Blow Holes Research Articles

Dolphins are exhalation champs

Every air-breathing marine mammal faces a multitude of challenges as it dives beneath the waves: carbon dioxide and nitrogen accumulation in the blood can cause unconsciousness, intoxication and decompression sickness, while low internal pressures in rigid lungs can force blood into the delicate airways. Yet, whales, dolphins and seals rarely seem to suffer these ill effects. Andreas Fahlman from Texas A&M University – Corpus Christi, USA, says, ‘It had been assumed that the respiratory systems of all marine mammals are similar, with a stiff upper airway and collapsible lungs’. However, there was little evidence to support the assumption and Fahlman was repeatedly told that the measurements couldn't be made for various reasons, including the incredibly high flow rates generated by exhaling dolphins.That was until Fahlman met Micah Brodsky, a consultant and wildlife veterinarian with an interest in mechanical engineering. Brodsky decided to take on the challenge of designing a small and portable pneumotachometer (air flow meter) that could be used to measure flows in excess of 200 l s−1 in less than 100 ms and would survive corrosive salt water. After 9 months of development with the help of Trevor Austin, and knowing that the preliminary measurements couldn't be made in the wild, Fahlman and Brodsky travelled to Dolphin Quest Oahu, to work with bottlenose dolphins. Fahlman recalls that the sympathetic relationship between the dolphins and their trainers, led by Julie Rocho-Levine, was also essential for their success. However, even though the dolphins were trained to respond to their trainers’ directions, they only participated voluntarily, ‘Which allowed us to test important physiological variables with no stress to the animals’, says Fahlman.Gently placing the pneumotachometer over each dolphin's blow hole as it waited patiently in the water, Fahlman, Brodsky and Greg Levine measured the airway pressures and airflows as the animals breathed normally and heavily. They were impressed to see that the dolphins could inhale at flow rates of up to 33.4 l s−1; however, when they measured the flow rate as the dolphins exhaled, they were astonished to register flows of up to 137.6 l s−1. ‘The cetaceans are the true champions of respiratory physiology’, says Fahlman, putting the dolphins’ performance into context by saying, ‘The maximal flow rates are at least twice, and probably three times, higher than those in the terrestrial champion, the horse’. And when the team analysed the airflows, they realised that the animals could exchange almost all of the air in their lungs in a single breath: ‘Their vital capacity is very high’, says Fahlman.Next, Fahlman and Steven Loring tested how rigid the dolphins’ lungs were by calculating their compliance, and they were delighted to confirm Per Scholander's 70 year old hypothesis that the lungs are compressible: rigid human lungs register a compliance of 0.08 cmH2O−1 while the dolphins’ compressible lungs had a compliance of 0.31 cmH2O−1. Fahlman also measured the amount of oxygen that the animals inhaled and exhaled and the carbon dioxide produced to calculate the animals’ metabolic rates on a breath-by-breath basis. He explains that measurements like this could directly impact dolphin health. ‘Lung function testing may be a novel way to investigate respiratory health of cetaceans under human care and we may be able to provide real-time information about oxygenation state and how animals are doing during a mass-stranding to help save animals’, says Fahlman.So, having overcome many technical challenges and measured the immense airflows generated by breathing dolphins, Fahlman is keen to study other cetaceans to learn more about their respiratory physiology and the effects of beaching on stranded animals.

Minimizing of Rejection in Cylinder Head Machining Using the Anova Method

The main rejections in the machining sections are exhaust valve port leak, injector bore blow hole, induction passage punchered, inlet valve port leak, top face unwash, valve guide hole blow hole, top face leak, joint face unwash, induction face unwash, rear face unwash, valve port unwash, water mixing with oil., water passage blocked, emf leak, injector bore leak, inlet valve port blocked, water way leak, oil way leak and defective jig location pad. This paper describes the method by which the rejections while maching the cylinder head, is minimized.

