George Baaklini - Academia.edu (original) (raw)

Papers by George Baaklini

Proceedings of the National Academy of Sciences, 2000

Membrane-type matrix metalloproteinase I (MT1-MMP)-deficient mice were found to have severe defec... more Membrane-type matrix metalloproteinase I (MT1-MMP)-deficient mice were found to have severe defects in skeletal development and angiogenesis. The craniofacial, axial, and appendicular skeletons were severely affected, leading to a short and domed skull, marked deceleration of postnatal growth, and death by 3 wk of age. Shortening of bones is a consequence of decreased chondrocyte proliferation in the proliferative zone of the growth plates. Defective vascular invasion of cartilage leads to enlargement of hypertrophic zones of growth plates and delayed formation of secondary ossification centers in long bones. In an in vivo corneal angiogenesis assay, null mice did not have angiogenic response to implanted FGF-2, suggesting that the defect in angiogenesis is not restricted to cartilage alone. In tissues from null mice, activation of latent matrix metalloproteinase 2 was deficient, suggesting that MT1-MMP is essential for its activation in vivo.

Review of Progress in Quantitative Nondestructive Evaluation, 1999

Prior studies have shown that ultrasonic velocity/time-of-flight imaging that uses back surface e... more Prior studies have shown that ultrasonic velocity/time-of-flight imaging that uses back surface echo reflections to gauge volumetric material quality is well suited (perhaps more so than is the commonlyused peak amplitude c-scanning) for quantitative characterization of microstructural gradients. Such gradients include those due to pore fraction, density, fiber fraction, and chemical composition variations [11]. Variations in these microstructural factors can affect the uniformity of physical performance (including mechanical [stiffness, strength], thermal [conductivity], and electrical [conductivity, superconducting transition temperature], etc. performance) of monolithic and composite [1,. A weakness of conventional ultrasonic velocityltime-of-flight imaging (as well as to a lesser extent ultrasonic peak amplitude c-scanning where back surface echoes are gated is that the image shows the effects of thickness as well as microstructural variations unless the part is uniformly thick. This limits this type of imaging's usefulness in practical applications. The effect of thickness is easily observed from the equation for pulse-echo waveform time-of-flight (2'r) between the first front surface echo (FS) and the first back surface echo (B I), or between two successive back surface echoes where:

Ceramic Engineering and Science Proceedings, 2000

ABSTRACT Nextel™ 312/Blackglas™ composite densification via repeated cycles of infiltration TM wi... more ABSTRACT Nextel™ 312/Blackglas™ composite densification via repeated cycles of infiltration TM with the Blackglas precursor materials and pyrolysis were studied. Nicalon™/Blackglas composite specimens with graphite foil as simulated delaminations in various layer locations were evaluated. Results show unique capabilities of nondestructive X-ray microtomographic and ultrasonic evaluation in characterizing processing- and failure-related microstructures.

Mater Eval, 1995

Capabilities and limitations of X-ray computed microtomography (CT) in characterizing relevant co... more Capabilities and limitations of X-ray computed microtomography (CT) in characterizing relevant composite material issues as identified during manufacturing processes were investigated. Damage in engine subcomponents was evaluated and compared with damage detected in pedigreed coupon type specimens. The system used is a newly developed state-of-the-art X-ray computed tomography system capable of providing digital radiography, computed tomography, and computed laminography. CT

Scaling up the Single Transducer Thickness-Independent Ultrasonic Imaging Method for Accurate Cha... more Scaling up the Single Transducer Thickness-Independent Ultrasonic Imaging Method for Accurate Characterization of Microstructural Gradients in Monolithic and Composite Tubular Structures. Don J Roth, Dorothy V Carney ...

