Mm Of Travel Research Articles

A Rapid Throughput System for Shock and Impact Characterization: Design and Examples in Compaction, Spallation, and Impact Welding

Many important physical phenomena are governed by intense mechanical shock and impulse. These can be used in material processing and manufacturing. Examples include the compaction or shearing of materials in ballistic, meteor, or other impacts, spallation in armor and impact to induce phase and residual stress changes. The traditional methods for measuring very high strain rate behavior usually include gas-guns that accelerate flyers up to km/s speeds over a distance of meters. The throughput of such experiments is usually limited to a few experiments per day and the equipment is usually large, requiring specialized laboratories. Here, a much more compact method based on the Vaporizing Foil Actuator (VFA) is used that can accelerate flyers to over 1 km/s over a few mm of travel is proposed for high throughput testing in a compact system. A system with this primary driver coupled with Photonic Doppler Velocimetry (PDV) is demonstrated to give insightful data in powder compaction allowing measurements of shock speed, spall testing giving fast and reasonable estimates of spall strength, and impact welding providing interface microstructure as a function of impact angle and speed. The essential features of the system are outlined, and it is noted that this approach can be extended to other dynamic tests as well.

Asisstance Arthroscopy in Juvenile Tillaux Fractures

Introduction:Juvenile Tillaux Fracture is an isolated fracture of the lateral portion of the distal tibial epiphysis, considered SALTER-HARRIS fracture type 3, wherein the fragment is moved by the anterolateral ligament anterior inferior tibiofibular. They occur at the beginning of the 2nd decade of life and are caused by a force external rotation. The pattern of injury is considered a result of the closing sequence of the distal tibial physis, which usually closes around 15 years of age in girls and 17 in boys, this process usually takes about 18 months, occurring first in the central area of the physis, extending medially and finally to side, being this epiphyseal portion which is open at the time of the vulnerable to fracture injury in this age group. The curriculum includes RX, and TAC, being more sensitive to detect fragments of 2 or more mm of travel, but may overestimate the true displacement. The non-displaced fracture can be treated with cast immobilization and displaced with closed reduction (plantar flexion external rotation in the pronated foot and direct pressure on the anterolateral epiphysis). An equal displacement or > 2 mm of the articular surface is indication of open reduction and percutaneous fixation, because it may increase the risk of osteoarthritis in the future.Objective:Presentation of a case Juvenile Tillaux Fractures with surgical resolution under arthroscopic assistance.Methods:Male patient 14 years old who suffered indirect trauma left ankle during practice sports (rugby) in September 2015, 48 hours of evolution. After performing X-rays and scans one left Salter Harris type III at the level of distal tibial epiphysis (Tillaux fracture) ankle fracture was diagnosed. It had a greater than 2 mm displacement. As a reduction treatment and percutaneous osteosynthesis with more osteodesis screw with arthroscopic assistance and fluoroscopy was performed. After surgery a long leg cast was placed for three weeks, continuing with three other short boot. By the third week the plug removal. After the sixth week began with partial load with Walker boot for a month and later full charge.Results:Fracture healing was evident in the eighth week. Now in his eighth postoperative month and has an excellent performance according to the AOFAS score of 96 points, with no pain, full range of motion and return to sport after 4th month.Discussion:There are reports such as A. Kaya et.al (2007) with excellent results (AOFAS 99.3) in a series of 10 patients treated by open reduction and internal fixation and in other hand A. Panagopoulus, L.van Kiekerk (2007) reports excellent results (AOFAS 100) in patients treated under arthroscopic assistance. Assistance arthroscopy in Tillaux fractures allows a reduction more accurate than that provided by percutaneous techniques fluoroscopy guided only by avoiding the problems associated with open techniques (lesion of the superficial peroneal nerve and necrosis of the fragment). It also allows patients to an early return to activities with a lower risk of stiffness and secondary osteoarthritis due to the reduction achieved under direct arthroscopic visualization.

Magnetic resonance imaging compatible remote catheter navigation system with 3 degrees of freedom.

