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Carbon fibre reinforced polymer (CFRP) composites are widely used in the aerospace industry; they are susceptible to impact damage from low-velocity impacts throughout their service life. Long pulse thermography (LPT) was proposed to detect defect in low-velocity impact test (LVIT). In this framework, the defects of matrix fractures, fibre cracks and interface delamination were produced by LVIT in the CFRP specimens. The halogen lamps LPT test system was applied to detect the low-velocity impact damage, and an A655sc infrared camera was applied to collect the surface temperature. In order to improve the efficiency of the impact damage detection, the infrared image sequences were processed by applying different post-processing techniques such as pulse phase thermography (PPT), thermal signal reconstruction (TSR), principal component analysis (PCA), total harmonic distortion (THD), linear discriminant analysis (LDA) and quadratic discriminant analysis (QDA). The results show that the signal-to-noise ratio (SNR) was improved by PPT, TSR, PCA, THD, LDA and QDA post-processing techniques. The proposed supervised learning (SL) QDA algorithm achieves better defect identification results than the above post-processing techniques. The detectability of real defects can provide a realistic assessment by the above post-processing techniques. [ABSTRACT FROM AUTHOR]

The load‐bearing capacity and failure characteristics of composite structures are closely related to their dimensions. In this study, low‐velocity impact, ultrasonic non‐destructive testing, and compression after impact tests were conducted on composite laminates of varying widths to investigate the influence of size effects. Distinct impact response profiles and compression failure modes were characterized. The results indicate that under impact loading, the delamination threshold load (6700 N ~ 7200 N) and the knee‐point energy (40 J) are not affected by width. However, variations in width lead to differences in indentation depth, impact duration, peak load, delamination characteristics, and energy absorption. Furthermore, increasing impact energy further magnifies these differences. Under compression loading, wider laminates exhibit lower residual strength, with the influence of impact energy on residual strength decreasing as width increases. Importantly, the observed compression failure deformation mode transitions from localized buckling to widespread sub‐layer delamination‐induced compression failure. This suggests that changes in width alter the governing mechanical mechanisms of CAI failure. Consequently, the use of a single‐size laminate to represent both LVI and CAI processes is not recommended. Based on experimental results, the reliability of the equivalent damage method in predicting the residual compression strength of laminates of different widths was confirmed, providing valuable insights for practical engineering applications. Highlights: Assess the variations in the low‐velocity impact process of laminates with different widths.Evaluate the delamination damage of laminates after impacts by ultrasonic C‐scan techniques.Investigate the effect of variation in widths on the compression behavior of laminates after impact.Validate the feasibility of equivalent damage modeling for calculating residual strength. [ABSTRACT FROM AUTHOR]

The calculation method of deterioration factor of durability test in China 6 emission regulation of light-duty vehicle is studied. The difference between multiplication and addition in the implementation of the regulations is obtained. The results show that the additive DF can keep the actual deterioration level of the car, while the multiplication DF will change the deterioration level of the car and enlarge the error; With the decrease of emission limit, multiplication DF makes it more difficult for vehicles to pass through emission limit value than add DF; For emission consistency inspection, the two degradation factors have advantages in different regions.

The new diagnostic items such as fuel system, VVT and cold start emission reduction strategy are tested for several vehicles meeting the requirements of the China 6 emission standards of light-duty vehicles. The test results show that the fuel system fault will increase the emissions of NMHC, NOx, CO and other pollutants by 0.7-7.5 times, and the emissions of lean mixture, rich mixture and uneven cylinder to cylinder faults will increase to different degrees; VVT fault will increase NMHC and CO emissions by 1.2-2.9 times and NOx by 1.6-6.1 times; The failure of cold start emission reduction strategy will increase NMHC, NOx and CO emissions by 4.2-9.0 times and NOx by 2.1-2.2 times; It is necessary to strengthen the monitoring of these diagnostic items and tighten the requirements in the future emission standards.

In order to obtain the coasting resistance of vehicles at different altitudes and temperatures, experiment selects three different types of vehicles, and conducts altitude coasting resistance research tests at four altitudes and temperatures. The results show that the modified coasting resistance method can accurately correct the coasting resistance of the vehicle under the condition of 0 meters and 20 °C to different altitudes and temperatures, while the error is controlled within 6%.The modified coasting resistance method can be kept within 4% in most cases, and it is applicable to different types of vehicles.

