Introduction: Platelet-rich plasma (PRP) preparations can be used in bone tissue healing but there are numerous doubts among clinical orthopedists about effectiveness of this method. Materials and methods: The studies were carried out in 12 rabbits of white termond breed. In operating room we operationally generated cylindrical, unicortical defects of the diameter of 4 mm in the middle of the shafts of both femurs. The defects in the left bones were left without filling and served as controls, and 0.7 ml of the ready-to-use PRP was administered to the defects in the right bones (experimental group). We evaluated the usefulness of the diagnostic methods applied: biomechanical tests, micro-CT tests, densitometry, typical radiology, macroscopic measurements, histopathological examinations. Results: The macroscopic measurements showed a statistically significant increase in the dimension in the area of the right defect filled with PRP in relation to the control group. In experimented group, the assessment of the X-ray images showed the formation of a callus cuff around the defects. Densitometric examinations showed no statistically significant differences between defects in the experimental and control group. The analysis of the micro-CT examina- tions showed an increase in the total volume of the tissue examined (Vb) and the low density tissue fraction (Vb2) in the experimental group. The biomechanical examinations revealed signi- ficant decrease in the maximum breaking force (F max) necessary to break the bone in the experi- mental group in relation to the control group. Conclusions: Platelet-rich plasma (PRP) stimulates bone formation in the area of bone defects and may accelerate bone regeneration.
Definition of a composite  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.
This study summarises the research efforts undertaken in iron foundry plants in which the process are mostly automated and mechanised. The research program was limited in scope, focusing on causes of surface defects in castings products that are attributable to the bentonite-containing sand and the mould system. One of the potential roots of surface defects is heterogeneity of sand grains, containing lumped ball-shaped grains and irregular pellets with a layered-structure. The moisture contents of those lumped grains is different than the moisture level required in the process, besides these grains may contain various elements and metallic compounds which, when cast into moulds, may react with molten metals in an uncontrolled manner. As a result, surface defects are produced, such as surface blowholes, burst penetration, sand holes, slag inclusions, pinhole porosity. This study investigated the efficiency of key sand preparation and moulding machines and installations integrated into the casting process line. The efficiency of machines and installations is defined in terms of quality parameters of sand mix and moulds, which are associated with the emergence of surface defects on castings.
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.
The powerful tool for defect analysis is an expert system. It is a computer programme based on the knowledge of experts for solving the quality of castings. We present the expert system developed in the VSB-Technical University of Ostrava called ‘ESWOD’. The ESWOD programme consists of three separate modules: identification, diagnosis / causes and prevention / remedy. The identification of casting defects in the actual form of the system is based on their visual aspect.
Changes of gas pressure in the moulding sand in the zone adjacent to mould cavity were analysed during pouring of cast iron. No significant effect of pressure on the surface quality of castings was observed. In the second series of tests, the concentration of hydrogen in the gas atmosphere was measured. It has been found that the value of this concentration depends on metal composition and is particularly high in cast iron containing magnesium. This is due to the reduction of water vapour with the element that has high affinity to oxygen. The presence of hydrogen causes the formation of gas-induced defects on the casting surface.
The article summarizes the theoretical knowledge from the field of brazing of graphitic cast iron, especially by means of conventional flame brazing using a filler metal based on CuZn (CuZn40SnSi – brass alloy). The experimental part of the thesis presents the results of performance assessment of brazed joints on other than CuZn basis using silicone (CuSi3Mn1) or aluminium bronze (CuAl10Fe). TIG electrical arc was used as a source of heat to melt these filler materials. The results show satisfactory brazed joints with a CuAl10Fe filler metal, while pre-heating is not necessary, which favours this method greatly while repairing sizeable castings. The technological procedure recommends the use of AC current with an increased frequency and a modified balance between positive and negative electric arc polarity to focus the heat on a filler metal without melting the base material. The suitability of the joint is evaluated on the basis of visual inspection, mechanic and metallographic testing.
Foundry technologists use their own style of gating system designing. Most of their patterns are caused by experience. The designs differ from plant to plant and give better or worse results. This shows that the theory of gating systems is not brought into general use sufficiently and therefore not applied in practise very often. Hence, this paper describes the theory and practical development of one part of gating systems - sprue base for automated horizontal moulding lines used for iron castings. Different geometries of sprue bases with gating system and casting were drawn in Solid Edge ST9. The metal flow through the gating systems was then simulated with use of MAGMA Express 188.8.131.52, and the results were achieved. The quality of flow was considered in a few categories: splashes, air entrapment, vortex generation and air contact. The economical aspect (weight of runner) was also taken under consideration. After quantitative evaluation, the best shape was chosen and optimised in other simulations with special attention on its impact on filling velocity and mould erosion. This design (a sprue base with notch placed in drag and cope) is recommended to be used in mass production iron foundries to reduce oxide creation in liquid metal and especially to still metal stream to improve filtration.
