Characterisation of coated lightweight brake rotors

Numerical and experimental studies were undertaken using lightweight brake rotors to reduce vehicle weight and thereby improve fuel efficiency and vehicle emissions. Abaqus finite element and Matlab software were used to construct one dimensional (1D), two dimensional (2D) and three dimensional (3D) thermal models to investigate the general thermal performance of disc brakes to develop a valid method of reduced scale testing. Five small scale solid brake rotors were investigated experimentally: grey cast iron, wrought aluminium alloy (6082), the same 6082 alloy with an alumina surface layer applied by plasma electrolytic oxidation (PEO), cast aluminium MMC (AMC640XA) and the same MMC with a PEO alumina surface layer. The disc and pad temperatures, brake pressure, coefficient of friction and brake torque were monitored during the tests for each material. Surface morphology, microstructure and micro hardness of the coatings and substrate were evaluated before and after the tests. Numerical simulations confirmed the equivalence between the full and small scale disc thermal performance using the proposed scaling methodology and also provide a good agreement with the experimental results. The coated 6082 alloy rotor was shown to give good thermal and friction performance up to relatively high rubbing surface temperatures of around 500oC. This rotor failed at a surface temperature of about 550oC due to brittle fracture of the wrought aluminium substrate. The proposed scaling methodology was shown to be a valid method of investigating a rotor design concept in the laboratory at low cost and reduced operating time. The PEO coating on aluminium alloy was denser and more uniform compared to the PEO coating on aluminium MMC. In addition, the PEO coating improved the hardness and thermal resistance of both the aluminium alloy and aluminium MMC. A sensitivity analysis based on the Taguchi approach was carried out on the PEO coated aluminium alloy rotor to investigate the effect of various parameters on thermal performance. Optimisation of the structure was carried out using a genetic algorithm to design coated aluminium alloy discs that are potentially technically viable on small-medium passenger cars

Reduced scale thermal characterization of automotive disc brake

The thermal behaviour of a disc brake is a critical factor that needs to be considered at the design phase. Most researchers utilise a full size brake dynamometer or a simple pin-on-disc rig to experimentally evaluate the performance of a friction pair (disc and pad). In the current paper, a scaling methodology is proposed to evaluate the thermal performance of a disc brake at a reduced scale. The resulting small scale disc brake has the advantage of low cost and reduced development time. The proposed scaling methodology was validated by comparing the results for the full and small scale discs using a conventional brake dynamometer. In addition, a two dimensional axisymmetric transient thermal finite element model was developed using Abaqus software to assist in the validation of the scaling methodology. The numerical simulations confirmed the equivalence between the full and small scale disc thermal performance using the proposed scaling methodology and also gave good agreement with the experimental results. It is concluded that the scaling methodology is an important tool with which to evaluate the thermal performance of disc brakes in the early design phase

Optimisation of alumina coated lightweight brake rotor

Aluminium alloys have been used extensively in the automotive industry to reduce the weight of a vehicle and improve fuel consumption which in turn leads to a reduction in engine emissions. The main aim of the current study is to replace the conventional cast iron rotor material with a lightweight alternative such as coated aluminium alloy. The main challenge has been to meet both the cost and functional demands of modern mass-produced automotive braking systems. A sensitivity analysis based on the Taguchi approach was carried out to investigate the effect of various parameters on the thermal performance of a typical candidate disc brake. Wrought aluminium disc brake rotors coated with alumina on the rubbing surfaces were determined to have the best potential for replacing the conventional cast iron rotor at reasonable cost. Optimisation of the structure was subsequently carried out using a genetic algorithm on the selected coated aluminium disc brake rotor. This determines the optimum thickness of the coating and the composition of the substrate based on selected criteria. Prototype aluminium disc brake rotors were coated with alumina using the Plasma Electrolytic Oxidation (PEO) technique and the thermal performance of these lightweight rotors was investigated experimentally using a brake dynamometer. A high speed thermal imaging system was used to evaluate and measure the rubbing surface temperature of the coated brake rotors. The experimental results showed generally good agreement with the numerical predictions. The coated wrought aluminium disc brake rotor was demonstrated to give good thermal and friction performance up to relatively high rubbing surface temperatures of the order of 500°C

Thermal performance of peo coated lightweight brake rotors compared with grey cast iron

Brake rotors play a significant role in converting the vehicle kinetic energy into heat energy that is dissipated through conduction and convection. The automotive industry has been looking for many years to develop lightweight brake rotors to reduce vehicle weight and subsequently improve fuel efficiency and vehicle emissions targets. Uncoated wrought aluminium alloys and metal matrix composite (Al-MMC) rotors have been reported to have insufficient safety margin for most passenger car applications. In this study, the thermal performance of coated and uncoated lightweight aluminium disc brake rotors was investigated numerically and experimentally, using both small scale and full size brake dynamometers. Five small scale solid brake rotors were investigated: grey cast iron, forged aluminium alloy (6082), the same 6082 alloy but with an alumina surface layer applied by plasma electrolytic oxidation (PEO), cast aluminium MMC (AMC640XA), and the same MMC again with PEO alumina surface layer. The disc and pad temperatures, brake pressure, coefficient of friction and brake torque were monitored during the tests for each disc brake material. In addition, a two dimensional axisymmetric finite element model was developed using Abaqus software in order to investigate the temperature distribution through the disc. The 2D FE model demonstrated good overall agreement with the experimental results and showed the same general trends. It was found that the PEO coated aluminium alloy has the best overall performance of the lightweight rotors tested in terms of friction and structural integrity at elevated temperature

