[en] Dissipated heat has been measured by thermographic technique during fatigue experiments on Ti-6Al-4V. Surface temperature of the specimen was found sensitive to the amount of fatigue damage accumulated in the material. An increased heat dissipation due to fatigue can be related to continuous change in the microstructure (increased dislocation density, stacking faults, etc.) of the material. A method based on passive thermography can be proposed to monitor damage accumulation in Ti-6Al-4V due to cyclic loading

[en] A method to characterize the deformation zone at a crack tip and predict upcoming fracture under load using white light interference microscopy was developed and studied. Cracks were initiated in notched Ti-6Al-4V specimens through fatigue loading. Following crack initiation, specimens were subjected to static loading during in-situ observation of the deformation area ahead of the crack. Nondestructive in-situ observations were performed using white light interference microscopy. Profilometer measurements quantified the area, volume, and shape of the deformation ahead of the crack front. Results showed an exponential relationship between the area and volume of deformation and the stress intensity factor of the cracked alloy. These findings also indicate that it is possible to determine a critical rate of change in deformation versus the stress intensity factor that can predict oncoming catastrophic failure. In addition, crack front deformation zones were measured as a function of time under sustained load, and crack tip deformation zone enlargement over time was observed

[en] The symposium, Nondestructive Methods for Materials Characterization, was held at the Materials Research Society 1999 Fall Meeting on November 29--30 in Boston, Massachusetts. The papers focused on advanced nondestructive evaluation (NDE) methodologies and instrumentation. Several X-ray techniques were developed or tailored for process control and deformation behavior in high- and low-density materials. Fracture, fatigue, and corrosion behavior of aging aircraft materials were characterized via linear and nonlinear acoustics. Structure-sensitive properties in magnetic materials and building materials were gauged with NDE parameters. Electric and dielectric properties in ceramics and composite materials were established. Thickness and interface properties in silicon wafers and thin films were studied. Advanced optical and infrared techniques were investigated for the characterization of capacitance, circuit boards, laser diodes, and material growth. Thirty five papers were processed separately for inclusion on the data base

[en] Variation in acoustic nonlinearity has been monitored in real time during fatigue, on four dog-bone specimens of Ti-6Al-4V, under low cycle fatigue conditions, from the virgin state all the way to fracture. The results of these experiments show that the acoustic nonlinearity undergoes large changes during the fatigue and follows a similar trend for the material under given fatigue test conditions. Transmission electron microscopic (TEM) examination of the samples with similar composition fatigues to different stages indicates a gradual change in the microstructure and dislocation density, which correlates with the changes in acoustic nonlinearity

[en] The nuclear security regime covers nuclear material and other radioactive material, both under and out of regulatory control, as well as associated facilities and activities during their lifetimes. The prevention of illicit trafficking of nuclear and other radioactive material is an important component of a State’s and the global nuclear security regime. The nuclear security architecture for preventing illicit trafficking should be based on the State’s legal and regulatory framework which must be in accordance with relevant international instruments and best practices. In order to establish, implement, maintain and sustain an effective and appropriate nuclear security regime to prevent, detect and respond to nuclear security events the legal and regulatory framework in the context of prevention of illicit trafficking should not be seen isolated. It is essential to integrate legislative and regulatory provisions for the prevention of illicit trafficking in the context of the prevention, detection of and response to criminal acts or unauthorized acts involving nuclear and other radioactive material out of regulatory control. (author)

[en] As part of the general security plan in Greece related to hosting the 2004 Olympic Games in Athens and from rising major security concerns internationally, there was a clear need for developing nuclear security architecture in the country to prevent, detect and respond to threats of nuclear terrorism. As a result, cooperation among the International Atomic Energy Agency (IAEA), the US Department of Energy and Greek competent authorities were initiated for the development and implementation of a comprehensive program adopting a multi-area coverage approach to nuclear security. As part of this program, state-of-the-art technology was applied at the borders to detect illicit trafficking of nuclear and other radioactive materials. (author)