Effects of welding parameters on fibre laser lap weldability of galvanised DP1000 steel

A 1000 MPa galvanised dual phase steel was fibre laser lap welded by different welding parameters. The surface appearance, cross-section macrostructure and tensile shear properties of laser lap welds were evaluated. The different methods for improving the laser lap weldability of galvanised steel were analysed. The results showed that the increasing laser power resulted in the formation of the keyhole, which could be used as the escape route for the vapourised zinc formed at the faying surface. Therefore, the weld defects, such as spatter, cavity and blow hole, were eliminated, and the full penetrated laser lap welds with smooth surface appearances were acquired. A proper joint gap also worked as the escape route for the zinc vapour and led to the formation of sound welds. Adding proper preheating procedures improved the mechanical properties of the welds to some degree, but weld defects still existed owing to the residual zinc.

High-cycle Fatigue Properties of Alloy718 Base Metal and Electron Beam Welded Joint

High-cycle fatigue properties of Alloy 718 plate and its electron beam (EB) welded joint were investigated at 293K and 77K under uniaxial loading. At 293K, the high-cycle fatigue strength of the EB welded joint with the post heat treatment exhibited somewhat lower values than that of the base metal. The fatigue strengths of both samples basically increased at 77K. However, in longer life region, the EB welded joint fractured from a blow hole formed in the welded zone, resulting in almost the same fatigue strength at 107 cycles as that at 293K.

A sparse-representation-based robust inspection system for hidden defects classification in casting components

In this paper, a robust sparse-representation-based inspection system for the detection and classification of casting hidden defects in radiographs is presented. Four common types of casting defects including cracks, blow holes, shrinkage porosities and shrinkage cavities are considered in our system. In the framework, a Gray Arranging Pairs (GAP) based segmentation method is implemented firstly. This method can deal with the case of casting that has complex structure well and is robust against non-uniform illumination variations and noise. Second, a Randomly Distributed Triangle (RDT) feature is extracted to represent the geometric characteristic of each defect. This feature uses random triangle samplings which are formed from the defect shape to produce a continuous probability distribution. It is simple and can discriminate defects correctly despite of rotation, scale and noise. Third, a Sparse Representation-based Classification (SRC) is trained to classify each of the input defect into one of the classes. The performance of the proposed method is shown in the experiment by comparing with the SVM classifier.

Analysis of Laser Weldments for Dual-Phase and Martensitic Steel Sheets for Automotive Applications

Laser weldability was investigated for advanced high-strength steel sheets for automotive applications. Dual-phase steel (DP780) and martensitic steel (MS1300) sheets were employed as base materials; laser-butt and overlap welding experiments were conducted on combinations of steels with similar and dissimilar strength. The tensile strength and metallurgical morphology were analysed for the butt-welded specimens; tensile-shear strength and bead shapes were analysed for the overlap-welded specimens. Even with laser welding, martensite in the heat-affected zone disintegrated and resulted in a softened, heat-affected zone as compared with the base materials. The tensile strength of a butt weldment was determined by the strength of the heat-affected zone. The tensile-shear strength of an overlap weldment was determined by not only the strength of the heat-affected zone but also bead shapes such as blow holes, underfill, and the bead width at the faying surface.

3D-Braided Thick Composites Made by Simultaneous Outside-in and Inside-out Resin Infusion

Thick composites made with traditional impregnation and with simultaneous resin infusion from the inside and outside were studied to compare two methods for optimizing permeability, dipping time, and structural organization. Permeability was greater, the dipping time was shorter, the impregnated resin was more uniformly distributed, and blow hole defects were fewer when infusion was performed simultaneously from the inside and outside of the braided structure. The resin flow channel was preset in the precast body, allowing simultaneous outside-in and inside-out dipping.

Blow Holes - A Surgical Artefact

Post-mortem artefacts are commonly encountered in forensic practice. They are sometimes very confusing for forensic experts to interpret and wrong interpretation may mislead the course of justice. A case is presented where a patient developed severe subcutaneous emphysema after a road traffic accident and was treated with multiple subcutaneous bilateral blowhole incision on the chest and upper part of abdomen. Confusion arose on autopsy about injuries whether they were therapeutic or homicidal in origin.

