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Humane Trap EvaluationJohnston, Norman C. 11 1900 (has links)
<p> A set of scales was created, the "Modified Conibear Scales" which can be used as a basis of comparison to rate the performance of other traps in the areas of impact energy, closing time and clamping force. Further, a detailed set of secondary non quantitative characteristics was presented.</p> <p> Using the above information, several promising traps were rated in order to assess these scales, give some immediate results and indicate promising traps or trap features. Further work in the field was facilitated by providing a detailed experimental procedure, complete lists of data and a calibrated trap for animal research.</p> / Thesis / Master of Engineering (MEngr)
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Evaluation Of Concrete Barrier As Rockfall ProtectionMusa, Abdisa 26 May 2015 (has links)
No description available.
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Hopkinson bar testing of cellular materialsPalamidi, Elisavet January 2010 (has links)
Cellular materials are often used as impact/blast attenuators due to their capacity to absorb kinetic energy when compressed to large strains. For such applications, three key material properties are the crushing stress, plateau stress and densification strain. The difficulties associated with obtaining these mechanical properties from dynamic/impact tests are outlined. The results of an experimental investigation of the quasi-static and dynamic mechanical properties of two types of cellular materials are reported.The dynamic tests were carried out using Hopkinson pressure bars. Experimentally determined propagation coefficients are employed to represent both dispersion and attenuation effects as stress waves travel along the bars. Propagation coefficients were determined for 20 mm and 40 mm diameter viscoelastic PMMA pressure bars and for elastic Magnesium pressure bars. The use of the elementary wave theory is shown to give satisfactory results for frequencies of up to approximately 15 kHz, 8 kHz and 30 kHz for the 20 mm and 40 mm diameter PMMA bars and the 23 mm diameter Magnesium bars respectively. The use of low impedance, viscoelastic pressure bars is shown to be preferable for testing low density, low strength materials.The quasi-static and dynamic compressive properties of balsa wood, Rohacell-51WF and Rohacell-110WF foams are investigated along all three principal directions. The dynamic properties were investigated by performing Split Hopkinson Pressure Bar (SHPB) and Direct Impact (DI) tests. In general, the crushing stress, the plateau stress and the densification strain remain constant with increasing strain rate of the SHPB tests. However, a dynamic enhancement of the crushing stress and plateau stress was revealed for balsa wood and Rohacell-51WF. In contrast, the plateau stresses of the Rohacell-110WF specimens are lower for SHPB than quasi-static tests. From the DI tests, it is shown that compaction waves have negligible effect on the stresses during dynamic compaction of along and across the grain balsa wood at impact speeds between approximately 20-100 m/s. Alternatively, the proximal end stresses of both Rohacell-51WF and 110WF foams increase with increasing impact velocity, following the quadratic trend predicted by 'shock theory'. This indicates that compaction waves are important for the case of Rohacell foam, even at low impact velocities.
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[en] CARACTHERIZATION OF MECHANICAL PROPERTIES ON SAE 4140 STEEL AFTER DIFFERENT TREATMENTS OF QUENCHING AND TEMPERING / [pt] CARACTERIZAÇÃO DAS PROPRIEDADES MECÂNICAS DO AÇO SAE 4140 APÓS DIFERENTES TRATAMENTOS DE TÊMPERA E REVENIDOLUIS PAULO PIRES GONCALVES RIBEIRO 14 March 2007 (has links)
[pt] Os aços de alta resistência e baixa liga (ARBL) pertencem
a uma classe de aços que desperta o interesse de
pesquisadores da área metal-mecânica. A pesquisa teve como
objetivos estudar a influência dos tratamentos térmicos de
têmpera e revenido sobre as propriedades do aço SAE 4140 e
avaliar o comportamento do aço SAE 4140 quando submetido
ao revenido na faixa de temperatura característica da
fragilização. Inicialmente, o material foi tratado
termicamente sob diferentes condições de têmpera e
revenido. Após a usinagem dos corpos de prova, foram
realizados ensaios de tração e energia ao impacto, bem
como caracterizações microestruturais e fractográficas. Os
resultados mostraram que as propriedades mecânicas do aço
SAE 4140 foram influenciadas pelos parâmetros de revenido,
em particular temperatura, além do tempo de permanência no
forno antes do resfriamento. / [en] The high strength and low alloy steels (HSLA) belong to a
class of steels in which researchers of the metal-mechanic
area have particular interest. The aim of this work is to
verify the influence of quenching and tempering heat
treatments on the properties of the SAE 4140 steel as well
as to evaluate its behaviour when subjected to tempering
in a temperature range associated with the material´s
embrittlement. At first, the material was heat treated
according with different quenching and tempering
conditions. In the sequence, specimens machined from the
treated material were subjected to tensile and impact
energy tests and characterized by microstructural and
fractographic analysis. The results showed that the
mechanical properties of the material were influenced by
the tempering parameters, specially temperature and time
of treatment as well as the permanence time of the
specimens in the furnace before cooling.
