Outer Spring Research Articles

Tunable topological interface states in one-dimensional inerter-based locally resonant lattices with damping

Wave dispersion and topology of phononic crystals in classical mechanical systems are well understood and extensively studied subjects. However, the topological properties of acoustic metamaterials with more complex unit cells having several masses, internal resonators, and inerter elements is an insufficiently investigated topic. In this work, we study a class of locally resonant acoustic systems having diatomic- and triatomic-like mass-in-mass unit cells with inerter elements and different springs connecting outer masses. Winding numbers and signs of band gaps are investigated to assess the topological characteristics of a lattice band structure that support edge/interface modes and whether that property is affected when inerter elements are embedded into the system. The dynamics of finite undamped and damped chains constituted of two connected sub-lattices are investigated to demonstrate the existence of interface modes and their localization in space. We reveal that the presented diatomic-like and triatomic-like mass-in-mass chains can generate several interface modes that reside within both lower and higher frequency band gaps. The concept is illustrated through the investigation of the eigenvalue spectrum for varying and fixed stiffness of outer springs and frequency response function. The effect of arbitrary viscous damping is explored based on steady-state responses of the lattice interface mass points. Numerical analysis reveals that the introduction of inerters in combination with local resonators can significantly shift the band gaps and corresponding interface modes to lower frequency values while keeping the main topological properties of the initial configuration without inerters. The effect of damping is shown to be significant and capable to attenuate both lower and higher frequency interface mode amplitudes. We anticipate that this study will pave the wave for future works on the topic that include more reliable models of inerters in the topological mechanical metamaterial design.

Seismic response of monopile supported offshore wind turbine in liquefiable soil

Offshore wind turbines (OWT) are now constructed in the seismically active regions due to rising energy demand. This study investigates the seismic response of the monopile supported OWT in liquefiable sand deposits under combined operational and seismic loads. A coupled soil-monopile-tower interaction model is developed in OpenSees. Monopile and tower are modelled as linear Euler – Bernoulli beam. Monopile-soil interaction is modelled using nonlinear p-y spring. Free-field motion at the outer spring nodes due to seismic motion is simulated by modelling a soil domain using a two-dimensional plane strain quadrilateral element considering a with a solid–fluid fully coupled model. Various historical strong motion records and spectrum consistent artificial strong motion data are scaled and applied on OWT structure and various operational loads on the structure. The effect of intensity, sustained maximum acceleration of earthquake, and depth of liquefaction on the dynamic response of the OWT structure is studied. A design implication is also suggested for the OWT structure in liquefiable soil.

Active Stiffness Tuning of a Spring-Based Continuum Robot for MRI-Guided Neurosurgery

Deep intracranial tumor removal can be achieved if the neurosurgical robot has sufficient flexibility and stability. Towards achieving this goal, we have developed a spring-based continuum robot, namely a Minimally Invasive Neurosurgical Intracranial Robot (MINIR-II) with novel tendon routing and tunable stiffness for use in a magnetic resonance imaging (MRI) environment. The robot consists of a pair of springs in parallel, i.e., an inner inter-connected spring that promotes flexibility with decoupled segment motion and an outer spring that maintains its smooth curved shape during its interaction with the tissue. We propose a shape memory alloy (SMA) spring backbone that provides local stiffness control and a tendon routing configuration that enables independent segment locking. In this work, we also present a detailed local stiffness analysis of the SMA backbone and model the relationship between the resistive force at the robot tip and the tension in the tendon. We also demonstrate through experiments, the validity of our local stiffness model of the SMA backbone and the correlation between the tendon tension and the resistive force. We also performed MRI compatibility studies of the 3-segment MINIR-II robot by attaching it to a robotic platform that consists of SMA spring actuators with integrated water cooling modules.

Toward the Development of a Flexible Mesoscale MRI-compatible Neurosurgical Continuum Robot.

Brain tumor, be it primary or metastatic, is usually life threatening for a person of any age. Primary surgical resection which is one of the most effective ways of treating brain tumors can have tremendously increased success rate if the appropriate imaging modality is used for complete tumor resection. Magnetic resonance imaging (MRI) is the imaging modality of choice for brain tumor imaging because of its excellent soft-tissue contrast. MRI combined with continuum soft robotics has immense potential to be the next major technological breakthrough in the field of brain cancer diagnosis and therapy. In this work, we present the design, kinematic, and force analysis of a flexible spring-based minimally invasive neurosurgical intracranial robot (MINIR-II). It is comprised of an inter-connected inner spring and an outer spring and is connected to actively cooled shape memory alloy spring actuators via tendon driven mechanism. Our robot has three serially connected 2-DoF segments which can be independently controlled due to the central tendon routing configuration. The kinematic and force analysis of the robot and the independent segment control were verified by experiments. Robot motion under forced cooling of SMA springs was evaluated as well as the MRI compatibility of the robot and its motion capability in brainlike gelatin environment.

Research on Coating Techniques of Locomotive Spring

This article is based on the analysis of locomotive springs packaging existing situation, combining with spring packaging requirements, giving a spring packaging technology program. The program is by using 0.6mm PE shrink film on the new U type coating machine to achieve reel wrapping package for locomotives inner and outer springs respectively, and then passing the BM-500 thermostatic shrink packaging machine to complete coating process technical solutions .In addition this paper gives a detailed description for the new U type coating machine structure design and working principle to make early program planning for the locomotive springs packaging production line.

Reducing Rifle Bolt Carrier Bounce

This work presents a recently-patented mechanical buffer design to reduce bolt carrier bounce in the M4 and M16 rifles. The buffer includes a main outer spring to store the energy in a rearward-traveling bolt carrier and a nested spring coupled to a mass to counter the rebound or “bounce” resulting in the impact of a forward-traveling bolt carrier. A dynamic model of the mechanical buffer is included to demonstrate bolt bounce and the mechanical buffer concept.

Angular velocity detector, method of detection of angular velocities using angular velocity detector, and method of fabricating angular velocity detector

An angular velocity detector using a vibrator made of an annular thin film. The detector also has electrodes arranged ingeniously to have high detection sensitivity for angular velocities. The detector can detect angular velocities in two axial directions simultaneously. The detector has support portions ( 1105 ), ( 1106 ) which are formed over a first substrate ( 1123 ) and poised above the surface of the first substrate ( 1100 ) at a certain spacing therefrom. Resilient support bodies are supported to the support portions and include outer springs ( 1102 ) and inner springs ( 1103 ). A vibrator ( 1101 ) is mounted via the resilient support. An exciting means consisting of a magnet ( 1124 ) and an exciting electrode ( 1108 ) excites the vibrator to vibrate in a certain direction of vibrations. When the vibrator ( 1101 ) is excited to vibrate in the direction of vibrations by the exciting means and an angular velocity acts from the outside, a displacement detection means consisting of a detection electrode ( 1109 ) and electrodes ( 1120 ) detects the displacement of the vibrator ( 1101 ) in a direction perpendicular to the direction of vibrations in response to the angular velocity. The vibrator ( 1101 ) or an angular velocity detection portion including the vibrator ( 1101 ) is electromagnetically driven to vibrate.