Entity

Time filter

Source Type


Vakkalagadda M.R.K.,Indian Institute of Technology Kharagpur | Vineesh K.P.,Indian Institute of Technology Kharagpur | Mishra A.,Research Designs and Standards Organisation | Racherla V.,Indian Institute of Technology Kharagpur
Engineering Failure Analysis | Year: 2015

Gauge change in straight plate, locomotive, railway wheels is studied using finite element analysis. The study accounts for residual stresses generated during wheel manufacturing and fitment of the wheel on locomotive axle. A validated thermal model accounting for heat loss to rail, brake blocks and ambient air is considered for accurate prediction of wheel temperatures for a given train running and braking history. Results are obtained for low- and high-friction, composite brake blocks used by Indian Railways for two limiting braking scenarios: (i) synchronized braking where braking effort is uniformly distributed on all brake blocks and (ii) independent braking where braking effort to decelerate a train is provided solely by locomotive brake blocks. Results show that bending at hub-disc interface predominantly governs the gauge change. While compressive hoop stresses in the tread region, occurring from rim heating during braking, cause gauge reduction, tensile hoop stresses in the tread region, occurring during wheel cool down cause an increase in wheel gauge. Importantly, while gauge condemning is a transient phenomenon occurring only during braking, gauge widening is "permanent" as it exists even after the wheels cool to room temperature. Allowable reduction of wheel gauge of 0.5. mm, currently used by Indian Railways, is found to be highly restrictive. In fact, in service wheel failure based on this criterion is observed in all braking scenarios considered. © 2015 Elsevier Inc. Source


Vineesh K.P.,Indian Institute of Technology Kharagpur | Vakkalagadda M.R.K.,Indian Institute of Technology Kharagpur | Tripathi A.K.,Diesel Loco shed | Mishra A.,Research Designs and Standards Organisation | Racherla V.,Indian Institute of Technology Kharagpur
Engineering Failure Analysis | Year: 2016

Non-uniform braking of wheel sets in locomotives and coaches/wagons can have disastrous consequences e.g. from wheel locking leading to derailments or thermal cracking, particularly under emergency braking conditions. Currently, while rigorous testing is used to characterize brake block characteristics and brake application time, no methods exist to determine the "variability" in braking across the different wheel sets, e.g. from differences in brake block characteristics, brake rigging, and performance of distributor valves. In this work, temperature rise in railway wheels is used to gauge normalized heat input coming in to wheels from braking. Two sets of field trial data are used to investigate variability of braking: (i) continuous rim temperature data for locomotive wheels and (ii) one time measurement of wheel rim temperatures of all wheels. The data is used to pin point the causes for non-uniformity in braking and to characterize the extent of non-uniformity. Non-uniformity in braking is found to be particularly severe in freight trains as compared to passenger trains. Faulty distributor valves are seen to result in maximum braking effort on wheels that is as high as seven times that of average braking effort in freight trains. © 2015 Elsevier Inc. Source


Vakkalagadda M.R.K.,Indian Institute of Technology Kharagpur | Vineesh K.P.,Indian Institute of Technology Kharagpur | Mishra A.,Research Designs and Standards Organisation | Racherla V.,Indian Institute of Technology Kharagpur
Engineering Failure Analysis | Year: 2016

A finite element model accounting for heat partitioning at brake block-wheel and rail-wheel interfaces is used to investigate the effect of locomotive wheel profile, wheel diameter, brake block type, nature of braking (independent, synchronized, and drag), braking frequency and braking cycles on wheel gauge for tread braked, locomotive wheel sets. A train running model estimates heat generation rates during braking for assumed operating and braking conditions. Wheel profiles and brake block types used in the work, match with that used by Indian Railways. Bending at hub-disc and disc-rim interfaces is seen to primarily control axial deflection of wheels. While gauge reduction is observed during braking, gauge increase is seen during subsequent cooling. Maximum gauge increase occurs as the wheels finally cool down to room temperature. S-shaped wheels are seen to be better suited than straight plate and parabolic profile wheels for avoiding excessive gauge change. Locomotive wheel failure from gauge widening and condemning, albeit at different times, is seen to occur with independent braking for locomotives fitted with straight plate, S-shaped as well as parabolic profile wheels. © 2015 Elsevier Inc.. Source


Vakkalagadda M.R.K.,Indian Institute of Technology Kharagpur | Srivastava D.K.,Research Designs and Standards Organisation | Mishra A.,Research Designs and Standards Organisation | Racherla V.,Indian Institute of Technology Kharagpur
Wear | Year: 2015

Friction characteristics of cast iron, two "L-type" and two "K-type" composite brake blocks, used by Indian Railways for tread braking, were obtained experimentally under dry conditions using full scale stop braking experiments. Apparent friction coefficient of brake blocks was seen to depend on brake load, sliding speed, as well as sliding distance. Brake block friction characteristics along with traction-slip and running resistance characteristics for wagons and locomotives were used to estimate frictional heat generation rates at brake block-wheel and rail-wheel interfaces as a function of brake block type, brake load, number of wagons, tonnage per axle, nature of terrain (flat, uphill, downhill, etc.), train speed and time lag in braking. Braking performance was more consistent for cast iron brake blocks than that for composite brake blocks. Further, thermal loads on locomotive wheels were also lower for cast iron brake blocks, particularly with time lag in braking. © 2015 Elsevier B.V. Source

Discover hidden collaborations