基于力学性能的钢货架立柱截面结构参数的敏感性研究

钢货架立柱是货架承受荷载的基础构件之一,其截面形状对立柱的力学性能有着极其重要的影响。基于理想轴心受压构件稳定理论,建立了受压立柱力学模型,推导了常见立柱截面的截面特性计算公式。以M120型号立柱为例,采用倍率化分析方法计算了立柱宽度,厚度等参数对立柱的稳定临界压力的敏感程度,为立柱的优化设计提供理论指导。     

机械式立体停车库钢结构骨架的优化设计

建立了机械式立体停车库钢结构骨架有限元分析模型，并应用遗传算法对结构进行了离散变量优化设计，优化结果表明，在满足一定性能约束条件下，通过调整构件的截面尺寸，可以有效地降低结构重量。     

Influence of high temperature diffusion bonding process parameters on mechanical and metallurgical characteristics of nickel superalloy to martensitic stainless steel

Welding of dissimilar metals is challenging because of the formation of microfissuring, strain age cracking and brittle intermetallic compounds. The above‐said problems can be avoided by controlled heating and cooling rates and the formation of beneficial intermetallic layers in the joint interface using solid‐state welding techniques such as diffusion bonding. This study investigates, the effect of diffusion bonding process parameters of dissimilar metals (AISI 410 martensitic stainless steel and nickel [Su 718] based superalloy). Fifteen joints were fabricated using different levels of bonding temperature (920–1,000°C), bonding pressure (10–18 MPa) and holding time (30–90 min). From this investigation, it is identified that joints fabricated at bonding temperature 980°C, bonding pressure 16 MPa and holding time 75 min yielded an extreme tensile strength (263 MPa) and hardness (450 HV) compared to the other joints. The tensile properties of the welded joints were assessed and associated with the microstructures. Optical Microscopy (OM), Scanning Electron Microscopy (SEM) and X‐Ray Diffraction (XRD) analysis were used to estimate the metallurgical characteristics of the weldment. The EDS examination was supported out to analyses the interface composition and to decide the composition at the interface. Furthermore, a lot of δ phase precipitates were likewise found in the bonded region.     

Effects of deformation parameters on the final microstructure and mechanical properties in warm rolling of a low-carbon steel

The effects of warm rolling parameters on the final microstructure and mechanical properties of a low-carbon steel were investigated. In doing so, the steel strips were pre-heated at various temperatures and rolled at different reductions and rolling speeds. Then, microstructural studies were performed and, also, the mechanical properties of the rolled samples were measured by tensile and hardness testing. An optimum rolling program was determined with the aids of experimental results and a mathematical model based on the finite element method (FEM) developed for the warm rolling conditions. The results show that, at high temperatures and low rolling speeds, the roll forces are reduced; however, the possibility of strain inhomogeneity and non-uniformity in the grain size distribution are increased. On the other hand, at very low temperatures, the roll force increases sharply. For the case of the employed steel, a temperature between 550–700°C and a rolling speed of 55–70 (rpm) are found to be the suitable rolling conditions for producing warm-rolled steels with uniform and fine-grain structures.     

Optimal gating system design for investment casting of sterling silver by computer-assisted simulation

The first requirement of all casting processes is complete filling without any defects after solidification. However, casting defects often occur in casting processes, especially incomplete filling. The causes of incomplete filling are related to poor gating system, incorrect pouring, and molding temperature. A suitable shape and dimension of gating system will increase the melt flow while it is feeding into mold cavity by eliminating excessive pouring and molding temperature. The objective of this study is to develop a new design of gating system for eliminating incomplete filling. The new shape and dimension of pouring cup, main sprue, and sprue base are proposed and investigated. The computational flow model is solved with the aid of computer simulation. The targets of an optimum solution are increasing the efficiency of metal flow and reducing turbulence. The experiments are conducted to validate the simulation data. The results of this study will aid in the elimination of casting defects and increase the productivity.     

