653 research outputs found
Hinge front-loading: A methodology to enable the near instantaneous selection of an optimal hinge
No full textIn the aerospace industry, demanding time constraints make it practically impossible to fully explore the design space of aircraft movable surfaces. The hinges, located at the interface of the movable surface, require a time-consuming analysis. This thesis presents a methodology enabling the near instantaneous selection of an optimal hinge. An efficient, multi-objective optimization method is developed. This method is used over a range of different requirements to create a database of optimal hinges. This database is used to enable the selection of the optimal hinge "off-the-shelf" during the movable surface design. This thesis resulted in an improvement of the hinge design methodology, in terms of fidelity, run-time and scalability.Aerospace Engineerin
Designing an interactive hinge with shape memory alloys and polymers
No full textThis research aims to design and simulate a hinge consisting of shape-memory alloys and polymers, which can be actuated along two axes. The hinge consists of a shape-memory body that is actuated externally by shape-memory alloy springs. To achieve maximum deformation, two small single hinges are made, of which the body has the shape of a plate and which are actuated externally by two springs. The two hinges are then stacked, where the second hinge is twisted 90 degrees, so it can move in two directions. Tensile tests of Nitinol wires were carried out to investigate the behavior. Shape-memory springs were manufactured with this Nitinol wire. Then, the springs were deformed, the temperature of the springs was increased in steps of 10 degrees C, and the force was measured at each temperature step. Simulations were also carried out and compared to the force tests. The best type of Nitinol was chosen for the shape of memory wires. A prototype of the hinge was built and tested. First, the small single hinges were tested, where the displacement was documented. The hinge was not deemed energy efficient. Finally, simulations were carried out for the single and stacked hinges, which showed that the results were similar to reality. Hereafter, the range of motion of the stacked hinge is determined.Mechanical Engineerin
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Approximation by hinge functions
Get PDFBreiman has defined {open_quotes}hinge functions{close_quotes} for use as basis functions in least squares approximations to data. A hinge function is the max (or min) function of two linear functions. In this paper, the author assumes the existence of smooth function f(x) and a set of samples of the form (x, f(x)) drawn from a probability distribution {rho}(x). The author hopes to find the best fitting hinge function h(x) in the least squares sense. There are two problems with this plan. First, Breiman has suggested an algorithm to perform this fit. The author shows that this algorithm is not robust and also shows how to create examples on which the algorithm diverges. Second, if the author tries to use the data to minimize the fit in the usual discrete least squares sense, the functional that must be minimized is continuous in the variables, but has a derivative which jumps at the data. This paper takes a different approach. This approach is an example of a method that the author has developed called {open_quotes}Monte Carlo Regression{close_quotes}. (A paper on the general theory is in preparation.) The author shall show that since the function f is continuous, the analytic form of the least squares equation is continuously differentiable. A local minimum is solved for by using Newton`s method, where the entries of the Hessian are estimated directly from the data by Monte Carlo. The algorithm has the desirable properties that it is quadratically convergent from any starting guess sufficiently close to a solution and that each iteration requires only a linear system solve
Transposed Hinge Structures in Lamellibranchs
Get PDFIn the course of study of a collection of Eocene fossils
from Claiborne, Alabama, the senior author of this paper noticed two valves, one right and one left, of the lamellibranch Venericardia parva Lea, in which the dentition is partially transposed. Subsequently, the author made an examination of more than five thousand lamellibranch valves, representing both recent and fossil shells, in search of further examples of hinge-transposition. We have found a total number of twenty-six valves exhibiting this variation.
Study of these specimens has revealed some hitherto unreported facts regarding the principles of hinge-transposition. Therefore in this paper, we shall describe and discuss these specimens, and shall present such conclusions as seem justified by the data assembled.
Citations to the literature are made by author, date, and
page, referring to the list at the end of the paper.</p
Transposed Hinge Structures in Lamellibranchs
Get PDFIn the course of study of a collection of Eocene fossils from Claiborne Bluff, Alabama, the senior author of this paper noticed two valves, one right and one left, of the lamellibranch Venericardia parva Lea, in which the dentition is partially transposed. Subsequently, the authors made an examination of more than five thousand lamellibranch valves, representing both recent and fossil shells, in search of further examples of hinge-transposition. We have found a total number of twenty-six valves exhibiting
this variation. Study of these specimens has revealed some hitherto unreported facts regarding the principles of hinge-transposition. Therefore in this paper, we shall describe and discuss these specimens, and shall present such conclusions as seem justified by the data assembled. Citations to the literature are made by author, date, and page, referring to the list at the end of the paper
Bending Collapse Of Rectangular Section Tubes In Relation To The Bus Roll Over Problem
Get PDFThe thesis is concerned with the theoretical determination of the overall
and local effects on the collapse behaviour of bus structures in a roll
over situation. The aim is to enable an early selection of structural
components, so that the finished body can absorb enough energy and
preserve sufficient strength to meet the roll over safety requirements.
