The use of hollow sections to form lightweight structures is widespread in common steel processin... more The use of hollow sections to form lightweight structures is widespread in common steel processing industries such as crane, commercial vehicle, steel bridge and agricultural machinery construction. The hollow sections are mainly designed as truss or frame structures, in some cases using high-strength and higher-strength steels in order to achieve optimum utilization of the component and material. A new collection of fatigue life data covering sequence effects and the accuracy of the linear damage accumulation is presented. Effects of the shape of the applied load spectra and sequence effects of different amplitudes have been investigated. This document covers tubes of 4 to 8 mm thickness made by low-carbon or mild steel S355J2H. In general, it was found that the spectrum shape and the loading sequence have an influence on the service life. Depending on the shape of the spectrum, random tests tended to lead to shorter service lives than tests with block-loading sequences. An influence of overloads was also found for the tests with interspersed overloads. Typical maximum linear damage sums taken from recommendations and codes of 0.2 or sometimes 0.5 are exceeded for all spectra investigated and in some of the cases even significantly above 1.0. Transferability of the recommendations to component-type structures like tubular joints needs revision to lift its lightweight potential. Using stress concentration factors (SCF) from finite element analysis, typical strength values for the structural and effective notch stress concepts are checked. All joints investigated show a significantly higher strength compared to the IIW recommendations using the structural stress approach or compared to the DVS 0905 with the effective notch stress approach. Tubular constructions • Carbon steels • Fatigue tests • Fatigue strength • Finite element analysis • Variable loading Nomenclature * Klemens Rother
Truss-like shapes can occur in topology optimization described by an assembly of finite elements ... more Truss-like shapes can occur in topology optimization described by an assembly of finite elements or its boundary represented as a polygon mesh. Such shape description does not cover a common engineering parametrization like the lines of a frame structure and its corresponding cross-section. This article addresses the truss-parametrization of such optimization using curve skeletons and Meta Balls. While the curve skeleton is common in the truss-parametrization, including Meta Balls can lead to an overall implicit and smooth shape description.
The aim of this study is to evaluate fatigue performance of joined assemblies (spot weld and/or a... more The aim of this study is to evaluate fatigue performance of joined assemblies (spot weld and/or adhesive bonding) in corrosive environment. Various assemblies have been tested in alternated and simultaneous fatigue‐corrosion modes. Adhesive joints are strongly affected by simultaneous fatigue‐corrosion with a large drop of the fatigue life compared to results in air. By alternating fatigue and corrosion, the reduction of fatigue life is important. For spot welding, fatigue life is decreased at higher load amplitudes and increased at lower amplitudes. These results are strongly linked to the opening of the gap near the spot weld at high load amplitudes. At low amplitudes, corrosion might limit the local stress at the notch root of the weld.
Welded hollow sections are typical in different industries. A database of fatigue life data of we... more Welded hollow sections are typical in different industries. A database of fatigue life data of welded hollow section joints covering sequence effects and the accuracy of the linear damage accumulation is presented. The effects of the shape of the applied load spectra, sequence effects of different amplitudes have been investigated using two high-strength steels. This document covers thin-walled tubes of 2-mm thickness made of low-carbon or mild steel 1.8849 (S460MH) and austenitic TWIP-steel 1.4678 + CP700 (X30MnCrN16-14). Constant amplitude and two-level load spectra are presented to check the linear damage accumulation. Using stress concentration factors from finite element analysis, typical FAT classes for the structural and the effective notch stress concepts are checked as well. Both structures show much higher strength compared IIW recommendations by structural stress approach and DVS 0905 by effective notch stress approach. Typical maximum linear damage sums taken from recomm...
The effective notch stress approach to estimate fatigue strength of welded components requires st... more The effective notch stress approach to estimate fatigue strength of welded components requires stress concentration factors of an idealized weld geometry using fictitious notch radii. This paper covers the estimation of those stress concentration factors for welded T-joints in different configurations. In comparison with different existing estimations, new methods using metamodeling by (a) the response surface method based on polynomial regression using coupling terms and (b) based on artificial neural networks are presented. The methods were trained by a large database of reference results obtained by finite element analysis. Besides higher quality of prognosis, the new metamodels enhance the range of allowable parameters of the T-joints compared to existing ones. The resulting methods provide means of obtaining stress concentration factors fast and of sufficient quality which could also be embedded in more complex applications as programmed solutions.
