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14 pages, 3786 KiB

Open AccessArticle

Welding Residual Stress Elimination Technique in the Top Chord of Main Truss of Steel Truss Bridge

by Long Piao, Jianfeng Yuan, Niujing Ma, Changqi Yue, Ronghui Wang and Gangbing Zheng

Buildings 2023, 13(5), 1267; https://doi.org/10.3390/buildings13051267 - 12 May 2023

Cited by 3 | Viewed by 2017

The large-amplitude fluctuations of ultrasound in high-energy ultrasonic stress relieving cause the crystal grains or lattices in the high residual stress zone to vibrate or creep alternately. This triggers secondary effects such as ultrasonic softening and dislocation movement. The sound field also produces periodic shock waves or intermittent shock waves, which form local pressure gradients at the wave front. These pressure gradients cause local heating of the grain boundary, accelerating material softening and promoting slip between grains, ultimately resulting in residual stress elimination. This technique was applied to detect the welding residual stress of the upper chord of the main truss of Sanguantang Bridge by using an ultrasonic stress meter. After the measurement, it was found that the welding residual stress in some areas was too large, and the welding residual stress needed to be eliminated. The welding seam was re-inspected after the residual stress relief operation was completed. The test results showed a maximum reduction rate of 63.91% and an average overall reduction rate ranging from 24.52% to 37.23%. The reduction effect is more significant in areas with higher welding residual stress. Full article

(This article belongs to the Special Issue Recent Scientific Developments in Steel Structure)

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25 pages, 6926 KiB

Open AccessReview

Application of Lightweight Structure in Automobile Bumper Beam: A Review

by Bing Du, Qichang Li, Changqi Zheng, Suozhu Wang, Cong Gao and Liliang Chen

Materials 2023, 16(3), 967; https://doi.org/10.3390/ma16030967 - 20 Jan 2023

Cited by 55 | Viewed by 15214

Abstract

The bumper beam is an important device to ensure the safety of the car, which can effectively alleviate the force and absorb energy when the car collides. Traditional bumper beams are mostly made of high-strength steel, which has high strength and a low production cost but a heavy weight. With the requirement of being lightweight, high-strength steel is not able to meet the needs of lightweight cars, and composite materials have become the answer to the problem of a light weight in cars due to their excellent performance of being lightweight and high strength. This article introduces the case study on materials of bumper beams and presents the application of traditional materials and composite materials in bumper beams. Then, the fabrications and processes of bumper beams, a performance assessment, experimental tests, and a finite element analysis of the bumper beam are carried out. This paper also represents the study of optimization in automobile bumper beams. Full article

(This article belongs to the Special Issue Lightweight and High-Strength Sandwich Panel)

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17 pages, 4405 KiB

Open AccessArticle

Preparation of Alkali Activated Cementitious Material by Upgraded Fly Ash from MSW Incineration

by Hongwei Chen, Runbo Zhao, Wu Zuo, Guanghui Dong, Dongyang He, Tengfei Zheng, Changqi Liu, Hao Xie and Xinye Wang

Int. J. Environ. Res. Public Health 2022, 19(20), 13666; https://doi.org/10.3390/ijerph192013666 - 21 Oct 2022

Cited by 8 | Viewed by 2540

Abstract

Utilization of municipal solid waste incineration fly ash (MSWI-FA) can avoid land occupation and environmental risks of landfill. In this paper, MSWI-FA was used to prepare alkali activated cementitious materials (AACMs) after two-step pretreatment. The ash calcination at 450 °C removed 93% of dioxins. The alkali washing with 0.2 g NaOH/g ash removed 89% of chlorine and retained almost 100% of calcium. The initial setting time of AACMs was too short to detect for 20% of MSWI-FA addition, and the prepared block had extensive cracks and expansion for CaClOH and CaSO₄ inside. Alkaline washing pretreatment increased the initial setting time by longer than 3 min with 30% ash addition and eliminated the cracks and expansion. The significance of the factors for compressive strength followed the modulus of alkali activator > silica fume amount > alkaline washing MSWI fly ash (AW-MSWI-FA) amount. When the activator modulus was 1.2, 1.4 and 1.6, the blocks with 30% of AW-MSWI-FA had a compressive strength of up to 36.73, 32.61 and 16.06 MPa, meeting MU15 grade. The leaching test shows that these AACM blocks were not hazardous waste and almost no Zn, Cu, Cd, Pb, Ba, Ni, Be and Ag were released in the leaching solution. Full article

(This article belongs to the Special Issue Solid Waste Pretreatment, Treatment and Disposal)

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9 pages, 2268 KiB

Open AccessCommunication

Mechanical Property of Long Glass Fiber Reinforced Polypropylene Composite: From Material to Car Seat Frame and Bumper Beam

by Bing Du, Zhengxuan Li, Huimin Bai, Qian Li, Changqi Zheng, Jingwei Liu, Feng Qiu, Zhenhua Fan, Hanjie Hu and Liming Chen

Polymers 2022, 14(9), 1814; https://doi.org/10.3390/polym14091814 - 29 Apr 2022

Cited by 34 | Viewed by 4467

Abstract

Long Fiber Reinforced Thermoplastic (LFT) is a lightweight, high-strength, and easy-to-recycle new vehicle composite material, and has good mechanical properties, heat resistance, and weather resistance, which has found increasing application in automobile industry. It is of importance to understand the relationship between micro phase, macro-mechanical properties and the structural performance of automobile components. This article evaluates the performance of LFT from the level of material to automobile components. The mechanical properties of LFT were numerically and theoretically predicted to provide instruction for the next material choice. Two typical structural components, namely, car seat frame and bumper beam, were selected to evaluate the performance of LGF/PP compared with other competing materials in terms of mechanical properties and cost. In the case of the same volume, the seat frame of 40% LECT/PP composite material is lighter and cheaper, which is conducive to energy saving and emission reduction. It was shown that the 40% LECT/PA66 car bumper beam had a higher energy absorption ratio, lighter weight, higher specific energy absorption, and advantageous material cost. LFT is a promising candidate for existing automobile components with its performance fulfilling the requirements. Full article

(This article belongs to the Special Issue Molecular Simulation and Modeling of Polymers)

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80 pages, 8682 KiB

Open AccessReview

Biological Activities of Some New Secondary Metabolites Isolated from Endophytic Fungi: A Review Study

by Ruihong Zheng, Shoujie Li, Xuan Zhang and Changqi Zhao

Int. J. Mol. Sci. 2021, 22(2), 959; https://doi.org/10.3390/ijms22020959 - 19 Jan 2021

Cited by 115 | Viewed by 9717

Abstract

Secondary metabolites isolated from plant endophytic fungi have been getting more and more attention. Some secondary metabolites exhibit high biological activities, hence, they have potential to be used for promising lead compounds in drug discovery. In this review, a total of 134 journal articles (from 2017 to 2019) were reviewed and the chemical structures of 449 new metabolites, including polyketides, terpenoids, steroids and so on, were summarized. Besides, various biological activities and structure-activity relationship of some compounds were aslo described. Full article

(This article belongs to the Section Biochemistry)

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