Anisotropic Relaxation of Internal Forces in a Wound Reel of Magnetic Tape

1967 ◽  
Vol 34 (4) ◽  
pp. 888-894 ◽  
Author(s):  
H. Tramposch
Keyword(s):  
Surface Roughness ◽  
Thermal Expansion ◽  
Stress Distribution ◽  
Magnetic Tape ◽  
Digital Computer ◽  
High Speed ◽  
Coefficient Of Thermal Expansion ◽  
Internal Stresses ◽  
Numerical Examples ◽  
Internal Forces

Equations were developed to describe the relaxation of the internal stresses of a wound reel of magnetic tape, with allowances for the effects of surface roughness between tape layers and unequal thermal expansion of hub and tape-layer body. Numerical examples obtained with the aid of a high-speed digital computer indicated that the surface roughness as well as the unequal thermal expansion of hub and tape-layer body greatly affect the internal stress distribution. Essentially independent of the surface roughness, a typical reel, when stored at 120 F after being wound at 70 F and when the coefficient of thermal expansion of the hub is three times the value of the tape material, will approach stress-free conditions about 80 percent earlier than when it is stored at the winding temperature.

Relaxation of Internal Forces in a Wound Reel of Magnetic Tape

1965 ◽  
Vol 32 (4) ◽  
pp. 865-873 ◽  
Author(s):  
H. Tramposch
Keyword(s):  
Magnetic Tape ◽  
Digital Computer ◽  
Isotropic Material ◽  
High Speed ◽  
Mechanical Damage ◽  
Elastic Behavior ◽  
Internal Stresses ◽  
Sufficient Time ◽  
Numerical Examples ◽  
Internal Forces

Equations were developed to predict the relaxation of the internal stresses of a wound reel of magnetic tape, assuming a homogeneous and isotropic material which, under shear, exhibits instantaneous elasticity, delayed elasticity, and creep; and under hydrostatic stressing, shows elastic behavior. Numerical examples obtained with the aid of a high-speed digital computer indicated that the internal stresses introduced during the winding operation continue to relax. Given sufficient time in storage, the wound reel will approach stress-free conditions, thus exposing the tape to mechanical damage during transportation and reuse.

scholarly journals Structure and Thermal Expansion of Cu−90 vol. % Graphite Composites

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7089
Author(s):  
Andrej Opálek ◽  
Štefan Emmer ◽  
Roman Čička ◽  
Naďa Beronská ◽  
Peter Oslanec ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Volume Fraction ◽  
Coefficient Of Thermal Expansion ◽  
Pure Copper ◽  
Hot Isostatic Pressing ◽  
Functional Materials ◽  
Electrical Equipment ◽  
Internal Stresses ◽  
Schapery Model ◽  
Graphite Composites

Copper–graphite composites are promising functional materials exhibiting application potential in electrical equipment and heat exchangers, due to their lower expansion coefficient and high electrical and thermal conductivities. Here, copper–graphite composites with 10–90 vol. % graphite were prepared by hot isostatic pressing, and their microstructure and coefficient of thermal expansion (CTE) were experimentally examined. The CTE decreased with increasing graphite volume fraction, from 17.8 × 10−6 K−1 for HIPed pure copper to 4.9 × 10−6 K−1 for 90 vol. % graphite. In the HIPed pure copper, the presence of cuprous oxide was detected by SEM-EDS. In contrast, Cu–graphite composites contained only a very small amount of oxygen (OHN analysis). There was only one exception, the composite with 90 vol. % graphite contained around 1.8 wt. % water absorbed inside the structure. The internal stresses in the composites were released during the first heating cycle of the CTE measurement. The permanent prolongation and shape of CTE curves were strongly affected by composition. After the release of internal stresses, the CTE curves of composites did not change any further. Finally, the modified Schapery model, including anisotropy and the clustering of graphite, was used to model the dependence of CTE on graphite volume fraction. Modeling suggested that the clustering of graphite via van der Waals bonds (out of hexagonal plane) is the most critical parameter and significantly affects the microstructure and CTE of the Cu–graphite composites when more than 30 vol. % graphite is present.

