Peak Vibration Research Articles

Experiment and Analysis of Wedge Cutting Angle on Cutting Effect

In the process of tunnel excavation, large charge wedge cutting blasting is widely used to improve the effect of cut blasting and speed up the excavation rate, which is tantamount to increasing the construction cost. In order to save economic cost and improve cutting blasting effect, wedge cutting models with five different cutting angles were experimented and studied by using concrete materials on the basis of similarity theory analysis. The relationships among cutting depth, blasting volume, blasting fragment, and cutting angle are studied and deduced by the dimensional analysis method. The polynomial fitting of cutting depth, blasting volume, blasting fragment, and cutting angle is carried out according to the experimental data, and the corresponding fitting formula is obtained. The optimum cutting depth, hole utilization rate, blasting volume, and blasting fragment were obtained when the wedge cutting angle was 67° under the same charge. The values were 1.665 × 10−1 m, 92.5%, 8.390 × 10−3 m3, and 49.07 mm, respectively. With the use of TC4850N type blasting vibration meter, the blasting vibrations on the wedge in four directions are tested and analyzed. The results show that when wedge cutting inclination is 65 degrees, the peak vibration velocity is the minimum and the vibration intensity of the wedge cutting inclined side is generally smaller than that of the vertical side. Considering the cutting depth, blasting volume, blasting fragment, blasting vibration hazard, drilling error, tunneling construction cost, and other factors, the 65°∼69° wedge cutting blasting in engineering practice can improve the blasting tunneling rate and increase economic benefits. The experimental results show that the blasting tunneling rate is increased and the economic benefit is increased with the minimum construction tunneling cost, which has certain engineering significance.

Experimental Study of Blast‐Induced Vibration Characteristics Based on the Delay‐Time Errors of Detonator

The delay‐time of detonators in hole‐by‐hole blasting is generally calculated accurately considering they have great influence on the blasting effect, such as blasting vibration and blasting slungshot. The high‐precision nonel detonator and digital electronic detonator are been commonly used because of their accuracy of delay‐time. However, each detonator has an allowable error range of delay‐time due to the difference in manufacturing process. In the initiation network, the errors of delay‐time often accumulate gradually as the number of detonators increases. Therefore, theoretical delay‐time and actual delay‐time with error in the detonating network were discussed based on the delay‐time errors of detonators. The single‐factor variable method was used to carry out the comparative test in deep hole blasting. The results showed that the particle peak vibration velocity (PPV) was 13.1783 cm/s and 3.4856 cm/s with a drop of 73.55% in comparison with a nonel detonator and digital electronic detonator, which proved that hole‐by‐hole blasting in the high‐precision nonel detonator network was not achieved due to the delay error of detonators. Furthermore, the location distribution map of holes where the same section of detonators might occur was obtained. Finally, the probability of blasting in the same section changes with the number of blast holes was discovered by theoretical analysis, which provided a basis for accurate hole‐by‐hole blasting.

Measurement of small vessel machinery vibration induced acoustic signature levels

Ship vibrations, airborne and underwater noise levels have always been a challenging topic from a performance point of view in ship design, building and operation. The measurement shall help in monitoring the self-noise and the technical state of their machinery mechanism. The vibration levels on the main engine and auxiliary Genset foundation, airborne noise levels of the engine room and underwater self-noise levels of a small mechanized fishing trawler was measured at the jetty in idling condition. The vibration levels on the foundation measured the average value of 0.207 mm/s for the main engine and 1.36 mm/s for auxiliary Genset. The airborne noise levels measured 99 dB (A) in the engine room. The peak underwater sound pressure levels measured 162 dB re 1µPa. The response spectra indicate the peak vibration and noise levels in the lower frequency region <1.2 kHz. The machinery excitation forces transferred to the hull surface as pressure fluctuations which generated the airborne and underwater noise levels. Though the measurement limited to jetty conditions, detailed analysis can be useful for detection, classification, and tracking of small vessels.