In order to satisfy regulations of CHINA 6 and the corresponding standards of fuel consumption, a variety of advanced technology are adopted. While manufacture calibrate engine based on WLTC and NEDC test cycle during development process, and the technical route is still a lack of a large number of test research on CLTC. This article firstly investigates mainstream technology on market, then in-depth study influence of different test cycle on emissions and fuel consumption, comparing difference of test data to evaluate the potential of each technology route for emission and fuel economy, as well as the adaptability of each technology route under CLTC. Finally, to seek the advanced technology route of energy-saving and emission reduction applicable to national conditions.

During the development of a model equipped with dual VVT engines, a higher temperature of the catalyst was discovered. Therefore, the sweep point of VVT is optimized under low speed and high load conditions. The test results show that VVT has a significant effect on the temperature of the catalytic converter, and the temperature of the catalytic converter has decreased after optimization. At the same time, the VVT opening has little effect on the dynamics. In addition, VVT has an effect on the knocking tendency of the engine. When the knocking tendency increases, the temperature of catalytic converter and power performance of the engine are deteriorated. On the contrary, if the ignition angle can be advanced, the performance of the engine can be optimized.

This study exhibits the effect of different damage mechanisms on the mechanical behavior of composite laminates subjected to low‐velocity impact load. To achieve this, seven low‐velocity impact energies were applied to laminates with five different thicknesses and four unique stacking sequences. The extent of damage was quantitatively evaluated through contact measurements and ultrasonic C‐scan techniques. Numerical simulations, showing good agreement with experimental results, characterized the distribution and evolution of damage within the laminates. The findings reveal that when matrix and delamination damage are predominant, the dent depth increases slowly and is visually invisible, while the delamination area expands almost linearly. Conversely, When fiber damage prevails, the laminate absorbs more energy, leading to rapid increases in dent depth, the appearance of visible cracks, and the occurrence of sharp fluctuations with multiple peaks in contact force and displacement curves. Nonetheless, the delamination area and projection tend to be stable and unchanged. Furthermore, alterations in thickness and stacking sequence directly affect the damage characteristics and energy absorption properties. This research offers valuable theoretical insights and serves as a reference for enhancing the comprehension of the failure mechanism of laminates and optimizing their performance. Highlights: Demonstrate the utility of dent depth in identifying changes in damage mechanisms.Evaluate the delamination damage of laminates after impacts by ultrasonic C‐scan techniques.Reveal the regulation of impact response parameters for different damage mechanisms.Investigate the effect of variation in thickness on damage characteristics and energy absorption.Evaluate the impact resistance of laminates with different stacking sequences. [ABSTRACT FROM AUTHOR]

In this paper, the light duty that meets the China 6 emission standard is selected to study the emission characteristics of different emission control technology routes under China light-duty vehicle test cycle (CLTC). The results show that the cold start stage of CLTC cycle is still the stage with the most pollutant emissions. The THC, CO and NOx emissions of vehicles on the supercharged direct injection technology are higher than those on the naturally aspirated port fuel injection technology. In terms of reducing the exhaust emission, PHEV technology route is the best, followed by naturally aspirated PFI technology route, and then turbocharged direct injection with GPF route.

According to the requirements of PVE proposed in the China 6 Emission Standard for light-duty vehicles, this paper compares a fault code respectively from cooling system monitoring, oxygen sensor monitoring and integrated component monitoring of Spark Ignition Engines, and analyzes the diagnosis principles and simulation methods under three engine control systems in detail. The results show that the fault diagnosis principles for UAES system and Bosch system are similar, and the simulation methods can learn from each other. The fault diagnosis principles of the two systems are different from those of Delphi system, and the simulation methods depend on the fault failure mode.

This paper focuses on light duty of china 6 with the same emission control technology. three vehicles, with different engine displacements, were selected to study the emission and fuel consumption characteristics under three test cycles of NEDC, WLTC and CLTC. The results show that the emissions of CO, THC and NOx under WLTC cycle are minimum, compared with the NEDC and CLTC circulation. with the decrease of the engine displacement, the difference of CO and THC emissions increases among different cycles, which shows small displacement engine vehicles are greatly affected by driving cycles. Compared with other testing conditions, the PN emissions are relatively larger, but the difference of PN emissions is very small among the three test cycles.The fuel consumption of the WLTC test cycle is the smallest among the three cycles. As the engine displacement decreases, the fuel consumption difference decreases, indicating that the fuel consumption of large displacement engine vehicles is greatly affected by the cycle condition.

