Flaking failure of bearings is caused by crack growth and stress concentration. The contact conditions between ball, retainer and race affect the durability of the bearings. Non-destructive methods ...that can be related to contact conditions are necessary to study and understand the phenomena caused by the contact stresses. In the present work, a scanning Hall probe microscope (SHPM) equipped with a GaAs film sensor was used to observe the asymmetric distribution of three-dimensional magnetic fields in bearing steel plates (JIS-SUJ2) before and after light load contact tests of 19.6N. It was found that only vertical components of the magnetic fields are slightly affected by the spherical Hertzian contact. Furthermore, the change in the three-dimensional magnetic fields is asymmetric to the contact center and magnetization center.
Fatigue failure of machine components is caused by cyclic load. Non-destructive observation methods that can be related to stress are necessary to study the fatigue phenomena. In the present work, a ...three-dimensional scanning Hall probe microscope (SHPM) equipped with GaAs film sensors was used to observe the fundamental features of the magnetic fields in a tool steel specimen (SKS93, JIS B 4404: 2006, equivalent to AISI W4 tool steel) during tensile loading. The nature of the magnetic fields during tensile loadings of 430μstrain and 640μstrain was observed using the SHPM. It was found that the magnetic fields decrease due to the tensile loading.
In biped walking humanoid robot, toughness, durability and lightweight of joint parts are crucial factors due to parts’ constant exposure to high torque and loads. Such ergonomically challenging ...conditions create the need for joint systems comprising independent elements capable of keeping the component operable for long periods of time. In our work, we focused on wear and thermal deformation in two different grades of both poly-ether-ether-ketone (PEEK) and polyoxymethylene (POM) plastic bushes. The components used for investigation were bushes typically employed in speed reduction devices in joint models for biped walking humanoid robots. In such joint systems, plastic bushes are directly connected to a crankshaft, playing an important role in the robot's movement ability. In order to acquire the knowledge of how to build more efficient systems, the influence of the titanium crankshaft roughness on the frictional heat occurring between the shaft and the polymer bush as well as the input axis-output axis backlash require close examination. Based on Rolling Contact Fatigue test, we established the optimal machining conditions for the crank shafts and bushes. Also, superior to other tested polymers as far as glass transition temperature, wear toughness and thermal deformation are concerned, PEEK was found to be the best suiting material for our investigation.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Due to constant exposure to high torque and loads toughness, compressive durability and light weight of joint parts are crucial factors for biped walking humanoid robot parts. When polymer ...transmission parts are used for the manufacture of humanoid robot joint, wear becomes an important factor in terms of transmission error (backlash) between the input and output axes, ex. between the motor and the robot’s leg joint. In such joint system, a polymer bushes is directly connected to a cam plate, playing an important role in the robot's movement ability. In this work, the influence of wear of reinforced poly-ether-ether-ketone (PEEK) polymer bushes in friction against 7075 aluminium alloy cam plates is investigated in order to establish the application possibilities in transmission parts in humanoid robot’s joint. The PEEK bush surface conditions as well as the input axis-output axis backlash require close examination, so that efficient systems can be built. Sliding wear tests were performed on bushes under 0-50kgfcm loaded torque while the cam plate oscillated. Based on the wear observation, it was found that in a high load range the backlash increased along with number of cycles due to PEEK bush wear. The bush surface roughness also increased during testing. Roughness of PEEK bush surface and the loaded torque for output axis were significantly related to backlash of output axis in robot joint.
In this work, wear of reinforced poly-ether-ether-ketone (PEEK containing PTFE, graphite and carbon fibres) polymer bushes in friction against 7075 aluminium alloy cam plates is investigated in order ...to establish the application possibilities in transmission parts in humanoid robot joints. The PEEK bush surface conditions as well as the input axis-output axis transmission error (backlash) require close examination. Sliding wear tests were performed on bushes under 900 kgfcm loaded torque, while the cam plate oscillated. Based on the wear observation, it was found that PEEK wear fragments in the interface between PEEK bush and aluminium alloy cam plate formed a PEEK film.
The present study was intended to assess whether the left ventricular end-diastolic diameter (LVDd), inferior vena cava diameter (IVCd) or their combination, estimated by ultrasonography, can be a ...useful index for determining the dry weight (DW) in patients undergoing hemodialysis (HD). Seventy-one consecutive patients were investigated in comparison with 40 age-matched healthy subjects. The LVDd and IVCd were significantly correlated with LV ejection fraction (EF; an index for LV systolic function, p<0.01) and E/A (an index for LV diastolic function, p<0.01), respectively. When compared to an arbitrary standard of the hemodialyzed cases, where the LVDd and IVCd were within 1 standard deviation of the mean (IVCd: 8.7mm-14.9mm, LVDd: 43.2-54.5mm), hypotension during HD was significantly more common among patients with either reduced LVDd or IVCd than in patients without such manifestations (8/15 versus 8/33, p<0.05). In half of the studied patients, the decrease in DW resulted in an improvement of EF as well as both LVDd and IVCd. However, in some patients who did not show an improvement of EF, the decrease in DW causes rapid reduction of either LVDd or IVCd. Our results suggest that the combined but not individual assessment of LVDd and IVCd can be a useful index for determining the adequate DW and preventing hypotension during HD.
We studied the effect of a synthetic eelcalcitonin analog (Elcatonin: ECT) on changes in bone mineral content in 61 patients with renal osteodystrophy undergoing chronic hemodialysis (32 males and 29 ...females; mean age: 51.1±12.8 years, mean duration of hemodialysis: 10.4±4.4 years). The patients were given a 40-IU infusion of ECT during each hemodialysis session for 12 months, and their bone mineral content was evaluated every 6 months. We determined the bone mineral content of the parietal bone and the 3rd lumbar vertebra by dual energy X-ray absorptiometry (DEXA) using an X-ray bone densitometer (QDR-1000/W, HOLOGIC Co., Ltd., USA). ECT administration caused an significant increase in the bone mineral content of the parietal bone, which is a cortical bone, but no significant change in the lumbar vertebra, a spongy bone. ECT administration significantly increased the bone mineral content of the parietal bone in patients with low bone mineral content and high PTH levels before ECT therapy. However, there does not appear to be any correlation between bone mineral content and the duration of hemodialysis. ECT therapy also significantly decreased ALP and OH-Pro levels, but did not affect PTH or ALPiso levels. These findings suggest that increases in bone mineral content by ECT are often observed in cortical bone in hemodialysis patients and that ECT has an inhibitory effect on bone absorption and an action which increases bone mineral content. On the other hand, determination of bone mineral content by DEXA is thought to be a useful method for the diagnosis of renal osteodystrophy and the evaluation of therapeutic effects.
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