Modeling forced convection in the thermal simulation of laser cladding processes

The International Journal of Advanced Manufacturing Technology - A comprehensive methodology for the implementation of thermal convection into the finite element (FE) analysis of laser direct...     

玻璃成形数值模拟技术研究概述

玻璃成形模拟技术的研究既具有重要的理论意义又具有广阔的应用前景,经过长期的研究和探索,人们对它的认识不断加深,研究范围不断扩大。但总体来说,目前对玻璃成形模拟技术的研究还较为薄弱,不够系统和深入,还需作更进一步的研究。这里对玻璃成形模拟技术的研究现状进行了综述。     

Methodology of 3D simulation of processes in technology of diamond-composite materials

In the present paper, the problem of increased effectiveness in manufacturing when using diamond abrasive tools is addressed. For this reason, a three-dimensional (3D) methodology is proposed. The aforementioned methodology consists of several parts containing 3D simulation that covers all the basic stages of the life cycle of the tools, from the sintering of diamond composite materials, grinding, and dressing of grinding wheels, to sharpening of single point tools and machining. Furthermore, the creation of expert systems for assignment of rational characteristics of diamond wheels and grinding modes is investigated. The results of these investigations allow reducing the volume of experimental work, offering optimum grinding conditions and allowing the development of new technologies, tools, and equipment.     

协同仿真/设计中存在的三个问题及解决的技术对策

为了完成基于复杂产品虚拟样机技术的协同仿真／设计任务,提出了一种控制模型移植和瞬时工作点线性分析的无缝集成解决方案。利用显式方程建模方法添加控制模型,并与多体系统动力学模型集成,由该模型求解器统一管理并组装成整机模型联立求解。当外包输出时,这种内部集成模型可以构建开环协同仿真,避免了代数循环问题。通过极小的协同步长设置,可控制多体系统动力学模型积分步长不协调所导致的输出偏差。为获得满足控制器设计要求的线性模型,采用了瞬时工作点的线性分析方法,因为准静平衡点对初始速度不敏感。对于曼彻斯特铁路客车标准模型,设计了直线通过垂向稳定的线性二次型高斯问题控制器,并验证了其鲁棒性。     

Computer aided simulation and performance evaluation of additive manufacturing technology for component parts manufacturing

The International Journal of Advanced Manufacturing Technology - Additive manufacturing technology involving the deposition of materials in successive layers provides a realistic possibility for...     

FEA simulation of thermal processes during the direct metal laser sintering of Ti64 titanium powder

With regard to the fact that laser sintering belongs to the high-temperature processes in which metal particles are sintered by a high-power laser, forming a homogenous structure, it is necessary and important to know the characteristics and the mechanism of these thermal processes. A high-power laser system produces three forms of heat that include convection, conduction, and radiation. These thermal processes affect the formation of internal stresses and tension that lead to deformations and rapidly influence the resulting quality, dimensions, density, micro-structure, and mechanical properties of fabricated parts. In response to this fact, it was important to analyse these heat transfer methods instantly during the direct metal laser sintering (DMLS) process simulation and subsequently monitor the parameters and settings of the sintering equipment in order to obtain acceptable manufacture outputs intended for further use. This work is focused on the creation of a FEA simulation model and the simulation of thermal processes across an object during and after the sintering process in the cooling stage, when it is important to consider a laser beam trajectory, temperatures of individual elements affected by the laser beam, and current laser energy in time. A 3D FEA simulation model was created in order to represent actual behaviour of a part during the sintering process. The simulation model consisted of two sub-models, particularly the building platform model with the dimensions of 250 mm × 250 mm × 22 mm, with stainless steel as the selected material, and the model of individual layers of sintered titanium powder with the dimensions of 10 mm × 10 mm × 0.03 mm. The total number of used layers was 12, which represents the total thickness of 0.36 mm. Applied power was P = 170 W. The simulation as such was carried out using the FEA software, Simulia Abaqus supported on the Windows x86-64 platform, which uses an integrated solver to make thermal and mechanic calculations. The calculations included also the impact of the protective argon atmosphere located in the process chamber. Mutual impact between individual layers was also considered. The simulation results were confronted with the results of already performed experimental studies of other scientific works, with the compliance and confirmation of assumptions being on a very good level.     

