Lightweight Manufacturing Research Articles

Current status and challenges of lightweight design and manufacturing technology for aerospace structures

Lightweight technology refers to the technology of reducing the structural mass by optimizing materials, structures and manufacturing processes while meeting the requirements of structural performance. It has become one of the key technologies for the development of the new generation of aerospace equipment. This paper first analyzes the development history of lightweight technology. Secondly, from the perspectives of design principles, composition methods and optimization methods, three types of lightweight design methods are introduced: bionic structure design, cellular structure design and efficient topology optimization design. Then, from the perspective of lightweight manufacturing processes and modes, the application of additive manufacturing, collaborative manufacturing and composite material manufacturing in lightweight manufacturing of aerospace structures is explained. Finally, the challenges and future development of lightweight technology are discussed.

Electrodeposition transition layer induced Cu/PPr hybrids

The high-performance metal-plastic hybrids have been widely applied in lightweight manufacturing. In this work, microstructures were prepared on the copper plate (Cu) surface using an electrodeposition process. Afterward, this microstructure was used to join with the pentatricopeptide repeats (PPr) to obtain Cu/PPr hybrids. The effect of electrodeposition process parameters on surface morphology was explored. The polyacrylic acid (PAA) content had the most significant effect on the surface morphology, and an increase in PAA content resulted in a shift from a lamellar to a granular structure. When the PAA content was 5 g/L, electrodeposition time was 300 s and the current density was 25 mA/cm2, the transition layer on the Cu surface was optimized, the roughness reached 164 nm, and the contact angle decreased to 2.41°. Meanwhile, the effect of molding temperature on the strength of the hybrids was explored, and the joining strength of the hybrids reached a maximum of 13.45 MPa when the temperature was 270 °C, which is 73.5 % of the strength of the PPr matrix. Further elevation of the molding temperature failed in the transition layer due to oxidation. The joining strength of the hybrids relies solely on the mechanical interlocking ability of the interface. The Cu/PPr hybrids provide design ideas for the practical production of copper-plastic composite pipes.

Computational design of auxetic microstructures via stress-based topology optimization

Material design plays a pivotal role in industries dedicated to lightweight manufacturing. In response to the needs of such industries, topology optimization (TO) has evolved beyond structural optimization to include designing material microstructures for improved structural performance. While conventional approaches often prioritize stiffness-oriented designs as a foundational aspect of structural integrity, it is equally imperative to emphasize strength-based design principles to ensure robustness against localized stress concentrations and potential failure modes. This paper explores the application of stress-constrained topology optimization (SCTO) for designing auxetic microstructures. The study commences with a comprehensive parametric analysis to examine the influence of the P-norm parameter, variations in volume fraction, and initial design adjustments on the resulting microstructures. Several optimized structures, accompanied by stress contours, are generated to showcase how the optimization process responds to these parameters. The approach employs the density-based solid isotropic material with penalization material interpolation scheme, and it utilizes the stress penalization technique to mitigate the singularity phenomenon. The multi-constraint optimization employs the method of moving asymptotes algorithm to update design variables. The effectiveness of the proposed approach to utilize actual strain fields, derived from macroscopic finite element analysis under service loads, for TO of an auxetic microstructure according to strength requirements is demonstrated. The application of the designed microstructure is explored through its integration into an auxetic cushion pad. This analysis confirms the microstructure’s effectiveness in practical applications, demonstrating its potential for broader usage in similar applications.

A novel multi-spot structure for joining aluminum and steel dissimilar thin-walled tubes by magnetic pulse crimping

