Cut Threads Research Articles

Reassessment of fatigue detail categories of bolts and rods according to EC 3-1-9

The paper deals with the reassessment of fatigue detail categories of bolts and rods in EC 3-1-9 based on published fatigue test data and further conducted investigations. An elaborate database structure has been set up to evaluate the available fatigue test data in a differentiated way. Detail categories of bolts and rods in tension and shear have been investigated and re-evaluated based on the developed data base. Moreover, fatigue tests and numerical investigations on prestressed bolts in T-joints, L-joints and different types of end plate connections have been performed. Several influences on the fatigue strength (e.g. material influence, size effect, fabrication differences) have been analysed and design recommendations are given. The conducted fatigue tests on bolts in tension fit into the spreading band of 573 tests results conducted in the past, confirming fatigue class 50. However, bolts with rolled threads show a higher fatigue strength than those with cut threads, which has been included into the recommendations for fatigue details of bolts. Fatigue class 100 for bolts in shear has also been confirmed, however based on few data. Numerical investigations show, that bolts should be placed as close as possible to the tension flanges, while end plates should be dimensioned thick enough with an overhang including an additional bolt row.

The Post-Classical Use of Latin in Bulgaria

The article summarizes the evidence about the use of Latin in Bulgariaduring the Middle Ages and the early modern period and comments the reasons for the lack of knowledge or the indifference to the literary tradition of the Latin West till the end of the nineteenth century. Beginning with the transformation of the Roman world in the Late Antiquity, the post-classical fate of Latinitas in the Bulgarian lands tells us for the most part a story about cut threads, periods of forced isolation from the Latin West (the spread of humanism and the access to the great achievements of the following cultural epochs in Europe were blocked by the Turkish invasion in 1396), and reconsidered confessional and political choices. My intention, however, is to present the few separate channels of transmitting Latin language and literary culture to the educated élite in Bulgaria, i.e. the diplomatic contacts with the Papacy and the European rulers, the direct or indirect translations from Latin sources, and the original works written in Latin by the Bulgarian Catholics in the seventeenth century. In these times, and later, indirect translations dominated, it was only in 1873 that the first major direct translation of a Latin text into Bulgarian appeared.

Ureteric Avulsion following Blind Attempts at Retrieval of Intrauterine Contraceptive Device: A Clinical Lesson to Primary Care Givers

Intra Uterine Contraceptive Device (IUCD) is the most popular method of reversible contraception in India because of their high efficacy for fertility regulation, low-risk, low-cost, and lack of required maintenance. Uterine perforation remains one of the most serious complications, with an incidence 0.87 per 1000 insertions. The IUCD strings are used to monitor and remove the device. Missing IUCD strings are observed in about 5% of the users. Such patients require localisation of the device using Transvaginal Scan (TVS) and X-Ray, and combined hysterolaparoscopic approach for its retrieval. Hereby we report a case of young primipara, who consulted a local practitioner requesting IUCD removal, as she was planning to conceive her second child. On examination, Cu-T threads were not found. A plain X-Ray of the pelvis was reported as: Cu-T limbs seen in the left side of the pelvis, “in the region of uterus”. Blind attempts led to damage to ovary and uterus along with the ureter. By reporting this case, we hope to raise awareness on the management of misplaced IUCD, among primary care givers; and the need for set protocols on the management of such cases.

Scleral fixation technique using a hydrophobic foldable intraocular lens with ring-shaped connecting bridges

We introduce a new method of scleral fixation using a hydrophobic foldable intraocular lens (IOL) with ring-shaped connecting bridges. A double-armed 10-0 polypropylene suturing needle is inserted using the routine ab externo technique. The midportion of the thread is pulled out through a main wound and cut. Using another 10-0 polypropylene needle, the IOL is sutured at both inner ring-shaped connecting bridges (inner shorter rim). The ring-shaped connecting-bridges IOL was carefully injected using the IOL cartridge with gentle pulling out of the thread. The externalized sutures were tied at the corresponding sites. All ties between 2 cut threads were performed using a European death knot. A scleral fixation outcome with the ring-shaped connecting-bridges IOL was similar to a poly(methyl methacrylate) IOL outcome; however, the surgeon should consider the possibility of a postoperative myopic shift. No author has a financial or proprietary interest in any material or method mentioned.