Materials Characterization and Model of PCB Thermal Expansion for Laminates With Various Copper Densities and Thicknesses

2004 ◽  
Author(s):  
William J. Cunningham ◽  
Dick Casali ◽  
Norman J. Armendariz
Keyword(s):  
Thermal Expansion ◽  
Thermal Management ◽  
High Speed ◽  
Printed Circuit Board ◽  
Coefficient Of Thermal Expansion ◽  
Materials Characterization ◽  
Circuit Board ◽  
Printed Circuit ◽  
Printed Circuit Board Manufacturing ◽  
Increasing Temperature

Abstract The SEMATECH/SEMI roadmap forecasts increased density requirements for printed circuit board manufacturing to accommodate smaller form factor interconnects, increased pin counts, and routing densities on a range of PCB sizes and thicknesses. As a result, the effect of materials. thermal expansion properties may further impact the structural or physical integrity and subsequent electrical properties for high speed and thermal management requirements. This study demonstrated that various sample coupons selected from PCB boards with different amounts of copper showed a corresponding coefficient of thermal expansion (CTE) correlation in the Z-axis (CTEZ) and can be modeled using a constitutive equation. Moreover, samples were further evaluated from the effect of increasing temperature and showed that the CTE indeed affects copper-interconnect physical structures such as copper vias and barrels in terms of elongation or strain.

scholarly journals Influence of the coefficient of thermal expansion on the stress distribution in ceramic veneers after thermal simulation

2020 ◽  
Vol 7 (9) ◽  
pp. 429-435
Author(s):  
Marco Aurélio de Carvalho ◽  
Mariane de Castro Boaventura ◽  
Tainah Costa Firmiano ◽  
Naysa Wink Neris ◽  
Adna Alvez Rocha ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Stress Distribution ◽  
Coefficient Of Thermal Expansion ◽  
Thermal Simulation

scholarly journals Field Monitoring of the Deformation and Internal Forces of the Surrounding Rock and Support Structures in the Construction of a Super-Span High-Speed Railway Tunnel—A Case Study

2020 ◽  
Vol 10 (15) ◽  
pp. 5182
Author(s):  
Daoping Liu ◽  
Dingli Zhang ◽  
Qian Fang ◽  
Zhenyu Sun ◽  
Jiwei Luo ◽  
...  
Keyword(s):  
Contact Pressure ◽  
High Speed ◽  
Field Monitoring ◽  
Surrounding Rock ◽  
Internal Stresses ◽  
Support Structures ◽  
Axial Forces ◽  
Geological Conditions ◽  
Internal Forces

A super-span tunnel that has the characteristics of a large excavation area, a small high-span ratio and a significant spatial effect exhibits a complex mechanical response during the excavation process. In this paper, taking the Badaling Great Wall station in Beijing, China as the engineering background, a case study of field monitoring a super-span tunnel has been presented. A typical monitoring section was selected in the super-span transition section of the tunnel and the deformation and forces of both the surrounding rock and the support structures were systematically monitored. The dynamic evolution and the spatial distribution characteristics of the monitoring data, including the internal displacement of the surrounding rock, the tunnel displacement, the contact pressure between the surrounding rock and the primary supports, the contact pressure between the primary and secondary supports, the axial forces in the bolts and cables, the internal forces in both the steel arches and the secondary supports and the internal stresses of the surrounding rock, were analyzed. The results of the monitoring and the analyses have shown that the deformation and the forces acting on both the surrounding rock and the tunnel’s lining are directly related to the construction procedures, the geological conditions and the locations in the super-span tunnel. According to the results, a few suggestions to improve the construction of the tunnel have been proposed.

Investigation of Thermal Expansion and Physical Properties of Carbon Nanotube Reinforced Nanocrystalline Aluminum Nanocomposite

2016 ◽  
Vol 71 (2) ◽  
pp. 165-174
Author(s):  
Manjula Sharma ◽  
Vimal Sharma
Keyword(s):  
Thermal Expansion ◽  
Carbon Nanotube ◽  
Coefficient Of Thermal Expansion ◽  
Aluminum Matrix ◽  
Fabrication Process ◽  
Aluminum Matrix Composites ◽  
Internal Stresses ◽  
Matrix Composites ◽  
Nanocrystalline Aluminum ◽  
Expansion Behaviour

