Unequal Diameters Research Articles

Semisolid Strip Casting of Aluminum Alloy by a Twin Roll Caster Equipped with a Channel Scraper

An unequal diameter twin-roll caster equipped with a channel scraper is proposed to improve center-line segregation. A semisolid metal layer was made by the channel scraper on the upper side of the strip and solidified by an upper roll. The twin-roll caster cast a strip of 5182 with equiaxed grain and without center-line segregation at a speed of 30 m/min and a unit roll load of 104 N/mm. The tensile stress and elongation after cold rolling and annealing were 294 MPa and 28%, respectively.

Casting of aluminum alloy clad strip by an unequal diameter twin-roll caster equipped with a scraper

A single-roll caster equipped with two scrapers and an unequal-diameter twin-roll caster equipped with two scrapers are proposed for casting clad strip without centerline porosity or segregation. Although usually found in roll cast 5182 strip, no centerline porosity or segregation occurred in the 5182 strip, which was the overlay clad strip cast by both types of roll casters. The interface between the 5182 strips and the 3003 base strip was clear. The two strips consisting of layers of the clad strip were bonded strongly at the interface. Both roll casters could cast the clad strip at 30 m/min. This casting speed is much higher than that for the conventional twin-roll caster for aluminum alloys.

Modelling pressure rolling of asymmetric rolling process

The paper presents a comparative analysis between experimental results and modelling in order to interpret the value of the contact pressure on the asymmetric longitudinal rolling. It is also intended action and the different behaviour of upper cylinder compared to the lower cylinder action in situations when both are driven, or only one operates. In the modelling will be presented on the basis of boundary conditions imposed rolling pressure variation in the degree of reduction and also re size arc length of contact. Determining a curve is also important to determine the locus of points which characterize symmetry conditions partial rolling process between unequal diameters cylinders.

Phase separation and flow pattern modulation with a T-type micro-drainage system

T-junction is a classical structure for the two-phase separation. The analysis of gas-liquid flow and the interface movement at the T-junction is very important to the mechanism understanding especially for T-micro-junctions with unequal diameter joint. A simulation of the passive draining process and the corresponding flow pattern modulation of slug flow in a tube with three T-micro-junctions are presented in this paper. Using the volume of fluid (VOF) method and the dynamic grid adaption method the interface movement was tracked precisely especially at the region of drainage junctions. As results, with the separation of liquid no apparent change of gas slugs’ length but shortened water plugs. The gas fraction in main tube is increased more than 10%. During the separation process, the interface movement at unequal diameter junctions mainly consisted of three stages: the generation of penetrating bubbles, a stable sliding stage and the retraction to mother bubble. These constitute one piston movement of penetrating bubbles, which is the vital mechanism of phase separation. The cooperation of interface pressure difference, surface tension, interphase shear force and characteristic sizes of micro-channel drainages brings into a separation. A preliminary model to optimize characteristic sizes of porous materials is proposed in order to getting a successful liquid separation from a slug flow, which could improve the condensation heat transfer performance.

Casting of aluminum alloy strip by an unequal diameter twin roll caster equipped with a scraper

Casting of aluminum alloy strip by an unequal diameter twin roll caster equipped with a scraper

異径双ロールキャスターによる半凝固温度範囲が広いAl合金板の鋳造

異径双ロールキャスターによる半凝固温度範囲が広いAl合金板の鋳造

Thermocapillary Flow and Coalescences of Heterogeneous Bubble Size Diameter in a Rotating Cylinder: 3D Study

Two dimensional axisymmetric and three-dimensional VOF simulations of gas/liquid transient flow were performed using a multiphase flow algorithm based on the finite-volume method. The results for motion of a multiple bubbles of a heterogeneous sizes aligned horizontally and perpendicular to a hot surface incorporating thermocapillary forces in a rotating liquid in a zero-gravity environment have been presented for the first time. No bubbles broke in any of the cases observed. The results also show that collision and agglomeration of bubbles of unequal sizes diameter are different from those of similar size diameters presented from earlier research work of Alhendal et al. Acta Astronaut. 117, 484–496 (2015). Different flow patterns such as thermocapillary bubble migration, collision, and stream function were observed and presented for the 2-D and 3-D models.

Mixing at double-Tee junctions with unequal pipe sizes in water distribution systems

Pipe flow mixing with various solute concentrations and flow rates at pipe junctions is investigated. The degree of mixing affects contaminant spread in a water distribution system, and many studies have focused on mixing at the cross junctions; however, only a few have focused on double-Tee junctions of unequal pipe diameters. To investigate the solute mixing at such junctions, a series of experiments was conducted in a turbulent regime (Re = 12,500-50,000) with different Reynolds number ratios and connecting pipe lengths. Dimensionless outlet concentrations were found to depend on mixing mechanism at the impinging interface of junctions, where junctions with a larger pipe diameter ratio were associated with more complete mixing. Further, the inlet Reynolds number ratio affected mixing more strongly than the outlet Reynolds number ratio. Finally, the dimensionless connecting pipe length in a double-Tee played an important and complicated role in the flow mixing. The results were used to develop two-dimensional isopleth maps for the calculation of normalized north outlet concentrations.