Lightweight manufacture for dissimilar thin-walled tube structures without additional liner support has always been a challenge. A novel magnetic pulse multi-spot joining structure was proposed for the non-weight gain mechanical connection of 6061 aluminum to SPCC (Steel Plate Cold-rolled Common) steel thin-walled tubes. Mechanical properties, microscopic features, and joining mechanism of the magnetic pulse crimping (MPC) joints were explored based on simulation and experiments. Under the geometric conditions of flyer tube with an outer diameter of 30 mm and a thickness of 1 mm, the optimal preformed groove depth and discharge energy for the MPC joints were 2 mm and 16 kJ, respectively. The corresponding maximum tensile and torsional strength were 10.6 kN and 131.2 N m, respectively. The corresponding relative thinning rate of aluminum outer tube was 13 %. The failure forms of the MPC joints were all pull out and torsion out failures. During the high-speed joining of aluminum tube to steel tube, stress concentration phenomena occurred successively at the circumferential bottom fillet, axial bottom fillet, and axial upper edge of the groove. This was due to a certain height difference between the circumferential and axial directions of the groove. It was related to induction distance, discharge energy, skin effect, proximity effect, and tip effect in the coupled field. The yielding and instability of the groove in the steel inner tube would lead to a decrease in the fitting area of the aluminum outer tube filled groove and the relative thinning rate of the aluminum outer tube. This caused a decrease in the mechanical interlocking force at the groove, which was detrimental to the mechanical properties of the MPC joints. This article provides a new approach and data support for the lightweight manufacture of dissimilar thin-walled tube structures.

Hollow Connecting Rod Thin Wall Austempered Ductile Iron (TWADI) for Manufacturing Light Weight Components

Hollow Connecting Rod Thin Wall Austempered Ductile Iron (TWADI) for Manufacturing Light Weight Components

Fabrication and failure mechanisms of ultralight all-CFRP sandwich cylinders under axial compression

Ultralight all-CFRP honeycomb sandwich cylinders were fabricated using a stretching process. Subsequently, critical failure loads corresponding to five typical failure modes of the sandwich cylinders under axial compression were obtained through theoretical derivation. Three-dimensional failure mechanism maps were generated, which intuitively revealed the influence of the dimensionless parameters on structural failure. The panel thickness was selected as a variable, and quasi-static axial compressive tests were performed on the sandwich cylinders. Two failure modes, intracellular buckling and face crushing, were observed, which is consistent with theory. The experimental results were analysed and discussed systematically. The ultralight all-CFRP honeycomb sandwich cylinders were compared with existing cylinders to reveal their bearing advantages. The established failure mechanism maps provide guidance for the preparation and optimisation of honeycomb sandwich cylinders. Compared with the traditional fabrication processes of honeycomb cores, the novel stretching process is expected to achieve mass production, which is helpful to provide technical support for the lightweight manufacturing of aerospace structural components.

Research progress on nanoparticles reinforced magnesium alloys

Magnesium alloys, acknowledged as the environmentally-friendly engineering material of the 21st century, are ideally suited to fulfill the requirements of lightweight manufacturing. However, the poor plasticity of magnesium alloys hampers their further application. Subsequently, development of nanoparticle-reinforced magnesium matrix composites has been proven to be a promising way to enhance the comprehensive performance of magnesium alloys. The exceptional performance achieved even by very small number of reinforcements stimulated innovation in preparation techniques and in-depth analysis of reinforcement mechanisms. This paper provides a review on key challenges related to their processing, the profound impact of different micro-nanoparticle reinforcements on the microstructure and properties of magnesium matrix composites during solidification and subsequent deformation machining. Additionally, the reinforcement mechanisms of the excellent mechanical performance of the composites are also discussed. This study can provide valuable insights for the understanding of the selection of appropriate reinforcements and processing to optimize the performance nanoparticle-reinforced magnesium matrix composites.

An optimization method of wall thickness distributions in T-shaped tube compound-forming method with unconventional tube blank

