Feasibility design of an interface damper for a space borne microbalance

Feasibility design of a damper based on superelastic shape memory alloys (SMAs) is presented. The design wants to develop a passive vibration insulator for the Contamination Assessment Microbalance instrument, a quartz crystal microbalance for monitoring and measuring contamination in space environment. The ability of SMAs to act as efficient vibration insulators comes from their pseudo-elastic capabilities as the hysteretic force versus displacement behavior allows for energy dissipation. A 3D model of the instrument was developed to perform modal and dynamic random analyses aimed to identify the insulator mechanical characteristics and verify the instrument mechanical resistance. Moreover, a setup was designed to measure superelastic damping capacity of a commercial pseudoelastic shape memory alloy wire in dynamic tensile mode. The wire' specific damping capacity was then tested in different conditions, i.e. changing the excitation frequency and the amplitude of the deformation within a range of interest. The experimental activity allowed validation of the selected SMA wire for the intended application

Validation of smart insoles for the measurement of vibration exposure of workers and athletes

Wearable sensors are becoming increasingly common in daily life for medical care, athletic training, or even daily activity monitoring [1]-[3]. As these systems advance, so do their potential application, but their use for monitoring vibration exposure is limited or absent, despite the adverse effects of vibration on health being well known among the scientific community. To address this deficit, we propose a system of sensorized smart insoles capable of measuring triaxial vibration exposure according to ISO 2631-1. Each insole allows measurement of the vibration exposure and contact pressure at the forefoot and rearfoot, as well as the temperature inside the shoe. We used the insoles to measure the vibration exposure of five male subjects in three different testing conditions: 1) indoor condition (Politecnico di Milano laboratory, atop a triaxial shaker; 2) outdoor condition riding a mountain bike; and 3) skiing. The vibration exposure along the three mutually perpendicular axes was compared with that measured using instrumentation compliant with the current standards (ISO 8041). Results show that the proposed system allows direct monitoring of vibration exposure at the feet, also accounting for the vibration reduction provided by the shoe sole

Characterization of the pseudoelastic damping capacity of shape memory alloy wire

The pseudoelastic hysteresis behavior of shape memory alloy (SMA) elements observed above the austenite finish temperature of the alloy, can be used to provide a large structural damping in different applications. In this work, the pseudoelastic damping capacity (SDC) of a NiTi SMA wire has been characterized using the complex modulus approach through testing under a dynamic tensile condition. A test setup has been specifically designed, built and validated for this measurement since a testing machine with the required performances was not available. Given the dynamic characteristic of the test the structure was designed to behave as a rigid body in the frequency range of interest. Different conditions have been tested, varying the excitation frequency, the amplitude of imposed deformation, and the pre-strain levels. Results show that the SDC has a nearly constant trend of 7.5% for low frequencies until 30 Hz. Moreover, variation of the amplitude of deformation, between 0.3% and 0.8%, causes an increasing of the damping capacity, which varies from 7.7% to 10.4%, respectively. Finally, the measured prestrain amplitude effect is in agreement with existing literature studies