Search results

The present paper aims to experimentally investigate the effect of external horizontal vibration on friction property of an aluminium disc sliding against stainless steel pin.

To do so, a pin‐on‐disc apparatus having facility of vibrating the test samples at horizontal direction was designed and fabricated. In the study, a dimensional analysis is done to correlate the friction coefficient of aluminium with sliding velocity, frequency and amplitude of vibration.

At 100 Hz frequency of vibration, it is seen that during the starting, value of friction coefficient is 0.39 which remains constant for few seconds then increases almost linearly up to 0.45 over a duration of 15 s of rubbing and after that it remains constant for the rest of the experimental time. Similar trends of behavior are observed for transverse vibration. These findings are in agreement with the findings of Chowdhury and Helali.

It is expected that the applications of these results will contribute to the improvement of different concerned mechanical systems.

The frictional behavior of glass fiber reinforced plastic (GFRP) under natural frequency of the experimental set‐up is yet to be investigated. The purpose of this paper is to investigate the frictional behavior of GFRP under natural frequency of the experimental set‐up.

Experimental vibration is generated artificially in such a way that direction, amplitude, and frequency of vibration can be controlled.

The presence of natural frequency of vibration indeed affects the friction force considerably. The natural frequency of vibration decreases with the increase of added dead loads to the experimental set‐up. The values of friction coefficient increase with the increase of natural frequency of vibration of the experimental set‐up. As the friction coefficient increases with increasing natural frequency of vibration, therefore maintaining appropriate level of natural frequency vibration friction may be kept to some lower value to improve mechanical processes.

It is expected that the applications of these results will contribute to the improvement of different concerned mechanical systems.

The research is carried out experimentally and it can be expected the experimental results can be used for designing mechanical machine and systems.

The purpose of this paper is to present the frictional behaviour of composite materials under external horizontal vibration. Variation of friction coefficient is investigated experimentally when mild steel pin slides on composite materials such as glass fiber reinforced plastic (GFRP) and cloth reinforced ebonite (commercially known as gear fiber).

A pin‐on‐disc apparatus having the facility of vibrating the test samples in a horizontal direction is designed and fabricated. Horizontal vibration is created along (longitudinal direction), and perpendicular (transverse direction) to, the sliding direction. The experimental set‐up has the facility to vary the amplitudes and frequencies of vibration while velocity of vibration is kept constant.

The relative frictional behaviour of these materials and their dimensional analysis are yet to be investigated. Therefore an attempt is made to investigate the relative frictional property of the GFRP and cloth reinforced ebonite (commercially known as gear fiber) and the results of these composite materials are analyzed by dimensional analysis under horizontal vibration.

It is expected that the applications of these results will contribute to the improvement of different concerned mechanical systems.

It can also be noted that there are no clear correlations between friction‐ and other vibration‐related operating parameters. Considering the above conclusion and lack of correlation, the paper meant to find out a suitable correlation and a way of observing the response of friction force by applying known frequency and amplitude of vibration in a particular direction. It is expected that the application of these results will contribute to the improvement of different concerned mechanical systems.

This paper aims to examine whether female representation on boards is significantly associated with audit fees paid by top Egyptian listed companies.

The authors collect data on audit fees, board of directors' characteristics and financial data for the top 100 companies listed on the Egyptian Exchange (EGX100) for a period of six years. The authors employ an ordinary least squares regression model to capture the relationship between board diversity (i.e. the proportion of female board directors) and the natural logarithm of audit fees while controlling for firm and industry fixed effects as well as other known firm characteristics.

The authors find that audit fees are significantly associated with the proportion of females serving on firms' boards of directors. The findings suggest a complementary relationship between females on boards, as a quality-enhancing board attribute; and audit fees, as a proxy for audit effort and audit quality.

Limitations of this study arise first from the relatively small sample size, and second from the fact that inferences may be specific to the Egyptian context and similar markets.

The results have important implications for Egyptian policy makers and regulators in terms of board composition.

This study provides empirical evidence that further enforces the business case for women's empowerment and the impact of this on the effectiveness of corporate governance.

To the best of the authors’ knowledge, this is the first archival study to examine the association between female board representation and audit fees in Egypt.

The purpose of this paper is to investigate experimentally the effect of external vertical vibration on wear property of mild steel.

A pin‐on‐disc apparatus capable of vibrating the test samples in a vertical direction is designed and fabricated. The experimental setup has the ability to vary the amplitudes and frequencies of vibration while velocity of vibration is kept constant. During the experiment, the frequency and amplitude of vibration are varied from 0 to 500 Hz and 0 to 200 μm, respectively.

Results show that the wear rate decreases with the increase of amplitude and frequency of vibration for mild steel. These results are analyzed by dimensional analysis to correlate the wear rate with sliding velocity, normal load, frequency and amplitude of vibration. The experimental results are also compared with those available in literature and simple physical explanations are provided. Considering the lack of correlation between wear rate and other vibration‐related operating parameters, the present research is started to find out suitable correlation and a way of reducing wear rate by applying known frequency and amplitude of vibration at a particular direction.

It is expected that the applications of these results will contribute to the improvement of different concerned mechanical systems.

The paper can be used for design‐related purposes.

