INFLUENCE OF VIBRATION MAGNITUDE IN MACHINING OF MATERIALS BY TURNING TECHNOLOGY

The basic task of any prosperous company is to minimize operating costs to a minimum. High-quality maintenance ensures an increase in the operational reliability of the machines. It is important to find a compromise between scheduled maintenance and production process requirements, so resources are spent to optimize the maintenance schedule. This is provided by technical diagnostics, which helps to monitor the technical condition and functional properties of the monitored machine under specified operating conditions. The publication is focused specifically on vibration diagnostics and its use in monitoring the transmission of vibrations during the turning of selected types of materials in the company with a focus on engineering, the ZVL AUTO s.r.o. The scope of research is mainly focused on the monitoring process in order to analyze the magnitude of vibration acceleration at two preselected parts of the machine tool - lathe.

A Novel Dual-Mass Accelerometer Exploiting Mode Localization in Electrostatically Coupled Resonators

A novel dual-mass accelerometer is proposed while exploiting the phenomenon of mode localization in two electrostatically coupled resonators with an adjustable coupling strength. The external inertial forces are transmitted differentially to the resonators in term of axial load change through the two levering mechanisms, breaking the balanced state and resulting in a drastic change in the amplitudes of the two resonators. Based on the Euler Bernoulli theory, the governing equations of the coupled system are derived and numerically solved. The sensitivity in term of relative shift of amplitude ratio can be improved by 4 orders of magnitude compared to frequency shift. Finally, the effect of the quality factor on the sensor dynamics has also been investigated, and the results show that it only affects the vibration magnitude of the resonators while operating below the critical amplitude.

Critical Hydraulic Eccentricity Estimation in Vertical Turbine Pump Impeller to Control Vibration

In many applications, pumps are tested against standard specifications to define the maximum allowable vibration amplitude limits of a pump. It is essential to identify the causes of vibration and methods to attenuate the same to ensure the safe and satisfactory operation of a pump. Causes of vibration can be classified mainly into mechanical and hydraulic nature. Respective unbalance masses are the two major factors which cause dynamic effects and excitation forces leading to undesirable vibrations. In this paper, the procedure of vibration magnitude measurement of a vertical turbine pump at site and the process of dynamic balancing to measure mechanical unbalance of an impeller are explained. After that, the impact of hydraulic eccentricity on the vibration displacement of a vertical turbine pump has been explained using numerical simulation procedure based on “One-way Fluid Structure Interaction (FSI).” The experimental results from a pump at site are used to compare the numerical results. After the solver validation, the one-way FSI approach is used to find the critical hydraulic eccentricity magnitude of a vertical turbine pump impeller to limit the vibration magnitudes on motor component to less than 100 μm. From the numerical simulations, it is deduced that the critical hydraulic eccentricity should be limited to 400 μm in X and Y direction. The process can be used as a guideline procedure for limiting the hydraulic unbalance in vertical turbine pumps by limiting the hydraulic eccentricity.

Stiffening Behavior of Supine Humans during En Route Care Transport

Previous studies of human response to whole-body vibration demonstrated nonlinear softening behaviors with increasing vibration magnitudes. Most of these studies were conducted at relatively low vibration magnitudes of less than 3 m/s2 root mean square (RMS), and not much knowledge is available to show if this softening behavior exists when humans are exposed to higher vibration magnitudes. In this work, 26 participants were transported in a supine position inside an army medical vehicle on a road that simulated field scenarios and were exposed to input acceleration magnitudes at 0.60, 0.98, 1.32, 3.25, 5.58, and 5.90 m/s2 RMS. Motion response data were collected at the head, torso, and pelvis of the participants using inertial sensors. Transmissibility and coherence graphs were used to investigate the type of nonlinearity induced under these transport conditions. Participant responses showed softening behavior when the vibration magnitude increased from 0.60 to 0.98 to 1.32 m/s2 RMS. However, this response behavior changed to stiffening when the vibration magnitude increased to 3.25, 5.58, and 5.90 m/s2 RMS. In the stiffening range, the transmissibility of the torso transformed from two dominant peaks to a single peak, which may indicate a tonic muscle behavior. The resulting stiffening behaviors may be considered in the design of transport systems subject to rough terrains.

Vibration Exposure Safety Guidelines for Surgeons Using Power-Assisted Liposuction (PAL)

Background As power-assisted liposuction (PAL) gains popular use, plastic surgeons operating these devices experience occupational exposure to hand-transmitted vibration, which can result in Hand-Arm Vibration Syndrome (HAVS), a debilitating neurovasculopathy. Objectives The objective of the study is to determine vibration exposure from the use of a PAL device during surgery in order to generate recommendations for safe use. Methods Vibration emission of a commonly used PAL system (MicroAire-650: Surgical Instruments) was examined using a vibration data logger under both controlled laboratory conditions and during 13 typical liposuction cases. Data were analysed and compared with established safety limits of vibration exposure. Results The experiments demonstrated a mean vibration magnitude of typical liposuction surgeries to be 5.69 ± 0.77 m/s2 (range 4.59 - 6.27 m/s2), which is significantly higher than the manufacturer declared value of 3.77 m/s2. Cannula size was shown to be the most significant contributor to vibration magnitude, with larger cannulas causing more vibration transmission. Conclusions These results indicate that recommendations must be made to prevent undue occupational exposure to vibration from PAL. The MicroAire-650 can generally be safely used for less than 1.5 hours per day. At exposure levels greater than 1.5 hours per day, there is increased risk of developing vibration-related injuries, and vibration reducing strategies should be implemented. At exposure levels greater than 6 hours per day, the safety limit is exceeded and there is significantly increased risk of developing HAVS and vibration exposure should be halted.

