Browsing by Author "Haque, R"

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    Effect of sheet material properties on residual stress profile in self-pierce riveted joint
    (Australian Institute of Nuclear Science and Engineering (AINSE), 2012-11-07) Haque, R; Durandet, Y; Paradowska, AM
    Self-Piercing Riveting (SPR) is a high-speed mechanical fastening technique which does not require pre-drilling. During SPR, a tubular rivet is driven through the top sheet, piercing the bottom sheet without breaking through it, accompanied by flaring of the legs in the bottom sheet under the guidance of a suitable die. The rivet material should have adequate hardness to pierce the sheets, and sufficient ductility to deform in the bottom sheet without cracking, thus producing a mechanical interlock between the sheets. An increase in strength or thickness of the ply materials narrows down the operating window in terms of joint quality and performance. It is important to know the residual stress distribution arising from the riveting process, and its dependence on the ply materials properties. to ensure a sound joint. In this study, four different joints consisting of two different hardnesses of materials and two different hardnesses of rivets were examined. Residual stresses were measured on the strain scanner Kowari at ANSTO at selected critical locations. The study revealed that the hardness of the rivet and a ply material influence the magnitude and distribution of compressive residual stress in the rivet joint. It was observed that the maximum compressive residual stress occurred in the rivet leg in the transverse direction relative to plane of sheet. The challenges related to the application of neutron diffraction technique to the measurements of residual stress in the riveted joints are presented and discussed.
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    The effects of Bi addition on the mechanical properties of eutectic Sn-Ag-Cu lead-free solder alloy
    (Australian Institute of Nuclear Science and Engineering (AINSE), 2020-11-11) Olofinjana, A; Shewchenko, L; Mata, JP; Haque, R
    Sn-Ag-Cu (SAC) solders are gaining momentum as the choice of Pb free electrical interconnect materials because of the legislative restrictions on the use of hazardous materials in electronic devices. However, SAC has high melting temperatures around 217oC. The role of Bi substitution to lowering solder joint processing temperatures are widely considered because of the low-temperature Sn-Bi eutectic. However, the embrittling effects of Bi addition require clarification on the maximum limits of substitution. In this work, the mechanical properties of eutectic SAC with gradual Bi substitution up to 10wt.% Bi was followed. It is shown that fracture strength (σ_f) increases from 50MPa plateauing at 60MPa between 1.4 and 1.8%Bi representing the limits of solid solution strengthening. Over this substitution range, strain at fracture (ε_f) dropped from 30% to 10% and reduction in area (RA) dropped from 80% to less than 5%. The σ_f was nearly 80MPa for 2%Bi and this increases gradually with %Bi concentration peaking at 93MPa for 7%Bi. Results of thermal analysis suggested that solidification went off eutectic after Bi concentration exceeded 2%. Using neutron diffraction techniques, the lattice parameter measurements suggest that the solubility limit of Bi in β Sn (in the multicomponent Sn-Ag-Cu) is about 2wt. %. The existence of Bi rich clusters was responsible for observed brittleness after 2wt.% Bi substitution. With the aid small angle neutron Scattering (SANS) and ultra-small angle neutron scattering (USANS), it was found that the intensity changes with respect to scattering factor (Q) especially for high Q region when the precipitations sizes are below 12.5 nm after concentration exceeded 2%Bi that confirms the existence of primary nanosized Bi precipitates that starts to grow into well-defined Bi phases for higher Bi content.
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    The effects of Bi substitution for Sn on mechanical properties of Sn-based lead-free solders
    (Springer Nature, 2021-08-02) Raza, M; Shewchenko, L; Olofinjana, A; Kent, D; Mata, JP; Haque, R
    Pb-free solders are gaining ground as the optimum choice for electrical interconnect materials, however, their higher melting temperature around 217 °C is still an issue that restricts wider adoption. The potential to employ Bi substitution for Sn to lower solder joint processing temperatures has been widely considered. In this work, the mechanical properties of eutectic SAC with gradually increasing Bi substitution up to 10 wt% Bi was studied. It is shown that fracture strength (σf) increases with Bi additions from 50 MPa plateauing at 60 MPa between 1.4 and 1.8% Bi which represents the limits of solid solution strengthening. Over this substitutional range, strain at fracture (εf) dropped from 30 to 10% which was also evidenced by smaller percentage reduction in area (%RA). The σf was nearly 80 MPa for 2% Bi increasing gradually with increasing Bi concentrations and peaking at 93 MPa for 7% Bi whilst maintaining 10% elongation at fracture. X-ray diffraction and DSC thermal studies suggests that the solubility limit of Bi in β-Sn (in the multicomponent SAC) is less than 2 wt% Bi. With the aid of small-angle neutron Scattering (SANS) and ultra-small-angle neutron scattering (USANS), it was found that the scattering intensity changes for alloys with Bi content in the range 0.8 – 1.5wt% compared to ternary SAC with less than 0.8% Bi at low scattering factors (Q > 10 - 2Å - 1) signifying microstructural differences at length scales of the order of 10–100 nm. There were no differences observed in scattering for alloy samples with more than 2 wt% Bi. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
