scholarly journals Compliant structures based on stiffness asymmetry

2018 ◽  
Vol 122 (1249) ◽  
pp. 442-461 ◽  
Author(s):  
C. Wang ◽  
H. H. Khodaparast ◽  
M. I. Friswell ◽  
A. D. Shaw
Keyword(s):  
Experimental Tests ◽  
Equivalent Model ◽  
Finite Element Models ◽  
Morphing Aircraft ◽  
Actuation Force ◽  
Compliant Structure ◽  
Morphing Structure ◽  
Wing Tip ◽  
Multiple Units

ABSTRACTOne of the key problems in the development of morphing aircraft is the morphing structure, which should be able to carry loads and change its geometry simultaneously. This paper investigates a compliant structure, which has the potential to change the dihedral angle of morphing wing-tip devices. The compliant structure is able to induce deformation by unsymmetrical stiffness allocation and carry aerodynamic loads if the total stiffness of the structure is sufficient.The concept has been introduced by building a simplified model of the structure and deriving the analytical equations. However, a properly designed stiffness asymmetry, which is optimised, can help to achieve the same deformation with a reduced actuation force.In this paper, round corrugated panels are used in the compliant structure and the stiffness asymmetry is introduced by changing the geometry of the corrugation panel. A new equivalent model of the round corrugated panel is developed, which takes the axial and bending coupling of the corrugated panel into account. The stiffness matrix of the corrugated panel is obtained using the equivalent model, and then the deflections of the compliant structure can be calculated. The results are compared to those from detailed finite element models built in the commercial software Abaqus. Samples with different geometries were manufactured for experimental tests.After verifying the equivalent model, optimisation is performed to find the optimum geometries of the compliant structures. The actuation force of a single compliant structure is first optimised, and then the optimisation is performed for a compliant structure consisting of multiple units. A case study is used to show the performance improvement obtained.

scholarly journals Development of a morphing wingtip based on compliant structures

2018 ◽  
Vol 29 (16) ◽  
pp. 3293-3304 ◽  
Author(s):  
Chen Wang ◽  
Hamed Haddad Khodaparast ◽  
Michael I Friswell ◽  
Alexander D Shaw ◽  
Yuying Xia ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Dihedral Angle ◽  
Honeycomb Structure ◽  
Equivalent Model ◽  
Morphing Aircraft ◽  
Aerodynamic Loads ◽  
Compliant Structure ◽  
Trailing Edges ◽  
Morphing Structure ◽  
Structural Solutions

Compliant structures, such as flexible corrugated panels and honeycomb structures, are promising structural solutions for morphing aircraft. The compliant structure can be tailored to carry aerodynamic loads and achieve the geometry change simultaneously, while the reliability of the morphing aircraft can be guaranteed if conventional components and materials are used in the fabrication of the morphing structure. In this article, a compliant structure is proposed to change the dihedral angle of a morphing wingtip. Unsymmetrical stiffness is introduced in the compliant structure to induce the rotation of the structure. Trapezoidal corrugated panels are used, whose geometry parameters can be tailored to provide the stiffness asymmetry. An equivalent model of the corrugated panel is employed to calculate the deformation of the compliant structure. To provide the airfoil shape, a flexible honeycomb structure is used in the leading and trailing edges. An optimisation is performed to determine the geometry variables, while also considering the actuator requirements and the available space to instal the compliant structure. An experimental prototype has been manufactured to demonstrate the deformation of the morphing wingtip and conduct basic wind tunnel tests.

scholarly journals Creation of Similarity Requirement with Field Equations in Steel Bearing Systems

2018 ◽  
Vol 12 (1) ◽  
pp. 134-149
Author(s):  
Ahmet C. Altunışık ◽  
Ebru Kalkan ◽  
Hasan Basri Başağa
Keyword(s):  
Experimental Studies ◽  
Experimental Tests ◽  
Structural Behavior ◽  
Influence Diagrams ◽  
Finite Element Models ◽  
Cantilever Beams ◽  
Field Equations ◽  
Similarity Relationships ◽  
Scaled Models ◽  
Scale Types

