Name: a novel biaxial testing apparatus for the determination of forming limit under hot stamping conditions
Uploaded: 2017-04-04T12:30:00
Description: Watch this Scientific Journal Video about A Novel Biaxial Testing Apparatus for the Determination of Forming Limit under Hot Stamping Conditions at JoVE.com

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. Preparation of Specimens
<ol>
	<li>Machine flat dog-bone and cruciform specimens from commercial material aluminum alloy 6082 (AA6082) using a laser cutter and a computer numerical control (CNC) milling machine (for formability tests at different strain paths including uniaxial, plane strain, and equi-biaxial straining states).</li>
	<li>Measure the thickness of each cruciform specimen and each dog-bone specimen with a vernier caliper three times in the central gauge region and calculate the average values. Ensure t...

<ol>
	<li>Karbasian, H., Tekkaya, A. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+review+on+hot+stamping.">A review on hot stamping.</a> J. of Mater. Process. Tech. 210 (15), 2103-2118 (2010).</li><li>Miller, W. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+development+in+aluminium+alloys+for+the+automotive+industry.">Recent development in aluminium alloys for the automotive industry.</a> Mater. Sci. and Eng. 280 (1), 37-49 (2000).</li><li>Shao, Z., Li, N., Lin, J., Dean, T. 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A. 10 (1), 41-46 (1979).</li><li>Shao, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+investigation+of+forming+limit+curves+and+deformation+features+in+warm+forming+of+an+aluminium+alloy.">Experimental investigation of forming limit curves and deformation features in warm forming of an aluminium alloy.</a> P. I. Mech. Eng. B-J. Eng. , (2016).</li><li>Marciniak, Z., Kuczynski, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Limit+strains+in+the+processes+of+stretch-forming+sheet+metal.">Limit strains in the processes of stretch-forming sheet metal.</a> Int. J. Mech. Sci. 9 (9), 609-620 (1967).</li><li>Li, D., Ghosh, A. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biaxial+warm+forming+behavior+of+aluminum+sheet+alloys.">Biaxial warm forming behavior of aluminum sheet alloys.</a> J. of Mater. Process. Tech. 145 (3), 281-293 (2004).</li><li>Palumbo, G., Sorgente, D., Tricarico, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+design+of+a+formability+test+in+warm+conditions+for+an+AZ31+magnesium+alloy+avoiding+friction+and+strain+rate+effects.">The design of a formability test in warm conditions for an AZ31 magnesium alloy avoiding friction and strain rate effects.</a> Int. J. Mach. Tool. Manu. 48 (14), 1535-1545 (2008).</li><li>Raghavan, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+simple+technique+to+generate+in-plane+forming+limit+curves+and+selected+applications.">A simple technique to generate in-plane forming limit curves and selected applications.</a> Metall. Mater. Trans. A. 26 (8), 2075-2084 (1995).</li><li>Ragab, A. R., Baudelet, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Forming+limit+curves:+out-of-plane+and+in-plane+stretching.">Forming limit curves: out-of-plane and in-plane stretching.</a> J. Mech. Work. Technol. 6 (4), 267-276 (1982).</li><li>Fan, X. -. b., He, Z. -. b., Zhou, W. -. x., Yuan, S. -. j. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Formability+and+strengthening+mechanism+of+solution+treated+Al-Mg-Si+alloy+sheet+under+hot+stamping+conditions.">Formability and strengthening mechanism of solution treated Al-Mg-Si alloy sheet under hot stamping conditions.</a> J. of Mater. Process. Tech. 228, 179-185 (2016).</li><li>Zidane, I., Guines, D., L&#233;otoing, L., Ragneau, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+an+in-plane+biaxial+test+for+forming+limit+curve+(FLC)+characterization+of+metallic+sheets.">Development of an in-plane biaxial test for forming limit curve (FLC) characterization of metallic sheets.</a> Meas. Sci. Technol. 21 (5), 055701 (2010).</li><li>Hannon, A., Tiernan, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+review+of+planar+biaxial+tensile+test+systems+for+sheet+metal.">A review of planar biaxial tensile test systems for sheet metal.</a> J. of Mater. Process. Tech. 198 (1-3), 1-13 (2008).</li><li>Garrett, R., Lin, J., Dean, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+investigation+of+the+effects+of+solution+heat+treatment+on+mechanical+properties+for+AA+6xxx+alloys:+experimentation+and+modelling.">An investigation of the effects of solution heat treatment on mechanical properties for AA 6xxx alloys: experimentation and modelling.</a> Int. J. Plasticity. 21 (8), 1640-1657 (2005).</li><li>Milkereit, B., Wanderka, N., Schick, C., Kessler, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Continuous+cooling+precipitation+diagrams+of+Al-Mg-Si+alloys.">Continuous cooling precipitation diagrams of Al-Mg-Si alloys.</a> Mater. Sci. Eng. A. 550, 87-96 (2012).</li><li>Crammond, G., Boyd, S. W., Dulieu-Barton, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Speckle+pattern+quality+assessment+for+digital+image+correlation.">Speckle pattern quality assessment for digital image correlation.</a> Opt. Laser. Eng. 51 (12), 1368-1378 (2013).</li></ol>

