共查询到20条相似文献,搜索用时 62 毫秒
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为了减小成形误差,提高激光选区熔化成形复杂特征结构件的能力,实验采用Ti6Al4V金属粉末,设计了不同倾斜角度的悬垂结构模型,研究了倾斜角度、扫描策略对悬垂结构SLM成形质量的影响。结果表明:倾斜角度越小,悬垂面的边缘线宽度误差越大(>80μm),表面粗糙度值越大(>20μm),翘曲变形越严重;岛形随机扫描策略的整体成形质量要低于Z形正交扫描策略,但对不同角度的悬垂结构影响不同。结合QM-Meltpool监控系统,从熔池的角度分析了倾斜角度和扫描策略的影响,为悬垂结构SLM成形提供了参考依据。 相似文献
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采用电子束选区熔化制造技术制备不同成型尺寸的Ti-6Al-4V(TC4)钛合金试样,通过金相显微镜、扫描电镜、万能试验机和X射线衍射仪等研究设备,探究了不同成型尺寸对电子束选区熔化成型TC4钛合金试样的显微组织与力学性能的影响。结果表明:在R05、R06和R07这3种不同成型尺寸的试样中,成型尺寸越大,则拉伸强度和屈服强度越大,同时弹性模量和延伸率越小,即塑性越差;试样R05、R06和R07均发生韧窝断裂,但试样R05断口塑性较差,更接近脆性断裂;试样R07上下段分别形成双态组织和等轴组织,且距离打印基板位置越远,试样的层间结合率和粉末熔化率越低,即打印情况越差;对于成型尺寸最大的试样R05,由于其每层扫描时间长、热传递效果好,故其β柱状晶内形成了细针状马氏体和魏氏组织,而成型尺寸较小的R06试样则由于较高加工温度中的冷却,形成了网篮组织和片状α相组织。 相似文献
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Bo Song Shujuan Dong Hanlin Liao Christian Coddet 《The International Journal of Advanced Manufacturing Technology》2012,61(9-12):967-974
Considering that the densification level and the attendant quality of selective laser melted Ti6Al4V parts depend strongly on the operating temperature of the melting system, which is mainly controlled by the processing parameters. The processing parameters of selective laser melting were thus investigated in this study to fabricate denser Ti6Al4V parts without post-processes. Temperature distribution calculation was firstly carried out based on a three-dimensional model. It was found that there exists a great temperature gradient from the surface of powder bed to the experimental platform, and the maximum depth of molten powder layer is about 45?μm, very close to the total thickness of powder bed (50?μm) under the condition of laser power of 110?W and scan rate of 0.2?m/s. The Ti6Al4V parts with lower porosity and higher density were then well fabricated by experimental method under the condition of laser power of 110?W and scan rate of 0.2?m/s. The experimental results also indicate that the microstructures exhibit more and more pores and the layer structures are more and more obvious with the increase in the scan rate. Moreover, the microhardness measurement yields different values with increasing scan rate, owing to the increase of α phase and porosity. 相似文献
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Hung-Yi Chen Shiuh-Jer Huang 《The International Journal of Advanced Manufacturing Technology》2004,24(9-10):667-674
It is well known that surface alloying quality may vary significantly with respect to process parameter variation. Thus a feedback control system is required to monitor the operating parameters for yielding a good quality control. Since this multi-input and multi-output (MIMO) system has nonlinear coupling and time-varying dynamic characteristics, it is very difficult to establish an accurate process model for designing a model-based controller. Hence an adaptive fuzzy sliding-mode controller (AFSMC) which combines an adaptive rule with fuzzy and sliding-mode control is employed in this study. It has an on-line learning ability for responding to a system’s nonlinear and time-varying behaviours. Two adaptive fuzzy sliding-mode controllers are designed for tuning the laser power and the traverse velocity simultaneously to tackle the absorptivitiy and geometrical variations of the work pieces. The simulation results show that good surface lapping performance is achieved by using this intelligent control strategy. 相似文献
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John Obielodan Brent Stucker 《The International Journal of Advanced Manufacturing Technology》2013,66(9-12):2053-2061
The design of engineering structures with function-specific material members is on the increase. This requires advanced fabrication technologies with capabilities for multi-material processing. A major challenge however is obtaining effective transition from one material to another. Dissimilar material systems made using laser metal deposition processes have been investigated. The fusion of materials having different physical properties and chemical compositions under high laser power often results in defects at the joints due to thermal expansion mismatch, the formation of intermetallics, or other mechanisms. Some solutions have been proffered in previous works based on evaluations using qualitative techniques. However, quantitative experimental studies are imperative to accurately assess the mechanical behavior of dual-material structures for real-life applications as predictive tools have not yet been validated. In this work, different designs of material transitions from Ti6Al4V alloy to Ti6Al4V/TiC composites were established. Experimental evaluations of their strengths at these joints were made using LENS-fabricated tensile and flexural test samples. The mode of transition from one material to another was found to have a significant effect on the tensile strengths of the structures. Also, material transition designs with optimum strengths were applied for the fabrication of simplified dual-material minimum-weight structures and tested. The structures failed at locations away from the material transition regions, thus proving the effectiveness of the joints. 相似文献
