Deformable Part Research Articles

System reliability and sensitivity analysis for extendible support structures with multiple assembly failure modes

The extendible support structure (ESS) is the indispensable ingredient of space antennas, and its assembly reliability is of significant importance for the work performance of the latter. Specifically, pointing accuracy of the panels is critical to the electromagnetic performance of the space antenna and angular error of the locking joints directly determines whether the joint can be successfully locked so as to maintain the structural configuration of the ESS. Thus, this paper proposes a novel analytical approach to system reliability and sensitivity analysis for the ESS considering pointing accuracy and angular errors. At first, the failure mechanism of the ESS due to pointing deviation and angular error is comprehensively analyzed. On this basis, system reliability with those multiple failure modes for the ESS is mathematically defined. To solve this problem, the structural error model of the ESS considering manufacturing errors, assembly deviations and part deformations is first established so that the limit-state functions characterizing the pointing deviation and angular errors are accordingly formulated. Then, a novel framework based on expectation propagation is explored for system reliability and sensitivity analysis with multiple failure modes, of which the notable merit is that it is analytical. Based on this novel expectation-propagation-based framework, the systematic assembly reliability of the ESS is conducted in a closed-form manner. Finally, case studies and practical experiments are conducted to validate the effectiveness of the proposed method. The results demonstrate that it can provide an accurate and efficient system reliability and sensitivity analysis for the ESS.

A constitutive model incorporating the interplay of dynamic recrystallization and twinning during hot deformation of AZ31 magnesium alloy

Dynamic recrystallization (DRX) and deformation twinning play a pivotal role in stress partitioning during hot deformation of magnesium alloy. However, the influence of twinning on stress is diverse, and the interaction between DRX and twinning is intricate. Existing constitutive models cannot simultaneously describe the relationship between DRX and twinning, as well as their effects on stress. In this study, the hot compression tests were conducted to study the flow behavior and microstructure evolution of AZ31. The obtained flow curves and microstructure revealed that AZ31 alloy undergoes simultaneously DRX softening and twinning hardening during hot deformation. Furthermore, texture evolution was significantly influenced by both DRX and twinning behaviors. As a result of DRX behavior, there was a decrease in twin volume fraction in the later stages of deformation. Consequently, a twin volume fraction model that incorporates the inhibitory effect of DRX was proposed. According to the experimental results of high temperatures and low strain rates, a constitutive model incorporating work hardening, dynamic recovery (DRV), and DRX was established. Additionally, the influence of twinning on flow stress was incorporated into the model, resulting in a constitutive model that considers both DRX and twinning simultaneously. Finally, the proposed model's reliability was validated through the wedging spinning process, successfully predicting both macroscopic deformation and microstructure evolution of the spinning parts.

Seismic Response Comparisons of Prefabricated and Cast In Situ Subway Station Structures in Liquefiable Site

Based on the engineering practice of the first prefabricated subway station (Shuangfeng Station) in Changchun, China, the applicability of prefabricated subway station structures (PSSSs) in liquefiable sites in seismically defended areas is investigated. In this paper, the finite difference software FLAC3D 5.0 is used to carry out the seismic response analysis of the PSSS in liquefiable ground, and the calculation results of the PSSS are compared with those of the same type of cast-in-place subway station condition. The results show that the trend of foundation excess pore pressure ratio (EPPR) in the PSSS condition is similar to that of the cast-in-place condition. For different ground vibration inputs, there is not much difference between the PSSS and the cast-in-place structure on the pore pressure (PP) of the surrounding liquefiable soil. The acceleration response of the PSSS is slightly smaller than that of the cast-in-place structure, and it has a better ability to adapt to ground deformation. The deformation of the upper part of the PSSS is slightly larger than that of the lower part, which is an important part of its deformation control, and the middle part is the key part of its strength control due to the presence of the center plate, which results in a significant increase in stiffness and stress. The flexible connection of the PSSS is easier to adapt to a larger vertical deformation than rigid connection, and its ability to resist overturning is better. Under the premise of ensuring static waterproofing, the PSSS can be constructed in liquefiable sites in earthquake-proof areas.

