Diameter Ball Bearings Research Articles

Fatigue life and fatigue crack growth rate analysis of high strength low alloy steel (42CrMo4)

This study presents a fatigue life and fatigue crack growth rate analysis of large diameter ball bearing under cyclic loading condition by using numerical and experimental methods. The large diameter of ball bearing was made up of high strength low alloy steel (42CrMo4), and the two dimensional finite element analysis (FEA) is used to predict the minimum life of ball bearing and validated by using of Basquin's relationship in the numerical study method, and its fatigue crack propagation is numerically and experimentally investigated. The specimen, notch preparation, and testing methods are performed according to ASTM-E647 standard in the experimental method. The crack propagation is found by experimentally, and the results are applied in the Paris equation for find the crack growth rate and stress intensity factor (delta-K) under the high cycle fatigue life loading by using of the mathematical relationship of da/dN = C(ΔK)n in the prediction. The predicted results are correlated with the experimental test results of 42CrMo4 material used large diameter ball bearings.

Object position and image magnification in dental panoramic radiography: a theoretical analysis

The purpose of our study was to investigate how image magnification and distortion in dental panoramic radiography are influenced by object size and position for a small round object such as a ball bearing used for calibration. Two ball bearings (2.5 mm and 6 mm in diameter) were placed at approximately the same position between the teeth of a plastic skull and radiographed 21 times. The skull was replaced each time. Their images were measured by software using edge detection and ellipse-fitting algorithms. Using a standard definition of magnification, equations were derived to enable an object's magnification to be determined from its position and vice versa knowing the diameter and machine parameters. The average magnification of the 2.5 mm ball bearing was 1.292 (0.0445) horizontally and 1.257 (0.0067) vertically with a mean ratio of 1.028 (0.0322); standard deviations are in parentheses. The figures for the 6 mm ball bearing were 1.286 (0.0068), 1.255 (0.0018) and 1.025 (0.0061), respectively. Derived positions of each ball bearing from magnification were more consistent horizontally than vertically. There was less variation in either direction for the 6 mm ball bearing than the 2.5 mm one. Automatic measurement of image size resulted in less variation in vertical magnification values than horizontal. There are only certain positions in the focal trough that achieve zero distortion. Object location can be determined from its diameter, measured magnification and machine parameters. The 6 mm diameter ball bearing is preferable to the 2.5 mm one for more reliable magnification measurement and position determination.

SU-E-J-33: Geometric Agreement Check for Imaging System with Radiation Beam by KV and MV-CBCT.

The verification method of the geometry agreement between a light field and/or a laser coordinate and treatment beam should be easy and quick. In this presentation, we propose a novel QA method by using both kV- and MV-CBCT for kV-IGRT system. This method confirms the temporal unchanging the agreement of geometry in the kV-IGRT system with the treatment beam geometry. 1) MV-flexmap: Sequential MV-projection images were acquired during gantry rotation by iViewGT (Elekta) and MV-CBCT was reconstructed by in-house software with a flexmap correction. The flexmap is displacement of gantry and detector panel related with gantry sag. The geometric change affects the deranging reconstructed image. To evaluate how much displacement of EPID panel and gantry was detectable, the images of 8mm diameter ball-bearing (BB) located at the radiation isocenter were reconstructed with improper Flexmap.2) A comparison between the kV-CBCT and the MV-CBCT: The kV-CBCT was provided by X-ray Volume image (XVI) system (Elekta). To confirm the agreement for the geometry between kV-IGRT system and treatment beam, the kV-CBCTs of BB are compared with that of MV-CBCTs. The flexmaps were modified to (b)1mm / (c)3mm shifted to the rotation direction and (d)3mm to the rotation axis. The MV-CBCT were reconstructed with the correct flexmap and with incorrect flexmap (b), (c) and (d).　The geometric confirmation for MV-CBCT was done by comparison of the width and center of the BB on the MV-CBCT. The discrepancy of center between kV-CBCT and MV-CBCT was less than 1mm. Less than 1mm of the geometrical changing to rotation direction for MV-detector panel could be recognized by reconstructed images of BB. Using kV- and MV-CBCT enable us to perform the simple comparison for geometrical non-idealities between the kV-IGRT system and the treatment beam. Dr. K. Nakagawa received research grant from Elekta.

