Designing Weldments. Группа авторов

properties of copper grades and alloys.

      27 Table 7.3 Mechanical properties of aluminum and its alloys, with temper.

      28 Table 7.4 Mechanical properties of various grades of Austenitic stainless steels.

      29 Table 7.5 Comparison of mechanical properties of grades of steel.

      30 Table 7.6 HSS rect property table.

      31 Table 7.7 Metric to US standard unit conversion.

      Foreword

      Designing Weldments by Ramesh Singh, addresses the importance of how properly designed welds in a structure can change the approach to its design, leading to greater structural integrity and potentially reduced cost. This book seeks to strengthen frequently neglected elements of design engineering involving structural load-bearing members of various metals, but particularly those of steel, and aluminum manufacture. Ramesh’s real-world experiences have led him to conclude that many engineers possess only a basic education about the welding. Consequently, many are ill-equipped with sufficient understanding of how welded structures respond to loading versus, for example, a wrought steel member in a structure. How do the presence of welds within the structure change stress types and concentrations, thereby having significant impact on the long term integrity of the structure? How can the designer take strategic advantage of welding technologies to strengthen the structural design while also reducing its weight and finished cost. Finally, this book also addresses the differences between a cast structure and a welded structure, and what factors need to be addressed when converting a cast structure design to a welded structure design, as might be done for a machine component.

      The importance of the type of weld joint preparation, for full penetration, or partial penetration, butt weld or fillet weld, or a combination of fillet and groove welds is addressed in detail. The book also provides an introduction to various welding processes, materials of construction, and their classifications.

      I have worked professionally with Ramesh for more than two decades. He is passionate about his work in metallurgy, corrosion, fabrication and welding, which spans more than half a century and multiple industries. Unlike many whose background is primarily academic; his knowledge has been acquired through practical experience in a variety of settings around the globe. An avid long distance bicycle rider, and dedicated marathon runner, Ramesh brings that same level of devotion and commitment to his profession.

      Designing Weldments will be an important resource and reference tool for structural designers and engineers. The book is replete with illustrations, tables and figures to bring visual clarity and substance to the technical nomenclature necessary for such a complex subject.

       W. M. Olson

      Sr. Vice President | Operations

      Gulf Interstate Engineering, in Houston TX

      Preface

      The idea of writing about the specifics of weld design has been in my mind for nearly all through my career. The concept of the Designing Weldments was inspired, and motivated by my experience with engineers that were often responsible for designing major structures for offshore platforms, PLEMS, risers, roads and bridges, and buildings etc.

      Most of the time very excellent design concepts got bogged down due the limited knowledge the of the impact welding does on materials’ behavior, and how a welded structure is different from other materials say, an extruded structural member.

      The subject is also complicated by the fact that different types, and grades of material have different metallurgical response to the fabrication processes, including welding which is a major component of such complex fabricated structural members. The details of metallurgical aspects of material is discussed in another book Applied Welding Engineering (ISBN 978-0-12-821348-3) published by the Elsevier publication. Interested readers are encouraged to read and reference this book.

      While the basic engineering principles related to loading, and stresses remain same, as for the design of any other structural member, the presence of weld changes the stress locations, stress direction, and develops stress concentration points. This significant change, demands different approach to the calculations, and providing for those specific conditions. A structure with weld is no longer a straight forward member. The presence of weld in a structural member is not all that bad news, welds are complex part of any structure, with good understanding of them, welds can be designed to be useful and contributing part of any structure. Welds can, and are also used to strengthen and stiffen any structure. The knowledge of all these attributes helps improve the design of welded structures.

      This book discusses properties of materials, as structure sensitive and insensitive properties, and how these properties affect the integrity of the structure, and how to evaluate these sensitive properties of material and use them to the advantage in design evaluation.

      The book further discusses the design load conditions with various joint configurations, and placement of welds, and with the consideration of how they have been made, and inspected.

      Weld types are discussed in details, and how the load is distributed through these welds. Where in the structure is the primary stress? What type of primary stress working on the weld? What is the stress category? These are all discussed and graphically shown for easy understanding.

The chapters also discusses the nomenclature of welds, especially that of fillet welds. The use of complex joint designs, and their application in tubular connections. And factors that affect such complex designs. Structures are not only made of steel, and iron, other materials are also used for structures, aluminum is other most common material used for construction. The properties and grades of aluminum is explained in the chapter. The unique properties of aluminum brings in other design challenges that needs engineers and designer’s attention.

      A weldment cannot be without welding, a basic introduction to most common cutting and joining process is introduced in the book. For more detailed information of arc welding process, readers are direct to another book Arc Welding Process (ISBN 978-1-119-81905-9), published by Scrivener Publishing.

      The knowledge of these welding specific structural challenges are often missing, or at least available in limited form, to the engineering and design groups. This deficiency is often filled by an experienced welding engineer. If no such help is available at the design stage, then those deficiencies are identified at the fabrication shop, and then corrective action, and reverse engineering ensues, causing costly repairs and delays. In the extreme cases if those design deficiencies are not caught intime and corrected, they lead to the structural failures. Often such failures occur several years in the service of the structure, and at that point very little can be attributed to the design failure. Phrases like “weld failed” and “weld became hard” are often used to pass of the cause of failures, pinning responsibility on welders, rather than finding if the weld was designed correctly.

      There are number of construction codes that address these issues, some of them are mandated as national standards, AWS D1.1 and W59 in Canada are the examples, but there are several segments of fabrication, and construction that do not fall within the construction codes’ scope or jurisdictions. And there are also places where there is no national building codes to get any guidelines. The details of joint configurations, and its impact on the integrity of the designed structure can be determined before any fabrication or construction begins, and suitable modifications can be incorporated in the design, and shown on the construction drawings. That includes, inclusion of welding related instructions, use of universally accepted and understood welding symbols to specify specific types of weld edge preparations, necessary inspections (NDE), and use of specific welding procedure, distortion control, and necessary heat treatment, where it is required.

      Designing Weldments intends to fill that serious gap, or at least