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An investigation on modification mechanism of CH

Qiang XIN, Shanghong HUANG

Frontiers of Structural and Civil Engineering 2017, Volume 11, Issue 3,   Pages 293-300 doi: 10.1007/s11709-017-0403-0

Abstract: Rising oil price has brought huge cost pressure for low grade highway construction, and it is urgent to find alternative resources. At the same time, there are nearly 50000–60000 tons of low temperature coal output in inner Mongolia region, China, which has high toxicity and high polluting. To make the low temperature coal be applicable for road constructions, the formaldehyde is used as cross linking agent, the concentrated sulfuric acid is used as catalyst, and the chemical modification of low temperature coal tar pitch in Inner Mongolia region is investigated. The road performance (softening point, penetration and ductility) of modified low temperature coal are tested. Results shown that the road performance of modified low temperature coal is increased significantly. Modification mechanism of low temperature coal is studied by Scanning Electron Microscopy and other analytical tools. Results show that, in the modified low temperature coal, resin content increases and the resin fiber diameter becomes larger with the increasing of formaldehyde content.

Keywords： low temperature     coal tar pitch     modification     road performance    

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Multi-scale investigation of active failure for various modes of wall movement

Frontiers of Structural and Civil Engineering 2021, Volume 15, Issue 4,   Pages 961-979 doi: 10.1007/s11709-021-0738-4

Abstract: Retained backfill response to wall movement depends on factors that range from boundary conditions to the geometrical characteristic of individual particles. Hence, mechanical understanding of the problem warrants multi-scale analyses that investigate reciprocal relationships between macro and micro effects. Accordingly, this study attempts a multi-scale examination of failure evolution in cohesionless backfills. Therefore, the transition of retained backfills from at-rest condition to the active state is modeled using the discrete element method (DEM). DEM allows conducting virtual experiments, with which the variation of particle and boundary properties is straightforward. Hence, various modes of wall movement (translation and rotation) toward the active state are modeled using two different backfills with distinct particle shapes (spherical and nonspherical) under varying surcharge. For each model, cumulative rotations of single particles are tracked, and the results are used to analyze the evolution of shear bands and their geometric characteristics. Moreover, dependencies of lateral pressure coefficients and coordination numbers, as respective macro and micro behavior indicators, on particle shape, boundary conditions, and surcharge levels are investigated. Additionally, contact force networks are visually determined, and their influences on pressure distribution and deformation mechanisms are discussed with reference to the associated modes of wall movement and particle shapes.

Keywords： discrete-element modelling     granular materials     retaining walls     particle shape     arching    

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Analytical and numerical investigation into the longitudinal vibration of uniform nanotubes

Masoud MASOUMI,Mehdi MASOUMI

Frontiers of Mechanical Engineering 2014, Volume 9, Issue 2,   Pages 142-149 doi: 10.1007/s11465-014-0292-z

Abstract:

In recent years, prediction of the behaviors of micro and nanostructures is going to be a matter of increasing concern considering their developments and uses in various engineering fields. Since carbon nanotubes show the specific properties such as strength and special electrical behaviors, they have become the main subject in nanotechnology researches. On the grounds that the classical continuum theory cannot accurately predict the mechanical behavior of nanostructures, nonlocal elasticity theory is used to model the nanoscaled systems. In this paper, a nonlocal model for nanorods is developed, and it is used to model the carbon nanotubes with the aim of the investigating into their longitudinal vibration. Following the derivation of governing equation of nanorods and estimation of nondimensional frequencies, the effect of nonlocal parameter and the length of the nanotube on the obtained frequencies are studied. Furthermore, differential quadrature method, as a numerical solution technique, is used to study the effect of these parameters on estimated frequencies for both classical and nonlocal theories.

Keywords： continuum theory     differential quadrature method     nanorod     longitudinal vibration    

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Molecular dynamics investigation of mechanical properties of single-layer phagraphene

Ali Hossein Nezhad SHIRAZI

Frontiers of Structural and Civil Engineering 2019, Volume 13, Issue 2,   Pages 495-503 doi: 10.1007/s11709-018-0492-4

Abstract: Phagraphene is a very attractive two-dimensional (2D) full carbon allotrope with very interesting mechanical, electronic, optical, and thermal properties. The objective of this study is to investigate the mechanical properties of this new graphene like 2D material. In this work, mechanical properties of phagraphene have been studied not only in the defect-free form, but also with the critical defect of line cracks, using the classical molecular dynamics simulations. Our study shows that the pristine phagraphene in zigzag direction experience a ductile behavior under uniaxial tensile loading and the nanosheet in this direction are less sensitive to temperature changes as compared to the armchair direction. We studied different crack lengths to explore the influence of defects on the mechanical properties of phagraphene. We also investigated the temperature effect on the mechanical properties of pristine and defective phagraphene. Our classical atomistic simulation results confirm that larger cracks can reduce the strength of the phagraphene. Moreover, it was shown the temperature has a considerable weakening effect on the tensile strength of phagraphene. The results of this study may be useful for the design of nano-devices using the phagraphene.

