TY - BOOK

T1 - Investigation of the deformation and fracture behaviour of two steel grades under cold heading conditions

AU - Stögner, Philipp

N1 - embargoed until 02-11-2024

PY - 2021

Y1 - 2021

N2 - The cold heading of steels is an important process in the manufacturing of screws and high strength fasteners. Therefore, it is vital to characterise the forming behaviour of low-alloyed steels, the class of materials deployed, under the predominant multiaxial stress states. The aim of this work is to describe the influences on the formability of two selected materials, a precipitation hardening ferritic-pearlitic steel, 27MnSiVS6, in as-rolled condition, and a quenching and tempering steel, 42CrMo4, annealed. In a first step, the forming behaviour is investigated on a sub-grain level using in-situ tensile testing with deformation examined using a SEM and novel digital image correlation (DIC) methods. This setup allowed a depiction of the localization of strain and deformation on a microstructural level. To complement the influence of the microstructure on formability, an application-oriented testing method is developed. This setup, which models the final heading step during industrial production of screws and fasteners, the cold heading test (CHT), is used to quantify the influence of stress-state on the deformation and damaging behaviour. The experiments are supported by a finite element (FE) simulation of the CHT to predict the damage accumulation and multiaxial stress state during forming. The combination of the aforementioned methods, as well as the high accuracy of the application-oriented testing setup concerning influences on workability enable a thorough characterisation of the influences on formability and the damaging behaviour of low-alloyed steels.

AB - The cold heading of steels is an important process in the manufacturing of screws and high strength fasteners. Therefore, it is vital to characterise the forming behaviour of low-alloyed steels, the class of materials deployed, under the predominant multiaxial stress states. The aim of this work is to describe the influences on the formability of two selected materials, a precipitation hardening ferritic-pearlitic steel, 27MnSiVS6, in as-rolled condition, and a quenching and tempering steel, 42CrMo4, annealed. In a first step, the forming behaviour is investigated on a sub-grain level using in-situ tensile testing with deformation examined using a SEM and novel digital image correlation (DIC) methods. This setup allowed a depiction of the localization of strain and deformation on a microstructural level. To complement the influence of the microstructure on formability, an application-oriented testing method is developed. This setup, which models the final heading step during industrial production of screws and fasteners, the cold heading test (CHT), is used to quantify the influence of stress-state on the deformation and damaging behaviour. The experiments are supported by a finite element (FE) simulation of the CHT to predict the damage accumulation and multiaxial stress state during forming. The combination of the aforementioned methods, as well as the high accuracy of the application-oriented testing setup concerning influences on workability enable a thorough characterisation of the influences on formability and the damaging behaviour of low-alloyed steels.

KW - niedriglegierte Stähle

KW - Untersuchung der Kaltumformbarkeit

KW - mehrachsiger Spannungszustand

KW - digital image correlation (DIC)

KW - Massivumformsimulation

KW - low-alloyed steels

KW - cold heading testing

KW - formability

KW - multiaxial stress state

KW - digital image correlation methods

KW - finite element simulation

M3 - Doctoral Thesis

ER -