Small Steel Ball Research Articles

Subsurface Zones Created Under Lubrication Conditions Studied by Positron Annihilation

We present positron annihilation studies of the subsurface zones induced in the sliding contact of two metals under lubrication conditions. The surfaces of copper samples were exposed to the sliding of a small steel ball and the open volume defects induced under the surface were detected using both a positron beam experiment and a conventional positron experiment. From our studies we deduced that the total range of subsurface zones was almost independent of the lubrication conditions. For the highest load of the ball we observed that the subsurface zone created under lubrication condition extends deeper than for the case where the zone was induced in the dry sliding contact. We found that sliding with lubricant induces a layer on the surface whose properties, as detected by positrons, were different than those of other samples. It seems that this layer could contain open volume defects that are larger than those in deeper layers. Our studies have shown that the positron beam technique is a suitable tool for defect characterization in tribotested samples.

Optimisation of autogenous grinding

Batch tests in a 0.6m diameter mill were used to simulate fully autogenous primary and secondary grinding. Substantial improvements in primary mill capacity were obtained by modifying the mill contents to simulate crushing of small pebbles and recycle of the crushed material. Secondary grinding efficiency (as measured by kWh per ton finer than 75 microns or Work Index), was improved substantially by reducing the pebble size to 20/28mm. The process as a whole was optimised when crushed rock coarser than 4 mm was recycled to primary mill, as the small pebbles were most efficient with “sand”. The benefit of using small grinding media has been known for some time, but the high cost and rapid consumption of small steel balls makes their use uneconomical. However a plentiful supply of small pebbles is available from a primary mill. A further and unexpected improvement in power efficiency was obtained when pebble milling was performed at 92% of critical speed.

Impact Resistance of Laminated Glass Using “Sacrificial Ply” Design Concept

Experimental results of low velocity, small steel ball impact tests on laminated architectural glass units are presented. These tests are part of an ongoing effort to develop a design method for laminated architectural glass units to resist windborne debris from sources such as roof gravel, as required in several current and proposed U.S. building codes and standards. A design concept known as “sacrificial ply” permits the exterior-facing, outer glass ply of a laminated glass unit to fracture during windborne debris impacts, but prevents fracture of the inner glass ply. This concept also depends on an inner glass ply designed to resist lateral wind pressures for the remainder of the windstorm so that the integrity of the building envelope is preserved. In these experiments, inner and outer glass ply thicknesses and polyvinyl butyral interlayer thickness were varied to determine their effects on the impact resistance of the inner glass ply of laminated architectural glass when impacted on the outer glass ply. Results show that inner glass ply thickness and PVB interlayer thickness have stronger effects on the impact resistance of the inner glass ply than does outer glass ply thickness.

破壊力学 弾丸による板ガラスのヘルツコーンの形態について

Plate glasses of windows and doors of buildings are often destroyed by the bullets in the criminal cases using firearms. When a plate glass is impacted by a projectile, the Hertzian cone is produced behind the impact point of this glass. It is known that the apex angle of the Hertzian cone crack in Pyrex glass caused by small steel ball impact varies in a systematic manner with the impact velocity. However, there are few reports especially on the results caused by the lead bullet impact. In order to obtain the basic data to estimate the impact velocities and the incident angles of the projectiles, an experiment about the morphology of the Hertzian cone was carried out.In the experiment, projectiles (11mm dia. steel balls and 0.38 inch (9mm) dia. lead bullets) were shot onto the float plate glasses (soda-lime glasses). A strong correlation was found between the ratio of the Hertzian cone diameter to the plate glass thickness and the impact velocity. It was also found that the Hertzian cone caused by inclined impact became the size equivalent to the velocity component which is normal to the glass surface. Thus, the morphology of the Hertzian cone can be one of the indexes for estimating the impact velocities and the incident angles of the projectiles.

New Manipulator Based on Surface Acoustic Wave Streaming

We report a new micromanipulator based on the surface acoustic wave (SAW) streaming. When a small solid object is loaded onto a water droplet placed on a SAW substrate and the SAW is excited, the object can be moved easily and smoothly with the droplet in the SAW propagation direction. Small steel balls of 0.5 to 4.0 mm in diameter were examined as manipulated samples to be loaded onto a droplet. The experimental results are compared with those of the direct drive method without preloading, by which an object is moved towards an operating interdigital transducer (IDT) in the direction opposite to the SAW propagation direction. It was observed, that the driving efficiency of the present method was sixty times larger than that of the direct drive method. Moreover, a teflon sheet, which is difficult to move by the direct drive method, can be moved with ease by the present method. We conclude that the present method has a high potential for practical use as a micromanipulator.

