 Welcome back mechanically. Did you know that volumetric strain determines whether a block of cement can be used to fill a gap in a wall while taking into account temperature changes in the area? This makes us wonder what is volumetric strain? Before we jump in, check out the previous part of the series to learn about what elastic constants are. Now, consider a rectangular solid under stresses sigma1, sigma2, and sigma3. Then epsilon1, epsilon2, and epsilon3 will each denote the respective strain in their directions. The new dimensions of the rectangle become this. Volumetric strain then is defined as the increased volume of the rectangular solid upon the original volume of the solid and is denoted by theta. Yield strength or yield stress is the material property defined as a stress at which a material begins to deform plastically, whereas yield point is the point where non-linear that is elastic and plastic deformation begins. Prior to the yield point, the material will deform elastically and will return to its original shape when the applied stress is removed. Once the yield point is passed, however, some of the fraction of the deformation will be permanent and non-reversible. Ultimate tensile strength is measured as the maximum stress that a material can withstand while being stretched or pulled before breaking. Some materials break very sharply without plastic deformation in what is called a brittle failure. Others which are more ductile including most metals experience some plastic deformation and possibly necking before fracture. Hence, we first saw what volumetric strain is and then saw what yield stress is and finally found out what ultimate stress is. So like, subscribe and comment with your feedback to help us make better videos. Thanks for watching. Also, thanks a lot for those constructive comments. You help the channel grow. So here are the top mechanical years of our last videos. In the next episode of Mechanical Year, find out what shear force and bending moment are.