Knowledge-based support in Non-Destructive Testing for health monitoring of aircraft structures

Maintenance manuals include general methods and procedures for industrial maintenance and they contain information about principles of maintenance methods. Particularly, Non-Destructive Testing (NDT) methods are important for the detection of aeronautical defects and they can be used for various kinds of material and in different environments. Conventional non-destructive evaluation inspections are done at periodic maintenance checks. Usually, the list of tools used in a maintenance program is simply located in the introduction of manuals, without any precision as regards to their characteristics, except for a short description of the manufacturer and tasks in which they are employed. Improving the identification concepts of the maintenance tools is needed to manage the set of equipments and establish a system of equivalence: it is necessary to have a consistent maintenance conceptualization, flexible enough to fit all current equipment, but also all those likely to be added/used in the future. Our contribution is related to the formal specification of the system of functional equivalences that can facilitate the maintenance activities with means to determine whether a tool can be substituted for another by observing their key parameters in the identified characteristics. Reasoning mechanisms of conceptual graphs constitute the baseline elements to measure the fit or unfit between an equipment model and a maintenance activity model. Graph operations are used for processing answers to a query and this graph-based approach to the search method is in-line with the logical view of information retrieval. The methodology described supports knowledge formalization and capitalization of experienced NDT practitioners. As a result, it enables the selection of a NDT technique and outlines its capabilities with acceptable alternatives

Lay-up optimisation of fibre–metal laminates panels for maximum impact absorption

This paper introduces a methodology utilising a ply-ply damage Finite Element models with Genetic algorithm optimisation procedure to investigate the effect of lay-up configuration on the impact absorption properties of fibre metal laminates (FMLs). The methodology was carried out in two steps. In the first step, a pseudo-2D model was used to explore the vast design space to identify potential optimised layup-configurations. In the second step, the optimised configurations were studied in full 3 D, with high fidelity simulations, verifying the results obtained from the optimisation process. The design variables used include thickness and material (including fibre orientation) of each ply. The results produced an optimised configuration consisting of a metallic ply on the impacted side followed by a cross-ply composite lay-up. The results also suggest that the first composite ply (second ply of the FML) should be about 3 times thicker than the other plie

Effects of acute fatigue on the volitional and magnetically-evoked electromechanical delay of the knee flexors in males and females

Neuromuscular performance capabilities, including those measured by evoked responses, may be adversely affected by fatigue; however, the capability of the neuromuscular system to initiate muscle force rapidly under these circumstances is yet to be established. Sex-differences in the acute responses of neuromuscular performance to exercise stress may be linked to evidence that females are much more vulnerable to ACL injury than males. Optimal functioning of the knee flexors is paramount to the dynamic stabilisation of the knee joint, therefore the aim of this investigation was to examine the effects of acute maximal intensity fatiguing exercise on the voluntary and magnetically-evoked electromechanical delay in the knee flexors of males and females. Knee flexor volitional and magnetically-evoked neuromuscular performance was assessed in seven male and nine females prior to and immediately after: (i) an intervention condition comprising a fatigue trial of 30-seconds maximal static exercise of the knee flexors, (ii) a control condition consisting of no exercise. The results showed that the fatigue intervention was associated with a substantive reduction in volitional peak force (PFV) that was greater in males compared to females (15.0%, 10.2%, respectively, p < 0.01) and impairment to volitional electromechanical delay (EMDV) in females exclusively (19.3%, p < 0.05). Similar improvements in magnetically-evoked electromechanical delay in males and females following fatigue (21%, p < 0.001), however, may suggest a vital facilitatory mechanism to overcome the effects of impaired voluntary capabilities, and a faster neuromuscular response that can be deployed during critical times to protect the joint system

Significance of designing the filling of an open rapid sand filter when removing impurities from water

Filtration is a mechanical process of squeezing, during which the passage of liquid occurs, in this paper, specifically water, through a porous layer of material. During that flow, the impurities are retained within that layer, which is called the filter, and the water is desired quality comes out of the filtering device. The goal of this work is to demonstrate the importance of dimensioning the filter itself, so reliably that during the actual filling of the filter, almost all impurities remain in that layer. There are different types of filters, and also different dimensions for each type. Which type will be specifically used depends on several factors such as the desired quality of the water coming out of the filter, the initial state of the water (pollution) coming into the filter, the amount of water reaching the filter, the speed of the filtration process itself, etc. In this paper, the importance of dimensioning sand filters, as well as the selection of the filter filling method, is highlighted

Significance of designing the filling of an open rapid sand filter when removing impurities from water

Filtration is a mechanical process of squeezing, during which the passage of liquid occurs, in this paper, specifically water, through a porous layer of material. During that flow, the impurities are retained within that layer, which is called the filter, and the water is desired quality comes out of the filtering device. The goal of this work is to demonstrate the importance of dimensioning the filter itself, so reliably that during the actual filling of the filter, almost all impurities remain in that layer. There are different types of filters, and also different dimensions for each type. Which type will be specifically used depends on several factors such as the desired quality of the water coming out of the filter, the initial state of the water (pollution) coming into the filter, the amount of water reaching the filter, the speed of the filtration process itself, etc. In this paper, the importance of dimensioning sand filters, as well as the selection of the filter filling method, is highlighted

