Passenger car disc brakes are safety-critical components whose performance depends strongly on contact conditions at the pad-to-rotor interface. The interface can be classified as a conformal dry s ...

Simulation of wear and contact pressure distribution at the pad-to-rotor interface in a disc brake using general purpose finite element analysis software

Ticks and tick-borne diseases are among the main causes of economic loss in the South African cattle industry through high morbidity and mortality rates. Concerns of the general public regarding chemical residues may tarnish their perceptions of food safety and environmental health when the husbandry of cattle includes frequent use of acaricides to manage ticks. The primary objective of this study was to identify single nucleotide polymorphism (SNP) markers associated with host resistance to ticks in South African Nguni cattle. Tick count data were collected monthly from 586 Nguni cattle reared in four herds under natural grazing conditions over a period of two years. The counts were recorded for six species of ticks attached in eight anatomical locations on the animals and were summed by species and anatomical location. This gave rise to 63 measured phenotypes or traits, with results for 12 of these traits being reported here. Tick count (x) data were transformed using log10(x+1) and the resulting values were examined for normality. DNA was extracted from hair and blood samples and was genotyped using the Illumina BovineSNP50 assay. After quality control (call rate >90%, minor allele frequency >0.02), 40,436 SNPs were retained for analysis. Genetic parameters were estimated and association analysis for tick resistance was carried out using two approaches: a genome-wide association (GWA) analysis using the GenABEL package and a regional heritability mapping (RHM) analysis. The Bonferroni genome-wide (P<0.05) corrected significance threshold was 1.24×10(-6), with 2.47×10(-5) as the suggestive significance threshold (P<0.10) (i.e., one false positive per genome scan) in the GWA analysis. Likelihood ratio test (LRT) thresholds for genome-wide and suggestive significance were 13.5 and 9.15 for the RHM analysis. Six ixodid tick species were identified, with Amblyomma hebraeum (the vector for Heartwater disease) being the dominant species. Heritability estimates (h(2)) from the fitted animal and sire models ranged from 0.02±0.00 to 0.17±0.04 for the transformed tick count data. Several genomic regions harbouring quantitative trait loci (QTL) were identified for different tick count traits by both the GWA and RHM approaches. Three genome-wide significant regions on chromosomes 7, 10 and 19 were identified for total tick count on the head, total body A. hebraeum tick count and total A. hebraeum on the perineum region, respectively. Additional regions significant at the suggestive level were identified on chromosomes 1, 3, 6, 7, 8, 10, 11, 12, 14, 15, 17, 19 and 26 for several of the traits. The GWA approach identified more genomic regions than did the RHM approach. The chromosomal regions identified here as harbouring QTL underlying variation in tick burden form the basis for further analyses to identify specific candidate genes and polymorphisms related to cattle tick resistance and provide the potential for marker-assisted selection in Nguni cattle.

Genome-wide association study for tick resistance in South African Nguni cattle

Experimental heat transfer

RDX Based Enhanced Energy Propellant for Tank Gun Ammunition

The erosion behaviour of a nickel-based alloy coating under high-speed hot airflow erosion caused by propellant combustion was studied. The coating was prepared on the PCrNi3MoVA steel substrate vi...

Erosion behavior of Ni-based coating under high-speed hot airflow

The Erosion of Gun Barrels leads to reduced gun performance and availability, and increases the expense of barrel replacement over the life time of a gun system. Wear in gun barrel usually increases the bore diameter near the commencement of rifiling. The wear spreads forwards toward the muzzle as the gun is fired continuously. The point of maximum wear remains near the commencement of rifiling. Worn barrels are objectionable because they allow gas to escape past the shot thus reducing muzzle velocity, range and accuracy. As the muzzle begins to wear the shot loses directional stability.The total wear that can be tolerated is called condemning limit. Its value depends on the size of the gun, the required accuracy and the factor of safety that must be maintained against catastrophic fatigue failure. On average barrels are condemned when the bore diameter increases by about 5%. Wear depends not only on the thermal load but also on the surface metallurgy of the bore and the chemical interactions between the propellant gas and the bore surface. The erosivity of different propellants have been investigated over the years using various numerical methods and some works have tested propellants or propellant gases in some form of simulated gun. This paper discusses the various types of erosion taking place in the gun barrel. It also gives a list on various methods developed over the years to mitigate the gun barrel wear.

