| 1. |
- Islam, Md. Shafiqul Islam, 1984-, et al.
(författare)
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Study of Shear Dominant Delamination in Thin Brittle-High Ductile Interface
- 2015
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Ingår i: National Agency for Finite Element Methods and Standards (NAFEMS).
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Konferensbidrag (populärvet., debatt m.m.)abstract
- Thin laminates of Aluminum (Al) and Low Density Polyethylene (LDPE) is an essential constituent of food packages where these two substrates are bonded together with a thin layer of LDPE acting as adhesive. Noticeably, Al is a low ductile/quasi brittle material whereas, LDPE is highly ductile. The mechanism of delamination and strength of bond between the interfaces dictates the continuum and damage behaviour of this composite. However, measuring the shear delamination is challenging as conventional test methods have limitations when the substrates are very thin. This study explains a method that uses uniaxial tensile testing on the pre-cracked specimen of this composite to find energy dissipation due to shear delamination and successfully use it in Finite Element Simulation in Abaqus. The delamination was observed in a narrow strip region close to fracture surfaces and measured with special visualization aid. Similar response was found in FEM simulation. Scanning Electron Microscopic (SEM) study of delaminated interface confirms the domination of shearing. In a cohesive zone modelling in Finite Element Simulation software, the shear delamination energy was used as input parameter along with an arbitrary bi-linear cohesive law. The substrates’ constitutive response was modelled considering non linear plasticity and softening. Finally proposed delamination energy separation method was validated with comparison between the physical tests and FEM simulations.
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| 2. |
- 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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| 3. |
- 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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| 4. |
- Barlo, Alexander, et al.
(författare)
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A Study of the Boundary Conditions in the ISO-16630 Hole Expansion Test
- 2022
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Ingår i: IOP Conference Series. - : IOP Publishing. - 1757-8981 .- 1757-899X. ; 1238
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Tidskriftsartikel (refereegranskat)abstract
- As new and more advanced sheet metal materials are introduced to the market, more accurate techniques for determination of failure limits are needed. One area that needs attention is edge formability, where the ISO-16630 standardized Hole Expansion Test currently is used to express this through the Hole Expansion Ratio. Over the years, this standard has been criticized for producing a large scatter in repeated tests. This paper investigates a new setup for the Hole Expansion Test which introduces draw beads into the setup to ensure sufficient restraining of the specimen during the test in an effort to reduced the scatter. In total 62 tests of a DP800 steel alloy were executed, but a large scatter in the results were still seen. It was therefore concluded that a lack of restraining force in the Hole Expansion Test was not the primary cause of the reported scatter seen in other tests.
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| 5. |
- Barlo, Alexander, M.Sc. Eng. 1994-, et al.
(författare)
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Determination of Edge Fracture Limit Strain for AHSS in the ISO-16630 Hole Expansion Test
- 2023
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Ingår i: 42ND CONFERENCE OF THE INTERNATIONAL DEEP DRAWING RESEARCH GROUP. - : IOP PUBLISHING LTD.
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Konferensbidrag (refereegranskat)abstract
- With the increased demand for application of sustainable materials and lightweight structures, the sheet metal forming industry is forced to push existing materials to the limits. One area where this is particular difficult is when it comes to assessing the formability limit for sheet edges. For decades, the ISO-16630 Hole Expansion Test (HET) has been the industry standard for expressing the edge formability of sheet metals through the Hole Expansion Ratio (HER). However, in recent years, this test has been criticized for its high scatter in results for repeated experiments. This scatter has been suspected to be caused by the operator-reliant post-processing of the test, or variations in the cutting conditions for the different test specimens. This study investigates the impact of shifting the evaluation point of the test from the through-thickness crack to the onset of surface failure on the reported scatter, as well as performs inverse modeling of the Hole Expansion Test to obtain an edge limit strain value.
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| 6. |
- Barlo, Alexander, et al.
(författare)
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Failure Prediction of Automotive Components Utilizing a Path Independent Forming Limit Criterion
- 2022
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Ingår i: Key Engineering Materials<em></em>. - : Trans Tech Publications Inc.. - 9783035717594 ; , s. 906-916
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Konferensbidrag (refereegranskat)abstract
- An area in the automotive industry that receives a lot of attention today is the introduction of lighter and more advanced material grades in order to reduce carbon emissions, both during production and through reduced fuel consumption. As the complexity of the introduced materials and component geometries increases, so does the need for more complex failure prediction approaches. A proposed path-independent failure criterion, based on a transformation of the limit curve into an alternative evaluation space, is investigated. Initially, the yield criterion used for this transformation of the limit curve was investigated. Here it was determined that the criterion for the transformation could not be decoupled from the material model used for the simulation. Subsequently, the approach using the transformed limit curve was tested on an industrial case from Volvo Cars, but a successful failure prediction was not obtained. © 2022 The Author(s). Published by Trans Tech Publications Ltd, Switzerland.
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| 7. |
- Barlo, Alexander, M.Sc. Eng. 1994-
(författare)
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Failure Prediction of Complex Load Cases in Sheet Metal Forming : Emphasis on Non-Linear Strain Paths, Stretch-Bending and Edge Effects
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the increased focus on reducing carbon emissions in today’s society, several industries have to overcome new challenges, where especially the automotive industry is under a lot of scrutiny to deliver improved and more environmentally friendly products. To meet the demands from customers and optimize vehicles aerodynamically, new cars often contain complex body geometries, together with advanced materials that are introduced to reduce the total vehicle weight. With the introduction of the complex body components and advanced materials,one area in the automotive industry that has to overcome these challenges is manufacturing engineering, and in particular the departments working with the sheet metal forming process. In this process complex body component geometries can lead to non-linear strain paths and stretch bending load cases, and newly introduced advanced materials can be prone to exhibit behaviour of edge cracks not observed in conventional sheet metals. This thesis takes it onset in the challenges seen in industry today with predicting failure of the three complex load cases: Non-Linear Strain Paths, Stretch-Bending,and Edge Cracks. Through Finite Element simulation attempts are made to accurately predict failure caused by aforementioned load cases in industrial components or experimental setups in an effort to develop post-processing methods that are applicable to all cases.
