• Journal of Welding and Joining
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• v.30 no.6
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• pp.113-119
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• 2012

Ultrasonic bonding is the novel packaging method for flip-chip with high yield and low-temperature bonding. The bonding module is a core part of the bonding machine, which can transfer the ultrasonic energy into the bonding spot. In this paper, we propose topology optimization technique which can make new design of boding modules due to the constraints on resonance frequency and mode shapes. The designed bonding module using topology optimization was fabricated in order to evaluate the bonding performance and reliable operation during the continuous bonding process. The actual production models based on the proposed design satisfied the target frequency range and ultrasonic power. The bonding test was performed using flip-chip with lead-free Sn-based bumps, the results confirmed that the bonding strength was sufficient with the designed bonding modules. Also the performance degradation of the bonding module was not observed after the 300-hour continuous process with bonding conditions.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.4
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• pp.239-245
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• 2000

A copper-tungsten sintered alloy(WCu) has been friction-welded to a tough pitch copper (Cu) in order to investigate friction weldability. The maximum tensile strength of the SWu-Cu friction welded joints had cp to 96% of those of the Cu base metal under the condition of friction time 0.6sec, friction pressure 45MPa, upset pressure 125MPa and upset time 5.0sec. And it is confirmed that the tensile strength of friction welded joints are influenced highly by upset pressure rather than friction time. And it is considered that mixed layer was formed in the Cu adjacent side to the weld interface, W particles included in mixed layer induced fracture in the Cu adjacent side to the weld interface and also, thickness of mixed layer was reduced as upset pressure increase.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.6
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• pp.43-50
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• 2002

In the design of structure, the forces acting on tai structure are key parameter fur noise and vibration control. However, in the complex structure, the forces at the injection point on the structure cannot be measured directly. So, it is necessary to find out Indirect force evaluation method. In this paper, forces have been measured with In-situ vibration responses and system information. And, three existing techniques of indirect force measurement, vita. direct inverse. principal component analysis and regularization have been compared. This paper shows that multi-vibration responses are essential for talc precise estimation of the forces. To check these conditions, rotary compressor is adopted as test sample, because it is very difficult to measure the injection forces from internal excitation to shell. It alas also been obtained that relatively higher force is transmitted through three welding paths to the compressor shell. It shows a good agreement between direct and indirect force evaluation with curvature shell and plate.

• Journal of Welding and Joining
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• v.25 no.1
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• pp.63-69
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• 2007

Once assessment of material failure characteristics is captured precisely in a unified way, it can bedirectly incorporated into the structural failure assessment under various loading environments, based on the theoretical backgrounds so called Local Approach to Fracture. The aim of this study is to develop a numerical fatigue test method by continuum damage mechanics applicable for the assessment of structural integrity throughout crack initiation and structural failure based on the Local Approach to Fracture. The generalized elasto-visco-plastic constitutive equation, which can consider the internal damage evolution behavior, is developed and employed in the 3-D FEA code in order to numerically evaluate the material and/or structural responses. Explicit information of the relationships between the mechanical properties and material constants, which are required for the mechanical constitutive and damage evolution equations for each material, are implemented in numerical fatigue test method. The material constants selected from constitutive equations are used directly in the failure assessment of material and/or structures. The performance of the developed system has been evaluated with assessing the S-N diagram of stainless steel materials.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.564-567
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• 1997

In the design of structure the forces acting on the structure are important parameter for noise and vibration control. However, in the complex structure, the forces at the injection point on the structure cannot be measured directly. Thus it is necessary to find out indirect force evaluation method. In this paper forces have been measured with in-situ vibration responses and system information. Three existing techniques of indirect force measurement, viz. direct inverse, principal component analysis and regularization have been compared. It has been shown that multi-vibration responses are essential for the precise estimation of the forces. To satisfy those conditions, Rotary compressor is adopted as test sample, because it is very difficult to measure the injection forces from internal excitation to shell. It has also been obtained that relatively higher force is transmitted though three welding paths to the compressor shell. It shows a good agreement between direct and indirect force evaluation with curvature shell and plate and is investigated the possibility of force evaluation of rotary compressor as a complex structure.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.3
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• pp.101-108
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• 2008

