Digital Control of Active Network Microstructures on Silicon Wafers

This chapter presents a promising digital control of active microstructures developed and tested on silicon chips by current division and thus independent Joule heating powers, especially for planar submillimeter two-dimensional (2-D) grid microstructures built on silicon wafers by surface microfabrication. Current division on such 2-D grid networks with 2 × 2, 3 × 3, and n × n loops was modeled and analyzed theoretically by employing Kirchhoff’s voltage law (KVL) and Kirchhoff’s current law (KCL), which demonstrated the feasibility of active control of the networks by Joule heating effect. Furthermore, in situ testing of a typical 2-D microstructure with 2 × 2 loops by different DC sources was carried out, and the thermomechanical deformation due to Joule heating was recorded. As a result, active control of the current division has been proven to be a reliable and efficient approach to achieving the digital actuation of 2-D microstructures on silicon chips. Digital control of such microstructural networks on silicon chips envisions great potential applications in active reconfigurable buses for microrobots and flexible electronics.

Thermomechanical deformation of the orthotropic shell taking into account the deformation anisotropy

A variant of the rotation shell in the particular form of a closed circular cylindrical shell, which is often used in the design practice of civil, power and other industrial structures, is considered. The specificity of the considered shell lies in the features of its material, which has a manifestation of dual anisotropy. In particular, this material is orthotropic in structure, and the nature of deformation shows the dependence of stiffness and strength on the type of stress state. The loading of the shell is assumed to be axisymmetric, taking into account the influence of a medium with variable thermal parameters. The temperature difference between the shell surfaces is taken into account here. The statement of the general thermomechanical problem is carried out in an unrelated form, taking into account a certain independence of the problems of thermodynamics and mechanics. Taking into account the limitations of the classical thermomechanical theories of shells made of materials with dual anisotropy and the fact that the known models for such materials have significant drawbacks, the authors used a variant of the normalized stress space. Differential equations of thermoelasticity for a cylindrical shell are obtained, taking into account the complicated thermomechanical properties of its material. Particular solutions with the features of the results of calculating the shell states are illustrated, and their analysis is carried out.

Thermomechanical powder processing of beta-eutectoid bearing near-alpha Ti alloys

This work focuses on developing near-alpha Ti alloys via the selective addition of small concentrations of low-cost eutectoid [Formula: see text]-stabilizers like Cu and Mn. In particular, these newly designed near-alpha Ti alloys are manufactured via the cheapest powder metallurgy route of cold pressing plus sintering. Moreover, thermomechanical deformation of the sintered alloys via hot forging in the [Formula: see text] and [Formula: see text] field was also investigated aiming to enhance the mechanical properties through reduction of the residual porosity and microstructural control. It is found that the initial addition of a small amount of eutectoid [Formula: see text]-stabilizers leads to higher tensile properties with comprision to pure Ti produced by powder metallurgy, and this is due to the formation of a coarse lamellar structure due to the presence of [Formula: see text]-stabilizers. Further enhancement of the strength is achieved by means of hot thermomechanical processing thanks to sealing of the residual pores, texturing, and refinement of the microstructural features.

Understanding thermomechanical failure of athletic textiles via the pendulum skid method

Fiber textiles worn by some athletes and basketball and volleyball players experience higher than usual thermomechanical stresses compared to everyday garments because these athletes slide and dive on hardwood courts. Common textile testing procedures, such as the Martindale abrasion tester, effectively test textiles under modest loads and thousands of cycles, but this methodology does not suffice for athletic textiles. In addition, there is not a robust model nor a repeatable test that mimics high thermomechanical stress on fabrics and provides insights on fabric abrasion resistance. We present a model to calculate the temperatures and strain rates that are seen by fabrics undergoing thermomechanical deformation. To enable validation of the model, a fabric pendulum abrasion tester, an adaptation of the Cooper pendulum skid tester, was developed. The tester characterizes high-strain fabric abrasion deformation. This adaptation is statistically reliable and induces repeatable and realistic fabric failure within tens to hundreds of cycles, proving to be analogous to the loads athletes place on their textiles. Analog electronics on the pendulum abrasion tester generate real-time temperature and velocity profiles. A series of 11 unique athletic fabrics were abrasion tested, and it was found that fabrics with macroporosity experience the largest abrasion degradation. Significant degradation sites were further explored using scanning electron microscopy and X-ray diffraction analysis, and it was shown that thermomechanical loading’s effect on fiber microstructure is a function of the fabric construction. This novel abrasion tester and quantitative relationships between fabric structure and degradation mechanisms will enable more data-driven decisions when designing textiles for thermomechanical loads.