Effect of strain hardening and strain softening on welding distortion and residual stress of A7N01-T4 aluminum alloy by simulation analysis

The effect of strain hardening and strain softening behavior of flow stress changing with temperature on welding residual stress, plastic strain and welding distortion of ATN0 1-T4 aluminum alloy was studied by finite simulation method. The simulation results show that the weld seam undergoes strain hardening in the temperature range of 180-250 ℃, however, it exhibits strain softening at temperature above 250 ℃ during welding heating and cooling process. As a result, the strain hardening and strain softening effects counteract each other, introducing slightly influence on the welding residual stress, residual plastic strain and distortion. The welding longitudinal residual stress was determined by ultrasonic stress measurement method for the flat plates of A7N01-T4 aluminum alloy. The simulation results are well accordant with test ones.

Analysis and Control of Soil Residual Film Pollution Load in Cotton Fields in the Yellow River Delta

[Objectives]This study was conducted to explore the characteristics of soil residual film pollution load in cotton fields in the Yellow River Delta,so as to effectively control soil film pollution.[Methods]Cotton field mulching film survey and residue monitoring were conducted in the Yellow River Delta area.[Results]The amount of mulching film residues in cotton fields in the Yellow River Delta was 37.7-128.7 kg/hm^(2),which had a significant increase compared with 5 years ago,and the differences between plots were large;and after straw was returned to the field,the soil residual film obviously gathered in the 20-30 cm soil layer.The residual film blocks with a size of more than 25 cm^(2) accounted for 62.6%,which was a relatively high proportion,indicating that soil pollution can be caused easily,and it is difficult to control.During a certain period of time,the soil residual film pollution may have a tendency to aggravate,and the ecological risk is higher.[Conclusions]This study has important theoretical and practical significance for improving soil quality in the region and ensuring the safety of cotton field ecosystem and environmental health.

Assessment of composite failure and ultimate strength without experiment on composite

This paper attempts to estimate the ultimate strength of a laminated composite only based on its con- stituent properties measured independently. Three important issues involved have been systematically addressed, i.e., stress calculation for the constituent fiber and matrix materials, failure detection for the lamina and laminate upon the internal stresses in their constituents, and input data determination of the constituents from monolithic measurements. There are three important factors to influence the accuracy of the strength prediction. One is the stress concentration factor （SCF） in the matrix. Another is matrix plasticity. The third is thermal residual stresses in the constituents. It is these three factors, however, that have not been sufficiently well realized in the composite community. One can easily find out the elastic and strength parameters of a great many laminae and laminates in the current literature. Unfortunately, necessary information to determine the SCF, the matrix plasticity, and the thermal residual stresses of the composites is rare or incomplete. A useful design methodology is demonstrated in the paper.

Characteristics of Mulching Plastic Film Residue in Cotton Fields in the Yellow River Delta

In order to get a clear picture of distribution characteristics of mulching plastic film residue in cotton fields in the Yellow River Delta and make scientific pollution prevention and control strategies, an investigation was conducted in Dongying City. Five typical cotton fields were chosen, and then the number, distri- bution density and area of residual film were measured. The results showed that the residual film was 18. 84-53. 53 kg/hm^2 in cotton fields for more than 20 years, and the differences between fields were larger. The residual density was 225-340 thousand per hectare. There were great differences among residual pieces. The proportion of residual pieces over 25 cm^2 was 94. 1%, that between 100 cm^2 and 500 cm^2 was more than 50. 0%, and that bigger than 500 cm^2 was about 21. 0%. In the Yellow River Delta cotton region, large, thin and difficult to recovery were the main characteristics of mulching plastic film residue, and it had the possibility of mi- grating to deep soil. Thus, the ecological risk of mulching plastic film residue was higher. Key words The Yellow River Delta; Cotton field; Residue of mulching plastic film; Distribution characteristic

Effect of Crystallographic Orientation on Quenching Stress during Martensitic Phase Transformation of Carbon Steel Plate

During quenching, the residual stresses are affected by the crystallographic orientation of martensite, because the nonuniform thermal stresses affect the crystallographic orientation of the lathshaped martensite and induce the anisotropic expansion. To simulate this process, the model of anisotropic transformation induced plasticity（TRIP） was built using the WLR-BM phenomenological theory. The equivalent expansion coefficient was introduced considering the thermal and plastic strains, which simplified the numerical simulation. Furthermore, the quenching residual stresses in carbon steel plates were calculated using the finite element method under ANSYS Workbench simulation environment. To evaluate the simulative results, distributions of residual stresses from the surface to the interior at the center of specimen were measured using the layer-by-layer hole-drilling method. Compared to the measured results, the simulative results considering the anisotropic expansion induced by the crystallographic orientation of martenstic laths were found to be more accurate than those without considering it.

Detection and threshold-adaptive segmentation of farmland residual plastic film images based on CBAM-DBNet

Robust, accurate, and fast monitoring of residual plastic film (RPF) pollution in farmlands has great significance. Based on CBAM-DBNet, this study proposed a threshold-adaptive joint framework for identifying the RPF on farmland surfaces and estimating its coverage rate. UAV imaging was used to gather images of the RPF from several locations with various soil backgrounds. RPFs were manually labeled, and the degree of RPF pollution was defined based on the RPF coverage rate. Combining differentiable binarization network (DBNet) with the convolutional block attention module (CBAM), whose feature extraction module was improved. A dynamic adaptive binarization threshold formula was defined for segmenting the RPF’s approximate binary map. Regarding the RPF image detection branch, the CBAM-DBNet exhibited a precision (P) value of 85.81%, a recall (R) value of 82.69%, and an F1-score (F1) value of 84.22%, which was 1.09 percentage points higher than the DBNet in the comprehensive index F1 value. For the RPF image segmentation branch, using CBAM-DBNet to segment the RPF image combined with an adaptive binarization threshold formula. Subsequently, the mean absolute percentage error (MAPE), root mean square error (RMSE), and mean absolute error (MAE) of the prediction of RPF’s coverage rate were 0.276, 0.366, and 0.605, respectively, outperforming the DBNet and the Iterative Threshold method. This study provides a theoretical reference for the further development of evaluation technology for RPF pollution based on UAV imaging.

Impact of agricultural residual plastic film on the growth and yield of drip-irrigated cotton in arid region of Xinjiang, China

Long-term and widespread use of plastic mulching has led to the accumulation of residual plastic film(RPF)in farmland soils of Xinjiang,China.However,there is no specific quantitative basis for RPF pollution or a clear understanding of the influence of residual film on crop growth.The aim of this study was to investigate the effect of RPF on the growth of cotton,an important cash crop of Xinjiang.Based on the field conditions and previous reports,various amount of residual film was applied in 0-30 cm soil layer.The growth index including emergence rate,dry matter,and yield of cotton was examined at different growth stages under different soil residual film levels.Results demonstrated a significant effect of RPF on soil moisture distribution and movement.Plastic residues had a significant effect on cotton growth at levels above 200 kg/hm2,and the yield decreased as the RPF amount increased.Based on these findings,200 kg/hm2 was suggested as a threshold level to determine the effects of RPF on cotton.This study provided a basis to rate RPF pollution in farmland soils and help understand the impact of pollution on crop productivity.