Structural Scheme Optimization Design for the Stationary Platen of a Precision Plastic Injection Molding Machine

The current development of precision plastic injection molding machines mainly focuses on how to save material and improve precision, but the two aims contradict each other. For a clamp unit, clamping precision improving depends on the design quality of the stationary platen. Compared with the parametric design of stationary platen, structural scheme design could obtain the optimization model with double objectives and multi-constraints. In this paper, a SE-160 precision plastic injection molding machine with 1600 kN clamping force is selected as the subject in the case study. During the motion of mold closing and opening, the stationary platen of SE-160 is subjected to a cyclic loading, which would cause the fatigue rupture of the tie bars in periodically long term operations. In order to reduce the deflection of the stationary platen, the FEA method is introduced to optimize the structure of the stationary platen. Firstly, an optimal topology model is established by variable density method. Then, structural topology optimizations of the stationary platen are done with the removable material from 50%, 60% to 70%. Secondly, the other two recommended optimization schemes are given and compared with the original structure. The result of performances comparison shows that the scheme II of the platen is the best one. By choosing the best alternative, the volume and the local maximal stress of the platen could be decreased, corresponding to cost-saving material and better mechanical properties. This paper proposes a structural optimization design scheme, which can save the material as well as improve the clamping precision of the precision plastic injection molding machine.

Experimental Research on Structural Behaviors of Glulam I-Beam with a Special-Shaped Section

In order to enhance the bearing capacity of structural components,save materials,and reduce cost,a glued laminated timber(glulam)I-beam that is theoretically suitable for engineering application was proposed.In this study,18 glulam specimens were fabricated using larch dimension lumber and resorcinol-formaldehyde resin.Four-point bending tests were carried out to compare the ultimate bearing capacity,strain,and deflection of various specimens.The results showed that:(1)The typical failure mode at bending is the web shear failure parallel to grain.Before the failure,cracks and sounds appear at the beam web,which represent the sudden brittle failure.(2)The cross-sectional strain of glulam beam changed linearly with the beam height,indicating that the plane section assumption was basically established.(3)Stiffener could improve the initial flexural stiffness of glulam beam,which experiences an increase of 28.21%.Larger the shear span ratio,smaller the initial flexural stiffness.The initial flexural stiffness improves by 10-23.5%with the increase in the thickness of the lower flange.(4)The effects of stiffener and shear-span ratio on shear strength are relatively significant.After the stiffeners are set at the support and the loading point in pairs,the shear strength of the glulam beam increases by 15.05%averagely.With the increase in the shear-span ratio,the shearing strength of the glulam I-beam gradually reduces.The equation of the shearing strength with the shear span ratio is obtained,which is shown by high fitting precision.(5)The shear strength correlation,as proposed by Soltis and Rammer,is suitable not only for rectangular beams,but also for glulam I-beams.

I-beam Crack Identification Based on Study of Local Flexibility due to Crack

Local flexibility of crack plays an important role in crack identification of structures.Analytical methods on local flexibility in a cracked beam with simple geometric crossing sections,such as rectangle,circle,have been made,but there are some difficulties in calculating local flexibility in a cracked beam with complex crossing section,such as pipe and I-beam.In this paper,an analytical method to calculate the local flexibility and rotational spring stiffness due to crack in I-beam is proposed.The local flexibility with respect to various crack depths can be calculated by dividing a cracked I-beam into a series of thin rectangles.The forward and inverse problems in crack detection of I-beam are studied.The forward problem comprises the construction of crack model exclusively for crack section and the construction of a numerically I-beam model to gain crack detection database.The inverse problem consists of the measurement of modal parameters and the detection of crack parameters.Two experiments including measurement of rotational spring stiffness and prediction of cracks in I-beam are conducted.Experimental results based on the current methods indicate that relative error of crack location is less than 3%,while the error of crack depth identification is less than 6%.Crack identification of I-beam is expected to contribute to the development of automated crack detection techniques for railway lines and building skeletons.

MECHANICAL ANALYSIS OF CYLINDERS BEING UPSET BETWEEN SPHERICAL CONCAVE PLATEN AND CONCAVE SUPPORTING PLATE

Mechanical analysis of cylinders being upset between spherical concave platen and concave supporting plate is conducted. Rigid-plastic mechanical models for cylinders are presented. When the ratio of height to diameter, is larger than 1, there exists two-dimensional tensile stress in the deformed body, when the ratio is smaller than 1, there exists shear stress in static hydraulic zone. The former breaks through the theory that there is three-dimensional compressive stress irrespective of any ratio of height to diameter. The latter satisfactorily explains the mechanism of layer-like cracks in disk-shaped forgings and the flanges of forged gear axles. The representation of the two models makes the upsetting, theory into correct and perfect stage.

