Name: a novel biaxial testing apparatus for the determination of forming limit under hot stamping conditions
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This research was supported by the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement No. 604240, project title "An industrial system enabling the use of a patented, lab-proven materials processing technology for Low Cost forming of Lightweight structures for transportation industries (LoCoLite)."

1. Preparação de Amostras <ol><li> Máquina plana cão-óssea e espécimes cruciformes de material comercial da liga de alumínio 6082 (AA6082) utilizando um cortador de laser e um computador de controlo numérico (CNC), a máquina de trituração (por testes de formabilidade em diferentes caminhos de tensão incluindo tensão uniaxial, plano, e escorrimento equi-biaxial estados). </li><li> Medir a espessura de cada espécime cruciformes e cada espécime cão de osso com um paquímetro três vezes na região calibre central e calcular os valores médios. Assegure-se que a espessura da secção de bitola num espécime cruciforme é de 0,7 ± 0,05 mm e se a espessura do espécime uniaxial é de 1,5 ± 0,1 mm. </li><li> Spray-pintar toda a superfície de topo de um espécime cruciformes usando, uma tinta spray preto resistente ao fogo (capaz de suportar temperaturas de até 1093 ° C). Aguardar até que a tinta seca e, em seguida, por pulverização, os pontos de tinta branca resistentes à chama a partir de comprimento do braço para criar um estocásticopulverização padrão a ser reconhecido pelo sistema CID (ver o exemplo na Figura 1). </li><li> Solda um par de termopares para o centro da superfície de trás (lado oposto à superfície pintada) do espécime. Ligue a outra extremidade do termopar para o sistema da máquina de ensaio uniaxial de controlo de temperatura de feedback para monitorar e controlar a história mudança de temperatura. </li></ol> 2. montagem do aparelho Biaxial Testing <ol><li> Montar todas as partes do aparelho de teste bi-axial, incluindo uma placa de base, um eixo central, de entrada e de saída de placas rotativas, carruagens, uma braçadeira, carris de guia, e hastes de ligação rígidos (o aparelho montado é mostrado na Figura 2). <ol><li> Usando uma vareta de ligação, o par placa rotativa de entrada directamente para a maxila móvel de uma resistência de aquecimento máquina de ensaio de tracção uniaxial, que fornece a força de tracção uniaxial. Acoplar a placa rotativa de entrada para o veio de accionamento central epar este veio de accionamento central para a placa rotativa de saída. </li><li> Certifique-se de que a rotação da placa rotativa de entrada à volta do eixo de rotação roda o veio de accionamento, fazendo assim rodar a placa rotativa de saída ao qual está acoplado em torno do eixo de rotação. </li><li> Numa extremidade, cada par de hastes de ligação rígidos para um dos pontos de ligação sobre a placa rotativa de saída. Par a outra extremidade a uma das carruagens. NOTA: Este irá fazer com que os carrinhos com suportes de amostra a deslizar para trás e para a frente ao longo das calhas de guia com baixo atrito, o qual pode aplicar uma força biaxial para o espécime cruciformes. </li><li> A utilização de parafusos de rosca, prender cada um dos braços do espécime cruciformes para um transporte com um suporte de amostra e uma placa de topo. </li></ol></li><li> Configurar apertos na câmara da máquina de ensaio de tracção uniaxial, como mostrado na Figura 3 (a). Ligue quatro cabos de solda para cada par de apertos, que são feitas de aço inoxidável e cobre, respectively, e, assim, conectar os cabos de solda para o fornecimento de energia elétrica. NOTA: A área condutor dos cabos de soldadura é de 50 mm2 e a corrente nominal é 345 A. <ol><li> Colocar os apertos e o grampo do dispositivo de teste biaxial para dentro das duas maxilas da máquina de ensaio de tracção uniaxial e apertá-los dentro (Figura 3 (a)). </li></ol></li><li> Defina-se o aparelho de ensaio biaxial na câmara da máquina de ensaio de tracção uniaxial, como mostrado na Figura 3 (b). <ol><li> Utilizar dois quadros e aparafusar os parafusos na parte superior e os lados do fundo da placa de base para fixar o aparelho na câmara da máquina de ensaio de tracção uniaxial. </li><li> Colocar a amostra no suporte da amostra na parte superior do aparelho de teste biaxial. </li><li> Ligar cada terminal dos cabos de solda para cada