To facilitate MRI-guided catheterization procedures, we present an MRI-compatible remote catheter navigation system that allows remote navigation of steerable catheters with 3 degrees of freedom. The system consists of a user interface (master), a robot (slave), and an ultrasonic motor control servomechanism. The interventionalist applies conventional motions (axial, radial and plunger manipulations) on an input catheter in the master unit; this user input is measured and used by the servomechanism to control a compact catheter manipulating robot, such that it replicates the interventionalist's input motion on the patient catheter. The performance of the system was evaluated in terms of MRI compatibility (SNR and artifact), feasibility of remote navigation under real-time MRI guidance, and motion replication accuracy. Real-time MRI experiments demonstrated that catheter was successfully navigated remotely to desired target references in all 3 degrees of freedom. The system had an absolute value error of [Formula: see text]1mm in axial catheter motion replication over 30mm of travel and [Formula: see text] for radial catheter motion replication over [Formula: see text]. The worst case SNR drop was observed to be [Formula: see text]3%; the robot did not introduce any artifacts in the MR images. An MRI-compatible compact remote catheter navigation system has been developed that allows remote navigation of steerable catheters with 3 degrees of freedom. The proposed system allows for safe and accurate remote catheter navigation, within conventional closed-bore scanners, without degrading MR image quality.

Shear strength properties of plain and spirally profiled cable bolts

An experimental investigation into the performance of two 22 mm diameter, 60 t tensile strength capacity Hilti cable bolts in shear was conducted using the double-shear testing apparatus at the laboratory of the School of Civil, Mining and Environmental Engineering, Faculty of Engineering and Information Sciences, University of Wollongong. The tested cable bolts were (i) Hilti 19 wire HTT-UXG plain strand and (ii) Hilti 19 wire HTT-IXG spirally profiled (smaller cross-sectional area than the plain one) cable bolt, with indentation only on the surface of the outer strands. These cable bolts are of sealed wire construction type, consisting of an outer 5.5 mm diameter wire layer overlying the middle 3 mm diameter wire strands. Both layers are wrapped around a single solid 7 mm diameter strand wire core. The double-shearing test was carried out in 40 MPa concrete blocks, contained in concrete moulds. Cable bolts were encapsulated in concrete using Orica FB400 pumpable grout. Prior to encapsulation, each cable bolt was pre-tensioned initially to 50 kN axial force. A 500 t capacity servocontrolled compression testing machine was used for both tests, and during each test the vertical shear displacement was limited to 70 mm of travel. The rate of vertical shear displacement was maintained constant at 1 mm/min. The maximum shear load achieved for the plain strand cable was 1024 kN, while the spiral cable peak load was 904 kN, before the cable bolt wires began to individually snap, leading to the cable bolt break-up into two sections. It is apparent that spiral profiles of the outer wires weaken both the tensile and shearing strength. Finally, another set of tests was undertaken using the British Standard single-shear approach, producing lower shear strength values.

Design of a Biaxial Mechanical Loading Bioreactor for Tissue Engineering

We designed a loading device that is capable of applying uniaxial or biaxial mechanical strain to a tissue engineered biocomposites fabricated for transplantation. While the device primarily functions as a bioreactor that mimics the native mechanical strains, it is also outfitted with a load cell for providing force feedback or mechanical testing of the constructs. The device subjects engineered cartilage constructs to biaxial mechanical loading with great precision of loading dose (amplitude and frequency) and is compact enough to fit inside a standard tissue culture incubator. It loads samples directly in a tissue culture plate, and multiple plate sizes are compatible with the system. The device has been designed using components manufactured for precision-guided laser applications. Bi-axial loading is accomplished by two orthogonal stages. The stages have a 50 mm travel range and are driven independently by stepper motor actuators, controlled by a closed-loop stepper motor driver that features micro-stepping capabilities, enabling step sizes of less than 50 nm. A polysulfone loading platen is coupled to the bi-axial moving platform. Movements of the stages are controlled by Thor-labs Advanced Positioning Technology (APT) software. The stepper motor driver is used with the software to adjust load parameters of frequency and amplitude of both shear and compression independently and simultaneously. Positional feedback is provided by linear optical encoders that have a bidirectional repeatability of 0.1 μm and a resolution of 20 nm, translating to a positional accuracy of less than 3 μm over the full 50 mm of travel. These encoders provide the necessary position feedback to the drive electronics to ensure true nanopositioning capabilities. In order to provide the force feedback to detect contact and evaluate loading responses, a precision miniature load cell is positioned between the loading platen and the moving platform. The load cell has high accuracies of 0.15% to 0.25% full scale.

