Pierre-Antoine Adragna

How Form Errors Impact on 2D Precision Assembly with Clearance

Most models of assembling simulations consider that form errors are negligible, but how can this assumption be assessed? When clearances are high, form deviations can be neglected, but on the case of very precise mechanisms with small clearances, this assumption can lead to non-accurate models. This paper is the continuation of our previous works presented at IPAS 2008 dealing with the assembly of two parts regarding their form deviation. The proposed method considers the positioning of the pair of surface with a given external force to identify contact points. The parts relative positioning is expressed by a small displacement torsor that can be transferred to any referee and compared to the functional requirement. The objective of this paper is to identify the clearance domain of a mechanical linkage regarding the form deviation of parts. Several parameters are identified as influent such as the clearance value, the straightness of the form deviation and the localization of the ideal least squared associated shape.

The pilot dimension method: Reconciling Steering and Conformity in Workshops

In machining workshops, workpieces are produced according to dimensions known as manufacturing dimensions. For the same workpiece and the same manufacturing plan, several sets of manufacturing dimensions can be used but none satisfies simultaneously the two main missions workshops need to fulfil: (a) ensuring conformity of products to their design dimension tolerances (also called blueprint tolerances); and (b) steering machines in order to compensate for tool wear. The set of manufacturing dimensions obtained from the design dimensions using the minimal chain of dimensions method is optimal for a conformity check of workpieces but is practically unusable for steering machines because of the complexity of its relationships toward the tool correctors and tools dimensions. The pilot dimensions method consists of, on the one hand, identifying and representing these tool correctors and these tool/program dimensions on the production drawings (besides the manufacturing dimensions) and, on the other hand, determining their correction values through a mathematical set of relations after having measured the manufacturing dimensions on a workpiece. Doing so will strongly reduce adjustment time, reduce the number of workpieces used for adjustments and greatly enhance the quality of workpiece batches.

Microstructure, Hardness, and Residual Stress Distributions in T-Joint Weld of HSLA S500MC Steel

Abstract This paper investigates the characterization of the microstructure, hardness, and residual stress distributions of MIG-welded high-strength low-alloy S500MC steel. The T-joint weld for 10-mm-thick plates was joined using a two passes MIG welding technology. The contour method was performed to measure longitudinal welding residual stress. The obtained results highlighted a good correlation between the metallurgical phase constituents and hardness distribution within the weld zones. In fact, the presence of bainite and smaller ferrite grain size in the weld-fusion zone might be the reason for the highest hardness measured in this region. A similar trend of the residual stress and hardness distributions was also obtained.

Rigid and Elastic Precision Domains of Ball Bearings

Ball bearings are complex components where local deformations are the main factor on the global behavior. One problem is the relation between a contact configuration and the load level. When those components are assembled, position errors have important effects on those contact configurations. A rigid ball bearing has very small clearances that give tolerances impossible to achieve. How can the designer write geometric specifications on the assembly taking into account bearing elastic behavior?. We propose a method to identify the limits of those errors according to the ball bearing limits and the clearances. The built model has been compared with industrial references with good accuracy.

Assessment of Sensitivity of Numerical Simulation in Sheet Metal Forming Process Applied for Robust Design

Considering variation of influent factors is a critical issue to enhance the robustness of sheet metal forming process in the product design process. The stochastic variability of uncontrollable factors results in the variations on the formed part which can lead to rejected parts. Since the inherent sources of variation in the sheet metal forming process comes from part-to-part, within batch and batch-to-batch variation. Therefore, the prediction and control of the variability influencing on the performance of the product is an essential demand of automotive and aeronautic manufacturers. Moreover, it is very necessary to have a numerically dedicated tool which predicts the process variability with a good confidence. In this paper, prediction of the variations of the formed part due to the variabilities of the sheet stamping process and the workpiece by numerical simulation will be carried out.