Analysis of welding properties using various horn-tip patterns in the ultrasonic metal welding process

The present study was conducted to investigate how the characteristics of welds are affected by the horn-tip pattern shape, in order to assess how to efficiently transfer the vibration energy to a base material through the horn. Energy transfer was evaluated using the indentation marks. The experiment was carried out with aluminum and copper by combining the conditions from four horn-tip patterns, six pressure values, and ten welding time values. The aspect ratio of the indentation marks on the weld surfaces was measured. The effects of the applied pressure, welding time, and horn-tip pattern shape on the aspect ratio were analyzed, and it was found that the horn-tip pattern shape affects the aspect ratio significantly. The aspect ratio was suggested as an analytical reference, and its correlations with the shear strength and the hardness of the welds were verified. In addition, the experiment performed with aluminum and copper, which have different mechanical properties, under the same welding conditions showed that the aspect ratio was dependent on the mechanical properties of the materials. In conclusion, as the density of the horn-tip pattern is decreased, less of the vibration energy was lost, increasing the strength of the welds. Experimental results showed that shear strength of copper was nearly 400 N when the aspect ratio was close to the value of 1. The highest peak of horn-tip pattern forms the lowest aspect ratio of the indentation mark, which can be indicated that the decrease of the aspect ratio effect to the improvement of welds strength. Aspect ratio of horn-tip pattern D, which dimensions are pitch 1.5 mm, height 0.75 mm and stub tooth 0.7 mm was closely to the value of 1 compared to the other patterns.

Assessment of Nano-Indentation Method in Mechanical Characterization of Heterogeneous Nanocomposite Materials Using Experimental and Computational Approaches

This study investigates the capacity of the nano-indentation method in the mechanical characterization of a heterogeneous dental restorative nanocomposite using experimental and computational approaches. In this respect, Filtek Z350 XT was selected as a nano-particle reinforced polymer nanocomposite with a specific range of the particle size (50 nm to 4 µm), within the range of indenter contact area of the nano-indentation experiment. A Sufficient number of nano-indentation tests were performed in various locations of the nanocomposite to extract the hardness and elastic modulus properties. A hybrid computational-experimental approach was developed to examine the extracted properties by linking the internal behaviour and the global response of the nanocomposite. In the computational part, several representative models of the nanocomposite were created in a finite element environment to simulate the mechanism of elastic-plastic deformation of the nanocomposite under Berkovich indenter. Dispersed values of hardness and elastic modulus were obtained through the experiment with 26.8 and 48.5 percent average errors, respectively, in comparison to the nanocomposite properties, respectively. A disordered shape was predicted for plastic deformation of the equilateral indentation mark, representing the interaction of the particles and matrix, which caused the experiment results reflect the local behaviour of the nanocomposite instead of the real material properties.

Effect of Heat Treatment on the Mechanical Properties and Interface Structure of 3-ply Ti/Cu/Ti Clad Composite

The effect of heat treatment on the mechanical properties and interface structure of 3-ply Ti/Cu/Ti clad composite was investigated. Strength decreased and the ductility increased with increase of heat treatment temperature. The gradual increase of hardness at 700°C and 800°C indicates the growth of intermetallic compounds at the interface. No visible intermetallic compound formation was observed up to 400°C. The intermetallic layer grew very rapidly above 600°C and its thickness reached ~10μm after heat treatment at 800°C. The absence of cracks emanating from the corners of the indentation mark indicates that intermetallics in Ti/Cu/Ti clad are ductile enough to accommodate the micro-plastic flow from indentation. Four intermetallic layers at the interface were confirmed to be Cu4Ti, Cu3Ti2, CuTi and CuTi2 based on the EDS spectra, XRD and phase diagram analyses.

Mechanical Performance of Ti/Cu-8Ag/S20C Clad Composite Processed by High Pressure Torsioning (HPT)

Ti/Cu-8Ag/S20C composite were processed by High Press Torsioning(HPT) and the effect of post-HPT heat treatment on the interfacial reaction products and the mechanical performance were studied. Intremetallic compound layer with the thickness of 11 μm was observed at the interface between Ti and Cu-8Ag for the clad heat-treated at 600°Cfor 24hrs. On the other hand, no intermetallic compounds were observed at the Cu-8Ag/S20C interface. No cracks were observed to be emanated from the corner of the indentation mark on the intremetallic compound layer at the Ti/Cu-8Ag interface, suggesting those intermetallic compounds is not so brittle. The stress-strain curves exhibited two steps in as-HPTed clad samples and those heat-treated at 600°C for 24hrs. The careful examination of the fractured plates revealed that S20C plate fractured first and then Ti and Cu-8Ag layers fractured together, suggesting the bonding strength between two layers is fairly high in the presence of intermetallic layer between Ti and Cu-8Ag layers

Effect of Post-HPT Heat Treatment on the Mechanical Performance in Ti/Cu-Cr/S20C Clad Materials

In this study Ti/Cu-Cr/S20C were clad by High Press Torsioning(HPT) and the effect of post-HPT heat treatment on the interfacial reaction products and the mechanical performance in Ti/CuCr/S20C clad material were studied. No cracks were observed to be emanated from the corner of the indentation mark on the intremetallic compound layer at the Ti/Cu-Cr interface, suggesting those intermetallic compounds is not so brittle. The stress-strain curves exhibited three steps in as-HPTed clad samples and those heat-treated at 500°C for 1hr. Step-wise fracture occurred in the sequence of S20C, Cu-Cr and Ti with each fracture resulting in the sudden drop of the stress. The stress-strain curves exhibited two steps in clad metals annealed at 600°C for 1hr, with first step corresponding to the fracture of S20C plate and the second one corresponding to the concurrent fracture of Ti and Cu-Cr plates. Ti/Cu-Cr/S20C heat-treated at 600°C for 24hrs exhibited just one step final fracture, suggesting that the bonding strengths are high enough to resist the localized strain concentration at the interfaces.

Fabrication of Nano-Laminar Glass/Metal Composites by Sintering Glass Flakes

Fabrication of nano-laminar ceramic composite by a simple sintering technique was examined. Glass flakes with a thickness of 0.7μm coated with silver were used as model materials, and were consolidated by pulsed current sintering with a uniaxial press of 7.1MPa or 30MPa. By sintering the flakes at 943K, we obtained a fairly dense composite where the flakes were aligned by uniaxial press. The silver coating remained on the flakes through the sintering, and an interface layer between the flakes was formed. The sample’s indentation test demonstrated its high resistance to crack propagation through the transverse direction of the lamellar; this result was attributed to crack deflection at the interface and the accumulation of microfractures around the indentation mark.