Response Surface Designs Robust against Nuisance Factors

This paper discusses an algorithmic approach to constructing trend-free and orthogonally-blocked response surface designs. The constructed designs have the main effects, 2-factor interactions and second-order effects being orthogonal or near-orthogonal to the nuisance factors such as the time-trend or the blocking factors. The paper also provides a catalogue of (near-) trend-free Box–Behnkens designs and orthogonally blocked Box–Behnkens designs arranged in rows and columns.

Influence of Second-Order Effects on Thermoelastic Behaviour in the Proximity of Crack Tips on Titanium

Background The Stress Intensity Factor (SIF) is used to describe the stress state and the mechanical behaviour of a material in the presence of cracks. SIF can be experimentally assessed using contactless techniques such as Thermoelastic Stress Analysis (TSA). The classic TSA theory concerns the relationship between temperature and stress variations and was successfully applied to fracture mechanics for SIF evaluation and crack tip location. This theory is no longer valid for some materials, such as titanium and aluminium, where the temperature variations also depend on the mean stress. Objective The objective of this work was to present a new thermoelastic equation that includes the mean stress dependence to investigate the thermoelastic effect in the proximity of crack tips on titanium. Methods Westergaard’s equations and Williams’s series expansion were employed in order to express the thermoelastic signal, including the second-order effect. Tests have been carried out to investigate the differences in SIF evaluation between the proposed approach and the classical one. Results A first qualitative evaluation of the importance of considering second-order effects in the thermoelastic signal in proximity of the crack tip in two loading conditions at two different loading ratios, R = 0.1 and R = 0.5, consisted of comparing the experimental signal and synthetic TSA maps. Moreover, the SIF, evaluated with the proposed and classical approaches, was compared with values from the ASTM standard formulas. Conclusions The new formulation demonstrates its improved capability for describing the stress distribution in the proximity of the crack tip. The effect of the correction cannot be neglected in either Williams’s or Westergaard’s model.

Forgotten Motivational Factors of Boyacense Colombian Entrepreneurs: A Subjective Analysis of Second-Generation Incidences

The main aim of this article was, using subjective information, to analyze the forgotten factors that influence the motivation of Boyacenses to become entrepreneurs. The study was carried out with entrepreneurs enrolled in the Boyacá Region Brand Program (BRBP). For the treatment of the collected data, the method of the experts and the theory of forgotten effects were used to identify second-generation incidences involving motivational factors in Boyacense entrepreneurs. The research questions that guided the study were as follows: What are the forgotten effects among the motivational factors of entrepreneurship? What are the intermediate factors that generate the second-order effects? What are the economic, psychological, cultural, and environmental factors that have second-order effects among them? Among the main findings, it was possible to visualize second-degree relationships between economic, cultural, and psychological factors. Additionally, in the case of entrepreneurs from Boyacá, the primary motivation for most of them to develop their business idea was economic independence, while the least motivating was the improvement of social status. Likewise, the need for achievement was highlighted. Finally, the country’s economic situation was found to work against the development of entrepreneurship.

Second-order torsion effects in concrete buildings

ABSTRACT: The internal forces due to torsion in global analysis of buildings, and its second-order effects, usually are not properly considered in structural design or even in design code’s prescriptions. Although the γZ coefficient, which is used to the evaluation of global second-order effects, has a wide, useful and consolidated application, it is true that specific torsional aspects are not well considered by it. This paper discusses the little-known γθ coefficient, an analogous proposition to the γZ coefficient, but focused specifically on the consideration of torsional effects. After the discussion on the concepts and the design methodology, several buildings are evaluated and their displacements and the coefficients γZ and γθ are calculated. Comparing these parameters, and also the results obtained by the P–Δ method, it is demonstrated the importance and the reliability of the γθ coefficient.