Surface Qualification Toolpath Optimization for Hybrid Manufacturing

Hybrid manufacturing machine tools have great potential to revolutionize manufacturing by combining both additive manufacturing (AM) and subtractive manufacturing (SM) processes on the same machine tool. A prominent issue that can occur when going from AM to SM is that the SM process toolpath does not account for geometric discrepancies caused by the previous AM step, which leads to increased production times and tool wear, particularly when wire-based directed energy deposition (DED) is used as the AM process. This work discusses a methodology for approximating a part’s surface topology using on-machine contact probing and formulating an optimized SM toolpath using the surface topology approximation. Three different geometric surface approximations were used: triangular, trapezoidal, and a hybrid of both. SM toolpaths were created using each geometric approximation and assessed according to three objectives: reducing total machining time, reducing surface roughness, and reducing cutting force. Different prioritization scenarios of the optimization goals were also investigated. The optimal surface approximation that yielded the most improvement in the optimization was determined to be the hybrid surface topology approximation. Furthermore, it was shown that when the machining time or cutting force optimization goals were prioritized, there was little improvement in the other optimization goals.

Development of means for experimental identification of navigator attention in ergatic systems of maritime transport

The article discusses the issues of identification of models of analysis of the navigational situation by the navigator during the passage in narrow places and port areas; this is especially relevant in critical situations. As part of the research, an analysis of literary sources was carried out, which made it possible to characterize this direction as actual for the development of special means of an experimental nature. As the main goal, the article presents formal-logical approaches to the development of software and hardware means for determining the areas of attention of the navigator as a subject of an ergatic system. A mechanism was determined for the formation the indexes of the analytical activities of the navigator during assessing the situation, mathematical models, and means for clarifying the position of the navigator on the navigation bridge. A geometric approximation of indexes was proposed, the metric of which can significantly reduce the identification time of critical situations and prevent negative consequences. The carried experiments by using the certified navigation simulator Navi Trainer 5000 confirmed the effectiveness and practical value of the proposed approaches, which will greatly improve the retraining of marine crew.

Estimation of NOx, SO2 and HCHO emissions from the megacity of Lahore, Pakistan using car MAX-DOAS observations and comparison with regional model and TROPOMI satellite data

<p>Lahore, megacity of Pakistan with more than 11 million inhabitants is a strong emission source of atmospheric pollutants. We present results of a top-down emission procedure for NOx and SO<sub>2</sub> for Lahore, based on car multi-axis differential optical absorption spectroscopy (car-MAX-DOAS) observations. Additionally, the total flux of HCHO from the city is determined which can be seen as an indicator for VOC emissions. Results from two extensive campaigns, which took place in summer 2017 and spring 2018 will be presented. From the measured spectra, we retrieve the vertically integrated concentration (the so-called tropospheric vertical column density, VCD) of the trace gases along the driving route by using the so-called geometric approximation method. By combining these observations with ECMWF Re-Analysis wind data, the total fluxes of NO<sub>x</sub>, SO<sub>2</sub> and HCHO from the city of Lahore are estimated. From both measurement campaigns, we also analyzed the seasonal variability of the above-mentioned species.</p><p>Derived NOx and SO<sub>2</sub> emissions are compared to the bottom-up emission inventory EDGAR. Spatial disributions of the tropospheric NO<sub>2</sub> and SO<sub>2</sub> VCDs observed by car MAX-DOAS are compared with those simulated using a coupled regional-global model system (MECO(n)). We find that, the model is able to account for the spatial variablity but the VCDs are systematically underestimated by the regional model. Finally, derived NOx emissions are also compared to the emissions estimated from TROPOMI satellite observations.</p>

Методика моделирования фаски отверстий в корпусах объектов подводного кораблестроения под вварку насыщения

При постройке современных объектов подводного кораблестроения остро встает вопрос повышения точности вварки различных конструкций в прочный корпус. В первую очередь сильно влияет на точность подготовка кромок отверстий в прочном корпусе. Ввиду большой толщины корпусных конструкций и произвольных положений ввариваемых объектов поверхность разделки отверстия под сварку имеет сложную форму. Применение криволинейной разделки под сварку, характерной для других отраслей промышленности в подобных задачах, в кораблестроении не используется вследствие технологических проблем при обработке. Вскрытие и обработку отверстий производят на стапеле ручным способом, что определяет низкую точность изготовления. При определении геометрии разделки применяются методы начертательной геометрии. Одним из способов, позволяющих кардинально повысить точность выполнения отверстий является применение мобильных технологических комплексов с числовым программным управлением. Однако для них характерна пониженная жесткость по сравнению со стационарными станками, обычно применяемых для механической обработки. Для эффективного применения мобильных технологических комплексов с числовым программным управлением требуется математическое описание поверхности разделки кромок отверстий под сварку. В статье рассмотрена типовая технология подготовки геометрии отверстий под вварку различного насыщения. Рассмотрены типовые требования нормативной документации к точности изготовления фаски отверстий. Предложен вариант моделирования фаски отверстий с помощью функционала современных САПР с применением поверхности дважды косого цилиндроида. Предложена методика геометрического моделирования криволинейных направляющих поверхности дважды косого цилиндроида. Предложен вариант геометрической аппроксимации плоской плавной кривой для построения первой криволинейной направляющей поверхности дважды косого цилиндроида на основе плоских сопряженных круговых дуг. Определено уравнение первой криволинейной направляющей поверхности дважды косого цилиндроида в случае выполнения отверстия на цилиндрической обечайке в плоскости, параллельной плоскости мидель-шпангоута.The problem of increasing the welding accuracy of various structures into a pressure hull in the construction of modern underwater shipbuilding is especially acute. First of all, the preparation of the holes edges in a pressure hull greatly affects the accuracy. Due to the large thickness of the hull structures and random positions of the welded objects, the bevels surface of the weld hole has a complex shape. The use of curvilinear bevel for welding, which is characteristic of other industries in similar tasks, is not used in shipbuilding due to technological problems. Opening and processing of holes is carried manually out on the slipway. It determines the low accuracy of manufacture. When determining the geometry of bevel, methods of descriptive geometry are used. One of the ways to fundamentally increase the accuracy of holes is the use of mobile technological systems with numerical control. However, they are characterized by reduced rigidity compared to stationary machines, usually used for machining. For the effective use of mobile technological systems with numerical control, a mathematical description of the surface for cutting the holes bevels for welding is required. The article describes a typical technology for preparing the geometry of holes for welding of various saturations. Typical requirements of standart documentation for the manufacturing accuracy of holes bevel are considered. A variant of modeling the holes bevel using the functionality of modern CAD systems using the surface of a double oblique cylindroid is proposed. A technique for geometric modeling of curved guiding surfaces of a double oblique cylindroid is proposed. A variant of geometric approximation of a flat smooth curve is proposed for constructing the first curved guide surface of a double oblique cylindroid based on flat circular arcs. The equation of the first curved guide surface of the double oblique cylindroid is determined in the case of making a hole on the cylindrical shell in a plane parallel to the plane of the midship.

Asymptotic properties of solutions of third order difference equations

We consider the difference equation of the form ?(rn?(pn?xn)) = anf (x?(n)) + bn. We present sufficient conditions under which, for a given solution y of the equation ?(rn?(pn?yn)) = 0, there exists a solution x of the nonlinear equation with the asymptotic behavior xn = yn + zn, where z is a sequence convergent to zero. Our approach allows us to control the degree of approximation, i.e., the rate of convergence of the sequence We examine two types of approximation: harmonic approximation when zn = o(ns), s ? 0, and geometric approximation when zn = o(?n), ? ? (0, 1).