TY - JOUR A1 - Falkenreck, Thora E. A1 - Böllinghaus, Thomas T1 - Blast resistance of high-strength structural steel welds N2 - As consequence for increasing threats by IEDs (Improvised Explosive Devices) on vehicles, the blast resistance of the welded frames and bodies becomes increasingly important. Considering vehicle welds subjected to blasting, the real configurations of the joints in the structure and the position of the blast loads have to be considered. The present contribution thus focuses on a weld joint at the explosion endangered wheel well of a tactical truck. The high-strength steel welds were subsequently impacted by explosion loads within the upper range from those experienced in practical military operation to cause not only deformation, but also to investigate the ultimate fracture behaviour of the high-strength weld. The interaction between cooling time t8/5 and displacement, crack path as well as fracture surface was analysed. The analyses of the fracture surfaces revealed ductile overload failure and also the size of the dimples was influenced by the cooling time t8/5. As a prominent feature, these investigations showed that the crack path of such high-strength steel welds under blasting is less influenced by the final hardness level in the respective weld microstructures but much more affected by the hardness gradient at the fusion line and inside the Heat Affected Zone (HAZ). KW - Explosions KW - High strength steels KW - MAG welding KW - Cooling rate PY - 2016 U6 - https://doi.org/10.1007/s40194-016-0307-y SN - 0043-2288 SN - 1878-6669 VL - 60 IS - 3 SP - 475 EP - 483 PB - Springer CY - Heidelberg, Germany AN - OPUS4-36378 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Falkenreck, Thora A1 - Klein, M. A1 - Lammers, Marco A1 - Böllinghaus, Thomas T1 - The effects of weld filler material and cooling time t8/5 on the dynamic impact behaviour of high-strength laser-hybrid welds N2 - The use of high-strength steels is wide spread in vehicle and crane manufacturing due to light weight reasons. These steels are used for impact of crash loaded components and therefore it is important to investigate high-strength welds at dynamic impact. Investigations of welds at high strain rates have been rarely conducted in the past. To determine the dynamic impact behaviour of hybrid laser-arc welds, the Split Hopkinson Pressure Bar (SHPB) technique was used. The base material was a quenched and tempered fine-grained structural steel with yield strength of 1100 MPa. The influence of two variables, cooling time t8/5 and strength of filler material, on the impact behaviour was studied. A matching and an under matching filler material were used. The cooling time t8/5 was varied to influence the microstructure in the heat affected zone (HAZ) and to analyse the effect on hardening and softening. Hardness measurements and optical microscopy was used to analyse the weld microstructure before and after the SHPB test. The investigations showed a correlation between the overall hardness of the weld, influenced by filler material and cooling time, on the maximum stress level during dynamic impact. T2 - Trends in Welding Research 2016 CY - Tokyo, Japan DA - 11.10.2016 KW - High strength steel KW - Split Hopkinson pressure bar KW - Welding PY - 2016 AN - OPUS4-38171 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Falkenreck, Thora A1 - Böllinghaus, Thomas T1 - Blast Resistance of High Strength Structural Steel Welds T2 - 68th IIW Annual Assembly CY - Helsinki, Finland DA - 2015-06-28 PY - 2015 AN - OPUS4-34837 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Falkenreck, Thora A1 - Böllinghaus, Thomas T1 - Blast Resistance of High Strength Structural Steel Welds T2 - IIW Intermadiate CY - Istanbul, Turkey DA - 2015-03-02 PY - 2015 AN - OPUS4-32859 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Falkenreck, Thora E. A1 - Kromm, Arne A1 - Böllinghaus, Thomas T1 - Investigation of physically simulated weld HAZ and CCT diagram of HSLA armour steel N2 - The phase transformation under various cooling rates and in different HAZ regions for high-strength armour steel was analysed by dilatometry. To develop a continuous cooling transformation (CCT) diagram, the samples were heated up to a peak temperature of 1250 °C to achieve a coarse-grained microstructure and then cooled down with a cooling time t 8/5 varying from 3 to 240 s. Analysis of dilatation curves revealed the austenite decomposition process, during which transformation temperatures were determined. The results showed martensitic transformations