Bolt Structure Research Articles

Imitation expansion bolts structural bonding interface: Enhancing the bonding properties of bamboo composites through host–guest molecular recognition

With the emphasis on sustainable development, the preparation of environmentally friendly bio-based adhesives has become a research hotspot in the wood and bamboo composites industry. In this study, a bio-based bamboo adhesive was developed with functionalized cellulose and β-cyclodextrin, and adamantane was grafted onto the bamboo surface. The host–guest recognition bonding interface was constructed by imitating expansion bolt structure and explored the enhancement of bonding properties by host–guest molecular recognition in the bonding system. The dry, hot, and boiling water lap shear strengths of the bamboo bonding composites were 15.80 MPa, 11.85 MPa, and 10.56 MPa, respectively. However, The dry lap shear strength of the samples without adamantane grafted on the bamboo surface was only 6.60 MPa. This shows that the construction of the host–guest recognition system plays an important role in the bonding performance, and the dry lap shear strength of the samples increased by 139.4 % and the boiling water tensile strength increased by 576.9 %. Not only that, but the bonding of wood, polytetrafluoroethylene, and glass can also be realized by this method. This study provides feasible methods for enhancing the bonding properties of bio-based adhesives.

Temperature compensation method for impedance signals of bolt loosening under temperature varying conditions using TransUnet

Abstract Piezoelectric transducer based electro-mechanical impedance technology is an effective and reliable detection method for bolt structure loosening under external load. However, temperature change usually causes some non-loosening factors to change the impedance spectrum of bolt structure. In order to reduce the misjudgment of loosening damage caused by temperature change, it is necessary to construct a temperature compensation model for impedance spectrum. In this paper, the convolutional structure in U-net and Transformer are effectively combined to form a TransUnet deep neural network structure suitable for input and output of one-dimensional data. Using impedance data between 10 °C and 50 °C and temperature as input to the network. After convolution operation, the convolutional block attention module is embedded in the U-net to optimize the encoder transmission characteristics and enhance the performance of the skip connection in the traditional U-shaped structure. The temperature compensation rate (TCR) is defined to measure the effect of temperature compensation. Then the lightweight convolutional neural network structure is used to recognize the bolt loosening damage of the compensated impedance signal. The generalization ability of the TransUnet was tested using impedance data that is not in the training dataset. The results show that the TransUnet proposed in the paper can realize the temperature compensation of multi-peak impedance signals. The TCR and recognition accuracy of bolt loose damage reaches reach 0.003 and 95.7%, respectively, which is 11% higher than that without temperature compensation. At 60 °C, the TCR and the identification accuracy of loosening damage can still reach 0.0055 and 90.2%, respectively, which show that the TransUnet has strong generalization ability.

Damage of special bolt structures based on multi-scale method evaluate research

Abstract During the service life of underwater bolt structures, the occurrence of fracture failures is influenced by environmental factors such as corrosion and external pressure. This study aims to evaluate the behavior of bolt structures underwater and establish reliable methods for damage assessment, which is crucial for ensuring the safe operation of underwater equipment. This article introduces the concept of multi-scale analysis, considering the influence of initial defects in materials on the structure’s performance. It explores the micro-macro crack evolution mechanism and employs surface-level methods. By utilizing the GTN-based multi-parameter damage constitutive model, the study investigates the extended behavior and stress range under various load states. The findings provide theoretical support for accurately assessing structural safety.

Tensile damage monitoring at different positions of double bolt structure by ultrafiltration membrane/buckypaper sensor

AbstractMulti‐bolted composite laminates are popular in various fields. Under different working conditions, it is a serious problem to produce different kinds and extent of damage at the joints. Real‐time monitoring of it is a challenging task. The objective of this artical is to use ultrafiltration membrane/buckypaper sensor to monitor the health status of the structure at different positions in the tensile environment. Firstly, the aperture ratio is selected by tensile test, and the feasibility of ultrafiltration membrane/buckypaper sensor to monitor the bolt structure and the different response degree to different strains are verified. Then, ultrafiltration membrane/buckypaper sensor layout position is designed, and the signal response of the sensor at different positions is analyzed. The damage degree and form of different bolts are visualized by ΔR/R0 change, and the SEM scanning diagram is used for auxiliary verification. The results show that The sensor can monitor the damage condition and damage form at different positions of the double bolt structure laminate in real time. Based on this method, it can be used to study the damage behavior of more complex multi‐bolt structure under tensile environment.Highlights Ultrafiltration membrane/buckypaper sensor was prepared by a simple and efficient process. The pore structure of the ultrafiltration membrane integrates the sensor with the double bolt structure. Monitor the different damage forms of double bolt structure caused by external load. Monitor the different degrees of strain and crack propagation stage of the double bolt structure.

