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. Preparación de muestras <ol><li> Máquina de hueso de perro plana y especímenes cruciformes de material comercial de aleación de aluminio 6082 (AA6082) utilizando un cortador de láser y un control numérico por computadora (CNC) de la máquina de fresado (para las pruebas de capacidad de deformación en diferentes trayectorias de deformación incluyendo cepa uniaxial, avión, y el esfuerzo equi-biaxial estados). </li><li> Medir el espesor de cada muestra cruciformes y cada espécimen de hueso de perro con un calibrador vernier tres veces en la región de calibre central y calcular los valores medios. Asegúrese de que el espesor de la sección de calibre en un espécimen cruciforme es 0,7 ± 0,05 mm y que el grosor de la muestra uniaxial es de 1,5 ± 0,1 mm. </li><li> Spray-pintar toda la superficie superior de una muestra de cruciformes mediante el uso de una, pintura de aerosol negro resistente a las llamas (capaz de soportar temperaturas de hasta 1093 ° C). Espere hasta que la pintura se seque y luego rociar, puntos de pintura blanca resistentes a la llama de la longitud del brazo para crear un estocásticomodelo de pulverización para ser reconocido por el sistema de DIC (ver el ejemplo de la Figura 1). </li><li> Weld un par de termopares para el centro de la superficie posterior (opuesta a la superficie pintada) de la muestra. Conecte el otro extremo del termopar al sistema de control de temperatura votaciones de la máquina de ensayo uniaxial para monitorear y controlar el historial de cambios de temperatura. </li></ol> 2. Montaje del aparato de ensayo biaxial <ol><li> Montar todas las partes del aparato de ensayo biaxial, que incluye una placa base, un eje central, de entrada y de salida placas giratorias, carros, una abrazadera, carriles de guía, y bielas rígidas (el aparato ensamblado se muestra en la Figura 2). <ol><li> El uso de una varilla de conexión, par la placa giratoria de entrada directamente a la mordaza móvil de una resistencia de calentamiento de la máquina de ensayo de tracción uniaxial, que proporciona la fuerza de tracción uniaxial. Pareja la placa giratoria de entrada al árbol de accionamiento central ypar este árbol central de accionamiento a la placa giratoria de salida. </li><li> Asegúrese de que la rotación de la placa giratoria de entrada en torno al eje de rotación hace girar el árbol de accionamiento, con lo que la rotación de la placa giratoria de salida a la que está acoplado alrededor del eje de rotación. </li><li> En un extremo, un par cada una de las bielas rígidas a uno de los puntos de conexión en la placa giratoria de salida. Pareja el otro extremo a uno de los carros. NOTA: Esto hará que los carros con soportes para muestras para deslizarse hacia atrás y adelante a lo largo de los carriles de guía con baja fricción, que puede aplicar una fuerza biaxial a la muestra cruciformes. </li><li> El uso de pernos roscados, sujetar cada brazo de la muestra cruciformes a un carro con un soporte de la muestra y una placa superior. </li></ol></li><li> Configurar empuñaduras en la cámara de la máquina de ensayo de tracción uniaxial, como se muestra en la Figura 3 (a). Adjuntar cuatro cables de soldadura a cada par de mordazas, que están hechas de acero inoxidable y cobre, Respectively, y así conectar los cables de soldadura a la fuente de alimentación eléctrica. NOTA: El área conductor de los cables de soldadura es de 50 mm 2 y la corriente nominal es 345 A. <ol><li> Poner las mordazas y la abrazadera del aparato de prueba biaxial en las dos mordazas de la máquina de ensayo de tracción uniaxial y apretarlos en el interior (Figura 3 (a)). </li></ol></li><li> Configurar el aparato de ensayo biaxial en la cámara de la máquina de ensayo de tracción uniaxial, como se muestra en la Figura 3 (b). <ol><li> Use dos marcos y atornillar los pernos en la parte superior y los lados inferiores de la placa de base para fijar el aparato en la cámara de la máquina de ensayo de tracción uniaxial. </li><li> Coloque la muestra en el soporte de la muestra en la parte superior del aparato de ensayo biaxial. </li><li> Conectar cada terminal de los cables de soldadura a cada región de sujeción de la muestra. </li></ol></li></ol> 3. Configuración del sistema de calefacción y enfriamiento rápido <ol><li> fuertemente connect cada región de sujeción de la muestra a la placa superior de acero inoxidable, que sirve como electrodo para la calefacción de resistencia. </li><li> Apretar