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The Effect of Cold Roller-Bending on the Mechanical & Geometric Properties of Steel Hollow Sections / Jonathon Richards

Swansea University Author: Jonathon Richards

DOI (Published version): 10.23889/Suthesis.52473

Abstract

In recent years there has been a significant increase in the use of steel hollow sections; in particular, where applications require a more aesthetic appeal. [1] As advances have been made in manufacturing and technology, the cost of hollow sections has decreased, however; it is still greater than t...

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Published: Swansea 2019
Institution: Swansea University
Degree level: Doctoral
Degree name: EngD
URI: https://cronfa.swan.ac.uk/Record/cronfa52473
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However, despite having a greater cost per tonne than open sections, hollow sections are being utilised increasingly due to a number of properties that make them an obvious choice for both aesthetically pleasing and utilitarian structures alike. Tata Steel Tubes is one of Europe's leading manufacturers of welded steel tubes and pipes. They produce many thousands of tonnes of hot-finished and cold-formed tubes each year that are used in a diverse range of applications including the construction sector. Another key sector is energy &amp; power which relies heavily on conveyance tubes. This project investigates the cold-roller-bending of plain carbon steel hollow sections for use in construction applications. The process of cold-roller-bending is widely considered to be an art rather than a science and therefore relatively little is known about the effects of the process on the physical and mechanical properties of the steel. In many cases it is assumed to be negligible[2] and therefore ignored by the standards and many of the guidance notes. Thus, the aim of this exercise was to determine and compare the effects of the cold bending process on the properties of hot-finished and cold-formed, plain-carbon steel, high-frequency induction (HFI) welded tubes. There is no current EU, British or American standard that specifies changes in the mechanical properties brought about by the bending process or a maximum allowed curvature. This is because the properties are considered to largely remain the same as the original unbent material and that any alterations in these properties are made up for by the shape of the section.[3]&#x2013;[5] This project refutes this assumption. Hot-finished and cold formed hollow sections were curved using roller-bending equipment to a range of strains with increasing curvature. The project has examined all of the requirements outlined by a structural engineering calculation, including the tensile strength, impact resistance, hardness and geometric resistances of the cross section. This has been performed in the hope of determining the most suitable section for the cold-bending process. The testing has determined that the process of cold-roller bending can be detrimental to many of the properties detailed above. All of the mechanical, mechanical and geometric properties examined in the experimentation were affected in some way. For example, the cross-sectional geometry of the section can be significantly altered by the bending process as the stresses involved distort the cross section of the tube. This leads to differences in the geometric properties when compared to the original unbent section. These properties include the sections resistance to bending and torsion. The tensile properties of the sections are also affected. During testing it was determined that cold-roller bending of steel leads to significantly reduced yield strength where the material is in compression during bending. This reduction in the elastic capacity of the section has been determined to have been caused by the Bauschinger effect; a phenomenon that occurs in many metals that leads to a reduction in capacity to resist stress and therefore yield stress of a section is reduced. The effect is observed when the section has underdone pre-strain beyond the materials yield point in the opposite direction to the current deformation. Further investigation around the Bauschinger effect revealed that it occurs when the section is first elongated and then compressed as well as where the section is compressed before elongation. For a number of applications, in Civil design, the plastic properties are not normally considered as a structure is not commonly designed to operate within its plastic region when in service. However, sections that have been curved using cold-roller bending will yield at significantly reduced stresses and therefore the plastic properties should be considered, particularly if the section is being used in a position where the bending loads are being reversed (from that of bending), for example, as an archway. Furthermore, this reduced capacity to resist bending will lead to spreading of the archway when loaded from above. This will lead to increased lateral load being exerted on a support structure which must be considered when designing a structure using curved steelwork. It was observed that both the hot-finished and cold-formed sections experienced a similar reduction in the yield strength during tensile testing (at the intrados) however; hot-finished sections regained their properties with further cold deformation more rapidly than the equivalent cold-formed product. This observation, coupled with improved impact resistances and superior geometric properties lead to the conclusion that hot-finished sections are considered to be more suitable for the cold-roller bending process.