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2022, 42(1): .

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2022, 42(1): .

Abstract(141) PDF(18)

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Study on Erosion Contact Search Algorithms for Explicit Finite Element

CHEN Chengjun, CHEN Xiaowei, LIU Ming

2022, 42(1): 1-10. doi:10.15918/j.tbit1001-0645.2021.127

Abstract(241) PDF(49)

Abstract:
An efficient and accurate erosion contact algorithm is essential for numerical simulation of impact dynamics problems, such as projectile perforation/penetration, high velocity contact, etc. Also,it is one of the most crucial algorithms of the explicit finite element code. In this paper one accurate and robust erosion contact searching algorithm was developed based on the node-to-segment discrete modeling. The ambiguity of contact between slave node and potential contacting master segments was resolved by introducing one history variable together with the contact strength conception. As a result, the slave node-master segment pair and the corresponding contact direction is determined accurately. In contact point computation, one kind of non-iterative algorithm was established, to improve the stability of erosion contact algorithm. All the algorithms were implemented based on explicit finite element code PANDA-Impact, and the effectiveness and robustness were verified by typical numerical examples. The simulation results show the proposed algorithms can be used to simulate complex engineering problems with high accuracy.

Study on Protective Performance of Three Kinds of Reinforced Concrete Anti-Blast Structures

WANG Cheng, ZHONG Yanxu, WANG Wanli, ZAN Wentao, CHI Liyuan, WEI Xinxi

2022, 42(1): 11-18. doi:10.15918/j.tbit1001-0645.2021.137

Abstract(316) PDF(38)

Abstract:
In view of the protection requirements for the safe production and storage of flammable, explosive and other hazardous chemicals, three types of new reinforced concrete anti-blast structures with different configurations were designed to replace the traditional protective embankment, including straight, oblique and L-shaped types. Based on the self-developed high-precision large-scale simulation software with completely independent intellectual property rights, taking TNT explosive as example, the full-scale high-precision numerical simulation on the anti-explosion performance of three different structures was carried out. The results show that all new reinforced concrete anti-blast structure can effectively obstruct the explosive blast wave. The peak overpressure of shock wave decreases drastically, and the L-shaped reinforced concrete anti-blast structure can provide a better protection than the straight and oblique structures. The findings possess significance for guiding the design and construction of the new reinforced concrete anti blast structures.

A Topology Optimization Method for Support Structure of Dry Disc Brake

REN Yiru, XIANG Jianhui, YANG Lingling, NING Keyan

2022, 42(1): 19-27. doi:10.15918/j.tbit1001-0645.2020.178

Abstract(156) PDF(16)

Abstract:
To control deformation of the support structure of dry disc brake, a topology optimization design model was proposed. Firstly, based on the variable density method, an optimization model was established with the minimum displacement of the key control points of the supporting structure as the objective function. It was arranged to control the deformation of the key position of the support structure by setting the minimum distance between the key point and its corresponding target coordinate. And then the weighting factors of key points were used to highlight the primary and secondary relationship of optimization objectives. The topological configuration of the supporting structure in three different design domains was analyzed, and the influence of constraint conditions on the topology optimization structure was studied. Finally, a composite hole and groove structure was designed for the support structure optimization pillar with a triangular-like through hole in the lower right corner and a larger shallow groove structure on the outer surface. The results show that as the volume reducing, the maximum deformation and maximum stress of the support structure will increase accordingly. In the case of the maximum displacement unchanged, the volume of the optimized support structure finally obtained can be reduced by 10.2%. In the case of the same volume, the maximum displacement can be reduced by 9.4%. When the volume is reduced by 6.0%, the maximum displacement can be reduced by 4.1%.

A New Crack Depth Evaluation Feature of Planetary Gear and Its Application

WU Shoujun, FENG Fuzhou, WU Chunzhi, JIA Ziyong

2022, 42(1): 28-35. doi:10.15918/j.tbit1001-0645.2020.184

Abstract(156) PDF(11)

Abstract:
In order to accurately evaluate the damage degree of planetary normal and to improve the evaluation guidance capability for equipment maintenance, a translation-torsion dynamic model was established for planetary gear train. Analyzing the variation of spectrum amplitude and crack degree of planetary gear train in dynamic simulation signal, a new crack depth evaluation feature was proposed based on the Ratio of Cumulative amplitude of Multiple Fault frequency to Amplitude of Meshing frequency (RCMFAM). The results show that, compared with the typical time-domain and frequency-domain features, the proposed feature can offer a better correlation and strong consistency with the crack damage degree. In the validating experiments with normal, 50% crack damage and broken tooth gear, the evaluation results are basically consistent with the actual crack depth, verifying the effectiveness of the proposed features.

