Blow Holes Research Articles

Defect control analysis for improving quality and productivity: an innovative Six Sigma case study

This research study proposes an innovative analysis for controlling the defects in aluminium die casting industry. In this analysis, casting process of a two-stroke engine oil pump body is concentrated. The component selected has often rejected due to blow hole defects. Six Sigma, the zero defect approach, is used in this study. Define measure, analyse, improve and control (DMAIC) problem solving methodology is applied for problem analysis. Taguchi’s experimental design is used for process validation and improvement. The confirmation experiment showed that the rejection rate was reduced to 4.8% from 17.22%. The application of Six Sigma program with Taguchi technique has developed an innovative cost effective methodology for controlling defects in die casting process in less experimental time.

Technical Research of Friction Stir Welding Repair in Aeroplane Aluminium Alloy Damage

This article briefly introduces traditional repair technical defects of the aeroplane aluminium alloy and the current situation of FSW. It demonstrates FSW technique feasibility using for aeroplane repair, and makes a initial research some damage forms adopting FSW repair technique, such as cracks, blow holes, and gaps, and so on. Besides, it indicates several development directions on the large-scale application of FSW in aeroplane repairing.

An alternative management option for colonic atresia preventing loss of the ileocecal valve

Purpose Management of colonic atresia is contentious, with primary anastomosis having a notable risk of anastomotic leak. In addition, resection of the terminal ileum and ileocecal (i-c) valve is frequently performed, risking side effects such as diarrhea, vitamin B 12 deficiency, and gall stone formation. Methods The hospital coding system was searched for all patients with a diagnosis of colonic atresia between July 2005 and July 2008. Four term neonates were managed by formation of an ileostomy, a “blow hole” stoma just proximal to the atresia, and a mucus fistula distal to the atresia. Results Average time to full feeds was 7.5 days (range, 3-12 days), and average length of stay was 23 days (range, 13-47 days). Stoma management, problematic in 2 infants, was individualized by a specialist stoma nurse. Ileostomy output was refed into the mucus fistula. Complications included 3 episodes of prolapse of the blow hole stoma in infant 2. All of the infants returned to the operating theater at 1 to 3 months of age for restoration of bowel continuity and closure of the ileostomy. The atretic segment was resected, and an end-to-end anastomosis was performed. Recovery was straightforward in all cases. Conclusion A procedure that retains the i-c valve and most of the colon through creation of a blow hole stoma in the distended proximal colon with a diverting ileostomy and mucus fistula is described. The technique is recommended in selected infants as bowel length and anatomy can be preserved, despite the use of multiple stomas.

Heat Conduction and Thermal Stress Analyses of a Strip with Semi-Elliptical Notch Under Electric Current

An electric current is applied in a thin strip conductor with an edge crack or a semi-elliptical notch. The electric current gives rise to two states, i.e., uniform and uneven Joule heat. The Joule heat gives rise to the temperature, and thus the heat flux and also free thermal expansion. Using a rational mapping function, problems of the electrical current, the Joule heat, the temperature, the heat flux and the thermal stress are analyzed and their each solution is obtained as a closed form. The heat conduction problem is solved as a temperature boundary value problem. The distributions of the electric current, the Joule heat, the temperature, and the heat flux are shown in figures. After a free thermal expansion is obtained and a support condition is given, the stress components are calculated. The crack problems are analyzed for the problems of the electric current, joule heat, heat flux and stress. The expressions for intensity of the electric current, the heat flux and the Joule heat at the crack tip are derived. The exact expression of the temperature at the crack tip (notch tip) is also given. The notch problems are analyzed, and the approximate expressions of the concentration are given for each problem, of which error is a few percent. The relations between the electric current density and the melting temperature and between the electric current density and Joule heat are investigated for some crack lengths of aluminum strip. The intensity of the Joule heat relates to the creation of the blow hole.

