25 research outputs found
Secondary Processing of Aramid With Awj and Optimization With Nsga-Iii
No full textThe secondary operations of composite parts are performed following thermal cure processes, which generate the final dimensions with desired tolerance and quality specifications. High-strength composites, on the other hand, especially aramid fiber-reinforced polymers (AFRP), are not suitable for conventional machining operations due in part to high operational costs and limited surface quality characterized by fuzziness and delamination. Abrasive Water Jet (AWJ) has been recently shown promising results in obtaining improved surface quality while ensuring significant cost advantages. This study investigates the AWJ processing of AFRP by implementing the analysis of variance and response surface methods. The effects of the control parameters (sand ratio, pressure, stand-off-distance, and feed rate) on the surface quality metrics (surface roughness, kerf angle, and dimensional error) are identified and comparatively evaluated. The surface quality of the AWJ processed AFRP specimens are investigated using Scanning Electron Microscopy (SEM). The trade-offs between the measured tolerances and surface roughness values are identified via a new genetic algorithm approach: Non-dominated Sorting Genetic Algorithm (NSGA-III). Also, operation regions are determined using the generated Pareto curves while improving the quality of various features of an AFRP component, critical to its functional performance during extended service life. As a result, the lowest Ra values obtained were 4.135 mu m for trimming, 5.962 mu m for pocketing, and 4.696 mu m for the hole-making operation. The maximum error in the accuracy of operating regions yields to 7% with independent measurements for validation.Turkiye Bilimsel ve Teknolojik Arastirma Kurumu [118M027]The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the Turkiye Bilimsel ve Teknolojik Arastirma Kurumu, (grant number 118M027)
Performance Enhancement of Abrasive Waterjet Cutting
No full textAbrasive Waterjet (AWJ) Machining is a recent non-traditional machining process. This technology is widely used in industry for cutting difficult-to-machine-materials, milling slots, polishing hard materials etc. AWJ machining has many advantages, e.g. it can cut net-shape parts, no heat is generated during the cutting process, it is particularly environmentally friendly as it is clean and it does not create dust. Although AWJ machining has many advantages, a big disadvantage of this technology is its relatively high cutting cost. Consequently, the reduction of the machining cost and the increase of the profit rate are big challenges in AWJ technology. To reduce the total cutting cost as well as to increase the profit rate, this research focuses on performance enhancement of AWJ cutting with two possible solutions including optimization in the cutting process and abrasive recycling. The first solution to enhance the AWJ cutting performance is the optimization of the AWJ cutting process. As a precondition, it is necessary to have a cutting process model for optimization. In order to use that model for this purpose, several important requirements are given. The most important requirement for such a model is that it can describe the âoptimum relationâ between the optimum abrasive mass flow rate and the maximum depth of cut. To develop a cutting process model which can be used for the AWJ optimization, many available models have been analyzed. Since the most important requirement for a process model (see above) can be obtained from Hoogstrate's model, an extension of this model is carried out. The extension model consists of three sub-models including pure waterjet model, abrasive waterjet model and abrasive-work material interaction model. The extension cutting process model is more accurate than the original one and it is capable to optimize AWJ systems. The influence of many process parameters, the work materials, the abrasive type and size have been taken into account. Up to now, there has not been a model for the prediction of AWJ nozzle wear. Therefore, modeling the nozzle wear rate has been carried out and a model for the wear rate of nozzles made from composite carbide has been proposed. Based on the extension cutting process model, two types of optimization applications have been carried out. They are related to technical problems and economical problems. From the results of these problems, regression models for determining the optimum nozzle exchange diameter and the optimum abrasive mass flow rate for various objectives have been proposed. The other solution to enhance the cutting performance is abrasive recycling. In this study, GMA garnet, the most popular abrasives for blast cleaning and waterjet cutting, has been chosen for the investigation. The recycling of GMA abrasives has been investigated on both technical side and economical side. On the technical side, the reusability and the cutting performance of the recycled and recharged