环氧树脂/碳纤维复合材料模压制品表面质量影响因素分析

通过正交试验研究了模压温度、模压压力、保压时间、合模速度对环氧树脂/碳纤维片状模塑料模压成型制品表面质量的影响,通过方差分析,表明各因素对表面粗糙度影响程度的主次顺序为：模压温度T>保压时间t>模压压力P>合模速度v。通过邓肯法多重比较进一步探讨了各影响因素中不同水平之间平均值的差异性,并绘制了各因素所对应的表面粗糙度实测平均值关系图。发现随着模压温度的增加,制品表面粗糙度先缓慢后急剧增大;保压时间与模压压力对表面粗糙度的影响作用相反;随着合模速度的增大,表面粗糙度不会发生明显的变化。获得最佳工艺参数为：模压温度T=130℃、模压压力P=600 kN、保压时间t=720 s、合模速度v=15 mm/s。通过模压成型实验验证：在最佳工艺参数下,表面粗糙度相对于正交实验结果中的最小值减小了19.3%,有效提高了模压成型制品表面质量。     

快速热循环工艺对玻纤增强注塑制品表面质量的影响研究

提出将快速热循环方法辅助注塑成型工艺,探究不同型腔温度对薄壁玻纤增强制品的表面质量的改善情况。结果表明:制品表面光泽度随着型腔温度的升高也有所提高,表面的"浮纤"缺陷得到明显的改善,但是制品表面粗糙度则随着型腔温度的升高而增大。通过提高型腔表面质量的同时辅助快速热循环工艺,可以明显改善制品的表面质量。     

热塑性挤出制品表面质量的影响因素

以聚丙烯(PP)为基体,研究了热塑性挤出制品表面质量的影响因素,并用Matlab对实验数据进行了拟合。结果表明:剪切速率、温度、口模长径比以及硅酮母粒对制品表面粗糙度都有影响,随着剪切速率、口模长径比的增加以及温度的降低,表面粗糙度增加;硅酮母粒的添加在一定程度上降低了制品的表面粗糙度。     

高铁白车身表面腻子打磨质量一致性研究

在高铁白车身表面腻子自动化打磨的过程中，打磨后的表面质量具有很大的差异，严重影响后续工序的加工制造。本文通过分析并控制影响表面质量的因素，试验研究在不同工艺条件下，表面粗糙度随打磨时间的变化关系，并通过改变打磨过程中的试验条件来保证打磨后的表面质量一致性。结果表明：正压力、主轴转速和砂纸粒度会对打磨后的表面粗糙度和砂纸使用寿命产生较大的影响，在此基础上，在试验过程中适时改变正压力，可以提高打磨后表面质量的一致性。     

FDM工艺参数及后处理对PLA筒形件成型质量的影响

为了提高熔融沉积成型（FDM）制件的尺寸精度和表面质量,以聚乳酸(PLA)筒形打印件为实验对象,采用正交试验设计方法,研究了分层厚度、喷头温度、打印速度和填充率对试样尺寸精度的影响规律,基于综合平衡法得出最优工艺参数组合为：分层厚度0.1 mm、喷嘴温度200 ℃、打印速度60 mm/s、填充率30 %;为了进一步提高试样的表面质量,对其进行蒸汽平滑处理,研究了处理温度和处理时间对试样表面粗糙度的影响。结果表明,粗糙度随处理温度的升高和处理时间的延长而降低,在50 ℃×7 min的处理条件下,试样表面粗糙度(Ra)从9.227 μm降低到3.435 μm,显著改善了试样表面质量。     

电解复合磁力研磨GH4169管内表面的光整研究

为解决GH4169合金管内表面质量问题,降低其表面粗糙度,本文采用电解复合磁力研磨光整加工方法进行了试验,研究了在电解复合磁力研磨条件下,磁粒粒径、电解液温度、电解电压对管内壁表面质量的影响,寻求了最优的工艺参数组合。结果表明,在磁粒粒径为185μm,电解液温度为35℃,电解电压为9 V的条件下,采用电解复合磁力研磨法对GH4169合金管内表面加工25 min,管内表面粗糙度Ra可由原始的1.8μm降至0.11μm。表面缺陷得到有效去除,表面质量得到了明显的改善。管内表面残余应力由+92 MPa转变为-68 MPa,获得了更好的应力状态,提高了表面抗疲劳强度。     

基于Moldex3D分析模具温度对PP发泡注塑制品的影响

对微孔发泡注塑过程进行模具温度控制,对制品进行扫描电子显微镜、弯曲强度、冲击强度、表面粗糙度测试,探讨模具温度对制品的力学性能与泡孔结构的影响。结果表明,当其他工艺参数不变时,提高模具温度,制品的泡孔更加致密,有助于提高制品的弯曲性能和冲击性能并且有助于降低制品表面粗糙度;通过Moldex3D模拟统计泡孔平均直径、密度以及尺寸标准差,验证了模具温度升高时,泡孔尺寸标准差降低,泡孔分布更加均匀;通过模拟验证了当模具温度升高时,泡孔尺寸以及制品减重比变化趋势与实验结果一致。     