Residual stress is one of the causes which make defects in engineering components and materials. Many methods have been developing to measure the residual stress. Though these methods provide the information of the residual stress, they also have disadvantage like a little damage, time consumption, etc. In this paper, we devised a new experimental technique to measure residual stress in materials with a combination of laser speckle pattern interferometry and spot heating. The speckle pattern interferometer measures in-plane deformation during the heat provides for much localized stress relief. 3-D shape is used for determining heat temperature and other parameters. The residual stresses are determined by the amount of strain that is measured subsequent to the heat and cool-down of the region being interrogated. A simple model is presented to provide a description of the method. In this paper, we could experimentally confirm that residual stress can be measured by using laser interferometry and spot heating method.

• Journal of Welding and Joining
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• v.32 no.5
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• pp.58-64
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• 2014

The shipbuilding industry is facing the various problems of less demand and oversupply owing to the global economic crisis and the increase in shipbuilding countries. Shipyards of the industry are making effort to strengthen their ability to handle the crisis via a smartwork technology for flexible working environment. In this study, we developed a smartwork system that manages the information in shipbuilding process with mobile devices such as smart phones and tablet PCs. To successfully apply the developed smartwork system to shipyards, we analyzed several best practices and management tasks of the shipbuilding processes. The developed system was designed by CBD approach that is a branch of service-oriented software engineering for reusability and flexibility on the system. As it is designed considering the flexible working environment, it supports to increase their productivity by reducing the time required to carry out tasks and by increasing the mobility required to manage work performance in field of shipyards.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.281-284
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• 2006

After building a ship in a shipyard, there are so many repeated inspection of welding seam defects and painting status before delivering to the ship's owner. An inspection on the bottom part of a ship in commercial service should be done in every two years for the purpose of safety and for the prevention of ship speed deterioration. conventional welding seam inspection systems are rely on the visual inspection by human or the ultrasonic inspection for the selective part of a ship. This paper suggests a remote controlled inspection system for the examination of large ships or steel structures. The proposed system moves in contact with the ship under inspection and have a CCD camera to provide visual-guidance information to a remotely located human worker. Additionally this system utilizes a weld line tracking algorithm for an optimal position control. We verified the effectiveness of the inspection system by experimental data.

• Safety and Health at Work
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• v.4 no.3
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• pp.123-135
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• 2013

Exposure to manganese (Mn) is associated with neurobehavioral effects. There is disagreement on whether commonly occurring exposures in welding, ferroalloy, and other industrial processes produce neurologically significant neurobehavioral changes representing parkinsonism. A reviewof methodological issues in the human epidemiological literature onMnidentified: (1) studies focused on idiopathic Parkinson disease without considering manganism, a parkinsonian syndrome; (2) studies with healthy worker effect bias; (3) studies with problematic statistical modeling; and (4) studies arising from case series derived from litigation. Investigations with adequate study design and exposure assessment revealed consistent neurobehavioral effects and attributable subclinical and clinical signs and symptoms of impairment. Twenty-eight studies show an exposure-response relationship between Mn and neurobehavioral effects, including 11 with continuous exposure metrics and six with three or four levels of contrasted exposure. The effects of sustained low-concentration exposures to Mn are consistent with the manifestations of early manganism, i.e., consistent with parkinsonism. This is compelling evidence thatMnis a neurotoxic chemical and there is good evidence that Mn exposures far below the current US standard of $5.0mg/m^3$ are causing impairment.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.5
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• pp.400-409
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• 2012

It is not easy to know the accurate mass and mass moment of inertia of robot. Because of this uncertainty, error may exist when we control the robot based on the inaccurate mass information. Moreover the properties of the portable robot can change during its operation. Therefore we developed the motion simulator based on the adaptive control. First, the computed torque control was carried out in order to minimize an error between target angles and real angles. The computed torque control is based on the equation of robot motion, which is derived from the Lagrange-Euler equation. To minimize the error between the real model and the approximated model, the adaptive control was carried out. During this simulation, the interference check was also carried out. The interference check verifies that the robot can move successfully without any collision.