Two novel additive processes to manufacture circuit boards: Direct laser writing and direct electrostatic transfer and deposition

Two new technologies are described to manufacture bare circuit boards. Both methods are dry processes and are additive by nature. The above technologies have advantages over the current methods used to produce circuit boards and will alleviate the total dependency on wet chemical processing by the industry. The first technology is a process whereby circuit runs are written directly on to the substrate from a CAD/CAM database. There is no need for artwork to be generated so that flexibility is increased at the design stage. A circuit board is manufactured by coating it with a film of heat actuable adhesive to a substrate and depositing on the film a layer of conductive powder. The powder and film are then fused by the heat provided by laser radiation to define the circuitry. The excess unfused powder is then removed and the substrate fired to achieve final curing and bonding of the conductive runs to the substrate. The second technology is directed towards higher volume production and requires the use of a master pattern. The fundamental principles involved are well understood in the photocopying field. The technology has exciting potential for circuit board production due to the high reproduction rates which are possible. The master pattern consists of a conductive base upon which there is a pattern layer. A coating can be applied to the conductive particles to enable them to accept an electrostatic charge. The master pattern is also easily created by direct laser writing as described previously. The pattern layer receives an electrostatic charge. The master pattern is contacted by a developer containing a conductive material in the form of a powder or ink and which transfers the conductive material to the pattern by electrostatic force. A substrate is then brought to a position closely adjacent to the master pattern and electrostatic force is used to deposit the particles from the pattern on to the substrate to accurately define the circuitry. The particles are then fixed by heating which also dissipates the electrostatic charges. Multiple layer circuit boards can be built up by depositing complete layers of non-conductive material.     

非圆光斑对金属激光快速成形的影响及对策

当不同方向扫描成形时,采用相同的扫描间距而忽视非圆光斑各向异性的影响,是造成金属快速成形件内部缺陷的一个重要原因.在不更换或调整原有硬件设备的情况下,采用变扫描间距法(即在不同方向上采用不同的扫描间距)与层间正交变向往复扫描相结合,实验结果表明试件的表面质量、成形精度和内部质量都有显著提高.     

Mechanical property study on rapid additive layer manufacture Hastelloy? X alloy by selective laser melting technology

Tensile mechanical properties of selective laser-melted Hastelloy? X alloy in as-deposited condition and after hot isostatic pressing (HIP) have been studied at ambient and elevated temperatures. Room temperature four-point bending and tension–tension fatigue properties have also been investigated in as-deposited condition and after HIP. The yield strength of the as-deposited selective laser-melted Hastelloy? X specimen is higher than the heat-treated (hot forged) samples. The ultimate strength is also higher than that of the hot forged samples while the elongation property is lower. This can be attributed to its ultrafine microstructure caused by rapid solidification, which is characteristic of the selective laser melting process. It is also found that the mechanical properties (tensile and fatigue) do not vary with samples built in different bed locations.     

提高激光制孔质量策略的研究进展

激光制孔是一种非接触式、无工具损耗的先进加工技术,现阶段已经在航空、航天和船舶等领域广泛应用;但激光制孔后会出现热影响区、再铸层和熔渣等质量缺陷以及锥度等形貌缺陷,极大地影响了孔的后续应用,因此,在激光制孔过程中增加额外的辅助手段以提升其质量是十分必要的.首先,从时间尺度上分析了激光与靶材的作用机理,阐述了激光加工时的物理现象,明确了提升制孔质量的切入点.针对国内外在激光制孔过程中应用的辅助手段进行了系统的综述,详细分析了介质辅助、焦点位移辅助和在线监测辅助对孔形孔性的提升机制,并探讨了激光制孔技术未来的发展方向.     

提高激光制孔质量策略的研究进展

激光制孔是一种非接触式、无工具损耗的先进加工技术,现阶段已经在航空、航天和船舶等领域广泛应用;但激光制孔后会出现热影响区、再铸层和熔渣等质量缺陷以及锥度等形貌缺陷,极大地影响了孔的后续应用,因此,在激光制孔过程中增加额外的辅助手段以提升其质量是十分必要的.首先,从时间尺度上分析了激光与靶材的作用机理,阐述了激光加工时的物理现象,明确了提升制孔质量的切入点.针对国内外在激光制孔过程中应用的辅助手段进行了系统的综述,详细分析了介质辅助、焦点位移辅助和在线监测辅助对孔形孔性的提升机制,并探讨了激光制孔技术未来的发展方向.     

