Central Mechanical Engineering Research Institute

Abstract: Porous castings commonly termed as cellular metals possess characteristics similar to that of solid equivalentThe proposed methodol. in this investigation is capable of producing structured foam using space holders through melt route.The geometric structure of cast iron foam described in this work is inspired by triply periodic minimal surface (TPMS) design, namely Schwarz, modified Schwarz and I-WP.Schwarz and I-WP profiles are not best suited for manufacturing foam through casting route due to poor flow ability.The porosity of exptl. sample is 61.8% against the numerically predicted porosity of 65% for sphere diameter of 6 mm with modified TPMS profile is found to be the best case.The compressive strength of cast foam sample is 177.4 MPa with hardness of 212.5 BHN.The gray cast iron struts microstructure at different positions reveals type A and B flakes with an average length of 105 μm and some locally fine graphite particles are observed due to the thin wall structure.The average size of the ferrite grains and pearlite lamellar spacing is 17.22 ± 2.5 μm and 0.36 ± 0.12 μm, resp., due to less carbon content and high cooling rate during solidification.The fracture facets of the structured foam are mainly brittle fracture with localized ductility due to the various-sized graphite particles and local ductility of the ferrite.

This study introduces an innovative design for a compliant micro gripper based on Shape Memory Alloy (SMA) technol., intended for micro-assembly applications where SMA wire is used as an active actuator for opening and closing the jaw of micro gripper and gripping the object because it has a flexible behavior with high strength and large defection.This SMA wire can achieve the active actuator property by shape-changing properties with temperatureTo control the temperature, the math. modeling and electro-mech. characterizations of SMA wire are carried out by applying Joule's heating law method for identifying shape-changing properties with temperatureAn exptl. testing setup is also developed for characterizations of SMA wire where the behavior of SMA wire is controlled by setting the control parameters using the Lab VIEW software.After testing the SMA wires, the key finding is that the SMA wire shows steadystate behavior.Further, an SMA-based compliant micro gripper is developed.This development demonstrates that SMA wire facilitate the opening and closing of the jaws during the handling of miniature objects which shows that this flexible SMA-based micro gripper can be utilized in futuristic micro-assembly applications.

This research reports developing and applying multi-walled carbon nanotube (MWCNT) embedded monolithic hyperelastic elastomeric sponge-based wearable electronic skin (e-skin) with ultra-high stretchability for human activity monitoring.The e-skin was fabricated by soaking conductive, MWCNT-based ink in a porous water-resistant sponge that was developed from an Ecoflex-NaCl combination followed by a salt dissolution technique.Material characterization studies revealed uniform distribution of MWCNTs inside the pores of the e-skin and adhesion of the MWCNTs to the sponge matrix.Elec. characterization results indicated a stretching span of 350% with minimal hysteresis and a fast dynamic response that was twice as high as reported compared to non-monolithic/ sandwiched MWCNT-elastomer structures.In addition, the sensor displayed excellent drift response, resolution of 1% strain at lower stretching limits, and repeatability of up to 10000 stretch-release cycles.The developed e-skin showed <1% response variations with temperature fluctuations within 50°C and was found to be water-resistant.The dynamic in-situ tensile testing results demonstrated the physics behind the piezoresistive properties of the fabricated e-skin.Finally, the e-skin worn over the finger, thoracic region, and epiglottis recognized finger bending angles, respiration rate, and distinguished English alphabets spoken by a subject, resp.The hyperelastic e-skin hence finds applications in wearable devices and healthcare robotics.