Vibration velocity control standard of buried pipeline under blast loading of adjacent tunnel

With the rapid development and construction of China’s transportation system, more and more projects are being conducted near existing buried pipelines, which will inevitably influence the safety of the pipelines. Among the safety issues related to buried pipelines, blasting during the construction of an adjacent tunnel is one of the most adverse factors for existing pipelines. To ensure the safety and normal operation of the pipelines, a method for determining the peak vibration velocity control standard for buried pipelines under blast loading is established in this study. The acceleration time-history function that acts on the rock mass under the blasting seismic wave is derived as external excitation acting on the pipeline. By using the acceleration time-history function as input and combining it with a dynamic and static analysis of the pipeline, the critical vibration velocity of pipelines under the action of blast loading can be determined by the von Mises yield criterion of the buried pipeline material. Using the Dashanpi No. 1 tunnel project in Shenzhen, China as a background, the critical velocity control standard for buried pipelines under tunnel blast loading can be set at 190 mm/s without considering either the initial defects or the corrosion conditions during the operation.

Dynamic characteristics and damage recognition of blast-induced ground vibration for natural gas transmission pipeline and its integrated systems

Abstract Natural gas pipeline network is a highly integrated network that moves natural gas throughout the continental and global services. Pipelines play a major role for the onshore and offshore gas transport, maintaining the record levels built up in recent years. However, once a rupture appears on a pipeline, the consequences of blast-induced incidents can pose a deadly threat in the vicinity of the failure location. Blast-induced ground vibration is the most significant impact that can seriously affect the surrounding parallel pipelines. In the present study, an experiment combined with a numerical investigation on the effect of blast-induced ground vibration of gas pipeline was undertaken. Dynamic characteristics such as peak vibration velocity, ground vibration acceleration, frequency response of blast-induced ground vibration were analyzed. Further, the modified prediction equations for blast-induced ground vibrational characteristics with distance were proposed. Ultimately, blast-induced displacement with the parallel pipeline was simulated, with a focus on risk vulnerability of gas pipeline. The main purpose of this paper is to facilitate a better understanding of the mechanical systems and dynamic characteristics governing the blast-induced ground vibration when the gas pipeline bursts, which is expected to be reliable for the safety spacing of buried integrated pipeline systems.

ИССЛЕДОВАНИЕ НЕЛИНЕЙНОЙ МОДЕЛИ ПОДВИЖНОЙ ПОДОВОЙ ПЛАТФОРМЫ ЭЛЕКТРИЧЕСКОЙ ПЕЧИ ДЛЯ ОБЖИГА СЫПУЧИХ МИНЕРАЛОВ

Актуальность. Электрические печи с подвижной подовой платформой имеют недостатки в конструкции системы вибротранспортирования – в расположенной под углом к горизонтальной плоскости самой платформы. Актуально использование горизонтальной подовой платформы, исключающей самопроизвольное скатывание округлых частиц материала и устраняющей возможность возникновения температурной тяги внутри пространства обжига, приводящей к охлаждению нагревательной системы печи и обжигаемого сыпучего материала. Цель работы состоит в исследовании динамики подвижной платформы с односторонним упругим элементом, обеспечивающим сильно выраженную нелинейную упругую характеристику, и процесса вибротранспортирования сыпучего материала по поверхности горизонтальной подовой плиты. Объект: подвижная подовая платформа электрической печи для обжига сыпучих минералов. Методика исследования базируется на разработке конструкции и модели подвижной подовой платформы электрической печи для обжига сыпучих минералов. Результаты исследования свойств специального упругого элемента подвижной подовой платформы печи позволили получить нелинейную аналитическую модель ее движения, характеризующуюся наклонной «скелетной» кривой ее амплитудно-частотной характеристики. Исследование динамики колебательной системы с односторонним упругим элементом, обеспечивающим сильно выраженную нелинейность, подтвердило, что система совершает несимметричные колебания с пиковыми значениями виброускорения 8,32 и 4,79 м/с2, соответствующими крайним положениям платформы и отличающимися в 1,74 раза. Показано, что при горизонтальной установке печи почти в три раза снижается чувствительность системы к флуктуациям частоты возбуждения, жесткости пружин, сил трения и других факторов, изменяющихся из-за влияния высокой температуры и внешних факторов. Подтвержден эффект устойчивого вибротранспортирования сыпучего материала по горизонтальной поверхности подовой плиты в тепловом поле печи.