Influence of Architecture on the Interfacial Properties of Polymers: Linear Chains, Stars, and Microgels.

Surface-active polymers have important applications as effective and responsive emulsifiers, foaming agents, and coatings. In this contribution, we explore the impact of the polymer architecture on the behavior at oil-water interfaces by comparing different poly(N-isopropylacrylamide) (pNIPAM)-based systems, namely, monolayers of linear and star-shaped macromolecules, ultralow cross-linked, regular cross-linked, and hollow microgels. Compression isotherms were determined experimentally as well as by computer simulations. The latter provides information about the conformational changes of the individual macromolecules as well as the interfacial properties of the monolayer, including the surface structure and the density distribution of an ensemble of interacting macromolecules near an interface. Surprisingly, the isotherms of the linear polymer, of the star polymer, and of the ultralow cross-linked microgel have an identical shape that differs from the isotherms of regular and hollow microgels. We introduced the mass fraction of adsorbed polymer, which gives a measure of the polymer segments contributing to the isotherm in relation to the most flexible architecture, i.e., the linear polymer, and allows a comparison of polymers with different architectures. The data demonstrate that increasing the number of cross-links leads to a significantly lower amount of polymer in the proximity of the interface as the increase in cross-linker reduces the deformability or softness of the polymers at the interface. The volume fraction profiles along the normal to the interface are essentially different in the microgel monolayers as compared to those in the linear and star polymer. The profiles through the microgel contact line and their growth upon initial compression are similar to those of the linear chains. Herewith, the profiles through the center of mass practically do not change upon compression. Therefore, the initial growth in the microgel surface pressure reveals the polymer-like behavior and is related to the deformation of the peripheral part of the microgel. Further compression of the microgel monolayer leads to 3D interactions of the microgels within the aqueous side of the interface and soft colloid-like behavior.

Effect of particle size distribution and printing parameters on alumina ceramics prepared by Additive Manufacturing

Vat photopolymerization-based additive manufacturing is a promising technology for the preparation of ceramic parts, owing to its short fabrication cycle and low manufacturing cost. However, its application is limited due to the low mechanical properties and deformation of ceramic parts. To improve the properties of ceramic parts, changing particle size and printing parameters have been found to be useful. Herein, alumina ceramic parts were prepared using three different powders with different particle size (Powder A: D50 = 1.3 μm, D90 = 6.1 μm; Powder B: D50 = 3.4 μm, D90 = 10.0 μm; Powder C: D50 = 1.3 μm, D90 = 2.8 μm), different layer thickness (50 μm, 75 μm, 100 μm), and different curing times (1 s, 3 s, 5 s, 8 s). The ceramics prepared with Powder A and Powder C, which possessed the same D50, had almost the same flexural strength, indicating that the flexural strength is closely related to the particle size and its distribution. With the increase in layer thickness, the flexural strength was increased. When the layer thickness was 100 μm, the flexural strength reached 18.5 MPa when samples were prepared with Powder A and Powder C. At the same time, the flexural strength firstly increased and subsequently decreased with increasing curing time. Based on the flexural strength and shrinkage of the sintered ceramics, using Powder A, layer thickness of 50 μm, and curing time of 5 s were regarded as the best fabrication conditions. The results indicate that adjusting powder particle size distribution, layer thickness, and curing time are promising methods for the fabrication of 3D printed ceramics with optimized properties.

