Which of the following is a method used for testing materials in product design?

Tensile testing is a fundamental method used for assessing the mechanical properties of materials, particularly their strength and ductility. In product design, understanding how a material behaves under tension is crucial for ensuring that it can withstand the forces it will encounter during use. During tensile testing, a sample of the material is stretched until it breaks, and data is collected on the amount of force applied and the resultant strain. This provides valuable information about the material's yield strength, ultimate tensile strength, and elongation, which are critical parameters in choosing materials for specific applications.

On the other hand, thermal analysis is more focused on how materials respond to changes in temperature, aesthetic evaluation pertains to the visual and subjective appeal of a product's design, and market comparison looks at how a product stacks up against similar offerings in the market. These methods are important in their own right, but they do not provide direct insights into the mechanical behavior of materials like tensile testing does.