Microstructural Features Controlling the onset of Crack Formation during the Bending of S700 and S960 High Strength hot rolled steels

Lead Research Organisation: University of Sheffield
Department Name: Mechanical Engineering

Abstract

Tata steel is currently developing a range of thick, hot rolled high strength steels with minimum yield strengths of 700, 900, 960 and 1100MPa for use: in the lifting and excavating sector. These grades often require cold forming via simple bending operations to produce final components such as crane booms. During the development of some of these grades, especially the S700 and S960 grades, whist the balance between strength and toughness has been excellent, the bendability of these steels has been poor and/or inconsistent. This poor bending behaviour is now limiting the markets which can be potentially supplied, and so there is a real need to firstly understand the factors controlling bendability, and then to improve bendability. The proposed work at Sheffield University wilI study the bending behaviour of thick, high strength steels using techniques such as high resolution digital image correlation and micro-gridding, and also study damage evolution at second phase particles during bending. The ultimate goal is to design microstructures which are more resistant to crack formation during bending.

To determine the microstructural features and stress-strain behaviour which control the onset of crack formation during the bending of high strength, thick, hot rolled strip. To make high resolution local strain measurements during bending to validate FE models of bending.

This work alines with the EPSRC's research aims as it will improve capability by keeping the UK as a world leader in material and steel research. This role will enable the development of leadership skills by leading the work with Tata steel in the professional environment. The impact will be accelerated by Tata Steel using the research to develop new products.

Tata steel are collaborating on this project.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/P510634/1 30/09/2016 29/09/2021
1803953 Studentship EP/P510634/1 01/11/2016 29/04/2021 Robert Dowding
 
Description Tooling and sample geometry developed to observed shear bands and damage at a localised region observed by the SEM. This has allowed the author to observe the interaction between shear bands, surface rippling and damage.
Using finite element modelling the shear bands have been generated in 2D models where the shear bands are observed at consistent spacing and surface rippling occurs where the shear bands bifurcate at 45 degrees from the surface.
In experimental work using the tooling and specimen geometry developed these shear bands patterns are replicated and waviness is found at the surface. This is found to localised strain and promote failure to occur at the shear bands.
Exploitation Route The updated tooling geometry and specimen shape will be used by future researchers to analyse the bendability of materials.
Sectors Manufacturing

including Industrial Biotechology

 
Description Expert SEM user
Geographic Reach Local/Municipal/Regional 
Policy Influence Type Influenced training of practitioners or researchers
 
Description Steel characterization and bend testing. 
Organisation University of Warwick
Department School of Engineering
Country United Kingdom 
Sector Academic/University 
PI Contribution The collaboration will have the steel characterised at the University of Warwick by Cameron Bee. These samples will then undergo bend testing by Robert Dowding at the University of Sheffield. The samples will then be analysed post testing by Cameron post testing.
Collaborator Contribution Cameron Bee will improve our insight into the material prior to the bend tests resulting in a greater understanding in the properties limiting bendability in high strength hot rolled steels.
Impact A plan has been presented to Tata Steel supervisor Didier Farrugia.
Start Year 2019
 
Description EUROMAT 2019 oral presentation 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Presented to the Euromat Conference to roughly 30 people and received questions and asked about presenting the work at another university.
Year(s) Of Engagement Activity 2019
 
Description Facilitator and camp rep at the University of Lincoln SPARK! Engineering Summer Camp 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact A summer camp was organised for 12-15 year old students with an interest in engineering. These students were given a project, taught engineering software and techniques.
Year(s) Of Engagement Activity 2018
 
Description Facilitator for the global engineering challenge at the University of Sheffield 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Undergraduate students
Results and Impact In 2019 Robert Dowding was selected to work as a facilitator for the global engineering challenge at the University of Sheffield where he taught 30 undergraduate students unsupervised for a week.

Students were recommended for being outstanding and feedback was received that the students were surprised that they enjoyed the weekend and learned skills that will be relevant to their future careers.
Year(s) Of Engagement Activity 2019
 
Description Posters and oral presentations at Tata Steel postgraduate research quarterly and yearly events. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Industry/Business
Results and Impact Tata Steel associated postgraduate students, lecturers and staff attend a conference and observed our posters and oral presentations. This promoted discussion and provided questions for us.
Year(s) Of Engagement Activity 2016,2017,2018,2019,2020
 
Description SSTT 2018 oral presentation 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Performed a presentation to researchers with about 100 people present on the tensile testing of materials and received questions.
Year(s) Of Engagement Activity 2018
 
Description Working as a graduate teaching assistant (GTA) in multiple subjects, performing lab demonstrations, teaching tutorial sessions, assessing and marking students and leading teaching activities. 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Undergraduate students
Results and Impact Working as a GTA teaching two or more modules per semester for the last four years means that far more than 500 students have been taught by Robert.

Feedback from students and supervisors has been very positive throughout Roberts time as a GTA. This culminated in a nomination for a student employee award.
Year(s) Of Engagement Activity 2016,2017,2018,2019