Aeronautical composite/metal bolted joint and its mechanical properties: a review

PurposeBolted joint is the most important connection method in aircraft composite/metal stacked connections due to its large load transfer capacity and high manufacturing reliability. Aircraft components are subjected to complex hybrid variable loads during service, and the mechanical properties of composite/metal bolted joint directly affect the overall safety of aircraft structures. Research on composite/metal bolted joint and their mechanical properties has also become a topic of general interests. This article reviews the current research status of aeronautical composite/metal bolted joint and its mechanical properties and looks forward to future research directions.Design/methodology/approachThis article reviews the research progress on static strength failure and fatigue failure of composite/metal bolted joint, focusing on exploring failure analysis and prediction methods from the perspective of the theoretical models. At the same time, the influence and correlation mechanism of hole-making quality and assembly accuracy on the mechanical properties of their connections are summarized from the hole-making processes and damage of composite/metal stacked structures.FindingsThe progressive damage analysis method can accurately analyze and predict the static strength failure of composite/metal stacked bolted joint structures by establishing a stress analysis model combined with composite material performance degradation schemes and failure criteria. The use of mature metal material fatigue cumulative damage models and composite material fatigue progressive damage analysis methods can effectively predict the fatigue of composite/metal bolted joints. The geometric errors such as aperture accuracy and holes perpendicularity have the most significant impact on the connection performance, and their mechanical responses mainly include ultimate strength, bearing stiffness, secondary bending effect and fatigue life.Research limitations/implicationsCurrent research on the theoretical prediction of the mechanical properties of composite/metal bolted joints is mainly based on ideal fits with no gaps or uniform gaps in the thickness direction, without considering the hole shape characteristics generated by stacked drilling. At the same time, the service performance evaluation of composite/metal stacked bolted joints structures is currently limited to static strength and fatigue failure tests of the sample-level components and needs to be improved and verified in higher complexity structures. At the same time, it also needs to be extended to the mechanical performance research under more complex forms of the external loads in more environments.Originality/valueThe mechanical performance of the connection structure directly affects the overall structural safety of the aircraft. Many scholars actively explore the theoretical prediction methods for static strength and fatigue failure of composite/metal bolted joints as well as the impact of hole-making accuracy on their mechanical properties. This article provides an original overview of the current research status of aeronautical composite/metal bolted joint and its mechanical properties, with a focus on exploring the failure analysis and prediction methods from the perspective of theoretical models for static strength and fatigue failure of composite/metal bolt joints and looks forward to future research directions.

Prediction of Pre-Loading Relaxation of Bolt Structure of Complex Equipment under Tangential Cyclic Load.

Bolts have the advantages of simple installation and easy removal. They are widely applied in aerospace and high-speed railway traffic. However, the loosening of bolts under mixed loads can lead to nonlinear decreases in pre-loading. This affects the safety performance of the structure and may lead to catastrophic consequences. Existing techniques cannot be used to monitor the bolt performance status in time. This has caused significant problems with the safety and reliability of equipment. In order to study the relaxation law of bolt pre-loading, this paper carries out an experimental analysis for 8.8-grade hexagonal bolts and calibrates the torque coefficient. We also studied different loading waveforms, nickel steel plate surface roughnesses, tangential displacement frequencies, four different strengths and bolt head contact areas of the bolt, the initial pre-loading, and the effects of tangential cyclic displacement on pre-loading relaxation. This was done in order to accurately predict the degree of bolt pre-loading loosening under external loads. The laws are described using the allometric model function and the nine-stage polynomial function. The least squares method is used to identify the parameters in the function. The results show that bolts with a smooth surface of the connected structure nickel steel flat plate, high-frequency working conditions, half-sine wave, and a high-strength have better anti-loosening properties. Taking 5-10 cycles of cyclic loading as a boundary, the pre-loading relaxation is divided into two stages. The first stage is a stage of rapid decrease in bolt pre-loading, and the second stage is the slow decrease process. The performance prediction study shows that the allometric model function is the worst fitted, at 71.7% for the small displacement condition. Other than that, the allometric model function and the nine-stage polynomial function can predict more than 85.5% and 90.4%, which require the use of least squares to identify two and ten unknown parameters, respectively. The complexity of the two is different, but both can by better indicators than the pre-loading relaxation law under specific conditions. It helps to improve the monitoring of bolt loosening and the system use cycle, and it can provide theoretical support for complex equipment working for a long time.

