Search

The present paper investigates the application of laser beam shaping and laser beam oscillations (wobbling) for laser processing of the crack-prone aluminum alloy 6013, used in automotive and aerospace applications. A comparison of different laser beam profiles, such as the commonly used Gaussian profile, a ring-core distribution with the intensity of 50 % in the ring and 50 % in the core, and a ring-shaped beam profile shows different cracking behavior of the material. The ring-shaped beam profile shows the most promising results due to a reduction of the thermal gradient G and an enhancement of the growth rate R, which isalso stated by the state of the art. A combination of laser beam shaping and laser beam oscillations shows reproducible crack-free processing of Al6013 sheets at all three beam profiles at different parameter combinations. The crack elimination can be attributed to the emergence of a more pronounced equiaxed grain structure in the fusion zone of the weld with the application of laser beam oscillations and laser beam shaping. Thus, the temperature gradient G, the growth rate R and, therefore, the cooling rate can be controlled with the presented variation of the laser beam shapes and scanning strategies. Furthermore, the penetration depth of the laser at a Gaussian beam profile can be reduced using laser beam shaping, showing shallower melt pools with a lower depth-to-width aspect ratio, also suitable for the process of powder bed fusion of metals using a laser-based system (PBF-LB/M).

High melting point materials are essential to many different industries because of their unique qualities, rendering them invaluable for various uses. This paper investigates the unique features of high melting point materials, summarizes current advancements in the field, and outlines the vast range of applications that these materials have in domains like materials science, aerospace, energy, and electronics. The discourse covers various materials, such as carbon-based, ceramics, intermetallic, and refractory metals, emphasizing their potential uses and new roles in contemporary technology. Thanks to developments in material science, new high melting point materials with enhanced mechanical strength, thermal stability, and resistance to harsh environments have been found and synthesized. These materials are used in manufacturing, electronics, aircraft, and energy. They are frequently distinguished by their resistance to temperatures significantly higher than those of ordinary materials. High melting point materials are used in the aerospace sector to manufacture heat-resistant parts that improve spacecraft and jet engines' overall performance and longevity. These materials are also essential to the energy sector's creation of sophisticated thermal management systems for nuclear reactors and high-temperature environments, improving energy generation efficiency and security. The electronic industry benefits from high melting point materials when producing semiconductors and other electronic components since their stability guarantees dependable operation even in harsh circumstances.Furthermore, high melting point materials are becoming increasingly popular in additive manufacturing procedures, allowing complex structures with exceptional heat resistance to be produced for various uses. Moreover, high melting point alloys and composites have been developed due to advances in metallurgy and nanotechnology, broadening their potential uses in industries including automobile engineering, medical technology, and military technology. The interdisciplinary aspect of high melting point material research and development is shown in this abstract, which also highlights the adaptability of materials and their revolutionary effects on various industries. The continuous investigation of these materials shows promise for future discoveries that will open up new avenues and applications in fields vital to the development of contemporary society.

CSAM (cold spray additive manufacturing) of Ti6Al4V is a challenging task and high-quality deposits conforming to the AM application standards have not been developed so far. In our study, two distinct feedstock Ti6Al4V powders with different morphology and microstructure, spherical and crystalline, were used and their influence on the deposits was investigated in terms of microstructure as well as tensile properties. The results indicate the mechanical strength and ductility of the as-deposited samples to be in the range of 8–30 % compared to wrought Ti6Al4V and highlight a significant anisotropy in different in-plane directions. The post-treatments of the deposits from the spherical, plasma atomized powder effectively reduced the porosity and triggered microstructural homogenization and recrystallization, leading to a significant increase in the yield and tensile strengths, reaching 892 MPa and 954 MPa, respectively, while achieving an enormous enhancement in the elongation to 21.6 % at the same time. This was in a striking contrast to the deposits from the crystalline powder: despite the yield and tensile strength increase to 853 MPa and 1058 MPa, respectively, the elongation remained virtually zero, highlighting the importance of the feedstock powder selection in cold spray additive manufacturing of Ti6Al4V.

Unmanned aerial vehicle (UAV) granular fertilizer spreading technology has been gradually applied in agricultural production. However, in the process of spreading operation, the actual influence effect of each factor in field operation is still unclear. Based on the self-developed UAV fertilizer spreading system, this paper explores the effects of three factors, the baffle retraction (B), spreading disc speed (D), and UAV flight altitude (H), on the granular fertilizer spreading effect in the actual field scenarios through the orthogonal test and taking the coefficient of variation (Cv) and relative error of fertilizer application rate (λ) as the evaluation indexes. The results showed that the optimal factor level combination of Cv was 11.23 % for BbDbHa (the baffle retraction is 6 %, spreading disc speed is 600r/min, and UAV flight height is 1.5 m) at UAV flight speed of 2 m/s. The best factor level combination for λ was BbDbHb of 7.99 % (the baffle retraction is 6 %, spreading disc speed is 600r/min, and UAV flight height is 2 m). In addition, by analysing the influence of the weather and the vortex of the rice canopy on the actual spreading effect, it was found that the weather has less influence on the spreading effect of this system, while the vortex caused by the airflow of the UAV rotor has a certain influence on the spreading effect, which is also relatively easy to ignore in fertilizer spreading operations. The results of the study can be used to explore the operational effects of actual fertilizer application by UAVs in rice field, which will help promote the development of UAV spreading technology and provide a reference for precision fertilizer application through agricultural aviation.