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Titanium alloy is a kind of typical hard-to-cut material due to its low thermal conductivity and high strength at elevated temperatures, this contributes to the fast tool wear in the milling of titanium alloys. The influence of cutting conditions on tool wear has been focused on the turning process, and their influence on tool wear in milling process as well as the influence of tool wear on cutting force coefficients has not been investigated comprehensively. To fully understand the tool wear behavior in milling process with inserts, the influence of cutting parameters on tool wear in the milling of titanium alloys Ti6Al4V by using indexable cutters is investigated. The tool wear rate and trends under different feed per tooth, cutting speed, axial depth of cut and radial depth of cut are analyzed. The results show that the feed rate per tooth and the radial depth of cut have a large influence on tool wear in milling Ti6Al4V with coated insert. To reduce tool wear, cutting parameters for coated inserts under experimental cutting conditions are set as: feed rate per tooth less than 0.07 mm, radial depth of cut less than 1.0 mm, and cutting speed sets between 60 and 150 m/min. Investigation on the relationship between tool wear and cutting force coefficients shows that tangential edge constant increases with tool wear and cutter edge chipping can lead to a great variety of tangential cutting force coefficient. The proposed research provides the basic data for evaluating the machinability of milling Ti6Al4V alloy with coated inserts, and the recommend cutting parameters can be immediately applied in practical production. 相似文献
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Lee Ho Jun Dao Van Hung Ma Young Wha Yu Jong Min Yoon Kee Bong 《Journal of Mechanical Science and Technology》2020,34(8):3261-3272
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... 相似文献
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Tribological and corrosion properties of Ti6Al4V alloy both bare and coated by diamond-like carbon (DLC) were investigated
in PBS solution. The films obtained by a PACVD technique present high hardness, good corrosion and wear resistance and lower
friction coefficient compared to bare alloy. Tribocorrosion tests on bare alloy showed that when wear stops, the alloy rapidly
passivates. DLC films present superior wear resistance under dry conditions. However, film life is greatly reduced during
tribocorrosion tests.
An erratum to this article can be found at 相似文献
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Balling behavior of stainless steel and nickel powder during selective laser melting process 总被引:1,自引:0,他引:1
Ruidi Li Jinhui Liu Yusheng Shi Li Wang Wei Jiang 《The International Journal of Advanced Manufacturing Technology》2012,59(9-12):1025-1035
Balling phenomenon, as a typical selective laser melting (SLM) defect, is detrimental to the forming quality. In this work, a detailed investigation into the balling behavior of selective laser melting of stainless steel and pure nickel powder was conducted. It was found that the SLM balling phenomenon can be divided into two types generally: the ellipsoidal balls with dimension of about 500?μm and the spherical balls with dimension of about 10?μm. The former is caused by worsened wetting ability and detrimental to SLM quality; the latter has no obvious detriment to SLM quality. The oxygen content plays an important role in determining the balling initiation, which can be considerably lessened by decreasing the oxygen content of atmosphere to 0.1%. A high laser line energy density, which can be obtained by applying high laser power and low scan speed, could enable a well-wetting characteristic. The effect of scan interval on balling initiation is not obvious as long as the scan track is continuous. The surface remelting procedure can also alleviate the balling effect in a certain extent, due to the melting and wetting of metal balls. Moreover, the balling phenomenon of pure nickel was also studied, and the results implied that the balling discipline had a universality. 相似文献