Keywords： phaqraphene     mechanical properties     crack propaqation     molecular dynamics     thermal effects    

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Numerical investigation of aerodynamic performance influenced by circumferentially pre-swirling coming

WANG Qikun, CHEN Kangmin

Frontiers in Energy 2007, Volume 1, Issue 4,   Pages 435-440 doi: 10.1007/s11708-007-0063-5

Abstract: Numerical investigation is implemented on aerodynamic performance inside the crossover and de-swirling

Keywords： aerodynamic     investigation     centrifugal     de-swirling     circumferent    

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Experimental investigation of the influence on static and cyclic deformation of structural soft clay

CHEN Yunmin, CHEN Yingping, HUANG Bo

Frontiers of Structural and Civil Engineering 2007, Volume 1, Issue 4,   Pages 422-429 doi: 10.1007/s11709-007-0057-4

Abstract: This paper presents the experimental results performed to study the static and cyclic deformation behavior of undisturbed and remolded soft clays sampling from Xiaoshan. The consolidation tests indicated that the vertical strains of

Keywords： consolidation     deformation     experimental     undisturbed    

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Numerical investigation of the effects of fuel spray type on the interaction of fuel spray and hot porous

ZHAO Zhiguo, XIE Maozhao

Frontiers in Energy 2008, Volume 2, Issue 1,   Pages 59-65 doi: 10.1007/s11708-008-0022-5

Abstract: The interaction between two types of fuel spray and a hot porous medium is studied numerically by using an improved version of KIVA-3V code. The improved KIVA-3V code is incorporated with an impingement model, a heat transfer model and a linearized instability sheet atomization (LISA) model to model the hollow cone spray. An evaporating fuel spray impingement on a hot plane surface was simulated under conditions of experiments performed by Senda to validate the reasonability of the KIVA-3V code. The numerical results conform well with experimental data for spray radius in the liquid and the vapor phases. Computational results on the interaction of two types of the fuel spray and the hot porous medium show that the fuel spray can be split, which provides conditions for quick evaporation of fuel droplets and mixing of fuel vapor with air. The possibility of fuel droplets from hollow cone spray crossing the porous medium reduces compared with that from solid cone spray, with the same initial kinetic energy of fuel droplets in both injection types.

Keywords： improved version     impingement     atomization     hollow     radius    

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Experimental investigation on desiccant air-conditioning system in India

Vijay MITTAL, B. Kant KHAN,

Frontiers in Energy 2010, Volume 4, Issue 2,   Pages 161-165 doi: 10.1007/s11708-009-0070-5

Abstract: An experimental investigation in India was presented to evaluate the performance and energy saving capacity

Keywords： air ratios     ambient conditions     desiccant air-conditioning     silica gel    

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An investigation into the vibration of harmonic drive systems

M. Masoumi, H. Alimohammadi

Frontiers of Mechanical Engineering 2013, Volume 8, Issue 4,   Pages 409-419 doi: 10.1007/s11465-013-0275-5

Abstract:

Harmonic drive systems are precise and specific transmission gear systems which are beneficial in terms of the high transmission ratio and almost zero backlash. These inherent and spectacular properties result in using this mechanism in robotic and space sciences where the precision and lightwieght play an important role. This paper presents a vibration analysis of harmonic drive systems using the shell theory. Equations of vibration for the flexspline and the circular spline of the system are derived and used to find the natural frequencies for both parts and, moreover, vibration response of the system under the operating condition is calculated. Also, obtained vibration equations are utilized to study the effects of different involved parameters such as the geometry of the flexspline and its gear tooth, eccentricity, and unbalancing on the vibrational behavior of the system.

