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.试样的制备<ol><li>机平坦狗骨和使用激光切割机和一个计算机数字控制（CNC）铣床（对于在不同的应变路径包括单轴，平面应变成形性试验从市售材料的铝合金6082（AA6082）十字形标本和等双轴应变状态）。 </li><li>测量每个十字形试和每个狗骨样品的厚度用游标卡尺三次在中央计区域，并计算平均值。确保在一个十字形试测量部分的厚度为0.7±0.05mm与该单轴试样的厚度为1.5±0.1毫米。 </li><li>通过使用耐火，黑色喷漆（能够承受的温度高达1093℃下的）喷漆十字形样品的整个顶表面。等到油漆变干，然后从手臂的长度来创建一个随机喷洒阻燃，白色油漆点喷雾图案由DIC系统识别（参见图1中的例子）。 </li><li>焊接的一对热电偶到后表面的中心（相对的涂漆的表面）的样品的。将热电偶连接到单轴试验机的反馈温度控制系统的另一端，以监视和控制的温度变化的历史。 </li></ol> 2.双轴试验设备的组装<ol><li>组装该双轴测试装置的所有部分，包括一个底板，一个中心轴，输入和输出可旋转板，车厢，夹具，导轨，和刚性的连接杆（组装装置示于图2）。 <ol><li>输入可旋转板直接使用连接杆，连接到电阻加热单轴拉伸试验机，它提供了单轴拉伸力的可动夹爪。耦合输入可旋转板的中心驱动轴和夫妇该中心驱动轴与输出可旋转板。 </li><li>确保围绕旋转轴线的可旋转输入盘的旋转而旋转的驱动轴，从而旋转输出旋转板其所围绕旋转轴线被耦合。 </li><li>在一个端部，一对每个刚性连接杆对输出可旋转板连接点中的一个的。夫妇的另一端连接到车厢中的一个。 注意:这将引起车厢与试样保持器滑动来回沿导轨以低摩擦，这可以应用双轴力到十字形样品。 </li><li>使用螺栓，所述十字形样品的每个臂夹紧到与试样保持器和顶板的滑架。 </li></ol></li><li>在单轴拉伸试验机的腔室设置把手， 如图3（a）中 。将四个焊接电缆到每对夹具的，这是由不锈钢和铜，respe沉着应对，因此，焊接电缆连接到电源。 注意:所述焊接电缆的导体面积为50mm 2和电流额定值是345 A. <ol><li>把夹具和双轴测试设备到单轴拉伸试验机的两个夹具的夹具和他们的内部拧紧（ 图3（a））。 </li></ol></li><li>在单轴拉伸试验机的腔室设置双轴测试装置， 如图3（b）中 。 <ol><li>使用两个帧，并且在顶部螺栓与底板的底侧固定装置在单轴拉伸试验机的腔室。 </li><li>把样品插入到样品支架上的双轴测试装置的顶部。 </li><li>所述焊接电缆的每个端子连到检查体的每个夹紧区域。 </li></ol></li></ol> 3.加热淬火系统的设置<ol><li>紧密合作nnect试样的每个夹紧区域到不锈钢顶板，其用作电阻加热的电极。 </li><li>拧紧与压接环端子焊接电缆连接到每个夹紧区域的顶板。 </li><li>连接在8000公斤/米2的压力，用于冷却喇叭形与软管喷嘴与调节的空气供给高流量骤冷系统。 </li><li>使用四个喷嘴以从试样的臂吹送空气到样本的中心区域。 注:喷嘴不引导到测量部分，用于冷却以避免阻塞从相机的视图中的中央区域。 </li></ol> 4. DIC系统的设置<ol><li>该DIC系统的高速相机连接用微透镜到计算机。调整相机的帧速率，以每秒25帧，50帧，并且从帧速率的菜单（用于以0.01 / s时，0.1 / s和1 / s时，分别在拉伸应变速率下测试）500帧。将所有我的决议法师到1280×1024像素。 注:帧速率取决于数据点收集的数量;至少200个数据点可以使用上述的设置来收集。 </li><li>使用一个额外的聚光灯下300 W的在高应变率测试电源。直接在单轴拉伸试验机的腔室指向聚光灯。 </li><li>调整相机镜头，使得它平行于所述室中的样品的顶部表面和聚焦相机上的测量部分。 </li></ol> 5.实验计划<ol><li>运行阻力通过点击在控制软件的三角运行按钮加热单轴拉伸试验机。 注:电力贯穿AA6082材料和以30℃/秒的加热速率加热到49的535°C 14的固溶热处理温度。该材料在535℃下浸泡1分钟，这是足够的析出物的全分辨率。嗳ř从急冷系统吹用于在在370-510℃的范围内100℃/秒15到一个3指定升高的温度下的冷却速度，淬灭材料。 </li><li>伸展用双轴测试装置试样在0.01-1 /秒的范围内的恒定应变速率和通过手动按压连接到高速照相机触发按钮记录变形历史。 注:从单轴试验机的输入位移双轴试验装置由单轴试验机的内置软件控制。 </li><li>在由单轴不同应变路径，平面应变，和双轴应变状态3通过调整双轴测试装置的结构进行测试。 <ol><li>断开单轴测试两个相对的连接杆。夹紧在双轴测试装置狗骨样品，并将其连接到焊接电缆，如在步骤3.1-3。4.重复步骤5.1-5.2。 </li><li>固定两个相对的滑架与螺栓的底板，以限制对平面应变状态下的检测相应的方向上的变形。夹紧在双轴测试装置十字形样品，并将其连接到焊接电缆，如步骤3.1-3.4。重复步骤5.1-5.2。 </li></ol></li><li>对于每个测试条件重复步骤5.3.1-5.3.2三次，使用新的狗骨和十字形标本。 </li></ol> 6.数据处理<ol><li>导入由高速照相机记录到后处理软件的所有图像和根据软件手册遵循标准步骤进行数据分析。 </li><li>使用ISO标准3，以确定通过点击软件的FLC模式按钮形成限制。 注:此方法已经被集成到图像相关处理软件。 </li><li>标记在不同温度下的成形限制每个结果在图中S，应变率，和应变路径。 </li><li>绘制在所有测试条件下的成形极限曲线，得到的合金的FLD热冲压条件下进行。 </li></ol>

