Residual Stresses in Welded Elements: Measurements, Fatigue Analysis and Beneficial Redistribution

Transcription

1 Residual Stresses in Welded Elements: Measurements, Fatigue Analysis and Beneficial Redistribution Y. Kudryavtsev and J. Kleiman Structural Integrity Technologies, Inc. (SINTEC) 1

2 OUTLINE OF THE PRESENTATION INTRODUCTION. RESIDUAL STRESS MANAGEMENT MEASUREMENT OF RESIDUAL STRESSES BY ULTRASONIC METHOD (UM) FATIGUE IMPROVEMENT BY ULTRASONIC IMPACT TREATMENT (UIT-UP) EXAMPLES OF INDUSTRIAL APPLICATION OF UM AND UIT-UP SUMMARY

3 Importance of Residual Stresses

4 Residual Stresses in Welded Elements Distribution of longitudinal (along the weld) and transverse components of residual stresses along the butt weld toe

5 Effect of Residual Stresses Fatigue curves of butt welded joint in low-carbon steel: 1 - without residual stresses;,3 - with high tensile residual stresses (fatigue testing and computation)

6 Effect of Residual Stresses Fatigue curves of non-load caring fillet welded joint in high strength steel: 1 -in as welded condition;,3- after application of ultrasonic peening (fatigue testing and computation)

7 IMPORTANCE OF RESIDUAL STRESS MANAGEMENT RESIDUAL STRESS ORIGINATED FROM: Differential plastic flow Differential cooling rates Phase transformations with volume changes etc. RESIDUAL STRESSES ARE CREATED BY: Welding Machining Forging Rolling Surface treatments Casting Heat treatment WHERE RESIDUAL STRESSES ARE IMPORTANT: Fatigue Life Corrosion Resistance Dimensional Stability Brittle Fracture Distortion

8 RESIDUAL STRESS MANAGEMENT is an important component of the process of DESIGN, MANUFACTURING, MAINTENANCE and REPAIR of PARTS and WELDED ELEMENTS

9 STAGES IN RESIDUAL STRESS (RS) MANAGEMENT Stage 1: RS Determination - MEASUREMENT: Destructive, Non-Destructive - COMPUTATION Stage : RS Effect Analysis - EXPERIMENTAL STUDIES - COMPUTATION Stage 3: RS Modification (if required) - CHANGES in TECHNOLOGY of MANUFACTORING / ASSEMBLY - APPLICATION of STRESS - RELIEVING TECHNIQUES

10 Equipment and Software UltraPeen RESIDUAL STRESS MANAGEMENT Proposed Complex of Advanced Engineering Tools Stage 1: RS Determination Ultrasonic Measurement of Applied and Residual Stresses (UM) Device and Software UltraMARS Stage : RS Effect Analysis Expert System for Fatigue Assessment and Optimization of Parts and Welded Elements - RESIsT Stage 3: RS Modification (if required) Ultrasonic Peening of Parts and Welded Elements (UP/UIT)

11 The Ultrasonic Computerized Complex for measurement of residual and applied stresses - UltraMARS

12 Ultrasonic Method of Residual Stress Measurement Ultrasonic stress measurement techniques are based on the acousticelasticity effect, according to which the velocity of elastic wave propagation in solids is dependent on the mechanical stress C/C 1-3 σ, MPa steel A (1) steel B () aluminum alloy (3) -C SX3 ; -C SX ; x - C L

13 Acoustic-Elastic Relationships > > + > > > + + > > > + > > + + > > = µ λ σ µ µ λ σ σ λ µ λ µ σ µ λ µ λ σ 4 ( ) ( 3 ) ( ) ( 3 ). ( ) ( 3 ) ( c b K K K b a C C C kk o lx lx lx ( ) + > + > > + > > > + + > + = σ µ σ µ λ σ σ µ µ λ µ σ c K K K b C C C kk Sx Sx Sx ( ) + > + > > + > > > + + > + = σ µ σ µ µ σ σ µ µ λ µ σ c K K K b C C C kk Sx Sx Sx C lx1 is the longitudinal wave propagation velocity, C sx and C sx3 are the polarized shear wave propagation velocities, σ 11, σ and σ 33 are the residual stresses in the corresponding directions, ρ, λ, µ, a, b, c and K are material constants

14 The main technical characteristics of UltraMARS measurement system: - stress can be measured in materials with thickness - 15 mm; - error of stress determination (from external load): 5-1 MPa; - error of residual stress determination:.1 σy (yield strength) MPa; - stress, strain and force measurement in fasteners (pins) 5-1 mm; - independent power supply (accumulator battery 1 V); - overall dimensions of measurement device: 3xx15 mm; - weight of unit with sensors: 7 kg.

