101 research outputs found
Determination of the Constants of GTN Damage Model Using Experiment, Polynomial Regression and Kriging Methods
No full textDamage models, particularly the Gurson–Tvergaard–Needleman (GTN) model, are widely used in numerical simulation of material deformations. Each damage model has some constants which must be identified for each material. The direct identification methods are costly and time consuming. In the current work, a combination of experimental, numerical simulation and optimization were used to determine the constants. Quasi-static and dynamic tests were carried out on notched specimens. The experimental profiles of the specimens were used to determine the constants. The constants of GTN damage model were identified through the proposed method and using the results of quasi-static tests. Numerical simulation of the dynamic test was performed utilizing the constants obtained from quasi-static experiments. The results showed a high precision in predicting the specimen’s profile in the dynamic testing. The sensitivity analysis was performed on the constants of GTN model to validate the proposed method. Finally, the experiments were simulated using the Johnson–Cook (J–C) damage model and the results were compared to those obtained from GTN damage model
Experimental videos in studying the influences of dry- and wet-bed downstream conditions on dam break multiphase flood waves in a reservoir with 20 cm sediment depth (67.7% silted-up)
No full textExperimental videos:
Herein, 24 distinct video files have been presented which related to dam break multiphase flood shock wave experiments, performed in the Shiraz University, Civil and Environmental Engineering Department’s Hydraulic Lab (Shiraz, Iran). The initial upstream sediment depth was 20 cm which makes the upstream reservoir 67.7% silted-up with respect to the total 30 cm height of the reservoir. Different initial downstream conditions have also been considered including dry-bed downstream and wet-bed downstream with different levels of standing water; 2 cm, 4 cm and 5 cm.
Considering three cameras which covered length of the flume, 4 different dam break scenarios and 2 repetitions conducted for each test, a total of 24 videos collected which presented in this document.
The additional explanations related to video files can be seen in “Explanation table of videos” file which attached to this document in Microsoft Word (DOCX/DOC) format.
Foad Vosoughi, Gholamreza Rakhshandehroo, Mohammad Reza Nikoo
Affiliations
1st Author: Foad Vosoughi, Research Associate, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran. [email protected]
2nd Author: Gholamreza Rakhshandehroo, Professor, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran.
3rd Author: Mohammad Reza Nikoo, Associate Professor, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran
Experimental videos in studying the influences of dry- and wet-bed downstream conditions on dam break multiphase flood waves in a reservoir with 3 cm sediment depth (10% silted-up)
No full textExperimental videos:
Herein, 24 distinct video files have been presented which related to dam break multiphase flood shock wave experiments, performed in the Shiraz University, Civil and Environmental Engineering Department’s Hydraulic Lab (Shiraz, Iran). The initial upstream sediment depth was 3 cm which makes the upstream reservoir 10% silted-up with respect to the total 30 cm height of the reservoir. Different initial downstream conditions have also been considered including dry-bed downstream and wet-bed downstream with different levels of standing water; 2 cm, 4 cm and 5 cm.
Considering three cameras which covered length of the flume, 4 different dam break scenarios and 2 repetitions conducted for each test, a total of 24 videos collected which presented in this document.
The additional explanations related to video files can be seen in “Explanation table of videos” file which attached to this document in Microsoft Word (DOCX/DOC) format.
Foad Vosoughi, Gholamreza Rakhshandehroo, Mohammad Reza Nikoo
Affiliations
1st Author: Foad Vosoughi, Research Associate, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran. [email protected]
2nd Author: Gholamreza Rakhshandehroo, Professor, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran.
3rd Author: Mohammad Reza Nikoo, Associate Professor, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran
Experimental videos in studying the influences of dry- and wet-bed downstream conditions on dam break multiphase flood waves in a reservoir with 7.5 cm sediment depth (25% silted-up)
No full textExperimental videos:
Herein, 24 distinct video files have been presented which related to dam break multiphase flood shock wave experiments, performed in the Shiraz University, Civil and Environmental Engineering Department’s Hydraulic Lab (Shiraz, Iran). The initial upstream sediment depth was 7.5 cm which makes the upstream reservoir 25% silted-up with respect to the total 30 cm height of the reservoir. Different initial downstream conditions have also been considered including dry-bed downstream and wet-bed downstream with different levels of standing water; 2 cm, 4 cm and 5 cm.
