Acousto-Ultrasonic Monitoring of Glueline Curing

Hard maple electrodes were bonded with three types of epoxies in a lap joint and acousto-ultrasonic transmission monitored during curing. The electrodes, 3.2 x 25 x 115 mm, were lapped for a 25- x 25-mm bond area. Standard acoustic emission sensors, 175 kHz transmitter and 75 kHz receiver, were used to provide an RMS voltage output, which increased as the adhesive cured. The transmission increase was quantified using a halftime to cure. The increase in transmission is comparable to the predicted increase in longitudinal modulus. Increasing glueline thickness from 0.05 to 0.5 mm caused an increase in apparent cure time as measured by the halftime. By controlling glueline temperature, an activation energy was determined from the halftime to cure

Development of an Acousto-Ultrasonic Scanning System for Nondestructive Evaluation of Wood and Wood Laminates

An acousto-ultrasonic (AU) scanning system was developed and optimized for wood products. It was found that AU probe alignment, coupling pressure, and stabilization time affect the repeatability of AU readings. After optimization of these factors, the error in AU reading (RMS) was negligible. AU transmission through solid wood also showed a relationship of acoustic attenuation to wood anisotropy. A calculated modulus of elasticity in the direction of wave propagation correlated with wave attenuation characteristics in the TR and LR planes. For wave propagation in the TR plane, the greatest attenuation was observed at a growth ring angle (GRA) of about 45°, corresponding to the lowest modulus of elasticity, which is in this plane. The effect of wood anisotropy (GRA) was found to be a major problem for evaluation of laminated wood, since the received signal was strongly affected by wood properties. Consequently, the effect of anisotropy and natural variability of wood will be the major limiting factor of any acoustic NDE technique applied to many wood products

Acoustic Monitoring of Cold-Setting Adhesive Curing in Wood Laminates: Effect of Clamping Pressure and Detection of Defective Bonds

Many variables affecting adhesive bonding of wood, including moisture content, temperature, surface roughness and contamination, and wood density, are difficult to control and/or measure in industrial conditions. However, the combined effect of these factors may be compensated by controlling process variables, such as clamping pressure and time, and adhesive viscosity, concentration, and spread. This research project investigated an ultrasonic method as a nondestructive means of monitoring bonding processes and assessing the quality of the cured bonds in wood laminates. Monitoring was performed simultaneously at normal and angular (5° nominal) incidence to the bond plane, using pairs of clear Douglas-fir laminates with a single bond line. It was previously reported that ultrasonic transmission is sensitive to curing phases, such as spreading, penetration, curing, and bond thickness. This paper reports the effect of bond defects (uncured, underspread, and uneven spread) and clamping pressure on ultrasonic transmission. The results showed that defective bonds can be detected using patterns of relative attenuation changes during curing and an "unloading effect," measured as the relative transmission reduction after the clamping load is released. Also, transmission through uncured bond lines was strongly affected by pressure, an observation that can be utilized to select optimum clamping pressure

Industrial applications and opportunities for nondestructive evaluation of structural wood members

This paper reviews techniques that can or have been used for determining the key properties of structural wood members, largely softwood lumber and structural panels. For solid wood materials, moisture content, density, and defects are underlying basic properties that must be assessed independently to arrive at structural values. In reconstituted materials, an additional variable, adhesive quality dominates. In addition to reviewing these properties, an assessment is provided for the state of maturity of the relevant technologies

Acousto-Ultrasonic Assessment of Internal Decay in Glulam Beams

An acousto-ultrasonic (AU) through-transmission technique was evaluated for assessing brown-rot decay in Douglas-fir glulam beams that had been removed from service. The effect of decay on different AU signal features was compared to that from normal variations in wood, such as growth ring angle, knots, and moisture gradient. The analysis was based on measurement of velocity, attenuation, shape, and frequency content of the received signals. All of the studied signal features were correlated with the degree of decay; however, they were affected by natural characteristics of wood. Attenuation and signal shape were more affected by the growth ring angle variations and knots than were velocity and frequency features. The effect of knots depended upon size, type, orientation, and distance from the surface. A steep moisture gradient obscured the detection of small degrees of decay, with the greatest effect on signal shape and frequency parameters. This study suggests that multiple signal feature analysis can be used to distinguish decay from certain types of natural wood characteristics such as growth ring angle variations and knots

Small-Scale Rack Testing of Wood-Frame Shear Walls

A series of racking tests were performed with small-scale (1.2-m X 1.2-m) plywood and OSB assemblies as a means of assessing the potential of reduced assembly sizes in screening variables for subsequent full-size tests. The plywood materials and configurations included variations in stud spacing, nailing, panel thickness and number, and addition of gypsum board. OSB assemblies differed in panel orientation and nailing. The framing used was KD Select Structural to minimize variations in fastening. Both of the standard assemblies (400-mm stud spacing) were also exposed to high relative humidity and effects of green framing. There were clear statistical differences between most plywood configurations, but the most prominent were for center-stud framing, and 9-mm-thick panels. The addition of gypsum board gave higher maximum load and greater stiffness, but the increased variability precluded finding significant differences with the basecase. OSB was significantly lower than plywood in most results. Moisture effects were minimal except for a greater deformation of OSB to the maximum load. The effect of green framing for the bottom plate was minimal

Left-right symmetry at LHC and precise 1-loop low energy data

Despite many tests, even the Minimal Manifest Left-Right Symmetric Model (MLRSM) has never been ultimately confirmed or falsified. LHC gives a new possibility to test directly the most conservative version of left-right symmetric models at so far not reachable energy scales. If we take into account precise limits on the model which come from low energy processes, like the muon decay, possible LHC signals are strongly limited through the correlations of parameters among heavy neutrinos, heavy gauge bosons and heavy Higgs particles. To illustrate the situation in the context of LHC, we consider the "golden" process $pp \to e^+ N$. For instance, in a case of degenerate heavy neutrinos and heavy Higgs masses at 15 TeV (in agreement with FCNC bounds) we get $\sigma(pp \to e^+ N)>10$ fb at $\sqrt{s}=14$ TeV which is consistent with muon decay data for a very limited $W_2$ masses in the range (3008 GeV, 3040 GeV). Without restrictions coming from the muon data, $W_2$ masses would be in the range (1.0 TeV, 3.5 TeV). Influence of heavy Higgs particles themselves on the considered LHC process is negligible (the same is true for the light, SM neutral Higgs scalar analog). In the paper decay modes of the right-handed heavy gauge bosons and heavy neutrinos are also discussed. Both scenarios with typical see-saw light-heavy neutrino mixings and the mixings which are independent of heavy neutrino masses are considered. In the second case heavy neutrino decays to the heavy charged gauge bosons not necessarily dominate over decay modes which include only light, SM-like particles.Comment: 16 pages, 10 figs, KL-KS and new ATLAS limits taken into accoun

Enhanced contribution to quark and neutron electric dipole moments with small mixing of right-handed currents and CKM CP violation

We study the light quark and the neutron electric dipole moments (EDMs) under the assumptions that the CP source is still in the usual CKM matrix and that there is a small mixing of right-handed charged currents in the quark sector. We find that the EDMs arise already at two loop order that are much larger than the standard model (SM) result even for a small mixing.Comment: 9 pages, revtex, axodraw.sty, 1 figure, published version in Phys. Rev. D. References updated, minor corrections and typos fixe