In this paper, small blocks of 17-4 PH stainless steel were manufactured via extrusion-based bound powder extrusion (BPE)/atomic diffusion additive manufacturing (ADAM) technology in two different orientations. Ultrasonic bending-fatigue and uniaxial tensile tests were carried out on the test specimens prepared from the AM blocks. Specifically, a recently-introduced small-size specimen design is employed to carry out time-efficient fatigue tests. Based on the results of the testing, the stress–life (S-N) curves were created in the very high-cycle fatigue (VHCF) regime. The effects of the printing orientation on the fatigue life and tensile strength were discussed, supported by fractography taken from the specimens’ fracture surfaces. The findings of the tensile test and the fatigue test revealed that vertically-oriented test specimens had lower ductility and a shorter fatigue life than their horizontally-oriented counterparts. The resulting S-N curves were also compared against existing data in the open literature. It is concluded that the large-sized pores (which originated from the extrusion process) along the track boundaries strongly affect the fatigue life and elongation of the AM parts.
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This content will become publicly available on February 26, 2025
Variability in membrane behavior of geosynthetic clay liners
Geosynthetic clay liners (GCLs) comprising sodium bentonite (NaB) have been shown to exhibit significant membrane behavior, whereby contaminants are restricted from passing through the clay due to electrostatic repulsion, potentially enhancing long-term containment performance. Recent membrane behavior research has focused on evaluating membrane efficiency () of enhanced bentonites (e.g., bentonite polymer composites) and testing under more complex conditions (e.g., elevated temperatures, unsaturated conditions), often drawing comparisons with earlier published data on NaB-GCLs. However, the validity of comparing NaB-GCL results across studies and from earlier work remains unclear. No prior study has evaluated the variability in reported values for the same type of NaB-GCL manufactured in different years. In this study, multistage membrane behavior tests were performed on specimens of the same NaB-GCL type manufactured at different dates. One specimen (GCL1) was taken from a NaB-GCL roll manufactured in the last five years. Another specimen (GCL2) was taken from a NaB-GCL roll that had been stored in a laboratory since 2005. Values of were measured for both specimens, and also compared to results reported in 2002 for the same type of NaB-GCL (GCL3). To support interpretation of the results, cation exchange capacity, mass per unit area, and swell index tests also were performed. For the same salt solution concentrations, GCL2 exhibited significantly lower than GCL1 and GCL3. Lower values of corresponded to lower bentonite mass per unit area. The results have important implications regarding limitations in comparing results of current membrane behavior research on enhanced materials and testing conditions to commonly cited literature data.
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- Award ID(s):
- 2143145
- PAR ID:
- 10522157
- Publisher / Repository:
- ASCE
- Date Published:
- ISSN:
- DOI 10.1061/9780784485323.03
- Format(s):
- Medium: X
- Location:
- Vancouver, Canada
- Sponsoring Org:
- National Science Foundation
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