Name: determination of the friction coefficients of icy pavements under different amounts of snowfall
Uploaded: 2023-01-06T12:40:00
Description: Watch this Scientific Journal Video about Determination of the Friction Coefficients of Icy Pavements Under Different Amounts of Snowfall at JoVE.com

The authors would like to acknowledge the Scientific Research Program Funded by the Shaanxi Provincial Education Department (Program No. 21JK0908).

1. Preparation of the equipment
<ol>
	<li>BPT
	<ol>
		<li>Ensure that the BPT (Figure 1) is within its service life and that the surface is clean and undamaged. 
		NOTE: The components of the BPT are the base, leveling spiral, leveling bubble, pointer, pendulum, lifting spiral, fastening spiral, handle, and dial.</li>
	</ol>
	</li>
	<li>Asphalt slabs
	<ol>
		<li>Ensure that the asphalt mixture sample size used for the experiment is 30 cm x 30 cm x 5 cm.</li>
	</ol>
	<...

<ol>
	<li>Rajamani, R., Piyabongkarn, N., Lew, J., Yi, K., Phanomchoeng, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tire-road+riction-coefficient+estimation.">Tire-road riction-coefficient estimation.</a> IEEE Control Systems Magazine. 30 (4), 54-69 (2010).</li><li>Wallman, C. -. G., &#197;str&#246;m, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Friction+measurement+methods+and+the+correlation+between+road+friction+and+traffic+safety:+A+literature+review.">Friction measurement methods and the correlation between road friction and traffic safety: A literature review.</a> Swedish National Road and Transport Research Institute. , (2001).</li><li>Kuttesch, J. 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SIRWEC. , (2010).</li><li>Ivanovi&#263;, V., 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+identification+of+dynamic+tire+friction+potential+on+ice+surfaces.">Experimental identification of dynamic tire friction potential on ice surfaces.</a> Vehicle System Dynamics. 44 (1), 93-103 (2006).</li><li>Gao, J., Zhang, Y., Du, Y., Li, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimization+of+the+tire+ice+traction+using+combined+Levenberg-Marquardt+(LM)+algorithm+and+neural+network.">Optimization of the tire ice traction using combined Levenberg-Marquardt (LM) algorithm and neural network.</a> Journal of the Brazilian Society of Mechanical Sciences and Engineering. 41, 40 (2019).</li><li>Nordstroem, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+validation+of+BV14,+a+new+twin+track+fixed+slip+friction+tested+for+winter+road+maintenance+monitoring+in+Sweden.">Development and validation of BV14, a new twin track fixed slip friction tested for winter road maintenance monitoring in Sweden.</a> Proceedings of XTH PIARC International Winter Road Congress. Swedish National Road and Transport Research Institute (VTI). , (1998).</li><li>Norem, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selection+of+strategies+for+winter+maintenance+of+roads+based+on+climatic+parameters.">Selection of strategies for winter maintenance of roads based on climatic parameters.</a> Journal of Cold Regions Engineering. 23 (4), 113-135 (2009).</li><li>Bergstr&#246;m, A., &#197;str&#246;m, H., Magnusson, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Friction+measurement+on+cycleways+using+a+portable+friction+tester.">Friction measurement on cycleways using a portable friction tester.</a> Journal of Cold Regions Engineering. 17 (1), 37-57 (2003).</li><li>Henry, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+pavement+friction+characteristics.">Evaluation of pavement friction characteristics.</a> Transportation Research Board. , (2000).</li><li>ASTM International. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ASTM+E303-93.+Standard+Test+Method+for+Measuring+Surface+Frictional+Properties+Using+the+British+Pendulum+Tester.">ASTM E303-93. Standard Test Method for Measuring Surface Frictional Properties Using the British Pendulum Tester.</a> ASTM International. , (2018).</li><li>ASTM International. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ASTM+D6926-20.+Standard+Practice+for+Preparation+of+Asphalt+Mixture+Specimens+Using+Marshall+Apparatus.">ASTM D6926-20. Standard Practice for Preparation of Asphalt Mixture Specimens Using Marshall Apparatus.</a> ASTM International. , (2020).</li><li>Oliver, J. W., Tredrea, P., Pratt, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Seasonal+variation+of+skid+resistance+in+Australia.+Special+Report+No+37.">Seasonal variation of skid resistance in Australia. Special Report No 37.</a> Australian Road Research Board. , (1988).</li><li>Steven, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Friction+Testing+of+Pavement+Preservation+Treatments:+Temperature+Corrections+and+Operator/Machine+Variability.">Friction Testing of Pavement Preservation Treatments: Temperature Corrections and Operator/Machine Variability.</a> University of California Pavement Research Center Davis and Berkely. , (2009).</li><li>Transport Research Laboratory. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=BS+7976-2:2002.+Pendulum+testers+-+Method+of+operation.">BS 7976-2:2002. Pendulum testers - Method of operation.</a> Transport Research Laboratory. , (2002).</li><li>Lu, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Friction+testing+of+pavement+preservation+treatments:+Literature+review.">Friction testing of pavement preservation treatments: Literature review.</a> UC Davis: University of California Pavement Research Center. , (2006).</li><li>Bazlamit, S. M., Reza, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Changes+in+asphalt+pavement+friction+components+and+adjustment+of+skid+number+for+temperature.">Changes in asphalt pavement friction components and adjustment of skid number for temperature.</a> Journal of Transportation Engineering. 131 (6), 470-476 (2005).</li></ol>

