Computer Simulation of the Process of Quenching Large-Size Parts in Water and Aqueous Solutions

The article presents results of the computer simulation of quenching large-size parts in water and aqueous solutions. It has been shown that the main attention should be paid to eliminating film boiling and providing uniform cooling at the surface of the part to be quenched. Simplified formulas for calculating the optimal time of cooling large-size steel parts are presented.

Homogenous strength-toughness match for 20Mn2SiCrMoV bainitic large-size parts via processing of VC particles and quenching control

The problem of insufficient hardenability in general large-size parts always occurs in product manufacturing because of their large size,etc.It is restricted mainly by its own alloy composition with micro-alloy and key quenching and partitioning(Q&P) process.The relationship between the cooling rate and properties of small samples was analyzed as the basis of the initial cooling rate at different positions corresponding to large-size parts combined with controlled austenization temperature in this work.Typical as-treated micro structure after a fast cooling rate is mainly composed of lath bainite,martensite,and retained austenite(RA),while bainite and RA after a slow cooling rate.Simulations showed that cooling control via decreasing spray intensity,meeting higher strength at the surface,and good strength and toughness match can be obtained both at the surface and in the center.As-treated large ring part has~1330 MPa tensile strength and~95 J impact energy at the surface,and meantime,~1191 MPa tensile strength and~70 J impact energy in the center,which narrows the property difference.

Optimization of Fixture Number in Large Thin-Walled Parts Assembly Based on IPSO

There are lots of researches on fixture layout optimization for large thin-walled parts.Current researches focus on the positioning problem,i.e.,optimizing the positions of a constant number of fixtures.However,how to determine the number of fixtures is ignored.In most cases,the number of fixtures located on large thin-walled parts is determined based on engineering experience,which leads to huge fixture number and extra waste.Therefore,this paper constructs an optimization model to minimize the number of fixtures.The constraints are set in the optimization model to ensure that the part deformation is within the surface profile tolerance.In addition,the assembly gap between two parts is also controlled.To conduct the optimization,this paper develops an improved particle swarm optimization(IPSO)algorithm by integrating the shrinkage factor and adaptive inertia weight.In the algorithm,particles are encoded according to the fixture position.Each dimension of the particle is assigned to a sub-region by constraining the optional position range of each fixture to improve the optimization efficiency.Finally,a case study on ship curved panel assembly is provided to prove that our method can optimize the number of fixtures while meeting the assembly quality requirements.This research proposes a method to optimize the number of fixtures,which can reduce the number of fixtures and achieve deformation control at the same time.

Development of Fixture Layout Optimization for Thin-Walled Parts:A Review

An increasing number of researchers have researched fixture layout optimization for thin-walled part assembly during the past decades.However,few papers systematically review these researches.By analyzing existing literature,this paper summarizes the process of fixture layout optimization and the methods applied.The process of optimization is made up of optimization objective setting,assembly variation/deformation modeling,and fixture layout optimization.This paper makes a review of the fixture layout for thin-walled parts according to these three steps.First,two different kinds of optimization objectives are introduced.Researchers usually consider in-plane variations or out-of-plane deformations when designing objectives.Then,modeling methods for assembly variation and deformation are divided into two categories:Mechanism-based and data-based methods.Several common methods are discussed respectively.After that,optimization algorithms are reviewed systematically.There are two kinds of optimization algorithms:Traditional nonlinear programming and heuristic algorithms.Finally,discussions on the current situation are provided.The research direction of fixture layout optimization in the future is discussed from three aspects:Objective setting,improving modeling accuracy and optimization algorithms.Also,a new research point for fixture layout optimization is discussed.This paper systematically reviews the research on fixture layout optimization for thin-walled parts,and provides a reference for future research in this field.

A thermal stress loading technique for large-sized hot dry rock mechanical tests

Testing of large-sized specimens is becoming increasingly important in deep underground rock mechanics and engineering.In traditional mechanical loading,stresses on large-sized specimens are achieved by large host frames and hydraulic pumps,which could lead to great investment.Low-cost testing machines clearly always have great appeal.In this study,a new approach is proposed using thermal expansion stress to load rock specimens,which may be particularly suitable for tests of deep hot dry rock with high temperatures.This is a different technical route from traditional mechanical loading through hydraulic pressure.For the rock mechanics test system of hot dry rock that already has an investment in heating systems,this technology may reduce the cost of the loading subsystem by fully utilizing the temperature changes.This paper presents the basic principle and a typical design of this technical solution.Preliminary feasibility analysis is then conducted based on numerical simulations.Although some technical details still need to be resolved,the feasibility of this loading approach has been preliminarily confirmed.