Research on the Selection of Light Source and Material Removal in Water Jet Guided Laser Processing

LI Jingyi, LI Yuan, DING Ye, WANG Yang, YANG Lijun

2022, 42(1): 36-45. doi:10.15918/j.tbit1001-0645.2021.053

Abstract(227) PDF(19)

Abstract:
The parameter of light source can influence greatly on the processing ability of water jet guided laser. Aiming at the selection of light source, a physical model was established to describe the interaction between laser and water so as to expand the application field of water jet guided laser processing. The evolution of free electron density in the focus region of laser under different pulse durations and wavelengths was simulated based on a Runge-kutta method. The influence of physical processes such as multiphoton ionization, avalanche ionization, electron diffusion and recombination on the free electron density was investigated. The theoretical breakdown thresholds of water with different laser parameters were determined, and the corresponding verification experiments were carried out. On these bases, using appropriate laser source, a water jet guided laser processing was carried out for 304 stainless steel. The results show that the application of proper laser source can be beneficial for promoting the coupling efficiency of laser and water jet and reducing the coupling loss as well as suppressing the generation of thermal defects, consequently can provide high processing quality.

Time Domain Simulation and Optimization of Ride Comfort for Vehicle Active Suspension

RONG Jili, DENG Zengkun, HE LI, WANG Xi, CHENG Xiuyan

2022, 42(1): 46-52. doi:10.15918/j.tbit1001-0645.2021.105

Abstract(201) PDF(15)

Abstract:
In order to eliminate the adverse effects of severe vibration on the ride comfort and stability of the vehicle, the Lagrange's equation was used to establish the 17 degree-of-freedom (DOF) dynamic equations of the road-vehicle coupling. A time domain model of road unevenness excitation was established by using linear filter white noise method. According to modern control theory, the state equation of suspension system with multiple inputs and multiple outputs was established. An active suspension controller was designed based on linear quadratic Gaussian (LQG) control theory, and the weighted parameters of the controller were optimized based on particle swarm optimization (PSO). The simulation results indicate that the ride comfort of the vehicle can be greatly improved under the control of the active suspension system. At the same time, the handling stability and structural stability of the vehicle can be enhanced, and the overall performance of the vehicle can be comprehensively improved.

Vehicle Product Family Design Based on Multidisciplinary Design Optimization

CHEN Xiaokai, WANG Chenyu, SHI Guobiao, YANG Zifa

2022, 42(1): 53-62. doi:10.15918/j.tbit1001-0645.2021.029

Abstract(162) PDF(17)

Abstract:
For the purpose of enhanced performance of automotive product platforms and product families as well as maintaining high development efficiency, a product family optimization design method that combines shared variable decision-making and multidisciplinary design optimization (MDO) was proposed.Firstly, the basic concepts related to product family design optimization were clarified.Then, the mathematical description and MDO model of the product family optimization problem were established, and an improved product family design process was elaborated as follows.Ultimately, the effectiveness and feasibility of the proposed optimization method was proven through the application to the chassis product family optimization problem of an automotive product platform.The results show that this proposed method can maximize the generalization rate of vehicle parts and components under the premise of ensuring key performance, handle collaborative optimization of multi-product and multi-object, and give full play to the advantages of product platforms, compared to Non-platform development.

Research on Redundant Control of AMT System Gear Shifting Process Based on Decision Tree Algorithm

LIU Haiou, LU Jiaxing, PENG Jianxin, QIAO Daoyun, ZHAO Yinong

2022, 42(1): 63-73. doi:10.15918/j.tbit1001-0645.2020.205

Abstract(211) PDF(15)

Abstract:
In order to improve redundant control of the AMT system gear shifting process, considering the failure condition of the gear shifting displacement sensor, a redundant control strategy was proposed based on decision tree algorithm. The air pressurep, the transmission input shaft speedn₁, the transmission output shaft speedn₂and the synchronous speed difference of the synchronizer Δnwere selected as the characteristic variables, and the gear shifting time was selected as the predicted value to establish a gear shifting time decision tree prediction model. To obtain an optimal decision tree model, a cross-validation and the original decision tree pruning were arranged. The results show that the prediction accuracy rate of the gear shifting time can reach up to 90% with the error less than 50 ms. The bench test and actual vehicle verification results show that, when the gear shifting sensor fails, the solenoid valve control strategy based on this algorithm can ensure the normal shifting operation. Comparing the actual transmission ratio with the theoretical transmission ratio predicted by the control strategy, the operation results show that the judgment error of the predicted shifting time is all within 50 ms.

Research on Nonlinear Dynamic Characteristics of Synchronizerless Transmission Based on Sliding Sleeve Position Angle

SONG Qiang, ZHANG Wei

2022, 42(1): 74-82. doi:10.15918/j.tbit1001-0645.2021.060

Abstract(131) PDF(13)

Abstract:
In order to analyze the influence of the dynamic characteristics of the sliding sleeve and the engagement ring gear on the shifting process in the two-speed automatic mechanical transmission system (AMT) without a synchronizer, a position angle of the sliding sleeve was defined to determine the specific collision between the sliding sleeve and the ring gear.Firstly, a nonlinear dynamic model of the sliding sleeve and the ring gear was established.Then, considering the non-linear factors such as meshing stiffness, meshing damping, tooth side clearance, and static error, a dynamic model of the gear shifting process was established.Comparing with the synchronizer model in simulation analysis, the advantages of the synchronizer-less AMT system were embodied.Finally, the simulation was carried out to analyze the influence of different magnitudes of axial thrust on the shifting process.The results show that 150N axial thrust is more appropriate.This analysis method can be taken as a reference for selecting the appropriate axial thrust and the application of the AMT system in engineering.