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| 8. |
- Barlo, Alexander, M.Sc. Eng. 1994-, et al.
(författare)
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Proposal of a New Tool for Pre-Straining Operations of Sheet Metals and an Initial Investigation of CR4 Mild Steel Formability
- 2023
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Ingår i: 42ND CONFERENCE OF THE INTERNATIONAL DEEP DRAWING RESEARCH GROUP. - : IOP PUBLISHING LTD.
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Konferensbidrag (refereegranskat)abstract
- With the increased focus on reducing carbon emissions in the automotive industry, more advanced materials are introduced to reduce the vehicle weight, and more complex component geometries are designed to both satisfy customer demands and to optimize the vehicle aerodynamically. With the increase in component complexity, the strain paths produced during the forming operation of car body components often display a highly non-linear behavior which makes the task of failure prediction during the manufacturing feasibility studies more difficult. Therefore, CAE engineers need better capabilities to predict failure induced by strain path nonlinearity. This study proposes a new tool designed for creating bi-linear strain paths, by performing a pre-strain of a sheet large enough to cut out Nakajima specimens to perform the post-straining in any direction. From five pre-straining tests the tool present a stable pre-straining operation with a uniform strain field in a radius of 100 [mm] from the centre, corresponding to the region of interest of a Nakajima specimen. From the five pre-strained samples, different Nakajima specimens are cut transverse and longitudinal to the rolling direction and a failure prediction approach in an alternative, path independent evaluation space was used to predict the onset of necking with promising results.
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| 9. |
- Huo, Xiaole, et al.
(författare)
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Effect of ultrasonic vibration on static properties of 5A06 aluminum alloy self-piercing riveting joints
- 2023
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Ingår i: Cailiao Kexue yu Gongyi/Material Science and Technology. - : Harbin Institute of Technology. - 1005-0299. ; 31:2, s. 44-49
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Tidskriftsartikel (refereegranskat)abstract
- Self-piercing riveting process is a new connection technology with excellent performance, green, and high efficiency. It can realize the connection of the similar, different, and multi-layer light alloy sheet materials and is widely used in new energy vehicles and other fields. Furthermore, it is becoming one of the critical technologies for achieving a lightweight body. However, because the self-piercing riveting joint is a typical tight connection component, fretting damage is prone to occur under the action of alternating stress or vibration, resulting in premature joint fatigue failure. This paper uses 5A06 aluminum alloy sheet material to carry out self-piercing riveting and ultrasonic self-piercing riveting composite connection tests under different ultrasonic welding tool heads. Based on the tensile-shear and electron microscope tests, the effect of ultrasonic vibration on the static properties of 5A06 aluminum alloy self-piercing riveted joints was studied. The results show that: ultrasonic vibration can effectively improve the static properties of self-piercing riveted joints; the ultrasonic metal welding will form a solid phase of welding between the sheets during the composite self-piercing riveting, which is the fundamental reason for improving the mechanical properties of the combined joint; the area of ultrasonic metal welding joints affects the mechanical properties of self-piercing riveted joints; the degree of ultrasonic solid-phase welding is higher when the welding area is more extensive; ultrasonic welding will increase the temperature of the rivet, which will affect the stability of the joints to a certain extent. © 2023 Harbin Institute of Technology. All rights reserved.
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| 10. |
- Islam, Md Shafiqul, 1984-
(författare)
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Fracture and Delamination in Packaging Materials : A Study of Experimental Methods and Simulation Techniques
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Packages are the means of preservation, distribution and convenience of use for food, medicine and other consumer products. The introduction of a new package-opening technique for a better opening experience requires additional prototype development and physical testing. In order for the design process to be more rapid and robust, finite element (FE) simulations are widely used in packaging industries to compliment and reduce the amount of physical testing.The goal of this work is to develop some building blocks for complete package-opening FE-simulation. To begin with, the study focuses on mechanical testing of packaging materials’ fracture and delamination; especially shear fracture. Use of tools like digital image correlation (DIC) and scanning electron microscope (SEM) greatly aided to the strain measuring technique and observation of fractured and delaminated surfaces respectively.A modified shear test specimen for polymer sheet testing was developed and its geometry was optimized by FE-simulation. A geometry correction factor of shear fracture toughness for the proposed specimen was derived based on linear elastic fracture mechanics (LEFM). It was found that the specimen ligament length should vary between twice the thickness and half the ligament width of the modified shear specimen to measure the essential work of fracture.Thin-flexible laminate of low-density polyethylene (LDPE) and aluminium (Al) is another key packaging material addressed in this study. The continuum and fracture testing of individual layers provided the base information and input for FE-modelling. The FE-simulation material parameters were calibrated from the physical test response through inverse analysis. Identification process of the laminate interface fracture energy (Gc) from peel tests was studied experimentally and theoretically. A successful FE-simulation optimization framework using artificial neural network and genetic algorithm was developed for the calibration of Gc. To address the challenge in quantifying shear Gc of laminate with very thin substrates, a convenient test technique was proposed. In a separate case, the tearing response of LDPE/PET (polyethylene terephthalate) laminate was studied to examine crack propagation, crack path deviation and delamination of the laminate in mode III fracture. Several tear EWF evaluation theories were proposed along with a cyclic tear test method.
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