Non-invasive Multidisciplinary Approach to the Study of Reproduction and Calf Development in Bottlenose Dolphin (Tursiops truncatus): The Rimini Delfinario Experience

Reproduction is a fundamental biological process that occurs only when all other vital needs are satisfied. In cetaceans reproduction takes place completely in water. From courtship and mating tocalf weaning, every step of the reproductive process occurs under the water’s surface. This complicates data acquisition in wild populations, making captive observations a useful complement to wild studies. By allowing close examination of phenomena, studies in captive environments are able to collect long-term data on known subjects, and sample, in detail, complete behavioural sequences while monitoring physiological or acoustic patterns. Studies of reproduction in bottlenose dolphins (Tursiops truncatus) were initiated at Rimini Delfinario (Italy) in 1995. Four bottlenose dolphin births (in 1995, 1997, 2003 and 2007) have occurred since the start of this research. Due to evidence suggesting that mother and calf associations are closest in the first year of the calf’s life, mothers and calves were studied from birth to the end of the first year. Beginning in 1997, studies encompassed the behaviour and physiology of dolphin mothers during gestation. Here, we report results of interdisciplinary studies of reproductive processes in bottlenose dolphins, including aspects of behaviour, physiology, endocrinology, and acoustics. In an effort to reduce the potential for bias brought about by invasive sampling, we investigated methods of sampling expired air from the dolphin’s blow hole as a means of monitoring steroid hormone levels. In summary, our research combines an interdisciplinary network with specialized professional alliances and offers a potentially crucial approach to the biological aspects of reproduction. At the same time, research findings presented here aim to help bridge the gap existing between captive and wild studies in favor of acommon aim of conservation biology.

Application of Computed Tomography in Manufacturing MetrologyAnwendung der Computer-Tomographie in der Fertigungsmesstechnik

Abstract Since the development of X-ray Computed Tomography (CT) and its rapid acceptance in medical diagnostics, it became not only a powerful tool for non-destructive testing but was also adopted in manufacturing metrology in the last decade. CT offers new possibilities for coordinate measurements as it is possible to acquire a volumetric model of the entire workpiece with a single measurement at which analyses known from coordinate metrology such as estimation of geometric features or nominal/actual value comparisons can be performed. But with data sets generated by tomographic measurements it is as well possible to analyze the entire volume of the workpiece, so detection and analysis of conventionally not accessible features like defects (flaws, blow holes, bubbles) or wall thickness analyses with uncertainties in the micrometer range are possible.

Total Quality Organization Thro’ People: 8-D Ate Thy Problems

Foundries provide bread and butter to the Foundrymen. If the butter gains-up unsaturated fats (defects), the health of a foundry may be threatened, and so on… impacting the people’s (Foundrymen’s) health too. The purpose of this paper is to look at the aberrations in the whole perspective of problem creation and problem solving and how a dedicated defect abatement process can be launched.The paper illustrates the Failure of a ‘Five Why’ process, and the use of a 5W-2H programme to analyse the defect case.The limitation for launching a Corrective Action (CA) to abate defects for once, Preventive Action (PA) to abate defects for all times, and subsequent necessity of a Global 8-D programme to use augmented competence is described, with the process map encompassing the journey from D1 to D8. The steps and their mandates describe that successful determination of due Escape points can continually equip the organisation for an ever increasing competency to defect abatement/Problem solving. Some examples of logical problems are exemplified, with special treatment to that of Blow Holes.

Structural and Chemical Comparison of Graphite and BN/AlN Caps Used for Annealing Ion Implanted SiC

The effectiveness of AlN/BN and graphite annealing caps for ion implanted SiC was examined morphologically, structurally, chemically, and electrically. The AlN/BN cap more effectively blocks the out-diffusion of silicon because it is essentially inert. Relatively small amounts of silicon from the SiC diffuse out into the graphite cap and react with it. This has the effect of lowering the Si vapor pressure so that it does not create blow holes in this relatively weak structure. The graphite cap can be removed easily with an oxygen plasma, while warm KOH has to be used to remove the nitride cap, and not all of it can be removed after an 1800°C anneal. The out-diffusion of silicon through the graphite cap is most severe at 1800°C, where it roughens the SiC surface and forms reaction products when the Si reacts with the graphite at a significant rate. At lower temperatures these reaction products form small particulates on the surface that are visible only at higher magnifications. In those regions where the graphite cap crystallized, isolated morphological damage on the SiC surface was also detected, appearing to be in the vicinity of the grain boundaries. Scratches on the substrate surface were not affected even at temperatures as high as 1800°C.

