We present results of numerical analysis of the Strehl ratio characteristics for the light sword optical element (LSOE). For comparison there were analyzed other optical imaging elements proposed for compensation of presbyopia such as the bifocal lens, the trifocal lens, the stenopeic contact lens, and elements with extended depth of focus (EDOF), such as the logarithmic and quartic axicons. The simulations were based on a human eye's model being a simplified version of the Gullstrand model. The results obtained allow to state that the LSOE exhibits much more uniform characteristics of the Strehl ratio comparing with other known hitherto elements and therefore it could be a promising aid to compensate for the insufficient accommodation range of the human eye.

The paper presents first experiments with a refractive light sword optical element (LSOE). A refractive version of the LSOE was prepared in photoresist by gray scale photolithography. Then we examined chromatic aberrations of the produced element and compared them with those corresponding to two different lenses. For this purpose we performed two experiments, the first one where white light illumination was used and the latter one by the help of monochromatic illumination with three different wavelengths. The obtained results lead to the conclusion that the refractive LSOE does not exhibit significant chromatic aberrations and can be successfully used for imaging with extended depth of focus in polychromatic illumination.

Comparative analysis of mechanical properties and energy absorption capabilities of functionally graded and non-graded thermoplastic sheet gyroid structuresAdditive manufacturing allows the tailoring of the structure of energyabsorbing materials. It is thus feasible now to use light, printed structures instead of other materials such as foams and honeycombs, signifying greater possibilities for customization. Some of these structures are triply periodic minimal-surface structures that is a family of different structures like the gyroid one. Another benefit of additively manufactured graded structures, which foams or honeycombs lack, is the flexibility to vary the internal parameters along one or more directions. This study focuses on the comparative analysis of graded and non-graded gyroid structures for four common thermoplastic materials used in additive manufacturing.These structures are compared with each other under quasi-static compression testing, as well as with expanded polystyrene foam and solid samples of the thermoplastic materials. The analysis includes investigation of the stress-strain and specific stress-strain curves, capability of absorbing energy per unit weight and per unit volume, ideality, total efficiency, and normalized energy vs. normalized stress characteristics.We also analyze the internal fracture mechanism of the structures. The objective is to obtain more extensive knowledge of the behavior of nongraded structures.

Author Comments:The authors after the review have prepared all the images to be published in black and white. Fig1 has been generated using PPT, fig 2 is a photo, fig 3 to 11 have been generated using excel and they have been introduced in a word or a power point. All the tables are generated using word.

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Mechanical properties of diamond lattice structures based on main parameters and strain rateThe diamond triply periodic minimal surface structure has a high mechanical property-weight ratio. They can be modified by changing their internal parameters or the material. They are generated using the additive manufacturing (AM) that possibilities the use of various materials for generating zones with different mechanical properties or by modifying their internal parameters.However, the effects of internal parameters in the mechanical properties have not been defined in detail. Furthermore, the strain rate modifies these mechanical properties. In this study, the effects of the internal parameters and strain rate were evaluated and additionally, the failure mechanism of the structures.

This work carries out an in-depth analysis of the influence of the manufacturing parameters on the behavior of a material with better mechanical properties than the usual ones, PLA and ABS, such as PETG (Polyethylene terephthalate with glycol), and the carbon fiber reinforced version. This study performs the experi-mental characterization on interlaminar fracture of this material, with the aim of acquiring a better knowledge of it, but also generates a model of material behavior that takes into account the effects on the properties of the printing profile, in other words, of the selected manufacturing parameters. In order to achieve such objective, a finite element numerical model has been developed, using cohesive elements to simulate the contact zones between layers. Also, failure and degradation modes of the material would be enclosed in the model behavior. A bilinear behavior model is used to simulate the response of the interlaminar zones. The properties of the model, as well as its subsequent adjustment, are supported from the results obtained in the experimental phase. As a final result of the work, the authors propose a series of graphs that allow the selection of these properties to be used in the model, depending on the manufacturing parameters selected for a future application. Keywords: FDM; PETG; DCB test; cohesive modeling