Continuous assessment of longitudinal temperature force on ballasted track using rail vibration frequency

In this study, the possibility of using the rail vibration frequency to assess the longitudinal temperature force on the rail of ballasted track was investigated experimentally. An empirical formula was subsequently derived to link the frequency index to multiple factors, including the longitudinal temperature force, under-rail stiffness, and fastener spacing. Further tests were conducted to analyse the applicability and accuracy of the frequency index in continuous longitudinal force measurements under different line conditions (i.e. in the non-expansion zone and expansion zone). A technique for using the frequency index to assess the longitudinal temperature force was finally developed. The main results are as follows. (1) The first-order pinned–pinned modal frequency and peak frequency of the mid-span response are very close, and they both change linearly with the longitudinal temperature force on the rail. The rate of change in the vertical direction is larger than that in the horizontal direction. (2) Even if influenced by multiple factors, the peak frequency of the rail mid-span response is suitable for continuous longitudinal temperature force assessment under appropriate measures, and longitudinal temperature force detection could be realized with proper preparation. (3) Using the mid-span response frequency to detect the temperature force of rail located in the expansion zone causes deviation of the results, and under-rail materials whose stiffnesses are insensitive to temperature help reduce this deviation.

Structural and tribological aspects of laser processing of tool steel process

The possibilities of purposeful use of the phenomenon of structural adaptability of products made of tool steel P6M5 to temperature-force operating conditions to increase the efficiency of strengthening laser processing are determined. The parameters of laser processing of steel that contribute to the creation of a structural state on the working surfaces of products that is indifferent to temperature and force loading, that is, resistant to softening for a long time, have been experimentally established.

STUDY OF THE INFLUENCE OF THE CARBON CONTENT IN STEEL ON THE STRUCTURE AND MICROHARDNESS OF THE SURFACE LAYER AFTER ELECTROMECHANICAL PROCESSING WITH IMPACT

Experimental data of metallographic and x-ray diffraction studies of the surface layer of various grades of steels subjected to electro-mechanical processing (EMO) with dynamic (shock) application of the deformation force are presented. The influence of the carbon content in steel on the formation of the structure, microhardness and depth of hardening of the surface layer obtained in the field of pulsed temperature-force action is considered.

Postfire Safety Investigation on Prestressed RPC Beams after Exposure to Elevated Temperatures

Since the postfire safety of prestressed RPC beams after exposure to elevated temperatures needs to be studied and proved, this paper prepares eight smart prestressed RPC beams with intelligent sensors built in to monitor the internal temperature, force, and strain. The residual bearing tests after fire are carried out. The failure process of the beams under static load with different fire durations cover thickness of tendons, load ratio, bonded and unbonded tendons, and partial prestressing ratio, which are investigated. The load-deflection curves, crack distributions and developments, and strain variations are obtained, in addition to the damage mechanism and failure mode of the beams. The results show that the load-deflection curve of the prestressed RPC beam after fire has obviously three polylines, and the deflection points are where the cracks expand and the tendons yield. The failure procedure is the same as that of under-reinforced beams, while the height of the crushing zone is much lower than that of the balanced-reinforced beam at room temperature. The whole span deformation demonstrates a strong catenary effect, and the midspan deflection is approximately 1/40 of the effective span. The postfire safety of the bonded prestressed RPC beams is superior to that of unbonded prestressed RPC beams. The test results of this paper provide a basis for the safety performance evaluation and control of prestressed RPC beams after fire.

Implementasi Pembelajaran Discovery Learning pada Materi Temperatur, Tekanan dan Energi untuk Meningkatkan Pembelajaran Fisika di SMA Kelas X

ABSTRACT[Implementation Of Discovery Learning (Dl) On Temperature, Force And Energy Material To Improve The Physics Learning At Grade X SMA]. This research aimed to describe the improvement of students’ cognitive learning result which was taught by using Discovery Learning (DL) model in teaching temperature, pressure, and energy materials at SMAN 1 Bengkulu Tengah and also to describe the differences of the improvement of students’ cognitive result between high, middle, and low group students. The subject of this research is grade X ipa 1 SMAN 1 Bengkulu Tengah students with total 30 students. This research was a quasi experiment research with one group pretest and posttest design. The data was collected by using test instrument which was multiple choice questions. The data of students’ score at the final test on the last semester became the base of grouping students’ score for high, middle, and low group. The data of pretest and posttest was analyzed descriptively and counted by using gain score which has been normalized and also analyzed by using Anava test. The result of N-gain based on the group which was high group was 0,74; middle group was 0,52; and low group was 0,38. Based on the Anova test which was done to know the differences of students’ cognitive result among the students’ group, it was found Fcount 4,04 > Ftable 3,35 and sig.1,81 ? 4,95. The conclusion of this research was Discovery Learning (DL) model in physics learning for temperature, pressure, and energy materials can improve the students’ cognitive result and there was a significant difference on the improvement of students’ cognitive learning result among high, middle, and low group of students. Keywords: Discovery Learning; Temperature, Pressure and Energy; Cognitive Learning.(Received November 19, 2018; Accepted April 15, 2019; Published June 18, 2019) AbstrakPenelitian ini bertujuan untuk menjelaskan peningkatan hasil belajar kognitif siswa yang diajarkan menggunakan model pembelajaran Discovery Learning (DL) dalam pembelajaran Temperatur, Tekanan dan Energi di SMA N 1 Bengkulu Tengah serta menjelaskan perbedaan peningkatan hasil belajar kognitif antara siswa kelompok tinggi, sedang dan rendah. Subjek penelitian ini adalah kelas XIpa1 SMA N 1 Bengkulu Tengah yang berjumlah 30 orang siswa. Jenis penelitian adalah quasi Eksperimen dengan desain one group pretest and posttest design. Data hasil belajar kognitif siswa diperoleh dengan instrumen tes yaitu soal pilihan ganda. Data hasil nilai uijan semester ganjil menjadi dasar pengelompokan siswa ke dalam kelompok tinggi, sedang dan rendah. Data hasil belajar kognitif berdasarkan nilai pretest dan posttest dianalisis secara deskriptif dan dihitung dengan menggunakan skor gain yang dinormalisasi serta dianalisis menggunakan uji Anava. Hasil penelitian N-gain berdasarkan kelompok yaitu kelompok tinggi sebesar 0,74; kelompok sedang sebesar 0,52; dan kelompok rendah sebesar 0,38. Berdasarkan uji anova yang dilakukan untuk mengetahui perbedaan hasil belajar kognitif antar kelompok siswa diperoleh Fhitung 4,04 > Ftabel 3,35 dan nilai sig. 1,81 ? 4,95. Kesimpulan penelitian ini adalah model pembelajaran Discovery Learning (DL) dalam pembelajaran fisika materi Temperatur, Tekanan dan Energi dapat meningkatkan hasil belajar kognitif siswa dan terdapat perbedaan peningkatan hasil belajar kognitif yang signifikan antara siswa kelompok tinggi, sedang dan rendah.Kata kunci: Discovery Learning; Temperatur, Tekanan dan Energi; Hasil belajar kognitif.