The thin-walled T-shaped tube is widely applied in aviation pipeline systems with the development of lightweight manufacturing technology. However, the severe wall thickness thickening is a bottleneck problem restricting the application of T-shaped tubes. In order to avoid excessive thickening and improve the overall performance of the formed parts, an optimization method of wall thickness distributions in T-shaped tube compound forming by using optimized unconventional tube blank is proposed. The strain spline method is adopted to investigate the stress-strain state and deformation mechanism of T-shaped compound forming. The optimization model of tube blank is established and includes two parts: the initial optimization based on the geometric analytic method and the iterative optimization based on the incremental finite element method. The optimal tube blank is achieved through two-step optimizations. The numerical simulations and experiments of T-shaped tube compound forming using conventional and optimized tube blanks are carried out to investigate the forming height and the wall thickness distributions. The simulation and experimental results agree with a no more than 20 % relative error. The optimal tube blank could effectively improve the wall thickness distributions compared with the T-shaped tube compound using the conventional tube blank. The final experimental results show that the maximum thickening rate decreases from 48.67 % to 28.67 %, the maximum thinning rate decreases from 25.33 % to 18 %, and the maximum difference in the wall thickness decreases from 1.11 mm to 0.7 mm. The comparison results are further verified to be the correctness of the optimization method and the effectiveness of the T-shaped tube compound forming method with unconventional tube blank in the actual experiments.

Effect of impinging behavior annular jet shielding gas and printing substrate on metal droplet stable ejection

Using coaxial shielding gas for low-oxygen protection in metal droplet-based 3D printing helps to promote flexible production and lightweight manufacturing. However, the presence of the printing substrate causes the shielding gas to exhibit complex annular impinging jet characteristics, making the stability of droplet ejection unpredictable. In the present work, the mechanisms of airflow pattern evolution on droplet formation and metal jet deflection were first revealed by incorporating shielding gas simulations, hydrodynamic modeling, and droplet ejection experiments. An innovative airflow disturbance suppression strategy for metal droplet ejection was proposed, which can remarkably reduce the shielding gas disturbance on droplet printing. Results show that the change in deposition distance leads to a transition between two typical airflow patterns, thus affecting the droplet ejection behavior. When the deposition distance exceeds 2.5 mm, metal jets would be stretched even to a secondary break under airflow pattern 1, accelerating droplets. For the deposition distance below 2.5 mm, metal jet shortening and droplet deceleration would occur under airflow pattern 2, deflecting jet trajectory. The negative airflow effect on droplet ejection could be avoided by controlling the deposition distance to the transition region of two airflow patterns. Furthermore, a ball grid array (BGA) chip ball-mounting and two thin-wall tube printing were realized based on metal droplet ejection in annular impinging jet shielding gas. This work provides theoretical and technical guidance for the stable ejection and accurate printing of metal droplets in an opening low-oxygen environment.

Simultaneous fabrication of Ti-MoS2 self-lubricating coatings and gradient structures to improve the wear resistance of AZ91D alloys

Magnesium alloys are essential for lightweight manufacturing. Nevertheless, defects such as low hardness and poor wear resistance severely restrict their further applications. Ultrasonic impact treatment (UIT) was used to simultaneously fabricate surface Ti-MoS2 self-lubricating coatings and interior gradient structures on AZ91D magnesium alloy for the first time. The surface morphology and microstructure were investigated, the tribological properties were evaluated at various normal loads, and the formation principles and anti-wear mechanisms of coatings and gradient structures were revealed. The findings indicate that the coatings present a particle-stacking microstructure. The gradient structures were characterized by grain, dislocation, and hardness distribution from greater to lesser along the depth direction. At all loads, the UIT samples exhibited superior anti-wear properties. Compared to untreated samples, the UIT sample's wear volume at 5 N, 15 N, and 25 N loads was reduced by 89.78 %, 84.23 %, and 43.88 %, respectively. The wear surface analysis indicates that the Ti-MoS2 coatings effectively enhance the lubricity of friction surfaces. Additionally, gradient structure works when the coatings fail and reduces the shear deformation, further reducing wear. This work presents a new method for fabricating simultaneously surface coatings and interior gradient structures using UIT, contributing to improving the anti-wear properties of magnesium alloys and enhancing their utilization in lightweight manufacturing fields.

Forming Performance of Multi-way Tubes in Hydroforming

The tube hydroforming technology is a rapid-forming technique in multi-way tube integrated and lightweight manufacturing. The forming performance of the multi-way tube under this technology was comprehensively analyzed and summarized in this paper. Firstly, the influencing factors, such as axial feed loading path and internal pressure, forming friction, and die transition fillet, in the process of multi-way tube forming were analyzed and summarized. Secondly, the optimization method of the multi-way tube forming performance in hydroforming was analyzed. Finally, the reduction of hydraulic expansion costs and the development of new hydroforming technologies were expounded.