Activities of the Structures Division, Lewis Research Center

The purpose of the NASA Lewis Research Center, Structures Division's 1990 Annual Report is to give a brief, but comprehensive, review of the technical accomplishments of the Division during the past calendar year. The report is organized topically to match the Center's Strategic Plan. Over the years, the Structures Division has developed the technology base necessary for improving the future of aeronautical and space propulsion systems. In the future, propulsion systems will need to be lighter, to operate at higher temperatures and to be more reliable in order to achieve higher performance. Achieving these goals is complex and challenging. Our approach has been to work cooperatively with both industry and universities to develop the technology necessary for state-of-the-art advancement in aeronautical and space propulsion systems. The Structures Division consists of four branches: Structural Mechanics, Fatigue and Fracture, Structural Dynamics, and Structural Integrity. This publication describes the work of the four branches by three topic areas of Research: (1) Basic Discipline; (2) Aeropropulsion; and (3) Space Propulsion. Each topic area is further divided into the following: (1) Materials; (2) Structural Mechanics; (3) Life Prediction; (4) Instruments, Controls, and Testing Techniques; and (5) Mechanisms. The publication covers 78 separate topics with a bibliography containing 159 citations. We hope you will find the publication interesting as well as useful

Mechatronic Model of a Compliant 3PRS Parallel Manipulator

Compliant mechanisms are widely used for instrumentation and measuring devices for their precision and high bandwidth. In this paper, the mechatronic model of a compliant 3PRS parallel manipulator is developed, integrating the inverse and direct kinematics, the inverse dynamic problem of the manipulator and the dynamics of the actuators and the control. The kinematic problem is solved, assuming a pseudo-rigid model for the deflection in the compliant revolute and spherical joints. The inverse dynamic problem is solved, using the Principle of Energy Equivalence. The mechatronic model allows the prediction of the bandwidth of the manipulator motion in the 3 degrees of freedom for a given control and set of actuators, helping in the design of the optimum solution. A prototype is built and validated, comparing experimental signals with the ones from the model.Authors would like to thank the Ministerio de Ciencia e Innovación of the Spanish government for funding the project PID2019-105262RB-I00

Engineering for a changing world: 60th Ilmenau Scientific Colloquium, Technische Universität Ilmenau, September 04-08, 2023 : programme

In 2023, the Ilmenau Scientific Colloquium is once more organised by the Department of Mechanical Engineering. The title of this year’s conference “Engineering for a Changing World” refers to limited natural resources of our planet, to massive changes in cooperation between continents, countries, institutions and people – enabled by the increased implementation of information technology as the probably most dominant driver in many fields. The Colloquium, supplemented by workshops, is characterised but not limited to the following topics: – Precision engineering and measurement technology Nanofabrication – Industry 4.0 and digitalisation in mechanical engineering – Mechatronics, biomechatronics and mechanism technology – Systems engineering – Productive teaming - Human-machine collaboration in the production environment The topics are oriented on key strategic aspects of research and teaching in Mechanical Engineering at our university

Numerical modelling techniques for fretting fatigue crack initiation and propagation

status: publishe

Fatigue modeling of nano-structured chip-to-package interconnections

Driven by the need for increase in system¡¯s functionality and decrease in the feature size, International Technology Roadmap for Semi-conductors has predicted that integrated chip packages will have interconnections with I/O pitch of 90 nm by the year 2018. Lead-based solder materials that have been used for many decades will not be able to satisfy the thermal mechanical requirements of these fines pitch packages. Of all the known interconnect technologies, nanostructured copper interconnects are the most promising for meeting the high performance requirements of next generation devices. However, there is a need to understand their material properties, deformation mechanisms and microstructural stability. The goal of this research is to study the mechanical strength and fatigue behavior of nanocrystalline copper using atomistic simulations and to evaluate their performance as nanostructured interconnect materials. The results from the crack growth analysis indicate that nanocrystalline copper is a suitable candidate for ultra-fine pitch interconnects applications. This study has also predicts that crack growth is a relatively small portion of the total fatigue life of interconnects under LCF conditions. The simulations result conducted on the single crystal copper nano-rods show that its main deformation mechanism is the nucleation of dislocations. In the case of nanocrystalline copper, material properties such as elastic modulus and yield strength have been found to be dependent on the grain size. Furthermore, it has been shown that there is competition between the dislocation activity and grain boundary sliding as the main deformation mode This research has shown that stress induced grain coarsening is the main reason for loss of mechanical performance of nanocrystalline copper during cyclic loading. Further, the simulation results have also shown that grain growth during fatigue loading is assisted by the dislocation activity and grain boundary migration. A fatigue model for nanostructured interconnects has been developed in this research using the above observations Lastly, simulations results have shown that addition of the antimony into nanocrystalline copper will not only increase the microstructure stability, it will also increase its strength.Ph.D.Committee Chair: Rao R. Tummala; Committee Co-Chair: Ashok Saxena; Committee Member: Karl Jacob; Committee Member: Suresh Sitaraman; Committee Member: Thomas H. Sanders, J