Effect of film properties on formability of aluminum pouch for secondary battery

유민숙,김도현,조정민,배성우,김동수 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.6

The present study was conducted to investigate the effect of film properties on the formability of aluminum pouches for secondary batteries. Among the physical properties of the film, the effects of the friction coefficient and the elongation rate on the formability wereinvestigated. The purpose of this study is to draw the improvement of formability according to the physical properties of the films forconstructing the aluminum pouch on the assumption that the Friction resistance between the mold and material in the forming processand the Tensile resistance generated when the material is deformed by the punch will affect the formability. The results showed that theformability was better when the friction coefficient was lower. Specially, the formability is improved more in the sample that had thenylon film with a reduced friction coefficient than in the sample with the CPP film that had a reduced friction coefficient. This indicatesthat the limit of bending deformation was extended as the friction coefficient of the nylon film get lower. In addition, we found that theformability depends on the elongation property. The formability is improved when the nylon film with isotropic property and a CPP filmwith stable elongation property were applied. In a sample NY.2/CPP.2 manufactured by using an isotropic nylon and a stably elongatedCPP film, the formability has maximum forming depth of 5.5 mm. This result verified that materials that have low friction coefficient,isotropy and a stable elongation property may be applied to improve the formability.

Application Of A New Semi-Empirical Model For Forming Limit Prediction Of Sheet Material Including Superposed Loads Of Bending And Shearing

Christian Held,Mathias Liewald,Ralf Schleich,Manfred Sindel 한국소성가공학회 2010 기타자료 Vol.2010 No.6

The use of lightweight materials offers substantial strength and weight advantages in car body design. Unfortunately such kinds of sheet material are more susceptible to wrinkling, spring back and fracture during press shop operations. For characterization of capability of sheet material dedicated to deep drawing processes in the automotive industry, mainly Forming Limit Diagrams (FLD) are used. However, new investigations at the Institute for Metal Forming Technology have shown that High Strength Steel Sheet Material and Aluminum Alloys show increased formability in case of bending loads are superposed to stretching loads. Likewise, by superposing shearing on in plane uniaxial or biaxial tension formability changes because of materials crystallographic texture. Such mixed stress and strain conditions including bending and shearing effects can occur in deep-drawing processes of complex car body parts as well as subsequent forming operations like flanging. But changes in formability cannot be described by using the conventional FLC. Hence, for purpose of improvement of failure prediction in numerical simulation codes significant failure criteria for these strain conditions are missing. Considering such aspects in defining suitable failure criteria which is easy to implement into FEA a new semi-empirical model has been developed considering the effect of bending and shearing in sheet metals formability. This failure criterion consists of the combination of the so called cFLC (combined Forming Limit Curve), which considers superposed bending load conditions and the SFLC (Shear Forming Limit Curve), which again includes the effect of shearing on sheet metal’s formability.

Application of adaptive neuro-fuzzy system in prediction of nanoscale and grain size effects on formability

Nan Yang,Meldi Suhatril,Khidhair Jasim Mohammed,H. Elhosiny Ali Techno-Press 2023 Advances in nano research Vol.14 No.2

Grain size in sheet metals in one of the main parameters in determining formability. Grain size control in industry requires delicate process control and equipment. In the present study, effects of grain size on the formability of steel sheets is investigated. Experimental investigation of effect of grain size is a cumbersome method which due to existence of many other effective parameters are not conclusive in some cases. On the other hand, since the average grain size of a crystalline material is a statistical parameter, using traditional methods are not sufficient for find the optimum grain size to maximize formability. Therefore, design of experiment (DoE) and artificial intelligence (AI) methods are coupled together in this study to find the optimum conditions for formability in terms of grain size and to predict forming limits of sheet metals under bi-stretch loading conditions. In this regard, a set of experiment is conducted to provide initial data for training and testing DoE and AI. Afterwards, the using response surface method (RSM) optimum grain size is calculated. Moreover, trained neural network is used to predict formability in the calculated optimum condition and the results compared to the experimental results. The findings of the present study show that DoE and AI could be a great aid in the design, determination and prediction of optimum grain size for maximizing sheet formability.

