Austenitic stainless steels have advantages, such as high ductility and good corrosion resistance. The cold working process can increase the hardness and strength of the material. However, because a metastable austenite phase occurs in that material, there is a phase change of γ austenite to α’-martensite and ε-martensite, which will reduce the ductility and its corrosion resistance. The strengthening process with dynamic plastic deformation (DPD) can prevent the formation of martensitic phases through repeated impact at high strain rates. This study analyzed microstructures and hardness evaluation on Cr-Mn austenitic stainless steel due to dynamic plastic deformation through the repetitive hammering method. Repetitive hammering with a strain rate of 6,2 s-1 on Cr-Mn austenitic stainless steels was carried out on five specimens with variations in the impact of 50, 100, 150, 250, and 350 times with impact energy of 486 J/cm2, 2.207 J/cm2, 2.569 J/cm2, 6.070 J/cm2, and 11.330 J/cm2 respectively. Microstructure, hardness, and XRD (X-ray diffraction) analyses were carried out on specimens before and after repetitive hammering. Metallography was carried out to observe the microstructure using an optical microscope. The hardness was tested through the Rockwell A hardness test. XRD examination was used to identify the phases formed and indications of nano-twins. The repetitive hammering process up to 350 times has succeeded in increasing hardness from 53.5 HRA to 71.6 HRA. Plastic deformation introduced by repetitive hammering produced slip bands, cross bands, wavy bands, and indication of nano-twins formation and increased the hardness.

In applications such light train application, sandwich materials require mechanical joints. One major load produced at the mechanical joining is the pull-out load. The scope of this literature review includes pull-out test results, failure mode during the pull-out test, failure load parameters, and an analytical method to determine the maximum pull-out load. The pullout resistance of the mechanical joint on sandwich material is determined by the failure load and the maximum load. The failure modes on sandwich material include core buckling, shear cracking, tensile rupture and delamination. The failure load of mechanical joints on the sandwich material will increase as insert depth, insert diameter, core thickness and core density increase. Meanwhile, two analytical methods (Aerospace Engineering and Zenkert Methods) are studied, and it is found that the Aerospace Engineering is more accurate. The multiplier for the maximum load value has been found to determine the failure load.