Investigation of the Anisotropic Structure of Travertine in Terms of Geological and Physico-Mechanical Properties: Sarıhıdır (Avanos-Nevşehir) Travertine Quarry

Travertine is a sedimentary rock with generally layered structure, mainly comprising carbonate. They are used for different purposes in interior and exterior spaces by cutting parallel or perpendicular to the bedding according to use. Travertine may contain several facies linked to variations in conditions during formation. With these features, travertine is one of the rocks with anisotropy most commonly observed. In this study, the anisotropic structure due to facies and layering in travertine was investigated considering geological and engineering properties. The Sarıhıdır travertine quarry face was divided into four different zones with different features. Chemical, mineralogic, physical, index and mechanical properties of the samples taken from these zones were determined. During determination of engineering parameters, samples were prepared parallel and perpendicular to bedding. The source of the travertine is a mixture of limestone, dolomite, evaporite and ultramafic rocks and they have epigean character, though they were affected by the hypogean environment. It appeared there were textural differences between the zones, rather than differences in chemical and mineralogic composition. When travertine was cut parallel to layering, all zones were suitable for decoration and facing. Only T-4 zone samples cut parallel were useable for flooring and load-bearing elements. In terms of compression and abrasion resistance, T-4 zone was better than the other zones. The cut direction of the travertine samples is an important factor for physical and mechanical behavior. Samples cut parallel to layering were observed to provide better results. According to the results, it is recommended to use products from the same travertine zone side-by-side in structures and to consider the cutting direction for long life of the building and to prevent economic losses.

SURVIVAL RATES OF IMPLANTS COMPROMISING ADJACENT TEETH AND THE ASSOCIATED COMPLICATIONS: AN OPG RETROSPECTIVE STUDY.

Purpose: This retrospective study evaluated the survival rates of implants compromising adjacent teeth and the associated complications. Methodology: Medical records and orthopantomographic images of 1,132 patients and 1,478 implants were retrospectively analyzed. Finally, 96 patients (52 females, 44 males) with 111 malpositioned implants were included in the study. The mean follow-up of the study was 32 ± 14 months. The patients were divided into two core groups: 1) adjacent teeth and dental implants were considerably close but tangent to each other (TAN), and 2) dental implant cutting the roots of the adjacent tooth (CUT). In addition, the CUT group was divided into two subcategories considering the possible cause of malangulation as angled implant (AI) or angled adjacent tooth (AT). Damage to adjacent teeth, future treatment requirements, and the survival rates of the implants were recorded. Results. Among the 111 implants, 4 (3.6%) implants failed, all of which belonged to the CUT category and the AI subgroup. Among the 88 preoperatively vital adjacent teeth, root canal treatment was performed in 18 (20.5%) teeth, whereas 2 (2.3%) teeth were extracted due to malpositioned implanting in follow-ups. Conclusions. The placement of implants too close to the adjacent teeth and even cutting direction did not have a statistically significant effect on the survival rates of implants. However, this could cause adjacent teeth to undergo unnecessary root canal treatment or extraction. Clinical relevance. Patients with malpositioned adjacent teeth or dilacerated root(s) adjacent to the edentulous area are at a higher risk for malpositioned implant complications. Most implant malposition complications are observed in the first premolar region (37% cases). Therefore, more attention should be given while placing implants in the first premolar region.

Theoretical studies of the “Workpiece-tool” system vibroacoustic dynamics of the turning group woodworking machines