região de fixação do corpo de prova. </li></ol></li></ol> 3. Instalação do sistema de aquecimento e resfriamento <ol><li> firmemente connect cada região de aperto da amostra para a placa de topo de aço inoxidável, que serve como eléctrodo para o aquecimento por resistência. </li><li> Apertar os cabos de soldadura com terminais de anel friso para a placa superior de cada região de aperto. </li><li> Ligação queimado bicos com mangueiras para o sistema de arrefecimento rápido com alto fluxo de alimentação de ar regulada em 8.000 kg / m 2 de pressão para o arrefecimento. </li><li> Use quatro bicos de sopro de ar a partir dos braços do espécime para a região central do espécime. NOTA: Os bicos não são dirigidas para a secção de indicador para arrefecimento para evitar o bloqueio da zona central a partir do ponto de vista da câmara. </li></ol> 4. Configuração do Sistema DIC <ol><li> Ligue a câmera de alta velocidade do sistema DIC com uma micro lente para um computador. Ajustar as taxas de quadros da câmara para 25 fps, 50 fps, e 500 fps a partir do menu de taxas de quadro (para os ensaios com as taxas de deformação de alongamento de 0,01 / s, 0.1 / s e 1 / s, respectivamente). Defina as resoluções de todos os imagos a 1.280 × 1.024 pixels. NOTA: As taxas de fotogramas depende do número de pontos de dados a ser recolhidos; pelo menos 200 pontos de dados podem ser obtidos utilizando as definições acima. </li><li> Usar um projector adicional com uma potência de 300 W para testes em altas taxas de deformação. Apontar o projector directamente na câmara da máquina de ensaio de tracção uniaxial. </li><li> Ajustar a lente de câmara de modo que é paralelo à superfície superior da amostra na câmara e focar a câmara na secção de calibre. </li></ol> 5. Programa Experimental <ol><li> Executar a resistência de aquecimento máquina de ensaio de tração uniaxial, clicando no botão de execução triangular no software de controle. NOTA: Electricidade corre através do material AA6082 e aquece a solução a temperatura de tratamento térmico de 535 ° C 14 a uma taxa de aquecimento de 30 ° C / s. O material é impregnado a 535 ° C durante 1 min, o que é suficiente para a resolução completa de precipitados. Air de sopro a partir do sistema de têmpera é utilizado para temperar o material a uma velocidade de arrefecimento de 15 a um de três temperaturas elevadas designadas 100 ° C / s na gama de 370-510 ° C. </li><li> Esticar o espécime com o aparelho de ensaio biaxial a uma velocidade de deformação constante na gama de 0,01-1 / s e registar a história de deformação premindo manualmente o botão de gatilho ligado à câmara de alta velocidade. NOTA: O deslocamento de entrada da máquina de ensaio uniaxial ao aparelho de ensaio biaxial foi controlado pelo software embutido da máquina de ensaio uniaxial. </li><li> Realizar os testes em diferentes caminhos de tensão constituídos por uniaxial, deformação plana, e estados esticando biaxiais 3, ajustando a configuração do aparelho de ensaio biaxial. <ol><li> Desligue duas bielas opostas para testes uniaxial. Fixe um espécime cão-osso sobre o aparelho de teste biaxial e conectá-lo a cabos de solda, como nos passos 3.1-3.4. Repita os passos 5,1-5,2. </li><li> Fixar duas carruagens oposição à placa de base com parafusos de rosca para restringir a deformação no sentido correspondente para testes sob estado plano de deformação. Grampo um cruciformes espécime no aparelho de ensaio biaxial e ligá-lo aos cabos de soldadura, tal como nos passos 3.1-3.4. Repita os passos 5,1-5,2. </li></ol></li><li> Repita os passos 5.3.1-5.3.2 para cada condição de teste três vezes, utilizando-cão novo osso e espécimes cruciformes. </li></ol> 6. Processamento de Dados <ol><li> Importe todas as imagens gravadas pela câmera de alta velocidade para o software de pós-processamento e siga os passos padrão para análise de dados de acordo com o manual do software. </li><li> Use o padrão ISO 3 para determinar os limites formando clicando no botão Modo de FLC no software. NOTA: Este método já foi integrado no software de processamento de imagem correlação. </li><li> Marcar cada resultado dos limites que formam a várias temperaturass, as taxas de deformação e de deformação caminhos em um diagrama. </li><li> Traçar as curvas de limite de conformação em todas as condições de teste para obter uma FLD de uma liga sob condições de estampagem a quente. </li></ol>