los cables de soldadura con terminales de anillo de plegar a la placa superior de cada zona de sujeción. </li><li> Conectar estalló boquillas con mangueras para el sistema de enfriamiento rápido de alto flujo con suministro de aire regulado a 8,000 kg / m 2 de presión para la refrigeración. </li><li> Utilice cuatro boquillas para soplar aire de los brazos de la muestra a la región central de la muestra. NOTA: Las boquillas no están dirigidas a la sección de calibre para la refrigeración para evitar el bloqueo de la zona central de la vista de la cámara. </li></ol> 4. Configuración del Sistema DIC <ol><li> Conecte la cámara de alta velocidad del sistema de la CID con una lente micro a un ordenador. Ajuste las velocidades de cuadro de la cámara a 25 fps, 50 fps, y 500 fps desde el menú de velocidades de cuadro (para los ensayos en las velocidades de deformación de estiramiento de 0.01 / s, 0,1 / s y 1 / s, respectivamente). Establecer las resoluciones de todo lomagos a 1.280 × 1.024 píxeles. NOTA: Las velocidades de cuadro en función del número de puntos de datos para ser recogidos; al menos 200 puntos de datos se pueden recoger usando los ajustes anteriores. </li><li> Use un foco adicional con una potencia de 300 W para las pruebas a altas velocidades de deformación. El punto el punto de mira directamente en la cámara de la máquina de ensayo de tracción uniaxial. </li><li> Ajuste la lente de la cámara para que sea paralela a la superficie superior de la muestra en la cámara y enfocar la cámara en la sección de calibre. </li></ol> 5. Programa Experimental <ol><li> Ejecutar el calentamiento por resistencia máquina de ensayo de tracción uniaxial haciendo clic en el botón de ejecución triangular en el software de control. NOTA: La electricidad se ejecuta a través del material AA6082 y lo calienta a la temperatura de tratamiento térmico en solución de 535 ° C 14 a una velocidad de calentamiento de 30 ° C / s. El material se empapa a 535 ° C durante 1 min, que es suficiente para la resolución completa de precipitados. Air sopla desde el sistema de enfriamiento rápido se utiliza para extinguir el material a una velocidad de enfriamiento de 15 a una de las 3 temperaturas elevadas designadas 100 ° C / s en el intervalo de 370-510 ° C. </li><li> Estirar el espécimen con el aparato de ensayo biaxial a una velocidad de deformación constante en el intervalo de 0,01-1 / s y registrar la historia de deformación presionando manualmente el botón de disparo conectado a la cámara de alta velocidad. NOTA: El desplazamiento de entrada de la máquina de ensayo uniaxial al aparato de pruebas biaxial fue controlado por el software integrado de la máquina de ensayo uniaxial. </li><li> Llevar a cabo las pruebas en diferentes trayectorias de deformación consisten en uniaxial, deformación plana, y estados esfuerzo biaxiales 3 mediante el ajuste de la configuración del aparato de ensayo biaxial. <ol><li> Desconectar dos bielas opuestas para las pruebas uniaxiales. Sujetar una muestra de hueso de perro en el aparato de prueba de dos ejes y conectarlo a los cables de soldadura, como en los pasos 3.1-3.4. Repetir los pasos 5.1 a 5.2. </li><li> Fijar dos carros opuestos a la placa de base con pernos roscados para restringir la deformación en la dirección correspondiente para las pruebas en estado de deformación plana. Abrazadera de un espécimen cruciformes en el aparato de ensayo biaxial y conectarlo a los cables de soldadura, como en los pasos 3.1-3.4. Repita los pasos 5.1-5.2. </li></ol></li><li> Repita los pasos 5.3.1-5.3.2 para cada condición de prueba tres veces, utilizando las nuevas de hueso de perro y las muestras cruciformes. </li></ol> 6. Proceso de Datos <ol><li> Importar todas las imágenes grabadas por la cámara de alta velocidad en el software de post-procesamiento y siga los pasos estándar para el análisis de datos de acuerdo con el manual del software. </li><li> Utilice el estándar ISO 3 para determinar los límites que forman haciendo clic en el botón de modo de FLC en el software. NOTA: Este método ya se ha integrado en el software de procesamiento de correlación de imágenes. </li><li> Marcar cada resultado de los límites que forman a varias temperaturass, velocidades de deformación, y deformación caminos en un diagrama. </li><li> Representar gráficamente las curvas de límite forman en todas las condiciones de prueba para obtener una FLD de una aleación en condiciones de estampación en caliente. </li></ol>

