| 1. |
- Abbas, Zeshan, et al.
(författare)
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Influence of Patterns on Mechanical Properties of Ultrasonically Welded Joints in Copper Substrate and Wire
- 2024
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Ingår i: Metals and Materials International. - : Springer Nature. - 1598-9623 .- 2005-4149.
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Tidskriftsartikel (refereegranskat)abstract
- Ultrasonic wire welding is considered a method of choice for creating reliable interconnects in electronics industry including aerospace, batteries and electric vehicles. In this paper, ultrasonic welding tests between EVR252 copper wire and substrate are carried out. Novel pattern morphologies are machined on substrates to explore its influence on mechanical properties of welded joint. Patterns are divided into three different categories e.g., original surface, vertical and horizontal shapes. Cracks, microstructure strength and tensile properties of welded joint are studied and its joining mechanism is analysed. Compared with the reference substrate (S1), the welded joint performance of the longitudinal patterns (S2, S3, S4) has been improved, among which the longitudinal pattern (S4) has the most significant improvement (+ 15%). Likewise, the performance of transverse pattern (S5) welded joints is relatively poor (− 16%). The microstructural analysis using SEM has revealed predominant joint strength on Cu wire surface while maintaining rock-like and compact properties of S4 substrate. Upper side of wire-harness compactness is frequently observed due to vertical direction of patterns on substrate and also increases the strength of welded joint. Values of failure load, failure displacement and failure energy absorption were increased by 7.9%, 72% and 35% for S2, 6.1%, 75% and 42% for S3 and 15%, 87% and 113% for S4 compared to S1. Failure modes of welded joints are mainly characterized into: 1-poor ductility or rupture (no deformation) failure in vertical 3-line pattern joints 2-cylindrical deep holes failure in vertical 3-line zigzag pattern joints and 3-bulging effect failure in horizontal 3-line zigzag pattern joints. Point and line scans EDS measurement were performed to investigate weaker and stable trends of different locations in welded joints. In S4 substrate, 17.9% carbon content at the position of welded joint was investigated, leading to content of less oxides and fraction impurities. However, S1 weld zone contains 38.7% carbon content which can weaken welded joint and reduce durability. Graphical Abstract: (Figure presented.). © The Author(s) under exclusive licence to The Korean Institute of Metals and Materials 2024.
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| 2. |
- Abbas, Zeshan, et al.
(författare)
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Surface-conformed approach for mechanical property analysis using ultrasonic welding of dissimilar metals
- 2024
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Ingår i: The International Journal of Advanced Manufacturing Technology. - : Springer Science+Business Media B.V.. - 0268-3768 .- 1433-3015.
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, dissimilar aluminum (Al) and copper (Cu) metals were joined together using ultrasonic metal welding (USMW), a solid-state welding technology. From the perspective of increasing the base metal welding contact area, the Cu/Al mating surface was innovatively prepared and ultrasonically welded. A comprehensive analysis was carried out on the forming quality, welding process temperature, interface structure, and mechanical properties of the welded joint. Defect-free and squeezed welds were successfully achieved by machining novel patterns especially C4-2. The results indicated that the reference joint can withstand higher loads, but its failure mode is very unstable. Failure may occur at welded interface and on the aluminum plate which is not good for actual production applications. Welded strength of reference joint was 4493 N, and the welded strength of C4-2 joint was 3691 N. However, microscopic analysis discovered that the welded joint internal morphology in C4-2 was more stable and hardest. C4-2 joint has successfully achieved higher tensile strength and stability under failure displacement of 38% which is higher than C4-1 joint. All welded joint failures occurred on aluminum plate, indicating that the joint strength is higher than that of bottom plate. This is attributed to unique structural design of chiseled joint and lesser thickness. SEM–EDS results investigated that the C4-2 joint can transfer more energy to area under welding head which provides welded joint with robust diffusion capacity. The transition layer has a higher thickness while the energy transferred to area away from welding head was smaller. Thickness of transition layer is significantly reduced and reference joint has similar diffusion characteristics. Conversely, the thickness of the transition layer at the corresponding position is smaller than that of pattern morphology. This is due to overall smaller thickness of the pattern joint which is more conducive to the transfer of welding energy. The surface-conformed approach and comprehensive temperature analysis provide a new understanding of USMW in dissimilar welded metals. © The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature 2024.
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| 3. |
- Kroon, Martin, Professor, 1974-, et al.
(författare)
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Experimental and theoretical study of stress relaxation in high-density polyethylene
- 2024
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Ingår i: Acta Mechanica. - : Springer. - 0001-5970 .- 1619-6937.
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Tidskriftsartikel (refereegranskat)abstract
- Stress relaxation of high-density polyethylene is addressed both experimentally and theoretically. Two types of stress relaxation testing are carried out: uniaxial tensile testing at constant test specimen length and compression testing of a 3D structure producing inhomogeneous deformation fields and relaxation. A constitutive model for isotropic, semi-crystalline polymers is also proposed. The model has the ability to model stress relaxation at different time scales. The developed model was implemented as a user subroutine in Abaqus (UMAT). The implicit integration scheme including an algorithmic tangent modulus is described in detail. The material model is calibrated by use of the uniaxial tensile tests, and the model is then validated by simulating the compression tests of the 3D structure. The model is able to describe the uniaxial tension tests well, and the comparison between the simulations and experimental testing of the 3D structure shows very good agreement. © 2024, The Author(s).
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