Comprehensive Study of Cut and Roll Threads

Comprehensive Study of Cut and Roll Threads

Optimum Thread Rolling Process that Improves SCC Resistance

Abstract Accelerated testing in environments aggressive for the specific material have shown that fastener threads that are rolled after strengthening heat treatments have improved resistance to stress corrosion cracking (SCC) initiation. For example, intergranular SCC was produced in one day when machined (cut) threads of high-strength steel (ASTM A193 B-7 and A354 Grade 8) were exposed to an aggressive aqueous environment containing 8 wt % boiling ammonium nitrate and stressed to about 40 % of the steel's yield strength. In similar testing conditions, bolts that were thread rolled before heat treatment (quench and temper) had similar high susceptibility to SCC. However, threads rolled after the strengthening heat treatment exhibited no SCC after a week of exposure, even when stressed to 100 % of the B-7 alloy yield strength. Similarly, intergranular SCC was produced in less than one day when machined (cut) threads of nickel-base alloys (X-750 and aged 625) were exposed to an aggressive 750°F doped steam environment (containing 100 ppm of chlorides, fluorides, sulfates, and nitrates) and stressed to about 80 % of the alloy yield strength. In similar testing conditions, threads rolled after strengthening exhibited no SCC after 50 days of exposure. This beneficial effect of the optimum thread rolling process (i.e., threads rolled after the strengthening heat treatment) is due to the retention of large residual compressive stresses in the thread roots (notches), which mitigate the applied notch tensile stresses resulting from joint design preloads. Use of these material-specific aggressive environments—“chemical cracking” tests—can provide an accelerated test to verify that threads were, in fact, produced by the optimum thread rolling process. The chemical cracking tests could also support fastener acceptance criteria or failure analysis of fasteners with unknown or uncertain manufacturing processes. The achievement of the optimum process effects may not always be detected by more conventional methods (e.g., metallography or hardness testing).

Effects of Synchronizing Errors on Cutting Performance in the Ultra-High-Speed Tapping

Synchronizing errors between the spindle motor and the z-axis motor directly influences the cutting characteristics in tapping, because the tapping process is accomplished by synchronizing the movement of the z-axis with the revolutionary spindle motion. The excessive synchronizing error can cause tap breakage due to the abrupt increase of cutting torque or damage the thread accuracy by overcutting the already cut threads. This paper describes the effects of the synchronizing errors on the cutting performance in the ultra high-speed tapping and presents a minimum level of synchronizing errors necessary to maintain the quality of the cut thread.

Effects of temperature, salinity and agitation on byssus thread formation of zebra musselDreissena polymorpha

Byssus thread production ofD. polymorpha under different conditions of temperature, salinity and agitation were studied in the laboratory. The acclimation to salinity and temperature greatly affects the byssus production ofD. polymorpha. Byssus production of mussels was significantly reduced when temperature increased beyond 20°C and decreased below 10°C. Mussels with cut threads (for counting), produced a substantially increased number of threads. However, mussels with uncut byssus threads were comparatively more mobile. Byssus production of mussels did not vary significantly at salinities up to 3‰. Beyond this salinity byssus production was reduced significantly. Mussels increased their byssus production with increasing frequency of agitation.

