, 2, 2.5 and 3 wt.%. Some adhesive joints with and without nanoparticles were tested under uniaxial loading to obtain their bonding strength. The results showed that the change in the bonding strength is a function of nanoparticles concentration. Furthermore, it was concluded that the addition of silica nanoparticles has a suitable effect on the joint strength at an optimum point, in which the joint strength takes its maximum value, and a further increase in the nanoparticles weight fraction causes the joint strength to decrease.  相似文献   

12.
微弧氧化对镁合金摩擦及胶接性能的影响   总被引:2,自引:0,他引:2  
为解决镁合金表面耐摩擦和胶接性能较差的问题,采用微弧氧化法在MB15镁合金原位生长微弧氧化膜层.利用X射线衍射、扫描电镜、摩擦磨损试验机和万能拉伸实验机对膜层的结构组成、表面形貌、摩擦性能和胶接性能进行了研究.结果表明:MB15镁合金表面微弧氧化后可以形成均匀多孔的陶瓷涂层,膜层由MgO和MgAl2O4组成,经微弧氧化...  相似文献   

13.
电场下天然橡胶与Fe的热硫化粘接   总被引:1,自引:1,他引:0  
为提高天然橡胶与Fe的粘接性能,在天然橡胶(NR)的硫化过程中施加电场,伴随着熔盐电解,通过硫磺硫化交联反应与电化学反应的共同作用,使NR与金属(Fe)实现以化学键合的良好粘接.依据熔盐电解的电化学作用以及NR硫化的交联反应,探究了粘合机理,描述粘接历程.通过对胶接破坏表面进行扫描电镜观察分析,明晰了NR-Fe粘接界面层的结构特征,并对影响粘合性能以及硫化胶物理机械性能的因素进行了研究分析.结果表明:施加的电场强度、NR硫化胶的导电性对粘合性能作用明显;渗硫剂用量变化不仅对粘合性能影响较大,而且影响NR硫化胶的物理机械性能.  相似文献   

14.
Even though friction stir welding (FSW) has been shown to produce high performing butt joints, stress concentration at the weld edges in overlap FSW significantly reduces the performance of these joints. By combining FSW and adhesive bonding into a friction stir (FS) weld bonding, joint mechanical performance is greatly improved. Quasistatic and fatigue strength of the proposed FS weld‐bonding joints was assessed and benchmarked against overlap FSW and adhesive bonding. The characterization of the structural adhesive is also presented, including differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), as well as mechanical characterization with curing temperature. A small process parameter study was made to select proper FSW parameters for AA6082‐T6 overlap FSW and FS weld‐bonded joints. FS weld bonding achieved a significant increase in quasistatic and fatigue strength when compared with overlap FSW, with 79.9% of the fatigue strength of adhesive‐bonded joints at 106 cycles, whereas FSW had 41.6%.  相似文献   

15.
为了给铝合金-玄武岩纤维增强树脂(BFRP)复合材料粘接结构在汽车工业中的应用提供参考和指导,加工了铝合金-BFRP复合材料粘接接头。结合汽车服役中的温度区间,选取?10℃和?40℃的低温老化环境,对接头进行0、10、20、30天的老化。对老化后的粘接接头进行准静态拉伸试验和剪切试验,得到不同老化时间下铝合金-BFRP粘接接头的准静态失效强度。结合DSC和FTIR分析低温老化对BFRP复合材料的影响,并对粘接接头的失效断面进行宏观分析和SEM分析。结果表明:在低温老化环境中,胶粘剂与BFRP复合材料的化学性质受低温老化作用影响不大,BFRP中的官能团与玻璃化转变温度(Tg)没有发生明显的变化,接头的失效强度和失效模式主要受胶粘剂与粘接基材的热应力影响。对于拉伸接头,随着低温老化时间的增加,BFRP复合材料纤维与树脂基体间的结合力降低,铝合金-BFRP复合材料接头的失效断面中纤维撕裂的比例逐渐减少,拉伸接头失效强度逐渐下降。老化后剪切接头仍为内聚失效,BFRP复合材料的低温老化对铝合金-BFRP复合材料剪切接头的失效强度几乎没有影响,剪切接头失效强度的下降主要是胶粘剂与粘接基材热膨胀系数不一致引起的热应力的影响。采用二次应力准则公式对?10℃和?40℃低温环境下,拉应力、剪应力值随老化时间的变化规律进行了拟合,在此失效准则的基础上,根据响应面原理,建立接头失效强度随老化时间变化的三维曲面,为粘接技术在车身结构中的工程应用提供参考。   相似文献   

