Laser transformation hardening in the solid state is shown to successfully provide a surface hardness increase of almost 40% for Ti-6Al-4V with a case depth over 2 . 5 mm while reducing surface damage. This was completed by testing a matrix of four conditions using a direct diode laser, varying the power and the travel speed, followed by a mechanical and microstructural analysis of the hardness development. A kinetic model was developed to predict these changes by explaining the amount of a that transforms to b upon heating and the fraction of martensitic a9 that forms with natural quenching. The model matched the experimental results reasonably well with the major separation due to the poor hardenability of Ti-6Al-4V.
Ångström's method has been used to quantify thermal diffusivity of materials for over 150 years via measurement of thermal waves propagating through a long, thin sample. However, the traditional Ångström's method has some limitations. First, the traditional method is insensitive to potential variability in thermal diffusivity along the length of a sample because only two sensors are used. Second, conventional contact-based sensing techniques such as thermocouples limit the method to samples that are sufficiently large so as to be unaffected by heat loss through the sensors. Here, we develop and validate the infrared microscopy enhanced Ångström's method that overcomes these limitations and enables measurement of microscale samples. This work demonstrates the accuracy and applicability of the technique through measurement of several commercially available polymer monofilaments and films and comparison of the data to published values. This method is particularly robust to uncertainty in emissivity making it attractive for characterization of semitransparent samples.
Although the hair care industry is a multi-billion dollar industry, there still remains a dearth in the available technologies and research methods to answer one simple question: What temperature and frequency of use will lead to permanent structural damage (i.e. heat damage) to curly hair? Currently, trained professionals in the hair industry cannot predict when heat damage will occur and often rely on heuristics and intuition in their hair care approaches. In addition, scientists that have conducted studies with heat and hair have often used European hair types, which cannot be generalized to all ethnic groups; they have also conducted experiments that are not ecologically consistent with individuals' use context. As a result, a number of lay scientists have emerged whose use contexts are ecologically valid, but are lacking the experimental and quantitative rigor that engineers can provide. In this work, we discuss an interdisciplinary approach to integrating customer needs, design methodology, and thermal sciences for application to the hair care industry. We discuss the formulation of a predictive model, the design of an experimental test-bed for collecting data, and present initial results.
Mixtures of Cr and Mo elemental powders, with the nominal compositions Cr 25 Mo 75 , Cr 50 Mo 50 , and Cr 75 Mo 25 , are processed by high-energy ball milling at ambient temperature. Milling is observed to force the mixing of the immiscible bcc elements Cr and Mo into solid solutions. The lattice parameter of these solid solutions, measured by X-ray diffraction (XRD), displays the expected positive deviation from Vegard's law. These deviations are compared to the ones predicted by Eshelby's inclusion model for dilute alloys. The conventional Williamson-Hall approach is shown to fail to determine the grain size in as-milled samples, probably due to the high density of dislocations. Annealing at 700°C for 10 hours under argon leads to a large reduction in structural defect density, without inducing any significant decomposition. The mixing measured in Cr-Mo is discussed in the broader context of the mechanical mixing forced by ball milling in moderately immiscible systems.
Lead users play an integral part in helping engineers to identify latent needs of customers, and this approach has been used in a variety of ways within the design community. However, despite their close resemblance to lead users, do-it-yourself (DIY) practitioners have not been directly examined by the design community. A seven-step framework is presented where the first four steps resemble a typical design process and the remaining steps are relevant for the approach of identifying DIY practitioners as lead users. A case study from the hair care industry is presented to illustrate this framework. This paper establishes a connection between these two groups of customers and demonstrates how the insights of DIY practitioners, which manifest as latent needs for knowledge, can inspire research for the development of new technologies.
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