House of Quality

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Citizen Science: A Study of People, Expertise and Sustainable Development

International Joint Conference on Neural Networks

Computational methods in optimization considering uncertainties – An overview

Review of uncertainty-based multidisciplinary design optimization methods for aerospace vehicles

Multiple tail models including inverse measures for structural design under uncertainties

Application of additively manufactured components is gaining popularity in functional application. Several polymer-based additive manufacturing processes such as fused deposition modelling (FDM), selective laser sintering (SLS), stereolithography apparatus (SLA) and poly-jet printing to name a few cater to automotive to medical applications. Reliability in service of these components has to be ascertained for using them for functional application. The components made from additive manufacturing have inherent anisotropy due to the process characteristics such as build orientation and laser scanning/deposition tool paths. Literature reports fatigue life characterization mostly in FDM parts. In this work, a fatigue life analysis was carried out on components manufactured by poly-jet printed parts. Also, two build orientations were used to study the effect of this process parameter on the tensile strength and fatigue life. Other process parameters such as layer thickness, finishing type and polymer material were kept constant. A standard test specimen as per ASTM standard D7791–12 was prepared using Stratasys® Eden 350 V™ poly-jet printer using Veroclear 720™ material in two build orientations. The specimens were tested for tensile test and tensile–tensile fatigue cycles to failure at different stress levels. The test results were analysed to understand the fatigue life characteristics, and it was found that the process parameter variation has significant effect on the part strength (tensile) and reliability (fatigue failure). The fractured surface was analysed using SEM images to corroborate the inferences from test results.

Fatigue Life Characterization of Additively Manufactured Acrylic like Poly-Jet Printed Parts

Nonlinear problems such as transient dynamic problems exhibit structural responses that can be discontinuous due to numerous bifurcations. This hinders gradient-based or response surface-based optimization. This paper proposes a novel approach to split the design space into regions where the response is continuous. This makes traditional optimization viable. A convex hull approach is adopted to isolate the points corresponding to unwanted bifurcations in the design space. The proposed approach is applied to a tube impacting a rigid wall representing a transient dynamic problem. Since nonlinear behavior is highly sensitive to small variations in design, reliability-based design optimization is performed. The proposed method provides the designer an optimal design with a prescribed dynamic behavior.

A convex hull approach for the reliability-based design optimization of transient dynamic problems

Visualization techniques in design space exploration with high dimensional data are helpful in enhancing the decision making in the context of multiple objective optimization. Visualization of Pareto solutions obtained is crucial to understand the trade-off between the objectives as it enables intuitive decision making. However, such a task is not trivial beyond three dimensions. In this work, we propose using interpretable self-organizing map (iSOM), to visualize Pareto solutions for MOO problems involving n objectives (\(n>3\)). iSOM enable simplified component plane plots that allow visual inspection of the Pareto fronts and also allow identifying clusters in the Pareto front and the corresponding design variables. Proposed approach is successfully demonstrated on 3 analytical examples.

Interpretable Self-Organizing Maps (iSOM) for Visualization of Pareto Front in Multiple Objective Optimization

Response surface methods which approximate the actual performance function using simple algebraic equations are widely used in structural reliability studies. The response surface approximations are often used to estimate the reliability of a structure. Errors in the response surface approximation affect the results of reliability analysis. This work investigates the error in the failure probability estimated using a response surface approximation. It is observed that small errors in the response surface may amplify to large errors in the failure probability. It is observed that the amplification occurs when the failure surface is far away from the response mean and the DOE has more points near the mean. Another situation is when the failure region is a small island encompassed within the safe region, and the points in the DOE fail to capture the failure region. Analytical and engineering application examples are investigated to understand the amplification of error in the failure probability.

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Palaniappan Ramu

Papers

Multiple tail models including inverse measures for structural design under uncertainties

Fatigue Life Characterization of Additively Manufactured Acrylic like Poly-Jet Printed Parts

A convex hull approach for the reliability-based design optimization of transient dynamic problems

Interpretable Self-Organizing Maps (iSOM) for Visualization of Pareto Front in Multiple Objective Optimization

Error Amplification in Failure Probability Estimates of Small Errors in Surrogates