Welded Joints | Definition, Types, Stress

By Mohit Uniyal|Updated : June 1st, 2022

In this modern technology world fabrication work would be impossible without welding. No single person was involved in the invention of welding.  The first is an electric arc welding between two carbon electrodes by using the battery as an energy source. It was introduced bySir Humphry Davy’ in 1880. After the invention, welding continued to evolve, bringing it to its modern-day form. 

In the various joining process, welding is one of the most used permanent joining processes. In riveted joint is required to consist of additional components like cover plates, straps, gusset plates, and clip angle. Which results in increases in the weight of the assembly. Welded is used as a substitute for a riveted joint. 

Table of Content

What are Welded Joints? 

A welded joint is a material joining process formed by the fusion of two similar or dissimilar, with or without the application of pressure and filler metal. Based on the method of joint preparation, welding can be classified into two types: 

  • Fusion welding – in this welding process, where welding joint is obtained from the melting of the parent metal 
  • Non-fusion welding – In this welding process joint is produced without melting the parent metal 

Types of Welded Joints 

As per the requirement, assembly, design, and operating condition it is very important to make a proper weld joint. So based on the above parameter it requires different types of welded joints. As per the shape of the weld component, the thickness of the weld component plate, and the direction of applied force We can classify welded joint are as follow: 

  1. Lap joint 
  2. Butt joint  
  3. Corner joint. 
  4. Edge joint. 
  5. T- joint. 

Lap joint  

When the joint is made by overlapping two parts, it is known as a lap joint. It is also known as a fillet joint. Based on the direction of the applied force There are three different types of fillet weld: 

  • Single transverse fillet joint. 
  • Double transverse fillet joint. 
  • Parallel fillet joint 

Transverse fillet weld  

It is the type of fillet weld where the direction of applied force is perpendicular to the weld. in transverse loading, one plate exerts a shear load and the other a tensile (or compressive) load on the weld.​ Mostly double transverse fillet weld is preferable, as in this case there is not any edge free to deflect. 

Parallel fillet weld 

In this type of fillet weld, the direction of applied force is parallel to the weld. For parallel loading, both plates exert a shear load on the weld.​ in this case, weld beads are on both sides of the plate. The asymmetric weld joint is prepared in case of an unsymmetrical section, in certain applications such as angle or “T”. 

Butt joint  

When the joint is when the two components lay approximately the same plan, it is known as the butt joint. In this welding, if the thickness of the plate is less than 5 mm then it is required beveling.  

In case of plate thickness, 5 mm to 12.5 mm beveling needs to be provided on one side or both sides of the plate. Based on this butt joint can be further classified as: 

  • Square butt joint. 
  • Single V-butt joint. 
  • Double V-butt joint. 
  • Single U-butt joint. 
  • Double U-butt joint. 

Corner joint 

When the corner of both components is joint at the perpendicular to each other, then this joint is known as the corner joint. 

Tee joint 

In a tee joint, when one of the components is perpendicular to the other, and form a “T” like structure, known as a tee joint. 

Edge joint 

When the edges of both the components are parallel to each other with at least one of their edges in common, the joint is made at the common edges known as an edge joint. 

Stress in Welded Joints

Depending on the type of welded joint and loading condition, tensile, compressive and shear stress are developed in the welded joint. It is very difficult to determine the stresses in the welded joint, as there is a variable and unpredictable parameter that comes into consideration.  

  • Homogeneities of the weld metal,  
  • Thermal stresses in the welds,  
  • Changes in physical properties due to high rate of cooling etc. 

While calculating the stresses in the weld joint, we have to consider the following assumptions 

  • The load is uniformly distributed over the entire length of the weld. 
  • The stress is spread uniformly over its effective section. 

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FAQs on Welded Joints

  • It is the location where the surface of two or more two metals or non-metals are joint together by the welding process with or without the application of pressure and filler metal. 

  • Based on the different types of a welded joint we can classify weld as follow: 

    1. Fillet weld 
    2. Groove weld 
    3. Surface weld 
    4. Plug weld  
    5. Slot weld 
    6. Spot weld 
    7. Seam Weld 
    8. Flange weld 
  • In welding, at initial we can classify welding into two groups. Based on the method and heat source further, we can be classified as follow: 

    1. Fusion welding 
    • Gas welding 
    • Arc welding 
    • Resistance welding 
    • Chemical welding 

    2. Non-Fusion welding 

    • Friction welding 
    • Friction Stir welding 
    • Explosive welding. 
    • Ultrasonic welding 
    • Hot pressure welding.
  • The advantages of a welded joint are as follows: 

    • Economical in terms of material used and fabrication cost.​ 
    • Permanent joint. ​ 
    • Weld part becomes a single entity.​ 
    • Achieve stronger weld joint by using high-strength filler material.​ 
  • The Limitations of a welded joint are as follows: 

    • Mostly performed manually and are expensive in terms of labor cost (skilled labor is required)​ 
    • It involves high energy and is inherently dangerous.​ 
    • As a permanent bond between components, it does not allow for conventional disassembly. ​ 
    • Welding should not be used as the assembly method.​ 
    • Certain weld quality defects are difficult to detect. ​ 
  • The various types of application of welded joint are as follow: 

    • Pressure vessel, boiler. 
    • Building structures and bridges 
    • Aircraft and spacecraft 
    • Railway coach and railway tracks 
    • Shipbuilding and submarine. 
    • Electrical and electronic equipment. 
    • Fabrication in sheet metal operation 

    The main importance of welded joint is that it is economical, efficient, and dependable.​ 

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