Flexible Mounting Research Articles

A model for computing vibration induced stresses of electronic components in a general flexible mounting

This paper develops a novel full analytic model for vibration analysis of solid-state electronic components. The model is just as accurate as finite element models and numerically light enough to permit for quick design trade-offs and statistical analysis. The paper shows the development of the model, comparison to finite elements and an application to a common engineering problem. A gull-wing flat pack component was selected as the benchmark test case, although the presented methodology is applicable to a wide range of component packages. Results showed very good agreement between the presented method and finite elements and demonstrated the usefulness of the method in how to use standard test data for a general application.

Pilot testing of fire sprinkler system in extremely corrosive industrial duct environments

Due to the extremely corrosive environments inside many exhaust ducts fabricated from combustible materials, the mechanical integrity of fire sprinkler system components is often prematurely compromised, leaving the system unable to protect against fires originating within these ducts [FM Global Loss Prevention Data Sheet, 7–78, Industrial Exhaust System, 2011; Understanding the Hazard, Fire in Industrial Exhaust Systems, FM Global, Johnston, RI, 2006]. Pilot testing of a new fire sprinkler system was conducted to protect the fiber‐reinforced plastic duct at a nitric/hydrofluoric (HF/HNO3) mixed acid pickling operation. Based on previous laboratory and field tests [Su and Doerr, Process Saf Prog 29 (2010) 70–78], this fire sprinkler system was composed of corrosion resistant sprinkler nozzles, a linear heat detector, flexible mounting connections, sprinkler piping, and controls. Pilot testing results have led to development and recommendation of a new fire protection system capable of protecting combustible exhaust ducts from fire in extremely corrosive environments. © 2013 American Institute of Chemical Engineers Process Saf Prog 32: 277–282, 2013

How to Meet the Challenge of Flexible Exposure of the Calot Triangle in SILS Cholecystectomy

Single-incision laparoscopy was developed to further reduce the operative trauma in routine laparoscopic procedures. However, the method remains challenging because the exposure of the Calot triangle is more difficult as the use of a singular traction device does not allow the flexible 3-dimensional mounting of the structures. We introduce a technical improvement involving both exposure and traction. After installation of the technical devices for single-incision laparoscopy cholecystectomy, as usual, a suture on a Keith needle is inserted subcostally from the right side of the patient, passed midway through the infundibulum, and extracted subcostally on the left side of the patient. The suture is fixed with 2 metal clips on each side of the gallbladder. The gallbladder can be tilted both medially and laterally on a horizontal line and the Calot triangle can be dissected from medial and lateral aspects following the "critical view of safety" criteria used in conventional laparoscopy.

Buffet suppression in long-span suspension bridges

We study the aerodynamic control of long-span suspension bridges and seek to raise the critical flutter wind speeds, while simultaneously suppressing buffeting. The control system design study is based on a simple flexible bridge section model that interacts with a constant-velocity air stream. A streamlined bridge deck is assumed and non-steady thin aerofoil theory is used to describe the interactions between the bridge deck and the air stream. Classical turbulence models, first developed in the aircraft industry, are used to model the buffet forces acting on the deck. While a wide variety of control systems is possible, we focus on a compensation scheme that can be implemented using passive mechanical components such as springs, dampers and a rack and pinion mechanism. A single-loop control system is investigated that controls a trailing-edge flap by sensing movements of the bridge deck; several such mechanisms are contemplated. The first finding is that the critical wind speed for flutter can be greatly increased, with good robustness characteristics, through passive feedback control. It is also possible simultaneously to suppress flutter using the same passive mechanical controller by solving a passive mixed H 2 / H ∞ control problem. The effect of flexible controller mounting arrangements are considered briefly.