abrasives have been analysed. The influence of the recycled and recharged abrasives on the cutting quality was studied. On the economical side, first, the prediction of the cost of recycled and recharged abrasives was done. Then, the economic comparisons for selecting abrasives have been carried out. In addition, the economics of cutting with recycled and recharged abrasives have been studied. Several suggestions for an abrasive recycling process which promises a more effective use of the grains have been proposed. By optimization in the cutting process and by abrasive recycling, the cutting performance can be increased, the total cutting cost can be reduced, and the profit rate can be enlarged considerably. Consequently, the performance of AWJ cutting can be enhanced significantly.Civil Engineering and Geoscience
Highway Code (Manchester 10k)
No full textHighway Code (Manchester 10k) is a short artists’ film centring around an urban area of Manchester during and after the annual 10km public run. The project investigates how rhythms of the city (such as traffic light signals) can be utilised in determining the rhythmic structure of the film, by tracing these rhythms onto the edit of the film. The film develops methods of editing, collaging and montaging differing views of place that utilise the rhythms of the city in order to realise this effect. Through this use of the city’s rhythms, in combination with the editing process, the city can be seen to partially determine the structure of the film and, to an extent, co-author or contribute to the work
Development and evaluation of ultra high pressure waterjet cutting
No full textAbrasive waterjet (AWJ) cutting is a machining process to cut wide range of materials from soft materials such as rubber, leather to hard materials such as metals by means of a high-velocity slurry jet, formed as a result of injecting abrasive particles into a waterjet. The machining action is the result of these particles impacting against a workpiece with a high velocity. Conventional AWJ equipments generate water pressures up to 400 MPa (=4000 bar = 58000 psi) and use orifices whose diameters are in the range of 0.08 mm to 1 mm to generate plain waterjet. The abrasive particles of sizes 0.07 mm to 0.36 mm in diameter entrain to the jet former with air and mix with the waterjet in the mixing chamber to form the three phase slurry jet. The abrasive particles are accelerated and focused in the focusing tube. The width of the focusing tube determines the cutting width which is in the range of 0.5 mm to 1.5 mm in diameter. This study investigates the applicability and the performance of waterjet (WJ) and AWJcutting process beyond 400 MPa water pressure, which is called ultra-high pressures during the study. One of the objectives is to expand the application domain of the process. With higher water pressure, plain WJ is capable of cutting harder materials and it is possible to cut intricate details with AWJ due to the availability of high energy density with small orifices. Moreover, reduction in cutting costs is expected as a result of higher feed speeds or reduced abrasive consumption. The initial focus of the research is to provide guidelines to develop a reliable AWJ cutting system above 400 MPa. It was shown that the plastic deformation takes place at the thick walled cylinders subjected to internal pressure of more than 700 MPa with the current types of materials that are generally used in high pressure components. Therefore, imposing compressive residual stress to the bore of the cylinder is necessary for the parts such as high pressure intensifier cylinder where plastic deformation is unacceptable. Autofrettage and multi layer construction are the two techniques to create residual stresses in the cylinder. An optimum autofrettage pressure exists due to the Bauschinger effect. Therefore, a multi layer cylinder construction provides cylinders with higher pressure capacity. A simplified model for predicting the pressure output for double acting pressure intensifiers is presented after the design considerations for thick walled cylinders in order to estimate the required attenuator volume and the high pressure cylinder dimensions to limit the pressure fluctuations. The model is in good agreement with the pressure measurements. The energy conversions and the related efficiencies during the AWJ formation process provide a perspective to the performance of the process. Energy density of the plain and abrasive waterjet is defined to correlate with the cutting performance. Reducing the focusing tube diameter and increasing the water pressure are the most beneficial methods to increase the energy density. Other methods such as increasing the orifice diameter or reducing the feed speed are in conflict with cutting intricate details and economical considerations. With the insight gained at the previous step, the performances of plain and abrasive waterjet are evaluated. The increase in pressure results in a more scattered jet. A diverted jet generates