The present paper examines the procedure for testing the friction coefficient of icy pavement using a BPT. Several points need to be comprehensively analyzed and are discussed in detail here. First, in terms of the preparation of the asphalt mixture samples, one should try to use road petroleum asphalt to prepare the samples, but this is not a requirement. The preparation of the asphalt mixture samples should be performed in strict accordance with the ASTM (D6926-20) experimental protocols, as this affects the accuracy o...

Pavement friction is defined as the grip between the vehicle tires and the underlying road surface1. The index most commonly associated with pavement friction in road design is the pavement friction coefficient. Friction is one of the most important factors in road design and is second only to durability. There is a strong and clear correlation between pavement friction performance and accident risk2. For example, there is a significant negative correlation between road accident rates and pavement skid resistance3,4,5. Several factors may contribute to a decrease in pavement friction, and one of the most direct and influential of these factors is snowfall6. Specifically, snowfall causes ice to form on the pavement, thereby resulting in a significant reduction in the road friction coefficient7,8. A study focusing on the factors that influence traffic accident rates in southern Finland noted that accident rates commonly peak on days with heavy snowfall and that more than 10 cm of snow can lead to a doubling of the accident rate9. Similar results have been found in studies performed both in Sweden and Canada10,11. Therefore, studying the friction properties of snow-frozen pavements is crucial for improving road safety.
Determining the friction coefficient of icy pavements is a complex process because the friction coefficient may vary under different snowfall levels and pavement ice thicknesses. Furthermore, varying temperatures and tire characteristics may also affect the friction coefficient. In the past, numerous experiments have been conducted to study the friction characteristics of tires on ice12. However, due to the differences in individual environments and tire characteristics, consistent results cannot be obtained and used as a basis for theoretical studies. Therefore, many researchers have attempted to develop theoretical models to analyze the friction of tires on ice. Hayhoe and Sahpley13 suggested the concept of wet friction heat exchange at the interface between tires and ice, while Peng et al.14 proposed an advanced data model to predict friction based on the above concept. In addition, Klapproth presented an innovative mathematical model for describing the friction of rough rubber on smooth ice15. However, the above models have been shown to have significant errors, mainly due to their inability to accurately and efficiently characterize the friction properties of tires on ice16.
To reduce the errors of theoretical models, a large amount of experimental data is needed. The Finnish Meteorological Agency developed a friction model for predicting icy pavement friction, and the formula for that model was primarily based on data obtained from road weather stations and through statistical analysis17. Furthermore, Ivanovi&#263; et al. gathered a significant amount of experimental data by analyzing the friction characteristics of tires on ice and calculated the friction coefficient of ice by regression analysis18. Gao et al. also proposed a novel prediction model of tire-rubber-ice traction by combining the Levenberg-Marquardt (LM) optimization algorithm with a neural network to obtain the formula for the friction coefficient on ice19. All the above models have been either validated or applied in practice and are, thus, considered feasible.
