Determination of loading capacity index of a continuous miner in soft rock roadway and virtual test method

To improve the loading efficiency and reduce energy consumption of a continuous miner in soft rock roadway, a seven-arm star wheel designed with Gaussian fitting method was proposed, and a coal loading model of the continuous miner star wheel loading mechanism was reconstructed with EDEM software. The loading capacity of the seven-arm star wheel and the three-arm star wheel of the EML340 continuous miner at different working speeds were studied respectively. The scientific and reasonable identification index was formulated and the index evaluation system of loading star wheel was established. It has been found that the performance of the loading star wheel is a collection of various identification indicators, the coal returning mass reducing the loading efficiency and increasing unnecessary energy consumption, therefore, it is difficult to identify by a single index. Loading coal and rock by the star wheel is a process that consumes energy and pays attention to output, therefore, the identification index should include two kinds of efficiency parameters and energy parameters. Rake coal torque and loading specific energy consumption have reflected the degree of energy utilization, which can be comprehensively used for preliminary design of the star wheel. The performance parameters such as loading power and loading efficiency are reliable indicators for designing and performance evaluation of the star wheel. Based on the statistical analysis of the test data, compared with the three-arm star wheel of the EML340 continuous miner, the loading efficiency of the seven-arm star wheel has been significantly improved. The loading power for coal loading has been reduced by 46%. The feasibility of the Gaussian design method of loading star wheel has been verified.

Characterization of a soft magnetic composite for use in road-embedded wireless-charging systems

The ferrite magnetic core is an integral component of road-embedded wireless charging systems for electric vehicles. However, the brittleness of ferrite makes it susceptible to premature fracture due to cyclic wheel loading from vehicles. This has motivated the development of a soft magnetic composite (SMC) composed of a flexible polyurethane and crushed ferrite as an alternative. An experimental investigation was conducted into the trade-offs between mechanical, thermal and magnetic properties at ferrite volume fractions between 45.9[Formula: see text]vol% and 80.6[Formula: see text]vol%. A comparison was made between measured properties and predictions from analytical models in order to further investigate the characteristics of the composite. The investigation showed a trade-off between the increase in magnetic permeability and the reduction in strain-to-failure as ferrite volume fraction increased. In addition, a large increase in flexural modulus and thermal conductivity, along with a slight increase in flexural strength was observed. More importantly, the strain-to-failure of the composite was 20 times higher than that of ferrite even at the highest volume fraction, indicating that the SMC was successful in providing a more ductile and flexible alternative.

Effect of Graphene nanoplatelets (GNP) reinforcement on grindability of zirconium diboride ceramics

The grindability of graphene nanoplatelets (GNP) reinforced ZrB2 was studied using resin bonded diamond grinding wheel under dry and wet conditions. A comparative study of grinding forces was performed at selected wheel surface speeds and depth of cuts for surface grinding. ZrB2-GNP showed lower normal grinding forces due to the reduced hardness. The presence of GNP reinforcement in ZrB2 resulted in lower tangential forces and reduced specific grinding energy due to the role of GNP as solid lubricant. The measured forces showed good correlation with the micro cutting model for ZrB2 and ZrB2-GNP under dry condition. The tangential forces showed same trend as normal forces at different depth of cuts and wheel surface speeds for both ZrB2 and ZrB2-GNP with average force ratios of 0.3 and 0.35 respectively. The presence of porosity in ZrB2 increased the normal grinding forces during wet grinding. Scanning Electron Microscope (SEM) images of the grinding chips indicated a mixture of both the ductile mode and the brittle mode of material removal with predominantly brittle fractured chips. Energy Dispersive Spectroscopy (EDS) confirmed the presence of GNPs in ZrB2-GNP grinding chips. The topography of the grinding wheel showed higher wheel loading after the dry grinding than that of wet grinding. The wet grinding resulted in relatively lower surface roughness (Ra values) compared to that of dry grinding.

