We thank Dr. K. C. Yang in the China-Steel Company for material support and wish to express our gratitude to Mr. L.D. Wang, C. K. Wang, and B. Y. Hong at the MIRDC for assistance with the experimental FSSW. This research was supported by the Metal Industries Research and Development Centre, Kaohsiung, Taiwan, ROC.

1. Material preparation
NOTE: Machine the 1.6 mm thick DP780 sheets into 40 mm x 125 mm coupons. The FSSW joints are designed as lap shear specimens for the mechanical tests. Join two 125 mm by 40 mm sheets with a 35 mm by 40 mm overlap following RSW standard NF ISO 18278-2; 2005. A geometry design polycrystalline diamond tool with a truncated cone shoulder. The geometry design is shown in Figure 1a. The diameter of the pin is 5 mm; the length is 2.5 mm, and the shoulder width is 10 mm. The real tool pin is shown in Figure 1b.
<ol>
	<li>Safety guidelines
	<ol>
		<li>Use devices such as a hood or baffle, goggles, and gloves for protection.</li>
		<li>Stand behind the hood or the baffle. Wear goggles and gloves to prevent splash contact or heat damage.</li>
	</ol>
	</li>
	<li>FSSW machine setting
	<ol>
		<li>Manufacture all joints using an MIRDC-made friction stir welder machine.</li>
		<li>Record the Z axial force and penetration depth during each joining operation using the embedded data acquisition (DAQ) system.</li>
	</ol>
	</li>
	<li>Parameter settings
	<ol>
		<li>In this study, use the following parameters: a tool pin rotation speed of 2,500 rpm, 4 s of tool pin dwell time, and a rate pf 0.5 mm/s of tool pin plunge into the sheet.</li>
		<li>Optimize the parameters for the operator. The range of the rotation speed is 1,000- 2,500 rpm. The range of the dwell time can be from 2-10 s, and the plunge rate can be 0.1-0.5 mm/s.</li>
	</ol>
	</li>
</ol>
2. Procedure
NOTE: The work space is shown in Figure 2. All the manufacturing procedures are completed in the work space. Before the procedure, the welding process sequences are comprised of a combination of tool rotations and penetration depths, as well as a series of sequences including preheating, plunging, dwelling, retracting, and post heating. All steps are shown in Figure 3 in the form of a work flowchart.
<ol>
	<li>DP780 workpiece preparation
	<ol>
		<li>Before the welding process, ensure that there are no impurity substrates contaminating the workpieces. Use knitted micro-fiber fabrics to wipe the surface of the workpiece to eliminate any small particles.</li>
	</ol>
	</li>
	<li>Place the DP780 workpiece, and clamp 2 DP780 sheets (size: 125 mm x 40 mm) with an overlap of 35 mm. Fix the clean workpieces on an anvil to prevent shifting.</li>
	<li>Ensure that the pin is clean to prevent impure substrate contamination. Use knitted microfiber fabrics to wipe the surface of the tool pin to eliminate small particles.</li>
	<li>Fix the pin with a clamp on the machine.
	<ol>
		<li>Screw on the tool pin tightly again for tool pin clamping.</li>
		<li>Pay attention to the pin clamping step. Ensure that the pin is clamped tight in the machine to avoid danger. The rotating tool is surrounded by a nonrotating clamping ring with which the workpieces are pressed firmly against one another before and during welding by applying a clamping force. The illustration shown in Figure 3a notes the clamp ring used to fix the tool pin. After this step, the production is shown in the flowchart.</li>
		<li>Ensure safety.</li>
		<li>Confirm that the high-speed rotation pin without a clamp ring loosens. When the tool pin is placed on the machine, ensure that the tool pin does not separate from the clamp during rotation for safety reasons. The tool pin uses a low rotation rate from 10 to 100 rpm in 1 minute. The speed can accelerate from 100 to 1,000 rpm within 1 minute (Figure 3b).</li>
	</ol>
	</li>
	<li>Machine settings
	<ol>
		<li>Use the following parameters: a rotational speed of 3,000 rpm, a dwell of 4 s, and a plunge rate of 0.5 mm/s (Figure 3c).</li>