Dynamical Analysis on a Mass at the Tip of a Flexible Rod on a Rotating Base

Abstract: A dynamical analysis on a mass fixed at the tip of a massless flexible rod mounting on a rotating rigid body is presented in which the motion of the mass is kept in the plane of rotation as small deformation of the rod is assumed. For the rigid body undergoing a constant angular velocity the centrifugal forces and Coriolis force on the mass are considered. There exist two dynamic frequencies in which the first order dynamic frequency decreases with rotational velocity up to zero that is associated with a limit rotational velocity of the system. The motion trajectories of the mass in the rotational plane at different rotational velocities exhibit multiple traces with respect to the conventional line trace and may be split into the non-eccentric and eccentric portions. With a view on the change of amplitudes a critical rotational velocity is discussed.

Beam steering for a long range Acoustic Hail and Warning Device for maritime applications

A new means for steering the beam of a phased line array, electromechanical steering, is described and applied to a long range Acoustic Hail and Warning Device (AHWD) developed for maritime applications. In electromechanical steering, the array elements pivot individually resulting in elements being off-set and rotated in the desired steered beam/sound projection direction. A digital signal processor is used to align the phase fronts of the elements due to the mechanical offsets. Electromechanical steering has several advantages over the purely electronic steering of the array. The electromechanically steered beams are not subject to the individual element aperture function attenuation that reduces the sound pressure level (SPL) that commonly occurs for electronically only steered beams at large steering angles. Also, the primary lobe distortion and (lower frequency) onset of grating lobes that occur when a beam is steered electronically is absent with electromechanical steering. In short, with electromechanical steering, the SPL and directivity from the AHWD is entirely equivalent to that obtained by rotating the AHWD to the desired angle with a conventional pan and tilt mount but requires much less space and provides for more flexible mounting options including improved system stealth. In addition, a novel type of line array phase shading is presented which allows the AHWD to be electronically switched from directional mode (typical beam steering highly focused mode) to non-directional wide field of regard for applications that require simultaneous ensonification of targets over large lateral angles. ©2011 Institute of Noise Control Engineering

Analysis of connection element classes and locations and of some structural requirements for the mounting of different superstructure types on transport vehicles

Analysis of connection element classes and locations and of some structural requirements for the mounting of different superstructure types on transport vehicles

Evaluation of a New Flexible Mounting Dispenser to Improve Point of Care Product Access in an Acute Care Hospital and the Resulting Effect on Hand Hygiene Compliance Rates

Evaluation of a New Flexible Mounting Dispenser to Improve Point of Care Product Access in an Acute Care Hospital and the Resulting Effect on Hand Hygiene Compliance Rates

Focus on nanoscience and nanotechnology

Focus on nanoscience and nanotechnology

Is your cold-stream working for you or against you? An in-depth look at temperature and sample motion

It is normally assumed that a commercial gaseous nitrogen cold-stream provides a sample environment near 100 K and that the force of the cold-stream does not induce movement in the sample. As might be expected, the reality is much more complex. Here, an investigation of one cold-stream, starting with the temperature profile, is presented. Using silicon single crystals and flexible mounting loops, an approximate force/vibration profile of the cold-stream is obtained. Results indicate that the center of the temperature profile is offset from the position suggested by the manufacturer-supplied alignment tool and coincides with the area within the cold-stream that has the most consistent force profile. Tests indicate that this region is only about one-third of the width of the cold-stream nozzle opening. To verify that the results were relevant to protein crystallographic data collection, the impact of cold-stream position on the final data quality for lysozyme crystals was analyzed. On the basis of the observations it is recommended that users perform a temperature profile of their cold-streams to ensure proper alignment instead of relying only on the alignment tool for setup. In addition, suggestions are made on what users can look for in data processing to identify problems with loop movement and what users can do to minimize the impact of these problems on their experiments.

