Effect of Mechanical and Geometric Mismatching on Fatigue and Damage of Welded Joints

The future of high technology welded constructions will be characterised by higher strength materials and improved weld quality with respect to fatigue resistance. The expected implementation of high quality high strength steel welds will require that more attention be given to the issues of crack initiation and mechanical mismatching. Experiments and finite element analyses were performed within the framework of continuum damage mechanics to investigate the effect of mismatching of welded joints on void nucleation and coalescence during monotonic loading. It was found that the damage of undermatched joints mainly occurred in the sandwich layer and the damageresistance of the joints decreases with the decrease of the sandwich layer width. The damage of over-matched joints mainly occurred in the base metal adjacent to the sandwich layer and the damage resistance of the joints increases with thedecrease of the sandwich layer width. The mechanisms of the initiation of the micro voids/cracks were found to be cracking of the inclusions or the embrittled second phase, and the debonding of the inclusions from the matrix. Experimental fatigue crack growth rate testing showed that the fatigue life of under-matched central crack panel specimens is longer than that of over-matched and even-matched specimens. Further investigation by the elastic-plastic finite element analysis indicated that fatigue crack closure, which originated from the inhomogeneousyielding adjacent to the crack tip, played an important role in the fatigue crack propagation. The applicability of the J integral concept to the mismatched specimens with crack extension under cyclic loading was assessed. The concept of fatigue class used by the International Institute of Welding was introduced in the parametric numerical analysis of several welded joints. The effect of weld geometry and load condition on fatigue strength of ferrite-pearlite steel joints was systematically evaluated based on linear elastic fracture mechanics. Joint types included lap joints, angle joints and butt joints. Various combinations of the tensile and bending loads were considered during the evaluation with the emphasis focused on the existence of both root and toe cracks. For a lap joint with asmall lack-of-penetration, a reasonably large weld leg and smaller flank angle were recommended for engineering practice in order to achieve higher fatigue strength. It was found that the fatigue strength of the angle joint depended strongly on the location and orientation of the preexisting crack-like welding defects, even if the joint was welded with full penetration. It is commonly believed that the double sided butt welds can have significantly higher fatigue strength than that of a single sided welds, but fatigue crack initiation and propagation can originate from the weld root if the welding procedure results in a partial penetration. It is clearly shown that the fatigue strength of the butt joint could be improved remarkably by ensuring full penetration. Nevertheless, increasing the fatigue strength of a butt joint by increasing the size of the weld is an uneconomical alternative.

Neuro-mechanical and metabolic adjustments to the repeated anaerobic sprint test in professional football players.

PURPOSE: This study aimed to determine the neuro-mechanical and metabolic adjustments in the lower limbs induced by the running anaerobic sprint test (the so-called RAST). METHODS: Eight professional football players performed 6 × 35 m sprints interspersed with 10 s of active recovery on artificial turf with their football shoes. Sprinting mechanics (plantar pressure insoles), root mean square activity of the vastus lateralis (VL), rectus femoris (RF), and biceps femoris (BF) muscles (surface electromyography, EMG) and VL muscle oxygenation (near-infrared spectroscopy) were monitored continuously. RESULTS: Sprint time, contact time and total stride duration increased from the first to the last repetition (+17.4, +20.0 and +16.6 %; all P < 0.05), while flight time and stride length remained constant. Stride frequency (-13.9 %; P < 0.001) and vertical stiffness decreased (-27.2 %; P < 0.001) across trials. Root mean square EMG activities of RF and BF (-18.7 and -18.1 %; P < 0.01 and 0.001, respectively), but not VL (-1.2 %; P > 0.05), decreased over sprint repetitions and were correlated with the increase in running time (r = -0.82 and -0.90; both P < 0.05). Together with a better maintenance of RF and BF muscles activation levels over sprint repetitions, players with a better repeated-sprint performance (lower cumulated times) also displayed faster muscle de- (during sprints) and re-oxygenation (during recovery) rates (r = -0.74 and -0.84; P < 0.05 and 0.01, respectively). CONCLUSION: The repeated anaerobic sprint test leads to substantial alterations in stride mechanics and leg-spring behaviour. Our results also strengthen the link between repeated-sprint ability and the change in neuromuscular activation as well as in muscle de- and re-oxygenation rates.