Effect of friction welding parameters on mechanical and metallurgical properties of ferritic stainless steel

Friction welding is one of the most economical and highly productive methods in joining similar and dissimilar metals. It is widely used in the automotive and aerospace industrial applications. Ferritic stainless steel (AISI430) is normally difficult to weld by fusion methods, due to the associated problems such as grain growth and retained austenite content. Such problems can be alleviated by the friction joining process. The present study utilized a continuous drive friction welding machine to join cylindrical specimens of ferritic stainless steel of similar composition and shape (equal diameter and length). The processing parameters such as friction pressure, friction time, upsetting pressure and upsetting time were changed in order to understand the role of parameters on the strength related aspects of friction processed joints. The joints were subjected to mechanical testing methods such as the uni-axial tension test, and charpy ‘v’ notch impact tests. The micro hardness variation across the joint zone was determined. Micro structural studies were also carried out. The characteristics such as tensile strength, toughness and microstructural aspects exhibited by friction processed joints were compared to parent materials.     

Effects of process parameters on the high temperature strength of 17-4PH stainless steel produced by selective laser melting

Journal of Mechanical Science and Technology - In this study, the effects of process parameters on the high temperature strength of 17-4PH stainless steel manufactured by selective laser melting...     

60t Consteel EAF-LF-CC流程生产高锰钢80Mn14工艺优化的研究

通过对高锰钢80Mn14采取C、Mn、Si等成分优化设计,合理控制出钢终点C以降低出钢过氧化,LF炉快白渣操作和严格控制浇铸过热度与二冷弱冷技术,并且在生产过程中通过严格控制P、S和Si等元素和LF精炼渣碱度等工艺优化措施,成功解决了80Mn14铸坯表面角部横向裂纹和轧制过程角部开裂的质量问题。     

结构参数对薄壁四点接触球轴承力学性能的影响分析

薄壁四点接触球轴承作为工业机器人传动部件,结构参数是影响其稳定性和寿命的关键因素.文中基于多体动力学与Hertz接触理论,以沟道曲率、径向游隙、滚珠数目为结构参数化变量,运用ADMAS建立参数化动力学分析模型,分析不同结构参数对轴承动力学性能的影响,其结果显示:沟道曲率增加会使滚珠与内圈接触力峰值增加;在径向游隙增加且...     

Studies on the correlation between mechanical properties and ultrasonic parameters of aging lCr-lMo-0.25V steel

Mechanical properties of in-service facilities are required to evaluate the integrity of power plants and chemical plants Non-destructive technique can be used to evaluate the mechanical properties To investigate the mechanical properties using ultrasonic technique, the four classes of thermally aged specimens were prepared using an artificially accelerated aging method Ultrasonic tests, tensile tests, fracture toughness tests, and hardness tests were performed for the specimens Then the mechanical properties were compared with ultrasonic parameters such as attenuation and non-linear parameter From the investigation, we confirm that the ultrasonic parameter can be used to evaluate the mechanical properties     

铸造高速钢轧辊的研究和应用

着重介绍铸造高速钢轧辊的性能特点、主要制造方法和在轧钢行业中的应用。     

"VE"在优化大型船用铸钢件挂舵臂工艺上的应用

对首件大型挂舵臂试制生产进行了价值工程分析，通过功能定义整理、评价及新、旧方案的比较，实施了铸造工艺方案的改进，取得了较大的经济及社会效益。     

基于Crussard-Jaoul的n值分析对高锰钢加工硬化机制的探讨

通过研究发现Crussard-Jaoul分析法能够精确反映高锰钢变形过程中加工硬化的特点。基于Crussard-Jaoul分析法所得的高锰钢应变硬化指数值的变化主要受位错密度和孪晶体积分数的影响,尤其随着形变孪晶量的增加,应变硬化指数获得迅速提高。当应变量低于0.1,高锰钢塑性变形以位错滑移为主要机制;当应变量超过形变孪晶产生的临界应变（0.06~0.08）后,高锰钢塑性变形以位错滑移和机械孪生两种方式进行。孪晶的产生能迅速提升高锰钢加工硬化性能,而仅位错强化不能使高锰钢获得优异的加工硬化性能。Crussard-Jaoul分析法能对金属塑性变形和加工硬化机制进行判断和预测。     