wider cuts with wider damaged zones and rounded edges in WJ cutting. In AWJ cutting, it accelerates the wear of the entry region of the focusing nozzle. The experiments show that the length and diameter of upstream tube play an important role in jet quality. The turbulences in the flow are reduced in the upstream tube. It should be sufficiently large to make the flow laminar. Moreover, when the streamlines are guided towards the orifice with a conical seal, the resultant jet disintegrates later. After the quality of the jet is ensured, the cutting performance tests are conducted. The maximum feed rate increases more than the hydraulic power of the waterjet which shows that increasing the pressure leads to a more power efficient process. Moreover, at the same hydraulic power, the smaller jets perform better. On the other hand, the increase in depth of cut with pressure is directly proportional with the hydraulic power. It is proposed that the depth of cut is directly proportional with the energy density of the jet. However, at the low feed rates the relation is no longer linear. Therefore, the feed rate term of the energy density equation is modified to predict the depth of cut. Due to the cutting mechanism of the plain waterjet, the surface quality is poor with burrs in the case of metals and fiber damages in the case of composite materials. Therefore, plain waterjet cutting is suitable for separating instead of precision cutting of metal sheets and composites. The mixing and acceleration of the particles with a waterjet determine the cutting ability of AWJ. It becomes less efficient at high abrasive loads. The momentum from the plain waterjet to the abrasives transfers more efficient with the increase in pressure at the same abrasive load ratio. The efficiency of power transferred from the water to the abrasives decreases when the abrasive load ratio exceeds 0.3 for low focusing tube to orifice diameter (df / do) ratios and 0.4 for high df /do ratio. The optimum abrasive flow rate does not depend on pressure. As it was in the plain waterjet, the energy density of the jet correlates well with the cutting ability of the jet. The linear relation between these parameters becomes non-linear at high energy densities due to the increased energy losses at longer traveling lengths through the material at higher depths of cut. The final consideration of this study is the economical aspects of ultra-high pressure AWJ cutting. The cost advantage depends on the increase of the cost of the pump, the maintenance and the life of the consumables with the pressure increase. The pressure increase is cost effective if the investment costs and maintenance costs are below certain values. If several engineering issues such as the lifetimes of the critical components and the availability of wear resistant sufficiently long focusing tubes are solved, the ultra-high abrasive waterjet cutting can be implemented successfully to industrial applications.PMAMechanical, Maritime and Materials Engineerin
An experimental study on abrasive waterjet cutting of CFRP/Ti6Al4V stacks for drilling operations
No full textPublisher Copyright: © 2015, The Author(s).In the present study, CFRP/Ti6Al4V stacks were machined with abrasive water jet using different process parameters in order evaluate the viability of AWJ industrial application as a substitute of conventional drilling. The effect of the stack configuration, the traverse feed rate, the cutting tool (combination of orifice and focusing tube diameter and abrasive mass flow rate), and the pressure over the kerf profile, taper angle, and surface roughness has been analyzed through an ANOVA analysis and related to the physical parameters of the AWJ process. As a result, a positive taper angle is observed in Ti6Al4V while a negative is observed in CFRP in almost all cutting conditions. This leads to obtain an X-type or barrel-type kerf profile depending on the stack configuration. In addition, the surface roughness can be as low as 6.5 μm in both CFRP and Ti6Al4V materials at 95 mm/min when CFRP/Ti6Al4V configuration is used.Peer reviewe
Abrasive Waterjet Machining of Engineering Materials
No full textPREFACE:
The manufacturing industry is getting more and more time conscious in the global economy, and the requirement for prototyping and small production batch is increasing. This trend has placed a need for the use of new and advanced technologies to quickly turn the raw materials into useable goods with no time required for tooling. The need for advanced processing technologies is particularly evident for machining advanced materials, such as ceramics and composites, and thermal sensitive materials that find extensive applications and are considered as “difficult-to-machine” by the conventional machining technologies such as the turning and milling processes. Abrasive waterjet (AWJ) machining is found to be one of the advanced technologies that meet these processing requirements due to its various distinct advantages over the other machining technologies.
