Shear deformable finite beam elements for composite box beams

The shear deformable thin-walled composite beams with closed cross-sections have been developed for coupled flexural, torsional, and buckling analyses. A theoretical model applicable to the thin-walled laminated composite box beams is presented by taking into account all the structural couplings coming from the material anisotropy and the shear deformation effects. The current composite beam includes the transverse shear and the restrained warping induced shear deformation by using the first-order shear deformation beam theory. Seven governing equations are derived for the coupled axial-flexural-torsional-shearing buckling based on the principle of minimum total potential energy. Based on the present analytical model, three different types of finite composite beam elements, namely, linear, quadratic and cubic elements are developed to analyze the flexural, torsional, and buckling problems. In order to demonstrate the accuracy and superiority of the beam theory and the finite beam elements developed by this study,numerical solutions are presented and compared with the results obtained by other researchers and the detailed threedimensional analysis results using the shell elements of ABAQUS. Especially, the influences of the modulus ratio and the simplified assumptions in stress-strain relations on the deflection, twisting angle, and critical buckling loads of composite box beams are investigated.

Mesoplasticity Approach to Studies of the Cutting Mechanism in Ultra-precision Machining

There have been various theoretical attempts by researchers worldwide to link up different scales of plasticity studies from the nano-, micro- and macro-scale of observation, based on molecular dynamics, crystal plasticity and continuum mechanics. Very few attempts, however, have been reported in ultra-precision machining studies. A mesoplasticity approach advocated by Lee and Yang is adopted by the authors and is successfully applied to studies of the micro-cutting mechanisms in ultra-precision machining. Traditionally, the shear angle in metal cutting, as well as the cutting force variation, can only be determined from cutting tests. In the pioneering work of the authors, the use of mesoplasticity theory enables prediction of the fluctuation of the shear angle and micro-cutting force, shear band formation, chip morphology in diamond turning and size effect in nano-indentation. These findings are verified by experiments. The mesoplasticity formulation opens up a new direction of studies to enable how the plastic behaviour of materials and their constitutive representations in deformation processing, such as machining can be predicted, assessed and deduced from the basic properties of the materials measurable at the microscale.

CRYSTALLOGRAPHIC ANALYSIS OF THE LATH MARTENSITE TRANSFORMATION IN Fe-Ni-Mn ALLOY

Habit plane rotation of lath martensite transformation in Fe-Ni-Mn alloy was predicted by means of Displacement Vector Theory. Its surface relief effect was observed and a math model for the quantitative analysis of habit plane rotation of lath martensite transformation was established by means of atomic force microscopy (AFM). The experiment showed that the largest rotation of habit plane of lath martensite transformation predicted by means of Displacement Vector Theory is 13.50°, and it's incompatible with the concept of invariant plane strain (IPS); surface relief of lath martensite revealed no character of IPS, i.e. it exhibited irregular 'N'-shaped 'surface relief packet', and 'surface relief packet' was composed of layers of several small surface reliefs, the AFM quantitative analysis of habit plane rotation of lath martensite transformation was 11.11°, which was in agreement with the prediction of Displacement Vector Theory (13.50°) and it firmly confirmed the habit plane rotation of lath martensite transformation and the correctness of Displacement Vector Theory.

Stability analysis of shallow tunnels subjected to eccentric loads by a boundary element method

This paper presents the results of the shear strength（frictional strength） of cemented paste backfillcemented paste backfill（CPB-CPB） and cemented paste backfillerock wall（CPB-rock） interfaces. The frictional behaviors of these interfaces were assessed for the short-term curing times（3 d and 7 d） using a direct shear apparatus RDS-200 from GCTS（Geotechnical Consulting ＆ Testing Systems）. The shear（friction） tests were performed at three different constant normal stress levels on flat and smooth interfaces. These tests aimed at understanding the mobilized shear strength at the CPB-rock and CPB-CPB interfaces during and/or after open stope filling（no exposed face）. The applied normal stress levels were varied in a range corresponding to the usually measured in-situ horizontal pressures（longitudinal or transverse） developed within paste-filled stopes（uniaxial compressive strength, s c 150 k Pa）. Results show that the mobilized shear strength is higher at the CPB-CPB interface than that at the CPB-rock interface. Also, the perfect elastoplastic behaviors observed for the CPB-rock interfaces were not observed for the CPB-CPB interfaces with low cement content which exhibits a strain-hardening behavior. These results are useful to estimate or validate numerical model for pressures determination in cemented backfill stope at short term. The tests were performed on real backfill and granite. The results may help understanding the mechanical behavior of the cemented paste backfill in general and, in particular, analyzing the shear strength at backfillebackfill and backfill-rock interfaces.

