Diameter Steel Ball Research Articles

Probabilistic Evaluation to Improve Design of Impact–Echo Sources

The aim of the study reported in this paper was to provide rational aid tools to quantify the performance of nondestructive testing (NDT) tools. This study focused on the quantification of the performance of impact–echo sources (steel balls of varied diameters), applied with a new, con-tactless robot, for duct void detection and thickness measurements in a reinforced concrete wall. Because of uncertainties during the testing, the data were analyzed in a probabilistic context, with the knowledge that on-site inspections were affected by uncertainties. The αδ method was used in this regard, where the probabilities of detection and false alarm rates were used to build receiver operating characteristic curves. The methodology was applied to data measured on the same wall with two steel ball diameters: 0.16 and 0.125 m. The quantity analyzed here was the impact–echo method (resonance) frequency. This methodology could be extended to other parameters of the impact–echo setup as well as to other NDT methods.

NON-DESTRUCTIVE EVALUATION FOR HORIZONTAL CRACKS IN EXISTING RC SLABS BY ANALYSIS-AIDED IMPACT ELASTIC-WAVE METHODS

In this study, impact elastic-wave method was performed at the bottom surface of RC slab cut from an existing highway bridges to survey the horizontal cracks. Before measurements by impact elastic-wave method, impact response analysis was applied to determine optimal steel ball diameter, distance between impact point and receiving point of elastic-wave. Efficiency of analysis-aided impact elastic-wave method was confirmed by drilling and observing the interior of the RC slab by stick scanner. Evaluation results by this method agreed well with results of visual inspection. Thus, validity of the analysis-aided impact elastic-wave method on detection of horizontal cracks in RC slabs of highway bridges was demonstrated.

Antiwar and Extreme Pressure Characteristics of Quinazolin-4-Ones Derivative as the Potential Lubricating Oil Additive

Tribological study on a 12.7 mm diameter steel ball bearing specimen has been carried out in a four-ball machine. The synthesis of 3-(N-n-octadecylammonium) quinazolin-4-ones was described. The 3-(N-n-octadecylammonium) quinazolin-4-ones has been found to be quite effective as a potential ashless additive without phosphorus and sulphur in liquid paraffin according to the experimental results. Employing scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), the film formed when the the additive interreacted with the metal was investigated.

오일 함침된 나노 기공 산화알루미늄 필름의 마찰 거동

Friction behavior of nanoporous anodic aluminum oxide(AAO) film was investigated. A 60 thick AAO film having nanopores of 45 nm diameter with 105 nm interpore-diatance was fabricated by mild anodization process. The AAO film was then saturated with paraffinic oil. Reciprocating ball-on-flat sliding friction tests using 1 mm diameter steel ball as the counterpart were carried out with normal load ranging from 0.1 N to 1 N in an ambient environment. The morphology of worn surfaces were analyzed using scanning electron microscopy. The friction coefficient significantly increased with the increase of load. The boundary lubrication layer of paraffinic oil contributed to the lower friction at relatively low load (0.1 N), but it is less effective at high load (1 N). Plastic deformed layer patches were formed on the worn surface of oil-enriched AAO at relatively low load (0.1 N) without evidence of tribochemical reaction. On the other hand, thick tribolayers were formed on the worn surface of both oil-enriched and as-prepared AAO at relatively high load (1 N) due to tribochemical reaction and material transfer.

A Study of (<i>N-octylic acid</i>)-N-Quinazolin-4-One Methylester as an Oil Additive

(n-octylic acid)-N-quinazolin-4-one methylester was synthesized as potential lubricating oil additive. The friction and wear behaviors of the synthesized compound as an additive in liquid paraffin on 12.7mm diameter steel ball bearing specimen were evaluated with a four-ball machine. The worn surfaces of the steel balls were observed using a scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that the novel compound as an additive in liquid paraffin was effective in improving the tribological performance.

