Jiping Lu

Obtaining uniform deposition with variable wire feeding direction during wire-feed additive manufacturing

ABSTRACT Wire-feed additive manufacturing is cost competitive and efficient in producing large and complex components in aerospace applications. However, for the additive manufacturing technologies with lateral wire feeding, including laser wire additive manufacturing, electron beam freeform fabrication, plasma arc welding, and gas tungsten arc welding, it is difficult to obtain uniform deposit due to the variable wire feeding direction. In this work, high-angle wire feeding method is proposed to obtain uniform deposit in gas tungsten arc welding-based additive manufacturing. The results illustrate that low wire feeding angle (30°–50°) causes the deposition to break at the back feeding, meanwhile too high wire feeding angle (70°) leads to many littered droplets on one side of the deposition at the condition of side feeding. A uniform deposition can be obtained at the optimal wire feeding angle of 60° in any wire feeding direction, and the reasons have been discussed based on the temperature distribution characteristics of the arc and molten pool. Furthermore, the deposition layers exhibit similar columnar prior β grains, basketweave microstructure, and tensile properties from different wire feeding directions.

Research on assembly quality evaluation based on Markov chain

Assembly processes involve a large number of operations and uncertain factors, which makes the random deviation of assembly quality. How to quantifiably evaluate the final assembly quality remains a question. This paper presents a new methodology to fulfill the task. Based on the analysis of the factors influencing assembly quality of missile cabin, assembly quality model is formulated to establish the relationship between the assembly status and quality loss. Then the transfer matrix of assembly process is built by the functions of quality loss for the missile cabin in terms of Markov chain. Finally, a case study of the assembly process of missile cabin has been used to support and validate the proposed model.

Study on design change review for small and medium-sized enterprises

Inadequate engineering change control method for Small and Medium-Sized Enterprises comparing to Large and Medium-Sized Enterprises, the model of engineering change management for SMEs is established, as well as its goal controlling source of engineering change and the main body reviewing design change. Three evaluation indexes are analyzed, constructing judgment matrix through method of the nine proportional scale, then proposing design changes review method which needed relevant departments to participate in decision-making. In this way, it can expose the problems early that may occur in the late change and reduce the repeated change caused by related change, so saving the cost of change, controlling engineering change of SMEs and improving its management level.

Optimization and Simulation of Machining Parameters in Radial-axial Ring Rolling Process

Ring rolling is a complicated process, in which rolling parameters influence directly the quality of ring. It is a process method with high productivity and few waste of material, widely used in transportation industry including automotive, shipbuilding, aerospace etc. During the rolling process of large-sized parts, crinkle and hollows often appear on surface, due to inconsistence of rolling motions with the deformation of ring part. Based on radial-axial ring rolling system configuration, motions and forces in rolling process are analyzed, and a dynamic model is formulated. Error of rings end flatness and roundness are defined as the characteristic parameters of ring quality. The relationship between core roller feed speed, drive roller speed, the upper taper roller feed speed, and quality of ring part are analyzed. The stress and strain of the part are simulated in the Finite Element Method by DEFORM software. The simulation results provide a reference for the definition of ring rolling process parame...

Tolerance-based Structural Design of Tubular-Structure Loading Equipments

Mechanical loading equipments are wildly used in transportation system. Positioning precision is one of the basic functions of machine tools, and structure design is the key to ensuring accuracy. According to the assembly process of tubular–structure, the paper analyzes motion modes to achieve tubular–structure loading. In terms of assembly tolerance of tubular–structure, a tolerance model to guide structure design of loading equipment is formulated. Based on tolerance analysis of each motion mode, the maximum available size of the tubular–structure is calculated under different linear rolling guide, and the minimum available size of the interior rail in the cover box is worked out under different ball screws, trapezoidal screw threads, worm and worm gears. To meet the requirement of tolerance in tubular–structure assembly, mechanisms for all motions are defined. The design of loading equipment is tested and assessed by experiments, and the result shows the design is highly qualified for its assembly.