CITATIONS 0 READS 15 5 authors, including:

AIAA Infotech@Aerospace 2010, 2010

Smart Sensor Phenomena, Technology, Networks, and Systems Integration 2014, 2014

Generally, rotating engine components undergo high centrifugal loading environment which subject ... more Generally, rotating engine components undergo high centrifugal loading environment which subject them to various types of failure initiation mechanisms. Health monitoring of these components is a necessity and is often challenging to implement. This is primarily due to numerous factors including the presence of scattered loading conditions, flaw sizes, component geometry and materials properties, all which hinder the simplicity of applying health monitoring applications. This paper represents a summary work of combined experimental and analytical modeling that included data collection from a spin test experiment of a rotor disk addressing the aforementioned durability issues. It further covers presentation of results obtained from a finite element modeling study to characterize the structural durability of a cracked rotor as it relates to the experimental findings. The experimental data include blade tip clearance, blade tip timing and shaft displacement measurements. The tests were conducted at the NASA Glenn Research Center's Rotordynamics Laboratory, a high precision spin rig. The results are evaluated and examined to determine their significance on the development of a health monitoring system to pre-predict cracks and other anomalies and to assist in initiating a supplemental physics based fault prediction analytical model.

… Memorandum, NASA/TM …, 2009

CITATIONS 0 READS 7 5 authors, including:

Health Monitoring of Structural and Biological Systems 2009, 2009

Rotor health monitoring and on-line damage detection have been increasingly gaining interest to m... more Rotor health monitoring and on-line damage detection have been increasingly gaining interest to manufacturers of aircraft engines, primarily to increase safety of operation and lower the high maintenance costs. But health monitoring in the presence of scatter in the loading conditions, crack size, disk geometry, and material property is rather challenging. However, detection factors that cause fractures and hidden internal

Nondestructive evaluation (NDE) is one of several technologies applied at NASA Glenn Research Cen... more Nondestructive evaluation (NDE) is one of several technologies applied at NASA Glenn Research Center to determine atypical deformities, cracks, and other anomalies experienced by structural components. NDE consists of applying high-quality imaging techniques (such as x-ray imaging and computed tomography (CT)) to discover hidden manufactured flaws in a structure. Efforts are in progress to integrate NDE with the finite element (FE) computational method to perform detailed structural analysis of a given component. This report presents the core outlines for an in-house technical procedure that incorporates this combined NDE-FE interrelation. An example is presented to demonstrate the applicability of this analytical procedure. FE analysis of a test specimen is performed, and the resulting von Mises stresses and the stress concentrations near the anomalies are observed, which indicates the fidelity of the procedure. Additional information elaborating on the steps needed to perform such an analysis is clearly presented in the form of mini step-by-step guidelines.

Smart Sensor Phenomena, Technology, Networks, and Systems Integration 2015, 2015

Efforts to update and improve turbine engine components in meeting flights safety and durability ... more Efforts to update and improve turbine engine components in meeting flights safety and durability requirements are commitments that engine manufacturers try to continuously fulfill. Most of their concerns and developments energies focus on the rotating components as rotor disks. These components typically undergo rigorous operating conditions and are subject to high centrifugal loadings which subject them to various failure mechanisms. Thus, developing highly advanced health monitoring technology to screen their efficacy and performance is very essential to their prolonged service life and operational success. Nondestructive evaluation techniques are among the many screening methods that presently are being used to pre-detect hidden flaws and mini cracks prior to any appalling events occurrence. Most of these methods or procedures are confined to evaluating material's discontinuities and other defects that have mature to a point where failure is eminent. Hence, development of more robust techniques to pre-predict faults prior to any catastrophic events in these components is highly vital. This paper is focused on presenting research activities covering the ongoing research efforts at NASA Glenn Research Center (GRC) rotor dynamics laboratory in support of developing a fault detection system for key critical turbine engine components. Data obtained from spin test experiments of a rotor disk that relates to investigating behavior of blade tip clearance, tip timing and shaft displacement based on measured data acquired from sensor devices such as eddy current, capacitive and microwave are presented. Additional results linking test data with finite element modeling to characterize the structural durability of a cracked rotor as it relays to the experimental tests and findings is also presented. An obvious difference in the vibration response is shown between the notched and the baseline no notch rotor disk indicating the presence of some type of irregularity.

