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The validity of the dynamic analysis based on simplified plate model was investigated using of FE-codes ANSYS in the present paper. The simplified clamped multi-layered plate model was first verified by comparison with the exact model. The simply supported plate model was confirmed to be not a suitable model due to its large error as comparing with exact model. Influence of dimensions of laminar diaphragm on nature frequencies was studied. Deflection and voltage response driven by mechanical and electric loads were described. The optimized thickness ratio of PZT layer to SiO₂ and Si layers was given in the paper to obtain the best deflection export of actuator in design. / Singapore-MIT Alliance (SMA)

The massive number of injuries sustained in trafficaccidents is a growing problem worldwide, especially indeveloping countries. In 1998, more than one million peoplewere killed in traffic accidents worldwide, while about tentimes as many people were injured. Injuries to the centralnervous system and in particular to the headare especiallycritical to human life. This thesis contains five researchpapers looking at head injuries and head protection, proposingnew and more efficient ways of protecting the head, especiallyin traffic accidents. In order to define the national dimensions of the patternsof injuries incurred in motorcycle and moped accidents inSweden, a statistical survey was performed on data spanning a13-year period (Paper A). In Sweden, 27,100 individualsreceived in-patient care for motorcycle and moped accidentinjuries between 1987 and 1999. The motorcycle and moped injuryrate reduced in the second half of the study period, so toowere the total number of days of treatment per year. Males hadeight times the incidence of injuries of females. Head injurieswere the single most frequent diagnosis, followed by fracturesof the lower limbs. Concussion was the most frequent headinjury. These statistics clearly show the need for better headinjury prevention systems. According to the statistics, the most common type of impactto the head in motorcycle and moped accidents is an obliqueimpact. Oblique impacts generate rotations of the head, whichare a common cause of the most severe head injuries. Thereforea new test rig was constructed to reproduce oblique impacts toa helmeted dummy head, simulating those occurring in real lifeaccidents (Paper B). The new test rig was shown to provideuseful data at speeds of up to 50 km/h and with impact anglesvarying from purely tangential to purely radial. Thisinnovative test rig appears to provide an accurate method formeasuring accelerations in oblique impacts to helmets. When testing the performances of motorcycle helmets,discrepancies are usually seen in the test results. In order toevaluate these discrepancies, the finite element method (FEM)was used for simulations of a few oblique helmet impacts (PaperC). Amongthe parameters studied, the coefficients of frictionbetween the impacting surface and the helmet and between thehead and the helmet had the most significant influence on therotational accelerations. Additionally, a thinner andconsequently also weaker shell and a weaker liner, providedbetter protection for the impacts studied. Since there are no generally accepted global injurythresholds for oblique impacts to the human head, a study wasdesigned to propose new injury tolerances accounting for bothtranslations and rotations of the head (Paper D). In thatstudy, FE models of (a) a human head, (b) a Hybrid III dummyhead, and (c) the experimental helmet were used. Differentcriteria were proposed for different impact scenarios. Both thetranslational and the rotational effects were found to beimportant when proposing a predictor equation for the strainlevels experienced by the human brain in simulated impacts tothe head. In order to reduce the level of head injuries in society andto better understand helmet impacts from different aspect, aballistic impact was also studied (Paper E). The effects ofdifferent helmet shell stiffness and different angles ofimpacts were simulated. In this study, the same FE head modelfrom Paper D was used, however here it was protected with amodel of a composite ballistic helmet. It was concluded thatthe helmet shell should be stiff enough to prevent the insideof the shell from striking the skull, and that the strainsarising in the brain tissue were higher for some obliqueimpacts than for purely radial ones. In conclusion, this thesis describes the injury pattern ofmotorcycle and moped accidents in Sweden. This thesis showsthat the injuries sustained from these accidents can bereduced. In order to study both translational as well asrotational impacts, a new laboratory test rig was designed. Byusing the finite element method, it is possible to simulaterealistic impacts to the head and also to predict how severehead injuries may potentially be prevented.

