Hello, I want to plot the motor torque and torque of the joints of a mechanical system. in this case, I need to enter at least the weight and materials of the majority of the system. Am I right? Do I need to enter the weight and material of small components such as washer, nuts, screws, etc.

Some body frames are made of aluminum alloy. Even so, there are several numbers and properties for this metal. I don't know the exact number. What shall I do?