This paper aims to characterize the surface damage as a consequence of fretting fatigue in aluminum alloy 7075-T6 plates in double-lap bolted joints through XRD, surface profilometry, and SEM analyses. The main focus was on the surface roughness and chemical phase composition of the damaged zone along with the identification of fretting fatigue crack initiations over the surface of the material...

ABSTRACT. The effectiveness of structural health monitoring via ultrasonic methods is seriously compromised by changing environmental conditions such as temperature. Variations in temperature can be spuriously identified as damage owing to thermal expansion or contraction of the material as well as changing of the wave propagation speed. This problem becomes even more serious when temperature c...

The detection, location, and sizing of a fatigue crack emanating from a fastener hole in an aluminum plate is investigated. Two linear arrays of surface mounted piezoelectric disk transducers send and receive ultrasonic guided waves that are transmitted, reflected, and scattered by both the joint geometry and the fatigue crack. A tomography algorithm is used to detect and locate the crack. Ampl...

The ability of the time reversal process to reconstruct sources of finite size relative to a wavelength is investigated. Specifically the quality of the spatial reconstruction of a finite sized source will be presented through the use of time reversal experiments conducted on an aluminum plate. The data presented in the paper show that time reversal can reconstruct a source equally well regardi...

We demonstrate terahertz THz pulse propagation on a cylindrical aluminum plate, with low loss and negligible dispersion via transverse-electric type whispering gallery WG modes. We observe an apparent superluminal effect where the group velocity is greater than c, and explain this phenomenon by means of a plane-wave description of the WG modes. The propagation loss is dominated by the diffracti...

Intermetallic (aluminum and zirconium) thermite molybdenum trioxide) projectiles were launched using a high velocity impact ignition testing system. The experiments designed to simulate reactivity in (argon) low (air) altitude environments. into chamber that included steel target plate for projectile penetration before impacting rear witness plate. was semi-sealed instrumented quasi-static pres...

We present experimental and theoretical studies on terahertz surface plasmon (TSP) propagation on slit and rectangular aperture arrays in an aluminum sheet. Terahertz waves are coupled onto the plasmonic structures via a parallel plate waveguide. Long-lasting oscillations are observed in the temporal pulse shape after propagating through the periodic structure, whose Fourier transformation into...

The cicada uses a rapid sequence of buckling ribs to initiate and sustain vibrations in its tymbal plate (the primary mechanical resonator in the cicada’s sound production system). The tymbalimba, a music controller based on this same mechanism, has a row of 4 convex aluminum ribs (as on the cicada’s tymbal) arranged much like the keys on a calimba. Each rib is spring loaded and capable of snap...

1. Easy to plate: steel, copper and brass. These can be coat* with adherent deposits that will riot fail at the deposit-substrate interface. 2. Special treatment: stainless steels, aluminum, beryllium, magnesium and plastics. These can also be coated with adherent deposits that will not fail at the deposit-substrate interface. 3. Very difsicult: titanium, molybdenum, tungsten, niobium, tantalum...

Using a transient calorimetric technique, the total hemispherical emissivities Eh of very pure copper, aluminum, and silver have been measured at various temperatures in the range 335-1100'K. By carrying out measurements on a sphere, a thin circular disk, and a thin square plate all made of the same copper sample, it is shown that the measured (, is practically independent of the shape of the s...