A multiscale overview of modelling rolling cyclic fatigue in bearing elements

During service, bearing components experience rolling cyclic fatigue (RCF), resulting in subsurface plasticity and decay of the parent microstructure. The accumulation of micro strains spans billions of rolling cycles, resulting in the continuous evolution of the bearing steel microstructure. The bearing steel composition, non-metallic inclusions, continuously evolving residual stresses, and substantial work hardening, followed by subsurface softening, create further complications in modelling bearing steel at different length scales. The current study presents a multiscale overview of modelling RCF in terms of plastic deformation and the corresponding microstructural alterations. This article investigates previous models to predict microstructural alterations and material hardening approaches widely adopted to mimic the cyclic hardening response of the evolved bearing steel microstructure. This review presents state-of-the-art, relevant reviews in terms of this subject and provides a robust academic critique to enhance the understanding of the elastoplastic response of bearing steel under non-proportional loadings, damage evolution, and the formation mechanics of microstructural alterations, leading to the increased fatigue life of bearing components. It is suggested that a multidisciplinary approach at various length scales is required to fully understand the micromechanical and metallurgical response of bearing steels widely used in industry. This review will make significant contributions to novel design methodologies and improved product design specifications to deliver the durability and reliability of bearing elements

Further investigations and parametric analysis of microstructural alterations under rolling contact fatigue

Bearing elements under rolling contact fatigue (RCF) exhibit microstructural features, known as white etching bands (WEBs) and dark etching regions (DERs). The formation mechanism of these microstructural features has been questionable and therefore warranted this study to gain further understanding. Current research describes mechanistic investigations of standard AISI 52100 bearing steel balls subjected to RCF testing under tempering conditions. Subsurface analyses of RCF-tested samples at tempering conditions have indicated that the microstructural alterations are progressed with subsurface yielding and primarily dominated by thermal tempering. Furthermore, bearing balls are subjected to static load tests in order to evaluate the effect of lattice deformation. It is suggested from the comparative analyses that a complete rolling sequence with non-proportional stress history is essential for the initiation and progression of WEBs, supported by the combination of carbon flux, assisted by dislocation and thermally activated carbon diffusion. These novel findings will lead to developing a contemporary and new-fangled prognostic model applied to microstructural alterations

Antimicrobial activity of Silver nanoparticles from Capsicum sp. against Staphylococcus sp., Bacillus sp., Pseudomonas sp. and Escherichia coli

The Pepper extract acts as a reducing and capping agent in the formation of silver nanoparticles. A UV–Vis spectrum of the aqueous medium containing silver nanoparticles demonstrated a peak at 480 nm corresponding to the Plasmon absorbance of rapidly synthesized silver nanoparticles that was characterize by UV–Visible spectrophotometer.The Antibacterial testing of Pepper extract was evaluate by disk diffusion method using bacteria like Staphylococcus aureus, Bacillus sp., Escherichia coli, and Pseudomonas sp. Study revealed the antibacterial activity of solvent extracts by using pepper; we prepared the silver nanoparticles to enhance its antibacterial property.Antibacterial disc were prepared in five different concentrations such as 100?l, 200?l, 300?l, 400?l and 500?l respectively. The antimicrobial activity of particles showed higher activity in concentration 500?l against the pathogenic Pseudomonas sp. (15) mm of inhibition zone. The higher activity was followed by Bacillus sp. (13) mm of inhibition zone, Staphylococcus sp. (11) mm of inhibition zone and E. coli (10) mm of inhibition zone. This study showed that the extract reveals the concentration dependent activity. The study revealed that the silver nanoparticles from plant extracts could be as a therapeutic agent for human microbial infections. The zone of inhibition seems in both gram positive and gram negative bacterial strains. This study reports that synthesis is useful to avoid toxic chemicals with adverse effects in medical applications rather than physical and chemical methods.Thus, the aim of the study to synthesize silver based bionanoparticles. The present investigations revealed with the isolation and monitoring of silver nanoparticles to produce novel drugs to overcome drug resistance and advance reaction. Keywords: Nanoparticles, Silver, Antimicrobial activity, Nano biosynthesis, standard disc diffusion method