Analysis of Surrounding Rock Vibration and the Influence of Soft Rock Mechanical Parameters During the Tunnel Blasting with Thin Bedrock Roof

The blasting construction of Shuidun Tunnel, China (a thin bedrock roof tunnel) is the engineering background in this paper. The numerical simulation method is adopted and combined with the verification of field measurement. The longitudinal, circumferential and radial distribution of the surrounding rock near the tunnel face is analyzed. The effects of various physical mechanical parameters of overlying soft rock on surrounding rock vibration are also discussed. The results may provide reference for construction safety control of similar projects. The main conclusions are as follows: The maximum value of the significant coefficient of cavity effect appears in the range of 2–4 m behind the tunnel face. The data like vault settlement within this range should be monitored emphatically. In the circumferential direction, the closer to the tunnel wall, the more significant the circumferential characteristic of the vibration velocity vector of surrounding rock is, and the maximum vibration velocity appears at the contact point between the rock layer interface and the tunnel contour wall. In the radial direction, the peak vibration velocity of surrounding rock decreases rapidly in the range of 1 m, while the attenuation tends to be gradual in the range of 2–4 m. The peak vibration velocity of surrounding rock near the tunnel face is positively correlated with the bulk density and poisson’s ratio of overlying soft stratum, and negatively correlated with its elastic modulus and internal friction angle of overlying soft stratum.

Characterization of vibration relative amplitude in direct detection Φ-OTDR using variable gain method

Vibration relative amplitude characterization has always been a tough problem in direct detection phase-sensitive optical time-domain reflectometry (Φ-OTDR) system due to the nonlinear relationship between the optical intensity and vibration amplitude. In this paper, a novel variable gain method is proposed to characterize the relative amplitude of external vibration. The mathematical model of Φ-OTDR is established, and the influence of external vibration on detected coherent Rayleigh back-scattering light in a single-mode fiber is simulated. Then, the vibration signals of different amplitudes imposed on the sensing fiber are further investigated, and the relationship between the interference amplitude peak power and vibration amplitude is derived. On the basis of the theoretical analysis, the variable gain method is carried out and implemented in Φ-OTDR system. The experimental results demonstrate that the calibrated interference peak power increases linearly with the applied vibration amplitude, and a high correlation coefficient (R2 = 0.93071) for linear fitting is obtained.

Optimal Design of an Inerter-Based Dynamic Vibration Absorber Connected to Ground

Abstract This paper addresses the optimal design of a novel nontraditional inerter-based dynamic vibration absorber (NTIDVA) installed on an undamped primary system of single degree-of-freedom under harmonic and transient excitations. Our NTIDVA is based on the traditional dynamic vibration absorber (TDVA) with the damper replaced by a grounded inerter-based mechanical network. Closed-form expressions of optimal parameters of NTIDVA are derived according to an extended version of fixed point theory developed in the literature and the stability maximization criterion. The transient response of the primary system is optimized when the coupled system becomes defective, namely having three pairs of coalesced conjugate poles, the proof of which is also spelt out in this paper. Moreover, the analogous relationship between NTIDVA and electromagnetic dynamic vibration absorber is highlighted, facilitating the practical implementation of the proposed absorber. Finally, numerical studies suggest that compared with TDVA, NTIDVA can decrease the peak vibration amplitude of the primary system and enlarge the frequency bandwidth of vibration suppression when optimized by the extended fixed point technique, while the stability maximization criterion shows an improved transient response in terms of larger modal damping ratio and accelerated attenuation rate.

Synchronous Vibration Measurements for Shrouded Blades Based on Fiber Optical Sensors with Lenses in a Steam Turbine.

It is important to obtain accurate dynamic vibrations of steam turbine blades for safe operation. Strain gauge (SG) measurements cannot fully obtain vibrations of all blades and nodal diameter (ND) details. The blade tip timing (BTT) technique could resolve this problem because it has the advantage of measuring all blades’ vibrations. This article proposed an improved BTT technique for measuring synchronous vibrations of shrouded blades in a steam turbine based on fiber optical sensors with lenses. The newly developed sensor was equipped with a Plano-convex lens, and the optical path was specifically designed to collimate the beam within a large working distance from 4 to 19 mm and improve the measuring accuracy. A method to search the spectra of all peak vibration amplitudes of all the blades was proposed to obtain the ND details of synchronous vibration. Experimental results validated the efficiency and accuracy of the proposed methods and sensors. Comparison results of BTT measurements with SG measurements showed that the relative errors of normalized frequency and strain were small and acceptable.