A Study of N Heterocyclic Compound as a Potential Lubricating Oil Additive

Lauric acid-N-quinazolin-4-one methylester was synthesized as potential lubricating oil additive. The friction and wear behaviors of the synthesized compound as an additive in liquid paraffin on 12.7mm diameter steel ball bearing specimen were evaluated with a four-ball machine. The worn surfaces of the steel balls were observed using a scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that the novel compound as an additive in liquid paraffin was effective in improving the tribological performance.

Development of a new rubber seismic isolator: ‘Ball Rubber Bearing (BRB)’

AbstractThis paper presents an experimental research aimed at developing a new rubber‐based seismic isolator called ‘Ball Rubber Bearing (BRB)’. The BRB is composed of a conventional steel‐reinforced multi‐layered rubber bearing with its central hole filled with small diameter steel balls that are used to provide energy dissipation capacity through friction. A large set of BRBs with different geometrical and material properties are manufactured and tested under reversed cyclic horizontal loading at different vertical compressive load levels. Extensive test results indicate that steel balls do not only increase the energy dissipation capacity of the elastomeric bearing (EB), but also increase its horizontal and vertical stiffness. It is also observed that the energy dissipation capacity of a BRB does not degrade as the number of loading cycles increases. Copyright © 2011 John Wiley & Sons, Ltd.

Characteristics of Progressive Damage of ZnO Nanowires during Contact Sliding under Relatively Low Loads

ZnO nanowires have received much interest owing to their particular structural and piezoelectric properties. For widespread application of ZnO nanowires in various nanotechnologies, the mechanical reliability of the nanowires should be assessed. In this paper, the damage characteristics of vertically grown ZnO nanowires due to contact sliding against a 2 mm diameter steel ball under relatively low loads were investigated. Frictional behavior and wear characteristics of the specimens were assessed. Furthermore, contact sliding tests were performed inside an SEM to monitor the progression of damage of the nanowires. It was found that the friction coefficient was about 0.35 under all loads while the damage characteristics of the nanowires were quite different for each load. The large diameter nanowires tended to fracture earlier than the small diameter nanowires. Wear tests performed inside the SEM confirmed the surface damage characteristics observed during the friction tests.

Sheet Formability Using Hemi-Spherical Punch AndRubber Die

In recent years, the elastomer forming technique has found acceptance on the shop floor and is used increasingly as a pressure- transmitting medium for various metal-forming operations. This is due mainly to the introduction of a new range of materials and of new concepts in tooling, which have served to kindle industrial interest in the process. The purpose of this paper is to study the sheet formability with compressible die (natural rubber). The forming was occurred using hemi-spherical punch and rubber die. Experimental tests were used to know the mechanical properties for rubber and sheet materials which were brass and aluminum. After that several forming processes were prepared with a 58 mm diameter steel ball as a punch to form 0.5 thickness brass and aluminum dishes with different diameters (15-40 mm). Force-stroke history was plotted through forming to find the stiffness of formed plate with rubber die and later to compare this parameter for different diameters. Wrinkling and springback were pointed for the formed dishes. It was found that the stiffness of the formed dish increases with diameter until reaching to the diameter at which wrinkling will takes place (about 33 mm for aluminum and 28mm for brass), and then the stiffness will decreases with diameter above this value. It was found that the springback ratio (ratio of final high to the stroke) was increased with diameter until wrinkling takes place, and this ratio is greater for aluminum than that for brass. The results show that it is able to use natural rubber as a die for sheet metal forming with limitation of using small sheet thickness

Tribological properties of nanoporous anodic aluminum oxide film

Friction and wear properties of nanostructured anodic aluminum oxide (AAO)) films were studied in relation to contact load and pore size (pore diameter). Uniformly arrayed nanoporous aluminum oxide films (pores of 28 nm, 45 nm, 95 nm, and 200 nm diameter and 60–100 μm thick) were synthesized by anodization. Reciprocating wear tests using 1 mm diameter steel balls as counterpart were carried out for a wide range of load (from 1 mN to 1 N) at ambient environment. The friction coefficient reduced with the increase of load. The friction coefficient decreased by approximately 30% when the load increased by 3 orders of magnitude. The pore density marginally affected the frictional properties of AAO films. The influence of pore size on the friction coefficient was significant at relatively high loads (0.1 N and 1 N) whereas it was negligible at low loads (1 mN and 10 mN). The worn surface of AAO films tested at low loads did not experience tribochemical reaction and exhibited only mild plastic deformation. Dispersed thick smooth films were formed on the worn surface of all samples at relatively high loads whereas only extremely thin smooth film patches were rarely formed at low loads. These thick smooth films were generated by combined influence of tribochemical reaction at the contact interface and plastic deformation of compacted debris particles as evidenced by energy-dispersive spectroscopy analysis. We suggest that these thick films mainly contributed to the decrease of friction regardless of the pore size.