Corrosion and Protection of Magnesium Alloys: Recent Advances and Future Perspectives

Magnesium alloys are of significant importance for lightweight manufacturing and weight-saving applications due to their high weight-to-strength ratio and good mechanical properties. However, the poor corrosion resistance of Mg alloys limits their large-scale practical application. An essential theoretical foundation for the development of corrosion-resistant magnesium alloys and their surface protection technologies can be elucidated via the investigation of the corrosion mechanism of the magnesium surface and the alteration of the corrosion rate after surface conversion and coating. This paper discusses some typical corrosion behaviors by originally describing the corrosion mechanism of magnesium alloys with and without different coatings and surface treatments. In order to predict the future theoretical investigation and research directions for the surface protection of magnesium alloys, some techniques and preventative measures to enhance the corrosion resistance of magnesium alloys are reviewed, and these protection techniques are intercompared for better understanding.

Failure analysis of a loader hydraulic cylinder and its end cap structure improvement

With the rapid development in the manufacturing sector, lightweight manufacturing has become an inevitable trend. However, achieving lightweight engineering machinery requires the structural redesign of most internal components, including the hydraulic cylinders in hydraulic systems. When evaluating the lifespan of redesigned loader hydraulic cylinders using simulated pulse experiments, it was evident that the fillet weld between the connecting end cap and cylinder barrel failed and fractured before reaching its full lifespan. Consequently, in order to assess the failure conditions of the loader hydraulic cylinder, the generation and extension of the failure cracks were explored using methods such as macroscopic fracturing, hardness testing, metallographic analysis, inclusion component analysis, and finite element analysis. During this process, the end cap structure of hydraulic cylinder was improved using finite element analysis. The results showed that the presence of numerous coarse spherical carbides at the tip of the weld cracks and the formation of dislocation tangles around the carbides, resulting in high stress concentrations and accelerated fatigue crack propagation. Additionally, the specific welding-joint structure of the hydraulic cylinder, resulting in high stress concentrations and accelerated fatigue crack initiation at the weld. After improving the hydraulic-cylinder end cap structure using finite element analysis, the fatigue life of the hydraulic cylinder was improved. This work provides a theoretical basis for the design and manufacture of lightweight and high-life hydraulic cylinders.

Tungsten carbide coating prepared by ultrasonic shot peening to improve the wear properties of magnesium alloys

To improve the wear properties of magnesium alloys, a novel technique for preparing coatings using ultrasonic shot peening was developed, and tungsten carbide (WC) coatings were prepared for the first time on the magnesium alloys. The surface morphology, microstructure characteristics, and wear properties were investigated. The findings showed that this method deposited a WC coating with a thickness of 20 μm and a surface hardness of 3.24 GPa on the substrate. A 5 μm composite layer and a 425 μm thick hardened layer existed beneath the coating. The formation mechanism of the hardened layer can be interpreted as dislocation slip and grain refinement, resulting in a hardness of 1.96 GPa at the layer's top. The treated sample exhibited excellent wear resistance due to the high hardness of the WC coating and hardened layer, with a wear volume of 0.737 × 108 μm3, representing a decrease of 49.52% and 35.29% compared to the untreated and ultrasonic shot peening one. The research provides a novel solution to improve the wear properties of magnesium alloys, and it contributes to enhancing magnesium alloys' applicability in practical engineering fields such as aerospace, new energy vehicles, and biomedicine while also contributing to meeting the demand for lightweight manufacturing in these fields.

