Mechanical behavior of sandwich panels with tetrahedral and Kagome truss cores fabricated from wires

Wires are great candidates as the raw material for truss periodic cellular metals because they can display high strength as in piano wires, are easy to fabricate, and can be controlled to be defect free. New approaches based on tri-axial weaving of wires to create ideal trusses, i.e., tetrahedral and Kagome truss have been presented. The mechanical properties of the sandwich panels with the truss cores fabricated by using the new approaches under compression and bending loadings are analyzed by elementary beam theory and experiments. The relative density, stiffness, and strength of the sandwich panels are estimated by the derived equations and compared with the measured results. The failure mechanisms of the sandwich panels are analyzed, and also benefits and shortcomings of each approach with respect to mechanical performance and production are discussed.     

Whole-body vibration: Evaluation of emission and exposure levels arising from agricultural tractors

A study was conducted to quantify whole-body vibration (WBV) emission and estimated exposure levels found upon a range of modern, state-of-the-art agricultural tractors, when operated in controlled conditions (traversing ISO ride vibration test tracks and performing selected agricultural operations) and whilst performing identical tasks during ‘on-farm’ use. The potential consequences of operator WBV exposure limitations, as prescribed by the European Physical Agents (Vibration) Directive:2002 (PA(V)D), upon tractor usage patterns were considered. Tractor WBV emission levels were found to be very dependent upon the nature of field operation performed, but largely independent of vehicle suspension system capability (due to the dominance of horizontal vibration). However, this trend was reversed during on-road transport. Few examples (9%) of tractor field operations approached or exceeded the PA(V)D Exposure Limit Value (ELV) during 8 h operation, but this figure increased (to 27%) during longer working days. However virtually all (95%) ‘on-farm’ vehicles exceeded the Exposure Action Value (EAV) during an 8-h day. The PA(V)D is not likely to restrict the operation of large, state-of-the-art tractors during an 8-h day, but will become a limitation if the working day lengthens significantly. Further ‘on-farm’ WBV data collection is required to enable creation of a robust, generic WBV emission database for agricultural tractor operations, to enable estimation of likely WBV exposure by employers.     

Dislocation emission from nanovoid with the effect of neighboring nanovoids and surface stresses

In the light of the vital mechanism for nanovoid evolution depending strongly on the effect of neighboring nanovoids, a generalized self-consistent model is suggested to describe nanovoid growth by the dislocation emission from nanovoid surface accounting for the effect of neighboring nanovoids and surface stresses in ductile porous materials. The explicit solution of the critical stress for dislocation emission is derived by means of the complex variable method. Analysis shows the advanced model can be implemented as the effective means to address the strong dependence of the nanovoid growth by the dislocation emission upon the size and volume fraction of nanovoid, growth/shrinkage of the neighboring nanovoid, remote applied stress as well as the surface effect.     

Control of formaldehyde emission from wood-based panels by doping adsorbents: optimization and application

This paper puts forward an approach to determine the optimal mode of doping adsorbents into the wood-based panels for control of their formaldehyde emission. Based on the optimization conclusion, a novel design method for low-emitting wood-based panels by daubing adsorbent layer on the panel’s surface is proposed. The formaldehyde emission results from the prepared laboratory specimens indicate the feasibility of the proposed method. This study provides a meaningful guidance on designing low-emitting wood-based panels.     

Modeling of K-shell Al and Mg radiation from compact single, double planar and cylindrical alloyed Al wire array plasmas produced on the 1 MA Zebra generator at UNR

Radiative emission from alloyed Al single, double and compact cylindrical wire arrays have been studied using the 1 MA Zebra UNR generator. Single planar wire arrays using ten wires and double planar wire arrays and compact cylindrical wire arrays (CCWA) that both had sixteen wires were utilized. The wire composition is Al-5056 (95% of Al and 5% of Mg). We have observed that implosion of these alloyed Al wire loads generated optically thick Al plasmas that can be diagnosed using K-shell Mg lines. In particular, among the considered loads, the K-shell lines of Al from implosions of the double planar wire arrays have the highest optical depth for He-like Al resonance transitions, which occurred near the stagnation phase. X-ray time-gated and time-integrated spectra and pinhole images as well as photoconductive detectors signals were analyzed to provide information on the plasma parameters; electron temperatures and densities, implosion dynamics features and power and yields of the X-ray radiation. Previously developed non-LTE models were applied to model axially-resolved time-integrated, as well as time-gated spatially-integrated, K-shell spectra from Al and Mg. The derived time-dependent electron temperature, density and axial opacity were studied and compared. In addition, the wire ablation dynamics model (WADM) was used to calculate the kinetic energy of the plasma, which with the aid of a Local Thermal Equilibrium (LTE) magneto-hydrodynamics (MHD) simulation, allowed to estimate the precursor and stagnated z-pinch plasma electron temperatures from implosions of wire array loads.