Correlation between welding and hardening parameters of friction stir welded joints of 2017 aluminum alloy

An experimental study was undertaken to express the hardening Swift law according to friction stir welding （FSW） aluminum alloy 2017. Tensile tests of welded joints were run in accordance with face centered composite design. Two types of identified models based on least square method and response surface method were used to assess the contribution of FSW independent factors on the hardening parameters. These models were introduced into finite-element code ＂Abaqus＂ to simulate tensile tests of welded joints. The relative average deviation criterion, between the experimental data and the numerical simulations of tension-elongation of tensile tests, shows good agreement between the experimental results and the predicted hardening models. These results can be used to perform multi-criteria optimization for carrying out specific welds or conducting numerical simulation of plastic deformation of forming process of FSW parts such as hydroforming, bending and forging.

An Intelligent Multi-robot Path Planning in a Dynamic Environment Using Improved Gravitational Search Algorithm

This paper proposes a new methodology to optimize trajectory of the path for multi-robots using improved gravitational search algorithm(IGSA) in clutter environment. Classical GSA has been improved in this paper based on the communication and memory characteristics of particle swarm optimization(PSO). IGSA technique is incorporated into the multi-robot system in a dynamic framework, which will provide robust performance, self-deterministic cooperation, and coping with an inhospitable environment. The robots in the team make independent decisions, coordinate, and cooperate with each other to accomplish a common goal using the developed IGSA. A path planning scheme has been developed using IGSA to optimally obtain the succeeding positions of the robots from the existing position in the proposed environment. Finally, the analytical and experimental results of the multi-robot path planning were compared with those obtained by IGSA, GSA and differential evolution(DE) in a similar environment. The simulation and the Khepera environment result show outperforms of IGSA as compared to GSA and DE with respect to the average total trajectory path deviation, average uncovered trajectory target distance and energy optimization in terms of rotation.

Virtual surgical planning is a useful tool in the surgical management of mandibular condylar fractures

Purpose:The aim of this study is to evaluate the application value of virtual surgical planning in the management of mandibular condylar fractures and to provide a reliable reference.Methods:This was a prospective randomized controlled study and recruited 50 patients requiring surgical treatment for their mandibular condylar fractures.The inclusion criteria were patients(1)diagnosed with a condylar fracture by two clinically experienced doctors and required surgical treatment;(2)have given consent for the surgical treatment;and(3)had no contraindications to the surgery.Patients were excluded from this study if:(1)they were diagnosed with a non-dislocated or only slightly dislocated condylar fracture;(2)the comminuted condylar fracture was too severe to be treated with internal reduction and fixation;or(3)patients could not complete follow-up for 3 months.There were 33 male and 17 female patients with 33 unilateral condylar fractures and 17 bilateral condylar fractures included.The 50 patients were randomly(random number)divided into control group(25 patients with 35 sides of condylar fractures)and experimental group(25 patients with 32 sides of condylar fractures).Virtual surgical planning was used in the experimental group,but only clinical experience was used in the control group.The patients were followed up for 1,3,6 and 12 months after operation.Variables including the rate of perfect reduction by radiological analysis,the average distance of deviation between preoperative and postoperative CT measurements using Geomagic software and postoperative clinical examinations(e.g.,mouth opening,occlusion)were investigated for outcome measurement.SPSS 19 was adopted for data analysis.Results:The average operation time was 180.60 min in the experimental group and 223.2 min in the control group.One week postoperatively,CT images showed that the anatomic reduction rate was 90.63%(29/32)in the experimental group and 68.57%(24/35)in the control group,revealing significant difference(X^(2)=4.919,p=0.027).Geomagic comparative analysis revealed that the average distance of deviation was also much smaller in the experimental group than that in the control group(0.639 mm vs.0.995 mm;t=3.824,p<0.001).Conclusion:These findings suggest that virtual surgical planning can assist surgeons in surgical procedures,reduce operative time,and improve the anatomic reduction rate&accuracy,and thus of value in the diagnosis and treatment of condylar fractures.