Study on Electromagnetic Fracture Mechanics of Material Systems for New Electromagnetic Devices

新型电磁器件的设计与开发需要对电磁断裂力学进行基础研究。本课题研究材料体系的电磁断裂力学。从电磁材料系统的理论考虑和实验结果可以得出以下结论：1)(a)我们考虑在垂直于裂纹表面的均匀磁场下，导电板中贯通裂纹对时谐弯曲波的散射，这是两种具有物理意义的特殊情况：完全导电性和准静态电磁场。计算了动矩强度因子与频率的关系，并以图形显示了磁场和入射角对归一化值的影响。(b)讨论了带贯通裂纹的软铁磁板在垂直于板表面的均匀磁场作用下的磁弹性相互作用和奇异矩。计算了静、动、多矩强度因子，并用图形显示了磁场对归一化值的影响。2)从理论和实验两方面研究了软磁束流板在横向磁场中的弯曲。用图形表示了磁场对挠度和应变的影响。将理论和实验结果进行了挠度和应变的比较，在考虑磁场的情况下，结果吻合较好。本文还研究了磁场对软磁束流板断裂行为的影响。3)对超导熔合磁体结构合金和焊接件在高磁场下的低温断裂行为进行了分析和实验研究。4) (a)考虑裂纹压电材料和复合材料的静动力问题。进行了数值计算，得到了应力强度因子、能量释放率和裂纹扩展率。我们还研究了附着在压电陶瓷表面电极附近的弹性和电变量的静态行为。(b)讨论了均匀电场作用下无限各向同性介电体中有限裂纹对正常入射纵波的散射。计算了动态应力强度因子与频率的关系，并用图形显示了电场对归一化值的影响。5) (a)我们对压电材料系统进行了弯曲试验，并检查了压电对挠度的影响。本文还采用有限元方法研究了压电材料系统的机电性能。数值结果与实验测量结果进行了比较。(b)对压电材料进行了维氏压痕试验，考察了外加电场、极化和载荷对断裂韧性的影响。利用有限元技术对试样的断裂行为进行了数值模拟。数值结果说明了感应电场的定性和定量行为。6)对材料系统的电磁断裂和变形进行了数值模拟分析。模拟得到的预测结果与实验结果吻合得很好。少

Design and development of new electromagnetic devices require basic research on electromagnetic fracture mechanics. In this research project, the electromagnetic fracture mechanics of material systems is investigated. From the theoretical considerations and experimental results for electromagnetic material systems, the following can be concluded1) (a) We consider the scattering of time harmonic flexural waves by a through crack in a conducting plate under a uniform magnetic field normal to the crack surface for two special cases, perfect conductivity and quasistatic electromagnetic field, which are of physical interest. The dynamic moment intensity factor versus frequency is computed and the influence of the magnetic field and the angle of incidence on the normalized values is displayed graphically.(b) We discuss the magneto-elastic interactions and singular moments in a soft ferromagnetic plate with a through crack under a uniform magnetic field normal to the plate surface. The static … More and dynamic moment intensity factors are computed and the influence of the magnetic field on the normalized values is displayed graphically.2) We examine the bending of a soft ferromagnetic beam plate in a transverse magnetic field both theoretically and experimentally. The effect of magnetic field on the deflection and strain is shown graphically. A comparison of the deflection and strain is made between theory and experiment, and the agreement is good for the magnetic field considered. We also study the effect of magnetic field on the fracture behavior of a soft ferromagnetic beam plate.3) We consider the cryogenic fracture behavior of structural alloys and weldments for superconductiong fusion magnets in high magnetic fields both analytically and experimentally.4) (a) We consider the static and dynamic problems of cracked piezoelectric materials and composites. Numerical calculations are carried out, and the stress intensity factor, energy release rate and crack growth rate are obtained. We also study the static behavior of the elastic and electric variables in the vicinity of a surface electrode attached to a piezoelectric ceramic.(b) We discuss the scattering of normally incident longitudinal waves by a finite crack in an infinite isotropic dielectric body under a uniform electric field. The dynamic stress intensity factor versus frequency is computed and the influence of the electric field on the normalized values is displayed graphically.5) (a) We perform the bending tests on piezoelectric material systems and examine the piezoelectric effects on the deflection. We also employ the finite element analysis to study the electromechanical behavior of piezoelectric material systems. Numerical results are compared with the experimentally measured response.(b) We carry out the Vickers indentation tests on piezoelectric materials and examine the influence of applied electric field, polarization and load on the fracture toughness. The specimen fracture behavior is also simulated numerically using the finite element technique. Numerical results are provided to illustrate both qualitative and quantitative behavior of the induced electromechanical fields.6) We performe the numerical simulation for analyzing the electromagnetic fracture and deformation of material systems. The predictions obtained from the simulation correlate very well with the experiments. Less