The Effect of Coatings on Cutting Force in Turning of C45 Steel

This article focuses on the development of a mathematical model of a cutting force that is applicable for coated and uncoated cutting tool inserts and aims to enable more accurate calculation of the cutting force. Two common PVD coatings, AlTiN and TiAlCrN, were used. Firstly, a mathematical model of the cutting force based on the specific cutting force and cutting area is proposed. This mathematical model considers the cutting speed and coating correction factor as well as the real cutting edge geometry, i.e., it includes both the straight and rounded parts of the cutting edge. For this proposed model, material constants for C45 steel, which was machined with uncoated inserts, were obtained. Before determining an equation for a coating correction factor and implementing it into the model, experimental cutting force data for coated and uncoated inserts were compared using a paired t-test. The result was that the difference between them was statistically significant. Their percentage difference was found to be up to 4%. The correction factor equation that was obtained and implemented into the mathematical model was applied to compare the calculated and experimental data of the coated inserts, also using a paired t-test. The result was that the difference between them was insignificant. Moreover, their percentage difference was found to be up to 0.6%.

Supernumerary teeth in premolar and molar area on CBCT: a pictorial review.

Objective: to build a descriptive classification of premolar and molar supernumerary teeth (ST) when preparing the cone beam computed tomography (CBCT) report. The aim is also to share wide range of CBCT images in the open access publishing model. Material and methods: For our review we systematically searched for articles from PubMed with 1) free full texts on ST in molar and premolar area and using CBCT, and 2) articles providing with information on complications related with the presence of ST in molar and premolar area. We also added to our review studies providing with classic ST classifications in premolar and molar area. Results: We found 29 cases of ST, and we freely illustrated them with 84 figures. We separated our pictorial review in: 1) unilateral ST in the mandible, 2) unilateral ST in the maxilla, 3) unilateral undersized ST, 4) bilateral ST, 5) ST with additional features, and 6) cases with major hyperdontia. Conclusions: we build up the classification matrix for premolar and molar ST with 11 descriptors and 50 boxes. The descriptors were: 1) location if the ST crown in axial view, 2) vertical location of the cusp tip in relation with closest erupted tooth in coronal view, 3) shape, 4) distribution, 5) Position (in relation to normal tooth eruption) in sagittal view, 6) State of eruption of the ST in the sagittal view, 7) Follicle size measurement in sagittal view, 8) External root resorption of adjacent teeth by ST and its location in relation to the long axis of the involved tooth, 9) Internal resorption of ST, 10) Adjacent tooth complication, and 11) Damage to surrounding structures if ST removal. The open access figures from the literature illustrated 11 boxes. With our pictorial review we were able to illustrate 45 out of 50 boxes, and freely provide the readership with the most complete description of ST in premolar and molar area on CBCT than in previously published studies.

A two-level macroscale continuum description with embedded discontinuities for nonlinear analysis of brick/block masonry

A great proportion of the existing architectural heritage, including historical and monumental constructions, is made of brick/block masonry. This material shows a strong anisotropic behaviour resulting from the specific arrangement of units and mortar joints, which renders the accurate simulation of the masonry response a complex task. In general, mesoscale modelling approaches provide realistic predictions due to the explicit representation of the masonry bond characteristics. However, these detailed models are very computationally demanding and mostly unsuitable for practical assessment of large structures. Macroscale models are more efficient, but they require complex calibration procedures to evaluate model material parameters. This paper presents an advanced continuum macroscale model based on a two-scale nonlinear description for masonry material which requires only simple calibration at structural scale. A continuum strain field is considered at the macroscale level, while a 3D distribution of embedded internal layers allows for the anisotropic mesoscale features at the local level. A damage-plasticity constitutive model is employed to mechanically characterise each internal layer using different material properties along the two main directions on the plane of the masonry panel and along its thickness. The accuracy of the proposed macroscale model is assessed considering the response of structural walls previously tested under in-plane and out-of-plane loading and modelled using the more refined mesoscale strategy. The results achieved confirm the significant potential and the ability of the proposed macroscale description for brick/block masonry to provide accurate and efficient response predictions under different monotonic and cyclic loading conditions.

THE STUDY OF HOMOGENEOUS AND HETEROGENEOUS SENSITIZED CRYSTALS OF CADMIUM SULFIDE. PART IV. FEATURES OF THE REVERSE PHOTOEXCITATION METHOD

For the first time, a reverse method of studying the spectral distribution curves of the photocurrent was applied, which allows to separate the contribution of equilibrium and non-equilibrium carriers. This publication is a continuation of the reviews [1-3]. In order to preserve the generality of the work, the numbering of sections is selected to be general. Numbers of formulas and figures are presented in sections. References to literature in each review are given individually. Cadmium sulfide crystals are used in our research as a convenient model material. The results obtained on them and the constructed models are also applied to other semiconductor substances.

