Surface Area Coefficient Research Articles

Comparative analysis of different lattice topologies for cellular structure optimization in additive manufacturing

Cellular structures are prominent over solid structures in Additive manufacturing because of their inherent features like reduced weight, more strength, and porosity. A cylindrical component was designed and then different lattice topologies like grid, vin tile and hexagon were used to create the internal cellular structure. A comparative analysis was then carried out on these cellular structures based on different unit cell sizes, variable strut thickness, coefficient of volume reduction (VRC) and surface area coefficient (SAC). The effect of these parameters on mechanical properties was studied and correlated. These different cellular structures were then fabricated using PLA (Polylactic acid) material on a Makerbot Replicator + 3-D printer. These cellular structures were then simulated through FEA by providing loading and boundary conditions and the results were then evaluated and validated with experimentation work. The yielded results shown lowest stress and smallest of the deformation for vin tile lattice structure as compared to grid and hexagon lattice cellular structures. Physical experimentation results also validated the simulation outputs. This study was not limited to only creation of different cellular structures but it also compared how the structures behave mechanically through unit cell parameters like VRC and SAC. The cellular structures were tested virtually using FEA and physical experimentation was carried out on the 3-d printed samples. The results obtained through both the tests confirmed that vin tile cellular structure bears less stress and lowest deformation as compared to grid and hexagon cellular structures when subjected to same compressive loading conditions.

Compression deformation analysis of cellular lattice structure for structural optimization in additive manufacturing

Additive manufacturing has Cellular structures as its prominent component because of their ability to overshadow the solid ones on account of more strength-to-weight ratio, porous and light-weight nature. A lattice structure called vintile was designed and the effect of change in unit size, lattice kernel position, volume reduction coefficient, and cellular structure optimization on mechanical properties were discussed in this study. Samples with different cell sizes, lattice kernel positions, were 3-D printed using Polylactic acid (PLA) material on MakerBot Replicator Plus 3D printer. Finite element analysis (FEA) and experimentation work was performed on the designed cellular structures so as to make the estimation and evaluation of the mechanical properties of these cellular structures. Output of the work shown that the vin tile lattice topology cellular structure with lattice kernels on both sides of the central hole geometry bears less stress and very little deformation than the other cellular structures with kernels on only either side. Experimental results were in conformation with simulation results. The study does not limit itself to design of cellular structure only but also compared mechanical behavior through volume reduction coefficient (VRC) and surface area coefficient (SAC). Final testing of vin tile cellular structures was done using FEA and experimental work have been carried out on fabricated samples. The results of both concluded that the optimized cellular structure had less stress and deformation than the non-optimized cellular structure.

The workability of concrete

Summary An analysis is made of a large number of tests for workability as measured by the compacting factor, in order to determine how workability is related to the grading and shape of aggregate, the mix proportions and the water/cement ratio. An index is developed which takes account of the influence of particle size on workability, and largely overcomes the limitations of the fineness modulus and surface area coefficients. Similarly, an angularity index is introduced which is based on a test on the aggregate and is shown to take account of its shape. The relation between workability and mix proportions is assessed. It is established that a proportion of the water, equivalent to a water/cement ratio of about 0·25, is required to wet the cement, and that any additional water may be regarded as available to make the mix workable. An approximate relation is given for the calculation of compacting factors, and a worked example illustrates the use of this relation for mix design.