Shipboard measurements of the hearing of the white-beaked dolphin Lagenorhynchus albirostris

This is the first report of an underwater audiogram from a dolphin in a capture-and-release scenario. Two bow-riding white-beaked dolphins Lagenorhynchus albirostris (a female and a male) were captured using the hoop-net technique in Faxaflói Bay, Iceland. The dolphins were transferred to a stretcher and hoisted into a plastic research tank on board a small fishing vessel. Two underwater transducers were used to cover the frequency range from 16 to 215 kHz. Two human EEG electrodes mounted in suction cups, one placed near the blow hole and the other on the dorsal fin, picked up bioelectrical responses to acoustic stimuli. Responses to about 1000 sinusoidal amplitude modulated stimuli for each amplitude/frequency combination were averaged and analyzed using a fast Fourier transform to obtain an evoked auditory response. Threshold was defined as the zero crossing of the response using linear regression. Two threshold frequencies at 50 kHz and 64 kHz were obtained from the female. An audiogram ranging from 16 to 181 kHz was obtained from an adult male and showed the typical ;U' shaped curve for odontocetes. The thresholds for both white-beaks were comparable and demonstrated the most sensitive high frequency hearing of any known dolphin and were as sensitive as the harbor porpoise.

Effect of Process Parameters on the Solidification Time of Al-7%Si Alloy Castings Produced by VAEPC Process

Casting is a manufacturing route that is of fundamental importance in the processing of metals because of its ability to produce complex shapes cheaply. A recent development, the Evaporative Pattern Casting (EPC) process, holds the promise of revolutionizing the manufacture of castings, making the process even more economically attractive. One serious limitation of this process is blow holes in the castings. The blow holes and/or gas porosity in EPC castings is because of the non-escape of the gas produced as a result of burning of polystyrene pattern in the sand mold. The hybrid-casting process is developed to improve the quality of castings. The developed hybrid-casting process has been termed as Vacuum-Assisted Evaporative Pattern Casting (VAEPC) process. This aricle investigates the effect of process parameters like degree of vacuum, pouring temperature, grain fineness number, amplitude of vibration, and time of vibration on the solidification time of Al-7%Si alloy castings. In order to evaluate the effect of selected process parameters, the Response Surface Methodology (RSM) is used to formulate a mathematical model that correlates the independent process parameters with the desired solidification time. The central composite rotatable design has been used to conduct the experiments. The analysis of results indicates that the solidification time decreases with increase in the degree of vacuum, amplitude of vibration, and time of vibration. However, solidification time increases with increase in pouring temperature and grain fineness number.

Comparison of Graphite and BN/AlN Annealing Caps for Ion Implanted SiC

4H-SiC samples implanted with 1020 Al were annealed at various temperatures with a BN/AlN or graphite cap, and there morphological, structural, and electrical properties are compared. No blow holes were observed in either cap. Some Si out-diffuses through the graphite cap which results in a rougher surface and a structurally modified region near the surface. The BN/AlN cap annealed at 1800°C cannot be readily removed, whereas the graphite cap can be removed easily after any annealing temperature. The sheet resistances for both types of samples were about the same.

Effect of process parameters on impact strength of Al-7% Si alloy castings produced by VAEPC process

The castings produced by the evaporative pattern casting (EPC) process have blow holes. The blow holes in EPC castings are because of the non-escape of the gas produced as a result of burning of polystyrene pattern in the sand mold. To overcome the problem of blow holes, the EPC process is combined with the vacuum (V)- process. The vacuum applied to EPC mold draws the decomposed gases and improves the casting quality produced by the EPC process. The developed hybrid process has been termed as the vacuum assisted evaporative pattern casting (VAEPC) process. The objective of this paper to investigates the effect of process parameters, i.e, degree of vacuum, pouring temperature, grainfineness number, amplitude of vibration and time of vibration on the impact strength of Al-7% Si alloy castings in VAEPC process. In order to evaluate the effect of selected process parameters, the response surface methodology (RSM) is used to formulate a mathematical model which correlates the independent process parameters with the desired impact strength. The central composite rotatable design has been used to conduct the experiments. The results indicate that the impact strength decreases with increases in the grainfineness number and pouring temperature. Whereas, it has an inverse relationship with amplitude of vibration, time of vibration and degree of vacuum. The best value of impact strength (2.34 N/mm2) has been obtained at 400 mm Hg degree of vacuum imposed, 650°C as pouring temperature, 60 as sand grainfineness number, 460 μm as amplitude of vibration, and 70 s as time of vibration.

