Integration Concept of Injection, Forming and Foaming: A Practical Approach to Manufacture Hybrid Structures

Motivated by the concept of the integrative production systems, the hybrid process of polymer injection molding and sheet metal forming, known as polymer injection forming (PIF), has been introduced to manufacture sheet metal-polymer components in a single operation. Despite the wide potential application of this technology, its implementation in actual industrial production has been hindered due to several challenges; a thick layer of polymer where there is deep deformation, non-uniform deformation due to pressure loss and the opposite phenomena of shrinkage and springback. To mitigate these practical issues, the novel idea of integrating supercritical fluid (Sc.F.) technology with the PIF process is introduced in this work. As the proposed technology is a manufacturing innovation, with no available information in the literature correlating to this concept, two sets of experiments are designed to investigate the feasibility of this integration. In the first set, the effect of blank material and shot volume as design variables were investigated over a range of Sc.F. weight percentage. To improve the cell morphology in experiments with the low-strength sheet material, several other processing scenarios are explored in the second set of experiments. The results of this study clearly demonstrate the capabilities of this concept manufacturing process in terms of initiating the foaming process within the simultaneous injection/forming process, ensuring weight reduction (of up to 16%) and complete elimination of issues related to shrinkage

Development of design principles for form-fit joints in lightweight frame structures

Based on fundamental technological investigations, alternative joining strategies using electromagnetic forming (EMF) for the flexible production of lightweight frame structures are developed in the collaborative research project SFB/TR10. The results of these investigations will also be used to create general design principles for the joining process itself as well as for the joining zone. The focus of this article will be on dominating form-fit joints of aluminum frame structures and the parameters which have a significant influence on the strength of those joints. For the development of design principles regarding the joining zone, the groove geometry of the connection elements was varied in terms of size and shape, and the influence of those variations was analyzed. In terms of the joining process itself the effect on the joint strength of different forming pressures for a given groove geometry was also investigated. In the first step these experiments were performed on solid mandrels. In order to reduce the weight of the structure, experiments were then performed with hollow connection elements and similar groove geometries to analyze how the reduced stiffness of those elements affected the strength of the joints

Comparing faceted and smoothed tool surface descriptions in sheet metal forming simulation

This study deals with different tool surface description methods used in the finite element analysis of sheet metal forming processes. The description of arbitrarily-shaped tool surfaces using the traditional linear finite elements is compared with two distinct smooth surface description approaches: (i) Bézier patches obtained from the ComputerAided Design model and (ii) smoothing the finite element mesh using Nagata patches. The contact search algorithm is presented for each approach, exploiting its special features in order to ensure an accurate and efficient contact detection. The influence of the tool modelling accuracy on the numerical results is analysed using two sheet forming examples, the unconstrained cylindrical bending and the reverse deep drawing of a cylindrical cup. Smoothing the contact surfaces with Nagata patches allows creating more accurate tool models, both in terms of shape and normal vectors, when compared with the conventional linear finite element mesh. The computational efficiency is evaluated in this study through the total number of increments and the required CPU time. The mesh refinement in the faceted description approach is not effective in terms of computational efficiency due to large discontinuities in the normal vector field across facets, even when adopting fine meshes.The authors gratefully acknowledge the financial support of the Portuguese Foundation for Science and Technology (FCT) via the projects PTDC/EME-TME/118420/2010 and PEst-C/EME/ UI0285/2013 and by FEDER funds through the program COMPETE – Programa Operacional Factores de Competitividade, under the project CENTRO-07-0224-FEDER-002001 (MT4MOBI). The first author is also grateful to the FCT for the PhD grant SFRH/BD/69140/2010.info:eu-repo/semantics/publishedVersio

Time-temperature-transformation diagram within the bainitic temperature range in a medium carbon steel

The time-temperature-transformation (ITT) diagram within the medium temperature range of medium carbon steel has been determined. A single type of C-curve is found within the bainite temperature range for the studied steel. Distinct reaction C-curves were not observed for both types of microstructure, upper bainite and lower bainite in the TTT diagram. Experimental results on the kinetics of the isothermal formation of bainite at different temperature have demonstrated that both type of microstructure, upper and lower bainite, possesses similar overall transformation kinetics. Some applications of phase transformation theory towards the formation of bainitic microstructures are discussed, with particular emphasis on the bainite start temperature, transition temperature from upper to lower bainite, martensite start temperature and the thickness of bainitic plates.Peer Reviewe

