ANS:B - fatigue

The Wohler test, also known as the fatigue test or S-N (stress-number of cycles to failure) curve test, is conducted to determine the fatigue strength of a prepared metal specimen. During the Wohler test, the specimen is subjected to cyclic loading that alternates between tension and compression. This cyclic loading simulates the repetitive stresses experienced by materials in real-world applications, such as machinery components subjected to fluctuating loads. The test measures the number of cycles the material can withstand before failure occurs at a given stress level. The results of the Wohler test are typically presented in the form of an S-N curve, which shows the relationship between stress amplitude (S) and the number of cycles to failure (N). From this curve, the fatigue strength of the material can be determined, which represents the stress level at which failure occurs after a specified number of cycles. Therefore, the correct answer is fatigue strength.