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1.	Bayani, Mohsen, 1981, et al. (author) Geometric robustness and dynamic response management by structural topometry optimisation to reduce the risk for squeak and rattle 2022 In: Design Science. - : Cambridge University Press (CUP). - 2053-4701. ; 8 Journal article (peer-reviewed)abstract Historically, squeak and rattle (S&R) sounds have been among the top quality problems and a major contributor to the warranty costs in passenger cars. Geometric variation is among the main causes of S&R. Though, geometric variation analysis and robust design techniques have been passively involved in the open-loop design activities in the predesign-freeze phases of car development. Despite the successful application of topometry optimisation to enhance attributes such as weight, durability, noise and vibration and crashworthiness in passenger cars, the implementation of closed-loop structural optimisation in the robust design context to reduce the risk for S&R has been limited. In this respect, the main obstacles have been the demanding computational resources and the absence of quantified S&R risk evaluation methods. In this work, a topometry optimisation approach is proposed to involve the geometric variation analysis in an attribute balancing problem together with the dynamic response of the system. The proposed method was used to identify the potential areas of a door component that needed structural reinforcement. The main objective was to enhance the design robustness to minimise the risk for S&R by improving the system response to static geometrical uncertainties and dynamic excitation.
2.	Bayani, Mohsen, 1981, et al. (author) Squeak and rattle prevention by geometric variation management using a two-stage evolutionary optimisation approach 2020 In: ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE). ; 2B-2020 Conference paper (peer-reviewed)abstract Squeak and rattle are annoying sounds that often are regarded as the indicators for defects and quality issues by the automotive customers. Among the major causes for the generation of squeak and rattle sounds, geometric variation or tolerance stack-up is a key contributor. In the assembly process, the dimensional variation in critical interfaces for generating squeak and rattle events can be magnified due to tolerance stackup. One provision to manage the tolerance stack-up in these critical interfaces is to optimise the location of connectors between parts in an assembly. Hence, the focus of this work is to prevent squeak and rattle by introducing a geometric variation management approach to be used in the design phase in the automotive industry. The objective is to identify connection configurations that result in minimum variation and deviation in selected measure points from the critical interfaces for squeak and rattle. In this study, a two-stage evolutionary optimisation scheme, based on the genetic algorithm employing the elitism pool, is introduced to fine-tune the connectors’ configuration in an assembly. The objective function was defined as the variation and the deviation in the normal direction and the squeak plane. In the first stage, the location of one-dimensional connectors was found by minimising the objective function in the rattle direction. In the second stage, the best combination of some of the connectors from the first stage was found to define planar fasteners to optimise the objective function both in the rattle direction and the squeak plane. It was shown that by using the proposed two-stage optimisation scheme, the variation and deviation results in critical interfaces for squeak and rattle improved compared to the baseline results.
3.	Bayani, Mohsen, 1981, et al. (author) Squeak and rattle prevention by geometric variation management using a two-stage evolutionary optimization approach 2022 In: Journal of Computing and Information Science in Engineering. - : ASME International. - 1530-9827 .- 1944-7078. ; 22:1 Journal article (peer-reviewed)abstract Squeak and rattle are annoying sounds that are often regarded as failure indicators by car users. Geometric variation is a key contributor to the generation of squeak and rattle sounds. Optimization of the connection configuration in assemblies can be a provision to minimize this risk. However, the optimization process for large assemblies can be computationally expensive. The focus of this work is to propose a two-stage evolutionary optimization scheme to find the fittest connection configurations that minimize the risk for squeak and rattle. This was done by defining the objective functions as the measured variation and deviation in the rattle direction and the squeak plane. In the first stage, the location of the fasteners primarily contributing to the rattle direction measures is identified. In the second stage, fasteners primarily contributing to the squeak plane measures are added to the fittest configuration from phase one. It was assumed that the fasteners from the squeak group plane have a lower-order effect on the rattle direction measures, compared to the fasteners from the rattle direction group. This assumption was falsified for a set of simplified geometries. Also, a new uniform space filler algorithm was introduced to efficiently generate an inclusive and feasible starting population for the optimization process by incorporating the problem constraints in the algorithm. For two industrial cases, it was shown that by using the proposed two-stage optimization scheme, the variation and deviation measures in critical interfaces for squeak and rattle improved compared to the baseline results.
4.	Bohlin, Robert, 1972, et al. (author) Data Flow and Communication Framework Supporting Digital Twin for Geometry Assurance 2018 In: ASME 2017 International Mechanical Engineering Congress and Exposition. ; 2 Conference paper (peer-reviewed)abstract Faster optimization algorithms, increased computer power and amount of available data, can leverage the area of simulation towards real-time control and optimization of products and production systems. This concept — often referred to as Digital Twin — enables real-time geometry assurance and allows moving from mass production to more individualized production. To master the challenges of a Digital Twin for Geometry Assurance the project Smart Assembly 4.0 gathers Swedish researchers within product development, automation, virtual manufacturing, control theory, data analysis and machine learning. The vision of Smart Assembly 4.0 is the autonomous, self-optimizing robotized assembly factory, which maximizes quality and throughput, while keeping flexibility and reducing cost, by a sensing, thinking and acting strategy. The concept is based on active part matching and self-adjusting equipment which improves geometric quality without tightening the tolerances of incoming parts. The goal is to assemble products with higher quality than the incoming parts. The concept utilizes information about individual parts to be joined (sensing), selects the best combination of parts (thinking) and adjust locator positions, clamps, weld/rivet positions and sequences (acting). The project is ongoing, and this paper specifies and highlights the infrastructure, components and data flows necessary in the Digital Twin in order to realize Smart Assembly 4.0. The framework is generic, but the paper focuses on a spot weld station where two robots join two sheet metal parts in an adjustable fixture.
5.	Carlson, Johan, 1972, et al. (author) Geometrical Inspection Point Reduction Based on Combined Cluster and Sensitivity Analysis 2003 In: ASME International Mechanical Engineering Congress & Exposition. Conference paper (peer-reviewed)
6.	Carlson, Johan, 1972, et al. (author) Multi-Fixture Assembly System Diagnosis Based on Part and Subassembly Measurement Data 2000 In: Proceedings of the ASME Design for Manufacture conference, September 10-13, Baltimore, Maryland, USA, DETC2000/DFM-14037. Conference paper (peer-reviewed)
7.	Carlson, Johan, 1972, et al. (author) Non-nominal path planning for robust robotic assembly 2013 In: Journal of Manufacturing Systems. - : Elsevier BV. - 0278-6125. ; 32:3, s. 429-435 Journal article (peer-reviewed)abstract In manufacturing and assembly processes it is important, in terms of time and money, to verify the feasi-bility of the operations at the design stage and at early production planning. To achieve that, veriﬁcationin a virtual environment is often performed by using methods such as path planning and simulation ofdimensional variation. Lately, these areas have gained interest both in industry and academia, however,they are almost always treated as separate activities, leading to unnecessary tight tolerances and on-lineadjustments.To resolve this, we present a novel procedure based on the interaction between path planning tech-niques and variation simulation. This combined tool is able to compute robust assembly paths forindustrial robots, i.e. paths less sensitive to the geometrical variation existing in the robot links, in itscontrol system, and in the environment. This may lead to increased productivity and may limit errorsources. The main idea to improve robustness is to enable robots to avoid motions in areas with highvariation, preferring instead low variation zones. The method is able to deal with the different geometricalvariation due to the different robot kinematic conﬁgurations. Computing variation might be a computa-tionally expensive task or variation data might be unavailable in the entire state space, therefore threedifferent ways to estimate variation are also proposed and compared. An industrial test case from theautomotive industry is successfully studied and the results are presented.