Fibre-reinforced composites as root canal posts

Fibre-reinforced composite (FRC) root canal posts are suggested to have biomechanical benefits over traditional metallic posts, but they lack good adhesion to resin composites. The aim of this series of studies was to evaluate the adhesion of individually formed fibre-reinforced composite material to composite resin and dentin, as well as some mechanical properties. Flexural properties were evaluated and compared between individually formed FRC post material and different prefabricated posts. The depth of polymerization of the individually formed FRC post material was evaluated with IR spectrophotometry and microhardness measurements, and compared to that of resin without fibres. Bonding properties of the individually formed FRC post to resin cements and dentin were tested using Pull-out- and Push-out-force tests, evaluated with scanning electron microscopy, and compared to those of prefabricated FRC and metal posts. Load-bearing capacity and microstrain were evaluated and failure mode assessment was made on incisors restored with individually formed FRC posts of different structures and prefabricated posts. The results of these studies show that the individually polymerized and formed FRC post material had higher flexural properties compared to the commercial prefabricated FRC posts. The individually polymerized FRC material showed almost the same degree of conversion after light polymerization as monomer resin without fibres. Moreover, it was found that the individually formed FRC post material with a semiinterpenetrating polymer network (IPN) polymer matrix bonded better to composite resin luting cement, than did the prefabricated posts with a cross-linked polymer matrix. Furthermore, it was found that, contrary to the other posts, there were no adhesive failures between the individually formed FRC posts and composite resin luting cement. This suggests better interfacial adhesion of cements to these posts. Although no differences in load-bearing capacity or microstrain could be seen, the incisors restored with individually formed FRC posts with a hollow structure showed more favourable failures compared to other prefabricated posts. These studies suggest that it is possible to use individually formed FRC material with semi-IPN polymer matrix as root canal post material. They also indicate that there are benefits especially regarding the bonding properties to composite resin and dentin with this material compared to prefabricated FRC post material with a cross-linked matrix. Furthermore, clinically more repairable failures were found with this material compared to those of prefabricated posts.

Development of rotating drum under mechanical and thermal load

A variable temperature field sets exacting demands to the structure under mechanical load. Most of all the lifetime of the rotating drum structure depends on temperature differences between parts inside the drum. The temperature difference was known because of the measurements made before. The list of demands was created based on customers’ needs. The limits of this paper were set to the inner structure of the drum. Creation of ideas for the inner structure was started open minded. The main principle in the creation process was to create new ideas for the function of the product with the help of sub-functions. The sub-functions were created as independent as possible. The best sub-functions were combined together and the new working principles were created based on them. Every working principle was calculated separately and criticized at the end of the calculation process. The main objective was to create the new kind of structure, which is not based too much to the old, inoperative structure. The affect of own weight of the inner structure to the stress values was quite small but it was also taken into consideration when calculating the maximum stress value of the structure. Because of very complex structures all of the calculations were made with the help of the ProE – Mechanica software. The fatigue analyze was made also for the best structure solution.

Purchasing Process Performance Definition and Improvement in the Mechanical Wood Industry

