scholarly journals Impact Dynamics of a Percussive System Based on Rotary-Percussive Ultrasonic Drill

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Yinchao Wang ◽  
Qiquan Quan ◽  
Hongying Yu ◽  
He Li ◽  
Deen Bai ◽  
...  
Keyword(s):  
High Speed ◽  
Longitudinal Vibration ◽  
Low Frequency ◽  
Load Condition ◽  
Camera System ◽  
Collision Model ◽  
Amplitude Vibration ◽  
Conservation Of Momentum ◽  
Mass Transfers ◽  
Drill Tool

This paper presents an impact dynamic analysis of a percussive system based on rotary-percussive ultrasonic drill (RPUD). The RPUD employs vibrations on two sides of one single piezoelectric stack to achieve rotary-percussive motion, which improves drilling efficiency. The RPUD’s percussive system is composed of a percussive horn, a free mass, and a drill tool. The percussive horn enlarges longitudinal vibration from piezoelectric stack and delivers the vibration to the drill tool through the free mass, which forms the percussive motion. Based on the theory of conservation of momentum and Newton’s impact law, collision process of the percussive system under no-load condition is analyzed to establish the collision model between the percussive horn, the free mass, and the drill tool. The collision model shows that free mass transfers high-frequency small-amplitude vibration of percussive horn into low-frequency large-amplitude vibration of drill tool through impact. As an important parameter of free mass, the greater the weight of the free mass, the higher the kinetic energy obtained by drill tool after collision. High-speed camera system and drilling experiments are employed to validate the inference results of collision model by using a prototype of the RPUD.

scholarly journals Research and Fabrication of Broadband Ring Flextensional Underwater Transducer

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1548
Author(s):  
Jiuling Hu ◽  
Lianjin Hong ◽  
Lili Yin ◽  
Yu Lan ◽  
Hao Sun ◽  
...  
Keyword(s):  
High Speed ◽  
Structural Parameters ◽  
Low Frequency ◽  
Flexural Vibration ◽  
Underwater Acoustic Communication ◽  
Voltage Response ◽  
Water Tank ◽  
Spherical Cap ◽  
Finite Element Software ◽  
Underwater Transducer

At present, high-speed underwater acoustic communication requires underwater transducers with the characteristics of low frequency and broadband. The low-frequency transducers also are expected to be low-frequency directional for realization of point-to-point communication. In order to achieve the above targets, this paper proposes a new type of flextensional transducer which is constructed of double mosaic piezoelectric ceramic rings and spherical cap metal shells. The transducer realizes broadband transmission by means of the coupling between radial vibration of the piezoelectric rings and high-order flexural vibration of the spherical cap metal shells. The low-frequency directional transmission of the transducer is realized by using excitation signals with different amplitude and phase on two mosaic piezoelectric rings. The relationship between transmitting voltage response (TVR), resonance frequency and structural parameters of the transducer is analyzed by finite element software COMSOL. The broadband performance of the transducer is also optimized. On this basis, the low-frequency directivity of the transducer is further analyzed and the ratio of the excitation signals of the two piezoelectric rings is obtained. Finally, a prototype of the broadband ring flextensional underwater transducer is fabricated according to the results of simulation. The electroacoustic performance of the transducer is tested in an anechoic water tank. Experimental results show that the maximum TVR of the transducer is 147.2 dB and the operation bandwidth is 1.5–4 kHz, which means that the transducer has good low-frequency, broadband transmission capability. Meanwhile, cardioid directivity is obtained at 1.4 kHz and low-frequency directivity is realized.

scholarly journals The Optimization of Alternating Current Electrospun PA 6 Solutions Using a Visual Analysis System

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2098
Author(s):  
Tomas Kalous ◽  
Pavel Holec ◽  
Jakub Erben ◽  
Martin Bilek ◽  
Ondrej Batka ◽  
...  
Keyword(s):  
High Voltage ◽  
High Speed ◽  
Visual Analysis ◽  
Polyamide 6 ◽  
Alternating Current ◽  
Sine Wave ◽  
Electrospinning Process ◽  
Camera System ◽  
Polymeric Solutions ◽  
Analysis System