During the development of a CN Ⅵ light vehicle equipped with a GDI gasoline engine, the phenomenon of high PN appeared. In response to the operating conditions of the engine running in the WLTC cycle, a corresponding SOI sweep was performed on the dyno bench. The PN emissions of the engine has reduced by optimizing of SOI. The results show that when the SOI is sufficiently advanced, the oil film formed by the collision of the spray and the piston causes the PN emissions to increase significantly. In order to avoid the deterioration of the PN emissions, the SOI should be appropriately postponed. In the low load conditions, it is more appropriate to calibrate the SOI at 295°CA and 290°CA. In the medium speed area, it is more suitable to set it at 300°CA or later. The SOI in the higher speed area can be slightly advanced if necessary. And the impact of SOI on fuel consumption is more obvious at low speeds, but it is not obvious at the conditions of medium to high loads and speeds.

Under transient conditions, the emission of turbocharged diesel engine will deteriorate to a certain extent, and the adoption of EGR is also a factor leading to the increase of some pollutants. For this reason, a high pressure common rail turbocharged and inter-cooled heavy duty diesel engine was used to study the influence of EGR closed-loop control method on the emission performance under typical transient conditions with constant speed and torque increasing in 5s. The results show: The NOx emission can not be effectively reduced when the air input is used as feedback parameter; When the intake oxygen concentration is used as feedback parameter, smoke emission will increase sharply; When exhaust oxygen concentration is used as feedback parameter, the smoke deterioration is less, the peak smoke is 15.8%. It has a better compromise relationship with NOx and fuel consumption, and can be used as closed-loop control parameter for diesel engine transient performance optimization.

Production Vehicle Evaluation (PVE) test mainly verifies the functionality of OBD system. PVE J2 test needs to verify the diagnostic mechanism for all the diagnostic Trouble Codes (DTC). While the design of fault simulation method is one of the technical difficulties of the whole PVE test. Due to the late start of PVE in China, test methods and technical skills are inadequate. This paper elaborates the failure monitoring principle and diagnosis mechanism of OBD system in detail,systematically introduces the PVE methods and J1, J2, J3 test procedures, studies and analyses the types of OBD malfunction and various fault simulation methods,finally forms a set of PVE test specifications.

The gasoline compression ignition (GCI) is deemed to be one of the effective ways to achieve efficient and clean combustion. However, the low in-cylinder temperature under idle and low-load conditions leads to certain problems, such as difficulties in the ignition and unstable combustion. In this paper, based on a refitted single-cylinder diesel engine, the combustion stability of the GCI mode under idling speed and low-load conditions was studied. The combustion stability and thermal efficiency were improved by adjusting the intake temperature, the coolant temperature and the injection strategy. During the test, the engine speed was set to 800 rpm at the idle condition and 1300 rpm at the low-load condition, and the gross indicated mean effective pressure was 5.5 bar. The injection mode of the fuel was direct injection with one injector. The results indicated that when the injection timing was −15°CA ATDC, and the intake temperature was increased from 50°C to 60°C under the idle condition; the gross indicated thermal efficiency (ITEg) was 39.7%, an increase of 8.5%. Under the low-load condition, increasing the coolant temperature can improve the combustion stability. Specifically, when the coolant temperature was increased from 70°C to 90°C and the injection timing was −27°CA ATDC, an ITEg of 52.1% can be realized. [ABSTRACT FROM AUTHOR]

Abstract\nHIGHLIGHTSThe high specific strength and stiffness of carbon fiber-reinforced polymer (CFRP) stiffened plates make them popular in aerospace and other fields. Nevertheless, CFRP stiffened plates have unique characteristics and complicated and diversified failure patterns, so it is impossible to determine its failure law with a uniform failure criterion accurately. Its load-carrying capacity has always been calculated on the conservative side of empirical estimation. This work uses the stressing state theory to investigate the stressing state evolution of composite stiffened plates under axial loading. It conducts three CFRP stiffened plates of the same configuration from a thermodynamic perspective. By equating stiffened plates to thermodynamic systems, the measured strain data are modeled as state variables, and renormalization and clustering algorithms are applied to determine the phase transition loads of the structure, while the characteristic points before and after normalization are verified for their reasonableness and stability. Accordingly, this work reveals the failure laws of CFRP stiffened plates by applying a thermodynamic-based method. It characterizes the structural failure features by defining catastrophe points throughout the failure process, which provides a new reference for the failure analysis and strength design of CFRP stiffened plates.Three full-scale CFRP stiffened plates of the same configuration were tested by axial loading.A network-free renormalization was applied to construct modes and characteristic parameters of CFRP stiffened plates.A clustering algorithm was applied to reveal the phase transition loads of CFRP stiffened plates.The stability and accuracy of the phase transition loads of CFRP stiffened plates are verified. [ABSTRACT FROM AUTHOR]