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Modern technologies of metal working
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Sheet metal bending
+48 95 762 08 61
Laser beam cutting
Laser cutting of tubes and sections
Robotic welding
Sheet metal bending
The sheet metal bending process using press brakes is one of the key stages in modern sheet metal processing. Although the technology itself seems simple in principle, in practice it requires deep knowledge of material properties and the mechanics of plastic deformation. This article focuses on a detailed analysis of the influence of material properties on the bending process, with particular emphasis on the phenomenon of springback, anisotropy of mechanical properties, and the influence of microstructure.
Yield strength (Re) is one of the most important parameters that determine the behavior of sheet metal during bending. It defines the moment when the material begins to deform plastically, i.e., permanently changes its shape. For the bending process, the following are crucial:
For example, S235JR steel with a yield strength of 235 MPa will require significantly less bending force than S700MC steel with a yield strength of 700 MPa, for the same material thickness.
Young's modulus (E), which is a measure of the material's stiffness, directly affects the amount of springback. Materials with a higher Young's modulus exhibit less springback, which translates to better predictability of the bending process.
Comparing different materials:
It is clear that under the same bending parameters, aluminum will exhibit significantly more springback than steel, requiring appropriate adjustment of the bending angle.
Springback is one of the most important phenomena to consider in the sheet metal bending process. It occurs due to:
During sheet bending, the material layers on the outer side of the bend are stretched, while those on the inner side are compressed. Between them lies the so-called neutral layer, which does not change its length. After releasing the pressure, part of the elastic deformation is reversed, leading to partial material relaxation and a change in the bending angle.
Springback depends on several key material properties:
Various mathematical models are used to determine the amount of springback, including:
Gardner's Model:
K = r/t * (Re/E) * (π/2 - α)
where:
Bozdemir-Göloğlu Model:
K = C * (Re/E) * (r/t)^n
where C and n are empirical constants dependent on the material
Experimental studies show that for high-strength steels (e.g., DP800), springback can be up to 300% greater than for low-carbon steels (e.g., DC01) under the same bending parameters.
Metal sheets exhibit anisotropy of mechanical properties resulting from their manufacturing process. The rolling direction significantly affects:
For example, DC04 steel intended for deep drawing is characterized by an r value > 1.6, indicating good resistance to thinning during forming, but it may also lead to non-uniform springback when bending in different directions relative to the rolling direction.
The minimum bending radius (rmin) is directly related to the material thickness (t) and its mechanical properties. The general relationship is often expressed by the formula:
rmin = K * t
where K is a coefficient dependent on the material and its condition:
The heat treatment condition of the material significantly affects the bending process:
High-strength steels (HSS) and advanced high-strength steels (AHSS) are characterized by:
For example, DP600 steel (dual-phase) with a yield strength of about 400 MPa exhibits about 30-40% more springback than DC04 steel with a yield strength of about 170 MPa.
Aluminum alloys, due to their lower modulus of elasticity, exhibit:
Comparing different aluminum alloys, the 5xxx series (e.g., 5083) is characterized by good bendability, while the 7xxx series alloys (e.g., 7075) require precise adjustment of bending parameters.
To compensate for the influence of material properties on the bending process, the following are used:
For materials with difficult bendability, the following techniques are used:
The press force required for bending is directly related to the material properties:
F = k * Re * b * t²/W
where:
Materials with higher yield strength require proportionally greater press force, which translates to higher requirements for press brake parameters.
The speed of the bending process can affect material behavior:
The modern approach to sheet metal bending processes includes advanced methods of testing material properties:
The development of numerical methods allows for more accurate prediction of material behavior during bending:
The increasing use of ultra-high-strength steels (UHSS) presents new challenges:
The growing use of multilayer and composite materials requires:
Material properties play a key role in the sheet metal bending process on press brakes. Understanding the influence of these properties allows for optimization of process parameters and achieving high-quality products. The most important material factors influencing the bending process are:
The modern approach to the sheet metal bending process includes advanced research and simulation methods, which allow for more accurate prediction of material behavior and optimization of process parameters. With the development of new materials with specific properties, bending techniques will evolve to meet the increasing quality and efficiency requirements in the industry.