Browsing by Author "Hellier, AK"

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    Effect of ultrasonic peening on fatigue crack propagation from a weld toe
    (International Institute of Welding, 2016-07-10) Hellier, AK; Prusty, BG; Pearce, GM; Reid, M; Paradowska, AM
    The objective of this work was to investigate the effect of ultrasonic peening on the fatigue propagation life for a semi-elliptical flaw at a T-butt weld toe. A number of T-butt joints have been fabricated from 10 mm thick A350 grade black mild steel plate. Through-thickness residual stresses at the weld toe have been measured using neutron diffraction for both as-welded and ultrasonically peened joints. Ultrasonic peening is relatively cheap, can be applied in-situ and offers significant improvements in the lifespan of welded components when applied correctly. Numerical analyses were conducted using BDKH stress intensity and HBC stress distribution parametric equations in conjunction with the Paris Law and Forman Equation fatigue crack growth models.
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    Effect of ultrasonic peening on residual stresses at a T-butt weld toe
    (Materials Research Forum LLC, 2016-07-03) Hellier, AK; Prusty, BG; Pearce, GM; Reid, M; Paradowska, AM; Simons, P
    The current paper presents the results of neutron diffraction measurements of the throughthickness residual stress field at the toe of a T-butt weld, made from 10mm thick A350 grade black mild steel plates, after successful ultrasonic peening. A single ultrasonic peening treatment was carried out at the weld toe. Residual stresses were measured using the KOWARI instrument at ANSTO. The neutron diffraction technique was chosen for this study because of its ability to measure three-dimensional residual stress deep within the component at high resolutions. Although the nominal yield stress of the A350 grade plate is 350 MPa the actual yield stress is generally higher, in this case averaging out to about 400 MPa. Ultrasonic peening was highly effective, leading to a residual stress redistribution with a maximum compressive stress of about 250 MPa at the weld toe surface and a maximum tensile stress of 220 MPa, at a depth of almost 3mm into the base plate. The resulting compressive residual stresses at the weld toe surface will almost certainly increase substantially both the fatigue initiation and propagation lives, or may prevent fatigue completely. Since A350 steel is widely used in buildings, bridges and offshore structures, ultrasonic peening shows great promise as an in-situ peening method in order to improve weld fatigue performance. © The Authors
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    Experimental and modelling approaches to the determination of fatigue crack growth from a structural steel T-butt weld toe
    (Engineers Australia, 2017-11-27) Tanulia, V; Prusty, BG; Pearce, GM; Hellier, AK; Li, H; Reid, M; Paradowska, AM
    T-butt welded joints are found in many structural steel applications including buildings, bridges and offshore structures and are susceptible to fatigue crack initiation and propagation,which often leads ultimately to fast fracture failure. An example ofthis was the I-35W bridge in Minneapolis, which collapsed in 2007 resulting in 13 fatalities, as shown in Figure 1 [1]. The experimental work for this project was conducted using A350 grade black mild steel plate. An ultrasonic peening treatment was applied to one T-butt specimen to introduce compressive residual stress at the weld toe, in order to reduce the effective fatigue crack propagation rate. The results generated from 3-D FEA modelling plus a FORTRAN program (implementing parametric stress intensity factor and crack propagation equations) will be compared with experimental fatigue test results. © (2017) by Engineers Australia
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    Hardness-tensile property relationships for HAZ in 6061-T651 aluminum
    (American Welding Society, 2014-08) Stathers, PA; Hellier, AK; Harrison, RP; Norrish, J
    High-strength aluminum is used extensively in industry, with welding being a widely used fabrication method. This work focuses on welding of 6061-T651 aluminum and establishment of the hardness–tensile properties relationship in the heat-affected zone (HAZ) of a gas metal arc weld using 4043 filler material. Test welds were prepared from 12.7-mm-thick plate with a single-V weld preparation. Base plate temperatures were measured with an array of eight embedded thermocouples during welding, relating temperature to properties at intervals from the weld. Through-thickness slices 1.7 mm thick were removed, by electric discharge machining, from the plate parallel to the weld at 2-mm intervals and extending from the weld centerline to 40 mm. into the HAZ and base plate. Tensile samples were prepared from these slices, and tensile properties and hardness values measured to establish a relationship between these two parameters. Both EQUOTIP (portable hardness tester) and Vickers microhardness measurements were conducted and related to tensile properties. Although a significant body of work exists relating tensile properties to hardness, no previous study was found that used this approach. Most work appeared to use cross-weld tensile tests, which only give the point of lowest strength. Sections of base plate material having a different thickness (31.75 mm) from that of the welded samples, and from a different source, were thermally aged to four hardness values and the hardness–tensile relationship was also established for this material. These results were compared with those of the HAZ samples; the results were found to fall within the scatter band of HAZ results.
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    Residual stress effects on fatigue crack growth from a T-butt weld toe
    (University of Wollongong Australia, 2018-11) Hellier, AK; Li, H; Prusty, BG; Pearce, GM; Reid, M; Paradowska, AM
    A350 grade black mild steel is one of the most widely used structural materials in the world, being commonly found in buildings, bridges and offshore structures.Welding is commonly used to join two plates of structural steel and this often takes the form of a T-butt.In addition, other more complex geometrical joints are often simplified for stress analysis purposes by approximating them as 2-D T-butt plate models (e.g. skewed T-joints, cruciform welded joints, tubular welded joints, pipe–plate joints, etc.).However, all such welds are potentially susceptible to fatigue crack initiation and slow but accelerating growth arising as a result of fluctuating service loads, often eventually resulting in fast fracture.
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    Weld toe SCF and stress distribution parametric equations for tension (membrane) loading
    (Trans Tech Publications, 2014-03) Hellier, AK; Brennan, FP; Carr, DG
    The results of linear elastic finite element analyses of stress concentration factor (SCF) and through-thickness stress distribution for 80 weld toe T-butt plate geometries are presented in parametric form for tension (membrane) loading. The closed-form solutions, which describe the stress state of the two-dimensional plane stress models studied in terms of weldment angle, weld toe radius, weld attachment width and plate thickness, are accurate and wide ranging. The SCF is presented in full parametric form and also as a simple reduced expression, quantifying the degree of error from raw data in each case. An expression for the stress distribution through the potential Mode I crack plane of the uncracked geometries is also presented in full parametric form. It is anticipated that these HBC equations will be particularly useful in the calculation of weight functions for stress intensity factors (SIFs) of fatigue cracks emanating from weld toes in T-butt welded joints, especially in the presence of known residual stresses, or those resulting from peening.© 2014, Trans Tech Publications