Study of Contact Detect Response for PMR and HAMR Media Using the Integrated Thermistor Based Proximity Sensor

As the Hard Disk Drive industry migrates from PMR to HAMR technology, it is important to understand differences in the measurement of contact detection between PMR vs. HAMR media. Compared to PMR media, HAMR media tends to be rougher and has a higher thermal conductance. Since some contact detection methods rely on interface heat transfer, it is important to understand the impact of media type on measurements. In the current paper, we present results from mechanical spinstand studies using the integrated thermistor in the head. The heater in the head is dithered at a fixed frequency and the thermistor response is analyzed at that frequency. Changes in the thermistor resistance as a function of head-media clearance are used to understand how thermal conduction differences between PMR vs. HAMR media may impact contact detection. We find that heat conduction is different between HAMR and PMR media types and can have an impact on contact detection.

Experimental Study on the Effect of Interface Heat Transfer on Performance of Thermoelectric Generators

Thermoelectric generators (TEGs) have attracted more and more attention for their usage in waste heat recovery techniques. A key challenge in thermoelectric power conversion is to create a significant temperature difference across the TEG. The interface heat transfer between heat exchanger and TEGs plays a key role in TEGs’ performance when the heat exchanger and TEGs have been determined. In this paper different thermal interface materials (TIMs) were used to create different interface heat transfer conditions. Firstly, the thermal interface conductance of TIMs is measured by using a steady state method. Then the performance of TEGs at different interface heat transfer condition was evaluated. It was found that interface heat transfer between heat exchanger and TEGs has a significant effects on the performance of TEGs.

Stacked-Cup Carbon Nanotube Flexible Paper Based on Soy Lecithin and Natural Rubber

Stacked-cup carbon nanotubes (SCCNTs) are generally referred to as carbon nanofibers (CNFs). SCCNTs are much less expensive to fabricate and are regarded as good polymer modifiers suitable for large-scale production. Flexible, SCCNT-based soy lecithin biocomposites were fabricated using liquid natural rubber latex as binder. Natural polymers and the SCCNTs were dispersed in a green solvent using a benchtop high-pressure homogenizer. The inks were simply brush-on painted onto cellulose fiber networks and compacted by a hydraulic press so as to transform into conductive paper-like form. The resulting flexible SCCNT papers demonstrated excellent resistance against severe folding and bending tests, with volume resistivity of about 85 Ω·cm at 20 wt % SCCNT loading. The solvent enabled formation of hydrogen bonding between natural rubber and soy lecithin. Thermomechanical measurements indicated that the biocomposites have good stability below and above glass transition points. Moreover, the SCCNT biocomposites had high through-plane thermal conductivity of 5 W/mK and 2000 kJ/m3K volumetric heat capacity, ideal for thermal interface heat transfer applications.

The Effect of Air Gap between Casting and Water-Cooled Mold on Interface Heat Transfer Coefficient

Water-cooled casting is a new casting process. It allows even large castings to solidify rapidly, thereby reducing segregation and grain refinement. It has drawn the attention of both domestic and foreign businesses. Heat transfer at the casting/water-cooled mold interface controls the cooling rate of the casting. During the solidification process, because of the contraction that takes place during casting, an air gap can form between the casting and the water-cooled mold. This air gap hinders heat transfer between the casting and the mold, leading to a rapid drop in the interface heat transfer coefficient (IHTC). The purpose of the present study was to assess the effects of the width of the air gap and the duration of gap formation on IHTC. During the experiment, the casting temperature curve was determined in the presence of the interface air gap, and then inverse calculation was performed using PROCAST software to determine the IHTC of casting/water-cooled mold. Results showed that, after the formation of the air gap, IHTC first exhibited a rapid decrease, followed by an increase and then another decrease; IHTC was found to decrease as gap width increased and as the duration of gap formation increased.

Identification of Friction Coefficient in Forging Processes by Means T-Shape Tests in High Temperature

In hot metal bulk forming and forging, the interface heat transfer and the friction between the tooling and the billet are of particular importance since they have a significant effect on material flow, deformation, forming forces, component surface finish and die wear. Several authors have used different characterization methods to measure the friction coefficient using cylindrical upsetting tests, ring compression tests, Spike tests and T-Shape tests among others.In the present paper, The T-Shape test has been used in order to measure the friction between aluminium billets and tool steel. In order to obtain the sensitivity of the test, a Finite Element (FE) parametric study has been performed which indicates that shape of specimen could be chosen to measure the friction. For this, compression tests for three specimens in dry conditions have been carried out and shape of specimen has been measured. These measurements and the use of adequate inverse modelling techniques enabled a precise characterization of the forging friction coefficient. Heat transfer coefficient (HTC) has been precisely characterised from the columnar upsetting thermal tests and later used in simulating the T-Shape tests to estimate the friction factor (m). Friction factor has been determined by comparing the experimental results with the numerical simulation results of T-Shape compression test. An encouragingly good agreement has been found between the experimental and numerical results.