Foamed steel applications in civil engineering are at their beginning stage. Compared to foamed aluminum, advantages of using steel as a base metal are distinct (e.g., higher strength and modulus). In order to investigate the mechanical properties of foamed steels and to obtain representative material constitutive parameters for finite element analysis, fourteen specimens were tested under monotonic and eleven different cyclic loading schemes in this study. The monotonic and cyclic tensile-to-yield ratios were 2.17 and 1.90 ± 0.17, respectively, and the energy dissipation coefficient ranged from 2.70 to 3.35. The cyclic hardening behavior of foamed steels comprised isotropic and kinematic hardening characteristics, and the isotropic part played the dominate role. Based on the test results, the corresponding material parameters for two cyclic constitutive models, including the Chaboche model and the Giuffré-Menegotto-Pinto model were obtained. Then, the accuracy of the parameters was verified by nonlinear analysis results in ABAQUS and OpenSEES. This work may provide a valuable reference for further research into the cyclic characteristics of foamed steels.
Bulk W-0.5 wt%ZrC (W-ZrC), W-1 wt%Re-0.5 wt%ZrC (W-1Re-ZrC), and W-3 wt%Re-0.5 wt%ZrC (W-3Re-ZrC) alloys were prepared and exposed to He 2+ ion irradiation with an incident energy of 500 keV at 400 °C. Post-irradiation analysis revealed the formation of He bubbles, with consistent number density and average size across all alloys. However, the W-3Re-ZrC alloy exhibited a notably higher density of dislocation loops within grain interiors compared to W-ZrC and W-1Re-ZrC. This led to a significant increase in the hardening rate of W-3Re-ZrC to 61.5 %, nearly twice that of the other alloys. By considering the binding energies of He-vacancy, He-He, and Re-He, the formation and growth behavior of irradiation-induced defects, including He bubbles and dislocation loops, were also discussed. This work provides valuable insight into the relationships among Re alloying, He-induced defects, and irradiation hardening in Re-alloyed W materials, thus offering valuable guidance for the design of W-based plasma-facing materials.
Xiaorong Dou,Zheqi Chen,Fuhao Ren,Lijun He,Jianxiong Chen,Li-Juan Yin,Yingwu Luo,Zhi-Min Dang,Jie Mao
Dielectric elastomer actuators (DEAs) face an acknowledged challenge: On the one hand, the majority of elastomers only achieve small electroactive deformation (<20%) in the absence of prestretch; on the other hand, rare elastomers capable of showing large electroactive deformation require relatively complicated processing and chemistry. This work addresses this challenge by fabricating an elastomer with a network of large side groups, which achieves a very large electroactive deformation (218%) without pre-stretch. This elastomer can be rapidly and massively fabricated within a few min, by polymerizing a commercial monomer with a large alkyl side group. The large side groups in the polymer network repel each other and extend the load-bearing strands, which results in a pronounced strain-hardening behavior. This behavior helps the elastomer to get rid of electromechanical instability during actuation and hence to exhibit a large electro-active deformation, a high energy density (>> human muscle), and a large output force (≈500 times self-weight). the elastomer capable of manufacturing a soft electroactive gripper is demonstrated with large deformation, large force, and rapid response, which enables grasping fragile objects of various complex shapes in an agile away.
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