Modeling of critical strain for dynamic recrystallization of niobium microalloyed steels

The critical strain for dynamic recrystallization (DRX) is most important in designing rolling schedules for the refinement of grain size by boundary-induced transformation mechanisms. Modeling of the critical strain for DRX from the stress-strain curves obtained from hot compression was physically built in this paper. The stress-strain behaviour of materials during hot deformation should be a combination of work-hardening and recrystallization softening. Before DRX occurred, the stress-strain behaviours could be described by a constitutive equation in which basic strain hardening and the effect of strain rate and temperature on stress-strain behaviour are included. Once DRX was promoted, obvious deviation between the experimental and calculated stress-strain curves appeared, which denoted the critical strain for DRX. The modeling in this work could be used not only to accurately calculate the critical strain for DRX but also to analyze the dynamic softening behaviours during hot deformation. To validate the calculated results, the stress-strain database was analyzed in the H beam sample deformed at 1000C with a strain rate of 0.1/s, and a critical strain of 0.22 was obtained by this novel method as an example. The calculated result is in good agreement with the experimental data obtained by micrographical observations.

Enhancement of Radar Detection Accuracy Using H-Beam Wave Polarization in Random Media

This work addresses the range in which the accuracy of object identification is enhanced regardless of radar parameters. We compute the radar cross-section (RCS) of conducting objects in free space and random media. We use beam wave incidence and postulate its coherency with a finite width around an object located in the far field. Accordingly, we examine the impact of radar parameters on the RCS, where these parameters include the incident angle, target size and complexity, medium fluctuation intensity and the beam size of the incident waves. H-wave polarization is assumed for the waves’ incidence.

Effects of Shear Tabs and High-Strength Bolts in Seismic Performance of Steel Moment Connections

A shear tab and high-strength bolts are often used to connect a steel H-beam to a column. The design demand and capacity of these elements vary from one standard to the other. To investigate the effect, this study applied a finite element method (FEM) to develop models for two steel moment connections and validated the effectiveness by test data. The connections were characteristic of bolted-web-and-welded-flange details. The FEM models were then used to study the design of shear tabs and high-strength bolts in accordance with the U.S. and Japan standards and compared to the Taiwan practice. The result showed a small difference in the peak loads of the connections. However, the U.S. direct welded flange connection had flange buckling and strength degradation at a relatively smaller drift. The connection had a thinner shear tab and fewer high-strength bolts. The other two connections had very similar design results and loading responses. The increase in shear-tab thickness reduced the stress concentration and fracture potential of the connections. It is, therefore, recommended to design a shear tab with moment capacity greater than the beam web. This will reduce the stress concentration of the base metal surrounding the beam-flange groove welds, increasing the connection ductility.

Experimental Study on the Bending Behavior of Steel-Wood Composite Beams

This paper proposes a steel-wood composite beam with H-shaped steel beam webs glued to the wood. As a new type of composite beam, it combines the advantages of low energy consumption of wood, high permeability, and less pollution and the advantages of light weight and high strength of steel, high degree of assembly, short construction period, and less construction waste generated. Carrying out research is of great significance to improve the mechanical properties of steel-wood composite beams and promote the development of steel-wood composite structures. In this paper, three hot-rolled H-beam-larch composite beams and one pure steel beam were tested for bending capacity. The composite beams are divided into two different combinations of A and B types. The two sides of the web are connected with larch wood by structural glue to form a composite beam. The type B composite beam is a larch wood glued on both sides of the H-shaped steel web and penetrates the bolts at the same time. Through the three-point monotonic static grading loading of the composite beam, the deflection change, failure phenomenon, and form of the specimen during the experiment were observed. Under the circumstances, the ultimate bearing capacity of the test piece was changed to study the combined effect of larch and hot-rolled H-shaped steel. The results show that the overall performance of the H-shaped steel-larch composite beam is good. Bonding wooden boards on both sides of the steel beam web can improve the bearing capacity, and the form of the member is more reasonable and effective; increasing the cross-sectional size of the H-beam in the steel-wood composite beam can further improve the bearing capacity of the composite beam; adding bolt anchorage on the basis of the structural glue used in the composite beam can further improve the bearing capacity of the composite beam. The superposition principle is used to simplify the calculation of the ultimate bearing capacity of H-shaped steel-larch composite beams. Comparing the calculation results with the test results, the data are in good agreement, which can provide a design reference for the practical application of such composite beams.

Desain Mekanisme Ballscrew untuk Retrofit Drilling axis Mesin Ficep H-Beam Drilling LFB-200-49

Proses retrofit adalah proses penggantian atau penambahan suatu komponen ke mesin dengan tujuan untuk memberikan nilai tambah pada performa mesin tersebut. Pada penelitian ini, proses retrofit diaplikasikan pada penggantian penggerak drilling axis mesin Ficep H-beam Drilling LFB-200-49. Proses retrofit ini membutuhkan komponen motor servo sebagai energi penggerak dan ballscrew sebagai pengubah rotasi motor menjadi gerakan linear twist drill saat melakukan proses pengeboran untuk menggantikan sistem hidrolik yang digunakan sebelumnya. Pada perancangan retrofit yang dilakukan terhadap mesin Ficep H-beam Drilling ini, gaya dorong yang dihasilkan sistem hidrolik digunakan sebagai acuan untuk mengetahui kebutuhan dynamic load yang harus ditransmisikan oleh ballscrew sedangkan thrust axial force dari mata bor digunakan sebagai acuan dalam menentukan daya motor servo. Dalam merancang penggantian sistem hidrolik ke sistem motor servo ini, komponen yang disarankan adalah ballscrew dengan pitch 10 mm dan diameter poros ballscrew 38 mm yang memenuhi syarat transmisi dynamic load 50.210,56 N dan motor servo dengan daya 8,12 kW dengan penambahan gear ratio 3 : 1. The retrofit process is the process of replacing or adding a component to a machine with the aim of adding value to the machine's performance. In this study, the retrofit process was applied to the replacement of the Ficep H-beam Drilling LFB-200-49 drilling machine axis. This retrofitting process requires a servo motor component as driving energy and a ballscrew to convert the motor rotation into a linear twist drill motion during the drilling process to replace the hydraulic system used previously. In the retrofit design carried out on the Ficep H-beam Drilling machine, the thrust generated by the hydraulic system is used as a reference to determine the dynamic load requirements that must be transmitted by the ballscrew while the thrust axial force from the drill bit is used as a reference in determining the power of the servo motor. In designing the replacement of the hydraulic system to this servo motor system, the recommended components are a ballscrew with a pitch of 10 mm and a ballscrew shaft diameter of 38 mm which meets the requirements for dynamic load transmission of 50,210.56 N and a servo motor with a power of 8.12 kW with the addition of a gear ratio of 3. : 1.