Crater formation in the laboratory: An introductory experiment in error analysis

One of the primary objectives of the introductory physics laboratory is to teach error analysis. We describe a very simple and inexpensive experiment which exposes students to the central ideas of estimation and uncertainty, and to the evaluation of theory by graphical display of data. The task is to measure the diameter of a crater formed by dropping a small steel ball into a sand-filled container, and then to deduce the functional dependence of the crater diameter on the kinetic energy of the falling ball.

Winners: How Successful Companies Innovate by Design

Winners: How Successful Companies Innovate by Design

Differences in mechanical response between fractured and non-fractured spines under high-speed impact

Objective. The differences in mechanical response between fractured and non-fractured spines were investigated using a porcine spine impact model. Design. Ten three-vertebrae segments (C3–C5) of porcine spine were subjected to a single impact to study the trauma mechanism. Small steel balls glued to the vertebra and a high-speed camera were used to observe the deformation of vertebral body and disc during impact. After trauma, the episodes of fractured specimens were compared with those of non-fractured specimens. Background. Experimental trauma models using the spines of mature animals have rarely been evaluated. Finding a well-controlled, reproducible protocol based on an easily accessible specimen was therefore important. These models will be promising if clinical fractures can be produced. Methods. All of the specimens were subjected to high-speed flexion-compression loading. The impact to the load cell and the operation of the high-speed camera were synchronized. The force-time sequence and disc deformation curve were recorded. The results from fractured and non-fractured spines were then compared. Results. There were three burst fractures, four pedicle fractures, one facet joint fracture, one compression fracture and one fracture-dislocation. All of these fractures were similar to clinical fractures. Compared to non-fractured specimens, the fractured specimens had lower maximal force and longer reaction time. The characteristic steep decline in the middle region of the force-time curve was also consistently noted in the fractured spines. Conclusions. Spinal fractures similar to those found clinically were successfully produced in porcine spines. The characteristics of the mechanical responses observed should be helpful in the interpretation of events which occur during impact.

Contact and Driving Condition of a Surface Acoustic Wave Motor

A simple simulation for surface acoustic wave motor is carried out to obtain valuable information about the operation conditions. Experiments using a small steel ball slider to make certain the contact condition of the slider to a stator are also curried out. Optimum pre-load conditions, speed of the motor and others are discussed. An actual linear motor design are proposed.

Experimental correlation of mechanical properties of joints and transverse vibrations in PMMA beams

An ultrathin joint in a poly(methyl methacrylate) (PMMA) beam was introduced by joining the two pieces using 1,2-dichloroethane. The viscoelastic property of the interfacial region was varied using dioctylphthalate (DOP) plasticizer and flexural waves in the beam were generated by impacting the beam with a small steel ball as well as with a calibrated experimental impact hammer. The acceleration vs. time data of a given point on a beam were used to optimally separate the wave emanating from the joint and were shown to correlate with the mechanical strength of the joint.

DEVELOPMENT OF A PNEUMATIC ON/OFF CONTROL VALVE USING A PZT FLIGHT HAMMER

This paper deals with the development of a pneumatic on/off valve driven by impulsive force of a multilayer PZT actuator. The displacement of the actuator is so small that it is necessary to design an amplifying mechanism. However, it subtracts the advantages of this actuator. On the other hand, the actuator can snap off a contacting small object like a hammer when the voltage is applied rapidly. This type of action is called a flight hammer. Using this action we hav developed an on/off valve with a nozzle-flapper mechanism, which is normally closed by the air pressure and is opened for a short time by the PZT actuator with the help of the spring force. The application of this valve is to blow off small objects by the air pulse flows that are generated by the on/off action of the valve. The air jet could blow up a small steel ball up to 20cm in height.