A Magnetic-Resonance-Imaging-Compatible Remote Catheter Navigation System

A remote catheter navigation system compatible with magnetic resonance imaging (MRI) has been developed to facilitate MRI-guided catheterization procedures. The interventionalist's conventional motions (axial motion and rotation) on an input catheter - acting as the master - are measured by a pair of optical encoders, and a custom embedded system relays the motions to a pair of ultrasonic motors. The ultrasonic motors drive the patient catheter (slave) within the MRI scanner, replicating the motion of the input catheter. The performance of the remote catheter navigation system was evaluated in terms of accuracy and delay of motion replication outside and within the bore of the magnet. While inside the scanner bore, motion accuracy was characterized during the acquisition of frequently used imaging sequences, including real-time gradient echo. The effect of the catheter navigation system on image signal-to-noise ratio (SNR) was also evaluated. The results show that the master-slave system has a maximum time delay of 41 ± 21 ms in replicating motion; an absolute value error of 2 ± 2° was measured for radial catheter motion replication over 360° and 1.0 ± 0.8 mm in axial catheter motion replication over 100 mm of travel. The worst-case SNR drop was observed to be 2.5%.

Experimental investigation of gasless detonation in metal-sulfur compositions

Samples of zinc-sulfur and manganese-sulfur mixtures are shocked using an explosive pentolite charge to investigate if a shock-initiated reaction is able to support continued shock wave propagation. Samples of two different nominal densities (62 and 86% of theoretical maximum density) are prepared as weakly confined cylinders 50 mm in diameter and are instrumented along their length (⩽280 mm) with sensitive piezoelectric pins. Experimental results showed that the shock wave transmitted into the sample by the explosive rapidly decays to an acoustic wave in all four sample types. Furthermore, in denser samples, the part of the sample farthest from the explosive is recovered intact and unreacted, which clearly indicates that the wave is unable to trigger reactions after 100 mm of travel along the sample. Thus, it is concluded that insufficient reaction energy is transmitted forward to the shock wave to prevent its decay as it travels along the sample.

High speed hydraulic scanner for deep X-ray lithography

From our research and development in hard x-ray lithography, we have found that our conventional leadscrew driven scanner stages do not provide adequate scan speed or travel. These considerations have led us to develop a scanning system based on a long stroke hydraulic drive with 635 mm of travel and closed loop feedback to position the stage to better than 100 micrometers. The control of the device is through a PC with a custom LabView interface coupled to simple x-ray beam diagnostics. This configuration allows us to set a variety of scan parameters, including target dose, scan range, scan rates, and dose rate. Results from our prototype system at beamline X-27B are described as well as progress on a production version for the X-14B beamline.

Oblique detonation stabilized on a hypervelocity projectile

We present new experimental results demonstrating the initiation and stabilization of an oblique detonation by a hypervelocity projectile. Projectiles 25 mm in diameter were launched at nominal velocities of 2700 m/s into stoichiometric H 2 -O 2 -N 2 mixtures at pressures between 0.1 and 2.5 bar. A critical threshold in initial pressure was found to be required for the establishment of detonations. Initiation events similar to DDT in propagating waves were observed after 300 mm of travel in H 2 -O 2 mixtures diluted with 25% N 2 . A more direct initiation process was observed in H 2 -air mixtures. A stabilized but overdriven oblique detonation was observed in a stoichiometric H 2 -air mixture at an initial pressure of 2.5 bar. The pressure threshold can be explained in terms of competing reaction and flow-quenching effects along a curving streamline in supersonic flow behind a curved shock wave. This competition can be characterized by a critical Damkohler number Da 0 , which is inversely proportional to the product of wave curvature κ and reaction zone thickness Δ. Only if the reaction zone is sufficiently thin in comparison with the projectile, Da>Da 0 , is it possible to obtain stabilized detonations. Otherwise, the reactions quench and the wave splits into a nonreactive shock wave followed by flamelike contact surface. The inverse pressure dependence Δ∼ P 0 −1 of the reaction zone length and the scaling of the wave curvature κ∼1/ a with the body radius a implies the standard binary scaling relationship P 0 a =constant for the critical conditions of stabilization for a given mixture composition characterized by a bimolecular rate-limiting step.