SU-GG-T-469: Geometric Uncertainty Evalution of Proton Beam Delivery

Purpose: To develop a method to measure the agreement between the isocenters of a proton beam and the x‐ray system used to position the patient. X‐ray portal images are performed for the setup and all proton beams. The isocenter of proton beams can vary with rotation of couch, gantry and MLC and differ from X‐ray isocenter. Couch corrections are determined for each gantry angle to maintain the concentricity with the proton beam and the virtual crosshair of the x‐ray system is adjusted with gantry angle before initial clinical use to account for the change. Method and Material: A 50.8‐mm diameter steel ball is placed at the isocenter and aligned with the 50.8‐mm sphere target exported from the Eclipse treatment planning system to Medcom's X‐ray acquisition system at the setup and different gantry angles. Variation of the metal ball from the spherical target at different gantry, MLC rotation and couch angles is quantified by delivering star pattern treatment plans that have 10‐mm width. Both MatrixX and films are used with Omnipro IMRT software. Different levels of isodose are used for the best recognition of metal ball and star patterns. The asymmetric magnitude is reported for the symmetric fields after centering the metal ball or elliptical beam center of star patterns. Results: When metal ball is aligned with virtual crosshair at setup position, up to 2 mm variation of isocenter is reported by both the X‐ray portal images and proton star patterns for the rotation of couch, gantry and MLC. When the metal ball is corrected with X‐ray virtual crosshair at different angles, the variation of proton beam isocenter is reduced to below 1 mm. Conclusion: A method is established to measure the concentricity of proton beams with X‐ray portal images and rotation of couch, gantry and MLC.

Foreign Object Damage Phenomenon by Steel Ball Projectiles in a SiC/SiC Ceramic Matrix Composite at Ambient and Elevated Temperatures

Foreign object damage (FOD) phenomenon of a gas‐turbine grade SiC/SiC ceramic matrix composite (CMC) was determined at 25° and 1316°C using impact velocities ranging from 115 to 440 m/s by 1.59‐mm diameter steel ball projectiles. Two types of target‐specimen support were employed at each temperature: fully supported and partially supported. For a given temperature, the degree of impact damage increased with increasing impact velocity, and was greater in partial support than in full support. The elevated‐temperature FOD resistance of the composite, particularly in partial support at higher impact velocities ≥350 m/s, was significantly less than the ambient‐temperature counterpart, attributed to a weakening effect of the composite. In full support, frontal contact stresses played a major role in generating composite damage; whereas, in partial support both frontal contact and backside tensile stresses were combined sources of damage generation. Formation of cone cracks initiating from impact site was also one of the key damage features. The SiC/SiC composite was able to survive higher energy impacts without complete structural failure, as compared with gas‐turbine grade AS800 and SN282 monolithic silicon nitrides.

Bouncing steel balls on water

The ‘skimming’ of stones on water is a subject of perennial fascination for children andadults alike. In this article I describe the construction of an apparatus for safely andreproducibly demonstrating a similar phenomenon: the bouncing of 25 mm diameter steelballs from a water surface. The ‘bouncing’ is technically known as a ricochet and the articlerecounts the use of the effect in the Second World War in the ‘Dam Busting’ airraids of 1943. A number of calculations are made which allow an estimate ofthe projectile speed and energy, and the use of simple experimental techniquesfor validating these estimates is suggested. The role of spin is discussed, and aliterature review collates the available empirical and theoretical results concerning theincident angle and speed for successful ricochet of spinning and non-spinningprojectiles.