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Parametric Study of Mixture Component Contributions to Compressive Strength and Impact Energy Absorption Capacity of a High Strength Cementitious Mix with no Coarse AggregateSarfin, Md. Abdullah Al 01 August 2019 (has links)
This research project has been undertaken to produce and characterize the behavior of High Strength Cementitious Mix (HSCM), which has considerably higher compressive strength compared to conventional concrete. Components of HSCM are cement, silica fume, sand, water, and high range water reducer. The material is tested for compressive strength and impact energy absorption capacity while the amount of above mentioned components are varied parametrically. The effect of these parameters are extensively studied and trends are reported. Finally, this research projects attempts to find correlations among compressive strength, compressive toughness, and impact toughness. Limitations of the experimental program are discussed and future direction for improvement and expansion of the research program is suggested.
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Design of compliant mechanism lattice structures for impact energy absorptionNajmon, Joel Christian 12 1900 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Lattice structures have seen increasing use in several industries including automotive, aerospace, and construction. Lattice structures are lightweight and can achieve a wide range of mechanical behaviors through their inherent cellular design. Moreover, the unit cells of lattice structures can easily be meshed and conformed to a wide variety of volumes. Compliant mechanism make suitable micro-structures for units cells in lattice structures that are designed for impact energy absorption. The flexibility of compliant mechanisms allows for energy dissipation via straining of the members and also mitigates the effects of impact direction uncertainties.
Density-based topology optimization methods can be used to synthesize compliant mechanisms. To aid with this task, a proposed optimization tool, coded in MATLAB, is created. The program is built on a modular structure and allows for the easy addition of new algorithms and objective functions beyond what is developed in this study. An adjacent investigation is also performed to determine the dependencies and trends of mechanical and geometric advantages of compliant mechanisms. The implications of such are discussed.
The result of this study is a compliant mechanism lattice structure for impact energy absorption. The performance of this structure is analyzed through the application of it in a football helmet. Two types of unit cell compliant mechanisms are synthesized and assembled into three liner configurations. Helmet liners are further developed through a series of ballistic impact analysis simulations to determine the best lattice structure configuration and mechanism rubber hardness. The final liner is compared with a traditional expanded polypropylene foam liner to appraise the protection capabilities of the proposed lattice structure.
