Search Results

You are looking at 1 - 3 of 3 items for

  • Author or Editor: A. Sepulveda x
  • Refine by Access: All Content x
Clear All Modify Search

The aim of this work was to identify new issues of the information demanded by beef consumers toward voluntary labelling. For this purpose, a total of 353 surveys were carried out to beef buyers who reside in three Spanish cities. To analyse the consumers’ demand information we used Chi-square tests. The results showed that information about sanitary and waste analysis and animal-rearing methods were the most demanded by consumers. Also, we found that there were clear links between the demand for information on the voluntary labelling of fresh beef and sociodemographic variables, such as gender, age, level of education, and the family income of the respondents.

Restricted access

Metastable effects on martensitic transformation in SMA

Part II. The grain growth effects in Cu-Al-Be alloy

Journal of Thermal Analysis and Calorimetry
Authors: A. Sepulveda, R. Muñoz, F. Lovey, C. Auguet, A. Isalgue, and V. Torra

Abstract  

The efficiency of shape memory alloy (SMA) as damper and/or standard actuator is truly enhanced when the material can be cycled without any relevant accumulation of the permanent deformation (i.e. under 0.5% for several hundreds of cycles). The particular properties of the CuAlBe alloy permit relevant grain growth with reasonable reduction of mechanical properties (from 300–350 to 250–300 MPa at fracture). Samples prepared with an appropriate heat thermal treatment (HTT) and relevant mean diameter of grain avoids accumulative deformation for series of cycles (near 500) up to 3.5% of deformation. The analysis of different wires of CuAlBe alloy shows, in the first part of HTT, a proportionality between the grain surface and the time at 1123 K. In the last part of the HTT the grain growth shows an increased complexity related with interactions between the grain boundaries and the external surface of the samples.

Restricted access

Metastable effects on martensitic transformation in SMA

Part VIII. Temperature effects on cycling

Journal of Thermal Analysis and Calorimetry
Authors: V. Torra, C. Auguet, A. Isalgue, F. Lovey, A. Sepulveda, and H. Soul

Abstract  

The use of Shape Memory Alloys (SMA) in technical applications as damping in civil engineering structures requires the characterization of the alloy for each specific application. This involves the evolution of the mechanical properties and damping capacity with the number of cycles, frequency, maximum deformation, applied stresses, and the evolution of the alloy with aging time and temperature. In particular, the temperature effects associated to self-heating need to be evaluated. In continuous cycling the effects of latent heat, the associated dissipation induced by the hysteresis, the heat flow to surroundings and the cycling frequency induce different states of temperature in the specimen, which in turn produces changes in the transformation-retransformation stresses. In this article, the temperature effects associated to cycling are outlined for different cycling frequencies. The results show that, for relatively faster frequency the temperature arrives at an oscillatory state superimposed to an exponential increase. For lower frequencies, some parts of the sample attain temperatures below room temperature. The experimental results are represented with an elementary model (the 1-body model or the Tian equation used in calorimetric representation) of heat transfer. For the higher fracture where life requirements are associated to damping in stayed cables for bridges, the results show (for the NiTi alloy) a reduction of the hysteresis width as the frequency increases for deformations up to 8%. For reduced deformation, under 2% appears an asymptotic behavior where the frictional area is practically independent of the cycling frequency (up to 20 Hz). In addition, it is shown that more than 4 million of working cycles can be attained if the maximum applied stress is kept below a threshold of about 200 MPa. Although under this condition the deformation must remain lower than 2% a reasonable damping capacity can still be obtained.

Restricted access