Temperature directly affects the performance of a spring, particularly in conditions of extreme heat or cold. The choice of both spring design and materials can determine the success of a project. Take for example, the coil springs used in vehicle suspension systems in cold regions, they must operate well even in very low temperatures. The selection and design of these springs revolve around materials and structures that can withstand such harsh conditions. In this article, we aim to explain how temperature impacts spring performance, and aid in selecting appropriate materials for your needs.
How Temperature Affects Spring Performance
Temperature influences both a spring's load carrying ability and spring rate. Higher temperatures cause materials to expand, decreasing the spring's stiffness. In contrast, lower temperatures cause materials to contract, increasing the spring's stiffness. For instance, consider the springs in an automobile's suspension system. Such springs can have differential reactions to different environmental temperature conditions. A vehicle performing in a warmer environment would likely have a softer suspension than the identical model in a cooler environment. This is due to the tendency of the spring to deflect more under increased temperature conditions, compared to its performance under cooler conditions.
Extreme temperatures can impact the spring's durability during repeated loads, known as the fatigue life. The acceleration of chemical reactions like oxidation at elevated temperatures can gradually weaken the spring material. Conversely, springs exposed to freezing temperatures can turn brittle, making them prone to breakage. For instance, springs positioned beside heat-generating components in an industrial assembly line could deteriorate quicker due to continuous heat exposure. Similarly, springs which function in cold environments might break due to brittleness induced by the low temperature.
Another impact of extreme temperatures on springs is the alteration in their response time. The main function of a spring is to store energy when compressed and release it when expanded. The speed of this energy transfer can be influenced by temperature fluctuations. High temperatures decrease the modulus of elasticity, a determinant of material's stiffness, thereby reducing the spring's responsiveness. Cold temperatures, on the other hand, can intensify this modulus and subsequently increase the spring's responsiveness. For example, in the context of aerospace mechanisms, where substantial temperature shifts are common, the spring's response would differ due to changes in its modulus of elasticity.
The material of a spring has a significant effect on its operation under extreme temperatures. During the design stage of the spring, the properties of the material under specific environmental conditions that the spring will face need to be evaluated.
When designing for high temperatures, it is necessary for the material to maintain its structural properties and to resist corrosion. Two materials that can suffice these requirements are Inconel and stainless steel alloys. Inconel, with a high proportion of nickel, has both heat and oxidation resistance properties. Stainless steel, an alloy mainly consisting of iron and a substantial amount of chromium, forms a chromium oxide surface layer. This layer provides high temperature strength and resistance to oxidation. The specific type and amount of alloying elements in the stainless steel determine its strength at high temperatures.
For springs operating at low temperatures, materials that remain flexible and not brittle are desired. Austenitic stainless steels and nickel alloys are suitable choices. The former, containing more quantities of nickel and lower carbon, maintain their toughness and strength at cold conditions. The latter, due to its high toughness, strength, and ductility, performs well even at extremely low temperatures. Different varieties of Nickel alloys may have differences in toughness at cold temperatures.
A well-estimated balance between the material's performance, cost, and availability is important in the selection process. Some materials like Invar and Elgiloy, despite having excellent temperature properties, may be expensive and not readily available for use in all designs. For instance, in aerospace applications where both high and low temperature performance is necessary, these materials might be used. But in less demanding situations such as a domestic appliance spring, the cost of these materials may be unjustifiable. Hence, in the final material selection, performance, cost, and material availability need to be taken into account.
Understanding the effects of temperature on spring function is critical in crafting springs for extreme temperatures. This understanding encompasses the prediction of likely operating temperatures and comprehension of the performance of materials under these conditions. Worthwhile factors such as cost and availability should be incorporated into a holistic approach. The utilization of design software tools propels this process, enabling an in-house approach to spring design and selection without the exhaustive need for external specialists.