Research on New Cleaning Method of Automobile Air Conditioner

on the car air conditioning cleaning market at present there are some problem of cleaning method has been widely criticized, simple and convenient cleaning method, in particular, the so-called clean air conditioning is “only spray cleaner, no water washing”, this will cause the pipeline internal dirt clean is not complete, easy to internal damage other parts of automobile air conditioning, affect the normal operation of the air conditioning, the remaining part of the chemical substances will also produce secondary pollution to the air inside the car, seriously affects people’s health and safety.

Internal Damage Analysis of Braided Composites Embedded in Carbon Nanotube Yarn

Carbon nanotube (CNT) yarn sensors were embedded in 3D braided composites in the form of arrays to detect the internal damage of specimens and study the internal damage monitoring of the 3D braided composites. The signals collected by the sensor array of CNT yarn were preprocessed using the dynamic wavelet threshold algorithm. The exact position of the damage was calculated based on the main features of the resistance signal matrix, which was calculated using the quadratic matrix singular value. The results show that the internal damage localization of the specimens was consistent with the actual damage. The localizations in this study can provide a basis for enhancing the structural health monitoring of smart 3D braided composites.

Diagnosis of interior damage with a convolutional neural network using simulation and measurement data

Current deep learning applications in structural health monitoring (SHM) are mostly related to surface damage such as cracks and rust. Methods using traditional image processing techniques (such as filtering and edge detection) usually face difficulties in diagnosing internal damage in thicker specimens of heterogeneous materials. In this paper, we propose a damage diagnosis framework using a deep convolutional neural network (CNN) and transfer learning, focusing on internal damage such as voids and cracks. We use thermography to study the heat transfer characteristics and infer the presence of damage in the structure. It is challenging to obtain sufficient data samples for training deep neural networks, especially in the field of SHM. Therefore we use finite element (FE) computer simulations to generate a large volume of training data for the deep neural network, considering multiple damage shapes and locations. These computer-simulated data are used along with pre-trained convolutional cores of a sophisticated computer vision-based deep convolutional network to facilitate effective transfer learning. The CNN automatically generates features for damage diagnosis as opposed to manual feature generation in traditional image processing. Systematic parameter selection study is carried out to investigate accuracy versus computational expense in generating the training data. The methodology is demonstrated with an example of damage diagnosis in concrete, a heterogeneous material, using both computer simulations and laboratory experiments. The combination of FE simulation, transfer learning and experimental data is found to achieve high accuracy in damage localization with affordable effort.

Fireside Corrosion of Heat Exchanger Materials for Advanced Solid Fuel Fired Power Plants

To address the challenge of climate change, future energy systems need to have reduced greenhouse gas emissions and increased efficiencies. For solid fuel fired combustion plants, one route towards achieving this is to increase the system’s steam temperatures and pressures. Another route is to co-fire renewable fuels (such as biomass) with coals. Fireside corrosion performance of two candidate superheater/reheater alloys has been characterised at higher heat exchanger surface temperature. Samples of the alloys (a stainless steel, Sanicro 25 and a nickel-based alloy, IN740) were exposed in fireside corrosion tests at 650 °C, 700 °C and 750 °C, in controlled atmosphere furnaces using the ‘deposit recoat’ test method to simulate superheater/reheater exposure for 1000 h. After exposure, the samples were analysed using dimensional metrology to determine the extent and distributions of corrosion damage in terms of surface recession and internal damage. At 650 °C, the stainless steel and nickel-based alloy performed similarly, while at 700 °C and above, the median damage to the steel was at least 3 times greater than for the nickel-based alloy. Optical and electronic microscopy studies were used to study samples’ damage morphologies after exposure. Intergranular damage and pits were found in sample cross sections, while chromium depletion was found in areas with internal damage. For high-temperature applications, the higher cost of the nickel-based alloy could be offset by the longer life they would allow in plant with higher operating temperatures.

Crack Evolution and Oxidation Failure Mechanism of a SiC-Ceramic Coating Reactively Sintered on Carbon/Carbon Composites

A SiC ceramic coating was prepared on carbon/carbon composites by pack cementation. The phase composition and microstructure of the coated specimens were characterized using X-ray diffraction instrument and scanning electron microscope. The results showed that the mass-loss percentage of the coated specimen was 9.5% after being oxidized for 20 h. The oxidation failure of the SiC ceramic coating at 1773 K was analysed by non-destructive X-ray computed tomography. The effective self-healing of cracks with widths below 12.7 μm introduced during the coating preparation process and generated while the specimens cooled down from the high oxidation temperature prevented the oxidation of carbon/carbon composites. X-ray computed tomography was used to obtain three-dimensional images revealing internal damage caused by spallation and open holes on the coating. Stress induced by heating and cooling caused the formation, growth and coalescence of cracks, which in turn led to exfoliation of the coating and subsequent failure of oxidation protection.