16.
The strength of adhesion between two over-moulded polymers, methylmethacrylate–butadiene–styrene copolymer (MABS) and thermoplastic polyurethane (TPU) that constitute a bi-component laminar system has been the subject of study. Results showed that at the bi-layer interface the adhesive fracture toughness increases as temperature and surface roughness are increased. Roughness has been demonstrated to be the most important parameter defining adhesion strength and failure. With the increase of roughness the failure was observed to change from adhesive towards cohesive type. An increase in either the temperature or the pressure applied to the samples caused a rise in adhesion energy. However, pressure seemed to have a minor effect in comparison to temperature. Significant increments in adhesion were obtained after applying the corona discharge treatment (CDT) to the attaching surfaces resulting in adhesion strengths almost double those of non-treated systems.  相似文献   

17.
根据经典薄板理论,建立约束阻尼板有限元模型,将其视作镶嵌于无限大刚性障板,利用Rayleigh积分法推导结构的辐射声功率及灵敏度表达式。以一阶峰值频率或频带激励下的声功率最小化为目标,约束阻尼材料体积分数为约束条件,建立拓扑优化模型,采用渐进优化算法,编制了优化计算程序,获得了约束阻尼材料的最优拓扑构型,并与全覆盖板及基板的辐射声功率进行了对比。研究表明:以声功率最小化为目标,对约束阻尼材料布局进行拓扑优化,能有效抑制结构的振动声辐射,为结构低噪声设计提供了重要的理论参考和技术手段。  相似文献   

18.
用锤击法和变时基技术进行黄河铁路桥的模态试验分析   总被引:13,自引:0,他引:13  
介绍了用力锤激励铁路运动实际桥梁模态分析的特别试验。试验采用了新技术,一、弹性聚能力锤延长了力的激励时间,使激励力的能量聚集在低频处;二、使用了变时基(Varied-Time-Base)传递函数模态分析方法,极大提高了大型结构的传递函数的分析精度,从而使锤击法进行大型土木结构的模态试验成为可能。本文是国内外首次利用锤击激励进行的铁路运行实际桥梁模态分析的成功试验,具有一定的科研和应用价值。  相似文献   

19.
The influence of imperfect bonding, owing to partial lack of adhesive, on the strength of composite non-crimp fabric (NCF) double-lap shear (DLS) joints was experimentally and numerically investigated. Fabrics were layered and compacted using a thermoplastic veil while infiltration of the preforms was done using the vacuum assisted process. Paste adhesive bonding was carried out by implementing the novel insertion squeeze flow process. Quality of adhesive bonding was tested using X-ray imaging and ultrasonic C-scan inspection. The tensile lap shear strength of the DLS joints was determined experimentally. Digital macrographs revealed that the specimens failed due to shear failure of the adhesive (debonding) and fracture of the composite boundary layer. As a second approach, a mesomechanical model based on the FE method and the (homogenized) progressive failure analysis method was developed. In the model, the areas without adhesion, as detected by the C-scans, were included. Numerical simulations of failure initiation and progression at the NCF joint and the adhesive indicated that it is possible to predict the strength and failure mechanisms of the imperfect bonded DLS joints.  相似文献   

20.
Surface pretreatment for adhesive bonding of aluminum with adhesive mediator The influence of three steps pretreatment degreasing, blasting and primer and the two steps pretreatment degreasing and blasting on the adhesive behaviour of aluminum alloy AlMg4,5Mn0,5 were investigated. The investigations were preformed using two cold hardening two‐components epoxy adhesives, one hot hardening one‐component epoxy adhesive and one cold hardening two‐components polyurethane adhesive. The three steps pretreatment indicate that the adhesion bonding strength by epoxy adhesives are higher than that by two steps pretreatment. On the other hand, the adhesion bonding strength was similar by using polyurethane adhesive independence of the pretreatment method. Leaving out the pretreatment step degreasing after corund blasting caused by using, PU, EP 2 and EP 3 adhesives a significant decreasing of the bonding strength in comparison with the only degreased specimen. This degreasing process was used to remove the residual blasting medium from the aluminum surfaces after blasting. The topographical structure of the surfaces after corund blasting was covered by further pretreatment with primer as a consequence of higher primer viscosity, which causes a decreasing in the surface roughness. The chemical composition of pretreated surfaces by three steps was different from that by two steps.  相似文献   

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