Current deformation in eastern part of Java derived from GPS observation 2017-2022

The eastern part of Java Island is a prone area with high seismic potential. Geologically, the seismicity in this area is dominated by the subduction zone in southern Java, reverse faults structure in the north extending along east to west part of Java Islands, and normal faults in Pasuruan and Probolinggo. Several studies have indicated the potential of earthquakes associated with these sources. The geodetic technique is employed to monitor the deformation activity in the eastern part of Java to understand the characteristics. We utilized the continuous GPS stations operated by Geospatial Agency of Indonesia (BIG) and processed them using the GAMIT/GLOBK software. The processing incorporates the IGS stations surrounding Indonesia. We also used precise orbit and 2nd-order ionospheric correction. The processing produces the velocity in the ITRF2014 reference frame, which generally indicates the south-eastward velocity up to 29 mm/year, mainly influenced by block rotation. Velocity referenced to the Sunda block shows a distinguished pattern between southern Java and northern Java. The velocity pattern in the southern part of Java tends to move northwest with a velocity variation of 3-6 mm/year, while several north stations show a velocity pattern to the south with a variation of 2-4 mm/yr. The strain analysis shows different patterns between eastern and western regions and different characteristics of southern and northern regions. Mainly the deformation is dominated by the compression due to the subduction in the south. Meanwhile, near to the central Java the deformation patterns significantly change due to the appearance of the east-west extension. The result indicates the different distinguished characteristics of the deformation source in the eastern part of Java. This result will have implications for seismic hazard analysis as a contribution to disaster risk reduction in the future.

The investigation of geodynamics parameters in the south of Egypt using geodetic and earthquake activities

ABSTRACT Egypt’s southern region has significant economic and historical importance. However, due to the lack of data, this area has not gotten sufficient geodynamic research. Minor, to moderate earthquake activity along tectonic structures originating in the region from several faults is felt in southern Egypt. The study’s geographical scope includes the Red Sea coast, the Eastern Desert, the Western Desert, Aswan, and Nasser Lake, and it lies between 22° and 27° 30 N and 25° to 34° E. In this paper, the crustal deformation and earthquake events in the southern part of Egypt have been studied. The Global Navigation Satellite System (GNSS) observations taken by Egyptian Permanent Geodetic Network (EPGN) have been processed and adjusted for the period 2010–2019 using Bernese v.5.2 software. In addition, we investigate the source mechanism of the significant earthquakes ≥3 magnitudes using the waveform data recorded by the Egyptian National Seismic Network (ENSN) during the period 2012–2019. The focal mechanisms of these earthquakes were constructed with high reliability based on the P-wave first motion polarities. The results show that the average residual velocity concerning Nubian fixed is about 0.5 ± 0.25 mm in the east direction and 1 ± 0.3 mm in the north direction.

Seismic assessment of Isolator-Damper hybrid structural system based on analysis of MDOF and modal 2DOF models

A hybrid structural system is introduced and assessed; by combining two widely used passive devices, isolator and damper, along with the use of the partial plan isolation technique in the conventional buildings. Four partial isolation cases in comparison with three limit cases including a full-base fixing, full-base isolating and ideal story damping (Skyhook) are used on a finite element model of a 12-story building. The mentioned four cases have been selected by changing the number of fixed and isolated columns which caused isolated mass ratio between 28% and 71%. Also, a simplified manifest of the seismic performance of this proposed hybrid system is presented in the form of a 2DOF model. Time history analyzes under far- and near-faults earthquakes, frequency analysis and stationary random analysis under white noise are performed. Various structural actions are investigated, including the root mean squares (rms) and maximum of drift, displacement, shear, acceleration, maximum total and plastic deformation and energies of different parts of this system. It can be inferred from the results that desired efficiency extent of this system occurs in the range of 30–70% for the mass isolation ratio. In addition, the novel approach has prevented the full isolation of the base columns (even up to 70% reduction in isolation capacity) and by removing operational limitations such as providing a large performance gap in dense urban areas, compared to a full-isolated structure, it reduces the cost of construction.

