This present study investigates experimentally and numerically the crush response and energy absorption performances of auxetic foam-filled square tubes under quasi-static axial loading. Three different structures: empty, conventional and auxetic foam-filled square tubes have been compared and examined with respect to the deformation modes and load–displacement curves. Standard compression tests were conducted on the tubes to evaluate the influence of auxetic foam in the energy absorption of empty tubes. Moreover, results from computer simulation have also been supplemented to further examine the abovementioned effect. It is discovered that the auxetic foam-filled square tube is superior to empty and conventional foam-filled square tubes in terms of all studied crashworthiness indicators. 相似文献
In this paper, multi-objective optimization of a rack-and-pinion steering linkage is proposed. This steering linkage is a common mechanism used in small cars with three advantages as it is simple to construct, economical to manufacture, and compact and easy to operate. In the previous works, many researchers tried to minimize a steering error but minimization of a turning radius is somewhat ignored. As a result, a multi-objective optimization problem is assigned to simultaneously minimize a steering error and a turning radius. The design variables are linkage dimensions. The design problem is solved by the hybrid of multi-objective population-based incremental learning and differential evolution with various constraint handling schemes. The new design strategy leads to effective design of rack-and-pinion steering linkages satisfying both steering error and turning radius criteria.
Carbon steel fibre reinforced lightweight aggregates (LWA) were produced in a pilot scale rotary kiln. Narrow size fractions as well as not-sieved (as received) material were investigated according to European standards with a main focus on strength and density and compared to a reference material without fibres. Depending on the size of the pellets a fraction of the fibres oxidized during firing. A strength increase proportional to the amount of non-oxidized fibres within the pellet was observed. The crushing resistance for as received fibre reinforced pellets (bulk density 452 kg/m3) was 3.0 MPa corresponding to an increase in strength of 140%. The enhanced strength was also confirmed by the single pellet compression test. 相似文献
The effect of temperature, strain rate, resin content, void content and methods of preparation (vibration and compaction) on the overall flexural behavior of a polyester resin based polymer concrete is studied under three-point bending. The strength and modulus of polyester polymer concrete are relatively independent of strain rate but decrease at varying rates with increase in temperature. Compaction of polymer concrete during preparation reduces the void content and enhances both the flexural strength and modulus. Modifications to composite stiffness models have been proposed to include excess polymer and excess sand phases for systems other than the optimal system. Using a combination of parallel and series models, it is possible to predict the flexural modular ratio and flexural modulus of polymer concrete. Modified tensile strength models are effective in predicting the flexural strength ratio and flexural strength of polymer concrete. 相似文献
Addition of several percent bentonite to geothermal grout formulations allows high W/S ratios to be used providing slurries with low densities and high fluidity. The hardened grouts barely meet the API requirements for permeability and require high silica additions to do this. Release of aluminum ions from the clay/Ca(OH)2 interaction produces Al-substituted tobermorite which persists to 250°C. This phase does provide a strong impermeable binder when the grouts are water cured, but it is rapidly carbonated. All grouts which contained tobermorite showed large increases in permeability when carbonated and low durability in the presence of carbonated fluids. 相似文献
Anodic dissolution and cathodic deposition of 20 transition metals in acidic solutions in liquid ammonia has been surveyed. The early transition metal elements Ti, Zr, V Nb, Mo and W form high oxidation-state insoluble amido complexes during anodic oxidation. Soluble ammines of normal metal oxidation states are produced with Cr(III), Mn(II), Fe(II), Co(III), Ni(II), Cu(II), Ag(I), Zn(II), Cd(II) and Hg(II) (Mn dissolves spontaneously). The metals Ru, Pd, Pt and Au only dissolve slightly after prolonged electrolysis. Anodic enrichment of Au in its alloys is unlike that in aqueous solution; in ammonia both Cu and Ag can be simultaneously depleted from a 9 carat gold alloy. Cathodic reduction of metal-bearing solutions follows wide variations of behaviour. Fe and Ru ammines reduce to amido-complexes with concomittant hydrogen evolution, but Cr is not reduced. Solutions of Mn, Co, Ni, Pd, Pt, Ag, Au, Zn, Cd and Hg give metallic cathode deposits under differing conditions. Electrodeposition is potential dependent for Ni, Cu and Ag; metal plate at low potentials, and powders at high potentials. The two different products are the result of reduction of species with different degrees of solvation. 相似文献
The influence of semi-rigid joint action on the behaviour and strength of laterally unsupported beams has been investigated using a finite element approach. The ultimate strength analysis allows for the effects of initial deflections, residual stresses and the gradual development of yielded zones. Connection behaviour is modelled with a multi-linear representation of in-plane moment-rotation (M-φ) behaviour. The validity of the program has been verified by checking against both analytical and experimental results. A parametric study has been conducted to assess both the importance of end-restraint effects and the sensitivity of the beam's strength to variations in the main problem variables. Studies of the spread of yield have been employed to explain the various phenomena observed. The results have been used as the basis for an assessment of the methods used to allow for end restraint in the new UK steelwork code. 相似文献
Longitudinal emission computed tomography (LECT), is shown to generate images with a reconstruction error independent of both the reconstruction algorithm and the physical performance of the viewing system. In general, activity will be predicted to extend into space beyond the true object boundary and the predicted, relative distribution of activity will be incorrect. A method is described which identifies the direction involving the maximum reconstruction error and gives a measure of the maximum error volume; its application in the optimisation of some common LECT systems is demonstrated. 相似文献