Lateral motion and edge wear of magnetic tapes

Lateral motion and edge wear are measured on magnetic tape, and the relationship between tape edge wear and tape lateral motion is investigated. Instrumentation for measuring tape edge force is described. Tape edge force is measured at the tape guiding position using a force-calibrated cantilever spring and a linear optical probe. Typical measurements of tape lateral motion are given as a function of tape tension, tape direction, and path position. A technique for measuring tape edge wear is introduced and wear measurements are presented as a function of load and the number of passes.     

磁力弹簧的工作特性分析

弹性分析显示 ,磁力弹簧的弹力与位移变化的特性曲线呈渐增型 ,具有显著的短行程减振和快速减振效果。简单地改变磁体的外形尺寸即可改变其特性曲线     

Nanotribological properties of novel lubricants for magnetic tapes

Two classes of novel lubricants, perfluoropolyethers (PFPE) and ionic liquids (ILs), were deposited on metal film magnetic tapes. The adhesive force and coefficient of friction of lubricated and unlubricated tapes were investigated at the nanoscale with an atomic force microscope (AFM) as a function of various humidity and temperature conditions. Microscale tests with a ball-on-flat tribometer were also performed in order to study the length-scale effects on friction. Wear at ultralow loads was simulated and the lubricant removal mechanism was investigated by monitoring the friction force, surface potential and contact resistance with the AFM. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) experiments were conducted to determine the chemical species that affect intermolecular bonding and as an aid in interpreting how the lubricant film tribological properties vary with the environmental conditions. Z-TETRAOL, one of the PFPEs, was found to exhibit the lowest adhesion and friction among the lubricant films studied. The ionic liquid 1,1′-(pentane-1,5-diyl)bis(3-hydroxyethyl-1H-imidazolium-1-yl) di[bis(trifluoromethanesulfonyl)imide)] exhibited comparable nanotribological properties with the PFPEs. This is attributed to the presence of hydroxyl groups at its chain ends, which can hydrogen bond with the surface similar to PFPEs.     

Measurement of dimensional stability of heat treated southern red oak (Quercus falcata Michx.)

The objective of this study was to investigate the effect of heat treatment on physical and mechanical properties including oven-dry density, weight loss, swelling, shrinkage, and hardness of southern red oak (Quercus falcata Michx.). The samples were treated at a temperature level of 190 °C for 3 h and 8 h. After heat treatment of the specimens, their dimensional stability in the form of swelling and shrinkage were determined by soaking them in water for 2 and 24 h. Hardness of samples as function of heat treatment was also measured using Janka hardness (ASTM D 1037–12). Tangential, radial and longitudinal swelling values of the samples exposed to 8 h heat treatment and soaked in water for 2 h were 0.245%, 0.236%, 0.098%, respectively. Corresponding values for the control samples were 0.504%, 0.455%, 0.135%. Overall hardness of the specimens was adversely influenced due to heat treatment. Based on the findings in this study shrinkage and swelling of the samples improved as a result of heat exposure. It appears that heat treatment would be a viable method to enhance dimensional stability of red oak for more effective utilization where enhanced hygroscopicity of such species is desired.     

Investigations of nano- and macro-wear of magnetic tape head materials

The nano- and macro-wear characteristics of calcium titanate, single crystal ferrite and polycrystalline ferrite were investigated using nano-scratch testing and wear bar testing. Nano- and micro-indentations were made to determine nano- and micro-hardness, and nano-scratch testing was used to evaluate relative wear rates on the nano-scale. The macro-wear characteristics of the various head materials against metal particle tapes was investigated as a function of tape speed using wear bars mounted in a DLT tape drive. The micro-indentation method was used to investigate wear of the head/tape interface in a linear tape drive. The results from nano- and macro-wear tests were analysed and correlated with the microstructure of the materials.     

Investigation of tape edge wear of magnetic recording tapes

Tape edge wear is studied for polyethylene naphthalate-based magnetic tape as a function of tape speed, tape tension, and tape guide surface roughness. The results show that tape edge wear is on the order of 0.04 nm per cycle at a constant force of 45 mN and that edge wear increases with increasing tape speed, tape tension and tape guide surface roughness. In addition, tape edge wear of three coated tapes with polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyaramid (PA) substrate is studied. It is found that edge wear of polyaramid based tape is similar to that of PET-based and PEN-based tapes.     

