Combination resonance analysis of a multi-DOF controllable close-chain linkage mechanism system

The two-DOF controllable close-chain linkage mechanism system is investigated in this paper. Based on the air-gap field of the non-uniform airspace of motors caused by the eccentricity of rotor, the electromechanical coupling relation in the real running state of motors is analyzed. The electromechanical coupling dynamic model of the system is established by means of the finite element method. The dynamic equation constitutes the basis on which the combination resonance characteristics of the system caused by electromagnetic parameter excitations of the two motors are analyzed by the multiple scales method. The first-order stationary solution is obtained under that condition, and the stability conditions of the stationary solution are also given. Finally, an experiment is presented. Results indicate that it is feasible and beneficial to explain some unexpected strong vibration phenomena in the high-speed operation of such multi-DOF controllable close-chain linkage mechanism using nonlinear combination resonance theories

Operating principle of vibratory stress relief device using coupled lateral-torsional resonance

The current process of vibratory stress relief is limited by centrifugal force produced by eccentric motor since the excitation frequency is mostly less than 200 Hz. The workpiece with high structural stiffness cannot generate enough dynamic stress by the traditional method. In the present work, the vibratory residual stress using pure lateral resonance and the theory of coupled lateral-torsional resonance are compared by the finite element method. Due to the interaction between lateral vibration and torsional vibration, the torsional vibration generated by external lateral excitation can induce coupled lateral-torsional resonance. The large enough dynamic stress is obtained to reduce the residual stress. The principle to reduce residual stress is analyzed by the Unified strength theory. Numeric solutions are obtained to describe the parametric condition to design the device of vibratory stress relief using coupled lateral-torsional resonance. The operating principle of the related device is introduced

Effects of the Grain Refiner Mg-Al-C Master Alloy on the Low Cycle Fatigue Life of AZ91D Magnesium Alloy

AbstractAdding various amounts of Mg-Al-C (Mg:Al:C=1:3:1,in weight ratio) grain refiner in AZ91D as-cast magnesium alloy can not only effectively refine the alloy grain but also substantially enhance the mechanical properties (including low cycle fatigue life). As the addition of Mg-Al-C grain refiner reaches 1.2%(wt), which is the most proper in ratio, the average grain size of the alloy is reduced from the maximum 162μm with no addition of grain refiner to the minimum 57μm, and the alloy can offer the best comprehensive mechanical properties. At the same strain amplitudes, the low cycle fatigue life of the magnesium alloy is proportional to the grain degree refined. When total strain amplitude, Δɛt/2 is 0.2%, the fatigue life of AZ91D + 1.2%Mg-Al-C alloy can reach 13615 cycles, compared with 7694 cycles of AZ91D with no refiner added; when Δɛt/2 reaches to 1.2%, the fatigue life of AZ91D alloy is improved from 21 cycles up to 113 cycles after adding 1.2%(wt) Mg-Al-C. Summarily, in the low-cycle fatigue experiments, both the initiation and propagation life of the fatigue crack can be prolonged with the addition of the grain refiner, so the whole fatigue life is increased

Combination resonance analysis of a multi-DOF controllable close-chain linkage mechanism system

The two-DOF controllable close-chain linkage mechanism system is investigated in this paper. Based on the air-gap field of the non-uniform airspace of motors caused by the eccentricity of rotor, the electromechanical coupling relation in the real running state of motors is analyzed. The electromechanical coupling dynamic model of the system is established by means of the finite element method. The dynamic equation constitutes the basis on which the combination resonance characteristics of the system caused by electromagnetic parameter excitations of the two motors are analyzed by the multiple scales method. The first-order stationary solution is obtained under that condition, and the stability conditions of the stationary solution are also given. Finally, an experiment is presented. Results indicate that it is feasible and beneficial to explain some unexpected strong vibration phenomena in the high-speed operation of such multi-DOF controllable close-chain linkage mechanism using nonlinear combination resonance theories

Evolutionary intelligence : a heuristic method of constructing conscious learning behavior and application to language development in infants

The topic of learning receives diverse perspectives in psychological cognitive and behavioral analysis. In this thesis, an evolutionary computational model is proposed to integrate both the cognitive and behavioral point of view. The constructed artificial intelligence (AI) was made to play Tic-Tac-Toe against experienced human opponents. The observed learning behavior of the AI, exhibited signs that could suggest ‘conscious learning’ behavior. This dialectic of learning is based on the hypothesis that learning is an evolutionary process (behavioral) mediated by certain internal memory organizing mechanism (cognitive). Genetic algorithm and cellular automaton are the two fundamental logic behind this model. Here in the game model, the AI is able to both successfully figure out rule(s) and strategies of the game. Adopting this approach, a simplified version of the AI is constructed to model infant language acquisition. In this infant model, we are able to mimic an infant’s initial phase of language development through the first three levels of consciousness via social interactions. This result could be of paramount importance in identifying infants with difficulty in acquiring language.Master of Scienc

The sinusoidal traversable wormhole.