Contact Stress Distribution of Large Diameter Ball Bearing Using Hertzian Elliptical Contact Theory

The large diameter bearings (diameter >400mm) are of great importance in complex engineering mechanisms such as Aircraft gas turbines, Rolling Mills and Nuclear Reactor etc, in which varying load and critical environmental conditions leads to the failure of such bearings. Majorly spalling failure occurs due to contact mechanism. The contact mechanism of ball and raceway of bearing behaves highly non-linear and it reduces the service life of component considerably. This paper presents to determine the contact stress of large diameter ball bearings using analytical and numerical methods. In analytical method the contact stress is found out using the Hertzian Elliptical Contact Theory. The calculation procedure consists of calculation of the maximum contact pressure on the rolling element, which is done by the in-house developed program, and detailed finite element analysis of the contact between the ball and the raceway. The finite element analysis also performed to predict contact pressure in ball and raceway. Comparison of the results is made at the end.

Comparison of Computed Tomography Scout Based Reference Point Localization to Conventional Film and Axial Computed Tomography

Identification of source positions after implantation is an important step in brachytherapy planning. Reconstruction is traditionally performed from films taken by conventional simulators, but these are gradually being replaced in the clinic by computed tomography (CT) simulators. The present study explored the use of a scout image–based reconstruction algorithm that replaces the use of traditional film, while exhibiting low sensitivity to metal-induced artifacts that can appear in 3D CT methods. In addition, the accuracy of an in-house graphical software implementation of scout-based reconstruction was compared with seed location reconstructions for 2 phantoms by conventional simulator and CT measurements. One phantom was constructed using a planar fixed grid of 1.5-mm diameter ball bearings (BBs) with 40-mm spacing. The second was a Fletcher-Suit applicator embedded in Styrofoam (Dow Chemical Co., Midland, MI) with one 3.2-mm-diameter BB inserted into each of 6 surrounding holes. Conventional simulator, kilovoltage CT (kVCT), megavoltage CT, and scout-based methods were evaluated by their ability to calculate the distance between seeds (40 mm for the fixed grid, 30–120 mm in Fletcher-Suit). All methods were able to reconstruct the fixed grid distances with an average deviation of <1%. The worst single deviations (approximately 6%) were exhibited in the 2 volumetric CT methods. In the Fletcher-Suit phantom, the intermodality agreement was within approximately 3%, with the conventional sim measuring marginally larger distances, with kVCT the smallest. All of the established reconstruction methods exhibited similar abilities to detect the distances between BBs. The 3D CT-based methods, with lower axial resolution, showed more variation, particularly with the smaller BBs. With a software implementation, scout-based reconstruction is an appealing approach because it simplifies data acquisition over film-based reconstruction without requiring any specialized equipment and does not carry risk of misreads caused by artifacts.

SU-FF-J-85: Evaluation of the Positioning Accuracy in Helical Tomotherapy for Stereotactic Intracranial Radiosurgery

Purpose: To assess the accuracy of patient alignment for intracranial stereotactic radiosurgery(SRS) on Tomotherapy using the standard for linac alignment assessment — hidden target port films. Method and Materials: For each trial, a small 6.5‐mm diameter ball bearing (target) was placed in one of four positions inside a Rando head phantom. A kilovolt computed tomography (kVCT) scan was used for both planning and as the dosimetryquality assurance (DQA) phantom. The DQA capabilities of the treatment planningsoftware were used to position the target to coincide with the isocenteric lasers of the Tomotherapy unit in the axial, sagittal, and coronal planes. Accurate registration of the MVCT to the kVCT should place the target at the isocenter. Lateral and Anterior‐Posterior (AP) port films were taken with only the center two binary multi‐leaf collimators (bMLC) open. The films were analyzed and shifts were measured in the AP, right‐left, and superior‐inferior directions relative to the radiation field. The process was repeated 15 times for each target location. Results:Analysis of 60 pairs of port film yielded the following millimeter errors in the AP, lateral, and average SI directions respectively for each of four trial locations: (1) 0.79±0.27, 0.77±0.11, 0.84±0.29; (2) 0.88±0.28, 0.39±0.14, 0.18±0.25; (3) 1.19±0.23, 0.57±0.19, 0.43±0.39; (4) 1.16±0.18, 0.34±0.35, 0.56±0.35. Across the trials the mean errors were seen to be 1.00±0.30 anterior, 0.50±0.40 superior and 0.52±0.27 to the patient's left. Conclusion: The results show a root‐mean‐square error of 1.33±0.28. The tight standard deviation in each direction suggests there may be systematic error in alignment, which may include measurement error (isocentric placement of phantom) or inaccuracy of MLC alignment.