Dynamic stability of ferromagnetic plate under transverse magnetic field and in-plane periodic compression

The dynamic stability of a soft ferromagnetic rectangular and simply supported plate immersed in an applied transverse magnetic field, as well as subjected to an in-plane periodic compression is presented in this paper. The fundamental equations involving magnetoelastic interaction and magnetic damping effect for the ferromagnetic plate are developed. In the theoretical model, the expression of induced magnetic force is based on a generalized magnetoelastic variational model, and the magnetic damping is due to the Lorentz body force arising from eddy current in the ferromagnetic material. By means of a linearized magnetoelastic theory and perturbation technique, the motion equation of the ferromagnetic plate is reduced to a damped Mathieu's equation and solved. The dynamic stability of the magnetoelastic system without in-plane compression is theoretically analyzed first, to show that there exist two stable states: magnetic damped stable oscillation, and over-damped asymptotically stable motion before static divergence instability of the ferromagnetic plate occurs. The dynamic instability and stability regions for the parametric excitation of the ferromagnetic plate due to the harmonically excited in-plane compression are obtained next. The effects of magnetic damping and excitation frequency of the in-plane periodic compression on the stability regions are discussed in detail.     

智能土工布力学性能测试系统的设计与实现

根据国家标准研制了一种智能土工布力学性能测试系统。该系统可以完成对土工布的各种力学性能测试试验，包括务样拉伸、握持拉伸、撕裂、CBR顶破等。通过对试样的实测数据分析，说明系统符合土工布力学能测试要求，具有较好的实用性。介绍了该测试系统的测试原理以及软、硬件设计和实现的关键技术。     

Measurement of mechanical and physical properties of particleboard by hybridization of kenaf with rubberwood particles

Kenaf is one of the potential raw materials available in Malaysia to use for particleboard manufacturing as an alternative solution to balance shortage of rubberwood (RW) supply. In this study, particleboard manufactured from kenaf stem (KS) and RW particle blends at different RW loading (0%, 50%, 70%, 100%) and resin levels (6%, 8%, 10%). Urea formaldehyde resin is used as a binder. The effects of RW:KS ratio and resin content on mechanical and dimensional stability properties of hybrid particleboard were determined. The results indicated that particleboards bonded with 10% resin level and 50:50 (RW:KS) had the highest strength (19.08 MPa) while particleboards made of 70:30 (RW:KS) display better stiffness (2.23 GPa). Statistical analysis using ANOVA and LSD were conducted on the obtained results. The results show that RW:KS ratio has greater influence over thickness swelling (TS) and water absorption (WA) of particleboard than the level of resin content. The relationship between internal bonding (IB) and TS of particleboards were also examined and obtained strong inverse relationship between IB and TS. Hybrid particleboards made from 70% RW and 30% KS with 10% resin content display over all good properties and comparable with 100% RW (control) samples. It concluded that kenaf stem can replace rubberwood particles up to 50% but the resin level must be kept at 10% or more because lower resin level (⩽8%) significantly decrease strength of the particleboard.     

微量P、Bi、In和Ga元素对Sn-Ag-Sb-Zn系无铅焊料性能的影响

传统的Sn -Pb焊料及其他Pb基焊料除有毒外,还存在力学性能低的问题。对Sn -Ag- Sb- Zn合金系并添加微量元素进行研究,对所选定的合金进行机械性能、物理性能试验。结果表明,微量元素的加入对合金的物理性能、润湿性能和力学性能都有益,并能明显提高接头剪切强度。新开发的焊料合金的综合性能已经超过了Sn- Pb焊料。     

圆柱面过盈连接的力学特性及设计方法

传统的圆柱面过盈连接设计将结合直径、结合宽度等因素视为定量,并且忽略边缘效应所引起的应力集中。为解决此问题,更好地研究圆柱面过盈连接的力学特性,寻求更合理的设计方法,结合有限元法和BP神经网络各自的优势,以ABAQUS为工具分析圆柱面过盈连接接触面的应力特性及结合直径、结合宽度、包容件外径及过盈量等因素对它的影响,将通过分析得到的大量接触边缘最大应力作为神经网络的训练样本,建立接触边缘最大应力的BP神经网络模型。将接触面应力的各种影响因素视为可调变量,结合接触边缘最大应力的BP神经网络模型,提出一种以接触边缘最大应力为优化目标的圆柱面过盈连接设计的BP神经网络动态调整算法。通过实例分析,表明该算法比传统的设计方法更为合理。     

