deep penetration
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Author(s):  
M. Möbus ◽  
P. Woizeschke

AbstractDeep-penetration laser beam welding is highly dynamic and affected by many parameters. Several investigations using differently sized laser spots, spot-in-spot laser systems, and multi-focus optics show that the intensity distribution is one of the most influential parameters; however, the targeted lateral and axial intensity design remains a major challenge. Therefore, a laser processing optic has been developed that coaxially combines two separate laser sources/beams with different beam characteristics and a measuring beam for optical coherence tomography (OCT). In comparison to current commercial spot-in-spot laser systems, this setup not only makes it possible to independently vary the powers of the two laser beams but also their focal planes, thus facilitating the investigation into the influence of specific energy densities along the beam axis. First investigations show that the weld penetration depth increases with increasing intensities in deeper focal positions until the reduced intensity at the sample surface, due to the deep focal position, is no longer sufficient to form a stable keyhole, causing the penetration depth to drop sharply.


2022 ◽  
Vol 9 ◽  
Author(s):  
Donato Coviello ◽  
Antonio D’Angola ◽  
Donato Sorgente

Keyhole laser welding is the benchmark for deep-penetration joining processes. It needs high incident laser beam power densities at the workpiece surface to take place. The gaseous phase plays a fundamental role to keep the deep and narrow keyhole cavity open during the process. The plasma created in this process is a mixture of ionized metal vapors and the environmental gas and it develops inside the keyhole (keyhole plasma) and above the workpiece surface (plasma plume). The presence of plasma implicates absorption, scattering, and refraction of laser beam rays. These phenomena alter the power density of the laser beam irradiating the workpiece surface and thus affect the resulting welding process. In this work, a mathematical and numerical model has been developed to calculate the keyhole shape taking into account the plasma absorption effects. The model considers the keyhole walls as the liquid-vapor interface and computes the keyhole geometry applying a local energy balance at this interface. In addition, the model takes into account the multiple reflections effects inside the cavity through an iterative ray-tracing technique, and calculates the absorption mechanism due to inverse Bremsstrahlung for each ray along its segmented path inside the keyhole. Results show the effect of plasma properties on the keyhole shape and depth.


Materials ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 316
Author(s):  
Aimin Sha ◽  
Baowen Lou ◽  
Diego Maria Barbieri ◽  
Inge Hoff

The microwave heating/healing technique is regarded as a green maintenance approach for asphalt pavements thanks to its promising environmental and economic benefits. However, the main concern about this technology is represented by the possible aging effect generated on bituminous binders. Currently, there is a significant lack of studies dealing with this topic. Based on these premises, the main purpose of this study is to appraise the feasibility of implementing microwave-based maintenance operations considering the associated aging effect. The assessment of fatigue life after cyclic microwave heating (MH) based on a linear amplitude sweep (LAS) test and the changes in the chemical groups detected through Fourier transform infrared (FTIR) spectroscopy document the aging phenomenon. The results indicate that the microwave aging degree on bituminous binder is nonlinear with MH cycles. The microwave radiation causes a distinct aging impact on binders during the first 10 cycles, then the values become constant. Furthermore, a feasibility analysis of MH technology is developed, encompassing four main multidisciplinary aspects: evaluation of microwave aging degree, working mechanism of MH equipment, safety assessment, and economic and ecological considerations. Despite the associated aging issue, the MH method is an efficient technology, considering its various advantages (i.e., rapidity of execution, uniform and non-pollutant treatment, and deep penetration). Meanwhile, the use of steel slag as a microwave absorber bolsters the sustainability of MH technology. This study provides a new perspective to evaluate the microwave heating technique in road engineering comprising the generated aging effect. Practice-oriented recommendations are also formulated regarding the safe implementation of MH technical operations.


Author(s):  
Youliang Tian ◽  
Huiting Zhou ◽  
Quan Cheng ◽  
Huiping Dang ◽  
Hongyun Qian ◽  
...  

Fluorescence imaging in the second near-infrared window (NIR-II, 1000–1700 nm) holds great promise for in vivo imaging and imaging-guided phototherapy with deep penetration and high spatiotemporal resolution. It is very...


2021 ◽  
Vol 3 (74) ◽  
pp. 69-72
Author(s):  
F. Khamkhoeva ◽  
Z. Khautieva

The penetration of the mathematical apparatus into the economy created the basis for the development of methods of economic analysis, econometrics, mathematical programming, economic statistics, etc. Today, the interpenetration of different branches of knowledge continues, in particular, the application of mathematical methods in the natural and social sciences and in the economic sphere. Among mathematical methods of data processing are polynomial, linear, quadratic, trigonometric, exponential and combined dependencies, differential and algebraic equations. The statistical processing of data from the evaluation of the structure and dynamics of the phenomenon has gone in the direction of correlation analysis and forecasting. The deep penetration of mathematics into specific sciences and the success achieved through a combination of methods from different branches of knowledge is described by many researchers. The possibilities of applying mathematics are increasingly being explored in areas of knowledge where phenomena are poorly structured and characterized by the high complexity of sociology, political science, management and economics. The article presents a retrospective analysis of the development of scientific and applied research concerning the process of mathematics of science and the possibilities of using mathematical methods in economics in particular. Problems and constraints encountered in applying mathematical methods in economic research have been identified. Measures have been identified to ensure the adequacy of the development of economic and mathematical models from the standpoint of approaches to their construction, the improvement of management processes and the improvement of the training of specialists in economic fields.