This paper presents the influences of the irregularity "insufficient penetration welding" on the ... more This paper presents the influences of the irregularity "insufficient penetration welding" on the fatigue strength based on experimental and numerical investigations. For this purpose, the fatigue strength of partial penetration butt welds of mild steel (S355) with different non-welded gaps were subjected to fatigue loading. Three different planned gap dimensions (h = 4, 6, 8 mm) at one-sided (Y-seam) and two-sided (DY-seam) partial penetration butt welds were analysed. The results were obtained on a small-scale test specimen with a steel plate thickness of t = 20 mm, without axial and angular misalignment. For the numerical effective notch stress approach, regression formula for efficient analysis of stress concentration factors was determined. The results show that butt joints which are not fully penetrated on one or both sides, and which were previously not permissible for welded joints subject to fatigue loading, can be evaluated in the future on the basis of these investigations. Keywords Fatigue • Partial penetration butt weld • S355 • Mild steel • Y-seam • DY-seam • Fatigue strength • Finite element model • Meta model • Effective notch stress approach • ISO 5817 • Weld quality Abbreviations Material, test specimen and state parameter f y Yield strength in [MPa] S355 Mild steel (S355) S355J2 + N, EN 10025 with a nominal yield strength of f y = 355 MPa t Plate thickness in [mm] Recommended for publication by Commission XIII-Fatigue of Welded Components and Structures.
In order to ensure high weld qualities and structural integrity of engineering structures, it is ... more In order to ensure high weld qualities and structural integrity of engineering structures, it is crucial to detect areas of high stress concentrations along weld seams. Traditional inspection methods rely on visual inspection and manual weld geometry measurements. Recent advances in the field of automated measurement techniques allow virtually unrestricted numbers of inspections by laser measurements of weld profiles; however, in order to compare weld qualities of different welding processes and manufacturers, a deeper understanding of statistical distributions of stress concentrations along weld seams is required. Hence, this study presents an approach to statistically characterize different types of butt joint weld seams. For this purpose, an artificial neural network is created from 945 finite element simulations to determine stress concentration factors at butt joints. Besides higher quality of predictions compared to empirical estimation functions, the new approach can directly...
Organisationen und Prozesse in der Fahrzeugentwicklung sind in den letzten Jahrzehnten vordringli... more Organisationen und Prozesse in der Fahrzeugentwicklung sind in den letzten Jahrzehnten vordringlich auf standardisierte Ablaufe einer Anderungskonstruktion ausgerichtet wurden. Simulationsunterstutze Entwicklung wurde vor allem im Hinblick auf die Steigerung der Prognosegute und standardisierter Simulationsprozesse optimiert. Eine Analyse des Entwicklungsprozess in der fruhen Phase bei einem grosen deutschen OEM (Damjanovic et al. 2014) hat ergeben, dass in Verbesserungen des Wissens- und Datenmanagements sowie der Modellierung von (nicht nur) konzeptioneller Geometrie inkl. Simulation auf 3D sowie die Verbesserung interdisziplinarer Zusammenarbeit erhebliche Potenziale schlummern. Losungsansatze ergeben sich hierzu beispielsweise im Aufbrechen einer strikten Trennung von fruher und spater Phase, in Modellierungstechniken, die durch Parametrisierung Variantenvielfalt fordern, durch Zugriff und damit Sicherstellung der Nachvollziehbarkeit des sich steigernden Detaillierungsgrads uber die PLM/SPDM-Systeme, in einer verbesserten simulations- und optimierungsgesteuerten Konstruktion mit ganzheitlich greifenden, d.h. holistischen Ansatzen, oder auch durch Verbesserung unternehmensweiter, effizienter Datenubertragung und einer Verminderung von Barrieren bzw. Interfaces.
Hybrid structures hold a high potential of lightweight design which is important for the automoti... more Hybrid structures hold a high potential of lightweight design which is important for the automotive industry. To find an appropriate design of those multi material parts is a key criterion for its application in a car body. In this paper a methodology is presented which allows the definition of an advantageous hybrid part design considering demands on structure stiffness, strength, local stability and weight. The analytical approach allows a rapid optimization of parameters, like the dimensions of a cross section, materials and boundary conditions. In order to improve understanding of the implementation and working method, an analogous model of a real car door sill is optimized. Two different concepts to reinforce the steel structure with CFRP are defined and investigated. A) CFRP reinforcement on each side of a rectangular crosssection leads to a weight saving of 31% compared to the reference structure with the same bending stiffness made of high-strength steel. At the same time th...