基于第一性原理的高压下TiAl结构、力学性能及热力学性质研究

采用第一性原理计算方法,研究了压力与温度对TiAl合金结构、力学性能与热力学性质的影响.结果显示,随着外加压力的增加,TiAl体积比降低. 计算了不同压力下TiAl的弹性常数Cij , 所有Cij均力学稳定性判据, 表明不同压力下的模拟结果均满足力学稳定性条件. 通过弹性常数, 计算了体模量与剪切模量, 发现在0 Gpa下的计算值与文献值相吻合,表明计算的准确性. 体模量与剪切模量可以用来反映材料抵抗变形能力, 随着压力的增加, 其数值增加, 表明材料抵抗变形能力得到提升. 由B/G发现, 当压力在10-20 Gpa之间时, TiAl由脆性材料转变为延性材料. 借助准谐德拜模型, 研究了当温度在0-1 000 K、 压力在0-50 Gpa下压力与温度对TiAl体模量、 德拜温度、 线膨胀系数以及热容的影响, 这有助于研究温度与压力对热力学参数的影响. 最后, 研究了不同压力下TiAl的电子结构, 随着压力的增加, 材料的态密度强度降低, Ti原子成键相互作用减弱, Al原子成键相互作用增强, 材料的延性得到提升.     

Effects of laser parameters on optoelectronic properties of polycrystalline silicon films prepared by two-step annealing process

Traditional finishing techniques, including grinding, honing, and lapping have several disadvantages and limitations due to their solid and rigid tools with complex geometries. To overcome these limitations, modern techniques known as nanofinishing techniques are introduced. This paper presents a new micro/nanofinishing technique used in different industries, especially high-tech industries like aerospace, military applications, and auto-making industry. This technique is called rotational abrasive finishing (RAF) method. In this technique, the medium inside the cylindrical workpiece is rotated using a bladed stirring axis. The medium hits against the surface of the workpiece while rotating in the opposite direction. In this way, material removal and finishing operation are achieved. In order to avoid medium discharge, two caps, one in upper side and one in the bottom side of workpiece, are used. RAF technique makes it possible to reduce surface roughness and achieve roughness in nanometer scales so that on our test workpiece roughness was reduced from 0.283 to 88 nm, indicating 70% improvement in surface quality by applying 20 min machining duration. It was practically proved that RAF is a fast, efficient, and cost-effective finishing technique for different products by which it is possible to achieve ultra-precise surface quality at nanometeric scales.     

Influence of process parameters on part quality and mechanical properties for DMLS and SLM with iron-based materials

Rapid manufacturing is an advanced manufacturing technology based on layer-by-layer manufacturing to produce a part. This paper presents experimental work carried out to investigate the effects of scan speed, layer thickness, and building direction on the following part features: dimensional error, surface roughness, and mechanical properties for DMLS with DS H20 powder and SLM with CL 20 powder (1.4404/AISI 316L). Findings were evaluated using ANOVA analysis. According to the experimental results, build direction has a significant effect on part quality, in terms of dimensional error and surface roughness. For the SLM process, the build direction has no influence on mechanical properties. Results of this research support industry estimating part quality and mechanical properties before the production of parts with additive manufacturing, using iron-based powders.     

高合金钢中铬锰的连续测定

主要介绍高合金钢中铬、锰元素的连续测定方法、原理及其在实际生产中的作用和意义。     

Optimization of green sand casting process parameters by using Taguchi’s method

This paper analyses various significant process parameters of the green sand casting process. An attempt has been made to obtain optimal settings of the green sand casting process in order to yield the optimum quality characteristics of the spheroidal graphite (SG) cast iron rigid coupling castings. The process parameters considered are: green strength, moisture content, permeability and mould hardness. The effect of selected process parameters and its levels on the casting defects and the subsequent optimal settings of the parameters have been accomplished using Taguchi’s parameter design approach. The result indicates that the selected process parameters significantly affect the casting defects of SG cast iron rigid coupling castings. The estimation of the optimum performance characteristics of green sand casting at the optimum levels of parameters is done in this paper and the results are verified by confirming with practical experiments.