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Klaus A Riede - One of the best experts on this subject based on the ideXlab platform.
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energy dissipation capacity of fibre reinforced concrete under Biaxial Tension compression load part ii determination of the fracture process zone with the acoustic emission technique
Cement & Concrete Composites, 2015Co-Authors: Elmar K. Tschegg, Andreas Schneemaye, Ildiko Merta, Klaus A RiedeAbstract:Abstract Part I of this paper showed that under Biaxial Tension–compression load the energy dissipation capacity of fibre reinforced concretes (FRC) is up to 30% lower than under uniaxial Tension load. In this part, the extent of the fracture process zone (FPZ) was studied with the acoustic emission technique and the decrease of the energy dissipation will be explained. It was found that plain concrete specimens have generally narrower/smaller FPZ compared to FRC specimens under both uniaxial Tension and Biaxial Tension–compression load case. Under Biaxial Tension–compression load for both unreinforced and fibre reinforced specimens the FPZ tends to become slightly wider compared to the uniaxial Tension load case. However with increasing Biaxial compression stress ratios the specimens energy absorption capacity decreases. In case of Biaxial load, the bond between the fibre and the matrix zone is affected by the lateral compression stresses, resulting in a smaller FPZ compared to the uniaxial load. This is believed to be the main reason for the lower dissipated energy.
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energy dissipation capacity of fibre reinforced concrete under Biaxial Tension compression load part i test equipment and work of fracture
Cement & Concrete Composites, 2015Co-Authors: Elmar K. Tschegg, Andreas Schneemaye, Ildiko Merta, Klaus A RiedeAbstract:Abstract The objective of this research was to analyse the differences in the dissipated energy under uniaxial Tension and Biaxial Tension–compression load of fibre reinforced concretes using the Wedge Splitting Test. Under Biaxial load the specimens were subjected to compressive stress ratios from 10% to 50% of the concrete compressive strength perpendicular to the direction of the tensile load. Under Biaxial Tension–compression load the energy dissipation capacity of the specimens decreases compared to the uniaxial Tension load case on average 20–30%. It is believed that the decrease is a result of the damage mechanism of the concrete matrix and deterioration of the fibre–matrix and/or aggregate–cement paste interfaces in case the section is additionally loaded with compression stresses. This indicates that dimensioning of concrete elements under Biaxial stress states using material parameters obtained from tests conducted on specimens under uniaxial tensile load is unsafe and could potentially lead to a non-conservative design. In the second part of this paper the extent of the fracture process zone under uniaxial Tension and Biaxial Tension–compression load will be examined with the Acoustic Emission technique and the reasons for decrease of the energy dissipation capacity under Biaxial load will be further discussed.
Jeong Whan Yoon - One of the best experts on this subject based on the ideXlab platform.
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correlation of the maximum shear stress with micro mechanisms of ductile fracture for metals with high strength to weight ratio
International Journal of Mechanical Sciences, 2018Co-Authors: Qi Chao, Jeong Whan Yoon, Junghan SongAbstract:Abstract Mechanisms of ductile fracture are investigated experimentally in a wide range of loading conditions from compressive upsetting to the balanced Biaxial Tension for two metals with high strength-to-density ratio of DP980 (t1.2) steel sheets and a bulk aluminum alloy of AA7075. Specimens are carefully designed to achieve various loading conditions from shear at low stress triaxiality to the balanced Biaxial Tension at high stress triaxiality for DP980, while both tensile and compressive tests are conducted for AA7075. Fractured specimen surfaces are analyzed macroscopically focusing on their relations with the maximum shear stress. It is observed that all the specimens tend to fail along the direction of the maximum shear stress in various loading states of plane strain compression, uniaxial compression, shear, uniaxial Tension, plane strain Tension and the balanced Biaxial Tension. Scanning electron microscope analyses of fracture surfaces are also conducted to explore the underlying mechanism of void coalescence since coalescence of voids is viewed as the last step of ductile fracture after nucleation and growth of voids. It is noted that fractured voids elongate along the direction of the maximum shear stress for all specimens with the stress triaxiality ranging from about −0.57 in compression to 0.67 in the balanced Biaxial Tension. The experiments of DP980 and AA7075 reveal that ductile fracture takes place along the direction of the maximum shear stress in the wide loading conditions of compressive upsetting, shear, uniaxial Tension, plane strain Tension and the balanced Biaxial Tension with stress triaxiality below 0.67. Thus, ductile fracture is expected to be governed by the maximum shear stress in these wide loading conditions of compression, shear and Tension. It is suggested that effect of the maximum shear stress must be correctly coupled in modeling of ductile fracture in these loading conditions with uncoupled and coupled ductile fracture criteria.