Unified approach for bridge deck design

Current Canadian Highway Bridge Design Code includes design provisions to establish live load demands in (i) reinforced concrete decks over longitudinal girders, (ii) orthotropic deck over longitudinal girders, and (iii) orthotropic deck over transverse beams. However, it only provides an equation for factored applied moment on concrete deck under single point load. Similar equations for orthotropic decks are as yet unavailable. As such, parametric study was conducted to lead to new empirical expressions for moment in bridge decks subjected to truck wheel loading considering each of the three cases of orthotropy: (i) relatively torsionally stiff, flexurally soft decks; (ii) relatively uniformly thick decks; and (iii) relatively torsionally soft, flexurally stiff decks. Using the proposed formulations, bridge deck design can be treated in a unified way across different deck types, accounting for longitudinal-transverse flexural rigidity of decks. Application of these methods can significantly simplify the analysis of decks and allow bridge engineers to make comparisons across different deck design alternatives.

Development and study of closure strip between precast deck panels in accelerated bridge construction

This research investigates the use of glass fiber reinforced polymer (GFRP) bars in bridge decks and ultra-high performance fibre-reinforced concrete (UHPFRC) as filling materials in (i) panelto- panel closure strips between transverse precast full-depth deck panels (FDDPs) supported over girders and (ii) the shear pockets for the panel-to-girder connection. The experimental research program included three phases. Phase I examined pullout strength of straight-end and headed-end GFRP bars embedded into UHPFRC to determine the required closure strip width to develop bar full strength. Phase II included the development and study of closure strip details incorporating UHPFRC as joint-filling materials and GFRP bars projecting into the joint. Three joints of width 200 mm between precast FDDPs were developed, namely: angle-shape joint (Ajoint), C-shape joint (C-shape), and zigzag-shape joint (Z-joint), with 175-mm projecting length of GFRP bars into the joint. Two series of 2500x600x200 mm one-way slabs were cast to investigate the flexural strength of the jointed precast slabs compared to cast-in-place slabs. Two types of concrete were used to fabricate the precast FDDPs, namely: normal concrete (NSC) and high-performance concrete (HPC). Correlation between experimental results and available design equations for moment and shear capacities, as well as CHBDC and AASHTO-LR applied factored design moments, was performed. All specimens failed in either flexural or flexural-shear mode outside the UHPFRC-filled joint. Phase III included testing three pairs of 3700x2500x200 mm laterally-restrained precast FDDPs incorporating the three developed joint details in the transverse direction of the girders. Each pair of specimens was tested under 600x250 mm wheel loading located beside the closure strip, considering (i) constant amplitude fatigue (CAF) loading up to 4 million cycles followed by increasing static loading to-collapse, and (ii) incremental variable amplitude fatigue (VAF) loading to-collapse. The failure mode of the tested slabs was punching shear, with the transverse UHPFRC joint diverting the extension of the punching shear plane to the adjacent precast FDDP segment. Results of fatigue load tests on the three-jointed pairs of slabs showed high fatigue performance. A new prediction model for fatigue life of the GFRP-reinforced, UHPFRC-filled jointed deck slabs was developed.

Unified approach for bridge deck design

Current Canadian Highway Bridge Design Code includes design provisions to establish live load demands in (i) reinforced concrete decks over longitudinal girders, (ii) orthotropic deck over longitudinal girders, and (iii) orthotropic deck over transverse beams. However, it only provides an equation for factored applied moment on concrete deck under single point load. Similar equations for orthotropic decks are as yet unavailable. As such, parametric study was conducted to lead to new empirical expressions for moment in bridge decks subjected to truck wheel loading considering each of the three cases of orthotropy: (i) relatively torsionally stiff, flexurally soft decks; (ii) relatively uniformly thick decks; and (iii) relatively torsionally soft, flexurally stiff decks. Using the proposed formulations, bridge deck design can be treated in a unified way across different deck types, accounting for longitudinal-transverse flexural rigidity of decks. Application of these methods can significantly simplify the analysis of decks and allow bridge engineers to make comparisons across different deck design alternatives.