Author(s):  
G.J. Yetirmishli ◽  
S.S. Ismailova ◽  
S.E. Kazimova

The Shamakhi-Ismailli seismogenic zone is known as the zone of the most powerful earthquakes in the Caucasus, which has been characterized by high seismic activity for centuries. Analysis of seismicity over the past 15 years has shown an increase in activity in this region. In October 2012, there was a devastating earthquake with a magnitude of 5.3. It is this earthquake that can be considered a trigger of activity in this region in subsequent years. In view of this, the task of studying seismicity, as well as the stress fields of the lithosphere of the region under study, seems to be especially urgent. The study of the seismicity of the Shamakhi-Ismailli zone provides additional information on the deep tectonic processes occurring in this region, which is important for seismic zoning. Aim. The article analyzes the seismic activity of the Shamakhi-Ismailli region, which began with an earthquake on February 5 at 19 h 19 min, with ml = 4.4, which occurred 11 minutes before the main shock with an intensity of 6 points, which occurred on February 5, 2019 at 19 h 31 m. Methods.The epicentral field was studied, as well as the distribution of foci in depth, solutions of the mechanisms of foci of the main shock and the most noticeable aftershock were constructed and analyzed. A diagram of the main elements of the rupture tectonics of the Shamakhi-Ismailli focal zone has been drawn, on which the mechanisms of the focal points of the lakes of the Ismailli field are plotted. Results. It has been established that the source area is located in the zone of intersection of the Vandam longitudinal fault with the West Caspian and transverse Akhsu strike-slip faults, which additionally characterizes the high seismic activity and deep penetration of the West Caspian right-sided orthogonal fault. Thus, it can be seen that, in terms of epicenters, they tend to the basement faults and the nodes of their intersection, i.e. The main shock that occurred on February 5, 2019, shows the agreement of the second nodal plane NP2 with the right-lateral Akhsu and West-Caspian transverse faults characterized by the type of displacement right-lateral strike-slip. An analysis of the orientation of the compression axes showed the NE-SW orientation, and the extension axes of the NW-SE orientation Шамахи-Исмаиллинская сейсмогенная зона известна как зона самых сильных землетрясений на Кавказе, которая на протяжении веков характеризовалась высокой сейсмической активностью. Анализ сейсмичности за последние 15 лет показал рост активности в этом регионе. В октябре 2012 года произошло разрушительное землетрясение магнитудой 5,3. Именно это землетрясение можно считать триггером активности в этом регионе в последующие годы. В связи с этим задача изучения сейсмичности, а также полей напряжений литосферы изучаемого региона представляется особенно актуальной. Изучение сейсмичности Шамахи-Исмаиллинской зоны дает дополнительную информацию о глубинных тектонических процессах, происходящих в этом регионе, что важно для сейсмического районирования. Цель работы.В статье проанализирована сейсмическая активность Шамахы-Исмаиллинского района, начавшаяся землетрясением 5 февраля в 19 ч 19 мин, с ml = 4,4, произошедшим за 11 минут до главного толчка с интенсивностью 6 баллов, произошедшего 5 февраля 2019 в 19 час 31 мин. Методы работы. Изучены эпицентральное поле, распределение очагов по глубине, построены и проанализированы решения механизмов очагов главного толчка и наиболее заметного афтершока. Составлена схема основных элементов разрывной тектоники Шамахы-Исмаиллинской очаговой зоны, на которой нанесены механизмы очагов озер Исмаиллинского месторождения. Результаты работы. Установлено, что очаговая область расположена в зоне пересечения Вандамского продольного разлома с Западно-Каспийским и поперечным Ахсуйским сдвигами, что дополнительно характеризует высокую сейсмическую активность и глубокое проникновение Западно-Каспийского правостороннего ортогонального разлома. Таким образом, видно, что в плане эпицентров они стремятся к разломам фундамента и узлам их пересечения, т.е. главный толчок, произошедший 5 февраля 2019 г., показывает совпадение второй узловой плоскости NP2 с правосторонним Ахсуйским и Западно-Каспийским поперечным разломом, характеризующимися правосторонним сдвиговым типом смещения. Анализ ориентации осей сжатия показал ориентацию СВ-ЮЗ, а оси растяжения – ориентацию СЗ-ЮВ.


2021 ◽  
Author(s):  
Eric Wasilewski ◽  
Nikolay Doynov ◽  
Ralf Ossenbrink ◽  
Vesselin Michailov

Abstract This work presents a comparative study of thermal conditions that occur during laser beam welding of high strength steel 100Cr6 that often leads to a loss of technological strength and may conditionally produce cold cracks. The results from both experiments and thermal-metallurgical FE-simulations indicate that the type of heat coupling changes significantly when welding with different process parameters, e.g., in the transition between conduction and deep penetration welding. Further, the simulations show that as a result of the high welding speeds and reduced energy per unit length, extremely high heating rates of up to 2x104 K s-1 (set A) resp. 4x105 K s-1 (set B) occur in the material. Both welds thus concern a range of values for which conventional Time-Temperature-Austenitization (TTA) diagrams are not currently defined, so that the material models can only be calibrated using general assumptions. This noted change in energy per unit length and welding speeds causes significantly steep temperature gradients with a slope of approximately 5x103 K mm-1 and strong drops in the heating and cooling rates, particularly in the heat affected zone near the weld metal. This means that even short distances along the length present a staggering difference in relation to the temperature peaks. The temperature cycles also show very different cooling rates for the respective parameter sets, although in both cases they are well below a cooling time t8/5 of one second, so that the phase transformation always leads to the formation of martensite. The results from this study are intended to be used for further detailed experimental and numerical investigation of microstructure, hydrogen distribution, and stress-strain development at different restrain conditions.


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