In addition to theoretical methods, many practical methods have been developed for measuring the friction coefficient of pavements in snowy and frozen areas. Due to the particularities of the weather, these methods have been widely used in Nordic countries such as Sweden, Norway, and Finland20. In Sweden, the following three main types of friction measuring devices are used: the BV11, SFT, and BV14. The BV14, a dual friction tester developed specifically for winter maintenance assessments, is directly connected to the measuring vehicle and measures the dry friction on both wheel paths simultaneously20. In Finland, the friction measuring vehicle (TIE 475) is used for winter road maintenance assessments, while in Norway, the ROAR friction measuring device (without water) is a commonly used piece of equipment2. Most of the winter friction measurements carried out in Sweden, Norway, and Finland have been performed using ordinary passenger cars with ABS and instruments measuring deceleration under braking2,20. The advantage of this method is that it is simple and relatively inexpensive, and the main disadvantage is that the accuracy of the method is very low.
The studies described above provide methods for predicting and detecting friction coefficients on ice. However, a uniform method and a specific value to guide road designers have still not been provided. Moreover, for winter roads, the friction coefficient between the tires and ice may vary with respect to different ice thicknesses, and different disposal measures should also be implemented21. Therefore, this paper aims to determine the friction coefficient of icy roads under different amounts of snowfall.
Internationally, the British portable tester (BPT) and the Swedish Road and Transport Research Institute portable friction tester (VTI PFT) are currently the most commonly used instruments for measuring the friction coefficient22,23. The PFT is a portable friction tester developed by VTI, and it allows the operator to take measurements in an upright position and save the data on the computer22. The PFT can measure most contoured road markings, but the number of instruments currently available is still very small2. The BPT is a pendulum friction coefficient tester that was developed by the British Road Research Laboratory (RRL, now TRL). The instrument is a dynamic pendulum impact-type tester used to measure the energy loss in cases when a rubber slider edge is propelled over a test surface. The results are reported as British Pendulum Numbers (BPNs) to emphasize that they are specific to this tester and not directly equivalent to those from other devices24. The instrument has been shown to be useful for the determination of friction coefficients in the experimental pavement field23. This experiment uses the BPT for the determination of friction coefficients.
The present study describes the experimental procedure for measuring the friction coefficient of icy pavements corresponding to different snowfall amounts indoors. The problems to be noted in the experiments, such as experimental calibration, experimental implementation, and the methods of data analysis, are explained in detail. The present experimental procedures can be summarized by the following five steps: 1) the preparation of the equipment, 2) the calculation and analysis of the snowfall, 3) equipment calibration, 4) friction coefficient determination, and 5) data analysis.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Brush</td>
			<td>Shenzhen Huarui Brush Industry Co., LTD</td>
			<td>L-31</td>
			<td></td>
		</tr>
		<tr>
			<td>Freezing equipment</td>
			<td>Haier Group</td>
			<td>BC/BD-251HD</td>
			<td></td>
		</tr>
		<tr>
			<td>Measuring cylinder</td>
			<td>Zhaoqing High-tech Zone Qianghong Plastic Mould Co., LTD</td>
			<td>lb1</td>
			<td></td>
		</tr>
		<tr>
			<td>Pavement thermometer&#160;</td>
			<td>Fluke Electronic Insrtument Company</td>
			<td>F62MAX</td>
			<td></td>
		</tr>
		<tr>
			<td>Pendulum Friction Cofficient Meter</td>
			<td>Muyang County Highway Instrument Co., LTD</td>
			<td>/</td>
			<td></td>
		</tr>
		<tr>
			<td>Rubber sheet</td>
			<td>Jiangsu Muyang Xinchen Highway Instrument Co., LTD</td>
			<td>785120123500</td>
			<td></td>
		</tr>
		<tr>
			<td>Sliding length ruler&#160;</td>
			<td>Jiangsu Muyang Xinchen Highway Instrument Co., LTD</td>
			<td>785120123500</td>
			<td></td>
		</tr>
		<tr>
			<td>Tripod</td>
			<td>Hangzhou Ruiqi Trading Co., LTD</td>
			<td>TRGC1169</td>
			<td></td>
		</tr>
	</tbody>
</table>

determination of the friction coefficients of icy pavements under different amounts of snowfall

