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K. Gawdzińska

Abstract

In this paper it is stated, that a set of quality features of metal matrix composite castings differs from the same set for castings of classic materials, although some features are common for both of these material groups. These features (pertaining to a set of quality characteristics of composite castings) have been named as specific, they have not been determined yet and a description of material quality should be performed (according to the qualitology) on a principle of description of quality characteristics of this product. Therefore, this set of features has been determined. It was proposed to add the following characteristics to the set of specific features of composite castings quality: matrix material, reinforcement material, binding between components and porosity of the composite casting. In this set a sub-set of quality characteristics of composite castings was also determined.

Open access

K. Gawdzińska

Abstract

Diagnostics of composite castings, due to their complex structure, requires that their characteristics are tested by an appropriate description method. Any deviation from the specific characteristic will be regarded as a material defect. The detection of defects in composite castings sometimes is not sufficient and the defects have to be identified. This study classifies defects found in the structures of saturated metallic composite castings and indicates those stages of the process where such defects are likely to be formed. Not only does the author determine the causes of structural defects, describe methods of their detection and identification, but also proposes a schematic procedure to be followed during detection and identification of structural defects of castings made from saturated reinforcement metallic composites. Alloys examination was conducted after technological process, while using destructive (macroscopic tests, light and scanning electron microscopy) and non-destructive (ultrasonic and X-ray defectoscopy, tomography, gravimetric method) methods. Research presented in this article are part of author’s work on castings quality.

Open access

K. Gawdzińska and M. Gucma

Abstract

The determination of potential areas of application for metal foams allows to precisely define properties these materials are expected to have. The characteristics of metal foams are strictly related to their cellular structure, which in turn depends on the manufacturing method and materials used. Obviously, metal foam producers should strive to make these materials using inexpensive, or cost-effective technologies, yielding possibly good quality and being environment-friendly. This paper briefly characterizes the manufacturing of metal and composite foams by casting methods. We determine an optimal manufacturing method based on a matrix diagram for metal and composite foams satisfying the two - criteria: “manufacturing costs” (depending on the price of production equipment and labour, cost of materials for foam manufacturing, environmental impact) and “foam quality” (depending on the manufacturing precision, homogeneity of the structure, pore size, shape, and volumetric fraction).

Open access

A. Bejger and K. Gawdzińska

Identification of Structural Defects of Metal Composite Castings with The Use of Elastic Waves

The method of elastic wave propagation was applied to detect defects in composite castings (ingots). If a defect occurs, which is detected by the radiography, elastic wave propagation changes locally, i.e. causes disturbance of elastic wave propagation. Methods of signal analysis based on wavelet decomposition were used. Calculations related with wavelet analysis were made in the MATLAB environment using standard Wavelet Toolbox functions.

Open access

K. Gawdzińska, D. Nagolska and M. Szweycerb

Abstract

Definition of a composite [1] describes an ideal composite material with perfect structure. In real composite materials, structure is usually imperfect - composites contain various types of defects [2, 3-5], especially as the casted composites are of concern. The reason for this is a specific structure of castings, related to course of the manufacturing process. In case of metal matrix composite castings, especially regarding these manufactured by saturation, there is no classification of these defects [2, 4]. Classification of defects in castings of classic materials (cast iron, cast steel, non-ferrous alloys) is insufficient and requires completion of specific defects of mentioned materials. This problem (noted during manufacturing metal matrix composite castings with saturated reinforcement in Institute of Basic Technical Sciences of Maritime University Szczecin) has become a reason of starting work aimed at creating such classification. As a result, this paper was prepared. It can contribute to improvement of quality of studied materials and, as a consequence, improve the environment protection level.

Open access

K. Gawdzińska, L. Chybowski and W. Przetakiewicz

Abstract

Owing to its properties, metallic foams can be used as insulation material. Thermal properties of cast metal-ceramic composite foams have applications in transport vehicles and can act as fire resistant and acoustic insulators of bulkheads. This paper presents basic thermal properties of cast and foamed aluminum, the values of thermal conductivity coefficient of selected gases used in foaming composites and thermal capabilities of composite foams (AlSi11/SiC). A certificate of non-combustibility test of cast aluminum-ceramic foam for marine applications was included inside the paper. The composite foam was prepared by the gas injection method, consisting in direct injection of gas into liquid metal. Foams with closed and open cells were examined. The foams were foaming with foaming gas consisting of nitrogen or air. This work is one of elements of researches connected with description of properties of composite foams. In author's other works acoustic properties of these materials will be presented.

Open access

K. Gawdzińska, J. Grabian, M. Szweycer and W. Przetakiewicz

Abstract

The Department of Marine Materials Engineering, Maritime University of Szczecin, has conducted research on the technology of metallic composites, focusing on composite aluminium foams stabilized with ceramic particles. One technology which enables efficient, inexpensive and diversified - in terms of foam structure - control of foam properties is the foundry technology consisting in gas injection into liquid metal. This method requires precise control of the process parameters, especially regarding temperature stabilization, as well as precise injection of the gas into the metal. The process of foaming of liquid aluminium or its silicon alloys can also be conducted using ceramic particles. This is a metallic-ceramic composite foaming process (patent PL 211439 B1). The paper presents the process of structure forming of metallic-ceramic foams.

Open access

K. Gawdzińska, K. Bryll and D. Nagolska

The authors attempted at examining the effect of heat treatment on abrasive wear resistance of metal composite castings. Metal matrix composites were made by infiltrating preforms created from unordered short fibers (graphite or silumin) with liquid aluminium alloy AlSi12(b). Thus prepared composites were subject to solution heat treatment at a temperature of 520°C for four hours, then aging at a temperature of 220°C for four hours. Abrasion resistance of the material was tested before and after thermal treatment.

Open access

K. Gawdzińska, L. Chybowski, W. Przetakiewicz and R. Laskowski

Abstract

Metal matrix composites (MMCs) are still scarcely described due to various combinations of used materials and a wide array of technologies. Applying the Failure Mode and Effect Analysis (FMEA) method to describe the quality of metal composite castings may contribute to eliminating specific (characteristic only to these materials) defects. This part of the analysis determines the criticality numbers, meaning the frequency of a given failure, detectability level and significance of a given failure to the group of specific composite casting failures. It contributes to establishing the priority number (P), which is a measure used to assess risk, a notion essential in discussing quality in a composite casting.

Open access

Leszek Chybowski, Katarzyna Gawdzińska and Bogusz Wiśnicki

Abstract

The paper presents an improved methodology of analysing the qualitative importance of components in the functional and reliability structures of the system. We present basic importance measures, i.e. the Birnbaum’s structural measure, the order of the smallest minimal cut-set, the repetition count of an i-th event in the Fault Tree and the streams measure. A subsystem of circulation pumps and fuel heaters in the main engine fuel supply system of a container vessel illustrates the qualitative importance analysis. We constructed a functional model and a Fault Tree which we analysed using qualitative measures. Additionally, we compared the calculated measures and introduced corrected measures as a tool for improving the analysis. We proposed scaled measures and a common measure taking into account the location of the component in the reliability and functional structures. Finally, we proposed an area where the measures could be applied.