Conventional formability test methods used to determine forming limits are usually applicable only at room temperature. The presented technique can be used to evaluate the formability of metals for hot sheet stamping applications by introducing a novel biaxial testing apparatus to a resistance heating uniaxial testing machine. This cannot be performed using conventional methods for hot stamping applications. The setup of heating and cooling systems and the DIC system is critical to controlling the uniformity of temperatu...

The automotive industry is facing a huge global challenge of reducing fuel consumption and minimizing environmental pollution from vehicle emissions. Weight reduction is beneficial to improving the performance of automobiles and can directly reduce energy consumption1. Due to the low formability of sheet metals at room temperature, hot stamping and cold die quenching processes (referred to as hot stamping)2 are used to improve the formability of alloys and thus to obtain complex shaped components in automotive applications.
A forming limit diagram (FLD) is a useful tool to evaluate the formability of an alloy3. Out-of-plane tests, such as the Nakazima test4,5, and in-plane tests, such as the Marciniak test6,7,8, are conventional experimental methods to obtain the FLDs of sheet metals under various conditions9,10,11. A servo-hydraulic biaxial testing machine has also been used to investigate the formability of alloys at room temperature12,13.
However, none of the methods above are applicable to formability tests under hot stamping conditions, since a cooling process prior to forming is required along with control of the heating and cooling rates. The deformation temperature and strain rate are difficult to obtain accurately. Therefore, a novel formability testing system is proposed in this study to experimentally determine the forming limits of sheet metals under hot stamping conditions.

<table border="0" cellpadding="0" cellspacing="0" width="923">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Aluminium Alloy&#160;</td>
			<td style="width:152px;">Smiths Metal</td>
			<td style="width:121px;">6082</td>
			<td style="width:421px;">Specimens machining</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Laser cutter</td>
			<td style="width:152px;">LVD Ltd</td>
			<td style="width:121px;">HELIUS 25/13</td>
			<td>Laser cutting specimens</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">CNC machine</td>
			<td style="width:152px;">HAAS Automation</td>
			<td style="width:121px;">TM-2CE</td>
			<td>Machine specimens by milling</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Vernier caliper</td>
			<td style="width:152px;">Mitutoyo</td>
			<td style="width:121px;">575-481</td>
			<td>Thickness measurement</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:229px;">Resistance heating uniaxial testing machine</td>
			<td style="width:152px;">Dynamic System Inc</td>
			<td style="width:121px;">Gleeble 3800</td>
			<td>Thermo-mechanical materials simulator</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">High flow quench system</td>
			<td style="width:152px;">Dynamic System Inc</td>
			<td style="width:121px;">38510</td>
			<td>For air cooling</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Thermocouples</td>
			<td style="width:152px;">Dynamic System Inc</td>
			<td style="width:121px;">K type</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Nozzles</td>
			<td style="width:152px;">Indexa</td>
			<td style="width:121px;"></td>
			<td>Nozzle flared 1/4 inch bore</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Welding cables</td>
			<td style="width:152px;">LAPP Group</td>
			<td style="width:121px;">H01N2-D</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">High-speed camera</td>
			<td style="width:152px;">Photron</td>
			<td style="width:121px;">UX50</td>
			<td>For DIC testing</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Camera lens</td>
			<td style="width:152px;">Nikon</td>
			<td style="width:121px;">Micro 200mm</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Lamp</td>
			<td style="width:152px;">Liliput</td>
			<td style="width:121px;">150ce</td>
			<td>300W</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Laptop</td>
			<td style="width:152px;">HP</td>
			<td style="width:121px;">Campaq 2530p</td>
			<td>For images recording</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:229px;">Biaxial testing apparatus</td>
			<td style="width:152px;">Manufactured independently</td>
			<td style="width:121px;"></td>
			<td style="width:421px;">All parts were designed and machinced by authors for biaxial testing</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:229px;">Steel&#160;</td>
			<td style="width:152px;">West Yorkshire Steel</td>
			<td style="width:121px;">H13</td>
			<td style="width:421px;">Mateials of the biaxial testing apparatus</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:229px;">Image correlation processing software</td>
			<td style="width:152px;">GOM</td>
			<td style="width:121px;">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