Enhancement of virtual data quality using pre-trained Bayesian transfer learning under inaccurate and insufficient measurement data

The accurate application of designed dimensions in manufacturing is crucial but complicated by certain limitations in the manufacturing process. Therefore, manufacturing and assembly conditions should be considered in product designs. However, predicting and managing the deformation quality of industrial products, composed of multiple components, is often challenging owing to part deformation during the manufacturing process and structural deformation at the assembly stage. Owing to the advancements in artificial intelligence, highly precise predictive models can be created if sufficient data are available. However, the acquisition of extensive labeled data required for model training can be expensive and time-consuming in the industrial sector. Traditional approaches such as computer-aided engineering, which are commonly used to produce virtual data, have limitations owing to uncertainties in the experimental data, making consistency correction both time-consuming and expensive. This study proposes a method for enhancing the quality of virtual data created in contexts with insufficient and inaccurate experimental data. Engineering properties were extracted from experimental data and integrated with transfer learning using a pre-trained Bayesian neural network. We applied the proposed method to a micro-LED case to predict assembly and manufacturing variations during the design phase under inaccurate and insufficient data. Consequently, the accuracy was significantly improved over the predictive model that predicted the amount of assembly deformation using only experimental data, resulting in a predictive model with an average R-squared prediction accuracy of 98.9% for the deformation resulting from the assembly.

Electroactive morphing effects on the aerodynamic performance through wobulation around an A320 wing with vibrating trailing edge at high Reynolds number

This study aims to investigate the effects of electroactive morphing on a 70cm chord A320 wing by means of near trailing edge slight deformation and vibration. Wing morphing is performed by Macro Fiber Composites (MFC) piezoelectric actuators distributed along the span of the “Reduced Scale” (RS) prototype of the H2020 European research project “Smart Morphing and Sensing for aeronautical configurations” - (SMS). The configuration studied corresponds to a low-subsonic regime (Mach number 0.063) with a 10∘ incidence and a Reynolds number of 1 Million. The numerical simulations are carried out with the Navier-Stokes Multi-Block (NSMB) solver, which takes into account the deformation of the rear part of the wing implemented experimentally with the piezoelectric actuators. A detailed physical analysis of the morphing effects on the wake dynamics and on the aerodynamic performance is conducted with a constant amplitude of 0.7mm over a wide range of actuation frequencies [10-600]Hz. Optimal vibration ranges of [180-192]Hz and [205-215]Hz were found to respectively provide a 1% drag reduction and a 2% lift-to-drag ratio increase compared to the non-morphing (static) configuration. The natural frequencies associated with the shear layer Kelvin-Helmholtz (KH) vortices and the Von-Kármán (VK) vortex shedding were found to play a central role in the modification of the wake dynamics by morphing as well as in the increase of the aerodynamic performance. Actuating at (or close to) the upper shear layer (USL) natural frequency (∼185Hz) provides an order of 1% drag reduction and 1% lift-to-drag ratio increase, while actuating at (or close to) the lower shear layer (LSL) natural frequency (∼208Hz) provides an order of 8% lift increase and 2% lift-to-drag increase. Furthermore, the linear modulation in time of the actuation frequency (wobulation) demonstrated, through an appropriate mapping, the ability to quickly and efficiently detect optimal constant actuation frequency ranges providing aerodynamic performance increase and simultaneously reducing the amplitude of the main instability modes.

BIOMECHANICAL SUBSTANTIATION OF THE ALGORITHM FOR CHOOSING THE OPTION OF DISTAL CORRECTIVE OSTEOTOMY OF THE II–IV METATARSAL BONES IN THE TREATMENT OF METATARSALGIA