異径双ロールキャスターによるすべり軸受材料板の鋳造に関する研究

異径双ロールキャスターによるすべり軸受材料板の鋳造に関する研究

Experimental investigation of bitubal circular energy absorbers under quasi-static axial load

In this article, bitubal circular energy absorbers consist of two AL-6063-O tubes with unequal diameters placed coaxially and compressed under quasi-static axial load are studied experimentally. The effects of diameter and wall-thickness of each tube and the interaction between two tubes on the crashworthiness parameters are investigated in detail. In order to reduce the high value of peak load induced in the bitubal absorbers, two worthwhile solutions are proposed. The first one is to use two tubes with different lengths and the other one is to cut groove at the end portion of one of the tubes.

Aerodynamics Study of Flow Past Two Tandem Bluff Bodies at Low Reynolds Number

Aerodynamics of flow past two tandem bluff bodies is a critical problem in fluid mechanics. In this work, the flow over two circular cylinders with unequal diameters in tandem arrangement is numerical investigated using lattice Boltzmann method. The diameter of the bigger one is adopted as the characteristic length, the diameter ratio is fixed as 2, and the Reynolds number is 100. Spacing between two cylinders (scaled by the characteristic length) are varied from 0 to 3 characteristic diameter, and the effects of which on the flow patterns of such a system are studied. The results show that flow patterns behind two tandem unequal circular cylinders are significantly different from that behind a single one. Due to the downstream cylinder, two classic vortex interaction modes are observed, known as destruction interaction mode and construction mode.

A novel quantitative petrophysical model for the stress sensitivity of tight sandstones

During the production life cycle of a reservoir, absolute permeability can change in response to an increase in the effective stress. In general, stress-dependent permeability has been measured using experimental methods with core samples. This paper focuses on presenting a petrophysical model of unequal diameter grains, based on the Hertz Theory, in that the true reservoir rocks are composed of closely packed grains of different sizes. The purpose of the model is to quantitatively evaluate the features of stress-dependent permeability in theory and to enhance the productivity of stress-dependent reservoirs. Control factors including the grain sizes, grain sorted behavior, mineral composition and cementation degree, which influence on the variation of stress-dependent permeability, can be calculated quantitatively and directly through the model while experiments cannot. Experiments were conducted on core samples of tight sandstones to verify the established model. Measurements were made at different confining pressures. The theoretical and experimental results obtained from the investigated rock were analyzed and compared. The results of the model show that control factors including the previous parameters have different influences on the stress-dependent permeability. The stress-sensitive curves calculated by the model have the desired behavior and are consistent with the laboratory data well, providing a more rigorous confirmation of the validity of the model and a new petrophysical insight into the significance and the role of the grain properties and grain contacts. The obtained theoretical results can exhibit the average features of stress-sensitive formation rather than the feature of only one point (a core plug sample) of a reservoir by laboratory test. Thus, the obtained formula through the model is of great benefit to being applied in reservoir numerical simulation.

Juncture flows around cylinders of unequal finite-height and diameter in tandem arrangement

This experimental study examines the effects of placing a control cylinder of small diameter and height in the upstream region of a main cylinder at a gap of 0.75 D in tandem arrangement on laminar junction flow at Re $$_D$$ = 1.3 $$\times $$ 10 $$^3$$ . The study is performed using 2D particle image velocimetry (PIV). The experiment clearly visualizes the changes in flow pattern with this arrangement and gives insight into the new flow pattern.

Experimental study on the flow around two tandem cylinders with unequal diameters

In this paper, flow around two circular cylinders in tandem arrangement with unequal diameters has been investigated using the particle image velocimetry technique (PIV) in a water channel. The upstream to downstream diameter ratio was kept constant at d/D = 2/3, the centre-to-centre distance was varied from 1.2D to 5D and the Reynolds number was varied from 1200 to 4800. The flow characteristics were analyzed through ensemble-averaged patterns of velocity, vorticity, normalized Reynolds stress contours and streamlines. Based on ensemble-averaged and instantaneous flow fields, different flow patterns, including single-wake-shedding at small spacing ratio, bi-stable flow behavior (alternating behavior of reattachment and vortex shedding) at intermediate spacing ratio and co-shedding pattern at large spacing ratio were observed. The effects of Reynolds number and the centre-to-centre spacing ratio on flow patterns and turbulent characteristics were also investigated. It was found that the diameter ratio appears to have a certain effect on the flow patterns at intermediate spacing ratios, where the reattachment of shear layer depends on the lateral width of the wake flow in the lee of the upstream cylinder. Extensive discussion on the distributions of Reynolds stress and turbulent kinetic energy was presented.