</abstract><type>E-Thesis</type><journal/><volume/><journalNumber/><paginationStart/><paginationEnd/><publisher/><placeOfPublication>Swansea</placeOfPublication><isbnPrint/><isbnElectronic/><issnPrint/><issnElectronic/><keywords>Roller-bending, Bauschinger, Tubes, Hollow sections</keywords><publishedDay>31</publishedDay><publishedMonth>12</publishedMonth><publishedYear>2019</publishedYear><publishedDate>2019-12-31</publishedDate><doi>10.23889/Suthesis.52473</doi><url/><notes>A selection of third party content is redacted or is partially redacted from this thesis.</notes><college>COLLEGE NANME</college><department>Science and Engineering - Faculty</department><CollegeCode>COLLEGE CODE</CollegeCode><DepartmentCode>FGSEN</DepartmentCode><institution>Swansea University</institution><degreelevel>Doctoral</degreelevel><degreename>EngD</degreename><degreesponsorsfunders>Tata Steel Europe, Angle Ring Ltd, EPSRC, WEFO</degreesponsorsfunders><apcterm/><funders/><projectreference/><lastEdited>2022-12-18T09:52:21.8889818</lastEdited><Created>2019-10-16T10:59:53.3614569</Created><path><level id="1">Faculty of Science and Engineering</level><level id="2">School of Engineering and Applied Sciences - Uncategorised</level></path><authors><author><firstname>Jonathon</firstname><surname>Richards</surname><order>1</order></author></authors><documents><document><filename>0052473-16102019121544.pdf</filename><originalFilename>Richards_Jonathon_K_PhD_Thesis_Final_Redacted.pdf</originalFilename><uploaded>2019-10-16T12:15:44.6130000</uploaded><type>Output</type><contentLength>18622023</contentLength><contentType>application/pdf</contentType><version>Redacted version - open access</version><cronfaStatus>true</cronfaStatus><embargoDate>2019-10-15T00:00:00.0000000</embargoDate><copyrightCorrect>true</copyrightCorrect></document></documents><OutputDurs/></rfc1807>
spelling 2022-12-18T09:52:21.8889818 v2 52473 2019-10-16 The Effect of Cold Roller-Bending on the Mechanical & Geometric Properties of Steel Hollow Sections dbea299a8fe09ecdd060142c1fb455a6 Jonathon Richards Jonathon Richards true false 2019-10-16 FGSEN In recent years there has been a significant increase in the use of steel hollow sections; in particular, where applications require a more aesthetic appeal. [1] As advances have been made in manufacturing and technology, the cost of hollow sections has decreased, however; it is still greater than that of hot-rolled open sections, such as Universal beams (I-beams). However, despite having a greater cost per tonne than open sections, hollow sections are being utilised increasingly due to a number of properties that make them an obvious choice for both aesthetically pleasing and utilitarian structures alike. Tata Steel Tubes is one of Europe's leading manufacturers of welded steel tubes and pipes. They produce many thousands of tonnes of hot-finished and cold-formed tubes each year that are used in a diverse range of applications including the construction sector. Another key sector is energy & power which relies heavily on conveyance tubes. This project investigates the cold-roller-bending of plain carbon steel hollow sections for use in construction applications. The process of cold-roller-bending is widely considered to be an art rather than a science and therefore relatively little is known about the effects of the process on the physical and mechanical properties of the steel. In many cases it is assumed to be negligible[2] and therefore ignored by the standards and many of the guidance notes. Thus, the aim of this exercise was to determine and compare the effects of the cold bending process on the properties of hot-finished and cold-formed, plain-carbon steel, high-frequency induction (HFI) welded tubes. There is no current EU, British or American standard that specifies changes in the mechanical properties brought about by the bending process or a maximum allowed curvature. This is because the properties are considered to largely remain the same as the original unbent material and that any alterations in these properties are made up for by the shape of the section.