Closed-form solutions to optimal parameters of dynamic vibration absorbers with negative stiffness under harmonic and transient excitation

In this present paper, two configurations of dynamic vibration absorber in conjunction with negative stiffness (NSDVA) are investigated and their parameter optimization is conducted according to two tuning methodologies: the fixed points theory and the stability maximization criterion. Closed-form solutions to the optimal parameters of NSDVAs are analytically derived and are expressed in terms of ratio between the negative stiffness and mechanical stiffness of primary system. Allowable bounds on negative stiffness are specified with the consideration of stability requirement, based on which the ultimate control performance of NSDVAs could be imagined. Furthermore, an optimal negative stiffness ratio is defined within the stable region when the NSDVAs are tuned by the fixed points theory. Finally, numerical simulations are carried out in both harmonic and free vibration scenarios. Simulation results suggest that the inclusion of negative stiffness in the coupled system can significantly improve the vibration control performance in terms of broadening the frequency bandwidth of vibration suppression, decreasing the peak vibration amplitude of primary system and confining the stroke length of NSDVAs. Meanwhile, the negative stiffness can enhance the damping capability of coupled system, engendering an accelerated convergence of transient disturbances.

Monitoring the Dynamic Response of a Buried Polyethylene Pipe to a Blast Wave: An Experimental Study

Although the use of polyethylene (PE) pipelines has become increasingly widespread in recent years, few studies have addressed their seismic design and ability to withstand blast waves. In order to establish their seismic capacity, the dynamic response of buried pipelines subjected to blast waves must be explored in depth. Here, we studied the dynamic response of PE pipes situated near an explosive source. Time histories of dynamic strains were measured by conventional strain gauges after simple waterproof treatment, and pipe and ground vibration velocity curves were obtained. Based on the experimental data, the attenuation law of the peak strains under the conditions of different charge masses and blast center distances was analyzed, and the spectrum characteristics of strain, velocity of the pipe, and ground velocity were studied. The results revealed that a large hoop strain on the PE pipes was produced due to the local impact near the explosive source. We found that peak hoop strain (PHS) or peak axial strain (PAS) had a power attenuation relationship with the scaled distance, and this relationship could also be derived by dimensional analysis. The average frequency of strains had the same attenuation form as the charge mass, which was between 10 Hz and 50 Hz. Additionally, the vibration of the pipe showed a low frequency. We also determined that the attenuation of the average frequency of pipe and ground vibration velocity was closely related to the charge mass and the scaled distance. Pipe peak vibration velocity (PPVV), ground peak particle velocity (GPPV), and the peak dynamic strain of pipe were highly positively correlated, which verifies the feasibility of using GPPV to characterize pipeline vibration and strain level. Thus, a blasting criterion of 10% minimum request strength (MRS) for PE pipe was proposed, which means that the additional PHS or PAS of the dangerous point must be less than 10% MRS, and we also propose limiting the safety distance–charge mass for blasts near buried PE pipelines by the criterion. Some results in this paper can serve as the basis for future in-depth theoretical research.

Experimental study of IERSFDs for vibration reduction of gear transmissions

Integral elastic ring squeeze film damper (IERSFD) is proposed to reduce and isolate the vibration of the gear transmissions. IERSFD offers the performance of a low radial stiffness and high squeeze film damping. This paper presents a mechanical model of an IERSFD elastic damping support and a single-degree-of-freedom vibration isolation system for the gear system. An open single-stage spur gear system was built to experimentally study the vibration characteristics of gear transmissions with rigid supports and with IERSFD elastic damping supports filled with damping fluids of different viscosities. The experimental results show that the IERSFD can effectively reduce the peak vibration acceleration of the gear shafts and can guarantee the smooth operation of the gear assembly over a range of speeds. This work shows that an IERSFD can reduce the shock and vibration of the gears’ meshing. It effectively attenuates vibration for most of the gears’ frequency components. Within a limited viscosity range, the vibration reduction is more effective with the higher-viscosity IERSFD damping fluids tested.