Considering three cameras which covered length of the flume, 4 different dam break scenarios and 2 repetitions conducted for each test, a total of 24 videos collected which presented in this document.
The additional explanations related to video files can be seen in “Explanation table of videos” file which attached to this document in Microsoft Word (DOCX/DOC) format.
Foad Vosoughi, Gholamreza Rakhshandehroo, Mohammad Reza Nikoo
Affiliations
1st Author: Foad Vosoughi, Research Associate, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran. [email protected]
2nd Author: Gholamreza Rakhshandehroo, Professor, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran.
3rd Author: Mohammad Reza Nikoo, Associate Professor, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran
Experimental videos in studying the influences of dry- and wet-bed downstream conditions on dam break multiphase flood waves in a reservoir with 15 cm sediment depth (50% silted-up)
No full textExperimental videos:
Herein, 24 distinct video files have been presented which related to dam break multiphase flood shock wave experiments, performed in the Shiraz University, Civil and Environmental Engineering Department’s Hydraulic Lab (Shiraz, Iran). The initial upstream sediment depth was 15 cm which makes the upstream reservoir 50% silted-up with respect to the total 30 cm height of the reservoir. Different initial downstream conditions have also been considered including dry-bed downstream and wet-bed downstream with different levels of standing water; 2 cm, 4 cm and 5 cm.
Considering three cameras which covered length of the flume, 4 different dam break scenarios and 2 repetitions conducted for each test, a total of 24 videos collected which presented in this document.
The additional explanations related to video files can be seen in “Explanation table of videos” file which attached to this document in Microsoft Word (DOCX/DOC) format.
Foad Vosoughi, Gholamreza Rakhshandehroo, Mohammad Reza Nikoo
Affiliations
1st Author: Foad Vosoughi, Research Associate, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran. [email protected]
2nd Author: Gholamreza Rakhshandehroo, Professor, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran.
3rd Author: Mohammad Reza Nikoo, Associate Professor, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran
Experimental videos in studying the influences of dry- and wet-bed downstream conditions on dam break multiphase flood waves in a reservoir with 17.5 cm sediment depth (58.3% silted-up)
No full textExperimental videos:
Herein, 24 distinct video files have been presented which related to dam break multiphase flood shock wave experiments, performed in the Shiraz University, Civil and Environmental Engineering Department’s Hydraulic Lab (Shiraz, Iran). The initial upstream sediment depth was 17.5 cm which makes the upstream reservoir 58.3% silted-up with respect to the total 30 cm height of the reservoir. Different initial downstream conditions have also been considered including dry-bed downstream and wet-bed downstream with different levels of standing water; 2 cm, 4 cm and 5 cm.
Considering three cameras which covered length of the flume, 4 different dam break scenarios and 2 repetitions conducted for each test, a total of 24 videos collected which presented in this document.
The additional explanations related to video files can be seen in “Explanation table of videos” file which attached to this document in Microsoft Word (DOCX/DOC) format.
Foad Vosoughi, Gholamreza Rakhshandehroo, Mohammad Reza Nikoo
Affiliations
1st Author: Foad Vosoughi, Research Associate, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran. [email protected]
2nd Author: Gholamreza Rakhshandehroo, Professor, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran.