Evaluation with Surface Analysis Equipment, of Casting Defects in Cast Iron Articles (review)

Authors have reported theses concerning the cast defect for publication in journal of Japanese Foundry Engineering Society and AFS Transactions. This is a review of these reports. There are various factors in the casting defect that occurs in the article of casting metal, and specific of the generation factor is difficult. Moreover, it is necessary to decrease the casting defect to reduce the cost of goods manufactured and energy of production. It is effective to the evaluation and the classification method of the casting defect to employ Scanning Electron Microscopy with Energy Dispersion Spectrometer (SEM-EDS) and Electron Probe Micro-Analysis (EPMA). Casting defects chose the one that the incidence was high and specific of the generation factor is difficult, and the pinhole defect and inclusion defects were classified according to the generation factor, and penetration defect showed the relation of physical factor, chemical factor, and those interactions, and examined whether specific of the factor was possible by the surface analysis equipment about other defects (Blow hole, Shrinkage, Orange peel, Cold shut, Cracks and Veining).

0131 ピストン外観鋳巣検査技術の開発(G10-5 計測,G10 機械力学・計測制御)

The product appearance is presently most popularly inspected visually, but the visual inspection has problems of quality variations due to overlooking and difference of individual inspectors, and others, and an automated inspection has been waited. Therefore, recently, the appearance blow hole inspection technology has been established and put into practical use on the basis of the expanded depth of field and high-reliability image processing algorithm, and this report describes the technology.

フラクタル次元によるダイカスト内空洞欠陥評価

The pore defects inside die casting have an influence on the mechanical properties or air leakage efficiency of products. In these days, the classification of these pore defects is not clearly determined, and accurate measures to reduce these pore defects in the production field are carried out by trial-and-error processes. The accurate classification of pore defects leads to the accurate clarification of the direct cause of these defects. For this purpose, it is necessary to estimate pore defects quantitatively, instead of qualitatively. We propose the fractal dimension as the quantitative indicator of the classification of pore defects. In this study, we examined the fractal analysis of the shapes of “blow hole” and “shrinkage porosity”, and the validity of applying fractal dimensions to pore defects is investigated. The fractal dimensions for shapes of boundary lines for “blow hole” and “shrinkage porosity” are about 1.05~1.09 and about 1.15~1.17, respectively. Therefore, it is shown that the quantitative classification of “blow hole” and “shrinkage porosity” using fractal dimensions is definitely feasible.

Simulation of defects in aluminium castings using CAD models of flaws and real X-ray images

In order to evaluate the sensitivity of defect inspection systems, it is convenient to examine simulated data. This gives the possibility to tune the parameters of the inspection method and to test the performance of the system in cases where the detection is known to be difficult. In this paper, an interactive environment for the simulation of defects in radioscopic images of aluminium castings is presented. The approach simulates only the flaws and not the whole radioscopic image of the object under test. A manifold surface is used to model a flaw with complex geometry, which is projected and superimposed onto real radioscopic images of a homogeneous object according to the exponential attenuation law for X-rays. The new grey value of a pixel, where the 3D flaw is projected, depends only on four parameters: a) the grey value of the original X-ray image without flaw; b) the linear absorption coefficient of the examined material; c) the maximal thickness observable in the radioscopic image; and d) the length of the intersection of the 3D flaw with the modelled X-ray beam, that is projected into the pixel. The approach allows the user the simulation of complex flaws at any position of an aluminium casting. Simulation results of flaws like blow holes and cracks on X-ray images are shown and contrasted with real digital images with real flaws.