	</ol>
	</li>
	<li>Calibrate the welding location (Figure 3d and the real product shown in Figure 4a).
	<ol>
		<li>Set the pin in the stir spot welder machine. The gap between the pin and the workpiece is smaller than 5 cm to calibrate the joint location. After the location is confirmed, move onto the welding process.</li>
	</ol>
	</li>
	<li>During welding, wear goggles and gloves to avoid injury.
	<ol>
		<li>Begin the welding process with the tool under high-speed rotation to plunge the tool pin into the workpiece. The tool shoulder contacts the workpieces and stops the rotation and retracts the pin.</li>
	</ol>
	</li>
	<li>Plunging
	<ol>
		<li>Turn the stir button on. When the machine warms up, confirm that the tool pin is consistently operating at a 2,500 rpm rotation speed. Ensure that the tool pin is clamped well under the high-speed rotation at 2,500 rpm. The pin plunges into the workpieces under a high-speed rotation and the shoulder contacts the workpieces at a high angular speed (Figure 3e). The real product is shown in Figure 4b.</li>
	</ol>
	</li>
	<li>Stirring
	<ol>
		<li>As the plunged tool pin continues stirring in the workpiece, soften the interface of the pin and the material from the friction heat to create the grain. When the shoulder of the tool pin comes into contact with the top of the workpiece, stop the process because the high rotation of the tool pin can generate high temperatures. It is important to wear protective gear that ensures operational safety (see Figure 3f.) The real product is shown in Figure 4c.</li>
	</ol>
	</li>
	<li>Retracting
	<ol>
		<li>Draw out the tool pin in the vertical direction. After the procedure, the pin creates the key-hole welding spot in the lap joint. Note that the friction stir spot weld stops in this step (Figure 3g). The real product is shown in Figure 4e.</li>
	</ol>
	</li>
	<li>Remove the workpieces.
	<ol>
		<li>Turn off the machine power.</li>
		<li>After the welding is finished, remove the workpieces from the anvil. Observe the samples for cracks and lack of fusion.</li>
		<li>Remove the tool pin.</li>
		<li>After the procedure, remove the tool pin from the clamp ring. The appearance of the tool pin is observed and checked (Figure 5).</li>
	</ol>
	</li>
</ol>
3. Mechanical property evaluation
<ol>
	<li>Microscopy examination of the FSSW welds (Figure 3h)
	<ol>
		<li>Microscopic sample preparation</li>
		<li>Measure the cross-sectional area of the bonded region using an optical microscope image and a secondary electron image analysis. Prepare the microscopic samples using grounded silicon carbide paper with a grit size ranging from 200 to 2,000 starting with a grit size of 200 and increasing in sequence. Polish the samples with 0.03% alumina and etch with a 4% nital solution for 7&#8211;10 s at room temperature.</li>
		<li>Microscopy observation</li>
		<li>Observe and characterize the microstructures using optical microscopy and scanning electron microscopy. Use a voltage of 20 kV, and a working distance of 10 &#956;m. From the optical microscopy, any tiny crack line or lack of a fusion zone can be determined. Use scanning electron microscopy to analyze the martensite and austenite distribution and the grain size.</li>
	</ol>
	</li>
	<li>Microhardness
	<ol>
		<li>Verify the microhardness experiments more than 3 times. The values were too small to clearly denote the standard deviation.</li>
		<li>Press the Vickers diamond indenter with a 300 g test load sample and 0.5 mm per test.</li>
		<li>Conduct the microhardness testing of the DP780 steel sheet using a microhardness testing machine with a 300 g load and a holding time of 15 s. The microhardness testing revealed the hardness distribution and the individual hardness values in the stir zone, the thermomechanical affect zone, the heat affected zone, and in the base metal of the welds.</li>
	</ol>
	</li>
</ol>

