Evaluation of stamping lubricants at various temperature levels using the ironing test

Lubricants are employed in stamping operations in order to (a) improve the material flow into the die cavity, (b) reduce wear and galling in the die and (c) obtain good surface finish of the part. Process conditions such as high temperatures and pressures could cause the lubricant to fail, thus resulting in galling or tearing of the part, damage to the tooling, and lost production. Therefore, selection of an appropriate lubricant based on the process conditions is important in the stamping industry. Several benchmark tests emulating stamping operations have been developed and are used to evaluate the performance of candidate lubricants. The major drawback of most of these tests is their inability to emulate high contact pressures and sliding velocities, which are crucial parameters for lubricity, especially in the case of high-speed progressive or transfer die operations involving ironing. Moreover, most of these tests are conducted at room temperature, while in reality; the process temperature can reach as high as 200 °C. The ironing tribotest developed at the Engineering Research Center for Net Shape Manufacturing (ERC/NSM) induces high contact pressures and temperatures, thus emulating the conditions in a production environment. Application of the test to screen candidate lubricants for stamping operations involving the ironing process is discussed in this paper.     

Phenelzine use throughout pregnancy and the puerperium: case report, review of the literature, and management recommendations

Adenotonsillar enlargement (ATE) can cause respiratory disorders during sleep in children. The treatment of choice for ATE is adenotonsillectomy and its efficacy must be assessed based on improvement in symptoms and polysomnographic patterns. We studied 11 children (7 boys and 4 girls, age 5.5 years) whose ATE symptoms were corrected by adenotonsillectomy. Two nighttime polysomnograms (SleepLab) were recorded, one at baseline and one 6 months after adenotonsillectomy. Polysomnographic recordings were analyzed by quantifying 1) only apneic or hypopneic events lasting > or = 10 sec and 2) all respiratory events > or = 5 sec. The most common symptoms were snoring, nocturnal dyspnea and sleep apnea. Symptoms resolved after adenotonsillectomy for most patients. Obstructive events, in particular shorter apneic events (> or = 5 sec) and instances of hypopnea, decreased after surgery. We found no changes in baseline SaO2, although the minimum SaO2 improved and the number of desaturations decreased, above all those stemming from respiratory events.     

Patient-size-dependent radiation dose optimisation technique for abdominal CT examinations

Since patient doses from computed tomography (CT) are relatively high, risk-benefit analysis requires dose to patients and image quality be optimised. The aim of this study was to develop a patient-dependent optimisation technique that uses patient diameter to select a combination of CT scanning parameters that minimise dose delivered to patients undergoing abdominal CT examinations. The study was performed using cylindrical phantoms of diameters ranging from 16 to 40 cm in order to establish the relationship between image degradation, CT scanning techniques, patient dose and patient size from two CT scanners. These relationships were established by scanning the phantoms using standard scanning technique followed by selected combinations of scanning parameters. The image noises through phantom images were determined using region of interest software available in both scanners. The energy depositions to the X-ray detector through phantoms were determined from measurements of CT dose index in air corrected for attenuation of the phantom materials. The results demonstrate that exposure settings (milliampere seconds) could be reduced by up to 82 % for smaller phantom relative to standard milliampere seconds, while detector signal could be reduced by up to 93 % for smaller phantom relative to energy depositions required when scanned using standard scanning protocols. It was further revealed that the use of the object-specific scanning parameters on studies performed with phantom of different diameters could reduce the incident radiation to small size object by up to 86 % to obtain the same image quality required for standard adult object. In view of the earlier mentioned fact, substantial dose saving from small-sized adults and children patients undergoing abdomen CT examinations could be achieved through optimal adjustment of CT scanning technique based on the patient transverse diameter.     