The chosen, typical causes of quality defects of cast-iron „alphin” rings embedded in aluminum cast are being presented in this paper. Diffusive joint of those inserts with the pistons casts is being used, due to extreme work conditions of destructive influence of the fuel mix and variable thermo-mechanical loads, which reign in the combustion motor working chamber.
Simulation software can be used not only for checking the correctness of a particular design but also for finding rules which could be used in majority of future designs. In the present work the recommendations for optimal distance between a side feeder and a casting wall were formulated. The shrinkage problems with application of side feeders may arise from overheating of the moulding sand layer between casting wall and the feeder in case the neck is too short as well as formation of a hot spot at the junction of the neck and the casting. A large number of simulations using commercial software were carried out, in which the main independent variables were: the feeder’s neck length, type and geometry of the feeder, as well as geometry and material of the casting. It was found that the shrinkage defects do not appear for tubular castings, whereas for flat walled castings the neck length and the feeders’ geometry are important parameters to be set properly in order to avoid the shrinkage defects. The rules for optimal lengths were found using the Rough Sets Theory approach, separately for traditional and exothermic feeders.
Simulation software dedicated for design of casting processes is usually tested and calibrated by comparisons of shrinkage defects distribution predicted by the modelling with that observed in real castings produced in a given foundry. However, a large amount of expertise obtained from different foundries, including especially made experiments, is available from literature, in the form of recommendations for design of the rigging systems. This kind of information can be also used for assessment of the simulation predictions. In the present work two parameters used in the design of feeding systems are considered: feeding ranges in horizontal and vertical plates as well as efficiency (yield) of feeders of various shapes. The simulation tests were conducted using especially designed steel and aluminium castings with risers and a commercial FDM based software. It was found that the simulations cannot predict appearance of shrinkage porosity in horizontal and vertical plates of even cross-sections which would mean, that the feeding ranges are practically unlimited. The yield of all types of feeders obtained from the simulations appeared to be much higher than that reported in the literature. It can be concluded that the feeding flow modelling included in the tested software does not reflect phenomena responsible for the feeding processes in real castings properly. Further tests, with different types of software and more fundamental studies on the feeding process modelling would be desirable.
Castability of thin-walled castings is sensitive to variation in casting parameters. The variation in casting parameters can lead to undesired casting conditions which result in defect formation. Variation in rejection rate due to casting defect from one batch to other is common problem in foundries and the cause of this variation usually remain unknown due to complexity of the process. In this work, variation in casting parameters resulting from human involvement in the process is investigated. Casting practices of different groups of casting operators were evaluated and resulting variations in casting parameters were discussed. The effect of these variations was evaluated by comparing the rejection statistics for each group. In order to minimize process variation, optimized casting practices were implemented by developing specific process instructions for the operators. The significance of variation in casting parameters in terms of their impact on foundry rejections was evaluated by comparing the number of rejected components before and after implementation of optimized casting practices. It was concluded that variation in casting parameters due to variation in casting practices of different groups has significant impact on casting quality. Variation in mould temperature, melt temperature and pouring rate due to variation in handling time and practice resulted in varying quality of component from one batch to other. By implementing the optimized casting instruction, both quality and process reliability were improved significantly.
The paper presents the results of experimental-simulation tests of expansion-shrinkage phenomena occurring in cast iron castings. The tests were based on the standard test for inspecting the tendency of steel-carbon alloys to create compacted discontinuities of the pipe shrinkage type. The cast alloy was a high-silicone ductile iron of GJS - 600 - 10 grade. The validation regarding correctness of prognoses of the shrinkage defects was applied mostly to the simulation code (system) NovaFlow & Solid CV (NFS CV). The obtained results were referred to the results obtained using the Procast system (macro- and micromodel). The analysis of sensitivity of the modules responsible for predicting the shrinkage discontinuities on selected pre-processing parameters was performed, focusing mostly on critical fractions concerning the feeding flows (mass and capillary) and variation of initial temperature of the alloy in the mould and heat transfer coefficient (HTC) on the casting - chill interface.
