Study on generalized friction coefficient between base and surface layers of asphalt pavement

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Tengjiang Yu ◽  
Haitao Zhang ◽  
Junfeng Sun ◽  
Yabo Wang ◽  
Shuang Huang ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Resilient Modulus ◽  
Asphalt Pavement ◽  
Structural Characteristics ◽  
Surface Layers ◽  
Typical Structure ◽  
Content Type ◽  
Characteristics Analysis ◽  
Cold Area ◽  
Technical Basis

Purpose Using typical structure of asphalt pavement in Harbin area of China, and the formula of generalized friction coefficient between base and surface layers of asphalt pavement in cold area is established. Design/methodology/approach Through structural characteristics analysis of asphalt pavement in cold area, the generalized formula of friction coefficient between base and surface layers of asphalt pavement in cold area is derived. The formula can quickly calculate the friction coefficient between layers of asphalt pavement. Findings Based on quantitative analysis to the contacting state between layers of asphalt pavement in cold area, the relationships between generalized friction coefficient and resilient modulus of asphalt mixtures, temperature shrinkage coefficient and temperature have been established. Originality/value The findings can enrich the description methods about the contacting state between layers of asphalt pavement, and have a certain theoretical and practical value. Through the application of the formula of generalized friction coefficient between layers, it can provide a technical basis for the asphalt pavement design, construction and maintenance in cold area.

Study on high-temperature wear and mechanism of Al-Si/graphite composites prepared by the die-casting process

2020 ◽  
Vol 72 (10) ◽  
pp. 1153-1158 ◽  
Author(s):  
Yafei Deng ◽  
Xiaotao Pan ◽  
Guoxun Zeng ◽  
Jie Liu ◽  
Sinong Xiao ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Wear Rate ◽  
Peer Review ◽  
Die Casting ◽  
Casting Machine ◽  
Injection Pressure ◽  
Casting Process ◽  
Matrix Alloy ◽  
Content Type ◽  
The Matrix

Purpose This paper aims to improve the tribological properties of aluminum alloys and reduce their wear rate. Design/methodology/approach Carbon is placed in the model at room temperature, pour 680°C of molten aluminum into the pressure chamber, and then pressed it into the mold containing carbon felt through a die casting machine, and waited for it to cool, which used an injection pressure of 52.8 MPa and held the same pressure for 15 s. Findings The result indicated that the mechanical properties of matrix and composite are similar, and the compressive strength of the composite is only 95% of the matrix alloy. However, the composite showed a low friction coefficient, the friction coefficient of Gr/Al composite is only 0.15, which just is two-third than that of the matrix alloy. Similarly, the wear rate of the composite is less than 4% of the matrix. In addition, the composite can avoid severe wear before 200°C, but the matrix alloy only 100°C. Originality/value This material has excellent friction properties and is able to maintain this excellent performance at high temperatures. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-10-2019-0454/

scholarly journals Test Analysis on Drainage Base Mixture of Asphalt Pavement in Cold Area

2020 ◽  
Vol 510 ◽  
pp. 052006
Author(s):  
Wei Gao ◽  
Naibao Dong ◽  
Xu Wang ◽  
Mingming Zeng
Keyword(s):  
Asphalt Pavement ◽  
Test Analysis ◽  
Cold Area

A novel technique for modeling friction behavior in knitted fabric simulation

2017 ◽  
Vol 29 (6) ◽  
pp. 776-792
Author(s):  
Vajiha Mozafary ◽  
Pedram Payvandy
Keyword(s):  
Friction Coefficient ◽  
Uniform Distribution ◽  
Friction Force ◽  
Experimental Result ◽  
Knitted Fabric ◽  
Friction Behavior ◽  
Content Type ◽  
Novel Technique ◽  
Fabric Structure ◽  
Fabric Surface

Purpose Fabric-object friction force is a fundamental factor in cloth simulation. A large number of parameters influence the frictional properties of fabrics such as fabric structure, yarn structure, and inherent properties of component fibers. The purpose of this paper is to propose a novel technique for modeling fabric-object friction force in knitted fabric simulation based on the mass spring model. Design/methodology/approach In this technique, unlike other studies, distribution of friction coefficient over the fabric surface is not uniform and depends on the fabric structure. The main reason for considering non-uniform distribution is that in various segments of fabric, contact percent of fabric-object is different. Findings The proposed technique and common methods based on friction coefficient uniform distribution are used to simulate the frictional behavior of knitted fabrics. The results show that simulation error values for proposed technique and common methods are 2.7 and 9.4 percent as compared with the experimental result, respectively. Originality/value In the existing methods of the friction force modeling, the friction coefficient of fabric is assumed uniform. But this assumption is not correct because fabric does not have an isotropic structure. Thus in this study, the friction coefficient distribution is considered based on fabric structure to achieve more of realistic simulations.

