Tempering of Tool Steels – A Multiscale Simulation

For tool steels, the prediction of properties obtained by a particular heat treatment is of major importance. The objective of this study is to precisely predict the relaxation of the internal stresses during tempering, taking explicitly into account changes in the microstructure. The accurate definition of material properties, phase transformation and precipitation kinetics are the most decisive input parameters for the success of such simulations. The necessary material parameters are measured for specified tempering conditions experimentally. The development of the yield stress during tempering has to be known to predict the stress relaxation precisely. Therefore, microstructural simulations are implemented. The yield stress evolution during tempering is simulated and verified with measurements. Results are used as input data for FEM simulation

Metallurgical influence on quench distortion of SAE 52100 long cylinders

Quenching of steel components results in complex and hard-to-predict dimensional and shape changes (distortion). Even the components manufactured from different parts of the same semifinished product may show significantly different distortion behaviours during quenching. The reason is thought to be non-uniform distribution of distortion potential carriers in the final component (i.e. alloying elements, segregations, residual stresses and phases) which are accumulated throughout the whole manufacturing chain. This study focuses on the effects of alloying element distribution and segregation on quench distortion. For this aim, long cylinders of various diameters were machined from 45 mm diameter SAE 52100 steel bars, and marked to define their exact positions in the initial bar. Then the cylinders were austenitised in a vertical furnace under nitrogen atmosphere and quenched in a gas nozzle field. The coordinate measurement results show that dimensional changes deviate significantly with machining position; however, the bending magnitudes and directions do not exhibit a distinct correlation with machining position and the cylinder diameter

Simulation of Deformation and Residual Stress Evolution during Quenching and Tempering of Tool Steel

The objective of this finite element simulation study is to predict deformations and residual stresses in the carbide rich cold work tool steel X220CrVMo13-4 after tempering. A thermo-metallurgical-mechanical model with experimentally determined phase transformation kinetics and phase dependent material properties is implemented to simulate the quenching and tempering cycles. Considering the transformation of retained austenite during tempering, high alloyed tool steels behave differently compared to most other ferritic or martensitic steels. For the steel under consideration, retained austenite remains stable up to higher temperatures (≈ 600 °C) and decomposes during cooling from tempering temperature. The transformation kinetics of this steel during tempering is investigated by dilatometer and differential scanning calorimetry (DSC) measurements. In order to achieve the mechanical properties of each phase that appears during tempering, compression tests have been conducted for several temperatures and phase compositions respectively. Eventually, the experimentally determined phase transformation kinetics of tempering as well as phase and temperature dependent material properties were implemented into the finite element analysis software Sysweld®. In order to verify the model, a specimen, hardened and tempered in a dilatometer has been modeled. The comparison of experimental and numerical results shows quite good agreement. Finally stress and deformation evolution during quenching and tempering have been simulated for a component with practical relevance

Prevalence of prostate cancer among men aged 40+ living in Osman Gazi Health Care district

Background: Prostate cancer is a risk for men aged 40+ even if it is rarely seen among men under the age of 50. It is asymptomatic disease in its early period and if the person does not have an enlarged prostate it will be overlooked without screening. Consequently, the only way to diagnose prostate cancer in its early period is to determine the serum PSA (prostate-specific antigen) level of men aged 40+ and to do a digital rectal examination (DRE). Objective: The aim of this study is to determine the prevalence of prostate cancer among men aged 40+, to mention the significance of DRE and PSA by means of a training to be done with the aid of a booklet about early diagnosis, and to encourage men to consult a doctor and get the right treatment at the right time. Methods: The research was a descriptive field study. carried out among 660 men aged 40+ out of 3,285 men who live in Osman Gazi Health Care District, connected with the Presidency of Training and Research Health Group of Bornova. This group was selected as the smallest sample size by the systematic sampling method within the frame of setting the prevalence of prostate cancer at 10%, the confidence interval as 95%, the standard error as 2%. A total of 264 men of the sample group (participation rate 40%) agreed to a survey of International Prostate Symptom Score (I-PSS) projected by the study, and underwent DRE and PSA with a blood sample. Results: Increase in the serum PSA level (4ng/mL<) was determined in 10 men. Nodules were detected in 3 men together with the increase in PSA. One further nodule was detected only in DRE one examination of 12 participants. In the light of these data, it was decided to conduct a biopsy on 25 people, who had an increase in PSE and/or whose abnormalities were detected during DRE, in company with TRUS, and prostate cancer was detected in the biopsies of 5 people (1.89%). Conclusions: It can be thought that before a decision is made on routinizing prostate cancer screening, it may be more suitable to make randomized controlled screening trials for prostate cancer

İlk yıl asistanı aydınlatılmıs onam alabilir mi?

Informed consent has been of utmost importance since the change in the Turkish Criminal Law. The purpose of this study was to determine whether first year surgical residents have sufficient knowledge in obtaining informed consent. Materials Methods : A total of 25 first-year residents attending the surgical clinics of Ege University Hospital were included in the study. Each resident was asked to list the risks, benefits and alternative approaches of procedures that were carried out most frequently. Besides, residents were evaluated according their answers to questions that patients may pose about the procedure.Results: No resident was able to list correctly the risks, benefits and alternatives of each procedure. Only 24% of residents had sufficient knowledge to explain the risks, benefits and alternatives of surgical procedures. Nevertheless, 58% of residents were able to correctly answer questions that patients may ask about the procedures. Conclusion: With respect to the developments in patient rights and establishments in the criminal law, it is essential that clinics should provide more time to educate residents for a better knowledge for informing the patient and to make informed consent competent.Değisen Türk Ceza Kanunu ile birlikte aydınlatılmıs onamın öneminin artması nedeni ile cerrahi kliniklerindeki ilk yıl asistanlarının bilgilendirilmis onam konusundaki yeterliliğini ortaya koymayı amaçladık. Gereç ve Yöntem: Çalısmaya Ege Üniversitesi Tıp Fakültesi Hastanesi’nin 7 cerrahi kliniğinde eğitim gören toplam 25 ilk yıl asistanı katıldı. Asistanlardan her bir klinikte en sık uygulanan cerrahi uygulamaların risklerini, yararlarını ve alternatif tedavi yöntemlerini kaydetmeleri istendi. Bunun yanı sıra, cerrahi isleme yönelik olarak hasta tarafından sık sorulabilecek soruları yanıtlayabilecek bilgi düzeyleri sorgulandı. Bulgular: Hiçbir asistanın uygulamanın risklerini, yararlarını ve alternatif tedavi yöntemlerini eksiksiz olarak aktaramadığı görüldü. Asistanların yalnızca % 24’ü uygulanan cerrahi islemlerin risklerini, yararlarını ve alternatif tedavi yöntemlerini hastaya aktaracak kadar yeterli bilgiye sahip idi. Yine, asistanların ancak %58’inin hasta tarafından sorulacak herhangi bir soruyu cevaplayabilecek düzeyde olduğu tespit edildi. Sonuç: Ülkemizde hasta hakları konusundaki gelismeler ve Türk Ceza Kanunu’ndaki düzenlemelerle, kliniklerin asistan eğitiminde ‘hasta bilgilendirme ve bilgilendirilmis onam’ konusuna daha genis yer vermeleri gerekmektedir