Mould filling simulation with consideration of surface tension and its application to a practical casting problem

An algorithm for mould filling simulation has been developed, based on the cubic interpolated propagation (CIP) method. In this study the surface tension was considered based on the continuum surface force (CSF) model, which is a typical model for treating surface tension as volume force. As an application to a practical casting problem, this scheme was applied to a die casting simulation and the numerical results compared with experimental data on the size and position of blow holes. Numerical results both with and without surface tension indicated the existence of blow holes. However, it was found that the simulation without surface tension tended to underestimate the size of blow holes. Through these numerical results, it is confirmed that the consideration of surface tension is very important for predicting the size and position of gas bubbles trapped in mould cavities. Furthermore, a criterion is proposed for estimating whether the gas remaining in mould cavities is compressed or expanded during mould filling. This criterion is applied to a practical die casting problem.

Some Engineering Countermeasures to Reduce Exposure to Welding Fumes and Gases Avoiding Occurrence of Blow Holes in Welded Material

Recently, open-type push-pull ventilation systems have been widely employed as effective substitutes for the conventional local exhaust ventilation system, and have prevailed at many welding workshops in Japan. In this study, the effect of the uniform velocity on carbon dioxide (CO2) shielding arc welding was examined by laboratory experiments. The ventilation system examined in the experiments successfully fulfilled the requirement for open-type push-pull ventilators prescribed in Japanese regulations (ordinances). It was proved that the velocity at any points in the capture zone fell in the range of 50 to 150% of the average capture zone velocity. Welding defects could be avoided by controlling the flow rate of shielding gas. Unless the capture velocity exceeded a 0.8 m/s, the formation of blow-holes in the welded metal could be prevented at the shielding gas flow rate of 20 L/min. If the flow rate was provided at 30 L/min and 40 L/min, blow-holes didn't form at the capture velocity of 1.2 m/s and 1.6 m/s, respectively. At a capture velocity of faster than 0.3 m/s, the fume concentration at welder's breathing zone was reduced to a level below the limit values: ACGIH (TLV) and Japan Welding Engineering Society (CLV#). These data are important for designing open-type push-pull ventilation in the welding workshop. The other engineering countermeasures currently employed in the welding work in Japan, such as fume collecting torch and general ventilation, are also concerned in this report. #: Control Limit Value.

노치변형률법을 적용한 용접구조상세의 피로수명평가

An evaluation of fatigue life of welded components is complicated due to various geometrically complex welding details and stress raisers in vicinity of weld beads, ego under cuts, overlaps and blow holes. These factors have a considerable influence on the fatigue strength of welded joints, as well as the welding residual stress which is relaxed depending on the distribution of local stress at the front of the stress raisers. To reasonably evaluate fatigue life, the effect of geometries and welding residual stress should be taken into account. The several methods based on the notch strain approach have been proposed in order to accomplish this. These methods, however, result in differences between analytical and experimental results due to discrepancies in estimated amount of relaxed welding residual stress present. In this paper, an approach that involves the use of a modified notch strain approach considering geometrical effects and a residual stress relaxation model based on experimental results was proposed. The fatigue life for five types of representative welding details, ego cruciform, cover plate, longitudinal stiffener, gusset and side attachment joint, are evaluated using this method.<br/>

Influence of surface preparation and process parameters on the porosity generation in aluminum alloys

The 4 kW cw Nd:yttrium–aluminum–garnet laser welding of solid solution hardened A5083 (5% Mg) and precipitation-hardened A356 (7% Si) alloys, sensitive to porosity formation was carried out at different welding speeds, under He gas shielding, and for partial penetration conditions, on bead on plate configuration. The porosity formation was examined through observation and evaluation of weld beads, based on x-ray radiography inspection coupled with image analysis, and quantification of gas volume percentage by densitometry. The results show that both surface preparation and dual-beam configuration can have a beneficial effect on the porosity content: (1) After polishing, laser cleaning, sand blasting, or degreasing of the surface, hydrogen and oxygen sources are decreased or removed. The resulting effect is a reduction from 15% to less than 2% of the porosity rate on A356 alloy, with better results, in the case of laser cleaning. (2) The use of dual beam conditions ensures a larger weld pool, facilitates the porosity’s ejection, and stabilizes the keyhole as compared with single beam configurations. For instance, a longitudinal bi-spot configuration reduces the porosity rate from 15% to less than 0.5% on A356 alloy. In A5083 welds, most of the macroporosities remain in the beads, due to an unstable keyhole (Mg vapors) which can collapse and entrap millimeter-like blow holes.