THE STRESS ANALYSIS OF VESSEL WALL IN THE ENTRANCE REGIONOF A TAPERED VESSEL

The present paper deals with the flow in an entrance region of a tapered vessel.Pressure distribution formula . axial and radial distribution formulas,shear stressdistribution formula of.flow field and shear stress distribution formula of vessel wallare derived. Relative numerical computations are made and analyzed.Discussion of the effects of tapered angle on the pressure distribution and vessel wall stress distributionare emphasized.

An erosion model for the discrete element method

A shear impact energy model （SIEM） of erosion suitable for both dilute and dense particle flows is pro- posed based on the shear impact energy of particles in discrete element method （DEM） simulations. A number of DEM simulations are performed to determine the relationship between the shear impact energy predicted by the DEM model and the theoretical erosion energy. Simulation results show that nearly one-quarter of the shear impact energy will be converted to erosion during an impingement. According to the ratio of the shear impact energy to the erosion energy, it is feasible to predict erosion from the shear impact energy, which can be accumulated at each time step for each impingement during the DEM simulation. The total erosion of the target surface can be obtained by summing the volume of material removed from each impingement. The proposed erosion model is validated against experiment and results show that the SIEM combined with DEM accurately predicts abrasive erosions.

Flow properties of three fuel powders

Flow and physical properties were measured for three fuel powders： sawdust, brown coal and hard coal. Besides physical properties, e.g., particle size, bulk density and moisture content, flowability was investigated using the standard shear testing technique of the Jenike shear cell. Flow functions of the three powders used for characterization of bulk flow and design of hoppers were determined, and then compared and discussed. The flow functions of the three powders are located in different regions： while brown coal and hard coal were classified respectively as easy flowing and cohesive material, sawdust was found in regions varying from cohesive to easy fowing at low consolidation stress. The measured effective angle of internal friction and angle of wall friction were 55° and 31.4° for sawdust; 36.2° and 26° for brown coal; and 43.3° and 27.8° for hard coal. Using the measured powder flow properties, Jenike＇s procedure was then followed to estimate and compare the critical hopper dimensions for mass flow of the three powders.

Relationship between single and bulk mechanical properties for zeolite ZSM5 spray-dried particles

In this work typical mechanical properties for a catalyst support material, ZSM5 （a spray-dried granular zeolite）, have been measured in order to relate the bulk behaviour of the powder material to the single particle mechanical properties. Particle shape and size distribution of the powders, determined by laser diffraction and scanning electron microscopy （SEM）, confirmed the spherical shape of the spray-dried particles. The excellent flowability of the material was assessed by typical methods such as the Hausner ratio and the Cart index, This was confirmed by bulk measurements of the particle-particle internal friction parameter and flow function using a Schulze shear cell, which also illustrated the low compressibility of the material. Single particle compression was used to characterize single particle mechanical properties such as reduced elastic modulus and strength from Hertz contact mechanics theory. Comparison with surface properties obtained from nanoindentation suggests heterogeneity, the surface being harder than the core. In order to evaluate the relationship between single particle mechanical properties and bulk compression behaviour, uniaxial confined compression was carried out. It was determined that the Adams model was suitable for describing the bulk compression and furthermore that the Adams model parameter, apparent strength of single particles, was in good agreement with the single particle strength determined from single particle compression test.

Glidant effect of hydrophobic and hydrophilic nanosilica on a cohesive powder： Comparison of different flow characterization techniques

The methods used for flow characterization of a powder mass include the angle of repose （AOR）, Carr index （CI）, and powder flow tester （PFT）. The use of nanosilica as a flow modifier （glidant） is very common in industry. This study aims to compare the glidant effect of hydrophobic and hydrophilic silica on a poorly flowable active pharmaceutical ingredient （ibuprofen） by different flow characterization techniques. Different percentages （0.5, 1.0, and 2.0 wt%） of both types of mixed silica–ibuprofen powders were evaluated by the AOR, CI, bulk density, and PFT. The flow factor, effective angle of friction, and cohesion were determined to explain the bulk powder properties. The results show that different types of silica show different levels of flow property improvement, but the techniques do not equally discriminate the differences. Hydrophobic silica results in better improvement of the flow property than hydrophilic silica, probably because of its better surface coverage of silica on the host particles. Change of the bulk density with applied pressure was significant for the different powders. This study demonstrates that combining several characterization methods provides a better understanding of bulk powder flow properties with respect to powder–process relationships than a single flow indicator.