Simultaneous & alternated fatigue-corrosion performance of joined materials for automotive applic... more Simultaneous & alternated fatigue-corrosion performance of joined materials for automotive applications
The use of hollow sections to form lightweight structures is widespread in common steel processin... more The use of hollow sections to form lightweight structures is widespread in common steel processing industries such as crane, commercial vehicle, steel bridge and agricultural machinery construction. The hollow sections are mainly designed as truss or frame structures, in some cases using high-strength and higher-strength steels in order to achieve optimum utilization of the component and material. A new collection of fatigue life data covering sequence effects and the accuracy of the linear damage accumulation is presented. Effects of the shape of the applied load spectra and sequence effects of different amplitudes have been investigated. This document covers tubes of 4 to 8 mm thickness made by low-carbon or mild steel S355J2H. In general, it was found that the spectrum shape and the loading sequence have an influence on the service life. Depending on the shape of the spectrum, random tests tended to lead to shorter service lives than tests with block-loading sequences. An influence of overloads was also found for the tests with interspersed overloads. Typical maximum linear damage sums taken from recommendations and codes of 0.2 or sometimes 0.5 are exceeded for all spectra investigated and in some of the cases even significantly above 1.0. Transferability of the recommendations to component-type structures like tubular joints needs revision to lift its lightweight potential. Using stress concentration factors (SCF) from finite element analysis, typical strength values for the structural and effective notch stress concepts are checked. All joints investigated show a significantly higher strength compared to the IIW recommendations using the structural stress approach or compared to the DVS 0905 with the effective notch stress approach. Tubular constructions • Carbon steels • Fatigue tests • Fatigue strength • Finite element analysis • Variable loading Nomenclature * Klemens Rother
Truss-like shapes can occur in topology optimization described by an assembly of finite elements ... more Truss-like shapes can occur in topology optimization described by an assembly of finite elements or its boundary represented as a polygon mesh. Such shape description does not cover a common engineering parametrization like the lines of a frame structure and its corresponding cross-section. This article addresses the truss-parametrization of such optimization using curve skeletons and Meta Balls. While the curve skeleton is common in the truss-parametrization, including Meta Balls can lead to an overall implicit and smooth shape description.
The aim of this study is to evaluate fatigue performance of joined assemblies (spot weld and/or a... more The aim of this study is to evaluate fatigue performance of joined assemblies (spot weld and/or adhesive bonding) in corrosive environment. Various assemblies have been tested in alternated and simultaneous fatigue‐corrosion modes. Adhesive joints are strongly affected by simultaneous fatigue‐corrosion with a large drop of the fatigue life compared to results in air. By alternating fatigue and corrosion, the reduction of fatigue life is important. For spot welding, fatigue life is decreased at higher load amplitudes and increased at lower amplitudes. These results are strongly linked to the opening of the gap near the spot weld at high load amplitudes. At low amplitudes, corrosion might limit the local stress at the notch root of the weld.
Welded hollow sections are typical in different industries. A database of fatigue life data of we... more Welded hollow sections are typical in different industries. A database of fatigue life data of welded hollow section joints covering sequence effects and the accuracy of the linear damage accumulation is presented. The effects of the shape of the applied load spectra, sequence effects of different amplitudes have been investigated using two high-strength steels. This document covers thin-walled tubes of 2-mm thickness made of low-carbon or mild steel 1.8849 (S460MH) and austenitic TWIP-steel 1.4678 + CP700 (X30MnCrN16-14). Constant amplitude and two-level load spectra are presented to check the linear damage accumulation. Using stress concentration factors from finite element analysis, typical FAT classes for the structural and the effective notch stress concepts are checked as well. Both structures show much higher strength compared IIW recommendations by structural stress approach and DVS 0905 by effective notch stress approach. Typical maximum linear damage sums taken from recomm...
The effective notch stress approach to estimate fatigue strength of welded components requires st... more The effective notch stress approach to estimate fatigue strength of welded components requires stress concentration factors of an idealized weld geometry using fictitious notch radii. This paper covers the estimation of those stress concentration factors for welded T-joints in different configurations. In comparison with different existing estimations, new methods using metamodeling by (a) the response surface method based on polynomial regression using coupling terms and (b) based on artificial neural networks are presented. The methods were trained by a large database of reference results obtained by finite element analysis. Besides higher quality of prognosis, the new metamodels enhance the range of allowable parameters of the T-joints compared to existing ones. The resulting methods provide means of obtaining stress concentration factors fast and of sufficient quality which could also be embedded in more complex applications as programmed solutions.