Ice on road surfaces can lead to a significant decrease in the friction coefficient, thus endangering driving safety. However, there are still no studies that provide exact friction coefficient values for pavements covered in ice, which is detrimental to both road design and the selection of winter road maintenance measures. Therefore, this article presents an experimental method to determine the friction coefficient of icy road surfaces in the winter. A British portable tester (BPT), also known as a pendulum friction coefficient meter, was employed for the experiment. The experiment was divided into the following five steps: the preparation of the equipment, the calculation and analysis of the snowfall, equipment calibration, friction coefficient determination, and data analysis. The accuracy of the final experiment is directly affected by the equipment accuracy, which is described in detail. Moreover, this article suggests a method for calculating the ice thickness for corresponding amounts of snowfall. The results illustrate that even patchy ice formed by very light snowfall may lead to a significant decrease in the friction coefficient of the pavement, thus endangering driving safety. Additionally, the friction coefficient is at its peak when the ice thickness reaches 5 mm, meaning protection measures should be taken to avoid the formation of such ice.

Sample 7 in Table 4 is the dry sample control group, while the remaining samples 1-6 correspond to ice thicknesses ranging from very light snow to a large blizzard.
When comparing sample 7 and the other six groups, ice formation was observed to significantly reduce the friction coefficient of the pavement. Furthermore, the pavement friction coefficient decreased with increasing ice thickness, and the ice thickness tended to stabilize at 5 mm, which corresponds to medium snow. ...

Watch this Scientific Journal Video about Determination of the Friction Coefficients of Icy Pavements Under Different Amounts of Snowfall at JoVE.com

Determination of the Friction Coefficients of Icy Pavements Under Different Amounts of Snowfall

Here, we present a method for determining the friction coefficient of pavements with different ice thicknesses indoors. The complete procedure includes the preparation of the equipment, the calculation and analysis of the snowfall, equipment calibration, friction coefficient determination, and data analysis.

Ice on road surfaces can lead to a significant decrease in the friction coefficient, thus endangering driving safety. However, there are still no studies ...