3rd Author: Mohammad Reza Nikoo, Associate Professor, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran
Experimental videos in studying the influences of dry- and wet-bed downstream conditions on dam break multiphase flood waves in a reservoir with 22 cm sediment depth (73.3% silted-up)
No full textExperimental videos:
Herein, 24 distinct video files have been presented which related to dam break multiphase flood shock wave experiments, performed in the Shiraz University, Civil and Environmental Engineering Department’s Hydraulic Lab (Shiraz, Iran). The initial upstream sediment depth was 22 cm which makes the upstream reservoir 73.3% silted-up with respect to the total 30 cm height of the reservoir. Different initial downstream conditions have also been considered including dry-bed downstream and wet-bed downstream with different levels of standing water; 2 cm, 4 cm and 5 cm.
Considering three cameras which covered length of the flume, 4 different dam break scenarios and 2 repetitions conducted for each test, a total of 24 videos collected which presented in this document.
The additional explanations related to video files can be seen in “Explanation table of videos” file which attached to this document in Microsoft Word (DOCX/DOC) format.
Foad Vosoughi, Gholamreza Rakhshandehroo, Mohammad Reza Nikoo
Affiliations
1st Author: Foad Vosoughi, Research Associate, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran. [email protected]
2nd Author: Gholamreza Rakhshandehroo, Professor, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran.
3rd Author: Mohammad Reza Nikoo, Associate Professor, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran
Experimental videos in studying the influences of dry- and wet-bed downstream conditions on dam break multiphase flood waves in a reservoir with 24 cm sediment depth (80% silted-up)
No full textExperimental videos:
Herein, 27 distinct video files have been presented which related to dam break multiphase flood shock wave experiments, performed in the Shiraz University, Civil and Environmental Engineering Department’s Hydraulic Lab (Shiraz, Iran). The initial upstream sediment depth was 24 cm which makes the upstream reservoir 80% silted-up with respect to the total 30 cm height of the reservoir. Different initial downstream conditions have also been considered including dry-bed downstream and wet-bed downstream with different levels of standing water; 2 cm, 4 cm and 5 cm.
Considering three cameras which covered length of the flume, 4 different dam break scenarios and 3 repetitions conducted for each test, a total of 27 videos collected which presented in this document.
The additional explanations related to video files can be seen in “Explanation table of videos” file which attached to this document in Microsoft Word (DOCX/DOC) format.
Foad Vosoughi, Gholamreza Rakhshandehroo, Mohammad Reza Nikoo
Affiliations
1st Author: Foad Vosoughi, Research Associate, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran. [email protected]
2nd Author: Gholamreza Rakhshandehroo, Professor, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran.
3rd Author: Mohammad Reza Nikoo, Associate Professor, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran
Experimental videos in studying the influences of dry- and wet-bed downstream conditions on dam break multiphase flood waves
No full textExperimental videos:
Herein, 27 distinct video files have been presented which related to dam break multiphase flood shock wave experiments which performed in the Shiraz University, Civil and Environmental Engineering Department’s Hydraulic Lab (Shiraz, Iran). The upstream reservoir was initially filled by clear water (no sediment) while different initial downstream conditions have been considered including dry-bed downstream and wet-bed downstream with different levels of standing water; 2 cm, 4 cm and 5 cm.
Considering three cameras which covered length of the flume, 4 different dam break scenarios and 3 repetitions conducted for each test, a total of 27 videos collected which presented in this document.
The additional explanations related to video files can be seen in “Explanation table of videos” file which attached to this document in Microsoft Word (DOCX/DOC) format.
Foad Vosoughi, Gholamreza Rakhshandehroo, Mohammad Reza Nikoo
Affiliations
1st Author: Foad Vosoughi, Research Associate, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran. [email protected]
2nd Author: Gholamreza Rakhshandehroo, Professor, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran.