8.	Carlson, Johan, 1972, et al. (author) Non-nominal Path Planning of Assembly Processes 2005 In: 2005 ASME International Mechanical Engineering Congress & Exposition. Conference paper (peer-reviewed)
9.	Dagman, Andreas, 1976, et al. (author) Form division in automobile design - linking design and manufacturability 2006 In: Design 2006 9th International Design Conference, May 15-18, 2006, Dubrovnik, Croatia, Editor Marjanovic´, D. - 9536313790 ; 1, s. 495-502 Conference paper (peer-reviewed)
10.	Dahlström, Stefan, 1972, et al. (author) Practical Implications in Tolerance Analysis of Sheet Metal Assemblies 2005 In: 9th CIRP Seminar on Computer-Aided Tolerancing, April 10-12, 2005, Tempe, Arizona,USA. Conference paper (other academic/artistic)
11.	Edholm, Peter, 1974, et al. (author) Geometrical Coupling Analysis to Reduce Complete Assembly Line Complexity 2012 In: Proceedings of the ASME 2012 International Mechanical Engineering Congress & Exposition, IMECE2012, November 9-15, 2012, Houston, Texas, USA. - 9780791845196 ; 3:PARTS A, B, AND C, s. 89-96 Conference paper (peer-reviewed)abstract Modern assembly lines for mass production need to fulfill several important criteria. One of them is to produce products with high geometrical quality (small geometric variation). For sheet metal assemblies, focused on in this paper, it is a very complex process to achieve good geometrical quality due to the large number of assembly steps and the geometrical variation (tolerances) of the incoming parts. One “golden rule” for sheet metal assembly lines is to always reuse fixturing points (locators) throughout the whole assembly line to minimize the geometrical variation and also the complexity of root cause analysis.A new method to measure the complexity in an assembly line has been developed and also implemented in a commercial software for Computer Aided Tolerancing. This new tool not only demonstrates the “golden rule” but could also be used to ensure minimum geometrical complexity in assembly lines to ensure controlled production and high quality products.
12.	Edholm, Peter, 1974, et al. (author) Geometry robustness evaluation for common parts in platform architecture 2011 In: International Journal of Shape Modeling. - 0218-6543. ; 16:1&2, s. 129-150 Journal article (peer-reviewed)abstract In this paper, a platform geometrical sensitivity value for a part has been defined. Calculation and simulation methods have been defined and tested to be used in industrial “real-life” environments. Present calculation and simulation methods for assembly analysis in a single product development have been used as a basis. These methods have been further developed and adapted to suit product family development, or platforms. The assembly geometrical sensitivity value can be used to predict the effect of tolerance stacking without having data of tolerance sizes available. Using sensitivity calculation in each assembly step gives an indication of the risk of functional failure and non-fulfilled specifications due to tolerance stacking. The platform geometrical sensitivity value could be used for optimization of a part or an assembly, by means of geometric variation, not only for one product environment but also for a complete product family simultaneously. This decreases the risk of sub-optimization of part location and assembly concepts. Using the platform geometrical sensitivity value, the effect of tolerance stacking could be predicted for all assemblies conceptually and the result can be used to dimension specific part tolerances. All equations and mathematical connections are described in detail in the paper but, due to the mathematical complexity of 3D modeling, the calculations have been performed in a geometry simulation tool. Further research needs to be done to establish a proper working procedure using platform geometrical sensitivity value.
13.	Edholm, Peter, 1974, et al. (author) Geometry robustness evaluation for common parts in platform architecture 2010 In: Proceedings of the 8th International Symposium on Tools and Methods of Competitive Engineering, TMCE 2010. April 12–16, 2010, Ancona, Italy. - 9789051550603 ; 2, s. 1003-1012 Conference paper (peer-reviewed)abstract In this paper, a platform geometry goodness value for a part has been defined. Calculation and simulation methods have been defined and tested to be used in industrial "real-life" environments. Present calculation and simulation methods for assembly analysis in a single product development have been used as a basis. These methods have been further developed and adapted to suit product family development, or platforms. The platform geometry robustness value could be used for optimization of a part or an assembly, by means of geometric variation, not only for one product environment but also for a complete product family simultaneously. This decreases the risk of suboptimization of part location and assembly concepts. All equations and mathematical connections are described in detail in the paper but, due to the mathematical complexity of 3D modelling, the calculations have been performed in a geometry simulation tool. The proposed theories are based on previous work by Söderberg [7] presented mainly in section 2. The new contribution from this paper is mainly presented in sections 4.2 and 5.
14.	Edholm, Peter, 1974, et al. (author) Minimizing Geometric Variation in Multiusage Assembly Line by Geometrical Decoupling 2011 In: ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE2011, November 11-17, 2011, Denver, Colorado, USA. - 9780791854891 ; 3, s. 63-71 Conference paper (peer-reviewed)abstract Geometrical part robustness is today used as an engineering criterion in many manufacturing companies. The goal is to minimize the effect of geometrical variation by optimizing the locating schemes for the parts. Several methods and tools are today present to support geometrical robustness optimization for parts but also for assemblies. In this paper focus is on geometrical decoupling, which is one parameter of geometrical robustness, of the different locating strategies in a complete assembly line. A goodness value is proposed that describe the level of geometrical couplings in a complete assembly line together with the part robustness value. By calculating this goodness value it is possible to predict the geometrical sensitivity of a complete assembly line as well as predicting the risk of geometrical variation on the final product. To illustrate the definition of this goodness value, and also the purpose of calculating it, a case study is used where a part of a sheet metal assembly line is described. Several different scenarios (assembly concepts) are applied to clarify the meaning and to validate this definition of the goodness value. The case study shows that the goodness value gives a good indication of the level of geometrical couplings within the assembly line and that this value could be used to evaluate different assembly concepts, with their locating concepts, against each other. The goal is to have a more robust and also geometrically decoupled assembly line which the root cause analysis in production and also optimizes the geometrical quality minimizing the effect of geometrical variation of the final product from the plant.