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The authors have nothing to disclose.

The plunging stage is the most important during the FSSW process. Without enough friction heat coming from the shoulder of the pin to soften the workpiece, the pin will fracture. Tool geometry, rotation speed, dwell time, and tool penetration depth26 parameters of the FSSW process play a critical role in determining the joint integrity. TPD and tool geometry27 particularly have an important effect on the weldability and joint properties was reported.
The geometry of the pins were cylindrical, Whorl, MX Tri&#64258;ute, Flared-Tri&#64258;ute, A-skew, and Re-stir designed by TWI28. They are suitable for butt welding but not for lap welding because the tool motion and the welding torque can be reduced by the traversing force caused by the intense stirring. Flared-Tri&#64258;ute, A-skew, and Re-stir tool pins are suitable for lap welding; the design is intended to increase the swept volume of the pin in order to expand the stir region to form a wider worked lap joint29. Meanwhile, during FSSW, friction generates heat at the interface of the rotating tool and the work piece. The tool geometry and FSSW parameters affect the strength of the FSSW welds4. The tool shoulder and pin are the main parts of the FSSW tool5. The pin generates friction heat, deforms the material around it, and stirs the heated material6. The size7, angle8, thread orientation9, length10 and profile11 of the pin depends on nugget formation. Meanwhile the tool shoulder generates heat during the FSSW process, forges the heated material, prevents material expulsion, and assists material movement around the tool12. The size and concavity of the shoulder are also important factors in friction stir spot welding13.
The pin materials are comprised of the following components: 12% Cr steel, low carbon steel, Mo and W alloy, W alloy, polycrystalline cubic boron nitride (PCBN), and polycrystalline cubic boron. Because tool wear occurred in the plunging period at the initial stage of welding, tool deformation and rubbing wear could be found in the tool. This problem can be resolved by choosing a suitable material for the pin that is hard and can withstand elevated temperatures compared to the workpieces for increasing the tool lifetime. In our research, we used the polycrystal diamond to weld the workpiece.
The pin length and the penetration depth are also factors that can influence the maximum loading in the welding process. It has been indicated that there will be an increased tool penetration depth and decreased pin length, resulting in a higher2.
The rotation rate is an important factor that leads to pin friction on the workpieces to begin the welding process. A speed ranging from 300-1,000 rpm can be used to detect the peak temperature from approximately 430 to 470 &#176;C in the welding center zone. Far from the welding zone, the heat effect zone exhibited a decrease in temperature to 350 &#176;C for the Al alloy (6061Al-T6)30. From other references, the friction situation at a low rotation speed with a stick can transform to a stick/slip at high speeds. The rotation rate is the key factor leading to the generation of the heat necessary to forge the workpiece. In the past, studies have been focused on Al alloy. However, in our study, the focus is on DP steel. There is no test value by which to identify the temperature. However, based on the fact that the microstructure at the centerline exhibited fine grain martensite, it can be inferred that the substrate temperature exceeded the Ac3 standard.
The study of FSSW workpieces in the past has concentrated on aluminum alloys because low melting temperature in metal welding leads to deformities and low strength that require being fixed via FSSW. Since the FSSW was developed, different materials have been used, including lightweight steel. Different kinds of DP steel welded with Al alloys are new areas for investigation. Based on commercial applications, the FSSW can be a useful method for different component alloys used in industrial production due to savings in terms of both time and cost.

Friction stir welding (FSW) was first reported in 1991 at TWI, Abington, UK1. In 2003, Piccini and Svoboda determined a superior method of enhancing the advantages of FSW called friction stir spot welding (FSSW) for use in commercial automobile manufacturing processes2. The FSSW method involves creating a spot lap joint with no bulk area melting. The most important development for the use of FSSW has been in aluminum alloys as Al alloys deform in the welding process under high temperature conditions. The first successful example was in the automotive industry, where FSSW was used in manufacturing the entire rear door of the Mazda&#39;s RX-81,3,4.
Meanwhile, high strength steel is the dominant material of the car body, specifically dual phase steel. The literature indicates that DP600 produced with FSSW can have the same properties as the base metal, where all welding regions have similar microstructures and degrees of hardness5. FSSW methods for the use of DP steel on their microstructure of the stir zone (SZ), the thermos-mechanically affected zone (TMAZ), and the failure model of DP590 and DP600 steel have been studied by a few researchers. They observed differences in the consistency of the microstructure (ferrite, bainite, and martensite) of DP590 and DP600 steel at various rotation speeds6,7,8,9,10. Some researchers conducted comparative studies of FSSW and RSW for DP780 steel8,9. They reported that longer joining times and higher tool rotation speeds resulted in an increased bonding area for all plunges, which led to a higher shear force and shifted the mode from interfacial to pull out. They also concluded that FSSW had a higher strength than RSW. The FSSW process includes 3 steps: plunging, stirring, and retraction. The first step is plunging with a rotation tool pin close to the sheet of the lap joint and plugged into the sheet. The rotating tool shoulder in the FSSW process can generate frictional heat. In the second step, the heat can soften the sheet and facilitate plugging of the tool pin into the sheet, as well as dwell in the materials to stir two workpieces together and mix around the pin area. Finally, the pressure from the tool shoulder press on the workpieces can enhance the bonding. After the welding process, the pin can be retracted from the keyhole. The benefits of FSSW compared with RSW are a lower welding temperature, no splashing, and more stability in the manufacturing process.
Even though studies on the FSSW of advanced high-strength steels (AHSS) have been reported by various researchers, studies on the FSSW of DP590, DP600, and DP780 have focused on the microstructure and on the mechanical and failure models using various process parameters. In the present study, the FSSW of DP780 steel was considered. The protocol of the FSSW process was reported in detail, and the individual hardness in the stir zone, the thermos-mechanically affected zone, and the heat-affected zone, as well as the base metal were evaluated based on the measured microhardness.
With the continuous growth and heavy demand for weight reduction in the automotive and aerospace industries, the automotive industry has shown an increasing interest in AHSS and lap joints. For example, the conventional steel body of a car, on average, has more than 2,000 spot weld lap joints11. There are 3 common welding processes for lap joints used in the industry, including resistance spot welding, laser spot welding, and friction spot welding12. One way to decrease the weight is by using advanced high-strength steels (AHSS). The most popular materials are dual-phase and transformation-induced plasticity (TRIP) steels, which are being increasingly used in the automotive industry13,14,15,16. Because the automotive industry has increased the strength standards due to improved fuel consumption and crash energy absorption under a decreased vehicle weight, the use of different materials and welding processes is becoming an important issue.