提高激光制孔质量策略的研究进展

激光制孔是一种非接触式、无工具损耗的先进加工技术,现阶段已经在航空、航天和船舶等领域广泛应用;但激光制孔后会出现热影响区、再铸层和熔渣等质量缺陷以及锥度等形貌缺陷,极大地影响了孔的后续应用,因此,在激光制孔过程中增加额外的辅助手段以提升其质量是十分必要的.首先,从时间尺度上分析了激光与靶材的作用机理,阐述了激光加工时的物理现象,明确了提升制孔质量的切入点.针对国内外在激光制孔过程中应用的辅助手段进行了系统的综述,详细分析了介质辅助、焦点位移辅助和在线监测辅助对孔形孔性的提升机制,并探讨了激光制孔技术未来的发展方向.     

提高激光制孔质量策略的研究进展

激光制孔是一种非接触式、无工具损耗的先进加工技术,现阶段已经在航空、航天和船舶等领域广泛应用;但激光制孔后会出现热影响区、再铸层和熔渣等质量缺陷以及锥度等形貌缺陷,极大地影响了孔的后续应用,因此,在激光制孔过程中增加额外的辅助手段以提升其质量是十分必要的.首先,从时间尺度上分析了激光与靶材的作用机理,阐述了激光加工时的物理现象,明确了提升制孔质量的切入点.针对国内外在激光制孔过程中应用的辅助手段进行了系统的综述,详细分析了介质辅助、焦点位移辅助和在线监测辅助对孔形孔性的提升机制,并探讨了激光制孔技术未来的发展方向.     

金属增材制造技术在航空航天领域的应用与展望

金属增材制造技术发展迅速,已成为先进制造业的重要组成部分。针对航空航天领域,介绍了金属增材制造技术的国内外发展应用状况,提出了该技术在航空航天领域应用发展面临的挑战,并对未来的发展进行了展望。     

Decomposition in stability analysis problems of systems with self-braking gears

Decomposition algorithms for studying the stability of systems with self-braking gears are presented. The developed dynamic models of systems with self-braking gears yield simple and physically transparent spectral criteria for the neutral stability of such systems. In design of the systems considered, the obtained criteria allow development of effective procedures for parametric synthesis ensuring the stability of motion in brake release regimes.     

金属切削加工过程的有限元数值模拟

运用有限元方法对切削过程进行数值模拟,分析不同切削速度在切削加工过程中对切削温度及切削力的影响,从而有助于深入了解加工过程,合理选择加工工艺参数。     

Review of materials used in laser-aided additive manufacturing processes to produce metallic products

Rapid prototyping (RP) or layered manufacturing (LM) technologies have been extensively used to manufacture prototypes composed mainly of plastics, polymers, paper, and wax due to the short product development time and low costs of these technologies. However, such technologies, with the exception of selective laser melting and sintering, are not used to fabricate metallic products because of the resulting poor life, short cycle, poor surface finish, and low structural integrity of the fabricated parts. The properties endowed by these parts do not match those of functional parts. Therefore, extensive research has been conducted to develop new additive manufacturing (AM) technologies by extending existing RP technologies. Several AM technologies have been developed for the fabrication of metallic objects. These technologies utilize materials, such as Ni-, Al-, and Ti-based alloys and stainless steel powders, to fabricate high-quality functional components. The present work reviews the type of materials used in laser-based AM processes for the manufacture of metallic products. The advantages and disadvantages of processes and different materials are summarized, and future research directions are discussed in the final section. This review can help experts select the ideal type of process or technology for the manufacturing of elements composed of a given alloy or material (Ni, Ti, Al, Pb, and stainless steel).     

冷金属过渡电弧增材制造技术研究进展

针对冷金属过渡(CMT)电弧增材制造技术存在的表面成形质量差、制件内部易形成孔隙等冶金缺陷、微观组织与性能调控困难等问题,从控形与控性两个方面出发,对CMT电弧增材制造技术研究进展进行了综述.首先,对CMT技术的原理及特点进行了分析与梳理;然后,对CMT电弧增材制造技术在"形"与"性"方面的调控方式进行了总结,具体阐述...