The goal of this thesis is to develop an efficient finite element model of a particular micro-positioning(MP) system, known as the 3RRR Mechanism. MP systems are capable of delivering accurate and controllable motion in the micro-metre to sub-micrometre range. Conventional mechanisms, which are often composed of rigid links with pinned connections are prone to friction, backlash and stiction, which are magnified at small displacements. As such MP systems utilize a new structure known as the compliant mechanism. The structure of most compliant mechanisms is based on conventional mechanisms; however they are monolithic devices which utilize flexible elements, instead of pins, to transform the input to a useful output position. One common flexible element found in compliant mechanisms is the right circular flexure hinge. The seminal work on flexure hinges was done by Paros and Weisbord(1965), the basis of which was to calculate compliance (the reciprocal of stiffness) in order to characterize the behaviour of the hinge when loaded. However they essentially modelled the flexure hinge as a 1-D beam, when it is in fact 3-D in nature. Researchers completing finite element models of MP systems and flexure hinges have extended the model to 2-D elements, still resulting in poor results when compared to experimental data. The task of completing a full 3-D finite element model of a MP system, let alone a right circular flexure hinge, is a major computational effort. For instance, a full 3-D model of the 3RRR mechanism would require over 1,000,000 degrees of freedom(DOF) dedicated to the flexure hinges alone. A 2-D model requires approximately 45,000 DOF in total; however, this number is still regarded as large. Given these facts, a new technique called the Equivalent Beam Methodology(EBM) has been developed to model the 3-D stiffness of any right circular flexure hinge with a low number of DOF. This method essentially maps the 3-D stiffness of the hinge to a number of 1-D beam elements. For comparison, the finite element model of the 3RRR mechanism which incorporates the beams of the EBM has under 300 DOF in total, and is more accurate than the 2-D model. This method is extremely accurate, easy to use, and has a very low number of DOF, which makes it suitable to many advanced finite element modelling analyses such as topographic optimization, dynamic and modal analysis.

For automotive plastic parts there is a clear demand on an increased quality of the FE models. This demand is related to the increased use of simulations, both due to a reduced number of prototypes and an increased number of load cases. There have been studies showing a change of dynamic properties in injection molded components. The conclusion from these studies are that the change depends on residual stresses built in during the injection process. This study use simple models to try to get a working method and from the results find out the basic relations between residual stresses and dynamic properties. A method was developed and the results showed that the residuals had a major impact on the dynamic properties. Continuation on this work would be to use more complex models, to try to mimic results from reference studies and tests.

The goal of this thesis is to develop an efficient finite element model of a particular micro-positioning(MP) system, known as the 3RRR Mechanism. MP systems are capable of delivering accurate and controllable motion in the micro-metre to sub-micrometre range. Conventional mechanisms, which are often composed of rigid links with pinned connections are prone to friction, backlash and stiction, which are magnified at small displacements. As such MP systems utilize a new structure known as the compliant mechanism. The structure of most compliant mechanisms is based on conventional mechanisms; however they are monolithic devices which utilize flexible elements, instead of pins, to transform the input to a useful output position. One common flexible element found in compliant mechanisms is the right circular flexure hinge. The seminal work on flexure hinges was done by Paros and Weisbord(1965), the basis of which was to calculate compliance (the reciprocal of stiffness) in order to characterize the behaviour of the hinge when loaded. However they essentially modelled the flexure hinge as a 1-D beam, when it is in fact 3-D in nature. Researchers completing finite element models of MP systems and flexure hinges have extended the model to 2-D elements, still resulting in poor results when compared to experimental data. The task of completing a full 3-D finite element model of a MP system, let alone a right circular flexure hinge, is a major computational effort. For instance, a full 3-D model of the 3RRR mechanism would require over 1,000,000 degrees of freedom(DOF) dedicated to the flexure hinges alone. A 2-D model requires approximately 45,000 DOF in total; however, this number is still regarded as large. Given these facts, a new technique called the Equivalent Beam Methodology(EBM) has been developed to model the 3-D stiffness of any right circular flexure hinge with a low number of DOF. This method essentially maps the 3-D stiffness of the hinge to a number of 1-D beam elements. For comparison, the finite element model of the 3RRR mechanism which incorporates the beams of the EBM has under 300 DOF in total, and is more accurate than the 2-D model. This method is extremely accurate, easy to use, and has a very low number of DOF, which makes it suitable to many advanced finite element modelling analyses such as topographic optimization, dynamic and modal analysis.

