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Article
Publication date: 25 February 2022

Jiabao Pan, Huaibiao Wu, Ao Wang, Qingwen Dai and Xiaolei Wang

This paper aims to investigate the influence of high-temperature thermal action on grease performance from the angle of film-forming performance.

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Abstract

Purpose

This paper aims to investigate the influence of high-temperature thermal action on grease performance from the angle of film-forming performance.

Design/methodology/approach

A static thermal aging method was used to prepare high-temperature thermal grease samples after high-temperature thermal action. On the basis of optical interference technology, the film-forming characteristics of fresh grease samples and the grease samples after high-temperature thermal action under variable speed and fixed speed conditions were explored.

Findings

The decrease in the structural entanglement performance of the grease after short-term high-temperature thermal action makes its film-forming performance better. The mechanism is that the lubricating grease soap fiber entanglement is reduced. Although the continuous high-temperature thermal action can make the grease film-forming performance better, its mechanism is that the soap fiber structure caused by high-temperature thermal action is damaged and is easy to be cut off under the action of shear.

Originality/value

The effect of structural system change on its film formation performance was discussed in combination with the change in grease structure characteristics, and the mechanism of action was revealed.

Details

Industrial Lubrication and Tribology, vol. 74 no. 5
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 27 April 2023

Jinliang Liu and Xincheng Su

The effects of carbon fiber reinforced polymer (CFRP) reinforcement form, adhesive type and pre-crack width on failure mode, shear capacity, deflection response, CFRP strain…

Abstract

Purpose

The effects of carbon fiber reinforced polymer (CFRP) reinforcement form, adhesive type and pre-crack width on failure mode, shear capacity, deflection response, CFRP strain response and crack patterns of strengthened specimens were investigated.

Design/methodology/approach

This paper presents a geopolymer adhesive that matches the performance requirements of CFRP adhesive, which is applied to pre-cracked beams reinforced with CFRP strips.

Findings

For specimens with varying structural properties, two failure modes, the CFRP-concrete interface substrate failure and the fracture failure of CFRP, are observed. Moreover, the shear capacity, ultimate deflection and bending stiffness of the U-shaped CFRP-strengthened beams are enhanced in comparison to the complete-wrapping CFRP-strengthened beams. With an increase in pre-crack width, the increase in shear capacity of RC beams shear-strengthened with CFRP strips is less than that of non-cracked beams, resulting in a limited influence on the stiffness of CFRP-strengthened beams. The comparison of experimental results showed that the proposed finite element model (FEM) effectively evaluated the mechanical characteristics of CFRP-strengthened RC beams.

Originality/value

Taking into consideration the reinforcement effect and the concept of environmental protection, the geopolymer adhesive reinforcement scheme is preferable to applying epoxy resin to the CFRP-strengthened RC beams.

Details

International Journal of Structural Integrity, vol. 14 no. 3
Type: Research Article
ISSN: 1757-9864

Keywords

Article
Publication date: 16 February 2023

M. Vishal and K.S. Satyanarayanan

This study delineates the effect of cover thickness on reinforced concrete (RC) columns and beams under an elevated fire scenario. Columns and beams are important load-carrying…

Abstract

Purpose

This study delineates the effect of cover thickness on reinforced concrete (RC) columns and beams under an elevated fire scenario. Columns and beams are important load-carrying structural members of buildings. Under all circumstances, the columns and beams were set to be free from damage to avoid structural failure. Under the high-temperature scenario, the RC element may fail because of the material deterioration that occurs owing to the thermal effect. This study attempts to determine the optimum cover thickness for beams and columns under extreme loads and fire conditions.

Design/methodology/approach

Cover thicknesses of 30, 40, 45, 50, 60 and 70 mm for the columns and 10, 20, 25, 30, 35, 40, 50, 60 and 70 mm for the beams were adopted in this study. Both steady-state and transient-state conditions under thermomechanical analysis were performed using the finite element method to determine the heat transfer through the RC section and to determine the effect of thermal stresses.

Findings

The results show that the RC elements have a greater influence on the additional cover thickness at extreme temperatures and higher load ratios than at the service stages. The safe limits of the structural members were obtained under the combined effects of elevated temperatures and structural loads. The results also indicate that the compression members have a better thermal performance than the flexural members.

Research limitations/implications

Numerical investigations concerning the high-temperature behavior of structural elements are useful. The lack of an experimental setup encourages researchers to perform numerical investigations. In this study, the finite element models were validated with existing finite element models and experimental results.

Practical implications

The obtained safe limit for the structural members could help to understand their resistance to fire in a real-time scenario. From the safe limit, a suitable design can be preferred while designing the structural members. This could probably save the structure from collapse.

Originality/value

There is a lack of both numerical and experimental research works. In numerical modeling, the research works found in the literature had difficulties in developing a numerical model that satisfactorily represents the structural members under fire, not being able to adequately understand their behavior at high temperatures. None of them considered the influence of the cover thickness under extreme fire and loading conditions. In this paper, this influence was evaluated and discussed.