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Anisotropic ductile fracture criterion based on linear transformation
International Journal of Plasticity, 2017Co-Authors: Jeong Whan YoonAbstract:Abstract An anisotropic ductile fracture criterion is proposed for ductile fracture of lightweight metals. The ductile fracture criterion couples effect of stress triaxiality on void growth, and assumes the shear linking-up of voids governed by the largest shear stress. The criterion is developed based on an isotropic strain rate potential computed from an isotropic damage equivalent strain rate vector, which is mapped from the plastic strain rate vector by a forth order linear transformation tensor. The proposed anisotropic ductile fracture criterion is applied to depict anisotropic ductile fracture of AA 6K21 in shear, uniaxial Tension and plane strain Tension along different loading directions, and the balanced Biaxial Tension. The predicted fracture strain and fracture locus are compared with experimental results for the verification of the proposed criterion. The comparison demonstrates that the ductile fracture criterion properly models the anisotropy in ductile fracture under shear, uniaxial Tension, plane strain Tension and balanced Biaxial Tension with high accuracy. It shows that the proposed anisotropic ductile fracture criterion can be utilized to predict the onset of ductile fracture in plastic deformation and metal forming of lightweight metals with approximately proportional loading.
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modeling of ductile fracture from shear to balanced Biaxial Tension for sheet metals
International Journal of Solids and Structures, 2017Co-Authors: Jeong Whan Yoon, Yanshan Lou, Lin Chen, Till Clausmeyer, Erman A TekkayaAbstract:Abstract A ductile fracture model is proposed to describe shear fracture of sheet metals from shear to balanced Biaxial Tension via uniaxial and plane strain Tension. The fracture criterion models plastic damage as strain-induced void nucleation, triaxiality-governed void enlargement, Lode-controlled void torsion, and shear-restrained coalescence of voids. Its flexibility is investigated by a parameter study of the ductile fracture model proposed. The fracture model is employed to describe ductile fracture behavior of an aluminum alloy AA6082 T6 (thickness: 1.0 mm). Dogbone specimens are strained to characterize the strain hardening properties, while another four different specimens are tested to characterize fracture behavior in shear, uniaxial Tension, plane strain Tension and balanced Biaxial Tension. The loading processes are analyzed numerically with the stress invariant-based Drucker yield function which is for the first time specified for body-centered cubic and face-centered cubic metals. Fracture strains in various loading conditions are measured with a hybrid experimental-numerical approach. The measured fracture strains are then used to calibrate the ductile fracture model proposed. The ductile fracture model calibrated above is employed to predict the onset of ductile fracture for these four specimens. For the purpose of comparison, the predicted fracture strokes of these four loading conditions are compared with those predicted by the modified Mohr–Coulomb model ( Bai and Wierzbicki, 2008 ), and two micromechanism-inspired criteria proposed recently ( Lou et al., 2012 , Lou et al., 2014 ). The comparison reveals that the proposed model predicts the fracture behavior in much better agreement compared with experimental results from shear to the balanced Biaxial Tension. Accordingly, the proposed ductile fracture criterion is recommended for the prediction of ductile fracture in sheet metal forming processes, optimization of forming parameters and design of tools for both solid elements and shell elements. Besides, the ductile fracture model proposed can also be applied in various bulk metal forming processes in case that the model is calibrated by proper sets of experiments.
