• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.4
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• pp.44-49
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• 2011

The crawler crane, which consists of a lattice boom, a driving system, and movable vehicle, is widely used in a construction site. It needs to be installed an overload limiter to prevent the overturning accident and the fracture of structure. This research is undertaken to provide the relation formula for designing the overload limiter as follows: First the relation formulas between the wire-rope tension and the hoisting load or the overturning ratio according to the luffing angle and length of a lattice boom are established. Secondly the derived formulas are corrected by using the compensated angle considering the deflection of boom through the finite element analysis. The stiffness analysis is carried out for 30-kinds of models as a combination of 6-kinds of luffing angle and 5-kinds of length of boom. Finally the shape design of a stick type load cell, which is the device to measure the wire-rope tension, is performed. 5-kinds of notch radius and 5-kinds of center hole radius are adopted as the design parameter for the strength analysis of the load cell.

• Transactions of Materials Processing
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• v.18 no.8
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• pp.640-645
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• 2009

Recently, boss and rib test based on backward extrusion process was proposed to quantitatively evaluate the interfacial friction condition in bulk forming process. In this test, the tube-shaped punch with hole pressurizes the workpiece so that the boss and rib are formed along the hole and outer surface of the punch. It was experimentally and numerically revealed that the height of boss is higher than that of the rib under the severe friction condition. This work is focused on the effect of the punch design and flow stress on deformation pattern in boss and rib test. From the boss and rib test simulations, it was found that there is slight variation in both the heights of boss and rib according to the length of punch land, nose radius, and face angle. However the hole diameter of the punch and the clearance between the punch and die have a significant influence on the calibration curves showing the heights of the boss and rib. In addition, the effect of flow stress on the calibration curves was investigated through FE simulations. It was found that there is no effect of strength coefficient of the workpiece on the calibration curves for estimation of friction condition. On the other hand, the strain-hardening exponent of the workpiece has a significant influence on the calibration curve.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.2
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• pp.189-198
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• 1997

This paper presents development of a practical tool deflection compensation system in order to reduce the machining error from the tool deflection compensation system in order to reduce the machining error from the tool deflection in the end-milling process. The devised system is a tool adapter which includes 1-axes force sensor for detecting tool deflection and 2-axes tool tilting device for adjusting tool position through computer interface on line process. Experimental in investigations for typical shaped workpieces representing various end milling situations are performed to verify the ability of the system to suppress the surface errors due to tool deflections. With the system, it is possible to get precise machining surface without any excessive machining error due to increased cutting force in more productive machining conditions.

• Transactions of Materials Processing
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• v.18 no.3
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• pp.210-216
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• 2009

Springback, an elastic material recovery after the unloading of stamping tools, causes variations and inconsistencies of final part dimensions. Recently, narrow and long surround molding parts around door frame are applied to high grade automobiles, but there are great difficulties in their die development, construction and tryout because of several springback modes including vertical movement and twist during flange forming process of them. So it is very important to predict springback's quantities of a surround molding part and, moreover, to compensate the die for them adequately, when they can't be corrected by the restrike operation. This paper presents a case study based on the die design for a surround molding part made of stainless steel. The forming and springback predictions, carried out using PAMSTAMP 2G, are reported and compared with the measurement data of the prototype. The predicted springback results were acceptable, so the processes of compensating die using Automatic Die Compensation Module of PAMSTAMP 2G were performed iteratively until the tolerances between the designed shape and the simulation data were satisfied.

• Transactions of Materials Processing
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• v.21 no.8
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• pp.479-484
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• 2012

The objective of this study is to compensate the elastic recovery in the flexible forming process using the predictive models. The target shape was limited to two-dimensional shape having only one curvature radius in the longitudinal-direction. In order to predict the shape error the regression and neural network models were established based on the finite element (FE) simulations. A series of simulations were conducted considering input variables such as the elastic pad thickness, the thickness of plate, and the objective curvature radius. Then, at sampling points in the longitudinal-direction, the shape errors between formed and objective shapes could be calculated from the FE simulations as an output variable. These shape errors were expressed to a representative error value by the root mean square error (RMSE). To obtain the correct objective shape the die shape was adjusted by the closed-loop using the neural network model since the neural network model shows a higher capability of estimating the shape error than the regression model. Finally the experimental result shows that the formed shape almost agreed with the objective shape.