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The authors have nothing to disclose.

métodos de ensayo de conformabilidad convencionales utilizados para determinar la formación de límites son generalmente aplicables sólo a temperatura ambiente. La técnica presentada puede utilizarse para evaluar la capacidad de conformación de metales para aplicaciones de hoja de estampado en caliente mediante la introducción de un nuevo aparato de ensayo biaxial a una resistencia de calentamiento máquina de ensayo uniaxial. Esto no se puede realizar usando métodos convencionales para aplicaciones de estampaci?...

La industria del automóvil se enfrenta a un enorme desafío global de reducir el consumo de combustible y reducir al mínimo la contaminación del medio ambiente de las emisiones de vehículos. La reducción de peso es beneficiosa para mejorar el rendimiento de los automóviles y puede reducir directamente el consumo de energía 1. Debido a la baja capacidad de conformado de láminas de metal a temperatura ambiente, estampado en caliente y procesos de enfriamiento rápido de troquel frío (referido como estampación en caliente) 2 se utilizan para mejorar la conformabilidad de las aleaciones y así obtener los componentes de formas complejas en aplicaciones de automoción. Un diagrama de límite de conformado (FLD) es una herramienta útil para evaluar la capacidad de conformación de una aleación 3. Fuera de plano de pruebas, como la prueba Nakazima 4, 5, y en el plano pruebas, como la Marciniak prueba 6, 7, 8, unare métodos experimentales convencionales para obtener los flds de metales de hoja en diversas condiciones 9, 10, 11. Una máquina de ensayo biaxial servo-hidráulico también se ha utilizado para investigar la conformabilidad de las aleaciones a temperatura ambiente 12, 13. Sin embargo, ninguno de los métodos anteriores son aplicables a las pruebas de capacidad de deformación bajo condiciones de estampación en caliente, ya que un proceso de enfriamiento antes de la formación que se requiere, junto con el control de las velocidades de calentamiento y enfriamiento. La temperatura de deformación y velocidad de deformación son difíciles de obtener con precisión. Por lo tanto, se propone un nuevo sistema de pruebas de la capacidad de conformado en este estudio para determinar experimentalmente los límites de formación de láminas de metal en condiciones de estampación en caliente.

<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

El estampado en caliente y el proceso de enfriamiento rápido de troquel frío se utiliza cada vez más para formar componentes estructurales de formas complejas de metales de hoja. enfoques experimentales convencionales, tales como fuera de plano y en el plano pruebas, no son aplicables a la determinación de la formación de límites cuando el calentamiento y los procesos de enfriamiento rápido se introduce antes de la formación de ensayos realizados en condiciones de estampación en caliente. Un sistema de prueba biaxial novela en el plano fue diseñado y utilizado para la determinación de la formación de límites de metales de hoja en varios caminos de deformación, las temperaturas y velocidades de deformación después del calentamiento y de enfriamiento procesos en una resistencia de calentamiento máquina de ensayo uniaxial. La parte central del sistema de ensayo biaxial es un aparato biaxial, que transfiere una fuerza uniaxial proporcionada por la máquina de ensayo uniaxial a una fuerza biaxial. Un tipo de espécimen cruciformes fue diseñado y verificado para la prueba de capacidad de conformación de la aleación de aluminio 6.082 usando el sistema de ensayo biaxial propuesto. El IM DIGITALSe utilizó el sistema de la edad de correlación (DIC) con una cámara de alta velocidad para la toma de medidas de deformación de una muestra durante una deformación. El objetivo de proponer este sistema de ensayo biaxial es permitir a los límites de formación de una aleación que se determinen a diversas temperaturas y velocidades de deformación en condiciones de estampación en caliente.

Desde flds son altamente dependiente de la trayectoria de deformación, la linealidad de la trayectoria de deformación para cada condición de ensayo se verificó mediante el análisis de los resultados DIC; las trayectorias de tensión son proporcionales a lo largo de deformación para cada condición de ensayo. El rango de la relación de deformación-menor a mayor es de aproximadamente -0,37 (condición uniaxial) a 0,26 (cerca de condición biaxial). Mediante el procesamiento de dato...

Watch this Scientific Journal Video about A Novel Biaxial Testing Apparatus for the Determination of Forming Limit under Hot Stamping Conditions at JoVE.com

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

Este protocolo propone un nuevo sistema de pruebas biaxial utilizado en una resistencia de calentamiento de la máquina de ensayo de tracción uniaxial con el fin de determinar el diagrama de la formación de límite (FLD) de láminas de metal en condiciones de estampación en caliente.

Un nuevo aparato de ensayo biaxiales para la Determinación del límite de conformación bajo estampación en caliente Condiciones

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 vistas.  Imperial College London.  Este protocolo propone un nuevo sistema de pruebas biaxial utilizado en una resistencia de calentamiento de la máquina de ensayo de tracción uniaxial con el fin de determinar el diagrama de la formación de límite (FLD) de láminas de metal en condiciones de estampación en caliente. 

Video: 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.

Deformación de alta presión, alta temperatura experimento utilizando el Griggs-tipo aparato de nueva generación

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 ...

Investigación

Medio ambiente

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 experimentales para procesos de enfriamiento Elastocaloric Investigación de memoria de forma basada y validación del modelo

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

Ingeniería

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.

Basada en el Conocimiento de la simulación de la nube FE de los Procesos de conformado de chapa 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.

Procedimiento experimental para hacer girar caliente de fundición, componentes de aluminio

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.

Fatiga ultrasónica prueba en el modo de tensión-compresión

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.

Elevada temperatura Normal y combinado de la presión de corte placa impacto experimentos mediante un sistema de calentador de Sabot de nalgas-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.

Aplicación de aspectos de diseño en el desarrollo de la máquina de carga 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.

Biaxiales caracterizaciones mecánicas de válvulas auriculoventricular del corazón

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

Bioingeniería

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.

Microdisección en capas de valvas de válvula tricúspide para caracterización mecánica biaxial y cuantificación microestructural

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.