Friction characteristic study on flat surface embedded with micro pit

Mechanical systems are always deal with wear and friction as the liability. The basic principle of the mechanical system is the surface interaction between surfaces which have a frictional force resulting in fatigue and damage to the mechanical components. Lubricant is used to minimize friction in order to solve the problem. A comparative friction characteristic analysis was then conducted to assess the coefficient of friction (COF) between Aluminum Alloy 5083 block and SKD 11 disk using two types of lubricant, that is SAE40 engine oil and RBD palm oil. The thickness of the oil film could be predicted in order to observe the influence of the different lubricants used. Pit pattern surface is required to research the function of the pit as a lubricant reservoir. The experiment was carried out in the laboratory according to the ASTM G99. Load is applied to experiments with loads of 1 kg, 5 kg and 10 kg, in order to find a COF correlation under different application condition. The rotational speed is held constant at 3m/s during the experiment. The results obtained revealed that when using RBD palm oil as a lubricant, the COF between block and disk is lower than when using SAE40 engine oil as a lubricant. The experimental result showed that RBD palm oil can minimize friction much lower than SAE40 engine oil. Based on the results of the comparison analysis on the flat surface and pit pattern surface, the finding revealed that the pit pattern may serve as a lubricant reservoir to retain and store the lubricant for longer than the flat surface that helps to reduce friction

Optical fiber Bragg grating-based pressure sensor for soil monitoring applications

An optical-based pressure sensor for a 150 × 150 mm surface was designed and fabricated. The sensor utilizes a fiber Bragg grating (FBG) attached to a 30 × 30 × 30 mm actuator as the pressure sensing mechanism. The middle section of the actuator, which is circular, can bend into an elliptical form and, in the process, pull the FBGP via both ends when force or pressure is applied, thus converting the pressure applied to its surface into a wavelength shift. In laboratory testing, a sensitivity of 0.152 nm∕kPa was obtained. Subsequently, the pressure sensor was tested in the field by burying it 20 cm underground to measure soil pressure, while another FBG was spliced in series to the FBGP to compensate for temperature variations. Testing shows that the proposed design can realize a compact optical-based pressure sensor with enhanced soil monitoring applications such as dynamic soil pressure caused by soil movement

The effect of boron friction modifier on the performance of brake pads

Friction and wear characteristics of material in an automotive brake system play important role for efficient and safe brake performance. Commercial brake friction materials normally contain mainly alumina (Al2O3) and other ingredients. In this investigation, five groups of locally developed semi-metallic composite friction materials were studied for friction and wear. Abrasive material named aluminium oxide which existed in ZMF formulation was taken out. It was replaced by consistent different weight percentages of boron, i.e., 0.6%, 1.0%, 1.5% and 2.0% and then mixed into the ZMF formulation. The friction tests were performed using the friction material test machine called CHASE machine. The results demonstrated that the formulation using boron mixed brake pads produced higher normal and hot friction coefficient at GG class value than those of the commercial brake pad samples. All friction coefficients of boron samples increased at the beginning of braking stages until 20 braking applications. It appeared that an overall friction coefficient value declined with the increase in drum temperature. However, the reduction of friction coefficient for all boron mixed brake pads was much more constant and stable as compared to the commercial brake pad

Nonlinear servomotor in single pulse simulation of Electrical Discharge Machining system modeling

Electrical Discharge Machining, EDM is a nonconventional and high precision machining. EDM system is considered a combination of servo system and EDM process. The servo system precisely controls the gap between electrode and workpiece for the continuous electrical discharges occurrence. Machining performance and stability depend on the performance of servo system. The EDM servo system usually modeled as a linear system, which ignores the nonlinearities of the motor. An assumption that the nonlinearities are insignificant in EDM system model may leads to modeling errors and result in poor control performance. In this study, nonlinear EDM servo system model was presented and the dynamic response of the model was analyzed and compared with the linear model. Simulation result shows a slightly difference in system response and a controller used in linear model is less efficient for a nonlinear EDM servo system model. The results are very useful for control strategy and can contribute to a better machining performance and stability of EDM applications