15.	Forslund, Anders, 1982, et al. (author) Minimizing Weld Variation Effects Using Permutation Genetic Algorithms and Virtual Locator Trimming 2018 In: Proceedings of the ASME 2017 International Mechanical Engineering Congress and Exposition. ; 2 Conference paper (peer-reviewed)abstract The mass production paradigm strives for uniformity, and for assembly operations to be identical for each individual product. To accommodate geometric variation between individual parts in such a process, tolerances are introduced into the design. However, for certain assembly operations this method can yield suboptimal quality. For instance, in welded assemblies, geometric variation in ingoing parts can significantly impair quality. When parts misalign in interfaces, excessive clamping force must be applied, resulting in additional residual stresses in the welded assemblies. This problem may not always be cost-effective to address simply by tightening tolerances. Therefore, under new paradigm of mass customization, the manufacturing approach can be adapted on an individual level. Since parts in welded assemblies are not easily disassembled and reused, interchangeability is not a relevant concern. This recognition means that each welded assembly can be adapted individually for the specific idiosyncrasies of ingoing parts. This paper focuses on two specific mass customization techniques; permutation genetic algorithms to assemble nominally identical parts, and virtual locator trimming. Based on these techniques, a six-step method is proposed, aimed at minimizing thing effects of geometric variation. The six steps are nominal reference point optimization, permutation GA configuration optimization, virtual locator trimming, clamping, welding simulation, and fatigue life evaluation. A case study is presented which focuses on one specific product; the turbine rear structure of a commercial turbofan engine. Using this simulation approach, the effects of using permutation genetic algorithms and virtual locator trimming to reduce variation are evaluated. The results show that both methods significantly reduce seam variation. However, virtual locator trimming is far more effective in the test case presented, since it virtually eliminates seam variation. This can be attributed to the orthogonality in fixturing. Seam variation is linked to weldability, which in turn has significant impact on estimated fatigue life. These results underscore the potential of virtual trimming and genetic algorithms in manufacturing, as a means both to reduce cost and increase functional quality.
16.	Forslund, Anders, 1982, et al. (author) Minimizing weld variation effects using permutation genetic algorithms and virtual locator trimming 2018 In: Journal of Computing and Information Science in Engineering. - : ASME International. - 1530-9827 .- 1944-7078. ; 18:4 Journal article (peer-reviewed)abstract The mass production paradigm strives for uniformity, and for assembly operations to be identical for each individual product. To accommodate geometric variation between individual parts, tolerances are introduced into the design. However, this method can yield suboptimal quality. In welded assemblies, geometric variation in ingoing parts can significantly impair quality. When parts misalign in interfaces, excessive clamping force must be applied, resulting in additional residual stresses in the welded assemblies. This problem may not always be cost-effective to address simply by tightening tolerances. Therefore, under new paradigm of mass customization, the manufacturing approach can be adapted on an individual level. This paper focuses on two specific mass customization techniques: permutation genetic algorithms (GA) and virtual locator trimming. Based on these techniques, a six-step method is proposed, aimed at minimizing the effects of geometric variation. The six steps are nominal reference point optimization, permutation GA configuration optimization, virtual locator trimming, clamping, welding simulation, and fatigue life evaluation. A case study is presented, which focuses on the selective assembly process of a turbine rear structure of a commercial turbofan engine, where 11 nominally identical parts are welded into a ring. Using this simulation approach, the effects of using permutation GAs and virtual locator trimming to reduce variation are evaluated. The results show that both methods significantly reduce seam variation. However, virtual locator trimming is far more effective in the test case presented, since it virtually eliminates seam variation. These results underscore the potential of virtual trimming and GAs in manufacturing, as a means both to reduce cost and increase functional quality.
17.	GUNNARSDÓTTIR, SOFFÍA ARNÞRÚÐUR, 1987, et al. (author) Towards Simulation of Geometrical Effects of Laser Tempering of Boron Steel before Self-Pierce Riveting 2016 In: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 44, s. 304-309 Conference paper (peer-reviewed)abstract The automotive industry is continuously developing and finding new ways to respond to the incremental demands of higher safety standards and lower environmental impact. As an answer to weight reduction of vehicles, the combination of boron steel and composite material is being developed along with their joining process, self-pierce riveting. Boron steel is an ultra-high strength material that needs to be locally softened before the joining process. However, the joining process deforms the part. This paper investigates factors affecting the geometrical deformation during the tempering process and lists important phenomena that need to be included when simulating the tempering process.
18.	Jareteg, Cornelia, 1986, et al. (author) Geometry Assurance Integrating Process Variation with Simulation of Spring-in for Composite Parts and Assemblies 2014 In: Proc. of ASME 2014 International Mechanical Engineering Congress & Exposition. - 9780791846438 ; 2A Conference paper (peer-reviewed)abstract Geometrical variation and deviation in all manufacturing processes affect quality of the final product. Therefore geometry assurance is an important tool in the design phase of a new product. In the automotive and aviation industries where the use of composite parts is increasing drastically, new tools within variation simulations are needed. Composite parts tend to deviate more from nominal specification compared to metal parts. Methods to simulate the manufacturing process of composites have been developed before. In this paper we present how to combine the process variation simulation of composites with traditional variation simulations. The proposed method is demonstrated on a real complex subassembly, representing part of an aircraft wing-box. Since traditional variation simulation methods are not able to capture the spring-in and the special deviation behavior of composites,the proposed method adds a new feature and reliability to the geometry assurance process of composite assemblies.
19.	Jareteg, Cornelia, 1986, et al. (author) Geometry Assurance Integrating Process Variation with Simulation of Spring-In for Composite Parts and Assemblies 2016 In: Journal of Computing and Information Science in Engineering. - : ASME International. - 1530-9827 .- 1944-7078. ; 16:3 Journal article (peer-reviewed)abstract Copyright © 2016 by ASME.Geometrical variation and deviation in all the manufacturing processes affect the quality of the final product. Therefore, geometry assurance is an important tool in the design phase of a new product. In the automotive and aviation industries where the use of composite parts is increasing drastically, new tools within variation simulations are needed. Composite parts tend to deviate more from nominal specification compared to metal parts. Methods to simulate the manufacturing process of composites have been developed before. In this paper, we present how to combine the process variation simulation of composites with traditional variation simulations. The proposed method is demonstrated on a real complex subassembly, representing part of an aircraft wing-box. Since traditional variation simulation methods are not able to capture the spring-in and the special deviation behavior of composites, the proposed method adds a new feature and reliability to the geometry assurance process of composite assemblies.
