Numerical Investigation of Optimal Rooftop Punch Shape for Force Reduction and Dimensional Accuracy Control

2019 ◽  
Author(s):  
Haoling Jia ◽  
Chao Pu ◽  
Jason Burton ◽  
Feng Zhu ◽  
Yu-wei Wang
Keyword(s):  
Numerical Investigation ◽  
Dimensional Accuracy ◽  
Accuracy Control ◽  
Force Reduction ◽  
Punch Shape

Study on the Propagation of Dimensional Deviation in the Hull Block Building Process

2020 ◽  
Vol 36 (02) ◽  
pp. 143-151
Author(s):  
Changhui Liu ◽  
Jianfeng Liu ◽  
Yansong Zhang ◽  
Sun Jin ◽  
Can Wang ◽  
...  
Keyword(s):  
Critical Role ◽  
Dimensional Accuracy ◽  
Butt Joint ◽  
Measured Data ◽  
Accuracy Control ◽  
Bottom Block ◽  
Whole Process ◽  
Building Process ◽  
Dimensional Deviation ◽  
Industry Practice

Dimensional accuracy of hull block plays a critical role in guaranteeing the whole ship accuracy and reducing the hull butt-joint cost. The current industry practice of dimensional control in shipbuilding mainly focuses on the prediction of cutting and welding deformation based on engineering experience. Its main limitation is that the propagation and accumulation of deviations in the whole building process are neglected. In this article, cutting errors, assembly deviations, welding shrinkages, turnover distortions, and thermal expansions generated at different stages are analyzed. The propagation and accumulation of deviations and variations in the double-bottom block building process are studied based on the measured data in the whole process. Finally, the correlations of deviations between the adjacent stage are concluded. The conclusions can be used to guide the accuracy control in the hull block building process and reduce dimension trimming.

Stochastic Assessment and Applications for Welding Shrinkage Impact on Production Cost

2012 ◽  
Author(s):  
H. Y. Heo ◽  
D. H. Youn ◽  
H. Chung
Keyword(s):  
Production Cost ◽  
Value Added ◽  
Dimensional Accuracy ◽  
Control Procedure ◽  
Total Production ◽  
Accuracy Control ◽  
Element Analysis ◽  
Intermediate Products ◽  
Welding Sequence

Since ship hull blocks are constructed by assembling numerous intermediate parts, negligible dimensional variations in the parts can easily accumulate to cause serious misalignment in block erection stage. Considering the welding – the primary joining process in ship production which inherently causes distortions, the quality of block’s dimensional variations during the assembly would deteriorate even faster. Thinking that the intermediate products with low dimensional quality in the ship production are not scrapped but reworked, the productivity of each workstation greatly depends on the dimensional quality of these dimensionally critical intermediate products. Reworks such as recutting, mechanical and/or thermal correction against misalignment, excessive welding for wide gap and thermal straightening are commonly subsequently increases the total production cost. One of the major dimensional accuracy control activities is the shrinkage margin design. The optimal length of excess edge is assigned to plates in order to compensate welding shrinkage. In the past, the welding shrinkage is predicted based mostly on the empirical formula or just designer's experience, so the accuracy of the assigned was relatively poor and could not effectively help reducing non-value-added rework activities. The simplified margin calculation procedure could not consider the welding sequence as well as process variations such as welding heat input. This work aims to develop the optimal shrinkage margin calculation system for dimensional quality improvement. The proposed system calculates the optimal shrinkage margin using computer-aided engineering toolsets based on finite element analysis as well as design point searching procedure adopting the quality loss function and statistical values considering shrinkage variation values during welding. The developed scheme improves the accuracy control procedure in the ship production process thus enhance competitiveness of shipbuilders in dimensional accuracy technology by minimizing the accuracy impact on productivity.

