VIBRATORY ACTIVITY INVESTIGATION OF GRINDING MACHINE ELECTRIC SPINDLES

The purpose of this work is to support dynamic properties of spindle units in grinding machines. For this there are problems under solution for the definition of the origin of the constituents in the spindle unit vibratory activity by means of the linear increase of electric spindle rotation frequency, obtaining and analyzing a vibratory acceleration signal for the possibility to determine a preload. The vibratory acceleration signal was investigated through a spectrum analysis method. A scientific novelty of investigation consists in the substantiation of possibility to determine a preload by means of the spectrum analysis of a vibration acceleration signal at the linear increase of spindle rotation frequency that is at starting. It gives, in its turn, a possibility for the automated estimate of the spindle unit state before cutting beginning. In the experimental way there are obtained temporal realizations of the vibratory acceleration signal at different efforts of the preload. A high-speed grinding motor-spindle is as a basic element of the bench, which was investigated through the methods of testing diagnostics in the operation. In the bench design there were made some alterations. The bench was supplemented with the systems essential to support motor-spindle full operation, in particular: with systems of lubrication, cooling and drive control. There was revealed a large number of harmonics multiple to 50 Hz, which tells of the connection with the frequency of power supply circuit. Their coincidence with the own frequencies of the spindle unit results in the considerable increase of their amplitudes. To increase dynamic quality one should avoid the cases of the coincidence of switching frequencies and circuit harmonics with own frequencies of the electric spindle. It is also necessary to bring a form of power voltage to a pure harmonic oscillation to decrease the impact of a drive electromagnetic field upon dynamic characteristics of the spindle unit.

Assessment of an acoustic chamber for testing structure-borne sound transmission in a double-panel assembly

An acoustic chamber was designed for testing structure-borne sound transmission in a double-panel assembly induced by point connectors. Several vibration isolators were tested and the overall effects on the noise transmitted through the assembly were predicted by establishing the link between the vibratory acceleration level (VAL) and the sound pressure level (SPL). A detailed assessment of the acoustic chamber showed that a major modification of the double-panel assembly is required before the acoustic performance of this assembly could be evaluated directly using insertion loss (IL) measurements where the sound pressure level (SPL) difference is the performance indicator. This thesis describes the assessment findings and retrofitting options. It is concluded that adjustments to the VAL-to-SPL relation are required to account for distance, radiation efficiency, and room effects. Further adjustments to the acoustic chamber are required to enhance its performance.

Assessment of an acoustic chamber for testing structure-borne sound transmission in a double-panel assembly

An acoustic chamber was designed for testing structure-borne sound transmission in a double-panel assembly induced by point connectors. Several vibration isolators were tested and the overall effects on the noise transmitted through the assembly were predicted by establishing the link between the vibratory acceleration level (VAL) and the sound pressure level (SPL). A detailed assessment of the acoustic chamber showed that a major modification of the double-panel assembly is required before the acoustic performance of this assembly could be evaluated directly using insertion loss (IL) measurements where the sound pressure level (SPL) difference is the performance indicator. This thesis describes the assessment findings and retrofitting options. It is concluded that adjustments to the VAL-to-SPL relation are required to account for distance, radiation efficiency, and room effects. Further adjustments to the acoustic chamber are required to enhance its performance.

Analysis of Vibratory Data Collected by the Space Acceleration Measurement System (SAMS) on Blue Origin, June 19, 2016

On Sunday, June 19, 2016, a Space Acceleration Measurement System triaxial sensor head flew on a suborbital flight aboard Blue Origin's New Shepard vehicle to collect precision vibratory accelerometry data. The Space Acceleration Measurement System (SAMS) sensor head was mounted inside of a Blue Origin single payload locker inside of the crew capsule. This paper describes the configuration, capture, and analysis of the SAMS data from this flight along with other, related flight log information provided by Blue Origin. Three overlapping periods during the flight were identified and characterized to provide future users of the platform with insight into options that may prove suitable for their research needs. Average accelerations in the Post-Separation Period were consistent with other low-g research platforms, while the shorter Microgravity Period in the middle of the flight showed ultra-quiet vibratory acceleration environments. Researchers can consider this microgravity quality versus time a tradeoff in their experimental designs.

Assessment of Real-Time Compaction Quality Test Indexes for Rockfill Material Based on Roller Vibratory Acceleration Analysis

Compaction quality is directly related to the structure and seepage stability of a rockfill dam. To timely and accurately test the compaction quality of the rockfill material, four real-time test indexes were chosen to characterize the soil compaction degree based on the analysis of roller vibratory acceleration, including acceleration peak value (ap), acceleration root mean square value (arms), crest factor value (CF), and compaction meter value (CMV). To determine which of these indexes is the most appropriate, a two-part field compaction experiment was conducted using a vibratory roller in different filling zones of the dam body. Data on rolling parameters, real-time test indexes, and compaction quality indexes were collected to perform statistical regression analyses. Combined with the spectrum analysis of the acceleration signal, it was found that the CF index best characterizes the compaction degree of the rockfill material among the four indexes. Furthermore, the quantitative relations between the real-time index and compaction quality index were established to determine the control criterion of CF, which can instruct the site work of compaction quality control in the rockfill rolling process.