Study of the Damage Evolution of Concrete with Different Initial Defect Rates under Uniaxial Compression with Acoustic Emission Technology

It is important to evaluate the internal damage of concrete under load conditions in order to evaluate its stability and usability for building applications. In this study, the uniaxial compression of concrete with initial defect was performed, and the internal damage of concrete was monitored by acoustic emission(AE) technology in real time to study the damage process and mechanism. The mechanical properties of concrete specimens with different initial defect were determined, and the cumulative impact count of AE was recorded. The response characteristics of AE in the process of concrete compression and damage were obtained. According to the analysis of the influence of the initial defect on the Kaiser effect and since the irreversibility of the AE process is related to the degree of damage caused by the material under the pre-load, it was determined that the initial defect will aggravate the damage inside the concrete under the same load level. Based on the statistics and analysis of the Weibull cumulative function, the correlation between AE parameters and damage variables was discussed.

Internal Damage Detection of Composite Structures Using Passive RFID Tag Antenna Deformation Method: Basic Research

This manuscript deals with the detection of internal cracks and defects in aeronautical fibreglass structures. In technical practice, it is problematic to accurately determine the service life or MTBF (Mean Time Between Failure) of composite materials by the methods used in metallic materials. The problem is mainly the inhomogeneous and anisotropic structure of composites, possibly due to the differences in the macrostructure during production, production processes, etc. Diagnostic methods for detecting internal cracks and damage are slightly different, and in practice, it is more difficult to detect defects using non-destructive testing (NDT). The article deals with the use of Radio frequency identification (RFID) technology integrated in the fibreglass laminates of aircraft structures to detect internal defects based on deformation behaviour of passive RFID tag antenna. The experiments proved the potential of using RFID technology in fibreglass composite laminates when using tensile tests applied on specimens with different structural properties. Therefore, the implementation of passive RFID tags into fibreglass composite structures presents the possibilities of detecting internal cracks and structural health monitoring. The result and conclusion of the basic research is determination of the application conditions for our proposed technology in practice. Moreover, the basic research provides recommendations for the applied research in terms of the use in real composite airframe structures.

Case study on application of digital radiography in cable

Because of the frequent occurrence of power cable fault, rapid and accurate fault diagnosis is an important subject in this field. In this paper, the DR detection cases of cables and related components with different voltage levels are described and analyzed based on the research work of radiographic detection carried out by our research group in the field of cables and their accessories in the recent three years. The results show that the technology can effectively detect and analyze the internal damage of cable outer breaking point, the ablative defect of cable buffer layer, the size and position deviation of cable joint. Due to the large number of cable layers and material types, the paper also gives some solutions to the problem of shielding copper core and some examples of abnormal image identification. Cable ontology, cable joints and other accessories produced by different manufacturers have certain structural differences due to numerous processes and procedures. It is necessary to continue to carry out research on DR testing for cable engineering structural parts of different types, establish relevant standard comparison atlas and provide reference for the application of DR technology in the field of cable testing.

How chain dynamics affects crack initiation in double-network gels

Double-network gels are a class of tough soft materials comprising two elastic networks with contrasting structures. The formation of a large internal damage zone ahead of the crack tip by the rupturing of the brittle network accounts for the large crack resistance of the materials. Understanding what determines the damage zone is the central question of the fracture mechanics of double-network gels. In this work, we found that at the onset of crack propagation, the size of necking zone, in which the brittle network breaks into fragments and the stretchable network is highly stretched, distinctly decreases with the increase of the solvent viscosity, resulting in a reduction in the fracture toughness of the material. This is in sharp contrast to the tensile behavior of the material that does not change with the solvent viscosity. This result suggests that the dynamics of stretchable network strands, triggered by the rupture of the brittle network, plays a role. To account for this solvent viscosity effect on the crack initiation, a delayed blunting mechanism regarding the polymer dynamics effect is proposed. The discovery on the role of the polymer dynamic adds an important missing piece to the fracture mechanism of this unique material.

The acoustic property and impact behaviour of 3D printed structures filled with shear thickening fluids

In this study, the microstructures of the silica and styrene/acrylate particles and rheological behaviour of the three STFs were measured. The acoustic property and impact behaviour of 3D printed structures filled with STFs were investigated. The results showed that sound transmission loss (STL) of the structures filled with 46.5 vol% silica-based and 58.8 vol% styrene/acrylate-based STFs have been significantly improved, while their sound absorption coefficient (SAC) reduced greatly. The internal damage mechanism and energy absorption of honeycomb structures filled with different volume fraction STFs under low-velocity impact (LVI) loading were analysed, finding that the volume fractions and nanoparticles hardness of STFs has a significant influence on the impact resistance of the 3D printed honeycomb structures.