Strengthening characteristic and mechanism of AlCoCrFeNi high-entropy alloy particles for Al-Cu dissimilar friction stir lap welded joint

Regarding the light-weight welding application, the strategy of non-tool penetration into lower hard sheet is considered as a promising dissimilar friction stir lap welding (FSLW) process for restriction of tool wear and reduction of welding force. In order to further improve the mechanical properties of the lap joint for such a case, AlCoCrFeNi high-entropy alloy (HEA) particles were selected as reinforcement for the Al-Cu dissimilar FSLW. A novel approach to incorporating HEA particles into lap weld, where a HEA particle-reinforced Al matrix was pre-prepared by FSLW, was proposed to prevent the overflow of particles from weld effectively during Al-Cu FSLW. The strengthening characteristic and mechanism of the HEA particles were systematically explored in this paper. Microstructural analyses indicate that the spherical HEA particles with large size contribute to the grain refinement via particle-stimulated nucleation mechanism, furthermore, nanoscale particles (Al3Ni and Al13Fe4) are formed adjacent to the HEA particles in the Al matrix. The induced grain refinement strengthening and secondary phase strengthening by the HEA particles are responsible for the significant improvement in the mechanical properties of Al-Cu lap joint. This study provides a technological approach and a theoretical foundation for the high-quality dissimilar FSLW used in light-weight manufacturing field.

International planetary sunshade concept with a function-integrated and scalable support structure based on coreless filament winding

Despite all current efforts, climate change is the greatest challenge of the 21st century. Since existing measures will fail to prevent critical tipping points from being reached, in addition to terrestrial geoengineering methods, efforts are underway to explore new ways to implement space-based geoengineering methods into the short-term construction of a buffer solution - the International Planetary Sunshade (IPSS). The IPSS system reduces solar irradiation mitigating the global mean temperature rise while offering a sustainable energy supply. The developement of the system poses multifaceted challenges only to be mastered by a collaboration of space agencies and private companies, while supported by society. Therefore, tackling the IPSS within international roadmaps is essential to exploit synergies, shorten development time, and promote international cooperation. An evolutionary concept achieves stepwise Earth independence by utilizing lunar resources. The feasibility of the IPSS also depends on the foil’s supporting structure. Therefore, a lightweight manufacturing technology that meets several criteria, such as scalability, adaptivity, material compatibility, full automation, on-orbit manufacturing, in-situ resource utilization, and digital design including function integration, must be adopted. Hence, coreless filament winding (CFW) may be a suitable technology for realizing the demanded mass savings. The prerequisite for the superiority of CFW structures is an application- and material-compliant component and fiber net design. Previous experience with CFW cannot be directly transferred to the IPSS system due to the changed requirements for space application. This paper will present a systematic design concept for the IPSS, initially exploring a CFW support structure by discussing segmentation and modularity, proposing a new connection system, and implementing function integration.

Numerical simulation of molten pool flow behavior and keyhole evolution behavior in dual-laser beam oscillating bilateral synchronous welding of T-joints

In the context of global warming and energy shortage, the key means to increase product competitiveness is how to achieve lightweight manufacturing of large spacecraft skin-stringer structures by welding instead of riveting. In this work, we propose dual-laser beam oscillating bilateral synchronous welding (DLBOW) by combining dual-laser beam synchronous welding (DLBW) with the oscillating process to overcome the long-standing porosity problem in T-joint welds and investigate the effect of different laser incidence angles on the porosity of the weld during welding. At the same time, the corresponding numerical model was established by computational fluid dynamics to analyze the molten pool flow behavior and keyhole evolution under molten pool coupling. This is the first time that complete wire melting process has been achieved in the T-joint dual-laser beam synchronous welding numerical model, reproducing more realistically the influence of the wire fusion behavior on the molten pool flow. Both experimental and simulation results show that the porosity is significantly reduced under DLBOW compared to DLBW; in addition, the porosity is lower when the laser incidence angle is smaller. An in-depth analysis of the numerical model reveals the mechanism of this physical phenomenon: First, the oscillation process optimizes the laser energy density distribution and reduces the peak temperature of the T-joint molten pool. The impact of the metal flow on the keyhole is weakened, which reduces the probability of bubble formation and thus significantly decreases the porosity. Moreover, for the oscillation process, the keyhole effect is more obvious at large laser incidence angles, and the actual heat input to the molten pool is larger, which makes the slender keyhole more prone to collapse and more likely to generate pores. This work provides new insight into the interrelationship between keyhole and pore in T-joint dual-laser beam synchronous welding.