20.	Jareteg, Cornelia, 1986, et al. (author) Variation simulation for composite parts and assemblies including variation in fiber orientation and thickness 2014 In: Procedia CIRP CATS 2014. 5th CATS 2014 - CIRP Conference on Assembly Technologies and Systems. - : Elsevier BV. - 2212-8271. ; 23, s. 235-240 Conference paper (peer-reviewed)abstract All manufacturing processes are afflicted by geometrical variation, which can lead to defect products. A simulation tool for geometry assurance analysis is therefore important in the design process. The use of composites has recently increased drastically, but there is still a lack of understanding about the effects of variation in such parts. A method for predicting variation in subassemblies, including variation in fiber orientation and ply thickness for composites is presented. The approach is demonstrated on an industrial case and finite element analysis is used to calculate the deformation. In particular, contribution from variation in material properties to the variation in critical points is analyzed. The results indicate that material uncertainties have a small impact on the geometric variation for the test case.
21.	Johansson, Björn, 1975, et al. (author) SUSTAINABLE PRODUCTION RESEARCH: AWARENESS, MEASURES AND DEVELOPMENT 2012 In: International Journal of Sustainable Development. - 1923-6662. ; 4:11, s. 95-104 Journal article (peer-reviewed)abstract This paper takes its standpoint in thehypothesis that awareness of sustainability is the keyto create sustainable products, and that this awarenessbegins already at research level. It describes thedevelopment and follow-up of a method forincreasing sustainability awareness in sustainableproduction research. Several activities were carriedout to increase the awareness. Firstly) workshopswith researchers and industry on sustainability.Secondly) development of measures based onliterature and interviews with researchers. Thirdly)monitoring of awareness through concept maps.Progress was evaluated by comparing the awarenessof the population when the project started in 2010,and then again in 2011. The results show that theparticipants had shifted their view from primaryemphasizing technology towards a more balancedview of sustainability where social aspects were moreoften taken into consideration. According to theconcept maps methodology, sustainability awarenessin the population increased with 25%.
22.	Kero, Timo, 1973, et al. (author) A Method for Improving Dental Crown Fit-Increasing the Robustness 2010 In: International Journal of Medicine and Medical Sciences. - 2073-2686. ; 1:3, s. 185-192 Journal article (peer-reviewed)abstract The introduction of mass-customization has enablednew ways to treat patients within medicine. However, theintroduction of industrialized treatments has also meant newobstacles. The purpose of this study was to introduce andtheoretically test a method for improving dental crown fit. The optimization method allocates support points in order to check the final variation for dental crowns. Three different types of geometries were tested and compared. The three geometries were also divided into three sub-geometries: Current method, Optimized method and Feasible method. The Optimized method, using the whole surface for support points, provided the best results. The results support the objective of the study. It also seems that the support optimization method can dramatically improve the robustness of dental crown treatments.
23.	Kero, Timo, 1973, et al. (author) Process Optimization Regarding Geometrical Variation and Sensitivity Involving Dental Drill- and Implant-Guided Surgeries 2007 In: International Journal of Biomedical Sciences. ; 2:4, s. 237-243 Journal article (peer-reviewed)abstract Within dental-guided surgery, there has been a lack of analytical methods for optimizing the treatment of the rehabilitation concepts regarding geometrical variation. The purpose of this study is to find the source of the greatest geometrical variation contributor and sensitivity contributor with the help of virtual variation simulation of a dental drill- and implant-guided surgery process using a methodical approach. It is believed that lower geometrical variation will lead to better patient security and higher quality of dental drill- and implant-guided surgeries. It was found that the origin of the greatest contributor to the most variation, and hence where the foci should be set, in order to minimize geometrical variation was in the assembly category (surgery). This was also the category that was the most sensitive for geometrical variation.
24.	Kero, Timo, 1973, et al. (author) VARIATION SIMULATION TOOLKIT FOR VIRTUAL VERIFICATION OF DENTAL DRILL-GUIDED SURGERIES 2007 In: III INTERNATIONAL CONGRESS ON COMPUTATIONAL BIOENGINEERING. - 9789806939103 ; , s. 333-338 Conference paper (peer-reviewed)abstract . Guided surgeries are becoming common in modern dental industry, and are used for a variety of treatments. The purpose of this study is to apply a dental software toolkit for virtual simulation of dental drill guided surgery. The hypothesis is that if a virtual simulation of dental drill guided surgery can be done, then the preplanned surgery can also be verified before the actual surgery. The dental drill guided concept is a planning and surgical implementation system that enables surgery with the help of a drill guide based on planning supported by computer aided design tools and CT-scan. The variation simulation predicts the final positions of the pre-defined critical production dimension at the apical part of the fixture. The results are based on variation simulation of two dental drill guided surgeries: Maxilla, seven implants and Mandible, nine implants. Maxilla resulted in a safe surgery while Mandible needed an optimization of the implant positions before the surgery. By analyzing the results, it was also found that both plans could be optimized in order to minimize the geometrical variation. Finally, it was found that the method used was suitable for predicting guided surgeries to achieve safer treatments.
25.	Lindau, Björn, 1961, et al. (author) Aspects of fixture clamp modeling in non-rigid variation simulation of sheet metal assemblies 2013 In: Proceedings of ASME 2013 International Mechanical Engineering Congress and Exposition. - 9780791856192 ; 2 B Conference paper (peer-reviewed)abstract Today there is an increased use of CAT-tools (Computer Aided Tolerancing) within the automotive industry. These kinds of virtual tools are getting increasingly important to ensure robust solutions as early as possible in the development processes, to minimize the use of test series and thereby reduce lead times and development costs.This paper focuses upon modeling of fixture locating scheme and the aspect of how many degrees of freedoms (DoF) a clamp actually locks. The clamps control part movement allowance, and it is of importance to investigate the influence from the friction forces between the clamping units and the fixated parts. Simulated forces in non-steering directions are compared to friction forces measured in real body shop production equipment. The non-rigid variation simulations have been performed based upon the Method of Influence Coefficients (MIC) and additional functionality for contact modeling, force estimation and weld sequence analysis.There are a variety of alternatives of how to build the simulation model and the made choices obviously influence the simulation results. The industrial case study shows significant differences in both estimated in-plane forces and geometric results after springback for different choices of modeling alternatives. It demonstrates the difficulties in taking the friction force into consideration in variation simulation of sheet metal assembly processes.
26.	Lindau, Björn, 1961, et al. (author) Body in White Geometry Measurements of Non-Rigid Components: a Virtual Perspective 2012 In: Proceedings of the ASME 2012 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference, IDETC/CIE 2012. - 9780791845042 ; 5, s. 497-505 Conference paper (peer-reviewed)abstract Increased use of virtual assembly tools within automotive industry places new demands on available geometry information. Unfortunately, the measurement results of non-rigid components depend heavily on the locating schemes used in the measurement fixtures. Non-rigid component measurements are mostly performed in an over-constrained condition, describing the shapes of the parts as presented in assembly processes or as mounted on nominal products. With these kinds of measurements, there is an information loss regarding the actual springback shapes in the stored historical geometry data. Knowledge about the components' shapes after springback is vital for virtual non-rigid fault propagation analysis.The objective of this paper is to show the possibilities for presenting the measurement results of components as they were over-constrained, even if the parts were measured in a constrained condition (in practice limited constrained). The aim is to minimize the information loss, to spare measurement resources and to allow for better use of inspection data in assembly simulations. Predicted over-constrained measurement results in the presented cases bear reasonably good resemblance to measured over-constrained conditions when the two are compared. The ability to present both constrained and over-constrained results from one measurement setup will spare measurement resources and improve conditions for further virtual analysis and support. Furthermore, the presented cases verify the use of Method of Influence Coefficients (MIC) in the clamping step.