Study on mechanical properties of bolted connection structure of carbon fiber resin matrix composites at low temperature

This article focuses on the impact of low temperature environments that composite materials may face in engineering applications. Through experimental testing, the bearing capacity of carbon fiber resin based composite bolted structures at -100 ℃ and 25 ℃ was obtained, and a continuous damage model (CDM) was established. The damage evolution mechanism of bolted connection structures between metal and carbon fiber resin matrix composites at -100 °C and 25 °C was elucidated through numerical simulation. Research has shown that the ultimate load of the structure at -100 °C is 3.99% lower than that at room temperature, and the failure mode of the composite material structure at low temperature is transverse fracture along the hole edge, which is different from the compression tensile fracture along the nail hole section at room temperature.

A Review of Cross-Scale Theoretical Contact Models for Bolted Joints Interfaces

Bolted joints structures are critical fastening components widely used in mechanical equipment. Under long-term loading conditions, the bolted joints interface generates strong nonlinearities within the system. The nonlinear stiffness inside the bolt leads to changes in the stiffness of the whole system. This affects the dynamic characteristics of the whole system. It brings challenges and difficulties to the performance prediction and reliability assessment of the equipment. A cross-scale theoretical model study based on the microscopic contact mechanism can provide a more comprehensive understanding and cognition of the degradation behavior of bolted joints interfaces. The current development status and deformation process of asperity models are summarized. The research progress of statistical summation model and contact fractal model based on microscopic contact mechanism is analyzed. The experimental methods for parameter identification of connection interfaces are reviewed. The study of numerical modelling of bolted joints structures from the surface contact mechanism is briefly described. Future research directions for cross-scale modelling of bolted joints structures are outlined.

A modified virtual time reversal method for enhancing monitoring sensitivity of bolt preloads based on ultrasonic guided waves

Bolted joints are prone to loosening due to inaccurate initial preloads and time-varying service conditions. Real-time monitoring of bolt preloads is therefore an important means to warrant the reliability and safety of a bolted structure, though it remains a daunting task to implement precise monitoring of early bolt loosening. A modified virtual time reversal (MVTR) method is developed in this study, aimed at enhanced sensitivity of bolt preload monitoring. To begin with, the frequency response function (FRF) of an intact bolted structure is ascertained using the excitation wave and the received wave signal through the bolt. Then a received wave signal captured from the bolted structure under monitoring is time-reversed, and a refocused signal is calculated in virtue of the time-reversed signal and the FRF in the intact state. Bolt tightness indices are established by the peak amplitude or energy of the refocused wave packet. To facilitate interpretation of the principle of the proposed MVTR, a semi-analytic model is developed, which combines the waveform superposition method and finite element method. With the model, the effects of interface contact length, wave mode and signal frequency on the tightness indices are investigated. The effectiveness of the proposed MVTR is experimentally verified using three representative bolted lap structures featuring single bolt or multiple bolts. The results confirm the findings from the semi-analytic model, demonstrating that the MVTR enhances monitoring sensitivity compared to prevailing approaches using linear or nonlinear guided wave features.

Effect of interference installation method on interfacial properties and fatigue failure behavior of bolted composite joints

A novel dynamic installation (DI) method is proposed to improve the problems of severe installation damage, small installable interference size, and low installation efficiency of traditional static installation (SI) methods for installing interference bolts in composite bolted structures. The stress distribution and CFRP damage around the hole wall due to interference fitting and subsequent cyclic loading were predicted by finite element simulations. In addition, the fatigue life of DI and SI specimens was evaluated and the fatigue failure mechanisms were discussed. The results showed that the DI method provides a visible improvement in fatigue life, which is about 4 times that of the SI interference specimens and 38 times that of the non-interference specimen. In addition, DI introduces relatively higher average residual compressive stresses than SI, especially at the inlet of the laminate, which also results in a more uniform distribution along the axial direction of DI specimens. Micromorphological analysis of the specimens after fatigue failure indicated that the uniform stress distribution and low initial installation damage at the assembly interface introduced by the DI method during interference fit prevents severe delamination and crack propagation in joints subjected to external cyclic loading, such as the SI specimen. Severe extrusion deformation of the hole wall and matrix crushing are the main failure modes of DI specimens. Therefore, it is necessary to improve the interference installation method of composite materials.