The electrospinning process that produces fine nanofibrous materials have a major disadvantage in the area of productivity. However, alternating current (AC) electrospinning might help to solve the problem via the modification of high voltage signal. The aforementioned productivity aspect can be observed via a camera system that focuses on the jet creation area and that measures the average lifespan. The paper describes the optimization of polyamide 6 (PA 6) solutions and demonstrates the change in the behavior of the process following the addition of a minor dose of oxoacid. This addition served to convert the previously unspinnable (using AC) solution to a high-quality electrospinning solution. The visual analysis of the AC electrospinning of polymeric solutions using a high-speed camera and a programmable power source was chosen as the method for the evaluation of the quality of the process. The solutions were exposed to high voltage applying two types of AC signal, i.e., the sine wave and the step change. All the recordings presented in the paper contained two sets of data: firstly, camera recordings that showed the visual expression of electrospinning and, secondly, signal recordings that provided information on the data position in the signal function.

Measurement of Dynamic Strain

1943 ◽  
Vol 10 (2) ◽  
pp. A85-A92
Author(s):  
C. O. Dohrenwend ◽  
W. R. Mehaffey
Keyword(s):  
High Speed ◽  
Shock Loading ◽  
Low Frequency ◽  
Dynamic Strain ◽  
Time Axis ◽  
Low Frequencies ◽  
Strain Measurements ◽  
Moving Vehicles ◽  
Machine Parts ◽  
Dynamic Strains

Abstract The measurement of dynamic strains of both high and low frequency give rise to a variety of problems in instrumentation. Two types of equipment and circuits designed and used by the authors are discussed in detail. The first type based on the amplitude-modulated method is for low frequencies from zero to about 15 per cent of the carrier frequency of 1025 cycles per sec. The equipment has application to strain measurements varying from static values to those produced in moving vehicles, various machine parts, structures such as crane bridges, in fact all strain measurements where the frequency is 150 cycles per sec or less. The second type of equipment discussed is a potentiometer type and is for high-frequency strain measurements from 100 cycles per sec to 8000 cycles per sec. This high-speed equipment is conveniently used for impact strain, such as produced in hammer blows, shock loading, forging equipment, and impact-factor determination. Both units are designed to be used with a cathode-ray oscillograph which lends itself to a variety of recording methods. The methods discussed include both the type where the time axis is obtained by sweeping the oscilloscope beam on a stationary film and where the time axis is obtained mechanically.

Study on bearing structure and joint seismic resistance of large span non-landing arch on high-speed railway station

2019 ◽  
Author(s):  
Liu Chuanping ◽  
Tianluan Liu ◽  
Jian Jia
Keyword(s):  
High Speed ◽  
Low Frequency ◽  
Large Earthquake ◽  
Scale Model ◽  
Railway Station ◽  
High Speed Railway ◽  
Long Span ◽  
Weak Component ◽  
Double Beam ◽  
Cyclic Loading Tests

<p>The main entrance of Chongqing West Railway Station adopts the non-landing compound arch with a span of 108m. In this paper, the nonlinear finite element theory is applied to analyze the bearing capacity and seismic ductility of the compound arch joints. Low frequency cyclic loading tests are performed on the 1/5 scale model. Based on the calculation and test results, a double beam structure and a section of steel truss are placed in the arch joints to bear the force of the arch. Moreover, the buckling-restrained brace (BRB) is placed in the lower part of the arch that enables most force directly transmit to the foundation of the arch. Unlike BRB’s common use as an inter-column support, it now acts as a buckling constraint support in the large earthquake. For instance, it can be yielded before the frame column to improve earthquake resistance. The research results indicate that the compound arch joint structure successfully accomplishes the seismic design goals of strong joints with weak component. Moreover, the study provides the theoretical basis and design reference for the application of BRB and long-span arch structures in high-speed railway station.</p>

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