Identification of flutter parameters for a wing model

A flexible mounting system has been developed for flutter tests with rigid wings in wind tunnel. The two-degree-of-freedom flutter obtained with this experimental system can be described as the combination of structural bending and torsion vibration modes. Active control schemes for flutter suppression, using a trailing edge flap as actuator, can be tested using this experimental setup. Previously to the development of the control scheme, dynamic and aeroelastic characteristics of the system must be investigated. Experimental modal analysis is performed and modes shape and frequencies are determined. Then, wind tunnel tests are performed to characterize the flutter phenomenon, determining critical flutter speed and frequency. Frequency response functions are also obtained for the range of velocities below the critical one showing the evolution of pitch and plunge modes and the coupling tendency with increasing velocity. Pitch and plunge data obtained in the time domain during these tests are used to evaluate the ability of the Extended Eigensystem Realization Algorithm to identify flutter parameter with increasing velocity. The results of the identification process are demonstrated in terms of the evolution of frequency and damping of the modes involved in flutter. Keywords : Identification, flutter, EERA, aeroelasticity

Production cell for laser joining of microsystems with modular “Pick and Join” tools

The ongoing trend in the Microtechnology field reflects a further increase of the product miniaturization and in the same time shortened lifetime cycles. These aspects are the basis for the development of new packaging and interconnection concepts with increased efficiency and reliability. The state-of-the-art to control and monitor crucial process steps includes the use of human operators generating this way high personnel costs. Combining flexible mounting and joining tools with progressive process monitoring strategies new production facilities can be established. Following this concept a semi-automatic prototype production cell for packaging and interconnection of optical and electro-optical microsystems has been developed. In order to prove the performances of the prototype production cell the mounting and assembly of cuboid shape components, consisting of optical transparent or semi-conducting materials, has been defined as demonstrative application. The joined cuboids have the contact surface precisely delimited in functional and joining area. The particularities of the joining area (small dimensions and limited access) and the well-known advantages of the laser material processing make the laser beam soldering the most suitable joining process for this application.

Apparatus having flexible mounting mechanism

An apparatus having a flexible mounting mechanism according to the present invention includes a storage section, a casing accommodating and holding the storage section, a protective housing accommodating and protecting the casing, a supporting member provided between the casing and the protective housing for supporting the casing, and a maintaining member supporting the protective housing. The supporting member and the maintaining member have different vibration damping characteristics.

Control of Low Frequency Structurally Radiated Noise with an Array of Weak Radiating Cells: An Experimental Study

The concept of a weak sound radiating cell to reduce low frequency radiated noise from structures is proposed. The cell consists of two mechanically coupled surfaces such that, when placed on a vibrating structure, the responses of the two surfaces are nearly out-of-phase and of equal strength over a wide frequency range. The cell thus behaves as an acoustic dipole and thus a therefore poor sound radiating source. The control of low frequency structurally radiated noise is achieved by covering the structure with an array of these weak radiating cells, i.e., surface treatment. Thus, the surface treatment essentially transforms the response of the structure to that of a distributed array of dipoles yielding a low sound radiating structure. For the implementation of the concept one surface of the cell is rigidly linked to the vibrating structure while the second surface is obtained by attaching a plate to the structure through a flexible mounting system. A dipole acoustic source is formed by designing the system so that the radiated sound from the plate is out-of-phase with the radiated sound from the rigidly linked surface. Experimental verification was performed by applying an array of weak radiating cells to a vibrating rectangular plate excited with white noise from 0-1600 Hz. An overall sound power level reduction of 10.2 dB was achieved between 100-1600 Hz with maximum reductions of 25 dB at discrete frequencies. These results demonstrate the potential of the weak radiating cell concept to reduce low frequency structurally radiated noise.

The closing behavior of Medtronic Hall mechanical heart valves.