Improvement of Glass Formability in Ultrasonic Vibration Assisted Molding Process

Tianfeng Zhou,Jiaqing Xie,Jiwang Yan,Kuriyagawa Tsunemoto,Xibin Wang 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.1

Micro optical elements with complex shapes are needed increasingly in optical, optoelectronic and biomedical industries. Since glass molding process is an effective approach to fabricate microstructures, and its surface quality strongly depends on the filling capacity of glass at high temperature. To improve the formability and reduce adhesion between the glass and the mold at high temperature, ultrasonic vibration is applied to improve the formability in the molding process. Fundamental experiments are carried out to test the effectiveness of ultrasonic vibration on friction force decrease and a bonding model on the glass-mold interface at elevated temperature is proposed. Finite element method (FEM) simulation and glass molding experiments are conducted to evaluate the improvements of material formability brought about by ultrasonic vibration. The results show that the ultrasonic vibration can significantly lower the friction force and increase the glass formability.

냉연 TRIP 강의 미세조직과 성형성에 미치는 베이나이트 변태온도의 영향

洪三永,全現助,朴晟浩,姜信煥,朴贊卿 대한금속재료학회 2001 대한금속·재료학회지 Vol.39 No.12

TRIP steels exhibits low formability under multi-axial stress condition. The purpose of the present study is to suggest a way of improving the formability of TRIP steels under plane strain mode. For this purpose, the formability under different stress states and their relationships with the microstructure of the secondary phases have been investigated in the cold rolled 0.2C-1.5Si-1.5Mn TRIP steels experienced with various bainitic isothermal transformation at 300, 350, 400 and 450℃. Two kinds of mechanical tests were conducted to evaluate the formability: the tensile test under uni-axial stress condition, and the Limiting Dome Height(LDH) test for the plane strain mode under multi-axial stress condition. The formability of the present TRIP steels strongly depends on the isothermal bainitic transformation temperatures. The discrepancy between EL and LDH at 350℃ could be explained by the stability of the retained austenite and the distribution of the secondary phases. Consequently, this study revealed that effects of the microstructure on the formability were different depending on the deformation modes in TRIP steels. In order to improve the EL property, the stability of RA should be controlled, and in order to improve the LDH property, the continuously networked RA and the fine bainite should be formed.

Formability and Effect of Hole Bridge in the Single Point Incremental Forming

Van-Cuong Do,샤오 샤오,안대철,김영석 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.3

This paper studies the mechanical properties, formability and effect of hole bridge (hole lancing) in the single point incremental forming for Al5052-O with the thickness of 0.8 mm. The mechanical properties, including anisotropy property and stress-strain relation, were evaluated by uniaxial tensile tests in three directions of 0°, 45°, 90° with the rolling direction. Varying wall angle conical frustum test was used to study the formability. The forming parameters of tool diameter, step depth, spin speed, and feed rate were optimized using multi-objective optimization with grey relational grade. The results show that the tool diameter strongly influences formability, springback and thickness reduction. To verify the effect of hole bridge on the formability, a predesigned hole bridge was machined by a laser on the blank shoulder nearby the forming periphery before forming. The optimized forming parameters found in previous step were applied for this test. As the result, the maximum forming angle was significantly improved in comparison with the non-hole-bridge part. Finite element simulation by ABAQUS explicit software was used to explain the strain evolution in the blank with cut-off hole of the incremental forming process. The simulation results were compared with experiment and discussed.

습·건열 열고정 조건이 스트레치 직물의 역학특성과의류형성성능에 미치는 영향

김현아,김승진 한국의류산업학회 2018 한국의류산업학회지 Vol.20 No.1

This paper investigated garment formability and fabric mechanical properties of one-way and two-way stretch fabrics according to the thermal treatment methods. One-way and two-way stretch fabrics were woven using 75d and 150d PET/spandex covering yarns and then these were wet thermal treated with four kinds of finishing machines. The fabric mechanical properties of these stretch fabrics specimens were measured and compared with the regular PET fabrics. The stretch ratio of one-way stretch fabric was ranged 12 to 26 percentage, 15 to 45 percentage for 2-way stretch fabrics and 4 to 10 percentage for regular fabrics. Garment formability of stretch fabric was superior than that of regular fabrics, in addition, 2-way stretch fabric was better than one-way. The garment formability of the stretch fabrics treated with CPB and Lava wet thermal machines showed the highest values, and the stretch ratio of these 2-way stretch fabrics was also the highest, which was ranged 20 to 45 percentage. This phenomenon was assumed to be due to high extensibility and bending rigidity with low shear modulus of the 2-way stretch fabric treated with CPB and Lava wet thermal machines. It was shown that the garment formability of stretch fabrics treated without dry thermal treatment was higher than that of dry thermal treated fabrics. It revealed that high stretch fabric was available under the condition of low process tension in the wet and dry thermal treatments of the finishing process, which makes high garment formability.