AbstractCarbon nanotube (CNT) reinforced nanocrystalline aluminum matrix composites are fabricated by a simple and effective physical mixing method with sonication. In this study, the microstructural characterisations and property evaluations of the nanocomposites were performed. The structural characterisations revealed that CNTs were dispersed, embedded, and anchored within the metal matrix. A strong interfacial adhesion appeared between CNTs and nanocrystalline aluminum as a result of the fabrication process. Raman and Fourier transform infrared spectroscopic studies also confirmed the surface adherence of CNTs with nanocrystalline aluminum matrix during the fabrication process. Thermal expansion behaviour of CNT-reinforced aluminum matrix composites was investigated up to 240°C using a dilatometer. The coefficient of thermal expansion of the nanocomposites decreased continuously with the increasing content of CNTs. The maximum reduction of 82% was found for 4 wt% CNTs in the nanocomposite. The coefficient of thermal expansion variation with CNTs was also compared with the predictions from the thermoelastic models. The expansion behaviour of the nanocomposites was correlated to the microstructure, internal stresses, and phase segregations. The electrical and thermal conductivity was also studied and was observed to decrease for all reinforced CNT weight fractions.

scholarly journals MONITORING AND EVALUATION OF A LONG-SPAN RAIWAY BRIDGE USING SENTINEL-1 DATA

2017 ◽  
Vol IV-2/W4 ◽  
pp. 457-463 ◽  
Author(s):  
Q. Huang ◽  
M. Crosetto ◽  
O. Monserrat ◽  
B. Crippa
Keyword(s):  
Thermal Expansion ◽  
High Speed ◽  
Coefficient Of Thermal Expansion ◽  
Monitoring And Evaluation ◽  
Strongly Correlated ◽  
Persistent Scatterer Interferometry ◽  
Long Span ◽  
Persistent Scatterer ◽  
Key Aspects

This paper is focused on displacement monitoring of a bridge, which is one of the key aspects of its structural health monitoring. A simplified Persistent Scatterer Interferometry (PSI) approach is used to monitor the displacements of the Nanjing Dashengguan Yangtze River High-speed Railway Bridge (China). This bridge is 1272 m long and hosts a total of 6 railway lines. The analysis was based on a set of twenty-nine Sentinel-1A images, acquired from April 2015 to August 2016. A dense set of measurement points were selected on the bridge. The PSI results show a maximum longitudinal displacement of 150 mm, on each side of the bridge. The displacements are strongly correlated with the temperature, showing that they are due to thermal expansion. Using the PSI results, the Coefficient of Thermal Expansion (CTE) of the whole bridge was estimated. The result agrees well with the CTE of the bridge materials. Using a regression model, the PSI-measured displacements were compared with in-situ measurements. The paper proposes a procedure to assess the performance of the movable bearings of the bridge, which is based on the PSI measurements.

Enhancement of EDM Performance by Using Copper-Silver Composite Electrode

2020 ◽  
Vol 38 (9A) ◽  
pp. 1352-1358
Author(s):  
Saad K. Shather ◽  
Abbas A. Ibrahim ◽  
Zainab H. Mohsein ◽  
Omar H. Hassoon
Keyword(s):  
Surface Roughness ◽  
Material Removal Rate ◽  
Material Removal ◽  
High Speed ◽  
Composite Electrode ◽  
Removal Rate ◽  
Pure Copper ◽  
High Speed Steel ◽  
Pulse On Time ◽  
Pulse Off Time

Discharge Machining is a non-traditional machining technique and usually applied for hard metals and complex shapes that difficult to machining in the traditional cutting process. This process depends on different parameters that can affect the material removal rate and surface roughness. The electrode material is one of the important parameters in Electro –Discharge Machining (EDM). In this paper, the experimental work carried out by using a composite material electrode and the workpiece material from a high-speed steel plate. The cutting conditions: current (10 Amps, 12 Amps, 14 Amps), pulse on time (100 µs, 150 µs, 200 µs), pulse off time 25 µs, casting technique has been carried out to prepare the composite electrodes copper-sliver. The experimental results showed that Copper-Sliver (weight ratio70:30) gives better results than commonly electrode copper, Material Removal Rate (MRR) Copper-Sliver composite electrode reach to 0.225 gm/min higher than the pure Copper electrode. The lower value of the tool wear rate achieved with the composite electrode is 0.0001 gm/min. The surface roughness of the workpiece improved with a composite electrode compared with the pure electrode.

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