3rd Author: Mohammad Reza Nikoo, Associate Professor, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran
Dynamic material characterization of polymeric foam by means of experimental, analytical, phenomenological and numerical methods
No full textThe main objective of this study was to advance the experimental, numerical, phenomenological and analytical methods of assessing the dynamic compressive response of polymeric foams, especially at an intermediate strain rate range of 50 s-1 to 600 s-1. Different experimental apparatuses and techniques, including the universal compression/tension testing machine (strain rates up to 0.5 s-1), custom-build droptower (a strain rate range of 50 s-1 to 200 s-1) and pneumatic testing apparatus (a strain rate range of 200 s-1 to 600 s-1) were utilized in the macro-mechanical characterization. The microstructure of the investigated polymeric foams was studied by means of Scanning Electron Microscopy (SEM) and Energy Dispersive x-ray Spectroscope (EDS). Numerical, analytical and phenomenological models were modified and calibrated to characterize and predict polymeric foams’ anisotropic rate-sensitive mechanical response. In the first phase of the study, the compressive response of polyether sulfone (PES) foam was investigated under both quasi-static and elevated strain rates. Anisotropic behavior was assessed by testing three orthogonal loading directions, revealing distinct deformation mechanisms. Elevated strain rates, ranging from 50 s-1 to 200 s-1, showcased a substantial rate dependency. The compressive response was simulated using Finite Element Analysis (FEA), achieving an impressive average validation metric of 97%. Localized deformation in the foam rise direction was identified, with specialized equations developed to quantify this phenomenon. The observed variation in the deformation mechanism and rate sensitivity of PES foams when loading in different material directions granted the need for further investigation on the influence of the specimen shape and profile on the mechanical characterization of polymeric foams. In the second phase, rigid Polyvinyl Chloride (PVC) foams were investigated for the effects of the specimen size and density variation on deformation mechanisms and mechanical properties. Different through-thickness direction density variation patterns, varying from 2.6% to 26.3%, governed localized deformation and post-yield stress drop-off behavior. Plateau stress exhibited sensitivity to foam density, while specimen thickness influenced loading elastic modulus. Intermittent unloading-reloading cyclic testing revealed that the thickness effect on the apparent unloading elastic modulus was negligible despite the thickness’s significant effect on the loading modulus. The limitations of Split Hopkinson Pressure Bar (SHPB) apparatuses in dynamic testing limited the exploration of specimen size influence in the dynamic mechanical response of polymeric foams. Consequently, most research on the influence of specimen size on the mechanical response was limited to the quasi-static loading regime. The specimen size effect was reported to be negligible in the quasi-static regime. A droptower testing machine equipped with a 45.45 kg dropping entity and a novel energy dissipation system was utilized to test specimens with different profile sizes and shapes dynamically. The findings from this work, for the first time, revealed that, unlike the quasi-static regime, dynamic behavior was sensitive to specimen profile, prompting the use of impact velocity rather than engineering strain rate in reporting rate sensitivity. Equations were developed to quantify the localized deformation of polymeric foams based on the specimen’s instantaneous dimensions during dynamic compression testing, revealing the significant effect of the specimen size on the correlation between the engineering and localized strain rates. Thus, the specimen thickness and profile size should be consistent in the quasi-static and dynamic experiments to achieve an accurate mechanical characterization, which has rarely been achieved in previous studies. In the study’s third phase, a pneumatic apparatus was utilized to characterize PVC foams under various strain rates, up to 600 s-1, corresponding to 15 m/s impacting velocity, and loading directions to address prior technical limitations. PVC foams with six different nominal densities were subjected to strain rates ranging from 0.005 s-1 to 600 s-1. Specimens possessing a consistent profile size and shape were utilized in the quasi-static and dynamic tests. A modified Nagy model coupled with a nonlinear Avalle relationship accurately represented stress/strain responses. It was found that conducting tests at a single dynamic strain rate (e.g. 400 s-1) effectively captures the rate sensitivity of PVC foam within the 200 s-1 to 600 s-1 strain rate range. Additionally, the influence of relative density on the foam’s rate sensitivity was quantified. In the final phase of the study, the characteristics of PVC foam obtained from the previous phases of this study were utilized to design, test and validate the foam section of a novel energy dissipation system involving AA6061 extrusions and a PVC foam. This hybrid energy dissipation system demonstrates enhanced mechanical performance, surpassing traditional axial crushing modes regarding energy absorption effectiveness
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