Deformations of the front part of the foot with valgus deformity of the first toe lead to a redistribution of the body weight load during walking between the heads of the metatarsal bones. At the same time, the load on the head of II and III, and sometimes IV metatarsal bones increases significantly. Objective. To substantiate the choice of the most correct distal metatarsal osteotomy for the treatment of patients with metatarsalgia. Materials and methods. Three variants of distal metatarsal osteotomy were simulated: Weil, Helal, and distal wedge-shaped metatarsal osteotomy. Result. Weil osteotomy allows you to raise the support point of the metatarsal head above the support surface from 2 to 7 mm, depending on the amount of displacement of the head in the proximal direction and the angle of inclination of the metatarsal bone relative to the plane of the support surface, which effectively reduces the load on the metatarsal head during walking, but under conditions of magnitude the angle of inclination of the axis of the metatarsal bone is more than 20°. Helal osteotomy with the subsequent displacement of the separated part proximally, ensures the lifting of the head above the conventional plane of support from 1 to 4 mm, contributes to the effective unloading of the head while standing and while walking. They are used only for severe metatarsalgia. The range of correction of the standing height of the support surface of the metatarsal head for performing a distal wedgeshaped osteotomy is determined to be from 0.6 to 2.9 mm. Its advantage is the independence of the amount of correction from the presence or absence of a decrease in the longitudinal arch of the foot. Conclusions. Weil osteotomy has the worst corrective possibilities of raising the head of the metatarsal bone, but is very easy to perform, so its use is advisable in the absence of reduction of the longitudinal arch of the foot. A wedge-shaped distal osteotomy has a range of correction of the metatarsal headelevation up to 3 mm, but it depends on its diameter, so it is used in the case of a head diameter of at least 10 mm. Helal osteotomy provides the widest range of elevation of the metatarsal head, which does not depend on the presence of any degree of flat feet, but has some technical limitations.

Thermal-structural hybrid Lagrangian solver and numerical simulation-based correction of shape deformation of stainless-steel parts produced by laser powder bed fusion

An efficient thermal-structural numerical solver for Additive Manufacturing has been developed based on a modified Lagrangian approach to solve the energy conservation equations in differential form. The heat transfer is modeled using the finite difference method applied to a deforming Lagrangian mesh. The structural solver has been enhanced with the proposed effective quasi-elastic differential approach for modeling the elastoplastic behavior of materials. The algorithm is relatively simple to implement yet is highly effective. The solver can predict shape deformations of metal parts printed using the laser powder bed fusion technique. The second key capability of the solver is the auto-compensation of distortions of 3D-printed parts by proposing a corrected geometry of a surface to be printed, in order to ensure minimal deviation of the actual printed part from the desired one, even under non-optimal operating conditions or for complex shapes. All the simulation results have been verified in real-life experiments for 3D parts of sizes ranging from 10 to 15 mm up to 40 mm.

An Accelerated Process Optimization Method to Minimize Deformations in Composites Using Theory-guided Probabilistic Machine Learning

While aerospace manufacturing and assembly technologies have significantly evolved, challenges persist in mitigating process-induced deformations (PIDs) in composite parts. Physics-based-simulation optimization strategies have been developed to address these challenges. However, they often prove ineffective or inefficient because of the time-consuming, costly, and deterministic characterization efforts they require. This study introduces a novel characterization- and simulation-free optimization approach for predicting and minimizing PIDs in composite parts. The method uses a theory-guided machine learning (TGML) framework, consisting of limited element-level experiments and Gaussian Process Regression (GPR) with integrated closed-form domain knowledge. This paper showcases the effectiveness of the proposed TGML method for two case studies, where an optimal layup and cure cycle are found and validated after a mere six experiments and without any material characterization or simulation efforts. The method presented in this paper aims to offer a cost-efficient and generalizable process optimization procedure to potentially mitigate PIDs in composite parts.

Research on Stability of Dam Substation on Inclined Soft Soil Foundation Reinforced by Pile Foundation

For the construction of dam substations in coastal or mountainous areas, inclined soft soil foundations are very common. The unique engineering characteristics of inclined soft soil foundations can bring great difficulties to the construction of dam substations. In this paper, a pile foundation reinforcement dam slope model on an inclined soft soil foundation is established; the influence of different pile spacings, the pile length, and the soft soil foundation angle on the slope safety factor is studied; and the failure mechanism and stability of pile-supported dam slope foundation are analyzed. The research results indicate that pile foundation reinforcement can reduce the deformation of the dam slope foundation and improve stability. The pile layout has an important impact on stability, but a change in the pile spacing has little effect on the settlement surface at the bottom of the dam slope. The pile length has a significant impact on the safety of the slope within a certain range. The main stress area of the pile is 0–2 m above the pile, and its main deformation is the lateral deformation of the upper part of the pile. The research results of this article can provide parameter support and theoretical guidance for the construction of dam substations.

