İlker Sugözü, Cengiz Öner, İbrahim Mutlu and Banu Sugözü
The purpose of this study was to investigate the use of boric acid as a friction modifier material in brake friction composites and to determine the effect of heat treatment…
Abstract
Purpose
The purpose of this study was to investigate the use of boric acid as a friction modifier material in brake friction composites and to determine the effect of heat treatment applied during production on braking performance.
Design/methodology/approach
The addition of five different amounts of boric acid was balanced with cashew, which is in the friction modifier material group. The samples were produced in the following order: dry mixing, preforming and hot-pressing. The effect of the heat treatment that can be applied after the hot-pressing process on the braking performance was investigated. The tribological and physical properties of the samples were determined using tests performed according to appropriate standards. The microstructures of the friction surfaces were investigated using scanning electron microscopy.
Findings
It was observed that the tribological properties of brake friction composites containing 20% by weight of boric acid were improved. It has also been observed that the heat treatment applied after hot pressing increased the friction coefficient of the samples by 7% on average and decreased the specific wear ratio of the samples. When the surface morphologies of the samples are examined, it is seen that the friction layers of the heat-treated samples are wider, and the microvoids and cracks are reduced.
Originality/value
This study showed that boric acid can be used as a friction modifier in brake friction composites. It also revealed the tribological and physical contribution of the applied heat treatment to the composite. Thus, it guides brake friction composite manufacturers in the industry and researchers working in this field.
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Ilker Sugozu, Ibrahim Can and Cengiz Oner
The purpose of this paper is to investigate use of calabrian pine (pinus brutia) cone (CPC) dust along with borax (BX) to assess the effect of friction coefficient. Despite the…
Abstract
Purpose
The purpose of this paper is to investigate use of calabrian pine (pinus brutia) cone (CPC) dust along with borax (BX) to assess the effect of friction coefficient. Despite the number of research studies completed on the mechanism of friction in automotive brake lining materials, the phenomenon is still not fully understood. Complex mechano-chemical processes occurring on the friction interface of a composite friction material make it difficult to understand the correlation between the formulation of brake lining and the frictional performance.
Design/methodology/approach
In this study, the use of CPC dust along with BX has been investigated for assessing the effect on friction coefficient. CPC has resin in it. BX is a boron production which is widely used in boron glass production and in ceramic industry for increasing the heat- resistant and -forming abrasion resistant. Newly formulated brake lining material with five different ingredients has been tested under Friction Assessment and Screening Test. Friction coefficient, wear rate and scanning electron microscope for friction surface were examined to assess the performance of these samples.
Findings
Analysis of the experimental results shows that the brake lining material containing CPC and BX significantly improved the stability of the friction coefficient, fade and wear resistance.
Originality/value
Several investigations have been conducted to use different materials in brake pads. The brake pad standards have been provided in previous studies, as well as the aims for economical and sustainable production. In the present study, production of brake pads by CPC dust and BX has been executed. Parallel results have been presented between previously reported and present study, in view of brake characteristics and wear resistance. Use of the lower cost and productive organic sources of material are the main improvement of the present study.
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Münevvere Yıldız and Letife Özdemir
Purpose: Investors and portfolio managers can earn profitably when they correctly predict when stock prices will go up or down. For this reason, it is crucial to know the effect…
Abstract
Purpose: Investors and portfolio managers can earn profitably when they correctly predict when stock prices will go up or down. For this reason, it is crucial to know the effect levels of the factors that affect stock prices. In addition to macroeconomic factors, the psychological behavior of investors also affects stock prices. Therefore, the study aims to reveal the different sensitivity levels of the stock index against macroeconomic and psychological factors.
Design/Methodology/Approach: In this study, dollar rate (USD), euro rate (EURO), time deposit interest rate (IR), gold price (GOLD), industrial production index (IPI), and consumer price index (CPI) (inflation (INF)) were used as macroeconomic factors, while Consumer Confidence Index (CCI) and VIX Fear Index (VIX) were used as psychological factors. In addition, the BIST-100 index, which is listed in Borsa Istanbul, was used as the stock index. The sensitivity of the stock index to macroeconomic and psychological factors was investigated using the Multivariate Adaptive Regression Spline (MARS) method using data from January 2012 to October 2020.