A Case Study of Heat Transfer from Hot Runner Mould to the Fix Platen of the Injection-moulding Machine

In an injection moulding process, the parallelism b et ween the tie bars of the injection moulding machine is very important as it will affect the mould closing and clamping system. In recent years, more and more ho t runner systems are being applied in the moulding industry to save material and decrease the losses of injection pressure. Heat transfer from hot runner system from the fixed half which is secured in the fix machine platen could transmit s o much heat that it may cause high temperature differential between the machine fix platen and moving platen. This will cause the tie bar to become unparallel. Part quality will be compromised and the wear of the tie bar will be excessive. Overhaul of the tie bar may be necessary after a short period of time which is c ostly. This raises the need to analyze the heat transfer from the hot runner sys tem to the machine fix platen and the methods of isolating or minimizing the hea t transfer. In this case study, a photo lens article mould was used. The mould w as built with a direct hot runner nozzle system. Heat conduction from hot runner and machine screw to machine fix platen were studied based on either using high temperature heat insulating plate put in placed between the mould and the mould ing machine fix platen or drill cooling channels in the front mould clamping pla te. The high temperature insulator is very costly as it is made out of glass re inforced polymer composite material. Experimental results were obtained and anal yzed to find the best method to minimize the unwanted heat transfer using the ch eapest and most effective method.

Finite element analysis on temperature field and residual stress of welding assembly for I-beam and end-plate

Based on full scale model of 1-beam and end-plate welding assembly with medium plate, welding temperature field and residual stress were simulated, infrared thermometers were employed to measure the real-time temperature Jbr verification purposes. Results show that the measured thermal cycle curves match well with the simulation result. Simulation results of welding residual stress indicate that the values of longitudinal and transverse stress on the upper surface of the plate are higher than the normal stress; higher tensile stresses exist at the end of the web weld toes and in the central area of the flange weld toes. The dangerous zones are located at the central areas of weld toes of the flange welds and near weld toes of the web welds.

Laser-Based Guided Wave Propagation and Mode Decomposition in Detecting the Integrity of Structural I-Beams

This paper addresses the studies carried out on an I-beam to reveal the wave propagation characteristics and tackle the multi-mode propagation of Lamb waves. The experimental setup consisted of a new 3D Scanning Laser Doppler Vibrometer manufactured by Polytec (3D-SLDV) and was used to acquire high resolution time-space Lamb waves that were propagating in the I-beam. A high power and pulsed Nd:YAG laser was used to emit the required Lamb waves. The emission and sensing of the waves were carried out simultaneously. The wave propagation data was recorded by scanning the surface of the I-beam in a sequential manner. The measured data was used to construct the wave patterns that were propagating in the I-beams at different time instants. Furthermore, as the waves in an I-Beam propagate with multiple modes even at low frequency range, filtering was carried out in the frequency-wavenum- ber domain in order to decompose the modes. The results presented thereby confirm that the new 3D-SLDV possesses tremendous capability in revealing the wave propagation characteristics and its interaction with defect. The results could be the first time that the waves propagating in a real I-beam can be visually observed, whilst in the past, it can only be visualized through simulation. The capability of using such totally laser-based 3D inspection system to reveal the characteristics of Lamb wave and its interaction with defects are substantial.

Two Multi-Objective Genetic Algorithms for Finding Optimum Design of an I-beam

Many engineering design problems are characterized by presence of several conflicting objectives. This requires efficient search of the feasible design region for optimal solutions which simultaneously satisfy multiple design objectives. Genetic algorithm optimization (GAO) is a powerful search technique with faster convergence rates than traditional evolutionary algorithms. This paper applies two GAO-based approaches to multi-objective engineering design and finds design variables through the feasible space. To demonstrate the utility of the proposed methods, the multi-objective design of an I-beam will be presented.

Effect of Web Opening on Buckling Instability of Simply Supported Steel I-Beam

The lateral torsional buckling phenomenon often governs design of steel I-beams. Although web opening is often used to accommodate the required mechanical and piping works in buildings, its effect on the buckling instability is not considered in the design codes. In this paper, the effect of web opening on both lateral torsional buckling and local buckling behaviors has been investigated. A simply supported steel I-beam has been studied under uniform bending moment around the major axis. Buckling analysis has been performed using the finite element method. Linear regression analysis has been conducted for output data to formulate an equation for the critical moment including web opening effect. The results have shown a limited reduction in the lateral torsional buckling capacity and a significant reduction in the local buckling capacity.