Effects of buprenorphine, carprofen and saline on thermal and mechanical nociceptive thresholds in cats

ObjectiveTo evaluate a prototype pressure stimulus device for use in the cat and to compare with a known thermal threshold device. AnimalsEight healthy adult cats weighing between 3.0 and 4.9 kg. MethodsPressure stimulation was given via a plastic bracelet taped around the forearm. Three 2.4 mm diameter ball bearings, in a 10-mm triangle, were advanced against the craniolateral surface of the antebrachium by manual inflation of a modified blood pressure bladder. Pressure in the cuff was recorded at the end point (leg shake and head turn). Thermal threshold was also tested. Stimuli were stopped if they reached 55 °C or 450 mmHg without response. After four pressure and thermal threshold baselines, each cat received SC buprenorphine 0.01 mg kg−1, carprofen 4 mg kg−1 or saline 0.3 mL in a three period cross-over study with a 1-week interval. The investigator was blinded to the treatment. Measurements were made at 0.25. 0.5, 0.75, 1, 2, 3, 4, 6, 8, and 24 hours after injection. Data were analyzed by using anova. ResultsThere were no significant changes in thermal or pressure threshold after administration of saline or carprofen, but thermal threshold increased from 60 minutes until 8 hours after administration of buprenorphine (p < 0.05). The maximum increase in threshold from baseline (ΔTmax) was 3.5 ± 3.1 °C at 2 hours. Pressure threshold increased 2 hours after administration of buprenorphine (p < 0.05) when the increase in threshold above baseline (ΔPmax) was 162 ± 189 mmHg. Conclusions and Clinical relevanceThis pressure device resulted in thresholds that were affected by analgesic treatment in a similar manner but to a lesser degree than the thermal method. Pressure stimulation may be a useful additional method for analgesic studies in cats.

Assessment of distortion in a three-dimensional rotational angiography system.

The purpose of this project was to determine the degree of geometrical distortion in a three-dimensional (3D) image volume generated by a digital fluorography system with rotational image acquisition capabilities. 3D imaging is a valuable adjunct in neuroangiography for visualization and measurement of cerebral aneurysms and for determination of the optimum projection for intervention. To enable spatially accurate 3D reconstruction the system must correct for geometrical distortion in the image intensifier television system as well as for deviations in gantry motion. 3D volumes were reconstructed from 100 X-ray projections acquired over a 180 degrees arc over a period of 8 s. A phantom was constructed to assess geometrical distortion in the three dimensions. The phantom consisted of 1 mm diameter ball bearings embedded in Perspex in a cubic lattice configuration. The ball bearings were placed at 20 mm intervals over a 140 mm cubic volume. Distortion was assessed by taking measurements between points of known separation and using a differential distortion measurement. The maximum error in the 3D location of objects was found to be 1.4 mm, while the differential distortion was found to range from -1.0% to +2.3%. The 3D images were found to have negligible visual distortion, enabling subjective assessments to be made with confidence to aid intervention.

Rolling contact fatigue testing of PM high speed steels (HSS): J A Whitehead, et al. (Powdrex Ltd, tonbridge, Kent, UK), Int. J. Powder Metallurgy, Vol 26, No 4, 1990, 345–349

The large diameter bearings (diameter >400 mm) are of great importance in complex engineering mechanisms such as Aircraft gas turbines, Rolling Mills and Nuclear Reactor etc, in which varying load and critical environmental conditions leads to the failure of such bearings. Majorly spalling failure occurs due to contact mechanism. The contact mechanism of ball and raceway of bearing behaves highly non-linear and it reduces the service life of component considerably. This paper presents to determine the contact stress of large diameter ball bearings using analytical and numerical methods. In analytical method the contact stress is found out using the Hertzian Elliptical Contact Theory. The calculation procedure consists of calculation of the maximum contact pressure on the rolling element, which is done by the in-house developed program, and detailed finite element analysis of the contact between the ball and the raceway. The finite element analysis also performed to predict contact pressure in ball and raceway. Comparison of the results is made at the end.