The rapid deceleration of mechanical heart valve leaflets or discs at closure, and their rebound after impact between the leaflets or discs and housing may produce conditions that favor cavitation inception. Precision measurements of the disc closing velocity using a laser sweeping technique (LST) were made on two Medtronic Hall (Med Hall) mitral valve models, the 29 mm Standard and D-16 Med Hall valves. The experiment was carried out in a pulsatile mock flow loop (PFL) by installing the tested valve in the mitral position of the PFL. Tests were conducted under physiologic pressures at heart rates of 70, 90, and 120 beats/min with flow rates of 5, 6, and 7.5 l/min, respectively. For each valve tested, the experimental series was carried out to include both a flexible mounting and a rigid mounting mechanism. The time history of the disc closing velocity during the last 3 degrees before final closure was measured. Results show that the disc approached the valve housing at a near constant velocity of approximately 1.3, 1.5, and 2.0 m/sec for the Med Hall Standard valve, and 1.9, 2.5, and 2.6 m/sec for the Med Hall D-16 valve at 70, 90, and 120 beats/min, respectively. After impact, the valve of disc rebounded with velocities that depended on the mounting modalities and heart rates. In the rigid mounting, the disc rebound velocities of the Med Hall Standard and D-16 valves were about 60%-70% and 70%-80% of their respective approaching velocities. For the flexible mounting, the rebound velocities were 15%-25% and 20%-30% of their respective approaching velocities. The results demonstrate that a slight modification in the seat stop geometry of Med Hall valves can significantly affect disc closure behavior.

Low-temperature intracavity photoacoustic spectrometer

A cryogenic photoacoustic cell has been developed for intracavity use in a tunable ring laser. Its design ensures uniform cooling of the gas sample and minimum loss to the laser cavity. Also implemented is a flexible microphone mounting system that reduces thermal stress during temperature changes.

Dynamic Analysis of Noncontacting Face Seals

The dynamic behavior of a noncontacting coned face seal is analyzed for the case of a rigidly mounted rotating seat and a flexibly mounted stationary ring taking into account various design parameters and operating conditions. The primary seal ring motion is expressed by a set of nonlinear equations for three degrees of freedom. These equations, which are solved numerically, allow identification of two dimensionless groups of parameters that affect the seal dynamic behavior. Stability maps for various seals are presented. These maps contain a stable-to-unstable transition region in which the ring wobbles at half the shaft frequency. The effect of various parameters on seal stability is discussed and an approximate expression for critical stability is offered. The theoretical model assumes frictionless flexible mounting of the seal ring such as in metal bellows. However, the results for critical stability can also be used as an upper limit for cases when friction in the secondary seal is present.

Motor vehicle suspension struts

MOTOR VEHICLE SUSPENSION STRUTS Abstract of the Disclosure: A suspension strut for a motor vehicle in which a steering knuckle is supported by a housing of a telescopic damper. A piston rod projecting from the damper housing has a support flange secured to its free end to form part of a flexible mounting for a body portion of the vehicle. A helical suspension spring is seated at its lower end on an annular bracket carried by the damper housing and at its upper end on a spring support plate surrounding the piston rod. A needle-roller thrust bearing is interposed between the piston rod support flange and the spring support plate to accommodate rotary movement of the spring and support plate during steering maneuvers. To provide a predetermined amount of bearing friction, a friction element in the form of a circular bead is arranged between the piston rod support flange and the spring support plate. The circular bead is formed as a part of a cage of plastic material serving to locate the individual needle rollers of the bearing.

Vibration isolation in the presence of Coulomb friction

Transmissibility curves for a Coulomb-damped flexible mounting are presented for both rigidly and elastically coupled damping. The closed solutions easily obtainable for the slipping and sticking phases of the motion are used in the method, and no conceptual approximation is involved. The transmissibility curves are compared with previously published approximations based on linearization of the damping. It is shown that the approximate method seriously underestimates the heights of significant resonant peaks and gives optimum friction values somewhat in error, but gives reasonable approximations to the transmissibilities at the high frequencies corresponding to effective isolation.

Significance of Disk Flexing in Viscous-Damped Jet Engine Dynamics

A new method of analyzing multishaft jet engine critical speeds and unbalance response is derived to account for flexible bladed disks, asymmetric mounting, and squeeze film bearing damping. The resulting elliptical shaft whirling drives traveling waves in disks at speeds equal to the sum and the difference of the rotating speed and the whirling speed. To illustrate a possible problem that cannot be predicted by current methods, a sample calculation shows a simplified model representing possible engine parameters tuned so that a critical speed associated with backward whirling is lowered into the operating range by reduction in disk stiffness. In contradiction to the current literature, the rotor is shown highly responsive to unbalance at this critical speed.