Elmar K. Tschegg - One of the best experts on this subject based on the ideXlab platform.
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energy dissipation capacity of fibre reinforced concrete under Biaxial Tension compression load part ii determination of the fracture process zone with the acoustic emission technique
Cement & Concrete Composites, 2015Co-Authors: Elmar K. Tschegg, Andreas Schneemaye, Ildiko Merta, Klaus A RiedeAbstract:Abstract Part I of this paper showed that under Biaxial Tension–compression load the energy dissipation capacity of fibre reinforced concretes (FRC) is up to 30% lower than under uniaxial Tension load. In this part, the extent of the fracture process zone (FPZ) was studied with the acoustic emission technique and the decrease of the energy dissipation will be explained. It was found that plain concrete specimens have generally narrower/smaller FPZ compared to FRC specimens under both uniaxial Tension and Biaxial Tension–compression load case. Under Biaxial Tension–compression load for both unreinforced and fibre reinforced specimens the FPZ tends to become slightly wider compared to the uniaxial Tension load case. However with increasing Biaxial compression stress ratios the specimens energy absorption capacity decreases. In case of Biaxial load, the bond between the fibre and the matrix zone is affected by the lateral compression stresses, resulting in a smaller FPZ compared to the uniaxial load. This is believed to be the main reason for the lower dissipated energy.
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energy dissipation capacity of fibre reinforced concrete under Biaxial Tension compression load part i test equipment and work of fracture
Cement & Concrete Composites, 2015Co-Authors: Elmar K. Tschegg, Andreas Schneemaye, Ildiko Merta, Klaus A RiedeAbstract:Abstract The objective of this research was to analyse the differences in the dissipated energy under uniaxial Tension and Biaxial Tension–compression load of fibre reinforced concretes using the Wedge Splitting Test. Under Biaxial load the specimens were subjected to compressive stress ratios from 10% to 50% of the concrete compressive strength perpendicular to the direction of the tensile load. Under Biaxial Tension–compression load the energy dissipation capacity of the specimens decreases compared to the uniaxial Tension load case on average 20–30%. It is believed that the decrease is a result of the damage mechanism of the concrete matrix and deterioration of the fibre–matrix and/or aggregate–cement paste interfaces in case the section is additionally loaded with compression stresses. This indicates that dimensioning of concrete elements under Biaxial stress states using material parameters obtained from tests conducted on specimens under uniaxial tensile load is unsafe and could potentially lead to a non-conservative design. In the second part of this paper the extent of the fracture process zone under uniaxial Tension and Biaxial Tension–compression load will be examined with the Acoustic Emission technique and the reasons for decrease of the energy dissipation capacity under Biaxial load will be further discussed.
Andreas Schneemaye - One of the best experts on this subject based on the ideXlab platform.
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energy dissipation capacity of fibre reinforced concrete under Biaxial Tension compression load part ii determination of the fracture process zone with the acoustic emission technique
Cement & Concrete Composites, 2015Co-Authors: Elmar K. Tschegg, Andreas Schneemaye, Ildiko Merta, Klaus A RiedeAbstract:Abstract Part I of this paper showed that under Biaxial Tension–compression load the energy dissipation capacity of fibre reinforced concretes (FRC) is up to 30% lower than under uniaxial Tension load. In this part, the extent of the fracture process zone (FPZ) was studied with the acoustic emission technique and the decrease of the energy dissipation will be explained. It was found that plain concrete specimens have generally narrower/smaller FPZ compared to FRC specimens under both uniaxial Tension and Biaxial Tension–compression load case. Under Biaxial Tension–compression load for both unreinforced and fibre reinforced specimens the FPZ tends to become slightly wider compared to the uniaxial Tension load case. However with increasing Biaxial compression stress ratios the specimens energy absorption capacity decreases. In case of Biaxial load, the bond between the fibre and the matrix zone is affected by the lateral compression stresses, resulting in a smaller FPZ compared to the uniaxial load. This is believed to be the main reason for the lower dissipated energy.