Details

Journal of Structural Fire Engineering, vol. 14 no. 4
Type: Research Article
ISSN: 2040-2317

Keywords

Article
Publication date: 10 August 2018

Yongliang Jin, Haitao Duan, Lei Wei, Song Chen, Xuzheng Qian, Dan Jia and Jian Li

This paper aims to investigate the tribological behavior and online infrared spectra of three types of lubricating oils containing dinonyl diphenylamine (DNDA) antioxidant, which…

Abstract

Purpose

This paper aims to investigate the tribological behavior and online infrared spectra of three types of lubricating oils containing dinonyl diphenylamine (DNDA) antioxidant, which are mineral oil (MO), poly alpha olefin (PAO) and trimethylolpropane trioleate (TMPTO), during the friction process at high temperature (temperature rising at first and isothermal holding afterwards).

Design/methodology/approach

A platform of low speed four-ball tribometer equipped with a temperature controller combined with infrared spectrometer was established. MO, PAO and TMPTO base oils were mixed with 1.0 Wt.% DNDA antioxidant, coded as MOa, PAOa and TMPTOa in sequence. The friction coefficient and online infrared spectra of the oils were tested during the friction process of temperature rising at first and isothermal holding afterwards, and the wear tracks of the upper balls were measured using a confocal scanning optical microscope.

Findings

The results indicated that the DNDA antioxidant was depleted to reduce the generation of alcohols and carbonyl products, and the depletion rate of DNDA followed the sequence of MOa > PAOa > TMPTOa. In the temperature rising friction process, the critical transition of friction coefficient was confirmed. The addition of DNDA antioxidant reduced the temperature of the oils at the critical transition of friction coefficient, and the temperature followed the sequence of TMPTOa > PAOa > MOa. After the critical transition, the friction coefficient was first increased and then declined to a steady value; the friction coefficient of MOa increased and declined first, followed by PAOa and TMPTOa. In the steady stage of friction, there was no obvious effect of DNDA on the friction coefficient of the oils. Moreover, DNDA enhanced the wear properties of MOa and PAOa; no obvious improvement was revealed for the wear property of TMPTOa.

Originality/value

The established platform of low speed four-ball tribometer combined with infrared spectrometer successfully realized online testing of the structure changes of lubricating oil during high temperature friction, which can give some reference on the oxidation and friction researches of lubricating oil.

Details

Industrial Lubrication and Tribology, vol. 70 no. 7
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 1 July 1931

Arthur Nutt

CONSIDERABLE interest has been shown during the last year or two in the use of high temperature liquid coolant for aircraft engines. Both evaporative cooling, which has been used…

Abstract

CONSIDERABLE interest has been shown during the last year or two in the use of high temperature liquid coolant for aircraft engines. Both evaporative cooling, which has been used experimentally on automobile and aircraft engines, and the use of high‐boiling‐point liquid have been considered. In England evaporative cooling has received probably more attention than high temperature liquid cooling, while in America the latter has received more attention.

Details

Aircraft Engineering and Aerospace Technology, vol. 3 no. 7
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 1 September 2002

C.P. Providakis and S.G. Kourtakis

The feasibility of advanced viscoplastic models for non‐linear boundary element analysis of metallic structural components with dependence on thermomechanical history is…

Abstract

The feasibility of advanced viscoplastic models for non‐linear boundary element analysis of metallic structural components with dependence on thermomechanical history is investigated. Several numerical examples are presented using the boundary element implementation of two different internal state variable viscoplastic models to the solution of time‐dependent inelastic problems arising in creeping metallic structural components under the combined action of high temperature loading gradients and quasi‐static mechanical loading conditions. To demonstrate the efficiency of the implemented viscoplastic models, the results obtained using the direct boundary element methodology are compared with those obtained by both analytical and finite element solution as well as, for different numerical results of plane strain thermoviscoplastic deformation problems under general thermomechanical loading.

Details

Engineering Computations, vol. 19 no. 6
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 1 April 2002

W.F. Sales, G. Guimarães, Á.R. Machado and E.O. Ezugwu

Many machining researches are focused on cutting tools mainly due to the wear developed as a result of high temperatures generated that accelerate thermally related wear…

Abstract

Many machining researches are focused on cutting tools mainly due to the wear developed as a result of high temperatures generated that accelerate thermally related wear mechanisms, consequently reducing tool life. Cutting fluids are used in machining operations to minimize cutting temperature although there is no available indicator of their cooling ability. In this study, a method to determine the cooling ability of cutting fluids is proposed. A thermocouple technique was used to verify the chip‐tool interface temperature of various cutting fluids during turning operation. The method consists of measuring the temperature drop from 300°C up to room temperature after heating a standardised AISI 8640 workpiece and fixing it to the chuck of a lathe and with a constant spindle speed of 150 rpm the cutting fluid was applied to a specific point. The temperature was measured and registered by an infrared thermosensor with the aid of an AC/DC data acquisition board and a PC. The convective heat exchange coefficient, h, was determined and used to classify the cooling ability of the cutting fluids. The machining tests showed that the application of the fluid with better cooling ability will not always guarantee lower chip‐tool interface temperature.