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Uticaj mikrostrukture na prelaznu temperaturu ADI materijala / Microstructure influence on ductile to brittle transition temperature of ADI materialsRajnović Dragan 10 July 2015 (has links)
<p>U disertaciji je izvršena karakterizacija mikrostrukture i mehaničkih osobina<br />nelegiranog austemperovanogi nodularnog liva (ADI materijala), kao i uticaja<br />mikrostrukture na prelaznu temperaturu u intervalu od -196 do +100°C.<br />Utvrđeno je da mehaničke osobine ADI-ja zavise od morfologije ausferitne<br />mikrostrukture i količine zadržanog austenita, tj. parametara austemperovanja.<br />Na osnovu mehaničkih osobina utvrđen je i opseg procesiranja u skladu sa<br />standardima ASTM, ISO i EN. Zaključeno je da prelazna temperatura ADI<br />materijala zavisi od količine i stabilnosti zadržanog austenita. U višem<br />temperaturnom opsegu (iznad cca. -25°C) dominantna je količina zadržanog<br />austenita, dok na nižim temperaturama, stabilnost. Visoka obogaćenost<br />ugljenikom, stabilnog zadržanog austenita sprečava stvaranje martenzita na<br />niskim temperaturama, a time i pojavu krtosti kod ADI-ja.</p> / <p>The object of this thesis was to characterize microstructure and mechanical properties<br />of the unalloyed ADI material (Austempered Ductile Iron). In addition, the influence of<br />microstructure on the ductile to brittle transition temperature (DBTT) by Charpy impact<br />test in temperature interval from 196 to +100°C has been studied. The all properties<br />obtained depend on the morphology of microstructure and the amount of retained<br />austenite, i.e. on the austempering parameters. According to the mechanical properties<br />and standard requirements (ASTM, ISO and EN) the processing window has been<br />proposed, also. It was found that DBTT is influenced by amount and stability of retained<br />austenite. In upper temperature range (above cca. 25°C) the most influence factor on<br />DBTT is amount of retained austenite, while at the lower temperatures the stability is<br />more prominent. Stability of high carbon retained austenite at lower temperatures<br />prevents transformation to martensite and thus the embrittlement of ADI.</p>
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Development, Classification and Biomedical Applications of Nano Composite Piezoresponsive FoamMerrell, Aaron Jake 01 April 2018 (has links)
This dissertation focuses on the development of and applications for Nano-Composite Piezoresponsive Foam (NCPF). This self-sensing foam sensor technology was discovered through research in a sister technology, High Deflection Strain Gauges (HDSG), and was subsequently developed with some of the same base materials. Both technologies use nano and micro conductive additives to provide electrically responsive properties to materials which otherwise are insulative. NCPF sensors differ from HDSGs in that they provide a dual electrical response to dynamic and static loading, which is measured through an internally generated charge, or a change in resistance. This dissertation focuses on the development of the dynamic or piezoresponsive aspect of the NCPF sensors which tends to have more consistent electrical response over a larger number of cycles. The primary development goal was to produce a sensor that was accurate, while providing a consistent, repeatable response over multiple impacts. The hypothesized electric generation is attributed to a triboelectric interaction between the conductive additives and the polyurethane foam matrix. This hypothesis was validated by examining different conductive additives with varying loading levels and specific surface areas while accounting for other design considerations such as the electrode used to harvest the response. The results of this analysis support the triboelectric model and point to carbon or nickel-based additives for optimal performance. The NCPF response measured by digital signal acquisition devices is directly dependent upon its input impedance. Increased input capacitance has a negative effect on the signal, however, higher input resistance has a positive linear correlation to voltage. Other considerations that affect the electrical response include the temperature and humidity in which the sensor is used and result in a scaled electrical response.NCPF sensors are ideally suited for use in systems which benefit from impact energy attenuation while measuring the same. This work demonstrates how the NCPF sensors can be used to detect severity and location of impacts in systems with multiple sensors (football helmets), and those with one continuous sensor (carpets). When NCPF sensors were used in a football helmet the impact severity and location of impact was accurately identified. NCPF sensors provide the benefit of simplified design by replacing existing foam while providing a direct measure of the forces. Additional research was conducted on the changes in material properties, specifically how it affects the foam structures ability to absorb energy in quasi static loading scenarios. NCPF sensors are demonstrated as viable tool to measure many different biomechanical systems.
