| 1. |
- Dahlström, Stefan, 1972, et al.
(författare)
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Variation simulation of sheet metal assemblies using the method of influence coefficients with contact modeling
- 2007
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Ingår i: Journal of Manufacturing Science and Engineering, Transactions of the ASME. - : ASME International. - 1087-1357 .- 1528-8935. ; 129:3, s. 615-622
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Tidskriftsartikel (refereegranskat)abstract
- Sheet metal assembly is a common assembly process for several products such as automobiles and airplanes. Since all manufacturing processes are affected by variation, and products need to have a high geometric quality, geometry-related production problems must be analyzed during early design phases. This paper discusses two methods of performing this analysis. One way of performing the simulations relatively fast is to establish linear relationships between part deviation and assembly springback deviation by using the method of influence coefficient (MIC). However, this method does not consider contact between the parts. This means that the parts are allowed to penetrate each other which can affect the accuracy of the simulation result. This paper presents a simple contact modeling technique that can be implemented in to MIC to avoid penetrations. The contact modeling consists of a contact detection and a contact equilibrium search algorithm. When implemented, MIC still only requires two finite element analysis (FEA) calculations. This paper describes the steps in the contact algorithm and how it can be used in MIC and finally the proposed contact modeling is verified by comparing the simulation result with commercial FEA software ABAQUS contact algorithm.
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| 2. |
- Eynian, Mahdi, 1980-, et al.
(författare)
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Chatter Stability of General Turning Operations With Process Damping
- 2009
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Ingår i: Journal of manufacturing science and engineering. - : The American Society of Mechanical Engineers. - 1087-1357 .- 1528-8935. ; 131:4
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Tidskriftsartikel (refereegranskat)abstract
- The accurate prediction of chatter stability in general turning operations requires the inclusion of tool geometry and cutting conditions. This paper presents regenerative chip and regenerative chip area/cutting edge contact length based dynamic cutting force models, which consider cutting conditions and turning tool geometry. The cutting process is modeled as it takes place along the equivalent chord length between the two end points of the cutting edge. The regenerative chip model is simple, and the stability can be solved directly. However, the three-dimensional model considers the effect of tool vibrations at the present and previous spindle revolutions on the chip area, chord length, and force directions and is solved using Nyquist stability criterion. The penetration of worn tool flank into the finish surface is considered as a source of process damping. The effects of the nose radius, approach angle of the tool, and feedrate are investigated. The proposed stability model is compared favorably against the experimental results.
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| 3. |
- Li, Zhijun, et al.
(författare)
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Multiobjective Optimization for Integrated Tolerance Allocation and Fixture Layout Design in Multistation Assembly
- 2008
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Ingår i: Journal of manufacturing science and engineering. - : ASME International. - 1087-1357 .- 1528-8935. ; 130:4, s. 0445011-0445016
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Tidskriftsartikel (refereegranskat)abstract
- Cost and dimensional variation of products are significant attributes in multistation assembly processes. These attributes depend on product/process tolerances and fixture layouts. Typically, tolerance allocation and fixture layout design are conducted separately without considering potential interrelations. In this work, we use multiobjective optimization for integrated tolerance allocation and fixture layout design to address interactions and to quantify tradeoffs among cost, product variation, and assembly process sensitivity. A nested optimization strategy is applied to a vehicle side frame assembly. Results demonstrate the presence and quantification of tradeoffs, based on which we introduce the concept of critical variation and critical budget requirements
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| 4. |
- Vedmar, Lars, et al.
(författare)
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A parametric Analysis of the Undeformed Chip Geometry in Gear Hobbing
- 2009
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Ingår i: Journal of Manufacturing Science and Engineering. - : ASME International. - 1528-8935 .- 1087-1357. ; 131:December 2009, s. 1-061003
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Forskningsöversikt (refereegranskat)abstract
- Hobbing is a common manufacturing method when producing helical, involute gears. In order to increase tool life and surface finish, an accurate method to determine chip geometry is needed. Although this accurateness may involve numeric solutions, the geometric description must, as far as possible, be analytic and give a description of the continuously changing chip geometry. In this report, the cutting edges of the tool are mathematically described using parametric and analytically differentiable functions. This gives the possibility to determine the geometry of the three-dimensional surface on the blank each cutting edge will cut, with numeric approximations kept to a minimum. By comparing successively cut surfaces, the chip geometry is determined using the tool and process parameters. The mathematical description gives the possibility to calculate the required characteristic properties of the chips. These are needed for increasing the tool life in order to develop more efficient tools and processes. An example is given in which characteristics, as the maximum chip thickness, the chip cross-section area, and the mean chip thickness are calculated. The reported theory describes in detail how the chip geometry is determined.
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| 5. |
- Wärmefjord, Kristina, 1976, et al.
(författare)
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A Measure of the Information Loss for Inspection Point Reduction
- 2009
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Ingår i: Journal of Manufacturing Science and Engineering, Transactions of the ASME. - : ASME International. - 1087-1357 .- 1528-8935. ; 131:5, s. 0510171-0510176
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Tidskriftsartikel (refereegranskat)abstract
- Since the vehicle program in the automotive industry gets more and more extensive, the costs related to inspection increase. Therefore, there are needs for more effective inspection preparation. In many situations, a large number of inspection points are measured, despite the fact that only a small subset of points is needed. A method, based on cluster analysis, for identifying redundant inspection points has earlier been successfully tested on industrial cases. Cluster analysis is used for grouping the variables into clusters, where the points in each cluster are highly correlated. From every cluster only one representing point is selected for inspection. In this paper the method is further developed, and multiple linear regression is used for evaluating how much of the information is lost when discarding an inspection point. The information loss can be quantified using an efficiency measure based on linear multiple regression, where the part of the variation in the discarded variables that can be explained by the remaining variables is calculated. This measure can be illustrated graphically and that helps to decide how many clusters that should be formed, i.e., how many inspection points that can be discarded.
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