A co-operative effect of closely spaced intruding objects puncturing into a soft solid.

When two or more closely spaced indenters puncture a soft solid, the puncturing load diminishes from that required when they are far apart. We have developed a method to examine this effect by embedding a planar tracer grid within a block of an elastic gel and by driving closely spaced syringe needles of different inter-tip spacing through this plane. These experiments show that in addition to a primary crack ahead of the needle-tip, there occurs also a periodically appearing secondary radial crack from its side. The strain field around the side crack remains non-monotonic with a characteristic length scale which varies with both solid modulus and needle diameter. For closely spaced multiple indenters the overlapping strain profiles cause compressive stress at the vicinity of the needles, which arrest the side cracks, the diminishing effect of which leads to stress concentration for the primary crack and the resultant decrease in required load for driving the indenters through the solid. We have shown that such a co-operative effect remains valid for materials of different types, e.g. brittle and ductile and for multiple-tip needles consisting of constituent tips of equal and unequal diameters.

Cylindrical Cam Profile by CMM Based on Pro/E Model

The development of CAD and CAM technology makes it more process to inspect surfaces of the part, this is usually carried out by CMM. With the research of the error analysis of cutter location for unequal diameter side milling of cylindrical cam, the technology using CMM to inspect surfaces by Pro/E CAD model is analysed from some key aspects: Pro/E modeling; set up coordinate ; and probe compensation.

Analysis of the Coupling Mechanism in Asymmetric Fused Fiber Couplers

We investigated experimentally and numerically the coupling mechanism in asymmetric fused fiber couplers consisting of different single-mode fibers with unequal core diameter and numerical aperture. We increased the maximum coupled power by pretapering one of the fibers achieving a nearly complete power transfer at a specific pretaper length. Experimental results are compared to numerical results obtained by using our own 3-D FFT-based beam propagation method (BPM) algorithm. The numerical model explains qualitatively the coupler performance and allows to gain insight into the coupling mechanism. We discuss the influence of the fiber cores on the excited super-modes of the cladding structure. A modal decomposition of the light field is carried out in order to analyze the evolution of the super-modes and to discuss the influence of pretapering on the excitation of these modes.

Influences of rotation speed on microstructures and mechanical properties of 6061-T6 aluminum alloy joints fabricated by self-reacting friction stir welding tool

A 6061-T6 aluminum alloy was self-reacting friction stir welded by using the specially designed tool with unequal shoulder diameters at a constant welding speed of 150 mm/min to investigate the effect of rotation speed on microstructure and mechanical properties of the joints. Excessive flash on the bottom surface of the joint and groove defects on both surfaces of the joint were formed when the lower shoulder diameter was much smaller. The suitable shoulder sizes were determined as 16 and 18 mm in lower shoulder diameter and upper shoulder diameter, respectively. The grain size and the dislocation density in the weld nugget zone (WNZ) increased with increasing rotation speed. The tensile strength of joints first increased with increasing rotating speed and then decreased remarkably as a result of the formation of void defect. The joints welded at lower rotation speeds were fractured in the thermal mechanically affected zone (TMAZ). However, the fracture locations of the defect-free joints were changed to the heat affected zone (HAZ) at higher rotation speeds.

Study on Lateral Pressure-Transfer Regularity of Tube SGMF under High Pressure

The mechanical model of Tube Solid Granules Medium Forming (SGMF) is simplified to three pressure-transfer models: uniform pressure model, unequal diameter model and tube SGMF model. Combining the conclusions of the SGMF investigation and the theories of powder mechanics, lateral pressure-transfer regularity of SGMF under high pressure has been investigated and the mathematical formulas of pressure distribution have been obtained. According to the theoretical analysis, the lateral pressure and the depth of solid granules can be expressed by a segmented function. An experimental set-up has been designed and manufactured to evaluate the theoretical results, good correlation has been observed between the theoretical results and the experimental data.

Flow Structures behind Cylinders of Different Diameters Arranged Side-by-Side at Small Gap Ratios

The flow structures and their interactions behind side-by-side cylinders of unequal diameters at small gap ratios are studied by dye-flow visualization and particle image velocimetry at Reynolds number 1000. The whole-field mean and fluctuating velocity distributions and evolutions in the wakes are studied by the particle image velocimetry. As the gap ratio decreases, the mutual interaction of the wakes behind side-by-side cylinders pushes the recirculation region behind the large cylinder farther downstream at the expense of deterioration of the wake behind small cylinder. This change is important and may be relevant to the applications of passive flow control strategy.