As a relatively new machining process, the AWJ cutting technology is still under flux and development. A large amount of research and development effort has been made to explore its scientific aspects, extend its application domain, and develop new cutting techniques to enhance its cutting performance and the strategies for optimizing the process parameters when machining various engineering materials. This book is an account for these aspects of research and essentially draws from the author’s work.
The emphasis of this book is placed on the practical applications of the AWJ machining technology and it contains sufficient details of the fundamental or scientific aspects. It provides a detailed analysis of the effects of the major process parameters on the cutting performance when machining some typical engineering materials as well as the novel cutting techniques for enhancing the cutting performance of this technology. Following a brief introductory chapter is a review on the fundamentals of the AWJ machining process including the material erosion mechanisms and the predictive machining performance models. The jet dynamic characteristics are then described based on a simulation study, which forms the fundamental basis for the understanding of the contents in the rest of the book. This is followed by the chapters on the cutting of some representative engineering materials in both straight-slit cutting and contouring. A critical analysis is then given of the mechanisms of surface striation formation and the various factors that result in the surface striations in AWJ machining. The book is ended with the description of the various techniques that can effectively enhance the cutting performance of AWJ machining.
The topics covered merely reflect the purpose of this book and some of the author’s research interests, and do not mean that other aspects are less important. Also the author has not attempted to made review on the large amount of work undertaken by others, and only that closely related to this book is referred to. The book is relevant to researchers as well as postgraduates and final year undergraduates specializing in manufacturing processes. It should also be found particularly useful for industrial practitioners in material processing who are responsible for making the AWJ machining process more efficient.
The author wishes to express his sincere gratitude to his students for their contributions to the work. He also wishes to thank his friends and colleagues, Professor Elias Siores and Dr Frank Chen, for their long-term research collaboration
Revised model of abrasive water jet cutting for industrial use
No full textResearch performed by the author in the last decade led him to a revision of his older analytical models used for a description and evaluation of abrasive water jet (AWJ) cutting. The review has shown that the power of 1.5 selected for the traverse speed thirty years ago was influenced by the precision of measuring devices. Therefore, the correlation of results calculated from a theoretical model with the results of experiments performed then led to an increasing of the traverse speed exponent above the value derived from the theoretical base. Contemporary measurements, with more precise devices, show that the power suitable for the traverse speed is essentially the same as the value derived in the theoretical description, i.e., it is equal to “one”. Simultaneously, the replacement of the diameter of the water nozzle (orifice) by the focusing (abrasive) tube diameter in the respective equations has been discussed, because this factor is very important for the AWJ machining. Some applications of the revised model are presented and discussed, particularly the reduced forms for a quick recalculation of the changed conditions. The correlation seems to be very good for the results calculated from the present model and those determined from experiments. The improved model shows potential to be a significant tool for preparation of the control software with higher precision in determination of results and higher calculation speed
Bibliometric analysis of abrasive water jet machining research