Guided wave-based damage assessment on bolt in precast beam-to-column joints

This paper deals with theoretical, numerical, and experimental investigations of guided wave-based damage assessment on bolts in the precast joints under cyclic loads. The mechanical behavior of precast bolted joints is analyzed, and the relationship between the force and drift ratio of the energy-dissipating (ED) bolt is derived. The propagation characteristic of guided wave in ED bolt is revealed through finite element simulation. The influence of tensile damage and looseness damage on the received signals is further studied, and two indexes are developed for evaluating the health status of ED bolts. Cyclic loading tests were carried out on four precast bolted beam-column joints with different precast beams, and the guided wave signals of ED bolts under each level of loading were monitored by arranging lead zirconate titanate (PZT) sensors. The bolt yield drift ratios were obtained by skeleton curves and FBG strain detectors respectively. The relationships between the two damage indexes and the drift ratio are obtained, and the two developed damage index trends were very well reproduced by analytical expressions. The health state assessment of ED bolts and precast bolted structures is realized by the proposed damage limit method, whether in daily maintenance or after the earthquake.

Simulation and experimental study on contact pressure distribution of contact interface in single and double bolted connection structures

Bolted joints play an important role in aerospace, machinery manufacturing, weapons and other fields, and the contact pressure distribution at the connection interface seriously affects the service performance of the bolts. Contact pressure analysis is an essential basis and reference for structural design, calibration, inspection, and safety monitoring of bolted connection structures. Considering the preload force and frictional contact between the joint components, a block mapping hexahedron mesh generation and finite element modeling method for bolted connections is presented, and the finite element models of single and double bolted structures are constructed. Then, an experimental test platform for measuring contact pressure distribution is constructed. Comparison of finite element analysis results with experimental results for the contact pressure distribution in the single and double-bolted joints; the root mean squared error of contact pressure distribution is less than 5%, which verifies the effectiveness of the finite element models. After that, the models are used to study the contact pressure distribution in single-bolted joints and contact pressure coupling effect of double-bolted joints, and the normal stress distribution features within members and contact pressure distribution contour are revealed for single and double-bolted joint. Finally, the finite element models are adopted to investigate the effects of the clamping length, preload, material properties, hole clearance, and bolt size on contact pressure distribution in single-bolted joints. The coupling effect of contact pressure distribution in double-bolted joints under different preloads and geometric parameters are also examined.

Analysis of the Effect of Turbine Operational Load on the Strength of Coupling Bolt Structure Using the Finite Element Method

In transmitting kinetic energy from the turbine to the generator, the coupling will experience stress and deformation, especially on the bolts that support the coupling. Therefore, it is important to analyze how the operational load of the turbine affects the strength of its bolt structure. The author has conducted a literature study and numerical simulation to analyze the problem. In the simulation that has been done, it was found that the maximum von misses stress and strain values received by the bolt were 196.34 MPa and 0.0009687 mm/mm at maximum loading. The relationship between operational load and von misses stress value is that if the operational load is higher, the von misses stress received by the bolt will also be higher. Furthermore, there is also a relationship between operational load and von misses strain value, namely that if the operational load is higher, the von misses strain received by the bolt will also be higher. DBy using AISI Type S5 Tool Steel – Oil Quenched to 55 HRC, a relationship was obtained between operational load and safety factor value. The relationship between operational load and safety factor value is that if the operational load is higher, the safety factor value will be lower. From the simulation that the author has done, it is found that there is a difference in safety factor if the material used in the bolt is changed. It was found that AISI Type S5 Tool steel - Oil Quenched to 55 HRC has a higher safety factor value of 8.8111.Meanwhile, the AISI Type S5 Tool Steel material, Austenitized 855 – 870°C (1575 – 1600°F), Oil Quenched to 45 HRC has a lower safety factor value, namely 5.7552.

