An Approach to Predict Geometrically and Thermo-Mechanically Induced Stress Concentrations in Ribbed Reinforcing Bars

Robl, Tobias; Wölfle, Christoph Hubertus; Hameed, Muhammed Zubair Shahul; Rappl, Stefan; Krempaszky, Christian; Werner, Ewald

doi:10.3390/met12030411

Cited by 4 publications

(24 citation statements)

References 34 publications

(63 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The decrease in the notch stress factor with increasing radius follows a logarithmic trend, as derived from the values found in the literature [13,19] and Equation (2).…”

supporting

confidence: 58%

“…In a German Research Foundation (DFG) research project, the production process of rebars and its effect on fatigue was investigated. The thermomechanical point of view and its consequence on the residual stress distribution was already published elsewhere (for further information, see Hameed et al [1] and Robl et al [2]). This study focuses specifically on the surface topography and the mechanical behavior of the microstructure.…”

Section: Introduction 1motivationmentioning

confidence: 99%

See 1 more Smart Citation

Mechanical and Surface Geometric Properties of Reinforcing Bars and Their Significance for the Development of Near-Surface Notch Stresses

et al. 2023

Self Cite

View full text Add to dashboard Cite

Due to the production process, reinforcing steel bars possess an inhomogeneous microstructure associated with different material properties over the cross-section (e.g., hardness, ductility or strength). Furthermore, the surface required for the bond has a negative effect on the fatigue behavior. The first investigations were carried out in the 1970s and detected the fillet radius r as a key influencing factor. Until now, few studies had been carried out that investigate the quantification of the surface properties on the fatigue behavior, and none of them compared these properties with the local strengths of the material. The current paper presents the first results of a reverse-engineered reinforcing steel bar based on a previously performed laser scanning process. The rebar models were used to calculate the notch stress factors for different diameters based on von Mises stresses taken from FEM simulations. The notch stress factors showed a functional relationship with the fillet radius, which was already shown in the literature. Further experimental investigations on the fatigue and tensile behavior of the structural components in the investigated Tempcore® rebars were carried out on microstructure specimens eroded by WEDM. The results of the tensile tests were used to derive a yield and tensile strength distribution in the cross-section. Depending on the microstructure, a yield strength between 415 N/mm2 (ferrite/pearlite core) and 690 N/mm2 (tempered martensite surface) was found. The acting notch stresses show a logarithmic dependency of the fillet radius, but do not reach the material strength of the surface.

show abstract

“…The decrease in the notch stress factor with increasing radius follows a logarithmic trend, as derived from the values found in the literature [13,19] and Equation (2).…”

supporting

confidence: 58%

Section: Introduction 1motivationmentioning

confidence: 99%

Mechanical and Surface Geometric Properties of Reinforcing Bars and Their Significance for the Development of Near-Surface Notch Stresses

et al. 2023

Self Cite

View full text Add to dashboard Cite

show abstract

“…At the same time, the martensitic rim is reheated and tempered by the heat from the core. By adjusting the heat-treatment parameters, e.g., by varying the quenching time, the TempCore TM process allows the production of rebars of different strengths and ductilities [ 3 , 4 , 5 ].…”

Section: Introductionmentioning

confidence: 99%

“…Also, in particular critical regions of the rebar surface, where most of the fatigue cracks form, i.e., the foot radius regions of the transverse ribs, residual stresses have not yet been investigated experimentally. A numerical model suggested by the authors of this study [ 3 ] overestimates the residual stress level in rebars quantitatively because presumably important effects have not been considered, such as transformation-induced plasticity (TRIP) and tempering of the martensitic rim during cooling in air.…”

Section: Introductionmentioning

confidence: 99%

“…In order to extend the knowledge about residual stresses in rebars, in this work residual stress measurements were carried out on a rebar specimen. The results of these measurements were compared to the results of numerical simulations of the TempCore TM process, whereas the numerical model used was an extended version of the model of Robl et al [ 3 ]. In the extended model, tempering of martensite and TRIP were considered.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Residual Stresses in Ribbed Reinforcing Bars