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energy dissipation capacity of fibre reinforced concrete under Biaxial Tension compression load part i test equipment and work of fracture
Cement & Concrete Composites, 2015Co-Authors: Elmar K. Tschegg, Andreas Schneemaye, Ildiko Merta, Klaus A RiedeAbstract:Abstract The objective of this research was to analyse the differences in the dissipated energy under uniaxial Tension and Biaxial Tension–compression load of fibre reinforced concretes using the Wedge Splitting Test. Under Biaxial load the specimens were subjected to compressive stress ratios from 10% to 50% of the concrete compressive strength perpendicular to the direction of the tensile load. Under Biaxial Tension–compression load the energy dissipation capacity of the specimens decreases compared to the uniaxial Tension load case on average 20–30%. It is believed that the decrease is a result of the damage mechanism of the concrete matrix and deterioration of the fibre–matrix and/or aggregate–cement paste interfaces in case the section is additionally loaded with compression stresses. This indicates that dimensioning of concrete elements under Biaxial stress states using material parameters obtained from tests conducted on specimens under uniaxial tensile load is unsafe and could potentially lead to a non-conservative design. In the second part of this paper the extent of the fracture process zone under uniaxial Tension and Biaxial Tension–compression load will be examined with the Acoustic Emission technique and the reasons for decrease of the energy dissipation capacity under Biaxial load will be further discussed.
Ildiko Merta - One of the best experts on this subject based on the ideXlab platform.
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energy dissipation capacity of fibre reinforced concrete under Biaxial Tension compression load part ii determination of the fracture process zone with the acoustic emission technique
Cement & Concrete Composites, 2015Co-Authors: Elmar K. Tschegg, Andreas Schneemaye, Ildiko Merta, Klaus A RiedeAbstract:Abstract Part I of this paper showed that under Biaxial Tension–compression load the energy dissipation capacity of fibre reinforced concretes (FRC) is up to 30% lower than under uniaxial Tension load. In this part, the extent of the fracture process zone (FPZ) was studied with the acoustic emission technique and the decrease of the energy dissipation will be explained. It was found that plain concrete specimens have generally narrower/smaller FPZ compared to FRC specimens under both uniaxial Tension and Biaxial Tension–compression load case. Under Biaxial Tension–compression load for both unreinforced and fibre reinforced specimens the FPZ tends to become slightly wider compared to the uniaxial Tension load case. However with increasing Biaxial compression stress ratios the specimens energy absorption capacity decreases. In case of Biaxial load, the bond between the fibre and the matrix zone is affected by the lateral compression stresses, resulting in a smaller FPZ compared to the uniaxial load. This is believed to be the main reason for the lower dissipated energy.
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energy dissipation capacity of fibre reinforced concrete under Biaxial Tension compression load part i test equipment and work of fracture
Cement & Concrete Composites, 2015Co-Authors: Elmar K. Tschegg, Andreas Schneemaye, Ildiko Merta, Klaus A RiedeAbstract:Abstract The objective of this research was to analyse the differences in the dissipated energy under uniaxial Tension and Biaxial Tension–compression load of fibre reinforced concretes using the Wedge Splitting Test. Under Biaxial load the specimens were subjected to compressive stress ratios from 10% to 50% of the concrete compressive strength perpendicular to the direction of the tensile load. Under Biaxial Tension–compression load the energy dissipation capacity of the specimens decreases compared to the uniaxial Tension load case on average 20–30%. It is believed that the decrease is a result of the damage mechanism of the concrete matrix and deterioration of the fibre–matrix and/or aggregate–cement paste interfaces in case the section is additionally loaded with compression stresses. This indicates that dimensioning of concrete elements under Biaxial stress states using material parameters obtained from tests conducted on specimens under uniaxial tensile load is unsafe and could potentially lead to a non-conservative design. In the second part of this paper the extent of the fracture process zone under uniaxial Tension and Biaxial Tension–compression load will be examined with the Acoustic Emission technique and the reasons for decrease of the energy dissipation capacity under Biaxial load will be further discussed.