Failure Analysis and the Evaluation of Forced-In Joint Reliability for Selected Operation Conditions

In this article, sample damage and wear of forced-in joints is presented, and their reliability evaluated. Compared were shafts without additional finish treatment, rolled shafts and those with a TiSiN coating. Tribological samples under investigation operated in rotational bending conditions. Recorded was the number of fatigue cycles at which damage might occur. Reliability indicators were plotted, which demonstrated that coated shafts are distinguished by the highest reliability and low damage intensity. Macroscopic observations of shaft surfaces demonstrated the traces of adhesive wear and, in the case of shafts without additional treatment and in the case of rolled shafts, fretting wear traces in the form of a ring comprising the entire shaft circumference. Microscopic observations showed numerous build-ups on the surface, microcracks, and the occurrence of wear products in the gap between the shaft and sleeve. The highest fatigue strength was demonstrated by shafts with a TiSiN coating. The shaft section change area was the place where fatigue wear occurred.

Experimental Study of Coal Sample Damage in Acidic Water Environments

We investigated the effects of acidic and circumneutral water on coal samples by uniaxial compression, acoustic emission, and a series of physical tests. In acidic water, the coal samples were damaged, and their ultrasonic velocities decreased, as minerals such as kaolinite and calcite underwent dissolution. When the pH was < 7, the uniaxial compressive strength and elastic modulus decreased, while the duration of the residual strength stage tended to increase. The reactions were stronger at higher H+ concentrations and the number of large pores increased; there was a significant increase in the accumulated acoustic emission counts and maximum average energy near the unstable crack growth stage. The post-peak stage of the coal samples was characterized in the different acidic waters and the failure modes were identified by spectrum analysis. Acidic water damaged the weak areas of coal samples by complex physical and chemical reactions, which made direct tensile failure more likely when the coal samples were loaded.

ASPECTS OF DEVELOPMENT OF FIREPROOF COMPOSITIONS FOR STRUCTURES WITH TEXTILE FUEL PRODUCTS

The results of experimental studies on the effectiveness of fire protection of easily erected structures made of flammable textile products are presented. An analysis of the directions of use of easily erected structures made of flammable textile products indicates a steady trend towards an increase in their use during the temporary fulfillment of certain tasks of the Armed Forces of Ukraine and units of the. During the heating of such structures, ignition and rapid spread of fire are possible. The operating statistics for easily erected structures have found a low level of safety due to the use of natural fibers (e.g., linen, cotton and blends), which are highly sensitive to heat and fire. Reduction of combustibility and the development of non-combustible and non-combustible materials is one of the main directions for preventing fires and solving the problem of expanding the scope of these materials. Treatment with fire protection means significantly affects the spread of the flame, allows you to reduce the smoke-generating ability and heat release significantly. After the test, it can be seen that the sample of the textile material sustains spontaneous combustion for more than 5 s; sample damage is more than 150 mm. After the test, it is clear that the sample of textile material does not support self-combustion for no more than 5 s; sample damage is no more than 100 mm. The inhibition of the process of ignition and flame propagation for such a sample is associated with the decomposition of fire retardants under the influence of temperature with the absorption of heat and the release of incombustible gases (nitrogen, carbon dioxide), a change in the direction of decomposition towards the formation of incombustible gases and a hardly combustible coke residue. This leads to an increase in the thickness of the coke layer and inhibition of the heat transfer of the high-temperature flame to the material, which indicates the possibility of the transition of textile materials during processing with a fire retardant composition to materials that are non-combustible, which do not spread the flame by the surface.

A microfluidic dosimetry cell to irradiate solutions with poorly penetrating radiations: a step towards online dosimetry for synchrotron beamlines

Synchrotron radiation can induce sample damage, whether intended or not. In the case of sensitive samples, such as biological ones, modifications can be significant. To understand and predict the effects due to exposure, it is necessary to know the ionizing radiation dose deposited in the sample. In the case of aqueous samples, deleterious effects are mostly induced by the production of reactive oxygen species via water radiolysis. These species are therefore good indicators of the dose. Here the application of a microfluidic cell specifically optimized for low penetrating soft X-ray radiation is reported. Sodium benzoate was used as a fluorescent dosimeter thanks to its specific detection of hydroxyl radicals, a radiolytic product of water. Measurements at 1.28 keV led to the determination of a hydroxyl production yield, G(HO . ), of 0.025 ± 0.004 µmol J−1. This result is in agreement with the literature and confirms the high linear energy transfer behavior of soft X-rays. An analysis of the important parameters of the microfluidic dosimetry cell, as well as their influences over dosimetry, is also reported.

Visco-elastoplastic Characterization of a Flax-fiber Reinforced Biocomposite

In the presented study, the load induced long-term behavior of a biocomposite material is analyzed. The studied material is a unidirectional flax fiber reinforced epoxy resin, material, whose quasi-static mechanical properties can compare with those of glass fiber composites. Samples with a fiber direction of 0� were subjected to two types of multi-level creep-recovery tests, one with a varying creep duration, and the other with a varying creep stress, with the purpose of discriminating the viscoplastic and viscoelastic behavior of the composite. Results show a significant viscous response in time, dependent on both creep duration and creep stress, up to 20% of the elastic one. Sample damage is absent, leading to the conclusion that the viscoplastic response is caused by the permanent reorganization of the fiber�s internal structure.