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The authors have nothing to disclose.

métodos de ensaio de formabilidade convencionais usados ​​para determinar os limites de formação são geralmente aplicáveis ​​apenas à temperatura ambiente. A técnica apresentada pode ser usada para avaliar a formabilidade de metais para aplicações de folha de estampagem a quente através da introdução de um aparelho de ensaio novo biaxial para um aquecimento por resistência máquina de ensaio uniaxial. Este não pode ser realizada utilizando métodos convencionais para aplicações de estampagem a qu...

A indústria automotiva está enfrentando um grande desafio global de reduzir o consumo de combustível e minimizar a poluição ambiental de emissões dos veículos. A redução de peso é benéfico para a melhoria do desempenho de automóveis e pode reduzir o consumo de energia directamente um. Devido à baixa formabilidade de chapas de metal à temperatura ambiente, de estampagem a quente e processos de têmpera die frio (referido como estampagem a quente) 2 são utilizados para melhorar a moldabilidade de ligas e, portanto, para obter componentes de formas complexas em aplicações automóveis. Um diagrama de limite de conformação (FLD) é uma ferramenta útil para avaliar a formabilidade de uma liga 3. Out-of-plano testes, tais como o teste Nakazima 4, 5, e os ensaios no plano, tais como o teste Marciniak 6, 7, 8, umare métodos experimentais convencionais para se obter os flds de metais de folha sob diferentes condições de 9, 10, 11. Uma máquina de ensaio biaxial servo-hidráulica também tem sido utilizado para investigar a formabilidade de ligas à temperatura ambiente, 12, 13. No entanto, nenhum dos métodos acima são aplicáveis ​​para testes de formabilidade em condições de estampagem a quente, uma vez que um processo de arrefecimento antes da formação é necessário juntamente com o controlo das taxas de aquecimento e de arrefecimento. A temperatura de deformação e da taxa de deformação são difíceis de obter com precisão. Portanto, um sistema de teste de formabilidade romance é proposto no presente estudo para determinar experimentalmente os limites formadoras de folhas de metal em condições de estampagem a quente.

<table><tbody><tr><td>Aluminium Alloy&amp;nbsp;</td><td>Smiths Metal</td><td>6082</td><td>Specimens machining</td></tr><tr><td>Laser cutter</td><td>LVD Ltd</td><td>HELIUS 25/13</td><td>Laser cutting specimens</td></tr><tr><td>CNC machine</td><td>HAAS Automation</td><td>TM-2CE</td><td>Machine specimens by milling</td></tr><tr><td>Vernier caliper</td><td>Mitutoyo</td><td>575-481</td><td>Thickness measurement</td></tr><tr><td>Resistance heating uniaxial testing machine</td><td>Dynamic System Inc</td><td>Gleeble 3800</td><td>Thermo-mechanical materials simulator</td></tr><tr><td>High flow quench system</td><td>Dynamic System Inc</td><td>38510</td><td>For air cooling</td></tr><tr><td>Thermocouples</td><td>Dynamic System Inc</td><td>K type</td><td></td></tr><tr><td>Nozzles</td><td>Indexa</td><td></td><td>Nozzle flared 1/4 inch bore</td></tr><tr><td>Welding cables</td><td>LAPP Group</td><td>H01N2-D</td><td></td></tr><tr><td>High-speed camera</td><td>Photron</td><td>UX50</td><td>For DIC testing</td></tr><tr><td>Camera lens</td><td>Nikon</td><td>Micro 200mm</td><td></td></tr><tr><td>Lamp</td><td>Liliput</td><td>150ce</td><td>300 W</td></tr><tr><td>Laptop</td><td>HP</td><td>Campaq 2530p</td><td>For images recording</td></tr><tr><td>Biaxial testing apparatus</td><td>Manufactured independently</td><td></td><td>All parts were designed and machinced by authors for biaxial testing</td></tr><tr><td>Steel&amp;nbsp;</td><td>West Yorkshire Steel</td><td>H13</td><td>Mateials of the biaxial testing apparatus</td></tr><tr><td>Image correlation processing software</td><td>GOM</td><td>ARAMIS</td><td>Non-contact measuring system and data post-pocessing</td></tr></tbody></table>