Introduction: This paper aimed to determine the structural behavior of steel bearing systems by creating similarity conditions with field equations. Scaling plays a crucial role in designing experiments aimed at understanding the structural behavior of systems where experimental studies are difficult to perform due to huge structures in the profession of engineering field. Scaling can be performed by using dimensional analysis or by normalizing differential equations that describe the dynamics of the system. If a model and prototype are dimensionally similar, it is possible to estimate experimental results from model to prototype. Methods: The use of scaled models is common on engineering applications because these models allow conducting experimental tests without the need of a physical system (i.e. prototype) to be constructed. Considering these advantages mentioned in this study, it is formed a similarity relation between prototype and scaled models of different steel bearing systems is established. Similarity relationships between systems are created by field equations. As an example, column and cantilever beams were selected and 1/2 and 1/4 scale procedure was applied. Results and Conclusion: The results obtained by finite element models in SAP2000 program for each system were compared with analytical results. The analysis results were examined and it was determined that scale factors are constant depending on scale types for different bearing systems. In addition, the influence diagrams of the systems were also examined and it was observed that the scale factor was fixed.

scholarly journals Bidirectional Spiral Pulley Negative Stiffness Mechanism for Passive Energy Balancing

2019 ◽  
Vol 11 (5) ◽  
Author(s):  
Jiaying Zhang ◽  
Alexander D. Shaw ◽  
Mohammadreza Amoozgar ◽  
Michael I. Friswell ◽  
Benjamin K. S. Woods
Keyword(s):  
Energy Conversion ◽  
Conversion Efficiency ◽  
Energy Conversion Efficiency ◽  
Negative Stiffness ◽  
Energy Balancing ◽  
Morphing Aircraft ◽  
Spring Force ◽  
Morphing Structure ◽  
Negative Stiffness Mechanism ◽  
Analytical Result

The energy balancing concept seeks to reduce actuation requirements for a morphing structure by strategically locating negative stiffness devices to tailor the required deployment forces and moments. One such device is the spiral pulley negative stiffness mechanism. This uses a cable connected with a pre-tension spring to convert the decreasing spring force into the increasing balanced torque. The kinematics of the spiral pulley is first developed for bidirectional actuation, and its geometry is then optimized by employing an energy conversion efficiency function. The performance of the optimized bidirectional spiral pulley is then evaluated through the net torque, the total required energy, and energy conversion efficiency. Then, an additional test rig tests the bidirectional negative stiffness property and compares the characteristics with the corresponding analytical result. Exploiting the negative stiffness mechanism is of significant interest not only in the field of morphing aircraft but also in many other energy and power reduction applications.

Electrostatic and Electrodynamic Field Analyses of 33kV Line Insulators

2006 ◽  
Vol 7 (3) ◽  
Author(s):  
Ibrahim A. Metwally ◽  
Md Abdus Salam ◽  
Ali Al-Maqrashi ◽  
Saif AR Sumry ◽  
Saif SH Al-Harthy
Keyword(s):  
Electric Field ◽  
Current Density ◽  
High Current Density ◽  
Experimental Tests ◽  
Finite Element Models ◽  
High Current ◽  
Density Profiles ◽  
Fully Integrated ◽  
Software Modules ◽  
Simulation Results