Comparative Analysis of Bridges with AASHTO and Florida I-Beam Girders

A comparative study of two pre-stressed girder bridges, one with AASHTO （American Association of State Highway and Transportation Officials） Type III girders and the other with new FIB （Florida l-beam） girders, is presented. FIB girders are expected to provide increased lateral stiffness, higher load carrying capacity, cost-efficiency and better reliability. In this paper, the first bridge that is analyzed is a 3-span bridge designed with six AASHTO Type III girders, and the second bridge has four FIB girders with the same span length, width and girder depth. The bridges are analyzed for Florida state legal loads SU4 and C5. Both bridges are analyzed using a sophisticated finite element method. The deflections, moment envelopes, section capacity and live load rating of the two bridges are obtained and compared. FIB girders have higher vertical stiffness, higher section capacity providing higher load rating than the AASHTO girders.

某660 MW超临界锅炉深度调峰过程中分隔屏超温计算分析及改造方案研究

针对660 MW超临界褐煤锅炉分隔屏实炉数据分析发现,在175 MW负荷下,分隔屏的超温报警主要发生在屏3、屏4靠近炉内的管子。为解决分隔屏超温报警问题,采用流动网络系统法,结合质量、能量和动量守恒方程建立了分隔屏水动力计算数学模型,提出添加节流圈以及升级管子材料两种改造方案。对分隔屏进行回路及管段划分,采用175 MW负荷实炉测量数据反推计算得到炉内实际热偏差,对低、中、高负荷下添加节流圈与升级材料为Super304H的分隔屏出口汽温进行计算。计算结果表明:添加节流圈后分隔屏出口汽温偏差变小,且屏3、屏4出口汽温降低至材料TP347H报警温度以下;升级材料为Super304H后分隔屏出口汽温均小于材料的报警温度,分隔屏可安全运行。对添加节流圈以及将材料升级为Super304H两种方案进行壁温计算及强度校核,结果显示两种改造方案在各个负荷下,壁温以及强度均是安全的。为给锅炉运行留出更大的安全裕度,建议在分隔屏最后一片屏上添加节流圈的同时将材料由TP347H升级为Super304H。

钢球堵塞引起S30432屏式过热器爆管的失效特征分析

以试运行阶段就发生因钢球堵塞造成过热蠕变爆管的某600MW超超临界锅炉屏式过热器为例,通过宏观检查、尺寸测量、化学成分分析、力学性能分析、金相分析、维氏硬度试验和扫描电镜观察等方法,并与相邻管子进行对比,得出了钢球堵塞引起S30432爆管失效的特征。结果表明:爆口部位的管径、壁厚、蠕变孔洞、蠕变裂纹及老化程度等方面存在明显特征,除爆口部位及弯管部位外的各项试验结果均符合标准对新管的要求,但其材质状态已明显差于相邻管子。

循环流化床锅炉屏式受热面变形原因分析及治理策略

为了掌握循环流化床(CFB)锅炉屏式受热面变形原因和治理因其导致的受热面爆管泄漏等问题,在探讨分析设备结构特征、工质流动特性、传热效果影响等基础上,结合国内现役CFB锅炉存在的屏式受热面变形问题,得到了工质流量不均匀、工质流量与热负荷不匹配、传热效果差异等是导致屏式受热面产生较大热偏差的主要原因,由此进一步诱发屏式受热面出现应力偏差造成了管屏变形现象,而屏式受热面竖直方向膨胀受阻也会导致不可逆的管屏变形。提出了屏式受热面“割管+分屏+扩径”管屏改造措施以减小管屏热偏差,“双吊架+密封改进”膨胀改造措施以实现管屏自由膨胀;从运行管理角度提出了CFB锅炉启动阶段运行控制技术措施,以减小该阶段屏式受热面的壁温偏差和热应力等。治理措施已取得良好实践改造效果,能有效解决屏式受热面的变形严重问题,具有普遍推广性。

