• Geomechanics and Engineering
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• v.8 no.4
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• pp.495-510
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• 2015

The applications of water jet cutting (WJC) in coal mine have progressed slowly. In this paper, we analyzed the possibility and reasonableness of WJC application to pressure relief in hard coal seam, simulated the distributive characteristics of stress and energy fields suffered by hard coal roadway wallrock and the internal relationships of the fields to the instability due to WJC (including horizontal radial slot and vertical annular slot) on roadway wallrock. The results showed that: (1) WJC can unload hard coal seam effectively by inducing stress release and energy dissipation in coal mass near its slots; its annular slots also can block or weaken stress and energy transfer in coal mass; (2) the two slots may cause "the beam structure" and "the small pillar skeleton", and "the layered energy reservoir structure", respectively, which lead to the increase in stress concentration and energy accumulation in coal element mass near the slots; (3) the reasonable design and optimization of slots' positions and their combination not only can significantly reduce the scope of stress concentration and energy accumulation, but also destroy coal mass structure on a larger scale to force stress to transfer deeper coal mass.

• Journal of Korean Society of Forest Science
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• v.54 no.1
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• pp.76-79
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• 1981

This thesis emphasize on diurnal changes of leaf water potential in relation to differences of cutting arrangement. 1. The more is leaves attached to the cutting, the higher is water stress in the cutting compared with less leaves. 2. The less is diameter of cut-part, the more are shown changes in increased and decrease in diurnal leaf water potential. 3. The more is length of stem, the more are shown water stress in diurnal leaf water potential 4. There is no differences between earthen-ball cutting and non-earthen ball cutting in diurnal leaf water potential. 5. Cuttings with two year's slip, compared with one year's leaf water potential increases slowly, dry weigh of root and numbers of rooted cutting are most likely dependent upon other factors rather than the water stress.

• Journal of Welding and Joining
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• v.21 no.5
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• pp.547-554
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• 2003

Apparent mechanical properties in structural components can be different from the initially designed values due to the formation of the residual stress in metal forming and welding. Therefore, the evaluation of residual stress has great importance in the reliability diagnosis of structural components. A nondestructive instrumented indentation technique has been proposed to evaluate various strength concerning mechanical properties from the analysis of load-depth curve. In this study, quantitative residual stress estimation on API X65 welded joints for natural gas pipeline was performed by analyzing the variation of indentation loading curve by residual stress through a new proposed theoretical model. The residual stress from the indentation method was compared with that from the saw-cutting method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.210-213
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• 2002

The Purpose of this study is to know temperature and thermal stress distribution in specimens during processing of WEDM. If it is constant to the cutting speed and the thickness of material, it is very important to the effect of temperature and the thermal stress distribution after cutting processing. This paper show the analysis result of the distribution of temperature and the residual stress along the direction of thickness before processing of WEDM and after when the cooling temperature is$20^{\circ}C$. The maximum temperature of edge of specimens is $1600^{\circ}C$. It has little temperature gradient in the depth which is 5mm away from edge of specimens. Equivalent residual stress is result in 180.7 MPa at maximum temperature.

• Journal of Welding and Joining
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• v.33 no.1
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• pp.72-79
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• 2015

Evaluation of fracture toughness of welded structures has a significant influence on the structural design. However the residual stresses is redistributed while the welded structures is cut for preparing specimens. This study investigated an effect of the welding residual stress redistribution on the impact absorption energy of Charpy specimen. SA516Gr70 steel plate by at the flux cored arc welding (FCAW) and gas tungsten arc welding(GTAW) was cutting. Specimens for Charpy impact testing were taken from the welded plate. Two material removal mechanisms (wire cutting and water jet) were used to make the specimens. Welding residual stress and redistribution residual stress were measured using the XRD (X-Ray Diffraction) method. The amount of redistribution of residual stress depends on the different material removal mechanism. Redistribution of residual stress of reduced the impact absorption energy by 15%.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.6
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• pp.68-74
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• 2018

Study on the Ti-6Al-4V have been carried out using cutting simulation, and researches for cutting force and chip shape prediction have been actively conducted under various conditions. However, a 3D printer application method using Ti-6Al-4V metal powder material as a high-power method has been studied for the purpose of prototyping, mold modification and product modification while lowering material removal rate. However, in the case of products / parts made of 3D printers using powder materials, problems may occur in the contact surface during tolerance management and assembly due to the degradation of the surface quality. As a result, even if a 3D printer is applied, post-processing through cutting is essential for surface quality improvement and tolerance management. In the cutting simulation, the cutting force and the chip shape were predicted based on the Johnson-Cook composition equation, but the shape of the shear type chip was not predictable. To solve this problem, we added a damaging term or strain softening term to the Johnson-Cook constitutive equation to predict chip shape. In this thesis, we applied the constant value of the S-K equations to the cutting simulation to predict the cutting force and compare with the experimental data to verify the validity of the cutting simulation and analyzed the machining characterization by considering conditions.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.5
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• pp.153-160
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• 1994

In this study, residual stress and surface roughness were investigated experimentally to evaluate surface integrity on surface layer machined by CBN, ceramics and WC cutting tools. When machining difficult-to-cut material (hardened STD11 steel $H_{R}$C 60), residual stresses remaining in machined surface layer were mainly compressive. The increase of flank wear caused a shift of the compressive residual stress maximum to greater workpiece depths, but the changes did not penetrate the workpiece beneath a depth of 300 .mu. m. Surface roughness was influenced considerably by variations of the cutting speed and feed. In machining hard material, CBN and A1$_{2}$ $O_{3}$ ceramics cutting tool materials proved significantly superior to mixed ceramics A1$_{2}$ $O_{3}$-TiC and WC in evaluation of surface integrity.y.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.125-130
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• 2008

A spherical indentation has been proposed as a nondestructive method of measuring local residual stress field in laser-voided joints. The apparent yield strengths interpreted from the spherical indentation data of as-welded cutting wheel were compared with the intrinsic yield strengths measured at nearly equivalent locations in annealed wheel. Their difference along the distance from the welding line is welding stress distribution because the intrinsic yield strength is invariant regardless of the elastic residual stress. The spherical indentations show that the laser-welded diamond cutting wheel displays a 10 min-wide distribution of the welding residual stress and has peak compressive and tensile stresses in the shank and tip regions, respectively.

• Journal of Korean Society of Steel Construction
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• v.16 no.5 s.72
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• pp.555-564
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• 2004

Steel materials, which are normally used in bridge structures, are prone to corrosion and have thin plate structures. Steel bridges that have been damaged through increased vehicle load and corrosion are frequently expected to be strengthened. Repair or strengthening methods generally include cutting, bolting, and welding. The basic characteristics of stress and deformation behavior generated by cutting and welding in the course of the repair work, however, are not yet understood. It is difficult to say whether the safety of the structure after welding conforms with existing safety evaluation methods.Therefore, to gain confidence in the material and to guarantee the safety of the structure after welding, the stress generated by heat, through welding and cutting, was generalized. The effect of additional loads with respect to stress generated by heat was also investigated.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.2
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• pp.252-261
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• 1988

Through the careful interpretation of the results of the cutting tests carried out in this study, it is found that under the cutting conditions when the internal shear of the chips take place the cutting can be treated essentially as a steady state problem. A new shear angle equation has been developed employing the conditions of force and moment equilibrium about the tool edge and the stress distribution model suggested by Zorev.The equation contains the chip-tool contact length C and stress distribution index n as important parameters.