The purpose of this paper is to investigate experimentally the effect of natural frequency of the experimental set‐up on wear rate of glass fiber‐reinforced plastic (GFRP).

Experimental and dimensional analysis. A pin‐on‐disc apparatus having facility of vibrating the test samples at different directions, amplitudes and frequencies was designed and fabricated. The natural frequency of the set‐up was varied by adding dead loads of the set‐up from 0 to 50 kg. At each added load, the wear rate has been measured.

The presence of natural frequency of vibration indeed affects the wear rate considerably. The values of wear rate increase with the increase of natural frequency of vibration of the experimental set‐up. As the wear rate increases with increasing natural frequency of vibration, therefore, maintaining appropriate level of natural frequency vibration wear may be kept to some lower value to improve mechanical processes. The empirical formula of wear rate is derived from the dimensionless analysis. The wear rate obtained from the correlation shows better relationship with experimental results.

It is expected that the applications of these results will contribute to the improvement of different concerned mechanical systems and machines.

Considering the lack of correlation among wear rate, natural frequency of the experimental set‐up and other operating parameters, the present research was started to find out suitable correlation and a way of reducing wear rate by applying known natural frequency of vibration at a particular direction. Therefore, in this paper, an attempt is made to investigate the wear behavior of GFRP under natural frequency of the experimental set‐up. It is expected that the applications of these results will contribute to the improvement of different concerned mechanical systems.

The purpose of this paper is to investigate experimentally the effect of external vertical vibration on the friction property of mild steel, glass fiber‐reinforced plastic and cloth‐reinforced ebonite.

A pin‐on‐disc apparatus having the facility of vibrating the test samples in a vertical direction was designed and fabricated. The experimental setup has the facility to vary the amplitudes and frequencies of vibration, while the velocity of vibration is kept constant. During the experiment, the frequency and amplitude of vibration were varied from 0 to 500 Hz and 0 to 200 μm, respectively. Studies have shown that the friction coefficient decreases with the increase of amplitude and frequency of vertical vibration for the above‐said materials. The rate of decrease of friction coefficient is different for different materials. The results of these materials are analyzed by dimensional analysis to correlate the friction coefficient with sliding velocity, frequency and amplitude of vibration. The experimental results are also compared with those available in the literature and simple physical explanations are provided.

It was found that reducing the friction coefficient of different materials was achieved by way of reducing the friction force by applying known frequency and vibration and correlating the friction coefficient with frequency, amplitude and sliding velocity.

The paper presents a way of reducing friction force by applying known frequency and vibration so that the mechanical process can be considerably improved (by considering the appropriate design of vibration).

The paper's originality lies in demonstrating the correlation among friction coefficient, amplitude, frequency and sliding velocity for different types of materials.

Itaconic acid was reacted with phenylene diamine (ortho, meta and para) and o‐tolidine in boiling dekalin, using Dean and Stark apparatus. The polymers prepared were evaluated for their suitability as antioxidants for natural rubber vulcanizates. The amide polymers prepared showed high efficiency as antioxidants for rubber vulcanizates, exceeding the performance of commercial antioxidants. In addition, the results obtained are encouraging and support the use of these polymers from both the environmental and economical points of view.

The present paper seeks to report the effect of duration of rubbing on friction coefficient for different polymer and composite materials. Variations of friction coefficient and wear rate with the normal load are also investigated experimentally when stainless steel (SS 304) pin slides on different types of materials such as cloth‐reinforced ebonite (commercially known as gear fiber), glass fiber‐reinforced plastic (glass fiber), nylon and polytetrafluoroethylene (PTFE).

A pin on disc apparatus is designed and fabricated. During experiment, the rpm of test samples was kept constant and relative humidity was 70 percent.

Studies have shown that the values of friction coefficient depend on applied load and duration of rubbing. It is observed that the values of friction coefficient decrease with the increase of normal load for glass fiber, nylon and PTFE. Different trend is observed for gear fiber, i.e. coefficient of friction increases with the increase of normal load. It is also found that wear rate increases with the increase of normal load for all the materials. The magnitudes of friction coefficient and wear rate are different for different materials.

It is expected that the applications of these results will contribute to the design of different mechanical components of these materials.

Within the observed range of applied normal load, the relative friction coefficient and wear rate of gear fiber, glass fiber, nylon and PTFE are experimentally investigated.

The purpose of this paper is to study the sliding and the vibrating fretting tests mechanism of h‐BN micro‐particles when used as a lubricating grease‐2 additive.

The fretting tests were conducted on steel/steel contacts using both vibrating fretting apparatus and the shaft‐sleeve slide fitted tester. The wear scars were characterized with profilometry. The tribological properties of grease‐2 compounded with h‐BN additive were also compared to those obtained for the commercial product Militec‐4.

The experiment showed significant differences between the results obtained from the vibrating fretting and the shaft‐sleeve sliding fitted tests. Adding h‐BN to the lubricant leads to a better performance in the shaft‐sleeve slide regime than in the steel/steel vibrating test condition.

The results of the experimental studies demonstrate the potential of h‐BN as an additive for preventing fretting sliding, and can very useful for further application of compound grease‐2 with h‐BN additive in industrial equipment.