[3]–[5] This project refutes this assumption. Hot-finished and cold formed hollow sections were curved using roller-bending equipment to a range of strains with increasing curvature. The project has examined all of the requirements outlined by a structural engineering calculation, including the tensile strength, impact resistance, hardness and geometric resistances of the cross section. This has been performed in the hope of determining the most suitable section for the cold-bending process. The testing has determined that the process of cold-roller bending can be detrimental to many of the properties detailed above. All of the mechanical, mechanical and geometric properties examined in the experimentation were affected in some way. For example, the cross-sectional geometry of the section can be significantly altered by the bending process as the stresses involved distort the cross section of the tube. This leads to differences in the geometric properties when compared to the original unbent section. These properties include the sections resistance to bending and torsion. The tensile properties of the sections are also affected. During testing it was determined that cold-roller bending of steel leads to significantly reduced yield strength where the material is in compression during bending. This reduction in the elastic capacity of the section has been determined to have been caused by the Bauschinger effect; a phenomenon that occurs in many metals that leads to a reduction in capacity to resist stress and therefore yield stress of a section is reduced. The effect is observed when the section has underdone pre-strain beyond the materials yield point in the opposite direction to the current deformation. Further investigation around the Bauschinger effect revealed that it occurs when the section is first elongated and then compressed as well as where the section is compressed before elongation. For a number of applications, in Civil design, the plastic properties are not normally considered as a structure is not commonly designed to operate within its plastic region when in service. However, sections that have been curved using cold-roller bending will yield at significantly reduced stresses and therefore the plastic properties should be considered, particularly if the section is being used in a position where the bending loads are being reversed (from that of bending), for example, as an archway. Furthermore, this reduced capacity to resist bending will lead to spreading of the archway when loaded from above. This will lead to increased lateral load being exerted on a support structure which must be considered when designing a structure using curved steelwork. It was observed that both the hot-finished and cold-formed sections experienced a similar reduction in the yield strength during tensile testing (at the intrados) however; hot-finished sections regained their properties with further cold deformation more rapidly than the equivalent cold-formed product. This observation, coupled with improved impact resistances and superior geometric properties lead to the conclusion that hot-finished sections are considered to be more suitable for the cold-roller bending process. E-Thesis Swansea Roller-bending, Bauschinger, Tubes, Hollow sections 31 12 2019 2019-12-31 10.23889/Suthesis.52473 A selection of third party content is redacted or is partially redacted from this thesis. COLLEGE NANME Science and Engineering - Faculty COLLEGE CODE FGSEN Swansea University Doctoral EngD Tata Steel Europe, Angle Ring Ltd, EPSRC, WEFO 2022-12-18T09:52:21.8889818 2019-10-16T10:59:53.3614569 Faculty of Science and Engineering School of Engineering and Applied Sciences - Uncategorised Jonathon Richards 1 0052473-16102019121544.pdf Richards_Jonathon_K_PhD_Thesis_Final_Redacted.pdf 2019-10-16T12:15:44.6130000 Output 18622023 application/pdf Redacted version - open access true 2019-10-15T00:00:00.0000000 true
title The Effect of Cold Roller-Bending on the Mechanical & Geometric Properties of Steel Hollow Sections
spellingShingle The Effect of Cold Roller-Bending on the Mechanical & Geometric Properties of Steel Hollow Sections
Jonathon Richards
title_short The Effect of Cold Roller-Bending on the Mechanical & Geometric Properties of Steel Hollow Sections
title_full The Effect of Cold Roller-Bending on the Mechanical & Geometric Properties of Steel Hollow Sections
title_fullStr The Effect of Cold Roller-Bending on the Mechanical & Geometric Properties of Steel Hollow Sections
title_full_unstemmed The Effect of Cold Roller-Bending on the Mechanical & Geometric Properties of Steel Hollow Sections
title_sort The Effect of Cold Roller-Bending on the Mechanical & Geometric Properties of Steel Hollow Sections
author_id_str_mv dbea299a8fe09ecdd060142c1fb455a6
author_id_fullname_str_mv dbea299a8fe09ecdd060142c1fb455a6_***_Jonathon Richards
author Jonathon Richards
author2 Jonathon Richards
format E-Thesis
publishDate 2019
institution Swansea University
doi_str_mv 10.23889/Suthesis.52473
college_str Faculty of Science and Engineering
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hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Engineering and Applied Sciences - Uncategorised{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Engineering and Applied Sciences - Uncategorised