This video is aimed to show the process of determining the coefficient of friction of an icy road surface. Using the pendulum friction coefficient meter. Ice on the road surface can lead to a significant reduction in the coefficient of friction and thus endanger driver safety.We want to establish a complete and scientific experimental procedure indoors to determine the coefficient of friction of icy road surfaces. A pendulum friction tester was used to conduct in the experiment and asphalt slabs and water layers were frozen simultaneously to simulate road icing. Different levels of snowfall was also simulated on asphalt slab with varying ice thickness to make the results more intuitive.Preparation of the equipment. First, the pendulum friction coefficient meter, during the experiment ensure that B P T is within its surface life and that surface is clean and undamaged. Its components are base, leveling spiral, leveling bubble, pointer, pendulum, lifting spiral, fastening spiral, huddle, and dial.Then the asphalt slab, ensure that asphalt mixture sample size use for experiment is 30 centimeters by 30 centimeters by five centimeters. The right figure shows the asphalt slab wrapped with molds. Next the freezing equipment, ensure that this equipment used in the experiment can freely regulate the temperature between subzero 20 centigrade to zero centigrade.Other equipment used in the experiment includes, tripod, measuring cylinder, rubber sheet, pavement thermometer, sliding length ruler and brush. The size of the rubber sheet used in the experiment is 6.35 millimeters by 25.4 millimeters by 76.2 millimeters and should meet the quality requirements given in the following table. During the experiment, ensure that the rubber sheet has no following defects:First, there are oil stains;Second, rubber sheet width edge wear is greater than 3.2 millimeters.Third, rubber sheet length direction wear is greater than 1.6 millimeters. Before using a new rubber sheet, ensure that the rubber sheet is measured 10 times on a dry surface before employed for official testing. Calculation and analysis of snowfall the table gives the snowfall class classification to consider extreme cases takes 24 hours of snowfall at the condition for the study.Moreover, to ensure the ease of experimentation the upper limits of each level of snowfall division as used for the corresponding calculation and analysis. After calculation, different levels of snowfall test at the corresponding water volume of the samples as provided in the table. Experiment does not consider the influence of the extraordinary snow storms and number the very light snow to big blizzard from 1 to 6.Equipment calibration Place the BPT in a suitable position. A suitable position means that the ground is flat and free of potholes, rotate the leveling spiral on the base of the BPT to keep the leveling bubble in the middle position. Loosen the fastening spiral, rotate the lifting spiral to make the pendulum lift and swing freely.Then tighten the fastening spiral. Place the pendulum arm on the right cantilever of the pendulum table keeping the arm in the risen toe position while rotating the pointer to the right side flush with the arm. Press the release button to let the pendulum arm swing freely and then the pendulum crosses the lowest point.To reach the highest point, hold it by hand. The pointer should indicate zero at this time. If the pointer does not show the zero point loosen and tighten the narrowing nut to make it show the zero point.Place the asphalt slab directly under the pendulum while loosening the fastening spiral so that the lowest edge of the rubber sheet touche the surface of the asphalt slab. Prepare the sliding length ruler and bring it close to the rubber sheet. Lift the carrying handle to make the left scale mark of the sliding length ruler flush with the lowest edge of the rubber sheet.Lift the carrying handle and move the pendulum to the right again so that the lowest edge of the rubber sheet only touches the surface of the asphalt slab. Observe further, the sliding length jeweler is flush with the edge of the rubber sheet. If flush, the sliding length meets a requirement of 136 millimeters.Otherwise, continue the following operation. Turn the lifting spiral to adjust the height of the pendulum to make the sliding length meet the requirements. Vital tan is needed.Twist the level spiral on the base. The level in bubble needs to remain centered during an adjustment. Friction coefficient determination.Select seven pieces of asphalt slabs. Clean their surface with a brush and dry naturally at room temperature. Number the asphalt slabs in turn place the asphalt slabs into modes and simultaneously coup and freeze with the water layer.The sevens samples were placed into the freezer at a controlled temperature in a sub zero 10 centigrade for 24 hours. After freezing, turn down the samples in turn, remove the modes and place them on the BPT centers, which have been leveled and zero use the pavement centimeter to measure the surface temperature of the sample and record, perform sliding length calibration. To ensure sliding distance of 126 millimeters press the pendulum arm release switch and when the pad arm crosses the lowest point and swings to the highest one held by hand, read and recorded restore both the pendulum arm and the pointer to the zero and horizon positions respectively.The sliding length should be re calibrated each time a new sample is tested. Repeat the steps for 10 times. Measure seven samples in sequence.Each sample has 10 measurement results and both the minimum and the maximum value difference should be less than three. Data analysis recorded data in the table and the average measurement results to get average values bring the temperature value measured into the equivalent. To obtain the temperature compensated value subtract the compensated BPN value from average BPN value in the table to obtain the final temperature compensated BPN value plot the final BPN values in table four and the bar graph for more intuitive results.Representative results:When comparing sample seven and the other six groups, I think it is observed to significantly reduce the friction coefficient of the pavement. Based on sample one very light snow force is not to have a serious impact on the road friction coefficient. With respect to sample two, three, and four the surface friction coefficient was observed to gradually decrease for sample four, five and six.The average final BPM values are identical. This may indicate that the road friction coefficient of the ice layer tends to stabilize and another measure of a thicker ice layer is not necessary. The bar graph can better reflect the wide ratio of friction coefficient.Sample one represents very light snow that adhere to the pavement surface after icing resulting the reduction in the pavement friction coefficient and its BPM value decreased by approximately 43%compared to the dry sample. Sample two, three and four correspond to light medium and heavy snow respectively. Among them the BPM value of medium snow is only one half that of light snow because the thickness of the iced layer corresponding to little snow is of like two minimum.The micro structure of the sample surface still affects the friction coefficient value and the BPN is larger. The BPNs of the heavy snow, blizzard and large blizzard samples are the same, which may stop an ice thickness reaches 11 minimum. The rubber sheets can no longer deformed the ice layer by compacting it.Conclusion:The friction coefficients of seven asphalt slabs were determined by means of a pendulum friction coefficient tester, and the final results were corrected for temperature. It can be seen that, the effect of pavement icing on the coefficient of friction is indeed significant, with even slightly light snow resulting in patches of ice reducing the pavement of friction coefficient by about 40%The final results can provide a reference for road design and winter pavement maintenance.

determination-friction-coefficients-icy-pavements-under-different

Research

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JoVE Core

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Mechanical Engineering

Engineering

Unit 1

Friction

SCIENTISTS IN ACTION

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 ...