27.	Lindau, Björn, 1961, et al. (author) Challenges Moving from Physical into Virtual Verification of Sheet Metal Assemblies 2015 In: Proceedings - ASME 2015 International Mechanical Engineering Congress and Exposition, IMECE 2015, Houston, United States, 13-19 November 2015. - 9780791857366 ; 2B-2015 Conference paper (peer-reviewed)abstract Within industry there is an established need for enhancedvirtual tools and methods to improve product tolerance setting and conditions for successful manufacturing of non-rigid assemblies. A significant amount of research has been performed in the area, but there is still a need to find efficient working methods and the right preconditions in practice. This paper reports experiences and findings made during recently performed virtual matching and trimming of sheet metals in a real automotive industrial setting. A case is presented, demonstrating the possible use of the Computer Aided Tolerance(CAT) tool RD&T, (Robust Design & Tolerancing), in order to predict the geometric behavior of non-rigid parts when assembled. Scanned parts are used as input and the analysis is performed using the described virtual platform instead of physical type-bound rigging equipment traditionally used for conflict, gap and final springback analysis. The proposed working procedure, and the reasons behind it, are presented. The need of additional radical and incremental innovations is broughtinto light, in order to make earlier predictions in the product realization process. Furthermore, it is discussed whether the necessary changes in working procedures can impose innovation barriers in the future.
28.	Lindau, Björn, 1961, et al. (author) Efficient Contact Modeling in Nonrigid Variation Simulation 2016 In: Journal of Computing and Information Science in Engineering. - : ASME International. - 1530-9827 .- 1944-7078. ; 16:1 Journal article (peer-reviewed)abstract Virtual tools and methods are becoming increasingly important in order to predict the geometric outcome in early phases of the product realization process. Method of influence coefficients (MIC) in combination with Monte Carlo simulation (MCS) is a well-known technique that can be used in non-rigid variation simulation. In these simulations, contact modeling is important to ensure a correct result. Contact modeling simulates how mating surfaces are hindered from penetrating each other, giving rise to contact forces that contribute to the deformation of the parts when assembled and the final shape of the subassembly after springback. These contact forces have to be taken into consideration in each MCS-iteration. To secure reasonable response times, the calculation of thecontact forces needs to be fast. In this paper, we formulate a quadratic programming(QP) problem to solve the contact problem. The case studies presented show that node-based contact modeling can be efficiently solved through QP.
29.	Lindau, Björn, 1961, et al. (author) Method for Handling Model Growth in Nonrigid Variation Simulation of Sheet Metal Assemblies 2014 In: Journal of Computing and Information Science in Engineering. - : ASME International. - 1530-9827 .- 1944-7078. ; 14:3 Journal article (peer-reviewed)abstract In automotive industry, virtual tools and methods are becoming increasingly important to ensure robust solutions as early as possible in the development processes. Today, techniques exist that combine Monte Carlo simulations (MCS) with finite element analysis (FEA) to capture the part's nonrigid geometric behavior when predicting variation in a critical dimension of a subassembly or product. A direct combination of MCS with full FEA requires high computational power and the calculations tend to be very time consuming. To overcome this problem, the method of influence coefficients (MIC) was proposed by Liu and Hu in the late 1990s. This well-known technique has since then been used in several studies of nonrigid assemblies and sensitivity analysis of the geometric fault propagation in multistation assembly processes. In detailed studies of the resulting subassemblies and levels of variation, functionality for color plots and the ability to study the geometry in arbitrary sections are desired to facilitate the analysis of the simulation results. However, when including all part nodes in combination with methods for contact and spot weld sequence modeling, the required sensitivity matrices grow exponentially. In this paper, a method is proposed, describing how traditional MIC calculations can be combined with a separate detailed subassembly analysis model, keeping the model sizes down and thus facilitating detailed studies of larger assembly structures.
30.	Lindau, Björn, 1961, et al. (author) Statistical shape modeling in virtual assembly using PCA-technique 2012 In: Technologies and Systems for Assembly Quality, Productive and Customization; ed. by Jack S. Hu; Proceedings of the 4th CIRP Conference on Assembly Technologies and Systems May 21 - 22, 2012, Ann Arbor, Michigan, USA. - 9780615640228 ; , s. 119 - 124 Conference paper (peer-reviewed)abstract The use of virtual assembly tools is one way to understand and improve the geometric product tolerance setting and the conditions for successful manufacturing. Recent developments enable consideration to be given to the deformability of parts when joined. However, in order to produce reliable results, the geometric faults of the mating surfaces must be correctly assumed. In this paper, statistical shape models built on the Principal Component Analysis-technique are proposed to be used to describe the part variation. A generalized model is presented. Furthermore, the underlying intentions and implications are discussed. The method is exemplified using the tool RD&T. In the presented case, a non-rigid sheet metal assembly is modeled and distorted to create a set of sample shapes from which a statistical model is built. In the result, the statistic representation bears a good resemblance to the nominal distorted model when the two are compared.
31.	Lindau, Björn, 1961, et al. (author) Statistical shape modeling in virtual assembly using PCA-technique 2013 In: Journal of Manufacturing Systems. - : Elsevier BV. - 0278-6125. ; 32:3 (speical issue), s. 456-463 Journal article (peer-reviewed)abstract The use of virtual assembly tools is one way to understand and improve the geometric product tolerance setting and the conditions for successful manufacturing. Recent developments enable consideration to be given to the deformability of parts (single components or subassemblies) when joined. In order to produce reliable results, the geometric deviations of the mating surfaces must be correctly assumed. In this paper, statistical shape models built on the Principal Component Analysis-technique (PCA) are proposed to be used to describe the part variation. A generalized model is presented and the underlying intentions and implications are discussed. It is demonstrated how the PCA-technique can be applied onbigger structures. The method is exemplified using the software RD&T. In the presented case, a non-rigid sheet metal assembly is modeled and distorted to create a set of sample shapes from which a statistical model is built. In the result, the statistic representation bears a good resemblance to the distorted nominal model when the two are compared.