a novel biaxial testing apparatus for the determination of forming limit under hot stamping conditions

A estampagem a quente e processo de têmpera molde frio é cada vez mais utilizado para formar os componentes estruturais em forma de complexos de metais de folha. abordagens experimentais convencionais, tal como para fora do plano e em plano testes, não são aplicáveis ​​para a determinação de formação de limites quando o aquecimento e processos de arrefecimento rápidas são introduzidas antes da formação para os ensaios efectuados sob condições de estampagem a quente. Um sistema de teste biaxial novo no plano foi concebido e utilizado para a determinação de formação de limites de chapas metálicas em vários caminhos de deformação, temperaturas e taxas de deformação após o aquecimento e arrefecimento em processos de um aquecimento por resistência máquina de ensaio uniaxial. A parte de núcleo do sistema de teste biaxial é um aparelho biaxial, o qual transfere uma força uniaxial fornecida pela máquina de ensaio uniaxial a uma força biaxial. Um tipo de espécime cruciformes foi concebido e verificada para o teste de conformabilidade da liga de alumínio 6082 utilizando o sistema de teste biaxial proposto. O im digitaissistema idade correlação (DIC) com uma câmara de alta velocidade foi utilizada para a tomada de medidas de deformação de um espécime durante uma deformação. O objectivo de propor esta biaxial sistema de teste consiste em permitir que os limites que formam de uma liga para ser determinada a diferentes temperaturas e taxas de deformação sob condições de estampagem a quente.

Desde flds são altamente estirpe dependente de caminho, a linearidade do percurso de tensão para cada condição de teste foi verificada por análise dos resultados de DIC; os caminhos de tensão são proporcionais ao longo de deformação para cada condição de teste. O intervalo da proporção menor estirpe-para-principal é aproximadamente -0,37 (condição uniaxial) a 0,26 (perto condição biaxial). Mediante o processamento de dados para diferentes condições AA6082, formando da...

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A Novel Biaxial Testing Apparatus for the Determination of Forming Limit under Hot Stamping Conditions

Este protocolo propõe um novo sistema de teste biaxial usado em um aquecimento por resistência à tracção uniaxial máquina de teste, a fim de determinar a formação de diagrama limite (FLD) de chapas de metal, sob condições de estampagem a quente.

Um novo aparelho Biaxial Teste para a Determinação do limite de conformação sob Hot Stamping Condições

The hot stamping and cold die quenching process is increasingly used to form complex shaped structural components of sheet metals. Conventional ...

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7.5K visualizações.  Imperial College London.  Este protocolo propõe um novo sistema de teste biaxial usado em um aquecimento por resistência à tracção uniaxial máquina de teste, a fim de determinar a formação de diagrama limite (FLD) de chapas de metal, sob condições de estampagem a quente. 

Vídeo: A Novel Biaxial Testing Apparatus for the Determination of Forming Limit under Hot Stamping Conditions

High-pressure, High-temperature Deformation Experiment Using the New Generation Griggs-type Apparatus

