Volume 6, Issue 3 (May 1978)
Mechanical Properties in Bending at Elevated Temperature of High Strength Copper Alloy Flat Spring Materials
The yield strength and modulus of elasticity in bending for several high strength copper alloy flat spring materials were determined in the temperature range 23 to 232°C (73 to 450°F) by both static and dynamic measurements. Results obtained by both methods are compared with those obtained by using a simple, short-time stress-relaxation test, and their applicability to the design of flat springs or connectors is discussed. The short-time stress-relaxation test is proposed as a simple acceptance test for flat spring materials. The alloys studied include one copper-nickel-tin alloy strengthened by spinodal decomposition (92% copper-4% nickel-4% tin), copper beryllium alloy (CA 172), copper cadmium alloy (CA 162), and copperiron-phosphorus alloy (CA 196). Long-time stress-relaxation data (2000 h) for the temperature range 23 to 232°C (73 to 450°F) confirm the observations made during the short-time relaxation tests, which showed that for extended service life applications springs made from either precipitation heat-treated CA 172 or appropriately aged 9244 alloy would operate satisfactorily at temperatures below 121°C (250°F) while those made from either of the other two alloys would not. Similar conclusions could not be drawn on the basis of bending yield strength.