<table>
	<tbody>
		<tr>
			<td>anvil</td>
			<td>MIRDC</td>
			<td></td>
			<td>made by MIRDC</td>
		</tr>
		<tr>
			<td>DP780</td>
			<td>China steel Corporation</td>
			<td>CSC DP780</td>
			<td></td>
		</tr>
		<tr>
			<td>stir spot welder machine</td>
			<td>MIRDC</td>
			<td></td>
			<td>made by MIRDC</td>
		</tr>
		<tr>
			<td>tool pin</td>
			<td>KINIK COMPANY</td>
			<td>DBN2B005B</td>
			<td></td>
		</tr>
	</tbody>
</table>

generating lap joints via friction stir spot welding on dp780 steel

Friction stir spot welding (FSSW), a derivative of friction stir welding (FSW), is a solid-state welding technique that was developed in 1991. An industry application was found in the automotive industry in 2003 for the aluminum alloy that was used in the rear doors of automobiles. Friction stir spot welding is mostly used in Al alloys to create lap joints. The benefits of friction stir spot welding include a nearly 80% melting temperature that lowers the thermal deformation welds without splashing compared to resistance spot welding. Friction stir spot welding includes 3 steps: plunging, stirring, and retraction. In the present study, other materials including high strength steel are also used in the friction stir welding method to create joints. DP780, whose traditional welding process involves the use of resistance spot welding, is one of several high strength steel materials used in the automotive industry. In this paper, DP780 was used for friction stir spot welding, and its microstructure and microhardness were measured. The microstructure data showed that there was a fusion zone with fine grain and a heat effect zone with island martensite. The microhardness results indicated that the center zone exhibited a greater degree of hardness compared with the base metal. All data indicated that the friction stir spot welding used in dual phase steel 780 can create a good lap joint. In the future, friction stir spot welding can be used in high-strength steel welding applied in industrial manufacturing processes.

There is a diagram in Figure 3 that demonstrates that the friction stir spot welding process is comprised of 3 parts: plunging (Figure 3e), stirring (Figure 3f), and retracting (Figure 3g). In our research, the welding spot could be generated. The penetration depth is one factor that was evaluated. In Figure 6a, the FSSW creates the keyhole in the center to create the joint for 2 sheets. The measurement depth of the keyhole is from the sheet top to the keyhole bottom surface (Figure 6b). The measurement values are shown in Figure 6c, for which the setting values are 2 cm and the real values are 1.92 to 1.98 cm. In Figure 7, the image shows the key-hole overall view of the welding spot in the DP780 sheet. The analysis of the base metal microstructure showed martensite islands in a ferrite matrix (Figure 8a). The microstructures of the TMAZ near the keyhole show a mixture of needle-like martensite and fine acicular ferrite (Figure 8b,c). The stir region around the keyhole revealed a fine grain martensite and porosity (Figure 8d).
Hsu et al.25 studied the hardness of a base metal compared with the original material property. In the HAZ intercritical region, the hardness value was found to be in a range of approximately 310 to 330 Hv. The hardness of TMAZ was approximately 360 Hv. The hardness in the stir zone of friction stir spot welds is significantly higher than in other regions; the values were found to be 370 Hv (Figure 9, modified from Hsu et al.25). If the welding process is not successful, there will be some cracks and a lack of fusion in the weld zone.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58633/58633fig1.jpg" /> 
Figure 1. A diagram of the tool pin. 
(a)&#160;The size and geometry of the tool pin (b) the actual tool pin&#160;<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58633/58633fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/58633/58633fig2.jpg" /> 
Figure 2. A diagram to demonstrate the work space. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58633/58633fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/58633/58633fig3.jpg" /> 
Figure 3. A flowchart to illustrate the friction stir spot welding process. 
(a) clamp pin (b) safety confirmed (c) machine setting confirmed (d) calibration (e) plunging (f) stirring (g) retracting (h) validation of the mechanical properties of the joints <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58633/58633fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/58633/58633fig4.jpg" /> 
Figure 4. The welding process. (a) calibration (b) plunging (c) stirring (d) retracting <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58633/58633fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/58633/58633fig5.jpg" /> 
Figure 5. A diagram showing the used pin. The pins are consumed at high temperatures. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58633/58633fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/58633/58633fig6.jpg" /> 
Figure 6. Confirmation of the dwell depth using a comparison of the settings. 
(a) The macro view of the FSSW creating the keyhole. (b) A diagram illustrating where the depths are measured (c) The dwell depths are set at 2 cm. The actual measurement values range from 1.92 to 1.98 cm. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58633/58633fig6large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/58633/58633fig7.jpg" /> 
Figure 7. An overall view of the friction stir spot welding. The analyzed area contained 4 parts: (I) base metal (II) HAZ (III) TMAZ, and (IV) the stir zone. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58633/58633fig7large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 8" class="xfigimg" src="/files/ftp_upload/58633/58633fig8.jpg" /> 
Figure 8. The microstructure composition of the joint created using FSSW. (a) base metal: the base metal of the workpieces is comprised of DP 780 sheets. The base metal shows no change in material properties (b) HAZ: the thermal cycle around the welding site with heat transfer. HAZ zone shows the martensite islands. (c) TMAZ: thermomechanically affected zone around the stir zone. The needle-like martensite and fine acicular ferrite shown in the TMAZ zone. (d) Stir zone: the pin hole created in the welding process with the formation of recrystallization grains. Fine grain smaller than 10 &#181;m appeared in the stir zone. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58633/58633fig8large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 9" class="xfigimg" src="/files/ftp_upload/58633/58633fig9.jpg" /> 
Figure 9. The microhardness values of the workpiece examined using a Vickers test machine with a loading weight of 300 g was held for 15 s. This figure was modified from Hsu et al.25. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58633/58633fig9large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Generating Lap Joints Via Friction Stir Spot Welding on DP780 Steel at JoVE.com

