Final answer:
The values above the heavy line on the load chart likely represent the failure in tensile strength, which is the ability of a material to resist being pulled apart. Tensile strength is a key parameter in understanding how materials behave under stretching forces and when they will ultimately fracture or break.
Step-by-step explanation:
The question pertains to a load chart, which is commonly used to represent the behavior of materials under load, often in the context of engineering and materials science. Specifically, it seems to be concerned with the limit above which failure occurs in materials due to different types of stresses. When referring to values for failure 'above the heavy line crossing the load chart', this typically indicates the material's breaking point for a particular type of stress.
Tensile strength is the measure of a material's ability to withstand tensile (stretching) forces. This is an important parameter in determining how a material will react when forces are applied that attempt to pull it apart. Compressive strength, on the other hand, measures a material's ability to withstand compressive (squeezing) forces. Both are pivotal in assessing the structural integrity of a material. For bending or sagging structures, as mentioned earlier, the top surface experiences compressive stress while the bottom surface experiences tensile stress.
Given the context provided, the values above the heavy line on the load chart are likely to represent the failure in tensile strength. This is because tensile stress tends to be the focus when discussing the stretching or fracture point of materials. Compressive stress, while equally significant in many engineering applications, is more commonly associated with the crushing or buckling of materials.