The use of carbon monoxide/hydrogen burning velocities to examine the rate of the CO+OH reaction

New measurements of burning velocity are reported for selected CO/H 2 mixtures in air, to provide datafor examining the rate of the CO+OH reaction. Burning velocities were obtained from measurements on constant-pressure expanding spherical flames. Flame speeds over the first 35 mm of travel were measured by high-speed schlieren cine photography and extrapolated to infinite radius, using a simple phenomenological model, to yield one-dimensional (1D) values. Extensive computational testing shows that the burning velocities obtained are accurate to within 3%. Experimental burning velocities were then compared with 1D computed values, obtained using full kinetics. Fuel mixtures of 95% CO+5% H 2 and 50% CO+50% H 2 with air were studied across the stoichiometricrange, along with stoichiometric mixtures with varying H 2 /CO ratio. The 95+5% mixture was the prime object of study, since computation revealed that burning velocities for this mixture had the greatest sensitivity to the CO+OH reaction. For the 95+5% mixture, the maximum burning velocity was 0.65 ±0.02 m s −1 at 51.7% fuel; the stoichiometric value was 0.34 m s −1 . For the 50+50% mixture, the corresponding velocities were 1.82±0.06 (at 47.2% fuel) and 1.20 m s −1 . Computed 1D burning velocities agreed well with experiment when the 1976 recommendation of Baulchet al. for the rate of the CO+OH reaction was used. A more recent recommendation gave values more than 20% too high. Further computation revealed that the reaction exerts its influence on the burning velocity of these flames at low temperatures, in a relatively narrow region around 1165 K. Use of different (artificially derived) rate expressions, but having a common value at 1165 K, produced essentially the same burning velocities. Implications of this for flame chemistry are explored.

A simple motorised slide with micrometre resolution

A micrometer drive with >20 mm of travel, stepper motor drive and resolution of the order of 1 mu m is described. While commercial units are available with similar specifications, they generally cost $1500 or more. The unit described is very simple, consisting of a commercial, good-quality nonrotating micrometer head, a high-resolution stepper motor, a frame and an electronic drive card. It can be made easily for under $100 (1983 prices). Backlash and nonlinearity are small.

Penetration with instrumented rods

The response of long rods during penetration is being examined by strain measurements performed with foil resistance gages. Early experiments in this investigation employed the reverse ballistic approach in which stationary rods were impacted by armor targets launched from a light-gas gun. Although satisfactory results were obtained for both normal and oblique impacts, the reverse ballistic approach strictly limited the target diameter, and the target mass limited the impact velocity to values below the range of current ballistic interest. In order to overcome the major limitations imposed by reverse ballistics a technique for launcing instrumented rods has been developed. With this technique strain gages on the rod are connected to thin metal contacts located on the front surface of the plastic sabot. Prior to impact, the contacts are pierced by stationary probes and a low-resistance electrical path is provided during approximately 100 mm of travel by the sabot. A series of impact tests has been performed at normal incidence with steel rods impacting steel targets at a velocity of 1000 m/s. Strain-time signals from these tests were amenable to a simple wave analysis which provided relationships between stress and strain, and particle velocity and strain, to strain of 15%. Results of the analysis are discussed in the context of their relationship to the experimental technique. Details of the experimental technique and its refinement are presented and problem areas are considered.

Fast-Acting Gas Valve

The design and operation of an electrodynamically driven valve, which is employed to deliver rapidly a gas pulse (0.6 cc STP) with a sharp front to the annulus of a coaxial plasmoid source of small aspect ratio (2-mm annulus at 2-cm radius), is described. The spring loaded piston holds the plenum closed against pressures up to 2 atm. The piston is driven open by eddy currents induced by discharging a capacitor through a coil surrounding the plenum. A piston velocity of 5 cm/msec is achieved in less than 20 μsec and is maintained for 7 mm of travel. The arrival of a gas front (air) at the annulus was detected in 100 μsec after firing, employing hot-wire anemometry. The subsequent axial position and velocity of this front in the source annulus were determined as functions of time and position, respectively. It was found that the initial axial velocity of the front exceeded the stagnation sound speed (though not the vacuum escape speed) and remained constant until the displacement thickness from wall friction reached the half-annulus spacing.

Parallel and rectilinear spring movements

This paper discusses the design of instrument movements in which the moving member is held by two equal and parallel leaf springs; the member can be moved parallel to itself by pushing it normally to the springs. In a constructed specimen the parallelism was maintained to within ± 3.5 sec of arc over 6 mm of travel by a simple method of balancing the springs. Arrangements are described for combining two or more spring systems to develop a rectilinear movement. Performances are quoted for three constructions, the best of which held a straight line within about ± 0.25 μ over 5 mm of travel, and ± 1 μ over 10 mm. In some applications spring movements are superior to kinematic slides.