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    Evaluation of residual stress in SPR joint by neutron diffraction
    (Trans Tech Publication Inc., 2012-01-01) Haque, R; Beynon, JH; Kirstein, O; Wong, YC; Durandet, Y
    The feasibility of measuring residual stresses in Self-Pierce Riveted (SPR) joints by neutron diffraction was evaluated in this study. Despite the small dimensions involved, meaningful results were obtained. It was observed that residual stress in the rivet head was higher in the centre and lower at the edge. For the SPR joints examined, the maximum value of residual stress evaluated was 550MPa, compressive and occurred in the rivet leg. Stresses in material adjacent to the rivet wall and at a distance of three times the rivet radius from the rivet axis were not significant. The results are discussed with respect to the physical events involved during SPR. © 2011, Trans Tech Publications
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    Feasibility of measuring residual stress profile in different self-pierce riveted joints
    (Maney Publishing, 2012-01-01) Haque, R; Beynon, JH; Durandet, Y; Kirstein, O; Blacket, S
    The feasibility of measuring residual stresses in self-pierce riveted (SPR) joints by neutron diffraction technique was investigated. The main challenge involved dealing with the very small dimensions of SPR joints. Two different joints were examined: aluminium‐steel and steel‐steel. Even though small dimensions were involved, meaningful results were obtained. In the rivet head, tensile stress was observed for the steel‐steel sample, whereas only compressive stress was observed for the aluminium‐steel. The residual stress in the rivet head was higher at the centre and lower at the edge for both joints. Stresses in the sheet material beside the rivet wall and at a distance of three times the rivet radius from the rivet axis were not significant. For the SPR joints examined, the maximum value of residual stress was compressive and occurred in the rivet leg. The results are discussed according to the physical events involved during the process.© 2012, Maney Publishing
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    Optimising parameters for meaningful measurement of residual strain by neutron diffraction in self-pierce riveted joints
    (Maney Publishing, 2013-11-18) Haque, R; Durandet, Y; Wong, YC; Paradowska, AM; Beynon, JH; Blacket, S
    The aim of this work is to examine the uncertainties involved in measuring residual strain and their dependence on both the gauge volume of the neutron beam and the acquisition time in self pierce riveted (SPR) joints while using the neutron diffraction technique. The main challenge involved dealing with the very small dimensions of SPR joints and developing optimum instrument configuration that allowed faster and/or more accurate stress measurement in SPR while maintaining the same time resolution required for the millimetre scale of the problem. Two different gauge volumes were used (0.125 and 1.0 mm(3)), and two different measuring directions were chosen in order to examine the rotational accuracy of the sample table. All measurements were conducted in steel–steel joints. Even though small sizes were involved, meaningful results were obtained and measurement errors were reduced by optimising the instrument parameters. © 2013, Maney Publishing
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    Residual stress profiles in riveted joints of steel sheets
    (Taylor and Francis, 2014-12-28) Haque, R; Wong, YC; Paradowska, AM; Durandet, Y
    The residual stress profiles in two different self-piercing riveted (SPR) joints were characterised using the neutron diffraction technique. The joints were produced using semi-tubular steel rivets and carbon steel sheets of different thicknesses and hardnesses. The residual stress in the sheet material inside the bore of the rivet was compressive at the centre and the stress became tensile away from the centre. The stresses found in the semi-tubular rivet were compressive, with a lower magnitude in the rivet head compared with those in the rivet leg. For the SPR joints examined, the compressive residual stress in the rivet leg was greater for the thin joint than the thick joint, and this was due to the higher force gradient encountered during the rivet flaring stage. The originality of this work was to relate the residual stress profile to the physical event that occurred during the SPR process. © 2021 Informa UK Limited
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    SPR characteristics curve and distribution of residual stress in self-piercing riveted joints of steel sheets
    (Hindawi, 2017-02-15) Haque, R; Wong, YC; Paradowska, AM; Blacket, S; Durandet, Y
    Neutron diffraction was used to describe the residual stress distributions in self-piercing riveted (SPR) joints. The sheet material displayed a compressive residual stress near the joint, and the stress gradually became tensile in the sheet material far away from the joint. The stress in the rivet leg was lower in the thick joint of the softer steel sheet than in the thin joint of the harder steel sheet. This lower magnitude was attributed to the lower force gradient during the rivet flaring stage of the SPR process curve. This study shows how the residual stress results may be related to the physical occurrences that happened during joining, using the characteristics curve. The study also shows that neutron diffraction technique enabled a crack in the rivet tip to be detected which was not apparent from a cross-section. © 2017 Rezwanul Haque et al. This is an open access article distributed under the Creative Commons Attribution License