Study on contact pressure and mechanical damage of apple under compression using pressure-sensitive film

In order to accurately predict the bruise area of apple subjected to compressive loading,the pressure distribution characteristics for apple compressed at different loads was investigated by the pressure-sensitive film technique combined with apple bruise measurements.Furthermore,the relationship between contact pressure area and bruise area was investigated and the range of pressure area that closed to the bruise area was determined.The result showed that the value of apple flesh failure stress was 0.29 MPa.Pressure distribution on the pressure-sensitive film showed that pressure of0.20~0.40 MPa accounted for 72% of the total pressure area and taken the major proportion of apple bruise area.The average pressure had little influence on the apple bruise.The measured pressure area was up to 9% higher than the actual bruise area.Only the area occupied by the pressure over than 0.10 MPa was much close to the bruise area with 1.66% relative error rate.The linear regression equation between bruise area and pressure area(A=0.98AP≥0.10+1.95)could precise estimate the bruise area of apple under static load.