• Transactions of Materials Processing
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• v.29 no.4
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• pp.188-193
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• 2020

Piping work of large ships or offshore plants is often done in a narrow and confined space, requiring precise bending and safety. In order to realize an accurate bending angle, it is very important to predict and correct a deformation that may be caused by elasticity in the bending process, that is, an angular deviation due to springback. Therefore, by using CAE analysis to develop a correction angle model for springback based on multiple tube bending angles and using trend line data derived from this correction angle model, at bending the tube as the diameter of the base former and the tube outer diameter change, the springback compensation angle at any angle can be obtained. In this study, the bending mechanism was analyzed to increase the bending precision, and a correction angle model was developed and a trend line was derived in consideration of springback occurring in the bending process. In order to derive a more accurate and reliable trend line, a tube tensile test was performed, and the reliability of the corrected angle trend line was verified by comparing the bending angle measurement and analysis results with a 3D scanner.

• Transactions of Materials Processing
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• v.23 no.7
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• pp.439-445
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• 2014

Changes in the accuracy of the geometrical shape after a surface treatment are often very large due to the variation of the deformation mechanisms such as edge draw-in and the variation in springback caused by the reduction in the coefficient of friction between the tool and the blank. In the present study, the resulting shape accuracy due to the changes in deformation is quantitatively examined in order to predict the variation and to remove any undesirable additional tool compensation for the center pillar member made from steel with a UTS of 980MPa. The study examines important process parameters that are closely related with the edge draw-in such as the blank holding force, the contact status between the tool and the blank and the friction coefficient. The proposed method is applied within the finite element analysis of the stamping process for tools after a surface treatment and the amount of edge draw-in and flush values are compared between the analysis and experiments. The results demonstrate that the proposed quantification and finite element scheme are applicable to complicated tool compensation procedures and compensation can be designed effectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1525-1530
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• 2014

In this research, we describe teaching based sweeping control for grinder robot has been proposed as a system which is suitable to work utilizing pressure sensitive alternative to human. Teaching method is used for grinder robots operations because of their position accuracy, path accuracy, and machining reaction force. A grinder robot for two-dimensional iron plate was developed on the basis of an force sensor based teaching method. An automatic-path-generation method and experimental results using specific points was adopted to reduce the number of teaching points and time. And also, in order to determine the proper machining conditions, various machining conditions such as grinder-wheel rotation speed and robot moving speed, were evaluated.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.3
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• pp.100-109
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• 2022

In this study, calibration technology that increases the alignment accuracy in large flexible flat panels was studied. For precise of calibration, a systematization of the calibration algorithm was established, and a calibration correction technique was studied to revise calibration errors. A coordinate systems of camera and UVW stage was established to get the global position of the mark, and equations for translational and rotational calibration were systematically derived based on geometrical analysis. Correction process for the calibration data was carried, and alignment experiments were performed sequentially in cases of the presence or absence of calibration-correction. Alignment results of both calibration correction and non-calibration correction showed accuracy performance less than 1㎛. On the other hand, the standard deviation in calibration-correction is smaller than non-calibration correction. Therefore, calibration correction showed improvement of the alignment repeatability.

• Transactions of Materials Processing
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• v.32 no.4
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• pp.215-220
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• 2023

In this study, the correction process of stress-strain curves obtained from hot compression test is introduced since the barreling induced by friction and adiabatic heat generation induced by plastic work occur under high strain rate. A shear friction factor was quantitatively estimated by measuring the dimension of barreling and temperature rise due to adiabatic heat generation was directly measured during compression test. Thereafter, the stress-strain curves were re-evaluated by introducing several equations to correct the effects of the friction and temperature rise. It was found that adiabatic factor at strain rate of 10/s is in the range of about 0.5 to 0.75 for Nimonic 80A and decreases as the assigned temperature increases.