32.	Lindau, Björn, 1961, et al. (author) Using Forming Simulation Results In Virtual Assembly Analysis 2012 In: Proceedings of the ASME 2012 International Mechanical Engineering Congress & Exposition, IMECE2012. - 9780791845196 ; 3:PARTS A, B, AND C, s. 31-38 Conference paper (peer-reviewed)abstract In Car Body Assembly Shops, Body in White (BIW), non-rigid sheet metal panels are assembled into car bodies. Depending upon the achieved degree of robustness in part and tool design, the produced items tend to deviate more or less from their nominal specifications. Catching eventual non-robust solutions early on in the development phases is important to minimize time-consuming, expensive testing and trimming activities late in the development- and industrialization phases. To meet these demands, there is today an increased use of virtual forming and assembly tools within the automotive industry. Significant amounts of research have been performed in the area of forming and assembly simulations, but there is still a need to find efficient working methods.This study has focused upon how forming simulation results can be used in virtual assembly analysis. The predicted springback shapes (offset and variation) of the stamped panels are used in the assembly simulation to study the effects of the part variation when assembled, producing a sub-assembly. The method used is described, and the simulation results are reported. The case shows the potential of using forming simulation results in virtual assembly analysis. Furthermore, the strength of using the Principal Component Analysis technique to describe the part variation in assembly simulations is shown.
33.	Lindau, Björn, 1961, et al. (author) Virtual fixturing: Inspection of a non-rigid detail resting on 3-points to estimate free state and over-constrained shapes 2020 In: ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE). ; 2B-2020 Conference paper (peer-reviewed)abstract When the geometry of a non-rigid part or pre-assembly is measured fully clamped (over-constrained) in a measurement fixture, the spring-back information and influence from gravity forces are usually lost in the collected data. From the 3D-measurement data, it is hard to understand built in tensions, and the detail's tendency to bend, twist and warp after release from the measurement fixture. These effects are however important to consider when analyzing each part´s contribution to geometrical deviations after assembly. In this paper a method is presented, describing how free state shape and over-constrained shape of a measured detail can be virtually estimated starting from acquired data when the part or the preassembly is resting on only 3-points. The objective is to minimize the information loss, to spare measurement resources and to allow for a wider use of the collected data, describing the geometry. Part stiffnesses, part to part contacts and gravity effects are considered in the proposed method. The method is based on 3D-scanning techniques to acquire the shape of the measured object. Necessary compensations for part stiffnesses and gravity effects are based upon Finite Element Analysis (FEA) and the Method of Influence Coefficients (MIC). The presented method is applied to an industrial case to demonstrate its potential. The results show that estimated over-constrained shapes show good resemblance with measurements acquired when part is over-constrained in its measurement fixture.
34.	Lindkvist, Lars, 1963, et al. (author) Computer Aided Tolerance Chain and Sensitivity Analysis 2003 In: Journal of Engineering Design. ; 14:1, s. 17-39 Journal article (peer-reviewed)
35.	Lindkvist, Lars, 1963, et al. (author) Concurrent Robust Product and Process Design 1999 In: Proccedings of the ASME Design Automation Conference, September 12-15, Las Vegas, Nevada, USA, DETC99/DAC-8687. Conference paper (peer-reviewed)
36.	Lindkvist, Lars, 1963, et al. (author) Tool for Assembly Locating Scheme Definition 2000 In: Proceedings of the 26th ASME Design Automation Conference, September 10-13, Baltimore, MAryland, USA, DETC2000/DAC-14498. Conference paper (peer-reviewed)
37.	Lindkvist, Lars, 1963, et al. (author) Variation Analysis Toolbox for Non-Nominal Path Planning for Industrial Robots 2007 In: ASME IMECE 2007, November 11-15, 2007, Seattle, Washington, USA. Conference paper (peer-reviewed)
38.	Lindkvist, Lars, 1963, et al. (author) Virtual Locator Trimming in Pre-Production-Rigid and Non-Rigid Analysis 2005 In: 2005 ASME International Mechanical Engineering Congress and Exposition, IMECE 2005; Orlando, FL; United States; 5 November 2005 through 11 November 2005. - 9780791842232 ; 16-1, s. 561-568 Conference paper (peer-reviewed)abstract In pre-production, during assembly of newly produced components geometrical deviations, caused by form errors of the parts, are discovered that can cause either functional or esthetical problems. One commonly used way of solving this is to reposition the components by adjusting their locators, also known as trimming. Traditionally this is done by assembling a number of components, measuring the deviations to surrounding parts, adjusting the locator points, reassembling the components and measuring the result. This is repeated until the result is satisfactory, and is a quite time and effort consuming activity. This paper presents a method and a tool that simplifies this process. Based on inspection data from the initial components all trimming activities are performed in the computer tool presented. After the locators are adjusted, the result is presented directly, which eliminates the need for physical inspection in order to verify the result of the trimming. The presented tool also includes optimization of the trimming. By formulating the problem of minimizing the geometrical deviations as a linear least square problem a general optimization package can be used. The optimization handles both boundaries on the allowed trimming and weighting of the different inspection features. By using the method of influence coefficients, also compliant (non-rigid) components can be handled.
39.	Lorin, Samuel C, 1983, et al. (author) COMBINING VARIATION SIMULATION WITH THERMAL EXPANSION FOR GEOMETRY ASSURANCE 2012 In: Proceedings of the ASME 2012 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference IDETC/CIE 2012. - 9780791845042 ; 5, s. 477-485 Conference paper (peer-reviewed)abstract In every set of assembled products there are geometrical variation and deviations from nominal dimensions. This can lead to products that are difficult to assemble or products not fulfilling functional or aesthetical requirements. In several industries variation simulation is used to predict assembly variation in the development phase. This analysis is usually done under the condition of room temperature only. However, for some materials, such as plastics, the thermal expansion can be significant in the intended environmental span of the product. In an assembly, this can lead to thermal stresses and parts that will deform. To avoid this problem, locating schemes need to be designed to allow for the right behavior while exposed to varying temperatures. In this work the effect of thermal expansion is studied in the context of variation simulation. A virtual tool for this end is also presented. An example from the automotive industry is used where the combined effect of thermal expansion and assembly variation is analyzed. It is shown that it may not be sufficient to simply add the result from thermal analysis to assembly variation. Hence, to assure the geometrical and functional quality of assembled products, during its use, variation simulations need to be combined with thermal stresses.