In order to address geological processes at great depths, rock deformation should ideally be tested at high pressure (&#62; 0.5 GPa) and high temperature (&#62; 300 &#176;C). However, because of the low stress resolution of current solid-pressure-medium apparatuses, high-resolution measurements are today restricted to low-pressure deformation experiments in the gas-pressure-medium apparatus. A new generation of solid-medium piston-cylinder (&#34;Griggs-type&#34;) apparatus is here described. Able to perform high-pressure deformation experiments up to 5 GPa and designed to adapt an internal load cell, such a new apparatus offers the potential to establish a technological basis for high-pressure rheology. This paper provides video-based detailed documentation of the procedure (using the &#34;conventional&#34; solid-salt assembly) to perform high-pressure, high-temperature experiments with the newly designed Griggs-type apparatus. A representative result of a Carrara marble sample deformed at 700 &#176;C, 1.5 GPa and 10-5 s-1 with the new press is also given. The related stress-time curve illustrates all steps of a Griggs-type experiment, from increasing pressure and temperature to sample quenching when deformation is stopped. Together with future developments, the critical steps and limitations of the Griggs apparatus are then discussed.

Rock deformation needs to be quantified at high pressure. A description of the procedure to perform deformation experiments in a newly designed solid-medium Griggs-type apparatus is here given. This provides technological basis for future rheological studies at pressures up to 5 GPa.

Experimento de alta pressão, alta temperatura de deformação usando o aparato de Griggs-tipo de nova geração

In order to address geological processes at great depths, rock deformation should ideally be tested at high pressure (&#62; 0.5 GPa) and high temperature ...

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Experimental Methods for Investigation of Shape Memory Based Elastocaloric Cooling Processes and Model Validation

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor compression based cooling process. Nickel-Titanium (Ni-Ti) based alloy systems, especially, show large elastocaloric effects. Furthermore, exhibit large latent heats which is a necessary material property for the development of an efficient solid-state based cooling process. A scientific test rig has been designed to investigate these processes and the elastocaloric effects in SMAs. The realized test rig enables independent control of an SMA&#39;s mechanical loading and unloading cycles, as well as conductive heat transfer between SMA cooling elements and a heat source/sink. The test rig is equipped with a comprehensive monitoring system capable of synchronized measurements of mechanical and thermal parameters. In addition to determining the process-dependent mechanical work, the system also enables measurement of thermal caloric aspects of the elastocaloric cooling effect through use of a high-performance infrared camera. This combination is of particular interest, because it allows illustrations of localization and rate effects &#8212; both important for efficient heat transfer from the medium to be cooled.
The work presented describes an experimental method to identify elastocaloric material properties in different materials and sample geometries. Furthermore, the test rig is used to investigate different cooling process variations. The introduced analysis methods enable a differentiated consideration of material, process and related boundary condition influences on the process efficiency. The comparison of the experimental data with the simulation results (of a thermomechanically coupled finite element model) allows for better understanding of the underlying physics of the elastocaloric effect. In addition, the experimental results, as well as the findings based on the simulation results, are used to improve the material properties.

Experimental methods for investigation of solid state cooling processes and characterization of elastocaloric material properties of Shape Memory Alloys (SMA) are presented. A custom-built test rig has been designed for controlling and comprehensive monitoring of elastocaloric cooling processes. Furthermore, it provides a validation platform for thermomechanically coupled modeling approaches.

Métodos experimentais para processos de resfriamento Elastocaloric Investigação de Memória de Forma baseada e Validação de Modelo

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor ...

Engenharia

Knowledge Based Cloud FE Simulation of Sheet Metal Forming Processes

The use of Finite Element (FE) simulation software to adequately predict the outcome of sheet metal forming processes is crucial to enhancing the efficiency and lowering the development time of such processes, whilst reducing costs involved in trial-and-error prototyping. Recent focus on the substitution of steel components with aluminum alloy alternatives in the automotive and aerospace sectors has increased the need to simulate the forming behavior of such alloys for ever more complex component geometries. However these alloys, and in particular their high strength variants, exhibit limited formability at room temperature, and high temperature manufacturing technologies have been developed to form them. Consequently, advanced constitutive models are required to reflect the associated temperature and strain rate effects. Simulating such behavior is computationally very expensive using conventional FE simulation techniques.
This paper presents a novel Knowledge Based Cloud FE (KBC-FE) simulation technique that combines advanced material and friction models with conventional FE simulations in an efficient manner thus enhancing the capability of commercial simulation software packages. The application of these methods is demonstrated through two example case studies, namely: the prediction of a material's forming limit under hot stamping conditions, and the tool life prediction under multi-cycle loading conditions.

