充电器外壳注射模塑件结构工艺性分析及设计计算

本文首先对充电器外壳塑件结构进行了分析,并从确定型腔数量及排列方式、模具结构形式的确定、注射机型号的确定、锁模力校核、注射压力校核、开模行程的校核这5个方面对模具结构形式与设计计算进行了论述。

三维注射模塑连接件的制造技术

三维注射模塑连接件(3D-MID)制造技术是一种新的注射成型技术,它提供了一种集机械和电子功能于一体的设计和制造方法。介绍了这种注射成型技术的特点、工艺过程、应用材料、市场以及应用前景等。能够集成的典型机械功能包括螺纹紧固、搭扣连接、插头连接等。3D-MID具有一系列传统印刷线路板所不具备的优点,应用领域包括汽车、电信、家电产品、医用器材等。

Integrated identification method of rheological model of sandstone in Sanmenxia bauxite

Based on the uniaxial compression creep experiments conducted on bauxite sandstone obtained from Sanmenxia,typical creep experiment curves were obtained.From the characteristics of strain component of creep curves,the creep strain is composed of instantaneous elastic strain,ε（me）,instantaneous plastic strain,ε（mp）,viscoelastic strain,ε（ce）,and viscoplastic strain,ε（cp）.Based on the characteristics of instantaneous plastic strain,a new element of instantaneous plastic rheology was introduced,instantaneous plastic modulus was defined,and the modified Burgers model was established.Then identification of direct screening method in this model was completed.According to the mechanical properties of rheological elements,one- and three-dimensional creep equations in different stress levels were obtained.One-dimensional model parameters were identified by the method of least squares,and in the process of computation,Gauss-Newton iteration method was applied.Finally,by fitting the experimental curves,the correctness of direct method model was verified,then the examination of posterior exclusive method of the model was accomplished.The results showed that in the improved Burgers models,the rheological characteristics of sandstone are embodied properly,microscopic analysis of creep curves is also achieved,and the correctness of comprehensive identification method of rheological model is verified.

Effects of process parameters on warpage of rapid heat cycle moulding plastic part

The effects of process parameters in rapid heat cycle moulding （RHCM） on parts warpage were investigated. A vehicle-used blue-tooth front shell （consisting of ABS material） was considered as a part example manufactured by RHCM method. The corresponding rapid heat response mould with an innovational conformal heating/cooling channel system and a dynamic mould temperature control system based on the Jll-W-160 type precise temperature controller was proposed. During heating/cooling process, the mould was able to be heated from room temperature to 160 ~C in 6 s and then cooled to 80 ~C in 22 s. The effects of processing conditions in RHCM on part warpage were investigated based on the single factor experimental method and Taguchi theory. Results reveal that the elevated mould temperature reduces unwanted freezing during the injection stage, thus improving mouldability and enhancing part quality, whereas the overheated of mould temperature will lead to defective product. The feasible mould temperature scope in RHCM should be no higher than 140 ~C, and the efficient mould temperature scope should be around the polymer heat distortion temperature. Melt temperature as well as injection pressure effects on warpage can be divided into two stages The lower stage gives a no explicit effect on warpage whereas the higher stage leads to a quasi-linear downtrend. But others affect the warpage as a V-type fluctuation, reaching to the minimum around the heat distortion temperature. Under the same mould temperature condition, the effects of process parameters on warpage decrease according to the following order, packing time, packing pressure, melt temperature, injection pressure and cooling time, respectively.

A Simulation Software for the Prediction of Thermal and Mechanical Properties of Wood Plastic Composites

Modelling and simulation has become an important tool in research and development. Simulation models are used to develop better understanding of the internal properties and impact of various parameters on the final quality of the product or process. Simulation model reduces the number of experiments and saves the wastage of material, time and money and are widely used in automobile industry, aircrafts manufacturing, process engineering, training for military, health care sector and many more. Wood Plastic Composite （WPC） is a bio-composite made by mixing wood fibers and plastic granules together at high temperature by compression molding or injection molding. A large quantity of WPC is rejected due to poor quality and low mechanical strength. There is a need to improve the understanding of the wood plastic composites, with both theoretical and experimental analysis. The impact of various parameters and processing conditions on the final product is not known to the industry people, due to less simulation models in this field. A new simulation software WPC Soft is developed to predict the mechanical and thermal properties of WPC. The software can predict the mechanical and thermal properties of WPC. The simulation results were validated with the experimental results and it was observed that the predicted values are quite close to the experimental values and with the further refining of the model, prediction can be further improved. The present simulation software can be easily used by the industry people and it requires very little knowledge of computers or modeling for its operation.

An improved hypoplastic constitutive model of rockfill considering effect of stress path

An incrementally nonlinear hypoplastic constitutive model was introduced, which was developed without recourse to the concepts in elastoplasticity theory such as yield surface, plastic potential and the decomposition of the deformation into elastic and plastic parts. Triaxial drained tests on rockfill were conducted on a large scale triaxial apparatus under two types of stress paths, which were the stress paths of constant stress ratio and the complex stress paths with transitional features. Motivated by the effect of stress path, the Gudehus-Bauer hypoplastic model was improved by considering the parameter variations with different ratios of stress increment. Fitting parameter a presents a piecewise linear relationship with cosine of the slope angle θ determined by instantaneous stress path. The improved hypoplastic model can present peak stress increasing and volumetric strain changing from dilatancy to contractancy with the increase of transitional confining pressure σ3t and the decrease of slope angle θ of stress path. Compared with the test data, it is shown that the model is capable of fully considering the effect of stress path on rockfill.