This paper presents the influences of the irregularity "insufficient penetration welding" on the ... more This paper presents the influences of the irregularity "insufficient penetration welding" on the fatigue strength based on experimental and numerical investigations. For this purpose, the fatigue strength of partial penetration butt welds of mild steel (S355) with different non-welded gaps were subjected to fatigue loading. Three different planned gap dimensions (h = 4, 6, 8 mm) at one-sided (Y-seam) and two-sided (DY-seam) partial penetration butt welds were analysed. The results were obtained on a small-scale test specimen with a steel plate thickness of t = 20 mm, without axial and angular misalignment. For the numerical effective notch stress approach, regression formula for efficient analysis of stress concentration factors was determined. The results show that butt joints which are not fully penetrated on one or both sides, and which were previously not permissible for welded joints subject to fatigue loading, can be evaluated in the future on the basis of these investigations. Keywords Fatigue • Partial penetration butt weld • S355 • Mild steel • Y-seam • DY-seam • Fatigue strength • Finite element model • Meta model • Effective notch stress approach • ISO 5817 • Weld quality Abbreviations Material, test specimen and state parameter f y Yield strength in [MPa] S355 Mild steel (S355) S355J2 + N, EN 10025 with a nominal yield strength of f y = 355 MPa t Plate thickness in [mm] Recommended for publication by Commission XIII-Fatigue of Welded Components and Structures.
In order to ensure high weld qualities and structural integrity of engineering structures, it is ... more In order to ensure high weld qualities and structural integrity of engineering structures, it is crucial to detect areas of high stress concentrations along weld seams. Traditional inspection methods rely on visual inspection and manual weld geometry measurements. Recent advances in the field of automated measurement techniques allow virtually unrestricted numbers of inspections by laser measurements of weld profiles; however, in order to compare weld qualities of different welding processes and manufacturers, a deeper understanding of statistical distributions of stress concentrations along weld seams is required. Hence, this study presents an approach to statistically characterize different types of butt joint weld seams. For this purpose, an artificial neural network is created from 945 finite element simulations to determine stress concentration factors at butt joints. Besides higher quality of predictions compared to empirical estimation functions, the new approach can directly...
Organisationen und Prozesse in der Fahrzeugentwicklung sind in den letzten Jahrzehnten vordringli... more Organisationen und Prozesse in der Fahrzeugentwicklung sind in den letzten Jahrzehnten vordringlich auf standardisierte Ablaufe einer Anderungskonstruktion ausgerichtet wurden. Simulationsunterstutze Entwicklung wurde vor allem im Hinblick auf die Steigerung der Prognosegute und standardisierter Simulationsprozesse optimiert. Eine Analyse des Entwicklungsprozess in der fruhen Phase bei einem grosen deutschen OEM (Damjanovic et al. 2014) hat ergeben, dass in Verbesserungen des Wissens- und Datenmanagements sowie der Modellierung von (nicht nur) konzeptioneller Geometrie inkl. Simulation auf 3D sowie die Verbesserung interdisziplinarer Zusammenarbeit erhebliche Potenziale schlummern. Losungsansatze ergeben sich hierzu beispielsweise im Aufbrechen einer strikten Trennung von fruher und spater Phase, in Modellierungstechniken, die durch Parametrisierung Variantenvielfalt fordern, durch Zugriff und damit Sicherstellung der Nachvollziehbarkeit des sich steigernden Detaillierungsgrads uber die PLM/SPDM-Systeme, in einer verbesserten simulations- und optimierungsgesteuerten Konstruktion mit ganzheitlich greifenden, d.h. holistischen Ansatzen, oder auch durch Verbesserung unternehmensweiter, effizienter Datenubertragung und einer Verminderung von Barrieren bzw. Interfaces.
Hybrid structures hold a high potential of lightweight design which is important for the automoti... more Hybrid structures hold a high potential of lightweight design which is important for the automotive industry. To find an appropriate design of those multi material parts is a key criterion for its application in a car body. In this paper a methodology is presented which allows the definition of an advantageous hybrid part design considering demands on structure stiffness, strength, local stability and weight. The analytical approach allows a rapid optimization of parameters, like the dimensions of a cross section, materials and boundary conditions. In order to improve understanding of the implementation and working method, an analogous model of a real car door sill is optimized. Two different concepts to reinforce the steel structure with CFRP are defined and investigated. A) CFRP reinforcement on each side of a rectangular crosssection leads to a weight saving of 31% compared to the reference structure with the same bending stiffness made of high-strength steel. At the same time th...
Simultaneous & alternated fatigue-corrosion performance of joined materials for automotive applic... more Simultaneous & alternated fatigue-corrosion performance of joined materials for automotive applications
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