Tolerance analysis is a critical step in designing and manufacturing of an aircraft. Huge problems may present during the assembly process if the tolerance study on a sub-component was not carried out or was ineffectual. These problems will introduce additional reworking time and product costs, which are not compatible with today's aircraft industry requirements. The approaches of the literature are not easy to apply, especially for complex aerospace assemblies, since they were born to deal with elementary features, such as plane, hole, pin and so on. So the aid of the computer is called for. Today Computer Aided Tolerancing (CAT) Softwares are readily available, but even if these tools provide good results, they have not been widely used. It may be explained by the lack of methods towards tolerancing problems. The aim of the present paper is to present a method for tolerance analysis of an assembly involving freeform surfaces by dealing with dimensional and geometric tolerances. The case of study involves aerodynamic surfaces of flaperon. It is a structural assembly of the aircraft. It is constituted by 1 skin, 8 ribs and 1 spar. These 10 components are made in composite and are connected by adhesive. Adhesive thickness between the faced surfaces to connect should be as constant as possible in order to obtain a right structural connection. The influence of the tolerances applied to the 10 components on the value of the gap thickness at the interfaces among each couple of components has been deeply investigated by means of the proposed method. The proposed method assists both the design and the assembly planning of complex shape components of an aircraft and constitutes a complementary technique to the current 3D tolerance analysis software packages, such as eMTolmate, since it is able to deal with the specificity and the complexity of an aircraft assembly.

Geometric and dimensional tolerances applied to free form surfaces of an aircraft in 2D tolerance analysis

POLINI, Wilma;
2005

Abstract

Tolerance analysis is a critical step in designing and manufacturing of an aircraft. Huge problems may present during the assembly process if the tolerance study on a sub-component was not carried out or was ineffectual. These problems will introduce additional reworking time and product costs, which are not compatible with today's aircraft industry requirements. The approaches of the literature are not easy to apply, especially for complex aerospace assemblies, since they were born to deal with elementary features, such as plane, hole, pin and so on. So the aid of the computer is called for. Today Computer Aided Tolerancing (CAT) Softwares are readily available, but even if these tools provide good results, they have not been widely used. It may be explained by the lack of methods towards tolerancing problems. The aim of the present paper is to present a method for tolerance analysis of an assembly involving freeform surfaces by dealing with dimensional and geometric tolerances. The case of study involves aerodynamic surfaces of flaperon. It is a structural assembly of the aircraft. It is constituted by 1 skin, 8 ribs and 1 spar. These 10 components are made in composite and are connected by adhesive. Adhesive thickness between the faced surfaces to connect should be as constant as possible in order to obtain a right structural connection. The influence of the tolerances applied to the 10 components on the value of the gap thickness at the interfaces among each couple of components has been deeply investigated by means of the proposed method. The proposed method assists both the design and the assembly planning of complex shape components of an aircraft and constitutes a complementary technique to the current 3D tolerance analysis software packages, such as eMTolmate, since it is able to deal with the specificity and the complexity of an aircraft assembly.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11580/10847
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