• 소성∙가공
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• 제28권3호
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• pp.115-122
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• 2019

In this paper, finite element analysis of an automatic five-stage precision cold forging process of a yoke, a steering part of a passenger's car, is conducted with emphasis on spring back analysis at the yoke-forming stage and its experimental verification is subsequently made. An elastoplastic finite element method with MINI-element technique employed for the analysis of the entire process is explained. There is emphasis that the thin film of material formed between the punch and die in the stage may result to some errors especially in elastoplastic finite element analysis of spring back due to frequent remeshing. The numerical robustness of the spring back analysis in regards to remeshing is hence shown first through investigation into its effect on the predicted spring back. Experimental measurement of displacement due to spring back is carried out for comparison with the predicted results, and they are in a qualitative agreement with each other.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.837-842
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• 2000

In the coiling process of helical steam generator tubes of integral reactor SMART, a considerable amount of spring back, which induces dimensional inaccuracy and difficulty in fabrication, has been arised. In this research, an analytical model was derived to evaluate the amount of the spring back for steam generator tubes. The model was developed on the basis of beam theory and elastic-perfectly plastic material property. This model was extended to consider the effect of plastic hardening and the effect of the tensile force on the spring back phenomena. Parametric studies were performed for various design variables of steam generator tubes in order to minimize the spring back in the design stage. A sensitivity analysis has shown that the low yield strength, the high elastic modulus, the small helix diameter, and the large tube diameter result in a small amount of the spring back. The amount of the spring back can be controlled by the selection of adequate design values in the basic design stage and reduced to an allowable limit by the application of the tensile force to the tube during the coiling process.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1999년도 추계학술발표회요약집
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• pp.355.2-355
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• 1999

The spnng back phenomena occurring in the coiling process of a steam generator tube induces the dimensional inaccuracy and makes the coiling procedure difficult. In this research, an analytical model was developed to evaluate the amount of the spring back for SMART steam generator tubes. The model was developed on the basis of beam theory and elastic-perfectly plastic material property. This model was extended to consider the effect of plastic hardening and the effect of the tensile force on the spring back phenomena. Parametric studies were performed for various design variables of steam generator tubes in order to minimize the spring back in the design stage. A sensitivity analysis has shown that the low yield strength, the high elastic modulus, the small helix diameter, and the large tube diameter result in a small amount of the spring back. The amount of the spring back can be controlled by the selection of adequate design values in the basic design stage and reduced to an allowable limit by the application of the tensile force to the tube during the coiling process.rocess.

• 한국항공운항학회지
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• 제19권4호
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• pp.51-57
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• 2011

The spin-up and the spring-back are most severe load cases in the aircraft landing gear design. These load cases are caused by reciprocal action of complex physical phenomenon such as the friction between a tire and ground, inertia of the rotation of a tire and the flexibility of a landing gear structure. Generally, the empirical formula or the theoretical formula is used to calculate the spin-up and spring-back load in the early stage of the development program of the aircraft landing gear. After the materialization of the design of a landing gear, spin-up and spring-back load are acquired by the free drop test. In this study, the spin-up and the spring-back load of the rubber shock absorber type KC-100 nose landing gear are calculated by the explicit finite element analysis. Through this analysis, more accurate and realistic spin-up and spring back loads could be applied to the early phase of the development of the aircraft landing gear.

• 대한기계학회논문집A
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• 제24권6호
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• pp.1499-1512
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• 2000

The dynamic explicit finite element method and the static implicit finite element method are applied effectively to analyze total auto-body panel stamping processes, which include the forming stage , the trimming stage and the spring-back stage.\The explicit time integration method has better merits in the forming stage including highly complicated three-dimensional contact conditions. On the contrary, the implicit time integration method is better for analyzing spring-back since the complicated contact conditions are removed and the computing time to get the final static state is short. In this work, brief descriptions of the formulation and the factor study are presented. Further, the simulated results for the total auto-body panel stamping processes are shown and discussed. The formability and the weld line movement in stamping with Tailor Welded Blanks were investigated through QTR-OTR-FRT.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.237-240
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• 1999

The elastic stress analysis of the die for helical gear forging has been calculated by using the nodal force at the final stage obtained from the rigid-plastic finite element analysis. In order to obtain more precise gear products. the elastic analysis of the die after release of punch and the elastic spring-back analysis of product after ejection have been performed and the final dimension of the computational product has been in good agreement with that of the experimental product.