Chapter 1 gives an introduction into the bus roll over problem, discusses
the present safety legislation and reveals that there is very little
information on the performance of buses in real accidents and that no
collapse analysis of the complete structure or bending collapse of its
details had been undertaken.
The investigation into 21 bus roll over accidents, summarised in Chapter
2, showed that structural safety relies on both the overall collapse
modes and hinge properties. Theoretical determination of the overall
collapse mechanism and maximum strength of a typical British coach is
carried out in Chapter 3 using the CRASHD collapse program. Some
peculiarities of the finite element modelling are demonstrated and the
analysis indicates that the collapse mechanism can be controlled by
careful selection of various structural components. Chapter 4 emphasises
the importance of a better understanding of the hinge behaviour in
vehicle structures.
Bending collapse of rectangular section tubes is investigated in Chapter
5 for hinge rotation angles up to 30-50 degrees. The analysis starts
with determination of the maximum strength of sections which may buckle
within elastic range. Repeatability of local collapse mechanisms
enabled the definition of the appropriate theoretical model. Kinematic
theorem of the limit analysis is then applied to derive the formula for
the hinge moment-rotation curve. Particular attention is paid to the
selection of the appropriate material properties. The agreement with
experimental evidence (Chapter 6) was very good for the complete range
of tubes tested. This range includes practically all the standard
sections that are used in the general structural design.
The theory is used in Chapter 7 to optimise sections from the safety
point of view and, in combination with the CRASHD program, to predict
the collapse behaviour of beams, bus rings and complete structure entirely
on the theoretical basis. Static and dynamic tests of bus rings gave
good agreement with theory.
The practical aspects of the work have been emphasised throughout the
thesis. Detailed explanation of all the major decisions has increased
the volume of the text, but the author believes that this will prove
useful for practicing engineers. People interested in essentials only
are referred to Chapter 8 where all the most important conclusions are
given
Design and modelling of a reversible shape memory alloy torsion hinge actuator
No full textConventional hinge actuators often face limitations including excessive weight, large size and unpleasant noise. Shape memory alloys (SMAs) offer a solution to address these issues due to their favorable characteristics, such as lightweight, high actuation force and small form factor. However, most existing SMA-based hinge actuators rely on the tension loading mode. Achieving an ideal actuation angle thereby necessitates the inclusion of long SMA wires, which inadvertently constrains the actuator size. Notably, the full potential of SMAs’ deformation capacities, encompassing torsion and bending, remains largely untapped and underutilized.In this research, a reversible torsion SMA hinge actuator is studied, which can reversibly open 60° during heating and cooling. The actuator weighs 2 g, and can produce actuation forces of up to 5 N. The mechanical performances of nitinol at different temperatures are measured. Based on the measurements, a model which can predict the opening and closing angle is proposed, with deviations of 13.5 ± 8.2 %. Gripper and butterfly demonstrators constructed by the hinge actuators are given as application examples. The actuators hold potential in many fields like soft robotics, aerospace and medical instruments
The nature of hinge propositions in Wittgenstein’s on certainty
No full textM.Phil.Ludwig Wittgenstein (1889 – 1951), one of the most influential philosophers in the 20th-century Western philosophy, is well known for his originality of thought. His book, On Certainty (hereafter, OC), the collection of remarks published posthumously, is no exception. In these remarks, Wittgenstein considers a kind of propositions which have the form of empirical propositions (OC 308). He notes that these propositions do not have any common characteristic (OC 674) and describes them as hinges on which our questions and doubts turn (OC 341, 343). I will follow the usual practice, referring to the analogy drawn in OC 341 and 343, to call them ‘hinge propositions’.This dissertation aims to examine the nature of hinge propositions. In order to clarify the nature of hinge propositions, in Chapter 1 I would first define the notion of “logical hinge propositions” according to the role that hinge propositions play in a language and then introduce a Differentiating Principle (DP) by which logical hinge propositions can be classified into logico-grammatical hinge propositions and logico-nongrammatical hinge propositions. In Chapter 