Tämän tutkimuksen ensisijaisena tavoitteena oli määrittää Schauman Wood Oy:n ostoprosessin suorituskyvyn nykytila yrityksen Suomen yksiköissä. Nykytila-arviointi suoritettiin uusien ja käytössä olevien mittaustulosten avulla. Tutkimuksessa verrattiin kymmenen tuotantolaitoksen ostoprosesseja keskenään. Keskeinen tutkimusongelma oli ostoprosessin suorituseroja aikaansaavien tekijöiden selvittäminen eri yksiköissä. Tutkimuksen tavoitteena oli saavuttaa yhtenäisemmät toimintatavat yrityksessä sekä laajentaa konsernin osto-organisaation hyödyntämistä hankintatoimessa. Tavoitteena oli ostoprosessin virtaviivaistaminen ja tehokkaamman seurantajärjestelmän kehittäminen. Ostotoimintojen suorituskyvyn jatkuva parantaminen perustuu osittain uusien mittareiden avulla saatavaan informaatioon ja täsmällisempään seurantaan. Sisäistä benchmarkingia käytettiin työkaluna suorituskyky-eroavaisuuksien määrittelyssä. Tietoa erilaisista toimintatavoista kerättiin haastattelemalla yrityksen ostajia ja tehdaspalvelupäälliköitä eri tehdaspaikkakunnilla. Sisäisen benchmarkingin avulla määriteltiin toimintatapa eroavaisuudet sekä kehitettiin seurantakortti, jossa jokaista yksikköä verrataan parhaaseen ja eniten kehittyneeseen yksikköön. Työn tuloksina muodostui ehdotuksia ostotoiminnon uusiksi mittareiksi. Uudet mittarit ovat tehokkuusmittareita, jotka kuvaavat resurssien käytön tehokkuutta sekä auttavat seuraamaan ostoprosessin tilaa entistä paremmin. Uusien mittareiden tavoitteena on myös vähentää mittareiden manipulaatiomahdollisuutta. Työn ulkopuolelle rajattiin informaatioteknologiajärjestelmien tietotekninen osuus. Eräs yrityksen tuotantolaitoksista rajattiin myös työn ulkopuolelle, koska sen ostoprosessit ovat huomattavasti kehittymättömämpiä kuin Schauman Woodin muiden tehtaiden ostoprosessit. Kyseisen yksikön kehittämisen tulee lähteä aivan ruohonjuuritasolta. Tutkimuksen teoriaosuus on kerätty alan ammattikirjallisuudesta ja tutkimuksen aihetta käsittelevistä uudehkoista tieteellisistä alan artikkeleista. Teorian tarkoituksena on tukea empiiristä osuutta sekä antaa lukijalle uusia näkemyksiä ostotoiminnan monista mahdollisuuksista. Tutkimuksen tuloksia ovat nykytila-analyysi, ehdotukset uusista ostotoiminnan mittareista sekä ehdotus MRO-tuotteiden ulkoistamiskokeilusta. Yrityksen ostotoiminnan tulisi kehittyä operatiivisesta tasosta kohti strategisempaa oston tasoa. Johdon sitoutuminen hankintatoimen kehityshankkeisiin on erityisen tärkeää, lisäksi hankintatoimi tulisi nähdä strategisempana osa-alueena yrityksessä. Hankintatoimen kehittämisen avulla yrityksen kustannustehokkuutta voidaan lisätä merkittävästi.

Traumatic injuries after mechanical cardiopulmonary resuscitation (LUCAS?2): a forensic autopsy study.

AIM: The aim of our study was to compare traumatic injuries observed after cardiopulmonary resuscitation (CPR) by means of standard (manual) or assisted (mechanical) chest compression by Lund University Cardiopulmonary Assist System, 2nd generation (LUCAS?2) device. METHODS: A retrospective study was conducted including cases from 2011 to 2013, analysing consecutive autopsy reports in two groups of patients who underwent medicolegal autopsy after unsuccessful CPR. We focused on traumatic injuries from dermal to internal trauma, collecting data according to a standardised protocol. RESULTS: The study group was comprised of 26 cases, while 32 cases were included in the control group. Cardiopulmonary resuscitation performed by LUCAS?2 was longer than manual CPR performed in control cases (study group: mean duration 51.5 min; controls 29.4 min; p = 0.004). Anterior chest lesions (from bruises to abrasions) were described in 18/26 patients in the LUCAS?2 group and in 6/32 of the control group. A mean of 6.6 rib fractures per case was observed in the LUCAS?2 group, but this was only 3.1 in the control group (p = 0.007). Rib fractures were less frequently observed in younger patients. The frequency of sternal factures was similar in both groups. A few trauma injuries to internal organs (mainly cardiac, pulmonary and hepatic bruises), and some petechiae (study 46 %; control 41 %; p = 0.79) were recorded in both groups. CONCLUSION: LUCAS?2-CPR is associated with more rib fractures than standard CPR. Typical round concentric skin lesions were observed in cases of mechanical reanimation. No life-threatening injuries were reported. Petechiae were common findings.

Neuro-mechanical determinants of repeated treadmill sprints - Usefulness of an "hypoxic to normoxic recovery" approach.