An Artificial Neural Network for Low-Energy Impact Monitoring

An artificial neural network has been developed that can analyze signals from piezoelectric sensors to detect the location and intensity of low-energy impact on a composite panel. The panel has two piezopolymer sensors attached some distance apart from each other. The signals are analyzed by the artificial neural network using a binary pattern associator. The binary pattern associator facilitates memory build-up during learn ing while simplifying signal discrimination during testing. The impact monitoring system, which consists of the artificial neural network and the piezoelectric sensors, has been used successfully to detect the location and height of impact when a small steel ball is dropped onto a composite laminate.

Validity of cephalometric landmarks. An experimental study on human skulls.

Cephalometric landmark validity (the difference between the estimated landmark and the true landmark) has surprisingly not previously been comprehensively evaluated, and no previous study has examined the validity of cephalometric angles and distances. The aim of this study was to investigate the validity of 15 commonly used skeletal and dental cephalometric landmarks, and the subsequent effects on 17 angles and distances. Small steel balls were glued on to 30 Chinese dry skulls to represent the true anatomical landmarks. The skulls were mounted in a purpose-designed skull holder and two cephalograms recorded of each skull, one with and one without the steel balls on the landmarks. Validity was expressed as the difference in the measurements between the assessments made with and without the steel ball markers. Measurements were made relative to X and Y co-ordinates which were constructed from reference points (steel balls) glued intracranially to the skulls. Seven out of the 10 skeletal landmarks and all five dental landmarks, were found to be non-valid along the X or the Y axes (P < 0.05). The standard deviations of the validity errors were large, being 1.0-2.5 mm, along at least one axis, for eight of the skeletal landmarks and three of the dental landmarks. Four of the cephalometric angles (SNA, SN/MnP, MxP/MnP, and LI/MnP) and three of the distances (N-Me, MxP-Me, and lower incisor edge to APg) were also found to be invalid (P < 0.05). The validity errors were greater for angles involving dental landmarks and for angles dependent on four landmarks compared to those dependent on three. The standard deviations of the validity errors for the skeletal angles ranged from 0.9 to 1.8 degrees, except for ANB (0.4 degrees), and for the dental angles from 3.2 to 5.8 degrees.

Acoustics of a Chinese hand-exercise ball

Pairs of steel balls, 3–4 cm in diameter, have been used in China as hand exercisers since the time of the Ming dynasty. Often a sounding device, consisting of a coil spring and a small steel ball, is placed inside the balls to produce a rather delicate tinkling sound as the balls are moved in circles in the hand. It is claimed that the balls can produce sounds ‘‘which are like the whistling of a dragon and singing of a phoenix.’’ The sound spectrum shows many strong partials up to 10 kHz or higher. The most identifiable pitch of G5 results from a partial at 773 Hz.

Control of Guideway Friction by Stress Wave (Effect of a single impact on the reduction in friction).

In general, when a slider is about to be moved, friction is always at the maximum. This phenomenon has made it difficult to locate a slider at a definite position with submicron accuracy. The authors attempted to challenge this widely accepted concept in this paper. The basic idea is to strike a guideway from the side with a small steel ball, so that stress waves are generated in the body of the guideway. The stress waves induce slight movement of the asperities on the surface of the guideway. The movement will lead to the breakage of metal-to-metal cohesion and will cause considerable decrease in friction. The idea was tested using a steel block with a hardened surface for a guideway and another smaller block for a slider. The results obtained are as follows. (1)Even a small ball can induce a considerable change in the relative slding speed of metal-to-metal contact regions between the guideway and the slider. The relative movement is strongly dependent on the kinetic energy of the ball. (2) The above movement causes a great reduction in the friction coefficient. When a ball of 25.4mm diameter is dropped from a height of 80mm, the coefficient of friction drops from 0.37 to 0.05 when the slider speed is 1 × 10-2mm/sec. (3) Though the low friction level is sustained for only 0.02sec, this period is long enough for a slider to start moving. (4) The lower the slider speed, the greater the reduction in friction.

