• Journal of Welding and Joining
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• v.28 no.2
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• pp.91-95
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• 2010

Stress distribution and deformation on the CT-type(Cross Tension type) spot welded lap joint subjected to out of plane tensile load were investigated by finite element method. Using the maximum principal stresses at the nugget edge obtained by FEM analysis, evaluated the fatigue strength of the CT-type spot welded lap joints having various dimensions and materials. and also, the influence of the geometrical parameters of CT-type spot welded lap joints on stress distribution and fatigue strength must be evaluated. thus, in this paper, ${\Delta}P-N_f$ curve were obtained by fatigue tests. Using these results, ${\Delta}P-N_f$ curve were systematically rearranged in the $\Delta\sigma-N_f$ relation with the hot spot stresses at the CT-type spot welded lab joints. It was found that the proposed $\Delta\sigma-N_f$ relation could provide a more reasonable fatigue design criterion for the CT-type spot welded lap joints.

• Korean Journal of Materials Research
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• v.12 no.10
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• pp.820-824
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• 2002

It is of importance to know that the bonding strength and interfacial stress of SOI wafer pairs to meet with mechanical and thermal stresses during process. We fabricated Si/2000$\AA$-SiO$_2$ ∥ 2000$\AA$-SiO$_2$/Si SOI wafer pairs with electric furnace annealing, rapid thermal annealing (RTA), and fast linear annealing (FLA), respectively, by varying the annealing temperatures at a given annealing process. Bonding strength and interfacial stress were measured by a razor blade crack opening method and a laser curvature characterization method, respectively. All the annealing process induced the tensile thermal stresses. Electrical furnace annealing achieved the maximum bonding strength at $1000^{\circ}C$-2 hr anneal, while it produced constant thermal tensile stress by $1000^{\circ}C$. RTA showed very small bonding strength due to premating failure during annealing. FLA showed enough bonding strength at $500^{\circ}C$, however large thermal tensile stress were induced. We confirmed that premated wafer pairs should have appropriate compressive interfacial stress to compensate the thermal tensile stress during a given annealing process.

• Korean Journal of Metals and Materials
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• v.46 no.5
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• pp.283-288
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• 2008

We observed the in-situ stress behavior of Cu and Ag thin films during deposition using a thermal evaporation method. Multi-beam curvature measurement system was used to monitor the evolution of in-situ stress in Cu and Ag thin films on 100 Si(100) substrates. The measured curvature was converted to film stress using Stoney formula. To investigate the effects of the deposition rates on the stress evolution in Cu and Ag thin films, Cu and Ag films were deposited at rates ranging from 0.1 to $3.0{\AA}/s$ for Cu and from 0.5 to $4.0{\AA}/s$ for Ag. Both Cu and Ag films showed a unique three stress stages, such as 'initial compressive', 'a tensile maximum' and followed by 'incremental compressive' stress. For both Cu and Ag films, there is no remarkable effect of deposition rate on the thickness and average stress at the tensile maximum. There is, however, a definite decrease in the incremental compressive stress with increasing deposition rate.

• Bulletin of the Society of Naval Architects of Korea
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• v.21 no.1
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• pp.43-47
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• 1984

The purpose of this paper is to investigate theoretically the effect of residual stress due to welding in stress intensity factor of a plate containing the Model I Crack in different crack size and location, and on fatigue crack growth rate. The initiation of crack is found to be possible only in the region of tensile residual stress. The most dangerous crack has the values of d/b and a/b equal to about 0.6 and 1.0, respectively, where d/b is the ratio of distance from the crack to welding bead and the width of tensile residual stress region and a/b is the ratio of crack length and tensile residual stress region. The crack perpendicular to and on the line of welding bead and with a/b equal to about 0.6 has maximum stress intensity factor. The theoretical fatigue crack growth rate under residual stress and applied stress, which is obtained from Forman's Law by stress superposition, is relatively in good agreement with Glinka's[8] experimental value. The fatigue crack growth is shown to be retarded due to residual stress distribution.

• Journal of Korea Foundry Society
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• v.9 no.3
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• pp.237-246
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• 1989

This study has been carried out to investigate the difference of rolling life and rolling wear characteristics for various high strength ductile iron castings under unlubricative dry rolling condition by Amsler type wear test with 9.09% sliding ratio. The tensile strength of the castings have been obtained 80, 90 and $100kg.f/mm^2$ as cast-state with pearlitic, bainitic and martensitic matrix structures alloyed with Mo, Cu and Ni. It has been found that the amount of rolling wear is decreased when the tensile strength and hardnees of the castings are increased. The amount of rolling wear is increased, when the maximum compressive stress are increased. The maximum weight loss ratio of rolling wear of the castings are same at the 70000 numbers of revolution with out the maximum compressive stress.