Analysis of Hiemenz flow of Reiner-Rivlin fluid over a stretching/shrinking sheet

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Golam Mortuja Sarkar ◽  
Suman Sarkar ◽  
Bikash Sahoo
Keyword(s):  
Nusselt Number ◽  
Stability Analysis ◽  
Friction Coefficient ◽  
Skin Friction Coefficient ◽  
Dual Solutions ◽  
Shrinking Sheet ◽  
Content Type ◽  
Hiemenz Flow ◽  
Self Similar ◽  
The Stability

Purpose This paper aims to theoretically and numerically investigate the steady two-dimensional (2D) Hiemenz flow with heat transfer of Reiner-Rivlin fluid over a linearly stretching/shrinking sheet. Design/methodology/approach The Navier–Stokes equations are transformed into self-similar equations using appropriate similarity transformations and then solved numerically by using shooting technique. A simple but effective mathematical analysis has been used to prove the existence of a solution for stretching case (λ> 0). Moreover, an attempt has been laid to carry the asymptotic solution behavior for large stretching. The obtained asymptotic solutions are compared with direct numerical solutions, and the comparison is quite remarkable. Findings It is observed that the self-similar equations exhibit dual solutions within the range [λc, −1] of shrinking parameter λ, where λc is the turning point from where the dual solutions bifurcate. Unique solution is found for all stretching case (λ > 0). It is noticed that the effects of cross-viscous parameter L and shrinking parameter λ on velocity and thermal fields show opposite character in the dual solution branches. Thus, a linear temporal stability analysis is performed to determine the basic feasible solution. The stability analysis is based on the sign of the smallest eigenvalue, where positive or negative sign leading to a stable or unstable solution. The stability analysis reveals that the first solution is stable that describes the main flow. Increase in cross-viscous parameter L resulting in a significant increment in skin friction coefficient, local Nusselt number and dual solutions domain. Originality/value This work’s originality is to examine the combined effects of cross-viscous parameter and stretching/shrinking parameter on skin friction coefficient, local Nusselt number, velocity and temperature profiles of Hiemenz flow over a stretching/shrinking sheet. Although many studies on viscous fluid and nanofluid have been investigated in this field, there are still limited discoveries on non-Newtonian fluids. The obtained results can be used as a benchmark for future studies of higher-grade non-Newtonian flows with several physical aspects. All the generated results are claimed to be novel and have not been published elsewhere.

Tribological performance of self-lubricated polyamide6/boric oxide composites after water conditioning

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Kawaljit Singh Randhawa ◽  
Ashwin Patel
Keyword(s):  
Friction Coefficient ◽  
Abrasion Resistance ◽  
Tribological Performance ◽  
Boric Oxide ◽  
Resistance Testing ◽  
Tribological Behaviour ◽  
Content Type ◽  
Wear Rates ◽  
Water Conditioning ◽  
Oxide Composites

Purpose This paper aims to investigate the tribological performance, i.e. abrasion resistance, friction coefficient and wear rates, of self-lubricated water conditioned polyamide6/boric oxide composites. Design/methodology/approach Polyamide6 and polyamide6/boric oxide self-lubricated composites were immersed in water for 15 days to analyze the effect of water conditioning on friction, wear and abrasion resistance. Tribological testing on pin-on-disc tribometer and abrasion resistance testing on TABER abrader were performed to see the friction coefficient and wear rates of materials. The scanning electron microscopy (SEM) characterizations were performed to analyze the wear tracks. Findings Tribological testing results revealed the loss in abrasive resistance, but there was an improvement in frictional coefficient and wear rates with steel after water absorption. The SEM images clearly show less depth of wear tracks in water-conditioned materials than dry ones. Water conditioning was found supportive in the formation of smooth lubricating transfer film on steel disc during the tribological testing. Originality/value The tribological behaviour of polymer composites is different in dry and in high humidity or water conditions. Experiments were performed to investigate B2O3 solid lubricant filler effectiveness on tribological behaviour of water-conditioned polyamide composites. Bonding between polyamide6 and water molecules plus the formation of orthoboric acid was found advantageous in decreasing the friction coefficient and wear rates of composites.