A Systematic Review of Computer Vision Techniques for Quality Control in End-of-Line Visual Inspection of Antenna Parts

The rapid evolution of wireless communication technologies has underscored the critical role of antennas in ensuring seamless connectivity.Antenna defects,ranging from manufacturing imperfections to environmental wear,pose significant challenges to the reliability and performance of communication systems.This review paper navigates the landscape of antenna defect detection,emphasizing the need for a nuanced understanding of various defect types and the associated challenges in visual detection.This review paper serves as a valuable resource for researchers,engineers,and practitioners engaged in the design and maintenance of communication systems.The insights presented here pave the way for enhanced reliability in antenna systems through targeted defect detection measures.In this study,a comprehensive literature analysis on computer vision algorithms that are employed in end-of-line visual inspection of antenna parts is presented.The PRISMA principles will be followed throughout the review,and its goals are to provide a summary of recent research,identify relevant computer vision techniques,and evaluate how effective these techniques are in discovering defects during inspections.It contains articles from scholarly journals as well as papers presented at conferences up until June 2023.This research utilized search phrases that were relevant,and papers were chosen based on whether or not they met certain inclusion and exclusion criteria.In this study,several different computer vision approaches,such as feature extraction and defect classification,are broken down and analyzed.Additionally,their applicability and performance are discussed.The review highlights the significance of utilizing a wide variety of datasets and measurement criteria.The findings of this study add to the existing body of knowledge and point researchers in the direction of promising new areas of investigation,such as real-time inspection systems and multispectral imaging.This review,on its whole,offers a complete study of computer vision approaches for quality control in antenna parts.It does so by providing helpful insights and drawing attention to areas that require additional exploration.

AN INTEGRATION BY PARTS FORMULA FOR STOCHASTIC HEAT EQUATIONS WITH FRACTIONAL NOISE

In this paper,we establish the integration by parts formula for the solution of fractional noise driven stochastic heat equations using the method of coupling.As an application,we also obtain the shift Harnack inequalities.

“三美论”视角下对比赏析When We Two Parted的汉译本——以查良铮和陈锡麟的译本为例

“三美论”是许渊冲先生提出的翻译理论,所谓的“三美”指的是意美、音美和形美。本文以许渊冲先生的“三美论”为理论指导,对比赏析查良铮和陈锡麟对乔治•戈登•拜伦诗歌When We Two Parted的两个中译本。从意美、音美和形美三个层面,对比赏析两个中译本对原文意境、诗歌节奏和尾韵以及诗歌形式上的再现。在诗歌汉译中,三美难以兼顾,译者在进行翻译时要分清主次,原则是意美大于音美,音美大于形美。

Rapid Manufacturing of Metal Parts

As a key technology of rapid prototyping and manufacturing (RP&M), rapid manufacturing of metal parts is a target of RP&M. Introducing selective laser sintering (SLS), an important branch of RP&M, this paper gives a new method oriented on low power SLS system to fabricate metal parts. With this kind of technology, the mixture of metal and polymer powder is sintered first to get green part, then, after debinding and metal infiltration, dense parts are gotten. In the end, influencing factors of this technology are analyzed. At the same time, some applications are given.

基于PARTS战略的应用型本科旅游管理专业实践教学改革探索

文章在旅游应用型人才培养现状与培养定位严重错位的背景下,以提高学生综合职业能力为目标,创新性地将源自战略管理竞合理论中的PARTS战略引入旅游管理专业实践教学改革中,从教学主体、合作利益、合作机制、教学方式、教学内容五个方面对实践教学体系改革进行了探索,以期提高旅游实践教学效果,强化旅游应用人才培养质量。

Purchasing policy model based on components/parts unification

This paper presents a mathematical model for components/parts unification (CPU) policy. This model considers two components/parts that are functionally interchangeable but purchased from suppliers with different prices and quality characteristics. Because of the buyer's quality preference and suppliers' discount rates for bulky purchases, the model assists the procurement manager to determine how best to purchase the components/parts to meet its demand while minimizing the total acquisition costs.