The hot stamping and cold die quenching process is increasingly used to form complex shaped structural components of sheet metals. Conventional experimental approaches, such as out-of-plane and in-plane tests, are not applicable to the determination of forming limits when heating and rapid cooling processes are introduced prior to forming for tests conducted under hot stamping conditions. A novel in-plane biaxial testing system was designed and used for the determination of forming limits of sheet metals at various strain paths, temperatures, and strain rates after heating and cooling processes in a resistance heating uniaxial testing machine. The core part of the biaxial testing system is a biaxial apparatus, which transfers a uniaxial force provided by the uniaxial testing machine to a biaxial force. One type of cruciform specimen was designed and verified for the formability test of aluminum alloy 6082 using the proposed biaxial testing system. The digital image correlation (DIC) system with a high-speed camera was used for taking strain measurements of a specimen during a deformation. The aim of proposing this biaxial testing system is to enable the forming limits of an alloy to be determined at various temperatures and strain rates under hot stamping conditions.

Since FLDs are highly strain path-dependent, the linearity of the strain path for each test condition was verified by analyzing the DIC results; the strain paths are proportional throughout deformation for each test condition. The range of the minor-to-major strain ratio is approximately -0.37 (uniaxial condition) to 0.26 (near biaxial condition). By processing data for different AA6082 conditions, forming limit data for different strain paths were determined and hence, the FLDs for AA608...

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

This protocol proposes a novel biaxial testing system used on a resistance heating uniaxial tensile test machine in order to determine the forming limit diagram (FLD) of sheet metals under hot stamping conditions.