Electrically Tunable Lens (ETL)-Based Variable Focus Imaging System for Parametric Surface Texture Analysis of Materials

Electrically tunable lenses (ETLs) are those with the ability to alter their optical power in response to an electric signal. This feature allows such systems to not only image the areas of interest but also obtain spatial depth perception (depth of field, DOF). The aim of the present study was to develop an ETL-based imaging system for quantitative surface analysis. Firstly, the system was calibrated to achieve high depth resolution, warranting the accurate measurement of the depth and to account for and correct any influences from external factors on the ETL. This was completed using the Tenengrad operator which effectively identified the plane of best focus as demonstrated by the linear relationship between the control current applied to the ETL and the height at which the optical system focuses. The system was then employed to measure amplitude, spatial, hybrid, and volume surface texture parameters of a model material (pharmaceutical dosage form) which were validated against the parameters obtained using a previously validated surface texture analysis technique, optical profilometry. There were no statistically significant differences between the surface texture parameters measured by the techniques, highlighting the potential application of ETL-based imaging systems as an easily adaptable and low-cost alternative surface texture analysis technique to conventional microscopy techniques.

Reactivity of Microcrystalline Cellulose with Methyltrimethoxysilane and 3-(2-Aminoethylamino) propyltrimethoxysilanes

In the presented research, two trialkoxysilanes were used to investigate their reactivity with microcrystalline cellulose (MCC) applied as a model material. As a continuation of the previous study, the research aimed at evaluation of the durability and potential reversibility of the silane treatment. Two different solvents and a mixture thereof were used for cellulose modification. The influence of amino group/pH, an excess of silanes and re-soaking with water on binding with cellulose was examined. The results obtained confirm that both selected silanes can effectively modify MCC. However, the treatment with 3-(2-aminoethylamino)propyltrimethoxysilane occurred more effective than with Methyltrimethoxysilane due to the presence of amino groups. Among the three tested solvents, the most effective was pure water. In contrast, the use of ethanol and a mixture of ethanol and water gave significantly worse results. Summarising, the presented research clearly shows how important the type of the functional group in alkoxysilanes is for its chemical reactivity with natural polymers, which is crucial for their application in waterlogged wood conservation.

Dislocation Loop Generation Differences between Thin Films and Bulk in EFDA Pure Iron under Self-Ion Irradiation at 20 MeV

In the present investigation, high-energy self-ion irradiation experiments (20 MeV Fe+4) were performed on two types of pure Fe samples to evaluate the formation of dislocation loops as a function of material volume. The choice of model material, namely EFDA pure Fe, was made to emulate experiments simulated with computational models that study defect evolution. The experimental conditions were an ion fluence of 4.25 and 8.5 × 1015 ions/cm2 and an irradiation temperature of 350 and 450 °C, respectively. First, the ions pass through the samples, which are thin films of less than 100 nm. With this procedure, the formation of the accumulated damage zone, which is the peak where the ions stop, and the injection of interstitials are prevented. As a result, the effect of two free surfaces on defect formation can be studied. In the second type of experiments, the same irradiations were performed on bulk samples to compare the creation of defects in the first 100 nm depth with the microstructure found in the whole thickness of the thin films. Apparent differences were found between the thin foil irradiation and the first 100 nm in bulk specimens in terms of dislocation loops, even with a similar primary knock-on atom (PKA) spectrum. In thin films, the most loops identified in all four experimental conditions were b ±a0<100>{200} type with sizes of hundreds of nm depending on the experimental conditions, similarly to bulk samples where practically no defects were detected. These important results would help validate computational simulations about the evolution of defects in alpha iron thin films irradiated with energetic ions at large doses, which would predict the dislocation nucleation and growth.

Atomistic Simulation of Ultra-Short Pulsed Laser Ablation of Al: An Extension for Non-Thermalized Electrons and Ballistic Transport

For our model material aluminum, the influence of the laser pulse duration in the range between 0.5 ps and 16 ps on the ablation depth is investigated in a computational study with a hybrid approach, combining molecular dynamics with the well known two-temperature model. A simple, yet expedient extension is proposed to account for the delayed thermalization as well as ballistic transport of the excited electrons. Comparing the simulated ablation depths to a series of our own experiments, the extension is found to considerably increase the predictive power of the model.