F
TY is the static Tensile Yield stress (the stress the metal can withstand under tension before it starts to plastically deform)
F
TU is the static Tensile Ultimate stress (the stress the metal can withstand under tension before it breaks)
F
SU is the Shear Ultimate stress (the shear stress the metal can withstand before it breaks)
KSI is thousands of pounds per square inch - unit of stress in materials
Not 100% sure about F
SU so I'd happily recieve any corrections