• Smart Structures and Systems
• /
• v.6 no.2
• /
• pp.135-146
• /
• 2010

This paper presents the perspective of the Structural Mechanics program of the Air Force Office of Scientific Research (AFOSR) on the damage assessment of structures for the period 2006-2009 when the author was serving as Program Manager at AFOSR. It is found that damage assessment of structures plays a very important role in assuring the safety and operational readiness of US Air Force fleet. The current fleet has many aging aircraft, which poses a considerable challenge for the operators and maintainers. The nondestructive evaluation technology is rather mature and able to detect damage with considerable reliability during the periodic maintenance inspections. The emerging structural health monitoring methodology has great potential, because it will use on-board damage detection sensors and systems, will be able to offer on-demand structural health bulletins. Considerable fundamental and applied research is still needed to enable the development, implementation, and dissemination of structural health monitoring technology.

• Computers and Concrete
• /
• v.7 no.2
• /
• pp.103-118
• /
• 2010

Penetration of a fragment-like projectile into Fiber Reinforced Concrete (FRC) was simulated using finite element (FE) and particle formulations. Extreme deformations and failure of the material during the penetration event were modeled with multiple approaches to evaluate how well each represented the actual physics of the penetration process and compared to experimental data. A Fragment Simulating Projectile(FSP) normally impacting a flat, square plate of FRC was modeled using two target thicknesses to examine the different levels of damage. The thinner plate was perforated by the FSP, while the thicker plate captured the FSP and only allowed penetration part way through the thickness. Full three dimensional simulations were performed, so the capability was present for non-symmetric FRC behavior and possible projectile rotation in all directions. These calculations assessed the ability of the finite element and particle formulations to calculate penetration response while assessing criteria necessary to perform the computations. The numerical code EPIC contains the element and particle formulations, as well as the explicit methodology and constitutive models, needed to perform these simulations.

• Strategy21
• /
• s.38
• /
• pp.83-111
• /
• 2015

In these days, 1949 revolt of admirals has a variety of evaluations. In 1949, many people thought that revolt of admirals is simply disobedience to Secretary of Defense. Revolt of admirals was considered that Navy was defeated to Air force. At that time, many people didn't put too much meaning this case. But at long last, the confidential documents about revolt of admirals opened to the public. This historic event's value was re-evaluated. Many researches were progressed in USA, On the other hand only some researches were progressed in Korea. So I try to study this topic and discover another meaning. Then, I will apply this lesson that obtained through study to our Korea Navy.

• KSTLE International Journal
• /
• v.4 no.2
• /
• pp.66-72
• /
• 2003

This paper presents the hydrodynamic effect by the journal speed, eccentricity and source positions in order to overcome the defects of air bearing such as low stiffness and damping coefficient. Choosing the two row source position of air bearing is different from existing investigations in the side of pressure distribution of air film because of the high speed of journal and the wedge effects by the eccentricity. These optimal choices of the two row source positions enable us to improve the performance of the film reaction force and loading force as making the high-speed spindle. In this paper, The pressure behavior in theory of air film in high speed region of journal according to the eccentricity of journal and the source positions analyzed. The theoretical analysis has been identified by experiments. The results of investigated characteristics may be applied to precision devices like ultra-precision grinding machine and ultra high-speed milling.

• Tribology and Lubricants
• /
• v.17 no.6
• /
• pp.476-481
• /
• 2001

This paper has been presented the hydrodynamic effect by the journal speed, eccentricity and source positions in order to overcome the defects of air bearing such as low stiffness and damping coefficient. Choosing the two row source position of air bearing is different from existed investigations in the side of pressure distribution of air film because of the high speed of journal and the wedge effects by the eccentricity. These optimal chooses of the two row source positions enable us to improve the performance of the film reaction force and loading force as making the high speed spindle. In this paper, The pressure behavior in theory of air film according to the eccentricity of journal and the source positions analyzed. The theoretical analysis have been identified by experiments. The results of investigated characteristics may be applied to precision devices like ultra-precision grinding machine and ultra high speed milling.

• The Journal of the Convergence on Culture Technology
• /
• v.9 no.3
• /
• pp.287-292
• /
• 2023

The U.S. National Aeronautics and Space Administration proposed a new concept of urban air mobility in the city's short-range air transport ecosystem in order to build a new low-altitude air, and the term uam is currently used worldwide. This paradigm is also being promoted by the Korean government with the goal of commercializing urban air transport services by 2025, and furthermore, the need to secure air maneuvers and transportation capacity is emerging due to the rapidly changing future operating environment and battlefield space. In other words, this study started to present the military necessity and military operation plan by introducing the 'Agility Prime' program of the US Air Force. 'Agility Prime' program was organized in order of background and concept of urban air mobility, development trend of Korean urban air mobility and analysis of the US Air Force's 'Agility Prime' program, and it is expected that this study will be followed by a follow-up study.

• The Korean Journal of Air & Space Law and Policy
• /
• v.14
• /
• pp.133-150
• /
• 2001

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2001.06a
• /
• pp.231-235
• /
• 2001

This paper has been presented the dynamic effect by the journal speed. eccentricity and source positions in order to overcome the defects of air bearing such as low stiffness and damping coefficient. Choosing the two row source position of air bearing is different from previous investigations in the side of pressure distribution of air film by the wedge effects. These optimal chooses of the two row source positions enable us to improve the performance of the film reaction force and loading force as making the high speed spindle. The results of investigated characteristics may be applied to precision devices like ultra-precision grinding machine and ultra high speed milling.

• Tribology and Lubricants
• /
• v.17 no.5
• /
• pp.365-372
• /
• 2001

This paper has been presented the hydrodynamic effect by the journal speed, eccentricity and source positions in order to overcome the defects of air bearing such as low stiffness and damping coefficient. Choosing the two row source position of air bearing is different from existed investigations in the side of pressure distribution of air film because of the high speed of journal and the wedge effects by the eccentricity. These optimal chooses of the two row source positions enable us to improve the performance of the film reaction force and loading force as making the high speed spindle. In this paper, The pressure behavior in theory of air film according to the eccentricity of journal and the source positions analyzed. The results of investigated characteristics may be applied to precision devices like ultra-precision grinding machine and ultra high speed milling.

• Safety and Health at Work
• /
• v.12 no.2
• /
• pp.282-283
• /
• 2021