Analysis of residual stress in materials is often done in static conditions in a laboratory. Accurate systems and methods for performing these analyses in a dynamic, non-laboratory environment are notoriously difficult and can be very inaccurate. A method using a portable, field deployable apparatus having greater accuracy than currently available is disclosed whereby accurate and repeatable residual stress analysis may be implemented in non-laboratory environments leading to greatly improved diagnostics, maintenance and life limit prediction. Especially the analysis of a pipe or channel can be facilitated with this invention.

Techniques for force sensing in additive fabrication are provided. According to some aspects, an additive fabrication device may include a force sensor configured to measure a force applied to a build platform during fabrication. A length of time taken for a layer of material to separate from a surface other than the build platform to which it is adhered may be determined based on measurements from the force sensor. Subsequent additive fabrication operations, such as subsequent motion of the build platform, may be adapted based on the determined length of time.

Systems and methods of performing a stress measurement of a chemically strengthened glass using a light-scattering polarimetry system include adjusting the intensity of a light beam from a light source in an illumination system using a rotatable half-wave plate and a first polarizer operably disposed between the light source and a rotating light diffuser that has a rotation time t.sub.R. The first polarizer is aligned with a second polarizer in a downstream optical compensator to have matching polarization directions by rotating the rotatable half-wave plate to a position where the exposure time t.sub.E falls within an exposure range t.sub.R≤t.sub.E. The method also includes performing an exposure using the exposure time t.sub.E to obtain the stress measurement. One or both of the half-wave plate and first polarizer can be tilted to avoid deleterious back-reflected light from entering the light source.

An apparatus for measuring material properties of an object of ferromagnetic material, the apparatus including a probe, the probe including an electromagnet core defining two spaced-apart poles for inducing a magnetic field in the object, and a drive coil wound around the electromagnet core, and means to supply an alternating electric current to the drive coil to generate an alternating magnetic field in the electromagnet core and consequently in the object, wherein the probe also includes two sensing coils arranged in the vicinity of each of the poles, for sensing the magnetic flux density that links the core and the object, such sensing coils are significantly more sensitive to changes in material properties than are sensing coils overwound onto the drive coil.

An ultrasonic test device and test method for service stress of a moving mechanical component, where the device comprises an ultrasonic probe, a coupling fluid, a pressure-maintaining cover and universal wheels. The cover is vertically arranged above an inspected position of an inspected component, an interior of the pressure-maintaining cover is filled with coupling fluid, a bottom of the cover is provided with a structure permeable to the coupling fluid to form a coupling fluid film between the inspected position and the bottom of the cover, and a top of the cover is equipped with the ultrasonic probe. A detection part at a lower part of the ultrasonic probe extends into the coupling fluid of the cover and is vertical to the bottom of the cover without contact. The distance between the ultrasonic probe and the inspected component is kept unchanged through the universal wheels.

It is an object to provide a stress history measurement method and a stress sensor by which the stress history of an object being measured can be measured easily with high accuracy over a wide stress measurement range. In the stress history measurement method, the stress history to which the object being measured has been subjected is measured on the basis of the ratio of twinned calcite particles after the object to be measured has been subjected to an external force, the object having a stress sensor embedded therein and capable of being deformed elastically when being subjected to the external force, the sensor including a number of calcite particles. The stress sensor is configured such that a number of calcite particles are hardened by a resin with adjacent particles kept in contact with each other.

A residual thermal strain distribution measurement method of measuring a residual thermal strain distribution as residual thermal deformation in a sample generated under application of a thermal load, comprises recording images of a periodic pattern present on the surface of the sample by an image recording unit at a first temperature and a sample formation temperature at which the sample is formed, generating moire fringes based on each recorded image of the periodic pattern, calculating a phase of the moire fringes for the sample at the first temperature, calculating a phase of the moire fringes for the sample at the sample formation temperature, acquiring a phase difference of the moire fringes at the sample formation temperature with respect to the first temperature, and calculating a residual thermal strain of the sample at the first temperature with respect to the sample formation temperature based on the acquired phase difference.

A fastener status detection system is presented. The fastener status detection system comprises a primary fastener, a secondary fastener, and a sensor. The secondary fastener is configured to be a back-up to the primary fastener. The sensor is positioned to measure at least a portion of a load between the primary fastener and the secondary fastener.

Disclosed are a method and an apparatus for testing residual stress in coatings. The method includes: obtaining elastic modulus of a coating and a substrate of a target object; obtaining a temperature during the coating preparation of the target object; obtaining a cross-sectional area of the coating and a cross-sectional area of the substrate of the target object; obtaining a thermal expansion coefficient of the coating and a thermal expansion coefficient of the substrate of the target object; and calculating the coating residual stress σ.sub.c of the target object by the following formula:

[00001]${\sigma }_c=\left(\frac{S_s}{S_c}\right).Math.\left[1-\left(\frac{E_s.Math.S_s}{E_c.Math.S_c}+\frac{{\alpha }_c}{{\alpha }_s}\right).Math.\text{/}.Math.\left(1+\frac{E_s.Math.S_s}{E_c.Math.S_c}\right)\right].Math.E_s.Math.{\alpha }_s.Math.\Delta .Math..Math.T_c,$

wherein, S.sub.c is the cross-section area of the coating, S.sub.s is the cross-section area of the substrate, E.sub.c is the elastic modulus of the coating, E.sub.s is the elastic modulus of the substrate, α.sub.c is the thermal expansion coefficient of the coating, α.sub.s is the thermal expansion coefficient of the substrate, and ΔT.sub.c is the temperature during the coating preparation.

In an embodiment, a distortion-measuring apparatus for measuring a distortion distribution of an entire vitreous silica crucible in a non-destructive way includes: a light source 11; a first polarizer 12 and a first quarter-wave plate 13 disposed between the light source 11 and an outer surface of a vitreous silica crucible wall; a camera 14 disposed inside of a vitreous silica crucible 1; a camera control mechanism 15 configured to control a photographing direction of the camera 14; a second polarizer 16 and a second quarter-wave plate 17 disposed between the camera 14 and an inner surface of the vitreous silica crucible wall. An optical axis of the second quarter-wave plate 17 inclines 90 degrees with respect to the first quarter-wave plate 13.