信息对抗技术专业毕业设计英文翻译说明.docx

1、信息对抗技术专业毕业设计英文翻译说明The ultrasonic wave propagation in composite materialand its characteristic evaluationJunjie Chang, Changliang Zheng, Qing-Qing Ni1. IntroductionFRP composite materials were applied to various fields, such as aircraft and space structures, because of the excellent characteristics,

2、e.g., light-weight, high ratio of relative intensity and high ratio of relative rigidity. Despite FRP having such outstanding characteristic, cracks in the matrix and fractures of the fiber make de bonding such kind of damage easy to occur between the fiber and the matrix, or the multi-layers. These

3、 damages are difficult to be detected directly by visual inspection from the sample surface, causing trouble to ensure the reliability and safety of the composite material and structures. Meanwhile, health monitoring technologies of materials are indispensable. Among them, the ultrasonic health moni

4、toring technology attracts lots of attentions in recent years. Simulations by finite element method have been performed for the development of apparatus for ultrasonic damage-detection, such as ultrasonic picture inspection and ultrasonic laser, and for the verification of their safety and validity.

5、 Researches and calculations on the propagation analysis of the ultrasonic wave in fiber strengthening composite materials have been well conducted and reported 18.On the solid interface, two kinds of boundaries can be considered. One is liquid contact in which thin lubricant is placed, and only pow

6、er and position movement perpendicular to the interface are transmitted. The other one is complete solid combination, which power and position movement both perpendicular to and parallel to the interface are transmitted. Fiber strengthening composite material, the interface between the fiber and the

7、 matrix can be considered to be solid contact. In the case of ,debonding existing between the matrix and the fiber, few literatures were found, since the conversions of the transmitted wave mode, reflection wave mode and reflection pulse phase (waveform) make the analysis very complicated. Provided

8、this problem to be solved, the quality of the materials, to some extent, can be estimated from the sound impedance of the reflector and the transmission object, and the optimal damage-detection method can be also assumed in a simulation.In this research, in the simulation of the technique monitoring

9、 the health by an ultrasonic wave method, the ultrasonic wave distribution pattern was analyzed with the basic theory for wave propagation by using the model for fiber strengthening composite material. Namely, it aims at obtaining the amplitude of the reflection wave and the amplitude of a transmitt

10、ed wave, when the longitudinal wave has unit amplitude incidence in model compound material. In the case of an ultrasonic wave propagation inside a model media, the rates of the reflective longitudinal, reflective traverse wave, transmission longitudinal wave and a transmission traverse wave generat

11、ed at a general incidence angle in the interface (a fiber and exfoliation) were analyzed and reflective coefficient and a transmission coefficient were gotten, respectively. Visualized studies separating into a longitudinal wave and a traverse wave were carried out, and the mechanisms of a longitudi

12、nal wave distribution and a traverse-wave distribution were elucidated when the ultrasonic wave propagated inside a composite material.2. Ultrasonic wave equationsConsider a single fiber composite, i.e., a single fiber is embedded in a matrix. Two dimensions analysis is conducted as shown in Fig. 2.

13、 In this case, when an ultrasonic wave propagates in this solid media, from Hookes law, the stressstrain relationship for two-dimensional plane strain in an isotropic media is written as follows 2: （1） （2） （3） （4）Where k and l are Lame constants, and the T superscript denotes the transposition.The u

14、ltrasonic wave equations of motion for two dimensional plane strain in an isotropic media are as follows: （5）Where, the first term on the left-hand side of Eq. (5) corresponds to a longitudinal wave, and the second term corresponds to a transverse wave. is density. If the longitudinal wave velocity

15、and transverse wave velocity are introduced the ultrasonic wave equations of motion for two-dimensional plane strain can be rewritten by （6）In the case of a plane advancing wave, the following formula is used to calculate for the oscillating energy generated by the ultrasonic wave per unit time: （7）

16、3. Results of analysis and simulation3.1. Transmission energy in different interface shapesWhen an incident vertical wave is obliquely irradiated, four waves as shown in Fig. 3, i.e., reflected longitudinal wave, reflected transverse wave, transmitted longitudinal wave and transmitted transverse wav