Generating Lap Joints Via Friction Stir Spot Welding on DP780 Steel

Here, we present a friction stir spot welding (FSSW) protocol on dual phase 780 steel. A tool pin with high-speed rotation generates heat from friction to soften the material, and then, the pin plunges into 2 sheet joints to create the lap joint.

Friction stir spot welding (FSSW), a derivative of friction stir welding (FSW), is a solid-state welding technique that was developed in 1991. An industry ...

generating-lap-joints-via-friction-stir-spot-welding-on-dp780-steel

Nanyang Technological University

Research

JoVE Journal

Engineering

6.9K Views.  Shu Zen College of Medicine and Management. Here, we present a friction stir spot welding (FSSW) protocol on dual phase 780 steel. A tool pin with high-speed rotation generates heat from friction to soften the material, and then, the pin plunges into 2 sheet joints to create the lap joint.

Video: Generating Lap Joints Via Friction Stir Spot Welding on DP780 Steel

Micropunching Lithography for Generating Micro- and Submicron-patterns on Polymer Substrates

Conducting polymers have attracted great attention since the discovery of high conductivity in doped polyacetylene in 19771. They offer the advantages of low weight, easy tailoring of properties and a wide spectrum of applications2,3. Due to sensitivity of conducting polymers to environmental conditions (e.g., air, oxygen, moisture, high temperature and chemical solutions), lithographic techniques present significant technical challenges when working with these materials4. For example, current photolithographic methods, such as ultra-violet (UV), are unsuitable for patterning the conducting polymers due to the involvement of wet and/or dry etching processes in these methods. In addition, current micro/nanosystems mainly have a planar form5,6. One layer of structures is built on the top surfaces of another layer of fabricated features. Multiple layers of these structures are stacked together to form numerous devices on a common substrate. The sidewall surfaces of the microstructures have not been used in constructing devices. On the other hand, sidewall patterns could be used, for example, to build 3-D circuits, modify fluidic channels and direct horizontal growth of nanowires and nanotubes.
A macropunching method has been applied in the manufacturing industry to create macropatterns in a sheet metal for over a hundred years. Motivated by this approach, we have developed a micropunching lithography method (MPL) to overcome the obstacles of patterning conducting polymers and generating sidewall patterns. Like the macropunching method, the MPL also includes two operations (Fig. 1): (i) cutting; and (ii) drawing. The "cutting" operation was applied to pattern three conducting polymers4, polypyrrole (PPy), Poly(3,4-ethylenedioxythiophen)-poly(4-styrenesulphonate) (PEDOT) and polyaniline (PANI). It was also employed to create Al microstructures7. The fabricated microstructures of conducting polymers have been used as humidity8, chemical8, and glucose sensors9. Combined microstructures of Al and conducting polymers have been employed to fabricate capacitors and various heterojunctions9,10,11. The "cutting" operation was also applied to generate submicron-patterns, such as 100- and 500-nm-wide PPy lines as well as 100-nm-wide Au wires. The "drawing" operation was employed for two applications: (i) produce Au sidewall patterns on high density polyethylene (HDPE) channels which could be used for building 3D microsystems12,13,14, and (ii) fabricate polydimethylsiloxane (PDMS) micropillars on HDPE substrates to increase the contact angle of the channel15.