Robl,

Hegele,

Krempaszky

et al. 2023

Materials

Self Cite

View full text Add to dashboard Cite

Ribbed reinforcing bars (rebars) are used for the reinforcement of concrete structures. In service, they are often subjected to cyclic loading. In general, the fatigue performance of rebars may be influenced by residual stresses originating from the manufacturing process. Knowledge about residual stresses in rebars and their origin, however, is sparse. So far, residual stress measurements are limited to individual stress components, viz., to the non-ribbed part of the rebar surface. At critical points of the rebar surface, where most of the fatigue cracks originate, i.e., the foot radius regions of transverse ribs, the residual stress state has not yet been investigated experimentally. To extend the knowledge about residual stresses in rebars within the scope of this work, residual stress measurements were carried out on a rebar specimen with a diameter of 28 mm made out of the rebar steel grade B500B. In addition, numerical simulations of the TempCoreTM process were carried out. The results of the experimental investigations show tensile residual stresses in the core and the transition zone of the examined rebar specimen. Low compressive residual stresses are measured at the non-ribbed part of the rebar surface, while high compressive residual stresses are present at the tip of the transverse ribs. The results of the numerical investigations are in reasonable accordance with the experimental results. Furthermore, the numerical results indicate moderate tensile stresses occurring on the rebar surface in the rib foot radius regions of the transverse ribs. High stress gradients directly beneath the rebar surface, which are reported in the literature and which are most likely related to a thin decarburized surface layer, could be reproduced qualitatively with the numerical model developed.

show abstract

Rib Reinforcement Bionic Topology Optimization under Multi-Scale Cyclic Excitation

Xiao

Zhu

et al. 2023

Mathematics

View full text Add to dashboard Cite

Thin-walled structures have problems such as low stiffness, large deflection, and vibration. The layout of rib reinforcement in thin-walled structures plays a vital role in providing structural strength and rigidity and reducing structural weight. A multi-scale bionic topology optimization method with a cyclic variable load is proposed in this paper to optimize dynamic flexibility by simulating the growth law of leaf vein formation and distribution. A material interpolation method is adopted to penalize the material attributes of rib reinforcement according to their thickness, based on polynomial interpolation. Combined with the layout of rib reinforcement and SIMP, the mathematical model of rib reinforcement layout optimization with cyclic variable loading is proposed, and the sensitivity of thin-walled dynamic flexibility to the rib reinforcement thickness is analyzed. Two typical examples of thin-walled structures are presented to validate the proposed method. Considering the impact effect of multi-scale cyclic loads such as wind speed, pressure, and raindrops acting on the leaf vein, the natural frequencies of bionic topological structures of heart-shaped and elliptical leaf veins are increased by 63.44% and 47.2%, respectively. Considering the change in radial thickness, the mass of the automotive door inner panel with a bionic topological structure increased by 3.2%, the maximum stress value was reduced by 1.4% and 36.8%, and deformation was reduced by 37.6% and 27.1% under the anti-concave and sinking conditions, respectively. Moreover, the first-order natural frequency of the automotive door’s inner panel with a bionic topological structure increased to 30.45%, 3.7% higher than the original.

show abstract

An Approach to Predict Geometrically and Thermo-Mechanically Induced Stress Concentrations in Ribbed Reinforcing Bars

Cited by 4 publications

References 34 publications

Mechanical and Surface Geometric Properties of Reinforcing Bars and Their Significance for the Development of Near-Surface Notch Stresses

Mechanical and Surface Geometric Properties of Reinforcing Bars and Their Significance for the Development of Near-Surface Notch Stresses

Residual Stresses in Ribbed Reinforcing Bars

Rib Reinforcement Bionic Topology Optimization under Multi-Scale Cyclic Excitation

Contact Info

Product

Resources

About