Damage evolution monitoring and failure level evaluation of composite bolted joints by MXene/CNTs sensors

AbstractThe composite bolted joints are the weak points of overall structure, lacking an effective and accurate monitoring method. In this paper, a novel MXene/CNTs film sensor with high sensitivity and stability was synthesized for the damage evolution monitoring of composite bolted joints. The correlation between the response signals of the sensors and the mechanical behaviors of the composite structures is established. Based on this research, the damage evolution monitoring and failure level evaluation of composite bolted joints were studied. The damage properties of the composite bolted joints can be reflected in real‐time by the resistance change rates of the sensors. The experimental results show that the failure level of composite bolted joints can be divided into four levels (I‐II‐III‐IV) according to the resistance change rates of sensors. Especially when the damage extended to the III stage, the surged from 0.3 to 0.75. The time point of this step signal occurred about 1 min earlier than the time point of max bearing strength, which can effectively warn the occurrence of structural failure.Highlights Research used high‐sensitivity MXene/CNTs sensor to monitor bolt structure Sensor array can be integrated with the composite bolted structure Structural damage of composite bolted joints was accurately monitored Failure level evaluation of composite bolted structure was achieved

Variability in measured resonance frequencies and loss factors of a bolted panel structure

Structural bolted joints are not perfectly contiguous or rigid. Instead, the joint stiffness, mass, and damping depend on many parameters including the joint thickness, number and size of bolts, the bolt preload, and the motion of the jointed region. Also, damping can vary with motion type (stick-slip for friction and impact for joint opening and closing) and amplitude. Finally, all joint dynamic parameters vary from installation to installation. We measured the variability of bolted joint stiffness and damping for four low-order modes of a bolted Aluminum panel structure - two flexural modes and two twisting/torsional modes. While a large portion of the bolted joint literature features a lap joint or an assembly of two beams, there are few studies dealing with flanged connections of plates. Two flanged rectangular panels were bolted together with two cap screws threaded into one of the flanges. Modal resonance frequencies and loss factors were tracked throughout a decaying vibration response induced by hammer impacts on the structure. Measurements were made for three bolt torques and two flange thicknesses, three impact force strengths, and three repeated assemblies (the panel was unbolted and bolted together again). Relative motion at the joint with respect to mode shape determines whether the joint primarily adds stiffness or mass, as well as the amount of added damping. Not surprisingly, reducing bolt preload reduces resonance frequencies. Only minor variability in resonance frequency and loss factor were observed for most conditions, except for cases with low bolt preload. In these cases mild nonlinearity is evident in the response, where resonance frequency decreases and loss factor increases with increasing vibration amplitude. Also, variability of resonance frequencies and loss factors between installations often exceeds that due to variability in preload and vibration amplitude.

Performance indices and fragility assessment of steel frame structure with bolted low-yield-point steel connection components

A resilient steel frame structure equipped with replaceable ductile and energy-dissipative connection components was developed in this study. Connective components, such as splice plates and T-stubs are made of low-yield-point steels (LYPs), which have superior ductility and energy dissipation capacity. The plastic hinge can be separated from the column surface by local weakening, thus concentrating local damage within low-yield-point steel connection components (LYP-Cs) to effectively enhance ductility of the structure. Five-story and ten-story bolted steel frame structures with four configuration parameters were designed to investigate the seismic performance and damage development of steel frame structures with LYP-Cs (SF-LYP-Cs). Corresponding numerical models were established. Welded steel frame structures with traditional reduced beam sections (SF-RBS) were also established for comparison. Pushover analyses were conducted to explore the effect of structural fuses and to obtain multi-stage performance indices of the resilient steel frame structure based on energy dissipation proportion (EDP) and damage behavior. Incremental dynamic analysis was performed to verify proposed performance indices, and seismic performance of SF-LYP-Cs was evaluated via fragility analysis. The results showed that LYP-Cs were not only effective structural fuses but also effectively delayed the damage development in the primary members, thus reducing the failure probability of the structures. The multi-stage performance indices were conductive to describe the multiple lines of resistance and effects of structural fuses. A larger weakening degree and smaller beam height mitigated plastic damage development in primary members. When LYP-Cs dominate the system’s energy dissipation, the section sizes of columns and the number of structural stories exert only slight influence on the structural performance indices.

