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Many challenges are associated with the injection compression molding process for producing a half-pallet (1320 mm × 1110 mm × 75 mm, length × width × height), which is butt-welded to another one for enhancing its strength. This pooled high-density polyethylene (HDPE) pallet is able to endure the impacts of a heavy load and a low ambient temperature. Reducing the warpage of a half-pallet is, therefore, essential for reducing the residual internal stress within the welded portions. An advanced Moldex3D package helps to detail the temperature distribution and warpage of a half-pallet. The pre-setting molding parameters from a mass-production factory produce half-pallets with worse flatness. In this investigation on using appropriate cooling water temperatures within the core and cavity plates of the mold, the numerical results show that the warpage of the top surface of the half-pallet was 11.549 mm, low warpage with respect to this large-scale pallet. Furthermore, the compression speed of 50–60 mm/s may have produced a low flatness of the half-pallet in this study. [ABSTRACT FROM AUTHOR]

Plastic pallets are essential devices for the transport of industrial products within containers and can be made from recycled plastics to be more environmentally friendly. However, numerous thin reinforcing ribs are required to mold such large-size pallets, thereby requiring a large-scale injection-molding machine. Many filling gates can reduce the welding lines to enhance the structural strength of the pallet to achieve injection molding using a lower locking force machine. This study simulated the production of recycled polypropylene plastic pellets using a 3500-ton super-large injection-molding machine and the Moldex3D package to derive the flow analysis of the moldability. The PTC Creo software is used to construct plastic pallets (1100 mm × 1100 mm × 140 mm), filled by twelve gates using a baffle cooling system. During the four-stage filling of the sequential valve gate system, the flow front spreads from the central gate to the four corners of the pallet, decreasing the number of welding lines, with an average filling pressure of 19.23 MPa by a sequential valve gate scheme which is approximately 65% of the concurrent valve gate opening scheme. The maximum clamping force by this sequential valve gate opening scheme in the molding of plastic pallet is 874.6 tons, only half of the one by concurrent valve gate opening scheme. The average welding angle was 85.7° in the concurrent valve gate opening scheme, with smaller angles than that of the sequential gates controlled scheme. The maximum temperatures during the filling by the two schemes with the concurrent valve gates opened and the sequential gates controlled were 230.5 and 232.5°C, respectively. The sequential valve gate opening scheme's warpages are smaller than the ones by the concurrent valve gate opening scheme. The warpages of the pallet by the sequential valve gate system are smaller than the ones by the concurrent valve gate system. A higher temperature of the cooling channel and a medium level of cooling time result in lower warpage of the pallet. [ABSTRACT FROM AUTHOR]

Abstract: An investigation is performed into the effects of repeated weld-repairs on the microstructural and mechanical properties of AISI 304L stainless steel. In preparing the specimens, the root weld is fabricated using gas tungsten arc welding (GTAW). The weld bead is then ground away, and the weld is repaired using shielded metal arc welding (SMAW). Two different weld-repair specimens are fabricated, namely one specimen repaired just one time (designated as WD-1) and one specimen repaired five times (designated as WD-5). The microstructures of the base metal (BM), WD-1 and WD-5 specimens are investigated using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron back scattering diffraction (EBSD). The results show that the microstructures of all three specimens comprise a BCC solid solution austenite matrix with interspersed ferrite phrase. The EBSD results show that the number of weld-repairs has no significant effect on the ∑1 boundaries of the fusion zone (FZ). In addition, no significant difference is observed in the texture orientations of the heat affected zone (HAZ) and the base metal (BM) regions of the WD-1 specimen. However, in the WD-5 specimen, the HAZ has a preferred orientation in the (111) plane, whereas the BM has a preferred orientation in the (212) plane. The grain boundaries (GBs) character results show that the low-energy coincident site lattice of the grain boundaries (∑CSL GBs) are formed predominantly in the HAZs of the two weld-repair specimens. Moreover, the fraction of low angle grain boundaries decreases with an increasing number of weld repairs, the high-energy ∑CSL GBs remained similar to those of the HAZs in the WD-1 and WD-5 specimens. The impact test results show that the number of weld-repairs has no significant effect on the impact strength of the specimens, but affects the fracture characteristics. Finally, the corrosion test results show that the BM and HAZ of the WD-1 and WD-5 specimens exhibit significant corrosion following immersion in a 3.5% NaCl solution. The depth of the corrosion pitting increases with an increasing number of weld-repairs due to the corresponding increase in the amount of short ferrite phase in the austenite matrix. [Copyright &y& Elsevier]

Abstract: Structures, strain, polarization, and dielectric permittivity of lead-free piezoceramics (1−x)(Bi0.5Na0.5)TiO3–xBaTiO3 for x=0.03, 0.07, and 0.11 (abbreviated as BNB3T, BNB7T, and BNB11T) have been investigated systematically as functions of electric (E) field and temperature. The results revealed that the piezoelectric behavior was significantly influenced by the domain configuration which depends on composition, E field, and lattice structure. The E-field induced strain in BNB7T composition can reach S max/E max=475pm/V, which is comparable with the soft Pb(Zr,Ti)O3 (PZT) piezoceramics. The large field-induced strain is likely originated from the development of the nano-polar regions (or clusters) with sizes of ~5–10nm, which could reduce the energy barriers of dipole reorientation (or switching) under E-field application. [Copyright &y& Elsevier]