A micropunching lithography approach is developed to generate micro- and submicron-patterns on top, sidewall and bottom surfaces of polymer substrates. It overcomes the obstacles of patterning conducting polymers and generating sidewall patterns. This method allows rapid fabrication of multiple features and is free of aggressive chemistry.

Conducting polymers have attracted great attention since the discovery of high conductivity in doped polyacetylene in 19771. They offer the advantages of ...

Mechanical Expansion of Steel Tubing as a Solution to Leaky Wellbores

Wellbore cement, a procedural component of wellbore completion operations, primarily provides zonal isolation and mechanical support of the metal pipe (casing), and protects metal components from corrosive fluids. These are essential for uncompromised wellbore integrity. Cements can undergo multiple forms of failure, such as debonding at the cement/rock and cement/metal interfaces, fracturing, and defects within the cement matrix. Failures and defects within the cement will ultimately lead to fluid migration, resulting in inter-zonal fluid migration and premature well abandonment. Currently, there are over 1.8 million operating wells worldwide and over one third of these wells have leak related problems defined as Sustained Casing Pressure (SCP)1. 
The focus of this research was to develop an experimental setup at bench-scale to explore the effect of mechanical manipulation of wellbore casing-cement composite samples as a potential technology for the remediation of gas leaks. 
The experimental methodology utilized in this study enabled formation of an impermeable seal at the pipe/cement interface in a simulated wellbore system. Successful nitrogen gas flow-through measurements demonstrated that an existing microannulus was sealed at laboratory experimental conditions and fluid flow prevented by mechanical manipulation of the metal/cement composite sample. Furthermore, this methodology can be applied not only for the remediation of leaky wellbores, but also in plugging and abandonment procedures as well as wellbore completions technology, and potentially preventing negative impacts of wellbores on subsurface and surface environments.

This article reports on a laboratory scale investigation of an existing field procedure and its adaptation for sealing of leaky wellbores. It consists of mechanical expansion of metal pipe, which results in an improved metal/cement bond, ultimate sealing of hydraulic pathways and prevention of gas leaks caused by the presence of a microannular channel.

Wellbore cement, a procedural component of wellbore completion operations, primarily provides zonal isolation and mechanical support of the metal pipe ...

Preparation and Friction Force Microscopy Measurements of Immiscible, Opposing Polymer Brushes

Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low friction at the interface. Nevertheless, these systems can be sensitive to wear due to interdigitation of the opposing brushes. In a recent publication, we have shown via molecular dynamics simulations and atomic force microscopy experiments, that using an immiscible polymer brush system terminating the substrate and the slider surfaces, respectively, can eliminate such interdigitation. As a consequence, wear in the contacts is reduced. Moreover, the friction force is two orders of magnitude lower compared to traditional miscible polymer brush systems. This newly proposed system therefore holds great potential for application in industry. Here, the methodology to construct an immiscible polymer brush system of two different brushes each solvated by their own preferred solvent is presented. The procedure how to graft poly(N-isopropylacrylamide) (PNIPAM) from a flat surface and poly(methyl methacrylate) (PMMA) from an atomic force microscopy (AFM) colloidal probe is described. PNIPAM is solvated in water and PMMA in acetophenone. Via friction force AFM measurements, it is shown that the friction for this system is indeed reduced by two orders of magnitude compared to the miscible system of PMMA on PMMA solvated in acetophenone.

The methodology to perform friction force microscopy experiments for contacting brushes is presented: Two polymer brushes that are grafted from (a) substrates and (b) colloidal probes are slid to show that, by using two contacting immiscible brush systems, friction in sliding contacts is reduced compared to miscible brush systems.

Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low ...

Ultrasonic Welding of Thermoplastic Composite Coupons for Mechanical Characterization of Welded Joints through Single Lap Shear Testing

This paper presents a novel straightforward method for ultrasonic welding of thermoplastic-composite coupons in optimum processing conditions. The ultrasonic welding process described in this paper is based on three main pillars. Firstly, flat energy directors are used for preferential heat generation at the joining interface during the welding process. A flat energy director is a neat thermoplastic resin film that is placed between the parts to be joined prior to the welding process and heats up preferentially owing to its lower compressive stiffness relative to the composite substrates. Consequently, flat energy directors provide a simple solution that does not require molding of resin protrusions on the surfaces of the composite substrates, as opposed to ultrasonic welding of unreinforced plastics. Secondly, the process data provided by the ultrasonic welder is used to rapidly define the optimum welding parameters for any thermoplastic composite material combination. Thirdly, displacement control is used in the welding process to ensure consistent quality of the welded joints. According to this method, thermoplastic-composite flat coupons are individually welded in a single lap configuration. Mechanical testing of the welded coupons allows determining the apparent lap shear strength of the joints, which is one of the properties most commonly used to quantify the strength of thermoplastic composite welded joints.