Decentralization—The Management Key to Effective Accuracy Control

1987 ◽  
Vol 3 (02) ◽  
pp. 75-86
Author(s):  
Tamara S. Upham ◽  
W. Mark Crawford
Keyword(s):  
Organizational Structure ◽  
Statistical Methods ◽  
Dimensional Accuracy ◽  
Accuracy Control ◽  
Statistical Accuracy ◽  
Three Phase ◽  
Control Department

This paper presents the organizational structure, methods, and results of National Steel and Shipbuilding Company's (NASSCO) efforts to decentralize the responsibility of statistical accuracy control from a central Accuracy Control Department to the hourly production workforce. It includes an accounting of the problems and successes encountered during implementation. The results are both quantitative and qualitative in form, including methods for measuring reductions in rework. During this study, workteams were established in the Hull Fabrication Shop. A three phase methodology was used to introduce the workteams to statistical methods for improving the dimensional accuracy of their products.

Modeling and Simulation of Material Removal Rates and Profile Accuracy Control in Abrasive Flow Machining of the Integrally Bladed Rotor Blade and Experimental Perspectives

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Kai Cheng ◽  
Yizhi Shao ◽  
Rodrigo Bodenhorst ◽  
Mitul Jadva
Keyword(s):  
Dimensional Accuracy ◽  
Accuracy Control ◽  
Abrasive Flow Machining ◽  
Virtual Machining ◽  
Computational Environment ◽  
Component Form ◽  
Simulation Based ◽  
Machining System ◽  
Bladed Rotor ◽  
Profile Accuracy

Abrasive flow machining (AFM) technology is getting more and more interest by the industry and research community particularly in the context of increasing demands for postprocessing of the additively manufactured and complex components. It is essentially important to develop an industrial feasible approach to controlling and improving the profile accuracy (form and dimensional) of components as well as their surface roughness. In this paper, a multiscale multiphysics simulation-based approach is presented to model and simulate the AFM process against the component form and dimensional accuracy control in particular. The simulation is developed in comsol which is a multiphysics computational environment. Well-designed AFM experiment trials are carried out on a purposely configured blade “coupon” to further evaluate and validate the simulations. The AFM machine and specific machining media for the experiments are provided by the industrial collaboration company, with their further industrial inputs. Both the simulation and experimental trial results illustrate that the approach is applicable to the blade profile prediction and accuracy control, which is used as a foundation for developing the simulation-based AFM virtual machining system.

Accuracy and Distortion Control Challenges in Lightweight Structural Unit Assembly at Northrop Grumman Ship Systems

2006 ◽  
Vol 22 (03) ◽  
pp. 147-154
Author(s):  
M. Spicknall ◽  
E. Hodges ◽  
T. D. Huang
Keyword(s):  
Dimensional Accuracy ◽  
Steel Structures ◽  
Cost Effective ◽  
Naval Research ◽  
Accuracy Control ◽  
Contributing Factors ◽  
Quality Performance ◽  
Lightweight Structures ◽  
Office Of Naval Research ◽  
Welding Processes

Shipboard applications of lightweight structures have increased over the past decade in both military and commercial vessels. Severe distortions have emerged as a major obstacle to the cost-effective fabrication of such lightweight structures. With a recent major initiative funded by the US Navy Office of Naval Research, Northrop Grumman Ship Systems (NGSS) has undertaken a comprehensive assessment of lightweight structure technology. This program includes a comprehensive investigation of the fabrication and assembly processes for thin steel structures and their contributions to the final dimensional accuracy and distortion. As part of this effort, substantial work was done to characterize current dimensional quality performance in partial subunit (PSU) and combined partial subunit (CPSU) assemblies, and to identify contributing factors to dimensional inaccuracy and distortion in unit assembly stages. This information will be used by NGSS as a basis for improvements in fitting and welding processes, jigging and fixturing methods, dimensioning and tolerancing, and accuracy control processes. This paper summarizes the current dimensional quality performance in PSU and CPSU at NGSS, and the factors contributing to current performance.

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