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Full-Scale Fatigue Testing using the Resonance Method


Welding is an activity that is employed to join two distinct pieces of the same material or remove any unwanted materials from metals. Quite simply, the welding can be broadly mentioned as the forging of two heated up metals by employing electrode which works as a slag and avoids the atmospheric contaminants. The art of welding started out when man started out forging tools from metals. The first form of welding that was available to mankind was steel forging by pounding a steel until these are fused together. [1]

Types of Welding:

We are in a world where we can fuse a metallic and separate an individual steel into many components. There are various available methods of welding to achieve this objective. They have got all been developed from the thought of forging and also have a high impact in the human being survival. Some of the several types of welding that are been used are:

  • Oxy-Acetylene gas welding
  • Shielded metallic arc welding (SMAW)
  • Gas tungsten arc welding (GTAW)
  • Electroslag welding (ESW)
  • Gas material arc welding (GMAW)
  • Submerged arc welding (Found)
  • magnetic pulse welding (MPW)
  • Electric amount of resistance welding (ERW)
  • Flux-cored arc welding (FCAW)
  • laser beam welding and
  • electron beam welding [2]

Weld Geometry:

Welding two metals depends on a numerous factor such as type of joints, kind of welds, groove face, main face, root edge, bevel perspective, depth of bevel, groove angle, groove face, groove radius, and root opening. Predicated on all these factors there are nine types of welds. They are

  • Groove Welds
  • Plug or Slot Welds
  • Spot or Projection Welds
  • Back or Support Welds
  • Flanged Welds
  • Fillet Welds
  • Stud Welds
  • Seam Welds
  • Surfacing Welds [3]

Figure 2: Type of Weld

Figure 1: Kind of joint

Figure 3: Process of a) Spot Welding b) Seam welding c) Projection Welding

Types of Failure:

A metal component is always put through stresses and stress. They impact on the total life of the component. A flaw that can cause disruption in the performance of your metal provides us a concept on the integrity of the metal. In case of welding the defect can occur in the area that is welded. Based on the study, it is discovered that the majority of the failing in the welds appear due to incorrect strategy, process conditions, bad weld groves, inappropriate consumables and operator problem. The normal types of failures that occurs in welding are scheduled to hydrogen embrittlement and residual tensions. So, the type of welding failing that can affect the life span of the material component are:

  • Arc strike cracking
  • Undercut
  • Cold cracking
  • Hot cracking
  • Crater crack
  • Root and feet cracks
  • Hat crack
  • Underbead crack
  • Lamellar tearing
  • Longitudinal crack
  • Gas inclusion
  • Reheat cracking
  • Distortion
  • Inclusions
  • Transverse crack
  • Lack of fusion and incomplete penetration [4]


Fatigue may be characterized as the weakening of steel caused by the recurrent application of cyclic loading and unloading. It causes progressive structural damage to the material. The fatigue strength is thought as the maximum power a materials can exhibit without breaking can be an important dimension that is employed to study the life circuit of the steel or the welded composition. The BS 7608 or DNV-RP-C203 offers us an idea about the tiredness power to the applied fill for different weld geometry.

Principle of Tiredness Testing:

Resonance Method Screening is employed for the research of tiredness in welds. "The procedure includes the excitation of the welded steel to be tested to its first mode of vibration through the use of rotational radial force at one end. " The rotational make causes a bending second in its longitudinal axis of the welded steel with two nodal items without any deflection. The welded metallic is supported at these details.

Figure 4: Theory of resonance fatigue testing (in two measurements).

Figure 5: Bending-stress-profile-in-a-resonance-fatigue-test-specimen-with-a-circular-cross-section

This method is utilized to analyze the bending stress in a metal. The resonant occurrence will depend on the mass and tightness of the material. Usually the tests are conducted below the resonant frequency to control the strain and in doing so regulating the strain and deflection. [5]

Figure 6: Resonant-response-of-specimen-deflection-controlled-by-changing-the-speed-of-rotation-of-the-excitation-force.

Industrial Program:

Resonant Examining Machines is the commonly utilized fatigue trials machine when compared to its counterpart Servo-hydraulic trials machines due to its advantages such as better efficiency, high occurrence, zero-maintenance and cost. They are being used for the fatigue analysis of aerospace and automotive fasteners, engine motor components, turbine cutting blades, chains etc.

Aerospace Industry:

Resonant test is employed in aerospace industry to review the fatigue power of the composite materials such as Glass Fiber content Reinforced Polymer (GFRP). They are used to review the fatigue strength of aerospace fasteners such as bolts, screw, studs and rivets. An airplane uses an extreme 3 million fasteners with bolts taking 25% and the rivets taking the others. So, fatigue test is done to analyze the dependability of the fasteners to the repeated pressure and temp cycles, variations in dynamic lots, and high vibration levels. [6]

Figure 7: Fatigue Toughness Screening with resistance heating tester.

Automotive Industry:

Resonant testing are being executed in structural dynamics laboratory in order to review the fatigue durability of high rigidity components such as the motor vehicle components such as joining rods, crankshafts, bolts, mounting brackets, gear teeth, knuckle etc. The test length of time is manipulated by the tightness of the material and the occurrence can go high as up to 100 Hz. [7]


  1. The_Technique_Handbook_Of_Arc_Welding_742pages_1973. pdf
  2. Online: https://en. wikipedia. org/wiki/Welding
  3. Online: http://nearyou. imeche. org/docs/default-source/hong-kong-branch/1- 20. pd
  4. Online: https://en. wikipedia. org/wiki/Welding_defect
  5. Online: http://www. twi-global. com/technical-knowledge/job-knowledge/full-scale-fatigue-testing-using-the-resonance-method-141/
  6. Online: http://www. fastenerandfixing. com/news/high-cycle-fatigue-evaluation-of-aerospace-fasteners
  7. Online:https://www. araiindia. com/services_RnD_services_structural_dynamics_engineering_services. asp
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