17、e, would appear on the interface. In other words, the shape of the interface between epoxy and glass may influence the propagation of the ultrasonic wave. For this reason, the model with different interface shapes as shown in Fig. 1 was used to investigate the influence of interface shape on wave pr

18、opagation behavior. The volume fraction proportion of both materials is 1:1, despite of the different interface shapes of the three models. That is to say, the glass-volume-percentage of all the models is 50%. The properties of each medium used in the analysis are shown in Table 1. As a boundary con

19、dition of the model, absorption is considered on the right and left edge, while it is symmetrical (the roller) on the up and down direction. The analytic condition and the input parameters were shown in Table 1.Fig. 2 shows the transmission energy of the ultrasonic wave propagation for these four mo

20、dels shown in Fig. 1.Fig. 1. Four different interface shapes between epoxy and glass. Here the transmission energy was defined by the average energy per unit area, lJ/mm2, at the receiver edge. As seen, in Model 1, the incident ultrasonic wave is perpendicular to the plane interface, and transmitted

21、 wave occurs along whole plane, so that the transmission energy is far larger than that in the other models. The full-reflection takes place in part of interface in both Model 2 and Model 3 when the incidence angle is larger than the critical angle because the ultrasonic wave radiates obliquely on a

22、 convex or concave interface. About one third of the incident wave experiences full-reflection in Model 2 and Model 3. However, the transmission energy of Model 3 is larger than that of Model 2. A second peak appears in the transmission curve of Model 3. Peak 1 is a reflected wave that propagates as

23、 a secondary wave source near the up-down-ward interface (in the glass region), while peak 2 is a transmitted wave in the central part of the glass region. The reason might be that near the interface, a refractive index distribution occurs, resulting in the appearance of the scattered waves, includi

24、ng refraction and reflection waves.The full-reflection takes place in interface of Model 4 (incidence angle is 45_). All primary incident waves were reflected, and the very small transmission energy that shows as figure is because the dispersion wave and the reflected wave penetrated the part as sec

25、ondary wave source from the vertical neighborhood.3.2. Influence of different fiber conditionsRefractive index distribution occurs near the second phase boundary due to the second phase compounding, resulting in the appearance of the scattered waves, including refraction and reflection in the compos

26、ite materials strengthened by fibers. In the next, the scattering of the ultrasonic wave shown in Fig. 1 will be taken into consideration. The scatters occur due to fibers embedded in composite materials. The incident wave, propagating in matrix region, is a sinusoidal wave. When the incident wave r

27、eaches the fiber, some is transmitted into the fiber, and the other is reflected on the fiber/matrix interface, and becomes a secondary wave source. According to the overlapping principle of wave functions, the whole wave function can be expressed as a sum of the incident wave and the scattered wave

28、. （8）Where the scattered wave includes all the waves scattering components generated due to the interface from the known wave.The model figure of the composite materials for the investigation of the scatters was designed as what shown in Fig. 3, where three fibers with different shapes were embedded

29、 in the matrix. The size of the model was. The board-shaped glass fiber with thickness was embedded in the center of the matrix of epoxy in Model 1, and was obliquely embedded in Model 2. A column shaped glass fiber with a diameter was embedded in the center of matrix in Model 3. The above three mod

30、els had a common fiber percentage of 20. The analytic condition and the input parameters were shown in Table 1.For the models in Fig. 3, when the incident wave on the left-hand side of the glass region arrived at the first interface between the epoxy and glass, the transmitted wave and the reflected

31、 wave arose. Then the reflected wave propagated to the incidence side, while the transmitted wave propagated to the receiver side and arrived at the second interface of the glass and epoxy through the glass region.The second transmitted wave and the second reflected wave arose at the second interfac

32、e, and a multiplex reflection occurred in the glass region. For the board-shaped fiber (plane fiber) and the column-shaped fiber (cylindrical fiber), Fig. 4 shows the comparisons of the analytic results in the cases of Model 1 (fiber thickness), Model 2 (fiber thickness, _) and Model 3 (fiber diameter) in Fig. 3, with an equivalent fiber volume fraction but with a different shape. As seen from the figure, the transmission energy of the Model 1 is far larger than that Model 2 and Model 3.From Fig. 4, which embedded the board-shaped fiber, two energy