Papers by Keyword: Slip

Abstract: Rolling and sliding contacts are common tribological interactions between surfaces in high-speed rotating components such as bearings, gears, and rail wheels. If the bearing is operated under mixed/boundary lubrication conditions, the major failure mechanism would be micro-pitting and wear, and its extent depends on the percentage slide between the contact pairs. This work compares the rolling contact fatigue (RCF) behavior of AISI 4140 steel under pure rolling (zero slip) and slip conditions by using base lubricant and formulated lubricant with graphene nanoadditives. Rolling contact fatigue performance under pure rolling and slip conditions shows a significant improvement with graphene lubrication compared to base lubrication. Under pure rolling conditions, the RCF L₁₀ life improved 3-fold with graphene lubricant compared to base lubricant. Similarly, under the slip condition, a significant improvement in the anti-wear performance was observed for the graphene lubrication compared with the base lubrication. A detailed wear track analysis was performed using scanning electron microscopy and Raman spectroscopy. The results reveal that the formation of tribo-films on the surface is the major reason for the improved anti-wear performance with graphene nanolubrication. According to the working conditions, the physical tribo-film was observed under pure rolling conditions, and the chemical tribo-film was observed under slip conditions.

Abstract: The ecological thinking and the development of new materials foreground the composite structures made of FRP (fiber reinforced polymers) and concrete. Before the use in real concrete structures, the material characteristics and composite action with concrete need numerical, analytical, and experimental evaluation. The key to developing the composite action of an FRP reinforcement in concrete is a sufficient bond between the reinforcement and concrete. The GFRP (Glass Fiber Reinforced Polymer) bars as the most common and affordable alternative to steel bars are used in this study to investigate the bond with concrete on the analytical model. The finite element model simulates the beam-bond test of GFRP and steel bars to concrete. The effect of bar diameter and type of reinforcement on the bond behavior are analyzed. Finally, the results obtained from the analytical model are compared with the experimental results from the literature.

Abstract: The tensile deformation behaviour of magnesium alloy AE44 (Mg-4Al-4RE) under strain rates ranging from 10^-6 to 10^-1 s^-1 has been investigated. Present study shows that the deformation mode begins with the activation of elastic (Stage 1), followed by <a> basal slip and twinning (Stage 2), <a> prismatic slip (Stage 3) and finally to <c+a> pyramidal slip (Stage 4). The commencement of these deformation mechanisms results in four distinct stages of strain hardening in the stress-strain curve. In this work, the four stages of deformation behaviour are modelled, and an empirical equation is proposed to predict the entire stress-strain curve. Overall, the model predictions are in good agreement with the experimental data. This study on the decomposition of stress-strain curve into four stages provides insights into the contribution of individual deformation mechanism to the overall deformation behaviour and opens a new way to assess mechanical properties of die-cast magnesium alloys.

Abstract: The present study concerns steady two-dimensional laminar mixed convective boundary layer Casson nanofluid flow along a stretching or shrinking sheet with multiple slip boundary conditions in a non-Darcian porous medium. The effect of viscous dissipation and non-linear radiation are considered. The governing partial differential equations, together with boundary conditions are transformed into a system of dimensionless coupled ordinary differential equations. Galerkin weighted residual method is then employed to solve the transformed coupled ordinary differential equations. The effect of various controlling parameters on dimensionless velocity, temperature, nanoparticle volume fraction, velocity gradient, temperature gradient and nanoparticle volume fraction gradient are presented graphically and discussed. The present approach is validated by comparing the result of this work and those available in the literature, and they are found to be in excellent agreement.

Abstract: In this paper investigation is done on the MHD Jeffrey nanofluid flow towards a stretching cylinder in the presence of non-linear thermal radiation, triple stratification, Soret and Dufour and slip. The governing equations are transformed into ordinary differential equations by using suitable transformations. The HAM method is used to solve these equations. The temperature profile and local Sherwood number increase when Dufour number is hiked where as local Nusselt number fall off. While increasing local Soret number, the concentration profile increases where as Sherwood number decreases.

Abstract: Deformation characteristics of brass alloy are still under discussion, particularly concerning the critical level of when the change of deformation mechanism occurs. Previous research showed that the addition of Mn on brass alloys resulted in grain refinement and mechanical properties alteration. However, the effects of Mn on the deformation characteristic of brass alloys have not been investigated. In this research, Cu-Zn-xMn alloys were manufactured by gravity casting process using pure Cu and Zn ingots, as well as Mn chips as the feeding materials. Mn addition was varied to 1.26, 3.48, and 5.83wt.%. As-cast samples were homogenized at 800 °C for 2 h in a muffle furnace. The samples were then cold-rolled with the level of deformation of 20, 40, and 70 %. Samples characterization includes chemical composition analysis, microstructure observation, tensile and hardness testing. The results showed that addition of Mn for 5.83 wt.% and above created β’ phase, which is richer in Mn compare to that in the matrix. This phase segregated in the grain and along the grain boundary with irregular forms. Significant increase in hardness, yield and tensile strengths was observed with addition of Mn. The maximum elongation was achieved by addition of 3.48 wt.% Mn, while further addition tended to decrease it. At 20% deformation, slip dominated and its density reduced with addition of Mn. When the deformation level increased to 40%, twinning replaced slip as the predominant mechanism. Twinning density is slightly increase with the presence of Mn. Further deformation at 70% produced shear bands and flattened the β’ phase. Greater Mn content led to formation of more shear band.

Abstract: The present study examined the effect of smooth construction joint and concrete unit weight on the shear friction behavior of concrete. From nine push-off test specimens, shear load-relative slip relationships, shear cracking stress, shear friction strength were measured. Test results showed that the shear cracking stress was hardly affected by the configuration of transverse reinforcement or concrete unit weight. The shear friction strength of monolithic normal-weight concrete was approximately three times higher than that of the companion specimens with construction joint. Meanwhile, the heavyweight concrete joints had a similar shear friction strength to normal-weight concrete ones.

Abstract: A slip controller that can move against the off-track and control excursion caused by slips while driving a motorized wheelchair is proposed. Detecting slips in a motorized wheelchair is to detect states of the motorized wheelchair and its motors in a traveling condition. For carrying it, slip ratios are calculated using a slip detection algorithm based on the information obtained from the six-axis IMU sensor and the encoders, which are connected to both left and right motors. The calculated slip ratios are used as control variables for improving the safety in a motorized wheelchair. In the experiment of the slip controller proposed in this study, slips are verified in a proposed track. Also, it is verified that the maximum slip ratio section is determined while turning left or right.

Abstract: Presentation of the numerical model describing a design and functionality of the prototype of surface condition detector is the paper subject. The detector, by monitoring the frictional coupling between so-called “tracking wheel” of the dedicated measuring transducer and a rail can analyse the condition of rail surface (presence of any factor that can deteriorate friction coefficient) [1]. Signal generated at the detector outlet, carrying information about local condition of rail surface, can be used to adjust braking torque of vehicles or machines moving on a track. Authors expect that implementation of the method will eliminated dangerous elongation of braking distance of rail vehicles in the result of loss of adhesion. Structure of detector of rail surface condition is described and its principle of operation is presented in a form of numerical model. Results of numerical simulations are given and they are compared with the measurements taken on the testing facility in real conditions.

Abstract: Through theoretical analysis of the working condition of the tension roller and stress, user can discuss the main reasons of tension roller slip, and put forward the preventive measures to eliminate tension roller slip by using Euler formula and the research on the tension roller slip phenomenon of cold rolling. This technology has significant practical meaning for improving both the quality and efficiency of product.