Mechanical Properties and Energy Absorption Abilities of Diamond TPMS Cylindrical Structures Fabricated by Selective Laser Melting with 316L Stainless Steel.

Triply periodic minimal surfaces (TPMS) are structures inspired by nature with unique properties. Numerous studies confirm the possibility of using TPMS structures for heat dissipation, mass transport, and biomedical and energy absorption applications. In this study, the compressive behavior, overall deformation mode, mechanical properties, and energy absorption ability of Diamond TPMS cylindrical structures produced by selective laser melting of 316L stainless steel powder were investigated. Based on the experimental studies, it was found that tested structures exhibited different cell strut deformation mechanisms (bending-dominated and stretch-dominated) and overall deformation modes (uniform and "layer-by-layer") depending on structural parameters. Consequently, the structural parameters had an impact on the mechanical properties and the energy absorption ability. The evaluation of basic absorption parameters shows the advantage of bending-dominated Diamond TPMS cylindrical structures in comparison with stretch-dominated Diamond TPMS cylindrical structures. However, their elastic modulus and yield strength were lower. Comparative analysis with the author's previous work showed a slight advantage for bending-dominated Diamond TPMS cylindrical structures in comparison with Gyroid TPMS cylindrical structures. The results of this research can be used to design and manufacture more efficient, lightweight components for energy absorption applications in the fields of healthcare, transportation, and aerospace.

Preliminary Studies into Cutting of a Novel Two Component 3D-Printed Stainless Steel-Polymer Composite Material by Abrasive Water Jet.

Composites are materials with a heterogeneous structure, composed of two or more components with different properties. The properties of composites are never the sum or average of the properties of their components. There is a lot of research and many models on the different property assessments of composite materials. Composites are used as construction materials in key areas of technology, including in civil and mechanical engineering, aviation and space technology, and others. This work presents a modern composite material created with 3D-printing technology using the SLM method, and the possibility of its processing with one of the advanced manufacturing technologies, i.e., the Abrasive Water Jet (AWJ). Tests planned using DoE methods were carried out by changing control parameters such as the pressure, abrasive flow, and traverse speed. As a dependent parameter, the surface roughness parameter Sq (squared mean height) was selected and measured in different places of the cut composite. Based on the S/N ratio, the most favorable control parameters of the cutting process were also determined to achieve the lowest roughness of the cut surface. A clear effect of the controlled cutting process on the surface roughness was observed, as well as roughness variation for the metal and polymer component. In addition, the contact surface of the polymer with the metal in the cut zone was analyzed. Analysis of the contact surfaces on the microscope showed that the gap between the polymer-metal contact surfaces does not exceed 2.5 µm.

The Influence of the Structure Parameters on the Mechanical Properties of Cylindrically Mapped Gyroid TPMS Fabricated by Selective Laser Melting with 316L Stainless Steel Powder.

The development of additive manufacturing techniques has made it possible to produce porous structures with complex geometry with unique properties as potential candidates for energy absorption, heat dissipation, biomedical, and vibration control application. Recently, there has been increased interest in additively manufacturing porous structures based on triply periodic minimal surfaces (TPMS) topology. In this paper, the mechanical properties and energy absorption abilities of cylindrical mapped TPMS structures with shell gyroid unit cells fabricated by selective laser melting (SLM) with 316L stainless steel under compression loading were investigated. Based on the experimental study, it was found that tested structures exhibited two different deformation modes. There is also a relationship between the number and shapes of unit cells in the structure and the elastic modulus, yield strength, plateau stress, and energy absorption. These results can be used to design and manufacture more efficient lightweight parts lattices for energy absorbing applications, e.g., in the field of biomedical and bumpers applications. The deformation mode for each tested sample was also presented on the records obtained from the ARAMIS system.

Analysis and Modeling of the Micro-Cutting Process of Ti-6Al-4V Titanium Alloy with Single Abrasive Grain.

Modeling of material displacements in the microcutting zone is complex due to the number and interdependence of factors affecting the results of the process. An important problem in the modeling process is the selection of the constitutive model and its parameters, which will correctly describe the properties of the material under the conditions of triaxial compression, which is characteristic for the areas of the contact zone of the blade and the processed material in abrasive machining processes. The aim of the work was to develop computer models (with the use of the finite element method) of the microcutting process with a single abrasive grain, which were verified with the results of experimental tests. The paper presents the methodology of modeling the processes of microcutting with abrasive grains, whose geometrical models were created based on optical scanning methods. Observations of the microcutting process were carried out with the use of a high-speed camera and an optical profilometer. This enabled a detailed observation of the chip formation process, as well as the analysis of the surface topography of microcutting traces. The results presented in the paper indicate the convergence of the results of the numerical and experimental simulations with regard to the geometric parameters describing the scratches formed in the microcutting process and the compliance of the chip-forming process. Thus, the correctness of the selection of the constitutive model (Johnson Cook equation) and its parameters was demonstrated, as well as the correctness of the applied methodology for creating a geometric model that allowed for a reflection of the geometrical parameters of the abrasive grains that coincided with the real objects, thanks to which it was possible to reflect in detail the phenomena occurring in the vicinity of the abrasive grain tip.

