Seam Welding Design for Butt Joint

Seam Welding Design for Butt Joint - Seam welding having an important role in the welding construction joint. In a post titled Shielded Metal Arc Welding Design has been described on how to design welding construction with welded joint strong and how the role of seam welding in overcoming the tensile loads and bending loads acting on the welds. Welding stress that occurs in the welding joint will be different for each type of seam welding. Therefore, in this post we will explain about how to design of seam welding for construction joint base on the seam type and welding strength.

To facilitate the design process more applicable, seam welding design will be described in more detail for each type of welding joint. Welding joint in question include butt joint, tee joint, corner joint, edge joint and a lap joint. But in this post is only limited to the topic of the Seam Welding Design for Butt Joint, whereas for the other welding joint will be explained in the next post.

Butt Joint is the most efficient type of connection. This connection is further divided into two namely, full penetration and penetration joint portion. Full penetration connections is divided further into connection with the auxiliary plate is subdivided into plates maid who also became part of the construction and auxiliary plate just as a helper at the welding process alone.

Butt Joint able to use some kind of seam welding such as seam square, vee seam, bevel seam, u-seam, double vee seam, double bevel seam and double u-seam. Selection of seam types and welding symbols can be seen in the table below. (More detailed for discussion about the seam type and welding symbols can be seen on the post Basic Welding Design)

Type of seam welding in the butt joint greatly affects the working efficiency, the efficiency of the connection and the power connection, so the selection of the proper seam shape is very important. The shape and size for butt joint welding seam is already widely standardized in AWS, BS, DIN, GOST, JSCC and others.

Each type of seam welding in butt joint has a different welding strength. Welding strength is meant here is the ability to withstand weld tensile stress, bending stress and shear stress. How welding stress that occurs for every type of welding seam on the butt joint, let us refer to the following description.

Single seam design for butt joint welding

Single seam welding is only made on one surface of the joint welding course. Which belong to the single seam welding are square seam, vee seam, bevel seam and u-seam. If the welds are given the force parallel to the attached plate as in the picture below, there will be tension in the cross section of the weld.

Tensile stress will make a deformation in the form of an extension of seam welding. (1) Seam welding will return to its original shape if the tensile stress is still below the limit of elasticity of welding material. (2) Seam welding will experience a permanent extension (plastic deformation) if the tensile stress is above the limit of elasticity of welding material. (3) Seam welding would break up if the tensile stress exceeds the maximum tensile strength of welding material. Tensile stress of butt joint with single seam welding can be calculated by the formula:

Note:

s_t = Tensile Stress (kg/mm2)

F = Force or Welding Load (kg)

h = Seam Width (mm)

l = Seam Length (mm)

If the butt joint is given two forces in opposite directions perpendicular to the plates which are connected as shown below, there will be shear stress at the weld cross section.

Both forces on the welding seam consist of the action and reaction force, so it has the same value and meet force equilibrium system. Seam welding will have cracks when the shear stress exceeds the capability of welding material (shear strength). Shear strength is calculated 40% of the maximum tensile strength of welding material. Shear stress of butt joint with single seam welding can be calculated by the formula:

Note:

t = Shear Stress (kg/mm2)

F = Force or Welding Load (kg)

h = Seam Width (mm)

l = Seam Length (mm)

If the force is perpendicular to the plate in the butt joint has a certain distance to a cross-seam welding, it will happen the bending moment like in the picture below. This condition causes the bending stress at the weld cross section.

Bending stress will cause a deflection on the seam welding of butt joint. (Calculation of deflection you can see in the post about the shaft design in the calculation of shaft deflection). Bending stress of butt joint with single seam welding can be calculated by the formula:

Note:

σ_b = Bending Stress (kg/mm2)

M = Bending Moment (kgmm)

h = Seam Width (mm)

l = Seam Length (mm)

Double seam design for butt joint welding

Double seam welding is made on the second surface of the welding seam joint with the same size or different. Which belong to the double seam welding are double vee seam, double-bevel seam and double u-seam. As well as the single seem welding some types of forces acting on the double seam welding will cause a tensile stress, shear stress and bending stress with different formulas.

The forces that cause tensile stress on the double seam welding for butt joint can be seen in the image below.

Tensile stress of butt joint with double seam welding can be calculated by formula:

Note:

s_t = Tensile Stress (kg/mm2)

F = Force or Welding Load (kg)

h₁  = Upper Seam Width (mm)

h₂  = Lower Seam Width (mm)

l = Seam Length (mm)

The forces that cause the shear stress on the double seam welding for a butt joint can be seen in the image below.

Shear stress of butt joint with double seam welding can be calculated by formula:

Note:

t = Shear Stress (kg/mm2)

F = Force or Welding Load (kg)

h₁  = Upper Seam Width (mm)

h₂  = Lower Seam Width (mm)

l = Seam Length (mm)

The forces that cause the bending stress on the double seam welding for a butt joint can be seen in the image below.

Bending stress of butt joint with double seam welding calculated by formula:

With,

h = h₁ + h₂

Note:

σ_b = Bending Stress (kg/mm2)

M = Bending Moment (kgmm)

T = Plate Thickness (mm)

h₁  = Upper Seam Width (mm)

h₂  = Lower Seam Width (mm)

l = Seam Length (mm)

That is a description about Seam Welding Design for Butt Joint. If you find misconceptions in the seam welding formula, please provide the correction in the comment box.