Keywords： harmonic drive system     strain wave gearing mechanism     vibration analysis     natural frequencies    

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An investigation on prevalent strategies for XFEM-based numerical modeling of crack growth in porous

Frontiers of Structural and Civil Engineering 2021, Volume 15, Issue 4,   Pages 914-936 doi: 10.1007/s11709-021-0750-8

Abstract: Crack growth modeling has always been one of the major challenges in fracture mechanics. Among all numerical methods, the extended finite element method (XFEM) has recently attracted much attention due to its ability to estimate the discontinuous deformation field. However, XFEM modeling does not directly lead to reliable results, and choosing a strategy of implementation is inevitable, especially in porous media. In this study, two prevalent XFEM strategies are evaluated: a) applying reduced Young’s modulus to pores and b) using different partitions to the model and enriching each part individually. We mention the advantages and limitations of each strategy via both analytical and experimental validations. Finally, the crack growth is modeled in a natural porous media (Fontainebleau sandstone). Our investigations proved that although both strategies can identically predict the stress distribution in the sample, the first strategy simulates only the initial crack propagation, while the second strategy could model multiple cracks growths. Both strategies are reliable and highly accurate in calculating the stress intensity factor, but the second strategy can compute a more reliable reaction force. Experimental tests showed that the second strategy is a more accurate strategy in predicting the preferred crack growth path and determining the maximum strength of the sample.

Keywords： numerical modeling     extended finite element method     porous media     crack growth     stress intensity factor    

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Test investigation on hydraulic losses in the discharge passage of an axial-flow pump

QIU Baoyun, CAO Haihong, JIANG Wei, GAO Zhaohui, WANG Fei

Frontiers of Mechanical Engineering 2007, Volume 2, Issue 1,   Pages 50-56 doi: 10.1007/s11465-007-0008-8

Abstract: In a discharge passage with a guide blade discharge circulation and secondary flow because of bend pipe, the flow in a 1-channel discharge passage of an axial flow pump is a complicated spiral flow. For a 2-channel passage, the discharge in the left channel is bigger than that in the right, and the passage hydraulic losses are abnormal. In this study, the section current energy of the passage is accurately measured and determined with a 5-hole probe. The hydraulic loss characteristics are determined and analyzed. The methods deducing the hydraulic losses are investigated. The results indicate that the passage hydraulic losses are not proportional to the flow discharge. Compared with a circular pipe, the hydraulic losses of a divergent discharge passage are smaller and the pump assembly efficiency is 10% 30% higher. As for the 1-channel passage, the axial-flow pump outlet circulation is usually too big; the passage hydraulic losses are also big, but a small circulation can slightly reduce hydraulic losses. As for the 2-channel passage, discharges in the two channels are not equal and the hydraulic losses increase. The outlet guide blade with a small discharge circulation or without circulation could reduce discharge passage hydraulic losses and increase pump assembly efficiency by 6% 11%.
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An investigation on stress distribution effect on multi- piezoelectric energy harvesters

Hailu YANG, Dongwei CAO

Frontiers of Structural and Civil Engineering 2017, Volume 11, Issue 3,   Pages 301-307 doi: 10.1007/s11709-017-0404-z

Abstract: With the fast development of piezoelectric materials and due to its green and renewable characteristics, the piezoelectric energy harvesting technology has been paid more and more attention by pavement engineers. The stress distribution will significantly affect the piezoelectric material performance. In this paper, the effects of multiple piezoelectric elements on the generation of electrical energy and output power are studied. In the case of constant external load, the number of the piezoelectric units does not necessarily produce more energy. When the same multi piezoelectric units work together, if the stress state of the piezoelectric units is different, the total output energy affected by the connection mode. For uneven stress distribution, the optimal output mode is that each of the piezoelectric units rectified before connected in parallel.

Keywords： piezoelectric transducer     uneven stress     impedance matching     optimal energy output    

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Experimental investigation on concrete overlaid with textile reinforced mortar: Influences of mix, temperature

Frontiers of Structural and Civil Engineering 2023, Volume 17, Issue 2,   Pages 271-283 doi: 10.1007/s11709-022-0896-z

Abstract: Textile reinforced mortar is widely used as an overlay for the repair, rehabilitation, and retrofitting of concrete structures. Recently, textile reinforced concrete has been identified as a suitable lining material for improving the durability of existing concrete structures. In this study, we developed a textile-reinforced mortar mix using river sand and evaluated the different characteristics of the textile-reinforced mortar under various exposure conditions. Studies were carried out in two phases. In the first phase, the pullout strength, temperature resistance, water absorption, and compressive and bending strength values of three different textile-reinforced mortar mixes with a single type of textile reinforcement were investigated. In the second phase, the chemical resistance of the mix that showed the best performance in the abovementioned tests was examined for use as an overlay for a concrete substrate. Investigations were performed on three different thicknesses of the textile reinforced mortar overlaid on concrete specimens that were subjected to acidic and alkaline environments. The flexural responses and degradations of the textile reinforced mortar overlaid specimens were examined by performing bending tests. The experimental findings indicated the feasibility of using textile reinforced mortar as an overlay for durable concrete construction practices.