In the woodworking industry, the issue of noise reduction is one of the fundamental ones. In most cases, it is an indicator of equipment and products quality, in addition, it negatively affects the performance and irritates the nervous system of machine operators. [1]. The cause of noise is the process of cutting tool interaction with wood and it also depends on the type of wood cutting tool. For wood manufacturing, the blade and abrasive cutting tools are used. The blade instrument has a specified number of fixed shape blades and is divided into disk, cylindrical, conical and plate-shaped ones according to the shape of the body. The abrasive cutting tool on the working surface contains an indefinite number of abrasive material particles. [2]. The edge of the cutter interacts with the surface under work, along the entire width, the cutting direction is perpendicular to the cutting edge. With a small cutting depth, this does not cause significant sound vibrations, but with intensive technological modes of the treated surface, this factor is of great importance in generating noise.There are a lot of works devoted to the study of different cutting tool dependence and noise characteristics [3-7]. For example, in [8] it was experimentally proved that the noise level increases by 1-5 dBA with an increase in the number of knives from 2 to 4. This article presents the results of the acoustic system theoretical studies “manufactured workpiece cutting tools” for cantilever fixing of the workpiece of turning group woodworking machines.

Investigation on the Exit Burr Formation in Micro Milling

The burr on micro part has harmful effect on the dimensional accuracy and service performance. The original control of exit burr formation during micro milling is desirable and advisable. In this paper, the formation mechanism of exit burr was studied based on the varying cutting direction during micro milling. Three exit burr control strategies were concluded, the material properties embrittlement, the support stiffness increasing and machining parameter optimizing operations. Then, micro milling experiments were carried out to investigate the exit burr morphology and size. It was found that the exit burr formation was attributed to the change of material flowing path at the exit surface, which was caused by the negative shear deformation zone that was induced by the discontinuous shape features. Different exit burr morphologies were classified; the triangle exit burr type was caused by the varying exit burr growing direction along the exit surface. The optimal machining parameters in micro milling to obtain a small exit burr were suggested.

Biomechanical Characteristics for Identifying the Cutting Direction of Professional Soccer Players

(1) Background: To understand the movement characteristics of soccer players when cutting in two directions (45° for the right and left cutting movements) through biomechanical analysis of the lower limbs to identify the cutting direction of the attacker; (2) Methods: A motion analysis system was used to capture the movements of 12 male professional soccer players dribbling to the left and right. Kinematics of the players’ cutting were analyzed, and the paired t-test was used for statistics, with a significant level of α = 0.05; (3) Results: When cutting towards the right, the height of the hip joint during the run-up was low (effect size, ES = 0.41, p = 0.031) at 91.8 ± 7.0 cm. When cutting towards the left, the value was 94.6 ± 6.7 cm. While cutting, the front foot was abducted by 4.3 ± 4.0° at landing when cutting towards the right and adducted by 2.7 ± 5.1° when cutting towards the left (ES = 0.38, p = 0.003); (4) Conclusions: When the attacker carries out the cutting action while approaching the defender, the cutting direction may be predicted by observing the attacker’s hip and foot movements.

Generation Mechanism and Dual Dynamic Simulations of Surface Patterns in Single-Point Diamond Turning of Single-Crystal Copper

Single-crystal copper (Cu), whose atom arrangement is in the same direction and has no grain boundary, is widely used in defense technology, civil electronics and network communication. As a diamond turnable material, fan-shaped patterns appear on the machined surface, which affects the machined surface quality and the optical function it carries. Previous studies on the surface generation mechanism in single-point diamond turning (SPDT) of Cu were limited to experimental analysis, while there is a lack of fundamental understanding of the fan-shaped pattern generation mechanism and suppression method. In the present study, the different fan-shaped patterns, surface quality, cutting force and chip morphology of the typical crystal planes (100), (110) and (111) planes of Cu were studied by both theoretical and experimental analyses. A molecular dynamics (MD) simulation was conducted to present the fundamental generation mechanism of the fan-shaped patterns from atom arrangement directions and its angle change with the main cutting direction, while a cutting dynamics model was established to simulate the generation of fan-shaped patterns on the machined surface. Based on theoretical and experimental analysis, it was found that the atom density arrangement directions of Cu and its angle change with the main cutting direction of SPDT caused fluctuations in the friction coefficient, which further caused the vibration of the cutting system and generated the fan-shaped patterns. The SPDT of crystal planes (100) can achieve the best surface quality. The present research provides a fundamental understanding of fan-shaped pattern formation on the machined surface, and provides an instruction for machining Cu to obtain better surface quality.