Enhanced joint strength between TC4 alloy and CFRTP via in-situ constructing sandwich interface with interlocking structure and multi-chemical bonding

Interfacial strength between CFRTP and titanium is still weak and restricts its application in lightweight manufacturing. In this work, a new concept by in-situ constructing a sandwich interface with an interlocking structure and multi-chemical bonding to enhance interfacial strength was proposed. A novel method by designing and presetting interlayers with intersect-curved structures and dissimilar compositions was put forward to realize this in-situ construction. On the one hand, through presetting interlayer with designed intersect-curved structures, surface of CFRTP is changed from continued-heating to alternated-heating, which increases the maximum heat-input tolerance of CFRTP and prolongs cooling time. These contribute to deeper pinning depths with fully-filled resin into intervals, which greatly improve the interlocking strength at interface. On the other hand, by choosing an interlayer with a constituent chemically active with both CFRTP and base metal, the interfacial reaction is further enhanced, resulting in multi-chemical bonding including Fe-Ti and Fe-O at interface. This sandwich interface contributes to high strength of 45 MPa, which was 55% higher than non-interlayer samples in high heat input and four-folds higher than non-interlayer samples in low heat input. Compared with existing pre-treatment methods, this method was quite worth being recommended due to outstanding performance and low cost.

Ultrasonic welding of AZ31B magnesium alloy and pure copper: microstructure, mechanical properties and finite element analysis

Magnesium alloy, copper and other light alloys are widely used in aerospace, new energy vehicles, lightweight manufacturing and other fields due to their excellent mechanical properties, but the connection between light alloys has always been a challenge. Ultrasonic welding is an advanced manufacturing technology that can realize high-strength connection between heterogeneous light alloys. In this study, ultrasonic welding between AZ31B magnesium and pure copper are carried out. The fracture, microstructure and tensile properties of the joint are studied, and its connection mechanism is analyzed. The finite element analysis model of magnesium-copper ultrasonic welding process is established. The fracture mode of magnesium-copper ultrasonic welded joint is interface-type fracture. The joint strength reaches the maximum value of 3798 N. The ultrasonic connection between magnesium alloy and copper is mainly realized by the interface diffusion layer formed in the welding process. The main component of the interface diffusion layer is Mg2Cu. The growth trend of interface diffusion layer is revealed. During welding, heat is generated in the central area of the solder joint, and then transferred around. The maximum temperature at the interface can reach 550 °C. The distribution law of temperature field and plastic deformation field of joint are revealed.

Effect of Laser Micro-Texturing on Laser Joining of Carbon Fiber Reinforced Thermosetting Composites to TC4 Alloy.

Carbon fiber reinforced thermosetting composites (CFRTS) and TC4 alloy are important structural materials for lightweight manufacturing. The hybrid structure of these two materials has been widely used in the aerospace field. However, the CFRTS-TC4 alloy joint formed by the traditional connection method has many challenges, such as poor environmental adaptability and stress concentration. Laser micro-texturing of metal surface-assisted laser connection of CFRTS and TC4 alloy has great potential in improving joint strength. In order to study the effect of laser micro-texturing on the laser bonding of CFRTS and TC4 alloy, the simulation and experimental research of laser welding of TC4 alloy and CFRTS based on laser micro-textures with different scanning spacings were carried out, and the interface hybrid pretreatment method of laser cleaning and laser plastic-covered treatment was introduced to assist the high-quality laser bonding of heterogeneous joints. The results showed that the established finite element model of CFRTS-TC4 alloy laser welding can predict the temperature field distribution of the joint during the welding process and reflect the forming mechanism of the joint. The laser micro-textures with different scanning spacings will lead to a difference in the temperature field distribution on the polyamide (PA6) interface, which leads to a change in heat input on the CFRTS surface. When the laser scanning spacing is 0.3 mm, the joint strength can reach 14.3 MPa. The failure mechanism of the joint mainly includes the cohesive failure of the internal tear of the carbon fiber and the interfacial failure of the interface between the PA6 resin and the TC4 alloy.