40.	Lorin, Samuel C, 1983, et al. (author) Combining Variation Simulation With Thermal Expansion Simulation for Geometry Assurance 2013 In: Journal of Computing and Information Science in Engineering. - : ASME International. - 1530-9827 .- 1944-7078. ; 13:3, s. artikel nr 031007- Journal article (peer-reviewed)abstract In every set of assembled products, there are geometrical variations and deviations from nominal dimensions. This can lead to products that are difficult to assemble or products not fulfilling functional or aesthetical requirements. In several industries, variation simulation is used to predict assembly variation in the development phase. This analysis is usually done under room temperature conditions only. However, for some materials, such as plastics, the thermal expansion can be significant in the intended environmental span of the product. In an assembly, this can lead to thermal stresses and parts that will deform. To avoid this problem, locating schemes need to be designed to allow for the right behavior while exposed to varying temperatures. In this work, the effect of thermal expansion is studied in the context of variation simulation. A virtual tool for this purpose is also presented. Two case studies from the automotive industry are used where the combined effect of thermal expansion and assembly variation is analyzed. It is shown that it may not be sufficient to simply add the result from thermal analysis to assembly variation. Hence, to assure the geometrical and functional quality of assembled products during usage variation simulations need to be combined with thermal expansion simulation.
41.	Lorin, Samuel C, 1983, et al. (author) Efficient Compliant Variation Simulation of Spot-Welded Assemblies 2019 In: Journal of Computing and Information Science in Engineering. - : ASME International. - 1530-9827 .- 1944-7078. ; 19:1 Journal article (peer-reviewed)abstract © 2019 by ASME. During product development one important aspect is the geometric robustness of the design. This is due to the fact that all manufacturing processes lead to products with variation. Failing to properly account for the variability of the process in the design phase may lead to expensive redesign. One important tool during the design phase in many industries is variation simulation, which makes it possible to predict and optimize the geometric quality of the design. However, despite the increase in computer power, calculation time is still an obstacle for the wider use of variation simulation. In this article, we propose a new method for efficient compliant variation simulation of spot-welded sheet metal assemblies. The method is exact, and we show that the method leads to time savings in simulation of approximately 40-50% compared to current state-of-the-art variation simulation.
42.	Lorin, Samuel C, 1983, et al. (author) Efficient variation simulation of spot-welded assemblies 2018 In: ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE). - 9780791852019 ; 2 Conference paper (peer-reviewed)abstract Variation simulation for assembled products is one important activity during product development. Variation simulation enables the designer to understand not only the features of the nominal product but also how uncertainty will affect production, functions and the aesthetic properties of the final product. For parts that are able to deform during assembly, compliant variation simulation is needed for accurate prediction. For this the Finite Element Method (FEM) is used. Despite many effective efforts to decrease simulation times for compliant variation simulation, simulation time is still considered an obstacle for full scale industrial use. In this paper, a new formulation for compliant variation simulation of assemblies that are joined in sequential spot-welding will be presented. In this formulation the deformation in the intermediate springback steps during the simulation of a spot-weld sequence do not have to be calculated. This is one of the most time consuming steps in sequential spot-welding simulation. Furthermore, avoiding the intermediate springback calculation will reduce the size of memory of the computer models since the number of sensitivity matrices is reduced. The formulation is implemented using the latest developments in compliant variation simulation, that is the Method of Influence Coefficients (MIC) where the Sherman-Morrison-Woodbury-formula is used to update the resulting sensitivity matrices and the contact- and weld forces are solved using a Quadratic Programme (QP). Industrial cases are used to demonstrate the reduced simulation time. It is believed that the reduction in simulation times will have future implications on sequence optimization for spot-welded assemblies.
43.	Lorin, Samuel C, 1983, et al. (author) Non-rigid variation simulation using the Sherman-Morrison-Woodbury formulas 2017 In: PROCEEDINGS OF THE ASME INTERNATIONAL MECHANICAL ENGINEERING CONGRESS AND EXPOSITION. - 9780791858356 ; 2 Conference paper (peer-reviewed)abstract Variation simulation is one important activity during early product development. It is used to simulate the statistical distribution of assemblies or sub assemblies in intended manufacturing process to assure that assembly, function and aesthetical properties comply with the requirements set. In non-rigid variation simulation, components or sub assemblies can deform during assembly. To simulate non-rigid variation the Method of Influence Coefficient (MIC) is typically used. Solving the necessary sensitivity matrices used by MIC is time consuming. In this article we will apply the Sherman-Morrison and Woodbury formula (SMW) for updating the sensitivity response in the different assembly steps. It is shown that SMW can lead to substantial saving in computation time, when compared to the standard MIC.
44.	Lorin, Samuel C, 1983, et al. (author) On the robustness of the volumetric shrinkage method in the context of variation simulation 2014 In: Proceedings of the ASME 2014 International Mechanical Engineering Congress & Exposition. - 9780791846438 ; 2A Conference paper (peer-reviewed)abstract Welding induces high temperatures that cause residual stresses and strains in the welded structure. With a welding simulation, these stresses and strains may be predicted. A full simulation implies performing a transient thermal and a quasi-static mechanical analysis. These analyses usually involve a large number of time steps that leads to long simulation times. For welding distortions, there are approximate methods that require considerably less time. This is useful when simulatinglarge structures or for analyses that use an iterative approach common in optimization or variation simulation. One of these methods is volumetric shrinkage, which has been shown to give reasonable results. Here it is assumed that the driving force in welding distortion is the contraction of the region that has been melted by the weld. In volumetric shrinkage, the nodes that are inside the melted region are assigned a uniform temperature and the distortion is calculated using elastic volumetric shrinkage. Although this method has been shown to give reasonable predictions, we will show that it is sensitiveto small perturbations, which is an essential part in variation simulation. We also propose a modification of the volumetric shrinkage method that addresses this lack of robustness; instead of defining the melted region by applying a uniform temperature to the nodes inside the zone, we formulate an optimization problem that finds a temperature distribution such that the local melted volume is preserved. A case study with application to variation simulation has been used to elicit the proposed method.
45.	Lorin, Samuel C, 1983, et al. (author) SIMULATING PART AND ASSEMBLY VARIATION FOR INJECTION MOLDED PARTS 2012 In: Proceedings of the ASME 2012 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference IDETC/CIE 2012. - 9780791845042 ; 5, s. 487-496 Conference paper (peer-reviewed)abstract Final geometrical variation and deviation have often a negative effect on product functionality and aesthetics. In the automotive industry, design concepts are being evaluated and optimized to withstand variation in the early phase of product development. For this end, simulation tools are employed. Input to these simulations is requirements on parts and fixtures or measurements from previously manufactured parts. In the case of plastic components, parts are often manufactured in the injection molding process. Here, different materials and process settings can make it difficult to predict deviation and variation based on similar parts. In order to perform accurate assembly variation simulation, part variation simulation need, therefore, to be included. In this work a methodology is presented to simulate part and assembly variation, due to process noise, for plastic components manufactured in the injection molding process. The methodology is based on designed computer experiment and utilizes the concept of geometrical covariance and principal component analysis to relate process noise to variation patterns using regression analysis. Part and assembly variation are simulated combined using the distribution of these variation patterns.The model used for part variation simulation has been verified against commercial injection molding software showing good agreement. An industrial case from the automotive industry is used to elicit the proposed methodology.
