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The water-retaining agent can relieve the evaporation of water of saline-alkali land to slow down the immigration of salt. At present, polyacrylamide is often used in the saline-alkali soils repairing, but the difficult in its degradation limited it using. In this paper, polyglutamic acid and seaweed extract were used to develop a new biological water-retaining agent. The salt migration rate, water evaporation was tested. The proportions of seaweed in the polyglutamic acid fermentation broth 100% was tested by the column experiment. Results showed that its rate of salt control is 28.5%, and the water evaporation rate was reduced by 43.25% than control. Compared to polyacrylamide with the same addition, the salt control rate of the new agent increased by 3.52times. The new water-retaining agent developed in this paper can not only maintaining water and resisting salt, but also promote the growth of crops and regulate the micro-ecology of soil, which showed a good prospect of application and development. [ABSTRACT FROM AUTHOR]

An integrated computational materials engineering method is proposed in this paper for analyzing the design and preforming process of woven carbon fiber composites. The goal is to reduce the cost and time needed for the mass production of structural composites. It integrates the simulation methods from the micro-scale to the macro-scale to capture the behavior of the composite material in the preforming process. In this way, the time consuming and high cost physical experiments and prototypes in the development of the manufacturing process can be circumvented. This method contains three parts: the micro-scale representative volume element (RVE) simulation to characterize the material; the metamodeling algorithm to generate the constitutive equations; and the macro-scale preforming simulation to predict the behavior of the composite material during forming. The results show the potential of this approach as a guidance to the design of composite materials and its manufacturing process. [ABSTRACT FROM AUTHOR]

Double-Sided Incremental Forming (DSIF) is a developing sheet metal manufacturing process that has gained a lot of attention in recent years due to its inherent flexibility, low-overhead cost, and die-less nature. However, it can be challenging to define the tool gap so as to achieve a desired pressure through the sheet thickness since one must first predict sheet thinning. In this investigation, a novel part design is proposed which varies in-plane curvature as a function of depth. A finite element model for DSIF is developed and the strain histories in various regions are extracted. It was concluded that if the supporting tool loses contact with the sheet, localized necking can occur prior to part failure. Additionally, part geometry can have significant effects on the tool contact area which, consequently, affects the evolution of strain. [ABSTRACT FROM AUTHOR]

As a result of international corporative benchmark works, material characterization of the woven fabric reinforced composites has been examined to better understand their mechanical properties and to provide the process design information for numerical analysis. Here, in order to predict thermo-forming behaviors of woven composites, the double dome stretching tests have been numerically performed for the balanced plain weave. To account for the change of fiber orientation under the large deformation, the non-orthogonal constitutive model has been utilized and nonlinear friction behavior is incorporated in the simulation. Also the equivalent material properties based on the contact status have been used for the thermo-stamping process. Blank draw-in, punch force history and fiber orientation after forming will be reported. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

The thermostamping of quality composite parts using thermoplastic woven fabrics requires the use of in-plane forces to prevent fabric wrinkling for compound curvature surfaces. These in-plane forces are developed during the stamping process by the friction between the fabric and tool. For multilayer stampings, the in-plane force is also a consequence of the interaction of the adjacent layers of fabric. If the in-plane forces are too low, then the stamped parts may wrinkle as the fabric deforms to assume the shape of the punch. If the in-plane forces are too high, then the fabric can become damaged by tearing and yarn separation. Thus, controlling the in-plane forces is critical to achieving a quality part. In the current research, the design of a load-control friction testing apparatus is presented. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Characterization of material hardening behavior has been investigated by many researchers in the past decades. Experimental investigation of thin sheet metals under cyclic loading has become a challenging issue. A new test fixture has been developed to use with a regular tensile-compression machine (for example, MTS machine). Experimental results of tension-compression tests are presented followed by a review of existing testing methods. Numerical modeling of the tested data is presented using a new kinematic hardening model. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Sheet metal stamping processes have been widely implemented in many industries due to its repeatability and productivity. In general, the simulations for a sheet metal forming process involve nonlinearity, complex material behavior and tool-material interaction. Instabilities in terms of tearing and wrinkling are major concerns in many sheet metal stamping processes. In this work, a sheet metal stamping process of a mild steel for a wheelhouse used in automobile industry is studied by using an explicit nonlinear finite element code and incorporating failure analysis (tearing and wrinkling) and design under uncertainty. Margins of tearing and wrinkling are quantitatively defined via stress-based criteria for system-level design. The forming process utilizes drawbeads instead of using the blank holder force to restrain the blank. The main parameters of interest in this work are friction conditions, drawbead configurations, sheet metal properties, and numerical errors. A robust design model is created to conduct a probabilistic design, which is made possible for this complex engineering process via an efficient uncertainty propagation technique. The method called the weighted three-point-based method estimates the statistical characteristics (mean and variance) of the responses of interest (margins of failures), and provide a systematic approach in designing a sheet metal forming process under the framework of design under uncertainty. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Micro-forming using meso-scale press has the potential of bringing up an entire new concept of manufacturing. Compared to macro-forming process, individual microstructure (i.e., the size, shapes and arrangement of grains) plays an even more critical role in deformation, process variation, interfacial behavior and wear in the micro-forming process. In this paper, reproducing kernel element method (RKEM) is employed to simulate the micro-forming process. As a meshfree method, RKEM can handle large deformation of material in the micro-forming process. The efficiency of RKEM can be improved with using the stabilized conforming nodal integration. Due to the natural conforming of approximation and no requirement of compatible mesh in RKEM, it is easy to remesh the model when moving interfacing (grain boundary) is considered. As the first step of a series investigation, the resulting force of deforming a pin in a micro-forming process is calculated with RKEM and is compared to the experimental result. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]