A straightforward procedure for ultrasonic welding of thermoplastic composite coupons for basic mechanical testing is described. Key characteristics of this ultrasonic welding process are the use of flat energy directors for simplified process preparation and the use of process data for the fast definition of optimum processing conditions.

This paper presents a novel straightforward method for ultrasonic welding of thermoplastic-composite coupons in optimum processing conditions. The ...

The Evolution of Silica Nanoparticle-polyester Coatings on Surfaces Exposed to Sunlight

Corrosion of metallic surfaces is prevalent in the environment and is of great concern in many areas, including the military, transport, aviation, building and food industries, amongst others. Polyester and coatings containing both polyester and silica nanoparticles (SiO2NPs) have been widely used to protect steel substrata from corrosion. In this study, we utilized X-ray photoelectron spectroscopy, attenuated total reflection infrared micro-spectroscopy, water contact angle measurements, optical profiling and atomic force microscopy to provide an insight into how exposure to sunlight can cause changes in the micro- and nanoscale integrity of the coatings. No significant change in surface micro-topography was detected using optical profilometry, however, statistically significant nanoscale changes to the surface were detected using atomic force microscopy. Analysis of the X-ray photoelectron spectroscopy and attenuated total reflection infrared micro-spectroscopy data revealed that degradation of the ester groups had occurred through exposure to ultraviolet light to form COO&#903;, -H2C&#903;, -O&#903;, -CO&#903; radicals. During the degradation process, CO and CO2 were also produced.

Two types of surfaces, polyester-coated steel and polyester coated with a layer of silica nanoparticles, were studied. Both surfaces were exposed to sunlight, which was found to cause substantial changes in the chemistry and nanoscale topography of the surface.

Corrosion of metallic surfaces is prevalent in the environment and is of great concern in many areas, including the military, transport, aviation, ...

Preparation and High-temperature Anti-adhesion Behavior of a Slippery Surface on Stainless Steel

Anti-adhesion surfaces with high-temperature resistance have a wide application potential in electrosurgical instruments, engines, and pipelines. A typical anti-wetting superhydrophobic surface easily fails when exposed to a high-temperature liquid. Recently, Nepenthes-inspired slippery surfaces demonstrated a new way to solve the adhesion problem. A lubricant layer on the slippery surface can act as a barrier between the repelled materials and the surface structure. However, the slippery surfaces in previous studies rarely showed high-temperature resistance. Here, we describe a protocol for the preparation of slippery surfaces with high-temperature resistance. A photolithography-assisted method was used to fabricate pillar structures on stainless steel. By functionalizing the surface with saline, a slippery surface was prepared by adding silicone oil. The prepared slippery surface maintained the anti-wetting property for water, even when the surface was heated to 300 &#176;C. Also, the slippery surface exhibited great anti-adhesion effects on soft tissues at high temperatures. This type of slippery surface on stainless steel has applications in medical devices, mechanical equipment, etc.

Slippery surfaces provide a new way to solve the adhesion problem. This protocol describes how to fabricate slippery surfaces at high temperatures. The results demonstrate that the slippery surfaces showed anti-wetting for liquids and a remarkable anti-adhesion effect on soft tissues at high temperatures.

Anti-adhesion surfaces with high-temperature resistance have a wide application potential in electrosurgical instruments, engines, and pipelines. A ...

Indoor Experimental Assessment of the Efficiency and Irradiance Spot of the Achromatic Doublet on Glass (ADG) Fresnel Lens for Concentrating Photovoltaics

We present a method to characterize achromatic Fresnel lenses for photovoltaic applications. The achromatic doublet on glass (ADG) Fresnel lens is composed of two materials, a plastic and an elastomer, whose dispersion characteristics (refractive index variation with wavelength) are different. We first designed the lens geometry and then used ray-tracing simulation, based on the Monte Carlo method, to analyze its performance from the point of view of both optical efficiency and the maximum attainable concentration. Afterwards, ADG Fresnel lens prototypes were manufactured using a simple and reliable method. It consists of a prior injection of plastic parts and a consecutive lamination, together with the elastomer and a glass substrate to fabricate the parquet of ADG Fresnel lenses. The accuracy of the manufactured lens profile is examined using an optical microscope while its optical performance is evaluated using a solar simulator for concentrator photovoltaic systems. The simulator is composed of a xenon flash lamp whose emitted light is reflected by a parabolic mirror. The collimated light has a spectral distribution and an angular aperture similar to the real Sun. We were able to assess the optical performance of the ADG Fresnel lenses by taking photographs of the irradiance spot cast by the lens using a charge-coupled device (CCD) camera and measuring the photocurrent generated by several types of multi junction (MJ) solar cells, which have been previously characterized at a solar simulator for concentrator solar cells. These measurements have demonstrated the achromatic behavior of ADG Fresnel lenses and, as a consequence, the suitability of the modelling and manufacturing methods.