Effect of 3D Printed Spatial Reinforcement on Flexural Characteristics of Conventional Mortar.

In their fourth decade of development, additive manufacturing technologies are slowly entering research programs dedicated to building materials. While the majority of research effort is focused on using 3D printing of concrete, the authors propose using the technology for creation of spatial plastic reinforcement. Obviously, the strength properties of a 3D printed polymer are much lower than those of steel. Nevertheless, the unconventional spatial shape of a 3D printed reinforcement can substitute for much of the lower mechanical performance of polymer. Flexural characteristics of a cement mortar prism specimen reinforced by hexagon spatial elements were tested and analyzed in this paper. The hexagonal geometric shape was chosen due to its high rigidness. It was proven that it is possible to efficiently reinforce concrete beams by spatial 3D printed polymer elements. Directions of needed research were pointed and discussed.

Effect of orthodontic debonding and residual adhesive removal on 3D enamel microroughness.

BACKGROUND: Termination of fixed orthodontic treatment is associated with bracket debonding and residual adhesive removal. These procedures increase enamel roughness to a degree that should depend on the tool used. Enamel roughening may be associated with bacterial retention and staining. However, a very limited data exists on the alteration of 3D enamel roughness resulting from the use of different tools for orthodontic clean-up. AIMS: 1. To perform a precise assessment of 3D enamel surface roughness resulting from residual adhesive removal following orthodontic debonding molar tubes. 2. To compare enamel surfaces resulting from the use of tungsten carbide bur, a one-step polisher and finisher and Adhesive Residue Remover. MATERIAL AND METHODS: Buccal surfaces of forty-five extracted human third molars were analysed using a confocal laser microscope at the magnification of 1080× and 3D roughness parameters were calculated. After 20 s etching, molar tubes were bonded, the teeth were stored in 0.9% saline solution for 24 hours and debonded. Residual adhesive was removed using in fifteen specimen each: a twelve-fluted tungsten carbide bur, a one-step finisher and polisher and Adhesive Residue Remover. Then, surface roughness analysis was repeated. Data normality was assessed using Shapiro-Wilk test. Analysis of variance (ANOVA) was used to compare between variables of normal distribution and for the latter-Kruskal-Wallis test. RESULTS: Sa (arithmetical mean height) was significantly different between the groups (p = 0, 01326); the smoothest and most repeatable surfaces were achieved using Adhesive Residue Remover. Similarly, Sq (root mean square height of the scale-limited surface) had the lowest and most homogenous values for Adhesive Residue Remover (p = 0, 01108). Sz (maximum height of the scale-limited surface) was statistically different between the groups (p = 0, 0327), however no statistically significant differences were found concerning Ssk (skewness of the scale-limited surface). DISCUSSION: Confocal laser microscopy allowed 3D surface analysis of enamel surface, avoiding the limitations of contact profilometry. Tungsten carbide burs are the most popular adhesive removing tools, however, the results of the present study indicate, that a one step polisher and finisher as well as Adhesive Residue Remover are less detrimental to the enamel. This is in agreement with a recent study based on direct 3D scanning enamel surface. It proved, that a one-step finisher and polisher as well as Adhesive Residue Remover are characterized by a similar effectiveness in removing residual remnants as tungsten carbide bur, but they remove significantly less enamel. CONCLUSION: Orthodontic debonding and removal of adhesive remnants increases enamel roughness. The smoothest surfaces were achieved using Adhesive Residue Remover, and the roughest using tungsten carbide bur.

Three-dimensional analysis of enamel surface alteration resulting from orthodontic clean-up -comparison of three different tools.

