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Flat Springs: Cantilever and Simple Beam
Flat Springs cover a lot of area. There are a large variety of parts that spring manufacturers either form or blank from strip material. These parts are not wire springs because they are made from flat stock spring steel.
These products perform like a spring. They store and release energy. They do this by getting deflected and pushing back. Another common use is as a holder holding other parts in location. Other examples would be stops, connectors, hinges, braces, fasteners and many others. They are always custom designed and made with special tooling. You can design simple flat springs using the formulas on this page, where -
The formulas become less accurate if the deflection is large. For example, 30% of the length of a cantilever spring. Also, if the width to thickness ratio is 20 or more the formulas are less accurate. If you look in the spring designers bible, Mechanical Springs, A.M. Wahl If your design has high stresses you neeed to pay attention to stress-concentration at sharp corners, holes, slots, and cut-outs. Take a special look at edges where blanking burrs may remain. The designer needs to be in communication with the spring manufacturer so the part marker knows the direction of deflection. This will help him make sure that any blanking burrs can be left on the compressively stressed side. 
Clamped edges need to be smoothed and rounded as this is where the maximum stress occurs. You need to avoid putting holes or cut-away sections in these areas. They will weaken the section and can add stress raisers. Flat springs are made from annealed spring strip and hardened after forming. Springs can also be made from prehardened strip. These springs have large residual stresses after forming (unless they are flat blanks). The direction of service loading will determine if these are favorable or unfavorable stresses. This is why it is important for the spring manufacturer to know the direction of loading so he can control the residual stress rate. Stress concentration at sharp corners can be estimated using the chart below. These stress concentration factors are normally only used for springs in fatigue service. In static service, very slight localized setting can result from high stress concentration.
Here are some additonal references pages you should review to help with design and application ideas-
-for material references: Spring Steel Types Used in Springmaking.
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, you will find correction factors for these cases and others.
