Steel Designer 39;s Manual

[Desiderato Chouinard]

Thisclassic manual on structural steelwork design was first published in 1955, since when it has sold many tens of thousands of copies worldwide. For the seventh edition of the Steel Designers' Manual all chapters have been comprehensively reviewed, revised to ensure they reflect current approaches and best practice, and brought in to compliance with EN 1993: Design of Steel Structures (the so-called Eurocode 3).

This classic manual on structural steelwork design has now been reissued as a paperback edition. It is identical to the hardback edition and retains the restructuring that was introduced in the fifth edition. All chapters have been comprehensively reviewed and revised. Key features of the 6th edition are:

1994. Blackwell. Fifth, first reprint. Softback. Book- VG. 9.5x6.5. 1266pp. Many b/w illus. This classic manual on structural steelwork design was first published in 1955. This edition was the first to be based entirely on limit state design and to take account of BS 5950 for buildings and BS 5400 for bridges. Seller Inventory # 1694463

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Sheet metal parts are known for their durability, which makes them great for end use applications (e.g. chassis). Parts used for low volume prototypes, and high volume production runs are most cost-effective due to large initial setup and material costs.

Because parts are formed from a single sheet of metal, designs must maintain a uniform thickness. Be sure to follow the design requirements and tolerances to ensure parts fall closer to design intent and cutting sheets of metal

Bending is performed by a press brake machine that can be automatically or manually loaded. Press brakes are available in a variety of different sizes and lengths (20-200 tons) depending on the process requirements.

The sheet is placed between the two and held in place by the backstop. The bend angle is determined by the depth that the punch forces the sheet into the die. This depth is precisely controlled to achieve the required bend.

The following are some terminology that are used in sheet metal. Designers need to adhere to machinery guidelines when designing for bending. Bends can be characterised by these parameters. Some critical dimensions that need to be considered when setting up sheet metal in CAD software are sheet metal thickness, the k-factor, and bend radius. One needs to check that these factors are consistent with the tooling that will be used in manufacturing. This manufacturing guide gives important guidelines for good design practice.

When considering sheet metal thickness, a single sheet with punches (holes) is a good rule of thumb. Some features such as countersinks are doable but counter bores and other machined features are difficult to produce as they require post machining.

Sheet metal bend brakes are used to bend material into the parts desired geometry. Bends that are in the same plane need to be designed in the same direction to avoid part re orientation, to save both money and time.

When bending a piece of sheet metal, the residual stresses in the material will cause the sheet to springback slightly after the bending operation. Due to this elastic recovery, it is necessary to over-bend the sheet a precise amount to achieve the desired bend radius and bend angle. The final bend radius will be greater than initially formed and the final bend angle will be smaller. The ratio of the final bend angle to the initial bend angle is defined as the springback factor, KS. The amount of springback depends upon several factors, including the material, bending operation, and the initial bend angle and bend radius.

Minimum bend radii requirements can vary depending on applications and material. For aerospace and space applications, the values may be higher. When the radius is less than recommended, this can cause material flow problems in soft material and fracturing in hard material. Localised necking or fracture may also occur in such cases. It is recommended that minimum inner bend radius should be at least 1 times material thickness.

The thickness of the material is not proportional to the tonnage like the v opening. Doubling the thickness does not mean doubling the tonnage. Instead the bending force is related by the square of the thickness. What this means is that if the material thickness is doubled the tonnage required increases 4 fold.

The Air Force Bending chart is a chart showing the tonnage used for bending different thickness sheet metal. It is useful for sheet metal designers as it specifies the bend radius and tooling to be used for different thicknesses. It is shown here for mild steel. Designers can use this as a guide when designing the minimum flange length possible with the tooling for different V blocks as well as the bend radius. The following charts are based on the Armada Air Force bend guide.

Extruding metal is one of the most extreme pressure applications in press working and generates lot of friction and heat. If an extruded hole is too close to the part edge, it can lead to deformation or tearing of the metal. It is recommended that the minimum distance between the extruded holes to part edge should be at least three times the thickness of sheet.

Certain distance should be maintained between two extruded holes in sheet metal designs. If extruded holes are too close it can lead to metal deformation. It is recommended that the minimum distance between two extruded holes should be six times the thickness of sheet metal.

The diameter of the hole in sheet metal part should not be very small, small holes are created by piercing operation and for manufacture small holes, small sizes punches are required. Small hole size in sheet metal requires smaller size punching tool which may leads to break during the operation. It is recommended that the diameter of the hole should be equal or more than the thickness of the sheet metal.

Laser cutting is a type of production that uses a laser to cut different metals. The laser has a high energy beam which easily burns through the material. Laser cutting can be used on materials such as metal, aluminium, plastic, wood, rubber, etc. Lasers use computer numerically controlled programming (CNC) to determine the shape and position ls of the cutouts. Material thicknesses of up to 20mm can be lasercut. There are advantages and disadvantages in using lasercutting. CO2 lasers are more traditional, and can cut thicker materials but do not deliver such an accurate cut as fibre lasers. Fibre lasers can generally cut thinner materials and have much higher cutting speeds than CO2 .

Advantages of lasercutting over cutting mechanically include better workholding, reduced workpiece contamination, better precision and reduced chance of warping as the heat affected zone is small. Some disadvantages are that lasercutting does not always cut well with some materials (for example not all aluminium) and it is not always consistent. Despite the disadvantages lasercutting is highly efficient and cost effective.

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