Interaction between body composition and impact-related parameters in male and female heel-toe runners

BackgroundBone fatigue resistance and more generally the ability to dissipate the stress sustained in dynamic tasks are partly affected by tissue properties. Men and women demonstrate substantial differences in body composition. Research questionTo assess whether gender, as a function of body composition, affects impact-related parameters in running. MethodsA qualitative study has been conducted. Twelve females and eighteen males performed four 2-min running trials at 2.8 m∙s−1, 3.3 m∙s−1, 3.9 m∙s−1, and 4.4 m∙s−1 while recording axial and transverse tibial acceleration. Peak acceleration and power spectral density within the impact-related frequency range (vibration content) were measured. Bone mineral content, fat mass, lean mass, and muscle mass were assessed using an impedance meter. Two-way (gender × speed) ANOVAs were computed. Multiple linear regressions were then used to assess the magnitude of the effect of body composition indicators on impact-related parameters. ResultsSignificant gender and speed effects were observed. Females and high running speeds were associated with greater peak acceleration and vibration content at the tibia. Small interactions were observed between muscle mass and axial peak acceleration and vibration content, and between bone mineral content and transverse peak acceleration and vibration content, and axial vibration content. SignificanceWomen demonstrated greater mechanical stress than men during running. High mechanical stress was associated with low bone mineral content and muscle mass. These findings may have implications in the prevention and management of bone overuse injuries in runners.

Analysis of general and local vibration at the workplace: the operator of a specialist road machine

The article discusses an attempt to evaluate the ergonomic vibration environment of selected technical sources used in various technological processes. The scope of the tests included measurement of general vibrations in the plane of the seat carrier and local vibrations occurring on the steering wheel of selected technical sources. The tests were carried out in two trucks and in a vibratory road roller. The measurements were carried out in 10 repetitions for each technical measure. On the basis of the obtained measurements, the mean value of vibration acceleration, effective vibration acceleration and peak vibration acceleration as well as the weighted vibration acceleration value were determined. The obtained results were confronted with the applicable standards. It was noted that the daily vibration exposure of general action in the case of road roll works in the horizontal direction was 1,11 m∙s-2 and exceeded the limit values for men and women in the working age. In the case of other vehicles tested, there was no exceedance of the permissible mechanical vibration value in any of the analyzed directions and do not pose a threat to the employee.

Experimental and Numerical Analysis and Prediction of Ground Vibrations Due to Heavy Haul Railway Viaduct

The ground vibration wave induced by the viaduct section of the heavy freight wagons is transformed into the ground vibration problem under the condition of point source excitation after it is transmitted to soil through pier. When the speed and axle load of wagon become larger and larger, the impact on the surrounding buildings will also increase. In this paper, the ground vibration around Shenshan Village in section of Shuo-Huang railway line is monitored and numerical analyzed; the 3D numerical model of the Bridge-Pier-Field-House system is established. The relationship between peak vibration velocity (PPV) and the distance to the pier caused by heavy freight wagons at different speeds and different type of wagons is analyzed. The power function relationship between the two when measuring line perpendicular to the centerline of railway is verified. Based on the modified Sodev’s equation, the relationship between PPV of ground points and wagon speed, axle load, and soil properties is proposed, and the value of every parameter in the formula is discussed in detail. The concept of energy index is put forward for the first time in the formula, and the relationship between energy index and wagon speed and wagon weight is analyzed by regression analysis. The accuracy of the calculation model and prediction formula is verified by comparing field test results; an analytical method is proposed to predict the ground vibration induced by viaduct.

Dynamic response of elliptical cylinders undergoing transverse flow-induced vibration

While the flow-induced vibration (FIV) of a circular cylinder has been characterised in considerable detail, the FIV of elliptical cylinders has not received similar attention. This study investigates the dynamic response of elastically-mounted elliptical cylinders with various cross-sectional aspect ratios (or elliptical ratios) in a free stream. The elliptical ratio is defined by ϵ=b∕a, where a and b are the streamwise and cross-flow dimensions, respectively, of the cross section of a cylinder placed at zero incidence angle. The elliptical ratios tested were in the restricted range of 0.67⩽ϵ⩽1.50, which was designed to achieve some but not too large a geometric deviation from a circular cylinder. The fluid–structure system was modelled using a low-friction air-bearing rig in conjunction with a free-surface recirculating water channel facility. This experimental set-up yielded very low mass and damping ratios. The FIV response was characterised as a function of reduced flow velocity. The results showed that the ellipses exhibited different response regimes as ϵ varied. Surprisingly, for the lowest elliptical ratio ϵ=0.67, there existed two separated lock-in regimes. However, for ϵ⩾0.80, lock-in occurred over only a single reduced velocity range that was characterised by different response regimes. As ϵ was increased above unity, lock-in tended to occur at considerably lower reduced velocities than for the circular cylinder case. Moreover, the peak vibration amplitude increased with the elliptical ratio. This means that the body vibration is enhanced, rather than attenuated, as the afterbody is reduced for an ellipse.

