Influence of the Cross–Sectional Shape and Corner Radius on the Compressive Behaviour of Concrete Columns Confined by FRP and Stirrups

Axial compression tests were carried out on 72 FRP (fiber reinforced polymer)–stirrup composite−confined concrete columns. Stirrups ensure the residual bearing capacity and ductility after the FRP fractures. To reduce the effect of stress concentration at the corners of the confined square−section concrete columns and improve the restraint effect, an FRP–stirrup composite−confined concrete structure with rounded corners is proposed. Different corner radii of the stirrup and outer FRP were designed, and the corner radius of the stirrup was adjusted accurately to meet the designed corner radius of the outer FRP. The cross−section of the specimens gradually changed from square to circular as the corner radius increased. The influence of the cross−sectional shape and corner radius on the compressive behaviour of FRP–stirrup composite−confined concrete was analysed. An increase in the corner radius can cause the strain distribution of the FRP to be more uniform and strengthen the restraint effect. The larger the corner radius of the specimen, the better the improvement of mechanical properties. The strength of the circular section specimen was greatly improved. In addition, the test parameters also included the FRP layers, FRP types and stirrup spacing. With the same corner radius, increasing the number of FRP layers or densifying the stirrup spacing effectively improved the mechanical properties of the specimens. Finally, a database of FRP–stirrup composite−confined concrete column test results with different corner radii was established. The general calculation models were proposed, respectively, for the peak points, ultimate points and stress–strain models that are applicable to FRP−, stirrup− and FRP–stirrup−confined concrete columns with different cross−sectional shapes under axial compression.

Die Design for Extrusion Process of Titanium Seamless Tube Using Finite Element Analysis

In this paper, the extrusion process of titanium seamless tubes was studied using several finite element (FE) analyses. First, the finite element result was compared with experimental extrusion data acquired to validate the current analysis. Then, the effect of design parameters of the die shape was numerically analyzed using commercial FE software, Forge NxT, for the metal forming process. Elastic FE analyses were also conducted for dies to analyze the maximum principal stress that affects the early fracture of dies during the extrusion process and the maximum von Mises stress that causes the severe deformation of dies. Consequently, the effect of the corner radius at the exit and land length on the extrusion load and die stress is negligible compared to that of the corner radius at the entrance and die angle. Finally, we suggested a die angle of 60° and a corner radius at the die entrance between 10 and 15 mm as an optimal design for the current extrusion process.

Machining of Inserts with PCD Cutting-Edge Technology and Determination of Optimum Machining Conditions Based on Roundness Deviation and Chip-Cross Section of AW 5083 AL-Alloy Verified with Grey Relation Analysis

This paper describes the important significance of cutting-edge technology in the machining of polycrystalline diamond (PCD) cutting inserts by comparing the evaluation criteria. The LASER technology of cutting-edge machining is compared with grinding and electrical discharge machining (EDM) technologies. To evaluate the data from the experiments, the Grey Relational Analysis (GRA) method was used to optimize the input factors of turning to achieve the required output parameters, namely the deviation of roundness and chip cross-section. The input factors of cutting speed, feed rate, depth of cut and corner radius were applied in the experiment for three different levels (minimum, medium and maximum). The optimal input factors for turning of aluminum alloy (AW 5083) were determined for the factorial plan according to Grey Relational Grade based on the GRA method for the multi-criteria of the output parameters. The results were confirmed by a verification test according to the GRA method and optimal values of input factors were recommended for the machining of Al-alloy (AW 5083) products. This material is currently being developed by engineers for forming selected components for the automotive and railway industries, mainly to reduce weight and energy costs. The best values of the output parameters were obtained at a cutting speed of 870 m/min, feed rate of 0.1 mm/min, depth of cut of 0.5 mm and a corner radius of 1.2 mm.

Research on Springback during Hot Stamping with Uniform and Local-Thickened Sheet Blanks

In this study, the effect of forming temperature, blank holder force, die entrance radius, die corner radius and blank local thickening on the springback of square cups were studied, by conducting finite element simulations of the hot stamping of 2024 aluminum alloy sheet blanks. Within the range of process parameters investigated in this study, increasing the forming temperature, blank holder force and die corner radius or decreasing the die entrance radius all lead to lower values of springback in hot stamped square cups after unloading. Compared to uniform blank, local-thickened sheet blank can significantly reduce the springback in hot stamped square cup. When the side length of the square-ring-shaped convex rib of the thickened blank is equal to the punch width and the convex rib faces downward, significant reductions in the springback, of at least 55.9%, can be achieved.

Bioinspired Honeycomb Core Design: An Experimental Study of the Role of Corner Radius, Coping and Interface

The honeybee’s comb has inspired the design of engineering honeycomb core that primarily abstract the hexagonal cell shape and exploit its mass minimizing properties to construct lightweight panels. This work explored three additional design features that are part of natural honeybee comb but have not been as well studied as design features of interest in honeycomb design: the radius at the corner of each cell, the coping at the top of the cell walls, and the interface between cell arrays. These features were first characterized in natural honeycomb using optical and X-ray techniques and then incorporated into honeycomb core design and fabricated using an additive manufacturing process. The honeycomb cores were then tested in out-of-plane compression and bending, and since all three design features added mass to the overall structure, all metrics of interest were examined per unit mass to assess performance gains despite these additions. The study concluded that the presence of an interface increases specific flexural modulus in bending, with no significant benefit in out-of-plane compression; coping radius positively impacts specific flexural strength, however, the corner radius has no significant effect in bending and actually is slightly detrimental for out-of-plane compression testing.

Surface Roughness Analysis for Radius End Mill in Cross Feed Direction Both Contour and Scanning Line Machinings

An optimum experimental condition, which realize good surface roughness in cross direction both contour and scanning lines, for radius end mill against some inclined surfaces is obtained and some features is these cutting processes is discussed in this paper. The optimum experimental condition, which consists of cutting type (or feed direction), spindle speed, feed rate, depth of immersion, inclination angle, corner radius of end mill and cross feed, is obtained and the influence degree of these parameters is calculated by using Taguchi method. The experiment is carried out based on L18 orthogonal array. Based on the influence degree and geometric contact status due to unique shape of radius end mill, some feature of radius end milling is introduced. As a result of the contour line machining, a scallop height is very influenced by the inclination angle and the corner radius, and surface machined by bottom edge must not be remained. Regarding the scanning line machining, “go-up” is good for the feed direction. Big corner radius is also suitable because side edge does not contact to workpiece. In other words, the cutting force in radial direction becomes small. Furthermore, the surface roughness of the scanning line machining is smaller than the one of the contour line machining.