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STUDY OF ENERGY ABSORPTION IN MICRO – STRUT LATTICE STRUCTURE PRODUCED BY SELECTIVE LASER MELTING / STUDY OF ENERGY ABSORPTION IN MICRO – STRUT LATTICE STRUCTURE PRODUCED BY SELECTIVE LASER MELTINGVrána, Radek January 2019 (has links)
Předložená dizertační práce je součástí většího výzkumného projektu, který si klade za cíl využití mikro prutové konstrukce vyrobené technologií SLM jako absorbér rázové energie s přesně navrženými vlastnostmi. Hlavním cílem práce je vývoj numerického modelu deformačního chování mikro-prutové konstrukce vyrobeného technologií Selective Laser Melting (SLM) z materiálu AlSi10Mg. Aby bylo možné dosáhnout hlavního cíle dizertační práce, bylo nutné analyzovat vliv procesních parametrů technologie SLM na tvorbu vnitřních materiálových vad a drsnost povrchu při výrobě mikro-prutové konstrukce. Tyto imperfekce degradují její mechanické vlastnosti a jejich odstranění zlepší možnosti a přesnost numerické predikce. Výsledky ukazují významný vliv dvou hlavních parametrů – skenovací rychlosti laseru a výkonu laseru. Na základě těchto poznatků byly dále definovány parametry vstupní energie Ein a lineární energie Elin, které zahrnují oba zmíněné parametry a byly definovány jejich limitní hodnoty pro minimalizaci vzniklých imperfekcí. Deformační chování vyrobené mikro-prutové konstrukce bylo analyzováno na navrženém pádové zařízení, které umožňuje testování s dopadovou energií až 120 J. Deformační chování je vyhodnocováno s využitím obrazové analýzy záznamu vysoko rychlostní kamery a silového průběhu z tenzometru. Výsledky analýzy byly využity pro validaci numerického modelu v programu ANSYS Explicit, do kterého byly implementovány poznatky o reálném tvaru vyrobeného mikro-prutového materiálu ve formě eliptického modelu geometrie a informace o reálných mechanických vlastnostech ve formě vyvinutého materiálového modelu. Výsledné porovnání výsledků experimentu s predikcí numerického modelu ukazují dobrou shodu v místě maximálního zatížení Fmax (odchylka 5 %) i průběhu celé deformace vzorku. Tyto poznatky budou v budoucnu využity při návrhu absorbéru energie s definovanými mechanickými vlastnostmi.
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The Influence of Fibre Processing and Treatments on Hemp Fibre/Epoxy and Hemp Fibre/PLA CompositesIslam, Mohammad Saiful January 2008 (has links)
In recent years, due to growing environmental awareness, considerable attention has been given to the development and production of natural fibre reinforced polymer (both thermoset and thermoplastic) composites. The main objective of this study was to reinforce epoxy and polylactic acid (PLA) with hemp fibre to produce improved composites by optimising the fibre treatment methods, composite processing methods, and fibre/matrix interfacial bonding. An investigation was conducted to obtain a suitable fibre alkali treatment method to: (i) remove non-cellulosic fibre components such as lignin (sensitive to ultra violet (UV) radiation) and hemicelluloses (sensitive to moisture) to improve long term composites stability (ii) roughen fibre surface to obtain mechanical interlocking with matrices (iii)expose cellulose hydroxyl groups to obtain hydrogen and covalent bonding with matrices (iv) separate the fibres from their fibre bundles to make the fibre surface available for bonding with matrices (v) retain tensile strength by keeping fibre damage to a minimum level and (vi) increase crystalline cellulose by better packing of cellulose chains to enhance the thermal stability of the fibres. An empirical model was developed for fibre tensile strength (TS) obtained with different treatment conditions (different sodium hydroxide (NaOH) and sodium sulphite (Na2SO3) concentrations, treatment temperatures, and digestion times) by a partial factorial design. Upon analysis of the alkali fibre treatments by single fibre tensile testing (SFTT), scanning electron microscopy (SEM), zeta potential measurements, differential thermal analysis/thermogravimetric analysis (DTA/TGA), wide angle X-ray diffraction (WAXRD), lignin analysis and Fourier transform infrared (FTIR) spectroscopy, a treatment consisting of 5 wt% NaOH and 2 wt% Na2SO3 concentrations, with a treatment temperature of 120oC and a digestion time of 60 minutes, was found to give the best combination of the required properties. This alkali treatment produced fibres with an average TS