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 ...

Experimental Protocol to Investigate Particle Aerosolization of a Product Under Abrasion and Under Environmental Weathering

The present article presents an experimental protocol to investigate particle aerosolization of a product under abrasion and under environmental weathering, which is a fundamental element to the approach of nanosafety-by-design of nanostructured products for their durable development. This approach is basically a preemptive one in which the focus is put on minimizing the emission of engineered nanomaterials' aerosols during the usage phase of the product's life cycle. This can be attained by altering its material properties during its design phase without compromising with any of its added benefits. In this article, an experimental protocol is presented to investigate the nanosafety-by-design of three commercial nanostructured products with respect to their mechanical solicitation and environmental weathering. The means chosen for applying the mechanical solicitation is an abrasion process and for the environmental weathering, it is an accelerated UV exposure in the presence of humidity and heat. The eventual emission of engineered nanomaterials is studied in terms of their number concentration, size distribution, morphology and chemical composition. The purpose of the protocol is to study the emission for test samples and experimental conditions which are corresponding to real life situations. It was found that the application of the mechanical stresses alone emits the engineered nanomaterials' aerosols in which the engineered nanomaterial is always embedded inside the product matrix, thus, a representative product element. In such a case, the emitted aerosols comprise of both nanoparticles as well as microparticles. But if the mechanical stresses are coupled with the environmental weathering, the experimental protocol reveals then the eventual deterioration of the product, after a certain weathering duration, may lead to the emission of the free engineered nanomaterial aerosols too.

In this article, an experimental protocol to investigate particle aerosolization of a product under abrasion and under environmental weathering is presented. Results on the emission of engineered nanomaterials, in the form of aerosols are presented. The specific experimental set-up is described in detail.

The present article presents an experimental protocol to investigate particle aerosolization of a product under abrasion and under environmental ...

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 ...

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.

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 ...

Determination of the Excitation and Coupling Rates Between Light Emitters and Surface Plasmon Polaritons

We have developed a unique method to measure the excitation and coupling rates between the light emitters and surface plasmon polaritons (SPPs) arising from metallic periodic arrays without involving time-resolved techniques. We have formulated the rates by quantities that can be measured by simple optical measurements. The instrumentation based on angle- and polarization-resolved reflectivity and photoluminescence spectroscopy will be described in detail here. Our approach is intriguing due to its simplicity, which requires routine optics and several mechanical stages, and thus is highly affordable to most of the research laboratories.

This protocol describes the instrumentation for determining the excitation and coupling rates between light emitters and Bloch-like surface plasmon polaritons arising from periodic arrays.

We have developed a unique method to measure the excitation and coupling rates between the light emitters and surface plasmon polaritons (SPPs) arising ...

One-Step Approach to Fabricating Polydimethylsiloxane Microfluidic Channels of Different Geometric Sections by Sequential Wet Etching Processes