The thesis is part of IBCleaning and Robotdalen project "Automated Ice-blasting" are based on blasting walls on the inside of cargo containers with dry ice using an industrial robot and therefore clean the surface. To insert the industrial robot in the dirty container a specially designed rail system has been developed.This thesis aims to analyze and calculate the strength parameters of the assembly consisting of the robot and the specially designed rail system. One more task is to examine whether there is an opportunity to contribute to an improvement proposal. The report describes briefly Ice Blasting and how the automation of this can be designed. Literature Studies in solid mechanics and tutoring in ANSYS has been performed in parallel with the work and used to compare, evaluate and resolve the various situations that occur in the construction. FEM analysis using “ANSYS program” has been implemented to support the calculations and analysis realized. ANSYS was also used when it was not possible to perform a manual calculation due to the complicated procedures or multiple operations simultaneously.I spent some of the time to realize 3D-drawings using ”Pro-Engineer program”, drawings that have been sent on to ANSYS to perform various tests on the design and obtain concrete results.The calculations are performed based partly on information from the company and partly on reasonable assumptions in order to supplement missing data in the spreadsheet calculations.

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Norrborns Industri AB in Bollnäs manufactures truck trailers with the brand Parator. One of their trailers is Parator LX 10-20. The trailer is designed to transport hooklift containers with the option to tip loose goods such as gravel, asphalt and seed. The container is mounted on a frame which is placed on the chassis. To reduce weight a redesign of the trailer is needed. The purpose of this study was to develop a concept that makes the frame lighter and easier to manufacture while maintaining safety and rigidity. The thesis also discusses factors to consider when designing with high-strength steel.   The optimization was based on existing 2D drawings of the frame. Analysis of the structure served as a basis for the optimization. First, a 3D model was created from the drawings. Then, the frame was analyzed with selected loads and boundary conditions. Initially simple models were used to develop concepts. From these, two concepts were selected and one of them was thoroughly analyzed.   The optimization resulted in a concept design weight of 732 kg, which is 179 kg less compared to the current frame at 911 kg. / Norrborns Industri AB i Bollnäs tillverkar lastbilssläp som säljs under varumärket Parator. Ett av deras släp är Parator LX 10-20 som är en lastväxlarvagn avsedd för att transportera olika lastbärare, t ex grusflak och containrar, som behöver kunna tippas. Lastbäraren sitter monterad på en tippram som i sin tur sitter på ett släpchassi. En omkonstruktion av detta släp önskas för att minska vikten. Syftet med examensarbetet var att ta fram förslag som gör tippramen lättare samt enklare att tillverka med bibehållen säkerhet och vridstyvhet. Examensarbetet tar även upp faktorer att tänka på vid konstruktion med höghållfast stål.   Optimeringen utgick från befintliga 2D-ritningar på ramen. Först skapades en 3D-modell från ritningarna. Sedan analyserades ramen utifrån valda laster och randvillkor. Analyserna av den nuvarande konstruktionen låg sedan till grund för optimeringen. Till en början användes enklare modeller för att ta fram koncept. Därefter modellerades två valda koncept varpå ett av dem har analyserats mer genomgående.   Arbetet resulterade i ett koncept som vägde 732 kg. Det är 179 kg lättare än den nuvarande konstruktionen på 911 kg.