In a baby universe or the universe at a very small scale, the geometry of space-time is believed to exist as a foamy structure; a term called quantum foam first suggested by John Wheeler. This final year thesis report explores the properties of a sinusoidal traversable wormhole and attempts to solve for the existence of a safe geodesic on the wormhole that elementary particles are able to move about. The aim of this thesis is to achieve a safe geodesic elementary particles may travel on during the very beginning of the formation of the universe. In this research I have managed to come out with a periodically safe geodesic which exists for one and a half cycle. This result is sufficient as the topology structure of the 'foamy' wormhole central to this research takes the shape of my sinusoidal wormhole, for half a cycle. For a minimum of one and a half period, the geodesic is guaranteed to be safe as it coils about the outer most region of the sinusoidal traversable wormhole.Bachelor of Science in Physic

Förbättrad produktivitet : Innovativa produktionsmetoder för ett omstrukturerat skrov

With the world shifting towards ever more sustainable practices and products, the maritime industry is expected to do the same. X Shore has found itself well-established in the new and niche industry of electric boats. Currently, the demand for their boats is remarkably high, and a natural transition towards automated production is required to fulfil this demand. Today the boats are mainly handmade, which is both time-consuming and costly. The goal of the project is to determine which production methods are viable for the company and what changes to their existing product will be required to successfully implement these production methods. First, by researching which methods are available on the market, eight major alternatives were noted. After briefly examining each method, they were limited to four viable options: ATL, AFP, Hybrid ATL and AFP, and Diaphragm moulding. These four methods were then compared against each other, which left AFP and Diaphragm moulding as the most viable alternatives now. With the most suitable production methods determined, it was then time to determine what modifications needed to take place for their existing product to function with these methods. For AFP, all tapered surfaces needed to be removed. Complex designs and rounded surfaces with radiuses below 30 mm also needed to be modified. For Diaphragm moulding, tapered surfaces could remain, but complex designs and radiuses below 40 mm required modifications. After further analysing the existing models and discussing with experts in the field of carbon fibre production, a conclusion was made that likely a full redesign of the hull - rather than modifying the existing one - was a better solution for the company when solely looking at producibility.Idag blir hållbara alternativ inom alla branscher allt mer efterfrågade. Båtindustrin förväntas följa samma trend. Företaget X Shore har nu placerat sig själva i en stark roll inom den nya och nischade industrin av elektriska båtar. I dagsläget har de en hög efterfrågan på sina båtar, och en naturlig övergång till automatiserad produktion behövs för att möta den här efterfrågan. I dagsläget är båtarna främst handgjorda, vilket inte bara är dyrt, utan även tidskrävande. Målet med projektet är att bedöma vilka produktionsmetoder som vore lämpliga för företaget, samt vilka ändringar som behöver implementeras på deras existerande produkter för att bli kompatibla med de valda metoderna. Först, genom analys av vilka metoder som finns på marknaden, så har åtta alternativ lyfts fram. Efter en kortare analys av dessa metoder, så kvarstod fyra stycken som potentiellt lämpliga; ATL, AFP, Hybrid ATL och AFP, samt Diaphragm moulding. Dessa fyra metoder har sedan jämförts med varandra, vilket lämnade AFP och Diaphragm moulding som de mest lämpade för företaget i dagsläget. Med de mest lämpade alternativen fastställda, så var det dags att granska de existerande produkterna och fastställa vilka modifikationer de behövde för att fungera med valda metoder. AFP krävde att alla koniska ytor togs bort. Utöver det behövde även komplexa designelement samt rundade ytor med en radie under 30 mm modifieras. För Diaphragm moulding så kunde koniska ytorna kvarstå, men komplexa designelement och radier under 40 mm behövde modifieras. Vidare analys av de existerande modellerna och diskussioner med experter inom området av kolfiber production gav vidare slutsats att en fullständig omdesign av modellen från grunden - istället för modifikationer - troligen var ett lämpligare alternativ för företaget när enbart produktion hålls i åtanke