Micro-Friction and Adhesion Measurements for Si Wafer and TiB 2 Thin Film

An apparatus was specifically developed for micro-friction and adhesion measurements. The force measurement range is 10–2000 μN with a horizontal speed of 10–400 μm/s. The apparatus was tested using a 0.7-mm diameter steel ball as the upper specimen to measure the micro friction and adhesion behaviour of a Si (100) wafer and a TiB 2 film. The effects of rest time, speed, and load were studied. The results show that the maximum static and sliding friction forces of both the Si (100) wafer and the TiB 2 film increase with the load. At low speeds, the influence of speed on the friction force is significant. The adhesion forces of the Si (100) wafer and the TiB 2 film increase with rest time, reaching stable values after about 3000 s. The TiB 2 film has significantly less adhesion and micro friction forces than the Si (100) wafer.

Impact resistance of environmental barrier coated SiC/SiC composites

Impact performance of 2D woven SiC/SiC composites coated with 225 and 525 μm thick environmental barrier coating (EBC) was investigated. The composites were fabricated by melt infiltration and the EBC was deposited by plasma spray. Impact tests were conducted at room temperature and at 1316 °C in air using 1.59 mm diameter steel-balls at projectile velocities ranging from 110 to 375 m/s. Both microscopy and non-destructive evaluation (NDE) methods were used to determine the extent of damage in the substrate and coating with increasing projectile velocity. The impacted specimens were tensile tested at room temperature to determine their residual mechanical properties. At projectile velocities less than 125 m/s, no detectable internal damage was noticed in the MI SiC/SiC composites coated with 525 μm EBC. With increase in projectile velocity beyond this value, spallation of EBC layers, delamination of fiber plies, and fiber fracture were detected. At a fixed projectile velocity, the composites coated with 525 μm EBC showed less damage than those coated with 225 μm EBC. Both types of coated composites retained a large fraction of the baseline properties of the as-fabricated composites and exhibited non-brittle failure after impact testing. Furnace exposure of impacted specimens in a moisture environment at 1316 °C for 500 h indicated that the through-the-thickness cracks in the coating and delamination cracks in the substrate generated after impact testing acted as conduits for internal oxidation.

Effects of relative humidity on tribological properties of boron carbide coating against steel

Boron carbide coatings of 100 nm thick were synthesized on silicon substrate by DC magnetron sputtering using B 4C target with a mixture of Ar and methane (CH 4 at 1.2 vol.%) as processing gases. Tribological properties of the coating were studied in relation to the effects of relative humidity (RH). Reciprocating wear tests using 3 mm diameter steel balls as a counterpart were carried out at three relative humidity conditions. Confocal microscopy was used to observe worn surfaces and the wear scars on the steel balls. Elemental composition of the coating and worn surfaces were characterized using X-ray photoelectron spectroscopy and Auger electron spectroscopy. The tribological properties of boron carbide coating slid against steel ball were strongly affected by relative humidity. Lower and steady friction coefficient and higher wear resistance for both the coating and the steel ball were achieved at higher relative humidity. At high RH, tribochemical reaction occurred in the sliding surfaces, forming boric acid and carbon in a graphitic form on the worn surface of coating and a soft layer on the ball surface. The formation of boric acid on boron carbide coating combined with graphite structure led to the low and stable friction of boron carbide coating in medium and high relative humidity conditions. Smooth layer was formed on the worn surface of the steel ball at high relative humidity due to the tribochemical reaction. Low and steady value of friction coefficient and reduction of wear loss of both steel ball and boron carbide coating were attributed to the formation of the soft layer.

Dry sliding tribology of dioctyldithiophosphoric acid deposited on steel at 150 °C

Dioctyldithiophosphoric acid was deposited on 7 nm (RMS) rough steel surfaces at 150 degrees C to create a densely packed (area-95%) deposit of glassy phosphate islands of maximum 500 nm height. This standard substrate was subjected to dry lubricated ball-on-disc tribology using a 2 mm diameter steel ball in the 25-500 mN normal load range at a sliding velocity of 1 mm/s. The experiments recorded friction coefficient of the order of 0.18 but the life of the film as it wears out with sliding distance was found to decline with increasing load. The life-load characteristics that we record in these experiments, we argue, can only be explained if there is a load induced growth of the deposited film during sliding. We record this load induced growth to yield phosphate islands which are significantly smaller but harder than those grown by thermal activation alone.