Studies on the Constituents of Aerial Parts of Scutellaria planipes

首次从木根黄芩地上部分分离出１３个化合物。经理化常数和光谱分析分别鉴定为异甘草甙元（ｉｓｏｌｉｑｕｉｒｉｔｉｇｅｎｉｎ），蓟黄素（ｃｉｒｓｉｍａｒｉｔｉｎ），汉黄芩素（ｗｏｇｏｎｉｎ），芹菜素（ａｐｉｇｅｎｉｎ），粘毛黄芩素Ⅲ（ｖｉｓｃｉｄｕｌｉｎⅢ），紫丁香甙（ｓｙｒｉｎｇｉｎ），白杨素６ＣβＤ葡萄糖８ＣαＬ阿拉伯糖甙（６ＣβＤｇｌｕｃｏｓｙｌ８ＣαＬａｒａｂｉｎｏｓｙｌｃｈｒｙｓｉｎ），白杨素６ＣαＬ阿拉伯糖８ＣβＤ葡萄糖甙（６ＣαＬａｒａｂｉｎｏｓｙｌ８ＣβＤｇｌｕｃｏｓｙｌｃｈｒｙｓｉｎ），黄芩甙（ｂａｉｃａｌｉｎ），汉黄芩甙（ｗｏｇｏｎｉｎ７ＯβＤｇｌｕｃｕｒｏｎｉｄｅ），白杨素７ＯβＤ葡萄糖醛酸甙（ｃｈｒｙｓｉｎ７ＯβＤｇｌｕｃｕｒｏｎｉｄｅ）和两个苯乙醇甙（ａｃｔｅｏｓｉｄｅ和ｍａｒｔｙｎｏｓｉｄｅ）。其中异甘草甙元，蓟黄素和紫丁香甙均为首次从黄芩属植物中分离得到。

Determination of Poliumoside and Forsythoside B in Different Parts of Callicarpa kwangtungensis and Its Plants from Different Habitats

[Objective] This study was conducted to determinate the contents of poliumoside and forsythoside B in Callicarpa kwangtungensis,so as to reveal the distribution of two index components（poliumoside and forsythoside B） in the plant and to compare the contents of these components in the medicinal materials from different habitats.[Methods] Comparison and analysis of the contents of the two target components in different parts（root,branch,leaf and fruit） of Callicarpa kwangtungensis from the same habitat and in Callicarpa kwangtungensis from different production areas were performed according to the pharmacopoeia standard.[Result]The highest content of poliumoside wasdetected in fruit,and the content of forsythoside B was the highest in the branch.The contents of the two kinds of components were in order of branch fruit leafroot;The contents of the components were four times higher than China pharmacopeia（0.5%） in Jian,Tonggu,Anyuan,and Ganzhou of Jiangxi Province and the fifth area,Taijiang County of Qiandongnan Miao and Dong Autonomous Prefecture（QMDAP）,among which Ganzhou and Taijiang showed the highest contents.[Conclusion] The differences of poliumoside and forsythoside B were obvious in different habitats and different parts of Callicarpa kwangtungensis.

Research on the Influence of Cutting Condition on the Surface Microstruct ure of Ultra-thin Wall Parts in Ultrasonic Vibration Cutting

In many fields of high-tech industry the ultra-t hi n wall parts are employed. In this paper the experiments were carried out to dis cuss the surface microstructure of the camera’s guided drawtube by applying ult rasonic vibration cutting device to the traditional lathe. The influence rule of the cutting condition on the surface roughness was put forward, which was drawn by comparing the ultrasonic cutting with the common cutting by use of the cemen ted carbide tool and the polycrystalline diamond (PCD) tool. The test results sh owed that the ultrasonic cutting performs better than the common cutting in the same condition. According to the test results analyzing, the surface characteriz ation is influenced clearly by the rigidity of the acoustic system and the machi ne tool, as well the setting height of the tool tip. Otherwise, the dense regula r low frequency vibration ripples will be scraped on the machined surface. When the tool tip is set higher than the rotating center of the work piece by three t imes of the amplitude of ultrasonic vibration, the vibration ripples behave alig ht; they turn light and shade alternatively when the tool tip is lower than the rotating center of the work piece by three times of the amplitude of ultrasonic vibration. According to the test result analyzing, the following conclusions are put forward: 1) The surface roughness in ultrasonic cutting is better than that in common cutting. Under a one third critical cutting velocity, the value of th e surface roughness in ultrasonic cutting rise slightly along with the cutting v elocity, while in common cutting it decreases contrast to the cutting velocity; the curves of the surface roughness in ultrasonic cutting and common cutting see m to be alike, both increase along with the feed rate and the cutting depth, but the value in ultrasonic cutting is smaller in the same condition.2) The influen ce of the coolant on the surface roughness cannot be ignored. The kerosene can b e employed to improve the surface roughness in ultrasonic machining.3) In ultras onic cutting process of aluminum alloy ultra-thin wall work piece, the PCD tool performs better than the cemented carbide tools.4) The vibration ripples result from the not enough rigidity of the acoustic system and the improper setting he ight of the tool tip. The departure of the tool tip from the rotating center of the work piece to some extent causes the vibration ripples on the machined surfa ce.

System optimization-oriented spare parts dynamic configuration model for multi-echelon multi-indenture system

In order to optimize the spares configuration project at different stages during the life cycle, the factor of time is considered to relax the assumption of the spares steady demand in multi-echelon technique for recoverable item control (METRIC) theory. According to the method of systems analysis, the dynamic palm theorem is introduced to establish the prediction model of the spares demand rate, and its main influence factors are analyzed, based on which, the spares support effectiveness evaluation index system is studied, and the system optimization-oriented spares dynamic configuration method for multi-echelon multi-indenture system is proposed. Through the analysis of the optimization algorithm, the layered marginal algorithm is designed to improve the model calculation efficiency. In a given example, the multi-stage spares configuration project during its life cycle is gotten, the research result conforms to the actual status, and it can provide a new way for the spares dynamic optimization.