Experimental and Numerical Investigations on Strains of Metal Sheet Parts Processed by Electromagnetic Forming

Electromagnetic forming is applied to form metal sheet parts from both non-ferrous and ferrous materials. In this paper, the electromagnetic forming behavior of aluminum alloy, copper and steel sheets was investigated through experiments. The disk-shaped specimens were electromagnetically free bulged with increasing deformation energies and parts with different deformation depths were obtained. The deformation was done with and without clamping the movement of the specimens’ edges. The specimens were printed with a mesh of diametrical lines and concentric circles with a predetermined pitch. The mesh served to determine the displacements in the mesh nodes after the deformation of the specimens, with which the axial, radial and circumferential strains were then calculated. The experimental data obtained was subjected to statistical correlation and regression analyses, and the mathematical models for the three main strains in each material were established. The strains of AlMn0.5Mg0.5 and Cu-OF parts are maximum in the center and have a similar variation, while the FeP04 parts have the maximum strains in an intermediate zone between the center and the edge.

Local environmental engineering for highly stable single-atom Pt1/CeO2 catalysts: first-principles insights

Single-atom Pt1/CeO2 catalysts may cope with the high cost and durability issues of fuel cell electrocatalysts. In the present study, the stability and underlying interaction mechanisms of the Pt1/CeO2 system are systematically investigated using first-principles calculations. The Pt adsorption energy on CeO2 surfaces can be divided into chemical interaction and surface deformation parts. The interaction energy, mainly associated with the local chemical environment, i.e. the number of Pt-O bonds, plays a major role in Pt1/CeO2 stability. When forming a Pt-4O configuration, the catalytic system has the highest stability and Pt is oxidized to Pt2+. An electronic metal-support interaction mechanism is proposed for understanding Pt1/CeO2 stability. In addition, our calculations show that the Pt1/CeO2(100) system is dynamically stable, and the external O environment can promote the further oxidation of Pt to Pt n+ (2 ≤ n < 4). The present study provides useful guidance for the experimental development of highly stable and efficient electrocatalysts for fuel cell applications.

Evolution characteristics of mid‐channel bars with a typical high/low bank structure in the Middle Yangtze River

AbstractAdjustments in mid‐channel bars (MCBs) often influence the stability of channel regime and the safety of river navigation in anabranching reaches. This study aims to investigate the evolution characteristics of the low and high parts of MCBs (L‐MCBs and H‐MCBs) in the Middle Yangtze River (MYR) and reveal the main factors influencing the deformation of these two components. Results show that the total exposed area of L‐MCBs decreased from 305 to 288 km2 in 2003–2019, whereas the H‐MCBs remained relatively stable. Taking the Nanyang bar with a typical high/low bank structure as an example, the deformation of the L‐MCB mainly occurred in the head zone, while the deformation of the H‐MCB was characterised by bank retreat in the tail zone and floodplain deposition on the top of the H‐MCB. In terms of influencing factors, the impacts of the altered flow–sediment conditions and the MCB's properties (soil composition and morphology characteristics) on the Nanyang bar deformation were investigated. On the one hand, the reduction in sediment concentration was the most direct factor causing the shrinkage of L‐MCBs, and the decrease in flood occurrence frequency made the deformation of H‐MCB less significant. On the other hand, the soil composition of the L‐MCB primarily consisted of fine sand with weak erosion resistance, while the large content of cohesive sediment made the H‐MCB difficult to be eroded by overbank flows; moreover, the riverbank of the H‐MCB in the bar‐tail zone was much steeper than that in the bar‐head zone, causing the deformation of the high part to mainly occur in the tail zone. Furthermore, the deformation of the high part was simulated using a bank erosion model at section scale, and the calculated safety factors of riverbank at a typical cross‐section show that the riverbank of the H‐MCB was the most unstable during the receding period.

316L Stainless Steel Thin-Walled Parts Hybrid-Layered Manufacturing Process Study.