Process Parameter Settings for Core Shooter Machine by Taguchi Approach

Most of the castings are produced by sand moulding method, but due to many factors involved in casting process defects like blow holes and sand drops are generally observed. The factors like resin content, priming time, gassing time and purging time are responsible for blow holes due to more gas evolution in core's produced by core shooter machine. Whereas, factors like Fresh sand percentage in moulding sand, compaction pressure and resin in no bake core are responsible for sand drop in castings. Before the completion of this project, factor levels for producing cold box cores and no bake cores are set on trial basis. The experimental and analysis work of this dissertation aims at applying “Taguchi” technique to identify the major factors involved in the core shooter machine which produces cold box core's and determine their optimum level in turn to obtain consistently good quality casting's by with minimum gas evolution of cold box core's.

질화처리된 저탄소강 레이저 용접부의 기공 감소

Gas nitriding is a surface hardening process where nitrogen is introduced into the surface of a ferrous alloy. During fusion welding of nitrided carbon steel, the nitride inside weld metal is dissolved and generates nitrogen gas, which causes porosities - blow holes and pits. In this study, several laser welding processes such as weaving welding, two-pass welding, dual beam welding and laser-arc hybrid welding were investigated to elongate the weld pool to enhance nitrogen gas evacuation. The surface pits were successfully eliminated with elongated weld pool. However blowholes inside the weld metal were effective reduced but not fully disappeared.

Obfuscation Does Not Provide Comfort

Obfuscation Does Not Provide Comfort

Investigations on Activated Charcoal, a Burn-Rate Enhancer in Composite Solid Propellant

Through careful experimentation, this paper establishes that moisture trapped inside the pores of activated charcoal was the reason for the burn-rate enhancement of composite solid propellant observed in literature. This paper demonstrates that, even with the presence of moisture in activated charcoal, the propellants can not only be cured to be free from blow holes and voids but also have good mechanical properties. Experiments were also carried out to examine the possible mechanism for high burn rates and burn-rate pressure index observed in composite propellants when moisture was present in activated charcoal. Scanning-electron-microscope images show that moisture in activated charcoal reduces the binder melt flow. It is noticed that formation of the bubbly layer is more when moisture is present in the binder. This bubbly layer might be exploding near the surface of the propellant and taking away the binder melt layer. This could be the cause for the observed increase in the burn rate and burn-rate pressure index of aluminized composite propellants.

Material Properties of Cast Aluminium Alloys Produced by Various Casting Processes

The material and mechanical properties of cast aluminium alloys, produced using various casting technologies, have been investigated experimentally. In this study, several casting processes were selected, including gravity casting (GC), cold-chamber diecasting (CD), hot-chamber diecasting (HD), squeeze diecasting (SQ), twin rolled continuous casting (TRC) and heated mould continuous casting (HMC). Although all cast samples were made of the same aluminium alloy of Al-Si-Cu (ADC12), different material properties were obtained, in particular microstructural characteristics, crystal orientation and residual stress. In this instance, the microstructures of the GC and CD samples were formed mainly of coarse α-Al phase and needle-shaped eutectic structures; and a microstructure of fine round grain and tiny eutectic structures were observed for the HC, TRC and HMC samples. On the other hand, spherical shaped α-Al phase with a relatively large size was detected in SQ. The different microstructural characteristics led to different mechanical properties. A uniformly orientated lattice structure was detected in the HMC and SQ samples, which gave high material ductility. High internal compressive stress high dislocation density, arising from the rolling process, led to the high tensile properties for the TRC procedure. Various cast defects, such as blow holes and shrinkage porosity, were detected in GC and CD, which gave a reduction in their tensile properties.

