4,329 research outputs found

    State of the Art of Laser Hardening and Cladding

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    In this paper an overview is given about laser surface modification processes, which are developed especially with the aim of hardness improvement for an enhanced fatigue and wear behaviour. The processes can be divided into such with and without filler material and in solid-state and melting processes. Actual work on shock hardening, transformation hardening, remelting, alloying and cladding is reviewed, where the main focus was on scientific work from the 21st century

    Creep Resistance Non-Ferrous Alloys

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    The article describes briefly creep phenomena and various metallurgical factors like grain size, alloy additions, dispersed phases, cold work, and heat treatment which influence creep properties. A review of the newer non-ferrous metal alloys like the aluminium-base, magnesium-base, copper-base, nickel-base, cobalt-base, chromium-base and others is presented in some detail depicting their particular significance and varied applications. A brief mention has also been made of the special significance of titanium-base and beryllium-base alloys stressing the need for development of those alloys specially in view of their industrial and strategic importance

    Temperature effects on material characteristics

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    Some of the physical properties of the main elements of interest in high temperature technology are reviewed. Some general trends emerge when these properties are viewed as a function of melting point, but there are a few notable exceptions. Titanium, zirconium, niobium and tantalum all have disappointingly low moduli; chromium is excellent in many ways, but has a limited ductility at lower temperatures; molybdenum oxidises catastrophically above about 700° C, and niobium suffers from severe oxygen embrittlement. Beryllium and carbon (in the graphitic form) both stand out as exceptional materials, both have very low densities, beryllium a very high modulus but an unfortunately low ductility, while graphite has a relatively low strength at the lower temperatures, although at temperatures of 2000° C and above it emerges as a quite exceptional (and probably as the ultimate) high temperature material. Some of the fundamental factors involved in high temperature material development are examined, in the light, particularly, of past progress with the nickel alloys. If a similar progress can be achieved with other base elements then a considerable margin still remains to be exploited. Protection from oxidation at high temperatures is evidently a factor of major concern, not only with metals, but with graphite also. Successful coatings are therefore of high importance and the questions they raise, such as bonding, differential thermal expansion, and so on, represent aspects of an even wider class covered by the term “composite structures". Such structures appear to offer the only serious solution to many high temperature requirements, and their design, construction and utilization has created a whole series of new exercises in materials assessment. Matters have become so complex, that a very radical and fundamental reassessment is required if we are to change, in any very significant way, the wasteful and ad hoc methods which characterise so much of present-day materials engineering

    tribological properties of wear resistant coatings obtained by cold gas dynamic spray

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    Abstract The aim of this study was obtaining good deposits of stellite-6 by Cold Gas Dynamic Spray (CGDS), in terms of low porosity and good adhesion and cohesion. In fact, the high strength and melting point of the investigated alloy lead to a high value of the particle critical velocity in CGDS and, therefore, good quality results are difficult to achieve. The tribological properties of the coatings were analyzed by micro-hardness measurements and pin-on-disk wear tests. Results revealed that spraying parameters can be optimized to obtain almost pore-free coatings

    The study on the integration of Activity Based Costing (ABC) system and six-sigma principle

