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Über dieses Buch

This book describes and systemizes analytical and numerical solutions for a broad range of instantaneous and continuous, stationary and moving, concentrated and distributed, 1D, 2D and 3D heat sources in semi-infinite bodies, thick plane layers, thin plates and cylinders under various boundary conditions. The analytical solutions were mainly obtained by the superimposing principle for various parts of the proposed 1D, 2D and 3D heat sources and based on the assumption that only heat conduction plays a major role in the thermal analysis of welds. Other complex effects of heat transfer in weld phenomena are incorporated in the solutions by means of various geometrical and energetic parameters of the heat source.

The book is divided into 13 chapters. Chapter 1 briefly reviews various welding processes and the energy characteristics of welding heat sources, while Chapter 2 covers the main thermophysical properties of the most commonly used alloys. Chapter 3 describes the physical fundamentals of heat conduction during welding, and Chapter 4 introduces several useful methods for solving the problem of heat conduction in welding. Chapters 5 and 6 focus on the derivation of analytical solutions for many types of heat sources in semi-infinite bodies, thick plane layers, thin plates and cylinders under various boundary conditions. The heat sources can be instantaneous or continuous, stationary or moving, concentrated or distributed (1D, 2D or 3D). In Chapter 7 the temperature field under programmed heat input (pulsed power sources and weaving sources) is analyzed.

In turn, Chapters 8 and 9 cover the thermal cycle, melting and solidification of the base metal. Heating and melting of filler metal are considered in Chapter 10. Chapter 11 addresses the formulation and solution of inverse heat conduction problems using zero-, first- and second-order algorithms, while Chapter 12 focuses on applying the solutions developed here to the optimization of welding conditions. In addition, case studies confirm the usefulness and feasibility of the respective solutions. Lastly, Chapter 13 demonstrates the prediction of local microstructure and mechanical properties of welded joint metals, while taking into account their thermal cycle.

The book is intended for all researches, welding engineers, mechanical design engineers, research engineers and postgraduate students who deal with problems such as microstructure modeling of welds, analysis of the mechanical properties of welded metals, weldability, residual stresses and distortions, optimization of welding and allied processes (prewelding heating, cladding, thermal cutting, additive technologies, etc.). It also offers a useful reference guide for software engineers who are interested in writing application software for simulating welding processes, microstructure modeling, residual stress analysis of welds, and for robotic-welding control systems.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Energy Characteristics of Welding Heat Sources

Abstract
In most cases welding is carried out with local heating of bodies up to the temperature which is determined by the type of welding and properties of the materials to be welded.
Victor A. Karkhin

Chapter 2. Thermophysical Properties of Metals

Abstract
In the analysis of thermal processes in welding the main properties of the metal are considered: thermal conductivity λ (W m−1 K−1), specific heat capacity c (J g−1 K−1) and density ρ (g m−3) and additional ones: thermal diffusivity a (m2 s−1) and specific enthalpy (specific heat content) H (J g−1).
Victor A. Karkhin

Chapter 3. Physical Fundamentals of Heat Conduction During Welding

Abstract
Temperature is a physical quantity that characterizes the degree of body heat. When the system is in the state of thermodynamic equilibrium, the temperatures of all the bodies forming the system are the same.
Victor A. Karkhin

Chapter 4. Methods for Solving the Problems of Heat Conduction in Welding

Abstract
The existing methods for solving the problems of heat conduction in welding are easy to classify according to the form of the solution results.
Victor A. Karkhin

Chapter 5. Temperature Fields in Fusion Welding

Abstract
Instantaneous concentrated sources are extremely important in solving the problems of heat conduction, since they are the basis for the construction of welding heat sources, distributed in space and time.
Victor A. Karkhin

Chapter 6. Temperature Fields in Welding with Pressure

Abstract
A distinctive feature of pressure welding methods is an additional parameter of welding conditions that is the external mechanical force which is applied to the workpiece during or right after heating.
Victor A. Karkhin

Chapter 7. Temperature Fields Under Programmed Heat Input

Abstract
Programming the heat input allows a better optimisation of the welding process to obtain a welded joint of the proper quality.
Victor A. Karkhin

Chapter 8. Thermal Cycles of Metal During Welding

Abstract
Heating of the welded joint is applied in almost all welding techniques. The thermal cycle of a metal (the change in the temperature of the metal in time) is determined by dimensions of the welded joint, initial and boundary conditions, thermophysical properties of the metal, parameters of the heating source and position of the metal to the source. Since the welding sources of heat are concentrated (as a rule, their dimensions are much smaller than the dimensions of the welded body), the heating of the metal is characterised by significant non-uniformity both in time and in space. For example, in arc welding of steel, the gradient of the peak temperature near the weld can reach hundreds of degrees per millimeter. Therefore, the thermal cycles of the metal of the adjacent zones of welded joint can be significantly different.
Victor A. Karkhin

Chapter 9. Melting and Solidification of Base Metal

Abstract
If the temperature field in the body is known, it is possible to highlight the region, heated above melting point Tm, and all its geometric characteristics: length Lm, width Wm, depth Hm and volume Vm of the weld pool and its cross-sectional area (weld cross-section) Am (Fig. 9.1).
Victor A. Karkhin

Chapter 10. Heating and Melting of Filler Metal

Abstract
Fusion welding relies on filler metal in the form of a covered electhrode (in manual metal arc welding), electrode wire (in mechanised arc welding and electroslag welding), wire, rods and bars (in gas tungsten arc welding, laser, electron beam and gas welding).
Victor A. Karkhin

Chapter 11. Inverse Heat Conduction Problems in Welding

Abstract
In the previous chapters, we addressed a direct heat conduction problem: the heat conduction problem is solved with allowance for input data (parameters of the welding heat source, body geometry and material properties). As a result, temperature field and all its characteristics are obtained. This procedure can be presented in a schematic form: independent input parameters p1, p2, …, pK of vector p are given, and a dependent vector (response function) T is obtained with the following parameters (output data): T1, T2, …, TJ.
Victor A. Karkhin

Chapter 12. Optimisation of Welding Conditions

Abstract
Chapter 11 provided insights into the inverse problem of heat conduction and methods of its solution. From certain effects of the welding source, its unknown parameters were obtained, and the entire temperature field was reconstructed. In principle, the inverse problem is an optimisation problem that can be solved using optimisation methods.
Victor A. Karkhin

Chapter 13. Prediction of Local Microstructure and Mechanical Properties of Welded Joint Metal with Allowance for Its Thermal Cycle

Abstract
The behaviour of a welded joint under external conditions (load, temperature, hostile environment, etc.) depends on the local microstructure and local mechanical properties of all welded joint zones (of the weld, HAZ and base metal). In order to predict the microstructure and properties, it is necessary to know the thermal processes in the welded joint, i.e. to solve the heat conduction problem with allowance for body geometry, boundary conditions, welding conditions, and the thermophysical properties of the metal (Fig. 13.1).
Victor A. Karkhin

Backmatter

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