• 소성∙가공
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• 제8권4호
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• pp.384-392
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• 1999

In metal forming, there are problems with recurrent geometric characteristics without explicitly prescibed boundary conditions. In such problems, so-called recurrent boundary conditions must be introduced. In this paper, as a practical application of the proposed method, the precision cold forging of a helical gear has been simulated by a three-dimensional rigid-plastic finite element method and compared with the experiment. The application of recurrent boundary conditions to helical gear forging analysis is proved to be effective and valid. the elastic stress analysis of the die for helical gear forging has been calculated by using the nodal force at the final stage obtained from the rigid-plastic finite element analysis. In order to obtain more precise gear products, the elastic analysis of the die after release of punch and the elastic spring-back analysis of product after ejection have been performed, and the final dimension of the computational product has been in good agreement with that of the experimental product.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.493-496
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• 2008

The residual stress generated in the boron steel blank formed via hot press forming process was predicted by JMatPro, a material property modeler, and Abaqus. The numerical predictions were compared by the experimental measurements obtained by the instrumented indentation. Both the predicted and measured principal stresses monitored at the outer surface of central bending position were qualitatively in good agreement. It was concluded that the residual stresses generated from hot forming process is not negligible as it has been generally assumed, although the spring back deformation is quite small. This should be specially considered from the part design stage since the tensile nature of the residual stress exhibited on the surface may lead to the stress corrosion cracking.

• 한국산학기술학회논문지
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• 제18권2호
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• pp.450-455
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• 2017

쉴드 커넥터는 자동차 전장부품으로 차량 내 전기 배선을 연결하는데 사용된다. 이 부품은 전기 전도도가 높은 인청동 재질을 사용하고 프로그레시브 프레스 성형으로 제작된다. 본 제품 형상의 기하학적인 측면을 고려했을 때 복잡하지 않지만, 드로잉, 밴딩 등의 소성가공과 피어싱, 노칭 등의 전단 가공을 실시하여 제품 성형을 완성해야 한다. 프로그레시브 금형을 설계하는 과정 중에 공정 및 스트립레이아웃 설계단계의 성형 해석 모듈을 활용하여 제품의 재질에 따른 두께 변화 및 성형 안전성, 스프링 백 (Spring Back) 검토를 수행하여, 균열 혹은 주름의 경향과 불완전 소성 변형에 대한 보정치를 예측 및 발생 가능한 문제들을 사전에 확인하고, 드로잉 공정 초기에 발생된 성형 불량에 대한 대책으로 드로잉 형상을 수정하여 공정 설계에 반영하였다. 공정설계에서 얻어진 제품의 블랭크 전개 형상은 효과적인 재료 이용을 위해 네스팅에 의한 최적화된 블랭크 배치로 재료의 손실을 최소화하여 3차원 스트립레이아웃 설계를 완성하였다. 본 연구를 통해 프로그레시브 성형을 통해 생산되는 쉴드커넥터 제품의 균열과 스프링백 현상을 사전에 개선하여 생산안정도를 향상시켰다.

• 한국기계가공학회지
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• 제7권4호
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• pp.44-49
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• 2008

The characteristic of magnesium alloy is the most light in utility metal, the effect of electromagnetic wave interception, excellent specific strength and absorptiveness of vibration. Although magnesium alloy with above characteristic is a subject matter which is suitable in world-wide tendency of electrical component frame, sheet magnesium alloy is difficult to process. Therefore, forming analysis of sheet magnesium alloy and applying warm-working to process are indispensable. Among Finite element method, the static implicit finite element method is applied effectively to analyze sheet magnesium alloy stamping process, which include the forming stage. In this study, it was focused on the crack, wrinkling and spring back on sheet magnesium alloy stamping by the static implicit analysis. According to this study, the result of simulation will give engineers good information to access the forming technique on sheet magnesium alloy. And its application is being increased especially in the production of electrical component frame for the cost reduction, saving of defective ratio, and improvement of Productivity.