The Material Breakage Features And Characterization Methods

The crashing characteristic is one of the important properties of materials. In this paper, three kinds of silica sand were selected as representative and used widely in casting manufacturer, which were used for mechanical impact testing, thermal shock testing and microstructure observation. The crushing characteristics of sinica sand and its broken mechanism had been explored. And a new method for characterizing the fracture characteristics was proposed. The main work and conclusions are shown as follows.(1) Situation of the silica sand which bored mechanical shock or thermal shock under industrial processing were analyzed. The method for characterizing material crashing properties, based on mechanical shock, thermal shockand microstructure observation, were proposed.(2) The broken method which characterized changes in material particle size before and after mechanical shock were studyed and designed. The impact of time and other parameters were optimized. The results showed that, after 40 minutes planetary ball milling, the AFS fineness of C hongqing A sand increased by 16.4. The value of Chongqing B sand was 15.7. The AFS fineness of Sichuan B sand increased by 54.2. It indicated that two kinds of C hongqing sand had well resistance to mechanical shock. However, the resistance to mechanical shock of Sichuan sand was very poor.(3) The repeated thermal cycling as thermal shock was designed. The characterization of materials crushing performance under thermal shock were studyed. To combine with foundry engineering, the temperature of thermal shock and time specification were assigned. Whether the number of thermal shock had a effect on material crushing properties were studyed. The results show that the thermal shock times had less impact on the increase of AFS fineness before and after thermal shock. The AFS fineness of C hongqing A sand after thermal shock was increased by 0.4. The AFS fineness of Chongqing B sand after thermal shock was increased by 0.3. The AFS fineness of Sichuan sand after thermal shock was increased by 0.3. The difference among the added AFS fineness of three sands was little. This described that thermal resistance of three kinds of sands were good.(4) Taking into account the foundry, silica sand could withstand mechanical shock and thermal shock at the same time. It was designed that C hongqing A sand, C hongqing B sand and Sichuan sand suffered thermal shock plus mechanical shock test. Results show that the AFS fineness value of C hongqing A sand after thermal shock plus mechanical shock increased by 39.1. The AFS fineness value of C hongqing B sand after thermal shock plus mechanical shock increased by 43.8. The AFS fineness value of Sichuan sand after thermal shock plus mechanical shock increased by 51.6. It introduced that the crushing resistance of C hongqing A sand and C hongqing B sand after thermal shock became poor. However, the resistance performance of Sichuan sand after thermal shock was insignificant.(5) Mechanical impact process on silica sand by planetary ball mill, as well as the screening process, would appear different. Due to dust and other factors, a certain difference loss in volume and yield were shown up. So when we handled data, we should have considered losses properly.(6) The morphology and surface cracks of three kinds of silica sand by SEM were observed. That was founded that the particles shape of Chongqing A sand were rounder. The surface of particles had a small number of larger cracks, dents and grooves. Chongqing B sand particles had a irregular shape. The surface attached small particles. Sichuan sand particle shape was irregular and had sharp edges and corners. The surface of particles had a large number of micro-cracks, which were attached to lots of small particles. There were good corresponding relationships between the characteristics of morphology and the results of testing, such as mechanical shock, thermal shock and thermal shock plus mechanical shock. It can be used as qualitative characteristics for fragmentation behavior. To combinate with qualitative and quantitative characterization methods, which would have characterized the material properties of crushing better. The mechanical shock and thermal shock can show the fragmentation behavior qualitatively.