Deep drawing of rectangle parts using variable blank holder force

When deep drawing rectangle parts, instead of adopting elastic or several segmented blank holders, a new thought of applying dual layers of blank holders, which are parallel to each other, has been achieved to asynchronously vary blank holder force (BHF) at different regions of sheet flange, by dint of replacing different little mandrils in length between dual layers of blank holders, thus to further improve the formability of products. At the same time, in order to solve two problems of how to judge which one distribution of one desired integral variable BHF, which was obtained from the thickness analyses with products in advance, on blank holder for asymmetric parts is the best and to evaluate lubricant in deep drawing, a probe sensor with structure of dual cantalevers, based on the theory of resistance strain slice, fixed into the inner space of die, was developed for measuring real-time friction coefficient of sheet flange’s surface. Through this special probe sensor, not only real-time BHF on sheet flange could be measured out, but also the real-time friction coefficient could be figured out. Finally, one example of rectangle part was carried out in tests to validate the feasibility of this thought. By the way of analyzing the distribution of variation with products’ thickness on products and judging whether the whole distribution of friction on sheet flange’s surface was uniform or not, one optimized BHF loading profile could be finally obtained over the whole punch stroke.     

A Polish multicenter survey of antimicrobial susceptibility and prevalence of beta-lactamase production among bacterial pathogens isolated from hospitalized and ambulatory patients

The aim of the study was to establish the frequency of occurrence of bacterial pathogens with beta-lactamase activity, and pattern of resistance among aerobic and anaerobic strains isolated from: respiratory tract, urinary tract, skin and soft tissues (hospitalized patients) and throat swabs (ambulatory patients). The study was conducted in 1994 year in 6 bacteriological laboratories in four Polish towns (Warszawa, Kraków, Katowice, Gdańsk) according to the protocol. Sensitivity of bacteria was tested by the disc method on the Müeller-Hinton agar or chocolate agar according to NCCLS, activity of beta-lactamase was tested with nitrocephin. A total 2038 clinical strains--1869 aerobic and 169 anaerobic was well-defined and tested for susceptibility to ten antibiotics--amoxicilin, augmentin, ofloxacin, gentamycin, cefradin, erythromycin, cefuroxim, kotrimoxazol, cefalexin and cefaclor. Among the isolated aerobes Staphylococcus aureus (25.1%), E. coli (23.2%) and Haemophilus influenzae (14.0%) were most frequent, and in the group of anaerobes the most frequent were Bacteroides spp (40.8%) We have found 45.8% of all tested aerobic strains with beta-lactamase production, the highest proportion in pathogens isolated from respiratory tract--51.4%, 46.6% from urinary tract, and 48.4% from skin and soft tissues. Among the isolated anaerobic--68.8% of Bacteroides and 28.6% others produced beta-lactamase. Forty percentage of all strains were sensitive to amoxicilin, 70-90% of aerobic bacteria were sensitive to augmentin. Augmentin had a high activity against anaerobic bacteria too. Only a small proportion of the tested aerobic bacteria (12.2%) were resistant to ofloxacin, gentamycin showed a sufficient activity against tested strains (24.4% were resistant). The most frequent pathogen--Staphylococcus aureus was resistant to amoxicilin in 83.1% hospitalized patients, and in 73.9% in ambulatory patients.     

Corrosion behavior of wire-arc-sprayed stainless steel coating on mild steel

The corrosion characteristics of a wire-are-sprayed stainless steel coating on mild steel have been investigated in regards to atomizing gases and sealing treatment. Salt spray test was performed. The corrosion behavior of the coating was observed under a microscope succesively through a cycling test of wetting and drying in a salt solution. The sealing-treated coating was found to rust faster compared with the non-sealing-treated coating; it protected the mild steel substrate against corrosion, but even it deteriorated the coating itself due to the interruption of the substrate as an anode. The air-atomized coating ruste more heavily than the nitrogen-atomized one. Four different phases were observed in the coating in regards to corrosion behavior; namely, chromium-based oxide, iron-based oxide, chromium-depleted metallic phase, and stainless steel matrix phase. It was found that the chromium-depleted metallic phase and the iron-based oxide are non-corrosion-resistant, whereas the chromium-based oxide and the stainless steel matrix phase are corrosion-resistant.     

Performance of thrust bearings operating with non-Newtonian lubricating films

A general solution for pressure distribution and load capacity is obtained for hydrodynamic bearings with non-Newtonian lubricating fluid films. The flow behaviour index of the power law model assumed for the velocity profile is shown to play a significant role in bearing performance. It is established that the load capacity of a thrust bearing, by way of example, may be increased to several-fold with increased values of the viscometric exponent.