In addition to traditional fertilizer applications, ammonia is being researched for use as a fuel for power generation, a storage medium for renewable energy, and particularly for the production and storage of hydrogen, leading to increased demand for large ammonia tanks. Ammonia has a tendency to cause Stress Corrosion Cracking (SCC) in high-strength steels. While this was not an issue for traditional applications such as 10,000 – 30,000 ton of storage tanks, it has become a concern with the current demand for larger tanks. We have recently carried out the design verification on a large-scale refrigerated liquid ammonia storage tank based on mild strength steel (A516 Grade 70N) and higher strength steels (A841 Class 2) using Thermo-Mechanical Control Process (TMCP). This paper describes various types of ammonia storage tank designs, trends in overseas ammonia tank design, design concepts and considerations for large-scale tanks, and also discusses preventive measures for ammonia SCC based on the results of laboratory tests.

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Adhesive bonding is increasingly adopted in automotive and aerospace industries due to its potential for weight reduction and recyclability. Recent studies have reported that the fracture toughness of adhesively bonded joints can vary due to the surface geometry of adherends, even when cohesive failure occurs within the adhesive layer. However, the underlying mechanical mechanism for this variation remains unclear. In this study, we investigate how periodic surface roughness affects the strain energy release rate (SERR) during cohesive crack propagation using finite element analysis. The surface geometry is simplified as periodic roughness with varying pitch and height. The SERR distribution along the crack front is evaluated, and periodic minima, which act as rate-limiting points for crack propagation, are extracted. A response surface model is constructed to express these minimum values as functions of geometric parameters. A comparison with experimental fracture toughness obtained from double cantilever beam (DCB) tests reveals a significant negative correlation between the response surface minimum and measured toughness. Furthermore, strain energy analysis shows that increased surface roughness leads to a redistribution of elastic energy from the adhesive to the adherend, indicating a reduction in stress concentration. These findings suggest that surface morphology optimization can contribute not only to preventing interfacial failure but also to improving cohesive fracture resistance, offering a new design perspective for adhesively bonded joints.

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