Experimental Investigation into Cyclic Shear Behaviors in the Interface Between Steel and Crushed Mudstone Particles

In the waterway construction projects of the upper streams of the Yangtze River, crushed mudstone particles are widely used to backfill the foundations of the rock-socketed concrete-filled steel tube (RSCFST) pile. The mudstone particles are prone to being crushed, which influences the mechanical properties of the soil and the interface between the soil and the steel cased on the RSCFST pile. The crushing of the particles will be aggravated by reciprocating shear of the interface when the pile experiences repeating lateral loads. The reciprocating shear of the interface may, therefore, weaken the bearing capacity of the pile. In this study, we develop a new apparatus to study the mechanical properties of the steel–soil interface under a reciprocating shear condition. With this apparatus, a set of large-scale direct shear experiments are carried out with two different boundary conditions, that is, a constant stress boundary and a constant stiffness boundary, respectively. Comparative experiments and parallel experiments are carried out to study the physical properties of steel–mudstone particle interface and the stability of the apparatus. Parallel experiments show that the instrument has good stability. The comparative experiment results also reveal the differences of the shear behaviors of the interface under two conditions. Analysis of the experiment results shows that the normal stiffness condition is closer to the real boundary condition when the soil–steel interface is cyclically sheared. The particle crushing and the attenuation of normal stress is the main reason causing the degrading of the interface.

Characterisation of SiPM Photon Emission in the Dark

In this paper, we report on the photon emission of Silicon Photomultipliers (SiPMs) from avalanche pulses generated in dark conditions, with the main objective of better understanding the associated systematics for next-generation, large area, SiPM-based physics experiments. A new apparatus for spectral and imaging analysis was developed at TRIUMF and used to measure the light emitted by the two SiPMs considered as photo-sensor candidates for the nEXO neutrinoless double-beta decay experiment: one Fondazione Bruno Kessler (FBK) VUV-HD Low Field (LF) Low After Pulse (Low AP) (VUV-HD3) SiPM and one Hamamatsu Photonics K.K. (HPK) VUV4 Multi-Pixel Photon Counter (MPPC). Spectral measurements of their light emissions were taken with varying over-voltage in the wavelength range of 450–1020 nm. For the FBK VUV-HD3, at an over-voltage of 12.1±1.0 V, we measured a secondary photon yield (number of photons (γ) emitted per charge carrier (e−)) of (4.04±0.02)×10−6γ/e−. The emission spectrum of the FBK VUV-HD3 contains an interference pattern consistent with thin-film interference. Additionally, emission microscopy images (EMMIs) of the FBK VUV-HD3 show a small number of highly localized regions with increased light intensity (hotspots) randomly distributed over the SiPM surface area. For the HPK VUV4 MPPC, at an over-voltage of 10.7±1.0 V, we measured a secondary photon yield of (8.71±0.04)×10−6γ/e−. In contrast to the FBK VUV-HD3, the emission spectra of the HPK VUV4 did not show an interference pattern—likely due to a thinner surface coating. The EMMIs of the HPK VUV4 also revealed a larger number of hotspots compared to the FBK VUV-HD3, especially in one of the corners of the device. The photon yield reported in this paper may be limited if compared with the one reported in previous studies due to the measurement wavelength range, which is only up to 1020 nm.

Development of apparatus to evaluate cutting resistance of protective fabrics

In recent decades, attention has been focused on the design of protective soft fabrics against cutting. The anticipated textiles should shield the wearer's body from threats caused by pointed or sharp-edged objects, such as a knife, sharp blade, or spike. Therefore, as it is of great importance to design slash-resistant fabrics, it is also necessary to have an apparatus that gives the possibility to simulate the conditions of cutting processes of the protective fabric. The main objective of the present work is to develop a new apparatus to test the slash-proof materials used in soft protective armor or gloves. The apparatus can test the material with different cutting angles, different speeds, and various normal forces applied to the sample at the point of contact between the material and the cutting blade, with the capability to change all the parameters affecting the cutting force. This study aims to develop a cutting apparatus to study the cutting mechanism of textile materials with the capability to change all the parameters affecting the cutting force. The cutting angle and cutting speed have a significant effect on the maximum cutting force; however, the latter showed a high decrease of the maximum cutting force.