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

The overall goal of this experiment is to determine the forming limits of sheet metals under hot stamping conditions through the use of a novel biaxial texting system. The main advantages of this technique is that it enables forming limits of sheet metals to be determined experimentally and accomplish forming conditions. Generally conventional formability tests are not applicable to hot stamping for two reasons.First, the cooling process occurs prior to deformation and the second, controlling the forming parameters is very difficult. We were the first in the field to have the idea of using a novel biaxial testing system to measure forming limits and the complex forming conditions. For a formability test, set different strain paths including uniaxial plain strain and equibiaxial straining states.Machine flat and dog bone cruciform specimens from commercial material aluminum alloy 6082. Use a laser cutter and a computer controlled milling machine. From each specimen, take the average of three thickness measurements made with vernier calipers or micrometers at each specimen's central gauge region.The cruciform specimen should measure 0.7 millimeters plus and minus five microns and the uniaxial specimen should measure 1.5 millimeters plus and minus 10 microns. Now, spray paint the entire top surface of a cruciform specimen with one coat of flame resistant black spray paint. The paint must withstand temperatures in excess of 1, 000 degrees Celsius.After the paint dries, use white flame resistant spray paint to add dots for recognition by the DIC system. Spray from one arm's length away to create a stochastic pattern. Then weld a pair of thermal couples to the center of the unpainted back surface.First, assemble all parts of the biaxial testing apparatus including a base plate, a central shaft, input and output rotatable plates, carriages, a clamp, guide rails, and rigid connecting rods. Next, attach four welding cables to each pair of stainless steel and copper grips. Thus, connect the welding cables to the electrical power supply.Now secure the grips of the biaxial testing apparatus in the uniaxial tensile test machine, and for added security, attach the apparatus with bolts to the topside, and to the bottom side of the base plate. Now load the specimen onto the specimen holders of the test apparatus and connect the thermal couples to the feedback temperature control system of the testing machine to monitor and control the temperature. Next, set up the heating and quenching system.Connect each terminal of the welding cables to each clamping region of the specimen. Then, tighten each clamping region to the top plate which serves as the electrode for resistance heating. For cooling, connect hoses with flared nozzles to a high flow quench system.Set the system to produce an air pressure of 8, 000 kilograms per square meter. Now, position four nozzles to move air from the specimen's arms to its central region. Be sure to position the nozzles so they are not blocking the camera's view of the central zone.Now, attach micro lens to the high speed camera of the DIC system and set it up to view the central zone. Then connect the camera to a laptop. Adjust the frame rate to the test according to the stretching strain.Plan to collect at least 200 frames of data per test. Set the capture resolution to 1, 280 by 1, 024. Now focus the camera on the gauge section with the lens parallel to the top surface of the specimen.For high strain tests point an additional 300 watt spotlight directly into the test chamber. To start the resistance heating uniaxial tensile test machine, click the triangular run button in the control software. Then start the camera using a trigger button so it records the deformation history.The specimen is now heat treated and stretched at the selected constant temperature and strain rate. Perform the tests at different strain paths consisting of uniaxial, plain strain, and biaxial states by adjusting the configuration of the biaxial testing apparatus. For uniaxial tests, disconnect the two opposed connecting rods and clamp a dog bone specimen to the apparatus.Then connect the welding cables and repeat the other preparatory steps. For plain strain state tests, fix two opposed carriages to the base plate with screw bolts. This restricts the deformation on the corresponding direction.Then proceed to collect data. Formability tests using the novel plain biaxial tensile testing system were conducted at the designated deformation temperatures and strain rates after the heating and cooling processes. A forming limit curve identifies the boundary between uniform deformation and the onset of plastic instability or diffuse necking which leads to failure.As the strain rate increased, the forming limit of the alloy increased. A monotonic increase in the forming limit from 370 to 510 degrees Celsius indicates that high formability of the alloy can be obtained at a higher temperature under hot stamping conditions. The three forming limit curves are quite close to each other.Thus, the sensitivity of the temperature dependence is larger for tension tension biaxial strain paths than for tension compression strain paths. After watching this video you should have a good understanding of how to set up an experiment and conduct the formability test at various temperatures and strain rates by using the proposed system. Following this procedure, forming limits of alloy sheet metals like magnesium alloy or boron steel, can also be melded in the hot stamping conditions.

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The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs and condition-based maintenance. These materials are adopted in a wide range of engineering applications, from aircraft and ship structures, to bridges, wind turbine blades, biomaterials and biomedical implants. Polymers are viscoelastic materials, and their response may be highly nonlinear and thus make it challenging to predict and monitor their in-service performance. The laboratory-scale testing platform presented herein assists the investigation of the influence of concurrent mechanical loadings and environmental conditions on these materials. The platform was designed to be low-cost and user-friendly. Its chemically resistant materials make the platform adaptable to studies of chemical degradation due to in-service exposure to fluids. An example of experiment was conducted at RT on closed-cell polyurethane foam samples loaded with a weight corresponding to ~50% of their ultimate static and dry load. Results show that the testing apparatus is appropriate for these studies. Results also highlight the larger vulnerability of the polymer under concurrent loading, based on the higher mid-point displacements and lower residual failure loads. Recommendations are made for additional improvements to the testing apparatus.

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Development of an Experimental Setup for the Measurement of the Coefficient of Restitution under Vacuum Conditions

The Discrete Element Method is used for the simulation of particulate systems to describe and analyze them, to predict and afterwards optimize their behavior for single stages of a process or even an entire process. For the simulation with occurring particle-particle and particle-wall contacts, the value of the coefficient of restitution is required. It can be determined experimentally. The coefficient of restitution depends on several parameters like the impact velocity. Especially for fine particles the impact velocity depends on the air pressure and under atmospheric pressure high impact velocities cannot be reached. For this, a new experimental setup for free-fall tests under vacuum conditions is developed. The coefficient of restitution is determined with the impact and rebound velocity which are detected by a high-speed camera. To not hinder the view, the vacuum chamber is made of glass. Also a new release mechanism to drop one single particle under vacuum conditions is constructed. Due to that, all properties of the particle can be characterized beforehand.

