Elements of Manufacturing Processes - Kindle edition by R.K.B.S. Nagendra Parashar Mittal. Download it once and read eBook features: Highlight, take notes. download Elements Of Manufacturing Processes by B. S. Nagendra Parashar, R. K. Mittal PDF Online. ISBN from PHI Learning. Download Free. List of Manufacturing Preocess ebooks. Manufacturing Processes and Materials: Exercises by usaascvb.info Metal Forming and Febrication Technology.
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The book is intended for undergraduate students of mechanical engineering, production engineering and industrial engineering. The diploma students and those preparing for AMIE, Indian Engineering Services and other competitive examinations will also find the book highly useful. Offers a good number of worked-out examples to help the students in mastering the concepts of the various manufacturing processes.
Table of Contents: 1. Manufacturing: Principles and Processes 2. Materials: Structures and Properties 3. Ferrous Metals: Irons and Steels 4.
Non-ferrous Metals and Other Materials 5. Foundry Processes: Molding and Casting 6. Metal Machining: Processes and Machine Tools 7. Electric and Gas Welding Processes 8.
Soldering and Brazing 9. Metal Forming: Hot- and Cold-working and Press-working Serial processes require that a process element must have been completed before the following element can commence. Parallel processes require that all parallel processes involved must have been completed at the lateral nodes so that they can be merged into a common process. In this model, the co-determinative processes must be adjusted to the determinative process Fig.
The following compatibility condition applies to the quantitative coupling of two consecutive process elements:. Process elements to be integrated as intermediate elements mainly include storage elements that are introduced for compensation purposes and which put a certain number of objects of change on hold for a defined period Fig.
A parallel arrangement is required if there are process elements with varying flow increments. In this case, a single, larger-flow element is coupled to several elements with smaller flows in such a way that an alignment is achieved. The spatial structure refers to the three-dimensional arrangement and coupling of the process elements.
It represents the spatial organisation of the technological process and thus of the production line as the entity that comprises all technical means [1. Its configuration can be varied according to the following types of spatial organisation:.
Basic types of arrangement are distinguished according to the process- or product-driven nature of the spatial arrangement.
Technical means that implement identical processes are grouped together in a spatial arrangement and treat various types of objects of change Fig. Technical means that implement different processes are grouped together in a spatial arrangement according to the work sequence required for a certain type of object of change Fig. Types of motion can be distinguished according to the state of motion between objects of change and technical means:. The objects of change OC remain at the same manufacturing station during the determinative basic operations.
The technical means Mt are mobile. They are moved towards the object of change, where they act on it, and are then moved to the next manufacturing station Fig. The principle of stationary production is used by a number of different systems, of which the following are of particular relevance to the production of wall and structural framework elements:.
The objects of change OC move from one manufacturing station to the next. The technical means Mt are stationary Fig. One or more work steps are carried out at each of the stations manufacturing units , which is why these work steps run parallel to each other [1. Block machines used to manufacture concrete products are another example of this manufacturing principle. Concrete products include durable goods made of concrete, reinforced concrete and prestressed concrete [1.
In accordance with these stages, concrete products are manufactured in the following sequence Fig. In this workflow, the production of concrete elements is the main process to shape and manufacture the concrete products.
The steps of mix production as well as fabrication of reinforcements, moulds and formwork may be allocated to one or several element production processes. They may also be located outside the boundaries of the factory; however, this would increase outlay for organisation and transportation. The manufacture of concrete products requires a number of changes in the state of the material to achieve a defined manufactured state at each of these stages.
During these changes in the state or condition, which are brought about by the intentional action of the technical means, the respective object i. In other words, this constitutes the reaction of the material to the action of the technical means.
The processing behaviour is thus process-driven. In accordance with the main classes defined for the types of change, main processing behaviour classes can also be established Table 1.
Just like finished concrete, the initial concrete mix is a very versatile material. With respect to its mechanical properties, it takes an intermediate status between a bulk material and a suspension. These mechanical characteristics undergo substantial changes during the compaction process, which thus alters the compaction behaviour.