Use of lead shields for radiation protection of superficial organs in patients undergoing head CT examinations

Head computed tomography examinations are often accompanied with unnecessary irradiation of superficial organs that are rarely the main target for the investigation. The aim of this work is to demonstrate that lead shields could be effectively used to protect superficial organs without compromising image quality where superficial organ itself is not a target and that the irradiation of the superficial organ is unavoidable. The objective was achieved by first assessing the image quality using phantom measurements made with and without lead shielding in order to determine optimal shielding thickness for patient applications. The entrance surface doses (ESDs) to superficial organs of sixty patients were measured using LiF-thermoluminescent dosemeters without, with one layer, or with two layers of lead shields. Phantom studies demonstrated that the use of modified lead shields of up to 0.25 mm thickness could be used without significant effect on the image quality for central and posterior regions. In these studies, lead shields of 0.25 mm thickness reduce the ESDs to the lens of the eyes and thyroid by 44 and 51%, respectively. The image quality reduction by eye shields was significant to the anterior (i.e. orbital) region but marginal to the central and posterior regions (cerebrum). In view of the above, the use of modified lead shields could reduce the dose to the superficial organs considerably without significantly compromising image quality.     

Database for real-time loading path prediction for tube hydroforming using multidimensional cubic spline interpolation

Tube hydroforming (THF) is a metal-forming process that uses a pressurized fluid in place of a hard tool to plastically deform a given tube into a desired shape. In addition to the internal pressure, the tube material is fed axially toward the die cavity. This process has various applications in the automotive, aerospace, and bicycle industries. Accurate coordination of the fluid pressure and axial feed, collectively referred to as a loading path, is critical to THF. Workable loading paths are currently determined by trial and error, which can be time consuming.This study discusses an innovative technique for developing an interactive, real-time database that would be able to predict loading paths for many THF components and hence reduce the computational time required. By classifying most of the commercial THF parts into families, parameters such as material properties, part geometry, and tribological factors were simulated by category and stored in the database. Multidimensional cubic spline interpolation was implemented to enable an end user to request from the database a loading path for a wide range of conditions. Test results from the database for different THF families were shown to approximate the simulated results. In addition to reducing the computation time, the use of interpolation techniques eliminates the need for carrying out multiple simulations for similar THF parts.     

Current status of patient radiation doses from computed tomography examinations in Tanzania

The aim of this study was to assess the magnitude of radiation dose imparted to patients undergoing CT (computed tomography) examinations in Tanzania. The effective doses to patients undergoing five common CT examinations were obtained from eight health centres. The doses to patients were estimated using measurements of CTDI, exposure-related parameters and the CTDOSE software based on NRPB conversion factors. The mean effective doses in Tanzania for CT examinations of head, lumbar spine, chest, abdomen and pelvis were 2.2+/-0.9, 5.4+/-2.3, 12.2+/-3.4, 15.3+/-6.0 and 13.4+/-7.3 mSv, respectively. The mean effective doses and the variations in dose between hospitals in Tanzania were mostly comparable with reported values in the literature for six different countries from Europe. The observed wide variation in mean effective dose for similar CT examination among hospitals was largely influenced by different CT scanning protocols employed among hospitals. In view of the observed causes of variation in patient doses, it was concluded that further studies are needed to investigate the methods that can reduce dose to patients without affecting image quality.     

Evaluation of new cold forging lubricants without zinc phosphate precoat

Zinc phosphate coatings plus metal soap lubrication system is required in nearly all steel cold forging operations. However, the chemical byproducts of this lubricant system are difficult to dispose of and have a negative environmental impact. In order to replace zinc phosphate based lubricants partially or completely, candidate lubricants were sought from lubricant manufacturers worldwide. The performance evaluation of these lubricants was conducted using the double cup backward extrusion test developed at the Engineering Research Center for Net Shape Manufacturing (ERC/NSM). With the use of the commercial FEM code DEFORM, friction factor calibration curves, i.e. cup height ratio vs. punch stroke, were established for different friction factor values. By matching the cup height ratio and the punch stroke from experiment to that obtained from FE simulations, the friction factor of the lubricants was determined. Three lubricants; namely, MEC Homat, Daido AquaLub, and MCI Z-Coat, were found to perform comparable to or better than zinc phosphate.