Chapter 15 Introduction to Nonferrous Metals 351 and measure the length of each wire just before it broke. • Record these lengths in a table of observations, together with an approximate time to failure. • Which wire stretched the longest before failure? What was the weight on that wire? • Is there a trend relating the amount of weight to the amount of stretch to failure? (If a wire failed outside of your marks on the wire, then the time and length to break does not count.) Analysis Based on what you know about tin-lead solder at room temperature, why do you think a cup-and-cone failure would be predicted? not get twisted or bent. And remember the first rule of metal failure analysis: Do not touch the broken ends together! 5. If the wire with the smallest weight has not failed in an hour, check it again after two, three, and four hours. If it still has not broken, check it again after eight hours, then twice a day until it does break. Though ts and Observations The prediction is that the breaks have a cup-and- cone shape. Does this prediction imply a brittle-type failure, or a ductile failure? Do you find cup-and-cone shapes? What type of failure do you think you have? • Take down the coat hanger and lay out the wires on a table, with the broken ends almost touching, Copyright Goodheart-Willcox Co., Inc.