Spiritualitas Karakter Tuang dalam Budaya Masyarakat Kampung Adat Cireundeu

Bagi masyarakat adat, prilaku makan atau tuang dalam bahasa Sunda tidak hanya berorientasi jasmaniah. Ada nilai-nilai khusus yang kemudian dijadikan entitas keyakinan yang mentradisi. Terlebih menjadikan singkong sebagai makanan pokok masyarakatnya. Penelitian ini bertujuan untuk mengungkap makna tuang bagi masyarakat Cireundeu. Tuang tidak sekedar bahasa simbolik, namum mengandung makna budaya, tradisi, adat istiadat bahkan ritual adat. Penelitian ini menggunakan pendekatan kualitatif dengan metode studi kasus. Pengumpulan data melalui observasi, wawancara, dokumentasi dan studi literatur. Dihasilkan dari penelitian ini, tuang dimaknai bukan sekedar hajat jasmaniah semata, tapi hakikat-nya sumber kekuatan spiritual. Istilah teu dahar asal kuat, bermakna filosofis sebagai sumber kekuatan, kehidupan, dan kemandirian bagi masyarakat Cireundeu. Tuang membawa makna mendalam dalam membangun karakter pasrah atas keadaan diri untuk mempertahankan godaan manusia dari dua hal; si ujang (duit), si nyai (beras). Godaan-godaan lingkungan harus dijaga, agar kelestarian dan keunikan suatu entitas kampung adat tetap terpelihara.For indigenous peoples, the behavior of eating or tuang in Sundanese is not only physically oriented. There are special values which are then made into a belief entity that is a derivative. Especially making cassava as a staple food for the people. This research aims to reveal the meaning of Tuang for the people of Cireundeu. Tuang is not just a symbolic language, but contains the meaning of culture, tradition, customs and even traditional rituals. This research uses a qualitative approach by case study method. Collecting data through observation, interviews, documentation and literature studies. As a result of this research, The term tuang is not just as a physical necessity but the essence of the source of spiritual strength. The term "teu dahar asal kuat" as philosophical meaning is a source of strength, life, and independence for the people of Cireundeu. Tuang brings deep meaning in building resigned character over the state of self that can defend human temptation from two things; si ujang (money), si nyai (rice). The Environmental temptations that must be guarded, so that the sustainability and uniqueness of a traditional village entity is maintained

IMPLEMENTASI STRATEGI PEMBELAJARAN VCT PADA PELAJARAN PAI DALAM MENYIKAPI KONFLIK SOSIAL DI SMK HARAPAN 1 RANCAEKEK BANDUNG

The purpose of this study was to work out the implementation of VCT (Value Clarification Technique) learning methods in Muslim Education lessons in responding to social conflicts at SMK Harapan one Rancaekek Bandung. This analysis uses a qualitative approach, with a descriptive analytic methodology. the info assortment uses interview, observation, and documentation techniques. Whereas knowledge analysis techniques through knowledge reduction, knowledge show, and drawing conclusions. The results of this study indicate that 1) RPP created by Curriculum Experts has not been fully maximized in the achievement of learning outcomes. 2) This VCT learning strategy is employed fitly, however there square measure many points that square measure uncomprehensible in its implementation. 3) The direct implication is that student’s square measure ready to show positive and negative attitudes through psychological feature, emotional and mental object responses. Whereas the indirect perspective of caring, tolerance, democracy, mutual cooperation, responsibility, and courtesy

Studi Komparasi Prestasi Belajar Siswa Menggunakan Model Pembelajaran Kooperatif Tipe Two Stay Two Stray (Tsts) dengan Numbered Heads Together (Nht) pada Pokok Bahasan Struktur Atom dan Sistem Periodik Unsur di Kelas X SMA Negeri 2 Dayun

The research about comparing cooperative learning models types Two Stay Two Stray (TSTS) with Numbered Head Together (NHT) has been done to improve student\u27s achievement on learning topic Atomic structure and periodic systems of elements at class X SMAN 2 Dayun. This research aimed to find out student\u27s achievement the better one between cooperative learning models types Two Stay Two Stray (TSTS) with Numbered Head Together (NHT) on learning topic of Atomic structure and periodic systems of elements by comparing these two models. This was a quasi experimental research with pretest-posttest design. Population on this research ware all classes X in SMAN 2 Dayun consisting of four classes. The subject of this research ware X4 as the experimental class of TSTS and X2 as the experimental class of NHT, which were determined randomly after conducting normality and homogeneity test. The data analysis to test the hypothesis was using two tail t-test. Based on the data analysis, it is obtained that tcount = 4,271 and ttable = 2,00 with α = 0,05, dk = 53. tcount ≥ ttable 4,271≥ 2,00. It means there are significant differences between the student\u27s achievement by using cooperative learning model type Two Stay Two Stray (TSTS) with the student\u27s achievement by using cooperative learning model type Numbered Head Together (NHT) on the learning topic of Atomic structure and periodic systems of elements in SMAN 2 Dayun