The Importance of Pad Aspect Ratio in the Thermal Analysis of a Reduced Scale Brake

The performance of a brake system can be assessed in its early stages through reduced scale testing. An established scaling methodology was used in this study to scale the brake pads based on constant energy density. The primary aim was to investigate the impact of the aspect ratio of a scaled brake pad on the thermal characteristics of a scaled disc during drag braking conditions. Brake pads with four different aspect ratios were used against the scaled disc and these were scaled relative to the brake disc and pads of a medium sized passenger car. Using relevant scaling relationships, a speed–pressure matrix, consisting of nine tests, was derived and utilised in the experimental analysis. The tests were conducted using a conventional brake dynamometer. Temperatures were measured using thermocouples on the disc and pad and, for specific tests a thermal imaging camera was also used. The experimental results showed that a strong dependency exists between the maximum rotor temperature and the pad aspect ratio. This suggests that consideration of pad aspect ratio be reflected within the scaling process. A relationship between the circumferential and radial dimensions of full scale and reduced scalebrake pads was established based on their measured thermal performance. The experimental results were also used to validate a finite element model of the system. This was subsequently able to highlight important limitations associated with the model that apply equally to simulations of full and small scale brakes

Comparison between AMPCP and SRP in a Shaly-sand reservoir in terms of sand production

Abstract Sand production is considered one of the major problems that would affect the economical value of any EOR project. The produced sand will start to accumulate in the wellbore till it kills the Well. This is done by increasing the pressure drop (both frictional and hydrostatic) in the borehole to a point where no more fluid can be produced. It can also exhibit a mechanical damage to the pipes, chokes, surface facility lines and would require continues cleaning. There are several sand control equipment that can be installed whether in the wellbore or in the formation itself. However, these sand control equipment not only add a cost element to the whole project, but also most of them reduce the Productivity Index of the well. Consequently more wells need to be drilled in order to compensate the production loss due to the installation of sand control equipment. This paper examines the effect of using Sucker Rod Pump (SRP) and All Metal Progressive Cavity Pump (AMPCP) on the sand production. Both pumps can handle solids to some degree, however, the mechanism of each pump will affect the building of sand arch and thus will impact the amount of sand volume produced. By comparing the sand production profiles of two vertical wells under Cyclic Steam Stimulation (CSS) completed in the same zone, it was found that the use of AMPCP can help reduce sand production significantly over the SRP. This is attributed to the difference in working mechanisms of both pumps. In AMPCP, the fluid is being pumped by a smooth movement, while in SRP, the upstroke and downstroke movement of the pump have an effect similar to the plunger, which adversely impact the sand arch building. As a result, SRP has a higher tendency to produce more sand compared to that of AMPCP.</jats:p

Cultures of fear: Perspectives on whistleblowing

Whistleblowing is in part defined by the protection that it offers and does not offer to those who speak. Why some organisations find it almost impossible to protect whistblowers depends more on the properties of the organisation than the act of the individual whistleblower. These properties are, to a greater or lesser degree, present in all organisations but they are particularly present in nursing with its longstanding culture of deference to authority. Not all organisations protect whistleblowers that, unfortunately, are perceived to represent a threat to the organisation and the individual for challenging the underpinning norms of the organisation

Schemes of eStories for Children with Social Communication Difficulties

The current paper presents the development and the evaluation of an Arabic application (app) for electronic stories (eStories) that can be used as an assistive tool in the rehabilitation of children with social communication difficulties. The development process involved engineers and researchers and speech and language pathologists (SLPs) from a rehabilitation hospital, who formulated the design methodology of the Arabic app. This process is critical when designing tools for children with communication difficulties since they have a wide range of differences in their abilities. The evaluation of the app from the standpoint of the SLPs at a local school suggests that the app is easy to use, and the involvement of these SLPs helped in developing a better solution. The results of the usability study on twenty-five students showed positive evaluation with an average score that signifies that the app has above-average usability. This paper highlights the importance of the evaluation process in catering the app for successful user experience

The Thermal Characterisation of a Disc Brake Rotor at reduced scale with particular reference to PAD Aspect Ratio

An integral part of the development of a disc brake system is associated with the physical test of the foundation brake using a brake dynamometer. Testing undertaken at full scale is both costly and time consuming and recent work, for example Prabhu et al. (2015), has shown that reduced scale testing is capable of replicating the tribological conditions at the interface such that the thermal response of the rotor approaches that of its full scale counterpart. The same work also demonstrated experimentally the connection between pad aspect ratio and rotor response and this had been omitted from the formal scaling methodology. This paper extends the scaling theory to reflect the presence of pad aspect ratio through the use of a validated finite element model of the reduced scale brake. The results show that for the given reduced scale brake, there exists a pad aspect ratio at which the thermal response of the rotor is at a minimum. The conclusions drawn apply equally to the behaviour of the rotor at full scale