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The authors have nothing to disclose.

用于确定成形限制常规的成形性的测试方法是通常只在室温下适用。所呈现的技术可用于通过引入新颖的双轴测试设备到电阻加热单轴试验机来评价金属用于热片冲压应用的可成形性。这可以不使用用于热冲压应用的常规方法来进行。加热和冷却系统和DIC系统的设置是为了控制在样品温度分布的均匀性，并因此记录拉伸试样的变形历史的关键。 在该技术中，加热和冷却速率?...

汽车行业正面临着降低燃油消耗和车辆排放减少环境污染的一个巨大的全球性挑战。轻量化对提高汽车的性能是有益的，并且可以直接降低能耗1。由于金属板在室温下，热冲压和冷模淬火工艺低的可成形性（称为热冲压）2用于改进合金的成形性并因此获得在汽车应用中复杂形状的部件。 成形极限图（FLD）是评价的合金3的成形性的有用工具。外的平面的测试，如测试Nakazima 4， 图5和面内测试，如测试Marciniak 6，7，8，一个再常规的实验方法，以获得各种条件9，10，11下的金属板的成形极限。甲伺服液压双轴测试机也已经用于研究合金在室温下12，13中的可成形性。 然而，没有上述方法适用于热冲压条件下的可成形性的测试中，因为与加热和冷却速率的控制一起，需要成形之前的冷却过程。变形温度和应变速率很难获得准确。因此，一种新的成形性的测试系统是在本研究中提出的通过实验来确定片材金属的热冲压条件下成形极限。

<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

热冲压和冷模淬火工艺越来越多地用于形成金属片的复杂形状的结构部件。常规的实验方法，如外的平面和平面内的测试中，并不适用于加热和快速冷却处理之前形成用于热冲压条件下进行测试时引入成形极限的确定。一种新颖的平面内双轴测试系统的设计和用于形成在电阻加热单轴试验机加热和冷却过程后的不同应变路径，温度和应变率的金属板的限制的确定。双轴测试系统的核心部分是一个双轴设备，其传送由单轴试验机提供到双轴力的单轴力。十字形样品的一种类型被设计和验证的使用提出的双轴测试系统铝合金6082的成形性试验。数字IM使用年龄相关性（DIC）系统用高速照相机对变形期间采取的试样的应变测量。提出该双轴测试系统的目的是使合金的成形极限，在热冲压条件下各种温度和应变速率来确定。

由于成形极限是高度应变路径依赖性的，对于每个测试条件下的应变路径的线性通过分析DIC结果验证;应变路径是整个变形对于每个测试条件成比例的。次要到主应变比的范围是约-0.37（单轴条件）至0.26（近双轴条件）。通过处理用于不同AA6082条件的数据，形成用于不同应变路径限制数据被确定并且因此，是通过曲线拟合获得的热冲压条件AA6082的成形极限。在图3</stro...

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

该协议提出上的电阻，以确定热冲压条件下的金属板的成形极限图（FLD）加热单轴拉伸试验机中使用的新颖的双轴测试系统。

一种新型双轴试验设备的成形极限的下烫印条件的决定

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 次观看.  Imperial College London. 该协议提出上的电阻，以确定热冲压条件下的金属板的成形极限图（FLD）加热单轴拉伸试验机中使用的新颖的双轴测试系统。 

视频: 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.

新一代格雷型装置高压高温变形试验

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 ...

科研

环境科学

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.

基于形状记忆调查Elastocaloric冷却过程和模型验证实验方法

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

工程学

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.

板料成形过程的知识基于云的有限元模拟

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.

铸铝零部件的暖纺纱实验程序

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.

拉伸压缩模式下的超声疲劳试验

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.

采用臀端穿甲弹加热系统进行高温常压联合压力-剪切板冲击试验

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.

设计方面在单轴加载机开发中的应用

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.

房室心脏瓣膜的双轴力学特性

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

生物工程

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.

三尖瓣瓣叶的层显微切割，用于双轴力学表征和微观结构定量

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.