磨削T21钛合金件表面质量的研究

本文研究和探讨了磨削加工工艺参数对加工表面质量影响,并通过对比不同方案磨削TC21钛合金的平面磨及外圆磨的工艺条件,发现了磨削加工参数与磨削件表面质量之间的规律,即表面粗糙度、表面变质层、表层金相显微组织以及残余应力变化与磨削工艺条件之间的规律。通过采用不同的试验条件及试验设计方法,研究和探索了TC21钛合金高效磨削加工时,加工件的表面完整性状况,加工参数与加工件表面完整性之间的规律,并给出了解决工程应用问题的建设性方案,这对工程应用和理论研究都具有重要的价值。     

选择性激光烧结聚苯乙烯蜡模的尺寸精度

以熔模精密铸造用聚苯乙烯(PS)蜡模阶梯式线性收缩件为例,以测试件的尺寸精度和表面质量为衡量指标,通过正交试验研究选择性激光烧结(SLS)工艺参数对测试件尺寸精度的影响,并对其进行浸蜡处理,分析浸蜡处理前后测试件尺寸精度及表面质量之间的变化及规律。结果表明,PS粉末SLS成型工艺的最佳工艺参数组合为激光功率30 W,填充速度3000 mm/s,粉层厚度0.14 mm,扫描间距0.31 mm,此时测试件的尺寸精度范围为–0.858%～1.898%,平均表面粗糙度为33.928 μm;最佳浸蜡温度组合为一次浸蜡温度65℃,待其冷却到室温后再进行75℃二次浸蜡。浸蜡后测试件尺寸精度范围为–0.390%～2.74%,平均表面粗糙度为2.203 μm;较PS测试件表面精度提高了93.5%。     

电解-磁力复合研磨镍基高温合金实验研究

为了改善镍基高温合金GH4169制造零部件的表面质量,降低其表面粗糙度,提出了一种高效率的电解-磁力复合研磨光整加工方法。设计了电解-磁力复合研磨光整加工的试验装置,与单纯磁力加工对比,对不同加工工艺下所得合金表面的表面粗糙度、表面成分、表面残余应力进行分析。结果表明,在同等条件下,复合研磨使表面粗糙度由Ra 6.3μm降至Ra 0.8μm,完善了表面质量且加工效率提高56%;加工后表面成分无太大变化;使表面残余应力由+215 MPa转变为-186 MPa,从而获得更好的表面应力状态。     

基于Moldflow和正交试验设计的注射成型工艺参数的优化

以保护盖为研究对象,采用Moldflow软件对其注射成型过程进行了数值模拟,结合正交试验设计方法,研究了熔体温度、模具表面温度、成型时间、保压时间与保压压力5个工艺因素对塑件体积收缩率和翘曲变形量的影响。通过对模拟结果的信噪比分析和方差分析,获得了各因素的最佳水平,进而获得了最优工艺参数组合。对最优组合工艺参数的注射成型进行模拟试验,验证了采用正交试验设计优化注射成型工艺参数的有效性。     

Experimental research on surface characteristics and subsurface damage behavior of monocrystal sapphire induced by helical micro abrasive tools

Sapphire crystals have been widely used in the fields of national defense and optical devices due to good chemical stability and high temperature resistance. In this study, the surface quality, edge fracture characteristic and subsurface damage behavior of sapphire induced by helical micro abrasive tools were experimentally investigated. Effects of geometrical structure of helix micro abrasive tool and process parameters on surface topography, section profile height and surface roughness of sapphire were analyzed. To reveal formation mechanism of subsurface damage of sapphire induced by micro-grinding process, the high temperature chemical corrosion was used to etch sapphire workpiece, and the transformation law of surface morphology and crack layer information with corrosion time were obtained. Besides, effects of geometrical structure of helix micro abrasive tool and process parameters on edge collapse feature and surface fracture length for sapphire crystals were discussed. Furthermore, the ratio of etching surface defect area was put forward to qualitatively the degree of subsurface damage and experimental results indicated that the ratio of etching surface defect area of sapphire was increased with the increase of feed speed and grinding depth. This research can supply a theoretical basis for understanding surface feature and subsurface damage behaviors of monocrystal sapphire involved in micro-grinding process and provide important guidance for high surface quality and low subsurface damage grinding of hard brittle materials.     