Salt Water and Hydrogen Sulfide Corrosion Fatigue of Work-Hardened, Threaded Elements

Abstract This work describes the results of a laboratory testing program undertaken to evaluate the merits of work-hardened, threaded machine elements when subjected to axial fatigue in the presence of a corrosive environment. The experimental apparatus is described, including details of the corrosive mediums. The most damaging corrosive medium consisted of a salt water solution through which hydrogen sulfide gas was bubbled. Lower corrosion fatigue damage was noted for aerated salt water and the least occurred for a deaerated salt water solution. The corrosion fatigue results are compared with results obtained in air for simple cut threads and fully cold-worked or rolled threads formed on AISI 8635 steel. The results show that at a life of 105 cycles the fully cold-worked threaded element had an endurance stress of 74 ksi (510 MPa) compared with 44 ksi (303 MPa) for the simple cut threaded element. Under the combined action of corrosion fatigue in the presence of a hydrogen sulfide saline solution these values were reduced to 46 ksi (317 MPa) and less than 20 ksi (138 MPa), respectively, which indicated that the fully cold-worked, threaded element was superior to all thread forms evaluated under a variety of environmental conditions.

The Critical Slit Length of Pressurized Coated Fabric Cylinders

Four different theories predicting the burst strength of longitudinally slit pressurized fabric cylinders are compared with tests of warp cylinders having various diameters and lengths, containing slits of various lengths and widths. The fabric used was a neoprene-coated Dacron polyester with a warp strength of about 150 lb/inch. An equation requiring three empirical constants, derived from Griffith's theory of rupture, fits the data very well. Other less empirical equations fit less well. An elastic theory of Hedgepeth's for a small number of cut threads is extended to long shts, but is too conservative.

The Effect of the Thread Rolling Conditions on the Fatigue Strength of the Rolled Screw Threads : 1st Report, Investigations on the Thread Rolling Conditions

The published literatures on the fatigue strength of the rolled threads have been surveyed by the author. One of the causes of the difference among the results of these investigations seems to be the thread rolling conditions. If the effect of the thread rolling conditions on the fatigue strength of the rolled threads is clarified, the rolling condition for the rolled threads of fatigue strength extremely higher than that of the cut threads may be obtained. The rolling conditions were analysed for the thread rolling processes used today. From this analysis it has been found that the rolling condition is expressed by the number of revolutions of the blank from the start to the end of rolling and the type of the rolling pressure curve. The rolling pressure curves are classified into 3 types ; namely the decreasing pressure type, the constant pressure type and the increasing pressure type. This analysis was confirmed by the experiments on the oil pressure type thread rolling machine with a special attachment.

The Effect of the Thread Rolling Conditions on the Fatigue Strength of the Rolled Screw Threads : 1st Report, Investigations on the Thread Rolling Conditions

The former investigations on the fatigue strength of the rolled threads were surveyed by the author. One of the causes of the difference among the results of these investigations seems to be the thread rolling conditions. If the effect of the thread rolling conditions on the fatigue strength of the rolled threads is clarified, the rolling condition for the rolled threads of fatigue strength extremely higher than that of the cut threads may be obtained. The rolling conditions were analysed for the thread rolling processes used today. From this analysis it has been found that the rolling condition is expressed by the number of revolutions of the blank from the start to the end of rolling and the type of the rolling pressure curve. The rolling pressure curves are classified into 3 types ; namely the decreasing pressure type, the constant pressure type and the increasing pressure type. This analysis was confirmed by the experiments on the oil pressure type thread rolling machine with special attachment.

Graphical Tensile-Testing Machine for Rubber Threads

Abstract AMONG the many types of physical testing equipment which have been designed for or applied to the needs of the rubber industry, there has never appeared an entirely satisfactory graphical machine for performing tensile tests on small rubber samples, such as the threads and tapes used in making golf balls and elastic fabrics and cords. None of the common machines can be applied directly to the testing of single threads, and even tests on pieces of dumbbell shape are quite unsatisfactory, largely because the standard machines are comparatively insensitive at low elongations and tensions and also because they depend on the personal accuracy of an operator to observe several points along the stress-strain curve. The Schopper ring test is not entirely successful for tests on threads. Accordingly it appeared that such tests on light rubber threads could best be made on a curve-drawing machine, designed and constructed especially for the purpose. In many cases, the use of any other machine would have been impossible because frequent tests had to be run on single, cut threads from factory production and on samples taken from storage or from woven fabric.