• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1614-1617
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• 2003

Actuator being used in the ship supplies engine with air. When actuator is out of order, engine is not operated. This out of order is due to fracture of piston or rotating of spindle in the case of plastic deformation of parallel part in locking plate. For this reason, locking plate must be guaranteed enough strength. Therefor in this paper, the effects of changes with the clearance of between spindle and parallel part, the contact height of parallel part and spindle, the side circle diameter of parallel part and the width of locking plate in the designated torque are investigated. The result of this investigation shows the relation between locking plate and spindle.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1561-1564
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• 2003

In the dynamic analysis model of full vehicles, the ball joint is usually modeled as an ideal joint. Searching a ball joint, the engineering plastic covers metal and the plastic has little compliance. It is expected that the compliance will physically have an influence on load transfer. This thesis presents a dynamic model considering the compliance of a ball joint, and studies an influence related to load transfer. It models the compliance of a ball joint to 3 directional spring. Likewise, it researches the load of a ball joint via a four-post simulation of a full vehicle, comparing with a model considered compliant and the model of an ideal joint. As a result, the difference between the compliance and the ideal joint model was determined. For this reasons, to conduct precision load prediction for durability analysis, dynamic analysis considering the compliance of bali joint should be required.

• Structural Engineering and Mechanics
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• 제58권4호
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• pp.627-639
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• 2016

The analysis of thermally induced stresses in engineering structures is a very important and necessary task with respect to design and modeling of pressurized containers, heat exchangers, aircrafts segments, etc. to prevent them from failure and improve working conditions. So, the purpose of this study is to investigate elasto-plastic thermal stresses and deformations in a thin annular plate embedded into rigid container. To this end, analytical research devoted to mathematically and physically rigorous stress/strain analysis is performed. In order to evaluate the effect of logarithmic thermal gradients, commonly applied to structures which incorporate thin plate geometries, different thermal parameters such as temperature mismatch and varying constraint temperature were introduced into the model of elastic perfectly-plastic annular plate obeying the von Mises yield criterion with its associated flow rule. The results obtained may be used in sensitive to temperature differences aircraft structures where the thermal effects on equipment must be kept in mind.

• Journal of Welding and Joining
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• 제21권7호
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• pp.49-58
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• 2003

It has been well known that ductile fracture of steel is accelerated by triaxiality stresses. The characteristics of ductile crack initiation in steels are evaluate quantitatively using two-parameter criterion based on equivalent plastic strain and stress triaxiality. Recently, the characteristics of critical crack initiation of steels are quantitatively estimated using the two-parameter, that is, equivalent plastic strain and stress triaxiality, criterion. This study is paid to the fundamental clarification of the effect of geometrical heterogeneity and strength mismatching, which can elevate plastic constraint due to heterogeneous plastic straining, and loading rate on critical condition to initiate ductile crack using two-parameter. Then, the crack initiation testing were conducted under static and dynamic loading. To evaluate the stress/strain state in the specimens especially under dynamic loading, thermal elastic-plastic dynamic FE-analysis considering the temperature rise was used. The result showed that the critical global strain to initiate ductile fracture in specimens with strength mismatch under various loading rate cu be estimated based on the local criterion, that is two-parameter criterion obtained on homogeneous specimens under static tension, by mean of FE-analysis taken into account accurately both strength mismatch and dynamic loading effects on stress/strain behavior.

• 한국해양공학회지
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• 제28권5호
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• pp.452-465
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• 2014

The application of friction stir welding (FSW) technology has been extended to all industries, including shipbuilding. A heat transfer analysis evaluates the weldability of a welded work piece, and elasto-plastic analysis predicts the residual stress and deformation after welding. A thermal elasto-plastic analysis based on the heat transfer analysis results is most frequently used today. However, its application to large objects such as offshore structures and hulls is impractical owing to its long computational time. This paper proposes a new method, namely an equivalent strain method using the inherent strain, to overcome the disadvantages of the extended analysis time. In the present study, a residual stress analysis of FSW was performed using this equivalent strain method. Additionally, in order to reflect the external constraints in FSW, the reaction force was predicted using a neural network, Finally, the approach was verified by comparing the experimental results and thermal elasto-plastic analysis results for the calculated residual stress distribution.