2 and 3, I would discuss and evaluate the interpretations of hinge propositions suggested by D. Moyal-Sharrock and Rush Rhees, respectively. Moyal-Sharrock thinks that all hinge propositions are grammatical. However, she is not aware of the fact that there are also logical hinge propositions. From his writing, we can see that Rhees is aware of the fact that there are logic-grammatical hinge propositions and logical-nongrammatical hinge propositions. However, he does not further characterize the difference between the two. Some other interpretations of hinge propositions suggested by Duncan Pritchard, Norman Malcolm and John Cook would also be considered in Chapter 4, respectively. Lastly, I would give my interpretation of hinge propositions, with the aid of the discussions in Philosophical Investigations 241 and 242, and the special theory of relativity in physics in Chapter 5.In general, this dissertation aims to argue for the conclusions that (a) There are only logical hinge propositions, and that (b) Logical hinge propositions can be classified into logico-grammatical hinge propositions and logico-nongrammatical hinge propositions.路德維希∙維根斯坦（1889–1951），二十世紀西方哲學其中一位最有影響力的哲學家，以其思想的原創性聞名。在其逝世後出版的著作《論確定性》（OC）亦不例外。維根斯坦在此書探討一種具有經驗命題外貌的命題（OC 308）。他留意到這些命題並沒有任何共同特徵（OC 674），並比擬為使我們的問題與懷疑賴以轉動的鉸鏈（OC 341,343）。我將按照慣例，參考在OC 341及343出現的類比，將這些命題稱為「樞紐命題」。本論文旨在考察樞紐命題的本質。為此，我將在第一章根據樞紐命題在語言中擔當的角色，首先定義「邏輯樞紐命題」，然後引進一條區分原則（DP），把邏輯樞紐命題區分為邏輯-文法樞紐命題及邏輯-非文法樞紐命題。在第二及第三章，我會分別地討論及評價由D.Moyal-Sharrock及Rush Rhees所提出對樞紐命題的詮釋。Moyal-Sharrock認為所有樞紐命題都是文法的。然而，她沒有注意到邏輯樞紐命題的存在。從他的著作，我們可以看到Rhees注意到邏輯-文法樞紐命題及邏輯-非文法樞紐命題的存在。然而，他並沒有進一步刻劃兩者的差異。在第四章，我也會分別地考慮由Duncan Pritchard，Norman Malcolm及John Cook提出對樞紐命題的詮釋。最後，在第五章，我會提出我對樞紐命題的詮釋，並以《哲學研究》241及242，及物理學的狹義相對論的討論作支持。總的來說，本論文旨在論證只有邏輯樞紐命題存在；並且亦論證邏輯樞紐命題可被分類為邏輯-文法樞紐命題及邏輯-非文法樞紐命題。Chow, Tsz Hin.Thesis M.Phil. Chinese University of Hong Kong 2018.Includes bibliographical references (leaves 110-114).Abstracts also in Chinese.Title from PDF title page (viewed on …)
Wing Stiffness and Hinge Release Threshold Effects on Folding Wingtip Gust Load Alleviation
No full textAn aeroelastic wind tunnel experiment to identify the influence of the wing stiffness and hinge release threshold on the gust load alleviation performance of a folding wingtip design is presented in this study. Five models with different stiffness and tailoring properties are tested and the wing root bending moment at different conditions is compared to the response with locked hinge conditions to assess the impact on the gust load alleviation capabilities of the folding wingtip. The results show that the structural properties do not have an important impact on the peak load alleviation but the hinge release threshold and timing do. Releasing with the correct timing can reduce significantly the peak loads. However, the dynamics of the system are affected by this release: the flutter speed is decreased and, although the performance can improve, load oscillations increase, which can be considered detrimental for reasons such as fatigue.AerodynamicsAerospace Structures & Computational Mechanic
Analysis of elastoplastic response of maritime structures in breaking waves using a double pendulum with a friction hinge
No full textWaves impacting on maritime structures can cause damage which endangers the environment around these structures. Due to high hydrodynamic loading, structures can enter the plastic regime, resulting possibly in structural failure. The understanding of the principles related to this structural failure due to waves is a key concept in this research. Due to a gap in existing literature, a simple approximation for the influence of plasticity on fluid-structure interaction is the first required step towards a better comprehension of structural failure of ship and offshore structures due to hydrodynamic loading. The choice is made to analyse a pendulum because of its ability to show clear and easy to interpret results, due to its few degrees of freedom. In an experiment, three different double pendulums are subjected to breaking waves created by dispersive focusing at three different locations in front of the pendulum. The top hinge of the pendulum is a normal hinge and the bottom hinge is a friction hinge that approximates plastic behaviour in a mechanical manner. The energy dissipated in the friction hinge, modelling plastic energy, and the energy transferred from the wave to the structure, called `total absorbed energy', decrease with increasing frictional torque. This means that when a structure allows for more plastic deformation, the energy that will be absorbed in total by the pendulum is larger. The energy transferred to the double pendulum shows more variability for the wave focused furthest away from the pendulum. A reduced-order model is constructed that can help explain the behaviour of the different pendulums.Marine Technolog
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