Simulation of Assembly Tolerance and Characteristics of High Pressure Common Rail Injector

Fuel injector is the key part of a high-pressure common rail fuel injection system. Its manufacturing precision and assembly quality affect systems property and performance. According to the characteristics and demands of assembly of the fuel injector, an intelligent optimization algorithm is proposed to resolve the problem of assembly sequence planning. Based on geometric modeling, assembly dimension chain of the injector control chamber is established, and the relationship between assembly tolerance and volume change of control chamber is analyzed. The optimization model of the assembly is established. The impact of assembly tolerance on injectors performance is simulated according to the optimization algorithm. The simulation result shows that quantity of injection fuel changes correspondingly with the change of assembly tolerance, while injection rate and pressure do not change significantly, and the response rate of needle considerably slow. Similarly, the leakage rate of fuel in control chamber is calculated, indicating that the assembly tolerance has obvious impact on fuel leakage and its rate. The study illuminates that injectors assembly tolerance has prominent effect on injection.

Analytic model of machining errors for thin walled parts based on the deformation of the workpiece-fixture system

The analytic model of machining errors caused by the deformation of workpiece-fixture system is put forward for the thin walled parts. To facility the analysis, the traditional mathematical model of tolerance zone is redefined. According to the deformation value of workpiece-fixture system calculated by FEA (Finite element analysis), transform matrixes of workpiece location and cutting points deviation have been constructed. So that location changes of the surface machining points can be acquired. Then machining error model is formulated to describe the deviations caused errors. Further for given surface tolerances the sensitive matrix is constructed to evaluate the influence of locators on the machining errors. The model has great potential to be applied toward fixture design verification and process design evaluation. Finally a study case is used to support and validate the proposed model.

A Novel Idea for Optimizing Condition-Based Maintenance Using Genetic Algorithms and Continuous Event Simulation Techniques

Effective maintenance strategies are of utmost significance for system engineering due to their direct linkage with financial aspects and safety of the plants’ operation. At a point where the state of a system, for instance, level of its deterioration, can be constantly observed, a strategy based on condition-based maintenance (CBM) may be affected; wherein upkeep of the system is done progressively on the premise of monitored state of the system. In this article, a multicomponent framework is considered that is continuously kept under observation. In order to decide an optimal deterioration stage for the said system, Genetic Algorithm (GA) technique has been utilized that figures out when its preventive maintenance should be carried out. The system is configured into a multiobjective problem that is aimed at optimizing the two desired objectives, namely, profitability and accessibility. For the sake of reality, a prognostic model portraying the advancements of deteriorating system has been employed that will be based on utilization of continuous event simulation techniques. In this regard, Monte Carlo (MC) simulation has been shortlisted as it can take into account a wide range of probable options that can help in reducing uncertainty. The inherent benefits proffered by the said simulation technique are fully utilized to display various elements of a deteriorating system working under stressed environment. The proposed synergic model (GA and MC) is considered to be more effective due to the employment of “drop-by-drop approach” that permits successful drive of the related search process with regard to the best optimal solutions.

The influence of cutting parameters on residual stress distribution during turning of 20Cr2Ni4 steel

A series of orthogonal experiments have been carried out to study the effect of different rake angles, cutting depths and spindle speeds on residual stress distribution during turning of 20Cr2Ni4 steel. Four characteristic values are selected from the typical residual stress distribution profile: surface residual stress, the depth of tensile stress, the maximum residual compressive stress and the depth of residual stress. The residual stress by turning were measured by X-ray diffraction method. In order to get the distribution of residual stress along depth direction, the specimens need to be etched layer by layer. From this investigation, it could be suggested that during turning of 20Cr2Ni4 steel, using the cutting parameters that low rake angle (5 degrees), large cutting depth (0.3 mm) and medium spindle speed (200 r/min) will result in low residual stress of parts.

Quality Evaluation of Multistage Manufacturing Systems by Jointly Considering the Incoming Part Quality and System Conditions

The quality performance of a multistage manufacturing systems (MMS) is jointly affected by incoming part quality, system condition unreliability due to batch-to-batch uncertainty, making it challenging to evaluate the quality performance of MMS. Previous research considered the incoming part quality and system conditions separately in systematic level. This paper aims to fill the gap by considering the joint effects of these two aspects to evaluate quality performance of a MMS from historical production data driven work. A system quality model was derived to predict the probability of producing good parts at each stage and entire MMS when the incoming good part quality rate and station conditions were given. To overcome the inconvenience of the quality model for its nonlinear transfer function, the concept of quality efficiency was developed to depict the joint effectiveness of incoming part quality and system conditions mathematically at each stage. Based on the quality model, on the paper also discusses how to maintain high good product quality rate. The results of this study suggested a possible approach of evaluating the impacts of system conditions on product quality. The results of the model will lead to guidelines of quality management in multistage manufacturing systems.Copyright