高速主軸のための直列形複合転がり軸受の試作

A hybrid bearing is proposed for high speed machine tool spindle. The bearing composed of two angular contact ball bearings in a series arrangement and has a middle race between double column rolling elements besides the inner and outer race. The third race rotates with keeping a balance of the inner and outer bearing's friction. The spindle rotates at the speed of the sum of the inner and outer bearing's speed. The friction torque of the proposed bearing is less than a conventional bearing's one. But the simulation showed that the bearing has an effective speed range due to the retainer speed and the centrifugal force of the balls. At the critical speed, the friction torque of the bearing coincides with a conventional bearing's one. The critical speed can be rised by use of ceramics balls or small steel balls and an optimum lubricant system. A preliminary experiment of the proposed bearing showed that the final temperature rise of outer race is three degrees C only at 10000 rpm. The experimental critical spindle speed was about 8000 rpm against theoretical 17500 rpm.

頭部Ｘ線規格写真による下顎骨形態の３次元分析法

Methods for three-dimensional analysis of mandibular morphology and its postoperative change in which three-dimensional coordinate values of the landmarks on the mandible were measured and standardized by a personal computer using simultaneously taken frontal and lateral cephalograms were described and the efficacy of their clinical application was evaluated.The deviations of standardized three-dimensional coordinate values of six small steel balls placed on the skull which were calculated from eight cephalograms taken in different positions as well as the differences in the distance of these balls calculated from cephalograms and direct measurements were found to be small enough for clinical use. With the exception of 0.7mm in the mean difference of mandibular outline on the ZY-plane, standard deviations of all values evaluated were within 0.5mm in the analysis of U1, L1 and outer shapes of the mandible in 25 patients whose cephalograms were taken preoperatively on two separate occasions within a period of 4 months.The prediction of postoperative position of the mandible consisted of measuring the amount and direction of the movement of defined points on a dental model and displaying the movement of other bony points in the cephalometric tracings by coordinate transformation. The accuracy of the prediction was studied by comparing the predicted and postoperative positions of the mandible in three-dimensions in 44 patients in whom mandibular prognathism was corrected by the sagittal split osteotomy. The mean differences of coordinate values at L1 were within 0.84mm and the mean differences of mandibular outlines on the XY-, ZY-and ZX-planes were 0.76, 1.09 and 1.58mm, respectively.Thus, the methods described here proved to be quite useful for the diagnosis, treatment planning and the assessment of postoperative changes in patients with skeletal deformity of the mandible.

Decontamination by Shotblasting of Radioactivity Deposited on an Asphalt Road

Long-lived fission products may be deposited in the environment after a serious reactor accident. From previous experiments it is known that if firehousing is to be used for decontamination it has to be done soon after the deposition. It is therefore worthwhile to study another decontamination method. An experimental study has been conducted of how well shotblasting can remove contamination from an asphalt road. In shotblasting a thin layer of the surface is loosened by the impact of small steel balls, and in the same procedure the surface dust is vacummed up and the steel balls recovered. The contaminant was 86Rb, which behaves as caesium. As reference, the weathering of identical contamination on an asphalt road, a concrete road and a road covered with small concrete stones was studied concurrently.

Spherical reflectors as laser-beam expanders

Lasers emit a narrow beam of light which, for many applications, is often required to be expanded and then collimated. A common type of device used for this purpose is a lens telescope in which a pin-hole is placed at the common focal point of the two lenses. In dye laser cavities, dispersion through a number of prisms gives an expanded beam. The divergence of a laser beam can also be achieved by a convex reflecting surface like a polished steel ball. Here the capability of a small steel ball as an inexpensive, simple and convenient laser-beam expander has been investigated experimentally. It has been shown, with the help of shearing interferograms and Ronchigrams, that the aberrations introduced from on-axis as well as off-axis illumination of the ball are less than 1/4 of a fringe.

Ultrasonic marker for physiologic diagnosis and method of using same

For non-invasive diagnosis of conditions subsequent to a medical operative procedure, at the time of operation a "target" is sutured to tissue. Later, by use of an ultrasonic imaging system or other diagnostic instrument, the location of the target can be accurately determined. Thereupon, non-invasive techniques may be used in the target area to determine changes in physiology subsequent to implanting the target. For example, a target consisting of a fused array of small stainless steel balls is sutured to a coronary artery bypass graft. Later, to determine if the bypass graft is patent, by ultrasonic methods the location of the target and hence the bypass graft is determined. Then, using a Doppler-effect flowmeter, flow through the bypass graft may be measured and compared with prior measurements. The marking technique is also believed to be useful in postoperative determination of tumor growth at the locus of said marker.