Tribological properties of composites of low density polyethylene (LDPE) reinforced with 1, 5, 10, 20 wt% micrometric Boehmite (B) and/or preheated Boehmite (HB) powders were studied in combination with two silane coupling agents (SCAs): vinyltri(2‐methoxyethoxy)‐silane (VTMES)‐SCA 972 and 3‐(trimethoxysilyl)‐propylmethacrylate (3MPS)‐SCA 989. When coupling agents are used, the samples not subjected to preheating provide higher yields of grafting and more bonds introduced on surfaces of Boehmite particles than heated ones. We have determined sliding wear by multiple scratching along the same groove using a micro scratch tester. Instantaneous penetration depth is lowered by the filler addition to LDPE. However, there is less viscoelastic recovery and the residual (healing) depths increase with increasing Boehmite concentration. Friction was determined using a pin‐on‐disk tribometer and also a moving sled friction device. Addition of 20 wt% untreated B and/or HB particles to LDPE matrix reduces friction. However, a more significant improvement of tribological properties results from incorporation of grafted particles; this occurs because of an increase of the filler/matrix interfacial adhesion. Surface morphology seen in scanning electron microscopy confirms this explanation. Friction values for all samples decrease along with the filler concentration increase. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

Effect of interfacial interactions on mechanical properties of composites of low‐density polyethylene reinforced with micrometric Boehmite powders were studied in combination with two silane coupling agents vinyltri(2‐methoxyethoxy)‐silane (VTMES)‐SCA 972 and 3‐(trimethoxysilyl)‐propylmethacrylate (3MPS)‐SCA 989. Samples were prepared via melt mixing followed by compression or injection molding. Morphology and mechanical behavior of the composites were investigated as a function of the filler loading. The modulus of the composites increases with increasing contents of micrometric Boehmite particles. Environmental scanning electron microscopy (ESEM) examination reveals formation of fibrous structures upon addition of the treated micro fillers. We presume the fibrillation of the LDPE phase is related to changes of the matrix viscosity. Improvements in mechanical properties are attributed to homogeneous dispersion and good interfacial adhesion between the filler and the matrix, as evidenced by ESEM. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers

A transient, thermomechanical model, METFORM, based on viscoplasticity and heat and mass transport theories has been developed specifically for the prediction of the flow behaviour of metals during hot rolling. The coupling of metal flow, heat transport and microstructural changes is discussed and a framework to account for the coupling behaviour is formulated. The model is partially verified by experiments and is applied to the hot strip mill roughing process, with the focus of interest on skid mark effects and related difficulties frequently observed in hot rolling. Methods for overcoming these difficulties are proposed based on the results obtained from the model. The coupling between microstructure development and the variations of local strain, strain gradient and temperature is confirmed by the predicted strain/strain gradients and micrographs obtained from a hot rolling experiment.

SUMMARYA new computational scheme, named the 'Integrated Load Increment' method (ILI), has been developed to handle elasto-plastic analysis of solids by the finite element variational technique. This scheme allows considerably larger loading steps to be applied to the structure without deviating from its nonlinear, load-deformation relationship. It has been shown that these relationships can be evaluated by integrating the nonlinear constitutive equations within each load increment under certain conditions. A numerical example on a pressurized thick-walled. cylinder indicates that a 240 per cent improvement in computational efficiency and substantial reduction of loading steps over the conventional load incremental method can be achieved by the ILI technique.

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