AB+CCircuits Design in Galois Fields Based on Quaternary Logic

WU Haixia, LI Lingyu, WANG Tian, WANG Xinghua, LI Xiaoran

2022, 42(1): 83-88. doi:10.15918/j.tbit1001-0645.2021.078

Abstract(145) PDF(12)

Abstract:
In order to reduce the long latency and circuit complexity, a quaternary algorithm ofAB+Cand its implementation were presented based on systolic array structures in GF(2⁴). The systolic structure was arranged to employ a quaternary logic technique based on dynamic source-coupled logic to do arithmetic operations, to use current-mode signals to decrease the initial delay, transistors and wires. A simulation evaluation was carried out with a 0.18 μm CMOS technology. The results show that, compared with the corresponding binary CMOS implementations reported in references, the initial delay and the sum of transistors and wires in this design can be reduced about 54% and 5%. The parallel-in parallel-out systolic structure proposed is simplicity, modularity and scalability, being suitable for VLSI implementations. The scheme of combining multiple-valued circuits and corresponding algorithms based on multiple-valued logic (MVL) is expected to be a feasible alternative for super performance arithmetic units in GF (2^k).

Multisatellite Signal Joint Acquisition Algorithm Based on Composite Pseudocode

ZHANG Tianqi, MENG Ying, WANG Xiaoye, CHEN Xianlu

2022, 42(1): 89-96. doi:10.15918/j.tbit1001-0645.2021.114

Abstract(154) PDF(9)

Abstract:
In order to reduce the first positioning time of Binary Offset Carrier (BOC) modulation signals during cold start, a multi-satellite signal joint acquisition algorithm was proposed based on composite pseudocode to realize the simultaneous acquisition of multiple satellite signals. Firstly, the pseudo-codes corresponding to different satellite signals were added together to generate the composite pseudo-codes. And then the received signals and the composite pseudo-codes were processed with the circle correlation to obtain the maximum correlation value. Finally the maximum correlation value was processed based on Teager-Kaiser to reduce the impact of noise. The simulation results show the advantages of this method, including the reduction of the acquisition time and the calculation amount. Under the same false alarm condition, the TK algorithm applied in this algorithm can improve the detection probability. Compared with the detection probability of direct correlation method, the maximum detection probability of this method can increase about 5 dB.

MDF-ANet:Vision Fusion Semantic Segmentation for Low-Light Autonomous Driving

CHANG Liang, BAI Jie, HU Huihui, ZHONG Hongliang

2022, 42(1): 97-104. doi:10.15918/j.tbit1001-0645.2021.076

Abstract(147) PDF(16)

Abstract:
To solve the problem of performance degradation of existing segmentation model with low light condition, MDF-ANet based on RGB and Depth feature fusion network was proposed. First, the two-way feature extraction network was arranged to extract the RGB and depth features respectively, so as to perform sufficient feature learning on the original data. Then, a feature fusion module was designed to fuse the output feature maps of two-way feature extraction network at different scales. Finally, the fused output feature maps of each scale were input into the multi-scale upsampling fusion module to learn complementary information between different receptive fields. And then upsampling was performed to obtain the final segmented image with a size equal to the original input size. A series of experiments were carried out on Cityscapes and its converted faked-night dataset. Results show that 62.44% mean intersection over union (mIOU) is achieved on validating dataset. Compared with models trained with only RGB, the proposed model can obtain a 9.1% improvement, improving the image segmentation performance with low light condition effectively.

Effect of Enzymatic Hydrolyzed Bone Powder on Calcium Supplement for Low Calcium Rats

LI Yujuan, XIAO Nan, LIU Shan, LIU Feifei, SUI Yan

2022, 42(1): 105-110. doi:10.15918/j.tbit1001-0645.2021.061

Abstract(461) PDF(15)

Abstract:
To investigate the effect of enzymatic hydrolyzed bone powder (EBP) on calcium supplement for low calcium rats. 6-week low calcium diet was used to establish a low calcium model. EBP (200, 400, 800 mg/kg) was orally administered to low calcium rats respectively for 4 weeks. The femur of rats was analyzed by HE staining.The mechanical index, dry weight, ash weight,and bone mineral density of the femur were measured. Femur calcium content, femur phosphorus content and the apparent absorption rate of calcium were determined. Results show that the bone trabecula is significantly decreased and the bone marrow cavity is remarkably enlarged in low calcium rats. After administration of EBP, the number of bone trabecula has increased and the area of bone marrow cavity has decreased. The bone mineral density of rats in high dose EBP can enhance by 14.1%. Besides, the content of calcium and phosphorus in the femur and the apparent absorption rate of calcium can increase significantly (p<0.05). These findings suggest that EBP can promote calcium absorption, increase bone mineral density and bone calcium content in low calcium rats, being a potential calcium supplement.

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