Compaction is closely related to the moulding behaviour of the concrete mix to produce the concrete product.
Moulding and compaction serve to transform the concrete mix into a quasi-solid geometric body of fresh concrete [1.
This process creates an artificial stone that has a low initial strength, the so-called green strength. The aim of the moulding process is to produce an accurately shaped concrete product. The concrete mix is poured into the mould so that it completely fills all the corners and edges. The placement behaviour of the concrete is crucial to achieve this goal and depends on the flow properties of the concrete mix.
For most types of concrete mixes used to manufacture concrete products, natural compaction effects are also utilised to support the placement process. Highly flowable mixes, such as self-compacting concretes SCCs , show a very good pouring behaviour because any remaining pores are removed by the gravity effect and the motion of the mix during the placement process.
As these concretes are already self-compacted, additional compaction is neither necessary nor possible. Compaction serves to largely eliminate the external porosity of the concrete mix. The reduction in the void volume should lead to higher densities and thus improve the strength and dimensional stability.
Concrete can be considered strong if an almost homogeneous body held together by adhesive and cohesive forces was created due to the high packing density of the concrete constituents. Concrete can be considered dimensionally stable if no significant dimensional changes occur under ambient conditions in both the loaded and the unloaded states.
Despite numerous attempts to find alternative methods, vibration — alone or in combination with other processes — continues to be the most popular method for moulding and compacting concrete mixes in order to manufacture both concrete products and precast elements [1. The type of action on the concrete mix is a crucial factor that determines the moulding and compaction behaviour.
As shown in Fig. With respect to the location of the action, and thus its direction, a fundamental distinction can be made between horizontal, vertical and three-dimensional actions.
As regards the function of the vibration action, harmonic and anharmonic modes of excitation can be distinguished. Both directional counter-acting and non-directional circular exciters can be used to introduce vibration into the concrete. Anharmonic exciter functions can be sub-divided further into periodic and pulsed actions.
For instance, a periodic exciter function can be a multi-frequency action that consists of several harmonic components. Pulsed excitation, also known as shock vibration, is generated by shock-like processes. This triggers the inherent oscillation of all system elements capable of vibration, i. Parameters that characterise the intensity of the action on the concrete mix are discussed in Section 1. The type of exciter function, the mode of action and number of exciters and, in particular, their phase position in relation to each other have a major influence on the moulding and compaction behaviour of the concrete mix.
For example, a phase coincidence of the harmonic vibration components of the vibrating table and tamper head would hardly achieve a good compaction effect.
The crucial factor is the generation of a dynamic pressure gradient between the layers of the mix that enables relative motion of these layers and mutual rotation of the mineral aggregate particles. These requirements must be met by state-of-the-art processes.
When producing large-scale precast elements, for example, the low-frequency action on the fresh concrete is complemented by a higher-frequency vertical excitation. In such a set-up, the frequency of the required vibrators is usually controlled via frequency converters.
When producing concrete products from stiff mixes, modern processes often combine vibration with pressing, as in block machines through the tamper head or in concrete pipe machines through a suitable arrangement of packer heads with several level counter-acting rollers. A special type of action on the concrete mix is created by the use of internal vibrators Fig. The actual compaction process, from start to finish, can be considered a dynamic process with a gradual transition from one rheological state to the next [1.
This concept is illustrated in Fig. In this model, the entire compaction process is divided into three phases that are described in more detail in [1. Each of these three phases represents a compaction stage where, according to [1. Both duration and delimitation of the individual phases, as well as the associated rheological body models, depend on the type of material mix to be compacted. It can thus be concluded that each concrete mix requires specific process and equipment parameters for the individual phases of its compaction in order to come as close as possible to an ideal compaction state in the shortest possible time [1.