Indoor Experimental Assessment of the Efficiency and Irradiance Spot of the Achromatic Doublet on Glass ADG Fresnel Lens for Concentrating Photovoltaics

The achromatic doublet on glass (ADG) Fresnel lens makes use of two materials with differing dispersion to reduce chromatic aberration and increase attainable concentration. In this paper, a protocol for the complete characterization of the ADG Fresnel lens is presented.

We present a method to characterize achromatic Fresnel lenses for photovoltaic applications. The achromatic doublet on glass (ADG) Fresnel lens is ...

Preparation of Aligned Steel Fiber Reinforced Cementitious Composite and Its Flexural Behavior

The aim of this work is to present an approach, inspired by the way in which a compass needle maintains a consistent orientation under the action of the Earth&#39;s magnetic field, for manufacturing a cementitious composite reinforced with aligned steel fibers. Aligned steel fiber reinforced cementitious composites (ASFRC) were prepared by applying a uniform electromagnetic field to fresh mortar containing short steel fibers, whereby the short steel fibers were driven to rotate in alignment with the magnetic field. The degree of alignment of steel fibers in hardened ASFRC was assessed both by counting steel fibers in fractured cross-sections and by X-ray computed tomography analysis. The results from the two methods show that the steel fibers in ASFRC were highly aligned while the steel fibers in non-magnetically treated composites were randomly distributed. The aligned steel fibers had a much higher reinforcing efficiency, and the composites, therefore, exhibited significantly enhanced flexural strength and toughness. The ASFRC is thus superior to SFRC in that it can withstand greater tensile stress and more effectively resist cracking.

This protocol describes an approach for manufacturing aligned steel fiber reinforced cementitious composite by applying a uniform electromagnetic field. Aligned steel fiber reinforced cementitious composite exhibits superior mechanical properties to ordinary fiber reinforced concrete.

The aim of this work is to present an approach, inspired by the way in which a compass needle maintains a consistent orientation under the action of the ...

Applicability Analysis of Assessment Methods for Morphological Parameters of Corroded Steel Bars

The irregular and uneven residual sections along the length of a corroded steel bar substantially change its mechanical properties and significantly dominate the safety and performance of an existing concrete structure. As a result, it is important to measure the geometry and amount of corrosion of a steel bar in a structure properly to assess the residual bearing capacity and service life of the structure. This paper introduces and compares five different methods for measuring the geometry and amount of corrosion of a steel bar. A single 500 mm long and 14 mm diameter steel bar is the specimen that is subjected to accelerated corrosion in this protocol. Its morphology and the amount of corrosion were carefully measured before and after using mass loss measurements, a Vernier caliper, drainage measurements, 3D scanning, and X-ray micro-computed tomography (XCT). The applicability and suitability of these different methods were then evaluated. The results show that the Vernier caliper is the best choice for measuring the morphology of a non-corroded bar, while 3D scanning is the most suitable for quantifying the morphology of a corroded bar.

This paper measures the geometry and the amount of corrosion of a steel bar using different methods: mass loss, calipers, drainage measurements, 3D scanning, and X-ray micro-computed tomography (XCT).

The irregular and uneven residual sections along the length of a corroded steel bar substantially change its mechanical properties and significantly ...

O-cresol Concentration Online Measurement Based On Near Infrared Spectroscopy Via Partial Least Square Regression

Unlike macroscopic process variables, near-infrared spectroscopy provides process information at the molecular level and can significantly improve the prediction of the components in industrial processes. The ability to record spectra for solid and liquid samples without any pretreatment is advantageous and the method is widely used. However, the disadvantages of analyzing high-dimensional near-infrared spectral data include information redundancy and multicollinearity of the spectral data. Thus, we propose to use partial least squares regression method, which has traditionally been used to reduce the data dimensionality and eliminate the collinearity between the original features. We implement the method for predicting the o-cresol concentration during the production of polyphenylene ether. The proposed approach offers the following advantages over component regression prediction methods: 1) partial least squares regression solves the multicollinearity problem of the independent variables and effectively avoids overfitting, which occurs in a regression analysis due to the high correlation between the independent variables; 2) the use of the near-infrared spectra results in high accuracy because it is a non-destructive and non-polluting method to obtain information at microscopic and molecular scales.

The protocol describes a method of predicting o-cresol concentration during the production of polyphenylene ether using near-infrared spectroscopy and partial least squares regression. To describe the process more clearly and completely, an example of predicting the o-cresol concentration during the production of polyphenylene is used to clarify the steps.

Unlike macroscopic process variables, near-infrared spectroscopy provides process information at the molecular level and can significantly improve the ...