| Impact Damage Identification of Composite Structures with Built-in Piezoelectric Sensor/Actuator Networks |
1999 |
36 pages |
| Authors:
Calvin S. Wang; J. H. Park; Fu-Kuo Chang; STANFORD UNIV CA DEPT OF AERONAUTICS AND ASTRONAUTICS
|
 | An investigation was performed to develop a self-diagnostic technique using a built-in piezoelectric wafer network to detect damage and to identify the extent of the damage in fiber-reinforced composite plates resulting from foreign-object impact. The principle of the technique was to use built-in piezoelectric wafers as actuators to generate stress waves and also use the neighboring piezoelectric wafers as sensors to receive the propagating waves. The difference in sensor measurements ... |
|
| Composite Repairs of Cracked Metallic Airframe Structures |
MAY 93 |
188 pages |
| Authors:
S. N. Atluri; J. H. Park; E. F. Punch; P. E. O'Donoghue; Rhys Jones; KNOWLEDGE SCIENCES INC ATLANTA GA
|
| This report summarizes work that quantifies the benefits of composite patch repairs on cracked metallic aircraft structures. The first chapter describes a data base on bonding methods and repair materials that can be used in design and analysis. In the second chapter, analytical models are derived for the stress intensity factor of cracks in metallic sheets with bonded orthotropic repairs. Specific configurations included through-the-thickness center cracks, through-the-thickness cracks at a ... |
|
| Superconducting Bi(PB)-Sr-Ca-Cu-O Fibres Drawn from Melt-Quenched Glasses |
93 |
|
| Authors:
J. H. Park; T. S. Hahn; S. S. Choi; KOREA INST OF SCIENCE AND TECHNOLOGY SEOUL*
|
 | Recently the glass-to-ceramic process for the fabrication of Bi(Pb)- Sr-Ca-Cu-O superconductor has been widely investigated. The experimental results have shown that this process has the advantages of obtaining highly dense and grain-oriented superconductors as well as the ease of fabrication of any shape. In addition, superconducting fibers could be fabricated by heat-treatment of glass fibers drawn from melt-quenched glass preforms. It is well known that fiber drawability is sensitive to ... |
|
| Transport Properties and Oxidation of Chromium and Fe-Cr Alloys Exposed to Oxygen at High Temperatures |
91 |
|
| Authors:
J. H. Park; K. Natesan; ARGONNE NATIONAL LAB IL MATERIALS AND COMPONENTS TECHNOLOGY DIV
|
| Alloys samples of Fe-25Cr, Fe-25Cr-0.3 and 1Y, and Fe-25Cr-1Ce were subjected to oxidation tests in a microbalance at temperatures between 700 and 1000 C and at oxygen partial pressures in the range of 1 to 10(-20) atm for time periods of 19 to 160 h; integrity of the scales was evaluated by quenching from the oxidation temperature to room temperature in =20 min; during quenching, the samples of Fe-25Cr that ... |
|
| Reduced Water Degradation of YBaCuO by Si3N4 Protective Coating |
90 |
|
| Authors:
T. S. Hahn; S. S. Yom; Y. T. Kim; J. H. Park; S. S. Choi; KOREA INST OF SCIENCE AND TECHNOLOGY SEOUL*
|
| It is reported that high T(sub c) superconductors of YBaCuO easily react with both water and carbon dioxide in atmosphere. Future practical device applications using YBaCuO require proper protective coating techniques. Recently, surface protection of YBaCuO with silver covering layers, polyfluorocarbon thin films, and dielectric films were reported. In this paper, we show that Si3N4 protective coating onto YBaCuO by plasma-enhanced chemical vapor deposition (CVD) significantly improved water degradation of ... |
|
| Role of Alloying Additions in the Oxidation-Sulfidation of Fe-Base Alloys |
MAR 89 |
|
| Authors:
K. Natesan; J. H. Park; ARGONNE NATIONAL LAB IL MATERIALS AND COMPONENTS TECHNOLOGY DIV*
|
| Thermogravimetric studies have been conducted on Fe-25Cr (wt.%) and Fe-25Cr-20Ni model alloys with and without additions of refractory metals such as Nb and Zr. In addition to bulk alloying, specimens of both alloys were prepared with surface implantation of Nb. The alloys with bulk additions of Nb and Zr exhibited chromia surface scales upon exposure to air and low-oxygen- pressure environments. The oxide grain size was much larger than that ... |
|
Reports by Author