基于DDPG的锅炉NO_(x)排放和屏式过热器超温的多目标优化

锅炉空气分级燃烧技术的使用虽降低了NO_(x)排放,但同时造成了炉内高温火焰上移,导致位于炉膛上部的屏式过热器吸热量增加和超温加剧,影响机组的安全运行.因此,锅炉亟需一个可对NO_(x)排放和屏式过热器超温进行协调优化的多目标控制策略.针对目前基于机器学习的锅炉优化模型普遍局限于针对单一锅炉运行目标的优化,提出了基于深度强化学习的锅炉多目标优化模型,包括预测模型和优化模型:预测模型采用深度神经网络构建锅炉运行参数与NO_(x)浓度和屏式过热器温度的非线性映射;优化模型采用深度确定性策略梯度(DDPG)算法训练策略网络,通过优化运行参数实现锅炉的多目标协同控制.对某600MW锅炉的研究结果表明,通过锅炉配风和过热器减温水量等参数的调整,可实现NO_(x)排放和屏式过热器超温率的协同优化,NO_(x)排放平均降低22.6 mg/m^(3),屏式过热器超温率平均降低0.161.

基于YOLOv3算法的变电站保护硬压板检测技术研究

针对目前变电站保护硬压板巡检多由人工进行读取和核对操作,费时费力且易出错,难以满足变电站二次设备智能化的要求的问题,研究了基于YOLOv3算法的变电站保护硬压板检测与状态识别技术。首先,通过对变电站保护硬压板进行数据采集和标注,建立了一个包含大量样本的数据集。然后,使用YOLOv3算法进行目标检测,实现了对变电站保护硬压板的准确定位和识别。针对硬压板的不同状态,设计了相应的特征提取和分类模块,通过对检测到的硬压板进行状态识别,实现了对硬压板状态的准确判别。实验结果表明,该方法在变电站保护硬压板检测和状态识别方面具有较高的准确性,对压板作业操作票确认、压板状态校核等业务实现具有一定参考价值,可为变电站设备的状态监测和故障的智能诊断提供有效的技术支持。

锅炉分隔屏过热器爆管原因分析及处理

通过宏观检查、化学成分分析、金相检验及力学性能分析等方法对某火电厂分隔屏过热器弯头爆管原因进行综合分析。分隔屏过热器爆管段因长时间过热致使组织严重球化、机械强度下降,同时弯头外弧侧壁厚较薄,且管内壁存在凹坑导致应力集中,多因素叠加最终导致该管段弯头外弧侧爆管。最后针对管子失效原因,提出了相应建议及处理措施。

变电站保护装置压板分析与投退注意事项

以某220 kV变电站运行人员因万用表档位选择不当导致的电气二次误操作事件为例,阐述变电站保护装置压板分类和主要功能投退方式,并对功能硬压板开入回路和出口硬压板开出回路的回路特点和电位开展具体分析,结合现场实际提出保护装置压板投退防误动预控措施。

智能压板系统在齐齐哈尔冯屯500kV变电站中的应用

目前变电站保护屏压板的位置只能由现场运行人员以人工方式检查确认,自动化水平较低。智能压板系统的应用实现了对压板运行状态的实时在线监视,对各种情况下的压板运行状态错误均能自动告警,实现了压板操作全过程的监视与防误预警提示,确保变电站压板投退安全可靠,并在齐齐哈尔冯屯500kV变电站的应用中取得了良好的效果。

高碱煤燃烧过程中屏式过热器分层结渣机理研究

中国的准东煤储量巨大,但由于其Na、Ca含量较高,燃烧准东煤的锅炉炉膛出口过热器表面上结渣和沾污问题严重。为了阐明其结渣机理,对某350 MW锅炉出口屏式过热器(烟气温度1 000℃左右)的焦样进行分析,发现焦体内部存在明显的分层结构,不同层焦样中元素含量明显不同,化合物形态也存在较大差异。这是由于在焦体发展过程中,随着沉积表面温度逐渐升高,焦体的灰颗粒之间发生差异较大的物理化学反应而形成的。通过对不同层焦样的化合物形态进行整理并详细分析,最终提出了各层不同化合物的形成机理。

岩石试件端面效应的变形局部化数值模拟研究

试件端面效应直接影响试件内的应力分布、试件破坏形式和剪切带图案。采用FLAC - 3D模拟了端面效应对岩石试件剪切带图案、速度场和位移场的影响。试样端部的缚束作用较强时 ,仅在试样中部出现X形的剪切带 ;反之 ,在试样端部出现了倾斜的剪切带。压头刚性越大 ,剪切带倾角越大。块体具有整体平移的特性 ,剪切带边缘位移梯度却较大 ,反映了块体沿剪切带发生滑动的剪切破坏本质。数值模拟结果可在众多的试验结果中找到佐证。