Smart Sensor Phenomena, Technology, Networks, and Systems Integration 2012, 2012

Detecting rotating engine component malfunctions and structural anomalies is increasingly becomin... more Detecting rotating engine component malfunctions and structural anomalies is increasingly becoming a crucial key feature that will help boost safety and lower maintenance cost. However, achievement of such technology, which can be referred to as a health monitoring remains somewhat challenging to implement. This is mostly due to presence of scattered loading conditions, crack sizes, component geometry and material properties that hinders the simplicity of imposing such application. Different approaches are being considered to assist in developing other means of health monitoring or nondestructive techniques to detect hidden flaws and mini cracks before any catastrophic events occur. These methods extend further to assess material discontinuities and other defects that have matured to the level where a failure is very likely. This paper is focused on presenting data obtained from spin test experiments of a turbine engine like rotor disk and their correlation to the development of a structural health monitoring and fault detection system. The data collected includes blade tip clearance, blade tip timing measurements and shaft displacements. The experimental results are collected at rotational speeds up to 10,000 Rpm and tests are conducted at the NASA Glenn Research Center's Rotordynamics Laboratory via a high precision spin system. Additionally, this study offers a closer glance at a selective online evaluation of a rotating disk using advanced capacitive, microwave and eddy current sensor technology.

Smart Sensor Phenomena, Technology, Networks, and Systems Integration 2013, 2013

ABSTRACT Safety and maintenance cost are among the major features that engine manufacturers striv... more ABSTRACT Safety and maintenance cost are among the major features that engine manufacturers strive for in their design approach to produce efficient and successful products. However, this design success is subject to manufacturing highly reliable rotating components that typically undergo high rotational loading conditions that subject them to various types of failure initiation mechanisms. To counter such design concerns; health monitoring of these components is becoming a necessity, yet, this attribute remains somewhat challenging to implement. This is mostly due to the fact that presence of scattered loading conditions, crack sizes, component geometry and material property hinders the simplicity of imposing such applications. Therefore, exploitation of suitable techniques to monitor the health of these rotating components is ongoing and investigating other means of inspections such as non-destructive approaches to pre-detect hidden flaws and mini cracks is also being considered. These approaches or techniques extend more to assess materials’ discontinuities and other defects that have matured to the level where a failure is likely. This paper is pertained to presenting data collected from a spin experiment of a turbine like rotor disk tested at a range of rotational speeds up to 12000 rpm. It further includes an analytical modeling of the rotor vibration response that is characterized by a combination of numerical and experimental data. The data include blade tip clearance, tip timing measurements and shaft displacements. The tests are conducted at the NASA Glenn Research Center’s Rotordynamics Laboratory, a high precision spin rig. The results are evaluated and scrutinized to explore their relevance towards the development of a crack detection system and a supplemental physics based fault prediction analytical model.

Emerging Technologies in Non-Destructive Testing V, 2012

Ceramic Engineering and Science Proceedings, 2002

... George Baaklini NASA Glenn Research Center 2 IOOO Brookpark Road Cleveland, OH 44 I35 ... Thu... more ... George Baaklini NASA Glenn Research Center 2 IOOO Brookpark Road Cleveland, OH 44 I35 ... Thus, thermal and bending fatigue may be responsible for the reductions in coupon strength and presence of damage as determined through NDE. ...

Journal of Reinforced Plastics and Composites, 2005

A universal winding machine is designed and constructed to manufacture a Multidirection Composite... more A universal winding machine is designed and constructed to manufacture a Multidirection Composite (MDC) flywheel. The machine has three translation axes (XYZ) for the main carriage, three rotation axes around XYZ and an axis of mandrel rotation. Radial rings comprising fibers in the radial direction and hoop rings with fibers in the hoop direction are manufactured using this machine. Multiple hoop and radial rings are assembled in a special assembly mold to form an MDC rim. Manufacturing details and results of nondestructive evaluation (NDE) using X-ray and thermal techniques conducted of radial and hoop rings are presented.

Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; General, 1994