The following paper presents a novel FE simulation technique (KBC-FE), which reduces computational cost by performing simulations on a cloud computing environment, through the application of individual modules. Moreover, it establishes a seamless collaborative network between world leading scientists, enabling the integration of cutting edge knowledge modules into FE simulations.

Conhecimento Baseado Simulação Nuvem FE dos Processos de formação de folha de metal

The use of Finite Element (FE) simulation software to adequately predict the outcome of sheet metal forming processes is crucial to enhancing the ...

Experimental Procedure for Warm Spinning of Cast Aluminum Components

High performance, cast aluminum automotive wheels are increasingly being incrementally formed via flow forming/metal spinning at elevated temperatures to improve material properties. With a wide array of processing parameters which can affect both the shape attained and resulting material properties, this type of processing is notoriously difficult to commission. A simplified, light-duty version of the process has been designed and implemented for full-size automotive wheels. The apparatus is intended to assist in understanding the deformation mechanisms and the material response to this type of processing. An experimental protocol has been developed to prepare for, and subsequently perform forming trials and is described for as-cast A356 wheel blanks. The thermal profile attained, along with instrumentation details are provided. Similitude with full-scale forming operations which impart significantly more deformation at faster rates is discussed.

An experimental protocol for instrumented warm rotary forming of cast aluminum alloys employing a bespoke industrially scaled apparatus is presented. Experimental considerations including thermal and mechanical effects are discussed, as well as similitude with full-scale processing of automotive wheels.

Procedimento Experimental para a fiação quente do elenco componentes de alumínio

High performance, cast aluminum automotive wheels are increasingly being incrementally formed via flow forming/metal spinning at elevated temperatures to ...

Ultrasonic Fatigue Testing in the Tension-Compression Mode

Ultrasonic fatigue testing is one of a few methods which allow investigating fatigue properties in the ultra-high cycle region. The method is based on exposing the specimen to longitudinal vibrations on its resonance frequency close to 20 kHz. With use of this method, it is possible to significantly decrease the time required for the test, when compared to conventional testing devices usually working at frequencies under 200 Hz. It is also used to simulate loading of material during operation in high speed conditions, such as those experienced by components of jet engines or car turbo pumps. It is necessary to operate only in the high and ultra-high cycle region, due to the possibility of extremely high deformation rates, which can have a significant influence on the test results. Specimen shape and dimensions have to be carefully selected and calculated to fulfill the resonance condition of the ultrasonic system; thus, it is not possible to test the full components or specimens of arbitrary shape. Before each test, it is necessary to harmonize the specimen with the frequency of the ultrasonic system to compensate for deviations of the real shape from the ideal one. It is not possible to run a test until a total fracture of the specimen, since the test is automatically terminated after initiation and propagation of the crack to a certain length, when the stiffness of the system changes enough to shift the system out of the resonance frequency. This manuscript describes the process of evaluation of materials' fatigue properties at high-frequency ultrasonic fatigue loading with use of mechanical resonance at a frequency close to 20 kHz. The protocol includes a detailed description of all steps required for a correct test, including specimen design, stress calculation, harmonizing with the resonance frequency, performing the test, and final static fracture.

A protocol for ultrasonic fatigue testing in the high and ultra-high cycle region in axial tension-compression loading mode.

Fadiga ultra-sônico de teste no modo de tensão-compressão

Ultrasonic fatigue testing is one of a few methods which allow investigating fatigue properties in the ultra-high cycle region. The method is based on ...

