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Based on the shock-loading technique of a two-stage light gas gun, the yield strength of copper was measured by the shock wavefront disturbance method for the first time. Additionally, based on Steinberg–Cochran–Guinan constitutive model, a numerical simulation procedure for the evolution of perturbed shock front in copper was first constructed. Combining numerical simulation results with experimental results, the yield strength of copper was found to be $0.72\pm 0.01$, $0.99\pm 0.02$, $1.31\pm 0.02$, $1.65\pm 0.03$ and $1.82\pm 0.02$GPa at pressures of 47.17, 60.67, 76.98, 101.35 and 124.26GPa, respectively. The results were in good agreement with those obtained by the AC method. According to the phase diagram of copper, there was no phase transition under experimental shock-loading pressure, and the yield strength of copper increased with increasing shock-loading pressure. Research on the yield strength of copper under shock loading was of great significance to various fields.

Recent rapid advancements in nano- and micro-machinery technologies call for an urgent need to understand the mechanical behaviour of materials of dimensions in the sub-micron regime. The initial yield strength of submicron crystals exhibits remarkable statistical scatter as well as dependence upon size and time under load. Submicron-sized materials are also found to creep many orders of magnitude faster than bulk counterparts. In this paper, the recent experimental evidence for these phenomena is reviewed. Theoretical explanation of these phenomena is also discussed. The statistical scatter and time dependence of the yield strength are interpreted by a scaling model derived from atomistic simulations. The results indicate that, within a certain load range, the strength of a sub-micron sized material is not deterministic and can only be described by a survival probability. The much faster creep in the submicron regime is interpreted in terms of the much shorter diffusion length compared to bulk creep.

Steinberg-Guinan constitutive model is widely used in impact engineering simulations. Shock wave profile measurements of Al, Cu, and W under shock pressures ranging from 4 GPa to 200 GPa were analyzed, and shear modulus G and yield strength Y of these materials were obtained by using the high-pressure sonic velocities and rate independent Lagrange analysis results. Then values of derivatives of G and Y with respect to pressure or temperature at the reference state of these three metals were determined. By analyzing the pressure and temperature dependence of shear modulus and yield strength, we conclude that the relations of Steinberg-Guinan constitutive model, Y/G=constant, are approximately correct on Hugoniot state for these materials. So this is a probable approach to solve the difficulty of measurement of Y under high-pressure and high-temperature directly.

This paper discusses the various joining methods with faying surface modifications used to join AA6063 and AISI304L dissimilar alloys by Rotary Friction Welding (RFW) process at different welding conditions mainly with friction pressure (FP), upset pressure (UP) and friction time (FT). This paper also studies the tensile behavior of the welded joints. The fabricated dissimilar joints were tested using universal testing machine against tensile load, and the mechanical properties of all 30 nos. of weld joints like elongation (%), strength coefficient ($K$), strain hardening exponent ($n$), strain hardening rate (TS/YS ratio), shear strength, etc. were calculated from the tensile testing results and plotted here with a standard error bar. Hollomon’s equation is considered here to study the stress and strain hardening relation and Von Mises yield criterion is considered for shear and yield stress correlation. Total elongation is also calculated from the initial and final length obtained during the tensile test. Since fracture ductility of the joints depends on the stress, strain, ‘$K$’ and ‘$n$’ values, it is important to study these mechanical properties and how the tensile results can be used for their estimation is detailed in this paper. The faying surfaces influence the mechanical properties as well.

Different mechanisms such as glide of lattice dislocation and grain boundary mediated processes may be active during the plastic deformation of polycrystals with small grain size. A continuum model for polycrystal plasticity has been developed to capture such a feature. Specifically, the strain gradient effect due to dislocation pile-up, dislocation emission/absorption at surface and grain boundary sliding have been taken into account from the perspective of energy storage. As an application of the model, a bicrystal under plane constrained shear has been considered. The dependence of yield strength on the thickness of the bicrystal has been investigated. It has been demonstrated the present model predicts the yield strength of the bicrystal first increases and then decrease with decrease in the thickness, which is similar to the inverse Hall–Petch behavior but with a different scaling. Such behavior is attributed to the transition in different dominant deformation mechanisms at different values of the thickness.

The axial stiffness and the yield strength are the two fundamental structural parameters of a buckling restrained brace (BRB) member and can be obtained by existing design procedure. However, they are inter-related in a certain sense. This paper starts from the formulas of the axial stiffness and the yield strength, and based on the discussion on the reasonable range of geometric parameters of a BRB member, establishes the matching relationship between them.

Yield strength (YS) is a key factor during design and application of Ni-based superalloys with complex compositions, hence it is of great significance to evaluate the YS prior to manufacturing. In this work, alloy diffusion-multiple technology was employed as a high-throughput way to yield the hardness dataset. Based on the composition and other descriptors, Pearson correlation coefficients, stability selection and feature importance were used to select the efficient feature variables. Thereafter, six different machine learning models were applied to predict the YS. Finally, the individual and interaction effect of Co and Mo could be effectively detected by the Gaussian process regression (GPR) model. The optimum composition of Ni-based superalloys with the largest YS at room temperature was determined using the trained GPR model and genetic algorithm. This method can be extended to predict the YS in other multicomponent alloys, such as Ti alloys, Co-based alloys, and high entropy alloys.

A low-cost P/M processing route has been developed for the production of randomly packed hollow sphere structures (RHS). A fluidized-bed process allows mass production of iron-based green spheres with a large choice of possible sphere diameters and wall thicknesses. The individual sphere diameter may vary between 0.5 and 10 mm with wall thicknesses ranging from 20 to 1000 µm. From these green spheres, hollow sphere structures are formed in a special die. The subsequent consolidation and joining of the individual spheres is accomplished in one sintering step. Thus significant cost savings can be achieved over former approaches, where cellular metallic structures were obtained by brazing or sinter bonding of single metallic spheres.

With this method, test specimens from stainless steel 316L have been manufactured and their physical properties, i.e. density and compression strength, were measured.

The screwed fastening is one of the weakness of ship shock resistance performance. As shown in the statistics, there are 40% of the damaged cases having relationships with screwed fastenings in the shock tests of the shipboard equipments. One problem is the implementation of impact to the screwed fastenings in the event of encountering a shock loads. By means of the split Hopkinson pressure bar and tie bar experiments, using the Johnson-Cook model to matching the experimental results, get the yield strength under different strain rates of the three kinds of screwed fastenings materials. By comparing with the yield strength getting from quasi-static experiment, the yield strength obtaining from shock tests has improved 1.3 times at least. Consequently, shock loads can improve the yield strength of screwed fastenings within certain limits and it is safe to choose the screwed fastenings basing on the machinery handbooks.