The correct answer to this question is D. All of the above. The internal stresses in an A36 steel bar can be influenced by various factors, such as bending stresses and ultimate stress. The yield strength of this type of steel is 36 Ksi, which means that it can withstand a certain amount of stress before it deforms. However, if the bending stresses exceed this limit, the steel bar will yield and experience plastic deformation. This means that it will not return to its original shape when the stress is removed.
Moreover, if the bending stresses exceed 1.5 times the yield strength of the steel bar, it will undergo yielding and plastic deformation. This is because the steel bar's elastic limit is exceeded, and it can no longer handle the stress applied to it.
Finally, if the ultimate stress is reached, the steel bar will fail and break. This is the maximum stress that the steel can withstand before it breaks. It is important to note that the internal stresses in steel bars can also be influenced by other factors, such as temperature, corrosion, and manufacturing processes. Therefore, it is essential to consider these factors when selecting the right type of steel for a particular application.