COGNITIVE REACTION TIME PERFORMANCE AND SUBJECTIVE DROWSINESS: A CRITICAL EVALUATION OF THE EFFECT OF WHOLE-BODY VIBRATIONS

It is believed that exposure to whole-body vibration (WBV) may increase seated occupant drowsiness, and seated occupant drowsiness may contribute to vehicular accidents. Previous studies on driver comfort have indicated that long-term exposure to WBV may have an adverse effect on musculoskeletal disorders. However, the effects of WBV on seated occupants’ drowsiness have been less rigorously studied. Thus, this study aims to investigate the association between exposure to WBV and drowsiness level. Laboratory experiments were designed and involved eighteen healthy male volunteers. Volunteers were exposed to random gaussian vibration for 20-minutes with the frequency between 1-15Hz. The transmitted vibration magnitude was adjusted for each volunteer to become 0.2ms-2 for low vibration magnitude and 0.4ms2 for medium vibration magnitude. Volunteers’ vigilance was measured by the Psychomotor Vigilance Task (PVT) before and after the vibration exposure. The analyses revealed a substantial drop in volunteers’ vigilance level after exposure to vibration and the effect was more pronounced in high vibration amplitude 0.4 ms-2. These findings suggested that exposure to vibration even as low as 20-minutes may attribute to the reduction of alertness level.

Measurements of Vibration and Noise Level at Different Cement Companies

The aim of this article is to compare Vibration and Noise measurements caused by different types of Machines at cement factories with the standard evaluation criteria of Vibration ISO 2631 – 4 EVS – EN 5349 – 2 and Noise following the standard ISO 9612 – 2009. Two cement companies were chosen, the first is located at Baddish district, 30km west of Mosul city (Iraq), which is called Baddish general cement company, while the other is located south of Mosul, and is called Hammam Al-Alil general cement company. Three stations were chosen for each company (raw materials grinding mills, cement grinding mills, and exhaust fan stations) having different electrical motor capacities. Noise level meter and vibration level meter manufactured by B & K (DENEMARK) were used for measurement. The location of bearing was chosen for vibration measurement, while the location of the operator’s ears for noise measurement, where chosen. It was found that most of the readings in vibration levels were unacceptable according to the evaluation criterion of vibration magnitude and noise level higher than 85dBA due to rotating unbalance misalignment and faulty gear matching (ISO 1940/1, 1990).

Analysis and evaluation of the effect of vibrations on historical buildings

Continued exposure of human induced vibrations contributes to the degradation of materials and joints, causing the initiation of cracks or the growth of existing ones, such that they may endanger the structure. Loads, which an undamaged structure could safely resist, can be critical if repeated numerous times. This risk is present in various types of historical buildings, and is influenced by changes in vibration magnitude, by the distance from their source, and by the quality of the building’s maintenance. Good maintenance, which includes regular inspections, allows early detection of any emerging damage and its subsequent repair. This article describes the methods and results of the measurement of dynamic response to road traffic and other types of technical seismicity in four historic buildings. The goal of this paper is to present some examples of analysis and evaluation of the effects of such human activity.

Vibration Transmitted to the Hand by Backpack Blowers

Backpack machines such as grasscutter and blower produce a vibration that is transmitted to the operator’s body and hand. Prolonged exposure to vibration can cause injuries known as Hand-Arm Vibration Syndrome. One of the machines used widely in the agriculture sector is the blower. The objective of this study is to evaluate the level of vibration emitted by blowers according to the method in the International Standard ISO 5349. Vibrations emitted by two backpack machines, mist blower and leaf blower, were acquired on ten subjects who were working and using the tools daily. Vibrations were recorded at operational and idle modes using an accelerometer installed in an aluminium palm adapter that was placed between the hand and the surface of the handle. The study has found that the median weighted Wh vibration magnitudes emitted by blowers to the hand were between 1.71 and 2.91 m/s2 r.m.s. acceleration for operational and idle modes, respectively. The mist blower has an idle mode weighted Wh vibration magnitude greater than its operational mode, whilst the leaf blower has an operational mode weighted Wh vibration magnitude greater than in its idle mode. This study suggests that vibrations emitted to the hand from a leaf blower and a mist blower can be greater than the exposure action value set by the European Directive 2002 if used for more than 7 hours (mist blower) or 5 hours (leaf blower) per day. Companies that use both machines should set appropriate actions and regulations to reduce the exposure, especially to workers using the machines daily.