Effect of Sheets’ Thickness and Rivet Geometry on Mechanical Properties of Orbital Riveted Aluminium Joints: Experimental and Numerical Analysis

Orbital riveting is an innovative joining technology used in various industrial fields. Despite its diffusion in recent years, it has not been accompanied by an equivalent interest from the scientific community, which has neglected the aspects of process optimization and joint performance. In this experimental/numerical study, six different configurations of orbital riveted joints were realised and tested to determine the effects of sheet thickness and rivet geometry on the mechanical properties of the joints and their failure modes. The results showed that the configuration of the joint significantly affects both its resistance and fracture mechanism. Moreover, it was possible to identify a transition between different failure modes by changing the rivet diameter. A non-optimal joint geometry favours a premature fracture at very low load (i.e., S9A21 batch with net tension fracture). The highest mechanical resistance was found in the S8A15 batch, which experienced unbuttoning failure. In order to better correlate the joint geometry with the mechanical behaviour and the relative stress distribution, a simplified numerical FEM was validated with the experimental results.

Study on the mechanism of water inrush in the arid western mining area

The analysis found that the coal mining process in the western mining area has the mining loss and disaster effect of the water-rich aquifer of the coal seam roof, which is mainly manifested by the overburden water in the roof. On this basis, the formation and development of the separation water of the roof is proposed, and the mechanism of the water inrush from the layer is revealed. It is found that there is hydrostatic pressure and hydrodynamic pressure in the separated water, under the combined action of bed separation water pressure, the mining-induced fracture and water-isolation layer tension fracture are connected, which causes water inrushing in the coal working face of the mine, and provides a theoretical guarantee for the large-scale development of coal resources in western mining areas.

Fracture Toughness Behaviour of 316L Stainless Steel Samples Manufactured Through Selective Laser Melting

Selective laser melting (SLM) is a relatively new manufacturing technique which offers many benefits. However the utilisation of SLM manufactured components depends on the assurance of their integrity during operation. Fracture toughness testing (JIC) has been performed on as-built compact tension fracture mechanics samples manufactured in three orthogonal directions. When the crack growth plane was transverse to the interface of the build layers, the fracture toughness values were found to be similar to those manufactured using conventional techniques. However, the fracture toughness is significantly reduced when the crack plane is parallel to the interface of the build layers. Simple heat treatments have been performed on Charpy fracture samples and the resulting impact energy values indicate that the fracture toughness of a component may be improved by heat treatment.

Challenges Associated With the Quantitative Analysis of Ductile Damage Using X-Ray Computed Tomography

We have recently reported on the mechanistic differences in ductile failure between stainless steel manufactured by hot isostatic pressing (HIP) and forging, from which it was established that the oxygen concentration must be properly controlled. As part of an ongoing investigation into the mechanics of ductile failure in novel HIP materials, X-ray CT has been employed as a tool to quantify and characterize the differences in ductile damage below the fracture surface of failed compact tension fracture toughness test specimens. Herein we report on some of the challenges associated with handling data relative to the fracture surface, which can extend far into the cores under investigation.

Research on Tensile Properties of Ni-Base Super Alloy GH3128

GH3128, which is one of the domestic Ni-base super alloy, shows good performances under high temperature. Preliminary research has shown that this alloy is promising as structural material for Intermediate Heat Exchangers (IHX), which are the key components of Very High Temperature Reactor (VHTR). In this paper, the tensile properties of GH3128 are tested by the uniaxial tension experiments, and then the fractographic evaluation is conducted by using the scanning electron microscope (SEM). In the paper, the variation tendency of tensile strengths of GH3128 as well as plasticity is described along with the variation of temperature. The results also show that the tension fracture mode will gradually transform from ductile fracture to cleavage-intergranular compound fracture with the increasing of temperature, and the transition of fracture mechanism corresponds well with the variation of alloy plasticity.