Keywords： textile reinforced mortar     bending tests     acid and alkaline environment     concrete overlay    

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Modal disturbance investigation of rod-shaped ultrasonic motor using bending vibrations

ZHANG Jiantao, ZHU Hua, ZHAO Chunsheng

Frontiers of Mechanical Engineering 2008, Volume 3, Issue 3,   Pages 343-347 doi: 10.1007/s11465-008-0058-6

Abstract: Modal disturbance of a rod-shaped ultrasonic motor using bending vibrations can cause problems such as low motor efficiency, instability, and poor control. In this paper, a dynamic analysis model of a stator is created on the basis of the finite element method (FEM) and Hamilton principle. The modal frequency sensitivities of the stator to the structure parameters are investigated by modal analysis. Accordingly, the structure parameters of the stator are modified to separate working modes from disturbance modes. A rod-shaped ultrasonic motor stator is fabricated, and the experimental results of its amplitude frequency response characteristics show that the purpose of modal separation is achieved. The frequency separation between working modes and disturbance modes is more than 2 kHz. The validity of the method is verified.

Keywords： Hamilton principle     disturbance     separation     frequency separation     dynamic analysis    

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Detection of critical road roughness sections by trend analysis and investigation of driver speed interaction

Meltem SAPLIOGLU; Ayse UNAL; Melek BOCEK

Frontiers of Structural and Civil Engineering 2022, Volume 16, Issue 4,   Pages 515-532 doi: 10.1007/s11709-022-0814-4

Abstract: Pavement roughness (IRI—International Roughness Index values) influence the stability of traffic movements both on intercity roads and urban roads. This study is to determine the exact locations of critical pavement roughness values that affect traffic motion stability and comfort in city centre highway arteries. Roughness data with 10 m intervals were collected on a 3140 m divided road containing three consecutive signalized intersections in the city centre arterial. These data were analysed using the distance-dependent Mann-Kendall trend analysis method and checkerboard model. The sections where roughness is important were determined at a 95% confidence interval. The results will show where future pavement improvements should be prioritized for municipalities and road maintenance engineers and will form a basis for the urban road management system.

Keywords： trend analysis     checkerboard model     IRI     driver speed    

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Title Author Date Type Operation

An investigation on modification mechanism of CH

Qiang XIN, Shanghong HUANG

Journal Article

Multi-scale investigation of active failure for various modes of wall movement

Journal Article

Analytical and numerical investigation into the longitudinal vibration of uniform nanotubes

Masoud MASOUMI,Mehdi MASOUMI

Journal Article

Molecular dynamics investigation of mechanical properties of single-layer phagraphene

Ali Hossein Nezhad SHIRAZI

Journal Article

Numerical investigation of aerodynamic performance influenced by circumferentially pre-swirling coming

WANG Qikun, CHEN Kangmin

Journal Article

Experimental investigation of the influence on static and cyclic deformation of structural soft clay

CHEN Yunmin, CHEN Yingping, HUANG Bo

Journal Article

Numerical investigation of the effects of fuel spray type on the interaction of fuel spray and hot porous

ZHAO Zhiguo, XIE Maozhao

Journal Article

Experimental investigation on desiccant air-conditioning system in India

Vijay MITTAL, B. Kant KHAN,

Journal Article

An investigation into the vibration of harmonic drive systems

M. Masoumi, H. Alimohammadi

Journal Article

An investigation on prevalent strategies for XFEM-based numerical modeling of crack growth in porous

Journal Article

Test investigation on hydraulic losses in the discharge passage of an axial-flow pump

QIU Baoyun, CAO Haihong, JIANG Wei, GAO Zhaohui, WANG Fei

Journal Article

An investigation on stress distribution effect on multi- piezoelectric energy harvesters

Hailu YANG, Dongwei CAO

Journal Article

Experimental investigation on concrete overlaid with textile reinforced mortar: Influences of mix, temperature

Journal Article

Modal disturbance investigation of rod-shaped ultrasonic motor using bending vibrations

ZHANG Jiantao, ZHU Hua, ZHAO Chunsheng

Journal Article

Detection of critical road roughness sections by trend analysis and investigation of driver speed interaction

Meltem SAPLIOGLU; Ayse UNAL; Melek BOCEK

Journal Article