Effect of X-ray free-electron laser-induced shockwaves on haemoglobin microcrystals delivered in a liquid jet

X-ray free-electron lasers (XFELs) enable obtaining novel insights in structural biology. The recently available MHz repetition rate XFELs allow full data sets to be collected in shorter time and can also decrease sample consumption. However, the microsecond spacing of MHz XFEL pulses raises new challenges, including possible sample damage induced by shock waves that are launched by preceding pulses in the sample-carrying jet. We explored this matter with an X-ray-pump/X-ray-probe experiment employing haemoglobin microcrystals transported via a liquid jet into the XFEL beam. Diffraction data were collected using a shock-wave-free single-pulse scheme as well as the dual-pulse pump-probe scheme. The latter, relative to the former, reveals significant degradation of crystal hit rate, diffraction resolution and data quality. Crystal structures extracted from the two data sets also differ. Since our pump-probe attributes were chosen to emulate EuXFEL operation at its 4.5 MHz maximum pulse rate, this prompts concern about such data collection.

Use of continuous sample translation to reduce radiation damage for XPCS studies of protein diffusion

An experimental setup to measure X-ray photon correlation spectroscopy during continuous sample translation is presented and its effectiveness as a means to avoid sample damage in dynamics studies of protein diffusion is evaluated. X-ray damage from focused coherent synchrotron radiation remains below tolerable levels as long as the sample is translated through the beam sufficiently quickly. Here it is shown that it is possible to separate sample dynamics from the effects associated with the transit of the sample through the beam. By varying the sample translation rate, the damage threshold level, D thresh = 1.8 kGy, for when beam damage begins to modify the dynamics under the conditions used, is also determined. Signal-to-noise ratios, R sn ≥ 20, are obtained down to the shortest delay times of 20 µs. The applicability of this method of data collection to the next generation of multi-bend achromat synchrotron sources is discussed and it is shown that sub-microsecond dynamics should be obtainable on protein samples.

Experimental Investigation and Mechanism Analysis on Rock Damage by High Voltage Spark Discharge in Water: Effect of Electrical Conductivity

High voltage spark discharge (HVSD) could generate strong pressure waves that can be combined with a rotary drill bit to improve the penetration rate in unconventional oil and gas drilling. However, there has been little investigation of the effect of electrical conductivity on rock damage and the fragmentation mechanism caused by HVSD. Therefore, we conducted experiments to destroy cement mortar, a rock-like material, in water with five conductivity levels, from 0.5 mS/cm to 20 mS/cm. We measured the discharge parameters, such as breakdown voltage, breakdown delay time, and electrical energy loss, and investigated the damage mechanism from stress waves propagation using X-ray computed tomography. Our study then analyzed the influence of conductivity on the surface damage of the sample by the pore size distribution and the cumulative pore area, as well as studied the dependence of internal damage on conductivity by through-transmission ultrasonic inspection technique. The results indicated that the increase in electrical conductivity decreased the breakdown voltage and breakdown delay time and increased the energy loss, which led to a reduction in the magnitude of the pressure wave and, ultimately, reduced the sample damage. It is worth mentioning that the relationship between the sample damage and electrical conductivity is non-linear, showing a two-stage pattern. The findings suggest that stress waves induced by the pressure waves play a significant role in sample damage where pores and two types of tensile cracks are the main failure features. Compressive stresses close horizontal cracks inside the sample and propagate vertical cracks, forming the tensile cracks-I. Tensile stresses generated at the sample–water interface due to the reflection of stress waves produce the tensile cracks-II. Our study is the first to investigate the relationship between rock damage and electrical conductivity, providing insights to guide the design of drilling tools based on HVSD.

The universal sample holders of microanalytical instruments of FIB, TEM, NanoSIMS, and STXM-NEXAFS for the coordinated analysis of extraterrestrial materials

We developed universal sample holders [the Kochi grid, Kochi clamp, and Okazaki cell) and a transfer vessel (facility-to-facility transfer container (FFTC)] to analyze sensitive and fragile samples, such as extremely small extraterrestrial materials. The holders and container prevent degradation, contamination due to the terrestrial atmosphere (water vapor and oxygen gas) and small particles, as well as mechanical sample damage. The FFTC can isolate the samples from the effects of the atmosphere for more than a week. The Kochi grid and clamp were made for a coordinated micro/nano-analysis that utilizes a focused-ion beam apparatus, transmission electron microscope, and nanoscale secondary ion mass spectrometry. The Okazaki cell was developed as an additional attachment for a scanning transmission X-ray microscope that uses near-edge X-ray absorption fine structure (NEXAFS). These new apparatuses help to minimize possible alterations from the exposure of the samples to air. The coordinated analysis involving these holders was successfully carried out without any sample damage or loss, thereby enabling us to obtain sufficient analytical datasets of textures, crystallography, elemental/isotopic abundances, and molecular functional groups for µm-sized minerals and organics in both the Antarctic micrometeorite and a carbonaceous chondrite. We will apply the coordinated analysis to acquire the complex characteristics in samples obtained by the future spacecraft sample return mission.