A motorized 5 m tape comparator for traceable measurements of tapes and rules

A motorized 5 m tape comparator was constructed in TUBITAK UME for calibration of tapes and rules up to 5 m length in one set-up and further lengths in multiple set-ups. The system is a practical development and provides a cost effective solution for calibration of tapes in which the highest grade’s accuracy requirement in OIML R35-1 e.g. is 600 μm for 5 m length and 1100 μm for 10 m length. It is mainly composed of 6 m rail system, mechanical parts, optical units and an integrated 6 m incremental linear encoder as a reference measurement axis for traceable measurements. The rails are kinematically located on a heavy marble construction and a motorized carriage, which employs a camera for probing of the scales on the tapes, is moved along the rails during the measurement. The image of the scale taken by the camera is viewed on the monitor screen together with the running software. The operator can perform the probing process by simply moving the carriage over the measured scales (tapes or rules) using a joystick. The carriage movement is measured by the incremental linear encoder previously calibrated by a laser interferometer and the software automatically takes the measurement results from the incremental linear encoder, applies correction values previously defined and determines the length of the tapes and rules as well as deviations from nominal lengths. The estimated expanded uncertainty of the steel tape measurement is U = 54 μm in one set-up (for 5 m length) and U = 77 μm in two set-ups (for 10 m length) at the confidence level of approximately 95%. Uncertainty budget for calibration of the device itself and for calibration of the test tapes are explained in detail. The results of extensive experimental work and analysis are provided by demonstrating application of science and technology of measurement and instrumentation. Investigations for long term stability of the system are given with the reported test results for the years of 2003-2011 and participated intercomparison results to validate the device scientifically are illustrated.     

In situ study of nano-cracking in multilayered magnetic tapes under monotonic and fatigue loading using an AFM

Atomic force microscopy (AFM) techniques are increasingly used for tribological studies of engineering surfaces on micro- to nano-scales. In situ surface characterization of local deformation of materials and thin coatings helps to develop a better understanding of failure mechanisms. In this study, an AFM-based technique has been developed for in situ monitoring of nano-crack formation and progression under fatigue loading. To conduct monotonic and fatigue loading tests, a tensile stage is used to mount samples on the AFM base and the same area on the sample surface is scanned intermittently during the loading process. Crack growth under monotonic and fatigue loading for multilayered magnetic tapes is studied and a crack growth mechanism for metallic magnetic tapes under monotonic loading is proposed. Fatigue strength for the metallic magnetic tapes is measured and a mathematical model based on theory of elasticity for fatigue life prediction is developed.     

A new method for determining the mechanical stability of lubricating greases

Mechanical stability is of central importance when dealing with the long-term service-length of grease-lubricated roller bearings. Poor stability will lead to consistency degradation of the grease, because of mechanical forces between the rolling parts of the bearing. The result can be leakage of grease through seals, or at worst a total failure of the bearing. The present investigation was initiated because present-day methods for prediction of mechanical stability show weak correlation with real service-length. The aim of the project was to develop a useful alternative. In order to fulfil this, both field tests and laboratory tests were carried out. In the field tests, nine different commercial greases were examined in the wheel bearings of five ore waggons, used for transporting ore by railroad from the Kiruna Mine in northern Sweden to Narvik in northern Norway for shipping to foreign markets. The test ore waggons travelled a distance of about 300,000 km during a period of 3 years. Small samples of greases were taken, on eight different occasions, for consistency testing. After the end of the test period, the damage on the bearings was also studied. In the laboratory tests, new undestroyed greases of the same brand as in the field tests were examined using conventional methods, such as the V2F, the Roll Stability Test and the Grease Worker. Comparisons between the field tests and these laboratory tests indicate poor correlation. In addition to these conventional methods, the relevance of the shear strength of the greases to the prediction of the mechanical stability was also tested. The shear stress τ_L depends on the applied pressure p, thus τ_L=τ₀+γ·p where τ₀ is the shear stress at atmospheric pressure. γ is a property of the lubricant in the same way as viscosity or density. It was found that γ correlates well with the mechanical stability in service. Increased γ values lead to a decrease in the mechanical stability. One reasonable explanation is that high γ values correspond to high shear stresses in the grease, and thus severe conditions for the thickener.     