15 PRESENTATION OF THE RESIDUAL STRESS MEASUREMENT DATA USING THE DEVELOPED SOFTWARE Distribution of residual stresses in a low carbon steel plate after local heating

16 Measurement of Residual Stresses by Ultrasonic Method in Shipbuilding Applications The process of RS measurement in welded samples and panel before fatigue testing

17 RS measurement at different locations (Line, 3, 4, 5 and 6) of welded panel after 1,, 1 and cycles of loading

18 Distribution of RS near the end of stiffener 3 3 Residual Stresses, MPa σ σ 33 Residual Stresses, MPa σ σ Distance from the Weld, mm Distance L, mm Distribution of RS in welded ample along lines 1 and.1

19 Measurement of Residual Stresses in a Welded Bridge

20 Residual Stress Measurement in One of the Welded Elements of the Pressure Hull of Submarine

21 RESIDUAL STRESS MANAGEMENT Expert System for Fatigue Assessment and Optimization of Parts and Welded Elements - RESIsT The RESIsT is an Expert System for optimization of welded elements and structures by fatigue criterion. The following important parameters of welded structures with the goal to enhance the fatigue performance are analyzed: preferred design of parts and welded elements; material selection; welding and other technological processes; residual stresses; application of improvement treatments; influence of possible repair technologies; realistic service conditions.

22 Residual Stress in Fatigue Analysis Fatigue curves of transverse loaded butt weld at R=: 1 - with high tensile residual stresses;, 3, 4, 5 and 6 - with residual stresses equals to MPa, MPa, 1 MPa, -1 MPa and - MPa

23

24 Technology and Equipment for Ultrasonic Peening (UP) of Welded elements

25 Replaceable working heads for different industrial applications

26 PRINCIPLE OF ULTRASONIC PEENING The technique is based on the combined effect of the: 1. High frequency impacts of the special strikers and. Ultrasonic oscillation in treated material.

27 The view of the butt welds in as-welded condition (left side sample) and after application of UP (right side sample)

28 The view of the fillet welds in as-welded condition (left side sample) and after application of UP (right side sample) 3mm 15mm

29 Effectiveness of UP in Manufacturing and Repair 5 3 σ max, MPa N, cycles Fatigue curves of welded element (transverse non-load-carrying attachment): 1 in as welded condition, UP was applied before fatigue testing, 3 UP was applied after fatigue loading with the number of cycles corresponding to 5% of expected fatigue life of samples in as-welded condition.

30 Effect of UP Treatment on Corrosion of Metals A Steel Not treated by UP After UP treatment HSLA Material Not treated by UP After UP treatment

31 The Advantages of UP: High (highest) efficiency Quick (treatment speed of ~.5 m of weld/min) Considerably reduced vibrations and noise levels, easier in use than for example hammer peening Deeper penetration Computer controllable Robotic line - ready Lighter with no need in forced water-cooling as compared with similar magnetostrictive systems.

32 Use of basic UP system for fatigue life improvement of tubular welded joint

33 UP system installed on a robot for automotive application

34 Ultrasonic Peening of Welded Bridges

35 Rehabilitation of Welded Bridge by Ultrasonic Peening (Indiana, USA) Total Length of UP Treated Welds - 5 meters Number of UP Treated Welded Elements -5

36 Application of UP for Rehabilitation of Mining Equipment UP of Fatigue Critical Welds of a Grinding Mill

37 Application of UP for Rehabilitation of Stamping Equipment UP of a Welded Reinforcement Plate

38 SUMMARY 1. Residual stresses play an important role in operating performance of materials, parts and structural elements. Their effect on the engineering properties of materials such as fatigue and fracture, corrosion resistance and dimensional stability can be considerable. The residual stresses, therefore, should be taken into account during design, fatigue assessment and manufacturing of parts and welded elements.

39 SUMMARY (continued). The developed advanced ultrasonic method (UM), based on it portable instrument and the supporting software can be used for non-destructive residual stress analysis in laboratory samples and real structure elements in many applications for a wide range of materials. The developed ultrasonic technique was applied in construction industry, shipbuilding, railway and highway bridges, aerospace industry, oil and gas engineering and in other areas during manufacturing, in service inspection and repair of real parts and structures

40 SUMMARY (continued) 3. Ultrasonic Peening (UP/UIT) is a promising technique for fatigue life improvement and could be efficiently used for manufacturing, rehabilitation and repair of welded elements and structures. The developed computerized complex for UP was successfully applied in different applications for increasing of the fatigue life of welded elements, elimination of distortions caused by welding and other technological processes, residual stress relieving, increasing of the hardness of the surface of materials and surface nanocrystallization.