Multi-Objective Optimization of Green Sand Mould System Parameters using Particle Swarm Optimization

This paper deals with multi-objective optimization of green sand mould system using Particle Swarm Optimization (PSO). It is important to note that the quality of cast products in green sand moulds is largely influenced by the mould properties (that is, responses), such as green compression strength, permeability, hardness and bulk density, which depend on the input (process) parameters (that is, grain fineness number, % clay, % water and number of strokes). In this study, non-linear regression equations developed between the control factors (process parameters) and responses have been considered for optimization utilizing PSO. An attempt is being made to form a single objective, after considering all the four individual objectives, to obtain a compromise solution, which satisfies all the four objectives. The results of this study show a good agreement with the experimental results The quality of the parts produced during moulding process depends on the properties (that is, green compression strength, permeability, hardness and bulk density) of moulding sand. It is important to note that improper levels of these properties leads to common casting defects, such as blow holes, pinhole porosity, poor surface finish, dimensional variation, scabs and rat tails, misruns etc. The properties of the mould are influenced by a large number of controllable parameters (that is, grain fineness number, % clay, % water and number of strokes). Hence, it is important to identify the levels of the input variables that provide required mould properties, which improves the quality of the parts produced by this mould. During 1960s and 70s, most of the research work on moulding sand was based on experimental and theoretical approaches. In [1], the relationship between permeability and transformation zones, mould pressure, void space control, etc., was developed through substantial mathematical equations. In addition to this, Frost and Hiller [2] established the pressure and hardness distributions in sand moulds. Later on, Wenninger [3] utilized the rigid water theory to explain sand-clay-water relationships. This approach was completely theoretical and not supported by a large number of experiments. Later on, statistical design of experiments (DOE) had been used by various investigators to study the effects of different variables on the green sand mould properties. In [4] Design of Experiments (DOE) technique was applied to study the effect of process variables on bulk density and green compression strength. Moreover, Casalino et al. [5] utilized Taguchi technique to establish third order model for permeability and compression strength in laser sintered sand moulds. Moreover, Parappagoudar et al. [6,7] developed linear and non-linear statistical models utilizing full factorial DOE, Central Composite Design (CCD) and Box-Bhenken design. In the above work, the authors had considered grain fineness number, % of clay, % of water and number of strokes as input parameters and green compression strength, permeability, hardness and bulk density as the responses. Among the non-linear regression equations developed by the above mentioned three approaches, CCD-based model was found to be the more accurate model for prediction of the responses. Optimization techniques are required to identify the optimal combination of parameters for achieving the desired performance of the green sand mould system. In single objective optimization, one attempts to obtain the best design or decision, which is usually the global maximum or minimum depending on the optimization problem. In green sand mould system, it is difficult to find a single optimal combination of parameters for green compression strength,

Technology Study of Thin-Walled Frame Used in XX Inertial Navigation System Casted by Differential Pressure Casting

Frame used in XX inertial navigation system has such characters as small scale, thin wall, complicated shape, etc. When it is casted by gravity casting, the defects such as shrinkage, porosity and blow holes are so many that the survival ratio is very low. In this paper, a new differential pressure casting method is designed to cast the frame by realizing self-hardening sand moulding, solving series of problems such as liquid rising pipe freezing and chemical composition being out of range, thus improving the quality of the cast.

Role of Heat Treatment on Al6061- Frit Particulate Composites

In recent decades, aluminium alloy based metal matrix composites are used in several applications. Al6061 has been used as matrix material due to its good formability, excellent mechanical properties and etc., wide spectrum of the applications in industrial sectors. Inclusion of Frit particulates as reinforcement in Al6061 alloy material system improves its hardness and decrease in density. In the present investigation Al6061-Frit particulate composites were produced by ‘VORTEX’ method with varying weight percentages of Frit particulate from 0 wt% to 10 wt% in steps of 2.The as cast matrix alloy and its composites have been subjected to solutionizing treatment at a temperature of 530℃ for 2 hours followed by quenching in different media such as air, water and ice. The quenched specimens were subjected to artificial ageing. Aged specimens were subjected to ultra-sonic test using ultra-sonic flaw detector testing apparatus to identify the common casting defects like porosity, blow holes. Macrostructure and microstructure studies were conducted on as cast and composites in order to investigate the distribution of frit particles retained in matrix material system. Micro structural studies were carried out to understand nature of structure. Density measurement was carried out on both Al6061matrix alloy and Al6061-Frit particulate composite. Hardness tests have been conducted both on Al6061 matrix alloy and Al6061-Frit particulate composite before and after heat treatment. It has been observed under identical heat treatment conditions adopted, Al6061-Frit particulate composites exhibited significant improvement in hardness when compared with Al6061 alloy.

