Application of fracture mechanics models to notched concrete disc specimens

Betonun gevrekliğini ve kırılma parametrelerini belirleyebilmek için günümüze dek kırılma mekaniğine dayanan çeşitli modeller önerildi. Bunlardan bazıları kırılma parametrelerinin belirlenmesi için sadece tepe yükünün ölçümüne dayanmaktadır. Sunulan bu  çalışmanın amacı, mod I (açılma modu) yüklemesi altında, farklı boyutlardaki beton disk numuneler üzerinde, boyut etkisini incelemektir. Bunun için aynı karışıma sahip beton numuneler kullanıldı. Numune boyutu arttıkça, hem çentikli hem de çentiksiz numunelerde nominal dayanım azalmaktadır, bu azalma çentiksiz numunelerde daha belirgindir. Deney sonuçları “Boyut Etkisi Kuralı”nı desteklemektedir. Elde edilen deneysel sonuçlar fraktal esasa dayanan iki modelle de karşılaştırıldı. Çoklu Fraktal Boyut Etkisi Yönteminin diğer yöntemlere göre daha yüksek korelasyon katsayısına sahip olduğu görüldü.  Anahtar Kelimeler: Beton disk numune, boyut etkisi, kırılma parametreleri, yarma-çekme dayanımı.Fracture of quasi-brittle materials such as concrete exhibits complex size effect. In recent years, several specimen geometries were used to study the strength dependence on size. So far, there is no acceptable test technique to determine the fracture parameters of concrete. On the other hand, there is little information about the fracture studies on the notched concrete disc specimens. Some fracture mechanics based models have been proposed for the determination of the fracture parameters and brittleness of concrete. Various test methods based on  peak load measurements were proposed to determine these parameters. The main objective of this work, however, is to study the size effect in concrete disc specimens with different sizes in mode I loading condition. All the specimens were cast from the same batch of concrete. As the dimensions of the specimens increase, the nominal strength decreases for both notched and un-notched specimens; the decrease was more noticeable in un-notched specimens. The test results obtained on the notched and un-notched specimens confirm the existence of the ?Size Effect Law?. The results were also compared with the approaches of two types of fractal based models. The correlation coefficient in Multi Fractal Scaling Law was greater than those of the others. Keywords: Concrete disc specimen, size effect, fracture parameters, splitting tensile strength

Prevalence of Accessory Sacroiliac Joint and Its Clinical Significance

Objective: To determine the prevalence of the accessory sacroiliac joint (ASIJ) on both computed tomography (CT) images and dry bones and ultimately, to contribute to the literature. Materials and Methods: CT images archived in the Radiology department of Gaziantep University Medical Faculty obtained from 145 individuals (104 males and 41 females) as well as 92 sacral bones were examined. Results: The prevalence of ASIJ among 92 sacral bones was 15.2%. The ASIJ was more commonly (52%) located at the posterior portion of the SIJ at the level of the second dorsal sacral foramen. In 48% of the bones, ASIJ was identified just above the first dorsal sacral foramen. Unilateral ASIJ was observed in 10.8% and bilateral ASIJ in 4.4% of the sacral bones. On CT images, ASIJ was found in 7.8% of the males and 7.2% of the females. The total prevalence of sacroiliac joint variations was 28.9%, and 6.8% of them were ASIJs. Conclusion: It should be kept in mind that ASIJ may be a source of arthritis and chronic hip pain. The presence of ASIJ should be sought through imaging studies for early diagnosis of ASIJ

Analysis of the process leading to termination of pregnancy in the third trimester

Objective: To evaluate fetal anomalies and processes leading to termination of pregnancy in the third trimester. Methods: The study includes all cases who underwent termination of pregnancy after 28 weeks of gestation due to fetal anomalies between 2017 and 2022. Results: Forty four of third trimester terminations were carried out in our clinic due to fetal anomalies incompatible with life or associated with severe sequelae. Structural anomalies including 35 (79.5%) cases were the most common reason of terminations followed by chromosomal or genetic abnormalities in 8 (18.2%) cases and intrauterine cytomegalovirus infection in 1 (2.3%) case. The processes leading to the third trimester termination were evaluated by dividing 44 patients into 5 groups. (1) Delayed diagnosis due to inadequate prenatal care (25 patients, 56.8%); (2) patients diagnosed with late-onset findings (5 patients, 11.4%); (3) patients with abnormal findings in prenatal care or history but delayed diagnosis (5 patients, 11.4%); (4) patients with abnormal findings requiring further evaluation (4 patients, 9.0%); (5) patients with a definitive diagnosis but latency in the decision of family for termination of pregnancy (5 patients, 11.4%). Conclusion: Termination of pregnancy in the third trimester has an important role in countries where unfollowed pregnancies are common and access to health services is poor due to low socio-economic status