Experimental study on the relationship between the friction coefficient and interference in locomotive axle press-fitting

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ting Wang ◽  
Hanfei Guo ◽  
Jianjun Qiao ◽  
Xiaoxue Liu ◽  
Zhixin Fan
Keyword(s):  
Friction Coefficient ◽  
Coefficient Of Friction ◽  
Friction Pair ◽  
Rolling Stock ◽  
Content Type ◽  
Press Fitting ◽  
The Press ◽  
The Coefficient Of Friction ◽  
The Relationship ◽  
Locomotive Wheels

PurposeTo address the lack of data in this field and determine the relationship between the coefficient of friction and the interference between locomotive wheels and axles, this study evaluates the theoretical relationship between the coefficient of friction and the interference under elastic deformation.Design/methodology/approachWhen using numerical analyses to study the mechanical state of the contacting components of the wheels and axle, the interference between the axle parts and the coefficient of friction between the axle parts are two important influencing factors. Currently, as the range of the coefficient of friction between the wheel and axle in interference remains unknown, it is generally considered that the coefficient of friction is only related to the materials of the friction pair; the relationship between the interference and the coefficient of friction is often neglected.FindingsA total of 520 press-fitting experiments were conducted for 130 sets of wheels and axles of the HXD2 locomotive with 4 types of interferences, in order to obtain the relationship between the coefficient of friction between the locomotive wheel and axle and the amount of interference. These results are expected to serve as a reference for selecting the coefficient of friction when designing axle structures with the rolling stock, research on the press-fitting process and evaluations of the fatigue life.Originality/valueThe study provides a basis for the selection of friction coefficient and interference amount in the design of locomotive wheels and axles.

Characteristics analysis of behavioural portfolio theory in the Markowitz portfolio theory framework

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Saksham Mittal ◽  
Sujoy Bhattacharya ◽  
Satrajit Mandal
Keyword(s):  
Emerging Markets ◽  
Asset Allocation ◽  
Portfolio Theory ◽  
Optimal Portfolio ◽  
Content Type ◽  
Major Index ◽  
Brics Countries ◽  
Trade Offs ◽  
Characteristics Analysis ◽  
Mean Variance

PurposeIn recent times, behavioural models for asset allocation have been getting more attention due to their probabilistic modelling for scenario consideration. Many investors are thinking about the trade-offs and benefits of using behavioural models over conventional mean-variance models. In this study, the authors compare asset allocations generated by the behavioural portfolio theory (BPT) developed by Shefrin and Statman (2000) against the Markowitz (1952) mean-variance theory (MVT).Design/methodology/approachThe data used have been culled from BRICS countries' major index constituents from 2009 to 2019. The authors consider a single period economy and generate future probable outcomes based on historical data in order to determine BPT optimal portfolios.FindingsThis study shows that a fair number of portfolios satisfy the first entry constraint of the BPT model. BPT optimal portfolio exhibits high risk and higher returns as compared to typical Markowitz optimal portfolio.Originality/valueThe BRICS countries' data were used because the dynamics of the emerging markets are significantly different from the developed markets, and many investors have been considering emerging markets as their new investment avenues.

Image processing procedure to quantify the internal structure of porous asphalt concrete

2019 ◽  
Vol 15 (1) ◽  
pp. 206-226 ◽  
Author(s):  
Kabiru Abdullahi Ahmad ◽  
Norhidayah Abdul Hassan ◽  
Mohd Ezree Abdullah ◽  
Munder A.M. Bilema ◽  
Nura Usman ◽  
...  
Keyword(s):  
Internal Structure ◽  
Asphalt Concrete ◽  
Functional Performance ◽  
Resilient Modulus ◽  
Asphalt Mixture ◽  
Content Type ◽  
Porous Asphalt ◽  
X Ray ◽  
Air Void ◽  
Aggregate Interlock

Purpose In order to fully understand the properties of porous asphalt, investigation should be conducted from different point of views. This is from the fact that porous asphalt mixture designed with the same aggregate gradation and air void content can give different infiltration rate due to the different formation of the internal structure. Therefore, the purpose of this paper is to investigate the micro-structural properties and functional performance of porous asphalt simultaneously. Design/methodology/approach The aim is to develop imaging techniques to process and analyze the internal structure of porous asphalt mixture. A few parameters were established to analyze the air void properties and aggregate interlock within the gyratory compacted samples captured using a non-destructive scanning technique of X-ray computed tomography (CT) throughout the samples. The results were then compared with the functional performance in terms of permeability. Four aggregate gradations used in different countries, i.e. Malaysia, Australia, the USA and Singapore. The samples were tested for resilient modulus and permeability. Quantitative analysis of the microstructure was used to establish the relationships between the air void properties and aggregate interlock and the resilient modulus and permeability. Findings Based on the results, it was found that the micro-structural properties investigated have successfully described the internal structure formation and they reflect the results of resilient modulus and permeability. In addition, the imaging technique which includes the image processing and image analysis for internal structure quantification seems to be very useful and perform well with the X-ray CT images based on the reliable results obtained from the analysis. Research limitations/implications In this study, attention was limited to the study of internal structure of porous asphalt samples prepared in the laboratory using X-ray CT but can also be used to assess the quality of finished asphalt pavements by taking core samples for quantitative and qualitative analysis. The use of CT for material characterization presents a lot of possibilities in the future of asphalt concrete mix design. Originality/value Based on the validation process which includes comparisons between the values obtained from the image analysis and those from the performance test and it was found that the developed procedure satisfactorily assesses the air voids distribution and the aggregate interlock for this reason, it can be used.

