Jacobian-based modeling of dispersions affecting pre-defined functional requirements of mechanical assemblies

2003 ◽  
Author(s):  
P. Lafond ◽  
L. Laperriere
Keyword(s):  
Functional Requirements ◽  
Mechanical Assemblies

Statistical Tolerance Analysis of Over-Constrained Mechanical Assemblies With Form Defects Considering Contact Types

2019 ◽  
Vol 19 (2) ◽  
Author(s):  
Edoh Goka ◽  
Lazhar Homri ◽  
Pierre Beaurepaire ◽  
Jean-Yves Dantan
Keyword(s):  
Tolerance Analysis ◽  
Optimization Methods ◽  
Optimization Techniques ◽  
Behavior Modeling ◽  
Functional Requirements ◽  
Mechanical Assembly ◽  
Mechanical Assemblies ◽  
Statistical Tolerance ◽  
The Individual ◽  
Statistical Tolerance Analysis

Tolerance analysis aims toward the verification impact of the individual tolerances on the assembly and functional requirements of a mechanism. The manufactured products have several types of contact and are inherent in imperfections, which often causes the failure of the assembly and its functioning. Tolerances are, therefore, allocated to each part of the mechanism in purpose to obtain an optimal quality of the final product. Three main issues are generally defined to realize the tolerance analysis of a mechanical assembly: the geometrical deviations modeling, the geometrical behavior modeling, and the tolerance analysis techniques. In this paper, a method is proposed to realize the tolerance analysis of an over-constrained mechanical assembly with form defects by considering the contacts nature (fixed, sliding, and floating contacts) in its geometrical behavior modeling. Different optimization methods are used to study the different contact types. The overall statistical tolerance analysis of the over-constrained mechanical assembly is carried out by determining the assembly and the functionality probabilities based on optimization techniques combined with a Monte Carlo simulation (MCS). An application to an over-constrained mechanical assembly is given at the end.

Geometric tolerance analysis through Jacobian model for rigid assemblies with translational deviations

2016 ◽  
Vol 36 (1) ◽  
pp. 72-79 ◽  
Author(s):  
Wilma Polini ◽  
Andrea Corrado
Keyword(s):  
Tolerance Analysis ◽  
Geometric Error ◽  
Functional Requirements ◽  
Content Type ◽  
Geometric Tolerances ◽  
Mechanical Assemblies ◽  
Geometric Deviations ◽  
2D And 3D ◽  
Practical Implications

Purpose – The purpose of this paper is to carry out a tolerance analysis with geometric tolerances by means of the Jacobian model. Tolerance analysis is an important task to design and to manufacture high-precision mechanical assemblies; it has received considerable attention by the literature. The Jacobian model is one of the methods proposed by the literature for tolerance analysis. The Jacobian model cannot deal with geometric tolerances for mechanical assemblies. The geometric tolerances may not be neglected for assemblies, as they significantly influence their functional requirements. Design/methodology/approach – This paper presents how it is possible to deal with geometric tolerances when a tolerance analysis is carried out by means of a Jacobian model for a 2D and 3D assemblies for which the geometric tolerances applied to the components involve only translational deviations. The three proposed approaches modify the expression of the stack-up function to overcome the shortage of Jacobian model that the geometric error cannot be processed. Findings – The proposed approach has been applied to a case study. The results of the case study show how, when a statistical approach is implemented, the Jacobian model with the three developed methods gives results very similar to those due to other models of the literature, such as vector loop and variational. Research limitations/implications – In particular, the proposed approach may be applied only when the applied geometrical tolerances involve translational variations in 3D assemblies. Practical implications – Tolerance analysis is a valid tool to foresee geometric interferences among the components of an assembly before getting the physical assembly. It involves a decrease of the manufacturing costs. Originality/value – The original contribution of the paper is due to three methods to make a Jacobian model able to consider form and geometric deviations.

Tolerances Modeling in Assemblies: An Approach Based on Graphs

2014 ◽  
Vol 902 ◽  
pp. 378-384
Author(s):  
R.L. Avila Rondón ◽  
R. Pérez Rodríguez ◽  
A. Cordovés García ◽  
R.P. Avila Alfaro ◽  
Z. Mendoza Núñez ◽  
...  
Keyword(s):  
Computer Aided Design ◽  
Mechanical Design ◽  
Tolerance Analysis ◽  
Functional Requirements ◽  
Mechanical Assemblies ◽  
Decisive Importance ◽  
Common Task ◽  
Design Systems ◽  
Aided Design ◽  
Graph Map

In the mechanical design process, the interpretation of geometrical and dimensional tolerances is a common task in a products life cycle because tolerances are of decisive importance in the decisions related to cost and quality. At present, there are numerous approaches and investigations related to the modeling of tolerances in mechanical assemblies, related to Computer Aided Design Systems. The goal of this paper is to show a method to modeling an assembly based on a graph map structure, to guarantee the resolution of dimensional chains and tolerance analysis. In this process, which is based on a graph map structure, the dimensional chains associated to the functional requirements that influence the relative location of the parts are determined. A subset of a belt conveyor as an example, illustrates the proposed method.