Carbothermal nitridation process of mechanically milled silica sand using Taguchi's method

This paper reported on the work performed to study the formation of silicon nitride and silicon carbide whiskers using the carbothermal nitridation process. A distinctive aspect of the present study lies in the use of the mechanical milling method to alter the regularity of the crystalline network of the silica sand. In order to optimise the processing parameters for the synthesis of silicon carbide, the concept of Taguchi's Design of Experiments was considered, the analysis being based on Taguchi's signal to noise ratio and variance techniques to obtain optimum combination of process parameters. Important factors influencing the formation of silicon carbide were the duration of the mechanical milling, followed by temperature, time and heating rate.     

注射成型工艺参数对注塑制品翘曲变形的影响研究

采用Taguchi实验设计技术设计了L9(34)实验矩阵进行实验,运用标准变量分析技术分析了模具温度、熔体温度、注射速率、保压压力等工艺参数对注塑制品翘曲变形的影响,预测最小翘曲变形并优化工艺参数。研究表明,所选择的工艺参数对X、Y、Z方向上的翘曲变形有不同程度的影响。通过优化工艺参数,可使所需方向上的翘曲变形最小,进而提高注塑制品的质量。     

可加工陶瓷材料机械加工技术的研究进展

随着可加工陶瓷材料的研发与应用,可加工陶瓷材料的机械加工技术逐渐成为当今的研究热点之一.本文综述了可加工陶瓷在机械加工过程中的材料去除特性、刀具磨损、加工工艺及可加工性评价,内容涉及加工表面质量、去除机理、加工损伤、材料去除率、刀具参数、切削参数、表面粗糙度、冷却和可加工性综合评价,并提出了今后的研究发展方向和趋势.     

Weighted Estimation of Harmonic Components in a Musical Sound Signal

The study of musical sound has become a popular research field. Harmonic regression signal plus noise statistical models have been used to analyze sound signals. However, it is common to give estimates of harmonic parameters without indications of their uncertainties. Least squares estimates for harmonic models have been studied and asymptotic variance expression have been developed. In practice, window-based estimates are used. This paper studies the statistical properties of such estimates; in particular, we use asymptotic variance expressions to develop standard errors and construct confidence intervals. We present applications and examples of the statistical techniques to musical sound signal analysis.     

Applying the Taguchi method to examine the optimal parameters of cotton fabric dyeing by biodegradable surfactant

Wastewater from the cotton fabric dyeing process causes high levels of environmental pollution. In order to address this problem, this study used a series of biodegradable surfactants in cotton fabric dyeing and applied the Taguchi method to analyse the optimal parameters of cotton fabric dyeing by such surfactants. The test parameters included the hydrophobic group chain length of the surfactant, and surfactant concentration and the processing time. This study calculated the signal‐to‐noise ratio of the experimental results by the‐larger‐the‐better characteristic and applied analysis of variance to discuss its impact on the dyeing results. The results confirmed that the most important influential factor is processing time, followed by surfactant concentration. Moreover, the addition of surfactant could promote a dyeing effect during processing.     

Effects of roughness parameters on slip resistance for different methods used to determine the coefficient of friction for ceramic floor tiles

This work attempts to evaluate the correlation between the roughness parameters and different standardized methodologies for determining the coefficient of friction of ceramic floor tiles. Eight different types of ceramic tiles were evaluated, and each one was characterized for their coefficient of friction/slip resistance in accordance with the standards NBR 13818, ANSI A137.1, and AS 4586. The surfaces were also characterized in relation to surface roughness by means of contact profilometry. The measured friction and roughness parameters were correlated by means of analysis of variance. The results showed a correlation tendency according to a third-degree equation for tests performed in wet conditions. The study results showed that the roughness parameters influence the coefficient of friction with a confidence level of 95%. Considering the safe values indicated for the respective standards for the evaluated methods, a Rz value of 25 μm ensures that a tested surface can be considered safe in a wet-condition test, regardless of the method used to determine the coefficient of friction.     

Growth of CeO2 Films on Sapphire and MgO by rf Magnetron Sputtering

pitaxial CeO₂ films on (1102) sapphire and (100) MgO were grown by rf magnetron sputtering. Substrate temperature, total pressure, and oxygen-to-argon mole ratio were varied to explore the optimal deposition condition. The X-ray diffraction spectra indicate that the degree of crystallinity of the deposited CeO₂ films depends on the oxygen- to-argon mole ratio and the substrate temperature. Atomic force microscopy images of the films on sapphire and MgO showed that substrate temperature and total pressure affect surface roughness. The best film surface is smooth with a 0.89 nm root-mean-square roughness. The quality of the films on MgO showed a strong dependence on substrate pretreatments. Epitaxial CeO₂ films could be grown on pre- annealed or pre-etched MgO if substrate temperatures reached higher than 790^deg;C. Additionally, the effect of ion bombardment at low total pressures on the crystallinity of the films was examined by growing the films outside the plasma region. Experimental results indicate that the ion bombardment does not prevent the films from preferred orientation.