Penerapan Strategi Pembelajaran Aktif Rotating Trio Exchange (Rte) Disertai Media Question Box Dapat Meningkatkan Prestasi Belajar Siswa pada Pokok Bahasan Laju Reaksi di Kelas XI IPA SMA Negeri 2 Pekanbaru

This study aimed at investigating the significant difference of students\u27 learning achievement between students taught using Rotating Trio Exchange(RTE) assisted with question box and students taught conventionally with question box in chemistry subject at SMAN 2 Pekanbaru. Subject of this research were students at XI MIA 3 as experiment class and XI MIA 1 as control class were randomely selected. Data analized after giving pretest and postest to each class by using ttest. The results revealed that application active learning strategy of RTE was capable to improve student\u27s achievement in chemistry especially in Reaction Rate Subject at 11th SMAN 2 Pekanbaru. The result of the study shows a significant difference of students\u27 learning achievement between students taught using RTE assisted with questions box and students taught conventionally with question box with tobserved 3,87 > ttabel 1,67. And n-gain score for exsperiment class is 0.65 and control class is 0.47, means the improvement of both classes achievement was in average category

Evaluation of dark etching regions for standard bearing steel under accelerated rolling contact fatigue

Subsurface microstructural alterations are formed in the later stages of rolling contact fatigue (RCF) under high contact pressure. The subsurface changes observed as a dark contrast under optical microscopy are classified as Dark Etching Regions (DERs). Despite the fact that DERs have been presented for several decades, the understanding of its development and growth is yet to comprehend. Current research employed a modified high-speed microprocessor rotary tribometer to conduct systematic RCF study under accelerated testing conditions with variable temperatures and contact pressures. Comprehensive RCF data has been acquired, analysed and is reported for the very first time with ball-on-ball point contact loading conditions. The subsurface microscopic investigations have shown the ongoing progression and development of DER extent and are reported to be associated with the accumulation of plasticity during RCF. The comparison of the DER with the responsible stress components have revealed that DER formation is more closely related to the von Mises stresses when superposed with residual stresses. The experimentally observed area fraction of dark etching zones has been evaluated in terms of DER% and compared with the dislocation assisted carbon diffusion model for DER formation. The overprediction of the numerical model in comparison with the presented results in current research manifests its limitations which can be improved with the incorporation of cyclic plasticity governed by evolved von Mises stresses. Detailed evaluated DER results are presented as 3D DER% maps incorporating the combined effects of contact stress, temperature and rolling cycles simultaneously which enables an in-depth RCF understanding within microstructural context and therefore can be used as guidelines for DER formation models

Faktor-faktor yang Dipertimbangkan Konsumen dalam Keputusan Pembelian Laptop Merek Acer di Kota Denpasar

Tujuan penelitian ini adalah untuk mengetahui faktor-faktor yang dipertimbangkan konsumen dalam keputusan pembelian laptop merek Acer di Kota Denpasar dan variabel yang mewakili setiap faktor-faktornya. Penelitian ini dilakukan di Kota Denpasar. Jumlah sampel yang diambil sebanyak 105 responden dengan teknik non probability sampling . Pengumpulan data dilakukan dengan metode kuisioner yang kemudian diolah menggunakan software SPSS (Statistical Package for the Social Sciences) dengan menggunakan teknik analisis faktor konfirmatori. Hasil penelitian menunjukkan bahwa faktor budaya, sosial, pribadi, psikologis dan bauran pemasaran adalah faktor yang dipertimbangkan konsumen dalam keputusan pembelian laptop merk Acer di Kota Denpasar. Variabel-variabel yang mewakili setiap faktor adalah : (1) variabel sub-budaya, (2) variablel teman , (3) variabel kepribadian diri, (4) variabel persepsi , dan (5) variabel saluran distribusi. Implikasi yang diharapkan dari penelitian ini adalah kebijakan-kebijakan pemasaran untuk konsumen sebaiknya menggunakan pendekatan-pendekatan pada faktor budaya, seperti iklan yang menampilkan bagaimana keseharian aktivitas masyarakat yang membutuhkan laptop sebagai penunjang kebutuhan sehari-hari dalam memenuhi kebutuhan teknologi dan informasi sehingga faktor budaya menjadi pertimbangan dalam memilih laptop merek Acer