No full textBibliometric research focuses on the statistical analysis of publications. It is a method that is frequently used to classify the information with various variables such as institutions, journals, countries and authors. This paper presents a general overview of research that has been reported on abrasive water jet machining by using the bibliometric indicators. The essential features of bibliometric indicators are that these indicators come out with a general picture of abrasive water jet research. The paper is divided into key analysis sections which focused on relevant journals, research papers, authors, institutions and countries that have contributed to abrasive water jet research. The bibliometric research is conducted through Web of Science database. The goal of this paper is to be informative with this topic, and the indicators summarize the essential research in this field. The analysis shows that the number of publications on abrasive water jet and their citations are consistently increasing over the past years. The data indicates that the Wang J is the most influential and active author in abrasive water jet research and some of the other main leaders in this field are Hloch S, Kovacevic R and Axinte D. The two most influential journals are the International Journal of Advanced Manufacturing Technology and the Journal of Materials Processing Technology and the most influential country is United States of America followed by Czech Republic in abrasive water jet research. Furthermore, the bibliometric analysis reveals the links among the co-authors, co-citation authors and partnering institutions working in AWJ research field. Keywords: Abrasive water jet (AWJ), Bibliometric indicators, Influential authors, Influential research organizations, Influential countrie
Fatigue probability model for AWJ-cut steel including surface roughness and residual stress
No full textAn analytical model for the fatigue probability of abrasive waterjet cut high strength steel as a function of surface roughness, surface residual stress, tensile strength and number of cycles to failure is presented. Based on the model, which is valid in the finite and infinite-life high cycle fatigue regime, the influence of the aforementioned parameters on the fatigue strength at different probability levels is studied. For validation, fatigue tests are performed on abrasive waterjet-cut dog-bone specimens manufactured from high-strength steel with a yield strength of 700 MPa. Residual stresses are measured parallel to the loading direction at the inlet, middle and outlet of the cut surface. Surface roughnesses are measured with laser line triangulation as well as a traditional contact stylus method, showing good agreement between both measurement techniques. The proposed probabilistic model shows good agreement with the experimental results with less than 4% error in the predicted mean fatigue limit. Furthermore, the applicability of the presented analytical expression in a probabilistic design framework is demonstrated. An engineering example is introduced demonstrating the implementation of the model in a finite-element simulation, accounting for both multiaxial loading and the statistical size effect. (c) 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).</p
Diagnosis of isolated pancreatic tuberculosis: The role of EUS-guided FNA cytology
No full text[No abstract available]Ahlawat Sushil K, 2005, JOP, V6, P598; Aljafari AS, 2004, CYTOPATHOLOGY, V15, P44, DOI 10.1111-j.1365-2303.2003.00119.x; Auerbach O, 1944, AM J PATHOL, V20, P121; BHANSALI SK, 1977, AM J GASTROENTEROL, V67, P324; Chang KJ, 1997, GASTROINTEST ENDOSC, V45, P387, DOI 10.1016-S0016-5107(97)70149-4; Cheng R, 2006, GASTROINTEST ENDOSC, V64, P660, DOI 10.1016-j.gie.2006.04.004; D'Cruz Sanjay, 2003, JOP, V4, P158; Hari S, 2005, Trop Gastroenterol, V26, P141; Jenney AWJ, 1998, SCAND J INFECT DIS, V30, P99; Kaushik Neeraj, 2006, JOP, V7, P205; Khan R, 2006, WORLD J GASTROENTERO, V12, P6371; Mallery JS, 2002, GASTROINTEST ENDOSC, V56, P218, DOI 10.1067-mge.2002.125826; Micames C, 2003, GASTROINTEST ENDOSC, V58, P690, DOI 10.1016-S0016-5107(03)02009-1; Paraf A, 1966, Rev Med Chir Mal Foie, V41, P101; Pombo F, 1998, ABDOM IMAGING, V23, P394, DOI 10.1007-s002619900367; Sachdev Atul, 2006, JOP, V7, P665; Schneider A, 2002, PANCREATOLOGY, V2, P69, DOI 10.1159-000049451; Song TJ, 2009, GASTROINTEST ENDOSC, V69, P484, DOI 10.1016-j.gie.2008.10.007; STAMBLER JB, 1982, GASTROENTEROLOGY, V83, P922; STOCK KP, 1981, ENDOSCOPY, V13, P178, DOI 10.1055-s-2007-1021678; Suits J, 1999, ARCH SURG-CHICAGO, V134, P639, DOI 10.1001-archsurg.134.6.639; Turan M, 2002, PANCREATOLOGY, V2, P561, DOI 10.1159-000066097; WARSHAW AL, 1991, AM J SURG, V161, P26, DOI 10.1016-0002-9610(91)90356-I; Weiss ES, 2005, J GASTROINTEST SURG, V9, P254, DOI 10.1016-j.gassur.2004.06.010; Williams DB, 1999, GUT, V44, P720; Woodfield JC, 2004, ANZ J SURG, V74, P368, DOI 10.1111-j.1445-1433.2004.02996.x; Xia F, 2003, WORLD J GASTROENTERO, V9, P1361; Yokoyama T, 1999, HEPATO-GASTROENTEROL, V46, P20111
