Compositions including a thermosetting polymer network and a mechanophore covalently bonded to the thermosetting polymer network are provided. Substrates including the compositions are provided. In addition, methods of making the compositions and methods of monitoring stress on a substrate comprising the compositions are provided.

Strain sensing compositions including a polymeric matrix material and a mechanophore component distributed throughout the polymeric material and covalently bonded to the polymeric material are provided. The mechanophore component undergoes a visible color change and the strain sensing composition exhibits a continuous three-dimensional (3D) spatial strain distribution including at least one color gradient upon direct or indirect impact by an object. Methods of forming strain sensing compositions are also provided. Methods of evaluating a strain distribution associated with an impact of a surrogate material comprising a mechanophore component are also provided.

The hybrid measurement system includes an evanescent prism coupling spectroscopy (EPCS) sub-system and a light-scattering polarimetry (LSP) sub-system. The EPCS sub-system includes an EPCS light source optically coupled to an EPCS detector system through an EPCS coupling prism. The LSP sub-system includes an LSP light source optically coupled to an optical compensator, which in turn is optically coupled to a LSP detector system via a LSP coupling prism. A support structure supports the EPCS and LSP coupling prisms to define a coupling prism assembly, which supports the two prisms at a measurement location. Stress measurements made using the EPCS and LSP sub-systems are combined to fully characterize the stress properties of a transparent chemically strengthened substrate. Methods of processing the EPCS and LSP measurements to improve measurement accuracy are also disclosed.

Apparatus can comprise a cavity at least partially defined by a first major surface of a reference block and configured to receive a sample. The apparatus can comprise a first polarization-switching light source configured to emit a first polarization-switched light beam toward the cavity and a first detector configured to detect a corresponding signal. The apparatus can comprise a second polarization-switching light source configured to emit a second polarization-switched light beam toward the cavity and a second detector configured to detect a corresponding signal. The first reference block can be positioned between the second detector and the second reference block. Methods of determining an estimated stress profile can comprise determining a central tension from a measured retardation profile of the sample. Methods can comprise determining an initial stress profile from a refractive index profile of the sample. Methods can comprise scaling and adjusting stress profiles.

A system and a method of monitoring physical properties of a physical medium over time are provided herein. The method may include the following steps: embedding a plurality of acoustic sensors into a physical medium before curing thereof; transmitting an acoustic wave by at least one transmitter coupled to or embedded within said physical medium; repeatedly calculating, over different points of time, a travel time of said acoustic wave between the at least one transmitter and the plurality of acoustic sensors; and analyzing said travel times, to detect a change over time in physical properties of said physical medium associated with said travel time.

A method and an apparatus for detecting a modification of a compound, the modification occurring during a transient period. The method may include: coupling at least one substance portion comprising ferro elastic material to a compound, the substance portion being configured to change a polarization level thereof continuously in response to a strain gradient applied thereto over the a transient period which results in said modification; sensing a physical property of said substance portion affected by the polarization level of the substance portion, due to the modification; and determining, using a computer processor, the modification, based on the sensed physical property of the substance portion.

Methods of improving the measurement of knee stress in an ion-exchanged chemically strengthened Li-containing glass sample that includes a knee are disclosed. One of the methods includes compensating for a shift in the location of the TIR-PR transition location associated with the critical angle location, wherein the shift is due to the presence of a leaky mode. Another method includes applying select criteria to the captured mode spectra image to ensure a high-quality image is used for the knee stress calculation. Another method combines direct and indirect measurements of the knee stress using the mode spectra from multiple samples to obtain greater accuracy and precision as compared to using either the direct measurement method or the indirect measurement method alone. Quality control methods of forming the glass samples using measured mode spectra and related techniques for ensuring an accurate measurement of the knee stress are also disclosed.

A tactile sensor including a camera positioned to capture images of marks. An elastically deformable skin including an outer surface having attributes and an undersurface having pins, ridges, or both. Each undersurface pin or ridge includes a mark. A processor detects displacement of the marks in captured images and compares the displaced positions of the marks in the captured images to stored sets of prelearned positions of marks, based on a distance function, to determine a quality of match value for each set of the prelearned positions of marks. A best quality matched prelearned pattern of forces is determined using a user selected function, to calculate a best matching set of the prelearned positions of marks. Identify a pattern of forces acting on the elastically deformable skin based on the determined best matched prelearned pattern of forces.

A tactile sensor including a cap having a top surface and an undersurface. The undersurface includes pins, each pin has a mark. A portion of the undersurface is attachable to a device. A camera positioned in view of the marks, captures images of the marks placed in motion by elastic deformation of the top surface of the cap. A processor receives the captured images and determines a set of relative positions of the marks in the captured images, by identifying measured image coordinates of locations in images of the captured images. Determine a net force tensor acting on the top surface using a stored machine vision algorithm, by matching the set of relative positions of the marks to a stored set of previously learned relative positions of the marks placed in motion. Control the device via a controller in response to the net force tensor determined in the processor.

An electronics system may include a substrate, an electronic device bonded to the substrate, a plurality of photoluminescent particles disposed on the electronic device, an illuminator, a sensor, and a control module. The illuminator can illuminate the electronic device. The sensor can capture a first set of positions of the photoluminescent particles on the electronic device when the electronic device is not operating under a load and a second set of positions of the photoluminescent particles when the electronic device is operating under a load. The control module can determine thermomechanical stress on the electronic device based at least in part on a difference between the first set of positions and the second set of positions.