Tribotechnical properties of sintered friction material based on copper with the additives of the ultrafine powder of aluminide of Ti–46Al–8Cr system

The article presents the results of study of the effect of additives of an ultrafine powder of the Ti–46Al–8Cr system obtained by MASHS on the tribotechnical properties of a friction material based on BrO6 bronze. It is shown that in the range of powder additive concentrations 0.5–1.5 wt. %, the dynamic coefficient of friction increases from 0.04 to 0.055, in the range of 1.5–2.5 % – to 0.055–0.058. The introduction of the 0.5–1.0 % Ti–46Al–8Cr powder permitted to reduce the wear rate of the friction material from 4.0 to 3.7 μm/km. An increase in the additive to 2.5 % led to an increase in the material wear rate up to 6 μm/km.

Introduction of a New In-Situ Measurement System for the Study of Touch-Feel Relevant Surface Properties

The touch-feel sensation of product surfaces arouses growing interest in various industry branches. To entangle the underlying physical and material parameters responsible for a specific touch-feel sensation, a new measurement system has been developed. This system aims to record the prime physical interaction parameters at a time, which is considered a necessary prerequisite for a successful physical description of the haptic sensation. The measurement setup enables one to measure the dynamic coefficient of friction, the macroscopic contact area of smooth and rough surfaces, the angle enclosed between the human finger and the soft-touch surfaces and the vibrations induced in the human finger during relative motion at a time. To validate the measurement stand, a test series has been conducted on two soft-touch surfaces of different roughness. While the individual results agree well with the literature, their combination revealed new insights. Finally, the investigation of the haptics of polymer coatings with the presented measuring system should facilitate the design of surfaces with tailor-made touch-feel properties.

Noise, vibration and harshness during dry clutch engagement oscillations

Determining the root causes of various noise, vibration and harshness phenomena in modern automotive drivetrains is a critical task for industry, since noise, vibration and harshness issues often result in worsened driving experience. The aim of the current research is to investigate the dynamics during dry clutch engagement and the associated – often problematic – oscillations. This paper reports the development and partial validation of numerical models to study dry clutch behaviour. The models are used to investigate the influence of clutch and throttle actuation on the occurrence of unwanted clutch oscillations. The dynamic coefficient of friction between the clutch interacting surfaces was measured using a pin-on-disc rig under different slip speeds and contact pressure conditions, which are representative of a typical clutch engagement manoeuvre. The paper highlights the occurrence of instability issues in clutch dynamics (disc radial mode) as potential generators of aggressive noise, vibration and harshness, particularly during two different clutch pedal actuations. Such analysis has not hitherto been reported in the open literature.

Study of the influence of compressive force on the coefficients of friction for wool-containing fabrics

Making use of appliance MXD-02, Labthink, China, coefficient of friction at rest with sliding tendency (static coefficient of friction) and coefficient of friction at sliding (dynamic coefficient of friction) for fabrics made of 100% wool as well as woolen fabrics with admixtures of polyamide and polyester were determined. The influence of the magnitude of normal pressure on the coefficients of friction was studied. Experiments taking into consideration the following different directions of relative fabric movement were performed: warp by warp threads, and warp by weft. An analysis of the obtained results was made.

Influence of 3% slip stabilizing paste added to flexographic inks on coefficient of friction of OPP cast film

For a number of years, flexographic printing has been used in the process for the production of flexible packaging as well as other applications where high quality is required. Today, this printing technology is highly automated in all phases of the process. Production time is shorter and product quality is constantly improved. Flexographic inks consist of three main ingredients: pigment, binder and solvent., Each of these components has different functions, however, one depends on the others. Additives used for ink can be of various types. They can be added during ink production or during the printing process to improve printing properties. The film coefficient of friction is one of very important parameters in the flexographic printing process. The determination of static and dynamic coefficient of friction is particularly useful for film substrates that are further processed in packaging and printing machines. The value of the COF is a guide for further processing and refers to the surface structure, which in turn is important for printing. Influencing COF gives packaging manufactures the opportunity to optimize performance and avoid problems during the printing and packaging process, transport, and storage of packaging. In order to examine the effect of the addition of slip stabilizing paste on COF of OPP cast film and on the printing process, a test was carried out in a printing house using the 8-colour UTECO machine with a central cylinder. The amount of 3% additive was added to flexographic ink.

Gait Speed with Anti-Slip Devices on Icy Pedestrian Crossings Relate to Perceived Fall-Risk and Balance

It is important to find criteria for preventive measures and appropriate assistive devices to reduce pedestrian injuries and increase walking in winter. Reducing the rate of falls on icy surfaces and improving people’s ability to safely cross a street in winter conditions by achieving an adequate walking speed, for example, need to be considered. This study explores pedestrian perceptions of fall risk, balance, and footfall transitions while using different designs for anti-slip devices on ice and snow-covered ice and relates these to measures of gait speed and friction. Trials were performed with nine pedestrians testing 19 anti-slip devices on ice and ice covered with snow. Laboratory tests of the dynamic coefficient of friction (DCOF) on plain ice were also performed. The findings suggest that there was conformity in the participants’ perceptions of good balance and low fall risk for one-fifth of the devices (three whole-foot designs and one design with built-in spikes). We also found that gait speed on icy pedestrian crossings is related to perceived fall-risk and balance control, but not to DCOF of the anti-slip devices.

Dynamic mechanical and thermogravimetric analysis of PTFE blended tailor-made textile woven basalt–vinyl ester composites

In this work, the authors prepared basalt–vinyl ester tailor-made green composites with uncoated and polytetrafluroethylene coated basalt woven fabric. These composites were subjected to dynamic composites-made mechanical analysis and thermo gravimetric analysis. Results revealed that a significant improvement of 18%, 14% and 13% was observed for storage and loss modulus and damping properties of polytetrafluroethylene-coated composite at low temperature region. The thermo gravimetric analysis results indicated a three-stage degradation for the polytetrafluroethylene-filled composites. Based on the acceptability from the literature, the tribo-test was performed only on the polytetrafluroethylene-coated composite for the selected PV limit of 400 MPa-mm/s (10 KN and 50 mm/s) in a flat-on-flat configuration. It was found that the influence of polytetrafluroethylene filler on the static and dynamic coefficient of friction and specific wear rate of the composite was more pronounced at dry wear test condition and it was found as 0.22, 0.12, and 4.87484 E-09, respectively. However, the results of improved storage and loss modulus and damping manifested negative correlation with the friction characteristics in the glassy region. Further, the SEM-coupled EDX spectral analysis was performed to understand the formation of transfer layer in counter surface. This polytetrafluroethylene blended composite is to be considered as an alternative to the bearing materials in offshore application.