Kayar baskı plakalı artımlı sac şekillendirme yöntemiyle şekillendirilen Erdemir 7136 sacının geri esneme davranışının araştırılması

Artımlı şekillendirme yöntemi ile kalıp imalatına ihtiyaç duyulmadanhızlı ve düşük maliyetli prototip parça üretimi yapılabilmektedir. Ancakbu yöntemdeki en önemli sorunlardan bir tanesi üretilen parçalarıngeometrik doğruluğudur. Geometriksel hatanın en büyük kaynağı isegeri esneme olayıdır. Bu çalışmada, kayar baskı plakalı artımlı sacşekillendirme metodu kullanılarak 1 mm kalınlığındaki Erdemir 7136sacı şekillendirilmiştir. Klemp sıkma (sacı tutma) basıncı, artım miktarı,form takım çapı ve ilerleme hızı parametrelerinin geri esnemeye olanetkileri araştırılmıştır. Araştırma neticesinde geri esneme açısınıntakım çapı arttıkça büyüdüğü, ilerleme hızı ve artım miktarının artmasıile düştüğü tespit edilmiştir. Çalışma kapsamında optimum parametredeğerleri 5.8776 bar klemp sıkma basıncı, 1500 mm/dk. ilerleme hızı,0.75 mm artım miktarı ve 5 mm takım çapı olarak belirlenmiştir.Rapid and low-cost prototype parts can be produced without the need for mold production with incremental forming method. One of the most important problems in this method is the geometry accuracy of the products produced. The biggest source of the geometric error is the springback event. In this study, Erdemir 7136 sheet with a thickness of 1 mm was formed by using rolling blank holder incremental sheet forming method. The effects of holding pressure, increment, tool diameter and feedrate parameters on springback were investigated. As a result of the research, it was found that the springback angle increased with increasing of form tool diameter and decreased with increasing of feedrate and increment. The optimal conditions for springback are determined as 5.8776 bar holding pressure, 1500.0 mm/min feedrate, 0.75 mm increment and 5 mm tool diameter.WOS:00061661880001

An assessment of the relationship between peri-implant status and dental anxiety and oral health-related quality of life

Background: The purpose of this study is to evaluate the relationship between peri-implant diseases and dental anxiety and oral health-related quality of life. Methods: In a total of 101 subjects (44 females, 57 males, mean age 56.9 ± 12.1), 325 implants were examined using modified plaque index, modified sulcus bleeding index, probing depth, bleeding on probing, clinical attachment level, suppuration, and keratinized mucosa width. The Oral Health Impact Profile (OHIP- 14) was used to measure the impact of oral health-related quality of life. For the purpose of assessing the dental anxiety level, Corah’s Dental Anxiety Scale (DAS) was performed. In addition to dental implant measurements, the periodontal status of the participants' natural teeth was assessed by the Community Periodontal Index (CPI) of the World Health Organization. Results: All created groups as peri-implantitis, peri-implant mucositis, and peri-implant healthy were compatible with each other in terms of gender, age, income level, smoking status, and oral hygiene practices (p>0.05). A statistically significant correlation was found indicating that the peri-implant condition worsened as the education level decreased (p=0.033). There was no statistically significant difference between study groups in terms of DAS, OHIP-14, and CPI. There was a significant correlation between the scores of DAS and OHIP-14 (p<0.001). Conclusion: No relationship was found between peri-implant diseases and dental anxiety and quality of life. It was determined that as the anxiety levels of the participants increased, their quality of life decreased

Investigation of formability of HC380LA material via the TPIF-RL incremental forming method

SECGIN, OMER/0000-0001-6158-3164WOS: 000507266100001Prototype parts can be produced rapidly and at low cost using the incremental forming method. The most important problem with this method is that it causes undesirable variations in wall thickness. Various methods have been developed to improve the wall thickness distribution of the part resulting from forming. One of these techniques, the rolling blank holder (TPIF-RL) method, was used in this study to form 1 mm-thick HC380LA sheet. The Taguchi experimental design was used to determine optimum levels of each of the parameters (forming force, surface roughness and wall thickness) separately via signal/noise analysis. Gray Relational Analysis was then performed to determine the parameters that optimize surface roughness and wall thickness together. In the study, it was determined that the use of low pressing force increases the wall thickness. As a result, a 6% increase in wall thickness was achieved by using the optimum parameters