This study presents a brief account of the seminal works on aeroelastic tailoring for aerospace applications. Tailoring using advanced composites is a revolutionary process in the ever-evolving realm of aerospace design. The rapid growth in scientific knowledge and research necessitates the consolidation of the latest research and technological advancements every few years. The current work is part of this process. The major portion of the study covers the latest developments and state-of-the-art research in this century, with a special focus on the last ten years. However, a brief account of the historical background, the theoretical foundation, and a few seminal works from the later part of the previous century and the early part of this century have also been included to form a comprehensive starting point for new researchers entering the field of aeroelastic tailoring and to assist them in identifying the directions of their future endeavours. A critical evaluation of different research contributions, including their advantages, limitations, and prospects for future work, has been presented. Emphasis has been laid on flutter mitigation and aeroelastic optimization for passive aeroelastic control. New material and structural technologies (like curvilinear fibres, tow steering, functional grading, thickness distributions, selective reinforcing, additive manufacturing, and unconventional structural configurations), and novel tailoring optimization techniques (like lamination parameters, blending constraints, active aeroelastic wing design, shape functions, surrogate modelling, reduced order modelling, uncertainty quantification, matrix perturbation theory, modal-strain-energy analyses, and multiple indigenous optimization algorithms) have been identified as active research areas and prospective enabling tools for future work. The challenges faced in the full-scale employment of aeroelastic tailoring include quick, robust, and cost-effective optimization to cater for all design variables and constraints, experimental validation of new methodologies, certification of new material and structural configurations through relevant bodies and standards and gaining the confidence of industrialists for investment in technologies with a few highly focused areas of applications.

Polyimide (PI)-silica aerogel composite aerogels with low shrinkage (3.7%), low density (0.061 g/cm3), low thermal conductivity (0.0216 W m−1 K−1), high hydrophobicity (146°) and good fire resistance were prepared by incorporating silica aerogel powders into PI matrix. The properties of the aerogels are affected by the type and content of silica aerogel powders. The samples show high compressibility, and the stress at 80% strain increases with the increase of silica aerogel powder content. The addition of inorganic silica aerogel powders (ISAp) can improve the thermal stability of the aerogel and the fire resistance and structural integrity of the sample under flame, but has adverse effect on moisture resistance. While the addition of polyvinylpolymethylsiloxane aerogel powders (PAp) improves the moisture resistance of the aerogel but weakens the thermal stability and fire resistance. The introduction of both ISAp and PAp can reduce the thermal conductivity of the aerogel, and the samples exhibit good thermal insulation performance. Furthermore, ground equivalent simulation tests were carried out to verify the adaptability of these aerogels in the space environment. The sample meets the standard requirements and shows stable structure and performance during the tests, which proves its potential application in the aerospace field.

The focus of this research is to develop a specialized multidisciplinary design optimization framework for composite sandwich-structured radomes. Radomes play a crucial role in safeguarding antenna systems from challenging environmental conditions. However, they can adversely impact the electromagnetic performance of the antenna. Unlike traditional approaches that separately address electromagnetic performance and mechanical responses, our framework considers both aspects concurrently, resulting in a more efficient process. The main objectives of the optimization are to enhance electromagnetic performance while also accounting for deformations, material integrity, and structural stability. To evaluate the electromagnetic performance, a 3-dimensional numerical simulation is employed to analyze parameters such as electromagnetic transmission loss, bore sight error, and side lobe characteristics. The model's accuracy is verified through experimental testing in an anechoic chamber, utilizing a hybrid sandwich structure. The results indicate minimal attenuation, with an average loss of only 1.5 % in the transmission of antenna signals, using the proposed radome thickness. Furthermore, the configuration of the material provides structural stability, ensuring a factor of safety of 2.5 while satisfying operational constraints. Hence, the proposed multidisciplinary optimization model represents an efficient and feasible approach to radome design. This advancement in the field equips engineers and researchers with a valuable tool to develop dependable and effective radome systems.

One of the earliest approaches in gain-scheduling control is the gridding based approach, in which a set of local linear time-invariant models are obtained at various gridded points corresponding to the varying parameters within the flight envelop. In order to ensure smooth and effective Linear Parameter-Varying control, aligning all the flexible modes within each local model and maintaining small number of representative local models over the gridded parameter space are crucial. In addition, since the flexible structural models tend to have large dimensions, a tractable model reduction process is necessary. In this paper, the notion of σ -shifted [Formula: see text]- and [Formula: see text]-norm are introduced and used as a metric to measure the model mismatch. A new modal alignment algorithm is developed which utilizes the defined metric for aligning all the local models over the entire gridded parameter space. Furthermore, an Adaptive Grid Step Size Determination algorithm is developed to minimize the number of local models required to represent the gridded parameter space. For model reduction, we propose to utilize the concept of Composite Modal Cost Analysis, through which the collective contribution of each flexible mode is computed and ranked. Therefore, a reduced-order model is constructed by retaining only those modes with significant contribution. The NASA Generic Transport Model operating at various flight speeds is studied for verification purpose, and the analysis and simulation results demonstrate the effectiveness of the proposed modeling approach.