Defects involving inadequate bonding, Mechanical Engineering

Assignment Help:

Defects Involving Inadequate Bonding


Lack of fusion

Involves lack of complete melting and fusion of some portion of the weld metal in a joint. It may occur either between parent metal and weld metal or between two layers of weld metal. This can occur in fusion welding and pressure welding. The following are the reasons for incomplete fusion:

  • Improper manipulation of electrodes
  • Incorrect position of electrodes
  • Low welding current
  • Too rapid arc advance
  • Improper joint fit up
  • Improper edge cleaning of slag after flame cutting
  • Impurities on the face of the joints in the case of pressure welding.

 


If lack of internal fusion is severe it is considered to be a serious defect. Incomplete fusion at the surface is of more serious consequence. As lack of fusion in the form of incomplete penetration of unbevelled or bevelled joints is not always revealed by radiography, ultrasonic examination is recommended as a supplementary test when lack of fusion is suspected.

 Incomplete penetration

This is incomplete penetration of the weld through the thickness of the joint. This usually occurs at the root of the weld or between the deposits made from both sides of a joint. In double welded joints lack of penetration may occur within the wall thickness as a 'buried' defect. Incomplete penetration at the root is more severe. The reasons are:

  • Incorrect joint design.
  • Improper welding parameters, particularly current.
  • Incorrect electrode size.
  • Incorrect polarity where DC is used.

 


Inadequate joint penetration is not tolerated to any extent in objects which are subjected to either tension or bending stresses. It can initiate brittle fracture under either static or dynamic loads. The unfused root causes stress concentration which could lead to failure without deformation and cracks are initiated from the unfused root. Lack of fusion and incomplete penetration are not permitted by pressure vessel code. This type of defects are easily detected by ultrasonic or radiography. In case of thin ferrous welds, magnetic particle examination can be used.


Related Discussions:- Defects involving inadequate bonding

Calculate stress to cause failure - creep parameters, Calculate stress to c...

Calculate stress to cause failure - Creep Parameters: From creep tests on 713 C alloy the constant C in Larson-Miller parameter is determined as - 85.75. In rupture test a spe

Process selection and sequencing, Process Selection and Sequencing In th...

Process Selection and Sequencing In this, some factors, which have an influence in all processes, are discussed. The factors include size, shape complexity, tolerances and produ

Rigid body and momentum, Rigid body and Momentum: Body : A body consi...

Rigid body and Momentum: Body : A body consists of a Number of particles, it has definite shape. Rigid body :   A rigid body can be defined as the combination of a large

Control surface and flow work - thermodynamics, Control Surface and Flow Wo...

Control Surface and Flow Work - thermodynamics: Cont r o l Surface: A control system has control volume that is separated from its surrounding by real or imaginary contro

Calculate the response of the system, A Spring - mass system which is subje...

A Spring - mass system which is subjected to a harmonic force FCoswt. calculate the response of the system, refer figure Given x (0) = 0.01 m x(0) = 0.04 m/sec w = 30 rad/

Engineering physics-1, how will you detect the depth of sea and application...

how will you detect the depth of sea and application?

Differences between direct stress and bending stress, Give differences betw...

Give differences between direct stress and bending stress. Direct tensile and compressive stress is set up because of load applied parallel to length of object, and direct shea

Calculate the compression ratio - maximum pressure of engine, (a) Derive an...

(a) Derive an expression for the otto cycle to determine the Mean Effective Pressure and efficiency. (b)The two engines are to perform on diesel and otto cycle with the followin

Types of polymerisation, Types Of Polymerisation When some of bifunctio...

Types Of Polymerisation When some of bifunctional molecules connect in a chain structure, the reaction is termed as addition polymerisation.  However, these polymerizations do

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd