Optimization of Forged 42CrMo4 Steel Piston Pin Hole Profile Using Finite Element Method

The fatigue failure of the piston pin hole is considered as a key factor affecting the service life of engines. In this work, the piston pin hole profile was designed as tapered shape following a power law. By combining finite element analysis and hydraulic pulsating fatigue tests, the pin hole profile was optimized. It has been found that the maximum contact pressure on the pin hole surface was reduced by 16,7% with appropriate increasing the radius enlarging rate of the piston pin hole, the maximum tensile stress of the piston pin seat was reduced by 13,1%, and the piston pin seat fatigue safety factor was increased by 41,4%, the piston pin hole fatigue safety factor was increased by 15,9%. The piston pin hole’s hydraulic pulsating fatigue test results were found to be consistent with the FEA results. It could be concluded that appropriate increasing the radius enlarging rate of the pin hole could significantly weaken the fatigue wear of the pin hole, further improving its fatigue resistance

Experimental study on the hydraulic fracture propagation of laminar argillaceous limestone continental shale

Laminar argillaceous limestone continental shale is an important oil reservoir in Jiyang Depression, Bohai Bay Basin of China. Affected by the laminar structure, the spatial propagation morphology of hydraulic fracturing is not clear. To reveal the propagation law of hydraulic fracturing pathway in laminar marl continental shale, the mineral content and basic rock mechanics test are firstly carried out on the cores from the wells in Jiyang Depression. Secondly the similar material cores with standard-size and large-size are manufactured and processed. Finally, combined with physical model experiments, acoustic emission and moment tensor inversion techniques, the hydraulic fracturing experiments on the large-size cores under different stress differences are conducted. The experimental results show that the in situ stress (confining stresses), laminar structure, and lithological distribution jointly affect the propagation mode of fractures. As the horizontal stress difference increases, the stimulated reservoir volume gradually decreases, and the number of shear fractures decreases accordingly. Macroscopically, the pump pressure curve shows obvious fluctuation in the case with lower horizontal stress difference, which is the external performance of hydraulic fracture initiation–obstruction–turning–penetrating–obstruction–turning. The content of brittle and plastic minerals has a significant impact on the fracture complexity, particularly the layers with high argillaceous content have a significant inhibitory effect on fracture propagation. The weakly cemented lamination or bedding plane is easy to capture the fracture and make it propagate along the bedding plane, thereby increasing the complexity of fracture network. The research results are expected to provide a theoretical reference for design and optimization of hydraulic fracturing parameter in continental shale oil exploration and development

MEDIATE: Learning to Match Entity Mentions across Text and Databases

Many real-world applications increasingly involve both structured data and text. A given real-world entity is often referred to in different ways, such as ``Helen Hunt'', and ``Mrs. H. E. Hunt'', both within and across the structured data and the text. Due to this {\em semantic heterogeneity}, it remains extremely difficult to glue together information about real-world entities from the available data sources and effectively utilize both types of information. This paper describes the \mediate\ system which automatically matches entity mentions {\em within\/} and {\em across\/} both text and databases. The system can handle multiple types of entities (e.g., people, movies, locations), is easily extensible to new entity types, and operates with no need for annotated training data. Given a relational database and a set of text documents, \mediate\ learns from the data a {\em generative model\/} that provides a probabilistic view on how a data creator might have generated mentions, then applies it to matching the mentions. The model exploits the similarity of mention names, common transformations across mentions, and context information such as age, gender, and entity co-occurrence. To maximize matching accuracy, \mediate\ also propagates information across contexts. Experiments on real-world data show that \mediate\ significantly outperforms existing methods that address aspects of this problem, and that it can exploit text to improve record linkage, and vice versa

Effect of Surface Micro-Hardness Change in Multistep Machining on Friction and Wear Characteristics of Titanium Alloy

The machined surface quality, especially the micro-hardness of machined surface layers, is strongly correlated to the friction and wear characteristics of titanium alloy engineering parts. Therefore, to explore relationship of the local surface micro-hardness change in multistep machining and the surface wear resistance of the machined parts is urgently necessary. The machined surfaces were acquired through two-step (roughing and finishing) and three step (roughing, semi-finishing, and finishing) cylindrical turning experiments. The dry friction and wear tests were carried out by UMT-2 friction and wear tester on the multistep final machined surface along the feed direction. The surface wear microtopography and subsurface microstructure were observed and analyzed by scanning electron microscope. The micro-hardness variation in the local area of the finishing surface will cause the extension of unstable friction time stage while withstanding the cyclic and alternating contact stresses, and the soft–hard alternating area should be the sources of friction and wear defects, for instance cracks, peeling pits, fracture striations and even the wear fracture zone to crack propagation and peeling off. This will be of great significance to accurately control the machined surface quality and adaptively improve the surface wear resistance of titanium alloy components

Surface Properties of Medium-Entropy Alloy Coatings Prepared through a Combined Process of Laser Cladding and Ultrasonic Burnishing

The preparation of functional coatings on metal substrates is an effective method to enhance the surface of steel structures with good serviceability in applications for engineering parts. The objective of this research is to analyze the surface properties of two sorts of medium-entropy alloy (MEA) coatings prepared by laser cladding. After cladding, the two prepared coatings were strengthened by ultrasonic burnishing (UB) treatment. Cladding coating samples before and after being UB-treated were comparatively tested in order to investigate the process effects of UB. When compared with corresponding untreated coating samples, the roughness values of the two sorts of UB-treated samples were decreased by 88.7% and 87.6%, the porosities were decreased by 63.8% and 73.4%, and the micro-hardness values were increased by 41.7% and 32.7%, respectively. Furthermore, the two sorts of UB-treated coating samples exhibited better mechanical properties and wear resistance than corresponding untreated samples