Boundary lubrication capabilities of alkylsilane monolayer self-assembled on aluminium as investigated using FTIR spectroscopy and nanotribometry

In pursuing the boundary lubrication tribology of aluminium, we first explore the change in chain mobility and conformational order of alkylsilane monolayer self-assembled on aluminium surface with different chain length using grazing angle FTIR spectroscopy. In tribology, a point on a surface rubbing against another surface is subjected to contact heating and cooling till next contact. We thus track conformational order as monolayers are subjected to heating and explore reversibility on cooling back. We report here the friction generated in sliding the monolayer against a 2 mm diameter steel ball in a ball on disc arrangement in the 25–100 mN load and 1 mm/s velocity under dry conditions. The friction at the commencement of sliding is found to correlate directly with conformational order of the molecule which is varied by changing the chain length and heat treatment temperature. We find this friction to vary linearly with full width half maxima (FWHM) which is an expression of chain mobility and packing density. The initial coefficient of friction is independent of normal load but the dynamic friction which evolves with sliding is not, although the change in dynamic coefficient of friction with normal load does relate qualitatively with the a priori conformational order of the monolayers.

Dosimetric accuracy of a staged radiosurgery treatment

For large cerebral arteriovenous malformations (AVMs), the efficacy of radiosurgery is limited since the large doses necessary to produce obliteration may increase the risk of radiation necrosis to unacceptable levels. An alternative is to stage the radiosurgery procedure over multiple stages (usually two), effectively irradiating a smaller volume of the AVM nidus with a therapeutic dose during each session. The difference between coordinate systems defined by sequential stereotactic frame placements can be represented by a translation and a rotation. A unique transformation can be determined based on the coordinates of several fiducial markers fixed to the skull and imaged in each stereotactic coordinate system. Using this transformation matrix, isocentre coordinates from the first stage can be displayed in the coordinate system of subsequent stages allowing computation of a combined dose distribution covering the entire AVM. The accuracy of this approach was tested on an anthropomorphic head phantom and was verified dosimetrically. Subtle defects in the phantom were used as control points, and 2 mm diameter steel balls attached to the surface were used as fiducial markers and reference points. CT images (2 mm thick) were acquired. Using a transformation matrix developed with two frame placements, the predicted locations of control and reference points had an average error of 0.6 mm near the fiducial markers and 1.0 mm near the control points. Dose distributions in a staged treatment approach were accurately calculated using the transformation matrix. This approach is simple, fast and accurate. Errors were small and clinically acceptable for Gamma Knife radiosurgery. Accuracy can be improved by reducing the CT slice thickness.

Mechanical properties of nanocrystalline Ti–B–(N) coatings produced by DC magnetron sputtering

Ti–B–(N) coatings have been deposited by DC magnetron sputtering using TiB2 targets in Ar/N2 gas mixtures. The influence of bias voltage and nitrogen flow on the mechanical and tribological properties of these coatings has been studied. Mechanical properties have been evaluated by ultra-microindentation techniques and scratch testing; tribology tests have been performed in a pin-on-disc apparatus with controlled humidity conditions.Microstructural characterization by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) demonstrates the nanocrystalline structure of Ti–B–(N) coatings and allows the interpretation of their mechanical behaviour.Hardness values up to 58 GPa have been achieved, depending on deposition conditions. Increasing the bias voltage on the substrates improves the hardness of coatings, while the addition of nitrogen significantly decreases these values. Coating adhesion obtained on high-speed steel is very good in most cases, reaching values higher than 60 N of critical load. Tribotests performed on these coatings against a steel contact (wear conditions: 0.98 N load, 10 cm/s, 50% RH, 10 mm bearing steel ball diameter) have yielded very low wear rates but friction coefficients in the range of 0.6–1.0.