Numerical Investigation of the Oxide Scale Deformation Behaviour with Consideration of Carbon Content during Hot Forging

Due to increasing product requirements the numerical simulation has become a powerful tool for the effective and efficient design of individual process steps as well as entire process chains. In order to model hot forging processes with finite element based numerical methods realistic models are required which consider the detailed mathematical description of the material behaviour during the forging process, the surface phenomena at die and workpiece as well as machine kinematics. Although this data exist for several steel grades, yet general mathematical models for steel groups based on alloying elements like carbon content are not available. In hot forging the surface properties are strongly affected by the growth of oxide scale, which influences material flow, friction as well as product quality of the finished components. The influence of different carbon contents on oxide scale growth and material behaviour is investigated by considering three different steel grades (C15, C45 and C60). For a general description of the material behaviour, an empirical approach is used to implement mathematical functions so as to express the relationship between flow stress and dominant influence variables like alloying elements, initial microstructure and reheating mode. The oxide scale consists of three different components namely wuestite, magnetite and haematite. In order to take the oxide scale into account, additional models are required to describe the growth kinematic and flow behaviour of the oxide scale components. The mathematical relationship between oxidation time, temperature, carbon content and oxide scale height is based on Arrhenius approach. The deformation behaviour of oxide scale is separately modelled for each component with parameterized flow curves. This paper gives first approaches on the numerical modelling of plastic deformation of oxide scale in a hot forging process. The main focus lies on the involvement of the different materials as well as the calculation and assignment of material properties in dependence of current process parameters by using subroutines. The numerical model and subroutines will be implemented in the FE-Software simufact.forming. A validation of the numerical model will be carried out by comparison of numerical results with experimental data

Massive rotator cuff tears: functional outcome after debridement or arthroscopic partial repair

Background The surgical treatment of massive rotator cuff tears (RCT) is still controversial and can be based on a variety of different surgical repair methods. This study investigated the effectiveness of arthroscopic debridement or arthroscopic partial repair in patients with massive RCT. Materials and methods This prospective, randomized study involved forty-two patients with massive RCT (fatty infiltration stage 3 or 4) treated with either arthroscopic partial repair or arthroscopic debridement were selected to detect possible differences in functional outcome. Both groups were matched according to age and gender. Patients were examined before, and 16 ± 3 and 24 ± 2 months after surgery. The status of the rotator cuff repair was determined using ultrasonographic evaluation. Results Regardless of the treatment group, postoperative results demonstrated highly significant improvements compared with preoperative values in most parameters. The overall Constant score in the partial repair group was superior to the outcome in the debridement group (P \ 0.01, F = 8.561), according to better results in abductio

Impairment of Auditory-Motor Timing and Compensatory Reorganization after Ventral Premotor Cortex Stimulation

Integrating auditory and motor information often requires precise timing as in speech and music. In humans, the position of the ventral premotor cortex (PMv) in the dorsal auditory stream renders this area a node for auditory-motor integration. Yet, it remains unknown whether the PMv is critical for auditory-motor timing and which activity increases help to preserve task performance following its disruption. 16 healthy volunteers participated in two sessions with fMRI measured at baseline and following rTMS (rTMS) of either the left PMv or a control region. Subjects synchronized left or right finger tapping to sub-second beat rates of auditory rhythms in the experimental task, and produced self-paced tapping during spectrally matched auditory stimuli in the control task. Left PMv rTMS impaired auditory-motor synchronization accuracy in the first sub-block following stimulation (p<0.01, Bonferroni corrected), but spared motor timing and attention to task. Task-related activity increased in the homologue right PMv, but did not predict the behavioral effect of rTMS. In contrast, anterior midline cerebellum revealed most pronounced activity increase in less impaired subjects. The present findings suggest a critical role of the left PMv in feed-forward computations enabling accurate auditory-motor timing, which can be compensated by activity modulations in the cerebellum, but not in the homologue region contralateral to stimulation

Effect of the Size of Clods Contained Covering Soil on the Seedling Emergence of Rice Plant Sown under Upland Field Condition

水稲農林23号を用いて, 覆土の土塊の大きさが, 乾田に深播き(覆土7cm)された個体の出芽ならびに幼苗諸器官の長さに及ぼす影響について, 覆土が3cmの場合と比較しながら検討した。乾田に播種された種子が大きい土塊で覆土されると, 覆土が3cmの場合には鞘葉の伸長が抑制される。しかし, 不完全葉はほとんどの個体で3cm以上に伸長する。また大土塊の間隙が小土塊で充足された場合は, 鞘葉および不完全葉ともに, 大土塊だけの場合よりも長くなる。その結果, すべての区の出芽率は, 播種後12日目には90%以上に達する。覆土が7cmの場合には, 覆土の土塊が大きくても, 鞘葉および不完全葉は覆土が3cmの場合よりも著しく長くなる。その結果, 第1本葉が不完全葉から抽出する位置が高められる。しかし, 鞘葉および不完全葉の伸長のみによっては出芽することはできず, 出芽するためには, 第2節間および第1本葉が伸長しなければならない。覆土の土塊が大きい場合には, 第2節間の伸長が抑制される。と同時に, 出芽までの間に幼芽の伸長を妨げる土塊の数も多くなるので, 出芽率は著しく低下する。しかし, 大土塊の間隙が小さい土塊によって充足されると, 第2節間が著しく長くなり, 第1本葉をおしあげる。その結果, 出芽率は単一土塊の場合に比べて著しく高まる。以上の結果と土壌中への光の侵入量との関係について, 若干考察した。 / This experiment was carried out to clarify the effects of size of clods in covering soil on the emergence and the elongation of rice seedling sown under upland field condition in pot (10cm×10cm×12cm) culture. Variety used was Norin No. 23. Seeds were covered with 3cm and 7cm depth of soil. In the case of 3cm in depth of seeding, if seeds were covered with larger clods, the elongation of coleoptile was inhibited, but the profile elongated longer than 3cm. When gaps between larger clods were filled with smaller clods, the length of coleoptile and profile became longer. Consequently, the emergence percentage of all plots reached more than 90% the 12th day after seeding. In the case of 7cm in depth of seeding, if seeds were covered with larger clods, coleoptile or profile elongated to 3 to 4cm in length, but the elongation of second internode was inhibited. As a result, the emergence percentage decreased significantly. When gaps between larger clods were filled with smaller clods, however, the length of second internode increased and first leaf was pushed up through the soil by second internode. Consequently, the emergence percentage increased significantly

Probing regional cortical excitability via input–output properties using transcranial magnetic stimulation and electroencephalography coupling

International audienc