Polydimethylsiloxane (PDMS) materials are substantially exploited to fabricate microfluidic devices by using soft lithography replica molding techniques. Customized channel layout designs are necessary for specific functions and integrated performance of microfluidic devices in numerous biomedical and chemical applications (e.g., cell culture, biosensing, chemical synthesis, and liquid handling). Owing to the nature of molding approaches using silicon wafers with photoresist layers patterned by photolithography as master molds, the microfluidic channels commonly have regular cross sections of rectangular shapes with identical heights. Typically, channels with multiple heights or different geometric sections are designed to possess particular functions and to perform in various microfluidic applications (e.g., hydrophoresis is used for sorting particles and in continuous flows for separating blood cells6,7,8,9). Therefore, a great deal of effort has been made in constructing channels with various sections through multiple-step approaches like photolithography using several photoresist layers and assembly of different PDMS thin sheets. Nevertheless, such multiple-step approaches usually involve tedious procedures and extensive instrumentation. Furthermore, the fabricated devices may not perform consistently and the resulted experimental data may be unpredictable. Here, a one-step approach is developed for the straightforward fabrication of microfluidic channels with different geometric cross sections through PDMS sequential wet etching processes, that introduces etchant into channels of planned single-layer layouts embedded in PDMS materials. Compared to the existing methods for manufacturing PDMS microfluidic channels with different geometries, the developed one-step approach can significantly simplify the process to fabricate channels with non-rectangular sections or various heights. Consequently, the technique is a way of constructing complex microfluidic channels, which provides a fabrication solution for the advancement of innovative microfluidic systems.

Several methods are available for the fabrication of channels of non-rectangular sections embedded in polydimethylsiloxane microfluidic devices. Most of them involve multistep manufacturing and extensive alignment. In this paper, a one-step approach is reported for fabricating microfluidic channels of different geometric cross sections by polydimethylsiloxane sequential wet etching.

Polydimethylsiloxane (PDMS) materials are substantially exploited to fabricate microfluidic devices by using soft lithography replica molding techniques. ...

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.

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 ...

Accurate Determination of the Equilibrium Surface Tension Values with Area Perturbation Tests

We demonstrate two robust protocols for determining the equilibrium surface tension (EST) values with area perturbation tests. The EST values should be indirectly determined from the dynamic surface tension (DST) values when surface tension (ST) values are at steady-state and stable against perturbations. The emerging bubble method (EBM) and the spinning bubble method (SBM) were chosen, because, with these methods, it is simple to introduce area perturbations while continuing dynamic tension measurements. Abrupt expansion or compression of an air bubble was used as a source of area perturbation for the EBM. For the SBM, changes in the rotation frequency of the sample solution were used to produce area perturbations. A Triton X-100 aqueous solution of a fixed concentration above its critical micelle concentration (CMC) was used as a model surfactant solution. The determined EST value of the model air/water interface from the EBM was 31.5 &#177; 0.1 mN&#183;m-1 and that from the SBM was 30.8 &#177; 0.2 mN&#183;m-1. The two protocols described in the article provide robust criteria for establishing the EST values.

Two protocols for determining the equilibrium surface tension (EST) values using the emerging bubble method (EBM) and the spinning bubble method (SBM) are presented for a surfactant-containing aqueous phase against air.

We demonstrate two robust protocols for determining the equilibrium surface tension (EST) values with area perturbation tests. The EST values should be ...

Determination of Aggregate Surface Morphology at the Interfacial Transition Zone (ITZ)

Here, we present a comprehensive method to illustrate the uneven distribution of the interfacial transition zone (ITZ) around the aggregate and the effect of aggregate surface morphology on the formation of ITZ. First, a model concrete sample is prepared with a spherical ceramic particle in roughly the central part of the cement matrix, acting as a coarse aggregate used in common concrete/mortar. After curing until the designed age, the sample is scanned by X-ray computed tomography to determine the relative location of the ceramic particle inside the cement matrix. Three locations of the ITZ are chosen: above the aggregate, on the side of the aggregate, and below the aggregate. After a series of treatments, the samples are scanned with a SEM-BSE detector. The resultant images were further processed using a digital image processing method (DIP) to obtain quantitative characteristics of the ITZ. The surface morphology is characterized at the pixel level based on the digital image. Thereafter, K-means clustering method is used to illustrate the effect of surface roughness on ITZ formation.

Determination of Aggregate Surface Morphology at the Interfacial Transition Zone ITZ

Hereby, we proposed a protocol to illustrate the effect of aggregate surface morphology on the ITZ microstructure. The SEM-BSE image were quantitatively analyzed to obtain ITZ's porosity gradient via digital image processing and a K-means clustering algorithm was further employed to establish a relationship between porosity gradient and surface roughness.

Here, we present a comprehensive method to illustrate the uneven distribution of the interfacial transition zone (ITZ) around the aggregate and the effect ...