Electrostatic and electrodynamic field analyses of 33kV line insulators were introduced to compare the electric-field and the current density profiles of commonly used line insulators in Oman; namely, silicone rubber (SiR) and porcelain line post insulators, and porcelain cap and pin insulator string. SLIM software package was used for such simulation, which is a fully integrated collection of software modules that provides facilities for the generation and solution of electromagnetic finite element models. The simulation results reveal that for the electrostatic simulation under pollution conditions, SiR and porcelain line-post insulators give maximum values of the electric field of 360kV/m and 1700kV/m, respectively. The latter value exceeds the recommended electric field level of 500kV/m. For the electrodynamic simulation under pollution conditions, the electric field and the current density are much higher for porcelain insulator compared to those of SiR insulator. The simulation of four cap-pin standard insulator string reveals that there is high electric field (1250kV/m) at the cap-insulator gap which can cause high current density for polluted case. Finally, the trend of the simulation results has been verified by experimental tests, which has been conducted on different 33kV line insulators having different designs and materials.

Simulation of the Influence of Manufacturing Quality on Reliability of Vias

1995 ◽  
Vol 117 (2) ◽  
pp. 141-146 ◽  
Author(s):  
A. Dasgupta ◽  
V. Ramappan
Keyword(s):  
Sensitivity Analysis ◽  
Mechanical Design ◽  
Finite Element Models ◽  
Electronic Packages ◽  
Simulation Studies ◽  
Physics Of Failure ◽  
Manufacturing Quality ◽  
Solder Reflow ◽  
Failure Models

Techniques based on physics-of-failure principles are fairly well established for mechanical design of electronic packages. This paper provides an example where such techniques can also be exploited to develop guidelines for assessment of manufacturing quality and its impact on reliability. As a case study, this study examines the influence of plating waviness in vias and Plated Through Holes (PTH), on reliability during solder reflow cycles and during subsequent operational thermal cycling. The stress analysis is performed with elastic-plastic finite element models which are seeded with various levels of plating waviness defects. Sensitivity analysis is done with factorial parametric simulation studies based on Design of Experiment (DOE) methods. Buckling and fatigue failure models are used to establish inspection criteria for acceptable thresholds of plating waviness.

Improving the Traditional RCA Methodology to Design a Most Efficient and Reliable Valve for LDPE Hypercompressors Leveraging Experimental Data From Test Bench Simulation: A Real Case Study

2013 ◽  
Author(s):  
Carmelo Maggi ◽  
Leonardo Tognarelli ◽  
Riccardo Bagagli ◽  
Jan Wojnar
Keyword(s):  
Failure Modes ◽  
Good Accuracy ◽  
Deep Understanding ◽  
Experimental Tests ◽  
Operating Conditions ◽  
Flow Coefficient ◽  
Gas Composition ◽  
Pressure Losses ◽  
Valve Operation

The behavior of the valves of Hypercompressors on LDPE plants is challenging to predict because it depends on many factors and often the expected and macroscopic gas parameters, such as pressure, temperature and gas composition are not sufficient to properly evaluate the valve behavior in the field. In fact valve operation is highly dependent on local phenomena such as localized pressure losses and presence of vortexes which are in turn influenced by the geometry of the valve and by its behavior. To better understand all these phenomena it is needed to characterize these valves through experimental tests aimed at defining, with a good accuracy, the valve dimensionless parameters Cd (drag coefficient) and Ks (flow coefficient) as a function of the geometry of the valve itself. If the coefficients Cd and Ks are not accurate, the expected behavior of the valve may be completely different from the evidence of the field and could not properly explain certain types of failure modes. With a more accurate evaluation of Cd and Ks, some types of damage which in first hypothesis would seem caused by factors external to the valve, in reality are proven to be intrinsically related to valve design and often dependent on valve malfunctioning. As a final step, through to a deep understanding of the valve behavior in the field an improvement of valve reliability and efficiency can be achieved through optimization of the design for various operating conditions.