Orbital-abrasion-assisted Electroforming of Non-rotating Parts

A novel technique of electroforming with orbital moving cathode was carried out for the fabrication of non-rotating thin-walled parts.This technique features a large number of insulating and insoluble hard particles as a real-time polishing to the cathode.When cathode moves,hard particles polish its surface and provide the nickel non-rotating parts with near-mirror finishing.Morphology,microstructure,surface roughness and micro hardness of deposits fabricated by novel method were studied in contrast with the sample produced by traditional electroforming methods.Theoretical analysis and experimental results showed that the novel technique could effectively remove the hydrogen bubbles and nodules,disturb the crystal nucleation,and refine the grains of layer.The mechanical properties were significantly improved over traditional method.The micro-hardness of the layer was in a uniform distribution ranging from 345 HV to 360 HV.It was confirmed that this technique had practical significance to non-rotating thin-walled parts.

Effect of Temperature and Ram Speed on Isothermal Extrusion for Large-size Tube with Piece-wing

Heat energy change during the extrusion of 7075 aluminium alloy large-size tube with piece-wing in a container was analyzed. Extrusion load vs ram displacement diagrams and exit temperature vs ram displacement diagrams at various speeds were obtained by 3D FEM simulation. Results show that the exit temperature becomes higher as the ram speed and displacement increase. For large-size tube with piece-wing, there is certainly a curve of ram speed decreasing with increasing ram displacement, which enables isothermal extrusion to be achieved. Therefore,an attempt was made to divide the working stroke into five different zones. Each of them has a preset speed that decreases from the ram displacement beginning to the ending. And then, new exit temperature vs ram displacement diagram was obtained by 3D FEM simulation for the five different speeds. It is shown that the variation of exit temperature is very small. Through the above research, a basic method for realizing isothermal extrusion of 7075 large-size tube with piece-wing was obtained, that is, the working stroke was divided into several different zones with a decreasing speed during extrusion, each zonest speed was real-time adjusted on the feedback signal of exit temperature by proportional hydraulic valve through closed-loop control. The engineering experiment verification was carried out on 100 MN aluminium extrusion press with oil-driven double action. The experimental results of the exit temperature agrees with the simulation ones. The achievements of this study may serve as a significant guide to the practice of the relevant processes, particularly for isothermal extrusion. The verified method has been used in the design and manufacture of 125 MN aluminium extrusion press with oil-driven double action.

A model of deformation of thin-wall surface parts during milling machining process

A three-dimensional finite element model was established for the milling of thin-walled parts. The physical model of the milling of the part was established using the AdvantEdge FEM software as the platform. The aluminum alloy impeller was designated as the object to be processed and the boundary conditions which met the actual machining were set. Through the solution, the physical quantities such as the three-way cutting force, the tool temperature, and the tool stress were obtained, and the calculation of the elastic deformation of the thin-walled blade of the free-form surface at the contact points between the tool and the workpiece was realized. The elastic deformation law of the thin-walled blade was then predicted. The results show that the maximum deviation between the predicted value and the actual measured machining value of the elastic deformation was 26.055 μm; the minimum deviation was 2.011 μm, with the average deviation being 10.154 μm. This shows that the prediction is in close agreement with the actual result.

Location and allocation problem for spare parts depots on integrated logistics support

In equipment integrated logistics support(ILS), the supply capability of spare parts is a significant factor. There are lots of depots in the traditional support system, which makes too many redundant spare parts and causes high cost of support. Meanwhile,the inconsistency among depots makes it difficult to manage spare parts. With the development of information technology and transportation, the supply network has become more efficient. In order to further improve the efficiency of supply-support work and the availability of the equipment system, building a system of one centralized depot with multiple depots becomes an appropriate way.In this case, location selection of the depots including centralized depots and multiple depots becomes a top priority in the support system. This paper will focus on the location selection problem of centralized depots considering ILS factors. Unlike the common location selection problem, depots in ILS require a higher service level. Therefore, it becomes desperately necessary to take the high requirement of the mission into account while determining location of depots. Based on this, we raise an optimal depot location model. First, the expected transportation cost is calculated.Next, factors in ILS such as response time, availability and fill rate are analyzed for evaluating positions of open depots. Then, an optimization model of depot location is developed with the minimum expected cost of transportation as objective and ILS factors as constraints. Finally, a numerical case is studied to prove the validity of the model by using the genetic algorithm. Results show that depot location obtained by this model can guarantee the effectiveness and capability of ILS well.