High-speed Video Capture Research Articles

A fast real time measurement system to track in and out of plane optical retardation/ birefringence, true stress, and true strain during biaxial stretching of polymer films

An instrumented and highly integrated biaxial stretching system was designed and constructed to obtain true stress, true strain, and optical behavior of polymeric films during biaxial stretching. With programmable drive motors, any form of temporally varying biaxial deformation profiles, including linear, exponential, logarithmic as well as cyclic, can be applied to a square-shaped films. This machine allows the investigation of mechano-optical behavior of films under profiles captured in industrial processes. To overcome the edge effects, the samples are painted with a dot pattern that is imaged using a high speed video capture system. This system accurately determines the locations of the each dot matrix in subsequent images acquired and calculates the true strains in both directions. The in-plane optical retardation is determined using spectral birefringence method that uses polarized white light and optical spectrometer in the optical train. This is carried out automatically at less than 10 nm in retardation resolution with the light beam passing through the symmetry center of the sample. Out of plane retardation is measured with an identical optical train tilted 45° to the plane of the film with its light beam going through the same spot on the sample as 0° beam. The true stress and birefringences are calculated with the determined instantaneous thickness of the film. With this system, the stress optical behavior of PET's is determined up to very large deformation levels at moderate to high deformation rates. Beyond the initial linear stress optical behavior, these films exhibit sudden positive deviation from linearity and this start of nonlinearity was directly associated with the stress induced crystallization.

On the wavelet-based simulation of anomalous diffusion

The field of microrheology is based on experiments involving particle diffusion. Microscopic tracer beads are placed into a non-Newtonian fluid and tracked using high speed video capture and light microscopy. The modelling of the behaviour of these beads is now an active scientific area which demands multiple stochastic and statistical methods. We propose an approximate wavelet-based simulation technique for two classes of continuous time anomalous diffusion models, the fractional Ornstein–Uhlenbeck process and the fractional generalized Langevin equation. The proposed algorithm is an iterative method that provides approximate discretizations that converge quickly and in an appropriate sense to the continuous time target process. As compared to previous works, it covers cases where the natural discretization of the target process does not have closed form in the time domain. Moreover, we propose to minimize the border effect via smoothing.

Robust QCT/FEA models of proximal femur stiffness and fracture load during a sideways fall on the hip.

Clinical implementation of quantitative computed tomography-based finite element analysis (QCT/FEA) of proximal femur stiffness and strength to assess the likelihood of proximal femur (hip) fractures requires a unified modeling procedure, consistency in predicting bone mechanical properties, and validation with realistic test data that represent typical hip fractures, specifically, a sideways fall on the hip. We, therefore, used two sets (n=9, each) of cadaveric femora with bone densities varying from normal to osteoporotic to build, refine, and validate a new class of QCT/FEA models for hip fracture under loading conditions that simulate a sideways fall on the hip. Convergence requirements of finite element models of the first set of femora led to the creation of a new meshing strategy and a robust process to model proximal femur geometry and material properties from QCT images. We used a second set of femora to cross-validate the model parameters derived from the first set. Refined models were validated experimentally by fracturing femora using specially designed fixtures, load cells, and high speed video capture. CT image reconstructions of fractured femora were created to classify the fractures. The predicted stiffness (cross-validation R (2)=0.87), fracture load (cross-validation R (2)=0.85), and fracture patterns (83% agreement) correlated well with experimental data.

Comparison of the mechanics of the brass players’ lips during slurred note transients.

When sounding a note on a brass instrument, a strong coupling is established between the vibrating lips of the player and the air column resonance. In moving between notes as smoothly as possible, or “slurring,” there is a transition from one strongly coupled, steady-state, regime of the lip/air column to a different steady-state coupling of the lip/air column. To the listener, there are sometimes subtle differences in the sound of the transition between notes depending on how this transition is achieved: by lip slur, valve slurs, and, in the case of the trombone, slide slurs. This paper uses data collected from high speed video capture of the players’ lips, synchronized with microphones in the mouthpiece and the bell of the instrument, to investigate and compare the motion of the brass players’ lips for different types of slurred internote transients.

Experimental Visualization of Distributed Magnetic Fields of Railguns

Electromagnetic launch produces distributed magnetic fields during firing. Data collection and visualization of this field provide a useful diagnostic tool to better understand electromagnetic launcher operation. This paper outlines an effort to visualize these fields during firing. The diagnostic tool is based on a ferrofluid that becomes strongly polarized in the presence of a magnetic field. A commercial off-the-shelf flexible film, incorporating microencapsulated ferrofluid, was draped along the top of a railgun during operation. High-speed video capture of launch provided proof of principle that the dynamics of magnetic field formation could be recorded. Conformal mapping of the video provided quantitative contours for validation of numerical models.

In mould painting using thermoset powder coating and thermoplastic substrate in closed tool injection moulding

In mould decoration (IMD) is attractive because a fully, or partially, decorated component is produced directly from the moulding process, with reduced emissions at lower process costs when compared to traditional techniques. A new IMD process has been developed to produce a painted component direct from the injection moulding tool. This incorporates the pressure spraying of thermoset powders through a valve into a closed mould. The residual heat of the tool initially softens the thermoset. The high temperature of thermoplastic polymer injected in a standard injection moulding subsequently cures the thermoset. The resultant product combines both thermoplastic and thermoset in a single injection moulding cycle. This paper presents frames from high speed video capture of powder mould filling and the results of INSPIRE (in mould spray painting, impact reduced on the environment) initial injection moulding using thermoset polyester and acrylonitrile butadiene styrene (ABS). The parameters that affect material distribution are examined and discussed. Similarities to the coinjection moulding process are noted.

Relationship Between Initial Absorption Behavior of Ink-Jet Inks and Three-Dimensional Distribution of the Fixed Inks in Paper

Novel techniques for examining fixation processes of a dye ink dot on paper and three-dimensional geometry of the fixed ink dot were developed and applied.Most magenta and black dye inks for ink-jet contain fluorescence agents or use fluorescence dyes specific of the color. Fluorescence emitted from those of the ink-jet inks provides a three dimensional ink distribution by the optical slicing function of a confocal laser scanning microscope. In applications, several facts were revealed. Ink dot shape was like a coin with a constant thickness on photo quality paper. Ink spreads over crack surfaces on high gloss type paper a few times deeper than the normal penetration.Microscopic high-speed video capture system was established to visualize ink drop spread on and penetration into paper. Changes in ink dot area and dot roughness with time were evaluated from microscopic video images. Ink drop behavior on trial coated paper from commercially available calcium carbonate pigment and from its ball-milled pigment was recorded. Small particle size by ball milling reduced the dot area, but dot area continued to change for a longer time than that for the untreated sample, as is explained in terms of small pore size according to Lucas-Washburn's equation.