for all welding-relevant cooling times. Furthermore, to analyse different heat-affected subzones of the weld, the peak temperature was varied between 550 and 1250 °C at a constant cooling time t 8/5 of 6 s. The simulated coarse-grained heat-affected zone (CGHAZ) and fine-grained-heat affected zone (FGHAZ) showed only martensitic transformations with transformation temperatures below 400 °C. The steel exhibited an inhomogeneous hardness with hardening in the CGHAZ and FGHAZ and softening in the intercritical and subcritical HAZ. The physically simulated microstructure was validated by a real hybrid laser-arc weld microstructure. KW - Dilatometry KW - High-strength steels KW - CCT diagrams KW - Heat-affected zone PY - 2018 U6 - https://doi.org/10.1007/s40194-017-0511-4 SN - 0043-2288 SN - 1878-6669 VL - 62 IS - 1 SP - 47 EP - 54 PB - Springer AN - OPUS4-44716 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Falkenreck, Thora A1 - Kromm, Arne A1 - Böllinghaus, Thomas T1 - Investigation of Physically Simulated Weld HAZ and CCT-diagram of HSLA steel N2 - The phase transformation under various cooling rates and in different HAZ regions for high strength armour steel was analysed by dilatometry. To develop a Continuous Colling Transformation (CCT) diagram, the samples were heated up to a peak temperature of 1250 °C to achieve a coarse grained microstructure and then cooled down with a cooling time t8/5 varying from 3 s to 240 s. Analysis of dilatation curves revealed the austenite decomposition process, during which transformation temperatures were determined. The results showed martensitic transformations for all welding relevant cooling times. Furthermore, to analyse different heat affected subzones of the weld, the peak temperature was varied between 550 °C and 1250 °C at a constant cooling time t8/5 of 6 s. The simulated coarse grained heat affected zone (CGHAZ) and fine grained heat affected zone (FGHAZ) showed only martensitic transformations with transformation temperatures below 400 °C. The steel exhibited an inhomogeneous hardness with hardening in the CGHAZ and FGHAZ and softening in the intercritical and subcritical HAZ. The physically simulated microstructure was validated by a real hybrid laser-arc weld microstructure. T2 - IIW Intermediate meeting, IX-L CY - Trollhättan, Sweden DA - 06.03.2017 KW - Dilatometry KW - High strength stells KW - CCT diagrams KW - Heat affected zone PY - 2017 AN - OPUS4-39437 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Falkenreck, Thora A1 - Klein, M. A1 - Böllinghaus, Thomas T1 - Dynamic compressive behaviour of weld joints N2 - Materials used in military applications have to withstand multiple threats like ballistics and explosions. Thus, high-strength low alloyed (HSLA) steels are used. The main joining technique for metals is welding. Therefore, analysing the dynamic impact behaviour of high-strength welds is very important to fulfil these demands. Investigation of welds at high strain rates has rarely been conducted in the past. To determine the dynamic impact behaviour of hybrid laser-arc welds, the Split Hopkinson Pressure Bar (SHPB) technique was used. The base material was a quenched and tempered fine-grained armour steel with yield strength of 1100 MPa. First, a full hybrid laser-arc weld was investigated by extracting specimens consisting of weld metal and heat affected base material. The influence of two variables, the cooling time between 800 °C and 500 °C (t8/5) and strength of filler material, on the impact behaviour was studied. The cooling time t8/5 was varied by preheating to influence the microstructure in the HAZ and to analyse the effect on the hardness and dynamic compressive strength. Subsequent analysis to detail the original Investigation was carried out by dilatometer heat treatment of specimens to create homogenous subzones of the weld. These specimens have a homogenous microstructure of HAZ and were tested by SHPB to determine the stress-strain characteristics for the different microstructures of HAZ. The results of the weld specimen showed the effect of preheating and filler material strength on the dynamic compressive behaviour. The analysis of the different microstructures of the HAZ indicated that especially the tempered microstructure caused a reduction in dynamic compressive strength. KW - SHPB KW - Hybrid laser-arc weld KW - Dilatometry PY - 2017 U6 - https://doi.org/10.1016/j.msea.2017.07.032 SN - 0921-5093 SN - 1873-4936 VL - 702 SP - 322 EP - 330 AN - OPUS4-41904 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -