Neutral Line Sheet Metal

Neutral axis and stresses resulting from bending.

Neutral line sheet metal.

The neutral axis is the zone or plane that separates the tension from the compression. The line where the transition from compression to stretching occurs is called the neutral axis. The location of the neutral axis varies and is based on the material s physical properties and its thickness. Its location in the material is a function of the forces used to form the part and the material yield and tensile strengths.

When you bend sheet metal the neutral axis shifts toward the inside surface of the bend. Neutral axis is an imaginary line. When a piece of sheet metal is bent the overall length of the piece changes because of compression on the inside of the bend and tension on the outside. Mold line mold line dimension and mold point k factor is the percentage of the material thickness.

The changes in length to the outside and inside surfaces can be related to the original flat length by two parameters the bend allowance and bend deduction which are defined below. The neutral line also called the neutral axis is an imaginary line that can be drawn through a cross section of the workpiece that represents the locus where no tensile nor compressive stresses are present on the work. Bend allowance and bend radius all the space between the band tangent lines is the bend allowance. As a result the length of this axis remains constant.

A line through the thickness of the bend called the neutral axis does not change in length when the part is bent. Notice how the sheet has thinned at the bend. I had a question on k factors for our 3 d modeling software. The bend allowance describes the length of the neutral axis between the bend lines or in other words the arc length of the bend.

The outside portion of the sheet will be in tension and will stretch while the inside portion experiences compression and shortens. The bend allowance and bend deduction are two measures that relate the bent length of a piece of sheet metal to the flat length. The neutral axis position depends on the bend angle inside bend radius and method of forming. The neutral axis is the boundary line inside the sheet metal along which no tension or compression forces are present.

This is known as the neutral line or neutral axis and occurs at a distance approximately 0 445 times the metal thickness 0 445 t from the inside of the radius of the bend. Figure 4 figure 4. The k factor is the ratio of the neutral axis location t to the material thickness mt. Bend allowance is used to account for bends in sheet metal fabrications.

The act of bending results in both tension and compression in the sheet metal. When metal is bent the top section is going to undergo compression and the bottom section will be stretched. Natural grain of the material is formed as the sheet is rolled from molten ingot. The neutral axis is the boundary line inside the sheet metal along which no tension or compression forces are present.

Look closely a figure 1. The neutral axis s behavior is the main reason the flat part needs to be smaller than the total of the formed piece s outside dimensions.