Findings: In the analyses performed using the MARS method, the coefficients of INF, USD, EURO, IR, CCI, and VIX Index were found to be statistically significant and effective on the stock index. Among these variables, INF has the highest effect on stocks. It is followed by USD, IR, EURO, CCI, and VIX. GOLD and IPI variables did not show statistical significance in the model. The most important difference of the MARS model from other regressions is that each factor’s effect on the stock index is analyzed by separating it according to the value of the factor. According to the results obtained from the MARS model: (1) it has been determined that USD, EURO, IR, and CPI have both positive and negative effects on the stock market index and (2) CCI and VIX have been found to have negative effects on stocks. These results provide essential information about how investors who plan to invest in the stock index should take into consideration different macroeconomic and psychological values.
Originality/value: This study contributes to the literature as it is one of the first studies to examine the effects of factors affecting the stock index by decomposing it according to the values it takes. Also, this study provides additional information by listing the factors affecting the stock index in order of importance. These results will help investors, portfolio managers, company executives, and policy-makers understand the stock markets.
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Selin Hanife Eryuruk, Burçak Karagüzel Kayaoglu and Fatma Kalaoglu
Surgical gowns should be designed and produced using special techniques to provide barrier properties against potential risks during surgery and healthcare procedures. Ultrasonic…
Abstract
Purpose
Surgical gowns should be designed and produced using special techniques to provide barrier properties against potential risks during surgery and healthcare procedures. Ultrasonic welding is one of these methods used to produce surgical gowns with determined barrier properties. The purpose of this paper is to analyse bond strength and permeability properties of ultrasonically welded nonwoven fabrics and compare them with traditional sewing techniques.
Design/methodology/approach
In this study, ultrasonic welding of nonwovens was performed to demonstrate its use as an assembly method. Performance requirements in the design of surgical gowns were determined. Fabric strengths and bond strengths of ultrasonic-welded and traditionally sewn fabrics were analysed. The performance properties, i.e., bond strength, air and water resistance of the fabrics and the joints obtained by ultrasonic and classical sewing methods were studied.
Findings
As a result, it was found that ultrasonic welding technique is a suitable method for joining layers in surgical gown production bringing the advantages of high water resistance together with acceptable bond strength.
Originality/value
The current study focuses on the use of ultrasonic welding of nonwovens used for disposable protective surgical gowns. Ultrasound welding technique was presented as an alternative to classic assembly methods and ultrasonic welding technology was applied to different fabric combinations simulating different layers in different joining sections of a surgical gown.
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Mahmut Kayar, Suleyman Ilker Mistik and Deniz Inan
– The purpose of this paper is to investigate the factors effecting ultrasonic seam tensile properties.
Abstract
Purpose
The purpose of this paper is to investigate the factors effecting ultrasonic seam tensile properties.
Design/methodology/approach
In this study, 100 percent polypropylene and 100 percent polyester spunbond and meltblown nonwoven fabrics were sewn by using ultrasonic sewing machine with different rollers which have two, three and four rows. Seam tensile properties of the sewn nonwoven fabrics were investigated. Four-Level Nested Anova Design was applied to the data by using Minitab 15 software program.
Findings
Higher seam strength values were obtained by using four rows roller, PP fiber, spunbond fabric and 50 g/m2 fabric area density for all nonwoven fabrics. Statistical significance was found between fabric area density, roller rows and seam tensile strength properties and between fabric type, roller rows and seam elongation at break values.
Originality/value
When the authors look at the studies related to ultrasonic sewing, several researchers studied on welding parameters of ultrasonic sewing but very limited studies were performed on assembling of nonwoven fabrics with ultrasonic sewing. Therefore effect of production methods of nonwoven fabrics on the properties of ultrasonic sewing such as seam strength and elongation at break should be investigated.
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Aims at finding out the senior managers' perceptions about the extent to which the components of KM contribute to the success of SMEs (small and medium enterprises) in Turkey.
Abstract
Purpose
Aims at finding out the senior managers' perceptions about the extent to which the components of KM contribute to the success of SMEs (small and medium enterprises) in Turkey.
Design/methodology/approach
In this paper, the current knowledge management practices in Turkish SMEs are searched through a survey. The survey is prepared depending on a basic model of knowledge management built by the author.
Findings
The results of the survey show that Turkish SMEs do not like to share knowledge even within the company. The managers are afraid of losing the control of knowledge. However, since they close the information channels, they also prevent the incoming knowledge.
Originality/value
This paper provides a basis for the research about knowledge management practices in SMEs in developing countries.