Conducting Elevated Temperature Normal and Combined Pressure-Shear Plate Impact Experiments Via a Breech-end Sabot Heater System

A novel approach for conducting normal and/or combined pressure-shear plate impact experiments at test temperatures up to 1000 &#176;C is presented. The method enables elevated temperature plate-impact experiments aimed towards probing dynamic behavior of materials under thermomechanical extremes, while mitigating several special experimental challenges faced while performing similar experiments using the conventional plate impact approach. Custom adaptations are made to the breech-end of a single-stage gas-gun at Case Western Reserve University; these adaptations include a precision-machined extension piece made from SAE 4340 steel, which is strategically designed to mate the existing gun-barrel while providing a high tolerance match to the bore and keyway. The extension piece contains a vertical cylindrical heater-well, which houses a heater assembly. A resistive coil heater-head, capable of reaching temperatures of up 1200 &#176;C, is attached to a vertical stem with axial/rotational degrees of freedoms; this enables thin metal specimens held at the front-end of a heat-resistant sabot to be heated uniformly across the diameter to the desired test temperatures. By heating the flyer plate (in this case, the sample) at the breech-end of the gun-barrel instead of at the target-end, several critical experimental challenges can be averted. These include: 1) severe changes in the alignment of the target plate during heating due to the thermal expansion of the several constituents of the target holder assembly; 2) challenges that arise due to the diagnostics elements, (i.e., polymer holographic gratings, and optical probes) being too close to the heated target assembly; 3) challenges that arise for target plates with an optical window, where crucial tolerances between the sample, bond layer, and window become increasingly difficult to maintain at high temperatures; 4) in the case of combined compression-shear plate impact experiments, the need for high-temperature resistant diffraction gratings for the measurement of transverse particle velocity at the free surface of the target; and 5) limitations imposed on the impact velocity necessary for unambiguous interpretation of the measured free surface velocity versus time profile due to thermal softening and possibly yielding of the bounding target plates.By utilizing the adaptations mentioned above, we present results from a series of reverse geometry normal plate impact experiments on commercial purity aluminum at a range of sample temperatures. These experiments show decreasing particle velocities in the impacted state, which are indicative of material softening (decrease in post-yield flow stress) with increasing sample temperatures.

Here, we present a detailed protocol of a new approach for conducting elevated temperature reverse normal plate impact, and combined pressure-and-shear plate impact. The approach involves the use of a breech-end resistive coil heater to heat a sample held at the front-end of a heat-resistant sabot to the desired temperature.

Realização de elevada temperatura Normal e combinados de pressão-tesoura chapa impacto experiências através de um sistema de aquecedor de Sabot culatra-final

A novel approach for conducting normal and/or combined pressure-shear plate impact experiments at test temperatures up to 1000 &#176;C is presented. The ...

Application of Design Aspects in Uniaxial Loading Machine Development

In terms of accurate and precise mechanical testing, machines run the continuum. Whereas commercial platforms offer excellent accuracy, they can be cost-prohibitive, often priced in the $100,000 - $200,000 price range. At the other extreme are stand-alone manual devices that often lack repeatability and accuracy (e.g., a manual crank device). However, if a single use is indicated, it is over-engineering to design and machine something overly elaborate. Nonetheless, there are occasions where machines are designed and built in-house to accomplish a motion not attainable with the existing machines in the laboratory. Described in detail here is one such device. It is a loading platform that enables pure uniaxial loading. Standard loading machines typically are biaxial in that linear loading occurs along the axis and rotary loading occurs about the axis. During testing with these machines, a load is applied to one end of the specimen while the other end remains fixed. These systems are not capable of conducting pure axial testing in which tension/compression is applied equally to the specimen ends. The platform developed in this paper enables the equal and opposite loading of specimens. While it can be used for compression, here the focus is on its use in pure tensile loading. The device incorporates commercial load cells and actuators (movers) and, as is the case with machines built in-house, a frame is machined to hold the commercial parts and fixtures for testing.

Here we present a protocol to develop a pure uniaxial loading machine. Critical design aspects are employed to ensure accurate and reproducible testing results.

Aplicação de aspectos do Design no desenvolvimento de máquina de carregamento Uniaxial

In terms of accurate and precise mechanical testing, machines run the continuum. Whereas commercial platforms offer excellent accuracy, they can be ...

