Demand For Lightweight Structures Research Articles

Analyzing the Influence of Titanium Content in 5087 Aluminum Filler Wires on Metal Inert Gas Welding Joints of AA5083 Alloy

As the demand for lightweight structures in the transportation industry continues to rise, AA5083 aluminum alloy has become increasingly prominent due to its superior corrosion resistance and weldability. To facilitate the production of high-quality, intricate AA5083 components, 5087 aluminum filler wire is commonly utilized in metal inert gas (MIG) welding processes for industrial applications. The optimization of filler wire composition is critical to enhancing the mechanical properties of AA5083 MIG-welded joints. This study investigates the effects of modifying 5087 aluminum filler wires with different titanium (Ti) contents on the microstructure and weldability of AA5083 alloy plates using MIG welding. The influence of Ti contents was systematically analyzed through comprehensive characterization techniques. The findings reveal that the constitutional supercooling induced by the Ti element and the formation of Al3Ti facilitate the heterogeneous nucleation of α(Al), thereby promoting grain refinement. When the Ti content of 5087 filler wire is 0.1 wt.%, the grain size of the weld center was 78.48 μm. This microstructural enhancement results in the improved ductility of the AA5083 MIG-welded joints, with a maximum elongation of 16.64% achieved at 0.1 wt.% Ti addition. The hardness of the joints was the lowest in the weld center zone. This study provides critical insights into the role of Ti content in MIG welding and contributes to the advancement of high-performance filler wire formulations.

Rigid–Flexible Coupled Modeling and Flexoelectric Control for Flexible Rotating Structures

The pursuit of lightweight structures has propelled spacecraft with large flexible appendages to the forefront of modern aerospace engineering. Flexoelectric actuators, with their inherent self-sensing and self-actuating capabilities, perfectly align with the demand for lightweight structures. This paper presents a dynamic model and a flexoelectric vibration control method tailored for spacecraft equipped with single-sided flexible appendages. The spacecraft system is a central rigid hub with flexible cantilever beam appendages that allow for single-axis rotation. The flexible beam has a flexoelectric element attached to it. Leveraging Hamilton’s principle, the equations of motion are derived, accounting for flexoelectric effects, the centrifugal stiffening effect, and the coupling between rigid body attitude and flexible beam vibration. A closed-loop proportional–derivative controller is crafted for attitude control of the system. Additionally, a flexoelectric patch is employed as an actuator for active vibration control of the flexible beam. The precision and efficacy of the proposed model and control scheme are meticulously validated through numerical simulation. The results indicate that the flexoelectric patch can effectively manage the vibration of the flexible beam, consequently impacting the attitude control performance of the system. Furthermore, the flexoelectric effect of the system under static conditions is scrutinized, and the influence of the flexoelectric actuator on the rigid–flexible coupling characteristics of the system is thoroughly analyzed. These analyses not only confirm the feasibility of flexoelectricity in rigid–flexible coupled systems, but also open avenues for applications and optimizations in intelligent control methods for flexible appendages.

Drilling carbon fiber reinforced plastics with pre-cooling treatment by cryogenic fluid

The high technological properties of carbon fiber reinforced plastics (CFRPs) have led to their ever-increasing use in recent decades for industrial applications, especially in the aerospace and automotive sectors, where the demand for lightweight structures is high. The panels of composite, to be assembled with other materials, may require repeated realization of holes, making the final quality of the union highly dependent on the drilling process. However, the heterogeneity of the composite material may lead to several inconveniencies, such as rapid tool wear and hole delamination, as during machining the drill bit encounters fiber and matrix alternatively, which have different properties. These damages could be reduced through cryogenic drilling, as demonstrated in the related literature, mainly because the machining behavior of composite changes at low temperatures. Starting from this evidence, the present paper proposes an experimental study conducted on CFRP panels using a new methodology of cryogenic drilling, based on the pre-cooling of the composite before starting the machining process, in order to create a uniformly refrigerated material. The analysis is aimed at comparing the hole quality obtained under dry and pre-cooled cryogenic conditions in terms of delamination, surface roughness and dimensional accuracy and at evaluating thrust force, tool wear and the influence of feed rate.

