Advanced Materials Research Vols. 97-101

Abstract: The fracture of the diaphragm is the main failure pattern of the non-contact electronic horn. The spring steel strip 50CrVA which is cold rolled was applied to manufacture the diaphragm of the non-contact electronic horn by means of sheet metal forming. The combination of the experiments with finite element method (FEM) was used to reveal mechanism of fracture failure of the diaphragm. The displacement field, the effective strain field and the effective stress field at the maximum amplitude value are obtained by simulating the genuine vibrating state of the diaphragm with the help of ANSYS finite element code. The maximum stress zone of the stress field of the diaphragm is responsible for the fracture zone of the diaphragm. The fatigue test of the diaphragm and microscopy of the fractured diaphragm indicates that the fracture pattern of the diaphragm agree well with finite element simulation results. Eventually, the measures to prevent the fracture of the diaphragm were taken in order to increase the endurance of the diaphragm.

Abstract: This document investigated the changes of the surface hardness of the front axle and transmission gear after strengthening under low-amplitude loads below the fatigue limit (SLAL). The experimental results showed that the strength changes of the front axle after strengthening under low-amplitude loads was almost proportional to hardness, but it was inverse ratio for the transmission gear. There was no difference in the change direction of surface hardness, caused by strengthening or damaging. The reason of surface hardness changes could be due to that the microstructure of material was improved after being strengthening under low-amplitude loads below the fatigue limit.

Abstract: The high strain rate compressive properties of UHMWPE/ vinyl ester 3D orthogonal woven composites are investigated experimentally. The composites are made from UHMWPE fiber 3D orthogonal woven preforms impregnated with vinyl ester resin by resin transfer molding. The samples are subjected to dynamic loading through the thickness direction using the Split Hopkinson Pressure Bar at three kinds of strain rate. The testing results are compared with the results of quasi-static tests on specimens with the same fiber volume fraction. The stress-strain relationships of UHMWPE/vinyl ester 3D orthogonal woven composites are rate dependent. It is found that the yield stress, strain at yield stress and modulus increased with the increased the strain rates. Additionally, the predominant failure mode of the composites under dynamic loading shear fracture from the optical microscopic images of fracture surfaces.

Abstract: An unfired mullite roller was produced by using mullite roller waste, white fused alumina, α-Al2O3, clay and micro silica, meanwhile silica sol was used to partially substitute for micro silica as the SiO2 source. The effect of silica sol on the properties of unfired mullite roller was investigated. The results showed that the microstructure and properties of the unfired mullite roller prepared with silica sol were improved. With the increase of silica sol, the COMR, bulk density and thermal shock resistance increased, and the water absorption rate decreased. When silica sol was 8w/t%, treated temperature was 1200°C, the CMOR of unfired mullite roller was more than 50MPa.

Abstract: The oxidation behavior of two ductile cast irons was investigated in this paper. The alloys were a high Si-Mo ductile and a ductile Ni-Resist cast iron which were developed by FAW Foundry. Polished sections were exposed at temperatures between 800 °C and 1000 °C, mostly for 80h. It has been found that the property of oxidation resistance of ductile Ni-Resist cast iron is excellent or better than that of high Si-Mo ductile by comparison and analysis.

Abstract: Based on mean yield criterion, an analytical solution for the mode I crack tip plastic zone (CTPZ) under small scale yielding was derived. The results reveal that the size of CTPZ determined by MY criterion is between those by Mises’ yield criterion the smallest, and by Tresca’s criterion the largest; while the zone is almost coincide with that by Mises’ one. The size of CTPZ is related to the ratio of fracture toughness to yield strength; with increasing of the ratio, the size of the zone increases, meaning the better of fracture toughness.

Abstract: In this paper, the corrosion behavior of Q235 steel by iron bacteria in the sedimentary water was studied by using static hanging piece method, and the corrosion characteristic was also studied by using potentiodynamic polarization curve technique and hysteresis loop methods. The results showed that, the corrosion current density of Q235 steel in iron bacteria was higher than in the sterile medium, and the corrosion potential moved negatively; Iron bacteria reduced the corrosion resistance of steel Q235; Anodic polarization curves of Q235 steel in iron bacteria didn’t showed passivation characteristic, and the cathodic polarization curves had obvious hydrogen depolarization characteristic; The presence of iron bacteria could accelerate the the pitting corrosion of Q235 steel.

Abstract: A finite element analysis is conducted to study the mutual interaction of two oblique surface cracks in rail under the wheel-rail full slip contact loading and frictional heating. In the present thermo-mechanical coupling finite element model, the heat-convection between the rail and ambient, heat transfer between the crack surfaces, and temperature-dependent material properties are taken into consideration. The variation of stress intensity factors with the distance between two cracks is investigated. The results reveal that the stress intensity factor K1 increases with an increase of the distance between the cracks. The effect of the distance between the cracks on the stress intensity factor range K2 is not significant.

Abstract: Traditional blast ammunition has a steel casing which turns into dangerous fragments after detonation. These steel fragments may kill civilians outside of the target. In order to adapt the need of fighting in an urban environment without hurting innocent bystanders in the process, one new kind of low collateral damage ammunition is put forward. The configuration and operational principle of this ammunition are introduced. From theoretical analysis it can be found the blast power is mainly determined by the metal powder. The effect of the metal powder’s type and magnitude on blast power is studied from static explosion test. In the test the overpressure curve is measured by the pressure sensor. The killing radius is computed from the sector target using the 25mm deal board. The initial casting velocity of the metal powder is obtained from the high speed photography. The results show tungsten powder is suitable for the low collateral damage ammunition, its diameter is about 50um. In this circumstance this ammunition can reduce collateral damage, however the damage effect is higher in the smaller area.

Abstract: The parameters on pore structure of Portland cement pastes blended respectively with 0, 10, 20, 30 and 40% perlite admixture at 3，28，60 curing day were determined by Mercury Intrusion Porosimetre and presented in the paper to investigate affection on performance of cement-based material due to mix the admixture. The research results indicated that since the second hydration reaction had gone on with curing time, perlite admixture could diminish porosity, decrease pore diameter and reduce pore surface area in cement paste. Pores were gradually evolved from original small pores to later smaller pores, moreover fully filled with hydration products and disappeared during hydration reaction. So that the total pore volume in the paste was descended, and the proportion of harmless pores (gel pores and micropores) to whole pores was increased but that of harmful pores (macropores) subtracted. It is concluded that perlite admixture should help to increase the mechanical strength and durability of cement-based materials.