Monitoring Data for Retrofit Assessment

2008 ◽  
Vol 56 ◽  
pp. 557-562
Author(s):  
Sara Casciati ◽  
Sebastiano Floridia ◽  
Nicola Impollonia ◽  
Enrico Reale
Keyword(s):  
Relative Efficiency ◽  
Experimental Tests ◽  
Monitoring Systems ◽  
Structural Systems ◽  
Numerical Studies ◽  
Load Carrying ◽  
Before And After ◽  
Complex Structural ◽  
Processing Techniques

A construction history that spans centuries often results in complex structural systems whose load-carrying behavior cannot be easily assessed by visual inspections. Their structural rehabilitation should be supported by numerical analyses during both the design and the implementation phases of a retrofit operation. Within this context, monitoring systems provide reliable information about the structure performance under serviceability conditions. When outputonly measurements are available for the dynamic system identification before and after the intervention, signals processing techniques can be applied to assess both the original deteriorated state of the structure, and the relative efficiency of the retrofit operation. The procedure is illustrated with reference to a specific case study, which concerns a part of the Archbishop Palace located in Siracusa, Italy. Experimental and numerical studies are carried out to evaluate the actual loads supported by an ancient stone arch. The arch is surmounted by a building which underwent several additions in elevation across the centuries. Experimental tests are performed using different excitation methods and accelerometer configurations. The measurements are taken before and after the retrofit of the arch. The elaboration and comparison of the collected data for the structural assessment of the system before and after its retrofit is the topic of this work.

scholarly journals Investigation of the Compressive Viscoelastic Properties of Brain Tissue Under Time and Frequency Dependent Loading Conditions

2021 ◽  
Author(s):  
Weiqi Li ◽  
Duncan E. T. Shepherd ◽  
Daniel M. Espino
Keyword(s):  
Finite Element ◽  
Brain Tissue ◽  
Time Domain ◽  
Viscoelastic Properties ◽  
Loss Modulus ◽  
Series Representation ◽  
Experimental Tests ◽  
Finite Element Models ◽  
Frequency Dependent

AbstractThe mechanical characterization of brain tissue has been generally analyzed in the frequency and time domain. It is crucial to understand the mechanics of the brain under realistic, dynamic conditions and convert it to enable mathematical modelling in a time domain. In this study, the compressive viscoelastic properties of brain tissue were investigated under time and frequency domains with the same physical conditions and the theory of viscoelasticity was applied to estimate the prediction of viscoelastic response in the time domain based on frequency-dependent mechanical moduli through Finite Element models. Storage and loss modulus were obtained from white and grey matter, of bovine brains, using dynamic mechanical analysis and time domain material functions were derived based on a Prony series representation. The material models were evaluated using brain testing data from stress relaxation and hysteresis in the time dependent analysis. The Finite Element models were able to represent the trend of viscoelastic characterization of brain tissue under both testing domains. The outcomes of this study contribute to a better understanding of brain tissue mechanical behaviour and demonstrate the feasibility of deriving time-domain viscoelastic parameters from frequency-dependent compressive data for biological tissue, as validated by comparing experimental tests with computational simulations.

scholarly journals Lighting conditions as the occupational health related issue – case study

2022 ◽  
Vol 354 ◽  
pp. 00059
Author(s):  
Luiza Dębska ◽  
Anita Białek
Keyword(s):  
Experimental Tests ◽  
Public Utility ◽  
Intelligent Building ◽  
Intelligent Buildings ◽  
Lighting Conditions ◽  
University Of Technology ◽  
Health Related ◽  
Different Seasons ◽  
Lighting Intensity

The paper deals with the important element of proper lighting conditions at a workplace. The case study has been focused on the intelligent building “Energis” of Kielce University of Technology, where the experimental tests took place. Several groups of volunteers filled in the questionnaires related to their subjective feelings of lighting conditions in lecture rooms at different seasons. Simultaneously, precise measurements of lighting intensity were carried out. The comparison of the expressions of the room users and the measurements enabled to draw conclusions about the conditions provided in the intelligent building related to lighting. The study provides valuable information of lighting conditions in the modern, intelligent buildings which are more and more common throughout the world and serve various purposes such as office, educational or other public utility buildings.

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