Additive manufacturing technology overcomes the limitations imposed by traditional manufacturing techniques, such as fixtures, tools, and molds, thereby enabling a high degree of design freedom for parts and attracting significant attention. Combined with subtractive manufacturing technology, additive and subtractive hybrid manufacturing (ASHM) has the potential to enhance surface quality and machining accuracy. This paper proposes a method for simulating the additive and subtractive manufacturing process, enabling accurate deformation prediction during processing. The relationship between stress distribution and thermal stress deformation of thin-walled 316L stainless steel parts prepared by Laser Metal Deposition (LMD) was investigated using linear scanning with a laser displacement sensor and finite element simulation. The changes in stress and deformation of these thin-walled parts after milling were also examined. Firstly, 316L stainless steel box-shaped thin-walled parts were fabricated using additive manufacturing, and the profile information was measured using a Micro Laser Displacement Sensor. Then, finite element software was employed to simulate the stress and deformation of the box-shaped thin-walled part during the additive manufacturing process. The experiments mentioned were conducted to validate the finite element model. Finally, based on the simulation of the box-shaped part, a simulation prediction was made for the box-shaped thin-walled parts produced by two-stage additive and subtractive manufacturing. The results show that the deformation tendency of outward twisting and expanding occurs in the additive process to the box-shaped thin-walled part, and the deformation increases gradually with the increase of the height. Meanwhile, the milling process is significant for improving the surface quality and dimensional accuracy of the additive parts. The research process and results of the thesis have laid the foundation for further research on the influence of subtractive process parameters on the surface quality of 316L stainless steel additive parts and subsequent additive and subtractive hybrid manufacturing of complex parts.

Perspectives on Developing Burn Resistant Titanium Based Coatings-An Opportunity for Cold Spraying.

Titanium alloys are crucial lightweight materials; however, they are susceptible to spontaneous combustion under high-temperature and high-pressure conditions, limiting their widespread use in aerospace engines. Improving the burn resistance of Ti alloys is essential for the structural safety and lightweight of aerospace equipment. Burn-resistant Ti alloys, such as Ti-V-Cr and Ti-Cu, however, face limitations such as high cost and low specific strength. Surface coatings provide a cost-effective solution while maintaining the high specific strength and good processability of the base material. Conventional surface treatments, such as laser cladding, result in defects and deformation of thin-walled parts. Cold spray technology offers a promising solution, as it uses kinetic energy to deposit coatings at low temperatures, avoiding defects and deformation. In this paper, we review the current research on burn-resistant surface technologies of Ti alloys and propose a new method of bimetallic coating by cold spraying and low-temperature heat treatment, which has the potential to solve the problem of spontaneous combustion of aerospace engine parts. The strategy presented can also guide the development of high-performance intermetallic compound-strengthened metal matrix composite coatings.

Folding, stowage, and deployment of composite thin-walled lenticular tubes

Composite thin-walled lenticular tube (CTLT) is a lightweight foldable and deployable structural material that enables large-scale deployable mechanisms for various space missions. A key step toward the structural design of CTLT is to understand its folding, stowage, and deployment behaviors. This work presents an integrated experimental and numerical investigation of the dynamic deployment behavior of CTLT that wraps around a central hub, with emphasis on the effect of long-term storage. A two-meter-long CTLT prototype was manufactured, and a gravity compensation system was designed and built for the on-ground dynamic deployment experiments. The deployment experiments were performed on the CTLT prototype both before and after it had been stowed for extended storage periods. The results indicate that after being stowed for 6 and 10.5 months the CTLT is deployed slower and the deployment time increases by 8.2% and 15.0%, respectively. Furthermore, a high-fidelity numerical model was constructed using the explicit dynamic finite element method, where the CTLT was modeled as a deformable part and the folding/deployment mechanisms were modeled as rigid bodies to perform the folding, stowage, and deployment simulations. The long-term storage effect was accounted for in the numerical analyses with the use of a viscoelastic fiber-reinforced composite material model, and a good agreement has been achieved between the experimental and numerical results.