土建结构工程的机械性与耐久性分析

工程结构机械性是结构防止破坏倒塌的能力,是结构工程最重要的质量指标.对工程结构的耐久性,我国土建结构的设计与施工规范,重点放在各种荷载作用下的结构强度要求,而对环境因素作用下的耐久性要求则相对考虑较少.     

Integrated laser/CMM system for the dimensional inspection of objects made of soft material

The applications of the coordinate measuring machines (CMMs) with a contact trigger probe to the dimensional inspection of manufactured products are restricted to the parts made of hard material, such as steel. By combining the laser and CMM, the applications of the CMMs can be extended to the inspection of objects made of soft materials, such as foils, plastics, wood, wax and clay materials. In this research, replacing the contact probe with an inexpensive laser sensor is attempted so as to eliminate the possible deflection of the component being measured when using contact probe. By combining a laser sensor with the existing automated inspection environment, a CAD-directed, three-dimensional coordinate sampling system which can perform non-contact dimensional inspection is developed.     

Measurement of temperature induced X-ray tube transmission target displacements for dimensional computed tomography

We characterised the displacement of a transmission X-ray tube target parallel to the beam axis due to thermal effects using interferometry. Displacements of up to 10 μm with a sensitivity of about 0.4 μm/W deposited power were measured relative to the X-ray tube's mechanical mounting position. They significantly influence the scale factor of dimensional computed tomography measurements by several 10⁻⁴ at high geometric magnifications. Finite element simulations revealed that the displacement is due to thermal deformation of the entire target assembly and helped to derive a linearised model that predicted the displacements within a few tenths of a micrometre. Radiographic measurements of a calibrated standard confirmed that the mechanical displacement of the target corresponded with the X-ray focal spot position. The findings help to increase the accuracy of dimensional X-ray computed tomography measurements and to ameliorate the design of transmission X-ray tubes.     

热处理时效温度对3J1材料力学性能的影响

Ni36CrTiAl(3J1)弹性合金是一种用于仪器仪表中的材料,对该合金进行不同热处理工艺的研究,获得该合金满意的力学性能.     

退火及回火处理对含Ni塑料模具钢性能的影响

通过研究2种不同成分的预硬型塑料模具钢锻后砂冷、退火及回火等状态下组织及力学性能并进行分析,发现退火组织由粒状贝氏体+下贝氏体+马氏体组成,降低粒状贝氏体量有利于提高材料的韧性和延伸率。残余奥氏体含量较低,对提高韧性作用不大。回火后残余奥氏体几乎全部分解,软相减少,屈服强度提高。Ni的增加降低了马氏体硬度,提高了贝氏体和退火后回火组织硬度。残余奥氏体对硬度的影响不大。     

真空逸气对复合材料尺寸稳定性的影响

为验证聚合物基体在真空环境产生的逸气效应对复合材料尺寸稳定性的影响,对环氧树脂和氰酸脂两种基体的碳纤维复合材料的真空逸气性能进行了试验研究。首先从理论上分析了膨胀系数与逸气系数之间的关系,获得了二者尺寸稳定性存在差异的理论依据。然后设计了能够精确测量尺寸和质量变化的试验组件,按照卫星环境试验条件对多组试验组件进行了3轮真空试验,精确测量了试验前后试验组件的尺寸和质量。试验结果表明:环氧树脂基体和氰酸脂基体的复合材料质损率(TML)分别为0.033%~0.06%和0.014%~0.029%;环氧树脂基体和氰酸脂基体的复合材料尺寸变化量分别为2~8μm和1~3μm。另外,环氧树脂基试件的质量变化约为氰酸脂基的2倍,说明两种材料在真空环境下的尺寸稳定性有差异。