A new Approach for experimental evaluation of contact stresses
In metal forming operations, the intensity and distribution of stresses at the tool/material interface have great influence on the pattern and mode of deformation. This is due to the effect of frictional forces in being resistive to material movements and hence affects material flow and the directionality of volume distribution of material inside die cavities. This paper explores the use of the pressure pin technique for the measurement of tool stresses at the interface between the tool and the deforming workpiece material. It also introduces a new experimental methodology for the measurement of stresses where the measuring device is concealed inside the tool and not subjected to the severe conditions at the interface surface. Each tool containing measuring devices is split into two parts, one part has the shape to be formed (industrial die), while the second part includes the pressure pin measuring column. Friction resistance and friction coefficient are evaluated across the billet surface and at different stages of deformation.
Surface stress measurement techniques in metal forming
Abstract This paper describes and classifies stress measurement techniques used in metal forming to provide research workers with a critical evaluation of usable methods. Eight techniques are considered; pressure transmitting pins, photoelasticity, ridged metallic sheets, paper sheets, split tools, strain gauged tools, orifices in tools and visioplasticity. In addition to these, some new transducer designs using optics and conical pins are presented. These are particularly useful for pressure measurement in hot forming operations.
Career Choice Inclination of the College Graduates——under the Analytic Framework on the Basis of LMS Theory
Employment difficulty of college graduates has become a social problem in China today.The research group has found that college graduates have a strong inclination in career choice considering units and regions.In terms of China's manpower market and the segmented labor market theory,it is found that their inclination is caused by the great income gap of different regions,the high cost of job transfer,and the sharp differences in social welfare.It is thus obvious that solution to the problem lies with the gradual breakdown of the institutional segment of labor market.