International Research Fellowship Program: Device Reliability and Fracture of Electroceramics

[402066 .琼斯国际研究奖学金计划使美国科学家和工程师能够到国外进行3至24个月的研究。该计划的奖励为联合研究提供了机会，并利用独特或互补的设施、专业知识和国外的实验条件。该奖项将支持Jacob L. Jones博士与澳大利亚悉尼新南威尔士大学Mark Hoffman博士合作12个月，与爱荷华州立大学Ersan Ustundag博士合作10个月。铁电材料耦合电能和机械能，使其成为医疗超声成像、压电蜂鸣器、超声电机、声纳和高精度测量系统等应用中的致动器、传感器和换能器中的有源元件的理想选择。在医疗和其他复杂的应用中，铁电器件的故障，特别是由于断裂，是不可接受的。本研究量化了微观结构在循环加载铁电器件裂纹萌生、扩展和失效中的作用，最终提高了可靠性。使用Hoffman博士提供的技术，观察和表征了包括地下微裂纹和断裂韧性随裂纹扩展（r曲线）的变化在内的损伤起始。显微结构参数包括应变、织构和成分在裂纹扩展实验中就地量化，采用新型衍射技术在Ustundag博士的研究中广泛应用。将这些实验结果结合起来，建立了铁电材料和铁弹性材料损伤演化的模型

0402066JonesThe International Research Fellowship Program enables U.S. scientists and engineers to conduct three to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-two month research fellowship by Dr. Jacob L. Jones to work with Dr. Mark Hoffman at the University of New South Wales in Sydney, Australia for 12 months, and Dr. Ersan Ustundag at Iowa State University for 10 months.Ferroelectric materials couple electrical and mechanical energy, making them ideal for active components in actuators, sensors and transducers in applications including medical ultrasonic imaging, piezoelectric buzzers, ultrasonic motors, sonar, and high-precision measurement systems. In medical and other sophisticated applications, failure of the ferroelectric device, particularly by fracture, is unacceptable. This research quantifies the role of microstructure in crack initiation, propagation and failure of cyclically loaded ferroelectric devices, leading ultimately to enhanced reliability. Damage initiation including subsurface microcracking and change in fracture toughness as a function of crack extension (R-curve) is observed and characterized using techniques offered by Dr. Hoffman. Microstructural parameters including strain, texture and composition are quantified in situ during crack propagation experiments using novel diffraction technologies applied extensively in Dr. Ustundag's research. The results from these experiments are combined to develop a model for damage evolution in ferroelectric and ferroelastic materials