http://inpressco.com/wp-content/uploads/2016/03/Paper49231-235.pdf

A Review on Gun Barrel Erosion

In the present work, different ventilated disc brake rotor configurations were analysed to enhance the heat transfer rate and obtain the uniform temperature distribution in the rotor. CFD code used in this work was validated at using experimental results obtained by conducting experiments on a test rig. The experimental analysis was performed to calculate the mass flow rate and heat dissipation through the rotor. Further, different types of rotor configurations viz. straight radial vane (SRV), tapered radial vane (TRV), alternate long and short vane (ALSV), variable diameter circular pillars (VDCP) were considered for the analysis. A rotor segment of 20° was considered for the numerical analysis due to its rotational symmetry. CFD results were in good agreement with the experiments. The maximum deviation of the numerical results were about 12 % from the experimental results. It is found from the analysis that among the different types of rotor configurations; variable diameter circular pillars (VDCP) rotor gives better rate of heat dissipation with more uniform temperature distribution in the flow passages. Hence for modern high speed vehicles VDCP rotor may be more appropriate.

Experimental investigation using cfd for thermal performance of ventilated disc brake rotor

The heat dissipation and thermal performance of ventilated brake discs strongly depends on the aerodynamic characteristics of the air flow through the rotor passages. In this paper, the thermal convection is analyzed using an analytical method, and the velocity distribution, temperature contours and Nusselt number are determined. Then numerical models for different rotors, pillar post rotors and vane rotors are generated and numerical simulations are conducted to determine the desired parameters. To analyze more realistic vane and pillar post rotor models, commercial CFD software packages, Fluent and Gambit, are used to simulate the heat flux rate, air flow rate, velocity distributions, temperature contours, and pressure distributions inside the rotors. Furthermore, sensitivity studies have been performed, to determine the effects of a different number of vanes or pillar posts, inner and outer radii and various angles of vanes.

http://inpressco.com/wp-content/uploads/2014/04/Paper27129-132.pdf

Thermal Analysis of Automotive Brake Rotor

In recent years a trend towards faster vehicles with powerful engines has developed. Heavy braking force & high retardation leads to high temperature at disc brake. An upper limit on the temperature of the brake assembly is dictated by certain material properties. Hence heat energy has to be disposed of more efficiently. Possibilities of increasing conduction and radiation are restrained by material properties and temperature limits. Therefore the focus is on convection. Different ventilated disc brake rotors are analyzed with CFD and the most optimum ventilated disc rotor is found for automobile industry. Various disc brake designs are used to describe a method for calculating temperatures of disc brakes. For the calculations a CFD code is employed that determines distributions of local temperatures in the flow field as well as on the disc brake rotor. In a ventilated disc brake rotor air must be circulated through the rotor to provide adequate cooling. The passages formed by the radial vanes between the braking surfaces, act as a centrifugal fan, facilitating the required air flow for cooling. To improve the performance of a ventilated disc brake rotor, radial vanes are modified and analysis is done for the same. After the CFD analysis the experimental verification is done with actual experimental setup. The CFD results are verified with the experimental results obtained on test rig.

Experimental analysis and investigation for thermal behaviour of ventilated disc brake rotor using CFD

http://inpressco.com/wp-content/uploads/2014/09/Paper473339-3345.pdf

Mahesh R. Chopade

Papers

A Review on Gun Barrel Erosion

Experimental investigation using cfd for thermal performance of ventilated disc brake rotor

Thermal Analysis of Automotive Brake Rotor

Experimental analysis and investigation for thermal behaviour of ventilated disc brake rotor using CFD

Experimental Analysis and Investigation for Thermal Performance of Ventilated Disc Brake Rotor Using CFD