46.	Lorin, Samuel C, 1983, et al. (author) Simulation of non-nominal welds by resolving the melted zone and its implication to variation simulation 2014 In: Proceeding of the ASME 2014 International Design Engineering Technical Conference & Computers and Information in Engineering Conference. ; 4 Conference paper (peer-reviewed)abstract The prediction of geometric variation and its consequences is one important aspect of product development. For welded assemblies it has been shown that positioning errors of the parts prior to welding affects the weld-induced distortion. Therefore, to accurately predict geometric variation in welded assemblies, variation simulation and welding simulation need to be performed in combination. This is usually a very time consuming task, and therefore, the relatively fast SCV-method is utilized. This method is used to calculate welding distortion when positioning errors are present and it consists of the fol-lowing three steps: 1) a steady state computation of the thermal distribution during welding, 2) the melted zone along the full joint is encapsulated by sweeping a two-dimensional convex hull along the weld gun path, and 3) a uniform temperature is applied to all nodes inside this zone. The two-dimensional convex hull is computed so that when swept along the weld path, it will encapsulate the melted zone from the steady state temperature computation. The weld-induced distortion is obtained from the elastic volumetric shrinkage. In this article the focus is on the ﬁrst step in this method; the temperature distribution computation. The positioning error can cause the connecting parts to have varying distances to each other at the joint, which cause the melted region to vary along the weld path. Therefore, it is not sufﬁcient to capture the steady state temperature distribution at only one location. Depending on the geometry surrounding the weld path, several locations may be needed. In this new approach, the two-dimensional convex hull that is to be swept along the weld path, can vary along the weld path, and is computed from an interpolation of the multiple two-dimensional convex hulls obtained from the multiple steady state temperature computations. A comparison of the melted region using transient temperature calculation, a single steady state temperature calculation and this new approach has been made. Furthermore, the implication on distortion calculation has been studied.
47.	Lorin, Samuel C, 1983, et al. (author) Variation Simulation of Stresses Using the Method of Influence Coefficients 2014 In: Journal of Computing and Information Science in Engineering. - : ASME International. - 1530-9827 .- 1944-7078. ; 14:1, s. 7- Journal article (peer-reviewed)abstract In every manufacturing situation there are geometric deviations leading to variation in properties of the manufactured products. Variation affects the manufacturability, functions and aesthetics of the products. Therefore, a number of methods and tools have been developed during the last 20 yr in order to assure the geometric quality and to minimize the effect of variability. These methods and tools have mainly been developed for rigid-or sheet metal components. Plastics or composites have been an increasingly popular material due to their flexible mechanical properties and their relative ease in manufacturing. However, their mechanical properties are introducing challenges that have not often been addressed in the process of geometry assurance. One challenge is to assure that the stresses introduced, as a consequence of non-nominal assembly, are kept well below critical limits during the conditions of use. In this paper, we are proposing the use of the method of influence coefficients (MIC) to simulate the distribution of von Mises stresses in assembled components. This method will be compared to the more flexible but computationally much heavier direct Monte Carlo (DMC) method, which is not suitable for variation simulation due to the large number of runs required for statistical inference. Two industrial case studies are presented to elicit the need of the proposed method.
48.	Lorin, Samuel C, 1983, et al. (author) Variation Simulation of Stresses using the Method Of Influence Coefficients 2014 In: Proceedings of the ASME 2013 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. - 9780791855911 ; 4 Conference paper (peer-reviewed)abstract In every manufacturing situation there are geometric deviations leading to variation in properties of the manufactured products. Variation affects the manufacturability, functions and aesthetics of the products. Therefore, a number of methods and tools have been developed during the last 20 years in order to assure the geometric quality and to minimize the effect of variability. These methods and tools have mainly been developed for rigid bodies or sheet metal components.Plastics or composites have been an increasingly popular material due to their flexible mechanical properties and their relative ease in manufacturing. However, their mechanical properties are introducing challenges that have not often been addressed in the process of geometry assurance. One challenge is to assure that the stresses introduced, as a consequence of non-nominal assembly in the positioning system, are kept well below critical limits during the conditions of use.In this paper, we are proposing the use of the method of influencing coefficients (MIC) to simulate the distribution of von Mises stresses in assembled components. This method will be compared to the more flexible but computationally much heavier Direct Monte Carlo (DMC) method, which is not suitable for variation simulation due to the large number of runs required for statistical inference.Two industrial case studies are presented to elicit the need of the proposed method.
49.	Lorin, Samuel C, 1983, et al. (author) Variation Simulation of Welded Assemblies Using a Thermo-Elastic Finite Element Model 2014 In: Journal of Computing and Information Science in Engineering. - : ASME International. - 1530-9827 .- 1944-7078. ; 14:3, s. Art. no. 031003- Journal article (peer-reviewed)abstract Every series of manufactured products has geometric variation. Variation can lead to products that are difficult to assemble or products not fulfilling functional or aesthetic requirements. In this paper, we will consider the effects of welding in variation simulation. Earlier work that has been combining variation simulation with welding simulation has either applied distortion based on nominal welding conditions onto the variation simulation result, hence loosing combination effects, or has used transient thermo-elasto-plastic simulation, which can be very time consuming since the number of runs required for statistical accuracy can be high. Here, we will present a new method to include the effects of welding in variation simulation. It is based on a technique that uses a thermo-elastic model, which previously has been shown to give distortion prediction within reasonable accuracy. This technique is suited for variation simulations due to the relative short computation times compared to conventional transient thermo-elasto-plastic simulations of welding phenomena. In a case study, it is shown that the presented method is able to give good predictions of both welding distortion and variation of welding distortions compared to transient thermo-elasto-plastic simulations.
50.	Lorin, Samuel C, 1983, et al. (author) Variation simulation of welded assemblies using a thermo-elastic finite element model 2013 In: Proceedings of the ASME 2013 International Mechanical Engineering Congress & Exposition IMECE2013. - 9780791856185 ; 2 A Conference paper (peer-reviewed)abstract Every series of manufactured products has geometric variation. Variation can lead to products that are difficult to assemble or products not fulfilling functional or aesthetical requirements. In this paper, we will consider the effects of welding in variation simulation. Earlier work that have been combining variation simulation with welding simulation have either applied distortion based on nominal welding conditions onto the variation simulation result, hence loosing combination effects, or have used transient thermo-elasto-plastic simulation, which can be very time consuming since the number of runs required for statistical accuracy can be high. Here, we will present a new method to include the effects of welding in variation simulation. It is based on a technique that uses a thermo-elastic model, which previously has been shown to give distortion prediction within reasonable accuracy. This technique is suited for variation simulations due to the relative short computation times compared to conventional transient thermo-elasto-plastic simulations of welding phenomena. In a case study, it is shown that the presented method is able to give good predictions of both welding distortion and variation of welding distortions compared to transient thermo-elasto-plastic simulations.

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