Numerical models for evaluating the vibro‐acoustic properties of acoustic metamaterials

AbstractThe demand for lightweight structures in aerospace and automotive is on the rise and so are the requirements regarding the vibro‐acoustic behavior. Materials with a high stiffness‐to‐mass ratio are often used in this field, but these materials typically have an unfavorable vibrational behavior regarding structure‐borne noise. Acoustic metamaterials offer a solution for improving the vibro‐acoustic performance of the structure, while the stiffness‐to‐mass ratio remains nearly constant. Such a metamaterial consists of periodic patterns of microstructures placed on the host structure. They modify the vibrational behavior of the host by adding local resonances and thus minimize vibrations at specific frequencies. Distinct resonances can have a major contribution to the acoustic behavior of a structure, so it is of interest to tailor microstructures, that generate stop bands at certain frequencies. This can be computationally expensive, so efficient numerical models are required for the design of acoustic metamaterials. Initial investigations show, that a parametric model order reduction (PMOR) method based on the Loewner framework can generate such models.

Mitigating distortion and residual stress by static thermal tensioning to improve fatigue crack growth performance of MIG AA5083 welds

The demand for lightweight structures in ship fabrication to improve performance and fuel savings has led to increasing use of thin-section structures. However, welding such structures often produces problems such as distortion and residual stress. The present investigation is aimed to mitigate distortion and residual stress using static thermal tensioning (STT) to improve fatigue performance in AA 5083 metal inert gas (MIG) welded joints. The STT treatments were performed by cooling the weld zone and its adjacent area during welding whereas both sides away from the weld were heated at various temperatures of 100, 200 and 300°C to generate thermal gradient. Subsequent experiments including distortion measurements, microscopical examination, hardness and tensile tests, measurements of residual stresses using neutron diffraction method and fatigue crack growth tests combined with SEM fractography were conducted. Results showed that an increase in heating temperature reduced convex longitudinal out of plane distortion. The minimum longitudinal out of plane distortion was achieved at a heating temperature of 200°C owing to the balance between buckling distortion induced by welding and that generated by static differential heating which opposed the weld distortion. Under such condition, fatigue crack growth performance was improved.

Manufacturing of Light Metal Matrix Composites by Combined Thermal Spray and Semisolid Forming Process – Summary of the Current State of Technology

The demand for lightweight structures in the automotive and aerospace industry increases permanently, and the importance of lightweight design principles is also increasing in other industrial branches, aiming towards improved energy efficiency and sustainability. Light metals are promising candidates to realize security relevant lightweight components because of their high specific strength; and amongst them, aluminum alloys are the most interesting materials due to their high plasticity and strain to failure, good processability, passivation in oxygen containing atmosphere, and low cost. However, for many applications, their stiffness as well as strength and fatigue behavior at elevated temperature are insufficient. Metal matrix composite (MMC) formation by integration of reinforcements in the form of continuous or discontinuous (short) fibers can yield a high increase in the alloys’ specific mechanical properties at room temperature and at elevated temperature. The integration of fibers with conventional manufacturing techniques like squeeze casting, hot pressing or diffusion bonding leads to restrictions in the component’s geometry. Moreover, these techniques result in elevated process costs mainly caused by long cycle times and the need of additional protective fiber coatings. In the present paper, an alternative method for the manufacturing of aluminum matrix composites is described, combining thermal spraying and semisolid forming (thixoforging) technologies for the formation of fiber prepregs and subsequent forming with simultaneous densification. Therefore, prepregs with the matrix alloy as a thick surface coating on the reinforcement fibers are manufactured in a fast, automated coating process, while reheating, densification and shaping are performed in a separate process, allowing an optimization of both processes towards cycle times and resulting material properties. Continuous fiber and short fiber reinforced aluminum matrix composites are manufactured using woven or parallel arranged continuous fibers, or short fibers as a fleece or fiber paper material. For the coating process, twin-wire electric arc spraying is applied as a well established, cost efficient thermal spray technology. The coating process is optimized towards microstructure of the matrix alloy prior to semisolid forming, which requires a globular alloy microstructure, and reduced fiber damage during the high-temperature liquid melt deposition. The thermally sprayed fine-grained matrix material enables semisolid forming at liquid contents of 40-60 vol% of the alloy, with short flow paths, reduced mechanical loads and short cycle times. Thus, limited fiber damage and residual stresses will occur, leading to good mechanical material properties. A production line for industrial-scale coating of fiber fabric coils in a continuous process is introduced in order to provide prepregs of various fiber-reinforcement materials and fiber architectures; moreover, a winding equipment for simultaneous fiber winding and coating is presented that enables local reinforcement for components with adapted, tailored composite material design.