The article presents an example of analysis of the influence of selected parameters deriving from data acquisition in foundries on the occurrence of Gas porosity defects (detected by Visual testing) in castings of ductile cast iron. The possibilities as well as related effectiveness of prediction of this kind of defects were assessed. The need to rationally limit the number of possible parameters affecting this kind of porosity was indicated. Authors also benefited from expert group's expertise in evaluating possible causes associated with the creation of the aforementioned defect. A ranking of these parameters was created and their impact on the occurrence of the defect was determined. The classic statistical tools were used. The possibility of unexpected links between parameters in case of uncritical use of these typical statistical tools was indicated. It was emphasized also that the acquisition realized in production conditions must be subject to a specific procedure ordering chronology and frequency of data measurements as well improving the casting quality control. Failure to meet these conditions will significantly affect the difficulties in implementing and correcting analysis results, from which INput/OUTput data is expected to be the basis for modelling for quality control.
The paper deals with fault diagnosis of nonlinear analogue integrated circuits. Soft spot short defects are analysed taking into account variations of the circuit parameters due to physical imperfections as well as self-heating of the chip. A method enabling to detect, locate and estimate the value of a spot defect has been developed. For this purpose an appropriate objective function was minimized using an optimization procedure based on the Fibonacci method. The proposed approach exploits DC measurements in the test phase, performed at a limited number of accessible points. For illustration three numerical examples are given.
A significant part of the knowledge used in the production processes is represented with natural language. Yet, the use of that knowledge in computer-assisted decision-making requires the application of appropriate formal and development tools. An interesting possibility is created by the use of an ontology that is understandable both for humans and for the computer. This paper presents a proposal for structuring the information about the foundry processes, based on the definition of ontology adapted to the physical structure of the ongoing technological operations that make up the process of producing castings.
Magnesium alloys due to their low density and high strength-to-weight ratio are promising material for the automotive and aerospace industries. Many elements made from magnesium alloys are produced by means of sand casting. It is essential to investigate impact of the applied mould components on the microstructure and the quality of the castings. For the research, six identical, 100x50x20mm plates has been sand cast from the Elektron 21 magnesium casting alloy. Each casting was fed and cooled in a different way: one, surrounded by mould sand, two with cast iron chills 20mm and 40mm thick applied, another two with the same chills as well as feeders applied and one with only the feeder applied. Solid solution grain size and eutectics volume fraction were evaluated quantitatively in Met-Ilo program, casting defects were observed on the scanning electron microscope Hitachi S3400N. The finest solid solution grain was observed in the castings with only the chills applied. Non metallic inclusions were observed in each plate. The smallest shrinkage porosity was observed in the castings with the feeders applied.
Gas atmosphere at the sand mould/cast alloy interface determines the quality of the casting obtained. Therefore the aim of this study was to measure and evaluate the gas forming tendency of selected moulding sands with alkyd resins. During direct and indirect gas measurements, the kinetics of gas evolution was recorded as a function of the temperature of the sand mixture undergoing the process of thermal destruction. The content of hydrogen and oxygen was continuously monitored to establish the type of the atmosphere created by the evolved gases (oxidizing/reducing). The existing research methodology [1, 7, 8] has been extended to include pressure-assisted technique of indirect measurement of the gas evolution rate. For this part of the studies, a new concept of the measurement was designed and tested. This article presents the results of measurements and compares gas emissions from two sand mixtures containing alkyd resins known under the trade name SL and SL2002, in which the polymerization process is initiated with isocyanate. Studies of the gas forming tendency were carried out by three methods on three test stands to record the gas evolution kinetics and evaluate the risk of gas formation in a moulding or core sand. Proprietary methods for indirect evaluation of the gas forming tendency have demonstrated a number of beneficial aspects, mainly due to the ability to record the quantity and composition of the evolved gases in real time and under stable and reproducible measurement conditions. Direct measurement of gas evolution rate from the tested sands during cast iron pouring process enables a comparison of the results with the results obtained by indirect methods.
