The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Investigation on diamond tool wear in ultrasonic vibration-assisted turning die steels

This paper presents comprehensive theoretical analyses and experimental investigations for evaluating the ultrasonic vibration-assisted turning (UVAT) of die steels with single-crystal diamond tools. The diamond tool wear was found to rely heavily on the feed rate and the cutting speed while being insensitive to the depth of cut and the tool relief angle under the cutting conditions used in the tests. The tool wear characteristics were further studied based on the observation of wear zone using Raman spectral analysis and energy-dispersive X-ray (EDX) analysis. The detection results of the tool worn topography, the phase transformation and the carbon diffusion of diamond crystals revealed that tool wear mainly occurred on the tool flank face due to the graphitization and the diffusion of the diamond tool. Analytical results of the function mechanisms of the ultrasonic turning indicated that the friction force between the tool flank face and the machined surface, which depended mainly on the ratio of the cutting speed and the vibration speed, could be effectively reduced in ultrasonic turning process. The analytical and experimental results indicated that compared with conventional turning (CT), the cutting performance, in terms of the tool life, was markedly improved by applying ultrasonic vibration to the cutting tool.     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Shape identification for water–ice interface within the cylindrical capsule in cold storage system by inverse heat transfer method

In this study, the inverse heat transfer method is applied to shape identification for the ice layer within the cylindrical capsule in cold storage system. The approach is constructed by combining the curvilinear grid generation scheme, the direct problem solver, the conjugate gradient optimization method, and the redistribution method. According to the practical condition of freezing ice, shape identification for the water–ice interface based on the data of the outer surface temperature is attempted. Results show that the profile of the water–ice interface is possible to be identified by using the inverse heat transfer approach and the accuracy of the ice shape identification is dependent on the uncertainty of the outer surface temperature data, the Biot number, the thickness of the ice layer, and the geometric configuration as well.     

力、热载荷作用下纤维在复合材料中的界面应力传递行为

采用三维光弹性实验应力分析和有限元计算两种方法,在拉拔载荷和热残余应力联合作用下,对单丝拔出树脂基复合材料三维冻结切片界面剪应力进行了研究。实验结果和计算表明,在单纤维与基体界面的埋入端及埋入末端附近出现界面残余剪应力的极值;力、热载荷作用下纤维界面剪应力呈抛物线分布,单丝埋入端附近是应力的主要传递区域,最先达到危险应力,出现界面脱胶破坏,然后剪应力沿纤维埋入长度由纤维埋入端附近向埋入末端逐渐传递;界面热残余应力对界面剪应力的影响是使纤维埋入末端应力集中程度降低,使界面剪应力最大值增大。      

Investigations into the improvement of the weather protection of unburnt brick masonry,part 1

In June 2006, the Chair of Structural Design at the Technical University of Dresden was commissioned by the Iranian cultural authority ICHHTO and the UNESCO to perform structural design services for the earthquake‐resistant repair and rebuilding of the Sistani House in the historic citadel Arg‐e‐Bam in the south of Iran. The citadel was until its almost complete destruction by an earthquake on 26 Dezember 2003 the largest building of unburnt brick masonry in the world and is listed as a World heritage Site by UNESCO because of its cultural and historical significance. Surveying and documentation work, archaeological rubble clearance and the rebuilding of the Sistani House after its destruction by the earthquake have taken the team from the department to Bam at regular intervals since 2006. In the course of the work, it became apparent that research was needed in the field of the repair of earthquake‐damaged unburnt brick masonry and into the improvement of the shear strength/earthquake resistance and the weather protection of unburnt brick masonry. The article is subdivided in Part 1, Introduction, test performance and assessment of results for additives to loam render as well as Part 2, Assessment of the results for surface treatment to unburnt bricks and the climatic chamber tests.     

具有多态功能的动态信号分析系统的研究

为了增加仪器使用功能的柔性,同时减轻柔性分析系统开发者的负担,提出了分析系统功能多态的概念和“仪器的使用者也是设计者”的设计思想。即在仪器运行过程中,用户可以动态重组数据分析流程,形成新的分析功能。根据该设计思想建立了共享参数模型的软件体系结构,完成了具有多态功能的动态信号分析系统的设计,并应用该系统生成了共振解调分析功能,对齿轮振动信号进行了正确的故障分析,该研究为分析仪器设计提供了一种全新的开发模式。     

Experimental and Numerical Study of Material Removal in Electrochemical Discharge Machining (ECDM)

In this paper a novel approach is proposed to investigate the characteristics of the plasma channel and material removal in electrochemical discharge machining (ECDM) of glass. For this purpose, a specific pulsed voltage was applied to the ECDM process to perform single discharging on the glass workpiece. In this way, a voltage slightly lower than the critical voltage was applied as the offset voltage. Meanwhile the working voltages above the critical voltage were applied to the process in a specific period of time to produce single sparks. The signatures of the single sparks on the workpiece surface were used to determine the characteristics of the plasma channel. According to the results, the average diameter of 260 µm was achieved for the plasma channel in the glass machining conditions. This paper also reports a thermophysical model for material removal in ECDM process based on the finite element method (FEM) and plasma channel diameter achieved in this study. The amount of the removed material as well as the diameter and depth of the crater, achieved by the FEM, was measured and compared with the experimental outcomes. The results demonstrate the consistency of the proposed model with the experimental observations.     

Shrinkage compensation approach proposed for ABS material in FDM process

Dimensional accuracy of parts manufactured by Fused Deposition Modelling (FDM) greatly suffers from the shrinkage problems of the available polymer materials. This paper proposes a constructive idea for resolving the shrinkage issues and explains how shrinkage could be managed by interior geometry of the artifacts fabricated on desktop 3D printers. The main principle for preventing the deterioration on dimensional accuracy of the holes/slots is to utilize the auxiliary lines located from the hole’s perimeter to the outer boundaries of the artifact. Thus, the shrinkage of these auxiliary line segments simply helps to pull the original hole backward, acting against the predicted contraction. In this paper, the proposed approach will be examined using a finite element analysis tool to predict the shrinkage behavior of the fabricated samples along with necessary measurements taken on the Coordinate Measuring Machine. Additionally, an analytical framework for modeling the shrinkage behavior of ABS is to be elaborated. The coherence of the simulations and the measurements are to be analyzed regarding the effect of the geometry and material color on the shrinkage behavior. The discussion involves the improvement on the dimensional accuracy of 3D printed features.     

Evaluation of fatigue life of steel using steel grain size

The insightful discussion of the relationship between the construction of metallographic and fatigue life and proposition of mathematical relationships describing this relationship was conducted in the paper. This paper presents a method for estimating the fatigue life, based on the construction of the microstructural material taking into account the grain size and the participation of ferrite and pearlite phase.