• Bulletin of the Society of Naval Architects of Korea
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• v.3 no.1
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• pp.19-24
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• 1966

The maximum shear stress distribution in a stiffening flat attached to a plat undergoing a single tensile force has been investigated by photoelastic method. In the experiments a photoelastic model, as shown in Fig. 1, has been studied in the fields of a polariscope, as shown in Fig. 2. Fig. 3 shows the isoclinics and Fig. 4 and 5 are stress trajectories of the principal stresses and maximum shear stresses, respectively. Fig. 6 is the isochromatics in light field. The maximum shear stress at each point in the stiffener were determined from the isochromatics in both of light field of light field and dark field. Then the maximum shear stresses were divided by the average shear stress in the model, to obtain the ratio ${\tau}max/{\tau}av$ at each point. Finaly the variations of the ratio ${\tau}max/{\tau}av$ along the horizontal and vertical lines in the stiffener have been plotted, as shown in Fig. 7 and 8. The conclusions reached in this investigation are as follows: (1) The shear stresses transmitted to the stiffener through the juncture are concentrated on the end portions. (2) The maximum shear stress at the ends of the stiffener reaches to about 4 times of average shear stress. (3) The irregularities in the stress distribution are restricted in the end portions of the stiffener.

• Journal of the korean Society of Automotive Engineers
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• v.13 no.6
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• pp.109-118
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• 1991

In this study, it is intended to investigate the effect of the grinding conditions such as table feed, down feed, cross feed of residual stress distribution. And this distribution is investigated upon the grinding direction and the its orthogonal direction at ground layers. The material is used carbon steel (SM20C) which usually used to motor axis. And in order to be considered as Bernoulli-Euler beam, the dimension of the specimen is appropriately designed. According as corroiding the ground surface, the residual stress layers are removed and strain which occured on account of unbalance of internal stress is detected by rosette-gate. Through A/D converter and computer, these values are saved and evaluated residual stress by stress-strain relation formula. Finally, these results are diagrammatized with Auto Cad. The results obtained are as follows. As the depth from the ground surface increases in grinding direction and its orthogonal direction, tensile residual stress exists in the surface, and subsequently it becomes compressive residual stress as it goes downward. As the table feed, the cross feed and the down feed increase, maximum residual stress is transformed form the tensile to the compressive.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.25-31
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• 2018

Selective Laser Melting is one of the representative 3D printing techniques for handling metal materials. The main factors influencing the characteristics of structures fabricated by the SLM method include the build-up angle of structures, laser power, laser scan speed, and scan spacing. In this study, the tensile properties of AlSi10Mg alloys were investigated by considering the build-up angle of tensile test specimens, laser scanning speed and scan spacing as variables. The yield stress, tensile strength, and elongation were considered as tensile properties. From the test results, it was confirmed that the yield stress values were lowered in the order of 0, 45, and 90 based on the manufacturing direction of the tensile specimen. The maximum yield stress value was obtained at 1870 mm / min based on the laser scan speed. The yield stress size decreased with decreasing scan speed. Based on the laser scan spacing, as the value increases, the yield stress increases, but the variation is smaller than the other test criteria. The tendency of the tensile strength and elongation variation depending on the test conditions was difficult to understand.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.18 no.2
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• pp.61-68
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• 2022

Accurate evaluation of residual stress is important for stress corrosion cracking assessment. In this paper, electron beam welding experiment is simulated via finite element analysis and the sensitivity of the parameters related to the combined heat source model is investigated. Predicted residual stresses arecompared with measured residual stresses. It is found that the welding efficiency affects the size of the tensile residual stress area and the magnitude of maximum longitudinal residual stress. It is also found that the parameter related to the ratio of energy distributed to the two-dimensional heat source has little effect on the size of tthe tensile residual stress area, but affects the size of the longitudinal residual stress in the center of the weld.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10a
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• pp.556-561
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• 1988

Shrink-rings (Stress-rings) are used in the fabrication of dies for cold forming and powder compaction processes to increase the allowable pressures for a given die material. Optimum procedures are to minimize a die thickness under the conditions that the stress distributions in the die and stress-rings utilize fully the strength available in each of the die elements. This paper proposes a new approach, where the maximum allowable shrinking pressures are calculated on shrinkage plans in the radial direction and the fractional shrinking pressures below the maximum allowable pressures are used as the design values. Two criteria for the optimal die design are used: Maximum shear stress limit for one-piece dies and zero tensile stress limit for combined dies. A computer program, DIECOM, is developed for illustrating the computer-aided design procedures. Finally, examples for each case are presented in this paper.