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

新型电磁器件的设计和开发需要电磁断裂力学的基础研究。在该研究项目中，研究了材料系统的电磁断裂力学。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，对于两种特殊情况（完美电导率和准静态电磁场），导电板中的贯通裂纹对时间谐波弯曲波的散射，这两种情况具有物理意义。计算动态力矩强度因子与频率的关系，并以图形方式显示磁场和入射角对归一化值的影响。（b）我们讨论了在垂直于板表面的均匀磁场下带有贯穿裂纹的软铁磁板中的磁弹性相互作用和奇异力矩。计算静态和动态力矩强度因子，并以图形方式显示磁场对归一化值的影响。2) 我们从理论上和实验上研究了软铁磁梁板在横向磁场中的弯曲。磁场对偏转和应变的影响以图形方式显示。将理论与实验进行了挠度和应变的比较，与所考虑的磁场吻合良好。我们还研究了磁场对软铁磁梁板断裂行为的影响。3）我们从分析和实验角度考虑了超导熔合磁体结构合金和焊件的低温断裂行为。4）（a）我们考虑了裂纹压电材料和复合材料的静态和动态问题。进行数值计算，得到应力强度因子、能量释放速率和裂纹扩展速率。我们还研究了附着在压电陶瓷上的表面电极附近的弹性变量和电变量的静态行为。(b)我们讨论了均匀电场下无限各向同性介电体中的有限裂纹对垂直入射纵波的散射。计算动态应力强度因子与频率的关系，并以图形方式显示电场对归一化值的影响。5) (a) 我们对压电材料系统进行弯曲测试，并检查压电对偏转的影响。我们还采用有限元分析来研究压电材料系统的机电行为。将数值结果与实验测量的响应进行比较。(b)我们对压电材料进行了维氏压痕试验，并考察了施加电场、极化和载荷对断裂韧性的影响。还使用有限元技术对样本断裂行为进行了数值模拟。提供了数值结果来说明感应机电场的定性和定量行为。6）我们进行了数值模拟来分析材料系统的电磁断裂和变形。从模拟中获得的预测与实验非常相关。较少的

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