The coefficient of restitution is a parameter that describes the loss of kinetic energy during collision. Here, a free-fall setup under vacuum conditions is developed to be able to determine the coefficient of restitution parameter for particles in micrometer range with high impact velocities.

The Discrete Element Method is used for the simulation of particulate systems to describe and analyze them, to predict and afterwards optimize their ...

Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film synthesis) for the purpose of exploratory materials research. Certain materials pose a challenge wherein the traditional bulk Hall bar device fabrication method is insufficient to produce a measureable device for sample transport measurement, principally because the single crystal size is too small to attach wire leads to the sample in a Hall bar configuration. This can be, for example, because the first batch of a new material synthesized yields very small single crystals or because flakes of samples of one to very few monolayers are desired. In order to enable rapid characterization of materials that may be carried out in parallel with improvements to their growth methodology, a method of device fabrication for very small samples has been devised to permit the characterization of novel materials as soon as a preliminary batch has been produced. A slight variation of this methodology is applicable to producing devices using exfoliated samples of two-dimensional materials such as graphene, hexagonal boron nitride (hBN), and transition metal dichalcogenides (TMDs), as well as multilayer heterostructures of such materials. Here we present detailed protocols for the experimental device fabrication of fragments and flakes of novel materials with micron-sized dimensions onto substrate and subsequent measurement in a commercial superconducting magnet, dry helium close-cycle cryostat magnetotransport system at temperatures down to 0.300 K and magnetic fields up to 12 T.

We describe the methodology of mechanical exfoliation and deposition of flakes of novel materials with micron-sized dimensions onto substrate, fabrication of experimental device structures for transport experimentation, and the magnetotransport measurement in a dry helium close-cycle cryostat at temperatures down to 0.300 K and magnetic fields up to 12 T.

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film ...

Spark Plasma Sintering Apparatus Used for the Formation of Strontium Titanate Bicrystals

A spark plasma sintering apparatus was used as a novel method for diffusion bonding of two single crystals of strontium titanate to form bicrystals with one twist grain boundary. This apparatus utilizes high uniaxial pressure and a pulsed direct current for rapid consolidation of material. Diffusion bonding of strontium titanate bicrystals without fracture, in a spark plasma sintering apparatus, is possible at high pressures due to the unusual temperature dependent plasticity behavior of strontium titanate. We demonstrate a method for the successful formation of bicrystals at accelerated time scales and lower temperatures in a spark plasma sintering apparatus compared to bicrystals formed by conventional diffusion bonding parameters. Bond quality was verified by scanning electron microscopy. A clean and atomically abrupt interface containing no secondary phases was observed using transmission electron microscopy techniques. Local changes in bonding across the boundary was characterized by simultaneous scanning transmission electron microscopy and spatially resolved electron energy-loss spectroscopy.

A viable technique for the formation of strontium titanate bicrystals at high pressure and fast heating rate via the spark plasma sintering apparatus is developed.

A spark plasma sintering apparatus was used as a novel method for diffusion bonding of two single crystals of strontium titanate to form bicrystals with ...

In Situ Visualization of the Phase Behavior of Oil Samples Under Refinery Process Conditions

To help address production issues in refineries caused by the fouling of process units and lines, we have developed a setup as well as a method to visualize the behavior of petroleum samples under process conditions. The experimental setup relies on a custom-built micro-reactor fitted with a sapphire window at the bottom, which is placed over the objective of an inverted microscope equipped with a cross-polarizer module. Using reflection microscopy enables the visualization of opaque samples, such as petroleum vacuum residues, or asphaltenes. The combination of the sapphire window from the micro-reactor with the cross-polarizer module of the microscope on the light path allows high-contrast imaging of isotropic and anisotropic media. While observations are carried out, the micro-reactor can be heated to the temperature range of cracking reactions (up to 450 &#176;C), can be subjected to H2 pressure relevant to hydroconversion reactions (up to 16 MPa), and can stir the sample by magnetic coupling. 
Observations are typically carried out by taking snapshots of the sample under cross-polarized light at regular time intervals. Image analyses may not only provide information on the temperature, pressure, and reactive conditions yielding phase separation, but may also give an estimate of the evolution of the chemical (absorption/reflection spectra) and physical (refractive index) properties of the sample before the onset of phase separation.

