Dongbum Kim

Finite element analysis for joining glass fiber reinforced plastic and aluminium alloy sheets

Self-piercing rivet(SPR) is mechanical joining methods and which can be joining dissimilar materials. Unlike conventional riveting, SPR also needs no pre-drilled holes. During plastically deformation, SPR pierces upper sheet and joins it to under sheet. SPR has been mainly applied to the joining the automobile body and some materials, such as glass fiber reinforced polymer and aluminum alloy, which represent the sheet-formed materials for lightweight automobile. Glass fiber reinforced plastic(GFRP) has been considered as a partial application of the automobile body which is lighter than steels and stronger than aluminium alloys. It is needed SPR to join Al alloy sheets and GFRP ones. In this paper, in order to design the rivet and anvil, which are suitable for GFRP, the joinability was examined through simulations of SPR joining between GFRP and Al alloy sheets. For this study, AutoCAD was used for the modeling and the simulated using commercial FEM code DEFORM-2D. The simulated results for SPR process joining between GFRP and Al alloys were confirmed by the same conditions as experimental trials.

A Study on the Mechanical Properties of Additive Manufactured Polymer Materials

Key Words: Additive Manufacturing(AM 적층조형), Rapid Prototyping(RP 쾌속조형), 3D Printing, Fused Deposition Modeling(FDM), PolyJet, Stereolithography Apparatus(SLA), Tensile Testing(인장시험) 초록: 적층조형(additive manufacturing, AM)은 액체, 고체 상태인 폴리머, 금속 등의 재료를 층층이 쌓아서 3 차원 형상을 제조하는 기술이다. AM 기술은 제품 개발 초기단계에서 시제품 제작에 주로 사용되었으나, 최근 들어 이를 실제 제품제작에 적용하는 것에 대한 관심이 높아지고 있다. 한편 AM 기술에서 적층방향은 최종성형품의 기계적 물성에 영향을 줄 수 있다. 따라서 본 연구에서는 폴리머 재료를 사용하는 대표적인 AM 기술인 FDM, PolyJet 그리고 SLA 방식으로 제작되는 재료의 기계적 물성을 실험을 통해 파악하여 보았다. 이때 시험편의 형상은 ASTM D 638을 참고하였고 적층방향을 달리하여 성형하였다. 시험편의 인장시험으로부터 얻은 응력–변형률 선도를 바탕으로 기계적 물성을 조사하였다. 또한 시험편의 파단부를 SEM촬영하여 물성차이의 결과를 분석하였다. Abstract: Traditionally, additive manufacturing (AM) technology has been used to fabricate prototypes in the early development phase of a product. This technology is being applied to release manufacturing of a product because of its low cost and fast fabrication. AM technology is a process of joining materials to fabricate a product from the 3D CAD data in a layer-by-layer manner. The orientation of a layer during manufacturing can affect the mechanical properties of the product because of its anisotropy. In this paper, tensile testing of polymer-based specimens were built with a typical AM process (FDM, PolyJet and SLA) to study the mechanical properties of the AM materials. The ASTM D 638 tensile testing standard was followed for building the specimens. The mechanical properties of the specimens were determined on the basis of stress–strain curves formed by tensile tests. In addition, the fracture surfaces of the specimens were observed by SEM to analyze the results.

Design of self-piercing rivet to joint in advanced high strength steel and aluminium alloy sheets

Abstract Self-piercing riveting is an joining method of advanced high strength steels (AHSS) and other dissimilar materials. It has attracted considerable interest from the automotive industry. The SPR has become an interesting alternative joining technique for difficult to weld materials such as steels and aluminium alloys. In this paper, self-piercing rivet and anvil for SPR were designed for the joining conditions with AHSS and aluminium alloy. Various conditions of SPR were simulated for the design of rivets and anvils. The simulated results were in good agreement with experimental ones. As a result, over HV500 rivet is desirable to joint SPFC780 AHSS and aluminum alloy.Key Words : Self-piercing rivet(SPR), Advanced high strength steels(AHSS), SILAFONT, Dissimilar sheet metals, Finite element method(FEM)ISSN 1225-6153Online ISSN 2287-8955 1. 서 론 초고장력강(AHSS)은 열처리에 따른 상변태로 인한 비강도를 갖는 강재로써 마르텐사이트, 베이나이트, 잔류 오스테나이트 등의 미세조직으로 구성될 수 있다. 1) 기계적 물성을 기준으로 항복강도와 인장강도가 각각 300 MPa, 600 MPa 이상인 초고장력강은 망간과 규소가 일반 강보다 많이 함유되어 강도와 인성이 높다.

Design of Helical Self-Piercing Rivet for Joining Aluminum Alloy and High-Strength Steel Sheets

A self-piercing rivet (SPR) is a mechanical component for joining dissimilar material sheets such as those of aluminum alloy and steel. Unlike conventional rivets, the SPR directly pierces sheets without the need for drilling them beforehand. However, the regular SPR can undergo buckling when it pierces a high-strength steel sheet, warranting the design of a helical SPR. In this study, the joining and forging processes using the helical SPR were simulated using the commercial FEM code, DEFORM-3D. High-tensile-strength steel sheets of different strengths were joined with aluminum alloy sheets using the designed helical SPR. The simulation results were found to agree with the experimental results, validating the optimal design of a helical SPR that can pierce high-strength steel sheets.

Finite Element Analysis for Design of Divided Shank of Self-Piercing Rivet

SPR(Self-Piercing rivet) is mechanical element of joining sheet metal components without the need for pre-punched or pre-drilled holes. Newly designed SPR is developed for high joining strength and shearing strength than semi-tubular rivet. In this study, divided shank of self-piercing rivet were designed for joining DP440 and SILAFONT. Newly designed SPR was simulated by using FEM code DEFORM-3D. In simulations of SPR process, various shape of self-piercing rivet were considered for semi-tubular and newly designed SPR. In other to examine the joinability, joining load and lap-shear load of newly designed SPR were compared with semi-tubular by simulated results and experimental ones.

Design of Helical SPR for Joining Advanced High Strength Steel and Aluminum Alloy Sheets

Self-piercing riveting (SPR) is a sheet-joining method that can be used for materials that are difficult or unsuitable for weld, such as aluminum alloys and other steel sheet metals. The increased application of lightweight materials has initiated many investigations into new SPR conditions for riveting dissimilar materials. However, buckling of the semi-tubular rivet occurs during the riveting of AHSS. In this study, a helical SPR was designed for the riveting of AHSS and Al-alloy. In addition, the reinforced helical SPR which has straight parts was designed. The riveting of AHSS and Al-alloy was simulated. Simulated results were verified by comparison with experimental ones.