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    Manufacturing organizations are facing much more challenges as compared to the earlier years. The important and crucial decisions have to be taken by the management in continuous basis in order to ensure the survival and competitiveness of company throughout the journey to become a successful organization. In order to make these decisions fast and correct, they need more accurate information related to financial and non-financial aspects. The conventional cost management systems, which were developed decades ago are unable to provide all information required to make right decision, justify the cost reduction and process improvements (Chen, 1996). This is because they were based on labor-intensive production system while today’s production processes are more sophisticated and faces constant changes. An alternative costing system, Activity Based Costing (ABC) has emerged to the new solution to costing system. It provides financial and non-financial information not only for product costing but also for each activity of manufacturing process. It can list and measure the cost of each activity individually in production and in supporting activities to deliver of a product or service right to customers (Sohal & Chung, 1998). ABC focuses on the activities performed to produce the products throughout the manufacturing process (Gunasekaran et al., 1999). By assigning other costs, such as marketing and administrative to cost object, ABC able to provide more accurate product costs. It helps to improve the operational performance by allocating overhead costs correctly. It provides cost information based on the actual consumption of the resources by each particular activity. The goal of ABC is to reveal cost allocation information by tracing the production costs accurately to activities and product (Gunasekaran et al., 1999). The implementation of ABC has provided many benefits, such as more accurate product costing, providing of cost behavior information and tracing resources consumptions. Realizing many benefits gain from implementation of ABC, many companies have embarked in applying ABC system. However, there are many problems and barriers they encountered during the implementation, which made some has decided to abort this system and not be able to exploit its advantages. It is the objective of this study to help foster the growth of Malaysian companies by helping them to provide better understanding,knowledge and skills to take advantage of using ABC as a tool to improve their manufacturing process. The title of the project is The Study on Integration of Activity-based Costing and Six-sigma Principle. The specific objective of the study is to determine success factors for ABC implementation in manufacturing companies based on Six-sigma process improvement principle. The focus of the study is to identify and understand the critical success factors in implementation of ABC, to identify and specified the problems and barriers and to understand their relationship with the ABC success. In order to identify, understand and formulate the proposed solution, this study will use a survey approach to get required data for further analysis. The survey will be based on mailed questionnaires to selected manufacturing industries in Malaysia. In order to formulate a comprehensive and relevant set of questionnaires, a comprehensive review of literature will be studied, followed by validation and verification process,which involved expert opinions and a pilot study. The next phase is where data from the study will be analyzed to identify areas related to the level of acceptance of ABC,the critical success factors and also to determine the relationship between the organization’s factors and the success of implementation of ABC system. The tangible outcome of this project is to provide a set of proposed guidelines and support tools for manufacturing organizations in applying Activity-based Costing for process improvement efforts as suggested by Six-sigma improvement principle

    Life prediction of materials exposed to monotonic and cyclic loading: A new technology survey

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    Reviewed and evaluated technical abstracts for about 100 significant documents are reported relating primarily to life prediction for structural materials exposed to monotonic and cyclic loading, particularly in elevated temperature environments. The abstracts in the report are mostly for publications in the period April 1962 through April 1974. The purpose of this report is to provide, in quick reference form, a dependable source for current informatio

    Dependence of stress rupture and superplasticity on structure in Co-W alloys, part I

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    Dependence of stress rupture and superplasticity on structure in Co-W alloy

    EFFECT OF COBALT IN THIN WALL DUCTILE IRON AND SOLID SOLUTION STRENGTHENED FERRITIC DUCTILE IRON

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    Ductile Iron is a material that is constantly evolving. Consequently, the ferrous industry is not only focusing on lightweighting but also on improving the impact strength and fracture toughness of typical ferritic-pearlitic ductile iron grades and solid solution strengthened ferritic ductile irons. Recently, the demand for thin-wall ductile iron and solid solution strengthened ferritic ductile iron grades has increased. The challenges behind the fabrication of these two ductile iron materials are the presence of carbides and the embrittlement of ferrite. In response, research has been focused on looking at alternative methods that can mitigate carbide formation in thin sections and counteract the detrimental effects of high silicon contents in the impact toughness of these materials. One way to reduce carbides is by increasing the silicon, but high silicon contents embrittle the ferrite and result in low static and dynamic mechanical properties. Cobalt in ductile iron is known to increase the nodule count resulting in a higher ferrite content in the as-cast condition, and it also hardens the ferrite via solid solution strengthening. Therefore, the ability of cobalt to inhibit carbide formation and its effect on the toughness of two different types of ductile irons was studied. Firstly, it was found that the addition of 4 wt.% Co reduces carbides in thin sections with a silicon level around 2.41 wt.% Si. Secondly, partial substitution of silicon with 2 wt.% and 3 wt% Co provided higher strength in a 600-10 SSFDI grade. Nonetheless, the impact strength and fracture toughness were not improved with cobalt additions. It was established that cobalt increases the ductile to brittle transition temperature

    Up-to-Date Knowledge and Outlooks for the Use of Metallic Biomaterials: Review Paper