Biaxial Mechanical Characterizations of Atrioventricular Heart Valves

Extensive biaxial mechanical testing of the atrioventricular heart valve leaflets can be utilized to derive&#160;optimal parameters used in constitutive models, which provide a mathematical representation of the mechanical function of those structures. This presented biaxial mechanical testing protocol involves (i) tissue acquisition, (ii) the preparation of tissue specimens, (iii) biaxial mechanical testing, and (iv) postprocessing of the acquired data. First, tissue acquisition requires obtaining porcine or ovine hearts from a local Food and Drug Administration-approved abattoir for later dissection to retrieve the valve leaflets. Second, tissue preparation requires using tissue specimen cutters on the leaflet tissue to extract a clear zone for testing. Third, biaxial mechanical testing of the leaflet specimen requires the use of a commercial biaxial mechanical tester, which consists of force-controlled, displacement-controlled, and stress-relaxation testing protocols to characterize the leaflet tissue&#39;s mechanical properties. Finally, post-processing requires the use of data image correlation techniques and force and displacement readings to summarize the tissue&#39;s mechanical behaviors in response to external loading. In general, results from biaxial testing demonstrate that the leaflet tissues yield a nonlinear, anisotropic mechanical response. The presented biaxial testing procedure is advantageous to other methods since the method presented here allows for a more comprehensive characterization of the valve leaflet tissue under one unified testing scheme, as opposed to separate testing protocols on different tissue specimens. The proposed testing method has its limitations in that shear stress is potentially present in the tissue sample. However, any potential shear is presumed negligible.

This protocol involves characterizations of atrioventricular valve leaflets with force-controlled, displacement-controlled, and stress-relaxation biaxial mechanical testing procedures. Results acquired with this protocol can be used for constitutive model development to simulate the mechanical behavior of functioning valves under a finite element simulation framework.

Biaxial caracterizações mecânicas das válvulas cardíacas Atrioventricular

Extensive biaxial mechanical testing of the atrioventricular heart valve leaflets can be utilized to derive&#160;optimal parameters used in constitutive ...

Bioengenharia

Layer Microdissection of Tricuspid Valve Leaflets for Biaxial Mechanical Characterization and Microstructural Quantification

The tricuspid valve (TV) regulates the unidirectional flow of unoxygenated blood from the right atrium to the right ventricle. The TV consists of three leaflets, each with unique mechanical behaviors. These variations among the three TV leaflets can be further understood by examining their four anatomical layers, which are the atrialis (A), spongiosa (S), fibrosa (F), and ventricularis (V). While these layers are present in all three TV leaflets, there are differences in their thicknesses and microstructural constituents that further influence their respective mechanical behaviors. 
This protocol includes four steps to elucidate the layer-specific differences: (i) characterize the mechanical and collagen fiber architectural behaviors of the intact TV leaflet, (ii) separate the composite layers (A/S and F/V) of the TV leaflet, (iii) carry out the same characterizations for the composite layers, and (iv) perform post-hoc histology assessment. This experimental framework uniquely allows the direct comparison of the intact TV tissue to each of its composite layers. As a result, detailed information regarding the microstructure and biomechanical function of the TV leaflets can be collected with this protocol. Such information can potentially be used to develop TV computational models that seek to provide guidance for the clinical treatment of TV disease.

This protocol describes the biaxial mechanical characterization, polarized spatial frequency domain imaging-based collagen quantification, and microdissection of tricuspid valve leaflets. The provided method elucidates how the leaflet layers contribute to the holistic leaflet behaviors.

Microdisseção de camada de folhetos de válvulas tricúsplicas para caracterização mecânica biaxial e quantificação microestrutural

The tricuspid valve (TV) regulates the unidirectional flow of unoxygenated blood from the right atrium to the right ventricle. The TV consists of three ...

Stress-Strain Characteristics of Steels

Source:&#160;Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA
The importance of materials to human development is clearly captured by the early classifications of world history into periods such as the Stone Age, Iron Age, and the Bronze Age. The introduction of the Siemens and Bessemer processes to produce steels in the mid-1800s is arguably the single most important development in launching the Industrial Revolution that transformed much of Europe and the USA in the second half of the 19th century from agrarian societies into the urban and mechanized societies of today. Steel, in its almost infinite variations, is all around us, from our kitchen appliances to cars, to lifelines such as electrical transmission networks and water distribution systems. In this experiment we will look at the stress-strain behavior of two types of steel that bound the range usually seen in civil engineering applications - from a very mild, hot rolled steel to a hard, cold rolled one.