Optimization of process parameters to enhance formability of AA 5182 alloy in deep drawing of square cups by hydroforming

Bharatkumar Modi,D. Ravi Kumar 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.11

The formability of 1 mm thick AA5182 aluminum alloy sheets in deep drawing of square cups by hydroforming was studied. The influence of process parameters (peak pressure, pressure path, and blank holding force) on formability was investigated through numerical simulations and validated with experimental work. The experiments were designed using the Taguchi method. The minimum thickness in the formed cups (at the bottom corners) and the minimum corner radius that can be achieved were considered as the criteria for evaluation of formability. The peak pressure was the most important process parameter affecting thinning and the minimum corner radius that can be achieved. The variation of the pressure path had the least effect on formability. Regression models were developed for prediction of minimum thickness in the cup and the corner radius as a function of peak pressure and blank holding force.

A Study on the Friction Variation of Galvanized Steel in Automotive Application for Formability Prediction

Gihak Yim(임기학),Jiyoung Kim(김지영),Byeoungkeuk Jin(진병극),Joosik Hyun(현주식) 한국자동차공학회 2021 한국자동차공학회 부문종합 학술대회 Vol.2021 No.6

The application of galvanized steel sheets is increasing as the quantity of outer panel applied to global automotive makers is increasing, and for this reason, predicting the formability of galvanized steel sheets is becoming more important for steel manufacturers to cope with quality issues when forming automotive parts. Since galvanized steel sheets and galvannealed steel sheet have different microstructures and properties, they have different forming characteristics and quality problems in forming process. when forming the outer panel, the main forming mode is deep drawing. At this time, the friction characteristic is one of the dominant factors that influence the part formability. However, in the case of galvanized steel sheets, the fluctuation of friction characteristics according to forming speed and load is different than that of galvannealed or non-coated cold rolled steel sheet. Therefore, in order to enhance the formability prediction of galvanized sheet, evaluation of friction variation by forming condition is important. However, not much research has been done to evaluate the friction variation of galvanized coated sheet by different forming condition or its application in forming analysis. In this study, friction variation of mild grade steel with different coating was derived for different speed and loading conditions, considering actual forming process. In addition, the effect of post treatment on friction was evaluated, and the application of friction variation in forming analysis was studied. To summarize, the aim of this paper is to evaluate the effect of coating, post treatment and forming condition on friction characteristics in steel sheets for outer panels, and to review methods to apply friction variation in forming analysis for formability prediction improvement.

Experimental study on the formability of aluminum pouch for lithium polymer battery by manufacturing processes

유민숙,송문용,김민하,김동수 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.9

Lithium polymer batteries are an improvement from the existing lithium ion batteries in terms of the risks of electrolyte leakage and explosion. Demand for lithium polymer batteries is rapidly increasing because of their advantages such as stability, light, and higher degree of freedom of shape. Accordingly, the demand for aluminum pouches, which are the exterior material of lithium polymer batteries, is increasing and research and development of aluminum pouches are actively being conducted. In the case of aluminum pouches, the forming area and depth that can accommodate the battery cell are increased according to the capacity of the battery, and stable formability is essential for aluminum pouches. In this study, manufacturing processes were changed to examine ways to improve formability. First, by changing the process order so that the surface treatment coatings on both sides of the aluminum foil were carried out simultaneously, the number of times when there was contact of the nylon film with the work roll was reduced. As a result, formability was improved because damage to the surface of the nylon film was reduced and the slipperiness was maintained. In addition, with regard to the drying temperature of the adhesive that constitutes the innermost layer, as the drying temperature increased (120 °C), solvent volatility increased, leading to stronger adhesion between the interfaces and resulting in improved formability.