Analysis of contribution degree of vibration transmission of bolted structure

In practical engineering, the vibration transmission between bolted structures supported by cantilever beams involves many factors. The vibration transmission effect is the embodiment of the coupling of various factors, so it is impossible to accurately and quantitatively evaluate the influence degree of various factors. In this paper, the influence factors of vibration between bolted plates in the form of cantilever beam are studied by numerical calculation method. The effects of friction coefficient, bolt preload, temperature and pressure on vibration characteristics are studied. Finally, the contribution of different influencing factors to vibration transmission is given.

Triangular Position Multi-Bolt Layout Structure Optimization

Stress concentration often occurs around bolt holes in load-bearing joint structures of large complex equipment, ships, aerospace and other complex machinery fields, which is an important mechanical factor leading to the failure of joint structures. It is of great engineering significance to study the phenomenon of stress concentration on connected structures for the safety of large and complex equipment; meanwhile, the layout of bolts seriously affects the stress around holes. Many scholars have studied the layout optimization of multi-bolted structures through experiments and simulations, but few algorithms have been applied to the layout optimization of bolted structures. And most of the studied types of multi-bolt structures are symmetrical. Therefore, in this paper, the gray wolf algorithm is used to optimize the layout of nickel steel plate connectors with a bolt layout in triangular position, and the optimal objective function is found based on the hole circumferential stress of the nickel steel plate, maximum shear stress of the bolt and bending stress of the nickel steel plate. Comparing the optimal values obtained by the fruit fly optimization algorithm, particle swarm optimization algorithm, gray wolf optimization algorithm, multiverse optimization algorithm and wind driven optimization algorithm, the accuracy of selecting the gray wolf algorithm for optimization is verified. A multi-bolt connection structure model was established in ABAQUS, and the surface stress before and after optimization was compared to verify the correctness of the gray wolf algorithm applied to the structure layout optimization of the nickel steel flat bolt connection. The results show that under the force of 15 KN, compared with the original bolt structure layout, the optimized upper side nickel steel plate bore peripheral stress is reduced by 73.1 MPa, and the optimization rate is 24%; bolt stress is reduced by 47.7 MPa, and the optimization rate is 12.5%; when the load is less than 18 KN, the optimization effect of both the upper nickel steel plate and bolt group is more than 10%. When the load is greater than 18 KN, the optimization effect is reduced, and when the load is greater than 21 KN, the nickel steel plate has exceeded the yield limit. Due to the existence of fixed constraints, the optimization of the lower nickel steel plate is not obvious. The results of this study can provide data and theoretical support for the layout optimization of the nickel steel flat bolt connection structure, and help to improve reliability analysis and health monitoring in complex assembly fields such as large complex equipment and aerospace.

Experimental and numerical investigations of textile-reinforced concrete thin-wall panel bolted connections

Textile Reinforced Concrete (TRC) is a novel building material that merges fine-grained concrete with textile fibers to produce a composite material exhibiting enhanced mechanical characteristics. This study examined the behavior of thin-walled TRC structures connected by bolts and found that the open box panel member is a promising solution for wall, floor, and roof applications. The investigation focused on three types of connections: moment joints, shear joints, and half-box connections. The study also revealed that bolt-to-edge distance significantly affects the bearing capacity of TRC structures. The location and type of cracks in moment-type joints depend on the number of bolts used during fabrication. All four specimens experienced damage at the bolted side in the half-box connection test, with significant cracks around the steel bolts. The specimens failed at about 74 % and 70.6 % of the original panel's bearing capacity. It could be concluded that the bolted connection was the weakest link in the structure. Improving the bolt structure or increasing the thickness of the ribs is necessary to maximize the panel's bearing capacity. Finite element models of the full panels and half-box connections on the ATENA software package were developed and verified with the experimental results. The proposed models accurately captured the load-carrying capacities, load-deflection relationships, and failure modes for both panels and connections.

Fubini–Study geometries in the higher-dimensional gravity

We construct approximate solutions to the Einstein–Maxwell theory with uplifting the four-dimensional Fubini–Study Kähler manifold. We find the solutions can be expressed as the integrals of two special functions. The solutions are regular almost everywhere except a bolt structure on a single point in any dimensionality. We also show that in the context of considered ansatzes for the metric function and the Maxwell field, the solutions are unique and cannot be nontrivially extended to include the cosmological constant in any dimensions.