• Journal of Welding and Joining
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• 제21권5호
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• pp.575-581
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• 2003

It has been well known that the ductile cracking of steel would be accelerated by triaxial stress state. Recently, the characteristics of critical crack initiation of steels are quantitatively estimated using the two-parameters, that is, equivalent plastic strain and stress triaxiality, criterion. This study is paid to the fundamental clarification of the effect of geometrical heterogeneity and strength mismatching, which can elevate plastic constraint due to heterogeneous plastic straining, and loading rate on ductile crack initiation behavior. Also, the ductile crack initiation testing were conducted under static and dynamic loading using round bar specimens with circumferential notch and strength mis-matching. The result showed that the nominal strain at ductile crack initiation of circumferential notch specimens small then the round bar specimens for effect of geometrical discontinuity. Also, the nominal strain at ductile crack initiation was decreased with decrease of notch root radius of curvature.

• 소성∙가공
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• 제13권4호
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• pp.342-349
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• 2004

The form-joining process (or clinching) uses a set of die and punch to impose the plastic deformation-induced geometric constraint on a sheet metal pair. The joining strength from the process ranges 50-70 percent of that of the resistance spot welding. In this paper, a new form-joining process with the aid of an adhesive is proposed in which an epoxy adhesive is applied to a sheet metal pair, and before it cures the pair is clinched to cause the geometric constraint in the form of a protrusion. In order to reduce the forming load and the height of protrusions, a new die and punch set with a very small clearance is devised to reduce the depth of drawing and the forming load. Taguchi method is employed to find the optimal values of design parameters. To implement each case of the orthogonal array, the finite element method is used. The experiments show that in the tensile-shear test, the bonding strength of the new form-joining process with an epoxy adhesive is approximately the same as that of the resistance spot welding; and in comparison with the other two form-joining processes with an epoxy adhesive, the height of protrusions is reduced by more than 65 percent and the forming load by 50 percent.

• 대한기계학회논문집A
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• 제30권3호
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• pp.269-278
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• 2006

This paper proposes slip line fields for bending of unequally notched specimens in plane strain that have a sharp crack in one side and a sharp V-notch in the other side. Depending on the back angle, two slip line fields are proposed, from which the limit moment and crack tip stress fields are obtained as a function of the back angle. Excellent agreement between slip line field solutions with those from detailed finite element limit analysis based on non-hardening plasticity provides confidence in the proposed slip line fields. One interesting point is that, for the unequally notched specimen, the difference between the crack tip triaxial stress for tension and that for bending increases significantly with increasing the back angle. This suggests that such a specimen could be potentially useful to investigate the crack tip constraint effect on fracture toughness of materials. In this respect, the possibility of designing a new toughness testing specimen with varying crack tip constraint is discussed.

• Structural Engineering and Mechanics
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• 제61권4호
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• pp.475-481
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• 2017

An overhead travelling crane structure of two doubly symmetric welded box beams is designed for minimum cost. The rails are placed over the inner webs of box beams. The following design constraints are considered: local buckling of web and flange plates, fatigue of the butt K weld under rail and fatigue of fillet welds joining the transverse diaphragms to the box beams, fatigue of CFRP (carbon fibre reinforced plastic) laminate, deflection constraint. For the formulation of constraints the relatively new standard for cranes EN 13001-3-1 (2010) is used. To fulfill the deflection constraint CFRP strengthening should be used. The application of CFRP materials in strengthening of steel and concrete structures are widely used in civil engineering applications due to their unique advantages. In our study, we wanted to show how the mechanical properties of traditional materials can be improved by the application of composite materials and how advanced materials and new production technologies can be applied. In the optimization the following cost parts are considered: material, assembly and welding of the steel structure, material and fabrication cost of CFRP strengthening. The optimization is performed by systematic search using a MathCAD program.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 춘계학술대회 논문집
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• pp.29-32
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• 2002

The mechanical joining process of a sheet metal pair has been developed in order to replace the resistance spot welding process in case that joining of mechanically unweldable materials and coated sheet metals with different thickness are needed. Form-joining or clinching, a kind of mechanical joining process, is defined as joining process of a sheet metal pair by geometric constraint imposed by plastic deformation of workpieces without any additive part. It has been reported that the joining strength by commercial form-joining apparatus is 50∼70 percent of that by resistance spot welding. Therefore, a two-step form-joining process with a secondary punch is proposed. The device is designed to improve the joining strength by increasing the geometric constraint of the deformed shape by combining a primary punch, a secondary punch and a female die. In order to verify the improved joining strength by the designed process, the tensile-shear strength, the peel-tension strength and the asymmetric peel-tension strength are compared with those by the TOX process and resistance spot welding.