Hidroformado

Sheet Metal Fabrication
By: Matthew Cloutier

ME 353 Instructor: Jesse Adams Due Date: 10/8/00

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I. Introduction Sheet metal fabrication plays an important role in the manufacturing world. Sheet metal is used to make everything from hinges to automobiles. There are many types of sheet metal fabrication for engineers to choose from. Deep drawing, stamping, rubber forming, hydroforming,and high-energy-rate (HERF) forming are all different methods used for creating desired shapes out of a sheet metal. It is the responsibility of design engineer to determine the mechanical properties of the material, select the material that meets these requirements, and select the best fabrication process for the job. There are other considerations a designer must decide on besides fabricationprocess when creating a new part or assembly. Cosmetic appearance, cost, engineering, manufacturing method, and assembly are just some of the factors to be taken into account when a new design is being developed. Figure 1. Engineering stress versus strain diagram

II. Material Properties

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Before the material is selected for a design project, engineers have to determine the mechanicalproperties of the material. Designing for strength, material class and mode of loading are important considerations. Several factors have to be considered when selecting a material such as, yield strength, ultimate tensile strength, ductility, thermal conductivity, wear, and corrosion resistance. When designing, all these factors are weighed against the properties of the available materials and it isthe job of the design engineer to select the material that best fits the application. The most common measure of strength is the yield strength. Yield strength is equal to the minimum load which produces permanent deformation (see Figure 1). The ultimate tensile strength is calculated by dividing the maximum load on the material by the initial cross section area.

σ ultimate = Pmax / Ao σ ultimate– maximum tensile strength Pmax – Maximum force (load) Ao – Original cross sectional area
Example: A rectangular beam, three inches wide by half inch thick is subjected to a maximum load of four hundred pounds. What is the ultimate tensile strength of the beam? Solution: Pmax = 400 lbs. Ao = (3.0*0.5) Ao = 1.5 square inches σ ultimate = 400 lbs/1.5 square inches σ ultimate = 267 psi Ductility isa measure of how much deformation a material can withstand before breaking. The most common measure of ductility is the percentage of change in the length after the material has broken. This is typically reported as % EI or percent elongation. Thermal conductivity is the rate of heat transfer through a material in a steady state. It is not easily measured, but reliable data is readily availablefor most common materials.

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Wear and corrosion resistance are properties that must be determined when evaluating the environment and performance of the design. While proper material selection is crucial to ensuring compatibility between components in a design, no single material property can describe compatibility between all possible materials. III. Material Selection After all engineeringparameters have been calculated and established, the next step is to select the type and size of sheet metal. Typically sheet metal can be purchased as sheet, plate, or coil stock ranging from .0187 inches to 12.0 inches in thickness. Sheet stock is a flat rectangular sheet of metal measured in thickness between .0187 inches (28 GA.) and .179 inches (7 GA.). Plate stock is a flat rectangularsheet of metal with a thickness between .187 inches to 18.0 inches. Coil stock is made from sheet metal slit or cut to a certain width then rolled up into a coil. Coil is generally cut to a width between .312 inches to 3.0 inch. When ordering coil or sheet stock it is usually ordered by gauge thickness (GA) and width. If coil is ordered the coil diameter (ranging from 36.0 inches to 72.0 inches) or...