Identification of Misconceptions on Cell Concepts among Biology Teachers by Using CRI Method

Abstract: This study aims (i) to assess the level of understanding and misconceptions of Biology teachers in Makassar regarding cell concepts, (ii) to identify the Basic Competence in which the teachers pose misconceptions, and (iii) to identify the factors cause misconceptions on cell concepts among biology teachers in Makassar. The study is a descriptive study which implements Certainty of Response Index (CRI) as the method to identify teachers’ misconception. Participants of the study (n=22) were selected through purposive sampling based on the representativeness of the school in Makassar area. The result of data analysis showed that there were teachers who possess misconceptions (40.30%), scientifically accepted conceptions (49.10%), and transitional conceptions (10.77%). The misconceptions were found in 6 Basic competences of the cell concepts. The highest misconceptions (55.68%) was found on Basic Competence 3.2. which require participants to distinguish transport mechanism on the (diffusion, osmosis, active transport, endocytosis, and exocytosis) based on observation. There were several factors which cause the occurrence of misconceptions among the participants in this study, including low level of reasoning ability, low retention of knowledge obtained in undergraduate, lack of learning resources, incomprehensible terms, and low interest of Biology teachers on cell concepts

Improving PBL in Empowering Meta cognitive Skill of Students

Abstract Objective: Problem-Based Learning (PBL) is a potential constructivist learning strategy that empowers students’ Meta cognitive skill. PBL focuses on problem, involves thinking activity to solve problems, and correlates to cognitive function of students. Methods: The implementation of PBL reveals various benefits, but there are also some weaknesses in this learning strategy. Thus, it is necessary to implement a certain learning strategy that can cover the PBL weaknesses, such as Reading, Questioning, and Answering (RQA) learning strategy. RQA is a new learning strategy developed based on a fact that almost all students do not read the next lecture materials, causing failure of learning strategy planned and finally the students’ comprehension becomes low. RQA is also potential to empower students’ Meta cognitive skill. Findings: The integration of RQA and PBL learning strategy is called PBL-RQA learning strategy. This study was a quasi-experimental study designed to compare the effect of PBL, RQA, and PBL-RQA learning strategies on the students’ Meta cognitive skill of Faculty of Mathematics and Science, State University of Makassar. Application: The results of the study showed that the potency of PBL learning strategy in empowering the students’ Meta cognitive skill has been increased by integrating it to RQA learning strategy. The meta cognitive skill mean score of the students taught by PBL-RQA learning strategy was 21% higher than that of the students taught by PBL and 26.9% higher than that of the students taught by RQA learning strategy. Keywords: Answering, Meta Cognitive Skill, Problem-Based Learning, Questioning, Reading, PBL-RQ

Geometry defeaturing and surface relaxation algorithms for all-hexahedral remeshing

Remeshing is composed of two steps: geometry defeaturing and generation of the new mesh. During the geometry defeaturing, grid or octree based mesh generation techniques requires detection of geometric edges, In this study, a new geometry based edge detection algorithm is presented

How do Epistemological Beliefs differ by gender and socio-economic status? [Epi·stemoloji·k i·nançlar ci·nsi·yete ve sosyoekonomi·k statüye göre nasil degi·şmektedi·r?]

The present study explores the differences in students' epistemological beliefs by gender and socio-economic status (SES). The Epistemological Beliefs Questionnaire (Conley, Pintrich, Vekiri, & Harrison, 2004) was adapted and administered to 1230 seventh grade students. The multivariate analysis of variance (MANOVA) revealed differences in epistemological beliefs among students by gender and SES. While girls had more sophisticated beliefs in justification of knowledge than boys, girls and boys appeared to be similar in their beliefs in the Source/Certainty and Development dimensions. According to the results, students having medium and high SES had more sophisticated beliefs on the Source/Certainty dimensions when compared with low SES group