Ebooka przeczytasz w aplikacjach Legimi na: Dlaczego warto? Przeczytaj fragment w darmowej aplikacji Legimi na: Ebooka przeczytasz na: Kindlu MOBI. Pobierz fragment dostosowany na: Opis Opinie Fragment Opis ebooka Manufacturing of Concrete Products and Precast Elements - Helmut Kuch The flexible use of prefabricated concrete products requires a continuously increasing diversity with regard to fresh concrete mix designs and properties, moulding processes, surface finishes and product characteristics.
This trend imposes ever-higher requirements on manufacturers of the associated production equipment and on precast plants. The main goal is to implement a flexible production system in all processing stages. The relevant correlations and interactions need to be thoroughly considered and evaluated in order to ensure that concrete products and precast elements are manufactured to the required quality standard. To date, no comprehensive description of these correlations has been published in the relevant literature.
This richly illustrated book closes the gap by describing the basic principles of the production processes, the fundamentals of materials, the composition of the concrete mix, and the equipment used for concrete production. Clearly arranged chapters detail the production processes and equipment used to manufacture small concrete products, concrete pipes and manholes, and precast elements.
The authors have used their many years of experience in the field of precast technology and their close ties to the industry. Their aim was to integrate modern testing and calculation methods from neighbouring disciplines into precast technology. This includes, for instance, modelling and simulation of the workability behaviour of mixes, implementation of the latest advancements in machine dynamics to the design and engineering of production equipment, and the use of stateof-the-art measuring and automation technology for quality control purposes.
Foreword Concrete is one of the most important building materials of our times. The flexible use of prefabricated concrete products results in a continuously increasing diversity with respect to — fresh concrete mix designs and properties, — external geometry and design, — surface finishes in terms of colour and design and — characteristics of the finished product quality.
We are also grateful to numerous companies for providing photographs. The authors particularly appreciate the assistance of the following industry partners in supplying useful information and images during the preparation of this book: Heike Becker Dipl. Jens Biehl Dipl. Frank Bombien Dipl. Barbara Janorschke Dipl. Simone Palzer Dipl. Kerstin Schalling Dipl. Christina Volland Dipl. Markus Walter The authors Weimar, August Introduction Building with state-of-the-art precast reinforced concrete construction evolved into an industrial construction method only over the last 60 years or so.
It has been written for everyone involved in the production of prefabricated concrete products, including: This necessitates clarification of the complex relationships between the various components of the concrete production process, namely: In many cases, however, these factors are still being dealt with on an empirical basis.
Modelling of equipment using — multi-body systems and — the Finite Element Method FEM can be used to investigate motion processes as well as stresses generated by dynamic loading.
The processes and equipment to manufacture precast concrete products are then discussed for the individual product groups: The production process I Input parameters O Output parameters E External conditions A Associated effects As is the case with any system, the basic characteristics of this production process are its function and structure. These are: These relationships govern the process layout and flow with respect to both space and time.
Therefore, the following parameters need to be determined to describe the production process fully: All existing objects can be assigned to one of the following main categories: The structure of the basic operations forms part of the technological microstructure Fig. Structure of the basic operation Structural elements thus include: Both sides of the structure are governed by the following underlying conditions that must be met by an appropriately designed structure: Process layout and flow comprise the set of arrangements and couplings between process elements.
These arrangements determine the position of process elements in space and time. The overall set of couplings comprises: A spatial coupling must fulfil the following conditions: This leads to specific coupling distances Fig. Spatial coupling of process elements: Serial process: Two process categories can be distinguished with respect to their temporal characteristics: The following factors are relevant to quantitative couplings: Parallel processes: Insertion of storage elements: Its configuration can be varied according to the following types of spatial organisation: Process-driven arrangement Fig.
Product-driven arrangement Fig. Stationary production Process-driven arrangement process principle: Product-driven arrangement product principle: Stationary production The objects of change OC remain at the same manufacturing station during the determinative basic operations.
The principle of stationary production is used by a number of different systems, of which the following are of particular relevance to the production of wall and structural framework elements: