传热反问题方法在漏钢预报中的应用

基于漏钢预报中实时监测结晶器铜板受热状态的需要,建立了二维稳态热传导模型,在Vc＋＋6.0平台下编制了传热反问题计算程序（IHCP_2D）,该程序能通过结晶器铜板中有限个热电偶的测量值,快速反算出铜板受热面上的热流密度和温度分布.通过对一组实测数据的分析,验证了程序的可靠性.     

Verification of Inverse Quench-Hardening Phenomena in Bearing Steel Specimens by Experiment and Computer Simulation

The appearance of lower hardness at the surface than at the core after through-hardening of steels is known as “inverse quench-hardening.” Pioneering work was performed in the 1970s by establishing a simple test procedure where cylindrical specimens were cooled by air and brine sequentially to produce the effect. This phenomenon was described in relation to the polymer quenching and its effect to the improvement in the fatigue strength of the steel in the 1990s. The hardening mechanism in the same specimens as the pioneering work was recently examined using a finite element simulation method. However, this work has not been completed for lack of experimental quenching cooling curves for the comparisons. In this study, the same experiments using 20mm diameter cylindrical specimens as those of the pioneering work were conducted to obtain cooling curves and hardness distributions for comparing simulated results. Experimental cooling curves showed a temperature recovery as predicted by the simulation. Also the inverse quench-hardening phenomena were found in the measured and simulated hardness distributions of the specimens.     

板坯连铸结晶器传热反算方法研究

基于连铸生产中实时监测结晶器受热状态的需要，建立了结晶器铜板水平截面的二维热传导模型，提出了基于最小二乘法原理的传热反问题数值计算方法，并在VC＋＋6．0平台下编制了计算程序。程序中利用控制容积法建立离散方程组，采用一维变带宽存储、holesky分解技术，提高了计算速度。通过与商业软件计算结果的对比，证明了二维假设的合理性。对一组实测数据进行分析，验证了算法和程序的可靠性，从而为实现连铸过程监控提供了可借鉴的实用方法。     

Simultaneous Determination of Flow Stress and Interface Friction by Finite Element Based Inverse Analysis Technique

A finite element based Inverse analysis technique has been developed to determine the flow stress and friction at the tool/workplace interface simultaneously from one set of material tests. The Inverse problem is aimed at minimizing the error between experimental data and predictions made by rigid-plastic finite element simulations. The ring compression test and the modified limiting dome height test (sheet blank with a hole at center stretched with a hemispherical punch) were selected for evaluating the method for bulk forming and for sheet forming, respectively. The determined flow stress data were compared with corresponding data obtained Independently using the well-lubricated cylinder compression test and hydraulic bulge test. Results show that the method discussed In the study is efficient and accurate.     

Dependence of heat transfer coefficient at quenching on diameter of cylindrical workpieces

Abstract

For computer simulation of a quenching process, the fundamental prerequisite is to have the relevant heat transfer coefficient (HTC) calculated as a function of the workpiece’s surface temperature and time respectively. In order to calculate the HTC experimental measurement of the temperature–time history (cooling curve) near the workpiece surface is necessary. In this investigation, cylindrical probes with diameters of 20, 50 and 80 mm are used. The cooling curve was always measured 1 mm below the surface of the probe. Special care has been taken to keep all other factors (e.g. design of the probes, temperature measurement, quenching conditions and calculation procedure), which can influence the calculated HTC, constant, in order to ensure that the only variable is the diameter of the probe. Assuming a radially symmetrical heat flow at the half length of the probe, the HTC was calculated using one-dimensional inverse heat conduction method. The unexpected striking result of this investigation is the fact that for the probe diameter (80 mm) the calculated HTC as a function of surface temperature does not show the film boiling phase. A plausible explanation for this effect is given, based on the critical heat flux density. The possibility of establishing a simple fixed relation (a correction factor) between the HTC and the diameter of cylinders is discussed.     

结晶器固态渣膜形成过程及传热研究

通过自制的模拟铜结晶器实验装置,模拟结晶器固态渣膜的形成过程,研究无氟渣膜形成过程中渣膜状态及热流密度的变化,并利用扫描电镜、X射线衍射仪研究了渣膜的微观结构及结晶矿物。结果表明,随着模拟铜结晶器实验装置浸入渣液时间的延长,结晶器壁渣膜呈逐渐增厚的趋势,晶体质渣膜的成长速度比玻璃质渣膜要快得多,且固态渣膜形成过程中结晶矿物种类不变;穿过固态渣膜的热流密度呈下降趋势,尤其在浸入渣液25 s内,热流密度的下降趋势更为显著;渣膜传热是固态渣膜中的气孔、结晶率和渣膜厚度三方面因素综合作用的结果。     

板材成形中毛坯外形的逆向多步算法研究

毛坯外形的设计是金属板料成形的重要环节。针对板料拉深成形过程的特点，很多适用于毛坯形状计算的算法被提出，其中的逆向多步算法得到了一定的研究。本文着重对多步法的几种典型算法进行了综合讨论和分析，并指出研究中存在的问题以及未来研究的发展方向。     

铜基体上爆炸喷涂钨涂层及其电子束热负荷实验研究

详细介绍了爆炸喷涂法在铜基体上制备钨涂层.磁约束核聚变面对等离子体材料要求有承受较高热负荷的性能,电子束辐照热负荷实验发现:0.3 mm的钨涂层可以承受5.13 MW/m2的热通量;在2 MW/m2、20s脉冲的条件下,样品能承受300周的疲劳而没出现破裂现象,且距离表面5 mm处铜基体的温度在70°C左右;5 MW/m2、2 s脉冲的条件下,样品可承受95周热疲劳,且距离表面5 mm处铜基体的温度不高于200°C.钨铜的热膨胀系数和杨氏模量相差很大,在加载热通量过程中,界面处产生应力,这将影响材料的耐热冲击性能,但爆炸喷涂仍然为制备核聚变较低热通量区域面对等离子体材料的一种参考方法.     

Cast-Bonding—a New Process for manufacturing Composite Wear Products

Abstract

A new process for producing composite products, consisting of a wear—or corrosion-resistant cladding alloy on a wrought steel substrate, is described. The cast-bonding process enables steel components of a wide range of geometries to be protected with heavy overlays of, for example, alloy white cast iron or cobalt-base material. Typical products include internally-clad pipe bends and fittings, composite valve seats and composite billet shear blades. The bond between the two materials forms primarily in the solid-state by diffusions processes following casting of the cladding alloy on to the preheated surface of the substrate. Apart from a very narrow band adjacent to the bond line, there is no dilution of the overlay material. Some degradation of the impact toughness of the substrate steel takes place in the near- bond regions on account of grain growth caused by the thermal cycle to which the steel is subjected during the cast-bonding process. The grain size is effectively refined however, and the impact properties are recovered, by a subsequent normalising treatment which also hardens alloy white cast iron overlays. Shear tests reveal that the strength of the bond is greater than that of the alloy white iron cladding, thereby giving confidence in the integrity of cast-bonded products.     

A revisit to some wheel–workpiece interaction problems in surface grinding

This paper revisited some wheel–workpiece interaction problems in surface grinding including the profile of heat flux and the variation of the wheel’s elastic modulus. A method of using an optical microscope and a CCD camera was applied to capture the depth and width of the heated zone, the details of the temperature field and the stability of the heat flux. It was found that the heat flux in up-grinding can be modeled as a triangle with its apex at the inlet of the wheel–workpiece contact arc. The elastic modulus of the grinding wheel decreases significantly when the grinding temperature is beyond a critical value and can be described by a power law. It was also found that the depth of cut has almost no effect on the partition of the grinding energy.     

一种求解水平连铸中瞬态界面换热系数的新方法

为有效提高温度场数值模拟的准确性，对界面换热系数的模型进行了改进和参数化，并基于这个3阶段演变模型，提出了数值模拟与优化计算相结合的反向求解方法。针对水平连铸中出现的非均匀间隙情况，获得了与位置相关的界面换热系数。算例采用了两种合金Sn-5Pb和Sn-15Pb作为算例进行计算。优化结果表明，对于两种合金3个热电偶处的模拟温度与实测值最大相对误差不超过5％。     

Investigation of thermal behavior on cylinder liner during its boring process

Research was conducted on the effect of cutting conditions on temperature rise of cylinder liner during cylinder-boring process. A finite element method (FEM) model was developed to confirm suitable cutting conditions by predicting the temperature distribution in a cylinder liner and thermal expansion of the cylinder liner. To analyze the temperature distribution in the cylinder liner during machining, the partition of the total heat generated during machining which flows into the cylinder liner has to be investigated. A method combining experiment with analysis, called an “inverse heat transfer method”, was used to estimate the heat percentage flowing to the cylinder liner in this paper. To capture the required data for the inverse heat transfer method, sets of dry and wet boring experiments were conducted to estimate the temperature distribution in the cylinder liner wall and the cutting force during machining. The influence of the cutting conditions (for example: cutting speed, feed rate, depth of cut, cutting fluid) on the cutting force and temperature distribution in a cylinder during machining was investigated, and the heat partition flowing to the workpiece under various cutting conditions (especially, under high-speed cutting, with a maximum cutting speed up to 900 m/min) was then determined. A three-dimensional FEM analysis model was developed to simulate the temperature distribution in the cylinder liner and thermal expansion of the cylinder liner during machining. Then, the suitable cutting conditions in cylinder boring were confirmed by FEM analysis. To investigate the influence of the air cooling on the temperature distribution in the cylinder liner after machining, the change of temperature distribution in the cylinder liner under air cooling was predicted.     

Dynamic explicit FE modeling of hot ring rolling process

1Introduction Ring rolling is an advanced process typically used to manufacture parts with revolved geometries.It makes use of rotating rolls to press a ring continuously and locally,causing the wall thickness of the ring to reduce,the diameter to expand …     

挂舵臂铸钢件冒口覆盖剂保温机理研究

以大型挂舵臂铸钢件为对象,重点研究了铸钢件冒口覆盖剂(GL-Ⅰ型覆盖剂)的配方、化学成分、物性参数及微观组织形貌,分析了其保温机理。结果表明:GL-Ⅰ型覆盖剂高温导热系数较小,λ=0.1 366 W/(m.K),高温烧结后内部呈层片状,且多孔洞,其膨胀性好,具有良好的保温隔热性能。     

天然气在吸热式气氛制备上的应用及流量模型的建立

液化气价格的上涨以及其储存站的消防安全隐患,使得天然气替代液化气作为热处理原料气已成为热处理行业发展的趋势.本文针对天然气在吸热式气氛制备上的应用,从工艺原理上进行了理论分析,同时建立吸热式气氛发生装置原料气入口流量模型,为天然气改造工程中管道的选择提供理论依据.     

Imaging defects with reduced space inversion of magnetic flux leakage fields

Magnetic flux leakage technique is being used for detection of defects inside a magnetically permeable bar by measuring the leakage fields outside the bar. Defects in magnetically permeable bar have been modeled as localized anti-dipoles whose moments and locations have to be determined. Generalized inverse or pseudo-inverse technique has been used to image the defects using least-square minimum-norm solution. An initial estimate of the defects is obtained by utilizing the generalized inverse of the lead matrix over the entire region of the sample space using the measured magnetic field data including random noise. By defining a suitable threshold, and ignoring the defect locations where the moment inferred in the initial estimate was below the chosen threshold, the image of the defect is again obtained by repeating the calculation in this reduced space for the lead matrix. The leakage fields from both a line defect and a deeply buried defect were simulated and utilized for inversion using this approach. It has been possible to image the defects and quantify the strengths of the moments with the correlation coefficient approaching unity for low-noise case and attain significant improvement in the correlation coefficient for data with reasonable levels of noise.