Beam stress is the application of pressure to a beam that can induce tension, compression, and buckling. These structural elements are engineered with some flexibility in order to yield rather than break under strain. If the load on a beam is applied uniformly, then there will be no problem; but if the load is not evenly distributed, then problems may arise. Stress can be classified as either internal or external. Internal stress results from the tendency of a material to try and return to its original shape. This stress does not affect the structure's ability to support external forces because the material can always restore itself to its original condition. External stress arises when a force is applied to a structure that tries to bend it beyond its normal form. If this force is large enough, then it will cause failure of the beam by buckling, bending, or breaking. The two main types of stress on beams are tensile and compressive. In tensile stress, the stretching of the beam causes it to become thinner while in compressive stress, the squeezing of the beam causes it to become thicker. Stress can also be divided into two categories: uniform and non-uniform. In a structure where all parts of the beam are subjected to the same load, such as one end supported, the stress is called uniform.