Variation of Femoral Component Size by Reference Points and Target Alignments in Total Knee Arthroplasty

Selecting appropriately sized components is important in total knee arthroplasty because they can affect postoperative knee function and pain. This study investigated size differences of 19 different femoral component placements from the standard position by three-dimensional virtual surgery using three-dimensional bone models of 101 varus osteoarthritic knees. Distal femoral bone was cut perpendicular to the femoral mechanical axis (MA) in the coronal plane. Twenty different component placements consisting of five cutting directions (perpendicular to MA, 3° and 5° extension/flexion relative to MA in the sagittal plane), two rotational alignments (clinical and surgical epicondylar axes), and two rotational types of anterior reference guide (central and medial) were simulated. The mean anteroposterior dimension of the standard position was 55.5 mm which means that the difference compared to 19 different methods ranged from -1.2 ± 0.2 mm to 7.1 ± 1.3 mm. Multiple regression analysis revealed that flexion cutting direction, surgical epicondylar axis, and central were associated with smaller component size. In conclusion, the femoral component size can be affected easily by not only cutting direction but also the reference guide type and the target alignment. Our findings could provide surgeons with clinically useful information to fine-tune for unintended loose or tight joint gaps by adjusting the component size.

Optimization of the effect of accelerated weathering conditions on wood surfaces via the Taguchi method

This study investigated the effect of accelerated weathering conditions on total color changes on Scots pine (Pinus sylvestris L.) and poplar (Populus x euroamericana) wood surfaces using the Taguchi method. The experiments, based on the L18 orthogonal array, were conducted separately for both tree species. The radial and tangential surfaces of wood specimens were subjected to an accelerated weathering process using 340 nm ultraviolet (UV) lamps and temperature conditions of 50 °C. The factors for the minimum color change were determined via the signal-to-noise (S/N) ratios of the four parameters thought to be effective on color change. These parameters were cutting direction (two levels), UV-irradiance, conditioning, and water (three levels each). The most important factor affecting the color change was then determined by analysis of variance (ANOVA) testing. The results showed that the maximum UV-irradiance (W/m2) had the largest effect on the total color change, while the cutting direction (radial and tangential) had the smallest effect. The factors that affected the total color change of the poplar and Scots pine wood specimens were the same. However, the analysis revealed that different application times had varying effects on the color change.

Investigation of the basic laws of cutting root crop tops

Purpose: to study the basic laws of cutting some plant materials, the knowledge of which will justify the rational parameters of a small unit for mechanization of removing the root crop tops. Materials and methods. The study was carried out experimentally on a computerized dynamometric unit, according to a non-compositional plan of the second order, using two most common types of root crops in cultivation in small holdings: table carrots and radishes. The value of the specific resistance of cutting tops was taken as an optimization parameter. Results. The study has shown that such factors as the blade incidence angle to the cutting direction, the blade width and the blade speed at the beginning of cutting are crucial and significantly affect the energy consumption of the top removal process. The most significant parameter is the blade width, the degree of influence of which is 2.2–18.2 times greater than the degree of influence of the other two factors. On average, a decrease in the blade width from 0.5 to 0.1 mm leads to a 3–5-fold decrease in the specific cutting force of the top, which confirms the prospects of using ultra-thin replaceable blades instead of a durable wide-faceted blade in the design of the plant-top removing machines. It was also found that at a blade speed of about 0.2 m/s and its blunted blade (b ≈ 0.5 mm), the tops are not cut, but crumpled or (in some cases) deflected by the knife. Conclusions. In general, the study allows to recommend the following rational parameters and operating modes of a small unit for mechanizing the root crops tops removal: the blade incidence angle to the cutting direction is from 30 to 45°; the blade width is about 0.1 mm; cutting speed is about 0.33 m/s.