Incremental profile ring rolling with axial and circumferential constraints

© 2017 If profile ring rolling could be achieved without part-specific tooling, significant savings in material, energy and downstream processing could be realised. One approach, ‘incremental ring rolling’ previously suffered difficulties controlling material flow, resulting in multiple form errors. Inspired by studying an expert using a potter's wheel, two additions to this process are proposed; the use of axial and circumferential constraints. A 12-axis ring rolling machine has been built to demonstrate these process enhancements, producing metal rings up to 1 m in diameter. The production of both rectangular and L-shape rings is examined, showing significant improvements in ring cross-sectional form and circularity.The first author was supported by an EPSRC I-Case Studentship (12220703), with Primetals Technologies Ltd. Prof. Allwood was supported by EPSRC grant EP/K018108/1

High Speed Cylindrical Roller Bearing Analysis, SKF Computer Program CYBEAN. Volume 1: Analysis

The CYBEAN (CYlindrical BEaring ANalysis) program was created to detail radially loaded, aligned and misaligned Cylindrical roller bearing performance under a variety of operating conditions. The models and associated mathematics used within CYBEAN are described. The user is referred to the material for formulation assumptions and algorithm detail

Review and critical analysis: Rolling-element bearings for system life and reliability

A ball and cylindrical roller bearing technical specification which incorporates the latest state-of-the-art advancements was prepared for the purpose of improving bearing reliability in U.S. Army aircraft. The current U.S. Army aviation bearing designs and applications, including life analyses, were analyzed. A bearing restoration and refurbishment specification was prepared to improve bearing availability

Numerical simulation of long and slender cylinders vibrating in axial flow applied to the Myrrha reactor

Flow induced vibrations are an important concern in the design of nuclear reactors. One of the possible designs of the 4th generation nuclear reactors is a lead-cooled fast reactor of which MYYRHA is a prototype. The combination of high liquid density, flow velocity, low pitch-to-diameter ratio and the absence of grid spacers makes this design prone to flow induced vibrations. Although most vibrations are induced by cross flow, axial flow around this slender structure could also induce vibrations. In order to gain insight in the possible vibrations (either induced by cross flow, axial flow or an external excitation) this study examines the change of eigenmodes and frequencies of a bare rod due to the lead-bismuth flow. To do so partitioned simulations of the fluid structure interaction are performed in which the structure is initially perturbed according to an in-air eigenmode

Ring rolling with variable wall thickness

Ring rolling processes today produce axisymmetric rings, wasting material, energy and labour if non-axisymmetric components such as eccentric bearing races and bossed pipe fittings are required. A new process is proposed to roll rings with variable wall thickness. In this work, roll gaps and speeds are controlled online in physical experiments to achieve a defined variable wall thickness, enabled by photogrammetry to capture the ring’s shape and position. The trials revealed two new process limits for which new analytical explanations have been developed: a maximum rate of change of thickness around the circumference and a loss of circularity.The first author is supported by an EPSRC I-Case Studentship (12220703), with Primetals Technologies Ltd. Dr. Arthington and Prof. Allwood were supported by EPSRC grant EP/K018108/1.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.cirp.2016.04.00

Dynamic Performance of Turbocharger Rotor-Bearing Systems

The objectives of this investigation were to design and construct a high speed turbocharger test rig (TTR) to measure dynamics of differing turbocharger rotor bearing systems and to develop a coupled rotor-cartridge model for the ball bearing rotor system to corroborate the experimental and analytical results. The ball bearing rotor is supported by an angular contact ball bearing cartridge. In order to achieve the objectives of the experimental aspect of this study, a TTR was designed and developed with the capability of reaching speeds in excess of 100,000 rpm driven by compressed air. The TTR was used to compare and contrast the whirl and friction characteristics of two identical turbochargers differing only by the support structure of the rotor system; one containing a floating ring bearing turbocharger (FRBT) and the other a ball bearing turbocharger (BBT). A pair of displacement sensors was installed to measure the whirl of the rotor near the end of the compressor. The BBT was shown to be significantly more rigid and stable as compared to the FRBT with an average reduction in radial rotor motion of 47%. The motion of the BBT consisted of mainly synchronous motion whereas the FRBT was dominated by subsynchronous motion throughout the entire range of speeds. The TTR was also used to compare frictional losses within the bearings. A study of run-down times after the pressurized air supply was removed indicated that the BBT has significantly lower frictional losses under all operating conditions tested with an average increase in run-down time of 14.1%

Design review of fluid film bearing testers

The designs of three existing testers (Hybrid Bearing Tester, OTV Bearing Tester, and Long Life Bearing Tester) owned by NASA were reviewed for their capability to serve as a multi-purpose cryogenic fluid film bearing tester. The primary tester function is the validation of analytical predictions for fluid film bearing steady state and dynamic performance. Evaluation criteria were established for test bearing configurations, test fluids, instrumentation, and test objectives. Each tester was evaluated with respect to these criteria. A determination was made of design improvements which would allow the testers to meet the stated criteria. The cost and time required to make the design changes were estimated. A recommendation based on the results of this study was made to proceed with the Hybrid Bearing Tester

Design, manufacture and spin test of high contact ratio helicopter transmission utilizing Self-Aligning Bearingless Planetary (SABP)

A 450 hp high ratio Self-Aligning Bearingless Planetary (SABP) for a helicopter application was designed, manufactured, and spin tested under NASA contract NAS3-24539. The objective of the program was to conduct research and development work on a high contact ratio helical gear SABP to reduce weight and noise and to improve efficiency. The results accomplished include the design, manufacturing, and no-load spin testing of two prototype helicopter transmissions, rated at 450 hp with an input speed of 35,000 rpm and an output speed of 350 rpm. The weight power density ratio of these gear units is 0.33 lb hp. The measured airborne noise at 35,000 rpm input speed and light load is 94 dB at 5 ft. The high speed, high contact ratio SABP transmission appears to be significantly lighter and quieter than comtemporary helicopter transmissions. The concept of the SABP is applicable not only to high ratio helicopter type transmissions but also to other rotorcraft and aircraft propulsion systems

The practical impact of elastohydrodynamic lubrication

The use of elastohydrodynamics in the analysis of rolling element bearings is discussed. Relationships for minimum film thickness and tractive force were incorporated into computer codes and used for bearing performance prediction. The lambda parameter (ratio of film thickness to composite surface roughness) was shown to be important in predicting bearing life and failure mode. Results indicate that at values of lambda below 3 failure modes other than the classic subsurface initiated fatigue can occur

Advances in Lubricated Bearings

This reprint features 12 research articles that contribute to the research on lubricated bearings. The articles focus on the latest steps in understanding bearing operating behavior, its interaction with lubricants, and its role as a component in the drive train. In addition to the description of novel modeling approaches, a variety of experimental data are presented to provide interesting identification results as well as validation data for the research and engineering community