Stenting of vertical vein in an infant with obstructed supracardiac total anomalous pulmonary venous drainage

A 1.7 kg infant with obstructed supracardiac total anomalous pulmonary venous drainage (TAPVD) presented with severe pulmonary hypertension secondary to vertical vein obstruction. The child, in addition, had a large omphalocele that was being managed conservatively. The combination of low weight, unoperated omphalocele, and severe pulmonary hypertension made corrective cardiac surgery very high-risk. Therefore, transcatheter stenting of the stenotic vertical vein, as a bridge to corrective surgery was carried out. The procedure was carried out through the right internal jugular vein (RIJ). The stenotic segment of the vertical vein was stented using a coronary stent. After procedure, the child was discharged well to the referred hospital for weight gain and spontaneous epithelialization of the omphalocele. Stenting of the vertical vein through the internal jugular vein can be considered in very small neonates as a bridge to repair obstructed supracardiac total anomalous venous drainage

The influence of lubricant viscosity in cold work forward extrusion using micro-pits tool

The present research concerns on the study of the effects of micro–pits arrays formed on taper die using cold forward plane strain extrusion experiments. Each pit was of reverse pyramids configuration having 330 microns diagonal length. The pits were 860 microns apart each others. Two additive free paraffinic mineral oils with low viscosity (P2) and high viscosity (P3) were used in this experimental work. The experimental results were compared with the results obtained from the plane strain extrusion experimental works with taper die without micro–pits (NA). The experimental results focused on the extrusion load, billet surface roughness and billet grid pattern on inclination slope. From the results, the existence of the micro–pits array on the taper die surface affected the extrusion load. At the same time, the micro–pits array affected the extruded billet surface roughness after the experiments. From this experiment, we could conclude that the micro–pits formed on the taper die (PA) would control the frictional constraint on the taper die compared to those without the micro–pits (NA). However, high viscosity lubricant (P3) was found to cause more effects compared to low viscosity lubricant (P2)

The influence of normal load in wear resistance characteristic of palm fatty acid distillate

The aims of this study were to determine the friction coefficient and the wear behaviour of palm fatty acid distillate (PFAD) using a four-ball tribotester, following the ASTM D-4172. In this paper, the normal load applied on the ball bearings varied from 40 kg to 120 kg. Experimental temperature was held constant at 75°C, while rotational speed was fixed at 1200 rpm. The test duration was one hour. Tests that were carried out using palm fatty acid distillate were conducted in exactly the same way using commercial hydraulic oil (HO) as a reference lubricant. The analyses focused on the friction coefficient and worn scar characteristic. Wear scar diameter was measured and the worn surface condition was observed using a high resolution microscope. Results showed that PFAD has a lower coefficient of friction than commercial hydraulic oil

Mechanical and wear behaviour of nanostructure tio2-ag coating on cobalt chromium alloys by air plasma spray and high velocity oxy-fuel

Cobalt chromium alloys constitutes the base of one important group of biometallic with excellent mechanical properties. However, due to its non-bioactive and non-antimicrobial surface, cobalt chromium alloys are vulnerable to wear corrosive attack and bacterial infection. Hence, coating cobalt chromium alloys surface with superior biomaterials is the best proven techniques. In this work, nanostructure silver adopted titanium dioxide coating was deposited on cobalt chromium alloys using air plasma spray (APS) and high velocity oxy-fuel (HVOF) techniques. Nanostructure TiO2-Ag coating demonstrated superior hardness, wear resistance and lower coefficient of friction when compared to bare CoCr alloys. Reduced plastic deformation detected by microstructural analysis indicate that the interference of nano-structure coating in metallic matrix help lower the wear rate of the sample. Meanwhile, low porosity of the coating produced by HVOF technique shown a better wear resistance result than APS technique. © 2019 Brazilian Metallurgical, Materials and Mining Association