This paper concerns the issues of measurement techniques, analysis and assessment of the machined surface geometric structure. The aim of this work was to show the application of surface analysis in diagnosing the causes of discrepancies occurring in the manufacturing process, which may result from ill-matched (poorly fitting) process parameters. An appropriate system of control and interpretation of results may allow early reaction to unfavorable trends (for example blunting of the tool) and prevention of undesirable defects. The subject of research was a waste basket used in the construction of retaining sewer systems. In this paper, the quality of the waste basket as well as its manufacturing process were analyzed and assessed. The research was carried out with the use of three measurement stands, i.e. optical microscopy (OM), scanning electron microscopy (SEM) and white light interferometer (WLI). The surface analysis proved to be important from the viewpoint of outlining the production process as well as improving the product quality. The software used for topographical analysis appeared to be significant for the success of the analysis, providing notable economic effects, namely the lack of defects.
The paper analyses specific defects of castings produced by semi-solid casting process, especially rheocasting method SEED, which uses mechanical swirling for reaching proper structure in semisolid state with high content of solid fraction. Heat treated alloy AlSi7Mg0.3 was applied for producing an Engine Bracket casting part. For observing structure, metallographic observation by light and SEM microscopy was used. To analyse the process, software ProCAST was used to simulate the movements in shot chamber and filling of the mold.
The results of researches of sorption processes of surface layers of components of sand moulds covered by protective coatings are presented in the hereby paper. Investigations comprised various types of sand grains of moulding sands with furan resin: silica sand, reclaimed sand and calcined in temperature of 700oC silica sand. Two kinds of alcoholic protective coatings were used – zirconium and zirconium – graphite. Tests were performed under condition of a constant temperature within the range 30 – 35oC and high relative air humidity 75 - 80%. To analyze the role of sand grains in sorption processes quantitavie moisture sorption with use of gravimetric method and ultrasonic method were used in measurements. The tendency to moisture sorption of surface layers of sand moulds according to the different kinds of sand grains was specified. The effectiveness of protective action of coatings from moisture sorption was analyzed as well. Knowledge of the role of sand grains from the viewpoint of capacity for moisture sorption is important due to the surface casting defects occurrence. In particular, that are defects of a gaseous origin caused by too high moisture content of moulds, especially in surface layers.
The FMEA (Failure Mode and Effects Analysis) method consists in analysis of failure modes and evaluation of their effects based on determination of cause-effect relationships for formation of possible product or process defects. Identified irregularities which occur during the production process of piston castings for internal combustion engines were ordered according to their failure rates, and using Pareto-Lorenz analysis, their per cent and cumulated shares were determined. The assessments of risk of defects occurrence and their causes were carried out in ten-point scale of integers, while taking three following criteria into account: significance of effects of the defect occurrence (LPZ), defect occurrence probability (LPW) and detectability of the defect found (LPO). A product of these quantities constituted the risk score index connected with a failure occurrence (a so-called “priority number,” LPR). Based on the observations of the piston casting process and on the knowledge of production supervisors, a set of corrective actions was developed and the FMEA was carried out again. It was shown that the proposed improvements reduce the risk of occurrence of process failures significantly, translating into a decrease in defects and irregularities during the production of piston castings for internal combustion engines.
Inconel 713C alloy belongs to the group of materials with high application potential in the aerospace industry. This nickel alloy has excellent features such as high strength, good surface stability, high creep and corrosion resistance. The paper presents the results of metallographic examinations of a base material and padding welds made by laser beam on the Inconel 713C alloy. The tests were made on precisely cast test plates imitating low - pressure turbine blades dedicated for the aerospace industry. Observations of the macro- and microstructure of the padding welds, heat-affected zone and base material indicate, that the Inconel 713C alloy should be classified as a hard-to-weld material. In the investigated joint, cracking of the material is disclosed mainly in the heat-affected zone and at the melted zone interface, where pad weld crystals formed on partially melted grains. The results show that phases rich with chromium and molybdenum were formed by high temperature during welding process, which was confirmed by EDS analysis of chemical composition.
This article presents a computer system for the identification of casting defects using the methodology of Case-Based Reasoning. The system is a decision support tool in the diagnosis of defects in castings and is designed for small and medium-sized plants, where it is not possible to take advantage of multi-criteria data. Without access to complete process data, the diagnosis of casting defects requires the use of methods which process the information based on the experience and observations of a technologist responsible for the inspection of ready castings. The problem, known and studied for a long time, was decided to be solved with a computer system using a CBR (CaseBased Reasoning) methodology. The CBR methodology not only allows using expert knowledge accumulated in the implementation phase, but also provides the system with an opportunity to "learn" by collecting new cases solved earlier by this system. The authors present a solution to the system of inference based on the accumulated cases, in which the main principle of operation is searching for similarities between the cases observed and cases stored in the knowledge base.