Detection of Damaged Tool in Injection Molding Process with Acoustic Emission

ABSTRACT

The measurement of acoustic emission (AE) signals during injection molding of polypropylene with new and damaged mold is presented. The damaged injection mold was fitted with a steel insert with cracks induced by laser surface heat treatment. Two resonant piezoelectric AE sensors were attached to the mold via AE waveguides. To improve the mold integrity prediction with smaller defects, AE signal frequency characteristics and a measure of AE signal amplitude probability distribution are implemented. A 5-dimensional feature vector with real-valued explanatory variables is proposed, providing the defining points in an appropriate multidimensional space to characterize the state of injection molding tool. Feature vectors are classified with neural network pattern recognition. The results confirm that presented AE technique offers characterizing the integrity of molds also with resonant sensors.     

Cystine-capped CdSe@ZnS nanocomposites: mechanochemical synthesis, properties, and the role of capping agent

Cystine-capped CdSe@ZnS nanocomposites were synthesized mechanochemically with the aim to prepare a material which could be used in medicine for biosensing applications. Although synthesized CdSe@ZnS nanocomposites were capped with l-cysteine, cystine was formed from l-cysteine during the milling process. It was proven that water plays the key role in this oxidative transformation. The novel material was characterized by the complex of physico-chemical methods (FTIR, XPS, SEM, EDX, surface area measurements) and CHNS analysis. The leakage of Cd²⁺ and Zn²⁺ ions into physiological solution was also studied.     

Structure and microstructure of EB-PVD yttria thin films grown on Si (111) substrate

Structure and microstructure of yttria thin films grown by electron beam physical vapour deposition on a stationary Si (111) substrate at room temperature (RT), 500° and 700 °C, were investigated by the grazing-incidence X-ray diffraction and scanning electron microscopy, respectively. X-ray photoelectron spectroscopy provided information on the surface contamination from the atmosphere and the Y oxidation state. A strong effect of the deposition temperature and the vapour flux incidence angle was found. The film deposited at RT is polycrystalline with very fine grains of the body-centered cubic (bcc) crystallographic symmetry. An increase of deposition temperature results in a rapid growth of bcc grains with an improved crystalline structure. Moreover, the based-centered monoclinic phase appears for the deposition temperature of 700 °C. Preferred grain orientation (texture) with two main components, (400) and (622), was observed in the films deposited at 500 °C whereas no texture was found for 700 °C. The microstructure exhibits the columnar feather-like structure of different degrees of perfection which can be explained by the shadowing effects caused by an oblique vapour flux incidence angle. Surface morphology of the films is governed by a combination of the triangular and four-sided (square) columns. All films were found to be dense with a little porosity between the columns.     

A chamber for biomechanical,electrochemical and electrophysiological measurements in functional segments of peripheral nerves

The aim of the work was to develop the chamber to be used in biomechanical, electrochemical and electrophysiological measurements in functional segments of peripheral nerves, when electrical stimulating pulses are selectively applied to preselected locations along the nerve and neural responses are measured.     

Model-based prognostics of gear health using stochastic dynamical models

In this paper we present a statistical approach to estimating the time in which an operating gear will reach a critical stage. The approach relies on measured vibration signals. From these signals features are first extracted and then their evolution over time is predicted. This is done based on a dynamic model that relates hidden degradation phenomena to measured outputs. The Expectation-Maximization algorithm is used to estimate the parameters of the underlying state-space model on line. The time to reach the safety alarm threshold is determined by estimating the distribution of the remaining useful life using the estimated linear model. The results obtained on a pilot test bed are presented.     

High-velocity impact experiment of aluminum foam sample using powder gun

Porous materials such as aluminum foam have been investigated for possible use as impact shock absorbers in transportation aeronautic applications. However, the response of aluminum foam during impacts at high velocities of more than 100 m/s is not yet fully understood. A high-velocity impact experiment was therefore carried out to clarify impact shock absorption properties of aluminum foam. A one-stage powder gun was used to accelerate an aluminum foam sample to impact a rigid wall. Velocity and deformation of the aluminum foam sample during impact was studied using a digital high-speed video camera, while the pressure wave in the aluminum foam sample was measured using a PVDF gauge. The experimental observations revealed uneven collapse of the aluminum foam sample structure during high speed impact with a general stress plateau effect, typical for cellular material structures when subjected to quasi-static loading.     

A model-based approach to the evaluation of flame-protective garments

High-quality protective garments are essential in many occupational assignments, e.g., in the petrochemical industry and for firefighting. The problem addressed in this paper is how to objectively asses the performance of protective garments designed to resist fire. We present a system based on a flame mannequin equipped with an array of temperature sensors that provide information about the temperature on the mannequin’s surface during exposure to fire. Particular attention is devoted to reconstructing the heat flux reaching the mannequin’s surface on the basis of the available temperature records (the inverse heat-conduction problem). The estimated heat flux is used in a skin-simulation model to predict the level of injury that would occur in human exposed to the same heat. The paper includes a novel computational procedure based on a detailed model of the temperature sensor and a numerical solution of the accompanying heat equation. The effectiveness of the solution is demonstrated with experimental data.     

Fines characterization through the methylene blue and sand equivalent test: comparison with other experimental techniques and application of criteria to the aggregate quality assessment

In road construction the general term fines is used to describe particles passing the 0.063, 0.074 or 0.08 mm sieve. Some types of fines are considered to be relatively inert and have almost no effect on pavement performance, whilst the presence of even small amounts of others can significantly affect the stiffness and freezing–thawing behaviour of unbound and hydraulically bound layers. This paper presents the results of research on 12 Slovenian aggregates produced from limestone and dolomite bedrock, and naturally occurring river alluvium gravel. At each production site three different materials were sampled and tested: the actual aggregate for unbound base layers, the clayey soils, which presented the most potentially harmful component at the specific location, and the stony dust, which presented the finest size of crushed aggregate and is typically found as coatings on the crushed grains. Six different methods were used to identify the nature of the fines: X-ray diffractometry, carbonate content determination, methylene blue, sand equivalent, Enslin–Neff water absorption, Atterberg limits test, soil suction measurements and soil water characteristic curves. Based on the results, the relationship between the properties of the different fines was determined and included in draft Slovenian national criteria for sand equivalent and methylene blue values currently being trialed.     

3-D reconstruction of 2-D crystals in real space

A new algorithm for three-dimensional reconstruction of two-dimensional crystals from projections is presented, and its applicability to biological macromolecules imaged using transmission electron microscopy (TEM) is investigated. Its main departures from the traditional approach is that it works in real space, rather than in Fourier space, and it is iterative. This has the advantage of making it convenient to introduce additional constraints (such as the support of the function to be reconstructed, which may be known from alternative measurements) and has the potential of more accurately modeling the TEM image formation process. Phantom experiments indicate the superiority of the new approach even without the introduction of constraints in addition to the projection data.