Abstract To address the limitations of traditional drilling equipment, such as large size, high power consumption, and difficulties with waterproofing, an underwater ultrasonic percussive drill (UUPD) based on piezoelectric drive is proposed. The structure size parameters actuator are designed its performance experimentally verified. maximum output amplitude 78.6 μm in air 52.3 water. Additionally, dynamic characteristics UUPD calculated theoretically analyzed by simulation, influence system...

The high-speed water-entry phenomenon of vehicles with a free and constant speed is numerically studied. different behaviors the cavities created by vertical water entry projectiles nose shapes, tail impact speeds are investigated. drag characteristics or compared. flow field compared analyzed. Unlike cavity induced free-speed entry, that constant-speed more stable maintained for longer time. expansion projectile can weaken effect re-jet flow, generated seal, on head prolong attachment time...

Compared with conventional drill, an ultrasonic drill can break into rocks under lower weight on bit and power, which is more suitable to sample in low gravity environment for deep-space exploration. However, the cannot remove rock cuttings effectively when drilling a certain depth. This paper proposed rotary-percussive (RPUD), depends single piezoelectric transducer produce moment cuttings. The RPUD consists of four parts: piezo-ceramics, percussive unit, rotary tool. Percussive unit...

A novel ultrasonic levitating bearing excited by three piezoelectric transducers is presented in this work. The are circumferentially equispaced a housing, with their center lines going through the rotation of spindle. This noncontact has ability to self-align and carry radical axial loads simultaneously. finite element model built ANSYS, modal analysis harmonious response conducted investigate its characteristics driving parameters. Based on nonlinear acoustic theory thermodynamic ideal...

The rocks on extraterrestrial objects contain plenty of original geological and biological information. Drilling sampling are an essential task in lunar exploration or future explorations other planets like mars. Due to the limitation payloads, energies, drill pressure, investigation a lightweight low‐powered rock‐drilling device is crucial for distant celestial bodies. ultrasonic driven by piezoelectric ceramics new drilling that can adapt arduous space tasks weak gravitational fields. An...

When precision materials or components are moved transported, traditional contact transport methods inevitably lead to some trouble such as wear, scarification, pollution and stress concentration. To solve these problems, a novel contact-free system based on Near-field Acoustic Levitation (NFAL) effect Negative Pressure Absorption (NPA) technology is proposed. As the core component of system, structure object stage presented fabricated. Its working principle revealed its service behavior...

As a potential alternative to conventional non-contact bearings, ultrasonic bearings are especially suitable for high-speed power machines and the torque-testing devices within small range. The friction characteristics of proposed bearing investigated. torques at low speeds high measured by pendulum balance method current feedback method, respectively. By means time-frequency spectrum analysis rotor center's orbits, running stability is studied when operates starting or stopping stage...

Abstract Recently, MOF‐derived (metal‐organic framework) 2D materials, due to the special structure of MOF inherited, have become a potential candidate for application in energy storage and conversion. In this work, new layered Co−MOF was synthesized as precursor fabricating Napoleon‐like Co 3 O 4 (NL−Co ). The monolayer thickness NL−Co is approximately 70 nm. unique porous derived from plays an important role improving electrochemical electro‐catalysis properties. As lithium ion battery...

Understanding the dynamic behavior of Lightweight Aggregate Self‐Compacting Concrete (LWASCC) is importance to safety concrete structures serving in loading conditions. In this study, fundamental properties LWASCC with three types LWA were investigated by impact resonance method. Results show that elastic and shear modulus generally decrease increase volume fraction, whereas exert limited influence on Poisson’s ratio. The good linear dependence upon compressive strength. inclusion...

The rotary-percussive ultrasonic drill (RPUD) employs vibrations on two sides of a piezoelectric stack to drive tool achieve simultaneous motion. It has the advantages being small and requiring low power, axial load, holding torque, making it suitable for extraterrestrial rock sampling, especially minor planet with weak gravitational field. This paper presents impact dynamics prediction percussive system RPUD, which is composed actuator, free mass, tool. Considering vibration RPUD weight...

High-pressure air compressor is one of the most important pieces equipment for ships, which main sources vibration on board. There are a lot welded plate structures in installation base compressor, have weak stiffness and low damping prone to radiation due excitation. In this paper, section taken as test object. Through analysis working principle, characteristics corresponding transmission path mastered. addition, it tested screened by filling different kinds materials. Finally, concluded...

In order to study the propagation law of shock wave and blast load distribution when an interior explosion occur in a box structure, numerical simulation within box-shaped structure is presented this paper using LS-DYNA. Overpressure-time history curve at measured points obtained by simulation, compared with experimental results. Numerical results are good agreement. The show that reflected superimposed many times structure. When TNT located center corner wall suffered maximum overpressure.

Different from conventional hydrostatic or hydrodynamic journal bearings, an ultrasonic bearing provides carrying force by air squeeze film generated high-frequency vibration of bush surfaces. Detailed investigation indicates that studies on levitating modeling based fluid dynamics for bearings are rarely conducted, and the existing theoretical models generally neglect some significant contributors to such as gas inertia, surface topography, rarefaction effect, boundary effect. A modified...