To improve our understanding of the limiting factors during repeated sprinting, we manipulated hypoxia severity during an initial set and examined the effects on performance and associated neuro-mechanical alterations during a subsequent set performed in normoxia. On separate days, 13 active males performed eight 5-s sprints (recovery = 25 s) on an instrumented treadmill in either normoxia near sea-level (SL; FiO2 = 20.9%), moderate (MH; FiO2 = 16.8%) or severe normobaric hypoxia (SH; FiO2 = 13.3%) followed, 6 min later, by four 5-s sprints (recovery = 25 s) in normoxia. Throughout the first set, along with distance covered [larger sprint decrement score in SH (-8.2%) compared to SL (-5.3%) and MH (-7.2%); P < 0.05], changes in contact time, step frequency and root mean square activity (surface electromyography) of the quadriceps (Rectus femoris muscle) in SH exceeded those in SL and MH (P < 0.05). During first sprint of the subsequent normoxic set, the distance covered (99.6, 96.4, and 98.3% of sprint 1 in SL, MH, and SH, respectively), the main kinetic (mean vertical, horizontal, and resultant forces) and kinematic (contact time and step frequency) variables as well as surface electromyogram of quadriceps and plantar flexor muscles were fully recovered, with no significant difference between conditions. Despite differing hypoxic severity levels during sprints 1-8, performance and neuro-mechanical patterns did not differ during the four sprints of the second set performed in normoxia. In summary, under the circumstances of this study (participant background, exercise-to-rest ratio, hypoxia exposure), sprint mechanical performance and neural alterations were largely influenced by the hypoxia severity in an initial set of repeated sprints. However, hypoxia had no residual effect during a subsequent set performed in normoxia. Hence, the recovery of performance and associated neuro-mechanical alterations was complete after resting for 6 min near sea level, with a similar fatigue pattern across conditions during subsequent repeated sprints in normoxia.

Toward on-the-fly quantum mechanical/molecular mechanical (QM/MM) docking: development and benchmark of a scoring function.

We address the challenges of treating polarization and covalent interactions in docking by developing a hybrid quantum mechanical/molecular mechanical (QM/MM) scoring function based on the semiempirical self-consistent charge density functional tight-binding (SCC-DFTB) method and the CHARMM force field. To benchmark this scoring function within the EADock DSS docking algorithm, we created a publicly available dataset of high-quality X-ray structures of zinc metalloproteins ( http://www.molecular-modelling.ch/resources.php ). For zinc-bound ligands (226 complexes), the QM/MM scoring yielded a substantially improved success rate compared to the classical scoring function (77.0% vs 61.5%), while, for allosteric ligands (55 complexes), the success rate remained constant (49.1%). The QM/MM scoring significantly improved the detection of correct zinc-binding geometries and improved the docking success rate by more than 20% for several important drug targets. The performance of both the classical and the QM/MM scoring functions compare favorably to the performance of AutoDock4, AutoDock4Zn, and AutoDock Vina.

Rectal enema is an alternative to full mechanical bowel preparation for primary rectal cancer surgery.

AIM: According to the French GRECCAR III randomized trial, full mechanical bowel preparation (MBP) for rectal surgery decreases the rate of postoperative morbidity, in particular postoperative infectious complications, but MBP is not well tolerated by the patient. The aim of the present study was to determine whether a preoperative rectal enema (RE) might be an alternative to MBP. METHODS: An analysis was performed of 96 matched cohort patients undergoing rectal resection with primary anastomosis and protective ileostomy at two different university teaching hospitals, whose rectal cancer management was comparable except for the choice of preoperative bowel preparation (MBP or RE). Prospective databases were retrospectively analysed. RESULTS: Patients were well matched for age, gender, body mass index and Charlson index. The surgical approach and cancer characteristics (level above anal verge, stage and use of neoadjuvant therapy) were comparable between the two groups. Anastomotic leakage occurred in 10% of patients having MBP and in 8% having RE (P = 1.00). Pelvic abscess formation (6% vs 2%, P = 0.63) and wound infection (8% vs 15%, P = 0.55) were also comparable. Extra-abdominal infection (13% vs 13%, P = 1.00) and non-infectious abdominal complications such as ileus and bleeding (27% and 31%, P = 0.83) were not significantly different. Overall morbidity was comparable in the two groups (50% vs 54%, P = 0.83). CONCLUSION: A simple RE before rectal surgery seems not to be associated with more postoperative infectious complications nor a higher overall morbidity than MBP.