Effects of Grease Characteristics on Sound and Vibration of a Linear-Guideway Type Recirculating Ball Bearing

This paper deals with the effects of grease characteristics on sound and vibration of a linear-guideway type ball bearing. First, sound, vibration, and temperature of a linear-guideway type ball bearing were measured by changing 16 types of greases. Next, in order to explain the effects of grease characteristics (absolute viscosity η0 of the base oil in the grease at atmospheric pressure, pressure–viscosity coefficient ξ of the base oil, and penetration P of grease) and linear velocity V on the sound pressure p and vibratory acceleration a of the linear bearing, dimensional analyses were carried out. The dimensional analyses derived dimensionless products Pp/(η0V) and η0ξV/P for the sound, and dimensionless products Pa/V2 and η0ξV/P for the vibration. The plot of the measured data using dimensionless products showed that both sound pressure p and vibratory acceleration a (under a certain linear velocity) decreased as the absolute viscosity η0 of the base oil in the grease at atmospheric pressure or the pressure–viscosity coefficient ξ increased. Whereas the sound pressure p decreased as the penetration P decreased, the vibratory acceleration a decreased as P increased.

Vibration and Acoustic Emission Measurements Evaluating the Separation of the Balls and Raceways With Lubricating Film in a Linear Bearing Under Grease Lubrication

This paper deals with vibration and acoustic emission (AE) measurements evaluating the separation of the balls and raceways with lubricating film in a linear-guideway–type recirculating ball bearing (linear bearing) under grease lubrication. In the experiments, three types of commercial grease, AS2, LG2, and PS2, were used. The vibratory acceleration, AE, temperature, and electric conductivity (contact voltage) in the test bearing were measured, while a carriage of the test bearing was driven at a certain linear velocity. Experimental results showed that the measured vibratory acceleration, AE, and contact voltage of the test bearing were affected by the linear velocity and the base oil viscosity of the grease. Next, the rail side film parameter ΛR and the carriage side film parameter ΛC were examined for the test bearing in operation, and it was shown that the ΛR value was lower than the ΛC value. In addition, a condition for the separation of all the balls and raceways with lubricating film was presented. Finally, it was shown that the measured root-mean-square (RMS) values of vibratory acceleration or AE can be used for evaluating the separation of all the balls and raceways with lubricating film in the test bearing.

Research on the ICP Acceleration Sensors Detecting Roadbed Compaction Degree Test

Compaction is an important influencing factor that makes various structural materials of road embankment and surface sufficiently dense, and it becomes more and more important that effective detecting methods of the compaction degree are employed to monitor the quality of compaction. In this paper, the testing methods and means that the compaction degree of sub grade soils was detected by the acceleration sensors during the compaction process of vibratory roller were presented, with which the field tests were performed to measure the acceleration of vibratory drum of the vibratory roller and the compaction degree of compacted soils, and then the relational expression between the vibratory acceleration and the compaction degree of soils were obtained. Results indicate that there exists such a significant positive correlation relationship between the virtual value of vibration acceleration and the soil compaction degree that the former can be used to characterize the latter accurately. Therefore, it provides a technical support for the development of nondestructive and live vibratory roller compaction degree detection technology.

Safety Assessment of Cargo Containment Systems in LNG Carriers Under the Impact of Iceberg-Ship Collision

Arctic and sub-arctic regions of Russia are home to some of the large gas reservoirs, attracting numerous energy development projects. A ship-borne transportation system connecting these potential gas fields to gas terminals in Gulf of Mexico will likely be established. In this case, the integrity and safety of LNG cargo containment systems under impact of the iceberg-ship collision should be carefully considered at conceptual and detailed design phase. The collision impact by an undetected iceberg should be considered to be an accidental load. Thereby, plastic deformations of the hull structure may be accepted provided the LNG will not leak out. Till now, view points of the safety evaluation have been limited to structural hull deformations by the collision. They have not examined effects of vibratory acceleration induced by the impact on the structure of LNG containment systems, even though it seems rather rational in case of substructure such as LNG containment systems in independent type or membrane type LNG carriers. In this paper, the iceberg-ship collision scenario is established based on International Ice Patrol’s reports. The comparative safety assessment of cargo containment systems for independent type (spherical and SPB) and membrane type (Mark-III and NO96) LNG carriers is performed through a computational simulation and the related experimental research works.