Details

Industrial Lubrication and Tribology, vol. 54 no. 2
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 26 September 2023

Jiabao Pan, Rui Li and Ao Wang

The adverse effects of temperature on the lubricating properties of nano magnetorheological grease are reduced by applying of a magnetic field.

Abstract

Purpose

The adverse effects of temperature on the lubricating properties of nano magnetorheological grease are reduced by applying of a magnetic field.

Design/methodology/approach

Nano magnetorheological grease was prepared via a thermal water bath with stirring. The lubricating properties of the grease were investigated at different temperatures. Then the lubricity of the prepared nano magnetorheological grease was investigated under the effect of thermomagnetic coupling.

Findings

As the temperature rises, the coefficient of friction of grease lubrication gradually increases, surface wear gradually increases and lubrication performance gradually decreases. Compared with grease, magnetorheological grease has a decreased coefficient of friction and enhanced lubrication effect under the action of a magnetic field at different temperatures.

Originality/value

A lubrication method using a magnetic field to reduce the effect of temperature is established, thereby providing new ideas for lubrication design under a wide range of temperature conditions.

Details

Industrial Lubrication and Tribology, vol. 75 no. 9
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 1 November 2006

Ertuğrul Durak, Cahit Kurbanoğlu and Recai Fatih Tunay

In this study, an attempt is made to show the linkage between the oil additive and journal bearing the running conditions such as temperature, load, speed, etc. in effecting…

Abstract

Purpose

In this study, an attempt is made to show the linkage between the oil additive and journal bearing the running conditions such as temperature, load, speed, etc. in effecting lubricating. It is well known that öne of the roles of additives is to form protective layer to reduce friction coeffıcient in lubricated contacts.

Design/methodology/approach

The tests were performed at three different loads, and eight speeds. The tests were carried out for three different commercial additives that are concentration ratio of 3 per cent.

Findings

The test results of the experimental coeffıcient of friction were graphically presented. The highest reduction in the friction coeffıcient was obtained at high temperature (100°C) in the tests than room temperature (25°C) tests.

Research limitations/implications

In this study, effects of commercial oil additives on the friction coefficîent in the journal bearing under statically loaded have been studied experimentally at 25 and 100°C temperatures.

Practical implications

Lubricating oils find applications in engines, industrial uses, greases and automotive transmissions. The majör uses of these oils are in engines (55 per cent), industry (27 per cent), processes (9 per cent), greases (5 per cent) and automotive transmissions (4 per cent). Lubricants perform a variety of functions in automotive application. One of the important functions is to reduce friction and wear in movîng machinery.

Originality/value

Generally, by adding additives to engine oil the lower friction coeffıcient were observed comparison engine oil both at 25 and 100°C temperatures. But, the smallest friction coefficient was obtained in the tests at 100°C comparison with the tests at 25°C in the additive addition to engine oil tests.

Details

Industrial Lubrication and Tribology, vol. 58 no. 6
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 15 May 2023

Yiming Li and Chenyang Lv

To extend the reuse method and rate of straw biomass, this paper investigated the effect of lignin synthetic phenolic resin (LPF) on the rheological properties of asphalt binder.

102

Abstract

Purpose

To extend the reuse method and rate of straw biomass, this paper investigated the effect of lignin synthetic phenolic resin (LPF) on the rheological properties of asphalt binder.

Design/methodology/approach

Four LPFs with 25%, 50%, 75% and 100% substitution rates were prepared by replacing phenol with lignin in synthetic resins and using it as a modifier to prepare a bio-asphalt binder. Temperature sweep tests were conducted to evaluate aging resistance and temperature sensitivity of the bio-asphalt binder. The rutting resistance of the bio-asphalt binder was evaluated by frequency sweeps and multiple stress creep recovery (MSCR) test. Linear amplitude sweep (LAS) tests were conducted to evaluate the fatigue resistance of the bio-asphalt binder. A master curve was constructed to further analyze the rheological properties of the bio-asphalt binder at different frequencies. The low-temperature cracking resistance of the binder was evaluated by G-R parameters, critical temperatures and ΔTc. Fourier transform infrared spectroscopy (FTIR) was performed to investigate the changes in the functional groups of the binder before and after aging.

Findings

The results indicated that adding LPF could improve the high-temperature rutting resistance, fatigue resistance, aging resistance of asphalt and the binders are less affected by temperature. Additionally, LPF slightly prohibited the low-temperature performance of the asphalt binder, which, however, was significantly lower than the base asphalt degradation during aging. Compared with base asphalt binders, the bio-asphalt binder showed no new absorption peaks generated after adding LPF, identifying that the improved asphalt binder performance by LPF was a mainly physical modification.

Originality/value

The main objective of this paper is to further improve the substitution rate (i.e. the mass substitution ratio of lignin to phenol) of lignin and broaden the application of biomass resins, thus realizing resource sustainability.

Details

Multidiscipline Modeling in Materials and Structures, vol. 19 no. 4
Type: Research Article
ISSN: 1573-6105

Keywords

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