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description In recent years there has been a significant increase in the use of steel hollow sections; in particular, where applications require a more aesthetic appeal. [1] As advances have been made in manufacturing and technology, the cost of hollow sections has decreased, however; it is still greater than that of hot-rolled open sections, such as Universal beams (I-beams). However, despite having a greater cost per tonne than open sections, hollow sections are being utilised increasingly due to a number of properties that make them an obvious choice for both aesthetically pleasing and utilitarian structures alike. Tata Steel Tubes is one of Europe's leading manufacturers of welded steel tubes and pipes. They produce many thousands of tonnes of hot-finished and cold-formed tubes each year that are used in a diverse range of applications including the construction sector. Another key sector is energy & power which relies heavily on conveyance tubes. This project investigates the cold-roller-bending of plain carbon steel hollow sections for use in construction applications. The process of cold-roller-bending is widely considered to be an art rather than a science and therefore relatively little is known about the effects of the process on the physical and mechanical properties of the steel. In many cases it is assumed to be negligible[2] and therefore ignored by the standards and many of the guidance notes. Thus, the aim of this exercise was to determine and compare the effects of the cold bending process on the properties of hot-finished and cold-formed, plain-carbon steel, high-frequency induction (HFI) welded tubes. There is no current EU, British or American standard that specifies changes in the mechanical properties brought about by the bending process or a maximum allowed curvature. This is because the properties are considered to largely remain the same as the original unbent material and that any alterations in these properties are made up for by the shape of the section.[3]–[5] This project refutes this assumption. Hot-finished and cold formed hollow sections were curved using roller-bending equipment to a range of strains with increasing curvature. The project has examined all of the requirements outlined by a structural engineering calculation, including the tensile strength, impact resistance, hardness and geometric resistances of the cross section. This has been performed in the hope of determining the most suitable section for the cold-bending process. The testing has determined that the process of cold-roller bending can be detrimental to many of the properties detailed above. All of the mechanical, mechanical and geometric properties examined in the experimentation were affected in some way. For example, the cross-sectional geometry of the section can be significantly altered by the bending process as the stresses involved distort the cross section of the tube. This leads to differences in the geometric properties when compared to the original unbent section. These properties include the sections resistance to bending and torsion. The tensile properties of the sections are also affected. During testing it was determined that cold-roller bending of steel leads to significantly reduced yield strength where the material is in compression during bending. This reduction in the elastic capacity of the section has been determined to have been caused by the Bauschinger effect; a phenomenon that occurs in many metals that leads to a reduction in capacity to resist stress and therefore yield stress of a section is reduced. The effect is observed when the section has underdone pre-strain beyond the materials yield point in the opposite direction to the current deformation. Further investigation around the Bauschinger effect revealed that it occurs when the section is first elongated and then compressed as well as where the section is compressed before elongation. For a number of applications, in Civil design, the plastic properties are not normally considered as a structure is not commonly designed to operate within its plastic region when in service. However, sections that have been curved using cold-roller bending will yield at significantly reduced stresses and therefore the plastic properties should be considered, particularly if the section is being used in a position where the bending loads are being reversed (from that of bending), for example, as an archway. Furthermore, this reduced capacity to resist bending will lead to spreading of the archway when loaded from above. This will lead to increased lateral load being exerted on a support structure which must be considered when designing a structure using curved steelwork. It was observed that both the hot-finished and cold-formed sections experienced a similar reduction in the yield strength during tensile testing (at the intrados) however; hot-finished sections regained their properties with further cold deformation more rapidly than the equivalent cold-formed product. This observation, coupled with improved impact resistances and superior geometric properties lead to the conclusion that hot-finished sections are considered to be more suitable for the cold-roller bending process.
published_date 2019-12-31T04:04:51Z
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