In Situ Visualization of the Phase Behavior of Oil Samples Under Refinery Process Conditions

This article describes a setup and method for the in situ visualization of oil samples under a variety of temperature and pressure conditions that aim to emulate refining and upgrading processes. It is primarily used for studying isotropic and anisotropic media involved in the fouling behavior of petroleum feeds.

To help address production issues in refineries caused by the fouling of process units and lines, we have developed a setup as well as a method to ...

Subsurface Defect Localization by Structured Heating Using Laser Projected Photothermal Thermography

The presented method is used to locate subsurface defects oriented perpendicularly to the surface. To achieve this, we create destructively interfering thermal wave fields that are disturbed by the defect. This effect is measured and used to locate the defect. We form the destructively interfering wave fields by using a modified projector. The original light engine of the projector is replaced with a fiber-coupled high-power diode laser. Its beam is shaped and aligned to the projector&#39;s spatial light modulator and optimized for optimal optical throughput and homogeneous projection by first characterizing the beam profile, and, second, correcting it mechanically and numerically. A high-performance infrared (IR) camera is set up according to the tight geometrical situation (including corrections of the geometrical image distortions) and the requirement to detect weak temperature oscillations at the sample surface. Data acquisition can be performed once a synchronization between the individual thermal wave field sources, the scanning stage, and the IR camera is established by using a dedicated experimental setup which needs to be tuned to the specific material being investigated. During data post-processing, the relevant information on the presence of a defect below the surface of the sample is extracted. It is retrieved from the oscillating part of the acquired thermal radiation coming from the so-called depletion line of the sample surface. The exact location of the defect is deduced from the analysis of the spatial-temporal shape of these oscillations in a final step. The method is reference-free and very sensitive to changes within the thermal wave field. So far, the method has been tested with steel samples but is applicable to different materials as well, in particular to temperature sensitive materials.

This method aims at locating vertical subsurface defects. Here, we couple a laser with a spatial light modulator and trigger its video input to heat a sample surface deterministically with two anti-phased modulated lines while acquiring highly resolved thermal images. The defect position is retrieved from evaluating thermal wave interference minima.

The presented method is used to locate subsurface defects oriented perpendicularly to the surface. To achieve this, we create destructively interfering ...

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and forging. Adoption of this technique is proceeding despite disagreement concerning the underlying mechanism responsible for EAD. The experimental procedure described herein enables a more explicit study compared to previous EAD research by removing thermal effects, which are responsible for disagreement in interpreting previous EAD results. Furthermore, as the procedure described here enables EAD observation in situ and in real time in a transmission electron microscope (TEM), it is superior to existing post-mortem methods that observe EAD effects post-test. Test samples consist of a single crystal copper (SCC) foil having a free-standing tensile test section of nanoscale thickness, fabricated using a combination of laser and ion beam milling. The SCC is mounted to an etched silicon base that provides mechanical support and electrical isolation while serving as a heat sink. Using this geometry, even at high current density (~3,500 A/mm2), the test section experiences a negligible temperature increase (&#60;0.02 &#176;C), thus eliminating Joule heating effects. Monitoring material deformation and identifying the corresponding changes to microstructures, e.g. dislocations, are accomplished by acquiring and analyzing a series of TEM images. Our sample preparation and in situ experiment procedures are robust and versatile as they can be readily utilized to test materials with different microstructures, e.g., single and polycrystalline copper.

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Isolating electrical and thermal effects on electrically assisted deformation (EAD) is very difficult using macroscopic samples. Metallic sample micro- and nanostructures together with a custom test procedure have been developed to evaluate the impact of applied current on the formation without joule heating and evolution of dislocations on these samples.

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and ...