BACKGROUND: The present study aimed at 3D analysis of adhesive remnants and enamel loss following the debonding of orthodontic molar tubes and orthodontic clean-up to assess the effectiveness and safety of One-Step Finisher and Polisher and Adhesive Residue Remover in comparison to tungsten carbide bur. MATERIALS AND METHODS: Thirty human molars were bonded with chemical-cure orthodontic adhesive (Unite, 3M, USA), stored 24 h in 0.9 % saline solution, debonded and cleaned using three methods (Three groups of ten): tungsten carbide bur (Dentaurum, Pforzheim, Germany), one-step finisher and polisher (One gloss, Shofu Dental, Kyoto, Japan) and Adhesive Residue Remover (Dentaurum, Pforzheim, Germany). Direct 3D scanning in blue-light technology to the nearest 2 µm was performed before etching and after adhesive removal. Adhesive remnant height and volume as well as enamel loss depth and volume were calculated. An index of effectiveness and safety was proposed and calculated for every tool; adhesive remnant volume and duplicated enamel lost volume were divided by a sum of multiplicands. Comparisons using parametric ANOVA or nonparametric ANOVA rank Kruskal-Wallis tests were used to compare between tools for adhesive remnant height and volume, enamel loss depth and volume as well as for the proposed index. RESULTS: No statistically significant differences in the volume (p = 0.35) or mean height (p = 0.24) of adhesive remnants were found (ANOVA rank Kruskal-Wallis test) between the groups of teeth cleaned using different tools. Mean volume of enamel loss was 2.159 mm(3) for tungsten carbide bur, 1.366 mm(3) for Shofu One Gloss and 0.659 mm(3) for Adhesive Residue Remover - (F = 2.816, p = 0.0078). A comparison of the proposed new index between tools revealed highly statistically significant differences (p = 0.0081), supporting the best value for Adhesive Residue Remover and the worst - for tungsten carbide bur. CONCLUSIONS: The evaluated tools were all characterized by similar effectiveness. The most destructive tool with regards to enamel was the tungsten carbide bur, and the least was Adhesive Residue Removal.

Effect of orthodontic debonding and adhesive removal on the enamel - current knowledge and future perspectives - a systematic review.

After orthodontic treatment, brackets are debonded and residual adhesive is removed, causing iatrogenic enamel damage. The aim of this study was to review the methods of orthodontic adhesive removal, find clear evidence, and provide a rationale for this procedure. A literature search was performed in PubMed, Dentistry and Oral Sciences, Scopus, Cochrane, Google, and Google Scholar using keywords: orthodontic adhesive removal, orthodontic debonding, orthodontic clean-up. Studies concerning human enamel roughness or loss from debonding and adhesive removal were considered. Forty-four full-text articles were analyzed and 3 were rejected after detailed reading; finally 41 papers were included. Fifteen qualitative studies, 13 studies based on indices of enamel surface, and 13 quantitative studies were found. No meta-analysis could be performed due to a lack of homogenous quantitative evidence. The most popular tools were tungsten carbide burs, which were faster and more effective than Sof-Lex discs, ultrasonic tools, hand instruments, rubbers, or composite burs. They remove a substantial layer of enamel and roughen its surface, but are less destructive than Arkansas stones, green stones, diamond burs, steel burs, and lasers. Multi-step Sof-Lex discs and pumice slurry are the most predictable enamel polishing tools. Arkansas stones, green stones, diamond burs, steel burs, and lasers should not be used for adhesive removal. The use of tungsten carbide bur requires multistep polishing. Further efforts should be made to find tools and methods for complete removal of adhesive remnants, minimizing enamel loss and achieving a smooth surface.

Three-dimensional quantitative analysis of adhesive remnants and enamel loss resulting from debonding orthodontic molar tubes.

AIMS: Presenting a new method for direct, quantitative analysis of enamel surface. Measurement of adhesive remnants and enamel loss resulting from debonding molar tubes. MATERIAL AND METHODS: Buccal surfaces of fifteen extracted human molars were directly scanned with an optic blue-light 3D scanner to the nearest 2 µm. After 20 s etching molar tubes were bonded and after 24 h storing in 0.9% saline - debonded. Then 3D scanning was repeated. Superimposition and comparison were proceeded and shape alterations of the entire objects were analyzed using specialized computer software. Residual adhesive heights as well as enamel loss depths have been obtained for the entire buccal surfaces. Residual adhesive volume and enamel loss volume have been calculated for every tooth. RESULTS: The maximum height of adhesive remaining on enamel surface was 0.76 mm and the volume on particular teeth ranged from 0.047 mm3 to 4.16 mm3. The median adhesive remnant volume was 0.988 mm3. Mean depths of enamel loss for particular teeth ranged from 0.0076 mm to 0.0416 mm. Highest maximum depth of enamel loss was 0.207 mm. Median volume of enamel loss was 0.104 mm3 and maximum volume was 1.484 mm3. CONCLUSIONS: Blue-light 3D scanning is able to provide direct precise scans of the enamel surface, which can be superimposed in order to calculate shape alterations. Debonding molar tubes leaves a certain amount of adhesive remnants on the enamel, however the interface fracture pattern varies for particular teeth and areas of enamel loss are present as well.