Tribological and electrical behavior of Cu-based composites with addition of Ti-doped NbSe2 nanoplatelets

2018 ◽  
Vol 70 (3) ◽  
pp. 560-567 ◽  
Author(s):  
Jian Feng Li ◽  
Qin Shi ◽  
HeJun Zhu ◽  
ChenYu Huang ◽  
Shuai Zhang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Solid State ◽  
Friction Coefficient ◽  
Electrical Properties ◽  
Tribological Properties ◽  
Solid State Reaction ◽  
Electrical Contact ◽  
Solid State Reaction Method ◽  
Content Type ◽  
Reaction Method

Purpose This paper aims to clarify the size and morphology of transition metal dichalcogenides has an impact on lubrication performance of Cu-based composites. This study is intended to show that Cu-based electrical contact materials containing Nb0.91Ti0.09Se2 have better electrical and tribological properties than those containing NbSe2. The tribological properties of Cu-based with different Ti-dopped NbSe2 content were also discussed. Design/methodology/approach The NbSe2 and Nb0.91Ti0.09Se2 particles were fabricated by thermal solid state reaction method. The powder metallurgy technique was used to fabricate composites with varying Nb0.91Ti0.09Se2 mass fraction. The phase composition of Cu-based composites was identified by X-ray diffraction, and the morphology of NbSe2/Nb0.91Ti0.09Se2 and the worn surface of composites were characterized by scanning electron microscopy and transmission electron microscopy. In addition, the tribological properties of composites were appraised using a ball-on-disk multi-functional tribometer. The data of friction coefficient and resistivity were analyzed and the corresponding conclusion was drawn. Findings In comparison with the pure copper, Cu-based composites containing Nb0.91Ti0.09Se2/NbSe2 had a lower friction coefficient, illustrating the Nb0.91Ti0.09Se2 with nano-size particles prepared in this work is a perfect choice for the fabrication of excellent electrical contact composites. Compared to composites with NbSe2, composites containing Nb0.91Ti0.09Se2 have better tribological and electrical properties. Research limitations/implications Because of the use of thermal solid state reaction method, the size of NbSe2 and Nb0.91Ti0.09Se2 is relatively large. Therefore, the fabrication of finer particles of Nb0.91Ti0.09Se2 is encouraged. Originality/value In this paper, the authors discuss the tribological and electrical properties of Cu-based composites, and the value of optimum obtained as Nb0.91Ti0.09Se2 content is 15 Wt.%.

The structure and changes of China’s land system

2019 ◽  
Vol 11 (3) ◽  
pp. 471-488 ◽  
Author(s):  
Liu Shouying
Keyword(s):  
Economic Growth ◽  
Institutional Change ◽  
Structural Changes ◽  
Structural Characteristics ◽  
Institutional Arrangements ◽  
Reform Process ◽  
Content Type ◽  
The Past ◽  
Land System ◽  
Rapid Economic Growth

Purpose The purpose of this paper is to analyze the structure and changes of China’s land system. To achieve this aim, the paper is divided into four parts. The first part gives a brief introduction to the structural characteristics of the Chinese land institutional arrangements; the second part analyzes the reform process of the land system in the past 40 years and its path of change; the third part engages the discussion about the historic contribution made by the land institutional change to rapid economic growth and structural changes; and the final part is conclusion and some policy implications. Design/methodology/approach After 40 years of reforms and opening up, China has not only created a growth miracle unparalleled for any major country in human history, but also transformed itself from a rural to an urban society. Behind this great transformation is a systemic reform in land institutions. Rural land institutions went from collectively owned to household responsibility system, thereby protecting farmers’ land rights. This process resulted in long-term sustainable growth in China’s agriculture, a massive rural-urban migration and a historical agricultural transformation. The conversion of agricultural land to non-agricultural uses and the introduction of market mechanisms made land a policy tool in driving high economic growth, industrialization and urbanization. Findings Research shows that the role of land and its relationship with the economy will inevitably change as China’s economy enters a new stage of medium-to-high speed growth. With economic restructuring, low-cost industrial land will be less effective. Urbanization is also shifting from rapid expansion to endogenous growth so that returns on land capitalization will decrease and risks will increase. Therefore, China must abandon land-dependent growth model through deepening land reforms and adapt a new pattern of economic development. Originality/value This paper gives a brief introduction to the structural characteristics of the Chinese land institutional arrangements, analyzes the reform process of the land system in the past 40 years and its path of change, and evaluates the historic contribution made by the land institutional change to rapid economic growth and structural changes.

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