[en] Since the hosting of the 2004 Olympic Games in Athens, and following recent major security concerns internationally, there was a clear need for a nuclear security program in Greece to prevent, detect and respond to threats of nuclear terrorism. As a result, cooperation between the International Atomic Energy Agency (IAEA), the US Department of Energy and Greek authorities started for the implementation of a comprehensive program adopting a multi-area coverage approach to nuclear security. In particular, nuclear security measures at six border cross-checking points were implemented during the preparation phase just before the Olympic Games, including installation of several Radiation Portal Monitors (RPM). Specifically, the Cargo Area of the seaport of Piraeus (5th Customs Office) was equipped with five RPMs, covering all inbound, outbound and transit cargoes. According to arrangements of the Piraeus Port Authority, the entrance of the cargo area of the seaport of Piraeus had to be separated in order to serve also the Piraeus Containers Terminal Company. For that reason, all five RPMs installed at this location were removed and placed again to new positions. Another four RPMs were additionally installed in order to cover the whole reconstructed entrance of the seaport, both inbound and outbound. (author)

[en] This paper outlines new concepts for the utilization of various ultrasonic techniques for the evaluation of different aspects of development and use of metal matrix composites. The authors introduce a novel mechanical parameter called interfacial shear stiffness coefficient which can be measured using ultrasonic shear wave reflectivity technique to characterize and quantify the matrix-fiber interface. Such nondestructive methods of interface characterization are essential because the utilization of metal matrix composites for aerospace applications require good characterization and evaluation of nascent composite systems in research and developmental stages. During development, it would be critical to evaluate (a) the compatibility of different types of matrix materials with different types of fibers, (b) the effect of different types of fiber coating on the load transfer between the matrix and the fiber, (c) the effect of processing conditions such as temperature, pressure, duration of processing, etc., (d) the suitability of the overall mechanical properties for the intended application, and (e) the mechanical behavior of the composite for life prediction studies

[en] Ultrasonic scanning acoustic microscopy is a nondestructive method useful for material elastic property quantification as well as crack size determination for surface and subsurface cracks. The advantage of the method over destructive methods for crack size determination is that the imaging technique can provide the crack sizing information while helping in the detection of interface degradation and early crack initiation so that their growth can be monitored during interrupted fatigue tests. Various metal matrix composite systems with titanium based matrix and SCS-6 fibers have been evaluated for this study [Ti-24Al-11Nb (atomic percent), Ti-6Al-2Sn-4Zr-2Mo (weight percent), and Ti-15Mo-3Nb-3Al-0.2Si (weight percent)]. The scanning acoustic microscope technique has been applied to materials subjected to both room temperature and elevated temperature fatigue cycling in addition to thermomechanical fatigue (in-phase and out-of-phase) conditions. A 50 MHz scanning acoustic microscope has been used for the imaging and evaluation of the damage initiation and growth of surface/subsurface cracks and interfacial degradation. All the images have been produced by exploiting the surface wave component of the ultrasonic signals from the scanning acoustic microscope because of the higher sensitivity of surface waves to both surface/subsurface cracks and perhaps also due to the changes in interfacial elastic properties. The results shown in this paper provide a very good understanding of the crack initiation and growth as well as interfacial degradation process of titanium based metal matrix composites when subjected to cyclical stresses at elevated temperatures and room temperature. The results indicate that the combination of high temperature and stress is very severe to the interface between the matrix and the fiber

[en] Highlights: • A novel Current injection phase thermography NDE method has been developed. • Blind impact damage has been successfully detected in composite laminates. • Carbon nanotubes enhance detection by improving of through thickness conductivity. • Detection is feasible with considerably less energy than for IR excited thermography. - Abstract: An innovative non-destructive evaluation (NDE) technique is presented based on current stimulated thermography. Modulated electric current is injected to Carbon Fibre Reinforced Plastics (CFRP) laminates as an external source of thermal excitation. Pulsed Phase Thermography (PPT) is concurrently employed to identify low velocity impact induced (LVI) damage. The efficiency of the proposed method is demonstrated for both plain and with Carbon Nanotubes (CNTs) modified laminates, which are subjected to low-velocity impact damaged composite laminates at different energy levels. The presence of the nano reinforcing phase is important in achieving a uniform current flow along the laminate, as it improves the through thickness conductivity. The acquired thermographs are compared with optical PPT, C-scan images and Computer Tomography (CT) representations. The typical energy input for successful damage identification with current injection is three to four orders of magnitude less compared to the energy required for optical PPT