Search

This paper presents a topology optimization framework for multi-material 3D structures to be used in mechanical load carrying applications. This framework is an extension of an ordered multi-material interpolation scheme originally proposed in 2D to the 3D minimum compliance problem implemented in MATLAB. The algorithm starts by using the Young���s moduli and cost of the selected materials, then picks binary combinations with ordered densities to interpolate the value for the current iteration. Following these interpolations, the next step of the design is the solution of the mechanical compliance problem until the desired minimum compliance is met subject to volume and cost constraints. The solution scheme is based on Optimality Criteria Method and standard density filtering schemes. The main contribution of this paper is that the proposed design scheme implemented in MATLAB is an easy-to-use 3D topology optimization scheme with multi-material constituents based on a modified SIMP interpolation. Results show that the 3D code is able to deliver similar design results when compared with the existing 2D version. This effectively expands the topology optimization based design capability to many practical 3D engineering problems in a standard topology optimization setting and easy-to-use implementation in MATLAB., Journal of Additive Manufacturing Technologies, Vol. 1 No. 2 (2021): J AM Tech

The use of lattice structures has received increasing interest in various engineering applications owing to their high strength to weight ratio. Advances in additive manufacturing technologies enabled the manufacturing of highly complex lattice structures such as triply periodic minimal surface (TPMS) models in recent years. The application of simulation tools is expected to enhance the performance of these designs further. Therefore, it is vital to understand their accuracy and computational efficiency. In this paper, modal characterization of additively manufactured TPMS structures is studied using five different modeling methods for a beam, which is composed of primitive, diamond, IWP, and gyroid unit cells. These methods include (1) shell modeling, (2) solid modeling, (3) homogenization, (4) super-element modeling, and (5) voxelization. The modal characterization is performed by using modal analysis, and the aforementioned models are compared in terms of their computational efficiency and accuracy. The results are experimentally validated by performing an experimental modal testing on a test specimen, made of HS188, and manufactured by direct metal laser melting. Finally, the relationship between the modal characteristics and volume fraction is derived by carrying out a parametric study for all types of TMPS structures considered in this paper. The complex modal characteristics of different TPMS types suggest that they can be jointly used to meet the ever-challenging design requirements using the modeling guidelines proposed in this study.

Additive manufacturing has opened new avenues for the manufacturing of structures to achieve challenging engineering tasks. Gyroid, a unique example of such structures, exhibits many attractive properties, such as high stiffness-to-weight ratio and impact characteristics. This study aimed to evaluate the dynamic performance of gyroid structures made from HS188 using direct metal laser melting. The frequency response predictions of a finite element-based model of the gyroid sandwich structure were first validated against the modal testing in terms of its natural frequencies and mode shapes using the Dewesoft software. Subsequently, the effects of the plate and gyroid wall thickness on the dynamic characteristics of the structure were investigated by varying these across their expected limit ranges as part of a parametric study using the validated finite element model. The findings from the parametric study were validated against modal testing. Moreover, the performance of the aforementioned structure was compared with that of a solid structure with the same mass. The simulation results indicated that the dynamic characteristics of the gyroid structure can be improved considering the structure's frequency response by using parametric models. It was concluded that simulation and optimization tools will play a crucial role in additive manufacturing techniques to attain optimal mechanical properties of complex structures.

Determining the mineral contents and cultivation potentials of forage species with different degrees of salt tolerance in soil having different chemical properties and salt contents can provide information about the fodder quality of forage species and the importance about animal feed. In the evaluation of saline soils, growing of salt tolerant or resistant plants is recently a widespread implementation. For this purpose, this study was planned to determine the effect of salinity stress on macro (P, K, Ca, Mg and Na) and micro (B, Mn, Cu, Fe and Zn) mineral accumulations of alfalfa (Medicago sativa L.), bird's foot trefoil (Lotus corniculatus L.) and sainfoin (Onobrychis sativa Lam.) species cultivated under non-saline soil (0.43 EC dS m(-1)) and saline soils (9.80 EC dS m(-1)) and to reveal whether or not the existing forage is adequate for mineral requirements of ruminants. Research was conducted in randomized blocks design with three replications on the Igdir Plain, located in eastern Turkey, between the years of 2011-2013. The mineral concentrations of the fodders were detected by ICP-OES. As a result of the study, significant differences were found among species in respect of the other minerals examined except for K and Na, and L.corniculatus was identified to be the richest species in terms of mineral content. Mineral compositions of the plants differed significantly among the year, and generally significant increases were recorded in mineral contents of the plants in years following the establishment year. In terms of soil types, only K, B, Mn and Cu contents were found statistically significant. The results of this study showed that soil salinity had no significant effect on especially the macro mineral contents of the plants. Besides, it was revealed that forage species cultivated in both soil types are an important mineral source (except for K) for ruminants.

The aim of this study was to determine mineral and heavy metal levels of some temperate fruit species such as sweet cherry, black mulberry, white mulberry, apricot, apple, plum, peach, pear, hawthorn and rosehip grown in Aras Valley, located in the east part of Turkey. The con-centration of mineral and heavy metal levels in the leaves and fruits of fruit species were detected by ICP-OES. The content of heavy metals in fruit samples were determined in the range of 50.16-90.11, 9.45-82.15, 12.69-65.24, 10.24-30.24,1.12-5.89,1.62-3.42,0.36-1.36 and 0.01-0.09 mg/kg for Fe, Cu, Mn, Zn, Cd, Pb, Ni and Cr, respectively. The highest content of Fe, Cu, Mn, Zn, Cd, Pb, Ni and Cr in fruit samples were detected in Plum (yellow), Sweet cherry, Plum (red), Black mulberry, Plum (sarali), Plum (yellow), White mulberry and Plum (red), respectively. All of fruit samples were found to be contaminated with high levels of Cu, Cd, Pb. Moreover, the contents of Zn in fruits were higher levels than the permissible limits of FAOAVHO. However, the contents of Ni, Cr, Fe and Mn did not appear to reach pollution levels in the fruit samples. The results illustrated that a strong relationship exists between leaf and fruit samples with regards to all minerals in the fruit species and cultivars.