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    In all cases, when a material has to be used in medical applications, the knowledge of its physical, chemical and biological properties is of fundamental significance, since the direct contact between the biological system and the considered device could generate reactions whose long-term effects must be clearly quantified. The class of materials that exhibits characteristics that allow their use for the considered applications are commonly called biomaterials. Patients suffering from different diseases generate a great demand for real therapies, where the use of biomaterials are mandatory. Commonly, metallic biomaterials are used because their structural functions; the high strength and resistance to fracture they can offer, provide reliable performance primarily in the fields of orthopedics and dentistry. In metals, because of their particular structure, plastic deformation takes place easier, inducing good formability in manufacturing. The present paper is not encyclopaedic, but reports in the first part some current literature data and perspectives about the possibility of use different class of metallic materials for medical applications, while the second part recalls some results of the current research in this field carried out by the authors

    Biodegradable Mg alloys –A review

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    لقد توسع سوق السبائك المستخدمة للزرع الجراحي، وخاصة تلك المصممة لزراعة العظام، بسرعة خلال العقد الماضي. حيث استفاد القطاع الطبي بشكل كبير من التقدم الكبير الذي تم تحقيقه من خلال دراسة السبائك القابلة للتحلل الحيوي القائمة على المغنيسيوم. حيث يعد البحث في هذا المجال خطوة للأمام لعدد من الأسباب، منها الرغبة في تحسين نوعية حياة الناس (محرك اجتماعي واقتصادي). من خلال تقليل الاعتماد على الغرسات المعدنية الدائمة المصنوعة من (الفولاذ المقاوم للصدأ، والسبائك القائمة على الكوبالت، وسبائك التيتانيوم)، والتي لها مجموعة عيوب خاصة بها والتي يمكن أن يكون لها تأثير سلبي على الصحة النفسية والجسدية للمرضى. تتم مناقشة سبائك المغنيسيوم القابلة للتحلل في هذه الورقة، إلى جانب تاريخ تطورها، والميزات المهمة التي تجعلها مرغوبة لمثل هذه التطبيقات (زراعة العظام)، والميزات التي يجب تعديلها (معدل التآكل والخواص الميكانيكية) للوصول إلى المنتج الأمثل للتطبيق المقصود. ويركز على تقنيات/طرق واستراتيجيات التوصيف الكهروكيميائية لتعزيز سلوك التآكل والخصائص الميكانيكية لأنواع مختلفة من السبائك القابلة للتحلل، بالإضافة إلى الآلية والميزات المرتبطة بسلوك التآكل لسبائك المغنيسيوم. المعايير التي سيتم تصميمها، والمتطلبات التي يجب أن تلبيها لغرسات السبائك القابلة للتحلل الحيوي التي تعتمد على المغنيسيوم، والميزات المرتبطة بكفاءتها، بالإضافة إلى طرق التحسين وتأثير العناصر المضافة لصناعة تلك السبائك.  The market for implant alloys, particularly those designed for orthopedic implants has expanded rapidly during the last decade. The medical sector has benefited greatly from the significant advances achieved in the study of Mg-based biodegradable alloy during this time. Research is a step up in this area for a number of reasons, including the desire to improving people quality of life (a social as well as an economic driver). By decreasing the prevalence of permanent metallic implants (such as those made of stainless steel, cobalt-based alloys, and titanium alloys), which have their own set of drawbacks (including stress shielding and metal ion releases) that can have a negative impact on patients\u27 mental and physical health. Biodegradable Mg alloys are discussed in this paper, along with their history of development, important features that make them desirable for such applications (orthopedic implants), and features that must be modulated (corrosion rate and mechanical properties) to arrive at the optimal product for the intended application. It emphasizes the electrochemical characterization techniques/methods and strategies to enhance the corrosion behavior and mechanical characteristics of various kinds of biodegradable alloys, as well as the mechanism and features linked to the corrosion behavior of Mg alloys. The criteria to be design, the requirements that implants of biodegradable alloys Mg-based must fulfill, and the features connected to their efficiency provided, as well as the methods of optimization, the category, and the influence of the alloying components
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