An Approach to Variation Simulation of Final Aircraft Assembly with Presence of Sealant

The article discusses the process of aeronautical structure assembly in the presence of a sealant between the parts to be joined. An attempt to estimate the influence of sealant on assembly quality in terms of variation analysis is presented. The sealant is considered as a highly viscous liquid that is applied to the surfaces of the assembled parts before the start of final assembly. The modeling approach is based on simulation of two-way coupled fluid-structure interaction between fluid sealant and compliant structural parts. Reynolds lubrication approximation is used in the fluid dynamics problem and variational formulation of contact problem combined with static condensation is used in the structural one. The joining of two aircraft panels is used as a numerical test for demonstration of developed approach. Various phenomena connected with the presence of sealant are demonstrated. In particular, the difference in the fastener loosening due to sealant flow between different types of fasteners is investigated. Results of variation simulation show that presence of sealant should be considered among determining factors in the analysis of assembly quality.

Simulation of English Linguistic Phonetic and Lexical Variation Based on Sociology Perspective

Objectives: From the perspective of sociology, the speech and vocabulary variation simulation of English linguistics is discussed in depth. Firstly, the background of the research object and the significance of the research are elaborated, and then the research theory related to the English phonetic and lexical variation simulation is analyzed. Methods: Through the design of the English phonetic intonation network teaching system, the design ideas that conform to the development of each function of the platform are proposed. Results: Furthermore, the English linguistic speech and lexical variation simulation model algorithm based on sociological perspective is used to design and verify the function of the teaching system, and the effectiveness of the algorithm is verified by empirical analysis. Conclusion: The final results of the experiment show that by using the Internet of Things (IoT) technology to develop a system tool that conforms to the teaching method and put it into specific teaching work can improve students’ English linguistics pronunciation and vocabulary learning ability.

Characteristics of Plasma Flow for Microwave Plasma Assisted Aerosol Deposition

To validate the possibility of the developed microwave plasma source with a novel structure for plasma aerosol deposition, the characteristics of the plasma flow velocity generated from the microwave plasma source were investigated by a Mach probe with pressure variation. Simulation with the turbulent model was introduced to deduce calibration factor of the Mach probe and to compare experimental measurements for analyses of collisional plasma conditions. The results show calibration factor does not seem to be a constant parameter and highly dependent on the collision parameter. The measured plasma flow velocity, which witnessed fluctuations produced by a shock flow, was between 400 and 700 m/s. The optimized conditions for microwave plasma assisted aerosol deposition were derived by the results obtained from analyses of the parameters of microwave plasma jet. Under the optimized conditions, Y2O3 coatings deposited on an aluminum substrate were investigated using scanning electron microscope. The results presented in this study show the microwave plasma assisted aerosol deposition with the developed microwave plasma source is highly feasible for thick films with >50 μm.

Exploring barriers for the use of FEA-based variation simulation in industrial development practice

Over the last decades, finite element analysis (FEA) has become a standard tool in industrial product development, allowing for virtual analysis of designs, quick turnaround times and prompt implementation of results. Although academic research also provides numerous approaches for evaluating a product’s robustness towards geometrical, material and load variations based on FEA analyses, this, however, stands in striking contrast to the limited use of these FEA-based variation simulations in industry. In order to bridge the existing gap between academic research and industrial application, this paper explores the barriers that limit the adoption of FEA-based variation simulation. The investigation is based on interviews with five lead engineers, followed by a case study that details the underlying technical challenges and allows for some initial suggestions for future solutions. The case study involves a sterile canister with seven geometrical variables. The design objective is to ensure sufficient sealing within the range of expected probabilistic variation. The combined study details the identified main barriers for a wider application, that is, the lack of robust CAD, practical guidelines to select an efficient design of experiments for design purposes, and the complexity of the automated processes. From a technical perspective, the case study results in estimations for main and interaction effects, an accurate metamodel and Monte Carlo simulations of 100,000 samples providing the design engineer with more detailed and actionable insights on the performance of the product compared with the traditional nominal or best/worst case simulations.

Complex Fastener Model for Simulation of Airframe Assembly Process

The complex model of fastener for the global modeling of aircraft assembly with regard to compliance and contact interaction of parts is introduced in the paper. The presented complex fastener model incorporates such effects as the stiffness of fastening elements; the loosening of fasteners and also the failure of fasteners (if the load exceeds the maximal value that fastener can hold). This model can be implemented for all types of fastening elements in variation simulation and assembly optimization analysis. It provides more realistic simulation results at expense of higher model dimension. The fastener is modeled as having an additional stretching stiffness. The option of fastener loosening is included by implementation of additional contact node in each fastening element. This option allows taking into account the pre-tension in fasteners and also enables the modeling of installation and removal of fasteners without change of stiffness matrix.

Approaches to Initial Gap Modeling in Final Aircraft Assembly Simulation

Variation simulation of final aircraft assembly concerning compliance and contact interaction of parts requires the specialized approaches to setting and generation of initial gaps between the joined parts. The initial gap reflects all assembly deviations for the joining parts. In this paper two models for the generation of the initial gap samples are considered: the random field model and the mode-based model. The random field model represents the initial gap as a random field with defined properties. The mode-based model decomposes the initial gap into a series of natural modes of the parts. Typically for the real assembly processes, there is not enough accessible information about initial gaps. If the measurements are not included in the production process, then the number of measured samples can be small. The goal of this paper is to compare how considered initial gap models cope with the small number of given measurements. The models are examined on the example of wing-to-fuselage assembly process. For the considered process both initial gap models are trained on different amounts of measurements, and generated gaps are applied for the variation simulations. The comparison with measured gaps allows to determine which method is the most suitable during variation simulation with limited measurement data. The performed study shows that the mode-based approach is more accurate for initial gap modeling in case of the small number of available measurements.

Identification of Variation Sources for High Precision Fabrication in a Digital Twin Context

The aerospace industry is increasing its focus on fabrication in manufacturing, foregoing large castings to instead assemble and join smaller parts into final products. This increases the total amount of geometrical variation introduced during the production process, since the unique variation from each individual part can add to a propagating effect putting the final assembled product outside of tolerance limits. Geometry assurance and variation simulation has traditionally been applied as a part of the design process to develop robust manufacturing concepts that are as insensitive as possible to variation. A concept for geometry assurance has been proposed where variation simulation is conducted for each individual assembly using real measurements from incoming parts, making it possible to make adaptive adjustments to production parameters to optimize results. It is however not feasible to measure and simulate every aspect of the process. This paper provides a summary of relevant sources of geometrical variation for a high precision fabrication process, based on input from a fabrication process in the aerospace industry. Variation sources are analyzed and discussed from an industrial perspective, putting them in the context of an actual fabrication process as well as in the context of digital twins for geometry assurance.

Clamping force integrated computer aided tolerancing in composite assembly

Traditional computer aided tolerancing method could not accomplish the tolerancing and variation simulation well in composite assembly. The paper presents a clamping force integrated computer aided tolerancing method for composite assembly. The stochastic variations and the stackup of variations are affected by clamping forces. The clamping force modified probability distribution is used to represent the modification based on the verified FEA model of the composite assembly. The clamping forces are coordinated based on the main deformation mode extracted by the principal component analysis to satisfy the coaxial tolerance requirements of the composite assembly. The assembly of an aircraft composite elevator is considered to illustrate the computational aspects of the proposed methods. The computer aided tolerancing method involving clamping forces outlined in the paper is found to be effective for composite assembly.