A variational model for 3D tolerance analysis with manufacturing signature and operating conditions

2018 ◽  
Vol 38 (1) ◽  
pp. 10-19 ◽  
Author(s):  
Andrea Corrado ◽  
Wilma Polini ◽  
Giovanni Moroni ◽  
Stefano Petrò
Keyword(s):  
Three Dimensional ◽  
Reference Value ◽  
Tolerance Analysis ◽  
Geometrical Model ◽  
Operating Conditions ◽  
Variational Model ◽  
Assembly Process ◽  
Functional Requirements ◽  
Content Type ◽  
Mechanical Assemblies

Purpose The purpose of this work is to present a variational model able to deal with form tolerances and assembly conditions. The variational model is one of the methods proposed in literature for tolerance analysis, but it cannot deal with form tolerances and assembly conditions that may influence the functional requirements of mechanical assemblies. Design/methodology/approach This work shows how to manage the actual surfaces generated by the manufacturing process and the operating conditions inside the variational model that has been modified to integrate the manufacturing signature left on the surfaces of the parts and the operating conditions that arise during an actual assembly, such as gravity and friction. Moreover, a geometrical model was developed to numerically simulate what happens in a real assembly process and to give a reference value. Findings The new variational model was applied to a three-dimensional case study. The obtained results were compared to those of the geometrical model and to those of the variational model to validate the new model and to show the improvements. Research limitations/implications The proposed approach may be extended to other models of literature. However, its limitation is that it is able to deal with a sphere–plane contact. Practical implications Tolerance analysis is a valid tool to foresee geometric interferences among the components of an assembly before getting the physical assembly. It involves a decrease in the manufacturing costs. Originality/value The main contributions of the study are the insertion of a systematic pattern characterizing the features manufactured by a process, assembly operating conditions and development of a geometrical model to reproduce what happens in a real assembly process.

scholarly journals A Method for Designing Assembly Tolerance Networks of Mechanical Assemblies

2012 ◽  
Vol 2012 ◽  
pp. 1-26 ◽  
Author(s):  
Yi Zhang ◽  
Zongbin Li ◽  
Jianmin Gao ◽  
Jun Hong ◽  
Francesco Villecco ◽  
...  
Keyword(s):  
Geometric Constraints ◽  
Production Costs ◽  
Functional Requirements ◽  
Tree Model ◽  
Assembly Tolerance ◽  
Mechanical Assemblies ◽  
Assembly Structure ◽  
Structure Tree ◽  
Relation Model ◽  
Set Up

When designing mechanical assemblies, assembly tolerance design is an important issue which must be seriously considered by designers. Assembly tolerances reflect functional requirements of assembling, which can be used to control assembling qualities and production costs. This paper proposes a new method for designing assembly tolerance networks of mechanical assemblies. The method establishes the assembly structure tree model of an assembly based on its product structure tree model. On this basis, assembly information model and assembly relation model are set up based on polychromatic sets (PS) theory. According to the two models, the systems of location relation equations and interference relation equations are established. Then, using methods of topologically related surfaces (TTRS) theory and variational geometric constraints (VGC) theory, three VGC reasoning matrices are constructed. According to corresponding relations between VGCs and assembly tolerance types, the reasoning matrices of tolerance types are also established by using contour matrices of PS. Finally, an exemplary product is used to construct its assembly tolerance networks and meanwhile to verify the feasibility and effectiveness of the proposed method.

An Integrated Approach for a Knowledge-based Clinical Workstation: Architecture and Experience

1998 ◽  
Vol 37 (01) ◽  
pp. 16-25 ◽  
Author(s):  
P. Ringleb ◽  
T. Steiner ◽  
P. Knaup ◽  
W. Hacke ◽  
R. Haux ◽  
...  
Keyword(s):  
Decision Support ◽  
Information Systems ◽  
Patient Care ◽  
Hospital Information Systems ◽  
Medical Decision ◽  
Daily Routine ◽  
Functional Requirements ◽  
Support Functions ◽  
Knowledge Based ◽  
Clinical Workstation

Abstract:Today, the demand for medical decision support to improve the quality of patient care and to reduce costs in health services is generally recognized. Nevertheless, decision support is not yet established in daily routine within hospital information systems which often show a heterogeneous architecture but offer possibilities of interoperability. Currently, the integration of decision support functions into clinical workstations is the most promising way. Therefore, we first discuss aspects of integrating decision support into clinical workstations including clinical needs, integration of database and knowledge base, knowledge sharing and reuse and the role of standardized terminology. In addition, we draw up functional requirements to support the physician dealing with patient care, medical research and administrative tasks. As a consequence, we propose a general architecture of an integrated knowledge-based clinical workstation. Based on an example application we discuss our experiences concerning clinical applicability and relevance. We show that, although our approach promotes the integration of decision support into hospital information systems, the success of decision support depends above all on an adequate transformation of clinical needs.

Urban Development Strategies of City Centers: The Case of Rafah City, Palestinian Territories

2014 ◽  
Vol 8 (3) ◽  
pp. 195
Author(s):  
Omar S. Asfour ◽  
Samar Abu Ghali
Keyword(s):  
Urban Development ◽  
Gaza Strip ◽  
Geographic Location ◽  
Development Strategies ◽  
Functional Requirements ◽  
City Center ◽  
Palestinian Territories ◽  
The Gaza Strip ◽  
The City ◽  
Commercial Center

City centers worldwide are perceived as essential parts of the city, where city memories are preserved and its identity is expressed. They are planned to satisfy the functional requirements and pleasurable qualities of the city. Under the accelerating urbanization of the modern city, several challenges face these centers including demographic, economic, and environmental challenges. This requires a continuous and incremental urban development process based on clear strategy and action plans. Thus, this study focuses on urban development strategies of city centers, with a focus on Rafah city located in the Gaza Strip, Palestinian Territories. The geographic location of this city near the Palestinian-Egyptian borders makes it a promising commercial city at local and regional levels. Thus, the current situation of Rafah city center has been analyzed, and several development strategies have been proposed. This has been done through a field survey based on observation and a questionnaire directed to city center users. It has been found that there is a great potential of Rafah city center to be developed as a commercial center. In this regard, several strategies and required actions have been proposed in the fields of transportation, environmental quality, shopping activities, investment opportunities, and visual perception.

Sign in / Sign up

Export Citation Format

Share Document