Surface Engineering

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Authors: Guo Qing Chen, Da Zhang, Jun Hui Song, Yan Song Zeng, Zhi Qiang Li, Wen Long Zhou
Abstract: The high pressure waterjet peening (WJP) was adopted to strengthen the surfaces of 7075-T651 aluminum alloy. The results demonstrate that the processing parameters such as shooting distance, holding time and water pressure affected the abrasive capacity of gas cavities significantly. Compared with non-peening and shot peening (SP) specimens, the fatigue life of as-WJPed specimens was improved by 22% and 6.6%, respectively. The maximum residual compressive stress generated by WJP and SP was approximately equivalent, which is −350 ≤ σ ≤ −400MPa. While the residual compressive stress near the strengthened surface introduced by WJP was higher than that of SP, hence the fatigue life of WJPed specimen increased much more. The surface roughness strengthened by WJP was also better than that of SP. Because the surface profile was well protected in WJP, the good surface qualities also insured a long fatigue life.
Authors: Gang Ma, Xiang Ling, Yuan Song Zeng
Abstract: A 3D finite element model is established to simulate the ultrasonic shot peening process by using a finite element software ABAQUS. The residual stress distribution of the AISI 304 stainless steel induced by ultrasonic shot peening (USP) is predicted by finite element analysis. Ultrasonic shot peening (USP) process can cause a compressive residual stress layer on the surface of the material. During the simulation, many factors, e.g., ultrasonic shot peening duration, initial residual stress, hourglass, etc., are taken into consideration for the purpose of optimizing the process. The simulation results show that ultrasonic shot peening can produce a compressive residual stress layer on the surface of the material even if there is initial residual tensile stress (250MPa) and the longer peening duration. The residual stress of simulation were compared with the experiment data which were obtained under the same ultrasonic shot peening parameters and have a good agreement with the measurement values by X-ray diffraction method. In conclusion, ultrasonic shot peening is an effective method for protecting weldments against stress corrosion cracking by introducing the compressive residual stress layer into the surface of stainless steel.
Authors: Hai Jiang, Xin Zhang, Yao Gang Yu, Zheng Gen Yu, Xin Bo Lan
Abstract: Through analyzing the causes and damage of the fouling in water channel of water cooling engine, this paper develops a new kind of compound cleaning and descaling agent and conducting polyaniline corrosion agent of the water tank. This new cleaning agent is stable and harmless, and can be added to the cooling system directly without the special equipment. With the circulation of the coolant, the agent can remove the scale, and then the removed scale flows out of the auto with the coolant. Except for this new cleaning agent, the antiseptic, whose major agent is the conducting polyaniline, can decrease and even stop the corrosion of the water tank and cooling system’s parts, and at the same time, the formation of the scale can also be restrained notably. When the agent is in use, it can be added(press 1% ratio to join) wholly into the water port, or complemented at any time, so that the quick cleaning and the anticorrosion are realized without disassembling and corroding the engine. By using these agents the cleaning efficiency of the engine cooling system is improved, the favorable engine’s technology situation is kept, and the engine’s life-span is also increased efficiently.

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