Geometrical Design and Investigation of a New Profile of the Three Screw Pump

This paper presents a new edge blunting method of the three screw pump rotor with an elliptic arc and equations of the rotor profile after edge blunting. Through comparisons of different geometrical parameters of the pump, i.e., flow area, contact line length per lobe, blow hole area, etc., the new profile is proved to be better than the existing profiles of the three screw pump. The new streamlined profile, with a significantly smaller blow hole area, is of reference significance for the optimization design and further improvement of three screw pump.

CO 2 laser-micro plasma arc hybrid welding for galvanized steel sheets

A laser lap welding process for zinc-coated steel has a well-known unsolved problem-porosity formation. The boiling temperature of coated zinc is lower than the melting temperature of the base metal, which is steel. In the autogenous laser welding, the zinc vapor generates from the lapped surfaces expels the molten pool and the expulsion causes numerous weld defects, such as spatters and blow holes on the weld surface and porosity inside the welds. The laser-arc hybrid welding was suggested as an alternative method for the laser lap welding because the arc can preheat or post-heat the weldment according to the arrangement of the laser beam and the arc. CO 2 laser-micro plasma hybrid welding was applied to the lap welding of zinc-coated steel with zero-gap. The relationships among the weld quality and process parameters of the laser-arc arrangement, and the laser-arc interspacing distance and arc current were investigated using a full-factorial experimental design. The effect of laser-arc arrangement is dominant because the leading plasma arc partially melts the upper steel sheets and vaporizes or oxidizes the coated zinc on the lapped surfaces. Compared with the result from the laser-TIG hybrid welding, the heat input from arc can be reduced by 40%.

Effects of Defects on Fatigue Strength of Aluminum Cast Alloys (AC4CH) and Evaluation of Fatigue Limit

The effects of H 2 gas content on fatigue strength of aluminum cast alloys (AC4CH) and improvement by atmosphric pressure casting, 1 MPa pressure casting and 773 K-100 MPa HIP treatment were investigated from the veiwpoint of defects, a method for evaluating the conservative fatigue limit was proposed. The main results obtained were ; (1) 1 MPa pressure casting and HIP treatment were effective in improving the fatigue limit of AC4CH, because the defect size in 1 MPa pressure casting and HIP treatment is smaller than that in atmospheric pressure casting. (2) The fracture origin proceeds from microshrinkage to adjoining blow holes as H 2 gas content increases, but the size of each blow hole is the same as that of the microshrinkage. Consequently, H 2 gas content has little effect on fatigue strength. (3) The conservative fatigue limit of aluminum cast alloys can be evaluated by substituting √area max estimated by extreme statistics in the following equation. σ w =α.σ B /(√area max ) 0.161

MODELAGEM DA FORMAÇÃO DE POROSIDADES NA SOLIDIFICAÇÃO DE TARUGOS PELO PROGRAMA THERMO-CALC

Blow and pin holes are the most common defects in open cast billet production. It is a cause of significant rolling mill scrap due to the incidence of cracks on end product. Many causes are pointed out as sources of these defects. However, few papers has studied their formation based on measured values of H, N e O gases in liquid steel and estimated ones at solidification front. The influence of several process variables are investigated in this paper, mainly those factors related to the amount of H in steel. Heats using sintering synthetic slags and conventional slags are compared. It is developed a blow - pin holes prediction model based on the chemical composition and gases, through Thermo-calc program. The model results are compared to literature ones and experimental data. The Thermo-Calc results are used to be possible, in real time, adjust the process and avoid the appearance of these defects.