Sustainability of Construction Processes – Requirements, Criteria, Evaluation Concept

The application of the principles of sustainable construction in practice is covered by research and legislative works, the effect of which are standards and other documents helping designers and investors in the assessment of construction products and buildings in their life cycle. The research, presented in the literature, focus primarily on the study of environmental impacts, particularly in the phase of manufacturing building products. However, there are no in-depth studies on the assessment of construction processes. This paper focuses on the analysis and evaluation of construction processes, from the perspective of the sustainable development requirements. The proposed methodology allows a systematic analysis of the three pillars of sustainable construction, i.e. the environmental, economic and social aspects, based on quantitative assessment indicators. Due to a limited scientific recognition in the area of social aspect assessment, it was subjected to a particularly thorough analysis and a procedure allowing the evaluation of the impact of construction works on the neighbourhood (surroundings) was developed. Noise, emissions of substances as well as vibrations and shocks were considered as the representative indicators characterizing the social aspect of the effects of construction on the environment. This approach is justified by the high harmfulness of these factors to health in the work environment. Depending on the nature of the impacts, their values were determined based on the noise level (noise), the concentration of respirable dusts (emissions of substances) as well as peak particle velocity and vibration levels (vibrations and shocks). It is recommended to represent them in the assessment by multiplicity of standards or reference levels. The proposed method of analysis of building processes may be applied to the planning of construction works with the least adverse impact on the environment.

Sintesis Nanoserat Selulosa dari Tandan Kosong Sawit (Tks) dengan Menggunakan Metode Tetramethyl Piperidine 1 Oxyl (TEMPO)

The isolation of nanofiber from empty fruit bunches using a TEMPO has been carried out. The research was done in two stages i.e. the synthesis process of α-cellulose from empty bunches and nanofiber process of using a oxidant TEMPO. Isolation α-cellulose from empty bunches delignified by using 3,5% of HNO3 and NaNO2 , the next cellulose delignified with 17,5% of NaOH and whitening by 10% H2O2 until the α-cellulose were produced. Nanocellulose fiber were shyntesis by adding NaBr, NaOCl, TEMPO, a buffer solution 10 and in the stirrer for 2,5 hours. FTIR spectrum from nanofiber shows the peak vibration of the carbonyl group C=O at 1743 cm -1 . Morphological analysis using SEM showed that the surface of the nanocelullose fibers appears homogeneous, more organized and have pores larger compare to α- cellulose with the diameter average by using TEM shows of 31,4 nm.

Cushioning perception is associated with both tibia acceleration peak and vibration magnitude in heel-toe running

Objective: To investigate the relationship between the perception of cushioning and variable measured using tibia acceleration in heel–toe running. Method: Ten rearfoot strikers’ runners ran at 3.9 m.s−1 on a stiff treadmill in seven footwear conditions presenting different mechanical properties through midsole geometries and/or materials. The perceived cushioning was quantified through a 100-mm visual analogic scale. Tibia accelerations were measured using a triaxial accelerometer from which six variables of interest were extracted based on time and frequency analyses. After pooling data of each subject in each condition (n = 70), Pearson correlation coefficients were calculated to test the correlation between the perceived cushioning and each biomechanical variables. The Cohen’s d effect size was calculated for significant correlation. Results: Significant correlations were found between the perceived cushioning and three axial acceleration-related variables which are the axial acceleration peak (r = −0.246, p = .04, small correlation), the kurtosis coefficient of the axial acceleration peak (r = −0.281, p = .056, small correlation), and the power spectral density of the axial acceleration within the 10–20 Hz bandwidth (r = −0.300, p = .018, small correlation). Conclusion: The present study highlights that the perception of running footwear cushioning was correlated to tibia impact peak and tibia vibration magnitude. Besides, no variable extracted from the transverse component of tibia acceleration was correlated to cushioning perception. These findings could have practical implications in running footwear design.