and Young's modulus (YM) of 463 MPa and 33 GPa respectively. The fibres obtained with the optimised alkali treatment were further treated with acetic anhydride and phenyltrimethoxy silane. However, acetylated and silane treated fibres were not found to give overall performance improvement. Cure kinetics of the neat epoxy (NE) and 40 wt% untreated fibre/epoxy (UTFE) composites were studied and it was found that the addition of fibres into epoxy resin increased the reaction rate and decreased the curing time. An increase in the nucleophilic activity of the amine groups in the presence of fibres is believed to have increased the reaction rate of the fibre/epoxy resin system and hence reduced the activation energies compared to NE. The highest interfacial shear strength (IFSS) value for alkali treated fibre/epoxy (ATFE) samples was 5.2 MPa which was larger than the highest value of 2.7 MPa for UTFE samples supporting that there was a stronger interface between alkali treated fibre and epoxy resin. The best fibre/epoxy bonding was found for an epoxy to curing agent ratio of 1:1 (E1C1) followed by epoxy to curing agent ratios of 1:1.2 (E1C1.2), 1: 0.8 (E1C0.8), and finally for 1:0.6 (E1C0.6). Long and short fibre reinforced epoxy composites were produced with various processing conditions using vacuum bag and compression moulding. A 65 wt% untreated long fibre/epoxy (UTLFE) composite produced by compression moulding at 70oC with a TS of 165 MPa, YM of 17 GPa, flexural strength of 180 MPa, flexural modulus of 10.1 GPa, impact energy (IE) of 14.5 kJ/m2, and fracture toughness (KIc) of 5 MPa.m1/2 was found to be the best in contrast to the trend of increased IFSS for ATFE samples. This is considered to be due to stress concentration as a result of increased fibre/fibre contact with the increased fibre content in the ATFE composites compared to the UTFE composites. Hygrothermal ageing of 65 wt% untreated and alkali treated long and short fibre/epoxy composites (produced by curing at 70oC) showed that long fibre/epoxy composites were more resistant than short fibre/epoxy composites and ATFE composites were more resistant than UTFE composites towards hygrothermal ageing environments as revealed from diffusion coefficients and tensile, flexural, impact, fracture toughness, SEM, TGA, and WAXRD test results. Accelerated ageing of 65 wt% UTLFE and alkali treated long fibre/epoxy (ATLFE) composites (produced by curing at 70oC) showed that ATLFE composites were more resistant than UTLFE composites towards hygrothermal ageing environments as revealed from tensile, flexural, impact, KIc, SEM, TGA, WAXRD, FTIR test results. IFSS obtained with untreated fibre/PLA (UFPLA) and alkali treated fibre/PLA (ATPLA) samples showed that ATPLA samples had greater IFSS than that of UFPLA samples. The increase in the formation of hydrogen bonding and mechanical interlocking of the alkali treated fibres with PLA could be responsible for the increased IFSS for ATPLA system compared to UFPLA system. Long and short fibre reinforced PLA composites were also produced with various processing conditions using compression moulding. A 32 wt% alkali treated long fibre PLA composite produced by film stacking with a TS of 83 MPa, YM of 11 GPa, flexural strength of 143 MPa, flexural modulus of 6.5 GPa, IE of 9 kJ/m2, and KIc of 3 MPa.m1/2 was found to be the best. This could be due to the better bonding of the alkali treated fibres with PLA. The mechanical properties of this composite have been found to be the best compared to the available literature. Hygrothermal and accelerated ageing of 32 wt% untreated and alkali treated long fibre/PLA composites ATPLA composites were more resistant than UFPLA composites towards hygrothermal and accelerated ageing environments as revealed from diffusion coefficients and tensile, flexural, impact, KIc, SEM, differential scanning calorimetry (DSC), WAXRD, and FTIR results. Increased potential hydrogen bond formation and mechanical interlocking of the alkali treated fibres with PLA could be responsible for the increased resistance of the ATPLA composites. Based on the present study, it can be said that the performance of natural fibre composites largely depend on fibre properties (e.g. length and orientation), matrix properties (e.g. cure kinetics and crystallinity), fibre treatment and processing methods, and composite processing methods.
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